Activation of PLC-delta1 by Gi/o-coupled receptor agonists |
| |
Authors: | Murthy Karnam S Zhou Huiping Huang Jiean Pentyala Srinivas N |
| |
Institution: | Department of Physiology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298, USA. skarnam@hsc.vcu.edu |
| |
Abstract: | The mechanism of phospholipase (PLC)- activation by G protein-coupled receptor agonists was examined in rabbit gastric smooth muscle. Ca2+ stimulated an eightfold increase in PLC- 1 activity in permeabilized muscle cells. Treatment of dispersed or cultured muscle cells with three Gi/o-coupled receptor agonists (somatostatin, -opioid agonist D-Pen2,D-Pen5]enkephalin, and A1 agonist cyclopentyl adenosine) caused delayed increase in phosphoinositide (PI) hydrolysis (8- to 10-fold) that was strongly inhibited by overexpression of dominant-negative PLC- 1(E341R/D343R; 6576%) or constitutively active RhoA(G14V). The response coincided with capacitative Ca2+ influx and was not observed in the absence of extracellular Ca2+, but was partly inhibited by nifedipine (1630%) and strongly inhibited by SKF-96365, a blocker of store-operated Ca2+ channels. Treatment of the cells with a Gq/13-coupled receptor agonist, CCK-8, caused only transient, PLC- 1-mediated PI hydrolysis. Unlike Gi/o-coupled receptor agonists, CCK-8 activated RhoA and stimulated RhoA:PLC- 1 association. Inhibition of RhoA activity with C3 exoenzyme or by overexpression of dominant-negative RhoA(T19N) or G 13 minigene unmasked a delayed increase in PI hydrolysis that was strongly inhibited by coexpression of PLC- 1(E341R/D343R) or by SKF-96365. Agonist-independent capacitative Ca2+ influx induced by thapsigargin stimulated PI hydrolysis (8-fold), which was partly inhibited by nifedipine ( 25%) and strongly inhibited by SKF-96365 ( 75%) and in cells expressing PLC- 1(E341R/D343R). Agonist-independent Ca2+ release or Ca2+ influx via voltage-gated Ca2+ channels stimulated only moderate PI hydrolysis (2- to 3-fold), which was abolished by PLC- 1 antibody or nifedipine. We conclude that PLC- 1 is activated by Gi/o-coupled receptor agonists that do not activate RhoA. The activation is preferentially mediated by Ca2+ influx via store-operated Ca2+ channels. phospholipase C; G protein |
| |
Keywords: | |
本文献已被 PubMed 等数据库收录! |
| 点击此处可从《American journal of physiology》浏览原始摘要信息 |
| 点击此处可从《American journal of physiology》下载免费的PDF全文 |
|