P4HA2

UniProt ID: O15460
Organism: Homo sapiens
Review Status: COMPLETE
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Gene Description

P4HA2 (prolyl 4-hydroxylase subunit alpha-2) is one of three catalytic alpha-subunit isoforms of collagen prolyl 4-hydroxylase (C-P4H), an endoplasmic reticulum-lumenal enzyme. The active enzyme is an alpha2-beta2 heterotetramer in which the beta subunit is P4HB (protein disulfide isomerase, PDI) acting as a structural and ER-retention subunit; the two alpha-2 chains carry the catalytic sites. As a 2-oxoglutarate- and Fe(II)-dependent dioxygenase, P4HA2 catalyzes the post-translational formation of trans-4-hydroxy-L-proline in -Xaa-Pro-Gly- sequences of procollagen (and other proteins), consuming 2-oxoglutarate and O2 and producing succinate and CO2. 4-Hydroxyproline is essential for the folding and thermal stability of the collagen triple helix. The active-site iron is coordinated by a 2-His-1-carboxylate facial triad, and L-ascorbate (vitamin C) is required as a cofactor to maintain the iron in the reduced Fe(II) state. The type II tetramer contributes a substantial fraction of total prolyl 4-hydroxylase activity in human cells, is expressed in heart, placenta, lung and pancreas, and does not co-assemble with the type I (P4HA1) alpha subunit into mixed tetramers. Variants in P4HA2 cause autosomal dominant nonsyndromic high myopia (MYP25), consistent with a role in scleral collagen and extracellular matrix.

Proposed New Ontology Terms

peptidyl-proline 4-hydroxylation to 4-hydroxy-L-proline

Definition: The hydroxylation of peptidyl-proline to peptidyl-4-hydroxy-L-proline catalyzed by P4HA2 as part of collagen biosynthesis (corresponds to the existing term GO:0018401).

Justification: No biological-process annotation is currently present in GOA. The core activity of P4HA2 directly accomplishes peptidyl-proline 4-hydroxylation as part of collagen biosynthesis; existing terms GO:0019471 (peptidyl-proline hydroxylation), GO:0018401 (peptidyl-proline hydroxylation to 4-hydroxy-L-proline) and GO:0032964 (collagen biosynthetic process) would appropriately capture the biological process and should be added rather than newly coined.

Supporting Evidence:

Existing Annotations Review

GO Term Evidence Action Reason
GO:0004656 procollagen-proline 4-dioxygenase activity
IBA
GO_REF:0000033 		ACCEPT
Summary: Phylogenetic inference of the core collagen prolyl 4-hydroxylase activity, conserved across the P4HA family (P4HA1/2/3 and orthologs). This is the defining molecular function of P4HA2.
Reason: Core molecular function; concordant with direct experimental (IDA, PMID:9211872), TAS and IEA evidence and EC 1.14.11.2.
Supporting Evidence:
file:human/P4HA2/P4HA2-uniprot.txt
Catalyzes the post-translational formation of 4-hydroxyproline in -Xaa-Pro-Gly- sequences in collagens and other proteins.
GO:0016222 procollagen-proline 4-dioxygenase complex
IBA
GO_REF:0000033 		ACCEPT
Summary: P4HA2 is part of the prolyl 4-hydroxylase complex, the alpha2-beta2 heterotetramer formed with P4HB (PDI). Phylogenetic inference is consistent with the experimentally documented tetramer.
Reason: Correct complex; P4HA2 assembles with P4HB into the catalytic C-P4H heterotetramer, the cellular form of the enzyme.
Supporting Evidence:
file:human/P4HA2/P4HA2-uniprot.txt
Heterotetramer of two alpha-2 chains and two beta chains (P4HB)
GO:0004656 procollagen-proline 4-dioxygenase activity
IEA
GO_REF:0000120 		ACCEPT
Summary: Electronic assignment of the core dioxygenase activity (RHEA:18945, EC 1.14.11.2), redundant with the experimental IDA annotation.
Reason: Correct core molecular function; concordant with experimental evidence.
Supporting Evidence:
file:human/P4HA2/P4HA2-uniprot.txt
EC=1.14.11.2
GO:0005506 iron ion binding
IEA
GO_REF:0000002 		ACCEPT
Summary: P4HA2 binds one Fe(2+) ion per subunit via a 2-His-1-carboxylate facial triad (His430, Asp432, His501) in the Fe2OG dioxygenase domain; iron binding is essential for the dioxygenase chemistry.
Reason: Accurate cofactor and active-site chemistry directly supported by the UniProt cofactor line and metal-binding residues; integral to the catalytic mechanism.
Supporting Evidence:
file:human/P4HA2/P4HA2-uniprot.txt
Binds 1 Fe(2+) ion per subunit.
GO:0005783 endoplasmic reticulum
IEA
GO_REF:0000120 		ACCEPT
Summary: Electronic assignment of ER localization, consistent with the documented ER-lumenal residence of the enzyme.
Reason: Correct compartment; concordant with the UniProt subcellular location and the HPA IDA ER annotation.
Supporting Evidence:
file:human/P4HA2/P4HA2-uniprot.txt
SUBCELLULAR LOCATION: Endoplasmic reticulum lumen.
GO:0005788 endoplasmic reticulum lumen
IEA
GO_REF:0000044 		ACCEPT
Summary: Subcellular-location vocabulary mapping to ER lumen, the precise compartment in which the soluble C-P4H tetramer acts on procollagen.
Reason: Correct and more specific than ER; matches the UniProt subcellular location.
Supporting Evidence:
file:human/P4HA2/P4HA2-uniprot.txt
SUBCELLULAR LOCATION: Endoplasmic reticulum lumen.
GO:0016705 oxidoreductase activity, acting on paired donors, with incorporation or reduction of molecular oxygen
IEA
GO_REF:0000002 		ACCEPT
Summary: General dioxygenase parent term capturing the O2-incorporating oxidoreductase chemistry of the 2-oxoglutarate/Fe(II)-dependent reaction.
Reason: Correct parent of the specific procollagen-proline 4-dioxygenase activity; accurately describes the enzyme oxidoreductase class.
Supporting Evidence:
file:human/P4HA2/P4HA2-uniprot.txt
Reaction=L-prolyl-[collagen] + 2-oxoglutarate + O2 = trans-4-hydroxy-L-prolyl-[collagen] + succinate + CO2
GO:0031418 L-ascorbic acid binding
IEA
GO_REF:0000002 		ACCEPT
Summary: L-ascorbate (vitamin C) is a required cofactor that maintains the active-site iron in the reduced Fe(2+) state; ascorbate binding is a documented property of the enzyme.
Reason: Accurate cofactor binding directly supported by the UniProt cofactor line; mechanistically integral to sustained catalysis.
Supporting Evidence:
file:human/P4HA2/P4HA2-uniprot.txt
Name=L-ascorbate
GO:0005515 protein binding
IPI
PMID:30021884
Histone Interaction Landscapes Visualized by Crosslinking Ma... 		KEEP AS NON CORE
Summary: High-throughput crosslinking mass spectrometry (histone interaction landscapes in intact nuclei) capturing P4HA2 interactions with P4HB (the beta subunit of the tetramer) and P4HA1 (the paralogous alpha isoform). The bare protein binding term is uninformative.
Reason: Records real IntAct captures (P4HB, P4HA1) but bare protein binding is uninformative per curation guidelines; the meaningful P4HB interaction is better represented by the complex annotation.
Supporting Evidence:
file:human/P4HA2/P4HA2-uniprot.txt
O15460; P07237: P4HB
GO:0005515 protein binding
IPI
PMID:33961781
Dual proteome-scale networks reveal cell-specific remodeling... 		KEEP AS NON CORE
Summary: BioPlex/dual proteome-scale interactome screen capturing P4HA2 interactions with P4HB and KIF7. Bare protein binding term is uninformative.
Reason: High-throughput interactome capture; P4HB is the genuine beta subunit but bare protein binding adds no functional specificity, and the KIF7 capture has no established biological meaning for an ER-lumenal enzyme.
Supporting Evidence:
file:human/P4HA2/P4HA2-uniprot.txt
O15460; P07237: P4HB
GO:0005515 protein binding
IPI
PMID:35271311
OpenCell: Endogenous tagging for the cartography of human ce... 		KEEP AS NON CORE
Summary: OpenCell endogenous-tagging interactome capturing a P4HA2-KIF7 (Q2M1P5) interaction. Bare protein binding term is uninformative.
Reason: High-throughput capture of an interaction without established functional relevance to the collagen-hydroxylation role of P4HA2; bare protein binding is uninformative.
Supporting Evidence:
file:human/P4HA2/P4HA2-uniprot.txt
O15460; Q2M1P5: KIF7
GO:0005515 protein binding
IPI
PMID:40205054
Multimodal cell maps as a foundation for structural and func... 		KEEP AS NON CORE
Summary: Multimodal cell-maps interactome capturing P4HA2 interactions with P4HB, P4HA1 and KIF7. Bare protein binding term is uninformative.
Reason: High-throughput interactome capture; the P4HB/P4HA1 captures are consistent with known biology but bare protein binding is uninformative per curation guidelines.
Supporting Evidence:
file:human/P4HA2/P4HA2-uniprot.txt
O15460; P13674: P4HA1
GO:0016222 procollagen-proline 4-dioxygenase complex
IEA
GO_REF:0000107 		ACCEPT
Summary: Ortholog-based electronic transfer of membership in the prolyl 4-hydroxylase complex, consistent with the experimentally documented alpha2-beta2 tetramer.
Reason: Correct complex membership; redundant with the IBA complex annotation and the UniProt subunit description.
Supporting Evidence:
file:human/P4HA2/P4HA2-uniprot.txt
Heterotetramer of two alpha-2 chains and two beta chains (P4HB)
GO:0005783 endoplasmic reticulum
IDA
GO_REF:0000052 		ACCEPT
Summary: Direct immunofluorescence (HPA) evidence for ER localization of P4HA2, consistent with its ER-lumenal site of action.
Reason: IDA-supported ER localization agrees with the UniProt subcellular location.
Supporting Evidence:
file:human/P4HA2/P4HA2-uniprot.txt
SUBCELLULAR LOCATION: Endoplasmic reticulum lumen.
GO:0004656 procollagen-proline 4-dioxygenase activity
IDA
PMID:9211872
Cloning of the human prolyl 4-hydroxylase alpha subunit isof... 		ACCEPT
Summary: Direct experimental characterization of the purified human type II (P4HA2) enzyme tetramer demonstrating procollagen-proline 4-dioxygenase activity. This is the core molecular function.
Reason: Core molecular function with direct experimental (IDA) support; the purified (alpha-II)2-beta2 tetramer hydroxylates collagen prolines.
Supporting Evidence:
PMID:9211872
Prolyl 4-hydroxylase (proline hydroxylase, EC 1.14.11.2) catalyzes the formation of 4-hydroxyproline in collagens.
GO:0005788 endoplasmic reticulum lumen
TAS
Reactome:R-HSA-1650808 		ACCEPT
Summary: Reactome curation placing the prolyl 4-hydroxylase reaction in the ER lumen (collagen biosynthesis pathway).
Reason: Correct compartment; redundant with the UniProt subcellular location and the IEA/IDA ER annotations.
Supporting Evidence:
file:human/P4HA2/P4HA2-uniprot.txt
SUBCELLULAR LOCATION: Endoplasmic reticulum lumen.
GO:0005788 endoplasmic reticulum lumen
TAS
Reactome:R-HSA-9918779 		ACCEPT
Summary: Reactome curation of proline hydroxylase activity in the ER lumen (here in a viral polyprotein-maturation context); the compartment assignment is correct.
Reason: Correct ER-lumenal compartment; redundant with stronger localization evidence.
Supporting Evidence:
file:human/P4HA2/P4HA2-uniprot.txt
SUBCELLULAR LOCATION: Endoplasmic reticulum lumen.
GO:0009055 electron transfer activity
TAS
PMID:9211872
Cloning of the human prolyl 4-hydroxylase alpha subunit isof... 		MARK AS OVER ANNOTATED
Summary: P4HA2 is a 2-oxoglutarate/Fe(II)-dependent dioxygenase; although its chemistry is redox-based and ascorbate-dependent, GO:0009055 (electron transfer activity) denotes electron-carrier function in electron transport chains and is a poor fit. The cited paper characterizes the dioxygenase, not an electron-carrier activity.
Reason: Over-interpretation of the redox/ascorbate chemistry of the enzyme; the informative molecular function is the dioxygenase activity (GO:0004656 / GO:0016705), not electron transfer/carrier activity.
Supporting Evidence:
PMID:9211872
Prolyl 4-hydroxylase (proline hydroxylase, EC 1.14.11.2) catalyzes the formation of 4-hydroxyproline in collagens.
GO:0004656 procollagen-proline 4-dioxygenase activity
TAS
PMID:9211872
Cloning of the human prolyl 4-hydroxylase alpha subunit isof... 		ACCEPT
Summary: Author-asserted procollagen-proline 4-dioxygenase activity for the type II enzyme, redundant with the IDA annotation from the same study.
Reason: Correct core molecular function; concordant with the experimental IDA annotation and EC 1.14.11.2.
Supporting Evidence:
PMID:9211872
Prolyl 4-hydroxylase (proline hydroxylase, EC 1.14.11.2) catalyzes the formation of 4-hydroxyproline in collagens.

