Control of granule mobility and exocytosis by Ca2+ -dependent formation of F-actin in pancreatic duct epithelial cells.
Control of granule mobility and exocytosis by Ca2+ -dependent formation of F-actin in pancreatic duct epithelial cells.
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DOI：
10.1111/j.1600-0854.2009.00884.x
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发表时间：
2009-04
期刊：
影响因子：
--
通讯作者：
Koh DS
中科院分区：
文献类型：
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作者：
Jung SR;Kim MH;Hille B;Koh DS
细胞内 Ca2+ 浓度 ([Ca2+]i) 的升高触发胰管上皮分泌颗粒的胞吐作用。在这项研究中，我们发现信号还控制颗粒运动。 [Ca2+]i 增加后，荧光标记颗粒的运动突然停止，这在动力学上与整个细胞质中丝状肌动蛋白 (F-肌动蛋白) 的形成一致。在高分辨率下，新的 F-肌动蛋白网络非常致密，以至于颗粒大小的细胞结构似乎被物理地困在其中。 F-肌动蛋白与 latrunculin B 的解聚阻断了 F-肌动蛋白的形成和颗粒的阻滞。有趣的是，当用全内反射荧光显微镜监测时，固定颗粒仍然缓慢而一致地向质膜移动。这种群体易位被肌球蛋白阻滞剂所消除。通过微安培法测量的胞吐作用表明，致密的 F-肌动蛋白网络的形成抑制了小 Ca2+ 上升 <1 μm 时的胞吐作用。由于颗粒的协调易位和与膜的融合，较大的 [Ca2+]i 升高，胞吐作用增加。我们建议 Ca2+ 依赖性颗粒冻结过滤掉弱输入，但通过控制颗粒运动在更强输入下允许胞吐作用。
Elevation of intracellular Ca2+ concentration ([Ca2+]i) triggers exocytosis of secretory granules in pancreatic duct epithelia. In this study, we find that the signal also controls granule movement. Motions of fluorescently labeled granules stopped abruptly after a [Ca2+]i increase, kinetically coincident with formation of filamentous actin (F-actin) in the whole cytoplasm. At high resolution, the new F-actin meshwork was so dense that cellular structures of granule size appeared physically trapped in it. Depolymerization of F-actin with latrunculin B blocked both the F-actin formation and the arrest of granules. Interestingly, when monitored with total internal reflection fluorescence microscopy, the immobilized granules still moved slowly and concertedly toward the plasma membrane. This group translocation was abolished by blockers of myosin. Exocytosis measured by microamperometry suggested that formation of a dense F-actin meshwork inhibited exocytosis at small Ca2+ rises <1 μm. Larger [Ca2+]i rises increased exocytosis because of the co-ordinate translocation of granules and fusion to the membrane. We propose that the Ca2+-dependent freezing of granules filters out weak inputs but allows exocytosis under stronger inputs by controlling granule movements.