Protein Misfolding and Aggregation

National Heart, Lung, And Blood Institute

Investigators

Linked publications, trials & patents

Abstract

We have carried out detailed investigations of membrane interactions and amyloid formation of alpha-synuclein that have provided residue-specific information and molecular insights into the mechanism of aggregation. Due to the complexity of the amyloid problem, the tools with which we attack have included molecular biology, spectroscopy, electron microscopy, and mass spectrometry. Through this work, we are developing a chemical understanding in how specific biomolecular interactions and cellular environments modulate protein structure and aggregation propensity. We have made substantial contributions in the biophysical studies of alpha-synuclein–lipid interactions and the biochemical analysis of alpha-synuclein in the lysosome, a cellular organelle for proteolysis. Broadly, we are exploring how alpha-synuclein structure responds to the complex nature of cellular milieu and testing the hypothesis that its conformational plasticity is modulating its function. Understanding how chemical environments influence alpha-synuclein conformation is crucial in defining cellular scenarios where amyloid formation occurs and how the aggregation process may lead to deleterious consequences such as membrane deformation and remodeling. In addition, we are interested in understanding the effect of post-translational modifications and processing on alpha-synuclein fibril formation and structure as it is highly relevant to the proteostasis network. In recent studies, we are evaluating the effect of alpha-syn truncations on fibril polymorphism and seeding capabilities, both of which are pertinent to disease progression. Our detailed investigation of the lysosome-derived N-terminally truncated alpha-syn(66‒140) shows that individual charged residues can dictate fibril polymorphism and impact fibril propagation, and thus could be targeted to inhibit fibril seeding and spread as a therapeutic strategy. Through peptide mapping by mass spectrometry, we provide the first direct evidence that N-terminally truncated alpha-syn species found in Lewy bodies, pathological hallmarks of PD are lysosomal in origin. The identification of these truncations is evidence of not only partial proteolysis in the lysosome, but that these truncated species are involved in amyloid formation. Furthermore, the assignment of the specific proteases involved offers new targets for modulating alpha-syn homeostasis as levels of protease activity will dictate which truncations are generated and to what extent. Our work establishes a critical role for N-terminal residues in fibril formation and the importance of N-terminal truncations in Lewy bodies.