A Novel Tool to Understand Insulin Production and Failure in Pancreatic beta-Cell

随着糖尿病患病率的增加，认识疾病进展的主要细胞和分子过程的必要性变得更加迫切。越来越清楚的是，在2型糖尿病患者中，P细胞无法完全代偿以维持正常血糖。 3-细胞缺乏症之前有一段时间，p-细胞仍可存活，但表现出胰岛素储存/分泌缺陷。内质网(ER)充满了胰岛素原，而正常胰岛素的产量下降。在p细胞死亡之前的这段“黄金时期”特别令人感兴趣，因为它可能突出了可逆的过程，这些过程可能会受到科学和治疗上的攻击。目前支持的一个假说是，胰岛素原的错误折叠加剧了3-细胞功能障碍，最终降低了胰腺胰岛素含量和3-细胞质量。与秋田小鼠一样，尽管野生型等位基因(常染色体显性遗传)提供了丰富的非突变胰岛素原，但改变其折叠的胰岛素原基因点突变会导致持续性先天性糖尿病。在K99年里，我开发了一种新的方法来研究活体动物的胰岛素含量和3细胞质量，以及探索正常和错误折叠的胰岛素原之间的潜在相互作用。用中区绿色荧光蛋白(GFP)标记的人胰岛素原可以在细胞系和称为hProins-CPepGFP的转基因小鼠中模拟天然胰岛素原的正常折叠、运输、加工和分泌。在Roo赠款中，我正在研究一种新的模型，在该模型中，将Akita突变直接引入hProins-CPepGFP转基因(顺式)中，以研究错误折叠的胰岛素原的命运。我还开发了一种新的转基因小鼠系，它带有标记为秋田原胰岛素的GFP，还带有一个额外的点突变，消除了要监测的伴侣(B7)游离硫醇基团，以发展显性阴性糖尿病。我计划培育针对瘦素受体缺陷db-/-小鼠的hProinsC(A7)Y-CPepGFP系，以检验胰岛素原错误折叠和胰岛素分泌需求增加之间的致病协同作用。这些研究将探索导致2型糖尿病的潜在可逆途径。

As the prevalence of Diabetes Mellitus increases, the need for recognizing the major cellular and molecular processes that underlie progression of the disease becomes more urgent. It is becoming increasingly clear that in patients with type 2 diabetes, P-cells are unable to fully compensate to maintain euglycemia overtime. 3-cell deficiency is preceded by a period in which p-cells are still viable but exhibit defective insulin storage/secretion. The endoplasmic reticulim (ER) becomes packed with proinsulin while production of normal insulin declines. This "golden period" before p-cell demise is of particular interest since it may highlight reversible processes that could be attacked both scientifically and therapeutically. A currently favored hypothesis is that proinsulin misfolding exacerbates 3-cell dysfunction, ultimately decreasing pancreatic insulin content and 3-cell mass. As in the Akita mouse, point mutations in proinsulin that alter its folding result in persistent congenital diabetes despite abundant nonmutant proinsulin available from wild-type alleles (autosomal dominant inheritance). In the K99 years, I have developed a novel approach to study insulin content and 3-cell mass in live animals, as well as to explore potential interactions between normal and misfolded proinsulin. Human proinsulin labeled with mid-region green fluorescent protein (GFP) can mimic the normal folding, trafficking, processing, and secretion of the native proinsulin in cell lines as well as in a transgenic mouse line called hProins-CpepGFP. In the ROO grant I am working on a new model in which the Akita mutation is introduced directly into the hProins-CpepGFP transgene (in cis) to study the fate of the misfolded proinsulin. I have also developed a new transgenic mouse line bearing GFP tagged Akita proinsulin that also bears an additional point mutation eliminating the partner (B7) free thiol group to be monitored for development of dominant negative diabetes. I plan to breed the hProinsC(A7)Y-CpepGFP line against Leptin receptor deficient db-/- mice in order to examine pathogenic synergies between proinsulin misfolding and increased insulin secretory demand. These studies will explore potentially reversible pathways leading to type 2 diabetes.