GLUCOKINASE GENE EXPRESSION IN THE PANCREATIC BETA CELL

胰岛β细胞的电、离子和分泌反应 葡萄糖是由糖的新陈代谢调节的。葡萄糖激酶(GK) 催化葡萄糖利用的初始步骤和限速步骤 在生理葡萄糖浓度下被β细胞激活，并被认为 在调节胰岛素分泌方面起着重要作用。为了研究 GK在β细胞中的功能和调节进一步，我们有 从肝脏和胰岛素瘤组织中鉴定编码GK的cDNA 并绘制了这两个组织中的转录单位图。我们的 研究表明，在一个GK基因中有两个不同的启动子。 一个启动子在肝脏中特异表达，似乎是 受胰岛素调控，而另一个启动子位于更上游， 仅在β细胞中表现活跃。我们建议研究 GK在胰岛素瘤细胞系中的功能和调节(AIM 1)和TO 使用融合基因分析检查GKβ细胞启动子(目标2)。在……里面 目标1将使用补充方法来测试GK AS的功能 贝塔细胞的“葡萄糖传感器”。通过将GK的表达改变为两个 我们希望改变不同的胰岛素瘤细胞系的“设定点” 葡萄糖刺激的胰岛素分泌。RINm5F细胞血糖正常 摄取，但似乎缺乏高千米葡萄糖磷酸化活性和 不会因为葡萄糖而分泌胰岛素。另一种细胞系，β-TC， 显示高千米葡萄糖使用量，但刺激分泌胰岛素的量较少 而不是正常的葡萄糖浓度。我们将确定 GK在RINm5f细胞中的表达及其作用 β-TC细胞中的反义RNA。在目标2中，对β细胞的分析 GK启动子将使用融合基因方法进行。都是5英尺高的 缺失分析和内部缺失突变体的使用应该能够 美国确定贝塔细胞特异性表达所需的元件 好的。对于GK的细胞类型表达很重要的元素可能是 结合对β细胞特异性基因表达很重要的因子。 将使用迁移率变化和甲基化来进一步研究这些因素 干扰分析。提纯和克隆这些因子之一的努力将 被启动。

The electrical, ionic, and secretory responses of pancreatic beta cells to glucose are mediated by the metabolism of the sugar. Glucokinase (GK) catalyzes the initial and rate limiting step in the utilization of glucose by the beta cell at physiologic glucose concentrations and is thought to play an important role in modulating insulin secretion. To study the function and regulation of GK in the beta cell further, we have characterized cDNAs encoding GK from both the liver and insulinoma tissue and have mapped the mapped the transcription units in both tissues. Our studies have shown there are two different promoters in a single GK gene. One promoter is expressed specifically in the liver and appears to be regulated by insulin while another promoter, located further upstream, appears active only in the beta cell. We are proposing to study the function and regulation of GK in insulinoma cell lines (Aim 1) and to examine the GK beta cell promoter using a fusion gene analysis (Aim 2). In Aim 1 complimentary approaches will be used to test the function of GK as the beta cell "glucose sensor". By altering the expression of GK in two different insulinoma cell lines we hope to alter the "set point" of glucose-stimulated insulin secretion. RINm5F cells have normal glucose uptake but appear to lack a high-Km glucose phosphorylating activity and do not secrete insulin in response to glucose. Another cell line, beta-TC, shows high-Km glucose usage but is stimulated to secrete insulin by less than normal glucose concentrations. We will determine the effects of expressing GK in the RINm5f cells and the effects of expressing GK antisense RNA in the beta-TC cells. In Aim 2 an analysis of the beta cell GK promoter will be undertaken using a fusion gene approach. Both a 5' deletional analysis and the use of internal deletion mutants should enable us to identify elements necessary for the beta cell-specific expression of GK. Elements important for the cell type expression of GK are likely to bind factors which are important for beta cell-specific gene expression. These factors will be studied further using mobility shift and methylation interference assays. Efforts to purify and clone one of these factors will be initiated.