ARL8 Relieves SKIP Autoinhibition to Enable Coupling of Lysosomes to Kinesin-1

• Published in: Current biology Vol. 31; no. 3; pp. 540 - 554.e5
• Main Authors: Keren-Kaplan, Tal, Bonifacino, Juan S.
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 08.02.2021
• Subjects: Adaptor Proteins, Signal Transducing - genetics; Adaptor Proteins, Signal Transducing - metabolism; ADP-Ribosylation Factors; GTP Phosphohydrolases; HeLa Cells; Humans; Kinesins; lysosome, kinesin, ARL8, SKIP, regulation, autoinhibition, cargo, activation, organelle transport, positioning; Lysosomes - metabolism; Microtubules - metabolism; lysosome, kinesin, ARL8, SKIP, regulation, autoinhibition, cargo, activation, organelle transport, positioning
• ISSN: 0960-9822; 1879-0445; 1879-0445
• DOI: 10.1016/j.cub.2020.10.071

Long-range movement of organelles within the cytoplasm relies on coupling to microtubule motors, a process that is often mediated by adaptor proteins. In many cases, this coupling involves organelle- or adaptor-induced activation of the microtubule motors by conformational reversal of an autoinhibited state. Herein, we show that a similar regulatory mechanism operates for an adaptor protein named SKIP (also known as PLEKHM2). SKIP binds to the small guanosine triphosphatase (GTPase) ARL8 on the lysosomal membrane to couple lysosomes to the anterograde microtubule motor kinesin-1. Structure-function analyses of SKIP reveal that the C-terminal region comprising three pleckstrin homology (PH) domains interacts with the N-terminal region comprising ARL8- and kinesin-1-binding sites. This interaction inhibits coupling of lysosomes to kinesin-1 and, consequently, lysosome movement toward the cell periphery. We also find that ARL8 does not just recruit SKIP to the lysosomal membrane but also relieves SKIP autoinhibition, promoting kinesin-1-driven, anterograde lysosome transport. Finally, our analyses show that the largely disordered middle region of SKIP mediates self-association and that this self-association enhances the interaction of SKIP with kinesin-1. These findings indicate that SKIP is not just a passive connector of lysosome-bound ARL8 to kinesin-1 but is itself subject to intra- and inter-molecular interactions that regulate its function. We anticipate that similar organelle- or GTPase-induced conformational changes could regulate the activity of other kinesin adaptors. [Display omitted] •SKIP is an adaptor that mediates regulated coupling of lysosomes to kinesin-1•SKIP is autoinhibited by intramolecular interaction of its N- and C-terminal parts•The GTPase ARL8 relieves SKIP autoinhibition besides recruiting SKIP to lysosomes•SKIP exemplifies the regulation of a kinesin adaptor by reversible autoinhibition Anterograde transport of lysosomes involves coupling to the microtubule motor kinesin-1 via the small GTPase ARL8 and the adaptor protein SKIP. Keren-Kaplan and Bonifacino show that ARL8 does not just recruit SKIP to lysosomes but also promotes SKIP activation through relief of an autoinhibited state.