Non-proton ligand-sensing domain of acid-sensing ion channel 3 is required for itch sensation.

Itch, the unpleasant sensation that evokes a desire to scratch, accompanies numerous skin and nervous system disorders. However, the molecular mechanisms of itch are unclear. Acid sensing ion channel 3 (ASIC3) is a sensor of acidic and primary inflammatory pain. The whole-cell patch-clamp technique was used to determine the effect of Chloroquine (CQ)on ASICs currents in primary sensory neurons or the Chinese hamster ovary (CHO) cells transfected with rat-ASIC1a or- ASIC3. Site-directed mutagenesis of plasmid was performed. Scratching behavior was evaluated by measuring the number of bouts during 30 minutes after injection. CQ, an anti-malarial drug defined as a histamine-independent pruritogen, selectively enhanced the sustained phase of ASIC3 current in a concentration-dependent manner either in ASIC3-transfected CHO cells or in primary cultured rat dorsal root ganglion (DRG) neurons. Further studies revealed that the effect of CQ on ASIC3 channels depends on the newly identified non-proton ligand sensing domain. Importantly, CQ-evoked scratching behavior was largely alleviated by APETx2, a selective ASIC3 channel blocker. Like CQ, other compounds such as amiloride, 2-guanidine-4-methylquinazoline (GMQ) and neuropeptide FF (NPFF), which have been previously reported to be non-proton ligands that activate ASIC3, undoubtedly evoked the scratching response. In conclusion, ASIC3, a proton-gated ion channel critical for pain sensation, also functions as an essential component of itch transduction. This article is protected by copyright. All rights reserved.