GAD AND GABA IN ISLET CELL DEVELOPMENT AND FUNCTION

胰岛β细胞和GABA能神经元表达合成 抑制神经递质GABA、谷氨酸的酶 脱羧酶。胰腺的阿尔法细胞，也许还有三角洲细胞 表达GABA/A受体和GABA可能作为旁分泌信号 胰腺内内分泌细胞间通讯的分子。 GAD由两个不同的基因GAD65和GAD67编码 主要在前100个氨基酸中，但在 剩余的蛋白质。人类β细胞只表达GAD65，而这 这种酶的形式是早期自身抗体的靶标 和晚期的β细胞破坏，导致1型糖尿病。 此外，GAD65已被证明是一种重要的T细胞自身抗原 在1型糖尿病的NOD-小鼠模型中。 本项目研究了GAD65和GAD67以及GABA在胰岛细胞中的作用 关注细胞的发育、功能和β细胞自身抗原性 GAD蛋白的生物学及转基因小鼠模型的应用 GAD和GABA表达异常。 第一个目标是表征GAD65分子的拓扑结构 是以亲水可溶分子的形式合成的，但后 平移修饰和加工成锚定在膜上 突触一样的微泡。 第二个目标是描述信号和靶向序列 以及赋予细胞亚细胞定位的修饰(S) GAD65。 第三个目标是描述OVER转基因小鼠模型的特征。 GAD65在β细胞中的表达及其后果 对胰岛细胞发育、功能和自身抗原性的影响。 第四个目标是建立过度表达的转基因小鼠模型。 GAD65处于发展后期，并检查对耐受性的后果 发育和自身抗原性。 第五个目标是确定胰岛细胞和神经功能的特征。 GAD65基因敲除小鼠以及野生型和野生型拯救的后果 GAD65的突变形式。 总体目标是阐明其作用的分子机制， GABA能系统的亚细胞定位和自身抗原性 在胰腺里。

Pancreatic beta cells and GABA-ergic neurons express the synthesizing enzyme for the inhibitory neurotransmitter GABA, glutamic acid decarboxylase. Pancreatic alpha cells and perhaps also delta cells express GABA/A receptors and GABA may function as a paracrine signaling molecule for communication among the endocrine cells in the pancreas. GAD is encoded by two distinct genes, GAD65 and GAD67, which differ mainly in the first 100 amino acids but share extensive homology in the remainder of the proteins. Human beta cells only express GAD65 and this form of the enzyme is a target of autoantibodies associated with early and late phases of beta cell destruction resulting in type 1 diabetes. Furthermore GAD65 has been shown to be an important T-cell autoantigen in the NOD-mouse model of type 1 diabetes. This project examines the role of GAD65 and GAD67, and GABA in islet cell development, function and beta cell autoantigenicity focusing on the cell biology of the GAD proteins and use of transgenic mouse models of aberrant GAD and GABA expression. The first aim is to characterize the topology of the GAD65 molecule which is synthesized as a hydrophilic soluble molecule, but is post- translationally modified and processed to become anchored to the membrane of synaptic like microvesicles. The second aim is to characterize the signaling and targeting sequences and the modification(s) that confer the subcellular localization of GAD65. The third aim is to characterize transgenic mouse models of over expression of GAD65 in beta cells and the consequences of such expression on islet cell development, function and autoantigenicity. The fourth aim is to generate transgenic mouse models over-expressing GAD65 late in development, and examine the consequences for tolerance development and autoantigenicity. The fifth aim is to characterize the islet cell and neurological function of GAD65 knock out mice and the consequences of rescue by wild type and mutant forms of GAD65. The overall goal is to elucidate the molecular mechanisms of function, subcellular localization and autoantigenicity of the GABA-ergic system in the pancreas.