Transmembrane signal transduction was investigated in four Dictyostelium discoideum mutants that belong to the fgd A complementation group. The results show the following. (a) Cell surface cAMP receptors are present in fgd A mutants, but cAMP does not induce any of the intracellular responses, including the activation of adenylate or guanylate cyclase and chemotaxis. (b) cAMP induces down-regulation and the covalent modification (presumably phosphorylation) of the cAMP receptor. (c) The inhibitory effects of GTP gamma S and GDP beta S on cAMP binding are reduced; the stimulatory effect of cAMP on GTP gamma S binding is lost in fgd A mutants. (d) Basal high-affinity GTPase activity is reduced 40% and the stimulatory effect of cAMP is decreased from 40% in wild type to 30% in fgd A. (e) GTP-mediated stimulation and inhibition of adenylate cyclase is normal in mutant membranes. The results suggest a defective interaction between cell surface cAMP receptors and a specific G-protein in fgd A mutants. This interaction appears to be essential for nearly all signal transduction pathways in Dictyostelium discoideum.
Signal transduction in Dictyostelium fgd A mutants with a defective interaction between surface cAMP receptors and a GTP-binding regulatory protein.
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F Kesbeke, B E Snaar-Jagalska, P J Van Haastert; Signal transduction in Dictyostelium fgd A mutants with a defective interaction between surface cAMP receptors and a GTP-binding regulatory protein.. J Cell Biol 1 August 1988; 107 (2): 521–528. doi: https://doi.org/10.1083/jcb.107.2.521
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