IDENTIFICATION OF THE GENES INVOLVED IN GLUCOSE-STIMULATED INSULIN SECRETION

RIN细胞来源于大鼠胰腺β细胞。经过多轮传代后，它们失去了对葡萄糖刺激和随后胰岛素分泌的敏感性，至少部分原因是葡萄糖激酶的表达减少。葡萄糖激酶被认为在胰腺细胞中扮演着葡萄糖传感器的重要角色。在本研究中，我们利用葡萄糖激酶过表达的RIN细胞和未处理的细胞，通过mRNA差异显示的方法，试图鉴定参与葡萄糖刺激胰岛素分泌的基因。我们在这个过程中鉴定了13个差异表达基因。在这些基因中，有5个基因的表达水平因葡萄糖激酶的过表达而升高。它们包括编码l型丙酮酸激酶、线粒体和尿卟啉原脱羧酶的基因，以及未知基因。编码钙调蛋白和糖基磷脂酰肌醇锚定蛋白的基因下调。有趣的是，钙调素已被证明在小鼠胰腺β细胞过度表达时可减少胰岛素分泌。此外，已知肝脏中l型丙酮酸激酶的表达与葡萄糖激酶类似，受胰岛素调节。这些结果表明，本研究中发现的基因可能通过与胰腺β细胞中葡萄糖激酶的相互作用与葡萄糖感知机制有关，并可能在胰岛素分泌中起关键作用。

RIN cells are originated from rat pancreatic beta cells. After multiple rounds of passages, they lose sensitivity to glucose stimulation and subsequent insulin secretion, at least in part through diminished expression of glucokinase. Glucokinase is thought to play a major role as a glucose sensor in pancreatic beta cells. In this study, we attempted to identify genes involved in glucose-stimulated insulin secretion by the method of mRNA differential display using glucokinase-overexpressed RIN cells and untreated cells. We identified thirteen differentially expressed genes in this process. Among these genes, the expression levels of five genes were increased by overexpression of glucokinase. They include genes encoding L-type pyruvate kinase, mitochondrion, and uroporphyrinogen decarboxyrase, and unknown genes. The genes encoding calmodulin and glycosylphosphatidyl -inositol-anchored protein were down regulated. Interestingly, calmodulin has been shown to decrease insulin secretion in mouse pancreatic beta cells when overexpressed. Furthemore, the expression of L-type pyruvate kinase in liver is known to be regulated by insulin in a similar manner to glucokinase. These results suggest that the genes identified in this study might be associated with the glucose-sensing mechanism via interaction with glucokinase in pancreatic beta cells and may play crucial roles insulin secretion.