Journal
CIRCULATION RESEARCH
Volume 103, Issue 5, Pages 519-526Publisher
LIPPINCOTT WILLIAMS & WILKINS
DOI: 10.1161/CIRCRESAHA.108.179069
Keywords
Cx43CT; particle-receptor interaction; gap junctions; connexin43; rotigaptide
Funding
- NIH [HL39707, GM057691]
- Danish National Research Foundation
- Danish Cardiovascular Research Academy
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Gap junctions provide a low-resistance pathway for cardiac electric propagation. The role of GJ regulation in arrhythmia is unclear, partly because of limited availability of pharmacological tools. Recently, we showed that a peptide called RXP-E binds to the carboxyl terminal of connexin43 and prevents chemically induced uncoupling in connexin43-expressing N2a cells. Here, pull-down experiments show RXP-E binding to adult cardiac connexin43. Patch-clamp studies revealed that RXP-E prevented heptanol-induced and acidification-induced uncoupling in pairs of neonatal rat ventricular myocytes. Separately, RXP-E was concatenated to a cytoplasmic transduction peptide (CTP) for cytoplasmic translocation (CTP-RXP-E). The effect of RXP-E on action potential propagation was assessed by high-resolution optical mapping in monolayers of neonatal rat ventricular myocytes, containing approximate to 20% of randomly distributed myofibroblasts. In contrast to control experiments, when heptanol (2 mmol/L) was added to the superfusate of monolayers loaded with CTP-RXP-E, action potential propagation was maintained, albeit at a slower velocity. Similarly, intracellular acidification (pH(i) 6.2) caused a loss of action potential propagation in control monolayers; however, propagation was maintained in CTP-RXP-E-treated cells, although at a slower rate. Patch-clamp experiments revealed that RXP-E did not prevent heptanol-induced block of sodium currents, nor did it alter voltage dependence or amplitude of Kir2.1/Kir2.3 currents. RXP-E is the first synthetic molecule known to: (1) bind cardiac connexin43; (2) prevent heptanol and acidification-induced uncoupling of cardiac gap junctions; and (3) preserve action potential propagation among cardiac myocytes. RXP-E can be used to characterize the role of gap junctions in the function of multicellular systems, including the heart. (Circ Res. 2008; 103: 519-526.)
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