The Ciliopathy-Associated Cep104 Protein Interacts with Tubulin and Nek1 Kinase

Abstract

SummaryCilia are thin cell projections with essential roles in cell motility, fluid movement, sensing, and signaling. They are templated from centrioles that dock against the plasma membrane and subsequently extend their peripheral microtubule array. The molecular mechanisms underpinning cilia assembly are incompletely understood. Cep104 is a key factor involved in cilia formation and length regulation that rides on the ends of elongating and shrinking cilia. It is mutated in Joubert syndrome, a genetically heterogeneous ciliopathy. Here we provide structural and biochemical data that Cep104 contains a tubulin-binding TOG (tumor overexpressed gene) domain and a novel C2HC zinc finger array. Furthermore, we identify the kinase Nek1, another ciliopathy-associated protein, as a potential binding partner of this array. Finally, we show that Nek1 competes for binding to Cep104 with the distal centriole-capping protein CP110. Our data suggest a model for Cep104 activity during ciliogenesis and provide a novel link between Cep104 and Nek1.

A Proximity Mapping Journey into the Biology of the Mammalian Centrosome/Cilium Complex

“…In the proximity maps generated for retinal degeneration-associated CCDC66 and Joubert syndrome-associated CEP104 and CEP120, proteins implicated in ciliogenesis were highly enriched. Consistent with these interactions, functional studies showed that CEP104 interacts with Nek1and functions in cilium length regulation, and CCDC66 interacts with the CEP290 and is required for cilium assembly [129,151]. Additionally, structural and interaction studies of CEP120 ciliopathy mutants defined its destabilization as a consequence of the mutations and showed that mutant cells were defective in their ability to ciliate [132].…”

“…To date, proximity mapping has been used to mechanistically dissect these processes using both targeted and systematic approaches. As for the targeted approaches, proximity interaction maps were generated for known regulators of cilium assembly as well as proteins mutated in ciliopathies including CEP72, CCDC66, CEP104, MIB1, ARL13B, CDC14A, LUZP1 and CEP120 [122,129,130,132,[134][135][136]151]. As with centriole duplication, these maps identified new functional modules required for specific steps of cilium assembly and revealed mechanisms that underlie ciliopathies.…”

A cryptic tubulin-binding domain links MEKK1 to curved tubulin protomers

“…S6 and Table S3 and refs. 50 and 51 ). The CEP104 and MEKK1 TOG domains both share a similar pair of arginine-rich C-terminal helices relative to canonical TOGs.…”

A cryptic tubulin-binding domain links MEKK1 to microtubule remodelling

“…At the structural level, MEKK1 has common TOG features, but also divergence at the N-and C-termini that may facilitate its role. One close structural homolog of MEKK1 is another recently-identified TOG domain from CEP104 (Supplementary Figure 5; Supplementary Table 3; (Al-Jassar et al, 2017;Rezabkova et al, 2016)). The CEP104 and MEKK1 TOG domains both share a similar pair of additional C-terminal helices relative to canonical TOGs.…”