Differential effects of wild-type and A53T mutant isoform of alpha-synuclein on the mitochondrial proteome of differentiated SH-SY5Y cells.

Increased levels of wild-type (WT) alpha-synuclein (alpha-syn) and mutant A53T alpha-syn are associated with Parkinson's disease (PD), a disease linked to abnormal mitochondrial function. This study compared mitochondria prepared from differentiated SH-SY5Y cells overexpressing WT or A53T alpha-syn with control cells, using 2-D difference in-gel electrophoresis. Statistical analysis was carried out primarily using ANOVA (p < 0.01; Host:WT:A53T) and subsequently using independent t tests (host vs WT, host vs A53T). Of the protein spots found to be differentially expressed (n = 71; p < 0.01, >1.8/<-1.8 fold change), 63 proteins were identified by LC-MS/MS, with the majority (77%) significantly altered in WT samples only. Twenty-three proteins known to be integral components of the mitochondria were abnormally expressed including those with roles in ATP synthesis, oxidoreduction, motor activity, carbohydrate metabolism, protein transcription, and protein folding. Thirteen forms of cytoskeletal proteins were also found to be overexpressed in the mitochondrial preparations from WT alpha-syn cells, suggesting an increased interaction of mitochondria with the cytoskeletal network. Altered levels of four mitochondrial proteins (HSPA9 (mortalin), NDUFS1, DLAT, ATP5A1) were confirmed using Western blot analysis. Furthermore, a significant reduction in OXPHOS 1 activity was observed in the WT alpha-syn cells, suggesting that there are functional consequences of the observed altered protein expression changes in the mitochondria.