HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (8) Citing Articles via Google Scholar Google Scholar Articles by Murthy, K. S. Articles by Pentyala, S. N. Search for Related Content PubMed PubMed Citation Articles by Murthy, K. S. Articles by Pentyala, S. N.

VASCULAR BIOLOGY

Activation of PLC-1 by G_i/o-coupled receptor agonists

¹Departments of Physiology and Medicine, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia 23298; and ²Department of Anesthesiology, School of Medicine, State University of New York, Stony Brook, New York 11794

Submitted 25 May 2004 ; accepted in final form 1 August 2004

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 G_i/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; 65–76%) 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 (16–30%) and strongly inhibited by SKF-96365, a blocker of store-operated Ca²⁺ channels. Treatment of the cells with a G_q/13-coupled receptor agonist, CCK-8, caused only transient, PLC-1-mediated PI hydrolysis. Unlike G_i/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 G₁₃ 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 G_i/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

This article has been cited by other articles:

				W. Hu, S. Mahavadi, J. Huang, F. Li, and K. S. Murthy Characterization of S1P1 and S1P2 receptor function in smooth muscle by receptor silencing and receptor protection Am J Physiol Gastrointest Liver Physiol, October 1, 2006; 291(4): G605 - G610. [Abstract] [Full Text] [PDF]

				O. B. Balemba, T. J. Heppner, A. D. Bonev, M. T. Nelson, and G. M. Mawe Calcium waves in intact guinea pig gallbladder smooth muscle cells Am J Physiol Gastrointest Liver Physiol, October 1, 2006; 291(4): G717 - G727. [Abstract] [Full Text] [PDF]

				S. Thore, O. Dyachok, E. Gylfe, and A. Tengholm Feedback activation of phospholipase C via intracellular mobilization and store-operated influx of Ca2+ in insulin-secreting {beta}-cells J. Cell Sci., October 1, 2005; 118(19): 4463 - 4471. [Abstract] [Full Text] [PDF]