Large conductance Ca(2+)-activated K(+) channels in human meningioma cells.
Cells from ten human meningiomas were electrophysiologically characterized in both living tissue slices and primary cultures. In whole cells, depolarization to voltages higher than +80 mV evoked a large K(+) outward current, which could be blocked by iberiotoxin (100 nm) and TEA (half blocking concentration IC(50) = 5.3 mm). Raising the internal Ca(2+) from 10 nm to 2 mm shifted the voltage of half-maximum activation (V(1/2)) of the K(+) current from +106 to +4 mV. Respective inside-out patch recordings showed a voltage- and Ca(2+)-activated (BK(Ca)) K(+) channel with a conductance of 296 pS (130 mm K(+) at both sides of the patch). V(1/2) of single-channel currents was +6, -12, -46, and -68 mV in the presence of 1, 10, 100, and 1000 microm Ca(2+), respectively, at the internal face of the patch. In cell-attached patches the open probability (P(o)) of BK(Ca) channels was nearly zero at potentials below +80 mV, matching the activation threshold for whole-cell K(+) currents with 10 nm Ca(2+) in the pipette. Application of 20 microm cytochalasin D increased P(o) of BK(Ca) channels in cell-attached patches within minutes. These data suggest that the activation of BK(Ca) channels in meningioma cells does not only depend on voltage and internal Ca(2+) but is also controlled by the cytoskeleton.
Kraft
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R
Institute of Pathology (Neuropathology), Friedrich-Schiller University of Jena, Bachstr. 18, D-07740 Jena, Germany.
Benndorf
K
K
Patt
S
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D000368:Aged; D002118:Calcium / Q000378:metabolism; D003599:Cytoskeleton / Q000502:physiology; D004594:Electrophysiology; D005260:Female; D006801:Humans; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008297:Male; D008579:Meningioma / Q000737:chemistry*; D008875:Middle Aged; D015221:Potassium Channels / Q000502:physiology*; D024681:Potassium Channels, Calcium-Activated; D014407:Tumor Cells, Cultured
D051036:Large-Conductance Calcium-Activated Potassium Channels; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D002118:Calcium