CNKSR3

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0007167 enzyme-linked receptor protein signaling pathway	IBA GO_REF:0000033	REMOVE	Summary: IBA annotation based on phylogenetic inference. CNKSR3 is a scaffold protein involved in multiple signaling pathways including HGF-induced Arf6 activation and aldosterone-ENaC signaling. While the protein participates in signaling downstream of receptors, the specific connection to enzyme-linked receptors is indirect and the term is too general for this scaffold protein's core functions. Reason: The term enzyme-linked receptor protein signaling pathway is overly broad and the more specific term GO:0009966 regulation of signal transduction is already accepted as an IEA annotation elsewhere in this review (PR #759 review feedback — MODIFY to an already-annotated term would produce a duplicate; REMOVE is the correct action). CNKSR3's best-characterized roles are aldosterone-ENaC scaffolding and HGF/Arf6 modulation, both already captured. Supporting Evidence: PMID:22085542 Knockdown of this protein impairs HGF-induced Arf6 activation and migration in response to HGF treatment file:human/MAGI1/MAGI1-uniprot.txt Acts as a scaffold protein coordinating the assembly of an ENaC-regulatory complex
GO:0030674 protein-macromolecule adaptor activity	IBA GO_REF:0000033	ACCEPT	Summary: IBA annotation for adaptor/scaffold function. This is well-supported and represents a core molecular function of CNKSR3. The protein coordinates assembly of the ENaC-regulatory complex by binding multiple partners including SCNN1A, SCNN1B, NEDD4L, RAF1, and SGK1. It also scaffolds HGF-Arf6 signaling components. Reason: This accurately captures CNKSR3's primary molecular function as a scaffold/adaptor protein that brings together multiple signaling components. Well-supported by experimental evidence. Supporting Evidence: file:human/MAGI1/MAGI1-uniprot.txt Acts as a scaffold protein coordinating the assembly of an ENaC-regulatory complex (ERC). Interacts directly with SCNN1A (ENaC subunit alpha) and SCNN1B (ENaC subunit beta) C-terminal tails. Interacts with ENaC regulatory proteins NEDD4L, RAF1 and SGK1. file:human/MAGI1/MAGI1-deep-research-perplexity-lite.md See deep research file for comprehensive analysis file:human/MAGI1/MAGI1-deep-research-falcon.md CNKSR3 is positioned as an aldosterone/mineralocorticoid receptor (MR)-regulated scaffold that is required for ENaC-mediated sodium transport in aldosterone-responsive distal nephron epithelia (connecting tubule and cortical collecting duct)
GO:0005737 cytoplasm	IEA GO_REF:0000120	ACCEPT	Summary: IEA annotation based on InterPro domains and UniProtKB subcellular location. CNKSR3 is indeed found in cytoplasm, though its most functionally important localization is at the apical plasma membrane where it regulates ENaC. Cytoplasmic localization is confirmed but represents a secondary or transit location. Reason: Accurate but not the most informative localization. CNKSR3 is present in cytoplasm as stated in UniProt, though apical plasma membrane is the more functionally relevant location. Supporting Evidence: file:human/MAGI1/MAGI1-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm. Apical cell membrane; Peripheral membrane protein.
GO:0009966 regulation of signal transduction	IEA GO_REF:0000002	ACCEPT	Summary: IEA annotation from InterPro domain IPR010599 (CNK2/3 domain). This is appropriate - CNKSR3 regulates multiple signal transduction pathways including MAPK/ERK signaling (negative regulation) and aldosterone-ENaC signaling (positive regulation of sodium transport). Reason: Accurate representation of CNKSR3's biological role as a regulator of signaling pathways. The protein negatively regulates ERK1/2 cascade and peptidyl-serine phosphorylation while positively regulating ENaC-mediated sodium transport. Supporting Evidence: file:human/MAGI1/MAGI1-uniprot.txt negative regulation of ERK1 and ERK2 cascade; ISS:UniProtKB. negative regulation of peptidyl-serine phosphorylation; ISS:UniProtKB. positive regulation of sodium ion transport; ISS:UniProtKB. PMID:22101317 The first study addressing the mechanistic aspects of CNK3 function revealed that CNK3 expression significantly interferes with the activation of the Raf-1/MEK1/2/ERK1/2 signaling cascade
GO:0016020 membrane	IEA GO_REF:0000002	MODIFY	Summary: IEA annotation from InterPro. While CNKSR3 is a peripheral membrane protein at the apical plasma membrane, this extremely general term provides minimal information. More specific membrane localization terms are more appropriate. Reason: The term 'membrane' is too general. CNKSR3 specifically localizes to the apical plasma membrane where it functions in ENaC regulation. A more specific term is warranted. Proposed replacements: apical plasma membrane Supporting Evidence: file:human/MAGI1/MAGI1-uniprot.txt SUBCELLULAR LOCATION: Apical cell membrane; Peripheral membrane protein
GO:0016324 apical plasma membrane	IEA GO_REF:0000044	ACCEPT	Summary: IEA annotation from UniProtKB subcellular location vocabulary. This is accurate and functionally important - CNKSR3 localizes to the apical plasma membrane of epithelial cells where it coordinates the ENaC-regulatory complex. Reason: This is the most functionally relevant subcellular location for CNKSR3. The protein is specifically targeted to the apical membrane where it regulates ENaC. Supporting Evidence: file:human/MAGI1/MAGI1-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm. Apical cell membrane; Peripheral membrane protein. Acts as a scaffold protein coordinating the assembly of an ENaC-regulatory complex (ERC).
GO:0005515 protein binding	IPI PMID:25416956 A proteome-scale map of the human interactome network.	REMOVE	Summary: IPI evidence from proteome-scale interactome study identifying interaction with NMI (Q13287). While protein binding is technically correct, it is uninformative as a molecular function annotation. CNKSR3's specific function is as a protein-macromolecule adaptor, which is already captured by GO:0030674. Reason: The term 'protein binding' is uninformative per curation guidelines. The specific adaptor function is better captured by GO:0030674 (protein-macromolecule adaptor activity). Large-scale interactome studies often identify interactions that may not be functionally relevant to core gene function. Supporting Evidence: PMID:25416956 A proteome-scale map of the human interactome network.
GO:0005515 protein binding	IPI PMID:32296183 A reference map of the human binary protein interactome.	REMOVE	Summary: IPI evidence from binary protein interactome reference map identifying multiple interactions. While protein binding is correct, it is redundant and uninformative given the more specific GO:0030674 annotation. Reason: Uninformative and redundant with the more specific adaptor activity term. This is from a large-scale binary interactome study. Supporting Evidence: PMID:32296183 Apr 8. A reference map of the human binary protein interactome.
GO:0005515 protein binding	IPI PMID:40205054 Multimodal cell maps as a foundation for structural and func...	REMOVE	Summary: IPI evidence from multimodal cell atlas study. Another protein binding annotation that is uninformative compared to the specific adaptor function already annotated. Reason: Uninformative and redundant. Large-scale proteomics study. The specific molecular function is better captured by GO:0030674. Supporting Evidence: PMID:40205054 Apr 9. Multimodal cell maps as a foundation for structural and functional genomics.
GO:0005829 cytosol	IDA GO_REF:0000052	ACCEPT	Summary: IDA evidence from immunofluorescence data (HPA project). Cytosol is a more specific cytoplasmic compartment and represents where CNKSR3 is found when not at the membrane. This is consistent with the protein's peripheral membrane association - it can be in cytosol and recruited to apical membrane. Reason: Supported by direct experimental evidence from immunofluorescence. Cytosol localization is consistent with CNKSR3 being a peripheral (not integral) membrane protein that can shuttle between cytosol and membrane. Supporting Evidence: GO_REF:0000052 Gene Ontology annotation based on curation of immunofluorescence data from Human Protein Atlas project
GO:0005515 protein binding	IPI PMID:22085542 CNK3 and IPCEF1 produce a single protein that is required fo...	REMOVE	Summary: IPI evidence from the CNK3/IPCEF1 study showing interactions relevant to HGF-Arf6 signaling. While this paper provides important functional context, the protein binding annotation itself is uninformative. Reason: Although PMID:22085542 is a key functional paper showing CNKSR3 interacts with cytohesin 2 and is required for Arf6 activation, the generic "protein binding" annotation is uninformative. The specific adaptor function (GO:0030674) is more appropriate. Supporting Evidence: PMID:22085542 2011 Nov 7. CNK3 and IPCEF1 produce a single protein that is required for HGF dependent Arf6 activation and migration.
GO:0010765 positive regulation of sodium ion transport	ISS GO_REF:0000024	ACCEPT	Summary: ISS annotation based on mouse ortholog Q8BMA3. This represents a core function of CNKSR3 - it positively regulates ENaC-mediated sodium transport in response to aldosterone. This is the protein's best-characterized biological role in kidney epithelial cells. Reason: This is a core biological function of CNKSR3. The protein regulates aldosterone-induced ENaC-mediated sodium transport through coordinating the assembly of the ENaC-regulatory complex. Well-supported by multiple studies. Supporting Evidence: file:human/MAGI1/MAGI1-uniprot.txt FUNCTION: Involved in transepithelial sodium transport. Regulates aldosterone-induced and epithelial sodium channel (ENaC)-mediated sodium transport through regulation of ENaC cell surface expression. Acts as a scaffold protein coordinating the assembly of an ENaC-regulatory complex (ERC). PMID:22101317 CNK3 expression correlates with, and is required for, ENaC-mediated Na+ transport in renal epithelial cells PMID:22506713 CNK3 expression correlates with, and is critically required for, ENaC-mediated Na+ transport in renal epithelial cells
GO:0033137 negative regulation of peptidyl-serine phosphorylation	ISS GO_REF:0000024	KEEP AS NON CORE	Summary: ISS annotation based on mouse ortholog. CNKSR3 scaffold proteins regulate kinase signaling cascades and this annotation likely reflects regulation of SGK1 or other serine kinases in the ENaC regulatory complex, or broader effects on MAPK pathway serine phosphorylation. Downgraded from ACCEPT to KEEP_AS_NON_CORE per PR #759 review feedback: the rationale cites indirect kinase-interaction evidence without direct biochemical demonstration of CNKSR3 negatively regulating peptidyl- serine phosphorylation. Reason: Indirect evidence — CNKSR3 interacts with SGK1 and RAF1, but no direct biochemical assay shows CNKSR3 reduces serine phosphorylation. The annotation is plausible but uncorroborated by direct evidence. Supporting Evidence: file:human/MAGI1/MAGI1-uniprot.txt Interacts with ENaC regulatory proteins NEDD4L, RAF1 and SGK1. The PDZ domain is required for interaction with ENaC and SGK1, but not for interaction with NEDDL4 and RAF1.
GO:0070373 negative regulation of ERK1 and ERK2 cascade	ISS GO_REF:0000024	ACCEPT	Summary: ISS annotation based on mouse ortholog. CNKSR3 negatively regulates MAPK/ERK signaling. CNK family proteins are known scaffold proteins in Ras/MAPK pathways, and CNKSR3 specifically acts as a negative regulator of the ERK1/2 cascade. Review literature explicitly links CNK3 to interference with the Raf-1/MEK1/2/ERK1/2 cascade. Reason: Represents an important regulatory function of CNKSR3 beyond its ENaC role. CNK proteins are scaffolds in Ras/MAPK signaling pathways, and CNKSR3 negatively regulates ERK1/2. This is consistent with the protein's domain structure and family membership. Supporting Evidence: file:human/MAGI1/MAGI1-uniprot.txt negative regulation of ERK1 and ERK2 cascade; ISS:UniProtKB. SIMILARITY - Belongs to the CNKSR family. PMID:22506713 The first study addressing the mechanistic aspects of CNK3 function revealed that CNK3 expression significantly interferes with the activation of the Raf-1/MEK1/2/ERK1/2 signaling cascade

Core Functions

Assembling and coordinating ENaC regulatory complex to control aldosterone-induced sodium transport at apical epithelial membranes

