O2 sensing by recombinant TWIK-related halothane-inhibitable K+ channel-1 background K+ channels heterologously expressed in human embryonic kidney cells.
Hypoxic inhibition of K+ channels provides a link between low O2 and cell function, and in glossopharyngeal neurons hypoxic inhibition of a TWIK-related halothane-inhibitable K+ channel-1 (THIK-1)-like background K+ channel regulates neuronal function. In the present study, we examined directly the O2 sensitivity of recombinant THIK-1 channels, expressed in human embryonic kidney (HE293) cells. THIK-1 expression conferred a moderately outwardly rectifying halothane-inhibited and arachidonic acid-potentiated K+ current and invoked a strongly hyperpolarized resting membrane potential. Endogenous K+ currents in untransfected cells were unaffected by either agent. Hypoxia (P(O2), 20 mmHg) reversibly inhibited THIK-1 currents and caused membrane depolarization, effects that were occluded by halothane. Neither the mitochondrial complex I inhibitors rotenone, myxothiazol and sodium cyanide, nor the NADPH oxidase inhibitors diphenylene iodonium and phenylarsine oxide, were effective in inhibiting the O2-sensitivity of THIK-1. Thus, hypoxic inhibition of THIK-1 occurs by a mechanism dissimilar to that which regulates the activity of other members of the background K+ channel family. Given the O2 sensitivity of THIK-1 channels and their abundant expression in the CNS, we raise for the first time the possibility of a physiological and/or pathological role for these channels during brain ischemia.
Campanucci
V A
VA
Department of Biology, McMaster University, 1280 Main St West, Hamilton, Canada ON L8S 4K1.
Brown
S T
ST
Hudasek
K
K
O'kelly
I M
IM
Nurse
C A
CA
Fearon
I M
IM
D002460:Cell Line; D006801:Humans; D020925:Hypoxia-Ischemia, Brain / Q000378:metabolism / Q000503:physiopathology*; D008564:Membrane Potentials / Q000502:physiology; D010100:Oxygen / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D024683:Potassium Channels, Tandem Pore Domain / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection
C486603:KCNK13 protein, human; D024683:Potassium Channels, Tandem Pore Domain; D011994:Recombinant Proteins; D010100:Oxygen