Phospholipase C involvement in activation of the muscarinic receptor-operated cationic current in guinea pig ileal smooth muscle cells
Phospholipase C involvement in activation of the muscarinic receptor-operated cationic current in guinea pig ileal smooth muscle cells
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DOI：
10.1254/jphs.fp0030635
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发表时间：
2004-06-01
影响因子：
3.5
通讯作者：
Komori, S
中科院分区：
文献类型：
--
作者：
Okamoto, H;Unno, T;Komori, S
在豚鼠单个回肠平滑肌细胞上，用电压钳技术研究了磷脂酶C（PLC）在毒蕈碱受体操纵的阳离子电流（I-cat）激活中的作用。PLC抑制剂U 73122可阻止毒蕈碱激动剂卡巴胆碱产生I-cat。该作用不涉及毒蕈碱受体阻断，因为它也阻断了I-cat，I-cat是由细胞内应用GTP γ S激活G蛋白而绕过毒蕈碱受体引起的。此外，似乎既不涉及阳离子通道阻断也不涉及其他可能的非特异性作用，因为其类似物（U 73343），结构上接近但缺乏PLC抑制活性，并不显著影响卡巴胆碱或GTP γ S诱发的I-cat。（Galpha（q）/Galpha（11）-抗体）仅阻断卡巴胆碱诱发的I-cat的小部分，这与[Ca 2 +]（i）增加有关，[Ca 2 +]（i）与G（q/11）蛋白调节的PLC活性增加有关。1-油酰基-2-乙酰基-sn-甘油（OAG）是通过PLC催化代谢产生的二酰基甘油（DAG）的类似物，其本身不产生或仅产生很小的电流，卡巴胆碱诱发的I-cat保持不变。这些结果为PLC在I-cat生成中的重要性提供了证据，它们也强烈地表明，PLC参与I-cat的初级激活的活性既不受G（q/11）蛋白的调节，也不依赖于DAG的作用。
In guinea pig single ileal smooth muscle cells held under voltage-clamp, the role of phospholipase C (PLC) in activation of the muscarinic receptor-operated cationic current (I-cat) was studied. U73122, a PLC inhibitor, prevented the generation of I-cat by the muscarinic agonist carbachol. The effect did not involve muscarinic receptor block since it also blocked I-cat which was evoked by GTPgammaS applied intracellularly to activate G proteins bypassing muscarinic receptors. Also, neither cationic channel block nor other possible nonspecific actions seemed to be involved since its analogue (U73343), structurally close but deficient of the PLC-inhibiting activity, did not significantly affect carbachol- or GTPgammaS-evoked I-cat. Antibodies against the a subunits of G(q)/G(11) proteins (Galpha(q)/Galpha(11)-antibody) blocked only the small component of carbachol-evoked I-cat, which was associated with an increase in [Ca2+](i) linked to an increase in G(q/11) protein-regulated PLC activity. 1-Oleoyl-2-acetyl-sn-glycerol (OAG), an analogue of diacylglycerol (DAG) produced via PLC-catalyzed metabolism, produced no or only a small current by itself, with the carbachol-evoked I-cat remaining unchanged. These results provide evidence for the importance of PLC in I-cat generation, and they also strongly suggest that the activity of PLC involved in the primary activation of I-cat is neither under regulation by G(q/11) proteins nor dependent on the action of DAG.