GAP JUNCTIONS AND IONIC CURRENTS IN DEVELOPING HEART

Summary

Principal Investigator: Jenny J Yang
Abstract: DESCRIPTION (provided by applicant): Gap junctions provide for the homeostasis of nearly every tissue by metabolically, chemically, and electrically coupling the cells into a functional syncytium. The heart is the only organ that requires gap junctions for rapid electrical transmission of the heartbeat that is essential to function for every second of life. Of the over twenty identified mammalian connexin genes, only four connexins, connexin40 (Cx40), connexin43 (Cx43), connexin45 (Cx45), and connexin 31.9 (Cx31.9), are expressed in the heart. It is not fully known how the differential functional properties of Cx40, Cx43, Cx45, and Cx31.9 contribute to the normal function of the heart. This project seeks to understand how the connexins form an intercellular ion channel and the molecular basis for the selective ionic conductance and permeability differences between Cx40 and Cx43. Utilizing a structure-function mutagenesis approach, we will provide new detailed information about the contribution of the cardiac connexin cytoplasmic amino terminal (NT) domain residues make to the formation of the cytoplasmic pore and its blockade by endogenous intracellular polyamines. Many of these loci have been associated with disease-causing connexin mutations such as oculodigitodental dysplasia (ODDD) and ascertaining the function of these specific amino acid loci sights will provide further insights into the possible disease-causing consequences of these connexin mutations. We have also produced novel connexin-mimetic NT peptides that exhibit specific inhibitory properties of heteromeric Cx43-Cx40 channel function or the blockade of Cx40 gap junctions by spermine. In a new final aim of this proposal, we demonstrate the functional significance of recently predicted Cx43 calmodulin (CaM) binding domain to the calcium regulation of myocardial gap junctions formed predominantly by Cx43 and Cx40. We further propose to examine the effect that ODDD mutations occurring on the second half of the connexin cytoplasmic loop (CL) domain might have on the newly identified intracellular Ca2?dependent gating mechanism of Cx43. Together, these connexin structural and functional approaches will provide new mechanistic insights into the contributions that the NT and CL domains make to the channel conductance, selective ion permeability, selective polyamine blockade, calcium open-closed gating, and functional consequences of genetically-linked human connexin disease mutations such as ODDD. These multiple mechanistic approaches to Cx40 and Cx43 gap junction channel function will identify new sub domains on the connexin molecules as possible selective therapeutic targets for future drug development. PUBLIC HEALTH RELEVANCE: The synchronized contraction of the heartbeat depends on the rapid electrical activation of the cardiac muscle carried by gap junctions. Connexin40 (Cx40) and connexin43 (Cx43) form the vast majority of these atrial and ventricular gap junctions. This project will determine the how these two proteins conduct electrical current, the molecular basis for their different conductance properties, and their differential block by intracellular polyamines, how these cell-to-cell channels are regulated open or closed by intracellular calcium and calmodulin, and effect that disease-causing mutations have on these vital functional properties. These combined experimental approaches will identify new molecular targets on the connexin proteins for the possible pharmacological modulation of cardiac electrical communication by new therapeutic agents.
Funding Period: 1988-09-30 - 2014-06-30
more information: NIH RePORT

