分泌時の細胞骨格系の役割:ラット耳下腺の頂端側形質膜によって惹起される分泌顆粒由来アミラーゼ分泌の調節

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To investigate the significance of cytoskeletal proteins in the exocytotic in vitro interaction system, we observed theeffects of two types of inhibitors, colchicine and cytochalasin D, which depolymerize the microtuble structure consistingof tubulin and microfilament consisting of actins, respectively. The apical plasma membrane-evoked amylase releasewas increased approximately two times by colchicine. These findings suggest that secretory granules could interactwith microtubles coexist via microfilament in the apical plasma membranes and the exocytotic membrane fusion mightbe suppressed by microtubules. When R18-labeled secretory granules were incubated with apical plasma membranesunder the same conditions, de-quenching clearly occurred. In addition, de-quenching was amplified by the addition ofcolchicine. In the intact cells, colchicine may induce disassembly of the microtubule resulting the inhibition of granuletransport to the apical plasma membrane by motor proteins. Based on in vitro observation, it is suggested that the microtubles,which also facilitate cross talk with actin, may modulate access of secretory granules to the apical plasmamembrane. On the other hands, cytochalasin D, an inhibitor of actin polymerization, in the cell-free reconstitution systemdid not affect apical plasma membrane-evoked amylase release. When fiber actin(F-actin)was added to the apicalplasma membrane-evoked amylase release system, it decreased amylase release in a concentration-dependent manner.Isolated apical plasma membranes contain microfilaments but the concentration may be not sufficient to functionas a barrier secretory granule access. These findings suggest that simplification of the exocytotic interaction system allowsobservation the direct effects of the cytoskeleton and that cytoskeletal protein inhibitors induce suppressive modulationof exocytotic membrane fusion.
2008-02-20

分泌時の細胞骨格系の役割:ラット耳下腺の頂端側形質膜によって惹起される分泌顆粒由来アミラーゼ分泌の調節

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