Back to Search Start Over

Orai1 interacts with STIM1 and mediates capacitative [Ca.sup.2+] entry in mouse pulmonary arterial smooth muscle cells

Authors :
ChyuanNg, Lih
Ramduny, Deepa
Airey, Judith A.
Singer, Cherie A.
Keller, Phillip S.
Shen, Xiao-Ming
Tian, Honglin
Valencik, Maria
Hume, Joseph R.
Source :
The American Journal of Physiology. Nov, 2010, Vol. 299 Issue 5, pC1079, 12 p.
Publication Year :
2010

Abstract

Previous studies in mouse pulmonary arterial smooth muscle cells (PASMCs) showed that cannonical transient receptor potential channel TRPCI and stromal interaction molecule 1 (STIM1) mediate the sustained component of capacitative [Ca.sup.2+] entry (CCE), but the molecular candidate(s) that mediate the transient component of CCE remain unknown. The aim of the present study was to examine whether Orai1 mediates the transient component of CCE through activation of STIM1 in mouse PASMCs. In primary cultured mouse PASMCs loaded with fura-2, cyclopiazonic acid (CPA) caused a transient followed by a sustained rise in intracellular [Ca.sup.2+] concentration ([[Ca.sup.2+]].sub.i]). The transient but not the sustained rise in [[Ca.sup.2+].sub.i] was partially inhibited by nifedipine. The nifedipine-insensitive transient rise in [[Ca.sup.2+].sub.i] and the increase in [Mn.sup.2+] quench of fura-2 fluorescence caused by CPA were both reduced in cells treated with Orai1 siRNA. These responses to CPA were further reduced in cells treated with Orai1 and STIM1 small interfering (si)RNA. Moreover, overexpression of STIM1 enhanced the rise in [[Ca.sup.2+].sub.i] and the increase in [Mn.sup.2+] quench of fura-2 fluorescence caused by CPA, and these responses were reduced in cells treated with Orai1 siRNA. RT-PCR revealed Orai1 and STIM1 mRNAs, and Western blot analysis identified Orai1 and STIM1 proteins in mouse PASMCs. Furthermore, Orai1 was found to coimmunoprecipitate with STIM1, and the precipitation level of Orai1 was increased in cells subjected to store-depletion. Immunostaining revealed colocalization of Orai1 and STIM1 proteins, and the colocalization of these proteins was more apparent after store-depletion. These data provide direct evidence that the transient component of CCE is mediated by Orai1 channel as a result of STIM1 activation in mouse PASMCs. stromal interaction molecule 1; store-depletion; intracellular [Ca.sup.2+] concentration doi: 10.1152/ajpcell.00548.2009.

Details

Language :
English
ISSN :
00029513
Volume :
299
Issue :
5
Database :
Gale General OneFile
Journal :
The American Journal of Physiology
Publication Type :
Academic Journal
Accession number :
edsgcl.242508611