The protein kinase C pathway is required for viability in quiescence in Saccharomyces cerevisiae.

Abstract	Protein kinase C, encoded by PKC1, regulates construction of the cell surface in vegetatively growing yeast cells. Pkc1 in part acts by regulating Mpk1, a MAP kinase. Mutants lacking Bck1, a component of the MAP kinase branch of the pathway, fail to respond normally to nitrogen starvation, which causes entry into quiescence. Given that the Tor1 and Tor2 proteins are key inhibitors of entry into quiescence, the Pkc1 pathway may regulate these proteins. We find that pkc1Delta and mpk1Delta mutants rapidly die by cell lysis upon carbon or nitrogen starvation. The Pkc1 pathway does not regulate the TOR proteins: transcriptional changes dependent on inhibition of the TORs occur normally in pkc1Delta and mpk1Delta mutants when starved for nitrogen; pkc1Delta and mpk1Delta mutants die rapidly upon treatment with rapamycin, an inhibitor of the TORs. We find that Mpk1 is transiently activated by rapamycin treatment via a novel mechanism. Finally, we find that rapamycin treatment or nitrogen starvation induces resistance to the cell wall-digesting enzyme zymolyase by a Pkc1-dependent mechanism. Thus, the Pkc1 pathway is not a nutrient sensor but acts downstream of TOR inhibition to maintain cell integrity in quiescence.
Authors	Sue Ann Krause, Joseph V Gray
Journal	Current biology : CB (Curr Biol) Vol. 12 Issue 7 Pg. 588-93 (Apr 02 2002) ISSN: 0960-9822 [Print] England
PMID	11937029 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References	Amino Acid Transport Systems Carrier Proteins Cation Transport Proteins Cell Cycle Proteins Fungal Proteins GAP1 protein, S cerevisiae MEP2 protein, S cerevisiae Membrane Proteins SLG1 protein, S cerevisiae Saccharomyces cerevisiae Proteins ras GTPase-Activating Proteins Protein Kinases Phosphotransferases (Alcohol Group Acceptor) TOR1 protein, S cerevisiae TOR2 protein, S cerevisiae BCK1 protein, S cerevisiae Protein Kinase C Mitogen-Activated Protein Kinases SLT2 protein, S cerevisiae Mitogen-Activated Protein Kinase Kinases
Topics	Amino Acid Transport Systems Carrier Proteins (metabolism) Cation Transport Proteins Cell Cycle Proteins Fungal Proteins (genetics, metabolism) Membrane Proteins (metabolism) Mitogen-Activated Protein Kinase Kinases Mitogen-Activated Protein Kinases (metabolism) Mutagenesis Phosphatidylinositol 3-Kinases Phosphotransferases (Alcohol Group Acceptor) (metabolism) Protein Kinase C (genetics, metabolism) Protein Kinases (genetics, metabolism) Saccharomyces cerevisiae (enzymology, growth & development) Saccharomyces cerevisiae Proteins Signal Transduction ras GTPase-Activating Proteins (metabolism)

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