Molecular Function:

protein-macromolecule adaptor activity

Directly Involved In:

positive regulation of sodium ion transport

Cellular Locations:

apical plasma membrane cytosol

Substrates:

SCNN1A (ENaC alpha subunit) SCNN1B (ENaC beta subunit) NEDD4L RAF1 SGK1

Supporting Evidence:

file:human/MAGI1/MAGI1-uniprot.txt
Acts as a scaffold protein coordinating the assembly of an ENaC-regulatory complex (ERC). Regulates aldosterone-induced and epithelial sodium channel (ENaC)-mediated sodium transport through regulation of ENaC cell surface expression. Interacts directly with SCNN1A and SCNN1B C-terminal tails. Interacts with ENaC regulatory proteins NEDD4L, RAF1 and SGK1.
PMID:22851176
Scaffold protein connector enhancer of kinase suppressor of Ras isoform 3 (CNK3) coordinates assembly of a multiprotein epithelial sodium channel (ENaC)-regulatory complex

Negatively regulating ERK1/2 cascade through scaffold-mediated modulation of MAPK signaling components

Molecular Function:

protein-macromolecule adaptor activity

Directly Involved In:

negative regulation of ERK1 and ERK2 cascade negative regulation of peptidyl-serine phosphorylation

Cellular Locations:

cytosol

Supporting Evidence:

file:human/MAGI1/MAGI1-uniprot.txt
negative regulation of ERK1 and ERK2 cascade; negative regulation of peptidyl-serine phosphorylation. Belongs to the CNKSR family
PMID:22101317
The first study addressing the mechanistic aspects of CNK3 function revealed that CNK3 expression significantly interferes with the activation of the Raf-1/MEK1/2/ERK1/2 signaling cascade

References

GO_REF:0000002

Gene Ontology annotation through association of InterPro records with GO terms.

GO_REF:0000024

Manual transfer of experimentally-verified manual GO annotation data to orthologs by curator judgment of sequence similarity.

GO_REF:0000033

Annotation inferences using phylogenetic trees

GO_REF:0000044

Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt.

GO_REF:0000052

Gene Ontology annotation based on curation of immunofluorescence data

GO_REF:0000120

Combined Automated Annotation using Multiple IEA Methods.

PMID:22085542

CNK3 and IPCEF1 produce a single protein that is required for HGF dependent Arf6 activation and migration.

CNKSR3 (CNK3/IPCEF1 fusion) is required for HGF-induced Arf6 activation and cell migration

"Knockdown of this protein impairs HGF-induced Arf6 activation and migration in response to HGF treatment"
The protein acts as a scaffold binding to cytohesin 2 (Arf6 GEF)

"IPCEF1, a scaffold that binds to cytohesin 2, is required for cytohesin-induced scattering"
IPCEF1 is actually the C-terminal half of CNK3

"We report here that IPCEF1 is actually the C-terminal half of CNK3"

PMID:25416956

A proteome-scale map of the human interactome network.

Large-scale systematic binary protein-protein interaction mapping study

"systematically screening half of the interactome space with minimal inspection bias, we more than doubled the number of high-quality binary PPIs available from the literature"

PMID:32296183

A reference map of the human binary protein interactome.

Systematic binary interactome reference map

"reference map of the human binary protein interactome"

PMID:40205054

Multimodal cell maps as a foundation for structural and functional genomics.

Multimodal proteomics atlas study

"Multimodal cell maps as a foundation for structural and functional genomics"

file:human/MAGI1/MAGI1-uniprot.txt

UniProt entry for CNKSR3 (Connector enhancer of kinase suppressor of ras 3)

Scaffold protein coordinating ENaC-regulatory complex assembly

"Acts as a scaffold protein coordinating the assembly of an ENaC-regulatory complex (ERC)"
Regulates aldosterone-induced sodium transport via ENaC

"Regulates aldosterone-induced and epithelial sodium channel (ENaC)-mediated sodium transport through regulation of ENaC cell surface expression"
Localizes to apical plasma membrane and cytoplasm

"SUBCELLULAR LOCATION: Cytoplasm. Apical cell membrane; Peripheral membrane protein"
Contains SAM, CRIC, PDZ, and DUF1170 domains

"DOMAIN 7..72 SAM...DOMAIN 80..174 CRIC...DOMAIN 211..293 PDZ...DOMAIN 325..546 DUF1170"
PDZ domain required for ENaC and SGK1 interaction

"The PDZ domain is required for interaction with ENaC and SGK1, but not for interaction with NEDDL4 and RAF1"
Interacts with SCNN1A, SCNN1B, NEDD4L, RAF1, SGK1

"Interacts directly with SCNN1A (ENaC subunit alpha) and SCNN1B (ENaC subunit beta) C-terminal tails. Interacts with ENaC regulatory proteins NEDD4L, RAF1 and SGK1"
Up-regulated by aldosterone

"INDUCTION: Up-regulated by aldosterone (at protein level)"
Negatively regulates ERK1/2 cascade and peptidyl-serine phosphorylation

"negative regulation of ERK1 and ERK2 cascade; negative regulation of peptidyl-serine phosphorylation"
Positively regulates sodium ion transport

"positive regulation of sodium ion transport"

PMID:22101317

The role of the ENaC-regulatory complex in aldosterone-mediated sodium transport.

CNK3 is rapidly induced by physiological aldosterone via two functional MR binding loci near its transcription start site, supporting direct MR target gene status

"CNK3, like SGK1 and GILZ1, is rapidly induced by physiological concentrations of aldosterone, and its promoter harbors two functional MR binding loci in close vicinity to the transcription start site, suggesting a direct mode of regulation"
CNK3 expression is required for ENaC-mediated Na+ transport in renal epithelial cells

"CNK3 expression correlates with, and is required for, ENaC-mediated Na+ transport in renal epithelial cells"
CNK3 negatively regulates the Raf-1/MEK1/2/ERK1/2 MAPK cascade

"The first study addressing the mechanistic aspects of CNK3 function revealed that CNK3 expression significantly interferes with the activation of the Raf-1/MEK1/2/ERK1/2 signaling cascade"
CNK3 is highly expressed in connecting tubule and cortical collecting duct, the aldosterone-sensitive distal nephron

"CNK3 is highly expressed in the connecting tubule (CNT) and the cortical collecting duct (CCD), the prime target segments of aldosterone-regulated Na+ retention in the kidney"
Working model proposes CNK3 as a central hormone-induced scaffolding platform that assists assembly of the ENaC-regulatory complex

"Our current hypothesis involves CNK3 as a central hormone-induced scaffolding platform, that possibly aids in the assembly of the ENaC-regulatory complex, thereby promoting appropriate signal transduction"
CNK3 has the modular SAM-CRIC-PDZ architecture typical of scaffold proteins and lacks the PH domain present in other CNK family members

"CNK3 is the third isoform of the mammalian CNK protein family, whose members possess a modular structure and contain common protein-protein interaction domains - an N-terminal sterile α motif (SAM), followed by a conserved region in CNK (CRIC) and a PDZ domain"
PP2A subunits identified as abundant CNK3 binding partners, suggesting phosphoregulation integrated into CNK3-centered scaffolding

"Peptides from all three subunits of the heterotrimeric serine/threonine phosphatase PP2A were detected as the most abundant binding partners of CNK3"

PMID:22506713

Organization of the ENaC-regulatory machinery.

CNK3 PDZ-containing scaffold characteristics make it an intriguing candidate for assembling regulatory components into a supramolecular ENaC-regulatory complex

"PDZ domain-containing scaffolding proteins can therefore function not only to bind an array of target proteins, but also to crosslink one another into complex assemblies, factors which make PDZ domain-containing scaffolds such as CNK3 intriguing candidates for the assembly of regulatory components into a large supramolecular ENaC-regulatory complex"
CNK3 expression interferes with Raf-1/MEK1/2/ERK1/2 activation

"The first study addressing the mechanistic aspects of CNK3 function revealed that CNK3 expression significantly interferes with the activation of the Raf-1/MEK1/2/ERK1/2 signaling cascade"
It remains unresolved whether CNK3 directly interacts with ENaC and whether it changes ENaC surface expression versus open probability

"although it is known that CNK3 positively regulates ENaC activity (Ziera et al., 2009), it remains to be seen if it can directly interact with and modulate the channel. It is also not known if CNK3 enhances ENaC surface expression or Po"

PMID:36994769

Aldosterone: Renal Action and Physiological Effects.

2023 review of aldosterone renal action discusses aldosterone-induced factors (including CNKSR3) acting via disinhibition of tonic inhibitory mechanisms rather than directly turning on transporters

"Aldosterone: Renal Action and Physiological Effects"

PMID:22851176

Scaffold protein connector enhancer of kinase suppressor of Ras isoform 3 (CNK3) coordinates assembly of a multiprotein epithelial sodium channel (ENaC)-regulatory complex.

CNKSR3 is an aldosterone-induced scaffold that nucleates assembly of an ENaC-regulatory complex (with Nedd4-2, GILZ1, Raf1, SGK1, 14-3-3) in cortical collecting duct cells, required for aldosterone-induced sodium reabsorption.

file:human/MAGI1/MAGI1-deep-research-perplexity-lite.md

Deep research on MAGI1 function

file:human/MAGI1/MAGI1-deep-research-falcon.md

Falcon deep research on CNKSR3/MAGI1 function (Edison Scientific Literature, 2026-05-29).

CNKSR3 is positioned as an aldosterone/MR-regulated scaffold required for ENaC-mediated sodium transport in aldosterone-responsive distal nephron epithelia

"CNKSR3 is positioned as an aldosterone/mineralocorticoid receptor (MR)-regulated scaffold that is required for ENaC-mediated sodium transport in aldosterone-responsive distal nephron epithelia (connecting tubule and cortical collecting duct)"
CNKSR3 is not an enzyme; its function is as a regulatory adaptor shaping signaling and trafficking assemblies controlling ENaC

"CNKSR3 is not an enzyme and no catalytic reaction is attributed to it in this evidence set; rather it is a regulatory adaptor that shapes signaling and trafficking/regulatory protein assemblies controlling ENaC"
2024 GWAS implicates a locus near SCAF8/CNKSR3 in diabetic kidney disease, providing human genetic anchor for kidney relevance

"rs12523822 near SCAF8/CNKSR3. Reported association OR = 0.73, p = 1.3×10−8 (meta-analysis of T1D+T2D DKD; 5,226 cases vs 8,510 controls)"

Suggested Experiments

Experiment: Determine crystal or cryo-EM structure of CNKSR3 PDZ domain in complex with ENaC subunit C-terminal peptides to understand binding specificity

Hypothesis: The PDZ domain has specific structural features that enable high-affinity binding to ENaC tails

Type: Structure determination

Experiment: Live-cell imaging of CNKSR3 dynamics at the apical membrane in response to aldosterone treatment to understand recruitment kinetics

Hypothesis: Aldosterone induces rapid recruitment of CNKSR3 to apical membrane where it stabilizes ENaC

Type: Cell biology/Imaging

Experiment: Reconstitute the complete ENaC-regulatory complex in vitro with purified CNKSR3, ENaC subunits, SGK1, RAF1, and NEDD4L to map binding interfaces and stoichiometry

Hypothesis: CNKSR3 can simultaneously bind multiple complex components through distinct domains

Type: Biochemistry

Experiment: CNKSR3 knockout in kidney epithelial cells with rescue by domain deletion mutants to determine which domains are essential for ENaC regulation versus Arf6/migration functions

Hypothesis: PDZ domain is critical for ENaC function but dispensable for Arf6 scaffolding

Type: Functional genomics

Experiment: Generate CNKSR3 conditional knockout mice and assess blood pressure, sodium handling, and response to aldosterone challenge

Hypothesis: Loss of CNKSR3 will impair aldosterone-mediated sodium retention and blood pressure regulation

Type: Physiological

Deep Research

Falcon

(MAGI1-deep-research-falcon.md)

this with annotations you find in gene/protein databases, but these can be outdated or inaccurate. Falcon Edison Scientific Literature 26 citations 2 artifacts 2026-05-29T19:30:35.931799

Edison artifact artifact-00 (text/markdown)

## Context ID: pqac-00000019 Figure 1 on page 20 provides a schematic model of the ENaC-regulatory complex (ERC). This diagram illustrates the organization of v (image/png)

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.

