Inositol 1,4,5'-triphosphate receptor II (IP3RII) calcium channel expression is increased in both hypertrophic failing human myocardium and experimentally induced models of the disease. The ectopiccalcium released from these receptors induces pro-hypertrophic gene expression and may promote arrhythmias. Here, we show that IP3RII expression was constitutively restrained by the muscle-specific miRNA, miR-133a. During the hypertrophic response to pressure overload or neurohormonal stimuli, miR-133adown-regulation permitted IP3RII levels to increase, instigating pro-hypertrophic calcium signaling and concomitant pathological remodeling. Using a combination of in vivo and in vitro approaches, we demonstrated that IP3-induced calcium release (IICR) initiated the hypertrophy-associated decrease in miR-133a. In this manner, hypertrophic stimuli that engage IICR set a feedforward mechanism in motion whereby IICR decreased miR-133a expression, further augmenting IP3RII levels and therefore pro-hypertrophic calcium release. Consequently, IICR can be considered as bothan initiating event and a driving force for pathological remodeling.
ASJC Scopus subject areas
- Cell Biology