The ARF (ADP-ribosylation factor) family of small GTPases regulate intracellular membrane trafficking by cycling between an inactive GDP- and an active GTP-bound form. Among the six known mammalian ARFs (ARF1–ARF6), ARF6 is the least conserved and plays critical roles in membrane trafficking and cytoskeletal dynamics near the cell surface. Since ARFs have undetectable levels of intrinsic GTP binding and hydrolysis, they are totally dependent on extrinsic GEFs (guanine nucleotide-exchange factors) for GTP binding and GAPs (GTPase-activating proteins) for GTP hydrolysis. We have recently isolated a novel KIF (kinesin) motor protein (KIF13B) that binds to centaurin-α1, an ARF6GAP that binds to the second messenger PIP3 [PtdIns(3,4,5)P3]. KIFs transport intracellular vesicles and recognize their cargo by binding to proteins (receptors) localized on the surface of the cargo vesicles. Identification of centaurin-α1 as a KIF13B interactor suggests that KIF13B may transport ARF6 and/or PIP3 using centaurin-α1 as its receptor. This paper reviews the studies carried out to assess the interaction and regulation of centaurin-α1 by KIF13B.

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