40 mouse model of AD, The treatment regimen utilized in this study strongly sup

EGF regulates survivin through ERK activation EGF signals through several downstream signaling path ways to induce b cell growth, including PI3K AKT, ERK1 2, JNK and JAK2, To determine which of these pathways might be required for EGF stimulated survivin protein expression, we treated MIN6 and INS 1 cells with MAPK 類 specific inhibitors of these pathways including: LY 294002, UO126, SP600125 and AG490, The EGF stimulated increase in survivin protein was only abrogated in the presence of the ERK1 2 inhibitor, sug gesting that the ERK pathway is the primary signaling pathway involved in EGF mediated survivin regulation. Interestingly, the response to the ERK inhibitor U0126 differed in the two cell lines.<br><br> U0126 treatment of INS 1 cells blocked survivin induction within MK-1775 構造 15 to 30 minutes, while treatment of MIN6 cells blocked survivin induc tion at later times with a further decrease in survivin observed at 180 360 minutes in these cells. This suggests that there is a cell or species specific kinetics regulating the ERK mediated increase in survivin levels, in response to EGF. EGF inhibits survivin protein degradation To determine the biochemical mechanism of the observed early increase in survivin protein levels follow ing EGF treatment in pancreatic b cells, we first evalu ated potential changes in survivin mRNA and survivin promoter activity. Serum deprived INS 1 cells were trea ted with EGF for 0. 5, 1, 2, and 4 hours prior to harvesting RNA for quantitative RT PCR. No significant changes in survivin mRNA were observed at any of these time points, suggesting that EGF does not likely regulate survivin transcription in INS 1 cells.<br><br> To validate this finding in primary islet cells, we isolated islets from 8 week old C57 Bl6 mice, serum starved them overnight then ms-275 溶解度 incubated them with EGF for 2 hours. Following mRNA preparation, we performed quantitative RT PCR using primers to detect total mouse survivin and three mouse survivin splice forms, survivin 121, survivin 140 and survivin 40, No significant increases in survivin mRNA follow ing EGF treatment were observed in the primary islets, similar to the results obtained in the INS 1 cells. To examine whether this observation correlated with a lack of stimulation of survivin promoter activity, we transfected MIN6 cells with luciferase reporter con structs containing different regions of the survivin pro moter, from 400 to 6000 bp upstream of the survivin ATG start site, Twenty four hours after transfec tion, cells were serum deprived overnight then treated with EGF or vehicle control for 2 hours.<br><br> No significant differences in reporter levels between EGF treated and untreated cells were observed, indicating an absence of EGF stimulated tran scriptional regulation sites within the survivin promoter. As no significant increases in survivin mRNA or its promoter activity were observed following EGF treatment, we hypothesized that EGF was acting at a post transcriptional level to either increase ribosomal mediated protein synthesis or to inhibit protein degrada tion. To test these possibilities, we treated INS 1 cells with the protein synthesis inhibitor, cyclohexamide, Cells were serum deprived overnight then trea ted with EGF.