We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.

We are interested in where in or outside the cell the gene product carries out its function.

We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.

Research report: CNKSR3 (UniProt Q6P9H4) functional annotation (Homo sapiens)

0) Target verification (critical disambiguation)

The research target here is CNKSR family member 3 (CNKSR3), also called CNK3 or connector enhancer of kinase suppressor of Ras 3, a CNK-family multidomain scaffold/adaptor implicated in aldosterone-dependent renal sodium handling. This identity is consistently used in mechanistic renal physiology literature describing a SAM–CRIC–PDZ protein regulating ENaC and MAPK signaling (soundararajan2012theroleof pages 5-7, soundararajan2012organizationofthe pages 11-12, soundararajan2012theroleof pages 4-5).

The synonym string sometimes encountered in resources (e.g., “MAGI1”) is potentially misleading in this context: MAGI1 is widely used for a different multi-PDZ tight-junction scaffold (not supported by the mechanistic CNK3/ENaC literature retrieved here). No mechanistic source in this evidence set uses MAGI1 as the accepted symbol for CNKSR3 (soundararajan2012theroleof pages 5-7, soundararajan2012organizationofthe pages 11-12).

1) Key concepts and definitions (current understanding)

1.1 CNKSR3 is a modular scaffold/adaptor

CNKSR3 (CNK3) is described as the third mammalian CNK isoform with a modular architecture typical of scaffold proteins: N-terminal SAM domain, a conserved CNK-specific region (CRIC), and a PDZ domain (soundararajan2012theroleof pages 5-7, soundararajan2012organizationofthe pages 11-12). Reviews further emphasize that CNKSR3 is smaller than other CNK homologs and lacks the C-terminal region that harbors a pleckstrin homology (PH) domain present in other family members (soundararajan2012theroleof pages 5-7, soundararajan2012theroleof pages 4-5).

These domains support a “connector/enhancer” role rather than enzymatic catalysis:
- SAM domain: mediates protein–protein interactions via homo/heterodimerization (soundararajan2012organizationofthe pages 11-12).
- CRIC domain: a conserved interaction region in CNK proteins; has documented interaction roles in CNK-family contexts (soundararajan2012organizationofthe pages 11-12).
- PDZ domain: binds specific C-terminal motifs of partner proteins; PDZ-containing proteins frequently serve as molecular scaffolds assembling multi-protein complexes (soundararajan2012organizationofthe pages 11-12).

1.2 ENaC-regulatory complex (ERC) concept

A central organizing concept in the CNKSR3 literature is the ENaC-regulatory complex (ERC)—a dynamic, multi-protein assembly at/near the plasma membrane that integrates aldosterone-driven signals (and other cues such as insulin/PI3K signaling) to control ENaC surface expression and activity (soundararajan2012theroleof pages 4-5, soundararajan2012theroleof pages 5-7, soundararajan2012organizationofthe media 483107b4). CNKSR3 is repeatedly proposed as a scaffold component of this ERC, coordinating stimulatory and inhibitory nodes (soundararajan2012theroleof pages 5-7, soundararajan2012organizationofthe pages 11-12).

2) Primary function, pathways, and cellular localization

2.1 Primary function (physiology-level)

Across reviews and experimental summaries, CNKSR3 is positioned as an aldosterone/mineralocorticoid receptor (MR)-regulated scaffold that is required for ENaC-mediated sodium transport in aldosterone-responsive distal nephron epithelia (connecting tubule and cortical collecting duct) (soundararajan2012theroleof pages 5-7, valinsky2019aldosteroneandion pages 4-7, ziera2009identificationandfunctional pages 56-60).

Importantly, CNKSR3 is not an enzyme and no catalytic reaction is attributed to it in this evidence set; rather it is a regulatory adaptor that shapes signaling and trafficking/regulatory protein assemblies controlling ENaC.

2.2 Pathway role: aldosterone/MR → CNKSR3 → ENaC (via disinhibition)

A 2023 authoritative review of aldosterone renal action frames aldosterone-induced factors (including CNKSR3) as often acting via disinhibition—suppressing tonic inhibitory mechanisms (e.g., Raf-MAPK/ERK and Nedd4-2) rather than directly “turning on” transporters (johnston2023aldosteronerenalaction pages 34-36). Within this framework, CNKSR3 is described as participating in the dynamic assemblies that ultimately enhance ENaC-dependent Na+ reabsorption in response to aldosterone (johnston2023aldosteronerenalaction pages 34-36).

2.3 Mechanistic linkage: suppression of Raf–MEK–ERK (MAPK) signaling

Mechanistically, CNKSR3 is repeatedly linked to modulation of the Raf-1/MEK1/2/ERK1/2 (MAPK) cascade:
- CNKSR3 expression is reported to interfere with activation of the Raf-1/MEK/ERK pathway, consistent with relief of ERK-mediated ENaC inhibition (soundararajan2012theroleof pages 5-7, soundararajan2012organizationofthe pages 11-12).
- In collecting-duct cell models, CNKSR3 knockdown increases MEK/ERK phosphorylation, and MEK inhibition (U0126) can increase ENaC-dependent transepithelial current in CNKSR3-silenced cells, supporting an ERK-dependent mechanism (ziera2009identificationandfunctional pages 60-63).

2.4 Subcellular localization and interaction partners

The most directly stated localization in this evidence set is that CNKSR3 participates in a plasma-membrane-localized ENaC regulatory complex, consistent with a tethering/scaffold function (valinsky2019aldosteroneandion pages 4-7). In that context, CNKSR3 is reported to interact with ENaC, SGK1, Raf-1, and Nedd4-2 in a membrane complex (valinsky2019aldosteroneandion pages 4-7).

In addition, proteomics summarized in a 2012 review identified peptides from all three PP2A subunits as abundant CNK3 binding partners, suggesting phosphoregulation may be integrated into CNKSR3-centered scaffolding (soundararajan2012theroleof pages 5-7).

A schematic depiction of the ERC (including CNK3/CNKSR3 and core regulators such as SGK1, GILZ1, Nedd4-2, and Raf-1) is shown in Figure 1 of Soundararajan et al. 2012 (soundararajan2012organizationofthe media 483107b4).

3) Experimental evidence base (selected highlights)

3.1 Direct MR target gene and aldosterone induction

Multiple sources converge on CNKSR3 being a direct MR target gene:
- Promoter-level regulation: CNKSR3’s promoter is described as harboring two functional MR-binding loci near the transcription start site (review summary) (soundararajan2012organizationofthe pages 11-12).
- ChIP and promoter-element mapping: ChIP-chip/ChIP-qPCR evidence identifies MR binding regions for cnksr3, and mutation analyses indicate three of four predicted GRE-like elements in a distal MR-binding region contribute to aldosterone responsiveness (ziera2009identificationandfunctional pages 63-65).
- Quantitative induction: In a review of aldosterone-ion channel regulation, aldosterone (1 nM) is reported to drive ~3-fold increase in CNKSR3 mRNA alongside MR binding at two promoter regions (valinsky2019aldosteroneandion pages 4-7).

3.2 Requirement for ENaC-mediated sodium transport

Functional perturbation experiments support necessity:
- CNKSR3 knockdown: An ~80% reduction in CNKSR3 mRNA was associated with an ~75% decrease in ENaC-mediated short-circuit current (valinsky2019aldosteroneandion pages 4-7).
- Overexpression/knockdown in collecting-duct models: CNKSR3 overexpression increased ENaC-dependent transepithelial Na+ transport, while silencing “almost abrogated” transport in an aldosterone-responsive collecting-duct cell model (ziera2009identificationandfunctional pages 56-60).

4) Recent developments (prioritizing 2023–2024)

4.1 2023: Integration into modern aldosterone physiology models

A 2023 Comprehensive Physiology review explicitly includes CNKSR3 among aldosterone-regulated genes participating in dynamic assemblies that increase Na+ absorption by suppressing tonic inhibitors of ENaC (johnston2023aldosteronerenalaction pages 34-36).
- Publication date/URL: March 2023; https://doi.org/10.1002/cphy.c190043 (johnston2023aldosteronerenalaction pages 34-36).

4.2 2024: Human genetic association with diabetic kidney disease (DKD)

A 2024 Frontiers in Endocrinology review summarizes genome-wide association evidence implicating a locus near SCAF8/CNKSR3 in DKD risk:
- Variant: rs12523822 near SCAF8/CNKSR3.
- Reported association: OR = 0.73, p = 1.3×10−8 (meta-analysis of T1D+T2D DKD; 5,226 cases vs 8,510 controls). A transethnic analysis reported a ~43% lower risk in American Indians (p = 5.7×10−9) (sandholm2023geneticandepigenetic pages 3-5).
The review further provides mechanistic plausibility by reiterating CNKSR3 as a direct MR target, highly expressed in renal cortical collecting ducts, involved in transepithelial sodium transport, and upregulated by physiologic aldosterone (sandholm2023geneticandepigenetic pages 3-5).
- Publication date/URL: May 2024; https://doi.org/10.3389/fendo.2023.1163001 (sandholm2023geneticandepigenetic pages 3-5).

4.3 2024: Epigenetic study (Agent Orange exposure and T2D)

A 2024 epigenetic/genetic study in Korean veterans reported CNKSR3 among genes linked to significant CpGs in the context of Agent Orange exposure and type 2 diabetes (T2D). In the excerpt, CNKSR3 is described as highly expressed in renal collecting ducts, regulating sodium transport, and upregulated by aldosterone (seo2024epigeneticlinkbetween pages 9-10). The study reported 2,135 AO-related differentially methylated positions (DMPs) overall, but the provided excerpt does not include CNKSR3-specific CpG identifiers or effect sizes (seo2024epigeneticlinkbetween pages 9-10).
- Publication date/URL: July 2024; https://doi.org/10.3389/fendo.2024.1375459 (seo2024epigeneticlinkbetween pages 9-10).

5) Current applications and real-world implementations

5.1 Disease relevance: blood pressure and renal disease pathways

Given CNKSR3’s role in aldosterone/MR-dependent ENaC control (central to sodium balance and blood pressure regulation), the gene is mechanistically relevant to disorders of sodium handling, including hypertension-related phenotypes, though definitive clinical translation remains limited in the retrieved primary mechanistic evidence (valinsky2019aldosteroneandion pages 4-7, soundararajan2012organizationofthe pages 11-12).

5.2 Human genetics–anchored translational relevance (DKD)

The DKD GWAS signal near SCAF8/CNKSR3 provides a human genetic anchor suggesting CNKSR3-regulated physiology may influence DKD susceptibility (sandholm2023geneticandepigenetic pages 3-5). This positions CNKSR3 as a candidate gene for mechanistic follow-up (e.g., eQTL colocalization in kidney, functional allelic assays in collecting-duct models), though the 2024 review itself emphasizes that many GWAS hits are noncoding and target-gene assignment requires additional regulatory mapping (sandholm2023geneticandepigenetic pages 3-5).

5.3 Platform-level evidence: hypothesis generation for pregnancy-induced hypertension and glomerulonephritis

Open Targets aggregates GWAS credible-set evidence connecting CNKSR3 to pregnancy-induced hypertension and glomerulonephritis (OpenTargets Search: -CNKSR3). These are best treated as hypothesis-generating associations rather than confirmed mechanisms, but they are consistent with CNKSR3’s role in kidney sodium handling pathways.
- URL: https://platform.opentargets.org/target/ENSG00000153721 (OpenTargets Search: -CNKSR3).

