title: TOR complex 2-Ypk1 signaling regulates actin polarization via reactive oxygen species.
abstract: The evolutionarily conserved mTOR complex 2 (mTORC2) signaling pathway is an important regulator of actin cytoskeletal architecture and, as such, is a candidate target for preventing cancer cell motility and invasion. Remarkably, the precise mechanism(s) by which mTORC2 regulates the actin cytoskeleton have remained elusive. Here we show that in budding yeast, TORC2 and its downstream kinase Ypk1 regulate actin polarization by controlling reactive oxygen species (ROS) accumulation. Specifically, we find that TORC2-Ypk1 regulates actin polarization both by vacuole-related ROS, controlled by the phospholipid flippase kinase Fpk1 and sphingolipids, and by mitochondria-mediated ROS, controlled by the PKA subunit Tpk3. In addition, we find that the protein kinase C (Pkc1)/MAPK cascade, a well-established regulator of actin, acts downstream of Ypk1 to regulate ROS, in part by promoting degradation of the oxidative stress responsive repressor, cyclin C. Furthermore, we show that Ypk1 regulates Pkc1 activity through proper localization of Rom2 at the plasma membrane, which is also dependent on Fpk1 and sphingolipids. Together these findings demonstrate important links between TORC2/Ypk1 signaling, Fpk1, sphingolipids, Pkc1, and ROS as regulators of actin and suggest that ROS may play an important role in mTORC2-dependent dysregulation of the actin cytoskeleton in cancer cells.
authors.affiliation: Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, Davis, CA 95616.
authors.forename: Brad J
authors.initials: BJ
authors.lastname: Niles
authors.affiliation: Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, Davis, CA 95616 tpowers@ucdavis.edu.
authors.forename: Ted
authors.initials: T
authors.lastname: Powers
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D015153:Blotting, Western; D056745:Cyclin C / Q000235:genetics / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism*; D000076225:Mechanistic Target of Rapamycin Complex 2; D008856:Microscopy, Fluorescence; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D046912:Multiprotein Complexes / Q000378:metabolism*; D009154:Mutation; D010766:Phosphorylation; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D021122:Protein Subunits / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D013107:Sphingolipids / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*
chemical_list: D000199:Actins; D056745:Cyclin C; D046912:Multiprotein Complexes; D021122:Protein Subunits; D017382:Reactive Oxygen Species; D029701:Saccharomyces cerevisiae Proteins; D013107:Sphingolipids; D011494:Protein Kinases; C533049:Fpk1 protein, S cerevisiae; D000076225:Mechanistic Target of Rapamycin Complex 2; D058570:TOR Serine-Threonine Kinases; C490702:PKC1 protein, S cerevisiae; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D038362:Glycogen Synthase Kinase 3; C068124:MCK1 protein, S cerevisiae