id: Q8IVL5 gene_symbol: P3H2 product_type: PROTEIN status: COMPLETE taxon: id: NCBITaxon:9606 label: Homo sapiens description: P3H2 (prolyl 3-hydroxylase 2, also LEPREL1/MLAT4) is an endoplasmic reticulum-lumenal, 2-oxoglutarate/Fe(II)-dependent dioxygenase (EC 1.14.11.7) of the leprecan/prolyl 3-hydroxylase family (P3H1/P3H2/P3H3). It catalyzes post-translational formation of (trans-)3-hydroxyproline on procollagen, hydroxylating the first proline in Gly-Pro-4Hyp triplets and requiring a pre-existing 4-hydroxyproline in the third position. P3H2 shows high activity toward the basement-membrane collagen type IV (COL4A1), which has the highest 3-hydroxyproline content of all collagens, and lower activity toward collagen I; it is thus considered the principal modifier of basement-membrane collagens, complementing the fibrillar-collagen isoenzyme P3H1. The enzyme uses Fe(II) and L-ascorbate (vitamin C) as cofactors and 2-oxoglutarate as a co-substrate. The 708-residue precursor has an N-terminal signal sequence, tetratricopeptide (TPR) repeats, an Fe2OG dioxygenase (prolyl 4-hydroxylase alpha-type) catalytic domain, and a C-terminal KDEL-type ER-retention motif that retains it in the ER/sarcoplasmic reticulum; it is also detected in the Golgi. P3H2 is broadly expressed with enrichment in basement-membrane-rich tissues such as kidney and in muscle. Loss-of-function variants cause autosomal-recessive high myopia with cataract and vitreoretinal degeneration (MCVD), consistent with a role in ocular/lens-capsule basement-membrane collagen biogenesis. alternative_products: - name: '1' id: Q8IVL5-1 - name: '2' id: Q8IVL5-2 sequence_note: VSP_053814 existing_annotations: - term: id: GO:0005783 label: endoplasmic reticulum evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: is_active_in review: summary: P3H2 acts in the endoplasmic reticulum, where collagen prolyl hydroxylation occurs prior to secretion. The phylogenetic (IBA) ER localization is consistent with direct experimental evidence (IDA) and the C-terminal ER-retention motif. action: ACCEPT reason: ER is the correct catalytic compartment; supported by IDA (PMID:15063763), the KDEL-type ER-retention motif, and the UniProt subcellular location. supported_by: - reference_id: file:human/P3H2/P3H2-uniprot.txt supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum' - term: id: GO:0019797 label: procollagen-proline 3-dioxygenase activity evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: enables review: summary: Procollagen-proline 3-dioxygenase activity is the core molecular function of P3H2, conserved across the P3H/leprecan family and directly demonstrated for human P3H2 on collagen IV-derived peptides. action: ACCEPT reason: Core molecular function; corroborated by IDA (PMID:18487197), EC 1.14.11.7, and family-level conservation. supported_by: - reference_id: file:human/P3H2/P3H2-uniprot.txt supporting_text: Prolyl 3-hydroxylase that catalyzes the post-translational formation of 3-hydroxyproline on collagens - term: id: GO:0032963 label: collagen metabolic process evidence_type: IBA original_reference_id: GO_REF:0000033 qualifier: involved_in review: summary: By 3-hydroxylating procollagen prolyl residues, P3H2 participates in collagen biosynthesis/metabolism; the phylogenetic annotation is consistent with the experimental IDA evidence. action: ACCEPT reason: Correct biological process; redundant with IDA (PMID:18487197) collagen metabolic process annotation. supported_by: - reference_id: file:human/P3H2/P3H2-uniprot.txt supporting_text: post-translational formation of 3-hydroxyproline on collagens - term: id: GO:0005506 label: iron ion binding evidence_type: IEA original_reference_id: GO_REF:0000002 qualifier: enables review: summary: As a 2-oxoglutarate/Fe(II)-dependent dioxygenase, P3H2 coordinates a catalytic Fe(II) ion (binding residues 580/582/652) required for hydroxylation. This cofactor binding supports, but is subsidiary to, the informative procollagen-proline 3-dioxygenase activity. action: KEEP_AS_NON_CORE reason: Accurate catalytic