Molecular cloning and permanent expression in a neuroblastoma cell line of a fast inactivating potassium channel from bovine adrenal medulla

Using a cDNA library from bovine adrenal medulla, we have isolated cDNAs coding for a potassium channel. Then cDNAs encode a 660-amino acid protein that has a molecular weight of 73.288 kDa and no amino-terminal signal peptide. We have called it BAK4. Analysis of its sequence reveals close similarity (94% homology) with a recently described potassium channel from rat brain (RCK4) and heart (RHK1). Neuroblastoma cells (Neuro-2a cell line) were stably transfected with BAK4 DNA. Expression of the DNA was under the control of a heat-shock promoter. Several clones, that were isolated by neomycin resistance selection, had integrated the plasmid DNA in a stable form. Upon heat induction, these cells produced BAK4 RNA and a potassium outward current, not present in control non-transfected cells. The current, which was transient and decayed markedly during the duration of 200 ms-pulses, can be described as ??? potassium current. The expression of these types of channels in brain (RCK4,RHK1), heart (RHK1) and adrenal medulla (BAK4) suggest their possible implication in important functions for the cell.