Biochemistry Department, University of Geneva, Geneva, Switzerland.
Department of Biochemistry and Biophysics, University of California, San Francisco, United States.
Elife. 2017 Sep 21;6:e26856. doi: 10.7554/eLife.26856.
Dynamin, which mediates membrane fission during endocytosis, binds endophilin and other members of the in-mphiphysin-vs (BAR) protein family. How endophilin influences endocytic membrane fission is still unclear. Here, we show that dynamin-mediated membrane fission is potently inhibited in vitro when an excess of endophilin co-assembles with dynamin around membrane tubules. We further show by electron microscopy that endophilin intercalates between turns of the dynamin helix and impairs fission by preventing interactions between dynamin rungs that are thought to play critical roles in membrane constriction. In living cells, overexpression of endophilin delayed both fission and transferrin uptake. Together, our observations suggest that while endophilin helps shape endocytic tubules and recruit dynamin to endocytic sites, it can also block membrane fission when present in excess by inhibiting inter-dynamin interactions. The sequence of recruitment and the relative stoichiometry of the two proteins may be critical to regulated endocytic fission.
动力蛋白在胞吞作用中介导膜裂变，与衔接蛋白和其他肌抑素（BAR）蛋白家族成员结合。衔接蛋白如何影响胞吞作用的膜裂变仍不清楚。在这里，我们显示当衔接蛋白过量组装在围绕膜小管的动力蛋白周围时，体外动力蛋白介导的膜裂变被强烈抑制。我们通过电子显微镜进一步显示，衔接蛋白插入动力蛋白螺旋的匝之间，并通过防止被认为在膜收缩中起关键作用的动力蛋白梯级之间的相互作用来阻碍裂变。在活细胞中，衔接蛋白的过表达延迟了裂变和转铁蛋白的摄取。总之，我们的观察结果表明，尽管衔接蛋白有助于塑造胞吞小管并将动力蛋白募集到胞吞部位，但当存在过量时，通过抑制动力蛋白之间的相互作用，它也可以阻断膜裂变。两种蛋白质的募集顺序和相对化学计量可能对调节胞吞作用的裂变至关重要。
