Key Laboratory of Systems Biomedicine (Ministry of Education), Center for Comparative Medicine, Institute of Systems Biomedicine, Shanghai Jiao Tong University, Shanghai 200240, China.
J Mol Cell Biol. 2012 Dec;4(6):362-76. doi: 10.1093/jmcb/mjs034. Epub 2012 Jun 21.
Dendritic patterning and spine morphogenesis are crucial for the assembly of neuronal circuitry to ensure normal brain development and synaptic connectivity as well as for understanding underlying mechanisms of neuropsychiatric diseases and cognitive impairments. The Rho GTPase family is essential for neuronal morphogenesis and synaptic plasticity by modulating and reorganizing the cytoskeleton. Here, we report that protocadherin (Pcdh) clusters and cell adhesion kinases (CAKs) play important roles in dendritic development and spine elaboration. The knockout of the entire Pcdhα cluster results in the dendritic simplification and spine loss in CA1 pyramidal neurons in vivo and in cultured primary hippocampal neurons in vitro. The knockdown of the whole Pcdhγ cluster or in combination with the Pcdhα knockout results in similar dendritic and spine defects in vitro. The overexpression of proline-rich tyrosine kinase 2 (Pyk2, also known as CAKβ, RAFTK, FAK2, and CADTK) recapitulates these defects and its knockdown rescues the phenotype. Moreover, the genetic deletion of the Pcdhα cluster results in phosphorylation and activation of Pyk2 and focal adhesion kinase (Fak) and the inhibition of Rho GTPases in vivo. Finally, the overexpression of Pyk2 leads to inactivation of Rac1 and, conversely, the constitutive active Rac1 rescues the dendritic and spine morphogenesis defects caused by the knockout of the Pcdhα cluster and the knockdown of the Pcdhγ cluster. Thus, the involvement of the Pcdh-CAK-Rho GTPase pathway in the dendritic development and spine morphogenesis has interesting implications for proper assembly of neuronal connections in the brain.
树突形态发生和棘突形态发生对于神经元回路的组装至关重要，以确保正常的大脑发育和突触连接，以及理解神经精神疾病和认知障碍的潜在机制。Rho GTPase 家族通过调节和重组细胞骨架对于神经元形态发生和突触可塑性至关重要。在这里，我们报告原钙黏蛋白（Pcdh）簇和细胞黏附激酶（CAKs）在树突发育和棘突细化中发挥重要作用。整个 Pcdhα 簇的敲除导致体内 CA1 锥体神经元和体外培养的原代海马神经元的树突简化和棘突丢失。整个 Pcdhγ 簇的敲低或与 Pcdhα 敲除结合导致体外类似的树突和棘突缺陷。富含脯氨酸的酪氨酸激酶 2（Pyk2，也称为 CAKβ、RAFTK、FAK2 和 CADTK）的过表达再现了这些缺陷，其敲低可挽救表型。此外，Pcdhα 簇的遗传缺失导致 Pyk2 和粘着斑激酶（Fak）的磷酸化和激活以及体内 Rho GTPases 的抑制。最后，Pyk2 的过表达导致 Rac1 的失活，相反，组成性激活的 Rac1 可挽救 Pcdhα 簇敲除和 Pcdhγ 簇敲低引起的树突和棘突形态发生缺陷。因此，Pcdh-CAK-Rho GTPase 通路在树突发育和棘突形态发生中的参与对于大脑中神经元连接的正确组装具有重要意义。
