Lysine residues at the first and second KTKEGV repeats mediate α-Synuclein binding to membrane phospholipids

While alpha-Synuclein (alpha-Syn) is mainly detected as a cytosolic protein, a portion of it is recovered bound to membranes. It is suggested that binding to membrane phospholipids controls alpha-Syn structure, physiology and pathogenesis. We aimed at investigating the role, of the positive charged lysine residues at the KTKEGV repeat motif, in mediating alpha-Syn associations with membrane phospholipids and in alpha-Syn oligomerization and aggregation. Specifically, two positive lysine(K) residues were replaced with two negative glutamic acid (E) residues at either the first or second KTKEGV repeat motifs. The effect of these mutations on membrane binding was determined by a quantitative phospholipid ELISA assay and compared to wild-type alpha-Syn and to the Parkinson's disease-causing mutations, A30P, E46K and A53T. We found that the K to E substitutions affected alpha-Syn binding to phospholipids. In addition, K to E substitutions resulted in a dramatically lower level of soluble alpha-Syn oligomers and larger intracellular inclusions. Together, our results suggest a critical role for lysine residues at the N-terminal repeat domain in the pathophysiology of alpha-Syn. (C) 2014 Elsevier Inc. All rights reserved.