Analysis of Interaction Characteristics Between Amyloid β and Lecanemab by HDX‐MS

Abstract

AbstractBackgroundSoluble amyloid‐β (Aβ) aggregates including protofibrils (PFs) have been reported to be more toxic than insoluble fibrils. Recently, pharmaceutical antibodies targeting these soluble Aβ aggregates have been developed. The structural dynamics and heterogeneity of soluble Aβ aggregates have made it difficult to analyze the structural characteristics and tertiary structure. To investigate conformational recognition of lecanemab to Aβ aggregates, the structural characteristics of Aβ PFs and their change upon binding to lecanemab, an antibody with preferential binding to Aβ protofibrils, were studied using hydrogen‐deuterium exchange mass spectrometry (HDX‐MS).MethodAβ (1‐42) PFs were prepared in vitro. The hydrogen/deuterium (H/D) exchange status for Aβ (1‐42) PFs and monomeric Aβ (1‐40) were studied by HDX‐MS in phosphate buffered saline (PBS) to explore characteristics of their regional structural dynamics. The effects of the anti–Aβ PF antibody lecanemab on H/D status of Aβ (1‐42) PFs and monomeric Aβ (1‐40) were studied to explore the structural basis for the characteristics of antibody‐ Aβ interaction and specificity against Aβ PFs.ResultAβ (1‐42) PFs were more protected from H/D exchange throughout the molecule than monomeric Aβ (1‐40), though the N‐terminal and the mid region of Aβ still showed relatively higher H/D exchange in Aβ (1‐42) PFs. Upon interaction with lecanemab, the mid region of Aβ (1‐42) PFs was also protected further in addition to the N‐terminal region, and its protection level of Aβ (1‐42) PFs was higher than monomeric Aβ (1‐40). The higher protection from H/D exchange both on N‐terminal and mid regions of Aβ PFs is considered to be characteristics of interaction between Aβ (1‐42) PFs and lecanemab.ConclusionThe results indicate that the mid region of Aβ has relatively high flexibility in PFs in addition to N‐terminal region. The mid region is suggested to be involved in the interaction with lecanemab as well as its N‐terminal region, and the conformational epitope formation was expected, though there are still possibility of structural change in the mid region upon lecanemab binding. The results indicated that the combinational action on the N‐terminal and mid regions of Aβ are involved in the modulation of Aβ PFs by lecanemab.