title: Tor2 directly phosphorylates the AGC kinase Ypk2 to regulate actin polarization.
abstract: The target of rapamycin (TOR) protein kinases, Tor1 and Tor2, form two distinct complexes (TOR complex 1 and 2) in the yeast Saccharomyces cerevisiae. TOR complex 2 (TORC2) contains Tor2 but not Tor1 and controls polarity of the actin cytoskeleton via the Rho1/Pkc1/MAPK cell integrity cascade. Substrates of TORC2 and how TORC2 regulates the cell integrity pathway are not well understood. Screening for multicopy suppressors of tor2, we obtained a plasmid expressing an N-terminally truncated Ypk2 protein kinase. This truncation appears to partially disrupt an autoinhibitory domain in Ypk2, and a point mutation in this region (Ypk2(D239A)) conferred upon full-length Ypk2 the ability to rescue growth of cells compromised in TORC2, but not TORC1, function. YPK2(D239A) also suppressed the lethality of tor2Delta cells, suggesting that Ypks play an essential role in TORC2 signaling. Ypk2 is phosphorylated directly by Tor2 in vitro, and Ypk2 activity is largely reduced in tor2Delta cells. In contrast, Ypk2(D239A) has increased and TOR2-independent activity in vivo. Thus, we propose that Ypk protein kinases are direct and essential targets of TORC2, coupling TORC2 to the cell integrity cascade.
authors.affiliation: Department of Cell Biology, National Institute for Basic Biology, Maiodaiji-Cho, Okazaki, Japan. yoshikam@nibb.ac.jp
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Kamada
authors.forename: Yuko
authors.initials: Y
authors.lastname: Fujioka
authors.forename: Nobuo N
authors.initials: NN
authors.lastname: Suzuki
authors.forename: Fuyuhiko
authors.initials: F
authors.lastname: Inagaki
authors.forename: Stephan
authors.initials: S
authors.lastname: Wullschleger
authors.forename: Robbie
authors.initials: R
authors.lastname: Loewith
authors.forename: Michael N
authors.initials: MN
authors.lastname: Hall
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Ohsumi
mesh_terms: D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D000483:Alleles; D000595:Amino Acid Sequence; D018797:Cell Cycle Proteins / Q000378:metabolism / Q000502:physiology*; D049109:Cell Proliferation; D003599:Cytoskeleton / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D015966:Gene Expression Regulation, Fungal; D047468:Immunoprecipitation; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D017354:Point Mutation; D011494:Protein Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013696:Temperature
chemical_list: D000199:Actins; D018797:Cell Cycle Proteins; D019869:Phosphatidylinositol 3-Kinases; D011494:Protein Kinases; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; C060388:YPK2 protein, S cerevisiae; C081135:TOR2 protein, S cerevisiae