Consistent with MPTP assays, administration of Tx14(A) peptide in transgenic PD mice effectively restored expression levels of TH, SYP1, PSD95, GPR37L1, ERK and p-ERK in SNpc and SYP1, PSD95, GPR37L1, ERK and p-ERK in SNPc and STR (Fig. 7C-F). Here, DLG4 is linked to Parkinson disease.