6) Expert opinions and open questions (authoritative synthesis)

Renal physiology reviews characterize CNKSR3 as a plausible hormone-induced scaffold that helps organize ENaC regulatory machinery and suppress inhibitory signaling (Raf–MEK–ERK and/or Nedd4-2 mediated effects), thereby enabling aldosterone-stimulated sodium reabsorption (johnston2023aldosteronerenalaction pages 34-36, soundararajan2012theroleof pages 5-7, soundararajan2012organizationofthe pages 11-12).

However, expert sources also explicitly highlight key remaining uncertainties:
- Whether CNKSR3 directly binds ENaC and whether it changes ENaC surface expression versus open probability remain unresolved in the summarized evidence (soundararajan2012organizationofthe pages 11-12, soundararajan2012organizationofthe pages 12-14).
- The precise ERC composition and how it varies by time/compartment (e.g., lipid raft association) are noted as open questions (soundararajan2012organizationofthe pages 12-14).

7) Relevant statistics and data summary

Aldosterone induction (reviewed experimental summary): CNKSR3 mRNA ~3-fold increased after 1 nM aldosterone with MR promoter binding (valinsky2019aldosteroneandion pages 4-7).
Functional perturbation: ~80% CNKSR3 knockdown → ~75% decrease in ENaC-mediated short-circuit current (valinsky2019aldosteroneandion pages 4-7).
Human genetics (DKD): rs12523822 near SCAF8/CNKSR3, OR 0.73, p = 1.3×10−8 (5,226 cases/8,510 controls); transethnic American Indian result indicating ~43% lower DKD risk, p = 5.7×10−9 (sandholm2023geneticandepigenetic pages 3-5).

Evidence summary table

The following table compiles key mechanistic, interaction, and 2023–2024 translational evidence, including quantitative statistics and URLs/DOIs.

Claim/Topic	Key findings	Evidence type (review/primary/GWAS/epigenetic/database)	Species/cell context	Quantitative data	Source (author year, journal)	URL/DOI
Identity verification	Target literature matches CNKSR3/CNK3 = connector enhancer of kinase suppressor of Ras 3, a CNK-family scaffold; retrieved mechanistic sources do not support conflation with MAGI1	Review synthesis	Human/mammalian renal physiology literature	None reported	Soundararajan et al. 2012, Mol Cell Endocrinol; Soundararajan et al. 2012, Crit Rev Biochem Mol Biol (soundararajan2012organizationofthe pages 11-12, soundararajan2012theroleof pages 5-7)	https://doi.org/10.1016/j.mce.2011.11.003 ; https://doi.org/10.3109/10409238.2012.678285
Domain architecture	CNKSR3 has SAM, CRIC, and PDZ domains; reviews note it is smaller than other CNKs and lacks the C-terminal PH domain present in other family members	Review	Mammalian CNK family; renal epithelial context	No effect size	Soundararajan et al. 2012, Mol Cell Endocrinol; Soundararajan et al. 2012, Crit Rev Biochem Mol Biol (soundararajan2012theroleof pages 5-7, soundararajan2012theroleof pages 4-5, soundararajan2012organizationofthe pages 11-12)	https://doi.org/10.1016/j.mce.2011.11.003 ; https://doi.org/10.3109/10409238.2012.678285
Inferred molecular role	Modular architecture supports a scaffold/adaptor role organizing aldosterone-responsive ENaC-regulatory machinery and modulating Raf-1/MEK/ERK signaling	Review/primary summary	Renal collecting duct epithelial models	No single numeric estimate	Ziera 2009; Soundararajan et al. 2012 (soundararajan2012theroleof pages 5-7, ziera2009identificationandfunctional pages 56-60)	https://doi.org/10.14279/depositonce-2286 ; https://doi.org/10.1016/j.mce.2011.11.003
Direct MR target gene	CNKSR3 is a direct mineralocorticoid receptor (MR) target; promoter harbors MR-binding loci and distal GRE cluster contributing to aldosterone responsiveness	Primary + review summary	HEK293-hMR+, M1-rMR+ cells; collecting duct	MR binding at 2 promoter regions; 3 of 4 predicted GREs in distal region contributed in mutation analysis	Ziera 2009; Soundararajan et al. 2012 (ziera2009identificationandfunctional pages 63-65, soundararajan2012organizationofthe pages 11-12, soundararajan2012theroleof pages 5-7)	https://doi.org/10.14279/depositonce-2286 ; https://doi.org/10.3109/10409238.2012.678285 ; https://doi.org/10.1016/j.mce.2011.11.003
Aldosterone induction	Aldosterone induces CNKSR3 transcript expression downstream of MR	Primary/review summary	Distal nephron/collecting duct models	~3-fold increase in CNKSR3 mRNA after 1 nM aldosterone; qPCR induction after 4 h, 10 nM aldosterone also reported	Valinsky et al. 2019, Vitam Horm; Ziera 2009 (valinsky2019aldosteroneandion pages 4-7, ziera2009identificationandfunctional pages 56-60)	https://doi.org/10.1016/bs.vh.2018.10.004 ; https://doi.org/10.14279/depositonce-2286
Tissue/localization pattern	High expression in connecting tubule (CNT) and cortical collecting duct (CCD), the aldosterone-sensitive nephron segments	Primary/review summary	Kidney distal nephron	No single numeric estimate	Ziera 2009; Soundararajan et al. 2012 (ziera2009identificationandfunctional pages 63-65, soundararajan2012theroleof pages 5-7, valinsky2019aldosteroneandion pages 4-7)	https://doi.org/10.14279/depositonce-2286 ; https://doi.org/10.1016/j.mce.2011.11.003 ; https://doi.org/10.1016/bs.vh.2018.10.004
ENaC regulation: necessity	CNKSR3 is required for ENaC-mediated Na+ transport; knockdown strongly impairs amiloride-sensitive current	Primary/review summary	Collecting duct epithelial cells / short-circuit current assays	~80% CNKSR3 knockdown caused ~75% decrease in ENaC-mediated short-circuit current; shRNA silencing “almost abrogated” transport	Valinsky et al. 2019; Ziera 2009 (valinsky2019aldosteroneandion pages 4-7, ziera2009identificationandfunctional pages 56-60)	https://doi.org/10.1016/bs.vh.2018.10.004 ; https://doi.org/10.14279/depositonce-2286
ENaC regulation: sufficiency	CNKSR3 overexpression enhances aldosterone-dependent ENaC-mediated transepithelial Na+ transport	Primary	M1-rMR+ collecting duct model	Directional increase reported; no precise fold value in retrieved excerpts	Ziera 2009 (ziera2009identificationandfunctional pages 56-60, ziera2009identificationandfunctional pages 60-63)	https://doi.org/10.14279/depositonce-2286
MAPK/ERK mechanism	CNKSR3 restrains Raf-1/MEK/ERK signaling; loss of CNKSR3 increases MEK1/2 and ERK1/2 phosphorylation, consistent with relief of tonic ENaC inhibition	Primary/review summary	M1-rMR+ cells; renal epithelial context	Knockdown increased phospho-MEK1/2 and phospho-ERK1/2; MEK inhibitor U0126 markedly increased ΔISC in CNKSR3-silenced cells	Ziera 2009; Soundararajan et al. 2012; Valinsky et al. 2019 (ziera2009identificationandfunctional pages 60-63, soundararajan2012theroleof pages 5-7, valinsky2019aldosteroneandion pages 4-7)	https://doi.org/10.14279/depositonce-2286 ; https://doi.org/10.1016/j.mce.2011.11.003 ; https://doi.org/10.1016/bs.vh.2018.10.004
Interaction partners / ERC	CNKSR3 is proposed/observed in an ENaC regulatory complex (ERC) with ENaC, SGK1, Raf-1, Nedd4-2 at/near the plasma membrane; GILZ may cooperate functionally, though direct inclusion was not consistently detected	Review/primary summary	Distal nephron epithelial models	No stoichiometric values	Valinsky et al. 2019; Soundararajan et al. 2012 (valinsky2019aldosteroneandion pages 4-7, soundararajan2012theroleof pages 5-7, soundararajan2012organizationofthe media 483107b4)	https://doi.org/10.1016/bs.vh.2018.10.004 ; https://doi.org/10.1016/j.mce.2011.11.003
Additional binding partners	Proteomics identified peptides from all three PP2A subunits as abundant CNKSR3-associated proteins, suggesting phosphoregulation-linked scaffolding	Review citing proteomics	Renal epithelial context	“Most abundant binding partners” in cited proteomics; no numeric enrichment in retrieved excerpt	Soundararajan et al. 2012 (soundararajan2012theroleof pages 5-7)	https://doi.org/10.1016/j.mce.2011.11.003
Expert interpretation	Reviews argue CNKSR3 likely acts as a hormone-induced scaffolding platform that disinhibits ENaC by coordinating stimulatory and inhibitory nodes, but direct effects on ENaC surface abundance vs. channel open probability remain unresolved	Review/expert opinion	Renal physiology	No quantitative metric	Johnston et al. 2023, Compr Physiol; Soundararajan et al. 2012 (johnston2023aldosteronerenalaction pages 34-36, soundararajan2012organizationofthe pages 11-12)	https://doi.org/10.1002/cphy.c190043 ; https://doi.org/10.3109/10409238.2012.678285
2023 development	Recent renal physiology review places CNKSR3 among aldosterone-induced genes that increase Na+ transport mainly by suppressing tonic inhibitory mechanisms rather than directly activating transporters	Review	Kidney/aldosterone physiology	No CNKSR3-specific fold value in this review	Johnston et al. 2023, Compr Physiol (johnston2023aldosteronerenalaction pages 34-36)	https://doi.org/10.1002/cphy.c190043
2024 development: DKD genetics	A GWAS/meta-analysis implicated a locus near SCAF8/CNKSR3 in diabetic kidney disease (DKD), giving human genetic support for kidney relevance	GWAS/review	Human, transethnic DKD cohorts	rs12523822; OR 0.73; p = 1.3×10−8 in T1D+T2D DKD meta-analysis; 43% lower risk in American Indians with p = 5.7×10−9; 5,226 cases / 8,510 controls; final meta-analysis 13,736 participants	Sandholm et al. 2024, Front Endocrinol (sandholm2023geneticandepigenetic pages 3-5)	https://doi.org/10.3389/fendo.2023.1163001
2024 development: epigenetics	Epigenetic study in Korean veterans linked significant T2D-associated CpGs to CNKSR3, highlighting it as a collecting-duct/aldosterone-responsive candidate in metabolic-kidney disease context	Epigenetic study	Human blood methylation/genotype analysis	Study reported 2,135 AO-related DMPs overall; CNKSR3 named among genes with significant CpGs, but no CNKSR3-specific effect size/p-value in retrieved excerpt	Seo et al. 2024, Front Endocrinol (seo2024epigeneticlinkbetween pages 9-10)	https://doi.org/10.3389/fendo.2024.1375459
Disease association aggregation	Open Targets links CNKSR3 to pregnancy-induced hypertension and glomerulonephritis via GWAS credible-set evidence; these are hypothesis-generating rather than definitive mechanistic proof	Database aggregation	Human disease genetics aggregation	Evidence size 5 for listed disease associations in retrieved output	Open Targets Platform query (2025 platform paper cited by tool) (OpenTargets Search: -CNKSR3)	https://platform.opentargets.org/target/ENSG00000153721

Table: This table compiles the main mechanistic, experimental, and recent human genetics evidence for human CNKSR3 (UniProt Q6P9H4). It highlights domain structure, aldosterone/MR and ENaC functions, interaction partners, and 2023–2024 disease-relevant findings with quantitative statistics where available.

Visual evidence: ENaC-regulatory complex model

A schematic model of the ENaC-regulatory complex including CNK3/CNKSR3 and key interacting regulators is shown in Soundararajan et al. (2012), Figure 1 (soundararajan2012organizationofthe media 483107b4).

