Ciliary Targeting of Olfactory CNG Channels Requires the CNGB1b Subunit and the Kinesin-2 Motor Protein, KIF17

Abstract

Nonmotile cilia on olfactory sensory neurons (OSNs) compartmentalize signaling molecules, including odorant receptors and cyclic nucleotide-gated (CNG) channels, allowing for efficient, spatially confined responses to sensory stimuli . Little is known about the mechanisms of the ciliary targeting of olfactory CNG channels, composed of three subunits: CNGA2, CNGA4, and CNGB1b . Recent reports suggest that subunit composition of the retinal CNG channel influences localization, leading to disease . However, the mechanistic role of subunits in properly targeting native olfactory CNG channels remains unclear. Here, we show that heteromeric assembly with CNGB1b, containing a critical carboxy-terminal motif (RVxP), is required for ciliary trafficking of olfactory CNG channels. Movement of proteins within the cilia is governed by intraflagellar transport (IFT), a process that facilitates bidirectional movement of cargo along microtubules. Work in C. elegans has established that heterotrimeric and homodimeric kinesin-2 family members play a critical role in anterograde transport . In mammalian systems, the heterotrimeric KIF3a/KIF3b/KAP-3 complex plays a clear role in IFT; however, no role has been established for KIF17, the mammalian homolog of OSM-3 . Here, we demonstrate that KIF17 is required for olfactory CNG channel targeting, providing novel insights into mechanisms of mammalian ciliary transport.