Aggregation of the protein called alpha-synuclein in nerve cells produces the hallmark pathology (Lewy bodies) of Parkinson´s disease (PD). The pathological events that lead to the aggregation of alpha-synuclein in patients’ brains are not completely understood. We hypothesize that in intact healthy neurons, alpha-synuclein exists in bunches called oligomers (principally tetramers = assemblies formed of four alpha-synuclein monomers) plus varying amounts of free monomers. We propose to study whether this equilibrium is altered under PD-relevant conditions.
We recently developed a reproducible, live-cell crosslinking method that enables the detection of the apparent assembly state of alpha-synuclein. Our project uses chemical compounds that can harmlessly enter intact cells and introduce stable chemical bonds between proteins that are in close contact. Employing extensive controls, our data suggest that crosslinked alpha-synuclein occurs principally as tetramers (plus some additional minor oligomers) as well as some uncrosslinked monomers. We now propose to extend this work to human samples, including red blood cells, fibroblasts and induced pluripotent stem cell-derived neurons from PD patients versus from healthy individuals.
Relevance to Diagnosis/Treatment of Parkinson’s Disease:
By determining how alpha-synuclein in cells of PD subjects differs from that in cells of healthy individuals, we aim to establish tetramer:monomer ratios as a potential biomarker for PD and related human synucleinopathies. Moreover, we hope to use our findings to identify drug compounds that could correct any abnormal tetramer:monomer ratios. Our new observations, which contrast to the traditional view that physiological alpha-synuclein in cells is principally monomeric, have led us to postulate that such drugs could open up new avenues for PD treatment.
We expect to learn whether native alpha-synuclein tetramers and related oligomers in living cells are useful for diagnosing and treating PD. Based on our evidence that alpha-synuclein tetramers resist aggregation better than do monomers, we expect that PD-relevant conditions (e.g. certain genetic mutations) can lead to an increase of aggregation-prone monomers.