Key references (publication dates and URLs)

Johnston JG et al. Aldosterone: Renal Action and Physiological Effects. Comprehensive Physiology (Mar 2023). https://doi.org/10.1002/cphy.c190043 (johnston2023aldosteronerenalaction pages 34-36)
Sandholm N et al. Genetic and epigenetic background of diabetic kidney disease. Frontiers in Endocrinology (May 2024; DOI minted 2023). https://doi.org/10.3389/fendo.2023.1163001 (sandholm2023geneticandepigenetic pages 3-5)
Seo S et al. Epigenetic link between Agent Orange exposure and type 2 diabetes in Korean veterans. Frontiers in Endocrinology (Jul 2024). https://doi.org/10.3389/fendo.2024.1375459 (seo2024epigeneticlinkbetween pages 9-10)
Soundararajan R et al. Organization of the ENaC-regulatory machinery. Critical Reviews in Biochemistry and Molecular Biology (Jun 2012). https://doi.org/10.3109/10409238.2012.678285 (soundararajan2012organizationofthe pages 11-12)
Soundararajan R et al. The role of the ENaC-regulatory complex in aldosterone-mediated sodium transport. Molecular and Cellular Endocrinology (Mar 2012). https://doi.org/10.1016/j.mce.2011.11.003 (soundararajan2012theroleof pages 5-7)
Valinsky WC et al. Aldosterone and Ion Channels. Vitamins and Hormones (Jan 2019). https://doi.org/10.1016/bs.vh.2018.10.004 (valinsky2019aldosteroneandion pages 4-7)
Open Targets Platform: CNKSR3 target page (accessed 2026-05-30). https://platform.opentargets.org/target/ENSG00000153721 (OpenTargets Search: -CNKSR3)

Limitations of this report

Some foundational primary results (notably the peer-reviewed FASEB Journal 2009 paper referenced by reviews) were not directly retrievable in this run, so several mechanistic claims rely on authoritative review summaries of those experiments. Where this occurs, the report labels the evidence as “review summary” and cites the reviewing source(s) (soundararajan2012theroleof pages 5-7, soundararajan2012organizationofthe pages 11-12, valinsky2019aldosteroneandion pages 4-7).

References

(soundararajan2012theroleof pages 5-7): Rama Soundararajan, David Pearce, and Tim Ziera. The role of the enac-regulatory complex in aldosterone-mediated sodium transport. Molecular and Cellular Endocrinology, 350:242-247, Mar 2012. URL: https://doi.org/10.1016/j.mce.2011.11.003, doi:10.1016/j.mce.2011.11.003. This article has 107 citations and is from a peer-reviewed journal.
(soundararajan2012organizationofthe pages 11-12): Rama Soundararajan, Ming Lu, and David Pearce. Organization of the enac-regulatory machinery. Critical Reviews in Biochemistry and Molecular Biology, 47:349-359, Jun 2012. URL: https://doi.org/10.3109/10409238.2012.678285, doi:10.3109/10409238.2012.678285. This article has 54 citations and is from a peer-reviewed journal.
(soundararajan2012theroleof pages 4-5): Rama Soundararajan, David Pearce, and Tim Ziera. The role of the enac-regulatory complex in aldosterone-mediated sodium transport. Molecular and Cellular Endocrinology, 350:242-247, Mar 2012. URL: https://doi.org/10.1016/j.mce.2011.11.003, doi:10.1016/j.mce.2011.11.003. This article has 107 citations and is from a peer-reviewed journal.
(soundararajan2012organizationofthe media 483107b4): Rama Soundararajan, Ming Lu, and David Pearce. Organization of the enac-regulatory machinery. Critical Reviews in Biochemistry and Molecular Biology, 47:349-359, Jun 2012. URL: https://doi.org/10.3109/10409238.2012.678285, doi:10.3109/10409238.2012.678285. This article has 54 citations and is from a peer-reviewed journal.
(valinsky2019aldosteroneandion pages 4-7): William C. Valinsky, Rhian M. Touyz, and Alvin Shrier. Aldosterone and ion channels. Vitamins and hormones, 109:105-131, Jan 2019. URL: https://doi.org/10.1016/bs.vh.2018.10.004, doi:10.1016/bs.vh.2018.10.004. This article has 23 citations.
(ziera2009identificationandfunctional pages 56-60): Tim Ziera. Identification and functional characterization of the novel mineralocorticoid receptor target gene cnksr3. ArXiv, Nov 2009. URL: https://doi.org/10.14279/depositonce-2286, doi:10.14279/depositonce-2286. This article has 0 citations.
(johnston2023aldosteronerenalaction pages 34-36): Jermaine G. Johnston, Amanda K. Welch, Brian D. Cain, Peter P. Sayeski, Michelle L. Gumz, and Charles S. Wingo. Aldosterone: renal action and physiological effects. Comprehensive Physiology, 13 2:4409-4491, Mar 2023. URL: https://doi.org/10.1002/cphy.c190043, doi:10.1002/cphy.c190043. This article has 35 citations and is from a peer-reviewed journal.
(ziera2009identificationandfunctional pages 60-63): Tim Ziera. Identification and functional characterization of the novel mineralocorticoid receptor target gene cnksr3. ArXiv, Nov 2009. URL: https://doi.org/10.14279/depositonce-2286, doi:10.14279/depositonce-2286. This article has 0 citations.
(ziera2009identificationandfunctional pages 63-65): Tim Ziera. Identification and functional characterization of the novel mineralocorticoid receptor target gene cnksr3. ArXiv, Nov 2009. URL: https://doi.org/10.14279/depositonce-2286, doi:10.14279/depositonce-2286. This article has 0 citations.
(sandholm2023geneticandepigenetic pages 3-5): Niina Sandholm, Emma H. Dahlström, and Per-Henrik Groop. Genetic and epigenetic background of diabetic kidney disease. Frontiers in Endocrinology, May 2024. URL: https://doi.org/10.3389/fendo.2023.1163001, doi:10.3389/fendo.2023.1163001. This article has 32 citations.
(seo2024epigeneticlinkbetween pages 9-10): Sujin Seo, Ye An Kim, Young Lee, Young Jin Kim, Bong-Jo Kim, Jae Hoon An, Heejin Jin, Ah Ra Do, Kyungtaek Park, Sungho Won, and Je Hyun Seo. Epigenetic link between agent orange exposure and type 2 diabetes in korean veterans. Frontiers in Endocrinology, Jul 2024. URL: https://doi.org/10.3389/fendo.2024.1375459, doi:10.3389/fendo.2024.1375459. This article has 1 citations.
(OpenTargets Search: -CNKSR3): Open Targets Query (-CNKSR3, 5 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.
(soundararajan2012organizationofthe pages 12-14): Rama Soundararajan, Ming Lu, and David Pearce. Organization of the enac-regulatory machinery. Critical Reviews in Biochemistry and Molecular Biology, 47:349-359, Jun 2012. URL: https://doi.org/10.3109/10409238.2012.678285, doi:10.3109/10409238.2012.678285. This article has 54 citations and is from a peer-reviewed journal.

Artifacts

Edison artifact artifact-00

Citations

soundararajan2012organizationofthe pages 11-12
johnston2023aldosteronerenalaction pages 34-36
ziera2009identificationandfunctional pages 60-63
valinsky2019aldosteroneandion pages 4-7
soundararajan2012theroleof pages 5-7
ziera2009identificationandfunctional pages 63-65
ziera2009identificationandfunctional pages 56-60
sandholm2023geneticandepigenetic pages 3-5
seo2024epigeneticlinkbetween pages 9-10
soundararajan2012organizationofthe pages 12-14
soundararajan2012theroleof pages 4-5
https://doi.org/10.1002/cphy.c190043
https://doi.org/10.3389/fendo.2023.1163001
https://doi.org/10.3389/fendo.2024.1375459
https://platform.opentargets.org/target/ENSG00000153721
https://doi.org/10.1016/j.mce.2011.11.003
https://doi.org/10.3109/10409238.2012.678285
https://doi.org/10.14279/depositonce-2286
https://doi.org/10.1016/bs.vh.2018.10.004
https://doi.org/10.1016/j.mce.2011.11.003,
https://doi.org/10.3109/10409238.2012.678285,
https://doi.org/10.1016/bs.vh.2018.10.004,
https://doi.org/10.14279/depositonce-2286,
https://doi.org/10.1002/cphy.c190043,
https://doi.org/10.3389/fendo.2023.1163001,
https://doi.org/10.3389/fendo.2024.1375459,

Perplexity

(MAGI1-deep-research-perplexity-lite.md)

1. Key Concepts and Definitions Perplexity sonar-pro 12 citations 2025-11-15T18:19:32.424247

The CNKSR3 gene (also known as MAGI1 in some contexts, though these are distinct genes/proteins—see note below) encodes a multifunctional scaffold protein involved in the regulation of key signaling pathways, ion transport, and cell adhesion. Below is a detailed research report on CNKSR3, focusing on its molecular function, biological processes, cellular localization, protein domains, interactions, and disease associations, with a brief clarification regarding MAGI1.

1. Key Concepts and Definitions

CNKSR3 (Connector Enhancer of Kinase Suppressor of Ras 3) is a protein-coding gene in humans, primarily functioning as a scaffold protein that integrates and regulates multiple signaling cascades, especially in epithelial and renal cells[1][3][7].
MAGI1 (Membrane Associated Guanylate Kinase, WW and PDZ Domain Containing 1) is a distinct gene/protein, also a scaffold protein, mainly involved in cell junctions and tumor suppression[2][4]. Some sources conflate the two, but they are separate entities.

2. Molecular Function

Scaffold Protein: CNKSR3 acts as a scaffold, coordinating the assembly of regulatory complexes at the plasma membrane, particularly those involved in sodium ion transport[1][3][7].
Regulation of Ion Channels: It is essential for aldosterone-induced regulation of the epithelial sodium channel (ENaC), affecting sodium reabsorption in the kidney[1][3][7].
Signal Transduction Modulation: CNKSR3 is involved in the negative regulation of the ERK1/2 (MAPK) signaling cascade and peptidyl-serine phosphorylation, linking membrane receptor activity to downstream effectors[1][3][8].

3. Biological Processes

Sodium Ion Transport: CNKSR3 positively regulates sodium ion transmembrane transporter activity, crucial for maintaining electrolyte balance and blood pressure[1][3][7].
MAPK Pathway Regulation: It negatively regulates the ERK1/2 cascade, impacting cell proliferation and differentiation[1][3][8].
Cell Migration and Inflammatory Response: CNKSR3 (also known as IPCEF1 in some contexts) is required for growth factor–induced Arf6 activation and cell migration, processes important in hepatocyte growth and immune cell responses[1].
Tumor Suppression: Amplification of CNKSR3 in uveal melanoma correlates with improved patient survival, suggesting a role in limiting metastatic progression[1].

4. Cellular Localization

Apical Plasma Membrane: CNKSR3 is predominantly localized at the apical plasma membrane of epithelial cells, where it regulates ENaC[1][3][7].
Cytoplasm: It is also found in the cytoplasm, where it may interact with other signaling molecules[1][3][7].

5. Protein Domains

Sterile Alpha Motif (SAM) Domain: CNKSR3 contains a SAM domain, which mediates protein-protein interactions and is characteristic of the CNKSR family[1].
Other Domains: While the full domain structure is less characterized than MAGI1, CNKSR3’s scaffold function is attributed to its ability to bind multiple partners via these domains[1][3].

6. Known Interactions

ENaC Regulatory Complex: CNKSR3 coordinates the assembly of a complex including ENaC, SGK1 (serum/glucocorticoid-regulated kinase 1), and Nedd4, regulating sodium channel activity[1][3][7].
MAPK Pathway Components: It interacts with proteins involved in the MAPK/ERK pathway, modulating their activity[1][3][8].
Arf6 Activation: In the context of cell migration, CNKSR3 is required for HGF-dependent Arf6 activation[1].

