CEP120 interacts with C2CD3 and Talpid3 and is required for centriole appendage assembly and ciliogenesis

Abstract

Centrosomal protein 120 (CEP120) was originally identified as a daughter centriole-enriched protein that participates in centriole elongation. Recent studies showed that CEP120 gene mutations cause complex ciliopathy phenotypes in humans, including Joubert syndrome and Jeune asphyxiating thoracic dystrophy, suggesting that CEP120 plays an additional role in ciliogenesis. To investigate the potential roles of CEP120 in centriole elongation and cilia formation, we knocked out the CEP120 gene in p53-deficient RPE1 cells using the CRISPR/Cas9 editing system, and performed various analyses. We herein report that loss of CEP120 produces short centrioles with no apparent distal and subdistal appendages. CEP120 knockout was also associated with defective centriole elongation, impaired recruitment of C2CD3 and Talpid3 to the distal ends of centrioles, and consequent defects in centriole appendage assembly and cilia formation. Interestingly, wild-type CEP120 interacts with C2CD3 and Talpid3, whereas a disease-associated CEP120 mutant (I975S) has a low affinity for C2CD3 binding and perturbs cilia assembly. Together, our findings reveal a novel role of CEP120 in ciliogenesis by showing that it interacts with C2CD3 and Talpid3 to assemble centriole appendages and by illuminating the molecular mechanism through which the CEP120 (I975S) mutation causes complex ciliopathies.

A ciliopathy complex builds distal appendages to initiate ciliogenesis

“…Consequent to their role in distal appendage formation, CEP90 and MNR are also required for subsequent events in ciliogenesis, including recruitment of the preciliary vesicles that give rise to the ciliary membrane, and loading of IFT88 (Sillibourne et al, 2013;Tanos et al, 2013). Unlike some other centriolar proteins, such as CEP120 (Tsai et al, 2019), CEP90 and MNR are specifically required for distal appendage formation, but dispensable for subdistal appendage formation, revealing that discrete mother centriolar complexes support distal and subdistal appendage assembly.…”

Phosphorylation and Ubiquitylation Regulate Protein Trafficking, Signaling, and the Biogenesis of Primary Cilia

“…In actively proliferating cells, the distal ends of both mother and daughter centrioles are capped by protein complexes of CP110 and CEP97 that suppress cilia formation (Spektor et al, 2007;Schmidt et al, 2009). Recruitment of these caps seems to follow a hierarchical scheme, the precise order of which awaits clarification (Ye et al, 2014;Tsai et al, 2019). One central component involved in ciliogenesis is the microtubule-depolymerizing kinesin KIF24 (Kobayashi et al, 2011).…”

With Age Comes Maturity: Biochemical and Structural Transformation of a Human Centriole in the Making

“…Over-elongation of older centrioles is also somehow counteracted by a component of the distal centriole end, Ofd1 [136]. Finally, a group of centriolar proteins including RTTN [137] (Ana3 in Drosophila [138]), PPP1R35 [139,140], Cep295 [141], POC5 [142], and C2CD3 [143,144], which are situated in the vicinity of procentriole MT walls, are all critical for the formation of full-length centrioles. RTTN, Cep295, and PPP1R35 are incorporated at the proximal ends of procentrioles in S 1 phase, while POC5 and C2CD3 are incorporated in G2 1 phase and are more distal (Figure 4).…”