The Experts below are selected from a list of 141 Experts worldwide ranked by ideXlab platform

Yoshinori Ohsumi - One of the best experts on this subject based on the ideXlab platform.

  • Tor, a Phosphatidylinositol Kinase homologue, controls autophagy in yeast
    Journal of Biological Chemistry, 1998
    Co-Authors: Takeshi Noda, Yoshinori Ohsumi
    Abstract:

    Autophagy is a bulk protein degradation process that is induced by starvation. The control mechanism for induction of autophagy is not well understood. We found that Tor, a Phosphatidylinositol Kinase homologue, is involved in the control of autophagy in the yeast, Saccharomyces cerevisiae. When rapamycin, an inhibitor of Tor function, is added, autophagy is induced even in cells growing in nutrient-rich medium. A temperature-sensitive tor mutant also leads to induction of autophagy at a nonpermissive temperature. These results indicate that Tor negatively regulates the induction of autophagy. Tor is the first molecule that is identified as a pivotal player in the starvation-signaling pathway of autophagy. Furthermore, we found that a high concentration of cAMP is inhibitory for induction of autophagy. APG gene products are involved in autophagy induced by starvation. Autophagy was not induced in apg mutants in the presence of rapamycin, indicating that the site of action of Tor is upstream of those of Apg proteins. In nutrient-rich medium, Apg proteins are involved also in the transport of aminopeptidase I from the cytosol to the vacuole. Tor may act to switch Apg function between autophagy and transport of aminopeptidase I.

Michael N. Hall - One of the best experts on this subject based on the ideXlab platform.

  • The Yeast Phosphatidylinositol Kinase Homolog TOR2 Activates RHO1 and RHO2 via the Exchange Factor ROM2
    Cell, 1997
    Co-Authors: Anja Schmidt, Marc Bickle, Thomas Beck, Michael N. Hall
    Abstract:

    The Saccharomyces cerevisiae Phosphatidylinositol Kinase homolog TOR2 is required for organization of the actin cytoskeleton. Overexpression of RHO1 or RHO2, encoding Rho-like GTPases, or ROM2, encoding a GDP/GTP exchange factor for RHO1 and RHO2, suppresses a tor2 mutation. Deletion of SAC7, a gene originally identified as a suppressor of an actin mutation, also suppresses a tor2 mutation. SAC7 is a novel GTPase-activating protein for RHO1. ROM2 exchange activity is reduced in a tor2 mutant, and overexpression of ROM2 lacking its PH domain can no longer suppress a tor2 mutation. Thus, TOR2 signals to the actin cytoskeleton through a GTPase switch composed of RHO1, RHO2, ROM2, and SAC7. TOR2 activates this switch via ROM2, possibly via the ROM2 PH domain.

  • TOR1 and TOR2 are structurally and functionally similar but not identical Phosphatidylinositol Kinase homologues in yeast.
    Molecular biology of the cell, 1994
    Co-Authors: Stephen B. Helliwell, Philipp Wagner, Jeannette Kunz, Maja Deuter-reinhard, Ruben Henriquez, Michael N. Hall
    Abstract:

    The Saccharomyces cerevisiae genes TOR1 and TOR2 were originally identified by mutations that confer resistance to the immunosuppressant rapamycin. TOR2 was previously shown to encode an essential 282-kDa Phosphatidylinositol Kinase (PI Kinase) homologue. The TOR1 gene product is also a large (281 kDa) PI Kinase homologue, with 67% identity to TOR2. TOR1 is not essential, but a TOR1 TOR2 double disruption uniquely confers a cell cycle (G1) arrest as does exposure to rapamycin; disruption of TOR2 alone is lethal but does not cause a cell cycle arrest. TOR1-TOR2 and TOR2-TOR1 hybrids indicate that carboxy-terminal domains of TOR1 and TOR2 containing a lipid Kinase sequence motif are interchangeable and therefore functionally equivalent; the other portions of TOR1 and TOR2 are not interchangeable. The TOR1-1 and TOR2-1 mutations, which confer rapamycin resistance, alter the same potential protein Kinase C site in the respective protein's lipid Kinase domain. Thus, TOR1 and TOR2 are likely similar but not identical, rapamycin-sensitive PI Kinases possibly regulated by phosphorylation. TOR1 and TOR2 may be components of a novel signal transduction pathway controlling progression through G1.

  • target of rapamycin in yeast tor2 is an essential Phosphatidylinositol Kinase homolog required for g1 progression
    Cell, 1993
    Co-Authors: Jeannette Kunz, Ruben Henriquez, Ulrich Schneider, Maja Deuterreinhard, Rao N Movva, Michael N. Hall
    Abstract:

    The yeast TOR2 gene encodes an essential 282 kd Phosphatidylinositol (PI) 3-Kinase homolog. TOR2 is related to the catalytic subunit of bovine PI 3-Kinase and to yeast VPS34, a vacuolar sorting protein also shown to have PI 3-Kinase activity. The immunosuppressant rapamycin most likely acts by inhibiting PI Kinase activity because TOR2 mutations confer resistance to rapamycin and because a TOR1 TOR2 double disruption (TOR1 is a nonessential TOR2 homolog) confers G1 arrest, as does rapamycin. Our results further suggest that 3-phosphorylated phosphoinositides, whose physiological significance has not been determined, are an important signal in cell cycle activation. In yeast, this signal may act in a signal transduction pathway similar to the interleukin-2 signal transduction pathway in T cells.

Leda Raptis - One of the best experts on this subject based on the ideXlab platform.

Takeshi Noda - One of the best experts on this subject based on the ideXlab platform.

  • Tor, a Phosphatidylinositol Kinase homologue, controls autophagy in yeast
    Journal of Biological Chemistry, 1998
    Co-Authors: Takeshi Noda, Yoshinori Ohsumi
    Abstract:

    Autophagy is a bulk protein degradation process that is induced by starvation. The control mechanism for induction of autophagy is not well understood. We found that Tor, a Phosphatidylinositol Kinase homologue, is involved in the control of autophagy in the yeast, Saccharomyces cerevisiae. When rapamycin, an inhibitor of Tor function, is added, autophagy is induced even in cells growing in nutrient-rich medium. A temperature-sensitive tor mutant also leads to induction of autophagy at a nonpermissive temperature. These results indicate that Tor negatively regulates the induction of autophagy. Tor is the first molecule that is identified as a pivotal player in the starvation-signaling pathway of autophagy. Furthermore, we found that a high concentration of cAMP is inhibitory for induction of autophagy. APG gene products are involved in autophagy induced by starvation. Autophagy was not induced in apg mutants in the presence of rapamycin, indicating that the site of action of Tor is upstream of those of Apg proteins. In nutrient-rich medium, Apg proteins are involved also in the transport of aminopeptidase I from the cytosol to the vacuole. Tor may act to switch Apg function between autophagy and transport of aminopeptidase I.

Richard C. Marcellus - One of the best experts on this subject based on the ideXlab platform.