Probing amphotericin B single channel activity by membrane dipole modifiers

Area of Science:

• Membrane biophysics
• Ion channel modulation
• Antifungal drug mechanisms

Background:

• Amphotericin B forms pores in sterol-containing membranes, crucial for its antifungal activity.
• Membrane dipole potential influences ion channel function.
• Sterol composition affects membrane properties and drug interactions.

Purpose of the Study:

• To investigate how dipole modifiers and structural analogs affect amphotericin B single channel activity.
• To elucidate the role of membrane dipole potential and sterol type in channel modulation.
• To understand the relationship between sterol concentration, membrane fluidity, and channel kinetics.

Main Methods:

• Single channel electrophysiology in planar lipid bilayers.
• Incorporation of sterols (cholesterol, ergosterol) and dipole modifiers (phloretin, quercetin, styryl dyes, 5α-androstan-3β-ol).
• Measurement of channel conductance, current amplitude, and dwell time.

Main Results:

• Phloretin and quercetin modulated amphotericin B channel conductance differently depending on the sterol type.
• Styryl dyes increased the current amplitude of amphotericin B pores.
• 5α-androstan-3β-ol increased channel conductance concentration-dependently.
• Channel dwell time increased with sterol concentration and was higher in cholesterol-containing membranes.

Conclusions:

• Observed effects are primarily attributed to changes in membrane dipole potential.
• Specific interactions between modifiers and sterol-polyene complexes may also play a role.
• Membrane fluidity, influenced by sterol composition, affects amphotericin B channel association/dissociation dynamics.