Localization of β and γ subunits of ENaC in sensory nerve endings in the rat foot pad

The molecular mechanisms underlying mechanoelectrical transduction and the receptors that detect light touch remain uncertain. Studies in Caenorhabditis elegans suggest that members of the DEG/ENaC cation channel family may be mechanoreceptors. Therefore, we tested the hypothesis that subunits of the mammalian epithelial Naf channel (ENaC) family are expressed in touch receptors in rat hairless skin. We detected beta ENaC and gamma ENaC, but not alpha ENaC transcripts in cervical and lumbar dorsal root ganglia (DRG). Using immunofluorescence, we found beta ENaC and gamma ENaC expressed in medium to large lumbar DRG neurons. Moreover, we detected these two subunits in Merkel cell-neurite complexes, Meissner-like corpuscles, and small lamellated corpuscles, specialized mechanosensory structures of the skin. Within these structures, beta ENaC and gamma ENaC were localized in the nerve fibers believed to contain the sensors responsive to mechanical stress. Thus beta and gamma ENaC subunits are good candidates as components of the molecular sensor that detects touch. (C) 2000 Elsevier Science B.V. All rights reserved.