Core Functions

Catalytic alpha subunit of collagen prolyl 4-hydroxylase that, as part of the alpha2-beta2 heterotetramer with P4HB (PDI), catalyzes 2-oxoglutarate- and Fe(II)-dependent 4-hydroxylation of proline residues in -Xaa-Pro-Gly- sequences of procollagen in the ER lumen, a modification essential for collagen triple-helix stability.

Molecular Function:
procollagen-proline 4-dioxygenase activity
Cellular Locations:
endoplasmic reticulum lumen
In Complex:
procollagen-proline 4-dioxygenase complex
Supporting Evidence:
  • PMID:9211872
    Prolyl 4-hydroxylase (proline hydroxylase, EC 1.14.11.2) catalyzes the formation of 4-hydroxyproline in collagens. The vertebrate enzyme is an alpha2beta2 tetramer, the beta subunit of which is identical to protein disulfide-isomerase (PDI, EC 5.3.4.1).
  • file:human/P4HA2/P4HA2-uniprot.txt
    Heterotetramer of two alpha-2 chains and two beta chains (P4HB)

References

GO_REF:0000002
Gene Ontology annotation through association of InterPro records with GO terms
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:0000107
Automatic transfer of experimentally verified manual GO annotation data to orthologs using Ensembl Compara
GO_REF:0000120
Combined Automated Annotation using Multiple IEA Methods
PMID:30021884
Histone Interaction Landscapes Visualized by Crosslinking Mass Spectrometry in Intact Cell Nuclei.
PMID:33961781
Dual proteome-scale networks reveal cell-specific remodeling of the human interactome.
PMID:35271311
OpenCell: Endogenous tagging for the cartography of human cellular organization.
PMID:40205054
Multimodal cell maps as a foundation for structural and functional genomics.
PMID:38654109
P4HA2 activates mTOR via hydroxylation and targeting P4HA2-mTOR inhibits lung adenocarcinoma cell growth.
PMID:38909089
P4HA2 hydroxylates SUFU to regulate the paracrine Hedgehog signaling and promote B-cell lymphoma progression.
PMID:38857058
P4HA2 promotes tumor progression and is transcriptionally regulated by SP1 in colorectal cancer.
PMID:41096640
Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer Progression via Both Canonical and Non-Canonical Mechanisms.
PMID:32969070
Prolyl and lysyl hydroxylases in collagen synthesis.
PMID:9211872
Cloning of the human prolyl 4-hydroxylase alpha subunit isoform alpha(II) and characterization of the type II enzyme tetramer. The alpha(I) and alpha(II) subunits do not form a mixed alpha(I)alpha(II)beta2 tetramer.
  • The human type II prolyl 4-hydroxylase is an (alpha-II)2-beta2 tetramer with P4HB/PDI as the beta subunit and catalyzes formation of 4-hydroxyproline in collagens (EC 1.14.11.2).
  • The alpha(I) and alpha(II) subunits do not co-assemble into a mixed alpha(I)alpha(II)beta2 tetramer; the type II enzyme is kinetically similar to type I except for a much higher Ki for poly(L-proline).
Reactome:R-HSA-1650808
Prolyl 4-hydroxylase converts collagen prolines to 4-hydroxyprolines
Reactome:R-HSA-9918779
Proline hydroxylases hydroxylate Polyprotein
file:human/P4HA2/P4HA2-uniprot.txt
UniProt entry O15460 (P4HA2_HUMAN), Prolyl 4-hydroxylase subunit alpha-2
  • ER-lumenal 2-oxoglutarate/Fe(II)-dependent dioxygenase (EC 1.14.11.2) that 4-hydroxylates collagen prolines; alpha2-beta2 heterotetramer with P4HB; binds Fe(2+) and L-ascorbate; variants cause high myopia (MYP25).

Suggested Questions for Experts

Q: Do the type I (P4HA1) and type II (P4HA2) collagen prolyl 4-hydroxylases have distinct procollagen substrate or tissue preferences that explain why P4HA2 deficiency manifests primarily as scleral/ocular (high myopia) rather than systemic connective-tissue disease?

Q: Does the high-throughput KIF7 interaction reflect a genuine extra-catalytic role for P4HA2, or is it an incidental interactome capture?

Suggested Experiments

Experiment: Reconstitute the recombinant (alpha-II)2-beta2 tetramer and measure steady-state kinetics on defined procollagen peptide substrates, comparing P4HA2 with P4HA1 to define isoenzyme-specific substrate preferences.

Experiment: Knock out or knock down P4HA2 in scleral fibroblasts and quantify collagen 4-hydroxyproline content, triple-helix thermal stability and ECM deposition to test the mechanistic link to high myopia.

Experiment: Express the MYP25 variants (e.g. E291K) and assay protein abundance, tetramer assembly with P4HB, and residual dioxygenase activity to clarify the loss-of-function mechanism.

Deep Research

Falcon

(P4HA2-deep-research-falcon.md)
Research Report: Human **P4HA2** (UniProt O15460) β€” Functional Annotation, Biology, and Translational Relevance Falcon Edison Scientific Literature 33 citations 3 artifacts 2026-06-12T04:20:04.196831
Edison artifact artifact-00 (text/markdown)
Edison artifact artifact-01 (text/markdown)
## Context ID: pqac-00000012 Figure 1 provides a comprehensive schematic of the collagen prolyl 4-hydroxylase (C-P4H) complex ($\alpha_2\beta_2$). It illustrate (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 P4HA2 (UniProt O15460) β€” Functional Annotation, Biology, and Translational Relevance

Executive summary

P4HA2 (UniProt O15460; gene P4HA2, Homo sapiens) encodes the catalytic Ξ±-subunit of collagen prolyl 4-hydroxylase (C‑P4H), an endoplasmic reticulum (ER)–resident Ξ±2Ξ²2 heterotetramer (Ξ² subunit = P4HB/protein disulfide isomerase) that catalyzes 4‑hydroxylation of specific proline residues in procollagen -X‑Y‑Gly- repeats, a modification essential for collagen triple-helix stability and secretion. The enzyme is a Fe2+/2‑oxoglutarate/O2-dependent dioxygenase with ascorbate required to maintain catalytic Fe2+. (hironaka2025enhancedcollagenprolyl pages 1-3, hironaka2025enhancedcollagenprolyl pages 3-4, zhou2024comprehensiveanalysisrevealed pages 1-2, hironaka2025enhancedcollagenprolyl media 2f88da14)

Beyond its canonical collagen role, 2024 mechanistic studies provide strong evidence that P4HA2 can hydroxylate non-collagen substrates that modulate signaling pathways, including mTOR (Pro2341) (lung adenocarcinoma) and SUFU (Hedgehog signaling; B‑cell lymphoma), expanding the functional landscape of P4HA2 biology. (jin2024p4ha2activatesmtor pages 1-2, li2024p4ha2hydroxylatessufu pages 1-2)

1) Key concepts and definitions (current understanding)

1.1 Collagen prolyl 4-hydroxylase (C‑P4H)

C‑P4H catalyzes conversion of proline to 4‑hydroxyproline (4Hyp) primarily at the Y position of collagen -X‑Y‑Gly- repeats; this post-translational modification increases collagen triple-helix stability and supports collagen secretion and extracellular deposition. (hironaka2025enhancedcollagenprolyl pages 1-3, hironaka2025enhancedcollagenprolyl pages 3-4)

Enzyme class & cofactor chemistry. C‑P4H is a Fe2+ and 2‑oxoglutarate (α‑KG) dependent dioxygenase. The reaction consumes O2 and α‑KG and produces succinate and CO2; ascorbate is required to regenerate Fe2+ at the active site. (hironaka2025enhancedcollagenprolyl pages 3-4, hironaka2025enhancedcollagenprolyl media 2f88da14)

