Functional expression of TREK-2 K+ channel in cultured rat brain astrocytes.
Background K+ channels whose subunit contains four transmembrane segments and two pore-forming domains (4TM/2P) have been cloned recently. We studied whether 4TM/2P K+ channels are functionally expressed in astrocytes that are known to have a large background (resting) K+ conductance and a large resting membrane potential. Reverse transcriptase-PCR analysis showed that, among five 4TM/2P K+ channels examined, TASK-1, TASK-3 and TREK-2 mRNAs were expressed in cultured astrocytes from rat cortex. In cell-attached patches, we mainly observed three K+ channels with single-channel conductances of 30, 117 and 176 pS (-40 mV) in symmetrical 140 mM KCl. The 30 pS channel was the inward rectifying K+ channel that has been previously described in astrocytes. The 117 pS K+ channel also showed inward rectification and was insensitive to 1 mM tetraethylammonium and 1 mM 4-aminopyridine. The 176 pS channel was the Ca2+-activated K+ channel. The 117 pS K+ channel was determined to be TREK-2, as judged by its electrophysiological properties and activation by membrane stretch, free fatty acids and intracellular acidosis. In approximately 50% of astrocytes in culture, whole-cell K+ current increased markedly following application of arachidonic acid. The number of TREK-2 channels in these cells was estimated to be approximately 500-1000/cell. Our results show that TREK-2 is functionally expressed in cortical astrocytes in culture, and suggest that TREK-2 may be involved in K+ homeostasis of astrocytes during pathological states.
Gnatenco
Carmen
C
Department of Physiology and Biophysics, Finch University of Health Sciences/The Chicago Medical School, 3333 Green Bay Road, North Chicago, IL 60064-3095, USA.
Han
Jaehee
J
Snyder
Ann K
AK
Kim
Donghee
D
D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D001921:Brain / Q000166:cytology*; D002478:Cells, Cultured; D004594:Electrophysiology; D005904:Glial Fibrillary Acidic Protein / Q000096:biosynthesis; D006706:Homeostasis / Q000502:physiology; D007150:Immunohistochemistry; D007700:Kinetics; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000096:biosynthesis* / Q000235:genetics; D024683:Potassium Channels, Tandem Pore Domain; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection
D005904:Glial Fibrillary Acidic Protein; C503444:Kcnk10 protein, rat; D015221:Potassium Channels; D024683:Potassium Channels, Tandem Pore Domain; D012333:RNA, Messenger