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J Cell Mol Med. 2017 Nov;21(11):2950-2962. doi: 10.1111/jcmm.13207. Epub 2017 May 25.

Excess cholesterol inhibits glucose-stimulated fusion pore dynamics in insulin exocytosis.

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Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.
Department of Bioengineering, Key Laboratory of Biomedical Engineering of Ministry of Education, Zhejiang University, Hangzhou, China.
Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA.
Department of Biochemistry, Weill Cornell Medical College, New York, NY, USA.


Type 2 diabetes is caused by defects in both insulin sensitivity and insulin secretion. Glucose triggers insulin secretion by causing exocytosis of insulin granules from pancreatic β-cells. High circulating cholesterol levels and a diminished capacity of serum to remove cholesterol from β-cells are observed in diabetic individuals. Both of these effects can lead to cholesterol accumulation in β-cells and contribute to β-cell dysfunction. However, the molecular mechanisms by which cholesterol accumulation impairs β-cell function remain largely unknown. Here, we used total internal reflection fluorescence microscopy to address, at the single-granule level, the role of cholesterol in regulating fusion pore dynamics during insulin exocytosis. We focused particularly on the effects of cholesterol overload, which is relevant to type 2 diabetes. We show that excess cholesterol reduced the number of glucose-stimulated fusion events, and modulated the proportion of full fusion and kiss-and-run fusion events. Analysis of single exocytic events revealed distinct fusion kinetics, with more clustered and compound exocytosis observed in cholesterol-overloaded β-cells. We provide evidence for the involvement of the GTPase dynamin, which is regulated in part by cholesterol-induced phosphatidylinositol 4,5-bisphosphate enrichment in the plasma membrane, in the switch between full fusion and kiss-and-run fusion. Characterization of insulin exocytosis offers insights into the role that elevated cholesterol may play in the development of type 2 diabetes.


total internal reflection fluorescence microscopy ; VAMP2-pHluorin; beta cell; cholesterol; diabetes; exocytosis; fusion pore; glucose; insulin

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