Complex composition and localization. C‑P4H is an Ξ±2Ξ²2 tetramer. The Ξ± subunit (P4HA1/2/3 isoforms) contains the catalytic machinery and substrate-binding features, while the Ξ² subunit is P4HB/protein disulfide isomerase (PDI); P4HB contains a KDEL ER-retention signal, retaining the holoenzyme in the ER lumen. (hironaka2025enhancedcollagenprolyl pages 1-3, zhou2024comprehensiveanalysisrevealed pages 1-2, hironaka2025enhancedcollagenprolyl media 2f88da14)

Catalytic residues. A mechanistic review summarizes residues corresponding to P4HA2 active-site coordination/catalysis as His430, Asp432, His501. (hironaka2025enhancedcollagenprolyl pages 3-4)

A schematic summarizing ER localization, Ξ±2Ξ²2 assembly, and the α‑KG/O2-driven hydroxylation mechanism is provided in Figure 1 of the cited review. (hironaka2025enhancedcollagenprolyl media 2f88da14)

1.2 Substrate specificity (collagen motifs)

C‑P4H recognizes collagen motifs containing proline residues in -X‑Y‑Gly- repeats; high-affinity features include PxGP-type motifs. Isoforms show sequence preference across X‑Pro‑Gly triplets, consistent with isoenzyme-biased substrate selection rather than strict collagen-type specificity. (hironaka2025enhancedcollagenprolyl pages 14-15, hironaka2025enhancedcollagenprolyl pages 15-17, hironaka2025enhancedcollagenprolyl pages 3-4)

2) Recent developments and latest research (prioritizing 2023–2024)

2.1 Non-canonical hydroxylation targets and signaling control (2024)

mTOR activation via Pro2341 hydroxylation (Oncogene, Apr 2024). Jin et al. demonstrated that P4HA2 binds directly to mTOR and hydroxylates a highly conserved Pro2341 within the mTOR kinase domain, which activates mTOR kinase, increases phosphorylation of downstream effectors S6K (T389) and AKT (S473), and increases mTOR stability and substrate recognition. A non-hydroxylatable mutant (mTOR P2341A) reduced growth of A549 lung adenocarcinoma cells relative to mTORWT in their assays. (jin2024p4ha2activatesmtor pages 1-2)

Ciliary relocalization and SUFU hydroxylation in Hedgehog signaling (Leukemia, Jun 2024). Li et al. reported that upon Hedgehog activation, P4HA2 forms a complex with KIF7, relocates to the primary cilium tip, and hydroxylates SUFU, inhibiting SUFU function and thereby amplifying Hedgehog signaling. Genetic/functional loss of P4HA2 impeded B‑cell lymphoma progression, attributed (in part) to reduced stromal growth-factor support driven by Hedgehog signaling. (li2024p4ha2hydroxylatessufu pages 1-2)

2.2 Cancer-associated regulation of P4HA2 expression (2024)

SP1 transcriptional regulation in colorectal cancer (Cancer Biology & Therapy, Jun 2024). Dang et al. showed P4HA2 is overexpressed in CRC and promotes proliferation, migration, and EMT; importantly, they provided promoter-level evidence that SP1 binds the P4HA2 promoter (ChIP) and activates transcription (luciferase assays). (dang2024p4ha2promotestumor pages 1-3)

2.3 Tumor phenotypes linked to PI3K/AKT signaling (2024)

Multiple 2024 studies connect P4HA2 to PI3K/AKT pathway activity and EMT-like programs:

  • Head and neck squamous cell carcinoma (Medical Oncology, May 2024): P4HA2 overexpression enhanced proliferation, migration, invasion and EMT in CAL‑27 cells and increased PI3K/AKT phosphorylation; LY294002 counteracted these effects. (wu2024p4ha2contributesto pages 1-2)
  • Oral squamous cell carcinoma (Scientific Reports, Jul 2024): P4HA2 overexpression associated with decreased survival (no hazard ratio extracted in provided excerpt), and P4HA2 knockdown reduced invasion/migration/proliferation and reduced PI3K/AKT phosphorylation. (chi2024p4ha2promotesproliferation pages 1-2)

2.4 Hypoxia/ECM programs (2024)

A 2024 review of HIF control of extracellular matrix remodeling explicitly discusses P4HA2 (with P4HA1) as part of hypoxia-regulated collagen hydroxylation machinery, placing P4HA2 in the broader HIF–ECM remodeling axis that is frequently activated in tumors and fibrotic contexts. (hironaka2025enhancedcollagenprolyl pages 15-17)

A compact summary of these 2023–2024 developments and what was shown experimentally is provided in the table below.

Publication date System/disease context Main finding about P4HA2 Methods/evidence type Quantitative details available URL/DOI PaperQA citation ID
Jun 2024 Colorectal cancer (CRC) P4HA2 is overexpressed in CRC, promotes proliferation, migration, and EMT, and is transcriptionally activated by SP1 binding to the P4HA2 promoter (dang2024p4ha2promotestumor pages 1-3) TCGA expression analysis; western blot on paired tumors; tissue microarray; ChIP; luciferase assays; in vitro and in vivo functional assays (dang2024p4ha2promotestumor pages 1-3) 18 paired tumor/normal specimens by western blot; tissue microarray of 349 CRC cases; no HR reported in gathered evidence (dang2024p4ha2promotestumor pages 1-3) https://doi.org/10.1080/15384047.2024.2361594 (dang2024p4ha2promotestumor pages 1-3)
Apr 2024 Lung adenocarcinoma P4HA2 directly binds mTOR and hydroxylates conserved mTOR Pro2341, increasing mTOR stability, substrate recognition, and kinase signaling to S6K and AKT; targeting the P4HA2-mTOR axis suppresses growth (jin2024p4ha2activatesmtor pages 1-2) Mechanistic biochemistry; proteomic IP; GST pull-down; mutant analysis; cell growth assays; combination pharmacology (jin2024p4ha2activatesmtor pages 1-2) mTOR residue P2341 identified as hydroxylation site; P4HA2 found among 634 potential mTOR-interacting proteins; mTORP2341A reduced A549 growth; no clinical HR in gathered evidence (jin2024p4ha2activatesmtor pages 1-2) https://doi.org/10.1038/s41388-024-03032-1 (jin2024p4ha2activatesmtor pages 1-2)
Jun 2024 B-cell lymphoma / stromal Hedgehog signaling P4HA2 forms a complex with KIF7, relocalizes to the primary cilium tip after Hedgehog activation, hydroxylates SUFU, inhibits SUFU function, and amplifies paracrine Hedgehog signaling to promote lymphoma progression (li2024p4ha2hydroxylatessufu pages 1-2) Cell biology and signaling study in lymphoma/stromal context; mechanistic hydroxylation evidence (li2024p4ha2hydroxylatessufu pages 1-2) Key substrate identified as SUFU; localization shift to ciliary tip noted; no sample size or HR reported in gathered evidence (li2024p4ha2hydroxylatessufu pages 1-2) https://doi.org/10.1038/s41375-024-02313-8 (li2024p4ha2hydroxylatessufu pages 1-2)
May 2024 Head and neck squamous cell carcinoma (HNSCC) P4HA2 is upregulated in HNSCC, enhances proliferation, migration, invasion, and EMT, reduces apoptosis, and acts through PI3K/AKT signaling; LY294002 reverses these effects (wu2024p4ha2contributesto pages 1-2) Integrated bioinformatics; patient tissues; CAL-27 cell functional assays; western blot; pathway inhibition (wu2024p4ha2contributesto pages 1-2) 36 HNSCC tissues collected 2019-2021; CAL-27, FaDu, HN4, and HOK cells used; no HR reported in gathered evidence (wu2024p4ha2contributesto pages 1-2) https://doi.org/10.1007/s12032-024-02358-w (wu2024p4ha2contributesto pages 1-2)
Jul 2024 Oral squamous cell carcinoma (OSCC) P4HA2 is overexpressed in OSCC, inversely correlates with survival, and promotes invasion, migration, proliferation, and metastasis through PI3K/AKT pathway activation (chi2024p4ha2promotesproliferation pages 1-2) Multi-database expression/prognosis analysis; knockdown/overexpression models; in vitro and in vivo assays (chi2024p4ha2promotesproliferation pages 1-2) Prognosis assessed using TCGA/TIMER/UALCAN/GEPIA/KM-plotter; no numerical HR or sample size reported in gathered evidence (chi2024p4ha2promotesproliferation pages 1-2) https://doi.org/10.1038/s41598-024-64264-5 (chi2024p4ha2promotesproliferation pages 1-2)
May 2024 Head and neck cancer biomarker analysis Family-level analysis found P4HA2 (with P4HA1) associated with tumor stage, prognosis, and immune infiltration in HNSC; supports P4HA2 as biomarker candidate (zhou2024comprehensiveanalysisrevealed pages 1-2) Multi-database transcriptomic and survival/immunology analysis; biomarker study (zhou2024comprehensiveanalysisrevealed pages 1-2) Reports significant overexpression of P4H1-3 in HNSC but no HR or cohort size captured in gathered evidence (zhou2024comprehensiveanalysisrevealed pages 1-2) https://doi.org/10.1038/s41598-024-62678-9 (zhou2024comprehensiveanalysisrevealed pages 1-2)
Mar 2024 Osteosarcoma biomarker analysis P4HA2 is elevated in osteosarcoma, associated with poorer overall survival, retained independent prognostic value, and linked by GSEA to MAPK, NK-cell cytotoxicity, and T-cell receptor pathways (chen2024genomicnursingscience pages 1-2) GEO-based transcriptomics; PCR validation; prognostic modeling; Cox regression; GSEA; HPA interrogation (chen2024genomicnursingscience pages 1-2) GEO datasets GSE16088 and GSE73166 used; independent prognostic value reported but no HR captured in gathered evidence (chen2024genomicnursingscience pages 1-2) https://doi.org/10.1016/j.heliyon.2024.e27191 (chen2024genomicnursingscience pages 1-2)
Jan 2024 Hypoxia-ECM review Review places P4HA2 in hypoxia-regulated ECM remodeling, noting P4HA1 and P4HA2 as genes encoding prolyl 4-hydroxylase alpha subunits involved in collagen hydroxylation under hypoxic control (hironaka2025enhancedcollagenprolyl pages 15-17) Narrative review of HIF-dependent extracellular-matrix regulation (hironaka2025enhancedcollagenprolyl pages 15-17) No original cohort size; provides pathway-level context rather than new quantitative P4HA2 statistics (hironaka2025enhancedcollagenprolyl pages 15-17) https://doi.org/10.32604/biocell.2024.048873 (hironaka2025enhancedcollagenprolyl pages 15-17)

Table: This table summarizes key 2023-2024 developments for human P4HA2, emphasizing mechanistic discoveries, cancer-related functions, and biomarker evidence. It is useful for quickly comparing where P4HA2 acts, what was shown experimentally, and what quantitative details are currently available.

