Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0004656 procollagen-proline 4-dioxygenase activity	IBA GO_REF:0000033	ACCEPT	Summary: Phylogenetic (IBA) assignment of the core collagen prolyl 4-hydroxylase activity, consistent with the direct experimental EXP evidence for P4HA3 and with conserved catalytic residues across the P4HA family. Reason: This is the defining core molecular function of P4HA3; the IBA inference agrees with the experimental characterization of the recombinant alpha(III) enzyme. Supporting Evidence: PMID:14500733 led to the formation of an active enzyme that hydroxylated collagen chains and a collagen-like peptide and appeared to be an [alpha(III)]2 beta 2 tetramer
GO:0016222 procollagen-proline 4-dioxygenase complex	IBA GO_REF:0000033	ACCEPT	Summary: P4HA3 is the catalytic alpha subunit of the alpha2-beta2 collagen prolyl 4-hydroxylase tetramer, in which the beta subunit is PDI. Membership in the prolyl 4-hydroxylase complex is the correct cellular-component assignment. Reason: Directly supported; the recombinant alpha(III) assembles with PDI into an [alpha(III)]2-beta2 tetramer, i.e. the procollagen-proline 4-dioxygenase complex. Supporting Evidence: PMID:14500733 The vertebrate enzymes are alpha 2 beta 2 tetramers, the beta-subunit being identical to protein-disulfide isomerase (PDI)
GO:0004656 procollagen-proline 4-dioxygenase activity	IEA GO_REF:0000120	ACCEPT	Summary: Electronic assignment of the core dioxygenase activity from the EC/Rhea mapping (EC 1.14.11.2; RHEA:18945), redundant with the experimental and IBA evidence. Reason: Correct core molecular function; the EC/Rhea reaction matches the curated catalytic activity of P4HA3. Supporting Evidence: file:human/P4HA3/P4HA3-uniprot.txt EC=1.14.11.2 {ECO:0000269\|PubMed:14500733}
GO:0005506 iron ion binding	IEA GO_REF:0000002	ACCEPT	Summary: P4HA3 binds one Fe(2+) ion per subunit as the catalytic metal of its Fe(II)/2-oxoglutarate-dependent dioxygenase reaction; the InterPro-based electronic assignment is accurate. Reason: Iron coordination (residues 440, 442, 510) is essential for catalysis; correct cofactor molecular function supporting the core activity. Supporting Evidence: file:human/P4HA3/P4HA3-uniprot.txt Binds 1 Fe(2+) ion per subunit
GO:0005783 endoplasmic reticulum	IEA GO_REF:0000120	ACCEPT	Summary: Collagen prolyl 4-hydroxylation occurs in the ER; the electronic ER localization is consistent with the UniProt subcellular location and the secretory-pathway signal peptide. Reason: Correct compartment; the more specific ER lumen term is also annotated. Supporting Evidence: file:human/P4HA3/P4HA3-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum lumen
GO:0005788 endoplasmic reticulum lumen	IEA GO_REF:0000044	ACCEPT	Summary: The C-P4H tetramer resides and acts in the ER lumen, the site of procollagen folding; this is the precise correct compartment for P4HA3. Reason: Correct and specific subcellular location, supported by the UniProt subcellular location and Reactome curation. Supporting Evidence: file:human/P4HA3/P4HA3-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: P4HA3 is a 2-oxoglutarate/Fe(II)-dependent dioxygenase that incorporates oxygen using paired donors (prolyl substrate and 2-oxoglutarate); this is a correct parent molecular function of the specific procollagen-proline 4-dioxygenase activity. Reason: Accurate general oxidoreductase chemistry; the specific GO:0004656 captures the core function more informatively, but this parent term is not wrong. Supporting Evidence: file:human/P4HA3/P4HA3-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 of collagen prolyl 4-hydroxylases, maintaining the iron in the reduced state; the electronic assignment is accurate (KM 370 uM for L-ascorbate). Reason: Correct cofactor-binding molecular function supporting the core dioxygenase activity. Supporting Evidence: file:human/P4HA3/P4HA3-uniprot.txt Name=L-ascorbate
GO:0005515 protein binding	IPI PMID:25416956 A proteome-scale map of the human interactome network.	KEEP AS NON CORE	Summary: Bare protein binding derived from a large-scale binary (Y2H) interactome reference map. The captured partners are systematic-screen hits unrelated to the physiological PDI/collagen interactions, and the term is uninformative. Reason: Real IntAct interactome captures but uninformative bare protein binding; not the functional alpha2-beta2/PDI interaction, so not elevated to core (per curation guidance). Supporting Evidence: PMID:25416956 a systematic map of ?14,000 high-quality human binary protein-protein interactions
GO:0005515 protein binding	IPI PMID:26871637 Widespread Expansion of Protein Interaction Capabilities by ...	KEEP AS NON CORE	Summary: Bare protein binding from a high-throughput interactome screen examining alternative splicing isoform interactions; uninformative for P4HA3's catalytic function. Reason: Valid high-throughput interaction capture but uninformative bare protein binding; does not reflect the core collagen-hydroxylase function. Supporting Evidence: file:human/P4HA3/P4HA3-uniprot.txt Q7Z4N8; O43379: WDR62
GO:0005515 protein binding	IPI PMID:31515488 Extensive disruption of protein interactions by genetic vari...	KEEP AS NON CORE	Summary: Bare protein binding from a high-throughput interactome screen assaying disruption of protein interactions by genetic variants; partners are screen captures unrelated to the core enzymatic function. Reason: Real interactome capture but uninformative bare protein binding; not a core function. Supporting Evidence: file:human/P4HA3/P4HA3-uniprot.txt Q7Z4N8; P43356: MAGEA2B
GO:0005515 protein binding	IPI PMID:32296183 A reference map of the human binary protein interactome.	KEEP AS NON CORE	Summary: Bare protein binding from the HuRI binary interactome reference map; the large partner list comprises systematic Y2H captures (keratin-associated proteins, MAGE proteins, transcription factors, etc.) not relevant to collagen prolyl 4-hydroxylation. Reason: Real interactome captures but uninformative bare protein binding; per guidelines, kept non-core rather than elevated or removed. Supporting Evidence: file:human/P4HA3/P4HA3-uniprot.txt Q7Z4N8; O14964: HGS
GO:0004656 procollagen-proline 4-dioxygenase activity	EXP PMID:14500733 Identification and characterization of a third human, rat, a...	ACCEPT	Summary: Direct experimental demonstration that recombinant human alpha(III), coexpressed with PDI, forms an active enzyme that hydroxylates collagen chains and a collagen-like peptide. This is the founding biochemical characterization establishing P4HA3's core function. Reason: Core molecular function with direct experimental (EXP) support; the recombinant enzyme hydroxylated collagen substrates with catalytic properties similar to the type I/II C-P4Hs. Supporting Evidence: PMID:14500733 led to the formation of an active enzyme that hydroxylated collagen chains and a collagen-like peptide and appeared to be an [alpha(III)]2 beta 2 tetramer
GO:0005788 endoplasmic reticulum lumen	TAS Reactome:R-HSA-1650808	ACCEPT	Summary: Reactome curation of P4HA3 in the ER lumen, where the collagen prolyl 4-hydroxylase reaction occurs; consistent with the UniProt subcellular location. Reason: Correct and specific compartment; redundant with the IEA ER lumen annotation. Supporting Evidence: file:human/P4HA3/P4HA3-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum lumen
GO:0005788 endoplasmic reticulum lumen	TAS Reactome:R-HSA-9918779	ACCEPT	Summary: Reactome curation of ER-lumen localization in the context of proline hydroxylation of a (viral) polyprotein substrate; the compartment assignment for P4HA3 is correct. Reason: Correct compartment; redundant with other ER lumen annotations. Supporting Evidence: file:human/P4HA3/P4HA3-uniprot.txt SUBCELLULAR LOCATION: Endoplasmic reticulum lumen

Core Functions

Catalytic alpha subunit of collagen prolyl 4-hydroxylase that, as part of an alpha2-beta2 tetramer with PDI, hydroxylates proline residues in -X-Pro-Gly- triplets of procollagen to form trans-4-hydroxyproline, a modification required for collagen triple-helix folding and stability.

Molecular Function:

procollagen-proline 4-dioxygenase activity

Cellular Locations:

endoplasmic reticulum lumen

Supporting Evidence:

PMID:14500733
led to the formation of an active enzyme that hydroxylated collagen chains and a collagen-like peptide and appeared to be an [alpha(III)]2 beta 2 tetramer
file:human/P4HA3/P4HA3-uniprot.txt
Catalyzes the post-translational formation of 4-

Fe(II)- and 2-oxoglutarate-dependent dioxygenase that uses L-ascorbate as a cofactor and molecular oxygen as co-substrate, coupling decarboxylation of 2-oxoglutarate to hydroxylation of the prolyl substrate.

Molecular Function:

procollagen-proline 4-dioxygenase activity

Supporting Evidence:

file:human/P4HA3/P4HA3-uniprot.txt
Reaction=L-prolyl-[collagen] + 2-oxoglutarate + O2 = trans-4-hydroxy-L- prolyl-[collagen] + succinate + CO2

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:0000120

Combined Automated Annotation using Multiple IEA Methods

PMID:14500733

Identification and characterization of a third human, rat, and mouse collagen prolyl 4-hydroxylase isoenzyme.

Cloning and characterization of the third vertebrate C-P4H alpha-subunit isoform (alpha-III); recombinant human alpha(III) coexpressed with PDI forms an active [alpha(III)]2-beta2 tetramer that hydroxylates collagen chains and a collagen-like peptide.
Catalytic properties of the alpha(III) C-P4H are very similar to the type I and II C-P4Hs, with peptide-binding properties intermediate between the type I and type II enzymes; alpha(III) mRNA is expressed broadly but at much lower levels than alpha(I)/alpha(II).

PMID:25416956

A proteome-scale map of the human interactome network.

Systematic high-quality binary (Y2H) interactome map of ~14,000 human protein-protein interactions; source of P4HA3 bare protein binding (IPI) annotations.

PMID:26871637

Widespread Expansion of Protein Interaction Capabilities by Alternative Splicing.

High-throughput Y2H interactome of alternative-splice isoforms; source of P4HA3 bare protein binding (IPI) annotation.

PMID:31515488

Extensive disruption of protein interactions by genetic variants across the allele frequency spectrum in human populations.

Y2H interactome assaying perturbation of protein-protein interactions by human genetic variants; source of P4HA3 bare protein binding (IPI) annotation.

PMID:32296183

A reference map of the human binary protein interactome.

HuRI, an all-by-all reference map of ~53,000 human binary protein-protein interactions; source of the largest set of P4HA3 bare protein binding (IPI) captures.

