Stabilization of exocytosis by dynamic F-actin coating of zymogen granules in pancreatic acini
Stabilization of exocytosis by dynamic F-actin coating of zymogen granules in pancreatic acini
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DOI：
10.1074/jbc.m403976200
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发表时间：
2004-09-03
影响因子：
4.8
通讯作者：
Kasai, H
中科院分区：
文献类型：
--
作者：
Nemoto, T;Kojima, T;Kasai, H
用双光子激发显微镜观察了小鼠胰腺腺泡细胞顶端区F-actin在酶原颗粒Ca 2+依赖性胞吐过程中的重组。颗粒被迅速包被F-肌动蛋白响应于激动剂刺激或光解的笼状-Ca 2+化合物。这种F-肌动蛋白涂层专门发生在颗粒的表面进行胞吐作用，并防止由latrunculin-A，抑制肌动蛋白聚合，或肉毒梭菌胞外酶C3，抑制小GTdR Rho。Latrunculin-A或外切酶C3也触发腺泡细胞中空泡的形成，这是急性胰腺炎的特征。刺激腺泡与高浓度的胆囊收缩素，导致急性胰腺炎的小鼠，也损害了F-肌动蛋白涂层的颗粒和诱导空泡形成。Latrunculin-A减少了胞吐的潜伏期，但不影响胞吐事件的总数，这表明F-肌动蛋白通过促进F-肌动蛋白涂层减缓并进一步稳定胞吐。因此，颗粒膜的Rho依赖性F-肌动蛋白涂层稳定了胞外结构，并且对于外分泌胰腺中的分离化合物胞吐的生理进展和预防急性胰腺炎是必要的。
Reorganization of F-actin in the apical region of mouse pancreatic acinar cells during Ca2+-dependent exocytosis of zymogen granules was investigated by two-photon excitation microscopy with intact acini. Granules were rapidly coated with F-actin in response to either agonist stimulation or photolysis of a caged-Ca2+ compound. Such F-actin coating occurred exclusively at the surface of granules undergoing exocytosis and was prevented either by latrunculin-A, which inhibits actin polymerization, or by Clostridium botulinum exoenzyme C3, which inhibits the small GTPase Rho. Latrunculin-A or exoenzyme C3 also triggered the formation of vacuoles in acinar cells, a characteristic of acute pancreatitis. Stimulation of acini with high concentrations of cholecystokinin, which cause acute pancreatitis in mice, also impaired the F-actin coating of granules and induced vacuole formation. Latrunculin-A reduced the latency to exocytosis but did not affect the total number of exocytic events, suggesting that F-actin slows and further stabilizes exocytosis by facilitating F-actin coating. Rho-dependent F-actin coating of granule membranes thus stabilizes exocytic structures and is necessary for physiological progression of sequetial compound exocytosis in the exocrine pancreas and for prevention of acute pancreatitis.