Gap junction (GJ) channels, which are multimers of connexin (Cx) proteins, mediate direct cell-cell transfer of ions and metabolites and are required for propagation of excitation in the heart. This project is based on our recent discovery of a new cardiac Cx (mCx30.2) and data showing that knockout of mCx30.2 accelerates conduction in the atrioventricular (AV) node and reduces the Wenckebach period. mCx30.2 is found to be expressed not only in the heart but also in many other organs and tissues including neurons. The experiments will combine immunohistochemical and biophysical characterization of Cx-based channels in cardiomyocytes and exogenously expressed in mammalian cell lines.
Specific Aim 1 focuses on gating and permeability properties of GJ channels and unapposed hemichannels formed of mCx30.2. We will determine whether two gates, 'fast'and 'slow', are also present in mCx30.2 GJs. We will determine the extent to which mCx30.2 hemichannels influence metabolic exchange across the plasma membrane.
In Specific Aim 2, we will determine gating and permeability properties of heterotypic gap junction channels formed from cardiac Cxs. To establish whether mCx30.2 exhibits a dominant negative effect on junctional communication and slows atrioventricular conduction, we will determine whether mCx30.2 together with other cardiac connexins can oligomerize into heteromeric connexons (hemichannels) and whether these connexons can form functional heteromeric hemichannels and cell-cell channels. To determine the domains underlying the distinctive biophysical properties of mCx30.2 channels, we will examine chimeras formed of mCx30.2 and Cx43.
In Specific Aim 3, we will examine an expression pattern of mCx30.2 and other cardiac Cxs in the AV-nodal region and correlate these data with measurements of passive electrical properties, excitability, refractoriness and resting potential to find why deletion of mCx30.2 accelerates AV conduction and reduces the Wenckebach period. In isolated cardiomyocytes of wild type and transfected with mCx30.2, we will examine whether homotypic, heterotypic and heteromeric GJ channels containing mCx30.2 form and function. We will determine whether mCx30.2 hemichannels are functional in cardiomyocytes and whether they contribute to slow propagation of excitation in the AV node and protection of ventricles from over excitation during atrial tachyarrhythmia.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL084464-04
Application #
7866533
Study Section
Electrical Signaling, Ion Transport, and Arrhythmias Study Section (ESTA)
Program Officer
Przywara, Dennis
Project Start
2007-08-15
Project End
2012-06-30
Budget Start
2010-07-01
Budget End
2012-06-30
Support Year
4
Fiscal Year
2010
Total Cost
$415,000
Indirect Cost
Name
Albert Einstein College of Medicine
Department
Neurosciences
Type
Schools of Medicine
DUNS #
110521739
City
Bronx
State
NY
Country
United States
Zip Code
10461
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Marandykina, Alina; Palacios-Prado, Nicolás; Rimkut?, Lina et al. (2013) Regulation of connexin36 gap junction channels by n-alkanols and arachidonic acid. J Physiol 591:2087-101
Palacios-Prado, Nicolás; Hoge, Gregory; Marandykina, Alina et al. (2013) Intracellular magnesium-dependent modulation of gap junction channels formed by neuronal connexin36. J Neurosci 33:4741-53
Wang, Nan; De Vuyst, Elke; Ponsaerts, Raf et al. (2013) Selective inhibition of Cx43 hemichannels by Gap19 and its impact on myocardial ischemia/reperfusion injury. Basic Res Cardiol 108:309
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Lübkemeier, Indra; Requardt, Robert Pascal; Lin, Xianming et al. (2013) Deletion of the last five C-terminal amino acid residues of connexin43 leads to lethal ventricular arrhythmias in mice without affecting coupling via gap junction channels. Basic Res Cardiol 108:348
Lübkemeier, Indra; Andrié, René; Lickfett, Lars et al. (2013) The Connexin40A96S mutation from a patient with atrial fibrillation causes decreased atrial conduction velocities and sustained episodes of induced atrial fibrillation in mice. J Mol Cell Cardiol 65:19-32
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Palacios-Prado, Nicolás; Bukauskas, Feliksas F (2012) Modulation of metabolic communication through gap junction channels by transjunctional voltage; synergistic and antagonistic effects of gating and ionophoresis. Biochim Biophys Acta 1818:1884-94
Wang, Nan; De Bock, Marijke; Antoons, Gudrun et al. (2012) Connexin mimetic peptides inhibit Cx43 hemichannel opening triggered by voltage and intracellular Ca2+ elevation. Basic Res Cardiol 107:304

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