Tobin V A, Ludwig M
Centre for Integrative Physiology, University of Edinburgh, George Square, Edinburgh EH8 9XD, U.K.
Biochem Soc Trans. 2007 Nov;35(Pt 5):1243-6. doi: 10.1042/BST0351243.
F-actin remodelling has been implicated in regulated secretion from many cell types, in particular secretion from neuron axon terminals and neuroendocrine cell types. Cortical F-actin has long been postulated to act as a barrier to vesicle movement and hence to inhibit secretion; however, more recent studies point to F-actin remodelling providing both supporting and restraining roles in secretion. Magnocellular neurons of the supraoptic nucleus secrete either oxytocin or vasopressin from their dendrites as well as their axon terminals; and peptide release from these two compartments can be differentially controlled to allow secretion from one compartment in isolation from the other. While oxytocin and vasopressin secretion can be provoked by F-actin depolymerization in both compartments, acutely stimulated secretion is dependent on F-actin remodelling in dendrites but not axon terminals, suggesting that F-actin plays a different role in regulating the readily releasable pool of secretory vesicles in the two compartments. In addition, activity-dependent secretion from the dendritic compartment can be primed by prior exposure to agents, including oxytocin, that stimulate release of Ca(2+) from intracellular stores. While remodelling of F-actin is involved, it is not solely responsible for priming secretory responses.
F-肌动蛋白重塑与多种细胞类型的调节性分泌有关，尤其是神经元轴突终末和神经内分泌细胞类型的分泌。长期以来，人们推测皮质F-肌动蛋白作为囊泡运动的屏障，从而抑制分泌；然而，最近的研究指出F-肌动蛋白重塑在分泌过程中既起到支持作用也起到抑制作用。视上核的大细胞神经元从其树突以及轴突终末分泌催产素或加压素；并且来自这两个区室的肽释放可以受到不同的控制，从而允许一个区室单独分泌而与另一个区室隔离。虽然催产素和加压素的分泌在两个区室中都可由F-肌动蛋白解聚引发，但急性刺激的分泌依赖于树突中的F-肌动蛋白重塑，而不是轴突终末中的F-肌动蛋白重塑，这表明F-肌动蛋白在调节两个区室中分泌囊泡的易释放池方面发挥不同的作用。此外，树突区室的活性依赖性分泌可以通过预先暴露于包括催产素在内的刺激细胞内钙库释放Ca(2+)的试剂来引发。虽然F-肌动蛋白的重塑参与其中，但它并非引发分泌反应的唯一原因。