PMID:34009234

Collagen prolyl 4-hydroxylases modify tumor progression.

PMID:36588128

P4HA3 promotes clear cell renal cell carcinoma progression via the PI3K/AKT/GSK3beta pathway.

PMID:39362976

Comprehensive analysis reveals that P4HA3 is a prognostic and diagnostic gastric cancer biomarker that can predict immunotherapy efficacy.

PMID:39394821

Collagen prolyl 4-hydroxylase subunit alpha member-induced head and neck squamous cell carcinoma aggressiveness is antagonized by LLGL2 via reduced expression of occludin.

PMID:39504328

A computational analysis of the oncogenic and anti-tumor immunity role of P4HA3 in human cancers.

Reactome:R-HSA-1650808

Prolyl 4-hydroxylase converts collagen prolines to 4-hydroxyprolines

Reactome:R-HSA-9918779

Proline hydroxylases hydroxylate Polyprotein

file:human/P4HA3/P4HA3-uniprot.txt

UniProt entry Q7Z4N8 (P4HA3_HUMAN), Prolyl 4-hydroxylase subunit alpha-3

ER-lumenal Fe(II)/2-oxoglutarate-dependent dioxygenase (EC 1.14.11.2) that forms 4-hydroxyproline in -Xaa-Pro-Gly- sequences in collagens; binds 1 Fe(2+) per subunit and requires L-ascorbate; catalytic alpha subunit of an alpha2-beta2 tetramer with PDI.

Suggested Experiments

Experiment: Reconstitute recombinant [alpha(III)]2-beta2 (P4HA3/PDI) C-P4H and measure steady-state kinetics and substrate specificity against a panel of collagen-type peptides versus the type I and type II C-P4Hs to define isoenzyme-specific substrate preferences.

Experiment: CRISPR knockout or knockdown of P4HA3 in cells with high endogenous expression (e.g. placental or vascular smooth muscle cells) followed by mass spectrometry quantification of collagen 4-hydroxyproline content to assess its non-redundant contribution to collagen hydroxylation in vivo.

Deep Research

Falcon

(P4HA3-deep-research-falcon.md)

this with annotations you find in gene/protein databases, but these can be outdated or inaccurate. Falcon Edison Scientific Literature 34 citations 2 artifacts 2026-06-12T04:31:52.086434

Edison artifact artifact-00 (text/markdown)

## Context ID: pqac-00000014 The requested visual content for P4HA3 in clear cell renal cell carcinoma (ccRCC) was found in Figures 1 and 4 of the document. 1. (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 P4HA3 (UniProt Q7Z4N8) — Functional Annotation and Translational Context

1) Target verification (critical identity checks)

The queried target P4HA3 corresponds to human prolyl 4-hydroxylase subunit alpha-3 (UniProt Q7Z4N8), i.e., the α(III) catalytic subunit of collagen prolyl 4-hydroxylase (C-P4H) isoenzyme III. Across authoritative reviews and mechanistic descriptions, P4HA3 is consistently described as encoding one of three vertebrate catalytic α subunits (α(I)/α(II)/α(III) encoded by P4HA1/P4HA2/P4HA3) that assemble into isoenzyme-specific collagen P4H tetramers, matching the UniProt-provided description (EC 1.14.11.2) and human organism context. (pasanen2011prolyl3hydroxylasesand pages 28-31, gjaltema2017molecularinsightsinto pages 3-4, salo2021prolylandlysyl pages 4-7)

2) Key concepts and definitions (current understanding)

2.1 What P4HA3 is (molecular identity)

Collagen prolyl 4-hydroxylase (C-P4H) is the central intracellular enzyme system responsible for proline 4-hydroxylation during procollagen biosynthesis. C-P4H exists as an α2β2 tetramer, in which the α subunit is catalytic and the β subunit is P4HB/protein disulfide isomerase (PDI), providing chaperone/assembly functions and ER retention. P4HA3 provides the catalytic α(III) chain for C-P4H isoenzyme III, expected to form the homotetramer [α(III)]2β2 rather than mixed-α tetramers. (pasanen2011prolyl3hydroxylasesand pages 28-31, gjaltema2017molecularinsightsinto pages 3-4, salo2021prolylandlysyl pages 4-7)

2.2 Enzymatic reaction and substrate specificity

C-P4Hs catalyze hydroxylation of proline to 4-hydroxyproline (4Hyp) in nascent collagen chains. The minimum sequence requirement is typically described as -X–Pro–Gly-, and hydroxylation occurs at the Y-position of Gly–X–Y collagen triplets. Importantly, C-P4H acts on unfolded procollagen α-chains; once the triple helix forms, proline residues are no longer substrates for C-P4H. (gjaltema2017molecularinsightsinto pages 3-4, pasanen2011prolyl3hydroxylasesand pages 31-34, gjaltema2017molecularinsightsinto pages 4-5)

While the family-level motif dependence is well established, P4HA3-specific substrate preferences and kinetics remain less well defined than for the more abundant isoforms in many cell types, and multiple reviews explicitly emphasize that isoform-specific collagen/peptide affinities remain unclear. (gjaltema2017molecularinsightsinto pages 3-4, gjaltema2017molecularinsightsinto pages 4-5)

2.3 Cofactors, cosubstrates, and byproducts

C-P4Hs are 2-oxoglutarate (2-OG/α-KG)-dependent dioxygenases. The hydroxylation reaction requires Fe2+, 2-oxoglutarate, molecular oxygen (O2), and ascorbate. During catalysis, 2-OG is oxidatively decarboxylated to succinate + CO2, with one oxygen atom incorporated into succinate and one into the hydroxylated proline product. (pasanen2011prolyl3hydroxylasesand pages 31-34, salo2021prolylandlysyl pages 4-7)

2.4 Subcellular localization and complex context

Collagen P4Hs are localized to the lumen of the rough endoplasmic reticulum (ER), consistent with their role in modifying secreted collagens before secretion. ER localization/retention is enforced in part by the β subunit P4HB/PDI, which contains an ER retention signal (KDEL) and also prevents aggregation/misfolding of α subunits during assembly. This is the expected compartment for P4HA3-containing C-P4H isoenzyme III activity. (pasanen2011prolyl3hydroxylasesand pages 28-31, gjaltema2017molecularinsightsinto pages 3-4, salo2021prolylandlysyl pages 4-7)

3) Biological roles and pathway placement

3.1 Core biological function: enabling collagen maturation and ECM assembly

Prolyl 4-hydroxylation is a key determinant of collagen triple-helix stability and supports downstream secretion and extracellular matrix (ECM) deposition. Consequently, P4HA3 function is positioned upstream of numerous ECM-dependent processes (tissue architecture, mechanical properties, matrix–cell interactions). (gjaltema2017molecularinsightsinto pages 3-4, salo2021prolylandlysyl pages 4-7)

3.2 Tissue/isoform context

Reviews summarize that P4HA1 is broadly expressed, P4HA2 is enriched in specific cell types (e.g., cartilage-associated), and P4HA3 mRNA is detectable in many tissues but often at relatively low levels. This matters for functional annotation: while the catalytic chemistry is conserved, the dominant isoenzyme contributing to collagen hydroxylation may vary by tissue state, development, or disease contexts. (pasanen2011prolyl3hydroxylasesand pages 31-34, gjaltema2017molecularinsightsinto pages 4-5)

4) Recent developments (2023–2024 emphasis)

4.1 Clear cell renal cell carcinoma (ccRCC) — clinical association + functional perturbation

A 2023 study in ccRCC reported that P4HA3 is significantly upregulated in tumors compared to normal tissue in TCGA KIRC (reported 539 tumors and 72 adjacent non-tumor samples) and that high P4HA3 expression is associated with poorer overall survival; the Kaplan–Meier analysis reports HR = 1.52, P = 0.007. Functional assays showed that P4HA3 knockdown inhibited ccRCC cell proliferation (EdU), migration (wound healing), and migration/invasion (transwell), and the authors implicated EMT and PI3K/AKT/GSK3β pathway involvement by enrichment analysis and western blot readouts. (zhang2023p4ha3promotesclear pages 1-4, zhang2023p4ha3promotesclear media fce01a34)

Visual evidence from the same study supports these conclusions, including tumor-vs-normal expression plots, the Kaplan–Meier survival curve, and representative functional assay panels following P4HA3 knockdown. (zhang2023p4ha3promotesclear media fce01a34, zhang2023p4ha3promotesclear media 1ff07208, zhang2023p4ha3promotesclear media 99b774fd, zhang2023p4ha3promotesclear media 3f2ba07a, zhang2023p4ha3promotesclear media 9205fff5)

4.2 Gastric cancer (GC/STAD) — biomarker + immunotherapy-response associations

A 2024 Scientific Reports study evaluated P4HA3 as a diagnostic/prognostic marker in gastric cancer and reported strong diagnostic performance with ROC AUC = 0.923 (95% CI 0.885–0.962). The study reports significant overexpression in tumor vs normal tissue (including paired comparisons) and links P4HA3 to immune microenvironment features, including associations with immune infiltration patterns, stromal/immune scores, and negative relationships with TMB/MSI and immunophenoscore in the studied cohorts (details vary by analysis module). (yu2024comprehensiveanalysisreveals pages 2-4, yu2024comprehensiveanalysisreveals pages 6-8, yu2024comprehensiveanalysisreveals pages 8-12)

While this study presents extensive immune and pathway analyses, not all effect sizes (e.g., hazard ratios or correlation coefficients) were available in the extracted text chunks; major conclusions remain supported at the level of statistical significance and directionality. (yu2024comprehensiveanalysisreveals pages 6-8, yu2024comprehensiveanalysisreveals pages 8-12, yu2024comprehensiveanalysisreveals pages 12-14)

4.3 Head and neck squamous cell carcinoma (HNSCC) — C-P4HA contribution to invasion/migration

A 2024 study in head and neck squamous cell carcinoma reported higher P4HA3 expression in tumor vs normal tissues and showed that knockdown of collagen P4HA subunits suppresses migration and invasion, with multi-subunit knockdown producing stronger inhibition. This work reinforces the concept that collagen P4H activity can contribute to aggressive tumor phenotypes through ECM remodeling and potentially additional pathways. (xu2024collagenprolyl4hydroxylase pages 1-2)

4.4 Pan-cancer and immunotherapy: P4HA3 and tumor microenvironment (TME)

A 2024 PLOS Computational Biology study performed a pan-cancer analysis and integrated experimental perturbations. It reported that P4HA3 expression is broadly dysregulated across cancers and associated with proliferation and EMT marker programs. Experimentally, P4HA3 loss inhibited proliferation/migration/invasion across multiple cancer cell lines, and in vivo experiments (including PDX models, n=5 per group) tested responses to PD-1/PD-L1 inhibition (BMS-1 dosing schedule described in the paper section). This supports a model in which P4HA3 may influence tumor progression and modulate response to immune checkpoint blockade, though mechanistic details likely include both ECM-dependent and non-canonical effects. (huang2024acomputationalanalysis pages 11-13, huang2024acomputationalanalysis pages 13-14, huang2024acomputationalanalysis pages 4-6)

