Affinage

POC5

Centrosomal protein POC5 · UniProt Q8NA72

Length
575 aa
Mass
63.4 kDa
Annotated
2026-04-28
12 papers in source corpus 8 papers cited in narrative 8 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

POC5 is a centrin-binding centriolar protein that localizes to the distal portion of centrioles and is essential for centriole elongation, ciliogenesis, and cell cycle progression. It contains Sfi1p-like repeats that mediate calcium-dependent interaction with centrin2; it is recruited to procentrioles during G2/M in a hyperphosphorylation-dependent manner and is required for building the distal half of centrioles, with its depletion causing G1 arrest or S-phase accumulation and cell death (PMID:19349582, PMID:23844208). POC5 interacts with multiple cilia and cytoskeleton components, is transiently incorporated into assembling basal bodies, and is required for basal body maturation and subsequent cilium formation in both vertebrate and ciliate systems (PMID:32350068, PMID:30845169, PMID:29272404). Bi-allelic loss-of-function variants in POC5 cause a syndromic ciliopathy featuring rod-cone dystrophy, insulin-resistant diabetes, and kidney disease, while heterozygous missense variants in the protein cause familial idiopathic scoliosis (PMID:40590205, PMID:25642776).

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 2009 High

    Establishing POC5 as a centriolar structural protein resolved how the distal half of centrioles is built: POC5 localizes to the distal centriole, is recruited during G2/M concomitant with hyperphosphorylation, and is essential for distal centriole elongation but dispensable for procentriole initiation.

    Evidence siRNA knockdown, immunofluorescence, electron microscopy, and cell cycle analysis in RPE1 and HeLa cells

    PMID:19349582

    Open questions at the time
    • Kinase(s) responsible for POC5 hyperphosphorylation not identified
    • Structural basis of POC5 incorporation into the distal centriole not resolved
    • Whether the G1 arrest upon POC5 loss is a direct cell cycle role or secondary to centriole defects is unclear
  2. 2013 Medium

    Demonstrating that POC5 linear assembly depends on centrin2's calcium-binding capacity established the molecular logic of the POC5–centrin interaction and showed that this pair can scaffold recruitment of other centrosomal proteins (PCM-1, NEDD1).

    Evidence Overexpression of POC5 in centrin-null DT40 cells with calcium-binding-deficient centrin2 mutants

    PMID:23844208

    Open questions at the time
    • Stoichiometry and direct binding affinity of the POC5–centrin2 complex not determined
    • Physiological relevance of the linear structures formed upon overexpression is uncertain
  3. 2015 High

    Identifying three POC5 missense variants that co-segregate with idiopathic scoliosis in families and recapitulate spine deformity in zebrafish established POC5 as a causative gene for adolescent idiopathic scoliosis.

    Evidence Genetic linkage and exome sequencing in multiple families, zebrafish mRNA injection with morphological phenotyping

    PMID:25642776

    Open questions at the time
    • Mechanism by which centriole/ciliary defects translate to asymmetric spine growth not elucidated
    • Tissue-specific requirement for POC5 in spine development not defined
  4. 2018 High

    Localizing POC5 to the photoreceptor connecting cilium and showing that its loss shortens outer segments and impairs visual function demonstrated a specific requirement for POC5 in retinal ciliogenesis.

    Evidence Morpholino knockdown in zebrafish with wild-type human POC5 mRNA rescue, immunohistochemistry, visual motor response assay

    PMID:29272404

    Open questions at the time
    • Whether POC5 acts in outer segment disc morphogenesis or only in cilium assembly is not distinguished
    • Mechanism of POC5 action at the connecting cilium not characterized
  5. 2019 Medium

    Showing that the AIS-associated A429V variant mislocalizes POC5, disrupts specific cilia/cytoskeleton protein interactions, and causes ciliary retraction linked the genetic variants to a concrete cellular defect.

    Evidence IP-MS interactome, immunofluorescence, and cell cycle analysis comparing wild-type and A429V POC5 in cultured cells

    PMID:30845169

    Open questions at the time
    • Specific interaction partners most critical for the scoliosis phenotype not pinpointed
    • Whether S-phase accumulation is primary or secondary to ciliary retraction is unknown
  6. 2020 High

    Complete genomic knockout in Tetrahymena revealed that Poc5 is transiently incorporated into assembling basal bodies and then removed, and is required for basal body maturation; its loss causes basal body overproduction but severely reduced ciliation, clarifying its role in the assembly-to-ciliation transition.

    Evidence Genomic knockout with rescue, live imaging, electron microscopy, and double-knockout epistasis with SFR1 in Tetrahymena

    PMID:32350068

    Open questions at the time
    • Mechanism of POC5 removal from mature basal bodies not defined
    • Whether the basal body overproduction phenotype reflects a feedback circuit involving POC5 is untested
    • Functional relationship between POC5 and SFR1 at the molecular level is not resolved
  7. 2023 Medium

    Identifying an estrogen response element in the POC5 promoter and showing ERα recruitment upon estradiol treatment established POC5 as a direct transcriptional target of estrogen signaling, providing a potential link between hormonal regulation and the sex bias of idiopathic scoliosis.

    Evidence Promoter reporter assays, ChIP for ERα at the POC5 ERE, gene/protein expression in osteoblasts treated with estradiol

    PMID:37239471

    Open questions at the time
    • In vivo relevance of estrogen-dependent POC5 regulation for scoliosis pathogenesis not tested
    • Whether other hormonal axes regulate POC5 expression is unknown
  8. 2025 Medium

    Demonstrating that bi-allelic loss-of-function POC5 variants cause a multi-organ ciliopathy syndrome broadened the disease spectrum from skeletal-only to systemic, confirming POC5 as essential for ciliary function across tissues.

