The pore of the sodium channel binds a variety of clinically-important drugs (local anesthetics, antileptics and antiarrhythmics). The overall goal of this proposal is to define, at a detailed molecular and biophysical level, the determinants of drug binding to voltage-dependent Na channels. Substantial progress has been made during the initial funding period using a combination of mutagenesis, electrophysiology and quantitative modelling. We have discovered major differences in lidocaine sensitivity between cardiac and skeletal muscle sodium channels, defined interactions between local anesthetic block and slow inactivation gating processes, and mapped the crucial determinants for high-affinity tetrodotoxin block in the outer pore. We now propose to continue functional characterization of normal and mutant channels while obtaining hard structural information on the Na channel pore and related drug binding sites. The central goals of the application are the following: 1) to elucidate the origin of the differences in lidocaine sensitivity between cardiac and skeletal muscle Na channels; 2) to define determinants of selectivity, conductance and drug block which lie outside the conventional selectivity filter region; 3) to determine the impact of pore flexibility on gating and drug block; 4) to test a model of the secondary structure in which a pore helix precedes the selectivity filter in each domain; and 5) to solubilize and purify the Na channel alpha subunit and/or a truncated protein containing the critical determinants of Na channel pore function and drug/toxin block. Given the central importance of sodium channels in normal physiology and in diseases of excitability (arrhythmias, epilepsy and myotonic disorders of muscle), this work promises not only to be of intrinsic biological interest but also of practical value in pharmacology.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL052768-07
Application #
6183823
Study Section
Pharmacology A Study Section (PHRA)
Project Start
1994-08-01
Project End
2004-07-31
Budget Start
2000-08-01
Budget End
2001-07-31
Support Year
7
Fiscal Year
2000
Total Cost
$453,110
Indirect Cost
Name
Johns Hopkins University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
045911138
City
Baltimore
State
MD
Country
United States
Zip Code
21218
Yamagishi, Toshio; Xiong, Wei; Kondratiev, Andre et al. (2009) Novel molecular determinants in the pore region of sodium channels regulate local anesthetic binding. Mol Pharmacol 76:861-71
Azene, Ezana M; Sang, Dongpei; Tsang, Suk-Ying et al. (2005) Pore-to-gate coupling of HCN channels revealed by a pore variant that contributes to gating but not permeation. Biochem Biophys Res Commun 327:1131-42
Azene, Ezana M; Xue, Tian; Marban, Eduardo et al. (2005) Non-equilibrium behavior of HCN channels: insights into the role of HCN channels in native and engineered pacemakers. Cardiovasc Res 67:263-73
Tsang, Suk Ying; Tsushima, Robert G; Tomaselli, Gordon F et al. (2005) A multifunctional aromatic residue in the external pore vestibule of Na+ channels contributes to the local anesthetic receptor. Mol Pharmacol 67:424-34
Moore, Jennifer C; van Laake, Linda W; Braam, Stefan R et al. (2005) Human embryonic stem cells: genetic manipulation on the way to cardiac cell therapies. Reprod Toxicol 20:377-91
Wang, Kai; Xue, Tian; Tsang, Suk-Ying et al. (2005) Electrophysiological properties of pluripotent human and mouse embryonic stem cells. Stem Cells 23:1526-34
Xue, Tian; Cho, Hee Cheol; Akar, Fadi G et al. (2005) Functional integration of electrically active cardiac derivatives from genetically engineered human embryonic stem cells with quiescent recipient ventricular cardiomyocytes: insights into the development of cell-based pacemakers. Circulation 111:11-20
Li, Ronald A; Tomaselli, Gordon F (2004) Using the deadly mu-conotoxins as probes of voltage-gated sodium channels. Toxicon 44:117-22
Tsang, Suk Ying; Lesso, Heinte; Li, Ronald A (2004) Critical intra-linker interactions of HCN1-encoded pacemaker channels revealed by interchange of S3-S4 determinants. Biochem Biophys Res Commun 322:652-8
Xue, Tian; Ennis, Irene L; Sato, Kazuki et al. (2003) Novel interactions identified between micro -Conotoxin and the Na+ channel domain I P-loop: implications for toxin-pore binding geometry. Biophys J 85:2299-310

Showing the most recent 10 out of 38 publications