Ogawa Research Unit, Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan.
Brain Res. 2009 Dec 22;1304:26-37. doi: 10.1016/j.brainres.2009.09.087. Epub 2009 Sep 29.
Reelin regulates radial migration of the projection neurons in the developing cerebral cortex by inducing tyrosine phosphorylation of an intracellular adaptor protein, Disabled-1 (Dab1), through activation of Src family tyrosine kinases (SFKs). Five tyrosine residues of Dab1 (Y185, Y198, Y200, Y220, and Y232) are capable of being phosphorylated by SFKs. Among them, phosphorylation of Y198, Y220, and Y232 has been demonstrated after Reelin stimulation, and Y185 has been suggested to be an additional Reelin-induced phosphorylation site. In this study we established a reconstitution system in which a migratory defect in the cortex of Dab1-deficient mice is rescued by transfection with a wild-type Dab1 gene. The transfected neurons in the mutant cortex migrated radially and split the superficial preplate into the marginal zone and subplate by a mechanism that depended on interaction between Dab1 and Reelin receptors. Although this migration rescue was also observed in the mutant cortex transfected with a Dab1 gene containing a single substitution at Y198 by phenylalanine (Y198F), Y220F, Y232F, both of the Y185F and Y200F (Y185F/Y200F), Y185F/Y220F, Y185F/Y232F, Y198F/Y220F, or Y198F/Y232F, it was never observed in the mutant cortex transfected with a Dab1 gene containing the Y185F/Y198F or Y220F/Y232F. These findings suggest that Reelin induces phosphorylation at Y185 of Dab1, and that there are two Reelin signaling pathways, one mediated by the Y185/Y198 phosphorylation of Dab1 and the other mediated by the Y220/Y232 phosphorylation of Dab1. The results also suggest that phosphorylation of either one of the residues in each pair is sufficient for the transmission of Reelin signaling.
Reelin 通过激活Src 家族酪氨酸激酶（SFKs）诱导细胞内衔接蛋白Disabled-1（Dab1）的酪氨酸磷酸化，从而调节发育中的大脑皮层中的投射神经元的放射状迁移。Dab1 的五个酪氨酸残基（Y185、Y198、Y200、Y220 和 Y232）能够被 SFKs 磷酸化。其中，Reelin 刺激后已经证明了 Y198、Y220 和 Y232 的磷酸化，并且 Y185 被认为是另外一个 Reelin 诱导的磷酸化位点。在这项研究中，我们建立了一个重组系统，其中 Dab1 缺陷型小鼠皮层中的迁移缺陷通过转染野生型 Dab1 基因得到挽救。突变皮层中的转染神经元通过一种依赖于 Dab1 和 Reelin 受体之间相互作用的机制进行放射状迁移，并将浅层基板分裂为边缘区和基板。尽管在突变皮层中转染含有单个 Y198 取代为苯丙氨酸（Y198F）、Y220F、Y232F 的 Dab1 基因也观察到了这种迁移挽救，但在突变皮层中转染含有 Y185F 和 Y200F（Y185F/Y200F）、Y185F/Y220F、Y185F/Y232F、Y198F/Y220F 或 Y198F/Y232F 的 Dab1 基因中从未观察到。这些发现表明 Reelin 诱导 Dab1 的 Y185 磷酸化，并且存在两种 Reelin 信号通路，一种由 Dab1 的 Y185/Y198 磷酸化介导，另一种由 Dab1 的 Y220/Y232 磷酸化介导。结果还表明，每个对中的一个残基的磷酸化足以传递 Reelin 信号。
