Lake Forest College, Lake Forest, IL 60045
The neurodegeneration pathology in Parkinson’s disease patients predominantly targets dopaminergic neurons in the midbrain. These neurons accumulate aggregated alpha-synuclein and this build-up may be linked to cell death. The misfolding of alpha-synuclein is thought to trigger its accumulation and aggregation. An attractive hypothesis is that excess amount of alpha-synuclein is due to dysfunctional degradation of the protein. Until recently, the proteasome was considered the major site for degrading alpha-synuclein, but recent studies suggest that the lysosome may also be involved. To test this latter hypothesis, we employed a budding yeast model for alpha-synuclein aggregation and toxicity to genetically evaluate the role of multivesicular body (MVB) pathway, a major route used by proteins to target the yeast vacuole (its lysosome) for degradation. ESCRT-1 is a major protein complex in the MVB pathway. We asked if alpha-synuclein would accumulate and increase toxicity in yeast that lacked important ESRCT-1 components, vps28 or mvb12. We demonstrate that the absence of vps28 altered wildtype, A53T, and E46K alpha-synuclein localization. Specifically, a significant proportion of alpha-synuclein shifted from its predominant plasma membrane location to diffuse and aggregated compartments within the cytoplasm. In contrast, the mvb12∆ strain retained plasma membrane alpha-synuclein localization. Our preliminary data indicates that the MVB pathway is involved in alpha-synuclein degradation, but not all proteins within ESRCT-1 participate. Complete analysis of the remaining ESCRT-I proteins and other ESCRT complexes is needed to fully understand the role of sorting proteins and MVBs in the alpha-synuclein lysosome degradation pathway.
A.A. is supported by Lake Forest College and by an NIH R15 AREA grant to S.D.
[Abstract (DOC)]