Phospholipase C in Dictyostelium discoideum. Identification of stimulatory and inhibitory surface receptors and G-proteins.
A combined biochemical and genetic approach was used to show that phospholipase C in the cellular slime mould Dictyostelium is under dual regulation by the chemoattractant cyclic AMP (cAMP). This dual regulation involves stimulatory and inhibitory surface receptors and G-proteins. In wild-type cells both cAMP and guanosine 5'-[gamma-thio]triphosphate (GTP[S]) stimulated phospholipase C. In contrast, mutant fgd A, lacking the G-protein alpha-subunit G alpha 2, showed no stimulation by either cAMP or GTP[S], indicating that G alpha 2 is the stimulatory G-protein. In mutant fgd C cAMP did not stimulate phospholipase C, but stimulation by GTP[S] was normal, suggesting that the defect in this mutant is upstream of the stimulatory G alpha 2. Inhibition of phospholipase C was achieved in wild-type cells by the partial antagonist 3'-deoxy-3'-aminoadenosine 3',5'-phosphate (3'NH-cAMP). This inhibition was no longer observed in transformed cell lines lacking either the surface cAMP receptor cAR1 or the G-protein alpha-subunit G alpha 1; in these cells the agonist cAMP still activated phospholipase C. These results indicate that Dictyostelium phospholipase C is regulated via a stimulatory and an inhibitory pathway. The inhibitory pathway is composed of the surface receptor cAR1 and the G-protein G1. The stimulatory pathway consists of an unknown cAMP receptor (possibly the fgd C gene product) and the G-protein G2.
Bominaar
A A
AA
Department of Biochemistry, University of Groningen, The Netherlands.
Van Haastert
P J
PJ
D000818:Animals; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004023:Dictyostelium / Q000201:enzymology* / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects; D019204:GTP-Binding Proteins / Q000502:physiology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D000072181:Inositol Polyphosphate 5-Phosphatases; D009154:Mutation; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D011953:Receptors, Cyclic AMP / Q000235:genetics / Q000502:physiology*; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism*
D011953:Receptors, Cyclic AMP; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C080252:3'-deoxy-3'aminocyclic-3',5'-AMP; D015544:Inositol 1,4,5-Trisphosphate; D000242:Cyclic AMP; D010744:Phosphoric Monoester Hydrolases; D000072181:Inositol Polyphosphate 5-Phosphatases; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins