Flexural Rigidity and Shear Stiffness of Flagella Estimated from Induced Bends and Counterbends
Flexural Rigidity and Shear Stiffness of Flagella Estimated from Induced Bends and Counterbends
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DOI：
10.1016/j.bpj.2016.05.017
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发表时间：
2016-06-21
影响因子：
3.4
通讯作者：
Bayly, Philip V.
中科院分区：
文献类型：
--
作者：
Xu, Gang;Wilson, Kate S.;Bayly, Philip V.
运动纤毛和鞭毛是鞭状细胞器，它们主动弯曲以推动细胞或移动气道、脑室和输卵管等通道中的液体。纤毛和鞭毛的有效运动功能取决于一系列运动蛋白的主动力与复杂的细胞骨架结构（轴丝）的被动机械阻力之间的协调相互作用。然而，这种协调的细节，包括轴丝力学，仍不清楚。我们研究了单细胞藻莱茵衣藻鞭毛轴丝的两个主要机械参数，即弯曲刚度和双联体间剪切刚度。结合实验、理论和有限元模型，我们证明轴丝的表观弯曲刚度取决于内在弯曲刚度（EI）和双联体间滑动的弹性阻力（剪切刚度，k（s））。我们估计体内野生型衣藻鞭毛的平均固有弯曲刚度和双联体间剪切刚度，通过钒酸盐使其不能运动，分别为 EI = 840 +/- 280pN.mu m(2) 和 k(s) = 79.6 +/- 10.5 pN/rad。 pf3对应的值； cnk11-6双突变体缺乏连接蛋白-动力蛋白调节复合物(N-DRC)，在相同条件下EI = 1011 +/- 183 pN.mu m(2) 和k(s) = 39.3 +/- 6.0 pN/rad。最后，在缺乏外动力蛋白臂和内动力蛋白臂 c 的 pf13A 突变体中，估计值为 EI = 777 +/- 184 pN.mu m(2) 和 k(s) = 43.3 +/- 7.7 pN/rad。在这两个突变株中，弯曲刚度与野生型没有显着差异（p > 0.05），但缺乏 N-DRC（在 pf3；cnk11-6 中）或动力蛋白臂（在 pf13A 中）显着降低了双联体间剪切刚度。这些差异可能代表了 N-DRC（类似于 40 pN/rad）和残余动力蛋白相互作用（类似于 35 pN/rad）对这些固定衣藻鞭毛中双联体滑动阻力的贡献。
Motile cilia and flagella are whiplike cellular organelles that bend actively to propel cells or move fluid in passages such as airways, brain ventricles, and the oviduct. Efficient motile function of cilia and flagella depends on coordinated interactions between active forces from an array of motor proteins and passive mechanical resistance from the complex cytoskeletal structure (the axoneme). However, details of this coordination, including axonemal mechanics, remain unclear. We investigated two major mechanical parameters, flexural rigidity and interdoublet shear stiffness, of the flagellar axoneme in the unicellular alga Chlamydomonas reinhardtii. Combining experiment, theory, and finite element models, we demonstrate that the apparent flexural rigidity of the axoneme depends on both the intrinsic flexural rigidity (EI) and the elastic resistance to interdoublet sliding (shear stiffness, k(s)). We estimated the average intrinsic flexural rigidity and interdoublet shear stiffness of wild-type Chlamydomonas flagella in vivo, rendered immotile by vanadate, to be EI = 840 +/- 280pN.mu m(2) and k(s) = 79.6 +/- 10.5 pN/rad, respectively. The corresponding values for the pf3; cnk11-6 double mutant, which lacks the nexin-dynein regulatory complex (N-DRC), were EI = 1011 +/- 183 pN.mu m(2) and k(s) = 39.3 +/- 6.0 pN/rad under the same conditions. Finally, in the pf13A mutant, which lacks outer dynein arms and inner dynein arm c, the estimates were EI = 777 +/- 184 pN.mu m(2) and k(s) = 43.3 +/- 7.7 pN/rad. In the two mutant strains, the flexural rigidity is not significantly different from wild-type (p > 0.05), but the lack of N-DRC (in pf3; cnk11-6) or dynein arms (in pf13A) significantly reduces interdoublet shear stiffness. These differences may represent the contributions of the N-DRCs (similar to 40 pN/rad) and residual dynein interactions (similar to 35 pN/rad) to interdoublet sliding resistance in these immobilized Chlamydomonas flagella.