Cell Regulation Laboratory, London Research Institute, Cancer Research UK, 44 Lincoln's Inn Fields, London, WC2A 3LY, UK.
Traffic. 2012 Nov;13(11):1481-95. doi: 10.1111/j.1600-0854.2012.01408.x. Epub 2012 Sep 7.
The exocyst complex tethers post-Golgi secretory vesicles to the plasma membrane prior to docking and fusion. In this study, we identify Sec3, the missing component of the Schizosaccharomyces pombe exocyst complex (SpSec3). SpSec3 shares many properties with its orthologs, and its mutants are rescued by human Sec3/EXOC1. Although involved in exocytosis, SpSec3 does not appear to mark the site of exocyst complex assembly at the plasma membrane. It does, however, mark the sites of actin cytoskeleton recruitment and controls the organization of all three yeast actin structures: the actin cables, endocytic actin patches and actomyosin ring. Specifically, SpSec3 physically interacts with For3 and sec3 mutants have no actin cables as a result of a failure to polarize this nucleating formin. SpSec3 also interacts with actin patch components and sec3 mutants have depolarized actin patches of reduced endocytic capacity. Finally, the constriction and disassembly of the cytokinetic actomyosin ring is compromised in these sec3 mutant cells. We propose that a role of SpSec3 is to spatially couple actin machineries and their independently polarized regulators. As a consequence of its dual role in secretion and actin organization, Sec3 appears as a major co-ordinator of cell morphology in fission yeast.
外核复合物在停靠和融合之前将高尔基体后分泌囊泡 tether 到质膜上。在这项研究中，我们鉴定了 Schizosaccharomyces pombe 外核复合物（SpSec3）的缺失成分 Sec3。SpSec3 与其同源物具有许多共同特性，其突变体可被人源 Sec3/EXOC1 拯救。尽管 SpSec3 参与胞吐作用，但它似乎不会在质膜上标记外核复合物组装的位点。然而，它确实标记了肌动蛋白细胞骨架募集的位点，并控制所有三种酵母肌动蛋白结构的组织：肌动蛋白电缆、内吞肌动蛋白斑和肌球蛋白环。具体来说，SpSec3 与 For3 发生物理相互作用，并且 sec3 突变体由于未能极化这种成核formin 而没有肌动蛋白电缆。SpSec3 还与肌动蛋白斑成分相互作用，并且 sec3 突变体具有去极化的肌动蛋白斑，其内吞能力降低。最后，在这些 sec3 突变细胞中，细胞分裂肌球蛋白环的收缩和解体受到损害。我们提出，SpSec3 的作用是空间偶联肌动蛋白机器及其独立极化的调节剂。由于其在分泌和肌动蛋白组织中的双重作用，Sec3 似乎是裂殖酵母细胞形态的主要协调者。
