097 An important role of TRPV3 in the temporal control of intracellular acidification in corneoptosis, a unique cell death process of keratinocytes

Abstract

Stratum corneum, the outermost layer of the epidermis, consists of dead anucleated keratinocytes called corneocytes, functioning as a barrier. The exact molecular mechanisms by which the top layer of living keratinocytes (SG1 cells) die has been largely unknown. Here, we demonstrate via intravital imaging procedures combined with intracellular Ca 2+ -and pHresponsive fluorescent probes, we aimed to clarify the SG1 death process in vivo. We found that SG1 cells die after prolonged (w60 min) intracellular Ca 2+ elevation at neutral pH (phase I). Subsequently, irreversibly sustained rapid intracellular acidification occurs (phase II). In cultured primary SG1 cells, phase I was accompanied by increased cell membrane permeability, an indicator of cell death in general, whereas phase II was essential for disappearance of keratohyalin granules and nuclear DNA. Intravital Ca 2+ -and pH-imaging of dorsal and ear skin of TRPV3-deficient mice revealed that the duration of these phases was tightly regulated by the transient receptor potential cation channel V3 (TRPV3), suggesting that TRPV3 acts as a timekeeper for phase I and II conditions. Our combined various fluorescent probes and a newly-developed in vitro culture system clarified the molecular mechanisms of the unique SG1 cell death, termed corneoptosis.