Takeuchi Shingo, Katoh Hironori, Negishi Manabu
Laboratory of Molecular Neurobiology, Graduate School of Biostudies, Kyoto University, Yoshidakonoe-cho, Sakyo-ku, Kyoto 606-8501, Japan.
Laboratory of Molecular Neurobiology, Graduate School of Biostudies, Kyoto University, Yoshidakonoe-cho, Sakyo-ku, Kyoto 606-8501, Japan
J Biochem. 2015 Sep;158(3):245-52. doi: 10.1093/jb/mvv042. Epub 2015 Apr 27.
Eph/ephrin signalling plays essential roles in various tissue developments, such as axon guidance, angiogenesis and tissue separation. Interaction between Ephs and ephrins upon cell-cell contact results in forward (towards Eph-expressing cells) and reverse (towards ephrin-expressing cells) signalling. Although the molecular mechanisms downstream of Eph/ephrin forward signalling have been extensively studied, the functions and intracellular molecular mechanisms of Eph/ephrin reverse signalling are not fully understood. Rho GTPases are key regulators of the actin cytoskeleton to regulate cell morphology. In this study, we revealed that stimulation with the extracellular domain of EphB2 to activate Eph/ephrin reverse signalling induced axonal retraction in hippocampal neurons. The reduction of axonal length and branching by Eph/ephrin reverse signalling was blocked by inhibition of RhoA or Rho-associated coiled-coil-containing protein kinase (ROCK). These results suggest that Eph/ephrin reverse signalling negatively regulates axonal outgrowth and branching through RhoA/ROCK pathway in hippocampal neurons.
Eph/ephrin信号通路在多种组织发育过程中发挥着至关重要的作用，如轴突导向、血管生成和组织分离。细胞间接触时，Ephs与ephrins之间的相互作用会导致正向（朝向表达Eph的细胞）和反向（朝向表达ephrin的细胞）信号传导。尽管Eph/ephrin正向信号通路下游的分子机制已得到广泛研究，但Eph/ephrin反向信号通路的功能和细胞内分子机制仍未完全阐明。Rho GTPases是肌动蛋白细胞骨架的关键调节因子，可调控细胞形态。在本研究中，我们发现用EphB2的胞外结构域刺激以激活Eph/ephrin反向信号通路会诱导海马神经元轴突回缩。Eph/ephrin反向信号通路导致的轴突长度和分支减少可通过抑制RhoA或Rho相关卷曲螺旋蛋白激酶（ROCK）来阻断。这些结果表明，Eph/ephrin反向信号通路通过RhoA/ROCK途径对海马神经元的轴突生长和分支起负向调节作用。
