Department of Biomedical Science, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Aichi 467-8603, Japan
Department of Biomedical Science, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Aichi 467-8603, Japan.
J Neurosci. 2020 Oct 21;40(43):8248-8261. doi: 10.1523/JNEUROSCI.1907-20.2020. Epub 2020 Oct 2.
Reelin plays versatile roles in neocortical development. The C-terminal region (CTR) of Reelin is required for the correct formation of the superficial structure of the neocortex; however, the mechanisms by which this position-specific effect occurs remain largely unknown. In this study, we demonstrate that Reelin with an intact CTR binds to neuropilin-1 (Nrp1), a transmembrane protein. Both male and female mice were used. Nrp1 is localized with very-low-density lipoprotein receptor (VLDLR), a canonical Reelin receptor, in the superficial layers of the developing neocortex. It forms a complex with VLDLR, and this interaction is modulated by the alternative splicing of VLDLR. Reelin with an intact CTR binds more strongly to the VLDLR/Nrp1 complex than to VLDLR alone. Knockdown of Nrp1 in neurons leads to the accumulation of Dab1 protein. Since the degradation of Dab1 is induced by Reelin signaling, it is suggested that Nrp1 augments Reelin signaling. The interaction between Reelin and Nrp1 is required for normal dendritic development in superficial-layer neurons. All of these characteristics of Reelin are abrogated by proteolytic processing of the six C-terminal amino acid residues of Reelin (0.17% of the whole protein). Therefore, Nrp1 is a coreceptor molecule for Reelin and, together with the proteolytic processing of Reelin, can account for context-specific Reelin function in brain development. Reelin often exhibits a context-dependent function during brain development; however, its underlying mechanism is not well understood. We found that neuropilin-1 (Nrp1) specifically binds to the CTR of Reelin and acts as a coreceptor for very-low-density lipoprotein receptor (VLDLR). The Nrp1/VLDLR complex is localized in the superficial layers of the neocortex, and its interaction with Reelin is essential for proper dendritic development in superficial-layer neurons. This study provides the first mechanistic evidence of the context-specific function of Reelin (>3400 residues) regulated by the C-terminal residues and Nrp1, a component of the canonical Reelin receptor complex.
Reelin 在新皮层发育中发挥多种作用。 Reelin 的 C 端区域（CTR）对于新皮层浅表层的正确形成是必需的；然而，这种位置特异性效应发生的机制在很大程度上仍然未知。在这项研究中，我们证明具有完整 CTR 的 Reelin 与跨膜蛋白神经纤毛蛋白 1（Nrp1）结合。使用了雄性和雌性小鼠。 Nrp1 与极低密度脂蛋白受体（VLDLR）一起定位于发育中的新皮层浅表层，后者是 Reelin 的经典受体。它与 VLDLR 形成复合物，这种相互作用受 VLDLR 选择性剪接的调节。具有完整 CTR 的 Reelin 与 VLDLR/Nrp1 复合物的结合比与 VLDLR 本身的结合更强。神经元中 Nrp1 的敲低导致 Dab1 蛋白的积累。由于 Dab1 的降解是由 Reelin 信号诱导的，因此推测 Nrp1 增强了 Reelin 信号。 Reelin 与 Nrp1 的相互作用对于浅表层神经元的正常树突发育是必需的。 Reelin 的所有这些特性都被 Reelin 的六个 C 末端氨基酸残基（占整个蛋白质的 0.17%）的蛋白水解处理所消除。因此，Nrp1 是 Reelin 的核心受体分子，并且与 Reelin 的蛋白水解处理一起，可以解释 Reelin 在大脑发育中的特定上下文功能。 Reelin 在大脑发育过程中经常表现出依赖于上下文的功能；然而，其潜在机制尚不清楚。我们发现神经纤毛蛋白 1（Nrp1）特异性结合 Reelin 的 CTR 并作为极低密度脂蛋白受体（VLDLR）的核心受体。 Nrp1/VLDLR 复合物定位于新皮层的浅表层，其与 Reelin 的相互作用对于浅表层神经元的正常树突发育是必需的。这项研究提供了第一个机制证据，证明 Reelin（>3400 个残基）的上下文特定功能受 C 端残基和 Nrp1 调节，后者是经典 Reelin 受体复合物的组成部分。