7. Disease Associations

Immunodeficiency 40: Mutations in CNKSR3 have been associated with this rare immunodeficiency disorder[3].
Xanthinuria: There is also an association with xanthinuria, a metabolic disorder[3].
Cancer: Amplification of CNKSR3 in uveal melanoma is linked to improved survival, suggesting a tumor-suppressive role[1].
Blood Pressure Regulation: Given its role in sodium transport, CNKSR3 is implicated in aldosterone signaling and may influence hypertension and related cardiovascular diseases[1][3][7].

8. Recent Developments and Latest Research (2023–2024)

MicroRNA Regulation: Recent studies highlight that CNKSR3 expression is regulated by specific microRNAs, suggesting a role as a molecular marker in cancer and possibly other diseases[1].
Clinical Implications: Ongoing research is exploring CNKSR3 as a potential therapeutic target in cancer and as a biomarker for disease progression, particularly in uveal melanoma[1].

9. Expert Opinions and Analysis

Central Regulator: Experts consider CNKSR3 a central regulator of signaling pathways, linking membrane receptor activity to downstream processes such as ion transport, MAPK modulation, and cell motility[1].
Therapeutic Potential: Its role in sodium transport and cancer progression makes it a promising target for therapeutic intervention in hypertension and oncology[1][3].

10. Relevant Statistics and Data

Expression: CNKSR3 is highly expressed in epithelial and renal tissues, consistent with its role in sodium transport[1][3][7].
Survival Correlation: In uveal melanoma, CNKSR3 amplification is statistically correlated with improved patient survival, though precise figures vary by study[1].

Note on MAGI1

MAGI1 is a separate gene encoding a multidomain scaffolding protein involved in cell junctions, tumor suppression, and vascular biology[2][4]. It contains five PDZ domains, two WW domains, and a GUK domain, and is localized at tight and adherens junctions in epithelial and neural cells[2][4][6]. MAGI1 is implicated in the regulation of PI3K/AKT and Wnt/β-catenin pathways and is downregulated in several cancers[2][4].

Key References:
- [1] Ma’ayan Lab Harmonizome, CNKSR3 Gene (2025)
- [2] PMC8231924, MAGI1 review (2021)
- [3] GeneCards, CNKSR3 (2025)
- [4] Ma’ayan Lab Harmonizome, MAGI1 Gene (2025)
- [7] UniProt, CNKSR3 (2025)
- [8] Wikipedia, CNKSR3 (2025)

For further details, see the cited sources above.

Citations

https://maayanlab.cloud/Harmonizome/gene/CNKSR3
https://pmc.ncbi.nlm.nih.gov/articles/PMC8231924/
https://www.genecards.org/cgi-bin/carddisp.pl?gene=CNKSR3
https://maayanlab.cloud/Harmonizome/gene/MAGI1
https://www.ncbi.nlm.nih.gov/gene?Db=gene&Cmd=DetailsSearch&Term=154043
https://www.proteinatlas.org/search/MAGI1
https://www.uniprot.org/uniprotkb/Q6P9H4/entry
https://en.wikipedia.org/wiki/CNKSR3
https://www.ncbi.nlm.nih.gov/gene/154043
https://www.proteinatlas.org/ENSG00000153721-CNKSR3
https://www.deciphergenomics.org/gene/CNKSR3/overview/clinical-info
http://biogps.org/gene/154043/

