Department of Physics, University of California, Merced, California 95343, USA.
Department of Physics, Oregon State University, Corvallis, Oregon 97331, USA.
J Chem Phys. 2018 Mar 28;148(12):123318. doi: 10.1063/1.5006806.
Kinesin-1 (hereafter referred to as kinesin) is a major microtubule-based motor protein for plus-end-directed intracellular transport in live cells. While the single-molecule functions of kinesin are well characterized, the physiologically relevant transport of membranous cargos by small teams of kinesins remains poorly understood. A key experimental challenge remains in the quantitative control of the number of motors driving transport. Here we utilized "motile fraction" to overcome this challenge and experimentally accessed transport by a single kinesin through the physiologically relevant transport by a small team of kinesins. We used a fluid lipid bilayer to model the cellular membrane in vitro and employed optical trapping to quantify the transport of membrane-enclosed cargos versus traditional membrane-free cargos under identical conditions. We found that coupling motors via a fluid membrane significantly enhances the velocity of cargo transport by small teams of kinesins. Importantly, enclosing a cargo in a fluid lipid membrane did not impact single-kinesin transport, indicating that membrane-dependent velocity enhancement for team-based transport arises from altered interactions between kinesins. Our study demonstrates that membrane-based coupling between motors is a key determinant of kinesin-based transport. Enhanced velocity may be critical for fast delivery of cargos in live cells.
驱动蛋白-1（以下简称驱动蛋白）是活细胞中正向指向细胞内运输的主要微管动力蛋白。虽然驱动蛋白的单分子功能已经得到很好的描述，但由少量驱动蛋白组成的膜结合货物的生理相关运输仍知之甚少。一个关键的实验挑战仍然是定量控制驱动运输的马达数量。在这里，我们利用“运动分数”来克服这一挑战，并通过实验访问单个驱动蛋白的运输，通过少量驱动蛋白的生理相关运输。我们使用流体脂质双层在体外模拟细胞膜，并采用光阱在相同条件下定量测量膜封闭货物与传统无膜货物的运输。我们发现，通过流体膜将马达耦合在一起，显著提高了小团队驱动蛋白的货物运输速度。重要的是，将货物封闭在流体脂质膜中并不影响单驱动蛋白的运输，这表明团队运输中基于膜的速度增强是由于驱动蛋白之间的相互作用发生改变。我们的研究表明，马达之间基于膜的耦合是驱动蛋白运输的关键决定因素。增强的速度可能对活细胞中货物的快速传递至关重要。
