HETEROMULTIMERIC CHANNELS FORMED BY RAT-BRAIN POTASSIUM-CHANNEL PROTEINS

AN important step towards understanding the molecular basis of the functional diversity of voltage-gated K+ channels in the mammalian brain has been the discovery of a family of genes encoding rat brain K+ channel-forming (RCK) proteins1-6. All species of these RCK proteins form homomultimeric voltage-gated K+ channels with distinct functional characteristics in Xenopus laevis oocytes following injection of the respective cRNAs2. RCK-specific mRNAs are coexpressed in several regions of the brain7, suggesting that RCK proteins also assemble into heteromultimeric K+ channels. In addition expression experiments with fractionated poly(A)+ mRNA have suggested that heteromultimeric K+ channels may occur in mammalian brain8. We report here that heteromultimeric K+ channels composed of two different RCK proteins (RCK1 and RCK4) assemble after cotransfection of HeLa cells with the corresponding cDNAs and after coinjection of the corresponding cRNAs into Xenopus oocytes. The heteromultimeric RCK1, 4 channel mediates a transient potassium outward current, similar to the RCK4 channel but inactivates more slowly, has a larger conductance and is more sensitive to block by dendrotoxin and tetraethylammonium chloride. © 1990 Nature Publishing Group.