PITPNA in pancreatic beta-cell dysfunction and diabetes pathogenesis

项目摘要 糖尿病治疗创新成功的关键是开发促进胰岛素的策略 释放并防止胰腺β细胞破坏。胰岛素治疗期间对胰岛素产生的慢性需求 抵抗和糖尿病加剧了细胞功能障碍，这是由ER和氧化应激复合。这 导致β细胞死亡和胰岛素产生的损失。最近的研究强调了胰岛素的缺陷 加工、胰岛素颗粒成熟和颗粒对接也与所有主要形式的糖尿病有关; 然而，在理解β细胞衰竭的原因和开发方法方面仍然存在概念上的差距， 逆转或预防β细胞功能障碍。 我们的初步研究建立了磷脂酰肌醇转移蛋白α（称为人源性）， PITPNA和小鼠Pitpna），作为胰岛素颗粒形成和分泌的主要调节剂。PITPNA穿梭巴士 磷脂酰肌醇（PI）从内质网（ER）到高尔基体网络（TGN）， 通过磷脂酰肌醇4-激酶（PI4-K）转化为磷脂酰肌醇-4磷酸的磷酸化 （PtdIns-4-P），一种丰富的膜磷脂，参与胰岛素颗粒对接和胞吐作用。我们 初步数据显示：1）PITPNA表达在人T2D受试者的β-细胞中显著沉默，2） 人胰岛中PITPNA的减少既降低了细胞PI4-P水平，也降低了胰岛素颗粒成熟， 增加胰岛素原的积累，和3）小鼠中Pitpna的条件性β细胞特异性缺失（Ins-Cre; Pitpnaflox/flox）导致胰岛素分泌和β细胞质量降低、随机喂养的高血糖症， ER应激蛋白在β细胞中的表达。 基于这些数据，我们假设T2D期间β细胞中PITPNA的减少导致T2D细胞中PITPNA的降低。 PI4-P用于通过TGN分布以及掺入胰岛素颗粒，从而破坏颗粒 成熟、对接和分泌。我们进一步假设颗粒形成减少导致蓄积 胰岛素原在内质网中的作用，导致内质网应激并最终导致β细胞死亡。我们建议恢复 T2D个体的β细胞中的PITPNA将逆转细胞功能障碍的这些方面。我们预计这些 研究表明，促进PITPNA功能和PI4-P形成是逆转PI4-P表达的新策略。 包括ER、线粒体和TGN在内的几个亚细胞区室中的β细胞功能障碍。这些 研究旨在强调细胞内膜之间PI4-P的恢复作为一种创新方法， 增加颗粒成熟和分泌以及逆转主要形式的糖尿病中的β细胞衰竭。

PROJECT SUMMARY Critical to successful innovation in treating diabetes is the development of strategies for promoting insulin release and preventing pancreatic beta-cell destruction. Chronic demand for insulin production during insulin resistance and diabetes exacerbates cell dysfunction and this is compounded by ER and oxidative stress. This results in beta-cell death and loss of insulin production. Recent studies have highlighted defects in insulin processing, insulin granule maturation, and granule docking that are also linked to all major forms of diabetes; however conceptual gaps remain in understanding the causes of beta-cell failure and developing methods to reverse or prevent beta-cell dysfunction. Our preliminary studies establish Phosphatidylinositol transfer protein alpha (referred to as human PITPNA and mouse Pitpna), as a major regulator of insulin granule formation and secretion. PITPNA shuttles phosphatidylinositol (PI) from the endoplasmic reticulum (ER) to the trans-Golgi network (TGN) for phosphorylation by Phosphatidylinositol 4-kinase (PI4-K) conversion to phosphatidylinositol-4 phosphate (PtdIns-4-P), an abundant membrane phospholipid involved in insulin granule docking and exocytosis. Our preliminary data shows: 1) PITPNA expression is dramatically silenced in beta-cells of human T2D subjects, 2) reduction of PITPNA in human islets both lowered cellular PI4-P levels and insulin granule maturation and increased accumulation of proinsulin, and 3) conditional beta-cell specific deletion of Pitpna in mice (Ins-Cre; Pitpnaflox/flox) results in decreased insulin secretion and beta-cell mass, random-fed hyperglycemia, and increased expression of ER stress proteins in beta cells. Based on these data, we hypothesize that decreased PITPNA in beta-cells during T2D leads to lower PI4-P for distribution by the TGN as well as incorporation into insulin granules, thereby disrupting granule maturation, docking and secretion. We further hypothesize the reduced granule formation results in accumulation of proinsulin in the ER, leading to ER stress and ultimately beta-cell death. We propose that restoration of PITPNA in beta-cells of T2D individuals will reverse these aspects of cellular dysfunction. We expect these studies will demonstrate that promoting PITPNA function and PI4-P formation is a novel strategy for reversing beta-cell dysfunction in several subcellular compartments including the ER, mitochondria, and the TGN. These studies aim to highlight restoration of PI4-P between intracellular membranes as an innovative approach for increasing granule maturation and secretion as well as reversing beta-cell failure in major forms of diabetes.