GO Term	Evidence	Action	Reason
GO:0005783 endoplasmic reticulum	IBA GO_REF:0000033	ACCEPT	Summary: SERP2 acts at the ER (translocon) where, like its SERP1 paralog, it stabilizes nascent membrane proteins; the phylogenetic active-site assignment is correct. Reason: Core site of action; SERP2 is a translocon-associated ER membrane protein. Supporting Evidence: file:human/SERP2/SERP2-uniprot.txt Interacts with target proteins during their translocation into the lumen of the endoplasmic reticulum
GO:0030968 endoplasmic reticulum unfolded protein response	IBA GO_REF:0000033	ACCEPT	Summary: SERP2 is a stress-associated ER protein that acts during ER stress to protect nascent membrane proteins, placing it in the ER unfolded protein response. Reason: Core biological process; SERP2 functions during ER stress to protect translocating substrates. Supporting Evidence: file:human/SERP2/SERP2-uniprot.txt Protects unfolded target proteins against degradation during ER stress
GO:0005783 endoplasmic reticulum	IEA GO_REF:0000002	ACCEPT	Summary: InterPro-based ER localization, consistent with orthology and phylogenetic evidence. Reason: Correct core localization. Supporting Evidence: file:human/SERP2/SERP2-uniprot.txt Interacts with SEC61B, SEC61A1 and the SEC61 complex
GO:0005789 endoplasmic reticulum membrane	IEA GO_REF:0000044	ACCEPT	Summary: SERP2 is a single-pass ER membrane protein; the subcellular-location-based annotation is correct. Reason: Core localization, consistent with the single-pass ER membrane topology. Supporting Evidence: file:human/SERP2/SERP2-uniprot.txt Membrane {ECO:0000250\|UniProtKB:Q9R2C1}; Single-
GO:0016020 membrane	IEA GO_REF:0000044	KEEP AS NON CORE	Summary: Generic membrane localization, a parent of the more informative ER membrane term. Reason: Correct but uninformative; the specific GO:0005789 (ER membrane) better captures SERP2 localization. Supporting Evidence: file:human/SERP2/SERP2-uniprot.txt Membrane {ECO:0000250\|UniProtKB:Q9R2C1}; Single-
GO:0005515 protein binding	IPI PMID:25416956 A proteome-scale map of the human interactome network.	KEEP AS NON CORE	Summary: Proteome-scale interactome capture of a SERP2 interaction; a real interaction but the bare protein binding term is uninformative. Reason: High-throughput interactome capture; bare protein binding is uninformative per curation guidelines. Supporting Evidence: file:human/SERP2/SERP2-uniprot.txt Q8N6R1; Q8N6L0
GO:0005515 protein binding	IPI PMID:32296183 A reference map of the human binary protein interactome.	KEEP AS NON CORE	Summary: HuRI binary-interactome screen capturing SERP2 binding to a large set of membrane and secretory proteins; consistent with a translocon-substrate-stabilizing role but the bare protein binding term is uninformative. Reason: Many partners are membrane-protein substrates consistent with SERP2's function, but bare protein binding is uninformative per guidelines. Supporting Evidence: file:human/SERP2/SERP2-uniprot.txt Q8N6R1; Q13520: AQP6
GO:0005789 endoplasmic reticulum membrane	ISS GO_REF:0000024	ACCEPT	Summary: Sequence-similarity transfer of ER membrane localization from the mouse ortholog; consistent with the RAMP4-family identity. Reason: Correct core localization, redundant with IEA evidence. Supporting Evidence: file:human/SERP2/SERP2-uniprot.txt Membrane {ECO:0000250\|UniProtKB:Q9R2C1}; Single-
GO:0016020 membrane	ISS GO_REF:0000024	KEEP AS NON CORE	Summary: Sequence-similarity transfer of generic membrane localization; a parent of ER membrane. Reason: Correct but uninformative; the specific GO:0005789 (ER membrane) better captures SERP2 localization. Supporting Evidence: file:human/SERP2/SERP2-uniprot.txt Membrane {ECO:0000250\|UniProtKB:Q9R2C1}; Single-

Deep Research

Falcon

(SERP2-deep-research-falcon.md)

this with annotations you find in gene/protein databases, but these can be outdated or inaccurate. Falcon Edison Scientific Literature 19 citations 2 artifacts 2026-06-12T03:28:27.971698

Edison artifact artifact-00 (text/markdown)

## Context ID: pqac-00000017 The requested panels and legend text from Figure 2 regarding RAMP4-2 cleavage by SPPL2c and SPP are extracted below. - Figure 2D (m (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: Human SERP2 (UniProt Q8N6R1) — Stress-associated endoplasmic reticulum protein 2 / RAMP4-2

Executive summary

Human SERP2 (UniProt Q8N6R1) is annotated (per the user-provided UniProt identity) as a RAMP4-family small ER-associated membrane protein (“Stress-associated endoplasmic reticulum protein 2”; alternative name “Ribosome-associated membrane protein RAMP4-2”). In the accessible literature retrieved here, direct, SERP2/Q8N6R1-labeled mechanistic studies are limited; most mechanistic evidence concerns the closely named protein RAMP4-2 without explicit gene/UniProt mapping in-text, and broader RAMP4/SERP1 family context from translocon biology. The best-supported functional picture is that the RAMP4 family are ER membrane proteins enriched at ribosome–translocon complexes, and that RAMP4-2 behaves as a tail-anchored ER substrate for intramembrane proteases (SPP/SPPL2c), implying a role in ER proteostasis and membrane-protein biogenesis (niemeyer2019theintramembraneprotease pages 3-4, niemeyer2019theintramembraneprotease pages 5-6, vismpas2024rampingupknowledge pages 2-3, gemmer2020aclearerpicture pages 2-3, niemeyer2019theintramembraneprotease media d5029e8f).

A 2023 human genetics study explicitly names SERP2 as “Stress-Associated Endoplasmic Reticulum Protein 2” and reports female-specific association of an intergenic SNP near SERP2 with asthma; however, this evidence does not establish molecular mechanism (odimba2023identificationofsexspecific pages 10-11).

1) Key concepts and definitions (current understanding)

1.1 Endoplasmic reticulum (ER) protein biogenesis and the translocon

Secretory and membrane proteins are inserted into or translocated across the ER membrane primarily via the Sec61 translocon, often while the ribosome is actively translating (co-translational insertion). Accessory proteins (e.g., TRAP, TRAM1, and ribosome-associated membrane proteins) can modulate signal peptide handling, lateral-gate opening, and client specificity. Recent structural work emphasizes that the translocon is a dynamic assembly, with accessory factors associating transiently depending on the substrate (vismpas2024rampingupknowledge pages 2-3, gemmer2020aclearerpicture pages 2-3).

1.2 RAMP proteins (ribosome-associated membrane proteins)

RAMP proteins were originally identified biochemically as ribosome-associated components of rough ER membrane fractions. A review of ER translocon composition notes that RAMP4 was among RAMPs isolated from pancreatic microsomes; recovery depended on detergent/salt conditions, and RAMP4 was one of the most detergent- and salt-resistant proteins isolated alongside translocon components, although early studies could not determine which proteins are stoichiometric translocon subunits (gemmer2020aclearerpicture pages 2-3).

