Identification and functional characterization of the intermediate-conductance Ca2+-activated K+ channel (IK-1) in biliary epithelium

AUTOR(ES)

Dutta, Amal K.

FONTE

American Physiological Society

RESUMO

In the liver, adenosine triphosphate (ATP) is an extracellular signaling molecule that is released into bile and stimulates a biliary epithelial cell secretory response via engagement of apical P2 receptors. The molecular identities of the ion channels involved in ATP-mediated secretory responses have not been fully identified. Intermediate-conductance Ca2+-activated K+ channels (IK) have been identified in biliary epithelium, but functional data are lacking. The aim of these studies therefore was to determine the location, function, and regulation of IK channels in biliary epithelial cells and to determine their potential contribution to ATP-stimulated secretion. Expression of IK-1 mRNA was found in both human Mz-Cha-1 biliary cells and polarized normal rat cholangiocyte (NRC) monolayers, and immunostaining revealed membrane localization with a predominant basolateral signal. In single Mz-Cha-1 cells, exposure to ATP activated K+ currents, increasing current density from 1.6 ± 0.1 to 7.6 ± 0.8 pA/pF. Currents were dependent on intracellular Ca2+ and sensitive to clotrimazole and TRAM-34 (specific IK channel inhibitors). Single-channel recording demonstrated that clotrimazole-sensitive K+ currents had a unitary conductance of 46.2 ± 1.5 pS, consistent with IK channels. In separate studies, 1-EBIO (an IK activator) stimulated K+ currents in single cells that were inhibited by clotrimazole. In polarized NRC monolayers, ATP significantly increased transepithelial secretion which was inhibited by clotrimazole. Lastly, ATP-stimulated K+ currents were inhibited by the P2Y receptor antagonist suramin and by the inositol 1,4,5-triphosphate (IP3) receptor inhibitor 2-APB. Together these studies demonstrate that IK channels are present in biliary epithelial cells and contribute to ATP-stimulated secretion through a P2Y-IP3 receptor pathway.

Documentos Relacionados

• Design of a potent and selective inhibitor of the intermediate-conductance Ca2+-activated K+ channel, IKCa1: A potential immunosuppressant
• Highly co-operative Ca2+ activation of intermediate-conductance K+ channels in granulocytes from a human cell line.
• Allosteric Control of Gating Mechanisms Revisited: The Large Conductance Ca2+-Activated K+ Channel
• A Protein Interaction Network for the Large Conductance Ca2+-activated K+ Channel in the Mouse Cochlea*
• Pregnancy modifies the large conductance Ca2+-activated K+ channel and cGMP-dependent signaling pathway in uterine vascular smooth muscle