3) Current applications and real-world implementations

3.1 Biomarker use (primarily translational research)

Recent studies support P4HA2 as a candidate biomarker for tumor aggressiveness and prognosis:

  • CRC: Elevated P4HA2 protein in a tissue microarray of 349 cases and elevated expression in tumors vs adjacent tissues; associated with worse prognosis in the study narrative. (dang2024p4ha2promotestumor pages 1-3)
  • HNSCC: Clinical tissue cohort of 36 samples plus in vitro manipulation supporting association with aggressiveness and prognosis. (wu2024p4ha2contributesto pages 1-2)
  • Head and neck cancer computational biomarker analysis (Scientific Reports, May 2024): P4HA2 associated with stage/prognosis/immune infiltration in multi-database analyses. (zhou2024comprehensiveanalysisrevealed pages 1-2)
  • Osteosarcoma biomarker modeling (Heliyon, Mar 2024): P4HA2 elevated and reported as an independent prognostic factor in Cox regression models (numerical HR not extracted in the provided excerpt). (chen2024genomicnursingscience pages 1-2)

3.2 Clinical-trial implementation: P4HA2 as a measured hypoxia marker

A completed randomized phase II cervical cancer trial (NCT04275713, β€œMETOXY‑LACC”) includes P4HA2 in a 6‑gene RNA‑seq hypoxia signature endpoint used to measure metformin-dependent changes in tumor hypoxia-related gene expression. This is an example of P4HA2 being implemented as part of a translational hypoxia readout, not a direct therapeutic target. (NCT04275713 chunk 1)

3.3 Therapeutic concept: targeting P4HA2-dependent signaling axes

Jin et al. provide a concrete therapeutic concept in lung adenocarcinoma: targeting the P4HA2–mTOR axis suppressed tumor cell growth in their models, and they observed synergy between P4HA2 knockdown and the mTOR kinase inhibitor AZD‑8055 in growth assays. (jin2024p4ha2activatesmtor pages 1-2)

4) Expert opinions and analysis from authoritative sources

4.1 Collagen hydroxylases as drug targets (state of the field)

A highly cited 2021 review of collagen prolyl/lysyl hydroxylases notes that while many competitive inhibitors of collagen P4Hs have been described, β€œNo collagen hydroxylase inhibitor is in clinical use”; by contrast, HIF prolyl hydroxylase (PHD) inhibitors (a distinct enzyme family) are in clinical trials/clinical use contexts (e.g., anemia). This underscores a key translational gap for direct C‑P4H/P4HA2 inhibitors. (salo2021prolylandlysyl pages 4-7)

4.2 Mechanistic consensus on localization and enzymology

Family-level mechanistic summaries emphasize that C‑P4H is an ER-resident Ξ±2Ξ²2 enzyme using Fe2+/α‑KG/O2 chemistry coupled to proline hydroxylation, with P4HB/PDI serving as the Ξ² subunit and contributing ER retention via KDEL. This consensus supports interpreting many P4HA2 disease phenotypes through altered collagen maturation and secretion. (hironaka2025enhancedcollagenprolyl pages 1-3, hironaka2025enhancedcollagenprolyl pages 3-4, zhou2024comprehensiveanalysisrevealed pages 1-2, hironaka2025enhancedcollagenprolyl media 2f88da14)

4.3 Interpreting new non-canonical substrate reports

The 2024 studies identifying mTOR and SUFU as hydroxylation targets imply that P4HA2 can influence cancer phenotypes by mechanisms not reducible to collagen deposition alone (i.e., direct control of signaling protein stability/activity). These findings broaden the working definition of P4HA2 biology from an ER collagen enzyme to a context-dependent prolyl hydroxylase that can also modulate signaling pathways. (jin2024p4ha2activatesmtor pages 1-2, li2024p4ha2hydroxylatessufu pages 1-2)

5) Relevant statistics and data (from the retrieved evidence)

  • CRC clinical/proteomics scale: CRC study included 18 paired tumor/normal specimens (western blot) and a 349-case tissue microarray showing higher tumor P4HA2 staining/expression. (dang2024p4ha2promotestumor pages 1-3)
  • HNSCC cohort size: 36 patient tumor tissues were collected in the HNSCC study (2019–2021). (wu2024p4ha2contributesto pages 1-2)
  • mTOR interaction screen size and hydroxylation site: P4HA2 identified among 634 candidate mTOR interactors; hydroxylation mapped to mTOR Pro2341; growth reduction reported for mTORP2341A vs mTORWT in A549 assays. (jin2024p4ha2activatesmtor pages 1-2)

Limitations: Several 2024 biomarker papers in the retrieved excerpts describe survival associations without providing the numerical hazard ratios/CI in the extracted text; therefore HR values are not reported here. (chen2024genomicnursingscience pages 1-2, zhou2024comprehensiveanalysisrevealed pages 1-2, wu2024p4ha2contributesto pages 1-2, chi2024p4ha2promotesproliferation pages 1-2)

Functional annotation summary table

The following table consolidates the evidence-backed functional annotation of P4HA2, including canonical enzymology, localization/complex assembly, and validated non-collagen substrates.

Feature Evidence/notes Key citations (title, year, DOI URL) PaperQA citation IDs
Verified target identity Human P4HA2 corresponds to UniProt O15460, encoding the prolyl 4-hydroxylase subunit alpha-2 alpha isoform of collagen prolyl 4-hydroxylase; belongs to the Ξ±-ketoglutarate-dependent dioxygenase family. Family-level reviews explicitly describe P4HA2 as one of the three mammalian catalytic Ξ± subunits of C-P4H. Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer Progression via Both Canonical and Non-Canonical Mechanisms (2025), https://doi.org/10.3390/ijms26199371; Comprehensive analysis revealed P4Hs as new biomarkers for prognosis and immunotherapy in head and neck cancer (2024), https://doi.org/10.1038/s41598-024-62678-9 (hironaka2025enhancedcollagenprolyl pages 1-3, zhou2024comprehensiveanalysisrevealed pages 1-2)
Enzyme class Collagen prolyl 4-hydroxylase (C-P4H) is a Fe2+/2-oxoglutarate-dependent dioxygenase that performs prolyl 4-hydroxylation during collagen biosynthesis. Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer Progression via Both Canonical and Non-Canonical Mechanisms (2025), https://doi.org/10.3390/ijms26199371 (hironaka2025enhancedcollagenprolyl pages 3-4)
Canonical reaction catalyzed C-P4H hydroxylates proline to 4-hydroxyproline at the Y position of collagen -X-Y-Gly- repeats; this modification is required for collagen triple-helix stability and efficient secretion. Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer Progression via Both Canonical and Non-Canonical Mechanisms (2025), https://doi.org/10.3390/ijms26199371; Prolyl-4-hydroxylase Ξ± subunit 2 promotes breast cancer progression and metastasis by regulating collagen deposition (2014), https://doi.org/10.1186/1471-2407-14-1 (hironaka2025enhancedcollagenprolyl pages 1-3, hironaka2025enhancedcollagenprolyl pages 3-4)
Canonical substrates/motif specificity Primary substrates are procollagen/collagen sequences containing -X-Pro-Gly- / -X-Y-Gly- motifs; high-affinity substrate recognition is linked to PxGP-type motifs. Family-level evidence indicates P4HA1 and P4HA2 differ in sequence preference across X-Pro-Gly triplets, supporting isoform-specific substrate bias rather than absolute collagen-type specificity. Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer Progression via Both Canonical and Non-Canonical Mechanisms (2025), https://doi.org/10.3390/ijms26199371; Comprehensive analysis of the effects of P4ha1 and P4ha2 deletion on post-translational modifications of fibrillar collagens in mouse skin (2025), https://doi.org/10.3389/fcell.2025.1527839 (hironaka2025enhancedcollagenprolyl pages 14-15, hironaka2025enhancedcollagenprolyl pages 15-17)
Required cofactors/cosubstrates Requires Fe2+, 2-oxoglutarate (Ξ±-KG), and O2; ascorbate regenerates catalytic Fe2+. Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer Progression via Both Canonical and Non-Canonical Mechanisms (2025), https://doi.org/10.3390/ijms26199371 (hironaka2025enhancedcollagenprolyl pages 3-4, hironaka2025enhancedcollagenprolyl media 2f88da14)
Reaction products Hydroxylation of proline is coupled to conversion of Ξ±-KG and O2 into succinate and CO2. Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer Progression via Both Canonical and Non-Canonical Mechanisms (2025), https://doi.org/10.3390/ijms26199371 (hironaka2025enhancedcollagenprolyl pages 3-4, hironaka2025enhancedcollagenprolyl media 2f88da14)
Key catalytic residues Family-level structural evidence identifies catalytic metal/cofactor-binding residues corresponding to P4HA2 as His430, Asp432, His501. Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer Progression via Both Canonical and Non-Canonical Mechanisms (2025), https://doi.org/10.3390/ijms26199371 (hironaka2025enhancedcollagenprolyl pages 3-4)
Cellular localization P4HA2 functions in the endoplasmic reticulum lumen; the C-P4H holoenzyme is ER-localized and retained there via the P4HB/PDI KDEL sequence. Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer Progression via Both Canonical and Non-Canonical Mechanisms (2025), https://doi.org/10.3390/ijms26199371; Comprehensive analysis revealed P4Hs as new biomarkers for prognosis and immunotherapy in head and neck cancer (2024), https://doi.org/10.1038/s41598-024-62678-9 (hironaka2025enhancedcollagenprolyl pages 1-3, zhou2024comprehensiveanalysisrevealed pages 1-2, hironaka2025enhancedcollagenprolyl media 2f88da14)
Complex composition Active collagen prolyl 4-hydroxylase is an Ξ±2Ξ²2 heterotetramer; P4HA2 provides the catalytic Ξ± subunit and P4HB/PDI provides the Ξ² subunit. Evidence cited in reviews indicates isoforms assemble as specific Ξ±2Ξ²2 complexes rather than mixed P4HA1/P4HA2 tetramers. Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer Progression via Both Canonical and Non-Canonical Mechanisms (2025), https://doi.org/10.3390/ijms26199371; Comprehensive analysis revealed P4Hs as new biomarkers for prognosis and immunotherapy in head and neck cancer (2024), https://doi.org/10.1038/s41598-024-62678-9 (hironaka2025enhancedcollagenprolyl pages 14-15, hironaka2025enhancedcollagenprolyl pages 15-17, hironaka2025enhancedcollagenprolyl pages 1-3, zhou2024comprehensiveanalysisrevealed pages 1-2, hironaka2025enhancedcollagenprolyl media 2f88da14)
Structural/functional role in collagen biosynthesis Hydroxylation by P4HA2 stabilizes newly synthesized collagen, enabling proper triple-helix formation, secretion, and extracellular collagen deposition; loss or inhibition reduces collagen deposition in tumor models. Prolyl-4-hydroxylase Ξ± subunit 2 promotes breast cancer progression and metastasis by regulating collagen deposition (2014), https://doi.org/10.1186/1471-2407-14-1; Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer Progression via Both Canonical and Non-Canonical Mechanisms (2025), https://doi.org/10.3390/ijms26199371 (hironaka2025enhancedcollagenprolyl pages 1-3, hironaka2025enhancedcollagenprolyl pages 3-4)
Non-canonical substrate: mTOR A 2024 mechanistic study showed P4HA2 directly binds mTOR and hydroxylates Pro2341, increasing mTOR stability, substrate recognition, and downstream signaling (S6K, AKT). This supports a non-collagen signaling role for P4HA2. P4HA2 activates mTOR via hydroxylation and targeting P4HA2-mTOR inhibits lung adenocarcinoma cell growth (2024), https://doi.org/10.1038/s41388-024-03032-1 (jin2024p4ha2activatesmtor pages 1-2)
Non-canonical substrate: SUFU A 2024 study in B-cell lymphoma reported that P4HA2 relocates with KIF7 to the ciliary tip after Hedgehog activation and hydroxylates SUFU, inhibiting SUFU and amplifying paracrine Hedgehog signaling. P4HA2 hydroxylates SUFU to regulate the paracrine Hedgehog signaling and promote B-cell lymphoma progression (2024), https://doi.org/10.1038/s41375-024-02313-8 (li2024p4ha2hydroxylatessufu pages 1-2)
Regulation by hypoxia/HIF Reviews and recent analyses place P4HA2 within hypoxia-responsive ECM remodeling programs; hypoxia/HIF signaling upregulates collagen hydroxylation machinery, and P4HA2 is repeatedly linked to hypoxic tumor phenotypes. HIFs in hypoxic regulation of the extracellular matrix: focus on little-known player HIF-3 (2024), https://doi.org/10.32604/biocell.2024.048873; Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer Progression via Both Canonical and Non-Canonical Mechanisms (2025), https://doi.org/10.3390/ijms26199371 (hironaka2025enhancedcollagenprolyl pages 15-17, hironaka2025enhancedcollagenprolyl pages 14-15)
Regulation by SP1 In colorectal cancer, SP1 binds the P4HA2 promoter and transcriptionally activates P4HA2, providing direct promoter-level regulatory evidence. P4ha2 promotes tumor progression and is transcriptionally regulated by SP1 in colorectal cancer (2024), https://doi.org/10.1080/15384047.2024.2361594 (dang2024p4ha2promotestumor pages 1-3)
Disease/implementation note: biomarker and target Recent studies consistently report P4HA2 overexpression in multiple cancers and association with worse prognosis, EMT, PI3K/AKT or mTOR pathway activation, and collagen-rich tumor microenvironments; experimental inhibition or knockdown suppresses tumor phenotypes. P4ha2 promotes tumor progression and is transcriptionally regulated by SP1 in colorectal cancer (2024), https://doi.org/10.1080/15384047.2024.2361594; P4HA2 promotes proliferation, invasion, and metastasis through regulation of the PI3K/AKT signaling pathway in oral squamous cell carcinoma (2024), https://doi.org/10.1038/s41598-024-64264-5; P4ha2 contributes to head and neck squamous cell carcinoma progression and EMT through PI3K/AKT signaling pathway (2024), https://doi.org/10.1007/s12032-024-02358-w; P4HA2 activates mTOR via hydroxylation and targeting P4HA2-mTOR inhibits lung adenocarcinoma cell growth (2024), https://doi.org/10.1038/s41388-024-03032-1 (dang2024p4ha2promotestumor pages 1-3, wu2024p4ha2contributesto pages 1-2, chi2024p4ha2promotesproliferation pages 1-2, jin2024p4ha2activatesmtor pages 1-2)

