C-terminal truncation modulates α-Synuclein's cytotoxicity and aggregation by promoting the interactions with membrane and chaperone

alpha-Synuclein (alpha-syn) is the main protein component of Lewy bodies, the major pathological hallmarks of Parkinson's disease (PD). C-terminally truncated alpha-syn is found in the brain of PD patients, reduces cell viability and tends to form fibrils. Nevertheless, little is known about the mechanisms underlying the role of C-terminal truncation on the cytotoxicity and aggregation of alpha-syn. Here, we use nuclear magnetic resonance spectroscopy to show that the truncation alters alpha-syn conformation, resulting in an attractive interaction of the N-terminus with membranes and molecular chaperone, protein disulfide isomerase (PDI). The truncated protein is more toxic to mitochondria than full-length protein and diminishes the effect of PDI on alpha-syn fibrillation. Our findings reveal a modulatory role for the C-terminus in the cytotoxicity and aggregation of alpha-syn by interfering with the N-terminus binding to membranes and chaperone, and provide a molecular basis for the pathological role of C-terminal truncation in PD pathogenesis. C-terminal truncation of a-syn results in a more extended and exposed conformation, providing further insight into the pathological role of this truncation event in the progression of Parkinson's disease.