DEG ENaC channels: a touchy superfamily that watches its salt

To the surprise of many, studies of molecular mechanisms of touch transduct ion and analyses of epithelial Na+ transport have converged to define a new class of ion channel subunits. Based on the names of the first two identif ied subfamilies, the Caenorhabditis elegans degenerins and the vertebrate e pithelial amiloride-sensitive Na+ channel, this ion channel class is called the DEG/ENaC superfamily. Members of the DEG/ENaC superfamily have been fo und in nematodes, flies, snails, and vertebrates. Family members share comm on topology, such that they span the membrane twice and have intracellular N- and C-termini; a large extracellular loop includes a conserved cysteine- rich region. DEG/ENaC channels have been implicated a broad spectrum of cel lular functions, including mechano-sensation, proprioception, pain sensatio n, gametogenesis, and epithelial Na+ transport. These channels exhibit dive rse gating properties, ranging from near constitutive opening to rapid inac tivation. We discuss working understanding of DEG/ENaC functions, channel p roperties, structure/activity correlations and possible evolutionary relati onship to other channel classes. (C) 1999 John Wiley & Sons, Inc.