ELKS, a protein structurally related to the active zoneassociated protein CAST, is expressed in pancreatic β cells and functions in insulin exocytosis:: Interaction of ELKS with exocytotic machinery analyzed by total internal reflection fluorescence microsscopy
ELKS, a protein structurally related to the active zoneassociated protein CAST, is expressed in pancreatic β cells and functions in insulin exocytosis:: Interaction of ELKS with exocytotic machinery analyzed by total internal reflection fluorescence microsscopy
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DOI：
10.1091/mbc.e04-09-0816
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发表时间：
2005-07-01
影响因子：
3.3
通讯作者：
Nagamatsu, S
中科院分区：
文献类型：
--
作者：
Ohara-Imaizumi, M;Ohtsuka, T;Nagamatsu, S
活性区 (CAZ) 的细胞基质与确定 Ca2+ 依赖性神经递质胞吐作用的位点有关。在这里，我们展示了 ELKS（一种与 CAZ 蛋白 CAST 结构相关的蛋白）在胰岛素胞吐作用中的表达和功能。共聚焦和免疫电子显微镜分析的结果表明，ELKS 存在于胰腺β细胞中，并且位于靠近停靠在面向质膜的血管上的胰岛素颗粒的位置。产生胰岛素的克隆细胞的全内反射荧光显微镜成像显示，ELKS 簇比富含于质膜的突触蛋白 1 簇密度低且分布不均匀。大多数 ELKS 簇位于与突触融合蛋白 1 簇共定位的胰岛素颗粒的对接位点。单颗粒运动的全内反射荧光图像显示，胰岛素颗粒的融合事件大多发生在ELKS簇上，有时会观察到重复的融合。当 ELKS 的巴松管结合区域被引入细胞时，胰岛素颗粒的对接和融合显着减少。此外，小干扰RNA减弱ELKS表达可减少葡萄糖诱发的胰岛素释放。这些数据表明 CAZ 相关蛋白 ELKS 在胰腺 β 细胞的胰岛素胞吐作用中发挥作用。
The cytomatrix at the active zone (CAZ) has been implicated in defining the site of Ca2+-dependent exocytosis of neurotransmitters. Here, we demonstrate the expression and function of ELKS, a protein structurally related to the CAZ protein CAST, in insulin exocytosis. The results of confocal and immunoelectron microscopic analysis showed that ELKS is present in pancreatic beta cells and is localized close to insulin granules docked on the plasma membrane-facing blood vessels. Total internal reflection fluorescence microscopy imaging in insulin-producing clonal cells revealed that the ELKS clusters are less dense and unevenly distributed than syntaxin 1 clusters, which are enriched in the plasma membrane. Most of the ELKS clusters were on the docking sites of insulin granules that were colocalized with syntaxin 1 clusters. Total internal reflection fluorescence images of single-granule motion showed that the fusion events of insulin granules mostly occurred on the ELKS cluster, where repeated fusion was sometimes observed. When the Bassoon-binding region of ELKS was introduced into the cells the docking and fusion of insulin granules were markedly reduced. Moreover, attenuation of ELKS expression by small interfering RNA reduced the glucose-evoked insulin release. These data suggest that the CAZ-related protein ELKS functions in insulin exocytosis from pancreatic beta cells.