Urotensin-II Signaling Mechanism in Rat Coronary Artery: Role of STIM1 and Orai1-Dependent Store Operated Calcium Influx in Vasoconstriction
Objective—Human urotensin-II (UII) is considered the most potent endogenous vasoconstrictor discovered to date, although the precise mechanism activated downstream of its receptor UTS2R in blood vessels remains elusive. The aim of this study was to determine the role of the store operated Ca2+ entry (SOCE) signaling pathway in UII-induced coronary artery vasoconstriction.
Methods and Results—We used a combination of isometric tension measurement, Ca2+ imaging, pharmacology, and molecular approaches to study UII-mediated rat coronary artery vasoconstriction and intracellular Ca2+ mobilization in coronary smooth muscle cells. We found that UII promoted dose-dependent vasoconstriction and elicited Ca2+ and Mn2+ influx, which were sensitive to classical SOCE inhibitors. In addition, knockdown of either STIM1 or Orai1 essentially inhibited UII-mediated SOCE and prevented UII but not high-KCL evoked contraction in transfected coronary artery. Moreover, we found that Ca2+-independent phospholipase A2β was involved in UII effects and that is colocalized with STIM1 in different submembrane compartments. Importantly, STIM1 but not Orai1 downregulation inhibits significantly independent phospholipase A2 activation. Furthermore, lysophosphatidylcholine, an independent phospholipase A2 product, activated Orai1 but not STIM1-dependent contraction and SOCE.
Conclusion—Here, we demonstrated that different critical players of SOCE signaling pathway are required for UII-induced vasoconstriction of rat coronary artery.
- Received July 25, 2011.
- Accepted December 21, 2011.
- © 2012 American Heart Association, Inc.