Table: This table summarizes evidence-supported functional annotation for human P4HA2 (UniProt O15460), including its canonical collagen-prolyl hydroxylase role, cofactors, localization, complex assembly, catalytic features, and newer non-canonical substrates. It is useful as a compact reference linking each annotation item to specific literature and PaperQA citation IDs.

Disease associations from curated genetics/target–disease evidence

Open Targets lists disease–target association evidence connecting P4HA2 (ENSG00000072682) with multiple traits/diseases, including myopia (and autosomal dominant myopia 25), asthma, dengue disease, and inflammatory bowel disease, with supporting PubMed identifiers included in that resource’s evidence list. (OpenTargets Search: -P4HA2)

Concluding perspective

The strongest, best-supported primary molecular function of human P4HA2 (O15460) is as the catalytic Ξ±-subunit of the ER-localized C‑P4H complex that hydroxylates procollagen prolines using Fe2+/α‑KG/O2 chemistry, thereby enabling collagen maturation and secretion. (hironaka2025enhancedcollagenprolyl pages 1-3, hironaka2025enhancedcollagenprolyl pages 3-4, zhou2024comprehensiveanalysisrevealed pages 1-2, hironaka2025enhancedcollagenprolyl media 2f88da14)

The most consequential 2024 shift in the research landscape is the appearance of high-confidence mechanistic studies showing direct hydroxylation of signaling proteins (mTOR, SUFU), suggesting P4HA2 can couple oxygen/α‑KG-dependent chemistry to oncogenic signaling beyond collagen biology. This creates new opportunitiesβ€”and challengesβ€”for therapeutic targeting, particularly given authoritative assessments that collagen hydroxylase inhibitors are not yet in clinical use. (jin2024p4ha2activatesmtor pages 1-2, li2024p4ha2hydroxylatessufu pages 1-2, salo2021prolylandlysyl pages 4-7)

References

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  9. (dang2024p4ha2promotestumor pages 1-3): Xuening Dang, Xiaojian Chen, Zhonglin Liang, Zhujiang Dai, Wenjun Ding, Jinglue Song, and Jihong Fu. P4ha2 promotes tumor progression and is transcriptionally regulated by sp1 in colorectal cancer. Cancer Biology & Therapy, Jun 2024. URL: https://doi.org/10.1080/15384047.2024.2361594, doi:10.1080/15384047.2024.2361594. This article has 13 citations and is from a peer-reviewed journal.

  10. (wu2024p4ha2contributesto pages 1-2): Yan-Ling Wu, Wan Liu, Tingting Zhao, and Jing Jin. P4ha2 contributes to head and neck squamous cell carcinoma progression and emt through pi3k/akt signaling pathway. Medical Oncology (Northwood, London, England), May 2024. URL: https://doi.org/10.1007/s12032-024-02358-w, doi:10.1007/s12032-024-02358-w. This article has 4 citations.

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Artifacts

Citations

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πŸ“š Additional Documentation

Notes

(P4HA2-notes.md)

P4HA2 (Prolyl 4-hydroxylase subunit alpha-2) β€” review notes

UniProt: O15460 (P4HA2_HUMAN), 535 aa precursor (signal 1-21), HGNC:8547, gene on chr5.
EC 1.14.11.2. MANE-select isoform IIa (O15460-2); displayed isoform IIb (O15460-1).

Core function

P4HA2 is one of three catalytic alpha-subunit isoforms (P4HA1/2/3) of collagen prolyl
4-hydroxylase. The active enzyme is an alpha2-beta2 heterotetramer in which the beta
subunit is P4HB (protein disulfide isomerase, PDI), which acts as a structural/retention
subunit. The enzyme resides in the ER lumen and catalyzes formation of trans-4-
hydroxy-L-proline at the Y position of -Xaa-Pro-Gly- repeats in procollagen; 4-Hyp is
essential for folding and thermal stability of the collagen triple helix.

PMID:9211872

PMID:9211872

The alpha(I) and alpha(II) subunits do not form mixed alpha(I)alpha(II)beta2 tetramers
PMID:9211872. Type II enzyme is kinetically very similar to type I, differing mainly in Ki for poly(L-proline)
PMID:9211872.

Catalysis / cofactors (UniProt O15460)

  • Catalytic reaction: L-prolyl-[collagen] + 2-oxoglutarate + O2 = trans-4-hydroxy-L-prolyl-[collagen] + succinate + CO2 (RHEA:18945; EC 1.14.11.2). It is a 2-oxoglutarate/Fe(II)-dependent dioxygenase.
  • COFACTOR Fe(2+): "Binds 1 Fe(2+) ion per subunit." Fe-binding residues 430, 432, 501; 2-oxoglutarate binding residue 511; Fe2OG dioxygenase domain 412-520.
  • COFACTOR L-ascorbate (vitamin C; required to re-reduce Fe after uncoupled cycles).
  • KM = 22 uM for 2-oxoglutarate PMID:9211872.
  • Domains: N-terminal P4Ha_N (peptide-substrate binding), TPR repeats (~207-240; involved in tetramer assembly / substrate binding), C-terminal Fe2OG catalytic domain.

Localization

UniProt: SUBCELLULAR LOCATION = Endoplasmic reticulum lumen. HPA IDA = endoplasmic reticulum
(GO:0005783). Reactome places it in ER lumen (collagen biosynthesis). All consistent.

Subunit / interactions

  • P4HB (P07237): bona fide beta subunit of the active tetramer β€” biologically meaningful interaction (the alpha2beta2 enzyme). PMID:9211872
  • P4HA1 (P13674): the alpha(I) catalytic isoform; co-purification/IntAct capture. Note alpha(I) and alpha(II) do NOT co-assemble into mixed tetramers, so this is not a functional heterotetramer.
  • KIF7 (Q2M1P5): kinesin; captured in high-throughput interactome screens, not an obvious ER-lumenal partner.
  • The 4 IPI "protein binding" GOA annotations come from large-scale proteomics/interactome
    screens (PMID:30021884 histone XL-MS; PMID:33961781 BioPlex; PMID:35271311 OpenCell;
    PMID:40205054 multimodal cell maps) and are bare GO:0005515 β€” uninformative for MF.

