Cilium-specific protein required to control the microtubule-based, ciliary axoneme structure. May act by maintaining the association between IFT subcomplexes A and B. Binds GTP but is not able to hydrolyze it; the GTPase activity remains unclear. Required to pattern the neural tube. Involved in cerebral cortex development: required for the initial formation of a polarized radial glial scaffold, the first step in the construction of the cerebral cortex, by regulating ciliary signaling. Regulates the migration and placement of postmitotic interneurons in the developing cerebral cortex. May regulate endocytic recycling traffic; however, additional evidence is required to confirm these data. Monomer (By similarity). Interacts with PIFO. Interacts with IFT complex B components IFT46 and IFT74 (By similarity) (PubMed:20643351, PubMed:24339792). Interacts with EXOC2; regulates ARL13B localization to the cilium membrane. Associates to the cilium membrane via palmitoylation. Localizes to proximal ciliary membranes, to an inversin-like subciliary membrane compartment, excluding the transition zone. Expressed in the developing brain. Sumoylation is required for PKD2 entry into cilium. The disease is caused by variants affecting the gene represented in this entry. Used as a ciliary marker because of its specific localization to microtubule doublets of the ciliary axoneme. Belongs to the small GTPase superfamily. Arf family. Was initially thought to form a homodimer (PubMed:18554500). However, 3D structure of C.reinhardtii ortholog showed that it is probably not the case.