Inwardly rectifying potassium currents in rat basophilic leukaemia (RBL-1) cells: regulation by spermine and implications for store-operated calcium influx.
In non-excitable cells, the major Ca(2+) influx pathway is the store-operated one. Store-operated Ca(2+) entry is intimately related to the prevalent membrane potential, in that hyperpolarisation enhances Ca(2+) influx and depolarisation reduces it. Inwardly rectifying potassium channels are important determinants of the membrane potential and hence will regulate, indirectly, the rate and extent of Ca(2+) entry through store-operated channels. Here we investigated inwardly rectifying potassium currents ( I(RK)) in rat basophilic leukaemia (RBL-1) cells, a model system for studying store-operated Ca(2+) influx. I(RK) was voltage dependent in that the current decays during strong hyperpolarisations. Recovery from this decay was both time and voltage dependent. Close to the resting potential of RBL-1 cells, however, I(RK) was stable. Neither store depletion per se nor the subsequent rise in intracellular [Ca(2+)] appeared to alter I(RK) activity. Receptor stimulation reduced the current only weakly. Unexpectedly, intracellular spermine inhibited I(RK) quite strongly and via a mechanism that seemed distinct from that responsible for current rectification. The relevance of these findings to store-operated Ca(2+) influx is discussed.
Laboratory of Molecular and Cellular Signalling, Department of Physiology, University of Oxford, Parks Road, Oxford OX1 3PT, UK.
Sebastian
S
Straube
Anant B
AB
Parekh
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D015471:Leukemia, Basophilic, Acute; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying / Q000378:metabolism*; D051381:Rats; D013096:Spermine / Q000494:pharmacology*; D013268:Stimulation, Chemical; D014407:Tumor Cells, Cultured / Q000502:physiology
D018679:Cholinergic Agonists; D024661:Potassium Channels, Inwardly Rectifying; D013096:Spermine; D002217:Carbachol; D011188:Potassium; D002118:Calcium