Leterrier J F, Käs J, Hartwig J, Vegners R, Janmey P A
U.298 INSERM, CHRU, 49033 Angers Cedex, France.
J Biol Chem. 1996 Jun 28;271(26):15687-94. doi: 10.1074/jbc.271.26.15687.
The structure of gels formed by bovine spinal cord neurofilaments was determined by fluorescence and electron microscopy and compared to mechanical properties measured by their elastic and viscous response to shear forces. Neurofilaments formed gels of high elastic modulus (>100 Pa) after addition of millimolar Mg2+. Gelation caused a slow increase in shear moduli to levels similar to those of vimentin intermediate filament networks, followed by a rapid rise due to formation of links between neurofilaments, mediated by cross-bridging structures that vimentin filaments lack. Neurofilament gels are more resistant to large deformations than are vimentin networks, suggesting the importance of cross-bridges for neurofilament mechanical properties. Fluorescence imaging of single neurofilaments showed flexible filaments that became straighter when they adhered to glass or were incorporated into filament bundles. Electron microscopy of neurofilament gels showed a system of bundles intertwined within a more isotropic network of individual filaments. Neurofilament gel formation was stimulated in vitro by acid phosphatase treatment or by inositol phospholipids. In contrast, addition of actin filaments reduced the resistance of neurofilament gels to large stresses. These results suggest that dynamic and regulated interactions occur between neurofilaments to form viscoelastic networks with properties distinct from other cytoskeletal structures.
通过荧光显微镜和电子显微镜确定了牛脊髓神经丝形成的凝胶结构，并将其与通过对剪切力的弹性和粘性响应测量的力学性能进行了比较。在加入毫摩尔浓度的Mg2+后，神经丝形成了高弹性模量（>100 Pa）的凝胶。凝胶化导致剪切模量缓慢增加至与波形蛋白中间丝网络相似的水平，随后由于神经丝之间形成连接而迅速上升，这种连接由波形蛋白丝所缺乏的交联结构介导。神经丝凝胶比波形蛋白网络更能抵抗大变形，这表明交联桥对神经丝力学性能的重要性。单个神经丝的荧光成像显示，柔性丝在粘附于玻璃或并入丝束时会变得更直。神经丝凝胶的电子显微镜显示，在更各向同性的单丝网络中，存在一个相互交织的束系统。在体外，酸性磷酸酶处理或肌醇磷脂可刺激神经丝凝胶的形成。相反，添加肌动蛋白丝会降低神经丝凝胶对大应力的抵抗力。这些结果表明，神经丝之间发生动态且受调控的相互作用，以形成具有不同于其他细胞骨架结构特性的粘弹性网络。