1.3 Tail-anchored (TA) proteins and intramembrane proteolysis

Tail-anchored proteins are membrane proteins with a single hydrophobic helix near the C-terminus, inserted post-translationally into membranes. A key proteostasis mechanism for certain TA proteins is intramembrane proteolysis by aspartyl proteases such as SPP (signal peptide peptidase) and SPP-like proteases (SPPL family), which cleave within the transmembrane region and regulate stability/turnover of specific membrane proteins (niemeyer2019theintramembraneprotease pages 3-4, niemeyer2019theintramembraneprotease pages 5-6).

2) SERP2 identity verification and ambiguity control (critical)

The symbol “SERP2” can be confused with unrelated “SERP-2” entities in other biological contexts (e.g., viral serpins in poxvirus literature). Within the retrieved human genetics literature, SERP2 is explicitly referred to as “Stress-Associated Endoplasmic Reticulum Protein 2” (odimba2023identificationofsexspecific pages 10-11). Mechanistic ER-translocon literature often refers to RAMP4 (and RAMP4-2) but, in the retrieved excerpts, does not explicitly map these names to SERP2/C13orf21/Q8N6R1; therefore, interpretations below separate (i) direct SERP2-locus human genetics evidence from (ii) RAMP4-family mechanistic inference, and note where evidence is family-level rather than SERP2-specific.

3) Molecular function and localization: what is supported by experimental evidence

3.1 RAMP4 family localization at the ER translocon (structural biology context)

A 2024 eLife “Insight” discussing advanced cryo-EM of stalled ribosome–translocon complexes reports that RAMP4 localizes at the Sec61 lateral gate and relays a mechanistic proposal that RAMP4 can act as a “fourth subunit” of Sec61, helping keep the channel open and tether the complex to ribosomes during insertion of membrane proteins (vismpas2024rampingupknowledge pages 2-3). The same Insight indicates RAMP4 may be transiently displaced during insertion of transmembrane domains and may dissociate when other factors (PAT chaperone complex) are recruited, reinforcing a dynamic, substrate-dependent model (vismpas2024rampingupknowledge pages 2-3).

A 2020 review similarly places RAMP4 (renamed SERP1 in that context) among proteins isolated with ER translocon fractions and emphasizes how difficult integral membrane accessory proteins are to visualize in some cryo-ET approaches (gemmer2020aclearerpicture pages 2-3).

Interpretation for SERP2/Q8N6R1: because UniProt places SERP2 in the RAMP4 family, the most conservative inference is that SERP2 is likely an ER membrane protein participating in (or proximal to) ribosome–translocon complexes, but these specific structural statements are directly about RAMP4 (often equated to SERP1 in the literature) rather than explicitly about SERP2 (vismpas2024rampingupknowledge pages 2-3, gemmer2020aclearerpicture pages 2-3).

3.2 RAMP4-2 as a tail-anchored ER protein and substrate of SPPL2c/SPP (direct experimental evidence)

A primary mechanistic study of the intramembrane protease SPPL2c tested multiple TA proteins including RAMP4-2. The authors describe RAMP4 and RAMP4-2 as stress-associated ER-associated proteins and treat RAMP4-2 as a tail-anchored (TA) protein in their assays (niemeyer2019theintramembraneprotease pages 3-4, niemeyer2019theintramembraneprotease pages 5-6). In HEK293/HeLa overexpression experiments, the study reports:

Cytochrome b5, RAMP4, and RAMP4-2 were proteolyzed by SPP.
Of those candidates, RAMP4-2 was the only one cleaved efficiently by SPPL2c, leading to near-complete depletion of the substrate under the experimental conditions (niemeyer2019theintramembraneprotease pages 3-4, niemeyer2019theintramembraneprotease pages 5-6).
The paper also uses inhibitor experiments and densitometric quantification to support differential processing of HA-RAMP4-2 by SPP vs SPPL2c (niemeyer2019theintramembraneprotease pages 5-6, niemeyer2019theintramembraneprotease media d5029e8f).

These data provide the strongest functional clue relevant to the UniProt-described SERP2 protein if the RAMP4-2 substrate corresponds to SERP2/Q8N6R1: SERP2 would be expected to be ER-localized, tail-anchored, and potentially regulated by SPPL2c/SPP-mediated intramembrane proteolysis (niemeyer2019theintramembraneprotease pages 3-4, niemeyer2019theintramembraneprotease pages 5-6, niemeyer2019theintramembraneprotease media d5029e8f). However, in the retrieved excerpt, RAMP4-2 is not explicitly mapped to SERP2/C13orf21/Q8N6R1, so this remains an inference that must be verified via sequence/accession mapping in the full text or databases.

3.3 2023: RAMP4-2 used as an SPPL2c activity readout and named as stress-associated ER protein family member 2

A 2023 mechanistic paper on regulation of SPPL2c uses HA-RAMP4-2 cleavage as a readout assay and explicitly refers to RAMP4-2 as “stress-associated endoplasmic reticulum protein family member 2 (RAMP4-2)” (contreras2023thetransmembranedomain pages 1-3, contreras2023thetransmembranedomain pages 4-7, contreras2023thetransmembranedomain pages 7-9). This supports the concept that RAMP4-2 is an ER stress-associated family member and that it is experimentally tractable as an intramembrane-protease substrate (contreras2023thetransmembranedomain pages 1-3).

4) Pathways and biological processes most plausibly linked to SERP2

Given the evidence available in this run, the best-supported pathway context for SERP2/Q8N6R1 is:

ER membrane protein biogenesis / ribosome–translocon biology: RAMP4-family proteins are positioned near Sec61’s lateral gate and implicated in keeping the translocon in an insertion-competent state in structural models (vismpas2024rampingupknowledge pages 2-3).
ER proteostasis / protein quality control via intramembrane proteolysis: RAMP4-2 is a TA substrate cleaved by SPPL2c/SPP, suggesting regulated turnover as part of proteostasis in ER membranes (niemeyer2019theintramembraneprotease pages 3-4, niemeyer2019theintramembraneprotease pages 5-6, niemeyer2019theintramembraneprotease media d5029e8f).

These two contexts are coherent: proteins that transiently associate with the translocon and integrate into ER membranes are often subject to quality control and regulated turnover, including intramembrane proteolysis.

5) Recent developments (prioritizing 2023–2024)

5.1 2024: cryo-EM-driven mechanistic model for RAMP4 at Sec61

The 2024 eLife Insight highlights that cryo-EM intermediates place RAMP4 at the Sec61 lateral gate and argue it may act as a functional subunit of Sec61 in certain translocon states, with possible dynamic association/dissociation during multi-pass insertion (vismpas2024rampingupknowledge pages 2-3). This represents a substantial conceptual development in how small accessory ER membrane proteins may regulate translocon conformational states.

5.2 2023: SPPL2c regulation studies keep RAMP4-2 as a central biochemical substrate

The 2023 CMLS paper uses RAMP4-2 cleavage assays to mechanistically dissect regulation of SPPL2c (via Frey1 motifs), reinforcing RAMP4-2 as a key experimental substrate for this intramembrane protease system (contreras2023thetransmembranedomain pages 4-7, contreras2023thetransmembranedomain pages 7-9).

5.3 2023: human genetics implicates SERP2 locus in female-specific asthma association

In a 2023 genome-wide SNP-by-sex interaction analysis (CLSA; n=23,323), the authors report that an intergenic SNP rs9525931 near SERP2 had a female-specific association with asthma after Bonferroni correction (odimba2023identificationofsexspecific pages 10-11). They further note that variants near SERP2 had been reported in prior GWAS for lung function measures (FEV1 and FEV1/FVC) and that SERP2-mapped CpGs/SNPs had been associated with Alzheimer’s disease in females (odimba2023identificationofsexspecific pages 10-11). This is “gene-level” support for clinical relevance but does not resolve molecular mechanism.

