Imaging analysis reveals mechanistic differences between first- and second-phase insulin exocytosis
Imaging analysis reveals mechanistic differences between first- and second-phase insulin exocytosis
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DOI：
10.1083/jcb.200608132
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发表时间：
2007-05-21
影响因子：
7.8
通讯作者：
Nagamatsu, Shinya
中科院分区：
文献类型：
--
作者：
Ohara-Imaizumi, Mica;Fujiwara, Tomonori;Nagamatsu, Shinya
葡萄糖诱导的双相胰岛素释放的机制尚不清楚。我们使用全内反射荧光（TIRF）成像分析来揭示胰腺β细胞中第一和第二相胰岛素胞吐的过程。该分析表明，先前对接的胰岛素颗粒在突触融合蛋白（Synt）1A簇的位点融合。第一阶段，然而，新成员融合在第二阶段外部的Synt 1A集群。为了揭示Synt 1A在相性胰岛素胞吐中的功能，我们产生了Synt 1A敲除（Synt 1A（-/-））小鼠。Synt 1A（-/-）β细胞显示较少的先前停靠颗粒，在过程中没有融合。第一阶段;来自新来者的第二阶段融合被保留。恢复Synt 1A表达的拯救实验证明了颗粒对接状态和融合事件的恢复。抑制其他突触融合蛋白Synt 3和Synt 4不影响第二相胰岛素胞吐作用。我们的结论是。第一阶段是Synt 1A依赖的，但第二阶段不是。这表明胰岛素胞吐的两个阶段在空间和机制上不同。
The mechanism of glucose-induced biphasic insulin release is unknown. We used total internal reflection fluorescence (TIRF) imaging analysis to reveal the process of first- and second-phase insulin exocytosis in pancreatic beta cells. This analysis showed that previously docked insulin granules fused at the site of syntaxin (Synt) 1A clusters during the. rst phase; however, the newcomers fused during the second phase external to the Synt1A clusters. To reveal the function of Synt1A in phasic insulin exocytosis, we generated Synt1A-knockout (Synt1A(-/-)) mice. Synt1A(-/-) beta cells showed fewer previously docked granules with no fusion during the. rst phase; second- phase fusion from newcomers was preserved. Rescue experiments restoring Synt1A expression demonstrated restoration of granule docking status and fusion events. Inhibition of other syntaxins, Synt3 and Synt4, did not affect second- phase insulin exocytosis. We conclude that the. rst phase is Synt1A dependent but the second phase is not. This indicates that the two phases of insulin exocytosis differ spatially and mechanistically.