GAD RELEASE FROM BETA CELLS IN TYPE 1 DIABETES

GAD 65（谷氨酸脱羧酶的Mr 65，000同种型）的循环自身抗体是导致I型糖尿病的自身免疫过程的最重要标志物之一。越来越多的证据表明GAD 65和小鼠中的GAD 67是自身免疫过程中的关键起始自身抗原。以前认为GAD 65是人类胰岛中表达的唯一GAD同种型。然而，我们已经表明，人类胰岛也产生GAD 67变体，GAD 25，作为选择性剪接事件的结果。初步数据表明，某些新诊断糖尿病的幼儿会产生GAD 25自身抗体。其他数据表明，β细胞释放GAD 65，可能沿着GAD 25，可能有助于触发胰岛自身免疫。我们的中心假设是GAD 65在1型糖尿病中作为一种主要的自身抗原发挥作用，因为它的囊泡结合使其对应激诱导的释放敏感，并且GAD 25也可能作为一种自身抗原发挥作用，因为它也可以被释放。该提议的具体目的是1）检验GAD 65和GAD 25通过生理应激物从人胰岛β细胞独特地释放的假设; 2）检验膜相关GAD是释放的GAD分子的细胞内来源的假设，并开始表征释放的机制，和3）检验GAD 25，凭借其定位和调节，是1型糖尿病的潜在自身抗原。本研究的长期目标是更好地了解GAD 65的早期免疫反应机制以及GAD 25所起的作用。沉淀胰岛自身免疫的因素的知识对于开发预防或抑制β细胞破坏的疗法至关重要，并可能导致新的治疗方法，以帮助保护移植的胰岛免受免疫介导的破坏。这项研究将为申请人作为I型糖尿病领域的独立研究者的学术生涯做好准备。他将获得进一步的分子生物学培训，学习进行基于人群的研究，并熟悉用于研究胰岛细胞生物学和生理学以及糖尿病自身反应性的关键方法和途径。向独立的过渡将得到特别丰富的培训环境的促进，首先是由R.H.威廉姆斯实验室，由Ake Lernmark领导，研究将在那里进行，第二，由周围大量高产的糖尿病研究人员组成的社区，所有人都在附近，威廉姆斯实验室是其中的一员。

Circulating autoantibodies to GAD65, the Mr 65,000 isoform of glutamic acid decarboxylase, are one of the most important markers of the autoimmune process that results in type I diabetes mellitus. A growing body of evidence implicates GAD65, and, in mice, GAD67, as key initiating autoantigens in the autoimmune process. Previously it was thought that GAD65 was the only GAD isoform expressed in human islets. We have shown, however, that human islets also produce a GAD67 variant, GAD25, as the result of an alternative splicing event. Preliminary data suggest that certain young children with newly diagnosed diabetes produce autoantibodies to GAD25. Other data suggest that release of GAD65 from beta cells, perhaps along with GAD25, may help trigger islet autoimmunity. Our central hypothesis is that GAD65 functions as a major autoantigen in type 1 diabetes because its vesicular association makes it susceptible to stress-induced release and also that GAD25 may function as an autoantigen because it, too, can be released. The specific aims of this proposal are 1) to test the hypothesis that GAD65 and GAD25 are uniquely released from human islet beta cells by physiologic stressors; 2) to test the hypothesis that membrane-associated GAD is the intracellular source of released GAD molecules and begin to characterize the mechanism of release and 3) to test the hypothesis that GAD25, by virtue of its localization and regulation, is a potential autoantigen in type 1 diabetes. The long-term objective of this research is to better understand the mechanisms underlying the early immune reaction to GAD65 and the role played by GAD25. Knowledge of the factors that precipitate islet autoimmunity will be vital for the development of therapies to prevent or inhibit beta cell destruction and could result in new treatments to help protect transplanted islets from immune-mediated destruction. This research will prepare the applicant for an academic career as an independent investigator in the field of type I diabetes. He will obtain further training in molecular biology, learn to conduct population-based studies and become acquainted with the key methodologies and approaches used to study islet cell biology and physiology and diabetogenic autoreactivity. The transition to independence will be facilitated by the especially rich training environment afforded, first, by the R.H. Williams Laboratory, headed by Ake Lernmark, where the research will be carried out and, second, by the large surrounding community of highly productive diabetes researchers, all in close proximity, of which the Williams Laboratory is a member.