Abstract
The primary cilium is a cellular sensor that detects light, chemicals, and movement and is important for morphogen and growth factor signaling. The small GTPase Rab11-Rab8 cascade is required for ciliogenesis. Rab11 traffics the guanine nucleotide exchange factor (GEF) Rabin8 to the centrosome to activate Rab8, needed for ciliary growth. Rabin8 also requires the transport particle protein complex (TRAPPC) proteins for centrosome recruitment during ciliogenesis. Here, using an MS-based approach for identifying Rabin8-interacting proteins, we identified C7orf43 (also known as microtubule-associated protein 11 (MAP11)) as being required for ciliation both in human cells and zebrafish embryos. We find that C7orf43 directly binds to Rabin8 and that C7orf43 knockdown diminishes Rabin8 preciliary centrosome accumulation. Interestingly, we found that C7orf43 co-sediments with TRAPPII complex subunits and directly interacts with TRAPPC proteins. Our findings establish that C7orf43 is a TRAPPII-specific complex component, referred to here as TRAPPC14. Additionally, we show that TRAPPC14 is dispensable for TRAPPII complex integrity but mediates Rabin8 association with the TRAPPII complex. Finally, we demonstrate that TRAPPC14 interacts with the distal appendage proteins Fas-binding factor 1 (FBF1) and centrosomal protein 83 (CEP83), which we show here are required for GFP-Rabin8 centrosomal accumulation, supporting a role for the TRAPPII complex in tethering preciliary vesicles to the mother centriole during ciliogenesis. In summary, our findings have revealed an uncharacterized TRAPPII-specific component, C7orf43/TRAPPC14, that regulates preciliary trafficking of Rabin8 and ciliogenesis and support previous findings that the TRAPPII complex functions as a membrane tether.
Highlights
The primary cilium is a cellular sensor that detects light, chemicals, and movement and is important for morphogen and growth factor signaling
We have identified an uncharacterized TRAPPII-specific component, C7orf43/TRAPPC14, that regulates Rabin8 preciliary trafficking and ciliogenesis
We demonstrate that TRAPPC14 directly binds to core TRAPP, TRAPPIIspecific subunits, and Rabin8 and is required for TRAPPII complex association with Rabin8
Summary
Adrian Cuenca‡, Christine Insinna‡, Huijie Zhao‡, Peter John‡, Matthew A. Weiss‡, X Quanlong Lu‡, Vijay Walia‡, Suzanne Specht‡, Selvambigai Manivannan§1, Jimmy Stauffer‡, X Andrew A. Westlake‡2 From the ‡Center for Cancer Research, NCI-Frederick, National Institutes of Health, Laboratory of Cellular and Developmental Signaling, Frederick, Maryland 21702 and the §Department of Biomedical Sciences, University of Sheffield, Sheffield S10 2TN, United Kingdom
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