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

J. Biol. Chem., Vol. 281, Issue 45, 34312-34323, November 10, 2006

This Article Full Text Full Text (PDF) All Versions of this Article: 281/45/34312    most recent M606765200v1 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 PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Umesh, A. Articles by Sham, J. S. K. Search for Related Content PubMed PubMed Citation Articles by Umesh, A. Articles by Sham, J. S. K.

Integrin Ligands Mobilize Ca²⁺ from Ryanodine Receptor-gated Stores and Lysosome-related Acidic Organelles in Pulmonary Arterial Smooth Muscle Cells^*

Anita Umesh, Michael A. Thompson, Eduardo N. Chini, Kay-Pong Yip^¶, and James S. K. Sham¹

From the Division of Pulmonary and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21224, the Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota 55905, and the ^¶Department of Physiology and Biophysics, University of South Florida, Tampa, Florida 33612

Extracellular matrix (ECM) protein receptors, or integrins, participate in vascular remodeling and the systemic myogenic response. Synthetic ligands and ECM fragments regulate the vascular smooth muscle cell contractile state by altering intracellular Ca²⁺ levels ([Ca²⁺]_i). Information on the Ca²⁺ effect of integrins in vascular smooth muscle cells is limited, but nonexistent in pulmonary arterial smooth muscle cells (PASMCs). We therefore characterized integrin expression in endothelium-denuded pulmonary arteries, and explored [Ca²⁺]_i mobilization pathways induced by soluble ligands in rat PASMCs. Reverse transcriptase-PCR showed mRNA expression of integrins ₁, ₂, ₃, ₄, ₅, ₇, ₈, _v, ₁, ₃, and ₄, and immunoblots of ₅, _v, ₁, and ₃ confirmed protein expression. Exposure of PASMCs to integrin-binding peptides (0.5 mM) containing the arginine-glycine-aspartate (RGD) motif elicited [Ca²⁺]_i responses with an order of potency of GRGDNP > GRGDSP > GRGDTP = cyclo-RGD. Pharmacological analysis revealed that the GRGDSP-induced Ca²⁺ response was unrelated to Ca²⁺ influx and the inositol triphosphate receptor-gated Ca²⁺ store, but partially blocked by ryanodine or inhibition of lysosomerelated acidic organelles with bafilomycin A1. Simultaneous inhibition of both pathways was necessary to abolish the response. GRGDSP treatment increased cyclic ADP-ribose, the endogenous activator of ryanodine receptors, by 70%. GRGDSP also rapidly reduced Lysotracker Red accumulation, confirming direct modulation of acidic organelles. These data are the first demonstration of integrin-mediated Ca²⁺ regulation in PASMCs. The presence of an array of integrins, and activation of ryanodine-sensitive Ca²⁺ stores and lysosome-like organelles by GRGDSP suggest important roles for integrin-dependent Ca²⁺ signaling in regulating PASMC function.

Received for publication, July 17, 2006 , and in revised form, September 8, 2006.

^* This work was supported by National Institutes of Health Grants HL075134 and HL071835 (to J. S. K. S.), a Pulmonary Hypertension Association fellowship (to A. U.), and funds from the American Heart Association (to E. N. C.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence should be addressed: 5501 Hopkins Bayview Circle, JHAAC, Baltimore, MD 21224. Tel.: 410-550-7751; Fax: 410-550-2612; E-mail: jsks{at}welchlink.welch.jhu.edu.

This article has been cited by other articles:

				L. Balasubramanian, A. Ahmed, C.-M. Lo, J. S. K. Sham, and K.-P. Yip Integrin-mediated mechanotransduction in renal vascular smooth muscle cells: activation of calcium sparks Am J Physiol Regulatory Integrative Comp Physiol, October 1, 2007; 293(4): R1586 - R1594. [Abstract] [Full Text] [PDF]

				M.-J. Lin, X.-R. Yang, Y.-N. Cao, and J. S. K. Sham Hydrogen peroxide-induced Ca2+ mobilization in pulmonary arterial smooth muscle cells Am J Physiol Lung Cell Mol Physiol, June 1, 2007; 292(6): L1598 - L1608. [Abstract] [Full Text] [PDF]