Stromal interaction molecule 1 haploinsufficiency causes maladaptive response to pressure overload

Stromal interaction molecule 1 (STIM1), an endo/sarcoplasmic reticulum Ca2+ sensor, has been shown to control a Ca2+- dependent signal that promotes cardiac hypertrophy. However, whether STIM1 has adaptive role that helps to protect against cardiac overload stress remains unknown. We hypothesized that STIM1 deficiency causes a maladaptive response to pressure overload stress. We investigated STIM1 heterozygous KO (STIM1(+/)-) mice hearts, in which STIM1 protein levels decreased to 27% of wild-type (WT) with no compensatory increase in STIM2. Under stress-free conditions, no significant differences were observed in electrocardiographic and echocardiographic parameters or blood pressure between STIM1(+/)-and WT mice. However, when STIM1(+/)-mice were subjected to transverse aortic constriction (TAC), STIM1(+/-) mice had a higher mortality rate than WT mice. The TAC-induced increase in the heart weight to body weight ratio (mean mg/g +/- standard error of the mean) was significantly inhibited in STIM1(+/-) mice (WT sham, 4.12 +/- 0.14; WT TAC, 6.23 +/- 0.40; STIM1(+/-) sham, 4.53 +/- 0.16; STIM1(+/-) TAC, 4.63 +/- 0.08). Reverse transcription- polymerase chain reaction analysis of the left ventricles of TAC-treated STIM1(+/-) mice showed inhibited induction of cardiac fetal genes, including those encoding brain and atrial natriuretic proteins. Western blot analysis showed upregulated expression of transient receptor potential channel 1 (TRPC1) in TAC-treated WT mice, but suppressed expression in TAC-treated STIM1(+/-) mice. Taken together, the hearts of STIM1 haploinsufficient mice had a superficial resemblance to the WT phenotype under stress-free conditions; however, STIM1 haploinsufficient mice showed a maladaptive response to cardiac pressure overload.