Apoptosis Pathway And Related Gene Mutation In Parkinson’s Disease

Parkinson’s disease has long been characterized for its classic motor symptoms and the development of Lewy bodies and the loss of dopaminergic neurons in substantia nigra.It is now recognized that Parkinson’s disease has a great deal of heterogeneity,with not only motor symptoms,but also obvious non-motor symptoms;in addition to dopaminergic neuron damage,there are other regions of the nervous system affected.With the development of modern high-throughput sequencing technology and bioinformatics,great progress has been made in the genetic factors of Parkinson’s disease.Proteins encoded by different genes participate in distinct pathogenesis through various molecular pathways,playing a certain role in dopaminergic neuron loss or apoptosis.Based on the study of environmental factors and genetic factors in the pathogenesis of Parkinson’s disease,it has been found that mitochondrial dysfunction,oxidative stress,protein handling and neurological inflammation are the main mechanisms of dopaminergic neuron loss of Parkinson’s disease and they have close relationship with apoptosis.Treatment of Parkinson’s disease is currently mainly focused on symptoms,which cannot delay the progress of the disease.Therefore,the future goal of Parkinson’s disease treatment should be the development of disease-modifying drugs,aiming to change or prevent the development of the disease.PartⅠGlu R6-mediated apoptosis pathway and its role as a therapeutic target in Parkinson’s diseaseApoptosis of dopaminergic neurons in substantia nigra is an important mechanism of the pathogenesis of Parkinson’s disease.The abnormal activation of c-Jun amino-terminal kinase(JNK)signaling pathway may be closely related to death of DA neurons.The over-activating of glutamate receptor is the key factor of dopaminergic neuronal damage;related studies have shown that Glu R6 is likely to be an upstream mediating receptor of JNK pathway.Since the Glu R6 intracellular carboxyl terminal sequence binds to the PDZ1 domain of the PSD-95 anchor protein in the postsynaptic dense region(PSD),and the upstream kinase MLK2 / 3 of JNK3 binds to PSD-95,Glu R6-PSD95-MLK3 signal module may be the structure basis of activation of JNK3 by Glu R6.In this study,Glu R6 was found to be overexpressed in PD cell model;Glu R6 and PSD95,Glu R6 and MLK3,PSD-95 and MLK3 were found to interact with each other by immunofluorescence,immunoprecipitation and immunohistochemistry.We also designed a small peptide capable of specifically antagonizing the binding of Glu R6 to PSD-95,based on the binding of Glu R6 to the carboxyl terminal sequence RLPGKETMA in PSD-95 PDZ1 domain.To make the peptide get into the cell easily,we took advantage of a domain in HIV virus(HIV Tat fusion peptide)which could penetrate the biological membrane without receptor or energy.The final sequence of the peptide integrated 9 amino acids(RLPGKETMA)of Glu R6 which could specifically binds to PSD95 and the HIV-1 Tat fusion peptide,which is Tyr-Gly-Arg-Lys-Lys-Arg-Arg-Gln-Arg-Arg-Arg-RLPGKETMA.The results showed that the small peptide we designed played a protective role in dopaminergic neuron.This study confirmed the important role of Glu R6 in DA cell apoptosis.The design of small peptide also lighted up a way to the study and development of novel drugs with little toxicity,high specificity and excellent therapeutic effect.Part II Screening of apoptosis-related gene HTRA2 and other genes in Parkinson’s diseaseHTRA2,also known as Omi,is a serine protease whose N-terminal has a targeting sequence of mitochondria and is located in the mitochondria intermembrane space.It will activate proapoptotic proteins upon its release from the damaged mitochondria;HTRA2 is considered an important risk factor for PD and was listed as PARK13.A recent study of a family of six generations by Gulsuner et al.found that HTRA2 p.G399 S mutation can lead to the occurrence of hereditary essential tremor,and homozygote will suffer from Parkinson’s disease;while validation studies from West Norway,Asia and other regions are controversial.Therefore,the aim of this study is to make a thorough screening of 8 exons and exon-intron boundaries of HTRA2 by Sanger sequencing in Chinese population to determine whether the HTRA2 coding region including p.G399 S was related with Parkinson’s disease and essential tremor in China.This study found two variants in HTRA2(rs2241028,rs2241027)with no association with Parkinson’s disease or essential tremor,therefore no evidence of the relationship of HTRA2 with Parkinson’s disease or essential tremor was found in this study.