title: Localization of Ras signaling complex in budding yeast.
abstract: In Saccharomyces cerevisiae, cAMP/pKA pathway plays a major role in metabolism, stress resistance and proliferation control. cAMP is produced by adenylate cyclase, which is activated both by Gpr1/Gpa2 system and Ras proteins, regulated by Cdc25/Sdc25 guanine exchange factors and Ira GTPase activator proteins. Recently, both Ras2 and Cdc25 RasGEF were reported to localize not only in plasma membrane but also in internal membranes. Here, the subcellular localization of Ras signaling complex proteins was investigated both by fluorescent tagging and by biochemical cell membrane fractionation on sucrose gradients. Although a consistent minor fraction of Ras signaling complex components was found in plasma membrane during exponential growth on glucose, Cdc25 appears to localize mainly on ER membranes, while Ira2 and Cyr1 are also significantly present on mitochondria. Moreover, PKA Tpk1 catalytic subunit overexpression induces Ira2 protein to move from mitochondria to ER membranes. These data confirm the hypothesis that different branches of Ras signaling pathways could involve different subcellular compartments, and that relocalization of Ras signaling complex components is subject to PKA control.
authors.affiliation: Department of Biotechnology and Biosciences, Umiversity of Milano-Bicocca, Milan, Italy.
authors.forename: Fiorella
authors.initials: F
authors.lastname: Belotti
authors.forename: Renata
authors.initials: R
authors.lastname: Tisi
authors.forename: Chiara
authors.initials: C
authors.lastname: Paiardi
authors.forename: Marco
authors.initials: M
authors.lastname: Rigamonti
authors.forename: Silvia
authors.initials: S
authors.lastname: Groppi
authors.forename: Enzo
authors.initials: E
authors.lastname: Martegani
mesh_terms: D020134:Catalytic Domain; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D051336:Mitochondrial Membranes / Q000378:metabolism; D046912:Multiprotein Complexes / Q000378:metabolism*; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D015398:Signal Transduction; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D046912:Multiprotein Complexes; D029701:Saccharomyces cerevisiae Proteins; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D017868:Cyclic AMP-Dependent Protein Kinases; D018631:ras Proteins