中间神经元ErbB4激活促NO生成机制及其介导的精神分裂症发病机理研究

Neuregulin 1(NRG1) is a trophic factor family, and NRG1 and its receptor ErbB4 are critical for neural development and synaptic plasticity schizophrenia. Schizophrenia is a highly heritable and disabling mental illness that affects 1% of the population worldwide, which lacks clear pathological lesions. Abnormal neurotransmission has implicated in etiopathogenesis of schizophrenia。The past few years have witnessed breakthrough in the discovery of schizophrenia susceptible genes including NRG1, ErbB4、PI3KCD/110δ、AKT1、NOS1 etc, however, little is known about the pathogenic mechanisms. NRG1 is a trophic factor family, and NRG1 and its receptor ErbB4 are critical for neural development and synaptic plasticity schizophrenia. Our previous studies have shown that acute treatment with NRG1 increases GABA release and GABA currents in the prefrontal cortex and hippocampus, which increases the firing of pyramidal neurons, and enhances long-term potentiation (LTP) at SC-CA1 synapse. The effect of NRG1 can be prevented by pharmacological inhibition of ErbB4 or genetic ablation of Erbb4 in interneuron. In support of genetic ablation of Erbb4 in pathogenesis of schizophrenia, recent studies showed this transgenic mice exhibit relevant behavioral deficits including social interaction, PPI, working memory etc. It is still unclear how activated ErbB4 in interneurons by NRG1 to improvement GABA release. Our preliminary results provide evidence that the effect of NRG1 could be related with nNOS-NO system in ErbB4 positive interneuron. In this proposal, we will study the underlying mechanisms of active nNOS by NRG1-ErbB4 and downstream signaling pathway to activated GABA release. In addition, we will study the Neural circuit and behavior defecits in inducible conditional knockout nNOS (NOS1) in ErbB4 interneuron from the molecular, cellular and neural circuit levels. The results will reveal insight into the pathophysiological mechanisms of schizophrenia.

神经调节素1（NRG1）在调节神经发育和突触传递及可塑性中发挥重要作用。我们前期研究发现NRG1可通过激活中间神经元上ErbB4 受体促进GABA 的释放。药理学阻断或敲除ErbB4基因都可以阻断NRG1的这种作用。然而NRG1促进GABA释放的机制及其导致行为学缺陷中的作用机理不清。我们预实验结果显示NRG1信号的这些作用可能和中间神经元上nNOS-NO生成有关，本标书将进一步深入研究NRG1如何促进ErbB4阳性中间神经元NO的生成，以及nNOS激活后如何增强GABA释放下游的信号通路。本标书将通过在ErbB4阳性中间神经元可诱导条件性敲除nNOS基因，从分子、细胞、神经环路和动物整体水平深入研究ErbB4激活促进中间神经元NO生成的机制及其可能对神经环路和行为的调控作用。由于NRG1、ErbB4 以及nNOS都是精神分裂症的易感基因，研究结果将有助于阐明于精神分裂症发病机理。

神经调节素1（NRG1）在调节神经发育和突触传递及可塑性中发挥重要作用。我们前期研究发现NRG1可通过激活中间神经元上ErbB4受体促进γ-氨基丁酸（GABA）的释放,然而机制不明。本项目通过脑片膜片钳、在体神经电生理记录技术,结合Western blot、免疫荧光等分子生物学技术，发现在小鼠海马脑片上药理学抑制ErbB4受体、PI3K/AKT、nNOS，均可以有效阻断NRG1增加GABA释放的作用；同时应用可诱导性ErbB4阳性神经元上条件性敲除nNOS敲除小鼠（Erbb4-Nos1-/-）进一步检测NRG1调节GABA释放的作用，确定ErbB4阳性神经元上表达的nNOS参与了NRG1促进GABA释放的作用。在其下游通路研究中，我们利用药理学和条件性基因打靶技术证明表明ErbB4阳性神经元上表达的TRPC6通道介导了NRG1增加GABA释放这一过程，此外我们进一步证明NRG1可以通过NO的生成来促进TRPC6通道的亚硝基化，从而影响GABA释放。同时，我们还发现条件性敲除nNOS可导致小鼠表现海马区域神经网络gamma振荡水平异常；并且伴随精神分裂症样的行为学缺陷，具体表现为过度活动、感觉门控能力受损、社交功能障碍、工作记忆受损等。综上所述，这一研究提示ErbB4-PI3K-AKT-nNOS-NO-TRPC6信号通路在调节NRG1促进GABA释放和行为学中的作用。这些结果不仅加深人们对中枢神经系统GABA释放调节机制的认识，而且还将促进对精神分裂症等精神疾病的病理生理更加深入的了解，为将来进一步干预治疗提供新的思路和靶点。