This Article Full Text Full Text (PDF) All Versions of this Article: biophysj.104.049338v1 87/6/3814    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Mead, F. C. Articles by Williams, A. J. Search for Related Content PubMed PubMed Citation Articles by Mead, F. C. Articles by Williams, A. J.

Electrostatic Mechanisms Underlie Neomycin Block of the Cardiac Ryanodine Receptor Channel (RyR2)

Cardiac Medicine, National Heart and Lung Institute, Faculty of Medicine, Imperial College London, London, United Kingdom

Correspondence: Address reprint requests to Fiona C. Mead, Cardiac Medicine, National Heart and Lung Institute, Faculty of Medicine, Imperial College London, London SW3 6LY, U.K. E-mail: f.mead{at}imperial.ac.uk.

Neomycin is a large, positively charged, aminoglycoside antibiotic that has previously been shown to induce a voltage-dependent substate block in the cardiac isoform of the ryanodine receptor (RyR2). It was proposed that block involved an electrostatic interaction between neomycin and putative regions of negative charge in both the cytosolic and luminal mouths of the pore. In this study, we have attempted to screen charge by increasing potassium concentration in single-channel experiments. Neomycin block is apparent at both cytosolic and luminal faces of the channel in all K⁺ concentrations tested and alterations in K⁺ concentration have no effect on the amplitudes of the neomycin-induced substates. However, the kinetics of both cytosolic and luminal block are sensitive to changes in K⁺ concentration. In both cases increasing the K⁺ concentration leads to an increase in dissociation constant (K_D). Underlying these changes are marked increases in rates of dissociation (k_off), with little change in rates of association (k_on). The increase in k_off is more marked at the luminal face of the channel. Changes in K⁺ concentration also result in alterations in the voltage dependence of block. We have interpreted these data as supporting the proposal that neomycin block of RyR2 involves electrostatic interactions with the polycation forming a poorly fitting "plug" in the mouths of the conduction pathway. These observations emphasize the usefulness of neomycin as a probe for regions of charge in both the cytosolic and luminal mouths of the RyR2 pore.

This article has been cited by other articles:

				J. Scholz-Starke, A. Carpaneto, and F. Gambale On the Interaction of Neomycin with the Slow Vacuolar Channel of Arabidopsis thaliana J. Gen. Physiol., February 27, 2006; 127(3): 329 - 340. [Abstract] [Full Text] [PDF]

				L. Xu, Y. Wang, D. Gillespie, and G. Meissner Two Rings of Negative Charges in the Cytosolic Vestibule of Type-1 Ryanodine Receptor Modulate Ion Fluxes Biophys. J., January 15, 2006; 90(2): 443 - 453. [Abstract] [Full Text] [PDF]