Design and Experimental Evaluation of a Peptide Antagonist against Amyloid β(1-42) Interactions with Calmodulin and Calbindin-D28k.

Amyloid β (Aβ(1-42)) oligomers have been linked to the pathogenesis of Alzheimer's disease (AD). Intracellular calcium (Ca) homeostasis dysregulation with subsequent alterations of neuronal excitability has been proposed to mediate Aβ neurotoxicity in AD. The Ca binding proteins calmodulin (CaM) and calbindin-D28k, whose expression levels are lowered in human AD brains, have relevant roles in neuronal survival and activity. In previous works, we have shown that CaM has a high affinity for Aβ(1-42) oligomers and extensively binds internalized Aβ(1-42) in neurons. In this work, we have designed a hydrophobic peptide of 10 amino acid residues: VFAFAMAFML (amidated-C-terminus amino acid) mimicking the interacting domain of CaM with Aβ (1-42), using a combined strategy based on the experimental results obtained for Aβ(1-42) binding to CaM and in silico docking analysis. The increase in the fluorescence intensity of Aβ(1-42) HiLyte-Fluor555 has been used to monitor the kinetics of complex formation with CaM and with calbindin-D28k. The complexation between nanomolar concentrations of Aβ(1-42) and calbindin-D28k is also a novel finding reported in this work. We found that the synthetic peptide VFAFAMAFML (amidated-C-terminus amino acid) is a potent inhibitor of the formation of Aβ(1-42):CaM and of Aβ(1-42):calbindin-D28k complexes.