6) Current applications and real-world implementations

Mechanistic cell biology tool substrate: RAMP4-2 is used as a biochemical substrate/readout for SPPL2c activity and regulation in cell-based assays (niemeyer2019theintramembraneprotease pages 5-6, contreras2023thetransmembranedomain pages 4-7).
Human genetics/biomarker hypothesis generation: SERP2-locus associations (e.g., rs9525931 near SERP2) provide candidates for sex-specific asthma susceptibility genetics and motivate follow-up functional genomics (odimba2023identificationofsexspecific pages 10-11).
Translocon structural biology and drug target context (indirect): While not SERP2-specific, the emerging view of small membrane accessory proteins (like RAMP4-family members) controlling Sec61 gating states informs the broader agenda of targeting ER protein biogenesis machinery in disease, although direct SERP2 targeting applications are not established in the retrieved set (vismpas2024rampingupknowledge pages 2-3, gemmer2020aclearerpicture pages 2-3).

7) Expert opinions / authoritative analysis (from reviews and insights)

The 2020 translocon review emphasizes that early biochemical isolation cannot fully resolve which RAMPs are stoichiometric translocon parts and underscores technical limitations in visualizing small integral membrane partners by cryo-ET, implying that mechanistic claims for these proteins must be evaluated in light of method constraints (gemmer2020aclearerpicture pages 2-3).
The 2024 eLife Insight interprets new structural intermediates to propose a more concrete role for RAMP4 as a lateral-gate-adjacent factor that may keep Sec61 open and tethered, but also suggests it may dissociate as other factors bind—highlighting an emerging consensus that “translocon composition is dynamic” rather than fixed (vismpas2024rampingupknowledge pages 2-3).

8) Key statistics and quantitative findings

Human asthma GWAS: 23,323 individuals; 416,562 SNPs after QC; 49 SNPs with interaction p < 10^-5 screened; rs9525931 near SERP2 showed female-specific association with asthma after Bonferroni correction (odimba2023identificationofsexspecific pages 10-11).
SPPL2c substrate screen (mouse testis proteomics): in SPPL2c knockout testis membrane fractions, tail-anchored candidates STX8 and PLN were enriched with ratios ~1.34 and ~1.59 (KO/WT), respectively, illustrating the quantitative framework used for identifying TA substrates of SPPL2c in vivo (niemeyer2019theintramembraneprotease pages 8-10). While not SERP2 itself, this supports the same mechanistic system in which RAMP4-2 is studied.
RAMP4-2 proteolysis: RAMP4-2 is described as the only one among tested TA candidates efficiently cleaved by SPPL2c in the cell-based substrate panel, with near-complete depletion under assay conditions; inhibitor and densitometric quantification data are presented in the figure panels retrieved (niemeyer2019theintramembraneprotease pages 3-4, niemeyer2019theintramembraneprotease pages 5-6, niemeyer2019theintramembraneprotease media d5029e8f).

9) Evidence table

The table below distinguishes direct SERP2 evidence from RAMP4-family context and RAMP4-2 mechanistic data.

Evidence type	What was shown	System/assay	Key quantitative findings (numbers)	Interpretation for SERP2 function/localization	Source (paper, year, URL)
Genetic association	Human SERP2 was explicitly named Stress-Associated Endoplasmic Reticulum Protein 2; an intergenic SNP near SERP2 showed a female-specific asthma association, and the paper also noted prior associations of SERP2-region variants with lung function/COPD and female Alzheimer’s disease signals.	SNP-by-sex interaction GWAS and sex-stratified analysis in 23,323 Canadian adults from CLSA	23,323 individuals analyzed; 49 SNPs with interaction p < 10^-5 screened; 3 female-specific SNPs passed Bonferroni correction, including rs9525931 near SERP2 (odimba2023identificationofsexspecific pages 10-11)	Confirms the existence of human SERP2 as a distinct gene; current direct evidence is genetic/association-based rather than mechanistic, with the name implying ER association but not proving biochemical function.	Odimba et al., 2023, Journal of Asthma and Allergy, https://doi.org/10.2147/JAA.S404670 (odimba2023identificationofsexspecific pages 10-11)
Structural/translocon (family context)	In recent cryo-EM interpretation, RAMP4 localizes near the Sec61 lateral gate and was proposed to behave like a fourth Sec61 subunit, helping keep the channel open and tether the complex to ribosomes during membrane protein insertion.	Cryo-EM/structural interpretation of stalled ribosome–translocon intermediates, reviewed in eLife Insight	No explicit stoichiometric number beyond the proposal of a "fourth subunit"; structural intermediates captured open-gate states (vismpas2024rampingupknowledge pages 2-3)	Supports a plausible ER translocon-associated role for the UniProt-defined SERP2/RAMP4-family protein, but this evidence is for RAMP4 family context and does not explicitly map the studied RAMP4 species to SERP2/Q8N6R1.	Vismpas & Förster, 2024, eLife, https://doi.org/10.7554/eLife.98548 (vismpas2024rampingupknowledge pages 2-3)
Structural/translocon (family context)	Earlier translocon review summarized that RAMP4/SERP1 was originally isolated among ribosome-associated membrane proteins and was unusually resistant to detergent/salt extraction with Sec61-associated material, but its exact stoichiometry/position was unresolved in older preparations.	Review of biochemical isolation and cryo-ET literature on mammalian ER translocons	No direct SERP2-specific numbers; key point is detergent- and salt-resistant recovery with translocon fractions (gemmer2020aclearerpicture pages 2-3)	Reinforces the inference that RAMP4-family proteins are ER membrane/ribosome-translocon associated; however, this remains family-level context, not direct evidence for human SERP2 specifically.	Gemmer & Förster, 2020, Journal of Cell Science, https://doi.org/10.1242/jcs.231340 (gemmer2020aclearerpicture pages 2-3)
Intramembrane proteolysis	RAMP4-2 was experimentally tested as a tail-anchored (TA) protein and was the only one among tested TA candidates efficiently cleaved by SPPL2c; it also overlapped with SPPL2c in the ER.	HEK293/HeLa overexpression, Western blot cleavage assays, immunofluorescence colocalization	In the tested panel, RAMP4-2 was the only candidate efficiently cleaved by SPPL2c; near-complete depletion was reported under assay conditions (niemeyer2019theintramembraneprotease pages 3-4, niemeyer2019theintramembraneprotease pages 5-6)	Provides the strongest functional/localization clue linked to the UniProt identity: if RAMP4-2 corresponds to SERP2/Q8N6R1, then SERP2 is likely an ER-localized TA membrane protein and a potential SPPL2c/SPP substrate. The limitation is that the retrieved paper text did not explicitly map RAMP4-2 to SERP2/C13orf21/Q8N6R1.	Niemeyer et al., 2019, EMBO Reports, https://doi.org/10.15252/embr.201846449 (niemeyer2019theintramembraneprotease pages 3-4, niemeyer2019theintramembraneprotease pages 5-6)
Intramembrane proteolysis / regulatory assay	HA-RAMP4-2 was used as the readout substrate in SPPL2c inhibition studies; the paper explicitly referred to RAMP4-2 as “stress-associated endoplasmic reticulum protein family member 2.”	HEK-cell SPPL2c inhibition and co-immunoprecipitation assays using HA-RAMP4-2 substrate	Multiple assays quantified inhibition of RAMP4-2 cleavage; exact effect sizes varied by mutant, but RAMP4-2 was the central substrate readout (contreras2023thetransmembranedomain pages 1-3, contreras2023thetransmembranedomain pages 4-7, contreras2023thetransmembranedomain pages 7-9)	Supports the designation of RAMP4-2 as an ER stress-associated family member 2, consistent with the UniProt annotation for SERP2; still, the paper excerpt did not provide the direct human gene symbol/UniProt mapping.	Contreras et al., 2023, Cellular and Molecular Life Sciences, https://doi.org/10.1007/s00018-023-04823-7 (contreras2023thetransmembranedomain pages 1-3, contreras2023thetransmembranedomain pages 4-7, contreras2023thetransmembranedomain pages 7-9)
Overall evidence quality / ambiguity	Retrieved literature repeatedly showed that SERP2 is ambiguous in the wider literature (e.g., viral/invertebrate “SERP-2” entries), while direct human SERP2 mechanistic studies were sparse; most mechanistic data came from RAMP4/RAMP4-2 family literature lacking explicit accession mapping.	Cross-literature verification across retrieved genetics, translocon, and protease papers	No direct number; key result is absence of explicit SERP2↔RAMP4-2/Q8N6R1 mapping in retrieved primary texts (odimba2023identificationofsexspecific pages 10-11, vismpas2024rampingupknowledge pages 2-3, niemeyer2019theintramembraneprotease pages 5-6, contreras2023thetransmembranedomain pages 1-3)	Best-supported conclusion is cautious: human SERP2/Q8N6R1 is likely an ER-associated RAMP4-family membrane protein, probably tail-anchored and potentially linked to translocon biology and intramembrane proteolysis, but the direct literature base is limited.	Synthesis from retrieved evidence (odimba2023identificationofsexspecific pages 10-11, vismpas2024rampingupknowledge pages 2-3, niemeyer2019theintramembraneprotease pages 5-6, contreras2023thetransmembranedomain pages 1-3)

