Modulation of the interaction between chemotactic cAMP‐receptor and N‐protein by cAMP‐dependent kinase in Dictyosteliumdiscoideum membranes

Abstract

Dictyostelium discoideum cells contain kinetically distinguishable surface CAMP receptors. Both GTP and GDP lower the receptor affinity by inducing conversion of slowly dissociating sites to fast dissociating sites, presumably by binding to a N-protein [(1985) Mol. Cell. B&hem. 67, 119-124, and (1986) Biochemistry 25, 1314. In this paper we show that treatment of isolated membranes with CAMP-dependent protein kinase abolished the GTP-induced receptor transition, but not the one induced by GDP. The effect of GTP on the receptor kinetics could be restored by treatment of the membranes with alkaline phosphatase. These results indicate that in D. discoideum membranes phosphorylation of a signal-transduction component reversibly abolishes the interaction of the CAMP receptor with the NGTP complex, but not that with the NGDP complex.(Dictyostelium discoideum)cyclic AMP receptor N-protein cyclic AMP dependence Protein kinase Desensitization Adaptation

Cyclic AMP functions as a primary sexual signal in gametes of Chlamydomonas reinhardtii.

“…The extent to which these mechanisms apply to cell contact-mediated and extracellular matrix-mediated transmembrane signaling is largely unknown. Studies of immune cell (13), platelet (19), Dictyostelium (50), and sperm-egg interactions (76) have begun to address these questions.…”

Molecular basis of transmembrane signal transduction in Dictyostelium discoideum.

“…Incubation of membranes under conditions designed to stimulate protein phosphorylation alters the binding properties of both the H and L and S and SS kinetic forms or their putative coupling to G-proteins or both (174,296,302). In addition it abolishes GTP stimulation of adenylate cyclase (307).…”

“…In addition it abolishes GTP stimulation of adenylate cyclase (307). These observations, however, give no insight into the relationship between binding and receptor modification, because possible physical alterations in the receptors resulting from phosphorylation were either not observed (296) or not investigated (174,302). The altered receptor binding properties were assumed to be caused by phosphorylations catalyzed by different kinases, such as protein kinase C (302), kinase A (174), or an endogenous membrane-bound kinase (296).…”