α-Synuclein binds the KATP channel at insulin-secretory granules and inhibits insulin secretion
α-Synuclein binds the KATP channel at insulin-secretory granules and inhibits insulin secretion
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DOI：
10.1152/ajpendo.00262.2010
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发表时间：
2011-02-01
影响因子：
5.1
通讯作者：
Drain, Peter
中科院分区：
文献类型：
--
作者：
Geng, Xuehui;Lou, Haiyan;Drain, Peter
耿X，楼辉，王军，李L，Swanson AL，Sun M，Beers-Stolz D，Watkins S，Perez RG，Dain P.α-突触核蛋白与胰岛素分泌颗粒上的K-ATP通道结合，抑制胰岛素的分泌。AM J生理学内分泌代谢酶300：E276-E286,2011。2010年9月21日首次出版；DOI：10.1152/ajpendo.00262.2010。-α-突触核蛋白已经在许多通常与分泌过程相关的细胞类型中进行了研究。因此，在胰岛β细胞中，α-突触核蛋白可能通过与参与胰岛素分泌的细胞器相互作用而发挥类似的作用。我们测试了定位于胰岛素分泌颗粒的α-突触核蛋白，并表征了它在葡萄糖刺激的胰岛素分泌中的作用。免疫组织化学和荧光磺酰基脲分别检测α-突触核蛋白在胰岛素颗粒中的定位，免疫沉淀和免疫印迹分析α-突触核蛋白与K-ATP通道的相互作用，ELISA法检测上调或下调α-突触核蛋白表达对INS1细胞或小鼠胰岛胰岛素分泌的影响。用共聚焦显微镜对荧光胰岛素生物传感器Ins-C-emGFP成像，并用透射电子显微镜观察，发现α-突触核蛋白基因敲除的β细胞和野生型β细胞的细胞表型存在差异。结果表明，抗α-突触核蛋白抗体标记了β细胞内的分泌细胞器。抗α-突触核蛋白抗体与K-ATP通道抗体、抗胰岛素抗体和抗C肽抗体共存。α-突触核蛋白在K-ATP通道复合体中免疫共沉淀。在2.8 mM的葡萄糖刺激下，α-突触核蛋白的表达下调胰岛素的分泌，但对16.7 mM的葡萄糖刺激几乎没有影响。α-突触核蛋白基因敲除的胰岛上调了2.8和8.4 mM的胰岛素分泌，但不能上调16.7 mM的葡萄糖，这与在这些胰岛中观察到的胰岛β细胞表膜上的胰岛素颗粒密度耗尽一致。这些发现表明，α-突触核蛋白与K-ATP通道和胰岛素分泌颗粒相互作用，并在功能上对葡萄糖刺激可以推翻的分泌起到刹车作用。α-突触核蛋白在糖尿病中的作用可能与它在包括阿尔茨海默氏症和帕金森氏症在内的其他退行性疾病中的作用相似。
Geng X, Lou H, Wang J, Li L, Swanson AL, Sun M, Beers-Stolz D, Watkins S, Perez RG, Drain P. alpha-Synuclein binds the K-ATP channel at insulin-secretory granules and inhibits insulin secretion. Am J Physiol Endocrinol Metab 300: E276-E286, 2011. First published September 21, 2010; doi: 10.1152/ajpendo.00262.2010.-alpha-Synuclein has been studied in numerous cell types often associated with secretory processes. In pancreatic beta-cells, alpha-synuclein might therefore play a similar role by interacting with organelles involved in insulin secretion. We tested for alpha-synuclein localizing to insulin-secretory granules and characterized its role in glucose-stimulated insulin secretion. Immunohistochemistry and fluorescent sulfonyl-ureas were used to test for alpha-synuclein localization to insulin granules in beta-cells, immunoprecipitation with Western blot analysis for interaction between alpha-synuclein and K-ATP channels, and ELISA assays for the effect of altering alpha-synuclein expression up or down on insulin secretion in INS1 cells or mouse islets, respectively. Differences in cellular phenotype between alpha-synuclein knockout and wild-type beta-cells were found by using confocal microscopy to image the fluorescent insulin biosensor Ins-C-emGFP and by using transmission electron microscopy. The results show that anti-alpha-synuclein antibodies labeled secretory organelles within beta-cells. Anti-alpha-synuclein antibodies colocalized with K-ATP channel, anti-insulin, and anti-C-peptide antibodies. alpha-Synuclein coimmunoprecipitated in complexes with K-ATP channels. Expression of alpha-synuclein downregulated insulin secretion at 2.8 mM glucose with little effect following 16.7 mM glucose stimulation. alpha-Synuclein knockout islets upregulated insulin secretion at 2.8 and 8.4 mM but not 16.7 mM glucose, consistent with the depleted insulin granule density at the beta-cell surface membranes observed in these islets. These findings demonstrate that alpha-synuclein interacts with K-ATP channels and insulin-secretory granules and functionally acts as a brake on secretion that glucose stimulation can override. alpha-Synuclein might play similar roles in diabetes as it does in other degenerative diseases, including Alzheimer's and Parkinson's diseases.