Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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.
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PMID:Functional expression of TREK-2 K+ channel in cultured rat brain astrocytes. 1189 89

Insulin secretion from pancreatic beta cells is partly regulated by cell membrane potential. Background K+ channels that stabilize the resting membrane potential would suppress excitability and insulin secretion. Recent studies show that members of the two-pore domain K+ (K2P) channel family behave as background K+ channels in many excitable cells. Therefore, the expression of K2P channels was studied in insulin-secreting MIN6 cells. Reverse transcriptase PCR showed that, among nine K2P channels tested, TASK-1, TASK-2, TASK-3, TREK-2, and TRESK-2 were expressed in MIN6 cells. Cell-attached recordings on MIN6 cells revealed five types of K+ channels that were open at rest. Two were ATP-sensitive and Ca2+-activated K+ channels, as judged by their sensitivity to ATP and Ca2+, respectively, and single-channel conductance. Among five K2P channels, only TREK-2 could be clearly identified in MIN6 cells. The molecular identity of two other K+ channels is not yet known. TREK-2 in MIN6 cells was activated by arachidonic acid, membrane stretch, and low pH solution (pH 5.8). Arachidonic acid increased Ba2+-sensitive whole-cell current in MIN6 cell. These results suggest that TREK-2 contributes to the background K+ conductance in MIN6 cells, and may regulate depolarization-induced secretion of insulin.
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PMID:Functional expression of TREK-2 in insulin-secreting MIN6 cells. 1535 40