Department of Neurobiology, Pharmacology, and Physiology, The University of Chicago, Chicago, IL 60637, USA.
Cell Metab. 2009 Oct;10(4):316-23. doi: 10.1016/j.cmet.2009.08.012.
Insulin secretion from pancreatic beta cells is dependent on maturation and acidification of the secretory granule, processes necessary for prohormone convertase cleavage of proinsulin. Previous studies in isolated beta cells revealed that acidification may be dependent on the granule membrane chloride channel ClC-3, in a step permissive for a regulated secretory response. In this study, immuno-EM of beta cells revealed colocalization of ClC-3 and insulin on secretory granules. Clcn3(-/-) mice as well as isolated islets demonstrate impaired insulin secretion; Clcn3(-/-) beta cells are defective in regulated insulin exocytosis and granular acidification. Increased amounts of proinsulin were found in the majority of secretory granules in the Clcn3(-/-) mice, while in Clcn3(+/+) cells, proinsulin was confined to the immature secretory granules. These results demonstrate that in pancreatic beta cells, chloride channels, specifically ClC-3, are localized on insulin granules and play a role in insulin processing as well as insulin secretion through regulation of granular acidification.
胰岛素分泌依赖于胰腺β细胞分泌颗粒的成熟和酸化，这是激素原转化酶切割胰岛素原所必需的过程。之前在分离的β细胞中的研究表明，酸化可能依赖于颗粒膜氯离子通道 ClC-3，这是调节分泌反应的必要步骤。在这项研究中，β细胞的免疫电镜显示 ClC-3 和胰岛素在分泌颗粒上共定位。Clcn3(-/-) 小鼠以及分离的胰岛显示胰岛素分泌受损；Clcn3(-/-)β细胞在调节胰岛素胞吐和颗粒酸化方面存在缺陷。在 Clcn3(-/-) 小鼠的大多数分泌颗粒中发现了更多的胰岛素原，而在 Clcn3(+/+) 细胞中，胰岛素原局限于不成熟的分泌颗粒中。这些结果表明，在胰腺β细胞中，氯离子通道，特别是 ClC-3，定位于胰岛素颗粒上，并通过调节颗粒酸化在胰岛素加工以及胰岛素分泌中发挥作用。
