Objective

Protein disulfide isomerases (PDIs) are oxidoreductases that are involved in catalyzing the formation and rearrangement of disulfide bonds during protein folding. One of the PDI members is the PDI-associated 6 (PDIA6) protein, which has been shown to play a vital role in β-cell dysfunction and diabetes. However, very little is known about the function of this protein in β-cells in vivo. This study aimed to describe the consequences of a point mutation in Pdia6 on β-cell development and function.

Methods

We generated an ENU mouse model carrying a missense mutation (Phe175Ser) in the second thioredoxin domain of the Pdia6 gene. Using biochemical and molecular tools, we determined the effects of the mutation on the β-cell development at embryonic day (E)18.5 and β-cell identity as well as function at postnatal stages.

Results

Mice homozygous for the Phe175Ser (F175S) mutation were mildly hyperglycemic at weaning and subsequently became hypoinsulinemic and overtly diabetic at the adult stage. Although no developmental phenotype was detected during embryogenesis, mutant mice displayed reduced insulin-expressing β-cells at P14 and P21 without any changes in the rate of cell death and proliferation. Further analysis revealed an increase in BiP and the PDI family member PDIA4, but without any concomitant apoptosis and cell death. Instead, the expression of prominent markers of β-cell maturation and function, such as Ins2, Mafa, and Slc2a2, along with increased expression of α-cell markers, Mafb, and glucagon was observed in adult mice, suggesting loss of β-cell identity.

Conclusions

The results demonstrate that a global Pdia6 mutation renders mice hypoinsulinemic and hyperglycemic. This occurs due to the loss of pancreatic β-cell function and identity, suggesting a critical role of PDIA6 specifically for β-cells.

中文翻译：

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Pdia6 基因的点突变导致胰腺 β 细胞特性丧失，从而导致明显的糖尿病

客观的

蛋白质二硫键异构酶 (PDI) 是参与催化蛋白质折叠过程中二硫键形成和重排的氧化还原酶。PDI 成员之一是 PDI 相关 6 (PDIA6) 蛋白，它已被证明在 β 细胞功能障碍和糖尿病中发挥重要作用。然而，关于这种蛋白质在体内β 细胞中的功能知之甚少。本研究旨在描述Pdia6中的点突变对 β 细胞发育和功能的影响。

方法

我们生成了一个在Pdia6基因的第二个硫氧还蛋白结构域中携带错义突变 (Phe175Ser) 的 ENU 小鼠模型。使用生化和分子工具，我们确定了突变对胚胎期 (E)18.5 的 β 细胞发育和 β 细胞身份以及出生后阶段功能的影响。

结果

Phe175Ser (F175S) 突变纯合小鼠在断奶时出现轻度高血糖，随后在成年阶段变为低胰岛素血症和明显糖尿病。尽管在胚胎发生过程中未检测到发育表型，但突变小鼠在 P14 和 P21 显示出表达胰岛素的 β 细胞减少，而细胞死亡和增殖率没有任何变化。进一步分析显示 BiP 和 PDI 家族成员 PDIA4 增加，但没有任何伴随的细胞凋亡和细胞死亡。相反，β 细胞成熟和功能的显着标志物（如Ins2、Mafa和Slc2a2）的表达，以及 α 细胞标志物Mafb的表达增加，并且在成年小鼠中观察到胰高血糖素，表明 β 细胞身份丧失。

结论

结果表明，全局Pdia6突变使小鼠出现低胰岛素血症和高血糖症。这是由于胰腺 β 细胞功能和特性的丧失，这表明 PDIA6 对 β 细胞具有关键作用。