Transcriptional Regulation of T-type Calcium Channel Cav3.2 During the Cardiac Hypertrophy

• Main Authors: Shao-Chun Hsu, 許紹君
• Other Authors: Chien-Chang Chen
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/02581012567545921845

博士 === 國立陽明大學 === 生化暨分子生物研究所 === 102 === The Cav3.2 T-channel plays a pivotal role in inducing calcineurin/nuclear factor of activated T cell (NFAT) signaling during cardiac hypertrophy. Because calcineurin/NFAT signaling is induced early after pressure overload, we hypothesized that Cav3.2 is induced by an early signal. Our aim is to investigate when and how Cav3.2 is induced during cardiac hypertrophy. The evolutionary conserved promoter Cav3.2-3500 from mouse genome was validated to express the reporter gene as endogenous Cav3.2 in cell lines and transgenic (Tg; Cav3.2-3500-Luc) mice. The early induction of luciferase in Tg mice and Cav3.2 mRNA in wild-type mice after transverse aortic banding (TAB) surgery supported our hypothesis that Cav3.2 is induced early during cardiac hypertrophy. The TAB-responding element (-81 to -41 bp upstream of the transcription start site [TSS] of mouse Cav3.2) was identified by in vivo gene transfer by injecting reporter constructs into the left ventricle followed by TAB surgery. EMSA and ChIP assays revealed that Egr1 bound to the TAB-responding element of Cav3.2. Egr1 level was increased with increased Cav3.2 mRNA level at 3 days after TAB. To demonstrate that Egr1 indeed regulates Cav3.2 expression after hypertrophic stimulation, knockdown of Egr1 with short hairpin RNA prevented the phenylephrine-induced upregulation of Cav3.2 expression and cellular hypertrophy in neonatal rat ventricular myocytes (NRVMs) and H9c2 cells. Furthermore, overexpression of Cav3.2 in Egr1-knockdown cells restored the phenylephrine-induced hypertrophy. Cav3.2 is induced early by Egr1 during cardiac hypertrophy and Cav3.2 is an important mediator of Egr1 in regulating cardiac hypertrophy.