TRP Channel Pentamerization and Vascular TRPV1
This section covers: (1) the discovery that TRP channels can adopt pentameric stoichiometry as a gain-of-function escalation state (Lansky 2023, 2025; Ren 2024); (2) functional TRPV1 expression in arteriolar smooth muscle and its role in vasoconstriction and myogenic tone (Cavanaugh 2011; Phan 2020, 2022); (3) TRP channel vascular roles in human tissue ex vivo (Rivera-Mancilla 2024); (4) a reference overview of the TRP channel family (Delmas 2020). Together these papers support the novel hypotheses that (a) pathological TRP channel over-activation in ME/CFS could escalate to a pentameric hyper-conductive state, and (b) arteriolar TRPV1 dysfunction could mediate the inappropriate vasoconstriction seen during post-exertional malaise.
1 Lansky et al. 2023 — A Pentameric TRPV3 Channel with a Dilated Pore
Full Citation:: Lansky S, Betancourt JM, Zhang J, Jiang Y, Kim ED, Paknejad N, Nimigean CM, Yuan P, Scheuring S. A pentameric TRPV3 channel with a dilated pore. Nature. 2023;621(7977):206–214. (Lansky et al. 2023) DOI:: 10.1038/s41586-023-06470-1 PMID:: 37648856 Study Design:: High-speed atomic force microscopy (HS-AFM) + cryo-EM structural biology; lipid bilayer reconstitution Key Findings::
- TRPV3 channels exist in dynamic equilibrium between canonical tetramers and pentamers via membrane diffusive protomer exchange
- Pentamer average lifetime ~3 minutes; DPBA agonist significantly increases pentamer frequency
- Pentameric pore is ~2.4-fold wider at selectivity filter vs.\ tetramer; subunits undergo 18-degree hinge motion
- Enlarged pore explains the well-documented "pore-dilation phenomenon": prolonged activation leads to increased conductance and permeability to large ions
- First demonstration of non-tetrameric stoichiometry with functional consequence in any TRP channelConclusion:: TRP channels are not constrained to tetrameric stoichiometry; pentamer formation represents a structurally distinct hyper-conductive state with dramatically increased ion flux. Limitations:: TRPV3 specifically; lipid bilayer reconstitution (not native membrane); whether pentamer formation occurs for TRPM3 or other ME/CFS-relevant channels is unknown and speculative. Certainty Assessment::
- *Quality:* High (Nature; high-resolution HS-AFM + cryo-EM; Scheuring group, leading structural biology lab)
- *Sample:* Biophysical — multiple independent preparations
- *Replication:* Structural finding confirmed by follow-up (Lansky 2025); pentamer existence replicated
- *Score:* 0.802 Lansky et al. 2025 — Structural Dynamics and Permeability of the TRPV3 Pentamer
Full Citation:: Lansky S, Wang Z, Clarke OB, Chipot C, Scheuring S. Structural dynamics and permeability of the TRPV3 pentamer. Nat Commun. 2025;16:4347. (Lansky et al. 2025) DOI:: 10.1038/s41467-025-59798-9 PMID:: 40374654 Study Design:: Cryo-EM at 4.07 Å resolution + molecular dynamics simulations Key Findings::
- Pentamer has domain-swapped architecture and collapsed vanilloid binding site
- Selectivity filter 5.3-fold wider than closed tetramer; gate 7.3-fold wider
- MD simulations: free passage of large organic cations (Tris+, NMDG+, 2-MAE+) through pentameric pore
- Multiple agonists (2-APB, camphor, propofol) destabilize tetramers and facilitate pentamer formation via intermediate states
- Authors propose pentamer = "hyper-activated state" with highly permissive permeationConclusion:: Provides atomic-resolution mechanism for large-cation permeability in pentameric TRPV3. Agonist-driven destabilization suggests pentamer formation could be promoted by any sufficiently potent activating stimulus. Limitations:: Computational (MD) component; generalization to other TRP subtypes not demonstrated; in vitro structural work. Certainty Assessment::
- *Quality:* High (Nature Communications; same Scheuring group; independent MD simulation validation)
- *Sample:* Structural/computational
- *Replication:* Direct follow-up confirming Lansky 2023 with higher resolution
- *Score:* 0.783 Cavanaugh et al. 2011 — TRPV1 Reporter Mice: Arteriolar Smooth Muscle Expression
