Cloning of two isoforms of the rat brain Na(+)-Ca2+ exchanger gene and their functional expression in HeLa cells

Two functional isoforms of the rat brain Na(+)-Ca2+ exchanger were isolated from a lambda ZAP hippocampus cDNA library. The open reading frame of clone RBE-1 codes for a protein 935 amino acids long, and that of clone RBE-2 codes for a protein 958 amino acids long. Expression HeLa cells of Na+ gradient dependent Ca2+ transport activity was determined following transfection of the cells with either RBE-1 or RBE-2. Both clones expressed proteins that exchange Na+ with Ca2+ in an electrogenic manner and none of them exhibited a dependency of the antiport on K, since they transported Ca2+ in an Na+ gradient dependent manner in external choline chloride as well.