Na+C/H+ exchangers:: Structure, function and regulation

Our knowledge of the structure and functional regulation of members of the Na+/H+ exchanger (NHE) family has advanced notably in recent years. To date, six mammalian NHE isoforms (NHE1-NHE6) have been identified. On the basis of their hydropathy profiles, all NHEs exhibit similar topologies. NHE1 is expressed in virtually all tissues and cells, but the distributions of NHE2, NHE3, NHE4 and NHE5 are more restricted than that of NHE1. NHE6 is ubiquitously expressed, although it is most abundant in mitochondria-rich tissues. NHE isoforms are most easily distinguished by their pharmacological properties, more specifically, by their sensitivity to amiloride and its analogs. The regulation of Na+/H+ exchange is influenced by Cl-, vesicular traffic and membrane-associated lipids, particularly phospholipids; however, the roles played by each of these different factors require further elucidation, (C) 1999 Prous Science. All rights reserved.