Targeted STIM deletion impairs calcium homeostasis, NFAT activation, and growth of smooth muscle

Abstract

The Ca(2+)-sensing stromal interaction molecule (STIM) proteins are crucial Ca(2+) signal coordinators. Cre-lox technology was used to generate smooth muscle (sm)-targeted STIM1-, STIM2-, and double STIM1/STIM2-knockout (KO) mouse models, which reveal the essential role of STIM proteins in Ca(2+) homeostasis and their crucial role in controlling function, growth, and development of smooth muscle cells (SMCs). Compared to Cre(+/-) littermates, sm-STIM1-KO mice showed high mortality (50% by 30 d) and reduced bodyweight. While sm-STIM2-KO was without detectable phenotype, the STIM1/STIM double-KO was perinatally lethal, revealing an essential role of STIM1 partially rescued by STIM2. Vascular and intestinal smooth muscle tissues from sm-STIM1-KO mice developed abnormally with distended, thinned morphology. While depolarization-induced aortic contraction was unchanged in sm-STIM1-KO mice, α1-adrenergic-mediated contraction was 26% reduced, and store-dependent contraction almost eliminated. Neointimal formation induced by carotid artery ligation was suppressed by 54%, and in vitro PDGF-induced proliferation was greatly reduced (79%) in sm-STIM1-KO. Notably, the Ca(2+) store-refilling rate in STIM1-KO SMCs was substantially reduced, and sustained PDGF-induced Ca(2+) entry was abolished. This defective Ca(2+) homeostasis prevents PDGF-induced NFAT activation in both contractile and proliferating SMCs. We conclude that STIM1-regulated Ca(2+) homeostasis is crucial for NFAT-mediated transcriptional control required for induction of SMC proliferation, development, and growth responses to injury.-Mancarella, S., Potireddy, S., Wang, Y., Gao, H., Gandhirajan, K., Autieri, M., Scalia, R., Cheng, Z., Wang, H., Madesh, M., Houser, S. R., Gill, D. L. Targeted STIM deletion impairs calcium homeostasis, NFAT activation, and growth of smooth muscle.

Orai channel-mediated Ca2+signals in vascular and airway smooth muscle

“…The use of external potassium chloride to assess depolarization-induced contraction on aortas of sm-STIM1-KO mice showed normal contractility in these mice. However, ␣ 1 -adrenergic-mediated contraction of sm-STIM1-KO mice was inhibited by ϳ26%, suggesting a defect in contractile ␣ 1 -adrenergic signaling (47). Consistent with previous results with rat balloon injury, neointima formation caused by carotid artery ligation was reduced by 54% in sm-STIM1-KO mice compared with littermate controls.…”

“…NFAT-regulated genes are involved in various processes, including inflammation, proliferation, and migration (33). In synthetic vascular SMCs, passive store depletion by thapsigargin or receptor stimulation by PDGF leads to the nuclear translocation of NFAT (47,104,106). Knockdown of STIM1 or Orai1 expression prevents nuclear translocation of NFAT in vascular SMCs, with a corresponding decrease in promoter activity, as assessed by luciferase reporter assays (104).…”

“…Giachini et al (28) stimulated vessels with thapsigargin to activate SOCE and relied on nonspecific inhibitors such as 2-APB and Gd 3ϩ at high concentrations (100 M) to link SOCE function to enhanced vessel contraction in hypertensive rats. Nevertheless, enhanced SOCE in hypertensive rats might indeed account for enhanced receptor signaling through contractile mediators (e.g., phenylephrine and angiotensin II) (38,47). Notwithstanding an effect on contractility, STIM1/Orai1 and SOCE upregulation in vessels from hypertensive animals might suggest the establishment of SMC remodeling, which is a major contributor to the chronic phase of hypertension.…”

Emerging roles of Orai3 in pathophysiology

“…STIM1 and Orai1 mediate SOCE and CRAC currents in response to the potent proliferative and migratory VSMC agonist, the platelet-derived growth factor (PDGF); 18,79,84 this Ca 2+ entry is required for nuclear translocation and transcriptional activity of nuclear factor for activated T cells (NFAT). 82,84 We recently reported that Orai3 proteins are also upregulated when VSMC switch to a synthetic phenotype.…”

“…STIM1 and Orai1 mediate SOCE and CRAC currents in response to the potent proliferative and migratory VSMC agonist, the platelet-derived growth factor (PDGF); 18,79,84 this Ca 2+ entry is required for nuclear translocation and transcriptional activity of nuclear factor for activated T cells (NFAT). 82,84 We recently reported that Orai3 proteins are also upregulated when VSMC switch to a synthetic phenotype. 21 Interestingly, Orai3 did not contribute to Ca 2+ entry activated by either passive store depletion or physiological stimulation with PDGF; instead, Orai3 was shown to play a crucial role in mediating Ca 2+ entry upon stimulation with another VSMC agonist, thrombin.…”