Orai1 and Stim1 regulate normal and hypertrophic growth in cardiomyocytes

Abstract

Cardiac hypertrophy is an independent risk for heart failure (HF) and sudden death. Deciphering signalling pathways dependent on extracellular calcium (Ca2+) influx that control normal and pathological cardiac growth may enable identification of novel therapeutic targets. The objective of the present study is to determine the role of the Ca2+ release-activated Ca2+ (CRAC) channel Orai1 and stromal interaction molecule 1 (Stim1) in postnatal cardiomycoyte store-operated Ca2+ entry (SOCE) and impact on normal and hypertrophic postnatal cardiomyocyte growth. Employing a combination of siRNA-mediated gene silencing, cultured neonatal rat ventricular cardiomyocytes together with indirect immunofluorescence, epifluorescent Ca2+ imaging and site-specific protein phosphorylation and real-time mRNA expression analysis, we show for the first time that both Orai1 and Stim1 are present in cardiomyocytes and required for SOCE due to intracellular Ca2+ store depletion by thapsigargin. Stim1-KD but not Orai1-KD significantly decreased diastolic Ca2+ levels and caffeine-releasable Ca2+ from the sarcoplasmic reticulum (SR). Conversely, Orai1-KD but not Stim1-KD significantly diminished basal NRCM cell size, anp and bnp mRNA levels and activity of the calcineurin (CnA) signaling pathway although diminishing both Orai1 and Stim1 protein similarly attenuated calmodulin kinase II (CamKII) and ERK1/2 activity under basal conditions. Both Orai1- and Stim1-KD completely abrogated phenylephrine (PE) mediated hypertrophic NRCM growth and enhanced natriuretic factor expression by inhibiting Gq-protein conveyed activation of the CaMKII and ERK1/2 signaling pathway. Interestingly, only Orai1-KD but not Stim1-KD prevented Gq-mediated CaN-dependent prohypertrophic signalling. This study shows for the first time that both Orai1 and Stim1 have a key role in cardiomyocyte SOCE regulating both normal and hypertrophic postnatal cardiac growth in vitro.

STIM1–Ca 2+ signaling modulates automaticity of the mouse sinoatrial node

“…SOCE is therefore an attractive candidate to link the Ca 2+ and membrane clocks that underlie SANC automaticity. Roles for STIM1-dependent SOCE have been suggested in the heart (10)(11)(12)(13)(14). Here, we show that STIM1 is selectively expressed in the SAN where it activates Ca 2+ entry via Orai1 channels and thereby modulates the Ca 2+ signals required for pacemaking activity of the SAN.…”

Nitric Oxide-cGMP-PKG Pathway Acts on Orai1 to Inhibit the Hypertrophy of Human Embryonic Stem Cell-Derived Cardiomyocytes

“…Previously, research in rodent models has demonstrated that SOCE, STIM1, and Orai1 play crucial roles in the development of cardiomyocyte hypertrophy [8][9][10], whereas NO, cGMP, and PKG exert antihypertrophic effect [6,11,34]. However, one of the challenges in exploring mechanistic insight of Orai1 and/or NO-cGMP-PKG effect is lack of human cardiomyocytes for research.…”

STIM1/Orai1-mediated SOCE: current perspectives and potential roles in cardiac function and pathology

“…Similar to their earlier study (78), they also found that TRPC1 expression was upregulated in response to ET-1; interestingly, this increase was also attenuated following knockdown of STIM1. Subsequently, Voelkers and colleagues showed that SOCE and hypertrophic signaling induced by PE treatment were reduced following knockdown of both STIM1 and Orai1 (130).…”