📄 View Raw YAML

id: Q6P9H4
gene_symbol: CNKSR3
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: Connector enhancer of kinase suppressor of Ras 3 (CNKSR3) is a 
  multi-domain scaffold protein that coordinates signaling complexes at the 
  apical plasma membrane of epithelial cells. Its primary characterized function
  is regulation of the epithelial sodium channel (ENaC), where it acts as a 
  central organizing platform for aldosterone-induced sodium transport. CNKSR3 
  also regulates cell migration through Arf6 activation and modulates MAPK 
  signaling. NOTE - This gene was formerly called MAGI1, but that name is now 
  assigned to the unrelated membrane-associated guanylate kinase Q96QZ7.
existing_annotations:
  - term:
      id: GO:0007167
      label: enzyme-linked receptor protein signaling pathway
    evidence_type: IBA
    original_reference_id: GO_REF:0000033
    review:
      summary: IBA annotation based on phylogenetic inference. CNKSR3 is a 
        scaffold protein involved in multiple signaling pathways including 
        HGF-induced Arf6 activation and aldosterone-ENaC signaling. While the 
        protein participates in signaling downstream of receptors, the specific 
        connection to enzyme-linked receptors is indirect and the term is too 
        general for this scaffold protein's core functions.
      action: REMOVE
      reason: |
        The term enzyme-linked receptor protein signaling pathway is overly
        broad and the more specific term GO:0009966 regulation of signal
        transduction is already accepted as an IEA annotation elsewhere in
        this review (PR #759 review feedback — MODIFY to an already-annotated
        term would produce a duplicate; REMOVE is the correct action).
        CNKSR3's best-characterized roles are aldosterone-ENaC scaffolding
        and HGF/Arf6 modulation, both already captured.
      supported_by:
        - reference_id: PMID:22085542
          supporting_text: Knockdown of this protein impairs HGF-induced Arf6
            activation and migration in response to HGF treatment
        - reference_id: file:human/MAGI1/MAGI1-uniprot.txt
          supporting_text: Acts as a scaffold protein coordinating the assembly
            of an ENaC-regulatory complex
  - term:
      id: GO:0030674
      label: protein-macromolecule adaptor activity
    evidence_type: IBA
    original_reference_id: GO_REF:0000033
    review:
      summary: IBA annotation for adaptor/scaffold function. This is 
        well-supported and represents a core molecular function of CNKSR3. The 
        protein coordinates assembly of the ENaC-regulatory complex by binding 
        multiple partners including SCNN1A, SCNN1B, NEDD4L, RAF1, and SGK1. It 
        also scaffolds HGF-Arf6 signaling components.
      action: ACCEPT
      reason: This accurately captures CNKSR3's primary molecular function as a 
        scaffold/adaptor protein that brings together multiple signaling 
        components. Well-supported by experimental evidence.
      supported_by:
        - reference_id: file:human/MAGI1/MAGI1-uniprot.txt
          supporting_text: Acts as a scaffold protein coordinating the assembly
            of an ENaC-regulatory complex (ERC). Interacts directly with SCNN1A
            (ENaC subunit alpha) and SCNN1B (ENaC subunit beta) C-terminal
            tails. Interacts with ENaC regulatory proteins NEDD4L, RAF1 and
            SGK1.
        - reference_id: file:human/MAGI1/MAGI1-deep-research-perplexity-lite.md
          supporting_text: See deep research file for comprehensive analysis
        - reference_id: file:human/MAGI1/MAGI1-deep-research-falcon.md
          supporting_text: CNKSR3 is positioned as an aldosterone/mineralocorticoid
            receptor (MR)-regulated scaffold that is required for ENaC-mediated
            sodium transport in aldosterone-responsive distal nephron epithelia
            (connecting tubule and cortical collecting duct)
  - term:
      id: GO:0005737
      label: cytoplasm
    evidence_type: IEA
    original_reference_id: GO_REF:0000120
    review:
      summary: IEA annotation based on InterPro domains and UniProtKB 
        subcellular location. CNKSR3 is indeed found in cytoplasm, though its 
        most functionally important localization is at the apical plasma 
        membrane where it regulates ENaC. Cytoplasmic localization is confirmed 
        but represents a secondary or transit location.
      action: ACCEPT
      reason: Accurate but not the most informative localization. CNKSR3 is 
        present in cytoplasm as stated in UniProt, though apical plasma membrane
        is the more functionally relevant location.
      supported_by:
        - reference_id: file:human/MAGI1/MAGI1-uniprot.txt
          supporting_text: 'SUBCELLULAR LOCATION: Cytoplasm. Apical cell membrane;
            Peripheral membrane protein.'
  - term:
      id: GO:0009966
      label: regulation of signal transduction
    evidence_type: IEA
    original_reference_id: GO_REF:0000002
    review:
      summary: IEA annotation from InterPro domain IPR010599 (CNK2/3 domain).
        This is appropriate - CNKSR3 regulates multiple signal transduction
        pathways including MAPK/ERK signaling (negative regulation) and
        aldosterone-ENaC signaling (positive regulation of sodium transport).
      action: ACCEPT
      reason: Accurate representation of CNKSR3's biological role as a regulator
        of signaling pathways. The protein negatively regulates ERK1/2 cascade
        and peptidyl-serine phosphorylation while positively regulating
        ENaC-mediated sodium transport.
      supported_by:
        - reference_id: file:human/MAGI1/MAGI1-uniprot.txt
          supporting_text: negative regulation of ERK1 and ERK2 cascade;
            ISS:UniProtKB. negative regulation of peptidyl-serine
            phosphorylation; ISS:UniProtKB. positive regulation of sodium ion
            transport; ISS:UniProtKB.
        - reference_id: PMID:22101317
          supporting_text: The first study addressing the mechanistic aspects of
            CNK3 function revealed that CNK3 expression significantly interferes
            with the activation of the Raf-1/MEK1/2/ERK1/2 signaling cascade
  - term:
      id: GO:0016020
      label: membrane
    evidence_type: IEA
    original_reference_id: GO_REF:0000002
    review:
      summary: IEA annotation from InterPro. While CNKSR3 is a peripheral 
        membrane protein at the apical plasma membrane, this extremely general 
        term provides minimal information. More specific membrane localization 
        terms are more appropriate.
      action: MODIFY
      reason: The term 'membrane' is too general. CNKSR3 specifically localizes 
        to the apical plasma membrane where it functions in ENaC regulation. A 
        more specific term is warranted.
      proposed_replacement_terms:
        - id: GO:0016324
          label: apical plasma membrane
      supported_by:
        - reference_id: file:human/MAGI1/MAGI1-uniprot.txt
          supporting_text: 'SUBCELLULAR LOCATION: Apical cell membrane; Peripheral
            membrane protein'
  - term:
      id: GO:0016324
      label: apical plasma membrane
    evidence_type: IEA
    original_reference_id: GO_REF:0000044
    review:
      summary: IEA annotation from UniProtKB subcellular location vocabulary. 
        This is accurate and functionally important - CNKSR3 localizes to the 
        apical plasma membrane of epithelial cells where it coordinates the 
        ENaC-regulatory complex.
      action: ACCEPT
      reason: This is the most functionally relevant subcellular location for 
        CNKSR3. The protein is specifically targeted to the apical membrane 
        where it regulates ENaC.
      supported_by:
        - reference_id: file:human/MAGI1/MAGI1-uniprot.txt
          supporting_text: 'SUBCELLULAR LOCATION: Cytoplasm. Apical cell membrane;
            Peripheral membrane protein. Acts as a scaffold protein coordinating the
            assembly of an ENaC-regulatory complex (ERC).'
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:25416956
    review:
      summary: IPI evidence from proteome-scale interactome study identifying 
        interaction with NMI (Q13287). While protein binding is technically 
        correct, it is uninformative as a molecular function annotation. 
        CNKSR3's specific function is as a protein-macromolecule adaptor, which 
        is already captured by GO:0030674.
      action: REMOVE
      reason: The term 'protein binding' is uninformative per curation 
        guidelines. The specific adaptor function is better captured by 
        GO:0030674 (protein-macromolecule adaptor activity). Large-scale 
        interactome studies often identify interactions that may not be 
        functionally relevant to core gene function.
      supported_by:
        - reference_id: PMID:25416956
          supporting_text: A proteome-scale map of the human interactome 
            network.
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:32296183
    review:
      summary: IPI evidence from binary protein interactome reference map 
        identifying multiple interactions. While protein binding is correct, it 
        is redundant and uninformative given the more specific GO:0030674 
        annotation.
      action: REMOVE
      reason: Uninformative and redundant with the more specific adaptor 
        activity term. This is from a large-scale binary interactome study.
      supported_by:
        - reference_id: PMID:32296183
          supporting_text: Apr 8. A reference map of the human binary protein 
            interactome.
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:40205054
    review:
      summary: IPI evidence from multimodal cell atlas study. Another protein 
        binding annotation that is uninformative compared to the specific 
        adaptor function already annotated.
      action: REMOVE
      reason: Uninformative and redundant. Large-scale proteomics study. The 
        specific molecular function is better captured by GO:0030674.
      supported_by:
        - reference_id: PMID:40205054
          supporting_text: Apr 9. Multimodal cell maps as a foundation for 
            structural and functional genomics.
  - term:
      id: GO:0005829
      label: cytosol
    evidence_type: IDA
    original_reference_id: GO_REF:0000052
    review:
      summary: IDA evidence from immunofluorescence data (HPA project). Cytosol 
        is a more specific cytoplasmic compartment and represents where CNKSR3 
        is found when not at the membrane. This is consistent with the protein's
        peripheral membrane association - it can be in cytosol and recruited to 
        apical membrane.
      action: ACCEPT
      reason: Supported by direct experimental evidence from immunofluorescence.
        Cytosol localization is consistent with CNKSR3 being a peripheral (not 
        integral) membrane protein that can shuttle between cytosol and 
        membrane.
      supported_by:
        - reference_id: GO_REF:0000052
          supporting_text: Gene Ontology annotation based on curation of 
            immunofluorescence data from Human Protein Atlas project
  - term:
      id: GO:0005515
      label: protein binding
    evidence_type: IPI
    original_reference_id: PMID:22085542
    review:
      summary: IPI evidence from the CNK3/IPCEF1 study showing interactions 
        relevant to HGF-Arf6 signaling. While this paper provides important 
        functional context, the protein binding annotation itself is 
        uninformative.
      action: REMOVE
      reason: Although PMID:22085542 is a key functional paper showing CNKSR3 
        interacts with cytohesin 2 and is required for Arf6 activation, the 
        generic "protein binding" annotation is uninformative. The specific 
        adaptor function (GO:0030674) is more appropriate.
      supported_by:
        - reference_id: PMID:22085542
          supporting_text: 2011 Nov 7. CNK3 and IPCEF1 produce a single protein 
            that is required for HGF dependent Arf6 activation and migration.
  - term:
      id: GO:0010765
      label: positive regulation of sodium ion transport
    evidence_type: ISS
    original_reference_id: GO_REF:0000024
    review:
      summary: ISS annotation based on mouse ortholog Q8BMA3. This represents a 
        core function of CNKSR3 - it positively regulates ENaC-mediated sodium 
        transport in response to aldosterone. This is the protein's 
        best-characterized biological role in kidney epithelial cells.
      action: ACCEPT
      reason: This is a core biological function of CNKSR3. The protein 
        regulates aldosterone-induced ENaC-mediated sodium transport through 
        coordinating the assembly of the ENaC-regulatory complex. Well-supported
        by multiple studies.
      supported_by:
        - reference_id: file:human/MAGI1/MAGI1-uniprot.txt
          supporting_text: 'FUNCTION: Involved in transepithelial sodium transport.
            Regulates aldosterone-induced and epithelial sodium channel (ENaC)-mediated
            sodium transport through regulation of ENaC cell surface expression. Acts
            as a scaffold protein coordinating the assembly of an ENaC-regulatory
            complex (ERC).'
        - reference_id: PMID:22101317
          supporting_text: CNK3 expression correlates with, and is required for,
            ENaC-mediated Na+ transport in renal epithelial cells
        - reference_id: PMID:22506713
          supporting_text: CNK3 expression correlates with, and is critically
            required for, ENaC-mediated Na+ transport in renal epithelial cells
  - term:
      id: GO:0033137
      label: negative regulation of peptidyl-serine phosphorylation
    evidence_type: ISS
    original_reference_id: GO_REF:0000024
    review:
      summary: |
        ISS annotation based on mouse ortholog. CNKSR3 scaffold proteins
        regulate kinase signaling cascades and this annotation likely reflects
        regulation of SGK1 or other serine kinases in the ENaC regulatory
        complex, or broader effects on MAPK pathway serine phosphorylation.
        Downgraded from ACCEPT to KEEP_AS_NON_CORE per PR #759 review feedback:
        the rationale cites indirect kinase-interaction evidence without direct
        biochemical demonstration of CNKSR3 negatively regulating peptidyl-
        serine phosphorylation.
      action: KEEP_AS_NON_CORE
      reason: |
        Indirect evidence — CNKSR3 interacts with SGK1 and RAF1, but no direct
        biochemical assay shows CNKSR3 reduces serine phosphorylation. The
        annotation is plausible but uncorroborated by direct evidence.
      supported_by:
        - reference_id: file:human/MAGI1/MAGI1-uniprot.txt
          supporting_text: Interacts with ENaC regulatory proteins NEDD4L, RAF1 
            and SGK1. The PDZ domain is required for interaction with ENaC and 
            SGK1, but not for interaction with NEDDL4 and RAF1.
  - term:
      id: GO:0070373
      label: negative regulation of ERK1 and ERK2 cascade
    evidence_type: ISS
    original_reference_id: GO_REF:0000024
    review:
      summary: ISS annotation based on mouse ortholog. CNKSR3 negatively
        regulates MAPK/ERK signaling. CNK family proteins are known scaffold
        proteins in Ras/MAPK pathways, and CNKSR3 specifically acts as a
        negative regulator of the ERK1/2 cascade. Review literature explicitly
        links CNK3 to interference with the Raf-1/MEK1/2/ERK1/2 cascade.
      action: ACCEPT
      reason: Represents an important regulatory function of CNKSR3 beyond its
        ENaC role. CNK proteins are scaffolds in Ras/MAPK signaling pathways,
        and CNKSR3 negatively regulates ERK1/2. This is consistent with the
        protein's domain structure and family membership.
      supported_by:
        - reference_id: file:human/MAGI1/MAGI1-uniprot.txt
          supporting_text: negative regulation of ERK1 and ERK2 cascade;
            ISS:UniProtKB. SIMILARITY - Belongs to the CNKSR family.
        - reference_id: PMID:22506713
          supporting_text: The first study addressing the mechanistic aspects of
            CNK3 function revealed that CNK3 expression significantly interferes
            with the activation of the Raf-1/MEK1/2/ERK1/2 signaling cascade
references:
  - id: GO_REF:0000002
    title: Gene Ontology annotation through association of InterPro records with
      GO terms.
    findings: []
  - id: GO_REF:0000024
    title: Manual transfer of experimentally-verified manual GO annotation data 
      to orthologs by curator judgment of sequence similarity.
    findings: []
  - id: GO_REF:0000033
    title: Annotation inferences using phylogenetic trees
    findings: []
  - id: GO_REF:0000044
    title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular 
      Location vocabulary mapping, accompanied by conservative changes to GO 
      terms applied by UniProt.
    findings: []
  - id: GO_REF:0000052
    title: Gene Ontology annotation based on curation of immunofluorescence data
    findings: []
  - id: GO_REF:0000120
    title: Combined Automated Annotation using Multiple IEA Methods.
    findings: []
  - id: PMID:22085542
    title: CNK3 and IPCEF1 produce a single protein that is required for HGF 
      dependent Arf6 activation and migration.
    findings:
      - statement: CNKSR3 (CNK3/IPCEF1 fusion) is required for HGF-induced Arf6 
          activation and cell migration
        supporting_text: Knockdown of this protein impairs HGF-induced Arf6 
          activation and migration in response to HGF treatment
      - statement: The protein acts as a scaffold binding to cytohesin 2 (Arf6 
          GEF)
        supporting_text: IPCEF1, a scaffold that binds to cytohesin 2, is 
          required for cytohesin-induced scattering
      - statement: IPCEF1 is actually the C-terminal half of CNK3
        supporting_text: We report here that IPCEF1 is actually the C-terminal 
          half of CNK3
  - id: PMID:25416956
    title: A proteome-scale map of the human interactome network.
    findings:
      - statement: Large-scale systematic binary protein-protein interaction 
          mapping study
        supporting_text: systematically screening half of the interactome space 
          with minimal inspection bias, we more than doubled the number of 
          high-quality binary PPIs available from the literature
  - id: PMID:32296183
    title: A reference map of the human binary protein interactome.
    findings:
      - statement: Systematic binary interactome reference map
        supporting_text: reference map of the human binary protein interactome
  - id: PMID:40205054
    title: Multimodal cell maps as a foundation for structural and functional 
      genomics.
    findings:
      - statement: Multimodal proteomics atlas study
        supporting_text: Multimodal cell maps as a foundation for structural and
          functional genomics
  - id: file:human/MAGI1/MAGI1-uniprot.txt
    title: UniProt entry for CNKSR3 (Connector enhancer of kinase suppressor of 
      ras 3)
    findings:
      - statement: Scaffold protein coordinating ENaC-regulatory complex 
          assembly
        supporting_text: Acts as a scaffold protein coordinating the assembly of
          an ENaC-regulatory complex (ERC)
      - statement: Regulates aldosterone-induced sodium transport via ENaC
        supporting_text: Regulates aldosterone-induced and epithelial sodium 
          channel (ENaC)-mediated sodium transport through regulation of ENaC 
          cell surface expression
      - statement: Localizes to apical plasma membrane and cytoplasm
        supporting_text: 'SUBCELLULAR LOCATION: Cytoplasm. Apical cell membrane; Peripheral
          membrane protein'
      - statement: Contains SAM, CRIC, PDZ, and DUF1170 domains
        supporting_text: DOMAIN 7..72 SAM...DOMAIN 80..174 CRIC...DOMAIN 
          211..293 PDZ...DOMAIN 325..546 DUF1170
      - statement: PDZ domain required for ENaC and SGK1 interaction
        supporting_text: The PDZ domain is required for interaction with ENaC 
          and SGK1, but not for interaction with NEDDL4 and RAF1
      - statement: Interacts with SCNN1A, SCNN1B, NEDD4L, RAF1, SGK1
        supporting_text: Interacts directly with SCNN1A (ENaC subunit alpha) and
          SCNN1B (ENaC subunit beta) C-terminal tails. Interacts with ENaC 
          regulatory proteins NEDD4L, RAF1 and SGK1
      - statement: Up-regulated by aldosterone
        supporting_text: 'INDUCTION: Up-regulated by aldosterone (at protein level)'
      - statement: Negatively regulates ERK1/2 cascade and peptidyl-serine 
          phosphorylation
        supporting_text: negative regulation of ERK1 and ERK2 cascade; negative 
          regulation of peptidyl-serine phosphorylation
      - statement: Positively regulates sodium ion transport
        supporting_text: positive regulation of sodium ion transport
  - id: PMID:22101317
    title: The role of the ENaC-regulatory complex in aldosterone-mediated sodium
      transport.
    findings:
      - statement: CNK3 is rapidly induced by physiological aldosterone via two
          functional MR binding loci near its transcription start site, supporting
          direct MR target gene status
        supporting_text: CNK3, like SGK1 and GILZ1, is rapidly induced by
          physiological concentrations of aldosterone, and its promoter harbors
          two functional MR binding loci in close vicinity to the transcription
          start site, suggesting a direct mode of regulation
      - statement: CNK3 expression is required for ENaC-mediated Na+ transport
          in renal epithelial cells
        supporting_text: CNK3 expression correlates with, and is required for,
          ENaC-mediated Na+ transport in renal epithelial cells
      - statement: CNK3 negatively regulates the Raf-1/MEK1/2/ERK1/2 MAPK cascade
        supporting_text: The first study addressing the mechanistic aspects of
          CNK3 function revealed that CNK3 expression significantly interferes
          with the activation of the Raf-1/MEK1/2/ERK1/2 signaling cascade
      - statement: CNK3 is highly expressed in connecting tubule and cortical
          collecting duct, the aldosterone-sensitive distal nephron
        supporting_text: CNK3 is highly expressed in the connecting tubule (CNT)
          and the cortical collecting duct (CCD), the prime target segments of
          aldosterone-regulated Na+ retention in the kidney
      - statement: Working model proposes CNK3 as a central hormone-induced
          scaffolding platform that assists assembly of the ENaC-regulatory
          complex
        supporting_text: Our current hypothesis involves CNK3 as a central
          hormone-induced scaffolding platform, that possibly aids in the
          assembly of the ENaC-regulatory complex, thereby promoting appropriate
          signal transduction
      - statement: CNK3 has the modular SAM-CRIC-PDZ architecture typical of
          scaffold proteins and lacks the PH domain present in other CNK family
          members
        supporting_text: CNK3 is the third isoform of the mammalian CNK protein
          family, whose members possess a modular structure and contain common
          protein-protein interaction domains - an N-terminal sterile α motif
          (SAM), followed by a conserved region in CNK (CRIC) and a PDZ domain
      - statement: PP2A subunits identified as abundant CNK3 binding partners,
          suggesting phosphoregulation integrated into CNK3-centered scaffolding
        supporting_text: Peptides from all three subunits of the heterotrimeric
          serine/threonine phosphatase PP2A were detected as the most abundant
          binding partners of CNK3
  - id: PMID:22506713
    title: "Organization of the ENaC-regulatory machinery."
    findings:
      - statement: CNK3 PDZ-containing scaffold characteristics make it an
          intriguing candidate for assembling regulatory components into a
          supramolecular ENaC-regulatory complex
        supporting_text: PDZ domain-containing scaffolding proteins can therefore
          function not only to bind an array of target proteins, but also to
          crosslink one another into complex assemblies, factors which make PDZ
          domain-containing scaffolds such as CNK3 intriguing candidates for the
          assembly of regulatory components into a large supramolecular
          ENaC-regulatory complex
      - statement: CNK3 expression interferes with Raf-1/MEK1/2/ERK1/2 activation
        supporting_text: The first study addressing the mechanistic aspects of
          CNK3 function revealed that CNK3 expression significantly interferes
          with the activation of the Raf-1/MEK1/2/ERK1/2 signaling cascade
      - statement: It remains unresolved whether CNK3 directly interacts with
          ENaC and whether it changes ENaC surface expression versus open
          probability
        supporting_text: although it is known that CNK3 positively regulates ENaC
          activity (Ziera et al., 2009), it remains to be seen if it can directly
          interact with and modulate the channel. It is also not known if CNK3
          enhances ENaC surface expression or Po
  - id: PMID:36994769
    title: "Aldosterone: Renal Action and Physiological Effects."
    findings:
      - statement: 2023 review of aldosterone renal action discusses
          aldosterone-induced factors (including CNKSR3) acting via disinhibition
          of tonic inhibitory mechanisms rather than directly turning on
          transporters
        supporting_text: 'Aldosterone: Renal Action and Physiological Effects'
  - id: PMID:22851176
    title: Scaffold protein connector enhancer of kinase suppressor of Ras
      isoform 3 (CNK3) coordinates assembly of a multiprotein epithelial sodium
      channel (ENaC)-regulatory complex.
    findings:
      - statement: CNKSR3 is an aldosterone-induced scaffold that nucleates
          assembly of an ENaC-regulatory complex (with Nedd4-2, GILZ1, Raf1,
          SGK1, 14-3-3) in cortical collecting duct cells, required for
          aldosterone-induced sodium reabsorption.
  - id: file:human/MAGI1/MAGI1-deep-research-perplexity-lite.md
    title: Deep research on MAGI1 function
    findings: []
  - id: file:human/MAGI1/MAGI1-deep-research-falcon.md
    title: Falcon deep research on CNKSR3/MAGI1 function (Edison Scientific
      Literature, 2026-05-29).
    findings:
      - statement: CNKSR3 is positioned as an aldosterone/MR-regulated scaffold
          required for ENaC-mediated sodium transport in aldosterone-responsive
          distal nephron epithelia
        supporting_text: CNKSR3 is positioned as an aldosterone/mineralocorticoid
          receptor (MR)-regulated scaffold that is required for ENaC-mediated
          sodium transport in aldosterone-responsive distal nephron epithelia
          (connecting tubule and cortical collecting duct)
      - statement: CNKSR3 is not an enzyme; its function is as a regulatory
          adaptor shaping signaling and trafficking assemblies controlling ENaC
        supporting_text: CNKSR3 is not an enzyme and no catalytic reaction is
          attributed to it in this evidence set; rather it is a regulatory
          adaptor that shapes signaling and trafficking/regulatory protein
          assemblies controlling ENaC
      - statement: 2024 GWAS implicates a locus near SCAF8/CNKSR3 in diabetic
          kidney disease, providing human genetic anchor for kidney relevance
        supporting_text: rs12523822 near SCAF8/CNKSR3. Reported association OR =
          0.73, p = 1.3×10−8 (meta-analysis of T1D+T2D DKD; 5,226 cases vs 8,510
          controls)
core_functions:
  - description: Assembling and coordinating ENaC regulatory complex to control 
      aldosterone-induced sodium transport at apical epithelial membranes
    molecular_function:
      id: GO:0030674
      label: protein-macromolecule adaptor activity
    directly_involved_in:
      - id: GO:0010765
        label: positive regulation of sodium ion transport
    locations:
      - id: GO:0016324
        label: apical plasma membrane
      - id: GO:0005829
        label: cytosol
    substrates:
      - id: UniProtKB:P37088
        label: SCNN1A (ENaC alpha subunit)
      - id: UniProtKB:P51168
        label: SCNN1B (ENaC beta subunit)
      - id: UniProtKB:Q96PU5
        label: NEDD4L
      - id: UniProtKB:P04049
        label: RAF1
      - id: UniProtKB:O00141
        label: SGK1
    supported_by:
      - reference_id: file:human/MAGI1/MAGI1-uniprot.txt
        supporting_text: Acts as a scaffold protein coordinating the assembly of
          an ENaC-regulatory complex (ERC). Regulates aldosterone-induced and 
          epithelial sodium channel (ENaC)-mediated sodium transport through 
          regulation of ENaC cell surface expression. Interacts directly with 
          SCNN1A and SCNN1B C-terminal tails. Interacts with ENaC regulatory 
          proteins NEDD4L, RAF1 and SGK1.
      - reference_id: PMID:22851176
        supporting_text: Scaffold protein connector enhancer of kinase 
          suppressor of Ras isoform 3 (CNK3) coordinates assembly of a 
          multiprotein epithelial sodium channel (ENaC)-regulatory complex
  - description: Negatively regulating ERK1/2 cascade through scaffold-mediated 
      modulation of MAPK signaling components
    molecular_function:
      id: GO:0030674
      label: protein-macromolecule adaptor activity
    directly_involved_in:
      - id: GO:0070373
        label: negative regulation of ERK1 and ERK2 cascade
      - id: GO:0033137
        label: negative regulation of peptidyl-serine phosphorylation
    locations:
      - id: GO:0005829
        label: cytosol
    supported_by:
      - reference_id: file:human/MAGI1/MAGI1-uniprot.txt
        supporting_text: negative regulation of ERK1 and ERK2 cascade; negative
          regulation of peptidyl-serine phosphorylation. Belongs to the CNKSR
          family
      - reference_id: PMID:22101317
        supporting_text: The first study addressing the mechanistic aspects of
          CNK3 function revealed that CNK3 expression significantly interferes
          with the activation of the Raf-1/MEK1/2/ERK1/2 signaling cascade
proposed_new_terms: []
suggested_questions:
  - question: What is the molecular mechanism by which CNKSR3 PDZ domain 
      selectively binds ENaC subunits versus other PDZ domain ligands?
    experts:
      - Structural biologists specializing in PDZ domain interactions
      - Renal physiologists studying ENaC regulation
  - question: How does aldosterone signaling lead to CNKSR3 upregulation and 
      recruitment to the apical membrane?
    experts:
      - Researchers studying mineralocorticoid receptor signaling
      - Epithelial cell biologists
  - question: What is the relative importance of CNKSR3's ENaC regulatory 
      function versus its HGF-Arf6 scaffolding function in different tissue 
      contexts?
    experts:
      - Renal physiologists
      - Cancer cell migration researchers
  - question: Does CNKSR3 have tissue-specific isoforms or splice variants with 
      distinct functions beyond the CNK3/IPCEF1 fusion proteins?
    experts:
      - RNA biology researchers
      - Epithelial tissue specialists
suggested_experiments:
  - experiment_type: Structure determination
    description: Determine crystal or cryo-EM structure of CNKSR3 PDZ domain in 
      complex with ENaC subunit C-terminal peptides to understand binding 
      specificity
    hypothesis: The PDZ domain has specific structural features that enable 
      high-affinity binding to ENaC tails
  - experiment_type: Cell biology/Imaging
    description: Live-cell imaging of CNKSR3 dynamics at the apical membrane in 
      response to aldosterone treatment to understand recruitment kinetics
    hypothesis: Aldosterone induces rapid recruitment of CNKSR3 to apical 
      membrane where it stabilizes ENaC
  - experiment_type: Biochemistry
    description: Reconstitute the complete ENaC-regulatory complex in vitro with
      purified CNKSR3, ENaC subunits, SGK1, RAF1, and NEDD4L to map binding 
      interfaces and stoichiometry
    hypothesis: CNKSR3 can simultaneously bind multiple complex components 
      through distinct domains
  - experiment_type: Functional genomics
    description: CNKSR3 knockout in kidney epithelial cells with rescue by 
      domain deletion mutants to determine which domains are essential for ENaC 
      regulation versus Arf6/migration functions
    hypothesis: PDZ domain is critical for ENaC function but dispensable for 
      Arf6 scaffolding
  - experiment_type: Physiological
    description: Generate CNKSR3 conditional knockout mice and assess blood 
      pressure, sodium handling, and response to aldosterone challenge
    hypothesis: Loss of CNKSR3 will impair aldosterone-mediated sodium retention
      and blood pressure regulation

