SYNJ1 Rescues Neural Functions Parkinson’s Disease Mice By Upregulating TSP-1 Expression

Background:Parkinson’s disease is typically characterized by a dense deposition of alpha-SYN and loss of dopaminergic neurons in the substantia nigra of the midbrain.At present,its therapeutic effect is not good,so there is an urgent need to explore new effective therapeutic targets.Our previous studies have found that SYNJ1 is an independent risk factor for Parkinson’s disease and is negatively correlated with disease severity and stage.The purpose of this study was to investigate the neuroprotective effect of SYNJ1 on mice with Parkinson’s disease and its mechanism.Methods:We first evaluated motor function,SYNJ1 protein expression,and pathological changes of Parkinson’s disease in hSNCA*A53T-Tg mice and MPTP-induced subacute Parkinson’s disease mice by open field test,rotarod test,and western blotting.Subsequently,we demonstrated SYNJ1’s neuroprotective effect on inherited and sporadic Parkinson’s disease mice by injecting rAdV-Synj1 virus into the striatum of 11-month-old hSNCA*A53T-Tg mice and MPTP-induced subacute Parkinson’s disease mice to induce upregulation of SYNJ1 expression.Then,SYNJ1 gene was knocked out in SH-SY5Y cells,and transcriptomic sequencing,bioinformatics analysis,qPCR validation and protein-protein virtual docking were performed to explore downstream proteins where SYNJ1 may act.The expression of TSP-1 was detected after overexpression of SYNJ1 and the interaction between SYNJ1 and TSP-1 was verified by co-IP assay.The possible downstream proteins of SYNJ1 were verified.Results:We demonstrated that,compared with normal mice,11-month-old hSNCA*A53T-Tg mice and MPTP-induced subacute Parkinson’s disease mice showed significant motor dysfunction,increased α-synaptic nucleoproteins(α-Syn),decreased tyrosine hydroxylase(TH)in dopaminergic neurons,and decreased SYNJ1 protein in the substantia nigra and striata.SYNJ1 overexpression saved the behavior disorder in both models of Parkinson’s disease and alleviated pathological damage,which was manifested by decreased α-Syn expression,increased TH expression and decreased dopaminergic neuron loss in the substantia nigra and striatum,suggesting that SYNJ1 has a neuroprotective effect Then,after SYNJ1 gene knockdown in SH-SY5Y cells,α-Syn aggregation was increased and TSP-1 expression was inhibited,and the differentially expressed genes mainly involved synaptic vesicular pathways.Protein-protein virtual docking suggests a possible interaction between SYNJ1 and TSP-1 proteins.Finally,SYNJ1-dependent expression of TSP-1 was found by overexpression of SYNJ1 in two types of Parkinson’s disease mice,and the interaction between SYNJ1 and TSP-1 was confirmed by co-IP experiments.Conclusion:Our study suggests that overexpression of SYNJ1 protects dopaminergic neurons in the substantia nigra in hSNCA*A53T-Tg mice and MPTP-induced Parkinson’s disease by up-regulating the expression of TSP-1 in the synaptic vesicular pathway.SYNJ1 may be a new target for the treatment of Parkinson’s disease.