Repression of Cathepsin D Expression in Adipocytes by MicroRNA-145

Cathepsin D (CtsD), an aspartyl peptidase, is involved in apoptosis, resulting in the release of cytochrome C from mitochondria in cells. Here, we investigated microRNA regulation of CtsD expression in 3T3-L1 cells First, we observed the expression of CtsD in cells in response to doxorubicin (Dox). As expected, the level of CtsD mRNA was increased in 3T3-L1 cells exposed to Dox in a dose-dependent manner. Cellular viability of ectopically expressed CtsD cells was also decreased. Next, we used the miRanda program to search for particular microRNA targeting CtsD. MiR-145 was selected as a putative controller for CtsD because miR-145 had a high mirSVR score. In a reporter assay, the luciferase activity of cells containing the CtsD 3’-UTR region was decreased in cells transfected with miR-145 mimic compared to that of a control. The level of CtsD expression was down-regulated in preadipocytes ectopically expressing miR-145 and up-regulated by an miR-145 inhibitor. Cells also suppressed miR-145 expression when exposed to Dox. The miR-145 inhibitor reduced the cellular viability of3T3-L1 cells. Taken together, these data suggest that miR-145 regulates CtsD-mediated cell death in adipocytes. These findings may have valuable implications concerning the molecular mechanism of CtsD-mediated cell death in obesity, suggesting that CtaD could be a useful therapeutic tool for the prevention and treatment of obesity by regulating fat cell numbers.