cofactor attribute (Fe cation cofactor; Fe-binding residues in the Fe2OG domain) but a supporting feature rather than the standalone core function. supported_by: - reference_id: file:human/P3H2/P3H2-uniprot.txt supporting_text: Name=Fe cation - term: id: GO:0005783 label: endoplasmic reticulum evidence_type: IEA original_reference_id: GO_REF:0000044 qualifier: located_in review: summary: Electronic transfer of ER localization from the UniProt subcellular location, consistent with the stronger IDA/IBA evidence. action: ACCEPT reason: Correct compartment; redundant with experimental ER localization. supported_by: - reference_id: file:human/P3H2/P3H2-uniprot.txt supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum' - term: id: GO:0005794 label: Golgi apparatus evidence_type: IEA original_reference_id: GO_REF:0000044 qualifier: located_in review: summary: Electronic transfer of the Golgi localization from the UniProt subcellular location. Golgi residence is a reported secondary localization; the catalytic site of action is the ER lumen. action: KEEP_AS_NON_CORE reason: Accurate reported localization (UniProt/IDA) but secondary to the ER, where collagen prolyl hydroxylation occurs; not the core site of action. supported_by: - reference_id: file:human/P3H2/P3H2-uniprot.txt supporting_text: Golgi apparatus - term: id: GO:0016529 label: sarcoplasmic reticulum evidence_type: IEA original_reference_id: GO_REF:0000044 qualifier: located_in review: summary: The sarcoplasmic reticulum is the specialized ER of muscle; this localization is consistent with the strong muscle expression and muscle-specific transcript of P3H2 reported by Jaernum et al. action: KEEP_AS_NON_CORE reason: Accurate UniProt-derived localization reflecting muscle-tissue ER, but a tissue-specific variant of the ER compartment rather than a distinct core function. supported_by: - reference_id: file:human/P3H2/P3H2-uniprot.txt supporting_text: Sarcoplasmic reticulum - 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: This is the parent oxidoreductase class for the dioxygenase reaction P3H2 catalyzes (it incorporates one atom of O2 into proline while reducing 2-oxoglutarate). Correct but less informative than the specific procollagen-proline 3-dioxygenase activity. action: KEEP_AS_NON_CORE reason: Correct but generic parent term; the specific GO:0019797 captures the core catalytic activity. supported_by: - reference_id: file:human/P3H2/P3H2-uniprot.txt supporting_text: EC=1.14.11.7 - term: id: GO:0019797 label: procollagen-proline 3-dioxygenase activity evidence_type: IEA original_reference_id: GO_REF:0000120 qualifier: enables review: summary: Electronic (multi-method, EC/Rhea-based) assignment of the core procollagen-proline 3-dioxygenase activity, consistent with the experimental IDA evidence and EC 1.14.11.7. action: ACCEPT reason: Correct core molecular function; redundant with IDA/IBA evidence. supported_by: - reference_id: file:human/P3H2/P3H2-uniprot.txt supporting_text: EC=1.14.11.7 - term: id: GO:0031418 label: L-ascorbic acid binding evidence_type: IEA original_reference_id: GO_REF:0000002 qualifier: enables review: summary: P3H2 uses L-ascorbate (vitamin C) as a cofactor to maintain the active-site iron in the reduced state, a hallmark of collagen prolyl hydroxylases. This cofactor binding supports the catalytic activity. action: KEEP_AS_NON_CORE reason: Accurate catalytic cofactor attribute (L-ascorbate cofactor; KM=110 uM for ascorbate) but subsidiary to the informative procollagen-proline 3-dioxygenase activity. supported_by: - reference_id: file:human/P3H2/P3H2-uniprot.txt supporting_text: Name=L-ascorbate - term: id: GO:0032963 label: collagen metabolic process evidence_type: IEA original_reference_id: GO_REF:0000120 qualifier: involved_in review: summary: Electronic assignment of the collagen metabolic process, consistent with the experimental IDA evidence. action: ACCEPT reason: Correct biological process; redundant with IDA (PMID:18487197). supported_by: - reference_id: file:human/P3H2/P3H2-uniprot.txt supporting_text: 