Involved in membrane protein trafficking at the base of the ciliary organelle. Mediates recruitment onto plasma membrane of the BBSome complex which would constitute a coat complex required for sorting of specific membrane proteins to the primary cilia. Together with the BBSome complex and LTZL1, controls SMO ciliary trafficking and contributes to the sonic hedgehog (SHH) pathway regulation. May regulate cilia assembly and disassembly and subsequent ciliary signaling events such as the Wnt signaling cascade. Isoform 2 may be required for proper retinal function and organization (By similarity). Interacts with SEC61B, ARL6IP1, ARL6IP2, ARL6IP3, ARL6IP4 ARL6IP5 and ARL6IP6. Interacts (GTP-bound form) with the BBSome a complex that contains BBS1, BBS2, BBS4, BBS5, BBS7, BBS8/TTC8, BBS9 and BBIP10. Interacts (GTP-free form) with IFT27. Appears in a pattern of punctae flanking the microtubule axoneme that likely correspond to small membrane-associated patches. Localizes to the so-called ciliary gate where vesicles carrying ciliary cargo fuse with the membrane (By similarity). Belongs to the small GTPase superfamily. Arf family.