Molecular Basis for Mambalgin-2 Interaction with Heterotrimeric α-ENaC/ASIC1a/γ-ENaC Channels in Cancer Cells

Area of Science:

• Ion channel biophysics
• Cancer biology
• Neuropharmacology

Background:

• Cancer progression involves microenvironmental acidification, prompting tumor cells to adapt via acid-sensing ion channels.
• The heterotrimeric α-ENaC/ASIC1a/γ-ENaC channel is a tumor-specific acid-sensing channel, representing a potential therapeutic target.
• Mambalgin-2, a venom-derived peptide, shows selective inhibition of this heterotrimer over homotrimeric ASIC1a, but the molecular basis was unclear.

Purpose of the Study:

• To elucidate the molecular mechanism behind mambalgin-2's selective inhibition of the α-ENaC/ASIC1a/γ-ENaC heterotrimeric channel.
• To investigate the structural basis for mambalgin-2's interaction with both heteromeric and homomeric acid-sensing ion channels.
• To explore novel allosteric regulation modes in ENaC channels and inform cancer treatment strategies.

Main Methods:

• Molecular modeling of mambalgin-2 complexes with α-ENaC/ASIC1a/γ-ENaC and ASIC1a channels.
• Molecular dynamics (MD) simulations to predict binding modes and differences.
• Site-directed mutagenesis and electrophysiology to validate the role of specific mambalgin-2 regions.

Main Results:

• The 'head' loop region of mambalgin-2 is crucial for its interaction with the heterotrimeric channel but not the homotrimeric channel.
• A novel allosteric regulation mechanism involving the thumb domain of ASIC1a and the palm domain of γ-ENaC was proposed for ENaC channels.
• Mambalgin-2's higher efficacy against the heterotrimer was structurally and functionally confirmed.

Conclusions:

• The study clarifies mambalgin-2 selectivity, identifying key interactions for heterotrimer inhibition.
• A new allosteric regulatory pathway in ENaC channels provides deeper understanding of channel function.
• Findings support the development of targeted cancer therapies by modulating tumor-specific acid-sensing ion channels.