Emerging Concepts in Ion Channel Biophysics

Emerging Concepts in Ion Channel Biophysics

Tuesday Speaker Abstracts

The Activation of Glycine Channels: A Single-Channel Perspective Lucia Sivilotti. University College London, United Kingdom. No Abstract

α7 Nicotinic Receptors at the Single-Channel Level Cecilia Bouzat . Instituto de Investigaciones Bioquímicas de Bahía Blanca, Argentina.

The α7 nicotinic receptor (nAChR), which is the homomeric member of the family, is involved in neurological, psychiatric and inflammatory disorders. Enhancement of α7 function by positive allosteric modulators (PAMs) is a promising therapeutic strategy to improve cognitive deficits. PAMs have been classified by their macroscopic effects as type I, which enhance agonist- induced currents, and type II, which also decrease desensitization. To decipher the molecular basis underlying the different activities, we explored their effects on single-channel currents. We found that all PAMs enhance open-channel lifetime and produce episodes of successive openings of different durations. We identified the structural determinants for the allosteric action and the temperature sensitivity of potentiation by different PAMs. In addition to the homomeric α7, emerging evidence demonstrates the expression in brain of a novel heteromeric α7β2 receptor whose role and functional properties remain unknown. To establish its functional stoichiometry, we used two different experimental approaches, concatemeric technology and the electrical fingerprinting strategy with an α7 subunit tagged with a reporter mutation. Our results, which include the first report of single α7β2 channels, revealed the stoichiometry of functional heteromeric receptors, the contribution of β2 subunit to channel kinetics and ion permeability, and the action of α7 PAMs at α7β2. This information is required for differentiating homomeric from heteromeric receptors in native cells, for understanding their distinct roles, and opens doors for the development of specific ligands.

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