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

Amyloid β 1-42 (Aβ(1-42)) oligomers have been linked to the pathogenesis of Alzheimer's disease (AD). Intracellular calcium (Ca 2+ ) homeostasis dysregulation with subsequent alterations of neuronal excitability has been proposed to mediate Aβ neurotoxicity in AD. The Ca 2+ 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 TM -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.