Effect of the inactivating "ball" peptide of Shaker B on intermediate conductance Ca(2+)-dependent inwardly rectifying K+ channels of HeLa cells.
The patch-clamp technique was used to study the effect of intracellularly added inactivating "ball" peptide (BP) of the Shaker B K+ channel upon Ca(2+)-dependent inwardly rectifying K+ channels of the intermediate conductance type expressed in HeLa cells. Intracellular BP caused only moderate inhibition of outward K+ currents when assayed at an intracellular Ca2+ concentration of 100 nmol/l. Increasing intracellular Ca2+ levels led in itself to some voltage-dependent blockade of K+ currents, which was absent when high extracellular K+ was used. An additional strong blockade by intracellular BP was nevertheless observed both in Na(+)- and K(+)-rich extracellular solutions. A non-inactivating BP analogue had no effect. At this higher intracellular Ca2+ concentration the inhibition of these intermediate conductance Ca(2+)-dependent channels by BP was voltage-dependent, being absent at hyperpolarizing potentials, and could be relieved by increasing extracellular K+. These data suggest that BP acts at an internal pore site in Ca(2+)-dependent intermediate conductance K+ channels of HeLa cells, and that these might possess a receptor site for the peptide similar to that of other K+ channels such as Ca(2+)-activated maxi-K+ channels.
Riquelme
G
G
Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile.
Fernández
A M
AM
Encinar
J A
JA
González-Ros
J M
JM
Sepúlveda
F V
FV
D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D004553:Electric Conductivity; D004594:Electrophysiology; D006367:HeLa Cells; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D010455:Peptides / Q000494:pharmacology*; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000187:drug effects* / Q000502:physiology; D024661:Potassium Channels, Inwardly Rectifying
D047908:Intracellular Signaling Peptides and Proteins; D010455:Peptides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; C076103:Shaker B inactivating peptide; D002118:Calcium