Glucose and nitrogen rapidly activate a Ca 2+-inhibitable, serine/threonine kinase activity toward microtubule-associated protein 2 in Saccharomyces cerevisiae

Abstract

Treatment of the glucose-starved yeast cells ( Saccharomyces cerevisiae) with 1% glucose or 2-deoxyglucose induced a rapid increase in a protein kinase activity in cell extracts that phosphorylated microtubule-associated protein 2 (MAP2) in vitro. Addition of 0.5% ammonium sulfate to the nitrogen-starved yeast cells also stimulated the kinase activity toward MAP2. The stimulated MAP2 kinase activities had the following common properties: (i) Activation was rapid and transient in response to stimuli; (ii) The kinase activity was serine/threonine-specific; and (iii) The kinase activity was inhibited by micromolar concentrations of free Ca 2+. These properties are very similar to those of the mitogen-activated, Ca 2+-sensitive MAP2 kinase we have recently found in mammalian fibroblastic cells. The MAP2 kinase activation may be involved in initiation of proliferation of yeast cells.