title: Physiological and molecular characterization of an IRK-type inward rectifier K+ channel in a tumour mast cell line.
abstract: The basophilic leucaemia cell line RBL-2H3 exhibits a robust inwardly rectifying potassium current, IKIR, which is likely to be modulated by G proteins. We examined the physiological and molecular properties of this KIR conductance to define the nature of the underlying channel species. The macroscopic conductance revealed characteristics typical of classical K+ inward rectifiers of the IRK type. Channel gating was rapid, first order (tau approximately 1 ms at -100 mV) and steeply voltage dependent. Both activation potential and slope conductance were dependent on extracellular K+ concentration ([K+]o) and inward rectification persisted in the absence of internal Mg2+. The current was susceptible to a concentration- and voltage-dependent block by extracellular Na+, Cs+ and Ba2+. Initial IKIR whole-cell amplitudes as well as current rundown were dependent on the presence of 1 mM internal ATP. Perfusion of intracellular guanosine 5'-Q-(3-thiotriphosphate) (GTP[gamma S]) suppressed IKIR with an average half-time of decline of approximately 400 s. It was demonstrated that the dominant IRK-type 25 pS conductance channel was indeed suppressed by 100 microM preloaded GTP[gamma S]. Reverse transcriptase-polymerase chain reactions (RT-PCR) with RBL cell poly(A)+ RNA identified a full length K+ inward rectifier with 94% base pair homology to the recently cloned mouse IRK1 channel. It is concluded that RBL cells express a classical voltage-dependent IRK-type K+ inward rectifier RBL-IRK1 which is negatively controlled by G proteins.
authors.affiliation: Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Wischmeyer
authors.forename: K U
authors.initials: KU
authors.lastname: Lentes
authors.forename: A
authors.initials: A
authors.lastname: Karschin
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D001464:Barium / Q000494:pharmacology; D001483:Base Sequence; D002586:Cesium / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D004553:Electric Conductivity; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D015640:Ion Channel Gating / Q000502:physiology; D007700:Kinetics; D015471:Leukemia, Basophilic, Acute; D008274:Magnesium / Q000494:pharmacology; D008407:Mast Cells / Q000502:physiology*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011188:Potassium / Q000494:pharmacology; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D051381:Rats; D012964:Sodium / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D015221:Potassium Channels; D002586:Cesium; D001464:Barium; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D000255:Adenosine Triphosphate; D004492:Edetic Acid; D012964:Sodium; D008274:Magnesium; D011188:Potassium