Table: This table summarizes the strongest retrieved evidence relevant to human SERP2/Q8N6R1 and separates direct human SERP2 findings from indirect RAMP4/RAMP4-2 family context. It is useful because the literature is sparse and symbol ambiguity makes careful evidence tracking essential.

10) Limitations and what remains unknown specifically for SERP2/Q8N6R1

Direct SERP2/Q8N6R1 mechanistic studies: In the retrieved corpus, there were no excerpts explicitly stating “SERP2 (C13orf21; Q8N6R1) = RAMP4-2” in the methods/construct definitions; thus, direct mapping of RAMP4-2 experimental substrate to UniProt Q8N6R1 remains unconfirmed in-text here.
Biochemical function: No enzymatic or transporter activity is suggested; rather, the plausible function is structural/regulatory as an ER membrane accessory factor and/or a proteostasis substrate.
Cellular localization: The best mechanistic evidence supports ER localization for RAMP4-2 in co-localization experiments, and translocon-associated localization for RAMP4 in cryo-EM models; SERP2-specific localization in human cells is not directly demonstrated in the retrieved excerpts.

11) Cited key sources (with dates and URLs)

Odimba U, Senthilselvan A, Farrell J, Gao Z. Identification of Sex-Specific Genetic Polymorphisms Associated with Asthma… Journal of Asthma and Allergy (May 2023). https://doi.org/10.2147/JAA.S404670 (odimba2023identificationofsexspecific pages 10-11)
Vismpas D, Förster F. RAMPing up knowledge of the translocon eLife (May 2024). https://doi.org/10.7554/eLife.98548 (vismpas2024rampingupknowledge pages 2-3)
Gemmer M, Förster F. A clearer picture of the ER translocon complex Journal of Cell Science (Feb 2020). https://doi.org/10.1242/jcs.231340 (gemmer2020aclearerpicture pages 2-3)
Niemeyer J et al. The intramembrane protease SPPL2c promotes male germ cell development by cleaving phospholamban EMBO reports (published online Feb 2019; issue year 2019). https://doi.org/10.15252/embr.201846449 (niemeyer2019theintramembraneprotease pages 3-4, niemeyer2019theintramembraneprotease pages 5-6, niemeyer2019theintramembraneprotease media d5029e8f)
Contreras W, Bazan JF, Mentrup T. The transmembrane domain of Frey1 harbors a transplantable inhibitory motif for intramembrane proteases Cellular and Molecular Life Sciences (Jun 2023). https://doi.org/10.1007/s00018-023-04823-7 (contreras2023thetransmembranedomain pages 1-3, contreras2023thetransmembranedomain pages 4-7, contreras2023thetransmembranedomain pages 7-9)

Figure-based evidence (key)

Niemeyer et al. Figure 2 panels show differential cleavage of HA-RAMP4-2 by SPPL2c vs SPP and inhibitor effects (niemeyer2019theintramembraneprotease media d5029e8f, niemeyer2019theintramembraneprotease media 721c9236, niemeyer2019theintramembraneprotease media da4109d7).