3-hydroxyproline on collagens - term: id: GO:0005604 label: basement membrane evidence_type: IEA original_reference_id: GO_REF:0000107 qualifier: located_in review: summary: Basement membrane is the location of P3H2's collagen IV substrate/product, not where the enzyme itself acts. P3H2 is an ER-resident enzyme (KDEL-type retention motif) that modifies procollagen in the ER lumen before secretion; it is not a structural component of the assembled basement membrane. This annotation is transferred electronically from the mouse ortholog. action: MARK_AS_OVER_ANNOTATED reason: Ortholog-transferred (Ensembl/ISS from Q8CG71) localization to basement membrane conflates the enzyme's ER site of action with the destination of its collagen IV substrate; P3H2 acts in the ER and is retained there by a KDEL-type motif. supported_by: - reference_id: file:human/P3H2/P3H2-uniprot.txt supporting_text: Prevents secretion from ER - term: id: GO:0005794 label: Golgi apparatus evidence_type: IDA original_reference_id: GO_REF:0000052 qualifier: located_in review: summary: Immunofluorescence (HPA) evidence for Golgi localization, consistent with the reported ER-and-Golgi distribution of P3H2. The catalytic site of action remains the ER lumen. action: KEEP_AS_NON_CORE reason: Direct (IDA) reported localization but secondary to the ER catalytic compartment; not the core site of action. supported_by: - reference_id: file:human/P3H2/P3H2-uniprot.txt supporting_text: Golgi apparatus - term: id: GO:0005788 label: endoplasmic reticulum lumen evidence_type: TAS original_reference_id: Reactome:R-HSA-1980233 qualifier: located_in review: summary: Reactome curation places P3H2 in the ER lumen, the precise compartment where collagen prolyl 3-hydroxylation occurs. This is the most informative cellular-component term for the enzyme. action: ACCEPT reason: Correct and precise catalytic compartment; consistent with the ER localization and ER-retention motif. supported_by: - reference_id: file:human/P3H2/P3H2-uniprot.txt supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum' - term: id: GO:0005788 label: endoplasmic reticulum lumen evidence_type: TAS original_reference_id: Reactome:R-HSA-8948226 qualifier: located_in review: summary: Reactome curation of P3H2 in the ER lumen during the collagen 3-hydroxylation reaction cycle. action: ACCEPT reason: Correct precise catalytic compartment; redundant with the other ER lumen TAS annotation. supported_by: - reference_id: file:human/P3H2/P3H2-uniprot.txt supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum' - term: id: GO:0005788 label: endoplasmic reticulum lumen evidence_type: TAS original_reference_id: Reactome:R-HSA-8948230 qualifier: located_in review: summary: Reactome curation of P3H2 in the ER lumen, where it binds 4-Hyp collagen propeptides. action: ACCEPT reason: Correct precise catalytic compartment; redundant with the other ER lumen TAS annotations. supported_by: - reference_id: file:human/P3H2/P3H2-uniprot.txt supporting_text: 'SUBCELLULAR LOCATION: Endoplasmic reticulum' - term: id: GO:0005604 label: basement membrane evidence_type: ISS original_reference_id: GO_REF:0000024 qualifier: located_in review: summary: Sequence-similarity (ISS, from mouse ortholog Q8CG71) transfer of basement membrane localization. As with the IEA version, this reflects the location of the collagen IV substrate/product rather than the ER-resident enzyme's site of action. action: MARK_AS_OVER_ANNOTATED reason: ISS transfer from the mouse ortholog conflates enzyme site of action (ER) with the destination of its collagen IV substrate; P3H2 is ER-retained via a KDEL-type motif. supported_by: - reference_id: file:human/P3H2/P3H2-uniprot.txt supporting_text: Prevents secretion from ER - term: id: GO:0019511 label: peptidyl-proline hydroxylation evidence_type: IDA original_reference_id: PMID:18487197 qualifier: involved_in review: summary: P3H2 directly hydroxylates peptidyl-proline residues; the recombinant enzyme assay demonstrated robust activity on (Gly-Pro-4Hyp)5 and collagen IV-derived peptides. This