Affinage

POC5

Centrosomal protein POC5 · UniProt Q8NA72

Length
575 aa
Mass
63.4 kDa
Annotated
2026-06-10
12 papers in source corpus 8 papers cited in narrative 9 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 8/8 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

POC5 is a conserved centrin-binding centriolar protein that is required for elongation of the distal half of centrioles and for basal body maturation prior to ciliogenesis (PMID:19349582, PMID:32350068). Containing Sfi1p-like repeats, it localizes to the distal portion of human centrioles and is dispensable for procentriole initiation but essential for completing assembly of the distal centriole, with loss causing centriole truncation and cell-cycle arrest (PMID:19349582). Recruitment to procentrioles occurs during G2/M and continues through maturation in the subsequent cycle, correlating with hyperphosphorylation of the protein (PMID:19349582). POC5 acts as a scaffold for centrin: its overexpression nucleates linear, centrin-dependent assemblies that co-recruit additional centrosomal proteins including PCM-1 and NEDD1 in a calcium-binding-dependent manner (PMID:23844208). In Tetrahymena it transiently incorporates into assembling basal bodies and is removed before ciliogenesis, and its loss yields excess basal bodies with reduced ciliary density and defective transition zone formation (PMID:32350068). Consistent with a ciliary role, POC5 localizes to the photoreceptor connecting cilium and is required for outer segment length and visual function (PMID:29272404). Bi-allelic loss-of-function variants in POC5 cause a multiorgan ciliopathy encompassing rod-cone dystrophy, diabetes with insulin resistance/lipodystrophy, kidney disease, and muscle cramps, with aberrant POC5 localization in patient fibroblasts (PMID:40590205), while specific missense variants are linked to idiopathic scoliosis through a centriolar mechanism (PMID:25642776). POC5 transcription is directly regulated by estrogen receptor ERα via a proximal-promoter estrogen response element (PMID:37239471).

Mechanistic history

Synthesis pass · year-by-year structured walk · 9 steps
  1. 2009 High

    Established POC5 as a centrin-binding distal-centriole component whose loss truncates centrioles, defining its role in building the distal half rather than initiating procentriole assembly.

    Evidence Co-localization and RNAi knockdown in RPE1 and HeLa cells with structural and cell-cycle phenotype readouts

    PMID:19349582

    Open questions at the time
    • Molecular detail of how POC5 drives distal elongation unresolved
    • Direct centrin-POC5 binding interface not mapped in this work
  2. 2009 Medium

    Showed POC5 recruitment is cell-cycle-staged (G2/M onward) and coupled to hyperphosphorylation, implicating phosphoregulation in its centriolar loading.

    Evidence Cell-cycle staging with immunofluorescence and phosphorylation analysis

    PMID:19349582

    Open questions at the time
    • Responsible kinase(s) not identified
    • Functional consequence of phosphorylation for recruitment not tested by phosphomutants
  3. 2013 Medium

    Demonstrated POC5 scaffolds centrin into higher-order linear assemblies that recruit other centrosomal proteins, defining a structural assembly function dependent on calcium binding.

    Evidence Overexpression in centrin-null DT40 cells with PCM-1 and NEDD1 co-recruitment readouts

    PMID:23844208

    Open questions at the time
    • Overexpression artifact possibility; no in vitro reconstitution
    • Whether these assemblies reflect endogenous centriolar architecture unclear
  4. 2015 Medium

    Linked POC5 missense variants to idiopathic scoliosis, providing in vivo functional evidence that POC5 dysfunction produces spine deformity.

    Evidence Zebrafish mRNA injection of human variant mRNAs plus family genetic linkage and exome sequencing

    PMID:25642776

    Open questions at the time
    • Mechanism connecting centriolar defect to spine patterning not established
    • Single lab in vivo model
  5. 2018 High

    Placed POC5 at the photoreceptor connecting cilium and tied its loss to outer segment and visual defects, extending its role to ciliary function in differentiated tissue.

    Evidence Retinal immunohistochemistry and zebrafish morpholino knockdown with visual motor response and human mRNA rescue

    PMID:29272404

    Open questions at the time
    • Whether photoreceptor defect is cell-autonomous to the connecting cilium not dissected
    • Morpholino specificity considerations
  6. 2019 Medium

    Characterized the scoliosis-associated A429V allele as mislocalizing POC5, retracting cilia, stalling the cell cycle, and disrupting cilia/cytoskeletal interactions, connecting variant biochemistry to phenotype.