References

(niemeyer2019theintramembraneprotease pages 3-4): Johannes Niemeyer, Torben Mentrup, Ronny Heidasch, Stephan A Müller, Uddipta Biswas, Rieke Meyer, Alkmini A Papadopoulou, Verena Dederer, Martina Haug‐Kröper, Vivian Adamski, Renate Lüllmann‐Rauch, Martin Bergmann, Artur Mayerhofer, Paul Saftig, Gunther Wennemuth, Rolf Jessberger, Regina Fluhrer, Stefan F Lichtenthaler, Marius K Lemberg, and Bernd Schröder. The intramembrane protease sppl2c promotes male germ cell development by cleaving phospholamban. EMBO reports, Mar 2019. URL: https://doi.org/10.15252/embr.201846449, doi:10.15252/embr.201846449. This article has 47 citations and is from a highest quality peer-reviewed journal.
(niemeyer2019theintramembraneprotease pages 5-6): Johannes Niemeyer, Torben Mentrup, Ronny Heidasch, Stephan A Müller, Uddipta Biswas, Rieke Meyer, Alkmini A Papadopoulou, Verena Dederer, Martina Haug‐Kröper, Vivian Adamski, Renate Lüllmann‐Rauch, Martin Bergmann, Artur Mayerhofer, Paul Saftig, Gunther Wennemuth, Rolf Jessberger, Regina Fluhrer, Stefan F Lichtenthaler, Marius K Lemberg, and Bernd Schröder. The intramembrane protease sppl2c promotes male germ cell development by cleaving phospholamban. EMBO reports, Mar 2019. URL: https://doi.org/10.15252/embr.201846449, doi:10.15252/embr.201846449. This article has 47 citations and is from a highest quality peer-reviewed journal.
(vismpas2024rampingupknowledge pages 2-3): Dimitrios Vismpas and Friedrich Förster. Ramping up knowledge of the translocon. eLife, May 2024. URL: https://doi.org/10.7554/elife.98548, doi:10.7554/elife.98548. This article has 2 citations and is from a domain leading peer-reviewed journal.
(gemmer2020aclearerpicture pages 2-3): Max Gemmer and Friedrich Förster. A clearer picture of the er translocon complex. Journal of Cell Science, Feb 2020. URL: https://doi.org/10.1242/jcs.231340, doi:10.1242/jcs.231340. This article has 144 citations and is from a domain leading peer-reviewed journal.
(niemeyer2019theintramembraneprotease media d5029e8f): Johannes Niemeyer, Torben Mentrup, Ronny Heidasch, Stephan A Müller, Uddipta Biswas, Rieke Meyer, Alkmini A Papadopoulou, Verena Dederer, Martina Haug‐Kröper, Vivian Adamski, Renate Lüllmann‐Rauch, Martin Bergmann, Artur Mayerhofer, Paul Saftig, Gunther Wennemuth, Rolf Jessberger, Regina Fluhrer, Stefan F Lichtenthaler, Marius K Lemberg, and Bernd Schröder. The intramembrane protease sppl2c promotes male germ cell development by cleaving phospholamban. EMBO reports, Mar 2019. URL: https://doi.org/10.15252/embr.201846449, doi:10.15252/embr.201846449. This article has 47 citations and is from a highest quality peer-reviewed journal.
(odimba2023identificationofsexspecific pages 10-11): Ugochukwu Odimba, Ambikaipakan Senthilselvan, Jamie Farrell, and Zhiwei Gao. Identification of sex-specific genetic polymorphisms associated with asthma in middle-aged and older canadian adults: an analysis of clsa data. Journal of Asthma and Allergy, 16:553-566, May 2023. URL: https://doi.org/10.2147/jaa.s404670, doi:10.2147/jaa.s404670. This article has 5 citations and is from a peer-reviewed journal.
(contreras2023thetransmembranedomain pages 1-3): Whendy Contreras, J. Fernando Bazan, and Torben Mentrup. The transmembrane domain of frey1 harbors a transplantable inhibitory motif for intramembrane proteases. Cellular and Molecular Life Sciences: CMLS, Jun 2023. URL: https://doi.org/10.1007/s00018-023-04823-7, doi:10.1007/s00018-023-04823-7. This article has 3 citations.
(contreras2023thetransmembranedomain pages 4-7): Whendy Contreras, J. Fernando Bazan, and Torben Mentrup. The transmembrane domain of frey1 harbors a transplantable inhibitory motif for intramembrane proteases. Cellular and Molecular Life Sciences: CMLS, Jun 2023. URL: https://doi.org/10.1007/s00018-023-04823-7, doi:10.1007/s00018-023-04823-7. This article has 3 citations.
(contreras2023thetransmembranedomain pages 7-9): Whendy Contreras, J. Fernando Bazan, and Torben Mentrup. The transmembrane domain of frey1 harbors a transplantable inhibitory motif for intramembrane proteases. Cellular and Molecular Life Sciences: CMLS, Jun 2023. URL: https://doi.org/10.1007/s00018-023-04823-7, doi:10.1007/s00018-023-04823-7. This article has 3 citations.
(niemeyer2019theintramembraneprotease pages 8-10): Johannes Niemeyer, Torben Mentrup, Ronny Heidasch, Stephan A Müller, Uddipta Biswas, Rieke Meyer, Alkmini A Papadopoulou, Verena Dederer, Martina Haug‐Kröper, Vivian Adamski, Renate Lüllmann‐Rauch, Martin Bergmann, Artur Mayerhofer, Paul Saftig, Gunther Wennemuth, Rolf Jessberger, Regina Fluhrer, Stefan F Lichtenthaler, Marius K Lemberg, and Bernd Schröder. The intramembrane protease sppl2c promotes male germ cell development by cleaving phospholamban. EMBO reports, Mar 2019. URL: https://doi.org/10.15252/embr.201846449, doi:10.15252/embr.201846449. This article has 47 citations and is from a highest quality peer-reviewed journal.
(niemeyer2019theintramembraneprotease media 721c9236): Johannes Niemeyer, Torben Mentrup, Ronny Heidasch, Stephan A Müller, Uddipta Biswas, Rieke Meyer, Alkmini A Papadopoulou, Verena Dederer, Martina Haug‐Kröper, Vivian Adamski, Renate Lüllmann‐Rauch, Martin Bergmann, Artur Mayerhofer, Paul Saftig, Gunther Wennemuth, Rolf Jessberger, Regina Fluhrer, Stefan F Lichtenthaler, Marius K Lemberg, and Bernd Schröder. The intramembrane protease sppl2c promotes male germ cell development by cleaving phospholamban. EMBO reports, Mar 2019. URL: https://doi.org/10.15252/embr.201846449, doi:10.15252/embr.201846449. This article has 47 citations and is from a highest quality peer-reviewed journal.
(niemeyer2019theintramembraneprotease media da4109d7): Johannes Niemeyer, Torben Mentrup, Ronny Heidasch, Stephan A Müller, Uddipta Biswas, Rieke Meyer, Alkmini A Papadopoulou, Verena Dederer, Martina Haug‐Kröper, Vivian Adamski, Renate Lüllmann‐Rauch, Martin Bergmann, Artur Mayerhofer, Paul Saftig, Gunther Wennemuth, Rolf Jessberger, Regina Fluhrer, Stefan F Lichtenthaler, Marius K Lemberg, and Bernd Schröder. The intramembrane protease sppl2c promotes male germ cell development by cleaving phospholamban. EMBO reports, Mar 2019. URL: https://doi.org/10.15252/embr.201846449, doi:10.15252/embr.201846449. This article has 47 citations and is from a highest quality peer-reviewed journal.

Artifacts

Edison artifact artifact-00

Citations

odimba2023identificationofsexspecific pages 10-11
gemmer2020aclearerpicture pages 2-3
vismpas2024rampingupknowledge pages 2-3
contreras2023thetransmembranedomain pages 1-3
niemeyer2019theintramembraneprotease pages 8-10
niemeyer2019theintramembraneprotease pages 3-4
niemeyer2019theintramembraneprotease pages 5-6
contreras2023thetransmembranedomain pages 4-7
contreras2023thetransmembranedomain pages 7-9
https://doi.org/10.2147/JAA.S404670
https://doi.org/10.7554/eLife.98548
https://doi.org/10.1242/jcs.231340
https://doi.org/10.15252/embr.201846449
https://doi.org/10.1007/s00018-023-04823-7
https://doi.org/10.15252/embr.201846449,
https://doi.org/10.7554/elife.98548,
https://doi.org/10.1242/jcs.231340,
https://doi.org/10.2147/jaa.s404670,
https://doi.org/10.1007/s00018-023-04823-7,

📚 Additional Documentation

Notes

(SERP2-notes.md)

SERP2 / RAMP4-2 (Stress-associated endoplasmic reticulum protein 2) — review notes

UniProt: Q8N6R1 (SERP2_HUMAN), 65 aa; AltName "Ribosome-associated membrane protein RAMP4-2". Single-pass ER membrane protein (TM 38-58). Paralog of SERP1/RAMP4; member of the RAMP4 family.

Core identity / function

Small translocon-associated ER membrane protein that stabilizes/protects nascent membrane and secretory proteins during ER stress; SERP1 paralog.
UniProt FUNCTION (by similarity to mouse Q9R2C1): "Interacts with target proteins during their translocation into the lumen of the endoplasmic reticulum. Protects unfolded target proteins against degradation during ER stress. May facilitate glycosylation of target proteins after termination of ER stress. May modulate the use of N-glycosylation sites on target proteins." [UniProt Q8N6R1]
UniProt SUBUNIT: "Interacts with SEC61B, SEC61A1 and the SEC61 complex. Interacts with CANX." -> translocon-associated.
No dedicated primary characterization paper in the GOA; function inferred by orthology/paralogy (RAMP4 family) and supported by phylogenetic (IBA) annotations. Less experimentally characterized than SERP1.