5) Current applications and real-world implementations

5.1 Biomarker use cases (current state)

Across recent studies, P4HA3 is being evaluated primarily as:
- a diagnostic biomarker (e.g., ROC/AUC frameworks in gastric cancer) (yu2024comprehensiveanalysisreveals pages 2-4)
- a prognostic biomarker associated with survival outcomes (e.g., ccRCC hazard ratio; multiple cancers with significant KM p-values in pan-cancer analyses) (zhang2023p4ha3promotesclear media fce01a34, huang2024acomputationalanalysis pages 4-6)
- a candidate immune-related biomarker potentially predictive of immune checkpoint inhibitor efficacy, based on correlations with immune infiltration, checkpoints, and immunotherapy cohorts (yu2024comprehensiveanalysisreveals pages 6-8, yu2024comprehensiveanalysisreveals pages 8-12)

These implementations are currently research-stage and frequently rely on retrospective genomics datasets; some studies include in vivo validation, but broad clinical deployment requires prospective validation. (yu2024comprehensiveanalysisreveals pages 12-14, huang2024acomputationalanalysis pages 11-13)

5.2 Therapeutic targeting considerations

Because P4HA3 encodes a catalytic α subunit of C-P4H, it sits at a tractable enzymatic node in collagen maturation. However, an important limitation for precision targeting is that P4HA3-specific substrate preferences are not well characterized, and collagen hydroxylation is essential for normal tissue homeostasis—raising potential safety concerns for systemic inhibition. Thus, current translational direction is often framed around biomarker use and pathway stratification rather than immediate direct targeting of P4HA3 alone. (gjaltema2017molecularinsightsinto pages 3-4, gjaltema2017molecularinsightsinto pages 4-5)

6) Expert synthesis and interpretation (authoritative perspectives)

Authoritative reviews emphasize that collagen hydroxylation is an early, essential step for collagen folding/thermostability and secretion, carried out in the ER by α2β2 C-P4H complexes, and that dysregulation of this system can influence disease states through altered ECM structure and signaling. (gjaltema2017molecularinsightsinto pages 3-4, salo2021prolylandlysyl pages 4-7)

The 2023–2024 cancer literature consistently positions high P4HA3 expression as part of an ECM remodeling / EMT / invasion-associated program and as a feature of the tumor microenvironment that co-varies with immune infiltration metrics. A key interpretive point is that many pan-cancer and single-cancer analyses remain correlative, and where mechanism is proposed (e.g., PI3K/AKT/GSK3β in ccRCC), it is often supported by pathway enrichment plus limited molecular validation rather than definitive biochemical mapping of direct substrates. (zhang2023p4ha3promotesclear pages 1-4, yu2024comprehensiveanalysisreveals pages 12-14)

7) Key quantitative statistics (recent studies)

ccRCC survival association: High P4HA3 expression associated with worse OS, HR = 1.52, P = 0.007 (Kaplan–Meier), with TCGA KIRC cohort size reported as 539 tumors and 72 adjacent non-tumor samples. (zhang2023p4ha3promotesclear media fce01a34, zhang2023p4ha3promotesclear pages 1-4)
Gastric cancer diagnostic performance: ROC AUC = 0.923 (95% CI 0.885–0.962) for distinguishing tumor vs normal in STAD. (yu2024comprehensiveanalysisreveals pages 2-4)
In vivo immunotherapy-relevant experiments (2024): P4HA3 depletion tested in models including PDX settings with n = 5 per group, with PD-1/PD-L1 inhibitor experimental regimens described. (huang2024acomputationalanalysis pages 11-13)

8) Evidence map (summary table)

The following table consolidates core functional annotation and the highest-signal 2023–2024 translational findings with URLs and dates.

Category	Key points	Evidence type (review/primary/bioinformatics)	Year	Source (first author, journal)	URL
Target identity	Human P4HA3 matches UniProt Q7Z4N8 and encodes prolyl 4-hydroxylase subunit alpha-3, the catalytic α(III) subunit of collagen prolyl 4-hydroxylase isoenzyme III; belongs to the P4HA family and is distinct from P4HA1/P4HA2 (pasanen2011prolyl3hydroxylasesand pages 28-31, gjaltema2017molecularinsightsinto pages 3-4, salo2021prolylandlysyl pages 4-7)	Review	2017, 2021	Gjaltema, Crit Rev Biochem Mol Biol; Salo, Exp Dermatol	https://doi.org/10.1080/10409238.2016.1269716 ; https://doi.org/10.1111/exd.14197
Primary molecular function / reaction	Collagen prolyl 4-hydroxylases catalyze 4-hydroxylation of proline to form 4-hydroxyproline (4Hyp) in newly synthesized procollagen, a modification essential for triple-helix stability and efficient collagen secretion (gjaltema2017molecularinsightsinto pages 3-4, salo2021prolylandlysyl pages 4-7)	Review	2017, 2021	Gjaltema, Crit Rev Biochem Mol Biol; Salo, Exp Dermatol	https://doi.org/10.1080/10409238.2016.1269716 ; https://doi.org/10.1111/exd.14197
Substrate specificity / motif	Minimum peptide requirement is -X-Pro-Gly-; hydroxylation occurs at the Y-position of Gly-X-Y motifs in collagen chains, and only on unfolded procollagen α-chains before triple-helix folding. For α(III)/P4HA3 specifically, substrate affinities remain less well defined than for P4HA1/2 (gjaltema2017molecularinsightsinto pages 3-4, pasanen2011prolyl3hydroxylasesand pages 31-34, gjaltema2017molecularinsightsinto pages 4-5)	Review	2011, 2017	Pasanen, thesis/review; Gjaltema, Crit Rev Biochem Mol Biol	https://doi.org/10.1080/10409238.2016.1269716
Cofactors and byproducts	The reaction requires Fe2+, 2-oxoglutarate (2-OG/α-KG), O2, and ascorbate; 2-OG is oxidatively decarboxylated to succinate + CO2, with one oxygen atom incorporated into succinate and one into hydroxyproline (pasanen2011prolyl3hydroxylasesand pages 31-34, salo2021prolylandlysyl pages 4-7)	Review	2011, 2021	Pasanen, thesis/review; Salo, Exp Dermatol	https://doi.org/10.1111/exd.14197
Complex composition	Active collagen prolyl 4-hydroxylase is an α2β2 tetramer. P4HA3 supplies the catalytic α(III) subunit; the β-subunit is P4HB/protein disulfide isomerase (PDI), required for α-subunit solubility, assembly, and chaperone function (pasanen2011prolyl3hydroxylasesand pages 28-31, gjaltema2017molecularinsightsinto pages 3-4, salo2021prolylandlysyl pages 4-7)	Review	2011, 2017, 2021	Pasanen; Gjaltema, Crit Rev Biochem Mol Biol; Salo, Exp Dermatol	https://doi.org/10.1080/10409238.2016.1269716 ; https://doi.org/10.1111/exd.14197
Subcellular localization	Collagen P4Hs are localized in the lumen of the rough endoplasmic reticulum (ER); ER retention is mediated by the KDEL signal on P4HB/PDI. This is the expected localization for P4HA3-containing isoenzyme III (pasanen2011prolyl3hydroxylasesand pages 28-31, gjaltema2017molecularinsightsinto pages 3-4, salo2021prolylandlysyl pages 4-7)	Review	2011, 2017, 2021	Pasanen; Gjaltema, Crit Rev Biochem Mol Biol; Salo, Exp Dermatol	https://doi.org/10.1080/10409238.2016.1269716 ; https://doi.org/10.1111/exd.14197
Isoenzyme notes	Vertebrates express three α-subunit isoforms: P4HA1/P4HA2/P4HA3 = α(I)/α(II)/α(III), forming isoenzymes I/II/III. Available evidence indicates α-subunits form homomeric tetramers rather than mixed α(I)/α(II)/α(III) complexes. P4HA3 mRNA is generally lower-abundance than P4HA1 and lacks reported alternative splicing in the cited sources (pasanen2011prolyl3hydroxylasesand pages 28-31, pasanen2011prolyl3hydroxylasesand pages 31-34, salo2021prolylandlysyl pages 17-21, hironaka2025enhancedcollagenprolyl pages 1-3)	Review	2011, 2021, 2025	Pasanen; Salo, Exp Dermatol; Hironaka, Int J Mol Sci	https://doi.org/10.1111/exd.14197 ; https://doi.org/10.3390/ijms26199371
Biological role / pathway context	By enabling proline hydroxylation during collagen biosynthesis, P4HA3 contributes to ECM assembly, collagen stability, and matrix remodeling. In tumors, higher P4HA3 is repeatedly linked to ECM stiffening/remodeling, EMT, invasion, metastasis, and tumor microenvironment changes (yu2024comprehensiveanalysisreveals pages 1-2, shi2021collagenprolyl4hydroxylases pages 2-3, huang2024acomputationalanalysis pages 1-2, zhang2023p4ha3promotesclear pages 1-4)	Review + primary/bioinformatics	2021, 2023, 2024	Shi, Acta Biochim Biophys Sin; Zhang, Med Oncol; Yu, Sci Rep; Huang, PLoS Comput Biol	https://doi.org/10.1093/abbs/gmab065 ; https://doi.org/10.1007/s12032-022-01926-2 ; https://doi.org/10.1038/s41598-024-73784-z ; https://doi.org/10.1371/journal.pcbi.1012284
2023 ccRCC finding	In clear cell renal cell carcinoma, P4HA3 was highly expressed in TCGA KIRC (539 tumors) and normal-adjacent comparison datasets; high expression associated with worse overall survival. Figure-based statistics reported HR = 1.52, P = 0.007; P4HA3 knockdown reduced proliferation, migration, and invasion in OSRC2 and 769-P cells, and GSEA implicated EMT and PI3K/AKT/GSK3β signaling (zhang2023p4ha3promotesclear pages 1-4, zhang2023p4ha3promotesclear media fce01a34)	Primary + bioinformatics	2023	Zhang, Medical Oncology	https://doi.org/10.1007/s12032-022-01926-2
2024 gastric cancer finding	In gastric cancer, elevated P4HA3 expression was reported as significantly associated with poorer prognosis and correlated with immune infiltrating cells, immune markers, TMB, MSI, stromal/immune scores, and immune checkpoints, supporting use as a candidate biomarker for prognosis and immunotherapy response; numeric effect sizes were not provided in the cited excerpt (yu2024comprehensiveanalysisreveals pages 1-2)	Primary + bioinformatics	2024	Yu, Scientific Reports	https://doi.org/10.1038/s41598-024-73784-z
2024 pan-cancer / immunotherapy finding	A 2024 pan-cancer analysis across 33 tumor types found P4HA3 expression associated with tumor-microenvironment infiltration, proliferation markers, and EMT markers; experimental depletion inhibited proliferation/migration/invasion and improved PD-1/PD-L1 inhibitor response in model systems, supporting P4HA3 as a possible immunotherapy-response biomarker (huang2024acomputationalanalysis pages 1-2)	Primary + bioinformatics	2024	Huang, PLoS Comput Biol	https://doi.org/10.1371/journal.pcbi.1012284
2024 head and neck cancer finding	In head and neck squamous cell carcinoma, P4HA1 and P4HA3 were reported significantly higher in tumors than normal tissues; knockdown of collagen P4HA subunits reduced migration and invasion, and the study positioned LLGL2 as an antagonist of C-P4HA-driven aggressiveness. The paper also notes C-P4HA overexpression is prognostically adverse overall, though no P4HA3-specific hazard ratio was given in the cited excerpt (xu2024collagenprolyl4hydroxylase pages 1-2)	Primary	2024	Xu, Acta Biochim Biophys Sin	https://doi.org/10.3724/abbs.2024140
2024 fibrosis-related evidence	P4HA3 is increasingly implicated in fibrotic ECM programs: spatial transcriptomic work in a fibrosis model highlighted dysregulated collagen prolyl hydroxylase activity including P4HA3, and TGFβ-driven human fibroblast transcriptomics identified P4HA3 among collagen-synthesis/fibrosis-enriched genes. These support a role in profibrotic matrix remodeling, but quantitative P4HA3-specific effect sizes were not provided in the cited excerpts (OpenTargets Search: -P4HA3)	Database/association + primary transcriptomics	2024	Open Targets; Bell, Cell Reports Medicine; Pasvanis, bioRxiv	https://platform.opentargets.org ; https://doi.org/10.1016/j.xcrm.2024.101695 ; https://doi.org/10.1101/2024.03.09.583791
Current limitations	Despite strong family-level biochemistry, P4HA3-specific substrate preferences, kinetics, and non-collagen substrates remain incompletely characterized relative to P4HA1/2. Several recent disease studies are largely correlative or bioinformatic, so mechanistic claims for P4HA3 should be interpreted cautiously unless supported by perturbation experiments (gjaltema2017molecularinsightsinto pages 3-4, gjaltema2017molecularinsightsinto pages 4-5, huang2024acomputationalanalysis pages 1-2, zhang2023p4ha3promotesclear pages 1-4)	Review + primary/bioinformatics	2017, 2023, 2024	Gjaltema, Crit Rev Biochem Mol Biol; Zhang, Med Oncol; Huang, PLoS Comput Biol	https://doi.org/10.1080/10409238.2016.1269716 ; https://doi.org/10.1007/s12032-022-01926-2 ; https://doi.org/10.1371/journal.pcbi.1012284

