TRPV3 and TRPV4 Mediate Warmth-evoked Currents in Primary Mouse Keratinocytes

Recently, a family of temperature-activated ion channels has been identified in mammalian and nonmammalian species that appear to contribute to thermosensation. Two of these proteins, TRPV3 and TRPV4, are ion channels activated by modest increases in ambient temperature. Localization studies have indicated that both proteins, in addition to being expressed in sensory neurons, are also expressed in skin keratinocytes. These and other findings have suggested that keratinocytes might act in concert with sensory neurons to perceive our thermal environment. In this study, we demonstrate that primary keratinocytes isolated from mouse skin exhibit two distinct heat-evoked current responses to mild increases in ambient temperature. The more common of these response types bears considerable similarity to responses mediated by recombinant TRPV4, is absent in mice lacking this ion channel, and is restored upon TRPV4 reintroduction. The second, rarer response strongly resembles those mediated by recombinant TRPV3. Together, these findings demonstrate that keratinocytes can indeed act as thermosensory cells and that they do so via at least two distinct transduction mechanisms.