REGULATION OF BETA CELL GENES BY GLUCOSE AND INCRETINS

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 葡萄糖和胰岛素激素触发遗传程序的表达，从而提高胰岛细胞的存活率，并在进食过程中促进胰岛素的释放。CAMP和钙通路的激活对这些信号的响应促进了胰岛基因的表达和β细胞的存活，部分是通过刺激CREB在Ser133处的磷酸化，这种修饰刺激了辅活化子类似物CBP和P300到启动子的募集。然而，CBP和P300基因敲击蛋白突变破坏了它们与CREB的关联的小鼠在cAMP依赖的转录中只出现了轻微的变化，这表明更多的CREB共激活子可能参与了这一过程。目前的研究集中在CREB辅活化子家族在促进胰岛基因表达中的作用，这些辅活化子被指定为CREB调节活性转导因子。初步研究表明，胰岛TORC蛋白在基础条件下保留在细胞质中，在cAMP和钙信号的响应下迁移到细胞核，在那里它们增强CREB靶基因的表达。具体目的I阐述TORC活性在基础条件下被抑制的机制，重点是TORC相关蛋白激酶通过与14-3-3蛋白相互作用促进TORC磷酸化和细胞质保留的作用。目的探讨环磷酸腺苷(CAMP)和钙离子对TORC的激活机制，特别强调丝氨酸/苏氨酸磷酸酶钙调神经磷酸酶在TORC去磷酸化和促进核进入中的作用。目的研究CREB：TorC和CREB：CBP复合体对胰岛基因表达的相对重要性。TORC和CBP/P300对CREB靶基因表达的调节作用也将通过RNAi介导的敲除来破坏每个辅助激活因子的表达。最后，TORCS在胰岛功能中的作用将通过产生有条件地敲除TORC基因的小鼠来确定。移植后糖尿病是接受钙调神经磷酸酶抑制剂(如FK506)进行免疫抑制的患者的常见并发症。拟议的研究将揭示这些抑制物是否促进胰岛细胞死亡，部分是通过CREB：TORC途径干扰胰岛生存基因的表达。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Glucose and incretin hormones trigger the expression of genetic programs that enhance islet cell survival and promote insulin release during feeding. The activation of cAMP and calcium pathways in response to these cues promotes islet gene expression and beta cell survival in part by stimulating the phosphorylation of CREB at Ser133, a modification that stimulates recruitment of the coactivator paralogs CBP and P300 to the promoter. Mice with knockin mutations in CBP and P300 that disrupt their association with CREB show only modest changes in cAMP dependent transcription, however, suggesting the potential involvement of additional CREB coactivators in this process. The current proposal focuses on the role of a novel family of CREB coactivators, designated TORCs for Transducers of Regulated CREB activity, in promoting islet gene expression. Preliminary studies reveal that islet TORC proteins are retained in the cytoplasm under basal conditions, migrating to the nucleus in response to cAMP and calcium signals where they potentiate CREB target gene expression. Specific Aim I addresses the mechanism by which TORC activity is suppressed under basal conditions, focusing on the role of a TORC associated protein kinase in promoting TORC phosphorylation and cytoplasmic retention via an interaction with 14-3-3 proteins. Aim II addresses the mechanism of TORC activation in response to cAMP and calcium, with particular emphasis on the role of the ser/thr phosphatase calcineurin in dephosphorylating and promoting nuclear entry of TORC. Aim III examines the relative importance of CREB:TORC and CREB:CBP complexes for pancreatic islet gene expression by using mutant CREB polypeptides that are defective in either CBP or TORC interaction. Regulatory contributions of TORC and CBP/P300 towards CREB target gene expression islet cells will also be explored by disrupting the expression of each coactivator through RNAi mediated knockdown. Finally, the role of TORCs in pancreatic islet function will be determined by generating mice with a conditional knockout of the TORC genes. Post-transplant diabetes is a frequent complication in patients receiving calcineurin inhibitors such as FK506 for immunosuppression. The proposed studies will reveal whether these inhibitors promote islet cell death, in part by interfering with expression of islet survival genes through the CREB:TORC pathway.