Regulatory mechanism for expression of GPX1 in response to glucose starvation and Ca2+in Saccharomyces cerevisiae: involvement of Snf1 and Ras/cAMP pathway in Ca2+signaling

Saccharomyces cerevisiae has three homologues of the glutathione peroxidase gene, GPX1, GPX2, and GPX3. We have previously reported that the expression of GPX3 was constitutive, but that of GPX2 was induced by oxidative stress and CaCl2, and uncovered the regulatory mechanisms involved. Here, we show that the expression of GPX1 is induced by glucose starvation and treatment with CaCl2. The induction of GPX1 expression in response to glucose starvation and Ca2+ was dependent on the transcription factors Msn2 and Msn4 and cis-acting elements [stress response element (STRE)] in the GPX1 promoter. The Ras/cAMP pathway is also involved in the expression of GPX1. We found that Snf1, a Ser/Thr protein kinase, is involved in the glucose starvation- and Ca2+-induced expression of GPX1. The activation of Snf1 is accompanied by phosphorylation of Thr210. We found that the Ca2+-treatment as well as glucose starvation causes the phosphorylation of Thr210 of Snf1 in a Tos3, Sak1, and Elm1 protein kinase-dependent manner. As the timing of the initiation of Ca2+-induced expression of GPX1 was retarded in an snf1 delta mutant, the activation of Snf1 seems pivotal to the early-stage-response of GPX1 to Ca2+.