is the biological-process view of the core catalytic function. action: ACCEPT reason: Directly demonstrated peptidyl-proline hydroxylation activity (IDA); the central biological process of P3H2. supported_by: - reference_id: PMID:18487197 supporting_text: A large amount of P3H activity was found in the P3H2 samples with (Gly-Pro-4Hyp)5 as a substrate - term: id: GO:0019797 label: procollagen-proline 3-dioxygenase activity evidence_type: IDA original_reference_id: PMID:18487197 qualifier: enables review: summary: Direct experimental demonstration that recombinant human P3H2 catalyzes prolyl 3-hydroxylation, with high activity toward collagen IV sequences. This is the core molecular function of the enzyme. action: ACCEPT reason: Core molecular function with direct experimental (IDA) support; defines P3H2 as the collagen IV-preferring prolyl 3-hydroxylase isoenzyme (EC 1.14.11.7). supported_by: - reference_id: PMID:18487197 supporting_text: P3H2 hydroxylated more effectively two synthetic peptides corresponding to sequences that are hydroxylated in collagen IV than a peptide corresponding to the 3-hydroxylation site in collagen I - term: id: GO:0032963 label: collagen metabolic process evidence_type: IDA original_reference_id: PMID:18487197 qualifier: involved_in review: summary: P3H2 contributes to collagen metabolism by modifying procollagen prolyl residues, with a preference for the basement-membrane collagen IV. action: ACCEPT reason: Directly supported (IDA) collagen-modifying process; central to P3H2's biological role. supported_by: - reference_id: PMID:18487197 supporting_text: P3H2 is responsible for the hydroxylation of collagen IV, which has the highest 3-hydroxyproline content of all collagens - term: id: GO:0005783 label: endoplasmic reticulum evidence_type: IDA original_reference_id: PMID:15063763 qualifier: located_in review: summary: Direct immunofluorescence evidence that LEPREL1/P3H2 localizes to the ER, consistent with its role as an ER-lumenal collagen-modifying enzyme and its KDEL-type retention motif. action: ACCEPT reason: IDA-supported ER localization agrees with the catalytic site of action and the ER-retention motif. supported_by: - reference_id: PMID:15063763 supporting_text: LEPREL1 is localized to the ER and Golgi network - term: id: GO:0005794 label: Golgi apparatus evidence_type: IDA original_reference_id: PMID:15063763 qualifier: located_in review: summary: Direct immunofluorescence evidence that LEPREL1/P3H2 also localizes to the Golgi. This is a reported secondary localization; the ER lumen is the catalytic compartment. action: KEEP_AS_NON_CORE reason: Direct (IDA) reported localization but secondary to the ER site of action for collagen prolyl hydroxylation. supported_by: - reference_id: PMID:15063763 supporting_text: LEPREL1 is localized to the ER and Golgi network - term: id: GO:0008285 label: negative regulation of cell population proliferation evidence_type: IDA original_reference_id: PMID:19436308 qualifier: involved_in review: summary: P3H2 is epigenetically silenced by promoter CpG methylation in breast cancer, and ectopic re-expression suppresses colony formation, indicating a tumor-suppressor-like anti-proliferative effect. The colony-suppression assay was performed with P3H2 cDNA in P3H2-silenced breast cancer cell lines (MCF7, T47D), so the experimental annotation is gene-specific and should be retained. However, this is a context-dependent, likely indirect phenotype rather than the enzyme's core ER collagen-modifying function. action: KEEP_AS_NON_CORE reason: Real gene-specific experimental (IDA) phenotype, but an indirect/context-dependent tumor-suppressor effect of overexpression in cancer cell lines, not the core catalytic function; retained as non-core per guidelines. supported_by: - reference_id: PMID:19436308 supporting_text: Ectopic expression of P3H2 and P3H3 in cell lines with silencing of the endogenous gene results in suppression of colony growth references: - id: GO_REF:0000002 title: Gene Ontology annotation through association of InterPro records