Cloning of two isoforms of the rat brain Na+Ca+ exchanger gene and their functional expression in HeLa cells

Abstract

Two functional isoforms of the rat brain Na⁺-Ca²⁺ exchanger were isolated from a λZAP 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 in HeLa cells of Na⁺ gradient dependent Ca²⁺ transport activity was determined following transfeetion 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.