The contractile function of the heart is controlled by the electrical activity initiated in the sinoatrial node and propagated throughout the heart. Specific ion channels generate the action potential and are regulated directly by membrane voltage or by ionic blockade. The excitatory inward and inhibitory outward ionic currents associated with the cardiac action potential are directly modulated by membrane voltage while the background potassium current (IK1) rectifies upon membrane depolarization due to intracellular polyamine (e.g. spermine) block of this anomalous inward rectifier potassium channel. Gap junctions are typically open at rest and, hence, do not require voltage dependent activation. {This project has provided new evidence indicating} that the transjunctional voltage-dependent inactivation possesses rapid kinetics (< 20 ms) at peak action potential voltages that can produce 40-60% reductions in junctional conductance during the duration of the action potential plateau. These same investigations reported the reactivation (recovery) {and facilitation} of the inactivated junctional conductance during the repolarization and early diastolic phases of the ventricular action potential. Slowed conduction is a hallmark property of reentrant arrhythmias and triggered activity arising during or after repolarization are likely mechanisms for premature extrasystoles that initiate reentrant tachycardia and eventual fibrillation. We will investigate the regulation of atrial and ventricular gap junctions and specific connexin gap junctions formed by connexins -40, -43, and -45 by pacemaker, atrial, and ventricular action potential waveforms at different rates of stimulation ranging from 240 (tachycardia) to 30 (bradycardia) beats/min. The same polyamines that modulate lK1 were shown by this laboratory to specifically block connexin40, but not connexin43 gap junctions. Thus, we have demonstrated previously unknown regulatory mechanisms for gap junctional communication that are also associated with the modulation of cardiac excitability. We will continue to examine the molecular basis for ionic blockade by intracellular polyamines or tetra-alkylammonium ions, the transjunctional voltage gating properties, and the gap junction channel conductance using site-directed mutagenesis of distinct connexin40 and connexin43 specific sequences. Several connexin amino terminal {and other} mutations already {proposed} will be further examined to {define} the connexin-specific {determinants} of {transjunctional voltage gating}, channel conductance, ion permeation, and occlusion. These unique cytosolic and pore- forming domain sequences represent possible therapeutic targets for regulating cardiovascular gap junctional communication.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL042220-16
Application #
7101011
Study Section
Electrical Signaling, Ion Transport, and Arrhythmias Study Section (ESTA)
Program Officer
Wang, Lan-Hsiang
Project Start
1988-09-30
Project End
2009-06-30
Budget Start
2006-07-01
Budget End
2007-06-30
Support Year
16
Fiscal Year
2006
Total Cost
$259,750
Indirect Cost
Name
Upstate Medical University
Department
Pharmacology
Type
Schools of Medicine
DUNS #
058889106
City
Syracuse
State
NY
Country
United States
Zip Code
13210
Zou, Juan; Salarian, Mani; Chen, Yanyi et al. (2017) Direct visualization of interaction between calmodulin and connexin45. Biochem J 474:4035-4051
Reddish, Florence N; Miller, Cassandra L; Gorkhali, Rakshya et al. (2017) Calcium Dynamics Mediated by the Endoplasmic/Sarcoplasmic Reticulum and Related Diseases. Int J Mol Sci 18:
Zou, Juan; Jiang, Jason Y; Yang, Jenny J (2017) Molecular Basis for Modulation of Metabotropic Glutamate Receptors and Their Drug Actions by Extracellular Ca2. Int J Mol Sci 18:
Turaga, Ravi Chakra; Yin, Lu; Yang, Jenny J et al. (2016) Rational design of a protein that binds integrin ?v?3 outside the ligand binding site. Nat Commun 7:11675
Veenstra, Richard D (2016) Establishment of the Dual Whole Cell Recording Patch Clamp Configuration for the Measurement of Gap Junction Conductance. Methods Mol Biol 1437:213-31
Xu, Qin; Lin, Xianming; Matiukas, Arvydas et al. (2016) Specificity of the connexin W3/4 locus for functional gap junction formation. Channels (Austin) 10:453-65
Hsieh, Ying-Hsin; Zou, Juan; Jin, Jin-Shan et al. (2015) Monitoring channel activities of proteoliposomes with SecA and Cx26 gap junction in single oocytes. Anal Biochem 480:58-66
Lin, Xianming; Xu, Qin; Veenstra, Richard D (2014) Functional formation of heterotypic gap junction channels by connexins-40 and -43. Channels (Austin) 8:433-43
Zou, Juan; Salarian, Mani; Chen, Yanyi et al. (2014) Gap junction regulation by calmodulin. FEBS Lett 588:1430-8
Patel, Dakshesh; Gemel, Joanna; Xu, Qin et al. (2014) Atrial fibrillation-associated connexin40 mutants make hemichannels and synergistically form gap junction channels with novel properties. FEBS Lett 588:1458-64

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