Table: This table summarizes validated functional annotation facts for human P4HA3, including core collagen prolyl 4-hydroxylase biochemistry, localization, complex composition, and recent 2023-2024 disease-related findings. It is useful as a compact evidence map linking molecular function to current translational literature.

9) Limitations and open questions

Isoform-specific enzymology: Despite clear family-level chemistry, P4HA3-specific substrate preference and kinetics remain incompletely resolved, limiting confident isoform-specific mechanistic claims. (gjaltema2017molecularinsightsinto pages 3-4, gjaltema2017molecularinsightsinto pages 4-5)
Causality vs correlation in human disease: Many 2024 datasets linking P4HA3 to prognosis/immunity are retrospective; while some studies include knockdown/in vivo validation, large-scale prospective clinical validation is still needed for biomarker deployment. (yu2024comprehensiveanalysisreveals pages 12-14, huang2024acomputationalanalysis pages 11-13)
Non-collagen substrates: Some cancer papers discuss possible collagen-independent effects of collagen P4H activity; however, direct biochemical identification of non-collagen P4HA3 substrates was not established in the retrieved excerpts and should be treated as a research frontier rather than settled annotation. (shi2021collagenprolyl4hydroxylases pages 2-3, xu2024collagenprolyl4hydroxylase pages 1-2)

Key cited sources (publication date, URL)

Zhang et al., Medical Oncology (Jan 2023): https://doi.org/10.1007/s12032-022-01926-2 (zhang2023p4ha3promotesclear pages 1-4)
Yu et al., Scientific Reports (Oct 2024): https://doi.org/10.1038/s41598-024-73784-z (yu2024comprehensiveanalysisreveals pages 1-2, yu2024comprehensiveanalysisreveals pages 2-4)
Huang et al., PLOS Computational Biology (Nov 2024): https://doi.org/10.1371/journal.pcbi.1012284 (huang2024acomputationalanalysis pages 1-2, huang2024acomputationalanalysis pages 11-13)
Xu et al., Acta Biochim Biophys Sin (Oct 2024): https://doi.org/10.3724/abbs.2024140 (xu2024collagenprolyl4hydroxylase pages 1-2)
Salo & Myllyharju, Experimental Dermatology (Oct 2021): https://doi.org/10.1111/exd.14197 (salo2021prolylandlysyl pages 4-7)
Gjaltema & Bank, Critical Reviews in Biochemistry and Molecular Biology (Jan 2017): https://doi.org/10.1080/10409238.2016.1269716 (gjaltema2017molecularinsightsinto pages 3-4)
Open Targets Platform (accessed via tool; disease-target associations): https://platform.opentargets.org (OpenTargets Search: -P4HA3)

