Nociception and pain in humans lacking a functional TRPV1 channel
Ben Katz, Rachel Zaguri, Simon Edvardson, Channa Maayan, Orly Elpeleg, Shaya Lev, Elyad Davidson, Maximilian Peters, Shlomit Kfir-Erenfeld, Esther Berger, Shifa Ghazalin, Alexander M. Binshtok, Baruch Minke
Ben Katz, Rachel Zaguri, Simon Edvardson, Channa Maayan, Orly Elpeleg, Shaya Lev, Elyad Davidson, Maximilian Peters, Shlomit Kfir-Erenfeld, Esther Berger, Shifa Ghazalin, Alexander M. Binshtok, Baruch Minke
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Clinical Medicine Neuroscience

Nociception and pain in humans lacking a functional TRPV1 channel

Abstract

BACKGROUND Chronic pain is a debilitating illness with currently limited therapy, in part due to difficulties in translating treatments derived from animal models to patients. The transient receptor potential vanilloid 1 (TRPV1) channel is associated with noxious heat detection and inflammatory pain, and reports of adverse effects in human trials have hindered extensive efforts in the clinical development of TRPV1 antagonists as novel pain relievers.METHODS We examined 2 affected individuals (A1 and A2) carrying a homozygous missense mutation in TRPV1, rendering the channel nonfunctional. Biochemical and functional assays were used to analyze the mutant channel. To identify possible phenotypes of the affected individuals, we performed psychophysical and medical examinations.RESULTS We demonstrated that diverse TRPV1 activators, acting at different sites of the channel protein, were unable to open the cloned mutant channel. This finding was not a consequence of impairment in the expression, cellular trafficking, or assembly of protein subunits. The affected individuals were insensitive to application of capsaicin to the mouth and skin and did not demonstrate aversive behavior toward capsaicin. Furthermore, quantitative sensory testing of A1 revealed an elevated heat-pain threshold but also, surprisingly, marked cold hypersensitivity, with cold pain reported at temperatures that are innocuous to healthy individuals, and extensive neurogenic inflammatory, flare, and pain responses following application of the TRPA1 channel activator mustard oil.CONCLUSION Our study provides direct evidence in humans for pain-related functional changes linked to TRPV1, which is a prime target in the development of pain relievers.FUNDING Supported by the Israel Science Foundation (368/19); Teva’s National Network of Excellence in Neuroscience grant (no. 0394886) and Teva’s National Network of Excellence in Neuroscience postdoctoral fellowship.

Authors

Ben Katz, Rachel Zaguri, Simon Edvardson, Channa Maayan, Orly Elpeleg, Shaya Lev, Elyad Davidson, Maximilian Peters, Shlomit Kfir-Erenfeld, Esther Berger, Shifa Ghazalin, Alexander M. Binshtok, Baruch Minke

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Figure 6

Cellular localization of the hTRPV1N331K channel.

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Cellular localization of the hTRPV1N331K channel. (A) Representative con...
(A) Representative confocal images of T-REx-293 cells expressing hTRPV1WT-GFP at LE levels or hTRPV1N331K-GFP at LE or HE levels. Left: Low-magnification (scale bar: 20 μm); middle and right, high-magnification (scale bar: 5 μm, the scale bar is applicable for the middle and right images); and right, high-magnification images at high contrast (HC). Note that the cellular distribution of hTRPV1WT-GFP is similar to that of hTRPV1N331K-GFP. (B) Mean fluorescence intensity measurements from high-magnification images of T-REx-293 cells expressing hTRPV1WT-GFP at LE (n = 7), hTRPV1N331K-GFP at LE (n = 12), and hTRPV1N331K-GFP at HE (n = 15). ****P < 0.0001, by 2-tailed Mann-Whitney U test with Bonferroni’s correction for multiple comparisons. Data indicate the mean ± SD. (C) Western blot analysis of T-REx-293 cells stably expressing hTRPV1WT or hTRPV1N331K after cell-surface biotinylation, using an anti-TRPV1 antibody (see Methods). Note that both hTRPV1WT and hTRPV1N331K show surface membrane expression (lanes 2 and 5). The intracellular protein actin was used to control the specificity of the assay for cell-surface proteins (n = 3). (D) Representative confocal images of naive T-REx-293 cells cotransfected with hTRPC3WT-mCherry (red or white) together with hTRPV1WT-GFP or hTRPV1N331K-GFP (green). First column (from left to right): Low-magnification merged images showing hTRPV1-GFP (green) and hTRPC3-mCherry (red). Scale bar: 20 μm (the scale bar is applicable to the first column panels only). Second column: High-magnification view of the boxed area showing hTRPV1-GFP (green). Scale bar: 5 μm (the scale bar is applicable to all panels except for those in the first column). Third column: High-magnification view of the boxed area showing hTRPC3-mCherry (white). Fourth column: High-magnification merged images showing hTRPV1-GFP (green) and hTRPC3-mCherry (red). Fifth column: Profile graphs indicate the fluorescence intensity along the white lines crossing the plasma membrane in the high-magnification merged images.