Dynamic lipid interactions in the plasma membrane Na⁺,K⁺-ATPase

Area of Science:

• Biochemistry
• Membrane Biology
• Computational Biophysics

Background:

• The function of ion-transporting Na+,K+-ATPase is critically dependent on its surrounding lipid environment.
• Known lipid interaction sites (A and B) influence protein activation and stabilization, while a proposed inhibitory site (C) lacks precise experimental confirmation.
• The impact of disease mutations on these lipid-protein interactions remains largely uncharacterized.

Purpose of the Study:

• To investigate wild-type and disease mutant lipid-protein interactions of human Na+,K+-ATPase α1β1FXYD in a plasma membrane model.
• To identify and characterize lipid interaction sites, including potential novel inhibitory sites.
• To understand how disease-associated mutations affect lipid interactions and protein function.

Main Methods:

• Simulated homology models of human Na+,K+-ATPase α1β1FXYD in E1 and E2 states.
• Utilized an asymmetric, multicomponent plasma membrane model for simulations.
• Analyzed lipid-protein interactions for both wild-type and mutant forms.

Main Results:

• Simulated wild-type lipid interactions at sites A and B confirmed experimental findings.
• The proposed inhibitory site C was not dominated by inhibitory lipids; instead, two novel inhibitory lipid sites were identified on the extracellular side, along with a cytoplasmic CHL-binding site.
• Three disease mutations (Leu302Arg, Glu840Arg, Met859Arg) at the lipid-protein interface caused significant alterations in lipid interactions.

Conclusions:

• Lipid interactions with Na+,K+-ATPase are highly dependent on the protein's conformational state (E1/E2).
• Disease mutations within the lipid interface can profoundly disrupt these interactions, potentially contributing to genetic disorders.
• Identified novel inhibitory lipid-binding sites offer new perspectives on Na+,K+-ATPase regulation and inhibition.