title: A WASp-binding type II phosphatidylinositol 4-kinase required for actin polymerization-driven endosome motility.
abstract: Endosomes in yeast have been hypothesized to move through the cytoplasm by the momentum gained after actin polymerization has driven endosome abscision from the plasma membrane. Alternatively, after abscission, ongoing actin polymerization on endosomes could power transport. Here, we tested these hypotheses by showing that the Arp2/3 complex activation domain (WCA) of Las17 (Wiskott-Aldrich syndrome protein [WASp] homologue) fused to an endocytic cargo protein (Ste2) rescued endosome motility in las17DeltaWCA mutants, and that capping actin filament barbed ends inhibited endosome motility but not endocytic internalization. Motility therefore requires continual actin polymerization on endosomes. We also explored how Las17 is regulated. Endosome motility required the Las17-binding protein Lsb6, a type II phosphatidylinositol 4-kinase. Catalytically inactive Lsb6 interacted with Las17 and promoted endosome motility. Lsb6 therefore is a novel regulator of Las17 that mediates endosome motility independent of phosphatidylinositol 4-phosphate synthesis. Mammalian type II phosphatidylinositol 4-kinases may regulate WASp proteins and endosome motility.
authors.affiliation: Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
authors.forename: Fanny S
authors.initials: FS
authors.lastname: Chang
authors.forename: Gil-Soo
authors.initials: GS
authors.lastname: Han
authors.forename: George M
authors.initials: GM
authors.lastname: Carman
authors.forename: Kendall J
authors.initials: KJ
authors.lastname: Blumer
mesh_terms: D019870:1-Phosphatidylinositol 4-Kinase / Q000235:genetics / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D001692:Biological Transport / Q000502:physiology; D011992:Endosomes / Q000737:chemistry / Q000378:metabolism*; D017353:Gene Deletion; D009068:Movement / Q000502:physiology; D009154:Mutation; D051964:Receptors, Mating Factor / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D040681:Structural Homology, Protein; D051316:Wiskott-Aldrich Syndrome Protein / Q000032:analysis / Q000235:genetics / Q000502:physiology*
chemical_list: D000199:Actins; C480361:LAS17 protein, S cerevisiae; D051964:Receptors, Mating Factor; C498031:STE2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D051316:Wiskott-Aldrich Syndrome Protein; D019870:1-Phosphatidylinositol 4-Kinase; C475080:LSB6 protein, S cerevisiae; C112465:STT4 protein, S cerevisiae