Top Publications

  1. pmc An amino-terminal lysine residue of rat connexin40 that is required for spermine block
    Xianming Lin
    Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
    J Physiol 570:251-69. 2006
  2. pmc Connexin hemichannel and pannexin channel electrophysiology: how do they differ?
    Dakshesh Patel
    Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY 13210, United States
    FEBS Lett 588:1372-8. 2014
  3. pmc Histone deacetylase inhibition reduces cardiac connexin43 expression and gap junction communication
    Qin Xu
    Department of Pharmacology, State University of New York Upstate Medical University Syracuse, NY, USA
    Front Pharmacol 4:44. 2013
  4. pmc Gating of connexin 43 gap junctions by a cytoplasmic loop calmodulin binding domain
    Qin Xu
    Department of Pharmacology, SUNY Upstate Medical University, 750 East Adams St, Syracuse, NY 13210, USA
    Am J Physiol Cell Physiol 302:C1548-56. 2012
  5. pmc Molecular interaction and functional regulation of connexin50 gap junctions by calmodulin
    Yanyi Chen
    Department of Chemistry, Georgia State University, Atlanta, GA 30303, USA
    Biochem J 435:711-22. 2011
  6. pmc Connexin40 and connexin43 determine gating properties of atrial gap junction channels
    Xianming Lin
    Department of Pharmacology, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA
    J Mol Cell Cardiol 48:238-45. 2010
  7. pmc Enhancement of ventricular gap-junction coupling by rotigaptide
    Xianming Lin
    Department of Pharmacology, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA
    Cardiovasc Res 79:416-26. 2008
  8. pmc Cx30.2 can form heteromeric gap junction channels with other cardiac connexins
    Joanna Gemel
    University of Chicago, Department of Pediatrics MC 4060, 5841 S Maryland Avenue, Chicago, IL 60637 1470, USA
    Biochem Biophys Res Commun 369:388-94. 2008
  9. pmc Effect of transjunctional KCl gradients on the spermine inhibition of connexin40 gap junctions
    Xianming Lin
    Department of Pharmacology, The State University of New York Upstate Medical University, Syracuse, New York 13210, USA
    Biophys J 93:483-95. 2007
  10. pmc Atrial fibrillation-associated connexin40 mutants make hemichannels and synergistically form gap junction channels with novel properties
    Dakshesh Patel
    Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY 13210, United States
    FEBS Lett 588:1458-64. 2014

Detail Information

Publications10

  1. pmc An amino-terminal lysine residue of rat connexin40 that is required for spermine block
    Xianming Lin
    Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
    J Physiol 570:251-69. 2006
    ....
  2. pmc Connexin hemichannel and pannexin channel electrophysiology: how do they differ?
    Dakshesh Patel
    Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY 13210, United States
    FEBS Lett 588:1372-8. 2014
    ..Cell pair electrophysiological assays permit the relative assessment of the connexin hemichannel/gap junction channel ratio not often considered when performing isolated cell hemichannel studies. ..
  3. pmc Histone deacetylase inhibition reduces cardiac connexin43 expression and gap junction communication
    Qin Xu
    Department of Pharmacology, State University of New York Upstate Medical University Syracuse, NY, USA
    Front Pharmacol 4:44. 2013
    ....
  4. pmc Gating of connexin 43 gap junctions by a cytoplasmic loop calmodulin binding domain
    Qin Xu
    Department of Pharmacology, SUNY Upstate Medical University, 750 East Adams St, Syracuse, NY 13210, USA
    Am J Physiol Cell Physiol 302:C1548-56. 2012
    ..This study provides the first evidence of intrinsic differences in the Ca(2+) regulatory properties of Cx43 and Cx40...
  5. pmc Molecular interaction and functional regulation of connexin50 gap junctions by calmodulin
    Yanyi Chen
    Department of Chemistry, Georgia State University, Atlanta, GA 30303, USA
    Biochem J 435:711-22. 2011
    ..Overall, these results demonstrate that the binding of Ca2+/CaM to the intracellular loop of Cx50 is critical for mediating the Ca2+-dependent inhibition of Cx50 gap junctions in the lens of the eye...
  6. pmc Connexin40 and connexin43 determine gating properties of atrial gap junction channels
    Xianming Lin
    Department of Pharmacology, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA
    J Mol Cell Cardiol 48:238-45. 2010
    ..Co-expression of Cx40 accounts for most, but not all, of the differences in the V(j)-dependent gating properties between atrium and ventricle that may play a role in the genesis of slow myocardial conduction and arrhythmias...
  7. pmc Enhancement of ventricular gap-junction coupling by rotigaptide
    Xianming Lin
    Department of Pharmacology, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA
    Cardiovasc Res 79:416-26. 2008
    ....
  8. pmc Cx30.2 can form heteromeric gap junction channels with other cardiac connexins
    Joanna Gemel
    University of Chicago, Department of Pediatrics MC 4060, 5841 S Maryland Avenue, Chicago, IL 60637 1470, USA
    Biochem Biophys Res Commun 369:388-94. 2008
    ..Our data suggest that connexin30.2 can form heteromers with the other cardiac connexins and that mixed channel formation will influence the gating properties of gap junctions in cardiac regions that co-express these connexins...
  9. pmc Effect of transjunctional KCl gradients on the spermine inhibition of connexin40 gap junctions
    Xianming Lin
    Department of Pharmacology, The State University of New York Upstate Medical University, Syracuse, New York 13210, USA
    Biophys J 93:483-95. 2007
    ..These data are consistent with a single spermine molecule being sufficient to occlude the Cx40 gap junction channel within the KCl permeation pathway...
  10. pmc Atrial fibrillation-associated connexin40 mutants make hemichannels and synergistically form gap junction channels with novel properties
    Dakshesh Patel
    Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY 13210, United States
    FEBS Lett 588:1458-64. 2014
    ..While co-expression of the two mutations had similar effects on Vj gating, it synergistically increased γj by 50%. Unlike WTCx40 or M163V, G38D induced activity of a dominant 271 pS hemichannel...

