Khaitlina S Yu
Institute of Cytology, Russian Academy of Sciences, St. Petersburg, 194064, Russia.
Biochemistry (Mosc). 2014 Sep;79(9):917-27. doi: 10.1134/S0006297914090089.
In addition to the intracellular transport of particles (cargo) along microtubules, there are in the cell two actin-based transport systems. In the actomyosin system the transport is driven by myosin, which moves the cargo along actin microfilaments. This transport requires the hydrolysis of ATP in the myosin molecule motor domain that induces conformational changes in the molecule resulting in the myosin movement along the actin filament. The other actin-based transport system of the cell does not involve myosin or other motor proteins. This system is based on a unidirectional actin polymerization, which depends on ATP hydrolysis in actin polymers and is initiated by proteins bound to the surface of transported particles. Obligatory components of the actin-based transport are proteins of the WASP/Scar family and a complex of Arp2/3 proteins. Moreover, the actin-based systems often contain dynamin and cortactin. It is known that a system of actin filaments formed on the surface of particles, the so-called "comet-like tail", is responsible for intracellular movements of pathogenic bacteria, micropinocytotic vesicles, clathrin-coated vesicles, and phagosomes. This movement is reproduced in a cell-free system containing extract of Xenopus oocytes. The formation of a comet-like structure capable of transporting vesicles from the plasma membrane into the cell depth has been studied in detail by high performance electron microscopy combined with electron tomography. A similar mechanism provides the movement of vesicles containing membrane rafts enriched with sphingolipids and cholesterol, changes in position of the nuclear spindle at meiosis, and other processes. This review will consider current ideas about actin polymerization and its regulation by actin-binding proteins and show how these mechanisms are realized in the intracellular actin-based vesicular transport system.
除了颗粒（货物）沿微管进行细胞内运输外，细胞中还存在两种基于肌动蛋白的运输系统。在肌动球蛋白系统中，运输由肌球蛋白驱动，它使货物沿着肌动蛋白微丝移动。这种运输需要肌球蛋白分子运动结构域中的ATP水解，这会诱导分子构象变化，从而导致肌球蛋白沿着肌动蛋白丝移动。细胞的另一种基于肌动蛋白的运输系统不涉及肌球蛋白或其他运动蛋白。该系统基于单向肌动蛋白聚合，这取决于肌动蛋白聚合物中的ATP水解，并由与运输颗粒表面结合的蛋白质启动。基于肌动蛋白的运输的必需成分是WASP/Scar家族的蛋白质和Arp2/3蛋白质复合物。此外，基于肌动蛋白的系统通常包含发动蛋白和皮层肌动蛋白。已知在颗粒表面形成的肌动蛋白丝系统，即所谓的“彗星样尾巴”，负责致病细菌、微胞饮小泡、网格蛋白包被小泡和吞噬体的细胞内运动。这种运动在含有非洲爪蟾卵母细胞提取物的无细胞系统中得以重现。通过高性能电子显微镜结合电子断层扫描，已详细研究了能够将小泡从质膜运输到细胞深处的彗星样结构的形成。类似的机制也参与了富含鞘脂和胆固醇的膜筏小泡的移动、减数分裂时核纺锤体位置的变化以及其他过程。本综述将探讨有关肌动蛋白聚合及其受肌动蛋白结合蛋白调控的当前观点，并展示这些机制在细胞内基于肌动蛋白的囊泡运输系统中是如何实现的。
