Molecular and functional characterization of a new potassium conductance in mouse ventricular fibroblasts

• Published in: Journal of molecular and cellular cardiology Vol. 46; no. 4; pp. 508 - 517
• Main Authors: Benamer, Najate, Moha Ou Maati, Hamid, Demolombe, Sophie, Cantereau, Anne, Delwail, Adriana, Bois, Patrick, Bescond, Jocelyn, Faivre, Jean-François
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.04.2009; Elsevier
• Subjects: Actins - metabolism; Animals; ATP-Binding Cassette Transporters - genetics; ATP-Binding Cassette Transporters - metabolism; Cardiac fibroblasts; Cardiology and cardiovascular system; Cardiovascular; Cell Proliferation - drug effects; Cells, Cultured; Cellular Biology; Fibroblasts - cytology; Fibroblasts - drug effects; Fibroblasts - metabolism; Fibroblasts - secretion; Gene Expression Regulation - drug effects; Glyburide - pharmacology; Heart Ventricles - cytology; Heart Ventricles - metabolism; Human health and pathology; IL-6; Interleukin-6 - secretion; Ion Channel Gating - drug effects; K-channel; KATP Channels; Life Sciences; Lysophospholipids - pharmacology; Mice; Pharmaceutical sciences; Pharmacology; Pinacidil - pharmacology; Potassium Channels, Inwardly Rectifying - genetics; Potassium Channels, Inwardly Rectifying - metabolism; Protein Subunits - genetics; Protein Subunits - metabolism; Receptors, Drug - genetics; Receptors, Drug - metabolism; RNA, Messenger - genetics; RNA, Messenger - metabolism; Sphingosine - analogs & derivatives; Sphingosine - pharmacology; Sphingosine-1-phosphate; Subcellular Processes; Sulfonylurea Receptors; SUR2/Kir6.1; SUR2/Kir6.1; Cardiac fibroblasts; K-channel; IL-6; Sphingosine-1-phosphate; SUR2/Kir6.1 K-channel Cardiac fibroblasts IL-6 Sphingosine-1-phosphate
• ISSN: 0022-2828; 1095-8584
• DOI: 10.1016/j.yjmcc.2008.12.016

Abstract The present work is aimed at identifying and characterizing, at a molecular and functional level, new ionic conductances potentially involved in the excitation–secretion coupling and proliferation of cardiac ventricular fibroblasts. Among potassium channel transcripts which were screened by high-throughput real-time PCR, SUR2 and Kir6.1 mRNAs were found to be the most abundant in ventricular fibroblasts. The corresponding proteins were not detected by western blot following 5 days of cell culture, but had appeared at 7 days, increasing with extended cell culture duration as the fibroblasts differentiated into myofibroblasts. Using the inside-out configuration of the patch-clamp technique, single potassium channels could be recorded. These had properties similar to those reported for SUR2/Kir6.1 channels, i.e. activation by pinacidil, inhibition by glibenclamide and activation by intracellular UDP. As already reported for this molecular signature, they were insensitive to intracellular ATP. In the whole-cell configuration, these channels have been shown to be responsible for a glibenclamide-sensitive macroscopic potassium current which can be activated not only by pinacidil, but also by nanomolar concentrations of the sphingolipid sphingosine-1-phosphate (S1P). The activation of this current resulted in an increase in cell proliferation and a decrease in IL-6 secretion, suggesting it has a functional role in situations where S1P increases. Overall, this work demonstrates for the first time that SUR2/Kir6.1 channels represent a significant potassium conductance in ventricular fibroblasts which may be activated in physio-pathological conditions and which may impact on fibroblast proliferation and function.