Cx43 hemichannel microdomain signaling at the intercalated disc enhances cardiac excitability
Maarten A.J. De Smet, Alessio Lissoni, Timur Nezlobinsky, Nan Wang, Eef Dries, Marta Pérez-Hernández, Xianming Lin, Matthew Amoni, Tim Vervliet, Katja Witschas, Eli Rothenberg, Geert Bultynck, Rainer Schulz, Alexander V. Panfilov, Mario Delmar, Karin R. Sipido, Luc Leybaert
Maarten A.J. De Smet, Alessio Lissoni, Timur Nezlobinsky, Nan Wang, Eef Dries, Marta Pérez-Hernández, Xianming Lin, Matthew Amoni, Tim Vervliet, Katja Witschas, Eli Rothenberg, Geert Bultynck, Rainer Schulz, Alexander V. Panfilov, Mario Delmar, Karin R. Sipido, Luc Leybaert
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Research Article Cardiology Cell biology

Cx43 hemichannel microdomain signaling at the intercalated disc enhances cardiac excitability

Abstract

Cx43, a major cardiac connexin, forms precursor hemichannels that accrue at the intercalated disc to assemble as gap junctions. While gap junctions are crucial for electrical conduction in the heart, little is known about the potential roles of hemichannels. Recent evidence suggests that inhibiting Cx43 hemichannel opening with Gap19 has antiarrhythmic effects. Here, we used multiple electrophysiology, imaging, and super-resolution techniques to understand and define the conditions underlying Cx43 hemichannel activation in ventricular cardiomyocytes, their contribution to diastolic Ca2+ release from the sarcoplasmic reticulum, and their impact on electrical stability. We showed that Cx43 hemichannels were activated during diastolic Ca2+ release in single ventricular cardiomyocytes and cardiomyocyte cell pairs from mice and pigs. This activation involved Cx43 hemichannel Ca2+ entry and coupling to Ca2+ release microdomains at the intercalated disc, resulting in enhanced Ca2+ dynamics. Hemichannel opening furthermore contributed to delayed afterdepolarizations and triggered action potentials. In single cardiomyocytes, cardiomyocyte cell pairs, and arterially perfused tissue wedges from failing human hearts, increased hemichannel activity contributed to electrical instability compared with nonfailing rejected donor hearts. We conclude that microdomain coupling between Cx43 hemichannels and Ca2+ release is a potentially novel, targetable mechanism of cardiac arrhythmogenesis in heart failure.

Authors

Maarten A.J. De Smet, Alessio Lissoni, Timur Nezlobinsky, Nan Wang, Eef Dries, Marta Pérez-Hernández, Xianming Lin, Matthew Amoni, Tim Vervliet, Katja Witschas, Eli Rothenberg, Geert Bultynck, Rainer Schulz, Alexander V. Panfilov, Mario Delmar, Karin R. Sipido, Luc Leybaert

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Figure 11

Microdomain-specific activation of Cx43 hemichannels in nonfailing and failing human cardiomyocytes.

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Microdomain-specific activation of Cx43 hemichannels in nonfailing and f...
(A) Transmitted light images of single cardiomyocyte (top) and cardiomyocyte cell pairs (middle, bottom). Triangle, square, circle, and diamond symbols indicate cell-attached macropatch positions at the lateral membrane and cell end of single cardiomyocytes and intercalated disc and side-side of cardiomyocyte cell pairs, respectively. (B) Example traces showing single channel currents recorded at the different macropatch recording positions. Traces recorded in nonfailing and failing human cardiomyocytes during caffeine superfusion (10 mM, 8 seconds) at –70 mV. (C) IV plots depicting linear current-voltage relationship with slope conductance of approximately 220 pS and Erev ≈ 0 mV (N/nNF = 3/10–15 per recording position, N/nHF = 3/10–15 per recording position). (D) Example traces showing single channel currents recorded at the different macropatch recording positions following TAT-Gap19 superfusion. (E) Summary histograms depicting number of channels per patch for the different macropatch recording positions (N/nNF = 3/10–15 per recording position, N/nHF = 3/10–15 per recording position). Black and red bars indicate recordings in nonfailing and failing human cardiomyocytes, respectively. (F) Heatmap summarizing single channel open probability at different macropatch recording positions with and without TAT-Gap19 in nonfailing and failing human single cardiomyocytes and cardiomyocyte cell pairs (N/nNF = 3/10–15 per recording position, N/nHF = 3/10–15 per recording position).