Gene Description

Existing Annotations Review

Core Functions

Assembling and coordinating ENaC regulatory complex to control aldosterone-induced sodium transport at apical epithelial membranes

Negatively regulating ERK1/2 cascade through scaffold-mediated modulation of MAPK signaling components

References

Suggested Questions for Experts

Suggested Experiments

Deep Research

Falcon

Research report: CNKSR3 (UniProt Q6P9H4) functional annotation (Homo sapiens)

0) Target verification (critical disambiguation)

1) Key concepts and definitions (current understanding)

1.1 CNKSR3 is a modular scaffold/adaptor

1.2 ENaC-regulatory complex (ERC) concept

2) Primary function, pathways, and cellular localization

2.1 Primary function (physiology-level)

2.2 Pathway role: aldosterone/MR → CNKSR3 → ENaC (via disinhibition)

2.3 Mechanistic linkage: suppression of Raf–MEK–ERK (MAPK) signaling

2.4 Subcellular localization and interaction partners

3) Experimental evidence base (selected highlights)

3.1 Direct MR target gene and aldosterone induction

3.2 Requirement for ENaC-mediated sodium transport

4) Recent developments (prioritizing 2023–2024)

4.1 2023: Integration into modern aldosterone physiology models

4.2 2024: Human genetic association with diabetic kidney disease (DKD)

4.3 2024: Epigenetic study (Agent Orange exposure and T2D)

5) Current applications and real-world implementations

5.1 Disease relevance: blood pressure and renal disease pathways

5.2 Human genetics–anchored translational relevance (DKD)

5.3 Platform-level evidence: hypothesis generation for pregnancy-induced hypertension and glomerulonephritis

6) Expert opinions and open questions (authoritative synthesis)

7) Relevant statistics and data summary

Evidence summary table

Visual evidence: ENaC-regulatory complex model

Key references (publication dates and URLs)

Limitations of this report

Artifacts

Citations

Perplexity

1. Key Concepts and Definitions

2. Molecular Function

3. Biological Processes

4. Cellular Localization

5. Protein Domains

6. Known Interactions

7. Disease Associations

8. Recent Developments and Latest Research (2023–2024)

9. Expert Opinions and Analysis

10. Relevant Statistics and Data

Note on MAGI1

Citations

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