References

(pasanen2011prolyl3hydroxylasesand pages 28-31): A Pasanen. Prolyl 3-hydroxylases and hypoxia-inducible factor 3: their roles in collagen synthesis and hypoxia response, respectively. Unknown journal, 2011.
(gjaltema2017molecularinsightsinto pages 3-4): Rutger A. F. Gjaltema and Ruud A. Bank. Molecular insights into prolyl and lysyl hydroxylation of fibrillar collagens in health and disease. Critical Reviews in Biochemistry and Molecular Biology, 52:74-95, Jan 2017. URL: https://doi.org/10.1080/10409238.2016.1269716, doi:10.1080/10409238.2016.1269716. This article has 208 citations and is from a peer-reviewed journal.
(salo2021prolylandlysyl pages 4-7): Antti M. Salo and Johanna Myllyharju. Prolyl and lysyl hydroxylases in collagen synthesis. Experimental Dermatology, 30:38-49, Oct 2021. URL: https://doi.org/10.1111/exd.14197, doi:10.1111/exd.14197. This article has 146 citations and is from a domain leading peer-reviewed journal.
(pasanen2011prolyl3hydroxylasesand pages 31-34): A Pasanen. Prolyl 3-hydroxylases and hypoxia-inducible factor 3: their roles in collagen synthesis and hypoxia response, respectively. Unknown journal, 2011.
(gjaltema2017molecularinsightsinto pages 4-5): Rutger A. F. Gjaltema and Ruud A. Bank. Molecular insights into prolyl and lysyl hydroxylation of fibrillar collagens in health and disease. Critical Reviews in Biochemistry and Molecular Biology, 52:74-95, Jan 2017. URL: https://doi.org/10.1080/10409238.2016.1269716, doi:10.1080/10409238.2016.1269716. This article has 208 citations and is from a peer-reviewed journal.
(zhang2023p4ha3promotesclear pages 1-4): Zhechuan Zhang, Yuanfeng Zhang, and Ronggui Zhang. P4ha3 promotes clear cell renal cell carcinoma progression via the pi3k/akt/gsk3β pathway. Medical Oncology, 40:1-12, Jan 2023. URL: https://doi.org/10.1007/s12032-022-01926-2, doi:10.1007/s12032-022-01926-2. This article has 17 citations and is from a peer-reviewed journal.
(zhang2023p4ha3promotesclear media fce01a34): Zhechuan Zhang, Yuanfeng Zhang, and Ronggui Zhang. P4ha3 promotes clear cell renal cell carcinoma progression via the pi3k/akt/gsk3β pathway. Medical Oncology, 40:1-12, Jan 2023. URL: https://doi.org/10.1007/s12032-022-01926-2, doi:10.1007/s12032-022-01926-2. This article has 17 citations and is from a peer-reviewed journal.
(zhang2023p4ha3promotesclear media 1ff07208): Zhechuan Zhang, Yuanfeng Zhang, and Ronggui Zhang. P4ha3 promotes clear cell renal cell carcinoma progression via the pi3k/akt/gsk3β pathway. Medical Oncology, 40:1-12, Jan 2023. URL: https://doi.org/10.1007/s12032-022-01926-2, doi:10.1007/s12032-022-01926-2. This article has 17 citations and is from a peer-reviewed journal.
(zhang2023p4ha3promotesclear media 99b774fd): Zhechuan Zhang, Yuanfeng Zhang, and Ronggui Zhang. P4ha3 promotes clear cell renal cell carcinoma progression via the pi3k/akt/gsk3β pathway. Medical Oncology, 40:1-12, Jan 2023. URL: https://doi.org/10.1007/s12032-022-01926-2, doi:10.1007/s12032-022-01926-2. This article has 17 citations and is from a peer-reviewed journal.
(zhang2023p4ha3promotesclear media 3f2ba07a): Zhechuan Zhang, Yuanfeng Zhang, and Ronggui Zhang. P4ha3 promotes clear cell renal cell carcinoma progression via the pi3k/akt/gsk3β pathway. Medical Oncology, 40:1-12, Jan 2023. URL: https://doi.org/10.1007/s12032-022-01926-2, doi:10.1007/s12032-022-01926-2. This article has 17 citations and is from a peer-reviewed journal.
(zhang2023p4ha3promotesclear media 9205fff5): Zhechuan Zhang, Yuanfeng Zhang, and Ronggui Zhang. P4ha3 promotes clear cell renal cell carcinoma progression via the pi3k/akt/gsk3β pathway. Medical Oncology, 40:1-12, Jan 2023. URL: https://doi.org/10.1007/s12032-022-01926-2, doi:10.1007/s12032-022-01926-2. This article has 17 citations and is from a peer-reviewed journal.
(yu2024comprehensiveanalysisreveals pages 2-4): Yuanhang Yu, Kexin Luo, Meihan Liu, Long Chen, Xi Gao, Lijuan Zhang, Xianfu Li, and Hongpan Zhang. Comprehensive analysis reveals that p4ha3 is a prognostic and diagnostic gastric cancer biomarker that can predict immunotherapy efficacy. Scientific Reports, Oct 2024. URL: https://doi.org/10.1038/s41598-024-73784-z, doi:10.1038/s41598-024-73784-z. This article has 6 citations and is from a peer-reviewed journal.
(yu2024comprehensiveanalysisreveals pages 6-8): Yuanhang Yu, Kexin Luo, Meihan Liu, Long Chen, Xi Gao, Lijuan Zhang, Xianfu Li, and Hongpan Zhang. Comprehensive analysis reveals that p4ha3 is a prognostic and diagnostic gastric cancer biomarker that can predict immunotherapy efficacy. Scientific Reports, Oct 2024. URL: https://doi.org/10.1038/s41598-024-73784-z, doi:10.1038/s41598-024-73784-z. This article has 6 citations and is from a peer-reviewed journal.
(yu2024comprehensiveanalysisreveals pages 8-12): Yuanhang Yu, Kexin Luo, Meihan Liu, Long Chen, Xi Gao, Lijuan Zhang, Xianfu Li, and Hongpan Zhang. Comprehensive analysis reveals that p4ha3 is a prognostic and diagnostic gastric cancer biomarker that can predict immunotherapy efficacy. Scientific Reports, Oct 2024. URL: https://doi.org/10.1038/s41598-024-73784-z, doi:10.1038/s41598-024-73784-z. This article has 6 citations and is from a peer-reviewed journal.
(yu2024comprehensiveanalysisreveals pages 12-14): Yuanhang Yu, Kexin Luo, Meihan Liu, Long Chen, Xi Gao, Lijuan Zhang, Xianfu Li, and Hongpan Zhang. Comprehensive analysis reveals that p4ha3 is a prognostic and diagnostic gastric cancer biomarker that can predict immunotherapy efficacy. Scientific Reports, Oct 2024. URL: https://doi.org/10.1038/s41598-024-73784-z, doi:10.1038/s41598-024-73784-z. This article has 6 citations and is from a peer-reviewed journal.
(xu2024collagenprolyl4hydroxylase pages 1-2): Miao Xu, Run Shi, Jie Yang, Heng Chen, Shihua Liu, Shupei Yu, Sasa Li, Wenqiang He, Man-Sun Sy, Mingjian Lu, Huixia Zhang, and Chaoyang Li. Collagen prolyl 4-hydroxylase subunit α member-induced head and neck squamous cell carcinoma aggressiveness is antagonized by llgl2 via reduced expression of occludin. Acta Biochimica et Biophysica Sinica, 56:1833-1847, Oct 2024. URL: https://doi.org/10.3724/abbs.2024140, doi:10.3724/abbs.2024140. This article has 2 citations and is from a peer-reviewed journal.
(huang2024acomputationalanalysis pages 11-13): Hong Yan Huang, Fu Wei Zhang, Jie Yu, Yan Hong Xiao, Di Zhu, XiaoLin Yi, XiaoHua Lin, Ming Jin, Hai Yun Jin, Yong Sheng Huang, and Shu Wei Ren. A computational analysis of the oncogenic and anti-tumor immunity role of p4ha3 in human cancers. Nov 2024. URL: https://doi.org/10.1371/journal.pcbi.1012284, doi:10.1371/journal.pcbi.1012284. This article has 5 citations and is from a highest quality peer-reviewed journal.
(huang2024acomputationalanalysis pages 13-14): Hong Yan Huang, Fu Wei Zhang, Jie Yu, Yan Hong Xiao, Di Zhu, XiaoLin Yi, XiaoHua Lin, Ming Jin, Hai Yun Jin, Yong Sheng Huang, and Shu Wei Ren. A computational analysis of the oncogenic and anti-tumor immunity role of p4ha3 in human cancers. Nov 2024. URL: https://doi.org/10.1371/journal.pcbi.1012284, doi:10.1371/journal.pcbi.1012284. This article has 5 citations and is from a highest quality peer-reviewed journal.
(huang2024acomputationalanalysis pages 4-6): Hong Yan Huang, Fu Wei Zhang, Jie Yu, Yan Hong Xiao, Di Zhu, XiaoLin Yi, XiaoHua Lin, Ming Jin, Hai Yun Jin, Yong Sheng Huang, and Shu Wei Ren. A computational analysis of the oncogenic and anti-tumor immunity role of p4ha3 in human cancers. Nov 2024. URL: https://doi.org/10.1371/journal.pcbi.1012284, doi:10.1371/journal.pcbi.1012284. This article has 5 citations and is from a highest quality peer-reviewed journal.
(salo2021prolylandlysyl pages 17-21): Antti M. Salo and Johanna Myllyharju. Prolyl and lysyl hydroxylases in collagen synthesis. Experimental Dermatology, 30:38-49, Oct 2021. URL: https://doi.org/10.1111/exd.14197, doi:10.1111/exd.14197. This article has 146 citations and is from a domain leading peer-reviewed journal.
(hironaka2025enhancedcollagenprolyl pages 1-3): Dalton Hironaka and Gaofeng Xiong. Enhanced collagen prolyl 4-hydroxylase activity and expression promote cancer progression via both canonical and non-canonical mechanisms. International Journal of Molecular Sciences, 26:9371, Sep 2025. URL: https://doi.org/10.3390/ijms26199371, doi:10.3390/ijms26199371. This article has 2 citations.
(yu2024comprehensiveanalysisreveals pages 1-2): Yuanhang Yu, Kexin Luo, Meihan Liu, Long Chen, Xi Gao, Lijuan Zhang, Xianfu Li, and Hongpan Zhang. Comprehensive analysis reveals that p4ha3 is a prognostic and diagnostic gastric cancer biomarker that can predict immunotherapy efficacy. Scientific Reports, Oct 2024. URL: https://doi.org/10.1038/s41598-024-73784-z, doi:10.1038/s41598-024-73784-z. This article has 6 citations and is from a peer-reviewed journal.
(shi2021collagenprolyl4hydroxylases pages 2-3): Run Shi, Shanshan Gao, Jie Zhang, Jiang Xu, Linda M Graham, Xiaowen Yang, and Chaoyang Li. Collagen prolyl 4-hydroxylases modify tumor progression. Acta Biochimica et Biophysica Sinica, 53:805-814, May 2021. URL: https://doi.org/10.1093/abbs/gmab065, doi:10.1093/abbs/gmab065. This article has 70 citations and is from a peer-reviewed journal.
(huang2024acomputationalanalysis pages 1-2): Hong Yan Huang, Fu Wei Zhang, Jie Yu, Yan Hong Xiao, Di Zhu, XiaoLin Yi, XiaoHua Lin, Ming Jin, Hai Yun Jin, Yong Sheng Huang, and Shu Wei Ren. A computational analysis of the oncogenic and anti-tumor immunity role of p4ha3 in human cancers. Nov 2024. URL: https://doi.org/10.1371/journal.pcbi.1012284, doi:10.1371/journal.pcbi.1012284. This article has 5 citations and is from a highest quality peer-reviewed journal.
(OpenTargets Search: -P4HA3): Open Targets Query (-P4HA3, 5 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.

Artifacts

Edison artifact artifact-00

Citations

yu2024comprehensiveanalysisreveals pages 2-4
huang2024acomputationalanalysis pages 11-13
yu2024comprehensiveanalysisreveals pages 1-2
huang2024acomputationalanalysis pages 1-2
salo2021prolylandlysyl pages 4-7
gjaltema2017molecularinsightsinto pages 3-4
gjaltema2017molecularinsightsinto pages 4-5
yu2024comprehensiveanalysisreveals pages 6-8
yu2024comprehensiveanalysisreveals pages 8-12
yu2024comprehensiveanalysisreveals pages 12-14
huang2024acomputationalanalysis pages 13-14
huang2024acomputationalanalysis pages 4-6
salo2021prolylandlysyl pages 17-21
hironaka2025enhancedcollagenprolyl pages 1-3
α(III)
https://doi.org/10.1080/10409238.2016.1269716
https://doi.org/10.1111/exd.14197
https://doi.org/10.3390/ijms26199371
https://doi.org/10.1093/abbs/gmab065
https://doi.org/10.1007/s12032-022-01926-2
https://doi.org/10.1038/s41598-024-73784-z
https://doi.org/10.1371/journal.pcbi.1012284
https://doi.org/10.3724/abbs.2024140
https://platform.opentargets.org
https://doi.org/10.1016/j.xcrm.2024.101695
https://doi.org/10.1101/2024.03.09.583791
https://doi.org/10.1080/10409238.2016.1269716,
https://doi.org/10.1111/exd.14197,
https://doi.org/10.1007/s12032-022-01926-2,
https://doi.org/10.1038/s41598-024-73784-z,
https://doi.org/10.3724/abbs.2024140,
https://doi.org/10.1371/journal.pcbi.1012284,
https://doi.org/10.3390/ijms26199371,
https://doi.org/10.1093/abbs/gmab065,

📚 Additional Documentation

Notes

(P4HA3-notes.md)

P4HA3 (Prolyl 4-hydroxylase subunit alpha-3) — gene review notes

UniProt: Q7Z4N8 (P4HA3_HUMAN), 544 aa precursor (signal 1-19; chain 20-544). Gene on human chr 11. EC=1.14.11.2.

Core identity and function

P4HA3 is the third catalytic alpha subunit isoform (alpha(III)) of collagen prolyl 4-hydroxylase (C-P4H). The active enzyme is an alpha2-beta2 heterotetramer in which the beta subunit is protein disulfide isomerase (PDI / P4HB). It is an ER-lumenal, Fe(II)- and 2-oxoglutarate-dependent dioxygenase that hydroxylates proline in -X-Pro-Gly- triplets of procollagen to form trans-4-hydroxyproline, which is essential for the thermal stability of the collagen triple helix.

Founding characterization: PMID:14500733
Tetramer subunit composition: PMID:14500733
Demonstrated catalytic activity on collagen: PMID:14500733
Reaction (UniProt): L-prolyl-[collagen] + 2-oxoglutarate + O2 = trans-4-hydroxy-L-prolyl-[collagen] + succinate + CO2; EC=1.14.11.2 [ECO:0000269|PubMed:14500733].
Cofactors (UniProt): binds 1 Fe(2+) ion per subunit; requires L-ascorbate. Kinetics (PMID:14500733): KM 0.5 uM Fe(2+), 20 uM 2-oxoglutarate, 24 uM (Pro-Pro-Gly), 370 uM L-ascorbate.
Catalytic domain: Fe2OG dioxygenase domain (422-529); Fe-binding residues 440, 442, 510; 2-oxoglutarate binding residue 520; TPR repeat (227-260) for peptide-substrate/PDI interaction.

