Molecular mechanism of Rab22a mediated regulation of KIF13A motility and cargo recycling

Abstract

Recycling endosomes (RE) are highly dynamic membranous structures, characterized by the heterogenous tubules and vesicles that associate with KIF13A, a member of kinesin-3 family, and the regulatory Rab proteins. We have previously shown that wild type KIF13A has a proline residue at the junction of NC-CC1 domain and prevents motor dimerization and motility in vitro. However, the deletion of this proline favors KIF13A dimerization and processive motility along the microtubule. However, the mechanism that precludes the effect of proline induced destabilization and regulates the motility properties of KIF13A motors on the REs remains largely unknown. In the present work, we show that exogenous expression of wild type KIF13A generates dense network of tubular REs in the cytoplasm and these REs tubules show colocalization with multiple Rab proteins. Remarkably, expression of proline deletion mutant showed significantly fewer RE tubules and accumulation of RE vesicles at the cell periphery significantly increased. We show that Rab22a is the major player that interacts with KIF13A and regulates the motility properties of KIF13A in RE tubule transport and biogenesis. Whereas monomeric KIF13A fails to generate RE tubules and microtubule-based motility, constitutive dimer leads to alteration in RE dynamics and their accumulation to the cell periphery indicating that NC-CC1 dimerization is critical for generating processive motility and cargo transport. In our study, we show for the first time a Rab22a mediated regulation of proline induced destabilization of KIF13A NC-CC1 domain and influence on motor dimerization and tuning the processive motility critical for RE tubule homeostasis.