Intracellular Membrane Trafficking Unit, Oral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, 30 Convent Dr. 303A, Bethesda, MD 20892-4340, USA.
Cell Mol Life Sci. 2013 Jun;70(12):2099-121. doi: 10.1007/s00018-012-1156-5. Epub 2012 Sep 18.
Regulated exocytosis is the main mechanism utilized by specialized secretory cells to deliver molecules to the cell surface by virtue of membranous containers (i.e., secretory vesicles). The process involves a series of highly coordinated and sequential steps, which include the biogenesis of the vesicles, their delivery to the cell periphery, their fusion with the plasma membrane, and the release of their content into the extracellular space. Each of these steps is regulated by the actin cytoskeleton. In this review, we summarize the current knowledge regarding the involvement of actin and its associated molecules during each of the exocytic steps in vertebrates, and suggest that the overall role of the actin cytoskeleton during regulated exocytosis is linked to the architecture and the physiology of the secretory cells under examination. Specifically, in neurons, neuroendocrine, endocrine, and hematopoietic cells, which contain small secretory vesicles that undergo rapid exocytosis (on the order of milliseconds), the actin cytoskeleton plays a role in pre-fusion events, where it acts primarily as a functional barrier and facilitates docking. In exocrine and other secretory cells, which contain large secretory vesicles that undergo slow exocytosis (seconds to minutes), the actin cytoskeleton plays a role in post-fusion events, where it regulates the dynamics of the fusion pore, facilitates the integration of the vesicles into the plasma membrane, provides structural support, and promotes the expulsion of large cargo molecules.
受调控的胞吐作用是专门分泌细胞将分子输送到细胞表面的主要机制，其利用的是膜性容器（即分泌囊泡）。这个过程涉及一系列高度协调和有序的步骤，包括囊泡的生物发生、它们向细胞边缘的输送、与质膜的融合以及内容物向细胞外空间的释放。这些步骤中的每一步都受到肌动蛋白细胞骨架的调节。在这篇综述中，我们总结了目前关于肌动蛋白及其相关分子在脊椎动物各胞吐步骤中的参与情况的知识，并提出，在受调控的胞吐作用中，肌动蛋白细胞骨架的总体作用与被研究的分泌细胞的结构和生理学有关。具体而言，在神经元、神经内分泌、内分泌和造血细胞中，含有经历快速胞吐作用（毫秒级）的小分泌囊泡，肌动蛋白细胞骨架在融合前事件中发挥作用，主要作为功能障碍并促进对接。在外分泌和其他分泌细胞中，含有经历缓慢胞吐作用（数秒至数分钟）的大分泌囊泡，肌动蛋白细胞骨架在融合后事件中发挥作用，调节融合孔的动力学，促进囊泡整合到质膜中，提供结构支撑，并促进大货物分子的排出。
