Activation of phospholipase C by G-protein beta gamma subunits in DDT1MF-2 cells.
Adenosine A1 receptors directly stimulate inositol phospholipid hydrolysis and Ca2+ mobilization through a pertussis toxin sensitive mechanism in DDT1MF-2 cells. In the present study we have investigated whether G protein beta gamma subunits (G beta gamma) are capable of stimulating phospholipase C in DDT1MF-2 cell membrane preparations using lipid vesicles containing [3H]phosphatidylinositol 4,5-bisphosphate. DDT1MF-2 cell membrane and soluble fractions were found to contain phospholipase C activity which was stimulated by increases in free Ca2+ ion concentration. G beta gamma purified from bovine retinal transducin produced significant increases in phospholipase C activity in DDT1MF-2 cell membranes. G beta gamma-dependent activation of phospholipase C, while virtually absent in the presence of low Ca2+ ion concentrations, increased markedly with increasing free Ca2+ ion concentration. These data suggest that membrane bound phospholipase C in DDT1MF-2 cells is sensitive to Ca2+, and may be stimulated conditionally by G beta gamma subunits, i.e. G beta gamma subunits activate the enzyme only in the presence of Ca2+. G beta gamma subunits also stimulated soluble phospholipase C in DDT1MF-2 cells. These findings support the hypothesis that Gi beta gamma subunits are involved in adenosine A1 receptor stimulated phospholipase C/Ca2+ signaling in DDT1MF-2 cells.
Dickenson
J M
JM
Department of Physiology and Pharmacology, Medical School, Queen's Medical Centre, Nottingham, UK.
Camps
M
M
Gierschik
P
P
Hill
S J
SJ
D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000494:pharmacology; D002460:Cell Line; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000378:metabolism*; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects / Q000201:enzymology*; D010738:Type C Phospholipases / Q000378:metabolism*
D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D002118:Calcium