Cx43 can form functional channels at the nuclear envelope and modulate gene expression in cardiac cells

Abstract

Conexina 43; Expresión génica; Translocación nuclear

Connexina 43; Expressió gènica; Translocació nuclear

Connexin 43; Gene expression; Nuclear translocation

Classically associated with gap junction-mediated intercellular communication, connexin43 (Cx43) is increasingly recognized to possess non-canonical biological functions, including gene expression regulation. However, the mechanisms governing the localization and role played by Cx43 in the nucleus, namely in transcription modulation, remain unknown. Using comprehensive and complementary approaches encompassing biochemical assays, super-resolution and immunogold transmission electron microscopy, we demonstrate that Cx43 localizes to the nuclear envelope of different cell types and in cardiac tissue. We show that translocation of Cx43 to the nucleus relies on Importin-β, and that Cx43 significantly impacts the cellular transcriptome, likely by interacting with transcriptional regulators. In vitro patch-clamp recordings from HEK293 and adult primary cardiomyocytes demonstrate that Cx43 forms active channels at the nuclear envelope, providing evidence that Cx43 can participate in nucleocytoplasmic shuttling of small molecules. The accumulation of nuclear Cx43 during myogenic differentiation of cardiomyoblasts is suggested to modulate expression of genes implicated in this process. Altogether, our study provides new evidence for further defining the biological roles of nuclear Cx43, namely in cardiac pathophysiology.

This work was supported by the European Regional Development Fund (ERDF) through the Operational Program for Competitiveness Factors (COMPETE) under the projects HealthyAging2020 CENTRO-01-0145-FEDER-000012-N2323, CENTRO-01-0145-FEDER-032179, CENTRO-01-0145-FEDER-032414, EXPL/MED-OUT/0590/2021, UIDB/04539/2020 and PPBI-Portuguese Platform of BioImaging (POCI-01-0145-FEDER-022122). This work was also supported by the European Union's Horizon 2020 research and innovation programme under grant agreement MIA-Portugal no. 857524 and the Comissão de Coordenação da Região Centro (CCDRC) through the Centro2020 Program. T.A. acknowledges funding from Instituto de Salud Carlos III, grant PI16/00772 co-financed by the ERDF, and Fundación Científica Asociación Española Contra el Cáncer (IDEAS20039AASE). This work used the platforms of the Grenoble Instruct-ERIC center (ISBG; UAR 3518 CNRS-CEA-UGA-EMBL) within the Grenoble Partnership for Structural Biology (PSB), supported by FRISBI (ANR-10-INBS-0005-02) and GRAL, financed within the University Grenoble Alpes graduate school (Ecoles Universitaires de Recherche) CBH-EUR-GS (ANR-17-EURE-0003), and the Microscopy and Bioimaging Lab (iLAB) at the Faculty of Medicine of the University of Coimbra (Coimbra, Portugal). The IBS Electron Microscope facility is supported by the Auvergne Rhône-Alpes Region, the Fonds Feder, the Fondation pour la Recherche Médicale and GIS-IBiSA. Super-resolution microscopy experiments benefited from access to CBI/IGBMC (Illkirch, France) and were supported by FRISBI (ANR-10-INBS-0005). Financial support was provided by Instruct-ERIC (PID 14677).