Capsaicin interaction with TRPV1 channels in a lipid bilayer: molecular dynamics simulation

Area of Science:

• Biophysics
• Molecular Biology
• Computational Chemistry

Background:

• Transient receptor potential vanilloid subtype 1 (TRPV1) is a key ion channel in pain signaling and capsaicin (hot chili pepper compound) binding.
• Recent TRPV1 structures suggest ligand binding sites within the S1-S4 domain, but the lipid bilayer's role is unclear.

Purpose of the Study:

• To investigate the role of the lipid bilayer in capsaicin binding to TRPV1.
• To explore capsaicin's dynamic behavior and accessibility to the TRPV1 binding site.

Main Methods:

• Molecular dynamics simulations of capsaicin in a lipid bilayer and with TRPV1 S1-S4 helices.
• Calculation of the potential of mean force to determine capsaicin's free energy profile within the bilayer.
• Simulations with capsaicin in various starting positions (aqueous phase, lipid, docked).

Main Results:

• Capsaicin exhibits a preferred interfacial localization within the lipid bilayer.
• A capsaicin molecule was observed flipping from the extracellular to the intracellular leaflet, enabling access to the intracellular TRPV1 binding site.
• A nontrivial but surmountable energy barrier exists for capsaicin flipping between bilayer leaflets.
• Y511, crucial for capsaicin binding, shows a distribution similar to capsaicin's aromatic group.
• Stable interactions were observed when simulations started from the cytosolic aqueous phase or with a docked pose, but not from within the bilayer.

Conclusions:

• The lipid bilayer plays a dynamic role in capsaicin binding to TRPV1.
• Capsaicin's ability to flip between lipid leaflets is a significant mechanism for accessing the intracellular binding site.
• Understanding these dynamics provides insights into TRPV1 activation and drug design.