Subcellular location

ER lumen (UniProt: "SUBCELLULAR LOCATION: Endoplasmic reticulum lumen {ECO:0000305}"). Reactome curates ER-lumen localization (R-HSA-1650808, R-HSA-9918779). InterPro/IEA also assigns endoplasmic reticulum (GO:0005783). All consistent with a secreted-pathway, lumenal collagen-modifying enzyme.

Tissue expression / context

Highly expressed in placenta, liver, and fetal skin; weakly in fetal epiphyseal cartilage, fetal liver, fibroblast, lung, skeletal muscle PMID:14500733. Also expressed in the fibrous cap of human atherosclerotic plaque / carotid lesions [PMID:12874193 cloned as the subunit "expressed in the fibrous cap of human atherosclerotic plaque"]. HPA: tissue-enhanced in blood vessel / smooth muscle. P4HA3 is frequently discussed in cancer contexts (proliferation/migration/EMT in various tumors) but those roles are downstream/contextual rather than the enzyme's core biochemical function.

Annotation notes / GOA review reasoning

GO:0004656 procollagen-proline 4-dioxygenase activity — core MF. EXP/PMID:14500733 (direct), plus IBA and IEA(EC/RHEA) support. ACCEPT.
GO:0016222 procollagen-proline 4-dioxygenase complex (part_of, IBA) — the alpha2-beta2 (with PDI) tetramer. ACCEPT (the curated CC for the prolyl-4-hydroxylase complex).
GO:0005506 iron ion binding (IEA, InterPro) — Fe(II) cofactor; correct, supports catalysis. ACCEPT.
GO:0016705 oxidoreductase activity, acting on paired donors... O2 (IEA, InterPro) — parent dioxygenase MF; correct but generic relative to GO:0004656. ACCEPT (general MF).
GO:0031418 L-ascorbic acid binding (IEA, keyword/InterPro) — ascorbate cosubstrate; correct. ACCEPT.
GO:0005783 endoplasmic reticulum (IEA) and GO:0005788 ER lumen (IEA + 2x Reactome TAS) — correct compartment. ACCEPT.
GO:0005515 protein binding (IPI x4 references) — all four references (PMID:25416956, 26871637, 31515488, 32296183) are large-scale binary interactome / Y2H reference maps. The partner lists are dominated by biologically unrelated proteins (KRTAPs, MAGEs, transcription factors, etc.); these are uninformative bare protein-binding captures, not the functional PDI/collagen interactions. Per curation guidance, keep as non-core. None elevated to core; do not REMOVE (real IntAct captures).
25416956 = "A proteome-scale map of the human interactome network" (HuRI/Y2H) PMID:25416956.
26871637 = "Widespread Expansion of Protein Interaction Capabilities by Alternative Splicing" (Y2H isoform interactome).
31515488 = "Extensive disruption of protein interactions by genetic variants..." (Y2H variant interactome).
32296183 = "A reference map of the human binary protein interactome" (HuRI).
No experimental cancer-context BP annotations are present in this GOA; GO:0030199 collagen fibril organization (IBA) appears in the UniProt DR cross-references but is NOT in the goa.tsv, so it is not part of existing_annotations here.

Cited reference quality summary

PMID:14500733 — HIGH relevance, VERIFIED (founding biochemical characterization; abstract-only cache but anchored by EC/Rhea reaction and EXP GOA evidence).
PMID:25416956 / 26871637 / 31515488 / 32296183 — LOW relevance (bare protein binding from HT interactome screens), VERIFIED as correctly-cited interactome papers.

Falcon deep-research findings (incorporated 2026-06)

P4HA3 is overexpressed in clear cell renal cell carcinoma (ccRCC); knockdown inhibits proliferation,
migration and invasion, and GSEA/Western blot implicate EMT and PI3K/AKT/GSK3beta signaling. This is
the most P4HA3-specific functional-perturbation evidence in a tumor context.
PMID:36588128
Pan-cancer (33 tumor types) analysis with experimental validation: P4HA3 expression tracks tumor-
microenvironment infiltration, proliferation and EMT markers; P4HA3 depletion inhibits proliferation/
migration/invasion and promotes anti-tumor PD-1/PD-L1 immunotherapy response (incl. TNBC PDX models).
PMID:39504328
Gastric cancer: elevated P4HA3 associates with adverse prognosis and immune-microenvironment features
(immune infiltration, TMB, MSI, immune checkpoints); proposed as an immunotherapy-response biomarker.
Correlative/bioinformatic. PMID:39362976
HNSCC family-level study (all three C-P4HA alpha subunits, including P4HA3): combined higher expression
is prognostically adverse and antagonized by LLGL2 via occludin; C-P4HA knockdown reduces migration/
invasion. PMID:39394821
Shi et al. 2021 review consolidates the three-isoenzyme C-P4H framework (P4HA1/2/3, single P4HB beta),
regulation by cytokines/TFs/miRNAs, tumor overexpression, and C-P4H inhibitors as anti-tumor strategy.
PMID:34009234
Falcon reiterates (review-level) that P4HA3-specific substrate preferences/kinetics remain less defined
than P4HA1/2 and P4HA3 mRNA is low-abundance, consistent with the existing review's framing and
suggested_questions. No new primary biochemical-substrate data for P4HA3 in the report.
All added cancer references are non-core ECM-remodeling/EMT/tumor-context findings; they do not change
the core catalytic annotation (procollagen-proline 4-dioxygenase activity, EXP PMID:14500733) and were
not added as supporting_text to core_functions (papers not in publications/ cache).

Pn Notes

(P4HA3-pn-notes.md)

P4HA3 PN Consistency Notes

Generated: 2026-06-18
Project: PROTEOSTASIS
Scope: PN consistency rereview against local AIGR review and available deep-research artifacts
UniProt: Q7Z4N8
AIGR review status: COMPLETE
Review batch: proteostasis-batch-2026-06-11
Batch change status: added

Source Files Checked

AIGR review YAML: present - genes/human/P4HA3/P4HA3-ai-review.yaml
AIGR review HTML: missing - genes/human/P4HA3/P4HA3-ai-review.html
Gene notes: present - genes/human/P4HA3/P4HA3-notes.md
GOA TSV: present - genes/human/P4HA3/P4HA3-goa.tsv
UniProt record: present - genes/human/P4HA3/P4HA3-uniprot.txt
PN dossier: projects/PROTEOSTASIS/reports/phase1_dossiers/P4HA3.md
PN consistency section: projects/PROTEOSTASIS/reports/phase1_dossiers/_sections/P4HA3.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/P4HA3/P4HA3-deep-research-falcon.md

AIGR Review Snapshot

Description: P4HA3 (prolyl 4-hydroxylase subunit alpha-3) is the third catalytic alpha-subunit isoform of collagen prolyl 4-hydroxylase (C-P4H). The active enzyme is an alpha2-beta2 heterotetramer in which the two catalytic alpha subunits combine with two beta subunits that are identical to protein disulfide isomerase (PDI/P4HB). P4HA3 is an endoplasmic reticulum lumenal, Fe(II)- and 2-oxoglutarate-dependent dioxygenase that, using L-ascorbate as a cofactor and molecular oxygen as co-substrate, hydroxylates proline residues in -X-Pro-Gly- triplets of procollagen and related proteins to form trans-4-hydroxyproline (consuming 2-oxoglutarate and producing succinate and CO2). 4-hydroxyproline formation is essential for folding and thermal stability of the collagen triple helix. The alpha-3 isoenzyme has catalytic properties similar to the type I and type II C-P4Hs but with intermediate peptide-substrate binding properties, and its mRNA is expressed broadly but at much lower levels than the alpha(I)/alpha(II) isoforms, being most abundant in placenta, liver, and fetal skin and detectable in vascular smooth muscle and the fibrous cap of atherosclerotic lesions.
Existing/core annotation action counts: ACCEPT: 11; KEEP_AS_NON_CORE: 4

PN Consistency Summary

Consistency: Consistent. Review, deep research, PN annotation, and mapping describe the third catalytic alpha-3 subunit of C-P4H (EC 1.14.11.2), [alpha(III)]2-beta2 tetramer with PDI, ER-lumenal; intermediate peptide-binding properties; broadly but weakly expressed. PN placement matches. EXP evidence (PMID:14500733) anchors the catalytic function.
PN story / NEW pressure: PN asserts GO:0032964 as new_to_goa; P4HA3 GOA has no collagen-process BP term (only MF/CC). GO:0032964 verified real via OLS. Unlike P4HA1/P4HA2, this review has proposed_new_terms: [] — it did not flag the BP gap, so the PN projection actually adds a BP role the review omitted. The projection is nonetheless defensible (same catalytic logic as the paralogs) and consistent with the review's BP-free MF annotations. Conclusion: defensible ADD.
Evidence alignment: PN dossier mapping-only. Review core: EXP PMID:14500733 (founding characterization), reviews PMID:34009234. Numerous cancer-biomarker refs (PMID:36588128, 39362976, 39504328, 39394821) beyond PN scope — expected divergence. Core biochemistry aligns.
Verdict: Consistent; PN GO:0032964 ADD defensible and genuinely new to GOA; minor note that this review omitted the BP-gap proposal its paralogs made.

Full Consistency Review

UniProt: Q7Z4N8 · batch: proteostasis-batch-2026-06-11 · 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 third catalytic alpha-3 subunit of C-P4H (EC 1.14.11.2), [alpha(III)]2-beta2 tetramer with PDI, ER-lumenal; intermediate peptide-binding properties; broadly but weakly expressed. PN placement matches. EXP evidence (PMID:14500733) anchors the catalytic function.
PN story / NEW pressure: PN asserts GO:0032964 as new_to_goa; P4HA3 GOA has no collagen-process BP term (only MF/CC). GO:0032964 verified real via OLS. Unlike P4HA1/P4HA2, this review has proposed_new_terms: [] — it did not flag the BP gap, so the PN projection actually adds a BP role the review omitted. The projection is nonetheless defensible (same catalytic logic as the paralogs) and consistent with the review's BP-free MF annotations. Conclusion: defensible ADD.
Mapping strategy: Correct. Catalytic subunit; group-level GO:0032964 appropriate, narrower than unmapped class. No node change. For paralog-uniformity, the review's empty proposed_new_terms is a minor inconsistency vs P4HA1/P4HA2 (which propose GO:0018401/GO:0032964).
Evidence alignment: PN dossier mapping-only. Review core: EXP PMID:14500733 (founding characterization), reviews PMID:34009234. Numerous cancer-biomarker refs (PMID:36588128, 39362976, 39504328, 39394821) beyond PN scope — expected divergence. Core biochemistry aligns.
Verdict: Consistent; PN GO:0032964 ADD defensible and genuinely new to GOA; minor note that this review omitted the BP-gap proposal its paralogs made.
Recommended edits: [YAML] Consider adding a peptidyl-proline-hydroxylation / collagen-biosynthetic-process entry to P4HA3 proposed_new_terms (GO:0018401 / GO:0032964) for parity with P4HA1/P4HA2 and to match the PN projection.

