Interaction Interface of Aβ42 with Human Na,K-ATPase Studied by MD and ITC and Inhibitor Screening by MD

Abstract

Alzheimer's disease (AD) is a neurodegenerative disease accompanied by progressive cognitive and memory dysfunction due to disruption of normal electrotonic properties of neurons and neuronal loss. The Na,K-ATPase interaction with beta amyloid (Aβ) plays an important role in AD pathogenesis. It has been shown that Na,K-ATPase activity in the AD brain was significantly lower than those in age-matched control brain. The interaction of Aβ₄₂ with Na,K-ATPase and subsequent oligomerization leads to inhibition of the enzyme activity. In this study interaction interfaces between three common Aβ₄₂ isoforms, and different conformations of human Na,K-ATPase (α1β1) have been obtained using molecular modeling, including docking and molecular dynamics (MD). Interaction sites of Na,K-ATPase with Aβ₄₂ are localized between extracellular parts of α- and β- subunits and are practically identical for Na,K-ATPase at different conformations. Thermodynamic parameters for the formation of Na,K-ATPase:Aβ₄₂ complex at different conformations acquired by isothermal titration calorimetry (ITC) are similar, which is in line with the data of molecular modeling. Similarity of Na,K-ATPase interaction interfaces with Aβ in all conformations allowed us to cross-screen potential inhibitors for this interaction and find pharmaceutical compounds that could block it.

Keywords: Alzheimer’s disease; Na,K-ATPase; beta amyloid; binding constants; conformations of Na,K-ATPase; interaction inhibitors screening; interaction interface; isothermal titration calorimetry; molecular dynamics; ouabain.

Figure 1

The workflow scheme for the inhibitor search for the Aβ₄₂–Na,K-ATPase interaction by computer modeling.

Figure 2

Superposition of Na,K-ATPase E1P, E2P states and Na,K-ATPase in complex with ouabain (OBN) embedded in DDPC membrane after 50 ns of MD (A). The Na,K-ATPase structure is shown in (B–D) for E1P (B), E2P (C), and OBN (D) states. The residues whose positions differed between conformations are shown with green (E1P), cyan (E2P), and magenta (OBN). Ouabain atoms are shown in orange.

Figure 3

The number of intermolecular contacts with three Aβ isoforms after 30–50 ns of MD in E1P (A), E2P (B), and OBN (C) conformations of α1 isoform of human Na, K-ATPase. The data for each conformation are summarized for 15 complexes that participated in the MD.