Surface receptor-mediated activation of adenylate cyclase in Dictyostelium. Regulation by guanine nucleotides in wild-type cells and aggregation deficient mutants.

摘要: GTP and analogs produced significant (up to 17-fold) persistent activation of adenylate cyclase in lysates Dictyostelium discoideum amoeba. The was enhanced 2- 4-fold by cAMP (the agonist for receptor-mediated activation), specific guanine nucleoside triphosphates, inhibited guanosine 5'-(O-2-thio)diphosphate. order potency nucleotides 5'-(O-3-thio)triphosphate greater than guanyl-5'-yl imidodiphosphate GTP; half-maximal observed with 1-10 microM nucleotide. Maximal occurred when the nucleotide added within seconds after cell lysis lysate preincubated 5 min prior assay. Under these optimal vitro conditions, capacity activate decreased, closely correlating adaptation or desensitization induced exposure intact cells during a period 10 min. These data strongly support that regulation occurs via receptor-linked GTP/GDP exchange protein. Two mutants, designated synag 7 49 were isolated which and/or not sufficient cyclase. wild-type pattern restored addition high-speed supernatant from cells. Characterization mutants demonstrates is required growth cell-type differentiation but essential cellular aggregation influences morphogenesis formation. This suggests may provide model suitable detailed genetic analysis surface receptor-guanine nucleotide-binding regulatory protein linked systems determining role development.