A quantitative analysis of contractility in active cytoskeletal protein networks
A quantitative analysis of contractility in active cytoskeletal protein networks
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DOI：
10.1529/biophysj.107.117960
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发表时间：
2008-04-15
影响因子：
3.4
通讯作者：
Weitz, David A.
中科院分区：
文献类型：
--
作者：
Bendix, Paul M.;Koenderink, Glisje H.;Weitz, David A.
细胞主动产生收缩力，用于包括胞质分裂和运动在内的各种过程。已知收缩依赖于肌球蛋白II马达，其将ATP水解产生的化学能转化为肌动蛋白丝上的力。然而，细胞收缩性的基本物理原理仍然知之甚少。我们在一个简化的模型系统的纯化F-肌动蛋白，肌肉肌球蛋白II电机，和α-辅肌动蛋白交联剂重构收缩。我们发现，收缩发生在阈值电机浓度和交联剂浓度的窗口内。我们还量化了成束网络的孔径，并发现在束之间的临界距离处发生收缩。我们提出了一个简单的收缩机制的基础上肌球蛋白丝拉相邻的束在一起成为一个聚集的结构。在散装和低维几何形状的观察表明，该重组系统的收缩凝胶拉和变形的收缩力类似于1 μ N，或类似于100 pN每F-肌动蛋白束的表面。在相同环境中收缩的细胞质提取物显示出与重建系统相似的行为和对肌球蛋白的依赖性。我们的研究结果表明，细胞收缩性可以通过调整分子马达的（局部）活性和交联剂的密度和结合亲和力来灵敏地调节。
Cells actively produce contractile forces for a variety of processes including cytokinesis and motility. Contractility is known to rely on myosin II motors which convert chemical energy from ATP hydrolysis into forces on actin filaments. However, the basic physical principles of cell contractility remain poorly understood. We reconstitute contractility in a simplified model system of purified F-actin, muscle myosin II motors, and a-actinin cross-linkers. We show that contractility occurs above a threshold motor concentration and within a window of cross-linker concentrations. We also quantify the pore size of the bundled networks and find contractility to occur at a critical distance between the bundles. We propose a simple mechanism of contraction based on myosin filaments pulling neighboring bundles together into an aggregated structure. Observations of this reconstituted system in both bulk and low-dimensional geometries show that the contracting gels pull on and deform their surface with a contractile force of similar to 1 mu N, or similar to 100 pN per F-actin bundle. Cytoplasmic extracts contracting in identical environments show a similar behavior and dependence on myosin as the reconstituted system. Our results suggest that cellular contractility can be sensitively regulated by tuning the (local) activity of molecular motors and the cross-linker density and binding affinity.