Signal Transduction in Dictyostelium fgd A Mutants with a Defective Interaction between Surface cAMP Receptors and a GTP-binding Regulatory Protein

Fanja Kesbeke, B. Ewa Snaar-Jagalska, Peter J. M. van Haastert

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Abstract

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 GTPγS and GDPβS on cAMP binding are reduced; the stimulatory effect of cAMP on GTPγS 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.
Original languageEnglish
Number of pages8
JournalThe Journal of Cell Biology
Volume107
Issue number2
DOIs
Publication statusPublished - 1988

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