Kabayama Hiroyuki, Nakamura Takeshi, Takeuchi Makoto, Iwasaki Hirohide, Taniguchi Masahiko, Tokushige Naoko, Mikoshiba Katsuhiko
Laboratory for Developmental Neurobiology, Brain Science Institute, The Institute of Physical and Chemical Research (RIKEN), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
Mol Cell Neurosci. 2009 Jan;40(1):27-38. doi: 10.1016/j.mcn.2008.08.009. Epub 2008 Sep 11.
Growth cone collapse occurs in repulsive axon guidance and is accompanied by a reduction in the surface area of the plasma membrane of growth cones. However, the mechanism of this reduction is unclear. Here, we show that during growth cone collapse, caffeine-induced Ca(2+) release from ryanodine-sensitive Ca(2+) stores triggers the formation of large vacuoles in growth cones by macropinocytosis, a clathrin-independent endocytosis for the massive retrieval of the cellular plasma membrane, and subsequent retrograde membrane transport. We observed a significant correlation of the area of caffeine-induced macropinosomes with growth cone collapse. We also detected macropinocytosis induced by semaphorin 3A, a typical repulsive cue, and correlation between the area of semaphorin 3A-induced macropinocytic vacuoles and growth cone collapse. Moreover, jasplakinolide, an inhibitor of F-actin depolymerization, blocked caffeine-induced macropinocytosis. We propose that the coordinated regulation of actin cytoskeletal reorganization and macropinocytosis-mediated retrograde membrane trafficking may contribute to Ca(2+)-induced axon growth inhibition.
生长锥塌陷发生在轴突排斥性导向过程中，并且伴随着生长锥质膜表面积的减少。然而，这种减少的机制尚不清楚。在此，我们表明，在生长锥塌陷过程中，咖啡因诱导的来自兰尼碱敏感钙库的钙离子释放通过巨胞饮作用触发生长锥中大型液泡的形成，巨胞饮是一种不依赖网格蛋白的内吞作用，用于大量回收细胞质膜，随后进行逆行膜转运。我们观察到咖啡因诱导的巨胞饮体面积与生长锥塌陷之间存在显著相关性。我们还检测到典型排斥信号分子3A诱导的巨胞饮作用，以及信号分子3A诱导的巨胞饮液泡面积与生长锥塌陷之间的相关性。此外，F-肌动蛋白解聚抑制剂茉莉酸丙酯可阻断咖啡因诱导的巨胞饮作用。我们提出，肌动蛋白细胞骨架重组和巨胞饮介导的逆行膜运输的协同调节可能有助于钙离子诱导的轴突生长抑制。
