Characterisation of large-conductance calcium-activated potassium channels (BK(Ca)) in human NT2-N cells.
Large-conductance calcium-activated potassium (BK(Ca)) channels were studied in inside-out patches of human NTERA2 neuronal cells (NT2-N). In symmetrical (140 mM) K(+) the channel mean conductance was 265 pS, the current reversing at approximately 0 mV. It was selective (P(K)/P(Na)=20:1) and blocked by internal paxilline and TEA. The open probability-voltage relationship for BK(Ca) was fitted with a Boltzmann function, the V((1/2)) being 76.3 mV, 33.6 mV and -14.1 mV at 0.1 muM, 3.3 muM and 10 muM [Ca(2+)](i), respectively. The relationship between open probability and [Ca(2+)](i) was fitted by the Hill equation (Hill coefficient 2.7, half maximal activation at 2.0 muM [Ca(2+)](i)). Open and closed dwell time histograms were fitted by the sum of two and three voltage-dependent exponentials, respectively. Increasing [Ca(2+)](i) produced both an increase in the longer open time constant and a decrease in the longest closed time constant, so increasing mean open time. "Intracellular" ATP evoked a concentration-dependent increase in NT2-N BK(Ca) activity. At +40 mV half-maximum activation occurred at an [ATP](i) of 3 mM (30 nM [Ca(2+)](i)). ADP and GTP were less potent, and AMP-PNP was inactive. This is the first characterisation of a potassium channel in NT2-N cells showing that it is similar to the BK(Ca) channel of other preparations.
Chapman
H
H
Welsh School of Pharmacy, Cardiff University, King Edward VII Avenue, Cardiff CF10 3XF, UK.
Piggot
C
C
Andrews
P W
PW
Wann
K T
KT
D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D013997:Time Factors
D051036:Large-Conductance Calcium-Activated Potassium Channels; D026902:Potassium Channel Blockers; D000255:Adenosine Triphosphate; D002118:Calcium