    Evidence Cohort phenotyping of 12 families with POC5 localization studies in patient-derived fibroblasts

    PMID:40590205

    Open questions at the time
    • Detailed ciliary ultrastructure in patient cells not reported
    • Genotype–phenotype correlations across different loss-of-function alleles not established
    • Whether residual POC5 function explains variable expressivity is untested

Open questions

Synthesis pass · forward-looking unresolved questions
  • The kinase(s) that phosphorylate POC5 to trigger its G2/M recruitment, the structural basis of its distal centriole integration, and the precise mechanism by which POC5 deficiency causes tissue-specific pathology across the ciliopathy spectrum remain unresolved.
  • No kinase identified for POC5 hyperphosphorylation
  • No high-resolution structure of POC5 or the POC5–centrin complex
  • Mechanism linking POC5 ciliary defects to tissue-specific disease manifestations unknown

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0008092 cytoskeletal protein binding 3 GO:0005198 structural molecule activity 2
Localization
GO:0005815 microtubule organizing center 3 GO:0005929 cilium 3
Pathway
R-HSA-1640170 Cell Cycle 2 R-HSA-1852241 Organelle biogenesis and maintenance 2
Partners
CETN2NEDD1PCM1

Evidence

Reading pass · 8 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2009 hPOC5 is a centrin-binding protein containing Sfi1p-like repeats that localizes to the distal portion of human centrioles. It is not required for initiation of procentriole assembly but is essential for building the distal half of centrioles. hPOC5 is recruited to procentrioles during G2/M and its recruitment is correlated with hyperphosphorylation of the protein. In the absence of hPOC5, RPE1 cells arrest in G1 phase and HeLa cells show extended S phase followed by cell death. Immunofluorescence localization, siRNA knockdown with cell cycle analysis, electron microscopy of centriole structure, identification of Sfi1p-like centrin-binding repeats The Journal of cell biology High 19349582
2013 Overexpression of POC5 leads to the assembly of linear, centrin-dependent structures that recruit other centrosomal proteins such as PCM-1 and NEDD1. This linear POC5 assembly requires the calcium-binding capacity of centrin2. Overexpression of POC5 in centrin-null DT40 cells, immunofluorescence imaging of linear structures, expression of calcium-binding-deficient centrin2 mutants PloS one Medium 23844208
2015 Three missense variants in POC5 (p.A446T, p.A455P, p.A429V) co-segregate with idiopathic scoliosis in families, and expression of any of these variants in zebrafish causes spine deformity without affecting other skeletal structures, establishing POC5 as a causative gene for idiopathic scoliosis. Genetic linkage analysis, exome sequencing, zebrafish mRNA injection rescue/variant expression with morphological phenotyping The Journal of clinical investigation High 25642776
2018 POC5 localizes to the photoreceptor connecting cilium, and morpholino knockdown of poc5 in zebrafish results in decreased length of photoreceptor outer segments and decreased visual motor response (retinal function), which is rescued by wild-type human POC5 mRNA, establishing POC5 as required for normal retinal development. Immunohistochemistry for localization, morpholino knockdown in zebrafish, mRNA rescue experiment, visual motor response assay Human molecular genetics High 29272404
2019 The AIS-associated POC5 variant (p.A429V) alters subcellular localization of POC5 and induces ciliary retraction. Immunoprecipitation coupled to mass spectrometry identified specific protein interaction partners of POC5, most of which are components of cilia and cytoskeleton, and several of these interactions are altered by the p.A429V mutation. Cells expressing POC5A429V accumulate in S-phase. Immunofluorescence localization of wt vs. mutant POC5, cilia length measurement, co-immunoprecipitation coupled to mass spectrometry, cell cycle analysis by flow cytometry PloS one Medium 30845169
2020 In Tetrahymena thermophila (a model organism ortholog study), Poc5 transiently incorporates into assembling basal bodies and is then removed from mature basal bodies prior to ciliogenesis. Genomic knockout of TtPOC5 causes increased production of basal bodies but markedly reduced ciliary density, both rescued by reintroduction of TtPoc5, demonstrating a requirement for Poc5 in building mature basal bodies. Co-deletion of TtPOC5 and a second POC5-like gene SFR1 exacerbates basal body overproduction and compromises cell viability. Genomic knockout, live cell imaging, electron microscopy, rescue by reintroduction, double knockout genetic epistasis Journal of cell science High 32350068
2023 POC5 is an estrogen-responsive gene regulated by estrogen receptor ERα. An estrogen response element (ERE) in the proximal promoter of POC5 confers estrogen responsiveness, and ERα is recruited to this ERE upon estradiol treatment. Estradiol upregulates POC5 in normal osteoblasts via direct genomic ERα signaling, with differential effects observed in cells expressing the AIS-associated POC5A429V variant. Promoter activity assays, gene and protein expression assays with estradiol treatment, chromatin immunoprecipitation (ERα recruitment to ERE) Genes Medium 37239471
2025 Bi-allelic loss-of-function variants in POC5 cause a syndromic ciliopathy. Localization studies in proband-derived fibroblast cell lines show aberrant POC5 localization, indicating a ciliary defect underlying the syndrome (rod-cone dystrophy, diabetes with severe insulin resistance and partial lipodystrophy, kidney disease, muscle cramps). Cohort phenotyping, POC5 localization studies in patient-derived fibroblast cell lines 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
2020 Tetrahymena Poc5 is a transient basal body component that is important for basal body maturation. Journal of cell science 6 32350068
2021 Prevalence of POC5 Coding Variants in French-Canadian and British AIS Cohort. Genes 5 34356048
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 3 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