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Degradation of a connexin40 mutant linked to atrial fibrillation is accelerated.
- Source :
-
Journal of molecular and cellular cardiology [J Mol Cell Cardiol] 2014 Sep; Vol. 74, pp. 330-9. Date of Electronic Publication: 2014 Jun 25. - Publication Year :
- 2014
-
Abstract
- Several Cx40 mutants have been identified in patients with atrial fibrillation (AF). We have been working to identify physiological or cell biological abnormalities of several of these human mutants that might explain how they contribute to disease pathogenesis. Wild type (wt) Cx40 or four different mutants (P88S, G38D, V85I, and L229M) were expressed by the transfection of communication-deficient HeLa cells or HL-1 cardiomyocytes. Biophysical channel properties and the sub-cellular localization and protein levels of Cx40 were characterized. Wild type Cx40 and all mutants except P88S formed gap junction plaques and induced significant gap junctional conductances. The functional mutants showed only modest alterations of single channel conductances or gating by trans-junctional voltage as compared to wtCx40. However, immunoblotting indicated that the steady state levels of G38D, V85I, and L229M were reduced relative to wtCx40; most strikingly, G38D was only 20-31% of wild type levels. After the inhibition of protein synthesis with cycloheximide, G38D (and to a lesser extent the other mutants) disappeared much faster than wtCx40. Treatment with the proteasomal inhibitor, epoxomicin, greatly increased levels of G38D and restored the abundance of gap junctions and the extent of intercellular dye transfer. Thus, G38D, V85I, and L229M are functional mutants of Cx40 with small alterations of physiological properties, but accelerated degradation by the proteasome. These findings suggest a novel mechanism (protein instability) for the pathogenesis of AF due to a connexin mutation and a novel approach to therapy (protease inhibition).<br /> (Copyright © 2014 Elsevier Ltd. All rights reserved.)
- Subjects :
- Action Potentials drug effects
Animals
Atrial Fibrillation genetics
Atrial Fibrillation metabolism
Atrial Fibrillation pathology
Cell Line, Tumor
Connexins metabolism
Cycloheximide pharmacology
Gap Junctions drug effects
Gap Junctions metabolism
Gene Expression Regulation
Heart Atria drug effects
Heart Atria pathology
Humans
Mice
Myocytes, Cardiac drug effects
Myocytes, Cardiac pathology
Oligopeptides pharmacology
Patch-Clamp Techniques
Proteasome Endopeptidase Complex drug effects
Proteasome Endopeptidase Complex metabolism
Proteasome Inhibitors pharmacology
Protein Stability
Protein Synthesis Inhibitors pharmacology
Proteolysis
Signal Transduction
Transgenes
Ubiquitination
Gap Junction alpha-5 Protein
Connexins genetics
Heart Atria metabolism
Mutation
Myocytes, Cardiac metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 1095-8584
- Volume :
- 74
- Database :
- MEDLINE
- Journal :
- Journal of molecular and cellular cardiology
- Publication Type :
- Academic Journal
- Accession number :
- 24973497
- Full Text :
- https://doi.org/10.1016/j.yjmcc.2014.06.010