TY - JOUR
T1 - Ultrastructure and regulation of lateralized connexin43 in the failing heart
AU - Hesketh, Geoffrey G.
AU - Shah, Manish H.
AU - Halperin, Victoria L.
AU - Cooke, Carol A.
AU - Akar, Fadi G.
AU - Yen, Timothy E.
AU - Kass, David A.
AU - MacHamer, Carolyn E.
AU - Van Eyk, Jennifer E.
AU - Tomaselli, Gordon F.
PY - 2010/4
Y1 - 2010/4
N2 - 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.
AB - 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.
KW - Autophagy
KW - Connexin43
KW - Gap junctions
KW - Heart failure
KW - Lipid rafts
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U2 - 10.1161/CIRCRESAHA.108.182147
DO - 10.1161/CIRCRESAHA.108.182147
M3 - Article
C2 - 20167932
AN - SCOPUS:77950993997
SN - 0009-7330
VL - 106
SP - 1153
EP - 1163
JO - Circulation Research
JF - Circulation Research
IS - 6
ER -