The WASH complex, an endosomal Arp2/3 activator, interacts with the Hermansky-Pudlak syndrome complex BLOC-1 and its cargo phosphatidylinositol-4-kinase type II?.

ABSTRACT: Vesicle biogenesis machinery components such as coat proteins can interact with the actin cytoskeleton for cargo sorting into multiple pathways. It is unknown, however, whether these interactions are a general requirement for the diverse endosome traffic routes. In this study, we identify actin cytoskeleton regulators as previously unrecognized interactors of complexes associated with the Hermansky-Pudlak syndrome. Two complexes mutated in the Hermansky-Pudlak syndrome, adaptor protein complex-3 and biogenesis of lysosome-related organelles complex-1 (BLOC-1), interact with and are regulated by the lipid kinase phosphatidylinositol-4-kinase type II? (PI4KII?). We therefore hypothesized that PI4KII? interacts with novel regulators of these complexes. To test this hypothesis, we immunoaffinity purified PI4KII? from isotope-labeled cell lysates to quantitatively identify interactors. Strikingly, PI4KII? isolation preferentially coenriched proteins that regulate the actin cytoskeleton, including guanine exchange factors for Rho family GTPases such as RhoGEF1 and several subunits of the WASH complex. We biochemically confirmed several of these PI4KII? interactions. Of importance, BLOC-1 complex, WASH complex, RhoGEF1, or PI4KII? depletions altered the content and/or subcellular distribution of the BLOC-1-sensitive cargoes PI4KII?, ATP7A, and VAMP7. We conclude that the Hermansky-Pudlak syndrome complex BLOC-1 and its cargo PI4KII? interact with regulators of the actin cytoskeleton.

SUBMITTER: Ryder PV 

PROVIDER: S-EPMC3708732 | biostudies-literature | 2013 Jul

REPOSITORIES: biostudies-literature