TRAPPC14

TRAPPC14 (C7orf43/MAP11) is a TRAPPII complex-specific subunit that links the multisubunit tethering complex to the early steps of ciliogenesis (PMID:31467083). It directly binds Rabin8, a Rab8 GEF, and is required for Rabin8 accumulation at the preciliary centrosome, thereby coupling TRAPPII to preciliary vesicle trafficking; although it mediates Rabin8 association with TRAPPII, it is itself dispensable for TRAPPII complex integrity (PMID:31467083). TRAPPC14 also engages the distal appendage proteins FBF1 and CEP83, which are themselves needed for Rabin8 centrosomal accumulation, consistent with TRAPPII tethering preciliary vesicles to the mother centriole (PMID:31467083). Independently, TRAPPC14 associates with mitotic spindles and physically interacts with α-tubulin during mitosis, with its expression preceding α-tubulin at sites of midbody gap formation during abscission, implicating it in spindle dynamics and cytokinesis (PMID:30715179). Loss of TRAPPC14 reduces cell proliferation without inducing apoptosis in human cells and produces microcephaly with decreased neuronal proliferation in zebrafish (PMID:30715179).

1. 2019 High

   Established TRAPPC14 as a dedicated TRAPPII-complex subunit that couples the tethering complex to the ciliogenesis machinery rather than to general complex assembly.

   Evidence Co-sedimentation, direct protein interaction assays, and knockdown/reconstitution showing TRAPPII association but dispensability for complex integrity

   PMID:31467083

   Open questions at the time

   • Structural basis of TRAPPC14 integration into TRAPPII not resolved
   • Whether TRAPPC14 modulates TRAPPII GEF activity is unknown
2. 2019 High

   Identified the direct Rabin8 interaction and its functional requirement, defining how TRAPPC14 routes a Rab8 GEF to the preciliary centrosome.

   Evidence MS-based interactome screen, direct binding assay, co-sedimentation, and knockdown with centrosome accumulation readout

   PMID:31467083

   Open questions at the time

   • Binding interface on Rabin8 not mapped
   • Downstream effect on Rab8 activation not directly measured
3. 2019 Medium

   Connected TRAPPC14/TRAPPII to mother-centriole distal appendages, providing a tethering mechanism for preciliary vesicle docking.

   Evidence Co-immunoprecipitation with FBF1/CEP83 and knockdown with fluorescence-based centrosome accumulation assay

   PMID:31467083

   Open questions at the time

   • Direct versus indirect nature of FBF1/CEP83 binding not resolved
   • Order of recruitment relative to Rabin8 not established
4. 2019 Medium

   Revealed a ciliogenesis-independent role at the mitotic spindle and midbody, suggesting TRAPPC14 acts as a microtubule-associated protein during cell division.

   Evidence Immunofluorescence co-localization and co-immunoprecipitation with α-tubulin in SH-SY5Y cells

   PMID:30715179

   Open questions at the time

   • Whether α-tubulin binding is direct is unclear
   • Functional requirement for spindle/midbody dynamics not tested by perturbation
5. 2019 Medium

   Linked TRAPPC14 loss to a proliferation defect and microcephaly, establishing physiological relevance for neurodevelopment.

   Evidence Lentiviral shRNA knockdown with proliferation/apoptosis assays in human cells and CRISPR/Cas9 knockout in zebrafish

   PMID:30715179

   Open questions at the time

   • Causal mutation in human microcephaly patients not described here
   • Mechanism connecting proliferation loss to ciliary versus mitotic functions unresolved
6. 2019 Low

   Proposed a transcriptional link to TERT expression via YAP1, hinting at a role in proliferative/telomere regulation.

   Evidence Genome-wide shRNA screen and TERT promoter assay mapping a responsive site

   PMID:30447097

   Open questions at the time

   • Single lab, limited mechanistic depth on the YAP1 connection
   • Direct molecular link between TRAPPC14 and the TERT promoter not demonstrated
   • Relationship to ciliary or mitotic functions unknown

• How TRAPPC14's roles in preciliary vesicle tethering and mitotic spindle/cytokinesis are mechanistically coordinated, and whether either underlies the proliferation/microcephaly phenotype, remains unresolved.
• No structural model of TRAPPC14 within TRAPPII
• PLK1 functional interaction not validated
• No reconstitution of the tethering step