Critical findings on the activation cascade of yeast plasma membrane H⁺-ATPase

Abstract

Strains of the yeast Saccharomyces cerevisiae, deficient in either of its two G-proteins, in the Snf3 and Rgt2 sensors, in the Gpr1 receptor and in various hexokinases were tested for their ability to start the activation cascade with a metabolizable monosaccharide that leads eventually to activation of plasma membrane H þ -ATPase. The acidification rate after addition of glucose to glucose-grown cells and of galactose to galactose-grown ones, and the rate of ATP hydrolysis by purified plasma membranes in both types of cells were studied. It appears unequivocally that phosphorylation of the monosaccharide is essential for the activation; the role of the Gpa2 protein (possibly in combination with the Gpr1 receptor) is very probable while the two sensors appear to play somewhat ambiguous roles^in the absence of both the activation was actually higher than in the parent strain. The Gpa1 G-protein is not involved in acidification but may function in ATPase activity where, in addition to the phosphorylation step, other factors can play a role. There appear to be alternative pathways leading to the ultimate activation of the H þ -ATPase, not necessarily involving G-proteins.

Glucose controls multiple processes inSaccharomyces cerevisiaethrough diverse combinations of signaling pathways

“…We have shown that activation of plasma membrane H 1 -ATPase by glucose was independent of the presence or absence of Snf3, Rgt2 and Gpr1 (Table 5). Although it has been reported that ATPase activation is decreased in some snf3 mutants (Souza et al, 2001;Kotyk et al, 2003;Trópia et al, 2006), in other genetic backgrounds Snf3 is dispensable (Kotyk et al, 2003;this study). The irrelevance of Gpr1 for the glucose-induced activation of plasma membrane H 1 -ATPase supports previous results showing that this activation does not depend on cAMP changes (Mazón et al, 1989).…”

Soybean Toxin (SBTX), a Protein from Soybeans That Inhibits the Life Cycle of Plant and Human Pathogenic Fungi

“…It is possible that such inhibition results from effects on plasma membrane permeabilization, as suggested by SYTOX uptake, and/or interference of the plasma membrane H + -ATPase pump. The proton pump in the cell membrane of fungi is responsible for the homeostasis of intracellular pH and maintenance of the electrochemical gradient of protons necessary for nutrient uptake , . Therefore, any disruption of plasma membrane can directly or indirectly alter the function of this translocating enzyme and the traffic of substances through the membrane leading to cell death .…”