The phosphatidylserine flippase β-subunit Tmem30a is essential for normal insulin maturation and secretion

• Published in: Molecular therapy 2021-09, Vol.29 (9), p.2854-2872
• Main Authors: Yang, Yeming, Sun, Kuanxiang, Liu, Wenjing, Li, Xiao, Tian, Wanli, Shuai, Ping, Zhu, Xianjun
• Format: Article
• Language: English
• Subjects: Animals; Cell Membrane - metabolism; Disease Models, Animal; Gene Knockout Techniques; Glucose - adverse effects; glucose intolerance; Glucose Intolerance - genetics; Glucose Intolerance - metabolism; Glucose Transporter Type 2 - metabolism; hyperglycemia; Hyperglycemia - genetics; Hyperglycemia - metabolism; Hyperinsulinism - genetics; Hyperinsulinism - metabolism; Insulin - metabolism; Insulin Resistance - genetics; Insulin Secretion; Insulin-Secreting Cells - cytology; Insulin-Secreting Cells - drug effects; Insulin-Secreting Cells - metabolism; Membrane Proteins - genetics; Mice; Obesity - genetics; Obesity - metabolism; Original; phosphatidylserine flippase; Phosphatidylserines - metabolism; Tmem30a; trans-Golgi Network - metabolism; Type 2 diabetes mellitus
• ISSN: 1525-0016; 1525-0024
• DOI: 10.1016/j.ymthe.2021.04.026

The processing, maturation, and secretion of insulin are under precise regulation, and dysregulation causes profound defects in glucose handling, leading to diabetes. Tmem30a is the β subunit of the phosphatidylserine (PS) flippase, which maintains the membrane asymmetric distribution of PS. Tmem30a regulates cell survival and the localization of subcellular structures and is thus critical to the normal function of multiple physiological systems. Here, we show that conditional knockout of Tmem30a specifically in pancreatic islet β cells leads to obesity, hyperglycemia, glucose intolerance, hyperinsulinemia, and insulin resistance in mice, due to insufficient insulin release. Moreover, we reveal that Tmem30a plays an essential role in clathrin-mediated vesicle transport between the trans Golgi network (TGN) and the plasma membrane (PM), which comprises immature secretory granule (ISG) budding at the TGN. We also find that Tmem30a deficiency impairs clathrin-mediated vesicle budding and thus blocks both insulin maturation in ISGs and the transport of glucose-sensing Glut2 to the PM. Collectively, these disruptions compromise both insulin secretion and glucose sensitivity, thus contributing to impairments in glucose-stimulated insulin secretion. Taken together, our data demonstrate an important role of Tmem30a in insulin maturation and glucose metabolic homeostasis and suggest the importance of membrane phospholipid distribution in metabolic disorders. [Display omitted] Corresponding authors and colleagues show that conditional knockout of Tmem30a specifically in pancreatic islet β cells leads to obesity, hyperglycemia, glucose intolerance, hyperinsulinemia, and insulin resistance in mice, due to insufficient insulin release. They demonstrate a novel role of Tmem30a in insulin maturation and glucose metabolic homeostasis.