with GO terms findings: [] - id: GO_REF:0000024 title: Manual transfer of experimentally-verified manual GO annotation data to orthologs by curator judgment of sequence similarity findings: [] - id: GO_REF:0000033 title: Annotation inferences using phylogenetic trees findings: [] - id: GO_REF:0000044 title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt findings: [] - id: GO_REF:0000052 title: Gene Ontology annotation based on curation of immunofluorescence data findings: [] - id: GO_REF: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:15063763 title: LEPREL1, a novel ER and Golgi resident member of the Leprecan family. findings: - statement: LEPREL1/P3H2 is an 80 kDa, 708-residue ER/Golgi-resident protein of the leprecan family with a signal sequence, four TPRs, a P4Halpha domain, and a C-terminal KDEL ER-retention motif; over-expression perturbs ER PDI staining. reference_section_type: ABSTRACT reference_review: relevance: HIGH correctness: VERIFIED review_notes: PubMed-verified original characterization of LEPREL1 (P3H2); establishes ER/Golgi localization and domain architecture. Abstract-only cache. - id: PMID:18487197 title: Characterization of recombinant human prolyl 3-hydroxylase isoenzyme 2, an enzyme modifying the basement membrane collagen IV. findings: - statement: Recombinant human P3H2 has prolyl 3-hydroxylase activity on (Gly-Pro-4Hyp)5 and preferentially hydroxylates collagen IV-derived peptides over a collagen I site, identifying P3H2 as the collagen IV-modifying isoenzyme; it is enriched in basement-membrane-rich tissues such as kidney and does not require CRTAP. reference_section_type: ABSTRACT reference_review: relevance: HIGH correctness: VERIFIED review_notes: PubMed-verified; the definitive enzymatic characterization underpinning the IDA molecular-function and process annotations and EC 1.14.11.7. Abstract-only cache. - id: PMID:19436308 title: The prolyl 3-hydroxylases P3H2 and P3H3 are novel targets for epigenetic silencing in breast cancer. findings: - statement: P3H2 (and P3H3) are silenced by promoter CpG hypermethylation in breast cancer; ectopic re-expression of P3H2 in silenced breast cancer cell lines suppresses colony growth, implying tumor-suppressor-like anti-proliferative activity. reference_section_type: RESULTS reference_review: relevance: MEDIUM correctness: VERIFIED review_notes: PubMed-verified, full text available; supports the GO:0008285 IDA. The anti-proliferative effect is an indirect/context-dependent phenotype, not the core enzymatic function. - id: PMID:29491144 title: Post-translational modification of type IV collagen with 3-hydroxyproline affects its interactions with glycoprotein VI and nidogens 1 and 2. findings: - statement: Using P3H2-knockout PFHR-9 cells and tandem MS, P3H2 is shown to be the major (but not the only) 3-hydroxyproline-modifying enzyme of type IV collagen; 3-Hyp on collagen IV modulates its interactions with glycoprotein VI (reduced 3-Hyp increases GP6 binding) and is required for nidogen 1/2 binding. reference_section_type: ABSTRACT reference_review: relevance: HIGH correctness: VERIFIED review_notes: PubMed-verified (DOI 10.1074/jbc.RA117.000406). Direct P3H2 KO study confirming P3H2 as the principal collagen IV 3-hydroxylase and linking the 3-Hyp mark to collagen IV interaction partners (GP6, nidogens). Supports the collagen IV substrate specificity and basement-membrane biological role. Not cached; no verbatim supporting_text added. - id: PMID:33918807 title: Prolyl 3-Hydroxylase 2 Is a Molecular Player of Angiogenesis. findings: - statement: P3H2 is induced by VEGF-A in human endothelial cells via VEGFR-2/p38 MAPK signaling; through its activity on type IV collagen it is required for angiogenic properties in vitro, and P3H2 knockdown prevents pathological angiogenesis in a laser-induced choroidal neovascularization model. reference_section_type: ABSTRACT reference_review: relevance: MEDIUM correctness: VERIFIED review_notes: PubMed-verified (DOI 10.3390/ijms22083896). Implicates P3H2 in VEGF-driven endothelial