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Proinsulin maturation, misfolding, and proteotoxicity

机译:胰岛素原成熟,折叠错误和蛋白毒性

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摘要

As a tool to explore proinsulin (PI) trafficking, a human PI cDNA has been constructed with GFP fused within the C peptide. In regulated secretory cells containing appropriate prohormone convertases, the hProCpepGFP construct undergoes endoproteolytic processing to CpepGFP and native human insulin, which are specifically detected and cosecreted in parallel with endogenous insulin. Expression of C(A7)Y mutant PI results in autosomal dominant diabetes in Akita mice. We directly identify the misfolded PI in Akita islets and also show that C(A7)Y mutant PI, either in the context of the hProCpepGFP chimera or not, engages directly in protein complexes with nonmu-tant PI, impairing the trafficking and recovery of nonmutant PI. This trapping mechanism decreases insulin production in β cells. Thereafter we observe a loss of β ceil viability. The data imply that PI misfolding leading to impaired endoplasmic reticulum exit of non-mutant PI may be a key early step in a chain reaction of β cell dysfunction and demise leading to onset and progression of diabetes.
机译:作为探索胰岛素原(PI)转运的工具,已经构建了人PI cDNA,GFP融合在C肽内。在含有适当激素原转化酶的调节型分泌细胞中,hProCpepGFP构建体经历了CpepGFP和天然人胰岛素的内蛋白水解过程,这些蛋白被特异性检测并与内源胰岛素平行共分泌。 C(A7)Y突变体PI的表达导致秋田小鼠常染色体显性遗传糖尿病。我们直接确定了秋田岛中错误折叠的PI,并且还表明C(A7)Y突变PI,无论是否存在hProCpepGFP嵌合体,都直接与非突变PI结合在蛋白质复合物中,从而损害了非突变PI的运输和恢复。 PI。这种捕集机制减少了β细胞中胰岛素的产生。此后,我们观察到β细胞活力的丧失。数据表明,PI错折叠导致非突变型PI的内质网出口受损,可能是导致β细胞功能障碍和死亡的连锁反应的关键早期步骤,从而导致糖尿病的发作和发展。

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