Muscarinic receptor-mediated tyrosine phosphorylation of phospholipase C-gamma. An alternative mechanism for cholinergic-induced phosphoinositide breakdown.
In Chinese hamster ovary cells transfected with m5 muscarinic receptors, carbachol stimulates both calcium influx and calcium release from intracellular stores. The marine toxin maitotoxin (MTX) elicits a similar response on calcium influx. Carbachol- and MTX-induced calcium influx can be inhibited by the proposed blockers of receptor-operated calcium channels (ROCC), CAI and SK&F 96365. Both carbachol and MTX induce a significant increase in total protein tyrosine phosphorylation, which is dependent on extracellular calcium and can be inhibited by CAI and SK&F 96365. Phospholipase C-gamma was identified as one of the substrates subject to calcium-dependent tyrosine phosphorylation following carbachol or MTX stimulation. Carbachol-induced [3H]inositol trisphosphate formation was partially inhibited by an inhibitor of tyrosine kinases, by removal of extracellular calcium, and by the inhibitor of receptor-operated calcium channels CAI suggesting that phosphorylation of phospholipase C-gamma plays a role in the muscarinic activation of phosphoinositide breakdown. Such an effect of carbachol is reminiscent of effects observed with peptide growth factors and represents a novel alternative signaling pathway for a muscarinic G protein-coupled receptor.
Gusovsky
F
F
Laboratory of Bioorganic Chemistry, National Institute of Digestive Diseases and Kidney, National Institutes of Health, Bethesda, Maryland 20892.
Lueders
J E
JE
Kohn
E C
EC
Felder
C C
CC
D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology*; D006224:Cricetinae; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D008387:Marine Toxins / Q000494:pharmacology; D035964:Oxocins; D010716:Phosphatidylinositols / Q000378:metabolism*; D010766:Phosphorylation; D019000:Phosphotyrosine; D011976:Receptors, Muscarinic / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D010738:Type C Phospholipases / Q000378:metabolism*; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000032:analysis; D000095702:Polyether Toxins
D002118:Calcium; D002121:Calcium Channel Blockers; D002217:Carbachol; D007527:Isoenzymes; D008387:Marine Toxins; D035964:Oxocins; D010716:Phosphatidylinositols; D019000:Phosphotyrosine; D011976:Receptors, Muscarinic; D010738:Type C Phospholipases; D014443:Tyrosine; C020394:maitotoxin; D000095702:Polyether Toxins