'Molecular cloning and chromosome localization of a putative basolateral Na⁺-K⁺-2Cl^- cotransporter from mouse inner medullary collecting duct (mIMCD-3) cells

Electroneutral Na⁺-K⁺-2Cl^- cotransporters represent one of the major routes for Cl^- movement in epithelia. A secretory form of the cotransporter has been described in the basolateral membrane of a variety of epithelia from fish to mammals. We isolated a putative bumetanide-sensitive Na⁺-K⁺-2Cl^- cotransporter cDNA, BSC2, from mIMCD-3 cells. Northern analysis indicates that in contrast to BSC1, the recently cloned renal-specific apical isoform of the cotransporter, BSC2 is expressed in secretory epithelia and thus appears to represent the basolateral isoform. Furthermore, BSC2 is also expressed in non-polarized cells, such as red cells and myocytes. Sequence comparison and chromosome localization demonstrate that BSC2 and BSC1 are different genes that diverged before the evolution of vertebrates.