PubMed · 5067965
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R L Westerman. 1972-07-31. Atropine coma.. https://doi.org/10.1001/jama.1972.03200180051023
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Receptor-mediated phospholipase D activation in human embryonic kidney (HEK) cells stably expressing the m3 muscarinic acetylcholine receptor (mAChR) apparently involves the small G protein RhoA. Here, activation of RhoA was examined by measuring cytosol-membrane translocation, which is a sign of RhoA activation. RhoA translocation was induced by guanosine 5'-O-(3-thio)triphosphate in digitonin-permeabilized HEK cells, and in intact cells by the agonist-activated mAChR and by direct activation of heterotrimeric G proteins. RhoA translocation was also induced by the phosphotyrosine phosphatase inhibitor pervanadate, while the tyrosine kinase inhibitors tyrphostin 23 and genistein inhibited the mAChR-induced RhoA translocation. These data suggest that translocation and thus activation of RhoA by the G protein-coupled m3 mAChR in HEK cells apparently involves a tyrosine kinase-dependent reaction.
The effect of carbachol, an acetylcholine receptor agonist, on rate of phosphatidylinositol (PI) turnover in cultured human meningioma cells was investigated. Exposure of meningioma cells for 2 h to carbachol (3.12-200 mumol/L) resulted in a dose-dependent stimulation of PI turnover to a maximum of 5.5-fold over basal controls. A time course study showed stimulation of IP3 formation after 30 s followed by increases in IP1 and IP2. The stimulatory effect of carbachol on PI turnover was completely abolished by the muscarinic receptor antagonist, atropine, but was unaltered by the nicotinic antagonist, hexamethonium. Reverse-transcription of meningioma-derived RNA into cDNA followed by amplification by the polymerase chain reaction using specific primers revealed presence of ml type muscarinic receptor mRNA. These results provide evidence that human meningioma cells possess muscarinic acetylcholine receptors the activation of which leads to PI hydrolysis.