In yeast, RAS proteins are controlling elements of adenylate cyclase

Life in the midst of scarcity: adaptations to nutrient availability in Saccharomyces cerevisiae

“…It is generally believed that the intracellular glucose phosphorylation signal is further transduced to the cAMP-PKA pathway via the Ras proteins, Ras1 and Ras2, which belong to the group of small G proteins. The GTPbound, active Ras proteins stimulate the activity of the adenylate cyclase Cyr1 (also known as Cdc35), the enzyme which catalyses the synthesis of cAMP from ATP (Casperson et al 1983(Casperson et al , 1985Matsumoto et al 1983Matsumoto et al , 1984Kataoka et al 1985;Toda et al 1985;Field et al 1988). The GDP/GTP exchange on the Ras proteins is controlled by the guanine nucleotide exchange factors (GEF) Cdc25 and Sdc25 (Broek et al 1987;Camonis and Jacquet 1988;Jones et al 1991;Camus et al 1994).…”

Adenylyl cyclase activity of the fission yeast Schizosaccharomyces pombe is not regulated by guanyl nucleotides

“…Several features of the adenylyl cyclase system in the baker yeast Saccharomyces cerevisiae are analogous to those of avian and mammalian systems: (i) S. cerevisiae adenylyl cyclase seems to be regulated by an external glucose signal [17]; (ii) the activity is regulated by a monomeric G-protein of the RAS family [18], where the GDP to GTP exchange is catalyzed by the CDC25 protein [19-221; and (iii) activation of the enzyme exhibits first-order kinetics similar to the pattern of activation of the avian and mammalian enzymes [22]. Yet, there are major differences between the avian and mammalian systems and the S. cerevisiae system: (i) the S. cerevisiae adenylyl cyclase is not activated by agents that activate avian and mammalian systems such as fluoride ions and forskolin [23]; (ii) the G-protein which regulates the S. cerevisiae adenylyl cyclase activation is a monomer highly homologous to the mammalian protooncogene ras [18] which is completely different from the heterotrimeric G-proteins; (iii) no inhibitory G-protein has been found yet in S. cerevisiae; and (iv) this enzyme system is not sensitive to cholera toxin or pertussis toxin [23].…”

“…Yet, there are major differences between the avian and mammalian systems and the S. cerevisiae system: (i) the S. cerevisiae adenylyl cyclase is not activated by agents that activate avian and mammalian systems such as fluoride ions and forskolin [23]; (ii) the G-protein which regulates the S. cerevisiae adenylyl cyclase activation is a monomer highly homologous to the mammalian protooncogene ras [18] which is completely different from the heterotrimeric G-proteins; (iii) no inhibitory G-protein has been found yet in S. cerevisiae; and (iv) this enzyme system is not sensitive to cholera toxin or pertussis toxin [23]. Measuring in vitro the adenylyl cyclase activity in the social amoeba Dictyostelium discoideum is problematic technically because cell lysates lose activity shortly after preparation probably due to enzyme sequestration [ In this communication we describe the adenylyl cyclase activity of the yeast Schizosaccharomyces pombe, an organism that can be easily manipulated genetically and studied biochemically.…”

Glycogen hyperaccumulation in Saccharomyces cerevisiae ras2 mutant A biochemical study

“…These mutants present alterations in glycogen accumulation. RAS2 proteins in yeast are involved in the production of CAMP [4,8,29]. Therefore, rus2 mutants maintain very low levels of CAMP and this results in the hyperaccumulation of glycogen [5].…”

“…Strains lacking RAS2 sporulate on rich media and hyperaccumulate glycogen 14-61. In yeast, RAS proteins control adenylate cyclase [4,7,8]. Compared to wild-type strains, adenylate cyclase is significantly depressed in rtls2 mutants and these cells maintain very low levels of cAMP.…”