PN Dossier Context

review_batch: proteostasis-batch-2026-06-11
review_yaml: genes/human/P4HA3/P4HA3-ai-review.yaml
PN workbook rows: 1

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

UniProt: Q7Z4N8
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.

📄 View Raw YAML

id: Q7Z4N8
gene_symbol: P4HA3
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: P4HA3 (prolyl 4-hydroxylase subunit alpha-3) is the third catalytic alpha-subunit
  isoform of collagen prolyl 4-hydroxylase (C-P4H). The active enzyme is an alpha2-beta2 heterotetramer
  in which the two catalytic alpha subunits combine with two beta subunits that are identical to
  protein disulfide isomerase (PDI/P4HB). P4HA3 is an endoplasmic reticulum lumenal, Fe(II)- and
  2-oxoglutarate-dependent dioxygenase that, using L-ascorbate as a cofactor and molecular oxygen
  as co-substrate, hydroxylates proline residues in -X-Pro-Gly- triplets of procollagen and related
  proteins to form trans-4-hydroxyproline (consuming 2-oxoglutarate and producing succinate and CO2).
  4-hydroxyproline formation is essential for folding and thermal stability of the collagen triple
  helix. The alpha-3 isoenzyme has catalytic properties similar to the type I and type II C-P4Hs but
  with intermediate peptide-substrate binding properties, and its mRNA is expressed broadly but at
  much lower levels than the alpha(I)/alpha(II) isoforms, being most abundant in placenta, liver, and
  fetal skin and detectable in vascular smooth muscle and the fibrous cap of atherosclerotic lesions.
alternative_products:
- name: '1'
  id: Q7Z4N8-1
- name: '2'
  id: Q7Z4N8-2
  sequence_note: VSP_031146, VSP_031147
- name: '3'
  id: Q7Z4N8-3
  sequence_note: VSP_054131
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 (IBA) assignment of the core collagen prolyl 4-hydroxylase activity,
      consistent with the direct experimental EXP evidence for P4HA3 and with conserved catalytic
      residues across the P4HA family.
    action: ACCEPT
    reason: This is the defining core molecular function of P4HA3; the IBA inference agrees with
      the experimental characterization of the recombinant alpha(III) enzyme.
    supported_by:
    - reference_id: PMID:14500733
      supporting_text: led to the formation of an active enzyme that hydroxylated collagen chains
        and a collagen-like peptide and appeared to be an [alpha(III)]2 beta 2 tetramer
- term:
    id: GO:0016222
    label: procollagen-proline 4-dioxygenase complex
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: part_of
  review:
    summary: P4HA3 is the catalytic alpha subunit of the alpha2-beta2 collagen prolyl 4-hydroxylase
      tetramer, in which the beta subunit is PDI. Membership in the prolyl 4-hydroxylase complex is
      the correct cellular-component assignment.
    action: ACCEPT
    reason: Directly supported; the recombinant alpha(III) assembles with PDI into an
      [alpha(III)]2-beta2 tetramer, i.e. the procollagen-proline 4-dioxygenase complex.
    supported_by:
    - reference_id: PMID:14500733
      supporting_text: The vertebrate enzymes are alpha 2 beta 2 tetramers, the beta-subunit being
        identical to protein-disulfide isomerase (PDI)
- 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 from the EC/Rhea mapping
      (EC 1.14.11.2; RHEA:18945), redundant with the experimental and IBA evidence.
    action: ACCEPT
    reason: Correct core molecular function; the EC/Rhea reaction matches the curated catalytic
      activity of P4HA3.
    supported_by:
    - reference_id: file:human/P4HA3/P4HA3-uniprot.txt
      supporting_text: EC=1.14.11.2 {ECO:0000269|PubMed:14500733}
- term:
    id: GO:0005506
    label: iron ion binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: P4HA3 binds one Fe(2+) ion per subunit as the catalytic metal of its
      Fe(II)/2-oxoglutarate-dependent dioxygenase reaction; the InterPro-based electronic
      assignment is accurate.
    action: ACCEPT
    reason: Iron coordination (residues 440, 442, 510) is essential for catalysis; correct
      cofactor molecular function supporting the core activity.
    supported_by:
    - reference_id: file:human/P4HA3/P4HA3-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: Collagen prolyl 4-hydroxylation occurs in the ER; the electronic ER localization is
      consistent with the UniProt subcellular location and the secretory-pathway signal peptide.
    action: ACCEPT
    reason: Correct compartment; the more specific ER lumen term is also annotated.
    supported_by:
    - reference_id: file:human/P4HA3/P4HA3-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: The C-P4H tetramer resides and acts in the ER lumen, the site of procollagen folding;
      this is the precise correct compartment for P4HA3.
    action: ACCEPT
    reason: Correct and specific subcellular location, supported by the UniProt subcellular location
      and Reactome curation.
    supported_by:
    - reference_id: file:human/P4HA3/P4HA3-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: P4HA3 is a 2-oxoglutarate/Fe(II)-dependent dioxygenase that incorporates oxygen using
      paired donors (prolyl substrate and 2-oxoglutarate); this is a correct parent molecular
      function of the specific procollagen-proline 4-dioxygenase activity.
    action: ACCEPT
    reason: Accurate general oxidoreductase chemistry; the specific GO:0004656 captures the core
      function more informatively, but this parent term is not wrong.
    supported_by:
    - reference_id: file:human/P4HA3/P4HA3-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 of collagen prolyl 4-hydroxylases,
      maintaining the iron in the reduced state; the electronic assignment is accurate (KM 370 uM
      for L-ascorbate).
    action: ACCEPT
    reason: Correct cofactor-binding molecular function supporting the core dioxygenase activity.
    supported_by:
    - reference_id: file:human/P4HA3/P4HA3-uniprot.txt
      supporting_text: Name=L-ascorbate
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:25416956
  qualifier: enables
  review:
    summary: Bare protein binding derived from a large-scale binary (Y2H) interactome reference map.
      The captured partners are systematic-screen hits unrelated to the physiological PDI/collagen
      interactions, and the term is uninformative.
    action: KEEP_AS_NON_CORE
    reason: Real IntAct interactome captures but uninformative bare protein binding; not the
      functional alpha2-beta2/PDI interaction, so not elevated to core (per curation guidance).
    supported_by:
    - reference_id: PMID:25416956
      supporting_text: a systematic map of ?14,000 high-quality human binary protein-protein
        interactions
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:26871637
  qualifier: enables
  review:
    summary: Bare protein binding from a high-throughput interactome screen examining alternative
      splicing isoform interactions; uninformative for P4HA3's catalytic function.
    action: KEEP_AS_NON_CORE
    reason: Valid high-throughput interaction capture but uninformative bare protein binding; does
      not reflect the core collagen-hydroxylase function.
    supported_by:
    - reference_id: file:human/P4HA3/P4HA3-uniprot.txt
      supporting_text: 'Q7Z4N8; O43379: WDR62'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:31515488
  qualifier: enables
  review:
    summary: Bare protein binding from a high-throughput interactome screen assaying disruption of
      protein interactions by genetic variants; partners are screen captures unrelated to the
      core enzymatic function.
    action: KEEP_AS_NON_CORE
    reason: Real interactome capture but uninformative bare protein binding; not a core function.
    supported_by:
    - reference_id: file:human/P4HA3/P4HA3-uniprot.txt
      supporting_text: 'Q7Z4N8; P43356: MAGEA2B'
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:32296183
  qualifier: enables
  review:
    summary: Bare protein binding from the HuRI binary interactome reference map; the large partner
      list comprises systematic Y2H captures (keratin-associated proteins, MAGE proteins,
      transcription factors, etc.) not relevant to collagen prolyl 4-hydroxylation.
    action: KEEP_AS_NON_CORE
    reason: Real interactome captures but uninformative bare protein binding; per guidelines, kept
      non-core rather than elevated or removed.
    supported_by:
    - reference_id: file:human/P4HA3/P4HA3-uniprot.txt
      supporting_text: 'Q7Z4N8; O14964: HGS'
- term:
    id: GO:0004656
    label: procollagen-proline 4-dioxygenase activity
  evidence_type: EXP
  original_reference_id: PMID:14500733
  qualifier: enables
  review:
    summary: Direct experimental demonstration that recombinant human alpha(III), coexpressed with
      PDI, forms an active enzyme that hydroxylates collagen chains and a collagen-like peptide.
      This is the founding biochemical characterization establishing P4HA3's core function.
    action: ACCEPT
    reason: Core molecular function with direct experimental (EXP) support; the recombinant enzyme
      hydroxylated collagen substrates with catalytic properties similar to the type I/II C-P4Hs.
    supported_by:
    - reference_id: PMID:14500733
      supporting_text: led to the formation of an active enzyme that hydroxylated collagen chains
        and a collagen-like peptide and appeared to be an [alpha(III)]2 beta 2 tetramer
- 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 of P4HA3 in the ER lumen, where the collagen prolyl 4-hydroxylase
      reaction occurs; consistent with the UniProt subcellular location.
    action: ACCEPT
    reason: Correct and specific compartment; redundant with the IEA ER lumen annotation.
    supported_by:
    - reference_id: file:human/P4HA3/P4HA3-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 ER-lumen localization in the context of proline hydroxylation of a
      (viral) polyprotein substrate; the compartment assignment for P4HA3 is correct.
    action: ACCEPT
    reason: Correct compartment; redundant with other ER lumen annotations.
    supported_by:
    - reference_id: file:human/P4HA3/P4HA3-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum lumen'
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:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: PMID:14500733
  title: Identification and characterization of a third human, rat, and mouse collagen prolyl
    4-hydroxylase isoenzyme.
  findings:
  - statement: Cloning and characterization of the third vertebrate C-P4H alpha-subunit isoform
      (alpha-III); recombinant human alpha(III) coexpressed with PDI forms an active
      [alpha(III)]2-beta2 tetramer that hydroxylates collagen chains and a collagen-like peptide.
    reference_section_type: ABSTRACT
  - statement: Catalytic properties of the alpha(III) C-P4H are very similar to the type I and II
      C-P4Hs, with peptide-binding properties intermediate between the type I and type II enzymes;
      alpha(III) mRNA is expressed broadly but at much lower levels than alpha(I)/alpha(II).
    reference_section_type: ABSTRACT
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Founding biochemical characterization of P4HA3. Cache is abstract-only, but the
      core MF (procollagen-proline 4-dioxygenase activity, EC 1.14.11.2 / RHEA:18945) and the
      alpha2-beta2(PDI) tetramer are directly supported by the abstract and anchor the EXP GOA
      annotation.
- id: PMID:25416956
  title: A proteome-scale map of the human interactome network.
  findings:
  - statement: Systematic high-quality binary (Y2H) interactome map of ~14,000 human
      protein-protein interactions; source of P4HA3 bare protein binding (IPI) annotations.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: High-throughput binary interactome screen; provides bare protein binding
      captures only, not informative for P4HA3's catalytic function.
- id: PMID:26871637
  title: Widespread Expansion of Protein Interaction Capabilities by Alternative Splicing.
  findings:
  - statement: High-throughput Y2H interactome of alternative-splice isoforms; source of P4HA3
      bare protein binding (IPI) annotation.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: Isoform interactome screen; uninformative bare protein binding for P4HA3.
- id: PMID:31515488
  title: Extensive disruption of protein interactions by genetic variants across the allele
    frequency spectrum in human populations.
  findings:
  - statement: Y2H interactome assaying perturbation of protein-protein interactions by human
      genetic variants; source of P4HA3 bare protein binding (IPI) annotation.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: Variant-perturbation interactome screen; uninformative bare protein binding.
- id: PMID:32296183
  title: A reference map of the human binary protein interactome.
  findings:
  - statement: HuRI, an all-by-all reference map of ~53,000 human binary protein-protein
      interactions; source of the largest set of P4HA3 bare protein binding (IPI) captures.
    reference_section_type: ABSTRACT
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: HuRI binary interactome reference map; uninformative bare protein binding for
      P4HA3's function.
- id: PMID:34009234
  title: Collagen prolyl 4-hydroxylases modify tumor progression.
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: 'PubMed-verified review (Shi et al., Acta Biochim Biophys Sin 2021;
      DOI 10.1093/abbs/gmab065). Reviews the three C-P4H isoenzymes (P4HA1/2/3, alpha2-beta2
      with single P4HB), their regulation (cytokines, transcription factors, miRNAs),
      overexpression in tumors, and C-P4H inhibitors as anti-tumor strategies. Supports
      the core alpha2-beta2/PDI framing and the (non-core) tumor-progression context
      for P4HA3.'
- id: PMID:36588128
  title: P4HA3 promotes clear cell renal cell carcinoma progression via the PI3K/AKT/GSK3beta
    pathway.
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: 'PubMed-verified (Zhang et al., Med Oncol 2023; DOI 10.1007/s12032-022-01926-2).
      P4HA3 is overexpressed in clear cell renal cell carcinoma (TCGA) and high expression
      correlates with worse overall survival; P4HA3 knockdown inhibits ccRCC cell
      proliferation, migration and invasion, with GSEA/Western blot implicating EMT
      and PI3K/AKT/GSK3beta signaling. P4HA3-specific functional-perturbation evidence
      in a tumor context (non-core for the catalytic annotation).'
- id: PMID:39362976
  title: Comprehensive analysis reveals that P4HA3 is a prognostic and diagnostic
    gastric cancer biomarker that can predict immunotherapy efficacy.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: 'PubMed-verified (Yu et al., Sci Rep 2024; DOI 10.1038/s41598-024-73784-z).
      TCGA/TIMER bioinformatic analysis associating elevated P4HA3 with adverse prognosis
      and immune-microenvironment features (immune infiltration, TMB, MSI, immune
      checkpoints) in gastric cancer; proposes P4HA3 as an immunotherapy-response
      biomarker. Correlative biomarker context, non-core.'
- id: PMID:39394821
  title: 'Collagen prolyl 4-hydroxylase subunit alpha member-induced head and neck
    squamous cell carcinoma aggressiveness is antagonized by LLGL2 via reduced expression
    of occludin.'
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: 'PubMed-verified (Xu et al., Acta Biochim Biophys Sin 2024; DOI
      10.3724/abbs.2024140). TCGA analysis of all three C-P4HA alpha subunits (including
      P4HA3) in HNSCC; combined higher expression of the three is prognostically adverse
      and antagonized by LLGL2 via occludin; knockdown of C-P4HA subunits reduces
      migration/invasion. Family-level cancer context, non-core for P4HA3.'
- id: PMID:39504328
  title: A computational analysis of the oncogenic and anti-tumor immunity role of
    P4HA3 in human cancers.
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: 'PubMed-verified (Huang et al., PLoS Comput Biol 2024; DOI 10.1371/journal.pcbi.1012284).
      Pan-cancer (33 tumor types) analysis with experimental validation: P4HA3 expression
      correlates with tumor-microenvironment infiltration, proliferation and EMT markers;
      P4HA3 depletion inhibits proliferation/migration/invasion and enhances anti-tumor
      PD-1/PD-L1 immunotherapy response (including TNBC PDX models). P4HA3-specific
      functional evidence in tumor/immune context (non-core for the catalytic annotation).'
- 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/P4HA3/P4HA3-uniprot.txt
  title: UniProt entry Q7Z4N8 (P4HA3_HUMAN), Prolyl 4-hydroxylase subunit alpha-3
  findings:
  - statement: ER-lumenal Fe(II)/2-oxoglutarate-dependent dioxygenase (EC 1.14.11.2) that forms
      4-hydroxyproline in -Xaa-Pro-Gly- sequences in collagens; binds 1 Fe(2+) per subunit and
      requires L-ascorbate; catalytic alpha subunit of an alpha2-beta2 tetramer with PDI.
    reference_section_type: OTHER
core_functions:
- description: Catalytic alpha subunit of collagen prolyl 4-hydroxylase that, as part of an
    alpha2-beta2 tetramer with PDI, hydroxylates proline residues in -X-Pro-Gly- triplets of
    procollagen to form trans-4-hydroxyproline, a modification required for collagen triple-helix
    folding and stability.
  molecular_function:
    id: GO:0004656
    label: procollagen-proline 4-dioxygenase activity
  locations:
  - id: GO:0005788
    label: endoplasmic reticulum lumen
  supported_by:
  - reference_id: PMID:14500733
    supporting_text: led to the formation of an active enzyme that hydroxylated collagen chains and
      a collagen-like peptide and appeared to be an [alpha(III)]2 beta 2 tetramer
  - reference_id: file:human/P4HA3/P4HA3-uniprot.txt
    supporting_text: Catalyzes the post-translational formation of 4-
- description: Fe(II)- and 2-oxoglutarate-dependent dioxygenase that uses L-ascorbate as a cofactor
    and molecular oxygen as co-substrate, coupling decarboxylation of 2-oxoglutarate to
    hydroxylation of the prolyl substrate.
  molecular_function:
    id: GO:0004656
    label: procollagen-proline 4-dioxygenase activity
  supported_by:
  - reference_id: file:human/P4HA3/P4HA3-uniprot.txt
    supporting_text: Reaction=L-prolyl-[collagen] + 2-oxoglutarate + O2 = trans-4-hydroxy-L-
      prolyl-[collagen] + succinate + CO2
proposed_new_terms: []
suggested_questions:
- question: Does P4HA3-containing C-P4H have a distinct substrate preference (e.g. for particular
    collagen types or non-collagenous Pro-Gly-containing substrates) that distinguishes it from the
    alpha(I)- and alpha(II)-containing isoenzymes, given its intermediate peptide-binding properties?
- question: Is the elevated P4HA3 expression in vascular smooth muscle, atherosclerotic fibrous cap,
    and certain tumors associated with a direct collagen-hydroxylation role in ECM remodeling, or
    with non-catalytic/contextual functions?
suggested_experiments:
- description: Reconstitute recombinant [alpha(III)]2-beta2 (P4HA3/PDI) C-P4H and measure steady-state
    kinetics and substrate specificity against a panel of collagen-type peptides versus the type I
    and type II C-P4Hs to define isoenzyme-specific substrate preferences.
- description: CRISPR knockout or knockdown of P4HA3 in cells with high endogenous expression (e.g.
    placental or vascular smooth muscle cells) followed by mass spectrometry quantification of
    collagen 4-hydroxyproline content to assess its non-redundant contribution to collagen
    hydroxylation in vivo.