Annotation assessment

GO:0005783 endoplasmic reticulum (IBA is_active_in; IEA) — CORE site of action/localization, ACCEPT.
GO:0005789 ER membrane (IEA, ISS) — CORE localization, ACCEPT.
GO:0016020 membrane (IEA, ISS) — generic parent; KEEP_AS_NON_CORE.
GO:0030968 ER unfolded protein response (IBA involved_in) — CORE process; stress-associated, acts during ER stress. ACCEPT.
GO:0005515 protein binding (IPI PMID:25416956; large HuRI set PMID:32296183) — bare protein binding; KEEP_AS_NON_CORE. Partners are largely membrane/secretory proteins consistent with translocon-substrate role.

Core function summary

SERP2/RAMP4-2 is a Sec61-translocon-associated single-pass ER membrane protein (SERP1/RAMP4 paralog) that binds and stabilizes nascent membrane/secretory proteins during ER stress and facilitates their subsequent N-glycosylation; functions in the ER unfolded protein response. Function is established largely by orthology/paralogy.

Falcon deep-research findings (incorporated 2026-06)

SERP2 = RAMP4-2: UniProt AltName for Q8N6R1 is "Ribosome-associated membrane protein RAMP4-2", so RAMP4-2 experimental data map to SERP2. (Falcon flagged that primary texts did not always print the Q8N6R1/C13orf21 accession, but the UniProt name equivalence is unambiguous.)
NEW direct experimental finding: RAMP4-2 (SERP2) is a tail-anchored ER protein and a substrate for intramembrane proteolysis. Among tail-anchored candidates tested, RAMP4-2 was the only one efficiently cleaved by SPPL2c, and it was also cleaved by SPP [PMID:30733280; Niemeyer et al. EMBO Rep 2019, DOI 10.15252/embr.201846449; Falcon report pages 3-6]. This implicates SERP2 in regulated ER-membrane proteostasis/turnover and is a substrate property not previously captured. Added as reference (MEDIUM relevance); no new GO annotation asserted (no cached verbatim text).
HA-RAMP4-2 (SERP2) cleavage is used as the readout substrate for SPPL2c activity/regulation in a 2023 study, corroborating the SPPL2c-substrate relationship [PMID:37261541; Contreras et al. Cell Mol Life Sci 2023, DOI 10.1007/s00018-023-04823-7]. Added as reference (LOW; tool-substrate use).
Family-level structural context: RAMP4-family proteins localize at the Sec61 lateral gate and may act as a dynamic, gating-modulating translocon component [PMID:38787756; Vismpas & Forster eLife 2024 Insight, DOI 10.7554/eLife.98548]. The underlying structural data are for RAMP4/SERP1, so this is inference for the paralog SERP2, not SERP2-specific evidence. Added as reference (MEDIUM, family context).
Gemmer & Forster 2020 translocon review supplies background RAMP4-family/Sec61 association PMID:32019826. Added as reference (LOW).
Possible disease link (NOT added to YAML; gene-level only): an intergenic SNP (rs9525931) near SERP2 showed a female-specific association with asthma in a 2023 CLSA GWAS [Odimba et al., J Asthma Allergy 2023, DOI 10.2147/JAA.S404670]. This is an intergenic-locus association, does not establish SERP2 molecular function, and was left notes-only.
No existing actions/annotations were changed; additions are reference-level only. None of these papers are cached in publications/, so no paraphrased verbatim supporting_text and no supported_by changes were made.

Pn Notes

(SERP2-pn-notes.md)

SERP2 PN Consistency Notes

Generated: 2026-06-18
Project: PROTEOSTASIS
Scope: PN consistency rereview against local AIGR review and available deep-research artifacts
UniProt: Q8N6R1
AIGR review status: COMPLETE
Review batch: proteostasis-batch-2026-06-11
Batch change status: added

Source Files Checked

AIGR review YAML: present - genes/human/SERP2/SERP2-ai-review.yaml
AIGR review HTML: missing - genes/human/SERP2/SERP2-ai-review.html
Gene notes: present - genes/human/SERP2/SERP2-notes.md
GOA TSV: present - genes/human/SERP2/SERP2-goa.tsv
UniProt record: present - genes/human/SERP2/SERP2-uniprot.txt
PN dossier: projects/PROTEOSTASIS/reports/phase1_dossiers/SERP2.md
PN consistency section: projects/PROTEOSTASIS/reports/phase1_dossiers/_sections/SERP2.md
PN projection report: projects/PROTEOSTASIS/reports/pn_projection/pn_projected_gene_go_summary.tsv
PN mapping audit: projects/PROTEOSTASIS/reports/pn_mapping_audit/current_mapping_scrutiny.tsv

Deep Research Files

genes/human/SERP2/SERP2-deep-research-falcon.md

AIGR Review Snapshot

Description: SERP2 (stress-associated endoplasmic reticulum protein 2, also RAMP4-2, ribosome-associated membrane protein RAMP4-2) is a small (65 aa) single-pass endoplasmic reticulum membrane protein of the RAMP4 family and a paralog of SERP1/RAMP4. Like SERP1, it associates with the Sec61 translocon and binds nascent membrane and secretory proteins during their translocation into the ER, protecting these still-unfolded substrates from degradation during ER stress and facilitating their N-glycosylation after stress resolves, including modulating which N-glycosylation sites are used. Through these activities SERP2 contributes to the endoplasmic reticulum unfolded protein response and to membrane-protein biogenesis at the translocon. It physically associates with components of the Sec61 complex (SEC61A1, SEC61B) and calnexin. Its function is established largely by orthology and paralogy, and it is less experimentally characterized than SERP1.
Existing/core annotation action counts: ACCEPT: 5; KEEP_AS_NON_CORE: 4

PN Consistency Summary

Consistency: Deep research ↔ review YAML ↔ PN annotation consistent. All describe SERP2/RAMP4-2 as a single-pass ER membrane RAMP4-family paralog of SERP1, translocon-associated, stabilizing nascent membrane/secretory substrates during ER stress; function established largely by orthology/paralogy (less experimentally characterized than SERP1). No contradictions. The review adds a SERP2-specific experimental fact the PN row omits: RAMP4-2 is a tail-anchored substrate of the SPPL2c/SPP intramembrane proteases (PMID:30733280, PMID:37261541).
PN story / NEW pressure: PN asserts only the unmapped accessory-protein grouping. SERP2's core functions — GO:0030968 ER unfolded protein response (IBA) and ER-membrane localization — are already in GOA/review. No defensible NEW GO term; review proposes none. Already captured. (The SPPL2c-substrate property is interesting but the review correctly added it as references only, no new GO assertion.)
Evidence alignment: PN row is terse; review references go well beyond it (SPPL2c substrate papers, translocon Insight PMID:38787756, Gemmer & Forster review PMID:32019826). Overlap is essentially at the family/orthology level since both rely on RAMP4-family inference rather than SERP2-specific GOA experimental annotations (GOA has only IBA + 2 bare protein-binding IPI).
Verdict: Consistent and well-curated. Recommend NOT propagating class-level GO:0015031 protein transport to SERP2 (over-reach); UPR + ER-membrane already captured.

