Application of Serum Peptidomics for Parkinson's Disease in SNCA-A30P Mice

Intraneuronal inclusions of alpha-synuclein (α-synuclein, α-syn) are commonly found in the brain of patients with Parkinson's disease (PD). The pathogenesis of the abundant α-syn protein in the blood has been extensively studied to understand its properties better. In recent years, peptidome analysis has received increasing attention. In this study, we identified and analyzed serum peptides from wild-type (WT) and the (Thy-1)-h[A30P] alpha-synuclein transgenic mice (SNCA-A30P mice) using liquid chromatography-tandem mass spectrometry (LC-MS/MS). One thousand eight hundred fifty-six peptides from 771 proteins were analyzed. Among them, 151 peptides from 107 proteins were significantly differentially expressed. The glycoprotein VI platelet pathway (GP6) was the pathway's most significant differentially expressed signaling pathway. Cleavage sites of the differentially expressed peptides may reflect protease distribution and activity. We selected the most significantly differentially expressed peptide, VGGDPI, and found that it contained cathepsin K (Ctsk) and trypsin-1 cleavage sites, suggesting that Ctsk and trypsin-1 may be key peptidases in PD. α-syn is a protein associated with the pathogenesis of PD. mutations in several genes, including SNCA, which encodes α-syn, are associated with the development of PD. Bioinformatics analysis of the physiological pathways related to SNCA genes and apoptosis genes found the five most markedly up-regulated proteins: formin homology 2 domain-containing 1 (FHOD1), insulin receptor substrate 1(IRS1), TRPM8 channel-associated factor 1 (TCAF1), glyceraldehyde 3-phosphate dehydrogenase (GAPDH), and interleukin-16 (IL-16). Therefore, the differentially expressed peptides in the five precursor protein domains may be potential bioactive peptides associated with α-syn and apoptosis. This study provides a validated peptidomics profile of SNCA-A30P mice and identifies potentially bioactive peptides linked to α-syn and apoptosis.