The Cavβ4 subunit of Cav1.2 channels antagonizes isoproterenol-induced hypertrophy in rat cardiac muscle cells by down-regulating miR-183-5p.

The Cavβ4 subunit of voltage-gated Cav1.2 channels regulates gene expression in neurons and cardiac cells. It increases the expression of interferon-β-related genes in H9c2 cardiomyocytes derived from rat ventricular tissue, but the possibility that it also regulates the expression of microRNAs (miRs) remains unexplored. Furthermore, its role in cardiac hypertrophy is unknown. Although the mechanisms underlying cardiac hypertrophy have been studied extensively, the antihypertrophic response is poorly understood. We conducted quantitative reverse-transcriptase polymerase chain reaction, western blot, and immunofluorescence experiments with H9c2 cardiomyocytes to examine the effects of Cavβ4 overexpression on isoproterenol-induced hypertrophy; the protein abundance of the transcription factors nuclear receptor 4A2 (NR4A2) and forkhead box O1 (FOXO1), which counter agonist-induced hypertrophic growth; and the expression of miR-183-5p, which targets NR4A2 and FOXO1 mRNAs. We found that the Cavβ4 subunit prevented the development of H9c2 cardiomyocyte hypertrophy, down-regulating miR-183-5p expression and increasing the protein abundance of NR4A2 and FOXO1. We also observed a transient decrease in Cavβ4 mRNA expression in rat ventricles at 6 h after isoproterenol injection. These results suggest that the Cavβ4 subunit plays a channel-independent role in the antihypertrophic response in cardiac muscle cells.