Emerging Concepts in Ion Channel Biophysics

Emerging Concepts in Ion Channel Biophysics

Friday Speaker Abstracts

Lipid-protein Interactions in Model Membranes Andrea Alessandrini . CNR-Institute of Nanoscience, Modena, Italy.

Lipids and proteins work together to ensure that the biological membrane fulfills its functions. In this teamwork, lipids can affect the activity of protein ion channels both by the action of specific interactions and, indirectly, by their physical-chemical properties. Here we will concentrate on how the lipid bilayer assembled in different model systems could affect the action of membrane proteins by means of its peculiar thermodynamic and mechanical properties. We will show that the presence of a phase coexistence state in a lipid bilayer is able to significantly affect the conductance, the open probability and the dwell times of KcsA channels. We will use different model systems (Black Lipid Membranes, Supported Lipid Bilayers) and biophysical techniques (Differential Scanning Calorimetry, Atomic Force Microscopy) to present a consistent interpretation of the single channel data obtained by the voltage-clamp technique. In particular, we will illustrate, by Atomic Force Microscopy imaging and Spectroscopy, that KcsA channels prefer to partition into the liquid disordered phase and that this phase is characterized by a mechanical softening behavior in the transition region. We will also show other examples in which it emerges that the physical properties of lipid bilayers should be included in the analysis of the effects of exogenous molecules on ion channels. These examples include the action of neurosteroids and antimicrobial peptides on model lipid bilayers. Neurosteroids are modulators of ligand gated ion channels whose mode of action probably involves a strong interaction with the lipid bilayer, whereas antimicrobial peptides are relevant host-defense peptides strongly interacting with the membrane of bacteria and fungi. In both cases we will use different model systems such as GUVs and SLBs.

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