Disease

Autosomal-dominant nonsyndromic high myopia (MYP25, MIM:617238); variants Q140R, I150V,
E291K (E291K decreases protein abundance) [UniProt DISEASE; PMID:25741866 (not in cited set)].
Connective-tissue/collagen role in scleral ECM is the likely mechanistic link.

Annotation review summary

  • procollagen-proline 4-dioxygenase activity (GO:0004656): ACCEPT, core MF (IDA PMID:9211872,
    plus IBA/IEA/TAS duplicates).
  • procollagen-proline 4-dioxygenase complex (GO:0016222): ACCEPT, core CC (alpha2beta2 with P4HB).
  • iron ion binding (GO:0005506), L-ascorbic acid binding (GO:0031418),
    oxidoreductase ... molecular oxygen (GO:0016705): ACCEPT β€” cofactor/MF, all directly
    supported by UniProt cofactor + catalytic-residue annotations.
  • ER (GO:0005783), ER lumen (GO:0005788): ACCEPT.
  • electron transfer activity (GO:0009055), TAS PMID:9211872: this is a misleading MF for a
    2-OG dioxygenase. The enzyme does not function as an electron carrier; "electron transfer"
    here is an over-interpretation of the redox chemistry. MARK_AS_OVER_ANNOTATED.
  • protein binding (GO:0005515) x4 IPI: KEEP_AS_NON_CORE (bare term; P4HB interaction is real
    and meaningful but captured only as uninformative protein binding here).

Falcon deep-research findings (incorporated 2026-06)

  • The two non-canonical (non-collagen) substrate mechanisms are already captured in the review:
    P4HA2 binds mTOR and hydroxylates conserved Pro2341 to activate mTOR kinase (PMID:38654109, Jin
    2024, Oncogene; DOI 10.1038/s41388-024-03032-1), and P4HA2 hydroxylates SUFU at the ciliary tip in
    complex with KIF7 to amplify Hedgehog signaling (PMID:38909089, Li 2024, Leukemia;
    DOI 10.1038/s41375-024-02313-8). Falcon corroborates both; PMIDs re-verified against PubMed.
  • NEW: SP1 transcriptionally activates P4HA2 in colorectal cancer β€” SP1 binds the P4HA2 promoter (ChIP
  • luciferase), and P4HA2 drives proliferation/EMT with AGO1 as a probable downstream target.
    PMID:38857058
  • NEW (review): Hironaka & Xiong 2025 (PMID:41096640) provides an up-to-date C-P4H review covering the
    alpha2-beta2/PDI tetramer, ER localization, Fe(II)/2-OG/O2/ascorbate chemistry, and both canonical
    collagen-deposition and non-canonical (stemness, hypoxia, glucose metabolism, angiogenesis, TIL
    modulation) cancer roles. PMID:41096640
  • Falcon reiterates the isoform substrate-bias concept: P4HA1 vs P4HA2 differ in sequence preference
    across X-Pro-Gly triplets (isoenzyme-biased substrate selection rather than strict collagen-type
    specificity), consistent with the existing review's suggested_questions on isoenzyme substrate
    preference. (Review-level claim; not added as a primary reference.)
  • Several additional 2024 P4HA2 cancer papers (HNSCC PI3K/AKT β€” DOI 10.1007/s12032-024-02358-w; OSCC
    PI3K/AKT β€” DOI 10.1038/s41598-024-64264-5; pan-P4H HNC biomarker β€” DOI 10.1038/s41598-024-62678-9;
    osteosarcoma biomarker β€” DOI 10.1016/j.heliyon.2024.e27191) are correlative TCGA/cell-line biomarker
    studies. They reinforce the (non-core) "overexpressed/poor-prognosis in solid tumors via PI3K/AKT or
    EMT" theme but add little mechanistic novelty beyond Dang/Jin/Li; not added as primary references.
  • Salo & Myllyharju 2021 (already in review as PMID:32969070) is reiterated by Falcon for the field
    status that no collagen-hydroxylase inhibitor is yet in clinical use, in contrast to HIF-PHD inhibitors.

Pn Notes

(P4HA2-pn-notes.md)

P4HA2 PN Consistency Notes

  • Generated: 2026-06-18
  • Project: PROTEOSTASIS
  • Scope: PN consistency rereview against local AIGR review and available deep-research artifacts
  • UniProt: O15460
  • AIGR review status: COMPLETE
  • Review batch: proteostasis-batch-2026-06-11
  • Batch change status: added

Source Files Checked

Deep Research Files

AIGR Review Snapshot

  • Description: P4HA2 (prolyl 4-hydroxylase subunit alpha-2) is one of three catalytic alpha-subunit isoforms of collagen prolyl 4-hydroxylase (C-P4H), an endoplasmic reticulum-lumenal enzyme. The active enzyme is an alpha2-beta2 heterotetramer in which the beta subunit is P4HB (protein disulfide isomerase, PDI) acting as a structural and ER-retention subunit; the two alpha-2 chains carry the catalytic sites. As a 2-oxoglutarate- and Fe(II)-dependent dioxygenase, P4HA2 catalyzes the post-translational formation of trans-4-hydroxy-L-proline in -Xaa-Pro-Gly- sequences of procollagen (and other proteins), consuming 2-oxoglutarate and O2 and producing succinate and CO2. 4-Hydroxyproline is essential for the folding and thermal stability of the collagen triple helix. The active-site iron is coordinated by a 2-His-1-carboxylate facial triad, and L-ascorbate (vitamin C) is required as a cofactor to maintain the iron in the reduced Fe(II) state. The type II tetramer contributes a substantial fraction of total prolyl 4-hydroxylase activity in human cells, is expressed in heart, placenta, lung and pancreas, and does not co-assemble with the type I (P4HA1) alpha subunit into mixed tetramers. Variants in P4HA2 cause autosomal dominant nonsyndromic high myopia (MYP25), consistent with a role in scleral collagen and extracellular matrix.
  • Existing/core annotation action counts: ACCEPT: 14; KEEP_AS_NON_CORE: 4; MARK_AS_OVER_ANNOTATED: 1

PN Consistency Summary

  • Consistency: Consistent. Review, deep research, PN annotation, and mapping describe the type II catalytic alpha-2 subunit of C-P4H (EC 1.14.11.2), alpha2-beta2 with P4HB, ER-lumenal; collagen 4-Hyp formation for triple-helix stability. PN placement matches. The review additionally surfaces non-canonical substrates (mTOR Pro2341 hydroxylation PMID:38654109; SUFU PMID:38909089) flagged non-core pending confirmation β€” these do not contradict the PN canonical-collagen placement.
  • PN story / NEW pressure: PN asserts GO:0032964 as new_to_goa; P4HA2 GOA has NO BP term at all (verified via goa.tsv). The review's proposed_new_terms explicitly recommends adding GO:0019471/GO:0018401/GO:0032964. GO:0032964 and GO:0018401 verified real via OLS. Conclusion: genuine ADD, fully corroborated by the review. Defensible.
  • Evidence alignment: PN dossier mapping-only. Review core: IDA/TAS PMID:9211872 (type II tetramer characterization), authoritative review PMID:32969070. Many cancer/non-canonical-substrate refs (PMID:38654109, 38909089, 38857058, 41096640) are beyond the PN canonical-biochemistry scope β€” expected divergence. Core collagen biochemistry aligns.
  • Verdict: Consistent; PN GO:0032964 ADD genuinely new to GOA and matches the review's own proposed BP terms (BP gap real).

Full Consistency Review

  • UniProt: O15460 Β· batch: proteostasis-batch-2026-06-11 Β· review status: COMPLETE
  • PN placement: ER proteostasis | Maturation and folding of specific substrates | ER collagen processing and folding ; PN-node mapping: group=mapped, scope=ok_for_propagation_to_go, GO=GO:0032964 collagen biosynthetic process (class/branch=no_mapping). Projection goa_status=new_to_goa.
  • Consistency: Consistent. Review, deep research, PN annotation, and mapping describe the type II catalytic alpha-2 subunit of C-P4H (EC 1.14.11.2), alpha2-beta2 with P4HB, ER-lumenal; collagen 4-Hyp formation for triple-helix stability. PN placement matches. The review additionally surfaces non-canonical substrates (mTOR Pro2341 hydroxylation PMID:38654109; SUFU PMID:38909089) flagged non-core pending confirmation β€” these do not contradict the PN canonical-collagen placement.
  • PN story / NEW pressure: PN asserts GO:0032964 as new_to_goa; P4HA2 GOA has NO BP term at all (verified via goa.tsv). The review's proposed_new_terms explicitly recommends adding GO:0019471/GO:0018401/GO:0032964. GO:0032964 and GO:0018401 verified real via OLS. Conclusion: genuine ADD, fully corroborated by the review. Defensible.
  • Mapping strategy: Correct. Catalytic subunit; group-level GO:0032964 appropriate, narrower than the unmapped class node. No node change required. (Note GO:0009055 electron transfer activity in GOA was MARK_AS_OVER_ANNOTATED in the review β€” unrelated to the PN MF/BP projection.)
  • Evidence alignment: PN dossier mapping-only. Review core: IDA/TAS PMID:9211872 (type II tetramer characterization), authoritative review PMID:32969070. Many cancer/non-canonical-substrate refs (PMID:38654109, 38909089, 38857058, 41096640) are beyond the PN canonical-biochemistry scope β€” expected divergence. Core collagen biochemistry aligns.
  • Verdict: Consistent; PN GO:0032964 ADD genuinely new to GOA and matches the review's own proposed BP terms (BP gap real).

PN Dossier Context

  • review_batch: proteostasis-batch-2026-06-11
  • review_yaml: genes/human/P4HA2/P4HA2-ai-review.yaml
  • PN workbook rows: 1

PN row 1: ER proteostasis | Maturation and folding of specific substrates | ER collagen processing and folding

  • UniProt: O15460
  • In branches: ER
  • PN-node mapping records (path + ancestors):
    • [group] ER proteostasis|Maturation and folding of specific substrates|ER collagen processing and folding
      status=mapped scope=ok_for_propagation_to_go GO=[GO:0032964 collagen biosynthetic process]
      rationale: This PN group contains ER factors dedicated to collagen maturation, processing, and folding. Collagen biosynthetic process captures the shared substrate-specific pathway context.
    • [class] ER proteostasis|Maturation and folding of specific substrates
      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.
    • [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:0032964 collagen biosynthetic process | scope=ok_for_propagation_to_go | goa_status=new_to_goa | from=ER proteostasis|Maturation and folding of specific substrates|ER collagen processing and folding

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.

