Identification And Function Of The Human Cd2ap Gene Promoter

The human CD2-associated protein (CD2AP) is involved in several molecular signaling pathways and is an important factor responsible for nephrotic syndrome. Here we report the identification of the transcription start point and promoter region of the human CD2AP gene in renal tubular epithelial cells. With luciferase assays and deletion analysis, we found that the region between -558 and -1 bp ahead of the transcription start point is indispensable for the promoter activity of the human CD2AP gene. A CREB site and two SP1 sites were essential for maintaining the basal transcriptional activity of the human CD2AP promoter. Overexpression of phosphorylated CREB and SP1 transactivated the human CD2AP promoter, whereas small interfering RNA-mediated blockage of CREB and SP1 genes expressions inhibited markedly its activity. These findings provide the first analysis of the human CD2AP gene promoter and demonstrate that not only CREB but also SP1 plays a critical role in regulating basal CD2AP promoter activity in renal tubular epithelial cells.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. Therefore we defined a new EGF/AP-1/CD2AP mediated cell-survival signaling in the human renal proximal tubular epithelial cell.The activity of CD2AP promoter was markedly decreased under oxidative stress conditions. Low-dose VEGF antagonized oxidative stress-induced down-regulation of CD2AP promoter activity in human embryonic kidney (HEK293) cells. At the early time of respiratory syncytial virus infection, the activity of CD2AP promoter was enhanced significantly, however, which gradually diminished in the later time of RSV infection. JunD and antiviral RIG-1/MAVS signaling were involved in the regulation of CD2AP promoter activity upon RSV infection.This study might be useful to clarify the molecular mechanisms responsible for CD2AP associated kidney diseases.