Many devastating neurodegenerative diseases are associated with the transformation of protein from their normal soluble forms to amyloid fibrils. Upon amyloidogenesis these proteins accumulate in the brain and cause diseases such as Parkinson's, Alzheimer's, type II diabetes, and Huntington's disease. α-synuclein (αS) is a “natively unfolded” 14 kD protein of unknown function that has been implicated in Parkinson's disease pathogenesis. Numerous studies have established the in vitro conversion of unfolded α-synuclein to a filamentous β-sheet aggregate. Despite exhaustive research efforts, the mechanism by which α-synuclein transforms, from a soluble unfolded protein to an insoluble aggregate, remain unclear. There is increasing evidence that small protein oligomers may be more toxic than the final fibrillar aggregates. Therefore it is critically important to characterize the species formed during the very early stages of aggregation. Our laboratory uses several techniques like NMR, fluorescence, electron microscopy, atomic force microscopy, circular dichroism, and computational methods to try to elucidate the initial stages of the α-synuclein aggregation mechanism.
α-synuclein aggregation and oxidative stress:
Very recently, it has been shown that in vivo, α-synuclein undergoes a co-translational modification, acetylation, in the N-terminus. This modification has been suggested to increase α-synuclein oligomerization states. The existence of these oligomeric states due to acetylation might interfere with the accepted aggregation view ofαS. The impact of acetylation on α-synuclein function and aggregation is still not fully understood. This discovery raises new questions:
- How does the in vivo acetylation influence α-synuclein aggregation?
- What are the timescales of the fluctuations and the extent of residual secondary structure in the different species and how do these relate to the rate of fibril formation?
- Does oxidative stress increases α-synuclein aggregation?
We are characterizing the acetylated α-synuclein and comparing it to the non-acetylated form to try to elucidate the real aggregation mechanism that occurs in vivo.
α-synuclein interactions for amyloid inhibition:
β-synuclein is a neuroprotective protein co-localized with α-synuclein in brain cells. Despite the sequence similarity to α-synuclein this protein does not aggregate. Interestingly, β-synuclein not only does not aggregate by itself, but it can also inhibit α-synuclein aggregation. However, a simple single point mutation in β-synuclein sequence causes it to aggregate, leading to dementia with Lewy Bodies (DLB) disease. It is still unknown how β-synuclein is able to inhibit α-synuclein aggregation or even how its mutants induce β-synuclein to aggregate. Using a multidisciplinary approach our laboratory is trying to uncover the β-synuclein neuroprotective mechanism.
DJ-1 is an antioxidative protein that inhibitsαS aggregation through an unknown mechanism. Familial mutants of DJ-1 lead to early onset Parkinson's Disease possibly due to impairment of DJ-1 function. Our lab aims to elucidate specific interactions between DJ-1 and αS that may be involved in αS aggregation inhibition in order to gain novel insight into the role of DJ-1 in Parkinson's Disease pathology.