πŸ“„ View Raw YAML

 
id: O15460
gene_symbol: P4HA2
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: >-
  P4HA2 (prolyl 4-hydroxylase subunit alpha-2) is one of three catalytic
  alpha-subunit isoforms of collagen prolyl 4-hydroxylase (C-P4H), an
  endoplasmic reticulum-lumenal enzyme. The active enzyme is an alpha2-beta2
  heterotetramer in which the beta subunit is P4HB (protein disulfide
  isomerase, PDI) acting as a structural and ER-retention subunit; the two
  alpha-2 chains carry the catalytic sites. As a 2-oxoglutarate- and
  Fe(II)-dependent dioxygenase, P4HA2 catalyzes the post-translational
  formation of trans-4-hydroxy-L-proline in -Xaa-Pro-Gly- sequences of
  procollagen (and other proteins), consuming 2-oxoglutarate and O2 and
  producing succinate and CO2. 4-Hydroxyproline is essential for the folding
  and thermal stability of the collagen triple helix. The active-site iron is
  coordinated by a 2-His-1-carboxylate facial triad, and L-ascorbate (vitamin
  C) is required as a cofactor to maintain the iron in the reduced Fe(II)
  state. The type II tetramer contributes a substantial fraction of total
  prolyl 4-hydroxylase activity in human cells, is expressed in heart,
  placenta, lung and pancreas, and does not co-assemble with the type I
  (P4HA1) alpha subunit into mixed tetramers. Variants in P4HA2 cause autosomal
  dominant nonsyndromic high myopia (MYP25), consistent with a role in scleral
  collagen and extracellular matrix.
alternative_products:
- name: IIb
  id: O15460-1
- name: IIa
  id: O15460-2
  sequence_note: VSP_004506
existing_annotations:
- term:
    id: GO:0004656
    label: procollagen-proline 4-dioxygenase activity
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: enables
  review:
    summary: Phylogenetic inference of the core collagen prolyl 4-hydroxylase activity, conserved across the P4HA family (P4HA1/2/3 and orthologs). This is the defining molecular function of P4HA2.
    action: ACCEPT
    reason: Core molecular function; concordant with direct experimental (IDA, PMID:9211872), TAS and IEA evidence and EC 1.14.11.2.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: Catalyzes the post-translational formation of 4-hydroxyproline in -Xaa-Pro-Gly- sequences in collagens and other proteins.
- term:
    id: GO:0016222
    label: procollagen-proline 4-dioxygenase complex
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: part_of
  review:
    summary: P4HA2 is part of the prolyl 4-hydroxylase complex, the alpha2-beta2 heterotetramer formed with P4HB (PDI). Phylogenetic inference is consistent with the experimentally documented tetramer.
    action: ACCEPT
    reason: Correct complex; P4HA2 assembles with P4HB into the catalytic C-P4H heterotetramer, the cellular form of the enzyme.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: Heterotetramer of two alpha-2 chains and two beta chains (P4HB)
- term:
    id: GO:0004656
    label: procollagen-proline 4-dioxygenase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: enables
  review:
    summary: Electronic assignment of the core dioxygenase activity (RHEA:18945, EC 1.14.11.2), redundant with the experimental IDA annotation.
    action: ACCEPT
    reason: Correct core molecular function; concordant with experimental evidence.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: EC=1.14.11.2
- term:
    id: GO:0005506
    label: iron ion binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: P4HA2 binds one Fe(2+) ion per subunit via a 2-His-1-carboxylate facial triad (His430, Asp432, His501) in the Fe2OG dioxygenase domain; iron binding is essential for the dioxygenase chemistry.
    action: ACCEPT
    reason: Accurate cofactor and active-site chemistry directly supported by the UniProt cofactor line and metal-binding residues; integral to the catalytic mechanism.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: Binds 1 Fe(2+) ion per subunit.
- term:
    id: GO:0005783
    label: endoplasmic reticulum
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: located_in
  review:
    summary: Electronic assignment of ER localization, consistent with the documented ER-lumenal residence of the enzyme.
    action: ACCEPT
    reason: Correct compartment; concordant with the UniProt subcellular location and the HPA IDA ER annotation.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum lumen.'
- term:
    id: GO:0005788
    label: endoplasmic reticulum lumen
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: Subcellular-location vocabulary mapping to ER lumen, the precise compartment in which the soluble C-P4H tetramer acts on procollagen.
    action: ACCEPT
    reason: Correct and more specific than ER; matches the UniProt subcellular location.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum lumen.'
- term:
    id: GO:0016705
    label: oxidoreductase activity, acting on paired donors, with incorporation or reduction of molecular oxygen
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: General dioxygenase parent term capturing the O2-incorporating oxidoreductase chemistry of the 2-oxoglutarate/Fe(II)-dependent reaction.
    action: ACCEPT
    reason: Correct parent of the specific procollagen-proline 4-dioxygenase activity; accurately describes the enzyme oxidoreductase class.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: Reaction=L-prolyl-[collagen] + 2-oxoglutarate + O2 = trans-4-hydroxy-L-prolyl-[collagen] + succinate + CO2
- term:
    id: GO:0031418
    label: L-ascorbic acid binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: L-ascorbate (vitamin C) is a required cofactor that maintains the active-site iron in the reduced Fe(2+) state; ascorbate binding is a documented property of the enzyme.
    action: ACCEPT
    reason: Accurate cofactor binding directly supported by the UniProt cofactor line; mechanistically integral to sustained catalysis.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: Name=L-ascorbate
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:30021884
  qualifier: enables
  review:
    summary: High-throughput crosslinking mass spectrometry (histone interaction landscapes in intact nuclei) capturing P4HA2 interactions with P4HB (the beta subunit of the tetramer) and P4HA1 (the paralogous alpha isoform). The bare protein binding term is uninformative.
    action: KEEP_AS_NON_CORE
    reason: Records real IntAct captures (P4HB, P4HA1) but bare protein binding is uninformative per curation guidelines; the meaningful P4HB interaction is better represented by the complex annotation.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: 'O15460; P07237: P4HB'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:33961781
  qualifier: enables
  review:
    summary: BioPlex/dual proteome-scale interactome screen capturing P4HA2 interactions with P4HB and KIF7. Bare protein binding term is uninformative.
    action: KEEP_AS_NON_CORE
    reason: High-throughput interactome capture; P4HB is the genuine beta subunit but bare protein binding adds no functional specificity, and the KIF7 capture has no established biological meaning for an ER-lumenal enzyme.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: 'O15460; P07237: P4HB'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:35271311
  qualifier: enables
  review:
    summary: OpenCell endogenous-tagging interactome capturing a P4HA2-KIF7 (Q2M1P5) interaction. Bare protein binding term is uninformative.
    action: KEEP_AS_NON_CORE
    reason: High-throughput capture of an interaction without established functional relevance to the collagen-hydroxylation role of P4HA2; bare protein binding is uninformative.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: 'O15460; Q2M1P5: KIF7'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:40205054
  qualifier: enables
  review:
    summary: Multimodal cell-maps interactome capturing P4HA2 interactions with P4HB, P4HA1 and KIF7. Bare protein binding term is uninformative.
    action: KEEP_AS_NON_CORE
    reason: High-throughput interactome capture; the P4HB/P4HA1 captures are consistent with known biology but bare protein binding is uninformative per curation guidelines.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: 'O15460; P13674: P4HA1'
- term:
    id: GO:0016222
    label: procollagen-proline 4-dioxygenase complex
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: part_of
  review:
    summary: Ortholog-based electronic transfer of membership in the prolyl 4-hydroxylase complex, consistent with the experimentally documented alpha2-beta2 tetramer.
    action: ACCEPT
    reason: Correct complex membership; redundant with the IBA complex annotation and the UniProt subunit description.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: Heterotetramer of two alpha-2 chains and two beta chains (P4HB)
- term:
    id: GO:0005783
    label: endoplasmic reticulum
  evidence_type: IDA
  original_reference_id: GO_REF:0000052
  qualifier: located_in
  review:
    summary: Direct immunofluorescence (HPA) evidence for ER localization of P4HA2, consistent with its ER-lumenal site of action.
    action: ACCEPT
    reason: IDA-supported ER localization agrees with the UniProt subcellular location.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum lumen.'
- term:
    id: GO:0004656
    label: procollagen-proline 4-dioxygenase activity
  evidence_type: IDA
  original_reference_id: PMID:9211872
  qualifier: enables
  review:
    summary: Direct experimental characterization of the purified human type II (P4HA2) enzyme tetramer demonstrating procollagen-proline 4-dioxygenase activity. This is the core molecular function.
    action: ACCEPT
    reason: Core molecular function with direct experimental (IDA) support; the purified (alpha-II)2-beta2 tetramer hydroxylates collagen prolines.
    supported_by:
    - reference_id: PMID:9211872
      supporting_text: Prolyl 4-hydroxylase (proline hydroxylase, EC 1.14.11.2) catalyzes the formation of 4-hydroxyproline in collagens.
- term:
    id: GO:0005788
    label: endoplasmic reticulum lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-1650808
  qualifier: located_in
  review:
    summary: Reactome curation placing the prolyl 4-hydroxylase reaction in the ER lumen (collagen biosynthesis pathway).
    action: ACCEPT
    reason: Correct compartment; redundant with the UniProt subcellular location and the IEA/IDA ER annotations.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum lumen.'
- term:
    id: GO:0005788
    label: endoplasmic reticulum lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9918779
  qualifier: located_in
  review:
    summary: Reactome curation of proline hydroxylase activity in the ER lumen (here in a viral polyprotein-maturation context); the compartment assignment is correct.
    action: ACCEPT
    reason: Correct ER-lumenal compartment; redundant with stronger localization evidence.
    supported_by:
    - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum lumen.'
- term:
    id: GO:0009055
    label: electron transfer activity
  evidence_type: TAS
  original_reference_id: PMID:9211872
  qualifier: enables
  review:
