Springer-Verlag
Berlin/Heidelberg
424
0031-6768
1432-2013
Pflügers Archiv - European Journal of Physiology
European Journal of Physiology
Pflugers Arch - Eur J Physiol
Biomedicine
Human Physiology
462
462
6
2
2
15
2011
7
9
2011
7
8
2011
8
2011
Springer-Verlag
2011
977
10.1007/s00424-011-0977-7
6
The GPR55 agonist lysophosphatidylinositol directly activates intermediate-conductance Ca2+-activated K+ channels
Cardiovascular Physiology
245
255
2011
5
11
2011
2
4
2011
4
27
2011
5
10
2011
5
21
The Author(s)
2011
Alexander
I.
Bondarenko
Roland
Malli
Wolfgang
F.
Graier
+43-316-3807565
+43-316-3809615
wolfgang.graier@medunigraz.at
Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine
Medical University of Graz
Harrachgasse 21/III
8010
Graz
Austria
Abstract
Lysophosphatidylinositol (LPI) was recently shown to act both as an extracellular mediator binding to G protein-coupled receptor 55 (GPR55) and as an intracellular messenger directly affecting a number of ion channels including large-conductance Ca2+ and voltage-gated potassium (BKCa) channels. Here, we explored the effect of LPI on intermediate-conductance Ca2+-activated K+ (IKCa) channels using excised inside-out patches from endothelial cells. The functional expression of IKCa was confirmed by the charybdotoxin- and TRAM-34-sensitive hyperpolarization to histamine and ATP. Moreover, the presence of single IKCa channels with a slope conductance of 39 pS in symmetric K+ gradient was directly confirmed in inside-out patches. When cytosolically applied in the range of concentrations of 0.3–10 μM, which are well below the herein determined critical micelle concentration of approximately 30 μM, LPI potentiated the IKCa single-channel activity in a concentration-dependent manner, while single-channel current amplitude was not affected. In the whole-cell configuration, LPI in the pipette was found to facilitate membrane hyperpolarization in response to low (0.5 μM) histamine concentrations in a TRAM-34-sensitive manner. These results demonstrate a so far not-described receptor-independent effect of LPI on the IKCa single-channel activity of endothelial cells, thus, highlighting LPI as a potent intracellular messenger capable of modulating electrical responses in the vasculature.
Keywords
IKCa channel
Cytosolic free Ca2+ elevation
Endothelial cells
Hyperpolarization
Membrane potential
Lipid mediators
Lysophosphatidylinositol