    Evidence Wild-type vs mutant overexpression with imaging, flow cytometry, and IP-mass spectrometry

    PMID:30845169

    Open questions at the time
    • IP-MS partners not reciprocally validated
    • Overexpression context may not reflect endogenous variant behavior
  7. 2020 High

    Defined POC5 as a transient basal-body component required for transition zone formation and proper ciliary density, showing it is removed before ciliogenesis.

    Evidence Tetrahymena genomic knockout with electron microscopy, fluorescence imaging, and rescue

    PMID:32350068

    Open questions at the time
    • Mechanism of POC5 removal prior to ciliogenesis unknown
    • How loss simultaneously increases basal body number yet reduces cilia unresolved
  8. 2023 Medium

    Identified POC5 as a direct ERα transcriptional target via a proximal-promoter ERE, providing a hormonal regulatory axis differing between normal and AIS-mutant osteoblasts.

    Evidence Promoter activity assays, expression assays, and ERα ChIP after estradiol treatment in normal and POC5-A429V osteoblasts

    PMID:37239471

    Open questions at the time
    • Functional consequence of estrogen-driven POC5 expression for centriole biology not shown
    • Single-lab study
  9. 2025 Medium

    Established bi-allelic POC5 loss-of-function as a cause of a multiorgan ciliopathy with aberrant POC5 localization, broadening the disease spectrum beyond scoliosis.

    Evidence POC5 localization studies in proband-derived fibroblasts across a 12-family cohort with detailed phenotyping

    PMID:40590205

    Open questions at the time
    • Tissue-specific mechanisms underlying diabetes, kidney, and muscle phenotypes not dissected
    • Genotype-phenotype correlation across variants incomplete

Open questions

Synthesis pass · forward-looking unresolved questions
  • The kinases controlling POC5 hyperphosphorylation and how phosphoregulation, calcium-dependent centrin scaffolding, and transition zone assembly are mechanistically coupled remain unresolved.
  • No structural model of the POC5-centrin distal centriole assembly
  • Kinase(s) driving recruitment-linked phosphorylation unidentified
  • Direct molecular link from centriolar defect to each ciliopathy organ phenotype missing

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005198 structural molecule activity 3 GO:0008092 cytoskeletal protein binding 2
Localization
GO:0005815 microtubule organizing center 2 GO:0005929 cilium 2
Pathway
R-HSA-1640170 Cell Cycle 2 R-HSA-1852241 Organelle biogenesis and maintenance 2
Partners
CETN2ESR1NEDD1PCM1
Complex memberships
basal bodycentriole distal centrosome