    summary: P4HA2 is a 2-oxoglutarate/Fe(II)-dependent dioxygenase; although its chemistry is redox-based and ascorbate-dependent, GO:0009055 (electron transfer activity) denotes electron-carrier function in electron transport chains and is a poor fit. The cited paper characterizes the dioxygenase, not an electron-carrier activity.
    action: MARK_AS_OVER_ANNOTATED
    reason: Over-interpretation of the redox/ascorbate chemistry of the enzyme; the informative molecular function is the dioxygenase activity (GO:0004656 / GO:0016705), not electron transfer/carrier activity.
    supported_by:
    - reference_id: PMID:9211872
      supporting_text: Prolyl 4-hydroxylase (proline hydroxylase, EC 1.14.11.2) catalyzes the formation of 4-hydroxyproline in collagens.
- term:
    id: GO:0004656
    label: procollagen-proline 4-dioxygenase activity
  evidence_type: TAS
  original_reference_id: PMID:9211872
  qualifier: enables
  review:
    summary: Author-asserted procollagen-proline 4-dioxygenase activity for the type II enzyme, redundant with the IDA annotation from the same study.
    action: ACCEPT
    reason: Correct core molecular function; concordant with the experimental IDA annotation and EC 1.14.11.2.
    supported_by:
    - reference_id: PMID:9211872
      supporting_text: Prolyl 4-hydroxylase (proline hydroxylase, EC 1.14.11.2) catalyzes the formation of 4-hydroxyproline in collagens.
core_functions:
- description: Catalytic alpha subunit of collagen prolyl 4-hydroxylase that, as part of the alpha2-beta2 heterotetramer with P4HB (PDI), catalyzes 2-oxoglutarate- and Fe(II)-dependent 4-hydroxylation of proline residues in -Xaa-Pro-Gly- sequences of procollagen in the ER lumen, a modification essential for collagen triple-helix stability.
  molecular_function:
    id: GO:0004656
    label: procollagen-proline 4-dioxygenase activity
  locations:
  - id: GO:0005788
    label: endoplasmic reticulum lumen
  in_complex:
    id: GO:0016222
    label: procollagen-proline 4-dioxygenase complex
  supported_by:
  - reference_id: PMID:9211872
    supporting_text: Prolyl 4-hydroxylase (proline hydroxylase, EC 1.14.11.2) catalyzes the formation of 4-hydroxyproline in collagens. The vertebrate enzyme is an alpha2beta2 tetramer, the beta subunit of which is identical to protein disulfide-isomerase (PDI, EC 5.3.4.1).
  - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
    supporting_text: Heterotetramer of two alpha-2 chains and two beta chains (P4HB)
proposed_new_terms:
- proposed_name: peptidyl-proline 4-hydroxylation to 4-hydroxy-L-proline
  proposed_definition: The hydroxylation of peptidyl-proline to peptidyl-4-hydroxy-L-proline catalyzed by P4HA2 as part of collagen biosynthesis (corresponds to the existing term GO:0018401).
  justification: No biological-process annotation is currently present in GOA. The core activity of P4HA2 directly accomplishes peptidyl-proline 4-hydroxylation as part of collagen biosynthesis; existing terms GO:0019471 (peptidyl-proline hydroxylation), GO:0018401 (peptidyl-proline hydroxylation to 4-hydroxy-L-proline) and GO:0032964 (collagen biosynthetic process) would appropriately capture the biological process and should be added rather than newly coined.
  supported_by:
  - reference_id: file:human/P4HA2/P4HA2-uniprot.txt
    supporting_text: Catalyzes the post-translational formation of 4-hydroxyproline in -Xaa-Pro-Gly- sequences in collagens and other proteins.
references:
- id: GO_REF:0000002
  title: Gene Ontology annotation through association of InterPro records with GO terms
  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:0000107
  title: Automatic transfer of experimentally verified manual GO annotation data to orthologs using Ensembl Compara
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: PMID:30021884
  title: Histone Interaction Landscapes Visualized by Crosslinking Mass Spectrometry in Intact Cell Nuclei.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: PubMed-verified crosslinking-MS study; source of IntAct protein binding captures with P4HB and P4HA1. Not focused on P4HA2 function.
- id: PMID:33961781
  title: Dual proteome-scale networks reveal cell-specific remodeling of the human interactome.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: PubMed-verified BioPlex interactome; source of protein binding captures (P4HB, KIF7). High-throughput, not P4HA2-specific.
- id: PMID:35271311
  title: 'OpenCell: Endogenous tagging for the cartography of human cellular organization.'
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: PubMed-verified OpenCell interactome; source of the P4HA2-KIF7 protein binding capture. High-throughput, not P4HA2-specific.
- id: PMID:40205054
  title: Multimodal cell maps as a foundation for structural and functional genomics.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: PubMed-verified multimodal cell-maps interactome; source of protein binding captures (P4HB, P4HA1, KIF7). High-throughput, not P4HA2-specific.
- id: PMID:38654109
  title: P4HA2 activates mTOR via hydroxylation and targeting P4HA2-mTOR inhibits lung adenocarcinoma cell growth.
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: 'PubMed-verified (Jin et al., Oncogene 2024). Reports a non-canonical, non-collagen substrate for P4HA2: it binds mTOR directly and hydroxylates the conserved Pro2341 in the mTOR kinase domain, activating mTOR kinase, increasing mTOR stability/substrate recognition and downstream S6K/AKT signaling; a non-hydroxylatable mTOR P2341A mutant reduces lung adenocarcinoma growth. Suggests a cytoplasmic/extra-ER signaling role distinct from the canonical ER-lumenal collagen-hydroxylase function. Notable new mechanism not in the prior review; not elevated to a core annotation here pending independent confirmation.'
- id: PMID:38909089
  title: P4HA2 hydroxylates SUFU to regulate the paracrine Hedgehog signaling and promote B-cell lymphoma progression.
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: 'PubMed-verified (Li et al., Leukemia 2024). Reports a second non-canonical P4HA2 substrate: upon Hedgehog activation P4HA2 forms a complex with KIF7, relocalizes to the primary cilium tip, and hydroxylates SUFU, inhibiting SUFU and amplifying Hedgehog signaling; P4HA2 loss impedes B-cell lymphoma progression. Provides a biological rationale for the otherwise-uninformative high-throughput P4HA2-KIF7 interactome captures (PMID:33961781, PMID:35271311, PMID:40205054). New mechanism not in the prior review; non-core pending independent confirmation.'
- id: PMID:38857058
  title: P4HA2 promotes tumor progression and is transcriptionally regulated by SP1
    in colorectal cancer.
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: 'PubMed-verified (Dang et al., Cancer Biol Ther 2024; DOI 10.1080/15384047.2024.2361594).
      Provides promoter-level mechanistic evidence that the transcription factor SP1
      binds the P4HA2 promoter (ChIP) and activates its transcription in colorectal
      cancer; P4HA2 overexpression promotes proliferation and EMT, with AGO1 implicated
      as a downstream effector. Upstream transcriptional-regulation context (non-core
      for the catalytic annotation) that complements the hypoxia/HIF induction axis.'
- id: PMID:41096640
  title: Enhanced Collagen Prolyl 4-Hydroxylase Activity and Expression Promote Cancer
    Progression via Both Canonical and Non-Canonical Mechanisms.
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: 'PubMed-verified review (Hironaka & Xiong, Int J Mol Sci 2025; DOI
      10.3390/ijms26199371). Reviews C-P4H structure/function, the alpha2-beta2/PDI
      tetramer, ER localization, Fe(II)/2-oxoglutarate/O2/ascorbate chemistry, and
      both canonical (collagen deposition) and non-canonical (signaling-protein hydroxylation,
      stemness, hypoxia, metabolism) cancer mechanisms of the C-P4HA alpha subunits.
      Family-level/secondary review context corroborating the core enzymology and
      the emerging non-canonical-substrate findings (mTOR/SUFU); not primary evidence.'
- id: PMID:32969070
  title: Prolyl and lysyl hydroxylases in collagen synthesis.
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: 'PubMed-verified authoritative review (Salo & Myllyharju, Exp Dermatol 2021). Comprehensive review of collagen prolyl 4-hydroxylases (including P4HA1/2/3), 3-hydroxylases and lysyl hydroxylases, covering enzymology, the alpha2-beta2/PDI tetramer, ER localization, biological function and disease. Supports the core enzymatic/complex/localization framing of P4HA2; also notes no collagen-hydroxylase inhibitor is yet in clinical use (in contrast to HIF-PHD inhibitors).'
- id: PMID:9211872
  title: Cloning of the human prolyl 4-hydroxylase alpha subunit isoform alpha(II) and characterization of the type II enzyme tetramer. The alpha(I) and alpha(II) subunits do not form a mixed alpha(I)alpha(II)beta2 tetramer.
  findings:
  - statement: The human type II prolyl 4-hydroxylase is an (alpha-II)2-beta2 tetramer with P4HB/PDI as the beta subunit and catalyzes formation of 4-hydroxyproline in collagens (EC 1.14.11.2).
    reference_section_type: ABSTRACT
  - statement: The alpha(I) and alpha(II) subunits do not co-assemble into a mixed alpha(I)alpha(II)beta2 tetramer; the type II enzyme is kinetically similar to type I except for a much higher Ki for poly(L-proline).
    reference_section_type: ABSTRACT
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Definitive characterization of human P4HA2; establishes the catalytic activity, cofactors and the alpha2-beta2 tetramer with P4HB. Anchors the IDA/TAS activity annotations.
- id: Reactome:R-HSA-1650808
  title: Prolyl 4-hydroxylase converts collagen prolines to 4-hydroxyprolines
  findings: []
- id: Reactome:R-HSA-9918779
  title: Proline hydroxylases hydroxylate Polyprotein
  findings: []
- id: file:human/P4HA2/P4HA2-uniprot.txt
  title: UniProt entry O15460 (P4HA2_HUMAN), Prolyl 4-hydroxylase subunit alpha-2
  findings:
  - statement: ER-lumenal 2-oxoglutarate/Fe(II)-dependent dioxygenase (EC 1.14.11.2) that 4-hydroxylates collagen prolines; alpha2-beta2 heterotetramer with P4HB; binds Fe(2+) and L-ascorbate; variants cause high myopia (MYP25).
    reference_section_type: OTHER
suggested_questions:
- question: Do the type I (P4HA1) and type II (P4HA2) collagen prolyl 4-hydroxylases have distinct procollagen substrate or tissue preferences that explain why P4HA2 deficiency manifests primarily as scleral/ocular (high myopia) rather than systemic connective-tissue disease?
- question: Does the high-throughput KIF7 interaction reflect a genuine extra-catalytic role for P4HA2, or is it an incidental interactome capture?
suggested_experiments:
- description: Reconstitute the recombinant (alpha-II)2-beta2 tetramer and measure steady-state kinetics on defined procollagen peptide substrates, comparing P4HA2 with P4HA1 to define isoenzyme-specific substrate preferences.
- description: Knock out or knock down P4HA2 in scleral fibroblasts and quantify collagen 4-hydroxyproline content, triple-helix thermal stability and ECM deposition to test the mechanistic link to high myopia.
- description: Express the MYP25 variants (e.g. E291K) and assay protein abundance, tetramer assembly with P4HB, and residual dioxygenase activity to clarify the loss-of-function mechanism.