Inhibition of TRPV1 by an Unsaturated Fatty Acid

Abstract

of noxious and non-noxious anesthetics inhibit agonist-evoked activation of mammalian but not drosophila TRPA1. Analysis of chimeric drosophila and mouse TRPA1 channels reveal that the 5th transmembrane domain (S5) is critical for anesthetic sensitivity. We identify two amino acids at the N-terminal S5 domain required for the inhibitory effects of GAs and introduction of these residues into dTRPA1 confers GA-induced block in these channels. Further, we show that activation by noxious GAs requires several amino acids in the S5, S6 and the first pore helix previously implicated in binding of the high-affinity antagonist, A-967079. Notably, isoflurane relieves A-967079mediated inhibition consistent with a competitive interaction and in silico modeling predicts that pungent GAs occupy the A-967079 binding pocket. Thus inhibition and activation by GAs are governed by distinct amino acids in the pore domain region. These data reveal the mechanism by which TRPA1 discriminates between pungent and non-pungent GAs, and provide structural requirements for designing antagonists to counter the noxious properties of GAs. channels are polymodal receptors whose open probability is under command of several stimuli such as temperature, pH and ligands. Several studies have involved TRPV1 channels in pain sensation related to inflammatory responses and tissue damage, leading the pharmaceutical industry to the search of novel compounds able to modulate their function in order to develop novel pain relief therapies. Capsazepine is the best known TRPV1 antagonist and the residues accounting for their binding to TRPV1 channels have been identified by mutagenesis and specie-specific effects. Nevertheless, the molecular mechanism underlying capsazepine-mediated channel inhibition has not been described at molecular level to date. We performed molecular dynamics simulations of the TRPV1 channel in the open state in the absence and the presence of Capsazepine and Capsaicin in order to identify the interactions accounting of TRPV1 channel. Even when Capsazepine shares in part their binding site with the well-known TRPV1 channel agonist Capsaicin, their ligand orientation resulted to be different. We also observed a dynamic hydrogen bond network at the neighbors of the vanilloid binding pocket that differs with those observed in both the absence of ligand and in the presence of capsaicin. Our results suggest that the subtle differences at the interaction network at the capsaicin binding pocket leads to completely opposite effects at the channel activation gate. 1400-Pos Board B377Extracellular Sodium is Required for Temperature-Dependent Gating in TRPV1 Channels Andres Jara-Oseguera, Chanhyung Bae, Kenton J. Swartz. Molecular Physiol/Biophys, NINDS, NIH, Bethesda, MD, USA. The TRPV1 channel in sensory neurons integrates pain-producing stimuli, including noxious temperature, acidosis, pungent vanilloid compounds and pro-inflammatory lipids. Measurements of TRPV1 channel activity at extreme positive and negative voltages in the presence of othe...