Voltage-dependent K (Kv) channels control action potential duration and firing frequency in excitable membranes, and, therefore, m targets of drugs that regulate excitability. The availability of Kv clones makes possible a molecular approach to drug sites and mechanisms. The objective of this research is to elucidate the structural relationships between drug binding sites and other functional domains of the Kv polypeptide, such M the gating, ion conduction and selectivity regions that are critical regulators of drug action.
The specific aims are to: (1) map the solvent accessible residues in the external and internal mouths of the pore that are critical for ion conductance and blockade; (2) investigate the mechanisms and sites whereby highly conserved polar, aromatic and charged residues which line the pore, influence ion selectivity, gating and drug blockade; (3) determine the functional relationships between critical regions by identifying residues that couple voltage-dependent gating with the pore. The hypotheses to be tested are that: (1) the inner mouth is a mosaic structure formed by contributions from several transmembrane and linker segments, whereas the outer mouth is specified in its entirety by a single linker segment (S5-S6 linker) (Aim l); (2) the rectification, conduction, selectivity and drug blockade in the pore are determined by a combination of multiple K selective ion binding sites associated with specific side chains within the narrow tunnel region of the pore and long-range electrostatic forces contributed by charged residues in the wide mouths at either end of the pore (Aim 2); (3) critical residues associated with 4AP and ThA blockade at the inner mouth are coupled to the voltage.sensing transmembrane segment (s4) which controls activation gating, such that access to the binding sites is gating-dependent, where- residues in the pore region which specify ion selectivity and external TEA block are independent of the gating mechanism (Aim 3).

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS029473-09
Application #
2771934
Study Section
Pharmacology A Study Section (PHRA)
Program Officer
Kitt, Cheryl A
Project Start
1991-09-30
Project End
2000-08-31
Budget Start
1998-09-01
Budget End
2000-08-31
Support Year
9
Fiscal Year
1998
Total Cost
Indirect Cost
Name
Case Western Reserve University
Department
Physiology
Type
Schools of Medicine
DUNS #
077758407
City
Cleveland
State
OH
Country
United States
Zip Code
44106
Klemic, K G; Kirsch, G E; Jones, S W (2001) U-type inactivation of Kv3.1 and Shaker potassium channels. Biophys J 81:814-26
Kirsch, G E (1999) Ion channel defects in cardiac arrhythmia. J Membr Biol 170:181-90
Klemic, K G; Shieh, C C; Kirsch, G E et al. (1998) Inactivation of Kv2.1 potassium channels. Biophys J 74:1779-89
Dumaine, R; Kirsch, G E (1998) Mechanism of lidocaine block of late current in long Q-T mutant Na+ channels. Am J Physiol 274:H477-87
Kramer, J W; Post, M A; Brown, A M et al. (1998) Modulation of potassium channel gating by coexpression of Kv2.1 with regulatory Kv5.1 or Kv6.1 alpha-subunits. Am J Physiol 274:C1501-10
Chen, S; Hartmann, H A; Kirsch, G E (1997) Cysteine mapping in the ion selectivity and toxin binding region of the cardiac Na+ channel pore. J Membr Biol 155:11-25
Pascual, J M; Shieh, C C; Kirsch, G E et al. (1997) Contribution of the NH2 terminus of Kv2.1 to channel activation. Am J Physiol 273:C1849-58
Shieh, C C; Klemic, K G; Kirsch, G E (1997) Role of transmembrane segment S5 on gating of voltage-dependent K+ channels. J Gen Physiol 109:767-78
Post, M A; Kirsch, G E; Brown, A M (1996) Kv2.1 and electrically silent Kv6.1 potassium channel subunits combine and express a novel current. FEBS Lett 399:177-82
Dumaine, R; Wang, Q; Keating, M T et al. (1996) Multiple mechanisms of Na+ channel--linked long-QT syndrome. Circ Res 78:916-24

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