Overexpression of SARAF Ameliorates Pressure Overload–Induced Cardiac Hypertrophy Through Suppressing STIM1-Orai1 in Mice

Abstract

Background/Aims: Activation of stromal interaction molecule 1 (STIM1) and Orai1 participates in the development of cardiac hypertrophy. Store-operated Ca²⁺ entry-associated regulatory factor (SARAF) is an intrinsic inhibitor of STIM1-Orai1 interaction. Thus, we hypothesized that SARAF could prevent cardiac hypertrophy. Methods: Male C57BL/6 mice, aged 8 weeks, were randomly divided into sham and abdominal aortic constriction surgery groups and were infected with lentiviruses expressing SARAF and GFP (Lenti-SARAF) or GFP alone (Lenti-GFP) via intramyocardial injection. At 4 weeks after aortic constriction, left ventricular structure and function were assessed by echocardiography and hemodynamic assays. The gene and protein expressions of SARAF, STIM1, and Orai1 were measured by quantitative PCR and Western blot, respectively. Results: Gene and protein expressions of SARAF were significantly decreased, while STIM1 and Orai1 were increased in the heart tissue compared with sham group. Overexpression of SARAF in the heart prevented the upregulation of STIM1 and Orai1, and importantly, attenuated aortic constriction-induced decrease in maximal rate of left ventricular pressure decay and increases in thickness of interventricular septum and left ventricular posterior wall, heart weight/body weight ratio, and size of cardiomyocytes. Blood pressure detected through the carotid artery and left ventricular systolic function were not affected by SARAF overexpression. In addition, overexpression of SARAF also attenuated angiotensin II-induced upregulation of STIM1 and Orai1 and hypertrophy of cultured cardiomyocytes. Conclusion: Overexpression of SARAF in the heart prevents cardiac hypertrophy, probably through suppressing the upregulation of STIM1/Orai1.

Orai1 channel inhibition preserves left ventricular systolic function and normal Ca2+ handling after pressure overload

“…Our combination of genetic and pharmacologic Orai1 inhibition approaches revealed a contribution of cardiomyocyte Orai1 channels in pressure overloadinduced systolic dysfunction. Consistent with previous studies, 5,12 Orai1 expression was increased after 5 weeks of TAC, exacerbating SOCE. Contrasting with compensated hypertrophic animal models that lack alteration of systolic function as assessed by the absence of LV fraction shortening modification, 12,24,32 our model of pressure overload-induced cardiac hypertrophy associated with ventricular dysfunction produces a more severe phenotype and lacks upregulation of STIM1 expression.…”

“…4,11 Likewise, it has been recently reported that in vivo overexpression of SOCE-associated regulatory factor in the heart prevents cardiac hypertrophy probably through suppressing the upregulation of STIM1 and Orai1. 12 Consequently, the question remains whether this deleterious effect is related to developmental or adult systemic or cardiac specific alteration. Overall, the contribution of Orai1 to Ca 2+ homeostasis and cardiac function remains elusive and conflicting.…”

Targeting Orai1-Mediated Store-Operated Ca2+ Entry in Heart Failure

“…Expression of Orai1 protein was first detected in 1-day-old neonate mice heart (Vig et al, 2008). Later on, many other studies described its expression in the NRVMs (Voelkers et al, 2010, Volkers et al, 2012Zhu-Mauldin et al, 2012;Wang et al, 2015;Sabourin et al, 2016;Ji et al, 2017;Zheng et al, 2017;Dominguez-Rodriguez et al, 2018;Dai et al, 2018;Malette et al, 2019). Orai1 expression decreased after birth in mice (Volkers et al, 2012).…”

“…Orai1 expression decreased after birth in mice (Volkers et al, 2012). In the adult heart, ventricular tissues, and isolated ventricular cardiomyocytes from rats, mice, cats, chickens, zebrafish, or even hibernator animal squirrels, Orai1 was also detected with a low or even moderate level of expression in rodents (Gross et al, 2007;Takahashi et al, 2007;Volkers et al, 2012;Wang et al, 2012;Zhu-Mauldin et al, 2012;Collins et al, 2014;Guzman et al, 2014;Horton et al, 2014;Correll et al, 2015;Dominguez-Rodriguez et al, 2015;Liu et al, 2015;Saliba et al, 2015;Li et al, 2017;Lu et al, 2017;Maus et al, 2017;Nakipova et al, 2017;Troupes et al, 2017;Zheng et al, 2017;Dai et al, 2018;Dominguez-Rodriguez et al, 2018;Lee et al, 2018;Sabourin et al, 2018;Bartoli et al, 2019;Bonilla et al, 2019;Segin et al, 2020). Orai1 is also expressed in HL-1 atrial muscle cell line (Touchberry et al, 2011;Shiou et al, 2019), in left atrial rat and mice myocytes (Wolkowicz et al, 2011;Liu et al, 2015), in human embryonic stem cell-derived cardiomyocytes (Che et al, 2015;Wang et al, 2015), and in the sarcolemma of mouse sinoatrial node cells (SANCs) and tissue (Zhang et al, 2013;Liu et al, 2015).…”

TRIC-A shapes oscillatory Ca2+ signals by interaction with STIM1/Orai1 complexes

“…Thus, increased SOCE, in the absence of TRIC-A, as we have observed with TRIC-A knockdown in the cardiac muscle cell line HL-1, can cause ER and mitochondrial Ca 2+ overload. It is also of interest that another ER-resident protein, SOCE-associated regulatory factor (SARAF), when overexpressed, can mitigate the effect of STIM1 in cardiac hypertrophy and diastolic dysfunction [39]. Interestingly, SARAF, like TRIC-A, is recruited to ER-PM junctions by STIM1, where it increases Ca 2+ -dependent inactivation of Orai1 [40].…”