Research Grants30

  1. CONNEXONS IN CARDIOVASCULAR CELL COMMUNICATION
    Eric C Beyer; Fiscal Year: 2013
    ..Disturbances of electrical conduction lead to abnormal heart rhythms such as atrial fibrillation. Our studies will clarify how abnormalities of the subunit gap junction proteins lead to arrhythmias such as atrial fibrillation. ..
  2. Cardiac Fibrillation: Mechanisms and Therapy
    James N Weiss; Fiscal Year: 2013
    ..Together, these studies will provide critical groundwork necessary to develop and advance novel therapies for this major complication and cause of mortality from heart disease. ..
  3. Integration and Arrhythmia Suppression with hESC-Derived Cardiomyocyte Grafts
    MICHAEL ALAN LAFLAMME; Fiscal Year: 2013
    ..Finally, in Aim 3, we will use in vitro models to develop Wnt5a-mediated chemotaxis as a complementary strategy to improve the integration of hESC-CM grafts. ..
  4. The Center for Native and Pacific Health Disparities Research
    MARJORIE K LEIMOMI MALA MAU; Fiscal Year: 2013
    ..5) To prepare and empower our diverse Native and Pacific People communities to take ownership of their own health and wellness. ..
  5. Renin angiotensin system and connexin43
    Samuel C Dudley; Fiscal Year: 2013
    ..Specifically, this application will give a more complete picture of the pro-arrhythmic effects of AngII on heart, which could lead to new diagnostic and therapeutic interventions. ..
  6. Model of Timothy Syndrome to Screen Drugs with Induced Pluripotent Stem Cells
    Masayuki Yazawa; Fiscal Year: 2013
    ..The proposed systems to screen a library of compounds to rescue TS phenotypes will provide a platform to find novel lead compounds that would be clinically useful for the treatment of not only TS but also other cardiac arrhythmias. ..
  7. A Multi-Scale Approach to Cardiac Arrhythmia: from the Molecule to the Organ
    Gideon Koren; Fiscal Year: 2013
    ....
  8. Cardiac Optogenetics: A Cell Delivery Approach
    Emilia Entcheva; Fiscal Year: 2013
    ....
  9. Integrative Analysis of Longitudinal Studies of Aging
    Andrea M Piccinin; Fiscal Year: 2013
    ..abstract_text> ..
  10. From human keratinocytes to biological pacemakers
    Ira S Cohen; Fiscal Year: 2013
    ..If the HFKT-pacemaker functions well in the canine heart, a future goal would be to advance this novel autologous, cellular approach towards clinical deployment. ..
  11. Immune-Based Interventions Against Infectious Diseases
    Alan L Rothman; Fiscal Year: 2013
    ..3. Recruit promising junior investigators and provide mentoring by established NIH-funded researchers. 4. Support a multidisciplinary research program led by junior investigators in translational infectious diseases immunology. ..
  12. Gap Junctional Patterning in Arrhythmic Heart
    Robert G Gourdie; Fiscal Year: 2013
    ..This project will deliver new insights on the function of a protein essential to a stable heartbeat called connexin43. The project aims to provide novel approaches to the prevention and treatment of heart attacks. ..
  13. Function and Integration of Stem Cell-derived Cardiac Tissue Patch
    Nenad Bursac; Fiscal Year: 2013
    ..The knowledge obtained in this project will allow us to pursue in the future engineering of a functional cardiac tissue patch made of human stem cells for potential clinical applications. ..
  14. Heart and Muscle K+ Channels: Assembly and Regulation
    Gideon Koren; Fiscal Year: 2013
    ....
  15. Novel Methods for Cardiac Micro-Impedance Measurement
    ANDREW EMIL POLLARD; Fiscal Year: 2013
    ..Thesaurus Terms: electrical impedance, electrical measurement, heart electrical activity, interstitial, intracellular, method development, cardiac myocyte, electrical conductance, membrane model, myocardium, electrode. ..