Full Consistency Review

UniProt: Q8N6R1 · batch: proteostasis-batch-2026-06-11 · review status: COMPLETE
PN placement: ER proteostasis|Protein transport|SEC61 channel accessory protein ; PN-node mapping: group "SEC61 channel accessory protein"=no_mapping (broad category); parent class "Protein transport"=mapped/ok GO:0015031 protein transport; branch=no_mapping.
Consistency: Deep research ↔ review YAML ↔ PN annotation consistent. All describe SERP2/RAMP4-2 as a single-pass ER membrane RAMP4-family paralog of SERP1, translocon-associated, stabilizing nascent membrane/secretory substrates during ER stress; function established largely by orthology/paralogy (less experimentally characterized than SERP1). No contradictions. The review adds a SERP2-specific experimental fact the PN row omits: RAMP4-2 is a tail-anchored substrate of the SPPL2c/SPP intramembrane proteases (PMID:30733280, PMID:37261541).
PN story / NEW pressure: PN asserts only the unmapped accessory-protein grouping. SERP2's core functions — GO:0030968 ER unfolded protein response (IBA) and ER-membrane localization — are already in GOA/review. No defensible NEW GO term; review proposes none. Already captured. (The SPPL2c-substrate property is interesting but the review correctly added it as references only, no new GO assertion.)
Mapping strategy: Concern — parent class node projects GO:0015031 protein transport as new_to_goa. As for SERP1, SERP2 is a translocon-associated stabilizer, not a transport carrier; GO:0015031 over-reaches (TOMM20/HSPA8/RAB7A precedent). The group-level no_mapping is correct; do not propagate class-level GO:0015031 to SERP2.
Evidence alignment: PN row is terse; review references go well beyond it (SPPL2c substrate papers, translocon Insight PMID:38787756, Gemmer & Forster review PMID:32019826). Overlap is essentially at the family/orthology level since both rely on RAMP4-family inference rather than SERP2-specific GOA experimental annotations (GOA has only IBA + 2 bare protein-binding IPI).
Verdict: Consistent and well-curated. Recommend NOT propagating class-level GO:0015031 protein transport to SERP2 (over-reach); UPR + ER-membrane already captured.

PN Dossier Context

review_batch: proteostasis-batch-2026-06-11
review_yaml: genes/human/SERP2/SERP2-ai-review.yaml
PN workbook rows: 1

PN row 1: ER proteostasis | Protein transport | SEC61 channel accessory protein

UniProt: Q8N6R1
In branches: ER
PN-node mapping records (path + ancestors):
- [group] ER proteostasis|Protein transport|SEC61 channel accessory protein
  status=no_mapping scope= GO=[]
  rationale: Reviewed as a broad PN category rather than a single GO class. The member genes span multiple activities, complexes, or contexts, so direct propagation from this node would overstate the shared biology.
- [class] ER proteostasis|Protein transport
  status=mapped scope=ok_for_propagation_to_go GO=[GO:0015031 protein transport]
  rationale: The PN ER Protein transport class groups ER-targeting and ER-insertion pathways. GO protein transport is the appropriate propagation target, while the source class remains ER-specific and broader than any single GO transport subtype.
- [branch] ER proteostasis
  status=no_mapping scope= GO=[]
  rationale: Reviewed as a top-level PN branch. This is a systems/taxonomy umbrella, not a direct GO assertion; narrower child curations carry any propagating GO mappings.

Projected GO annotations (1)

GO:0015031 protein transport | scope=ok_for_propagation_to_go | goa_status=new_to_goa | from=ER proteostasis|Protein transport

Note

This file is generated from the current PROTEOSTASIS phase-1 dossier and local gene-review artifacts. Edit the source review, PN mapping, or dossier rather than this generated note when correcting the underlying curation.

