Gusovsky F, Lueders J E, Kohn E C, Felder C C
Laboratory of Bioorganic Chemistry, National Institute of Digestive Diseases and Kidney, National Institutes of Health, Bethesda, Maryland 20892.
J Biol Chem. 1993 Apr 15;268(11):7768-72.
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.
在转染了m5毒蕈碱受体的中国仓鼠卵巢细胞中，卡巴胆碱可刺激细胞外钙内流以及细胞内钙库的钙释放。海洋毒素 maitotoxin（MTX）对钙内流也引发类似反应。卡巴胆碱和MTX诱导的钙内流可被提议的受体操纵性钙通道（ROCC）阻滞剂CAI和SK&F 96365抑制。卡巴胆碱和MTX均可诱导总蛋白酪氨酸磷酸化显著增加，这依赖于细胞外钙，且可被CAI和SK&F 96365抑制。磷脂酶C-γ被鉴定为在卡巴胆碱或MTX刺激后发生钙依赖性酪氨酸磷酸化的底物之一。酪氨酸激酶抑制剂、去除细胞外钙以及受体操纵性钙通道抑制剂CAI均可部分抑制卡巴胆碱诱导的[3H]肌醇三磷酸形成，这表明磷脂酶C-γ的磷酸化在毒蕈碱激活磷脂酰肌醇分解中发挥作用。卡巴胆碱的这种效应让人联想到肽生长因子所观察到的效应，代表了毒蕈碱G蛋白偶联受体一种新的替代信号通路。
