DeGeer Jonathan, Kaplan Andrew, Mattar Pierre, Morabito Morgane, Stochaj Ursula, Kennedy Timothy E, Debant Anne, Cayouette Michel, Fournier Alyson E, Lamarche-Vane Nathalie
Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec H3A 0C7, Canada The Research Institute of McGill University Health Centre, Montreal, Quebec H4A 3J1, Canada.
Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec H3A 2B4, Canada.
J Cell Biol. 2015 Aug 31;210(5):817-32. doi: 10.1083/jcb.201505084.
During development, netrin-1 is both an attractive and repulsive axon guidance cue and mediates its attractive function through the receptor Deleted in Colorectal Cancer (DCC). The activation of Rho guanosine triphosphatases within the extending growth cone facilitates the dynamic reorganization of the cytoskeleton required to drive axon extension. The Rac1 guanine nucleotide exchange factor (GEF) Trio is essential for netrin-1-induced axon outgrowth and guidance. Here, we identify the molecular chaperone heat shock cognate protein 70 (Hsc70) as a novel Trio regulator. Hsc70 dynamically associated with the N-terminal region and Rac1 GEF domain of Trio. Whereas Hsc70 expression supported Trio-dependent Rac1 activation, adenosine triphosphatase-deficient Hsc70 (D10N) abrogated Trio Rac1 GEF activity and netrin-1-induced Rac1 activation. Hsc70 was required for netrin-1-mediated axon growth and attraction in vitro, whereas Hsc70 activity supported callosal projections and radial neuronal migration in the embryonic neocortex. These findings demonstrate that Hsc70 chaperone activity is required for Rac1 activation by Trio and this function underlies netrin-1/DCC-dependent axon outgrowth and guidance.
在发育过程中，网蛋白-1既是一种吸引性又是一种排斥性轴突导向线索，并通过结直肠癌缺失受体（DCC）介导其吸引功能。延伸生长锥内的 Rho 鸟苷三磷酸酶的激活促进了驱动轴突延伸所需的细胞骨架的动态重组。Rac1 鸟嘌呤核苷酸交换因子（GEF）Trio 对于网蛋白-1诱导的轴突生长和导向至关重要。在这里，我们确定分子伴侣热休克同源蛋白 70（Hsc70）是一种新型的 Trio 调节剂。Hsc70 与 Trio 的 N 端区域和 Rac1 GEF 结构域动态相关。虽然 Hsc70 的表达支持 Trio 依赖的 Rac1 激活，但腺苷三磷酸酶缺陷型 Hsc70（D10N）消除了 Trio 的 Rac1 GEF 活性和网蛋白-1诱导的 Rac1 激活。在体外，网蛋白-1介导的轴突生长和吸引需要 Hsc70，而 Hsc70 的活性支持胚胎新皮质中的胼胝体投射和放射状神经元迁移。这些发现表明，Trio 激活 Rac1 需要 Hsc70 的伴侣活性，并且该功能是网蛋白-1/DCC 依赖的轴突生长和导向的基础。
