Fellowship: Robert Nathan Correll: Regulation of Cardiac L-Type Calcium Channel Function by REM GTPase

linked GlcNAc transferase (OGT1). However, the exact mechanisms by which O-GlcNAc modification of proteins leads to the development of diabetes is unknown. Recent data indicate that OGT1 in a complex with the co-repressors HDAC1 and mSin3A inhibits gene expression in liver cells. We found that OGT1 is in a complex with HDAC1 in the insulin producing MIN6 cell line and that this complex is recruited to the insulin promoter at low levels of glucose. Based on this observation, we hypothesize that OGT1 in a complex with HDAC1 down regulates insulin gene expression when glucose is scarce. To test this hypothesis, I propose to: 1. Study the role of OGT1 in down regulation of insulin gene expression. In this specific aim, I will overexpress the TPR domain of OGT1 in MIN6 cells (that functions as a dominant negative and interferes with endogenous OGT1 function) and analyze whether insulin gene transcription is altered. 2. Identify the transcription factor(s) that recruits the OGT1-HDAC1 complex to the insulin gene promoter. Since neither OGT1 nor HDAQ,1bind DNA directly, it is likely the OGT1-HDAC1 complex is recruited to the insulin gene promoter by a specific DNA binding protein. The goal of this specific aim to identify the transcription factor(s) that recruits the OGT1-HDAC1 complex to the insulin gene promoter. 3. Study the regulation of the OGT1 gene expression by glucose and increased O-linked GlcNAc protein modification. Using DNA microarray screens, we found that the expression of the OGT1 gene is upregulated by high glucose and O-GlcNAc levels. This aim focuses to identify the regulatory elements and the DNA binding proteins involved in regulation of OGT1 gene expression. The data obtained from this proposal will help to understand how increases in O-GlcNAc levels contribute to the pathogenesis diabetes and will be valuable in the design of novel clinical interventions to prevent and treat the secondary complications such as cardiovascular disease associated with chronic hyperglycemia.