Journal
CIRCULATION RESEARCH
Volume 106, Issue 6, Pages 1153-U327Publisher
LIPPINCOTT WILLIAMS & WILKINS
DOI: 10.1161/CIRCRESAHA.108.182147
Keywords
gap junctions; connexin43; heart failure; autophagy; lipid rafts
Funding
- NIH [P01 HL077180]
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Rationale: Gap junctions mediate cell-to-cell electric coupling of cardiomyocytes. The primary gap junction protein in the working myocardium, connexin43 (Cx43), exhibits increased localization at the lateral membranes of cardiomyocytes in a variety of heart diseases, although the precise location and function of this population is unknown. Objective: To define the subcellular location of lateralized gap junctions at the light and electron microscopic level, and further characterize the biochemical regulation of gap junction turnover. Methods and Results: By electron microscopy, we characterized gap junctions formed between cardiomyocyte lateral membranes in failing canine ventricular myocardium. These gap junctions were varied in structure and appeared to be extensively internalizing. Internalized gap junctions were incorporated into multilamellar membrane structures, with features characteristic of autophagosomes. Intracellular Cx43 extensively colocalized with the autophagosome marker GFP-LC3 when both proteins were exogenously expressed in HeLa cells, and endogenous Cx43 colocalized with GFP-LC3 in neonatal rat ventricular myocytes. Furthermore, a distinct phosphorylated form of Cx43, as well as the autophagosome-targeted form of LC3 (microtubule-associated protein light chain 3) targeted to lipid rafts in cardiac tissue, and both were increased in heart failure. Conclusions: Our data demonstrate a previously unrecognized pathway of gap junction internalization and degradation in the heart and identify a cellular pathway with potential therapeutic implications. (Circ Res. 2010; 106: 1153-1163.)
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