Ligand-induced dynamic membrane changes and cell deletion conferred by vanilloid receptor 1

The real time dynamics of vanilloid-induced cytotoxicity and the specific d eletion of nociceptive neurons expressing the wild-type vanilloid receptor (VR1) were investigated. VR1 was C-terminally tagged with either the 27-kDa enhanced green fluorescent protein (eGFP) or a 12-amino acid epsilon -epit ope. Upon exposure to resiniferatoxin, VR1eGFP- or VR1 epsilon -expressing cells exhibited pharmacological responses similar to those of cells express ing the untagged VR1. Within seconds of vanilloid exposure, the intracellul ar free calcium ([Ca2+](i)) was elevated in cells expressing VR1, A functio nal pool of VR1 also was localized to the endoplasmic reticulum that, in th e absence of extracellular calcium, also was capable of releasing calcium u pon agonist treatment. Confocal imaging disclosed that resiniferatoxin trea tment: induced vesiculation of the mitochondria and the endoplasmic reticul um (similar to1 min), nuclear membrane disruption (5-10 min), and cell lysi s (1-2 h), Nociceptive primary sensory neurons endogenously express VR1, an d resiniferatoxin treatment induced a sudden increase in [Ca2+](i) and mito chondrial disruption which was cell-selective, as glia and non-VR1-expressi ng neurons were unaffected. Early hallmarks of cytotoxicity were followed b y specific deletion of VR1-expressing cells. These data demonstrate that va nilloids disrupt vital organelles within the cell body and, if administered to sensory ganglia, may be employed to rapidly and selectively delete noci ceptive neurons.