The long term goal of this research is to understand the molecular basis of cardiac excitability. In this proposal the investigators will study molecular determinants of voltage-gated K+ channel block by antiarrhythmic drugs and local anesthetics. Voltage-gated K+ channels play a crucial role in controlling cardiac excitability and repolarization and are the molecular target for many new antiarrhythmic agents. The investigators will utilize cloned subunits that are considered to contribute to native cardiac currents (Kv1.5, Kv4.2, HERG, KvLQT1). Increasing evidence indicates that the molecular architecture of the channel protein complex includes function-altering accessory subunits (beta subunits, minK) which may impact on drug binding. The hypotheses to be tested include that specific pore residues in the S6 segment are involved in binding of open channel blocking drugs. Furthermore, the investigators will test whether hydrophobic interactions determine affinity and stereoselectivity of drug block. In addition, they will test whether amino acid differences in the pore lining segments explain isoform-specific affinities for antiarrhythmic drugs. They will address whether antiarrhythmic drugs utilize a conserved receptor site for inactivating beta-subunits by testing for mutual interactions in the inner mouth of the pore. Finally, they will test whether the intrinsic pharmacology of KcLQT1 is altered when it co-assembles with the minK subunit to reconstitute the native current Iks. In these studies they will use contemporary techniques of molecular biology to modify channel structure and a variety of patch clamp techniques to test for specific functional changes. The results will be interpreted in terms of mathematical and thermodynamic models for channel gating and drug action. These studies will address molecular determinants of drug block and drug interactions with activation and inactivation gates . The information gained from this project will expand our knowledge of the molecular pharmacology of these important channels, which may ultimately result in improved understanding of mechanisms of arrhythmias and the development of better antiarrhythmic treatments.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL059689-03
Application #
6013708
Study Section
Pharmacology A Study Section (PHRA)
Project Start
1998-01-01
Project End
2003-02-28
Budget Start
2000-03-01
Budget End
2001-02-28
Support Year
3
Fiscal Year
2000
Total Cost
$113,576
Indirect Cost
Name
University of Antwerp
Department
Type
DUNS #
City
Antwerpen
State
Country
Belgium
Zip Code
2020
Ottschytsch, Natacha; Raes, Adam L; Timmermans, Jean-Pierre et al. (2005) Domain analysis of Kv6.3, an electrically silent channel. J Physiol 568:737-47
Labro, Alain J; Raes, Adam L; Snyders, Dirk J (2005) Coupling of voltage sensing to channel opening reflects intrasubunit interactions in kv channels. J Gen Physiol 125:71-80
Paulussen, Aimee D C; Raes, Adam; Jongbloed, Roselie J et al. (2005) HERG mutation predicts short QT based on channel kinetics but causes long QT by heterotetrameric trafficking deficiency. Cardiovasc Res 67:467-75
Labro, Alain J; Raes, Adam L; Bellens, Iris et al. (2003) Gating of shaker-type channels requires the flexibility of S6 caused by prolines. J Biol Chem 278:50724-31
Van Hoorick, Diane; Raes, Adam; Keysers, Wim et al. (2003) Differential modulation of Kv4 kinetics by KCHIP1 splice variants. Mol Cell Neurosci 24:357-66
Rich, Thomas C; Yeola, Sarita W; Tamkun, Michael M et al. (2002) Mutations throughout the S6 region of the hKv1.5 channel alter the stability of the activation gate. Am J Physiol Cell Physiol 282:C161-71
Paulussen, Aimee; Raes, Adam; Matthijs, Gert et al. (2002) A novel mutation (T65P) in the PAS domain of the human potassium channel HERG results in the long QT syndrome by trafficking deficiency. J Biol Chem 277:48610-6
Snyders, D J (1999) Structure and function of cardiac potassium channels. Cardiovasc Res 42:377-90