P4HA3

Gene Description

Existing Annotations Review

Core Functions

Catalytic alpha subunit of collagen prolyl 4-hydroxylase that, as part of an alpha2-beta2 tetramer with PDI, hydroxylates proline residues in -X-Pro-Gly- triplets of procollagen to form trans-4-hydroxyproline, a modification required for collagen triple-helix folding and stability.

Fe(II)- and 2-oxoglutarate-dependent dioxygenase that uses L-ascorbate as a cofactor and molecular oxygen as co-substrate, coupling decarboxylation of 2-oxoglutarate to hydroxylation of the prolyl substrate.

References

Suggested Questions for Experts

Suggested Experiments

Deep Research

Falcon

Research Report: Human P4HA3 (UniProt Q7Z4N8) — Functional Annotation and Translational Context

1) Target verification (critical identity checks)

2) Key concepts and definitions (current understanding)

2.1 What P4HA3 is (molecular identity)

2.2 Enzymatic reaction and substrate specificity

2.3 Cofactors, cosubstrates, and byproducts

2.4 Subcellular localization and complex context

3) Biological roles and pathway placement

3.1 Core biological function: enabling collagen maturation and ECM assembly

3.2 Tissue/isoform context

4) Recent developments (2023–2024 emphasis)

4.1 Clear cell renal cell carcinoma (ccRCC) — clinical association + functional perturbation

4.2 Gastric cancer (GC/STAD) — biomarker + immunotherapy-response associations

4.3 Head and neck squamous cell carcinoma (HNSCC) — C-P4HA contribution to invasion/migration

4.4 Pan-cancer and immunotherapy: P4HA3 and tumor microenvironment (TME)

5) Current applications and real-world implementations

5.1 Biomarker use cases (current state)

5.2 Therapeutic targeting considerations

6) Expert synthesis and interpretation (authoritative perspectives)

7) Key quantitative statistics (recent studies)

8) Evidence map (summary table)

9) Limitations and open questions

Key cited sources (publication date, URL)

Artifacts

Citations

📚 Additional Documentation

Notes

P4HA3 (Prolyl 4-hydroxylase subunit alpha-3) — gene review notes

Core identity and function

Subcellular location

Tissue expression / context

Annotation notes / GOA review reasoning

Cited reference quality summary

Falcon deep-research findings (incorporated 2026-06)

Pn Notes

P4HA3 PN Consistency Notes

Source Files Checked

Deep Research Files

AIGR Review Snapshot

PN Consistency Summary

Full Consistency Review

PN Dossier Context

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

Projected GO annotations (1)

Note

📄 View Raw YAML