Opposing actions of Perl and Cry2 in the regulation of Perl target gene expression in the liver and kidney.

摘要

Mounting evidence suggests that the circadian clock plays an integral role in the regulation of many physiological processes including blood pressure, renal function, and metabolism. The canonical molecular clock functions via activation of circadian target genes by Clock/Bmall and repression of Clock/Bmall activity by Perl-3 and Cryl/2. However, we have previously shown that Perl activates genes important for renal sodium reabsorption, which contradicts the canonical role of Perl as a repressor. Moreover, Perl knockout (KO) mice exhibit a lowered blood pressure and heavier body weight phenotype similar to Clock KO mice, and opposite that of Cryl/2 KO mice. Recent work has highlighted the potential role of Perl in repression of Cry2. Therefore, we postulated that Perl potentially activates target genes through a Cry2-Clock/Bmall-dependent mechanism, in which Perl antagonizes Cry2, preventing its repression of Clock/Bmall. This hypothesis was tested in vitro and in vivo. The Perl target genes alphaENaC and Fxyd5 were identified as Clock targets in mpkCCD_(c14) cells, a model of the renal cortical collecting duct. We identified PPARa and DEC1 as novel Perl targets in the mouse hepatocyte cell line, AML12, and in the liver in vivo. Perl knockdown resulted in upregulation of Cry2 in vitro, and this result was confirmed in vivo in mice with reduced expression of Perl. Importantly, siRNA-mediated knockdown of Cry2 and Perl demonstrated opposing actions for Cry2 and Perl on Perl target genes, supporting the potential Cry2-Clock/Bmall-dependent mechanism underlying Perl action in the liver and kidney.