Biochemical Identification of a Linear Cholesterol-Binding Domain within Alzheimer's β Amyloid Peptide

Alzheimer's beta-amyloid (A beta) peptides can self-organize into amyloid pores that may induce acute neurotoxic effects in brain cells. Membrane cholesterol, which regulates A beta production and oligomerization, plays a key role in this process. Although several data suggested that cholesterol could bind to A beta peptides, the molecular mechanisms underlying cholesterol/A beta interactions are mostly unknown. On the basis of docking studies, we identified the linear fragment 22-35 of A beta as a potential cholesterol-binding domain. This domain consists of an atypical concatenation of polar/apolar amino acid residues that was not previously found in cholesterol-binding motifs. Using the Langmuir film balance technique, we showed that synthetic peptides A beta 17-40 and A beta 22-35, but not A beta 1-16, could efficiently penetrate into cholesterol monolayers. The interaction between A beta 22-35 and cholesterol was fully saturable and lipid-specific. Single-point mutations of Val-24 and Lys-28 in A beta 22-35 prevented cholesterol binding, whereas mutations at residues 29, 33, and 34 had little to no effect. These data were consistent with the in silico identification of Val-24 and Lys-28 as critical residues for cholesterol binding. We conclude that the linear fragment 22-35 of A beta is a functional cholesterol-binding domain that could promote the insertion of beta-amyloid peptides or amyloid pore formation in cholesterol-rich membrane domains.