title: A cell-density sensing factor regulates the lifetime of a chemoattractant-induced G alpha-GTP conformation.
abstract: Starving Dictyostelium discoideum cells monitor the local density of other starving cells by simultaneously secreting and sensing CMF. CMF regulates signal transduction through the chemoattractant cAMP receptor, cAR1. cAR1 activates a heterotrimeric G protein by stimulating G alpha 2 to release GDP and bind GTP. We show here that the rate of cAMP-stimulated GTP hydrolysis in membranes from cells exposed to CMF is roughly 4 times slower than in membranes from untreated cells, even though the rate of GTP binding is the same. This hydrolysis is abolished in cells lacking G alpha 2. Our data thus suggest that CMF regulates cAMP signal transduction in part by prolonging the lifetime of the G alpha 2-GTP complex.
authors.affiliation: Howard Hughes Medical Institute, Department of Biochemistry and Cell Biology, Houston, TX 77251-1892, USA.
authors.forename: D T
authors.initials: DT
authors.lastname: Brazill
authors.forename: R
authors.initials: R
authors.lastname: Gundersen
authors.forename: R H
authors.initials: RH
authors.lastname: Gomer
mesh_terms: D000818:Animals; D015815:Cell Adhesion Molecules / Q000502:physiology*; D018925:Chemokines / Q000494:pharmacology*; D000242:Cyclic AMP / Q000502:physiology; D004023:Dictyostelium / Q000166:cytology* / Q000235:genetics / Q000254:growth & development; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000737:chemistry / Q000378:metabolism*; D006868:Hydrolysis; D011487:Protein Conformation / Q000187:drug effects*; D015800:Protozoan Proteins; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D015815:Cell Adhesion Molecules; D018925:Chemokines; D015800:Protozoan Proteins; C052291:cell cohesion molecule, Dictyostelium; D006160:Guanosine Triphosphate; D000242:Cyclic AMP; D019204:GTP-Binding Proteins