CONNEXINS & DISEASES: Intercellular signalling through connexin channels - a key to the understanding of cardiovascular diseases

• Forschungsstelle: EU FRP
• Projektnummer: 99.0368-1
• Projekttitel Englisch: CONNEXINS & DISEASES: Intercellular signalling through connexin channels - a key to the understanding of cardiovascular diseases

Schlüsselwörter (Englisch)

Gap junction channels; electrophysiology; cardiovascular disease

Alternative Projektnummern (Englisch)

EU project number: QLG1-1999-00516

Forschungsprogramme (Englisch)

EU-programme: 5. Frame Research Programme - 1.1.8 Generic R&D activities

Kurzbeschreibung (Englisch)

See abstract

Partner und Internationale Organisationen (Englisch)

Coordinator: Centre National de la Recherche, Marseille (F)

Abstract (Englisch)

Biophysical properties of connexin channels
Our research interest is focussing on the biophysical properties of gap junction channels. These channels consist of two hemichannels in series, each hemichannel comprising 6 protein subunits or connexins (Cx). They establish functional contacts between adjacent cells and are present in most tissues of vertebrates. Experiments were performed on transfected cells using electrical (voltage clamp) and diffusional methods (video-imaging) on pairs of cells and single cells.
One project explored the electrical properties of Zebrafish connexin43.3 channels, an orthologue of mammalian and avian Cx45. Measurements of transjunctional currents were also performed on mouse and chicken Cx45. The results yielded subtle species differences of both conductance and kinetic parameters. Another project examined the kinetic properties of channels consisting of mouse Cx40, Cx43 and Cx45, i.e. the most abundant connexins of cardiac tissue. We found that the time course of both current inactivation and recovery from inactivation followed an exponential, irrespective of voltage. The faster the inactivation, the slower was the recovery from inactivation and vice versa. Based on the analysis, we conclude that Cx45 channels are most vulnerable to impair impulse propagation in heart. The data gained are crucial for a better understanding of the role of gap junctions during tachycardia. Another project was aimed at identifying and characterising electrophysiologically heteromeric gap junction channels. They consist of more than one type of Cx. We used transfected HeLa cells expressing Cx43 and Cx45, alone or together. The multichannel current signals obtained from different kinds of cell pairs could not be explained sufficiently in terms of homotypic and heterotypic channels. This suggests that heteromeric channels may be involved. Another project dealt with the electrical properties of Cx hemichannels. Measurements were carried on multichannel currents. We explored the conditions for channel opening and determined the conductive, kinetic and gating properties of Cx45 channels in detail.
Currently we are pursuing a project on diffusional properties of gap junction channels and hemichannels. The studies are performed on single cells and cell pairs expressing Cx40, Cx43 or Cx45. The diffusional studies are complemented by electrical measurements to assess the permeability of single channels. The properties of hemichannels are explored on single cells. Loading and unloading of cells with fluorescent dye molecules of different size and electric charge occurs via open hemichannels. The properties of gap junction channels are assessed on cell pair preparations. The experimental procedure for both types of experiments is working. Currently, we are busy optimising the recording conditions.

Datenbankreferenzen (Englisch)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 99.0368-1