Altschuler Y, Barbas S M, Terlecky L J, Tang K, Hardy S, Mostov K E, Schmid S L
Department of Anatomy, University of California, San Francisco, California 94143, USA.
J Cell Biol. 1998 Dec 28;143(7):1871-81. doi: 10.1083/jcb.143.7.1871.
A role for dynamin in clathrin-mediated endocytosis is now well established. However, mammals express three closely related, tissue-specific dynamin isoforms, each with multiple splice variants. Thus, an important question is whether these isoforms and splice variants function in vesicle formation from distinct intracellular organelles. There are conflicting data as to a role for dynamin-2 in vesicle budding from the TGN. To resolve this issue, we compared the effects of overexpression of dominant-negative mutants of dynamin-1 (the neuronal isoform) and dynamin-2 (the ubiquitously expressed isoform) on endocytic and biosynthetic membrane trafficking in HeLa cells and polarized MDCK cells. Both dyn1(K44A) and dyn2(K44A) were potent inhibitors of receptor-mediated endocytosis; however neither mutant directly affected other membrane trafficking events, including transport mediated by four distinct classes of vesicles budding from the TGN. Dyn2(K44A) more potently inhibited receptor-mediated endocytosis than dyn1(K44A) in HeLa cells and at the basolateral surface of MDCK cells. In contrast, dyn1(K44A) more potently inhibited endocytosis at the apical surface of MDCK cells. The two dynamin isoforms have redundant functions in endocytic vesicle formation, but can be targeted to and function differentially at subdomains of the plasma membrane.
发动蛋白在网格蛋白介导的内吞作用中的作用现已得到充分证实。然而，哺乳动物表达三种密切相关的、组织特异性的发动蛋白异构体，每种异构体都有多个剪接变体。因此，一个重要的问题是这些异构体和剪接变体是否在不同细胞内细胞器的囊泡形成中发挥作用。关于发动蛋白-2在高尔基体反面网状结构（TGN）的囊泡出芽中的作用，存在相互矛盾的数据。为了解决这个问题，我们比较了发动蛋白-1（神经元异构体）和发动蛋白-2（普遍表达的异构体）的显性负性突变体过表达对HeLa细胞和极化的MDCK细胞内吞和生物合成膜运输的影响。dyn1(K44A)和dyn2(K44A)都是受体介导的内吞作用的有效抑制剂；然而，这两种突变体都没有直接影响其他膜运输事件，包括由从TGN出芽的四类不同囊泡介导的运输。在HeLa细胞和MDCK细胞的基底外侧表面，dyn2(K44A)比dyn1(K44A)更有效地抑制受体介导的内吞作用。相反，dyn1(K44A)在MDCK细胞的顶端表面更有效地抑制内吞作用。这两种发动蛋白异构体在内吞囊泡形成中具有冗余功能，但可以靶向质膜亚结构域并在其中发挥不同的作用。
