Expression of a genomic clone encoding a brain potassium channel in mammalian cells using lipofection

A genomic clone encoding a mouse brain K+ channel (MBK1) was isolated, characterized and expressed in COS cells using the lipofection technique. Transfected COS cells expressed voltage-dependent K+ currents that activated within 20 ms at 0 mV and showed less than 10% inactivation during 250 ms depolarizing pulses at 60 mV. Expressed K+ currents were reversibly blocked by 4-aminopyridine and tetraethylammonium, and were moderately sensitive to dendrotoxin, but insensitive to charybdotoxin. Thus MBK1, expressed transiently in a mammalian cell line, exhibits features characteristic of non-inactivating K+ channels with a conspicuous insensitivity to charybdotoxin. Lipofection is, therefore, a valuable strategy for expression of channel proteins in mammalian cells.