basement-membrane (collagen IV) remodeling and angiogenesis; a context-dependent physiological role downstream of the core collagen IV-modifying activity. Not cached; no verbatim supporting_text added. - id: PMID:35499085 title: Loss of the collagen IV modifier prolyl 3-hydroxylase 2 causes thin basement membrane nephropathy. findings: - statement: P3H2 was identified as a glomerular basement membrane (GBM) modifier in a cohort of patients with albuminuria; it 3-hydroxylates prolines in collagen IV subchains in the ER, and podocyte-specific loss in mice produces a thin basement membrane nephropathy (TBMN) phenotype with progressive microhematuria and microalbuminuria. Loss/mutation of P3H2 causes TBMN and focal segmental glomerulosclerosis (FSGS) in mice and humans. reference_section_type: ABSTRACT reference_review: relevance: HIGH correctness: VERIFIED review_notes: PubMed-verified (DOI 10.1172/JCI147253). First identification of P3H2 as a GBM modifier; in vivo confirmation of collagen IV as the physiological substrate and a new renal disease association (TBMN/FSGS) complementing the ocular (MCVD high myopia) phenotype. Not cached; no verbatim supporting_text added. - id: Reactome:R-HSA-1980233 title: Collagen prolyl 3-hydroxylase converts 4-Hyp collagen to 3,4-Hyp collagen findings: [] - id: Reactome:R-HSA-8948226 title: Prolyl 3-hydroxylases:Fe2+:3,4-Hyp collagen propeptides dissociates findings: [] - id: Reactome:R-HSA-8948230 title: P3HB binds 4-Hyp-collagen propeptides findings: [] - id: file:human/P3H2/P3H2-uniprot.txt title: UniProt entry Q8IVL5 (P3H2_HUMAN), prolyl 3-hydroxylase 2 findings: - statement: ER-lumenal 2-oxoglutarate/Fe(II)-dependent dioxygenase (EC 1.14.11.7) that 3-hydroxylates procollagen prolyl residues (high activity on collagen IV/COL4A1, lower on COL1A1); uses Fe cation and L-ascorbate cofactors; contains an Fe2OG dioxygenase domain and a C-terminal KDEL-type ER-retention motif; ER/sarcoplasmic reticulum/Golgi localization; loss-of-function variant causes MCVD high myopia. reference_section_type: OTHER core_functions: - description: ER-lumenal 2-oxoglutarate/Fe(II)-dependent prolyl 3-hydroxylase that catalyzes post-translational 3-hydroxylation of specific prolyl residues in procollagen (the first Pro of Gly-Pro-4Hyp triplets), acting preferentially on basement-membrane collagen type IV. molecular_function: id: GO:0019797 label: procollagen-proline 3-dioxygenase activity locations: - id: GO:0005788 label: endoplasmic reticulum lumen supported_by: - reference_id: PMID:18487197 supporting_text: P3H2 hydroxylated more effectively two synthetic peptides corresponding to sequences that are hydroxylated in collagen IV than a peptide corresponding to the 3-hydroxylation site in collagen I - reference_id: file:human/P3H2/P3H2-uniprot.txt supporting_text: Prolyl 3-hydroxylase that catalyzes the post-translational formation of 3-hydroxyproline on collagens directly_involved_in: - id: GO:0019511 label: peptidyl-proline hydroxylation - id: GO:0032963 label: collagen metabolic process proposed_new_terms: [] suggested_questions: - question: Does P3H2 act as a monomer or within a multiprotein complex in the ER lumen, and does it (like P3H1/CRTAP/PPIB) have additional chaperone/foldase or non-catalytic roles in basement-membrane collagen biogenesis? - question: Is the anti-proliferative/tumor-suppressor effect of P3H2 in breast cancer a consequence of its collagen-modifying enzymatic activity (e.g. altered ECM signaling) or an activity-independent moonlighting function? suggested_experiments: - description: Quantitative mass spectrometry of 3-hydroxyproline sites on collagen IV (and other basement-membrane collagens) from P3H2-knockout versus wild-type cells/tissues to define the in vivo substrate site repertoire and confirm collagen IV specificity. - description: Structure-function analysis of the MCVD G508V variant (and active-site mutants) measuring prolyl 3-hydroxylase activity, folding/solubility, and ER retention to establish the molecular basis of the loss of function underlying high myopia.