A single TRPV1 amino acid controls species sensitivity to capsaicin

Ying Chu,Bruce E Cohen,Huai-Hu Chuang

doi:10.1038/s41598-020-64584-2

Abstract

Chili peppers produce capsaicin (a vanilloid) that activates the transient receptor potential cation channel subfamily V member 1 (TRPV1) on sensory neurons to alter their membrane potential and induce pain. To identify residues responsible for differential TRPV1 capsaicin sensitivity among species, we used intracellular Ca2+ imaging to characterize chimeras composed of capsaicin-sensitive rat TRPV1 (rTRPV1) and capsaicin-insensitive chicken TRPV1 (cTRPV1) exposed to a series of capsaicinoids. We found that chimeras containing rat E570-V686 swapped into chicken receptors displayed capsaicin sensitivity, and that simply changing the alanine at position 578 in the S4-S5 helix of the chicken receptor to a glutamic acid was sufficient to endow it with capsaicin sensitivity in the micromolar range. Moreover, introduction of lysine, glutamine or proline at residue A578 also elicited capsaicin sensitivity in cTRPV1. Similarly, replacing corresponding rTRPV1 residue E570 with lysine or glutamine retained capsaicin sensitivity. The hydrophilic capsaicin analog Cap-EA activated a cTRPV1-A578E mutant, suggesting that A578 may participate in vanilloid binding. The hydrophilic vanilloid agonist zingerone did not activate any A578 mutants with capsaicin sensitivity, suggesting that the vanilloid group alone is not sufficient for receptor activation. Our study demonstrates that a subtle modification of TRPV1 in different species globally alters capsaicin responses.

Highlights

Chili peppers produce capsaicin that activates the transient receptor potential cation channel subfamily V member 1 (TRPV1) on sensory neurons to alter their membrane potential and induce pain
We added two strong vanilloids, capsaicin and RTX7,30, in order to ensure activation of mutated channels. Apart from these two vanilloids, our cocktail solution contained phenylarsine oxide (PAO), which functioned as a surrogate for oxidative stress to potentiate activation of chicken and rat TRPV131, as well as cesium ions to maximize responses
Our results show that 30 μM capsaicin activated both rat TRPV1 (rTRPV1) and chicken TRPV1 (cTRPV1), but the response was relatively weak for cTRPV1 (Fig. 1b,c)

Summary

Introduction

Chili peppers produce capsaicin (a vanilloid) that activates the transient receptor potential cation channel subfamily V member 1 (TRPV1) on sensory neurons to alter their membrane potential and induce pain. A key exogenous ligand for studying environmental stimuli of TRPV1 is capsaicin, a small lipophilic molecule in chili peppers that induces sensations of heat. A previous study revealed that specific mutations of the Y511 or S512 residues in the intracellular domain of TRPV1 suppressed the capsaicin responsiveness of rat receptors without affecting their proton-induced current[16]. Residues A561 and Y523 in frog TRPV1 (xTRPV1) (corresponding to T550 and S512 in the rat receptor) have been reported as responsible for its limited capsaicin sensitivity[15]. Studies on human TRPV1 have identified the same amino acids as rat TRPV1 as being responsible for capsaicin sensitivity, and found additional important residues such as L518, F591 and L67025,26

Methods

Results

Conclusion