Xu Mengqi, Rutkowski David M, Rebowski Grzegorz, Boczkowska Malgorzata, Pollard Luther W, Dominguez Roberto, Vavylonis Dimitrios, Ostap E Michael
Department of Physiology, Pennsylvania Muscle Institute, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104.
Department of Physics, Lehigh University, Bethlehem, PA.
bioRxiv. 2024 Feb 12:2024.02.09.579714. doi: 10.1101/2024.02.09.579714.
Myosin-Is colocalize with Arp2/3 complex-nucleated actin networks at sites of membrane protrusion and invagination, but the mechanisms by which myosin-I motor activity coordinates with branched actin assembly to generate force are unknown. We mimicked the interplay of these proteins using the "comet tail" bead motility assay, where branched actin networks are nucleated by Arp2/3 complex on the surface of beads coated with myosin-I and the WCA domain of N-WASP. We observed that myosin-I increased bead movement efficiency by thinning actin networks without affecting growth rates. Remarkably, myosin-I triggered symmetry breaking and comet-tail formation in dense networks resistant to spontaneous fracturing. Even with arrested actin assembly, myosin-I alone could break the network. Computational modeling recapitulated these observations suggesting myosin-I acts as a repulsive force shaping the network's architecture and boosting its force-generating capacity. We propose that myosin-I leverages its power stroke to amplify the forces generated by Arp2/3 complex-nucleated actin networks.
肌球蛋白-I在膜突出和内陷部位与Arp2/3复合体成核的肌动蛋白网络共定位，但肌球蛋白-I的运动活性与分支肌动蛋白组装协同产生力的机制尚不清楚。我们使用“彗星尾”珠子运动测定法模拟了这些蛋白质之间的相互作用，在该测定法中，分支肌动蛋白网络由Arp2/3复合体在涂有肌球蛋白-I和N-WASP的WCA结构域的珠子表面成核。我们观察到，肌球蛋白-I通过使肌动蛋白网络变薄来提高珠子运动效率，而不影响生长速率。值得注意的是，肌球蛋白-I在抗自发断裂的致密网络中引发了对称性破坏和彗星尾形成。即使肌动蛋白组装停止，仅肌球蛋白-I就能破坏网络。计算模型概括了这些观察结果，表明肌球蛋白-I作为一种排斥力塑造网络结构并增强其力产生能力。我们提出，肌球蛋白-I利用其动力冲程来放大由Arp2/3复合体成核的肌动蛋白网络产生的力。