📄 View Raw YAML

id: Q8N6R1
gene_symbol: SERP2
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: SERP2 (stress-associated endoplasmic reticulum protein 2, also RAMP4-2, ribosome-associated membrane protein RAMP4-2) is a small (65 aa) single-pass endoplasmic reticulum membrane protein of the RAMP4 family and a paralog of SERP1/RAMP4. Like SERP1, it associates with the Sec61 translocon and binds nascent membrane and secretory proteins during their translocation into the ER, protecting these still-unfolded substrates from degradation during ER stress and facilitating their N-glycosylation after stress resolves, including modulating which N-glycosylation sites are used. Through these activities SERP2 contributes to the endoplasmic reticulum unfolded protein response and to membrane-protein biogenesis at the translocon. It physically associates with components of the Sec61 complex (SEC61A1, SEC61B) and calnexin. Its function is established largely by orthology and paralogy, and it is less experimentally characterized than SERP1.
existing_annotations:
- term:
    id: GO:0005783
    label: endoplasmic reticulum
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: is_active_in
  review:
    summary: SERP2 acts at the ER (translocon) where, like its SERP1 paralog, it stabilizes nascent membrane proteins; the phylogenetic active-site assignment is correct.
    action: ACCEPT
    reason: Core site of action; SERP2 is a translocon-associated ER membrane protein.
    supported_by:
    - reference_id: file:human/SERP2/SERP2-uniprot.txt
      supporting_text: Interacts with target proteins during their translocation into the lumen of the endoplasmic reticulum
- term:
    id: GO:0030968
    label: endoplasmic reticulum unfolded protein response
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: SERP2 is a stress-associated ER protein that acts during ER stress to protect nascent membrane proteins, placing it in the ER unfolded protein response.
    action: ACCEPT
    reason: Core biological process; SERP2 functions during ER stress to protect translocating substrates.
    supported_by:
    - reference_id: file:human/SERP2/SERP2-uniprot.txt
      supporting_text: Protects unfolded target proteins against degradation during ER stress
- term:
    id: GO:0005783
    label: endoplasmic reticulum
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: located_in
  review:
    summary: InterPro-based ER localization, consistent with orthology and phylogenetic evidence.
    action: ACCEPT
    reason: Correct core localization.
    supported_by:
    - reference_id: file:human/SERP2/SERP2-uniprot.txt
      supporting_text: Interacts with SEC61B, SEC61A1 and the SEC61 complex
- term:
    id: GO:0005789
    label: endoplasmic reticulum membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: SERP2 is a single-pass ER membrane protein; the subcellular-location-based annotation is correct.
    action: ACCEPT
    reason: Core localization, consistent with the single-pass ER membrane topology.
    supported_by:
    - reference_id: file:human/SERP2/SERP2-uniprot.txt
      supporting_text: 'Membrane {ECO:0000250|UniProtKB:Q9R2C1}; Single-'
- term:
    id: GO:0016020
    label: membrane
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: Generic membrane localization, a parent of the more informative ER membrane term.
    action: KEEP_AS_NON_CORE
    reason: Correct but uninformative; the specific GO:0005789 (ER membrane) better captures SERP2 localization.
    supported_by:
    - reference_id: file:human/SERP2/SERP2-uniprot.txt
      supporting_text: 'Membrane {ECO:0000250|UniProtKB:Q9R2C1}; Single-'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:25416956
  qualifier: enables
  review:
    summary: Proteome-scale interactome capture of a SERP2 interaction; a real interaction but the bare protein binding term is uninformative.
    action: KEEP_AS_NON_CORE
    reason: High-throughput interactome capture; bare protein binding is uninformative per curation guidelines.
    supported_by:
    - reference_id: file:human/SERP2/SERP2-uniprot.txt
      supporting_text: 'Q8N6R1; Q8N6L0'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:32296183
  qualifier: enables
  review:
    summary: HuRI binary-interactome screen capturing SERP2 binding to a large set of membrane and secretory proteins; consistent with a translocon-substrate-stabilizing role but the bare protein binding term is uninformative.
    action: KEEP_AS_NON_CORE
    reason: Many partners are membrane-protein substrates consistent with SERP2's function, but bare protein binding is uninformative per guidelines.
    supported_by:
    - reference_id: file:human/SERP2/SERP2-uniprot.txt
      supporting_text: 'Q8N6R1; Q13520: AQP6'
- term:
    id: GO:0005789
    label: endoplasmic reticulum membrane
  evidence_type: ISS
  original_reference_id: GO_REF:0000024
  qualifier: located_in
  review:
    summary: Sequence-similarity transfer of ER membrane localization from the mouse ortholog; consistent with the RAMP4-family identity.
    action: ACCEPT
    reason: Correct core localization, redundant with IEA evidence.
    supported_by:
    - reference_id: file:human/SERP2/SERP2-uniprot.txt
      supporting_text: 'Membrane {ECO:0000250|UniProtKB:Q9R2C1}; Single-'
- term:
    id: GO:0016020
    label: membrane
  evidence_type: ISS
  original_reference_id: GO_REF:0000024
  qualifier: located_in
  review:
    summary: Sequence-similarity transfer of generic membrane localization; a parent of ER membrane.
    action: KEEP_AS_NON_CORE
    reason: Correct but uninformative; the specific GO:0005789 (ER membrane) better captures SERP2 localization.
    supported_by:
    - reference_id: file:human/SERP2/SERP2-uniprot.txt
      supporting_text: 'Membrane {ECO:0000250|UniProtKB:Q9R2C1}; Single-'
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
  findings: []
- id: PMID:25416956
  title: A proteome-scale map of the human interactome network.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: High-throughput interactome; source of a bare protein binding annotation, not relevant to SERP2's core function.
- id: PMID:32296183
  title: A reference map of the human binary protein interactome.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: HuRI binary-interactome map; source of many bare protein binding annotations, largely with membrane/secretory proteins consistent with SERP2's translocon role but individually uninformative.
- id: file:human/SERP2/SERP2-uniprot.txt
  title: UniProt entry Q8N6R1 (SERP2_HUMAN), stress-associated endoplasmic reticulum protein 2 / RAMP4-2
  findings:
  - statement: Single-pass ER membrane protein of the RAMP4 family (SERP1 paralog) that interacts with target proteins during ER translocation, protects unfolded targets against degradation during ER stress, and facilitates their glycosylation after stress; interacts with the SEC61 complex and calnexin.
    reference_section_type: OTHER
- id: PMID:30733280
  title: The intramembrane protease SPPL2c promotes male germ cell development by cleaving phospholamban.
  findings:
  - statement: RAMP4-2 (= SERP2; UniProt AltName "Ribosome-associated membrane protein RAMP4-2") is a tail-anchored ER membrane protein experimentally shown to be a substrate for intramembrane proteolysis; among the tail-anchored candidates tested it was efficiently cleaved by SPPL2c (and also by SPP), implicating SERP2 in regulated ER-membrane proteostasis/turnover.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: PubMed-verified (Niemeyer et al., EMBO Rep 2019; DOI 10.15252/embr.201846449). Direct experimental evidence that RAMP4-2 (=SERP2 per UniProt AltName) is a tail-anchored ER protein and an SPPL2c/SPP intramembrane-protease substrate. The paper's primary focus is SPPL2c/phospholamban; the cached text was not available to anchor a verbatim supporting_text, so reference id only is added (no new GO annotation asserted).
- id: PMID:37261541
  title: The transmembrane domain of Frey1 harbors a transplantable inhibitory motif for intramembrane proteases.
  findings:
  - statement: Uses HA-RAMP4-2 (=SERP2) cleavage as the readout substrate for SPPL2c activity, corroborating that RAMP4-2/SERP2 is a tail-anchored ER substrate of the SPPL2c intramembrane protease.
    reference_section_type: OTHER
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: PubMed-verified (Contreras, Bazan, Mentrup, Cell Mol Life Sci 2023; DOI 10.1007/s00018-023-04823-7). RAMP4-2/SERP2 is used as a biochemical tool substrate for SPPL2c regulation rather than studied for its own function; supporting/contextual. Not cached.
- id: PMID:38787756
  title: RAMPing up knowledge of the translocon.
  findings:
  - statement: eLife Insight on cryo-EM of ribosome-translocon complexes; RAMP4-family proteins localize at the Sec61 lateral gate and are proposed to act as a dynamic, gating-modulating component of the translocon, providing family-level context for the RAMP4-family member SERP2.
    reference_section_type: OTHER
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: PubMed-verified (Vismpas & Forster, eLife 2024; DOI 10.7554/eLife.98548). Editorial/Insight discussing RAMP4 at the Sec61 lateral gate; the structural data concern RAMP4/SERP1, so this is family-level inference for SERP2, not SERP2-specific evidence. Not cached.
- id: PMID:32019826
  title: A clearer picture of the ER translocon complex.
  findings:
  - statement: Review of the ER translocon; the RAMP4 family is among ribosome-associated membrane proteins recovered with Sec61 translocon fractions, supporting translocon-associated localization for the RAMP4-family member SERP2 by family context.
    reference_section_type: OTHER
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: PubMed-verified (Gemmer & Forster, J Cell Sci 2020; DOI 10.1242/jcs.231340). Family-level/background context for the RAMP4 family; not SERP2-specific. Not cached.
core_functions:
- description: Sec61-translocon-associated ER membrane protein (SERP1/RAMP4 paralog) that binds and stabilizes nascent membrane and secretory proteins during ER stress, protecting them from premature degradation, and contributes to the ER unfolded protein response.
  supported_by:
  - reference_id: file:human/SERP2/SERP2-uniprot.txt
    supporting_text: Protects unfolded target proteins against degradation during ER stress
  locations:
  - id: GO:0005789
    label: endoplasmic reticulum membrane
  directly_involved_in:
  - id: GO:0030968
    label: endoplasmic reticulum unfolded protein response
proposed_new_terms: []
suggested_questions:
- question: Is SERP2/RAMP4-2 functionally redundant with SERP1/RAMP4, or does it have distinct substrate preferences, tissue expression, or stress-response behavior?
- question: Which nascent membrane-protein substrates depend on SERP2 for stabilization or correct N-glycosylation during ER stress?
suggested_experiments:
- description: Generate SERP2 single and SERP1/SERP2 double knockouts and assess membrane-protein stability, surface expression, and glycosylation under ER stress to test redundancy with SERP1.
- description: Proximity proteomics of SERP2 at the Sec61 translocon under basal and ER-stress conditions to define its substrate interactome and compare it with SERP1's.

SERP2

Gene Description

Existing Annotations Review

Core Functions

Sec61-translocon-associated ER membrane protein (SERP1/RAMP4 paralog) that binds and stabilizes nascent membrane and secretory proteins during ER stress, protecting them from premature degradation, and contributes to the ER unfolded protein response.