Pedersen Ross Ta, Snoberger Aaron, Pyrpassopoulos Serapion, Safer Daniel, Drubin David G, Ostap E Michael
Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720.
Present address: Department of Embryology, Carnegie Institution for Science, Baltimore, MD 21218.
bioRxiv. 2023 Jun 30:2023.03.21.533689. doi: 10.1101/2023.03.21.533689.
Myosins are required for clathrin-mediated endocytosis, but their precise molecular roles in this process are not known. This is, in part, because the biophysical properties of the relevant motors have not been investigated. Myosins have diverse mechanochemical activities, ranging from powerful contractility against mechanical loads to force-sensitive anchoring. To better understand the essential molecular contribution of myosin to endocytosis, we studied the in vitro force-dependent kinetics of the endocytic type I myosin called Myo5, a motor whose role in clathrin-mediated endocytosis has been meticulously studied in vivo. We report that Myo5 is a low-duty-ratio motor that is activated ∼10-fold by phosphorylation, and that its working stroke and actin-detachment kinetics are relatively force-insensitive. Strikingly, the in vitro mechanochemistry of Myo5 is more like that of cardiac myosin than like that of slow anchoring myosin-1s found on endosomal membranes. We therefore propose that Myo5 generates power to augment actin assembly-based forces during endocytosis in cells.
Pedersen, Snoberger et al. measure the force-sensitivity of the yeast endocytic the myosin-1 called Myo5 and find that it is more likely to generate power than to serve as a force-sensitive anchor in cells. Implications for Myo5's role in clathrin-mediated endocytosis are discussed.
网格蛋白介导的内吞作用需要肌球蛋白，但它们在这一过程中的确切分子作用尚不清楚。部分原因是相关马达蛋白的生物物理特性尚未得到研究。肌球蛋白具有多种机械化学活性，从抵抗机械负荷的强大收缩力到力敏感锚定。为了更好地理解肌球蛋白对胞吞作用的基本分子贡献，我们研究了参与内吞作用的I型肌球蛋白Myo5的体外力依赖动力学，该马达蛋白在网格蛋白介导的内吞作用中的作用已在体内得到了细致研究。我们报告称，Myo5是一种低占空比马达蛋白，通过磷酸化可被激活约10倍，并且其工作行程和肌动蛋白解离动力学相对不敏感于力。引人注目的是，Myo5的体外机械化学更类似于心肌肌球蛋白，而不是在内体膜上发现的缓慢锚定肌球蛋白-1s。因此，我们提出Myo5在细胞内吞作用过程中产生动力以增强基于肌动蛋白组装的力。
佩德森、斯诺伯格等人测量了酵母内吞作用中称为Myo5的肌球蛋白-1的力敏感性，发现它在细胞中更有可能产生动力而不是作为力敏感锚定。讨论了Myo5在网格蛋白介导的内吞作用中的作用。
