Role of perlecan in islet amyloid formation

描述（由申请人提供）： 胰岛淀粉样蛋白沉积发生在约90%的2型糖尿病受试者中，并导致表征该疾病的胰岛β细胞质量和功能的进行性丧失。了解胰岛淀粉样蛋白沉积的机制将有助于开发预防其形成以及由此导致的β细胞损失和功能障碍的方法。胰岛淀粉样蛋白包括β-细胞肽胰岛淀粉样多肽（IAPP，胰淀素）和硫酸乙酰肝素蛋白聚糖串珠素。串珠素可通过其硫酸乙酰肝素糖胺聚糖（HS GAG）侧链结合淀粉样蛋白生成的人IAPP（hIAPP）来刺激胰岛淀粉样蛋白形成。我们最近发现胰岛β细胞表达串珠素，β细胞串珠素通过其HS GAG链与hIAPP结合。我们还表明，从表达缺乏HS GAG链的串珠素的小鼠分离的胰岛显示出体外胰岛淀粉样蛋白沉积的显著减少。因此，我们假设串珠素HS GAG对于胰岛淀粉样蛋白沉积及其引起β细胞损失和功能障碍的作用是至关重要的。将进行以下研究，以确定是否： 1.串珠素HS GAG是体外和体内胰岛淀粉样蛋白形成所必需的。将表达串珠素突变形式的小鼠与我们的胰岛淀粉样蛋白形成的hIAPP转基因小鼠模型杂交。我们期望突变串珠素的表达能减少胰岛淀粉样蛋白的形成，并改善培养7天的胰岛和高脂饮食喂养12个月的小鼠的胰岛素释放和β细胞体积。 2.串珠素HS GAG是淀粉样蛋白在移植后引起胰岛移植物衰竭的作用所必需的。上述小鼠将在此用作胰岛移植供体和受体。我们先前已经表明，移植hIAPP转基因胰岛导致胰岛淀粉样蛋白形成，高血糖症复发和移植胰岛移植物中β细胞体积减少。我们预期突变串珠素的表达将阻止胰岛淀粉样蛋白的形成并提高胰岛移植物的存活率。 3.串珠藻聚糖HS GAG增强淀粉样蛋白形成的机制。我们将表征β-细胞串珠素的HS GAG组成及其在体外结合hIAPP和刺激hIAPP原纤维形成的能力。这项申请的成功资助将为我提供工资和受保护的研究时间，以实现我成为2型糖尿病领域独立研究者的职业目标。

DESCRIPTION (provided by applicant): Islet amyloid deposition occurs in approximately approximately 90% of subjects with type 2 diabetes and contributes to the progressive loss of islet beta-cell mass and function that characterize the disease. Understanding the mechanism(s) that underlie islet amyloid deposition will allow the development of approaches to prevent its formation and the resulting beta-cell loss and dysfunction. Islet amyloid comprises the beta-cell peptide islet amyloid polypeptide (IAPP, amylin) and the heparan sulfate proteoglycan perlecan. Perlecan may stimulate islet amyloid formation by binding amyloidogenic human IAPP (hIAPP) through its heparan sulfate glycosaminoglycan (HS GAG) side chains. We have recently shown that islet beta-cells express perlecan and that beta-cell perlecan binds hIAPP through its HS GAG chains. We have also shown that isolated islets, from mice expressing perlecan that lacks HS GAG chains, show a marked reduction in islet amyloid deposition in vitro. Thus, we hypothesize that perlecan HS GAGs are critical for islet amyloid deposition and its effects to cause beta-cell loss and dysfunction. The following studies will be performed to determine whether: 1. Perlecan HS GAGs are required for islet amyloid formation in vitro and in vivo. Mice expressing a mutant form of perlecan will be cross-bred with our hIAPP transgenic mouse model of islet amyloid formation. We expect expression of mutant perlecan to reduce islet amyloid formation and improve both insulin release and beta-cell volume in isolated islets cultured for seven days and in mice fed a high fat diet for 12 months. 2. Perlecan HS GAGs are required for the effect of amyloid to cause islet graft failure following transplantation. The mice described above will be used here as islet transplant donors and recipients. We have previously shown that transplantation of hIAPP transgenic islets results in islet amyloid formation, recurrence of hyperglycemia and reduced beta-cell volume in the transplanted islet graft. We expect that expression of mutant perlecan will prevent islet amyloid formation and improve islet graft survival. 3. The mechanism by which perlecan HS GAGs enhance amyloid formation. We will characterize the HS GAG composition of beta-cell perlecan and its ability to bind hIAPP and stimulate hIAPP fibril formation in vitro. Successful funding of this application will provide me with salary and protected research time in order to achieve my career goal of becoming an independent investigator in the field of type 2 diabetes.