Ca2+-activated K channel of the BK-type in the inner mitochondrial membrane of a human glioma cell line.
A single channel current was recorded from mitoplasts (i.e., inner mitochondrial membrane) of the human glioma cell line LN229 using patch-clamp techniques in the mitoplast-attached mode. We frequently found a 295 +/- 18 pS channel that showed a straight i-E relation in the range +/-60 mV in 150 mM KCl solutions on either side of the mitoplast. If KCl in the bath was exchanged against NaCl, outward currents were undetectable, indicating potassium selectivity. Channel activity determined as open probability increased with increasing Ca2+ concentrations (EC50 = 0.9 microM at 60 mV). Open probability was voltage dependent. An e-fold increase of time spent in the open state was induced by a depolarization of 10.5 mV. Open probability was decreased by charybdotoxin concentration and voltage dependently (EC50 = 1.4 nM). In conclusion, we show for the first time that the inner mitochondrial membrane in human glioma cells contains a calcium-dependent K channel of the BK-type.
Siemen
D
D
Department of Physiology, Tuebingen, Gmelinstrasse 5, D-72076, Germany. detlef.siemen@uni-tuebingen.de
Loupatatzis
C
C
Borecky
J
J
Gulbins
E
E
Lang
F
F
D002118:Calcium / Q000494:pharmacology; D018999:Charybdotoxin / Q000494:pharmacology; D002794:Choline / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005910:Glioma / Q000378:metabolism; D005942:Gluconates / Q000494:pharmacology; D006801:Humans; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism*; D015640:Ion Channel Gating / Q000187:drug effects; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000145:classification / Q000378:metabolism*; D024681:Potassium Channels, Calcium-Activated; D011189:Potassium Chloride / Q000378:metabolism / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D005942:Gluconates; D051036:Large-Conductance Calcium-Activated Potassium Channels; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D018999:Charybdotoxin; D012965:Sodium Chloride; D011189:Potassium Chloride; D012964:Sodium; D002794:Choline; D002118:Calcium