Study Of Neurexin 1?-ErbB4 Interaction In Long-term Potentiation

Schizophrenia is a serious psychiatric illness.Since lacking of obvious pathological features,the pathogenesis of schizophrenia has not been fully illuminated.Several lines of evidence suggest that genetic factors are likely to play an essential role in developing of schizophrenia.Moreover,environment,epigenetic factors and other factors have been involved in the pathogenesis.Recent studies suggest that neuregulin 1(NRG1)and ErbB4 are susceptibility genes of schizophrenia.Nowdays,they have become a hotspot of neuroscience research.Abnormal expression of NRG 1 or ErbB4 has been reported in the brain of schizophrenia patients.Furthermore,ErbB4 mutant mice also exhibit schizophrenia-like symptoms.Therefore,it is important to study the effect of these proteins in the schizophrenia.ErbB4 is mainly localized at parvalbumin(PV)-positive interneurons.These neurons are connected with pyramidal neurons(PN)by synapses and form excitement-inhibition micro loop.They project to the PN and also accept signals of PN.Abnormality of the micro-loop is associates with the onset of schizophrenia.The family of Neurexins(Nrxs)belongs to neuronal adhesion molecules,enriches in the presynaptic membrane of excitatory or inhibitory synapses.Nrxs plays an important role in neurotransmission and synaptic differentiation.Proper execution of these functions requires trans-synaptic complexes of receptors on postsynaptic dendrites opposite matching Nrxs on presynaptic axons.Currently,patients with schizophrenia and autism have been found mutation in neurexin gene,indicating that synaptic dysfunction caused by the Nrxs may be the pathogenesis of such diseases.However,the role of Nrxs-ErbB4 signaling in the micro-loop has not been reported.Studies have shown that ErbB4 increases the activity of GABAergic neurons and suppress long-term potentiation(LTP).Thus,the proper regulation of ErbB4 activity is thought to be important for the regulation GABAergic neurons and the maintenance of higher brain function.The main purpose of this paper is to study the effect of Nrx 1?-ErbB4 signaling in LTP,which further elucidate the pathogenesis of schizophrenia.Using the methods of electrophysiology,cell culture,immunoblotting,immunopreciptation,immunofluorescene combined with molecular biology methods and technologies such as small peptides interference,we try to solve two problems:1)Is ErbB4 interacts with Nrx 1? in LTP?2)If there is interaction between ErbB4 and Nrx 1?,how they regulate the LTP?Firstly,we investigate the molecular basis of the interaction between ErbB4 and Nrx 1? by molecular techniques.After specific blocking ErbB4-Nrx 1? binding in LTP,we study its effect on synapse formation and observe whether excitatory synapses formation is affected.We focus on the number of presynaptic markers vesicular glutamate transporterl(vGluT1)or postsynaptic density-95(PSD-95)in PV-positive interneurons.Our results showed that:1)Interaction between ErbB4 and Nrx 1? increased in high frequency stimulation(HFS)-induced rat brain slices or primary cultured cortical neurons induced by chemical LTP.2)ErbB4 also combined with Nrx 1?after ErbB4 and Nrx 1? expression plasmids transfected into HEK293T cells,which further confirm the interaction between ErbB4 and Nrx 1?.3)After different domains deletion mutants of ErbB4 constructed,ErbB4 mutants and Nrx 1? were cotransfected into HEK293T cells.We found that ErbB4 extracellular 71-86 domain was the primary region to binding with the Nrx 1?.4)Interference small peptide ErbB4-16P inhibited interaction between ErbB4 and Nrx 1?,and reduced formation of excitatory synapses after chemical induction of LTP in primary cultured cortical neurons.Based on the above results,we draw the following conclusions:Nrx 1?-ErbB4 signaling pathways are involved in the LTP in primary cultured cortical neurons.ErbB4 interacts with Nrx 1? and regulates LTP by ways of negative feedback,which will maintain homeostasis in brain.