Molecular Mechanisms for Pancreatic Islet Disfunction in Development of Diabetes Mellitus-a study using WFS1 knockout mice

WFS 1缺陷型胰岛素瘤细胞系的建立为了检测WFS 1缺陷在同质β细胞群中的特异性影响，通过将wfs 1 ^-/->小鼠与在胰岛素启动子下表达猿猴病毒40大T抗原的IT 6小鼠杂交来建立β细胞系。我们发现受损的胰岛素分泌在响应高葡萄糖，这是恢复的腺病毒介导的表达野生型WFS 1，但没有突变WFS 1蛋白在Wolfram综合征patients.Role WFS 1蛋白在细胞内钙稳态。我们分析了WFS 1敲低和过表达的HEK 293细胞，发现WFS 1蛋白<er>通过正向调节ER Ca^2+摄取来调节[Ca^2 +]_，这与Ca^2+库耗竭引起的[Ca^2+]_反应的变化有关<cyt>。在WFS 1缺陷型胰岛中的表达谱显示4 E-BPI表达增加。我们发现，在糖尿病小鼠模型中，ER应激下胰岛中4 E-BP 1的表达也增强。发现4 E-BP 1的诱导由转录因子ATF 4介导。4 E-BP 1缺陷的MIN 6 β细胞更容易受到ER应激触发的凋亡，并且C/EBP同源蛋白的诱导更大。此外，在ER应激的小鼠糖尿病模型中，Eif 4 ebp 1缺失加剧了高血糖，加速了β细胞衰竭。因此，4 E-BP 1诱导是ER应激下β-细胞的促存活信号和糖尿病的潜在治疗靶点。丙酮酸盐先前显示刺激胰高血糖素分泌。在这项研究中，我们发现在WFS 1缺陷的胰岛中，α细胞数量增加，且胰高血糖素刺激的胰高血糖素分泌增强。在Wolfram综合征小鼠模型中，多种异常被认为有助于糖尿病的发展。

Establishment of WFS1-deficient insulinoma cell lines. To examine the influence of WFS1-deficiency specifically in a homogenous β-cell population, β-cell lines were established by crossing wfs1^<-/-> mice with IT6 mice expressing simian virus 40 large T antigen under the insulin promoter. We found impaired insulin secretion in response to high glucose, which was recovered by adenovirus-mediated expression of wild-type WFS 1 but not of mutant WFS1 proteins found in Wolfram-syndrome patients.Role of WFS1 protein in intracellular calcium homeostasis. We analyzed WFS1-knockdown and-overexpressing HEK293 cells, and found that WFS1 protein modulates [Ca^<2+>]_<er> by positively regulating the ER Ca^<2+> uptake, which is associated with changes in the [Ca^<2+>]_<cyt> response evoked by Ca^<2+> store depletion.Identification of the translational suppressor 4E-BP1 as a pro-survival factor in β-cells under ER stress. Expression profiling in WFS1-deficient islets revealed increased 4E-BPI expression. We found that expression of 4E-BP1 was also enhanced in islets under ER stress in mouse models of diabetes. 4E-BP1 induction was found to be mediated by the transcription factor ATF4. 4E-BP1-deficient MIN6 β-cells were more vulnerable to apoptosis triggered by ER stress, with greater induction of C/EBP homologue protein. Furthermore, Eif4ebp1 deletion exacerbated hyperglycemia, with accelerated (3-cell failure, in mouse diabetes models with ER stress. Thus, 4E-BP1 induction is a pro-survival signal for (3-cells under ER stress and a potential therapeutic target for diabetes.Increased glucagon secretion from WFS1-deficient islets. Pyruvate was previously shown to stimulate glucagon secretion. In this study, we found increased alpha cell numbers and enhanced pyruvate-stimulated glucagon secretion in WFS1-deficient islets.Multiple abnormalities are suggested to contribute development of diabetes in the mouse model of Wolfram syndrome.