CCDC47

CCDC47 is an ER-resident component of the ribosome-associated multipass translocon that governs the co-translational biogenesis of multi-spanning membrane proteins (PMID:32820719). It functions as the obligate heterodimeric partner of Asterix (WDR83OS) in the PAT intramembrane chaperone complex, which engages nascent transmembrane domains bearing unshielded hydrophilic side chains within the bilayer and disengages once the substrate folds; loss of either subunit reduces the biogenesis of numerous multi-spanning membrane proteins (PMID:32814900). Mechanistically, CCDC47 occludes and latches the Sec61 lateral gate closed, while Asterix captures the substrate and redirects it to a semi-enclosed, lipid-filled cavity behind Sec61 where multiple TMDs insert and fold (PMID:36261528); a gating role for CCDC47 in restricting Sec61 access is structurally conserved in a fungal SND translocon (PMID:41162385). Independently of this chaperone role, CCDC47 participates in ER-associated degradation, co-immunoprecipitating with p97, BIP, Derlin-1, Derlin-2, and VIMP and supporting misfolded-protein turnover and ER-to-cytosol dislocation (PMID:25009997), and it is required for ER Ca2+ homeostasis, with bi-allelic loss-of-function variants in patients impairing ER Ca2+ storage, IP3R-mediated release, and store-operated Ca2+ entry (PMID:30401460). Loss of CCDC47 in mouse embryos causes ER stress and embryonic lethality (PMID:25009997).

1. 2014 High

   Established the first molecular role for CCDC47 (calumin) by placing it in the ERAD machinery, addressing what cellular process this ER protein serves.

   Evidence Co-IP with p97/BIP/Derlin-1/Derlin-2/VIMP plus ERAD functional assays and knockout mouse embryo analysis

   PMID:25009997

   Open questions at the time

   • Did not resolve whether CCDC47 acts directly in dislocation or as a scaffold
   • No structural basis for the ERAD partner interactions
   • Relationship to its later-defined chaperone role left undefined
2. 2018 Medium

   Linked CCDC47 to ER Ca2+ homeostasis in humans, showing its loss disrupts Ca2+ storage and signaling and answering whether CCDC47 dysfunction has a physiological/clinical consequence.

   Evidence Patient-derived cells with bi-allelic loss-of-function variants assayed for ER Ca2+ stores, IP3R release, and SOCE

   PMID:30401460

   Open questions at the time

   • Mechanism connecting CCDC47 to IP3R and SOCE machinery not defined
   • Single lab
   • Whether Ca2+ defects are direct or secondary to translocon/ERAD dysfunction unresolved
3. 2018 Low

   Provided a gain-of-function correlate for the Ca2+ role, showing CCDC47 overexpression enhances cardiomyocyte Ca2+ release and reuptake.

   Evidence CCDC47 overexpression in rat H9C2 cells with ionomycin-induced Ca2+ assay

   PMID:30140426

   Open questions at the time

   • Single overexpression experiment in one cell line and method
   • No mechanistic interaction established
   • Not validated by loss-of-function
4. 2020 High

   Defined CCDC47 as a constituent of a large ribosome-associated multipass translocon selective for multi-spanning clients, reframing it as a biogenesis factor.

   Evidence Cryo-EM of the ~360 kDa translocon, client mRNA-seq profiling, and knockout reducing the multi-pass client EAAT1

   PMID:32820719

   Open questions at the time

   • Did not define CCDC47's specific molecular action within the assembly
   • Mechanism of client selectivity unresolved
5. 2020 High

   Identified the obligate CCDC47–Asterix PAT heterodimer as an intramembrane chaperone that engages unshielded TMDs, establishing the molecular function underlying multipass biogenesis.

   Evidence Reciprocal Co-IP, PAT complex reconstitution, and loss-of-function assays across many multi-spanning substrates

   PMID:32814900

   Open questions at the time

   • Did not yet show the structural mechanism of substrate handoff
   • Division of labor between CCDC47 and Asterix not resolved at this stage
6. 2022 High

   Resolved the mechanism of action: CCDC47 latches the Sec61 lateral gate closed while Asterix redirects substrates into a lipid-filled cavity behind Sec61 for folding.

   Evidence Cryo-EM of trapped biogenesis intermediates with biochemical trapping and Sec61 lateral-gate inhibitor assays

   PMID:36261528

   Open questions at the time

   • Dynamics and kinetics of gate latching not quantified
   • How specific TMD features trigger PAT engagement/release not fully defined
7. 2025 Medium

   Showed CCDC47-mediated gating of the Sec61 translocon is conserved in a fungal SND-pathway translocon, generalizing the latching role.

   Evidence Cryo-EM of the Chaetomium thermophilum SND3 translocon with SEC61 and TRAPα

   PMID:41162385

   Open questions at the time

   • Single study in a fungal ortholog
   • Functional consequence of SND-context gating not assayed
8. 2025 Medium

   Connected CCDC47 physically to SOCE machinery, identifying SPCA2C, STIM1, and Orai1 partners and a domain dependence for Ca2+ enhancement.

   Evidence Co-IP, co-localization, co-expression SOCE assays in HEK-Orai1 cells, and domain-deletion mapping to the coiled-coil/TM regions

   PMID:40783819

   Open questions at the time

   • Single lab
   • Whether interactions are direct vs. complex-mediated not established
   • Physiological relevance beyond overexpression context unknown

• It remains unresolved how CCDC47's three reported roles — PAT-complex chaperoning, ERAD support, and Ca2+ handling — are mechanistically integrated within the same ER protein.
• No unified model linking translocon gating to Ca2+ regulation
• Direct vs. indirect basis of Ca2+ phenotypes undefined
• Structural basis of ERAD partner engagement uncharacterized