Knockdown of stromal interaction molecule 1 attenuates store-operated Ca²⁺ entry and Ca²⁺ responses to acute hypoxia in pulmonary arterial smooth muscle

Abstract

from an EF-hand motif in the NH 2 -terminal region of STIM1 located within the SR/ER lumen, translocation of STIM1 proteins to form oligomeric collections termed "puncta" in portions of the SR/ER membrane close to SOC in plasma membrane, and interactions of STIM1 with SOC and/or associated regulatory proteins that lead to channel activation and SOCE (13,59,62). Indeed, it has been proposed that fulfillment of these functions by STIM1 should define SOC (58). Closely related to STIM1 is STIM2, a 105-kDa protein detected in SR/ER but not plasma membrane, which has 61% structural homology with STIM1, including an EF-hand domain, a protein-protein interaction site known as the sterile ␣-motif domain, and a coiled-coils membrane spanning region within an ezrin/radixin/moesin (ERM) domain (9). The function of STIM2 is not as well understood as that of STIM1. Some studies indicate that STIM2 has little or no effect on SOCE (22,30,36,51), whereas others suggest that STIM2 may inhibit STIM1 (50), act to maintain basal cytoplasmic and SR/ER luminal Ca 2ϩ (4), or regulate store-dependent and -independent activation of SOC (35). Although STIM2 was detected in airway and coronary arterial smooth muscle (36, 51), expression in PASMC has not been reported.In a previous study of distal and proximal pulmonary arteries (24), we found that STIM1 expression, SOCE, and [Ca 2ϩ ] i responses to hypoxia but not KCl were greater in myocytes from distal arteries, which are thought to be the major locus of HPV (45,47). In this study, we examined STIM2 expression and used RNA interference to evaluate the roles of STIM1 and STIM2 in SOCE and [Ca 2ϩ ] i responses to acute hypoxia in distal PASMC. METHODSIsolation and culture of rat distal PASMC. Animal protocols were approved by the Animal Care and Use Committee of the Johns Hopkins Medical Institutions. PASMC were harvested from distal (Ͼ4th generation) intrapulmonary arteries of anesthetized (pentobarbital, 65 mg/kg ip) male Wistar rats (300 -500 g body wt) and cultured

Thapsigargin activates Ca2+ entry both by store-dependent, STIM1/Orai1-mediated, and store-independent, TRPC3/PLC/PKC-mediated pathways in human endothelial cells

“…Interestingly, even though the silencing efficiency was of between 65 and 80% at the protein level, an important residual Ca 2+ entry persisted upon store depletion. Such a "partial" SOCE reduction was already observed, for instance in smooth muscle cells [52][53][54] or HEK cells [20], but in most cell types, the inhibition of SOCE upon STIM1 invalidation is very pronounced [3,39,55,56]. This finding prompted us to investigate the mechanism of the residual TG-induced Ca 2+ entry.…”

Attenuated mesangial cell proliferation related to store-operated Ca2+ entry in aged rat: the role of STIM 1 and Orai 1

“…Ca 2+ influx through SOCE involves keeping a sustained high Ca 2+ concentration in the Ca 2+ stores and refilling the SR when it releases Ca 2+ . SOCE was shown to be upregulated in proliferating porcine bronchial smooth muscle cells, aortic smooth muscle cells, and pulmonary artery smooth muscle cells (Sweeney et al 2002;Lu et al 2009;Berra-Romani et al 2008). Our data suggest that SOCE activity contributes to mesangial cell proliferation and that decreased SOCE contributed to a lower proliferation rate in GMCs.…”

Redox regulation of calcium ion channels: Chemical and physiological aspects

“…Two studies suggested that this activation is governed by up-regulation of TRP channels [196,197] while others localized the ER as the target-site [198][199][200][201][202].…”

“…Lu et al proposed that SOCE activation by hypoxia is via STIM1 while STIM2 played no significant role in this context [200]. Conversely, Berna-Erro et al [201] reported that STIM2 is essential for the hypoxia induced Ca 2+ overload, while manipulations of STIM1 expression had no significant effect.…”