School of Life Sciences, Nanchang University, Nanchang, China.
Institute of Life Science, Nanchang University, Nanchang, China.
Transl Psychiatry. 2021 Jun 29;11(1):361. doi: 10.1038/s41398-021-01485-6.
The precise control of the nervous system function under the vitality of synapses is extremely critical. Efforts have been taken to explore the underlying cellular and molecular mechanisms for synapse formation. Cell adhesion molecules have been found important for synapse assembly in the brain. Many trans-adhesion complexes have been identified to modulate excitatory synapse formation. However, little is known about the synaptogenic mechanisms for inhibitory synapses. ErbB4 is a receptor tyrosine kinase enriched in interneurons. Here, we showed that overexpressing ErbB4 in HEK293T cells induced gephyrin or GABAR α1 puncta in co-cultured primary hippocampal neurons. This induction of ErbB4 was independent of its kinase activity. K751M, a kinase-dead mutant of ErbB4, can also induce gephyrin or GABAR α1 puncta in the co-culture system. We further constructed K751M knock-in mice and found that the homozygous were viable at birth and fertile without changes in gross brain structure. The number of interneurons and inhibitory synapses onto pyramidal neurons (PyNs) were comparable between K751M and wild-type mice but decreased in ErbB4-Null mice. Moreover, ErbB4 can interact in trans with Slitrk3, a transmembrane postsynaptic protein at inhibitory synapses, through the extracellular RLD domain of ErbB4. The deletion of RLD diminished the induction of gephyrin or GABAR α1 puncta by ErbB4. Finally, disruption of ErbB4-Slitrk3 interaction through neutralization of Slitrk3 by secretable RLD decreased inhibitory synapses onto PyNs and impaired GABAergic transmission. These results identify that ErbB4, as a cell adhesion molecule, promotes inhibitory synapse formation onto PyNs by interacting with Slitrk3 and in a kinase-independent manner, providing an unexpected mechanism of ErbB4 in inhibitory synapse formation.
突触活力下神经系统功能的精确控制极其关键。人们一直致力于探索突触形成的潜在细胞和分子机制。已经发现细胞粘附分子对于脑内突触组装很重要。许多跨粘附复合物已被鉴定为调节兴奋性突触形成。然而，对于抑制性突触的突触发生机制知之甚少。ErbB4 是一种富含中间神经元的受体酪氨酸激酶。在这里，我们发现在 HEK293T 细胞中过表达 ErbB4 可诱导共培养的原代海马神经元中出现神经胶质纤维酸性蛋白或 GABARα1 斑点。这种 ErbB4 的诱导不依赖于其激酶活性。ErbB4 的激酶失活突变体 K751M 也可以在共培养系统中诱导神经胶质纤维酸性蛋白或 GABARα1 斑点。我们进一步构建了 K751M 敲入小鼠，并发现杂合子在出生时具有活力且可育，大脑结构没有变化。K751M 和野生型小鼠的中间神经元和抑制性突触数量与锥体神经元（PyNs）相当，但 ErbB4 缺失型小鼠的数量减少。此外，ErbB4 可以通过其细胞外 RLD 结构域与抑制性突触上的跨膜突触后蛋白 Slitrk3 发生反式相互作用。RLD 缺失减少了 ErbB4 诱导的神经胶质纤维酸性蛋白或 GABARα1 斑点的形成。最后，通过 Slitrk3 的可分泌 RLD 中和来破坏 ErbB4-Slitrk3 相互作用，减少了 PyNs 上的抑制性突触，并损害了 GABA 能传递。这些结果表明，ErbB4 作为一种细胞粘附分子，通过与 Slitrk3 相互作用并以非激酶依赖的方式促进抑制性突触形成到 PyNs 上，为 ErbB4 在抑制性突触形成中的作用提供了一种意想不到的机制。
