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

Mol Biol Cell. 2013 Jul;24(14):2269-84. doi: 10.1091/mbc.E13-02-0088. Epub 2013 May 15.


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 IIα (PI4KIIα). We therefore hypothesized that PI4KIIα interacts with novel regulators of these complexes. To test this hypothesis, we immunoaffinity purified PI4KIIα from isotope-labeled cell lysates to quantitatively identify interactors. Strikingly, PI4KIIα 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 PI4KIIα interactions. Of importance, BLOC-1 complex, WASH complex, RhoGEF1, or PI4KIIα depletions altered the content and/or subcellular distribution of the BLOC-1-sensitive cargoes PI4KIIα, ATP7A, and VAMP7. We conclude that the Hermansky-Pudlak syndrome complex BLOC-1 and its cargo PI4KIIα interact with regulators of the actin cytoskeleton.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Actin Cytoskeleton / genetics
  • Actin Cytoskeleton / metabolism*
  • Actin-Related Protein 2-3 Complex / genetics
  • Actin-Related Protein 2-3 Complex / metabolism*
  • Cell Line, Tumor
  • Endosomes / genetics
  • Endosomes / metabolism*
  • Gene Expression Regulation
  • HEK293 Cells
  • Hermanski-Pudlak Syndrome / genetics
  • Hermanski-Pudlak Syndrome / metabolism
  • Humans
  • Immunoprecipitation
  • Isoenzymes / genetics
  • Isoenzymes / metabolism
  • Microfilament Proteins / genetics
  • Microfilament Proteins / metabolism*
  • Minor Histocompatibility Antigens
  • Nerve Tissue Proteins / genetics
  • Nerve Tissue Proteins / metabolism*
  • Neurons / cytology
  • Neurons / metabolism*
  • Phosphotransferases (Alcohol Group Acceptor) / genetics
  • Phosphotransferases (Alcohol Group Acceptor) / metabolism*
  • Protein Binding
  • Signal Transduction
  • rho GTP-Binding Proteins / genetics
  • rho GTP-Binding Proteins / metabolism


  • Actin-Related Protein 2-3 Complex
  • BLOC1S1 protein, human
  • Isoenzymes
  • Microfilament Proteins
  • Minor Histocompatibility Antigens
  • Nerve Tissue Proteins
  • WASH protein, human
  • Phosphotransferases (Alcohol Group Acceptor)
  • phosphatidylinositol phosphate 4-kinase
  • rho GTP-Binding Proteins