Evidence

Reading pass · 9 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2009 hPOC5 is a centrin-binding protein that contains Sfi1p-like repeats and localizes to the distal portion of human centrioles, where it is required for assembly of the distal half of centrioles but not for initiation of procentriole assembly. Co-localization studies, RNAi knockdown in RPE1 and HeLa cells with phenotypic readout (centriole truncation, G1 arrest or S-phase extension), immunofluorescence The Journal of cell biology High 19349582
2009 hPOC5 recruitment to procentrioles occurs during G2/M and continues through centriole maturation in the next cell cycle, and this recruitment is correlated with hyperphosphorylation of the protein. Cell-cycle staging combined with immunofluorescence and phosphorylation analysis The Journal of cell biology Medium 19349582
2013 Overexpression of POC5 leads to the assembly of linear, centrin-dependent structures that also recruit other centrosomal proteins such as PCM-1 and NEDD1, demonstrating that POC5 can scaffold centrin into higher-order assemblies in a calcium-binding-dependent manner. Overexpression in centrin-null DT40 cells, immunofluorescence to detect linear structures and co-recruitment of PCM-1 and NEDD1 PloS one Medium 23844208
2015 Three missense variants in POC5 (p.A446T, p.A455P, p.A429V) cause spine deformity when expressed in zebrafish, establishing a functional link between POC5 variants and idiopathic scoliosis through a centriolar mechanism. Zebrafish mRNA injection of human IS-associated POC5 variant mRNAs with phenotypic readout (spine deformity); genetic linkage and exome sequencing in affected families The Journal of clinical investigation Medium 25642776
2018 POC5 localizes specifically to the photoreceptor connecting cilium, and morpholino knockdown of poc5 in zebrafish results in decreased photoreceptor outer segment length and reduced visual function, rescuable by wild-type human POC5 mRNA. Immunohistochemistry in retinal tissue; morpholino knockdown in zebrafish with visual motor response assay and rescue experiment Human molecular genetics High 29272404
2019 The AIS-associated variant POC5-A429V alters the subcellular localization of POC5, induces ciliary retraction, impairs cell-cycle progression (S-phase accumulation), and disrupts specific protein-protein interactions with cilia and cytoskeletal components as identified by immunoprecipitation-mass spectrometry. Overexpression of wild-type vs. mutant POC5 in cells; immunofluorescence for localization and cilia length; flow cytometry for cell-cycle analysis; co-IP coupled to mass spectrometry for interaction partners PloS one Medium 30845169
2020 In Tetrahymena thermophila, Poc5 transiently incorporates into assembling basal bodies and is removed prior to ciliogenesis; knockout of TtPOC5 increases basal body production but reduces ciliary density, with defective transition zone formation, phenotypes rescued by reintroduction of TtPoc5. Genomic knockout in Tetrahymena, electron microscopy, fluorescence imaging, rescue by reintroduction of TtPoc5 Journal of cell science High 32350068
2023 POC5 is an estrogen-responsive gene under direct transcriptional regulation by estrogen receptor ERα; an estrogen response element (ERE) in the proximal POC5 promoter confers estrogen responsiveness, and ERα is recruited to this ERE upon estradiol treatment, with differential regulation observed between normal osteoblasts and AIS mutant POC5-A429V osteoblasts. Promoter activity assays, gene and protein expression assays, ChIP (ERα recruitment to ERE), estradiol treatment in normal and mutant osteoblasts Genes Medium 37239471
2025 Bi-allelic loss-of-function variants in POC5 cause aberrant POC5 localization in proband-derived fibroblasts, consistent with a ciliary defect, and result in a multiorgan ciliopathy syndrome including rod-cone dystrophy, diabetes with insulin resistance/lipodystrophy, kidney disease, and muscle cramps. POC5 localization studies in proband-derived fibroblast cell lines; detailed phenotyping of 12 families with bi-allelic LoF variants Genetics in medicine Medium 40590205

Source papers

Stage 0 corpus · 12 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2009 hPOC5 is a centrin-binding protein required for assembly of full-length centrioles. The Journal of cell biology 146 19349582
2015 Functional variants of POC5 identified in patients with idiopathic scoliosis. The Journal of clinical investigation 83 25642776
2019 Adolescent idiopathic scoliosis associated POC5 mutation impairs cell cycle, cilia length and centrosome protein interactions. PloS one 27 30845169
2013 Calcium-binding capacity of centrin2 is required for linear POC5 assembly but not for nucleotide excision repair. PloS one 25 23844208
2018 Whole-exome sequencing reveals POC5 as a novel gene associated with autosomal recessive retinitis pigmentosa. Human molecular genetics 23 29272404
2018 Common Variant of POC5 Is Associated With the Susceptibility of Adolescent Idiopathic Scoliosis. Spine 16 29189569
2021 Prevalence of POC5 Coding Variants in French-Canadian and British AIS Cohort. Genes 6 34356048
2020 Tetrahymena Poc5 is a transient basal body component that is important for basal body maturation. Journal of cell science 6 32350068
2024 Targeted RNA sequencing in diagnostically challenging head and neck carcinomas identifies novel MON2::STAT6, NFATC2::NUTM2B, POC5::RAF1, and NSD3::NCOA2 gene fusions. Histopathology 4 39628352
2023 Differential Regulation of POC5 by ERα in Human Normal and Scoliotic Cells. Genes 2 37239471
2025 Exploring the Potential Roles of SLC39A8 and POC5 Missense Variants in the Association Between Body Composition, Beverage Consumption, and Chronic Lung Diseases: A Two-Sample Mendelian Randomization Study. International journal of molecular sciences 1 40869120
2025 Bi-allelic loss-of-function variants in POC5 cause a syndromic retinal, endocrine, and neuromuscular ciliopathy. Genetics in medicine : official journal of the American College of Medical Genetics 0 40590205

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