Umeshima Hiroki, Nomura Ken-Ichi, Yoshikawa Shuhei, Hörning Marcel, Tanaka Motomu, Sakuma Shinya, Arai Fumihito, Kaneko Makoto, Kengaku Mineko
Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Yoshida-Honmachi, Sakyo-ku, Kyoto, 606-8501, Japan.
Graduate School of Engineering, Osaka University 2-1, Yamadaoka, Suita, Osaka, 565-0871, Japan.
Neurosci Res. 2019 May;142:38-48. doi: 10.1016/j.neures.2018.04.001. Epub 2018 Apr 5.
Somal translocation in long bipolar neurons is regulated by actomyosin contractile forces, yet the precise spatiotemporal sites of force generation are unknown. Here we investigate the force dynamics generated during somal translocation using traction force microscopy. Neurons with a short leading process generated a traction force in the growth cone and counteracting forces in the leading and trailing processes. In contrast, neurons with a long leading process generated a force dipole with opposing traction forces in the proximal leading process during nuclear translocation. Transient accumulation of actin filaments was observed at the dipole center of the two opposing forces, which was abolished by inhibition of myosin II activity. A swelling in the leading process emerged and generated a traction force that pulled the nucleus when nuclear translocation was physically hampered. The traction force in the leading process swelling was uncoupled from somal translocation in neurons expressing a dominant negative mutant of the KASH protein, which disrupts the interaction between cytoskeletal components and the nuclear envelope. Our results suggest that the leading process is the site of generation of actomyosin-dependent traction force in long bipolar neurons, and that the traction force is transmitted to the nucleus via KASH proteins.
长双极神经元中的胞体转位受肌动球蛋白收缩力调控，但力产生的确切时空位点尚不清楚。在此，我们使用牵引力显微镜研究胞体转位过程中产生的力动态。具有短前端突起的神经元在生长锥中产生牵引力，并在前导和尾随突起中产生反作用力。相比之下，具有长前端突起的神经元在核转位期间在前导突起近端产生具有相反牵引力的力偶极。在两个相反力的偶极中心观察到肌动蛋白丝的瞬时积累，这在肌球蛋白II活性受到抑制时被消除。当核转位受到物理阻碍时，前端突起中出现肿胀并产生拉动细胞核的牵引力。在表达KASH蛋白显性负突变体的神经元中，前端突起肿胀中的牵引力与胞体转位解偶联，该突变体破坏了细胞骨架成分与核膜之间的相互作用。我们的结果表明，前端突起是长双极神经元中肌动球蛋白依赖性牵引力产生的位点，并且该牵引力通过KASH蛋白传递到细胞核。
