A cell-density sensing factor regulates the lifetime of a chemoattractant-induced G alpha-GTP conformation.
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.
Brazill
D T
DT
Howard Hughes Medical Institute, Department of Biochemistry and Cell Biology, Houston, TX 77251-1892, USA.
Gundersen
R
R
Gomer
R H
RH
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
D015815:Cell Adhesion Molecules; D018925:Chemokines; D015800:Protozoan Proteins; C052291:cell cohesion molecule, Dictyostelium; D006160:Guanosine Triphosphate; D000242:Cyclic AMP; D019204:GTP-Binding Proteins