Structural basis of the inhibition of TRPV1 by analgesic sesquiterpenes

Significance

The TRPV1 ion channel plays several important physiological roles including the detection of nociceptive and inflammatory stimuli. Several activators of TRPV1 have been described but very few natural antagonists have been found. For hundreds of years, plants containing sesquiterpenes, such as α-humulene (AH) found in Cannabis and others, have been used for their analgesic properties. Here, we show that AH inhibits pain in rodents by stabilizing the closed conformation. Our cryo-EM structure solved with AH and site-directed mutagenesis experiments, provide evidence of AH’s binding to a previously undescribed inhibitory site in the TRPV1 channel, expanding our knowledge of its interactions with small molecules of a nonopioid origin, which will aid in the development of therapeutic agents.

Abstract

The Transient Receptor Potential Vanilloid 1 (TRPV1) ion channel is expressed in primary nociceptive afferents, which participate in processes such as pain and inflammation. Considerable efforts have been directed toward finding inhibitors of TRPV1 and understanding the molecular details of their interactions with this channel. α-humulene (AH) is a sesquiterpene derived from plants such as hops and other members of Cannabaceae family, with a long history of popular use as an analgesic and anti-inflammatory. Using a combination of behavioral assays, electrophysiology, site-directed mutagenesis, cryo-EM, and molecular dynamics simulations, we show that AH inhibits TRPV1-related pain responses and currents by interacting with a region composed of the S2, S2-S3 linker, and S3 transmembrane segments and stabilizing the closed conformation of the channel. The interaction of ligands in this region of the TRPV1 channel has not been previously described and the results of the present study highlight that it may constitute part of a negative regulatory region. These findings allow us to understand the molecular basis by which substances such as some sesquiterpenes, abundantly found in medicinal plants used by humans for hundreds of years, reduce pain. Pain management can include the use of opioids, which results in hepatic and renal damage and possible addiction. Our study offers insight into a poorly understood group of compounds that could be used as scaffold to produce novel nonopioid analgesic therapies and clarifies the molecular mechanisms that underlie the effects of these analgesic molecules.

This work was done in collaboration with Dr. Tamara Rosenbaum team from Departamento de Neurociencia Cognitiva, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City.