EGF-recruited JunD/c- fos complexes activate CD2AP gene promoter and suppress apoptosis in renal tubular epithelial cells

Abstract

CD2-associated protein (CD2AP) plays a critical role in the maintenance of the kidney filtration barrier. In this study, we showed that epidermal growth factor (EGF) led to an increase of the CD2AP protein and mRNA in the human renal proximal tubular epithelial cell line HK-2 cells, which was due to the elevation of CD2AP promoter activity. Upon deletion and mutation analysis, electrophoretic mobility shift assays and chromatin immunoprecipitation, an AP-1-like element within CD2AP promoter was characterized, by which EGF recruited c- fos and JunD, two components of AP-1, to the human CD2AP gene promoter and suppressed angiotensin II-induced apoptosis in HK-2 cells. Specific siRNA was synthesized to knock down the human CD2AP gene in HK-2 cells. We found that CD2AP deficiency attenuated the inhibitory effects of EGF and predisposed the renal tubular epithelial cells to undergo angiotensin II-induced apoptosis. Furthermore, EGF-induced increases of CD2AP protein and mRNA expressions in HK-2 cells were significantly inhibited by the transfection of dominant negative JunD or c- fos vector, which was in parallel with a marked reduction of antiapoptotic effect of EGF. These results indicated that the antiapoptotic effect of EGF/CD2AP signal transduction was mediated by JunD and c- fos, at least partially. This study defined a new EGF/AP-1/CD2AP mediated cell-survival signaling, which might be useful to clarify the molecular mechanisms responsible for CD2AP associated kidney diseases.