Glucose controls multiple processes in Saccharomyces cerevisiae through diverse combinations of signaling pathways.

We have studied how the lack of glucose sensors in the plasma membrane, or of the enzymes Hxk1, Hxk2, Glk1, which catalyze the first intracellular step in glucose metabolism, affect the different responses of Saccharomyces cerevisiae to glucose. Lack of the G-protein-coupled receptor Gpr1 or of Snf3/Rgt2 did not affect glucose repression of different genes or activation by glucose of plasma membrane ATPase, whereas lack of Gpr1 decreased, in an additive manner with lack of Mth1, the degradation of fructose 1,6-bisphosphatase that takes place in the presence of glucose. In an hxk1 hxk2 glk1 strain, unable to phosphorylate glucose, all of these responses to the sugar were suppressed or strongly reduced. In the absence of Hxk2 (or Hxk1 and Hxk2), glucose repression of SUC2, GAL1 and GDH2 was relieved, but that of FBP1 and ICL1 was maintained. Hxk1 or Hxk2 were needed for activation of plasma membrane ATPase but not for degradation of FbPase.