PDF(Pubmed)
Abstract：
BACKGROUND: Nephrin is a transmembrane protein with well-established signaling roles in kidney podocytes, and a smaller set of secretory functions in pancreatic β cells are implicated in diabetes. Nephrin signaling is mediated in part through its 3 cytoplasmic YDxV motifs, which can be tyrosine phosphorylated by high glucose and β cell injuries. Although in vitro studies demonstrate these phosphorylated motifs can regulate β cell vesicle trafficking and insulin release, in vivo evidence of their role in this cell type remains to be determined.
METHODS: To further explore the role of nephrin YDxV phosphorylation in β cells, we used a mouse line with tyrosine to phenylalanine substitutions at each YDxV motif (nephrin-Y3F) to inhibit phosphorylation. We assessed islet function via primary islet glucose-stimulated insulin secretion assays and oral glucose tolerance tests.
RESULTS: Nephrin-Y3F mice successfully developed pancreatic endocrine and exocrine tissues with minimal structural differences. Unexpectedly, male and female nephrin-Y3F mice showed elevated insulin secretion, with a stronger increase observed in male mice. At 8 months of age, no differences in glucose tolerance were observed between wild-type (WT) and nephrin-Y3F mice. However, aged nephrin-Y3F mice (16 months of age) demonstrated more rapid glucose clearance compared to WT controls.
CONCLUSIONS: Taken together, loss of nephrin YDxV phosphorylation does not alter baseline islet function. Instead, our data suggest a mechanism linking impaired nephrin YDxV phosphorylation to improved islet secretory ability with age. Targeting nephrin phosphorylation could provide novel therapeutic opportunities to improve β cell function.
METHODS: To further explore the role of nephrin YDxV phosphorylation in β cells, we used a mouse line with tyrosine to phenylalanine substitutions at each YDxV motif (nephrin-Y3F) to inhibit phosphorylation. We assessed islet function via primary islet glucose-stimulated insulin secretion assays and oral glucose tolerance tests.
RESULTS: Nephrin-Y3F mice successfully developed pancreatic endocrine and exocrine tissues with minimal structural differences. Unexpectedly, male and female nephrin-Y3F mice showed elevated insulin secretion, with a stronger increase observed in male mice. At 8 months of age, no differences in glucose tolerance were observed between wild-type (WT) and nephrin-Y3F mice. However, aged nephrin-Y3F mice (16 months of age) demonstrated more rapid glucose clearance compared to WT controls.
CONCLUSIONS: Taken together, loss of nephrin YDxV phosphorylation does not alter baseline islet function. Instead, our data suggest a mechanism linking impaired nephrin YDxV phosphorylation to improved islet secretory ability with age. Targeting nephrin phosphorylation could provide novel therapeutic opportunities to improve β cell function.
摘要：
背景：Nephrin是一种跨膜蛋白，在肾足细胞中具有明确的信号传导作用，胰腺β细胞的少量分泌功能与糖尿病有关。Nephrin信号部分通过其三个细胞质YDxV基序介导，高糖和β细胞损伤可使酪氨酸磷酸化。尽管体外研究表明这些磷酸化基序可以调节β细胞囊泡运输和胰岛素释放，它们在这种细胞类型中的作用的体内证据仍有待确定。
方法：为了进一步探讨nephrinYDxV磷酸化在β细胞中的作用，我们使用在每个YDxV基序(nephrin-Y3F)具有酪氨酸至苯丙氨酸取代的小鼠细胞系来抑制磷酸化。我们通过原发性胰岛葡萄糖刺激的胰岛素分泌测定和口服葡萄糖耐量试验来评估胰岛功能。
结果：Nephrin-Y3F小鼠成功开发了具有最小结构差异的胰腺内分泌和外分泌组织。出乎意料的是,雄性和雌性nephrin-Y3F小鼠显示胰岛素分泌升高，在雄性小鼠中观察到更强的增加。在8个月大的时候，在WT和nephrin-Y3F小鼠之间没有观察到葡萄糖耐量的差异。然而,与WT对照相比,老年nephrin-Y3F小鼠(16月龄)表现出更快的葡萄糖清除。
结论：综合来看，nephrinYDxV磷酸化的缺失不会改变基线胰岛功能。相反，我们的数据表明,nephrinYDxV磷酸化受损与胰岛分泌能力随年龄增长而改善相关的机制.靶向nephrin磷酸化可以为改善β细胞功能提供新的治疗机会。
方法：为了进一步探讨nephrinYDxV磷酸化在β细胞中的作用，我们使用在每个YDxV基序(nephrin-Y3F)具有酪氨酸至苯丙氨酸取代的小鼠细胞系来抑制磷酸化。我们通过原发性胰岛葡萄糖刺激的胰岛素分泌测定和口服葡萄糖耐量试验来评估胰岛功能。
结果：Nephrin-Y3F小鼠成功开发了具有最小结构差异的胰腺内分泌和外分泌组织。出乎意料的是,雄性和雌性nephrin-Y3F小鼠显示胰岛素分泌升高，在雄性小鼠中观察到更强的增加。在8个月大的时候，在WT和nephrin-Y3F小鼠之间没有观察到葡萄糖耐量的差异。然而,与WT对照相比,老年nephrin-Y3F小鼠(16月龄)表现出更快的葡萄糖清除。
结论：综合来看，nephrinYDxV磷酸化的缺失不会改变基线胰岛功能。相反，我们的数据表明,nephrinYDxV磷酸化受损与胰岛分泌能力随年龄增长而改善相关的机制.靶向nephrin磷酸化可以为改善β细胞功能提供新的治疗机会。
