Increased inwardly rectifying potassium currents in HEK-293 cells expressing murine transient receptor potential 4.
Drosophila transient receptor potential (Trp) and its mammalian homologues are postulated to form capacitative Ca2+ entry or store-operated channels. Here we show that expression of murine Trp4 in HEK 293 cells also leads to an increase in inwardly rectifying K+ currents. No similar increase was found in cell lines expressing Trp1, Trp3 or Trp6. Consistent with typical characteristics of inward rectifiers, the K+ currents in Trp4-expressing cells were blocked by low millimolar concentrations of Cs+ and Ba2+, but not by 1.2 mM Ca2+, and were only slightly inhibited by 5 mM tetraethylammonium. Single channel recordings of excised inside-out patches revealed the presence of two conducting states of 51 pS and 94 pS in Trp4-expressing cells. The outward current in the excised patches was blocked by 1 mM spermine, but not by 1 mM Mg2+. How Trp4 expression causes the increase in the K+ currents is not known. We propose that Trp4 either participates in the formation of a novel K+ channel or up-regulates the expression or activity of endogenous inwardly rectifying K+ channels.
Neurobiotechnology Center and Department of Neuroscience, Ohio State University, 168 Rightmire Hall, 1060 Carmack Road, Columbus, OH 43210, USA.
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D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D027682:Cation Transport Proteins; D002460:Cell Line; D004553:Electric Conductivity; D006801:Humans; D007700:Kinetics; D051379:Mice; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying; D050052:TRPC Cation Channels; D014162:Transfection
D015220:Calcium Channels; D027682:Cation Transport Proteins; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D050052:TRPC Cation Channels; C104603:TRPC3 cation channel; C489571:TRPC4 ion channel; D011188:Potassium; D002118:Calcium