Full Citation:: Cavanaugh DJ, Chesler AT, Jackson AC, Sigal YM, Yamanaka H, Grant R, O’Donnell D, Nicoll RA, Shah NM, Julius D, Basbaum AI. Trpv1 reporter mice reveal highly restricted brain distribution and functional expression in arteriolar smooth muscle cells. J Neurosci. 2011;31(13):5067–5077. (Cavanaugh et al. 2011) DOI:: 10.1523/JNEUROSCI.6451-10.2011 PMID:: 21451044 Study Design:: Genetic reporter mouse (TRPV1-Cre x reporter); calcium imaging; pharmacological vasomotion assays; cross-species immunostaining (mouse, rat, monkey, human) Key Findings::
- Neuronal TRPV1 restricted to nociceptors in primary sensory ganglia + discrete hypothalamic band
- TRPV1 expressed in arteriolar smooth muscle cells in thermoregulatory tissues: cremaster, dura, tongue, trachea, skin
- Capsaicin increases calcium in smooth muscle cells and causes vasoconstriction
- Vascular TRPV1 vasoconstriction counteracts the vasodilation produced by neuronal TRPV1 (opposite functional roles)
- Pattern conserved across mouse, rat, monkey, human brain and vasculatureConclusion:: TRPV1 has dual roles: nociception (neuronal) and vasoconstriction (arteriolar smooth muscle). These are anatomically and functionally distinct and may act in opposition. Limitations:: Reporter mouse system — expression pattern may not perfectly reflect endogenous protein levels; TRPV1-Cre lineage tracing could include earlier developmental expression; functional vasomotion studies use exogenous capsaicin at supraphysiological concentrations. Certainty Assessment::
- *Quality:* High (Journal of Neuroscience; Julius/Basbaum group — Nobel-prize associated; genetic reporter gold standard)
- *Sample:* Multiple mouse cohorts + cross-species histology
- *Replication:* Vascular expression finding confirmed by Phan 2020, 2022
- *Score:* 0.754 Phan et al. 2020 — TRPV1 Throughout the Arterial Circulation Regulates Blood Pressure
Full Citation:: Phan TX, Ton HT, Gulyás H, Pórszász R, Tóth A, Russo R, Kay MW, Sahibzada N, Ahern GP. TRPV1 expressed throughout the arterial circulation regulates vasoconstriction and blood pressure. J Physiol. 2020;598(24):5639–5659. (Phan et al. 2020) DOI:: 10.1113/JP279909 PMID:: 32944976 Study Design:: Pharmacological TRPV1 antagonism + TRPV1 global knockout mice; isolated artery experiments; in vivo blood pressure measurement; sensory nerve ablation controls Key Findings::
- TRPV1 localizes to terminal arterioles in skeletal muscle, heart, adipose tissue; absent from large arteries
- Capsaicin causes dose-dependent vasoconstriction and increased systemic blood pressure in mice and rats
- Effect persists after sensory nerve ablation: confirms vascular smooth muscle origin, not neuronal
- Arteriolar TRPV1 is resistant to activity-induced desensitization (unlike sensory neurons) — enables sustained vasoconstriction
- Lysophosphatidic acid (LPA), an endogenous inflammatory lipid, activates arteriolar TRPV1
- Mechanism: TRPV1 depolarization -> L-type Ca2+ channel activation -> sustained vasoconstrictionConclusion:: Arteriolar TRPV1 is a functionally distinct vasoconstrictor activated by inflammatory lipids; its resistance to desensitization makes it capable of sustained pressure effects. Limitations:: Rodent models; human arteriolar TRPV1 expression and function not directly demonstrated; LPA is not a specific TRPV1 agonist (multiple receptor targets). ME/CFS relevance:: During PEM, inflammatory lipids (LPA, lysophosphatidylcholine, oxidized phospholipids) accumulate in exercising tissue. These could activate arteriolar TRPV1, producing vasoconstriction and impaired perfusion — the opposite of normal exercise hyperaemia. The non-desensitizing property would sustain this abnormal response. Certainty Assessment::
- *Quality:* High (Journal of Physiology; multi-method, genetic and pharmacological; independent replication by Phan 2022)
- *Sample:* Multiple mouse cohorts + pharmacological replication in rats
- *Replication:* Confirmed by companion paper Phan 2022; tissue-specific expression confirmed by Cavanaugh 2011
- *Score:* 0.725 Phan et al. 2022 — TRPV1 Enables Rapid Myogenic Tone in Arteries
Full Citation:: Phan TX, Ton HT, Gulyás H, Pórszász R, Tóth A, Russo R, Kay MW, Sahibzada N, Ahern GP. TRPV1 in arteries enables a rapid myogenic tone. J Physiol. 2022;600(7):1651–1666. (Phan et al. 2022) DOI:: 10.1113/JP281873 PMID:: 35020949 Study Design:: TRPV1 KO mice + pharmacological antagonism; pressure myography; in vivo skeletal muscle and coronary flow; pharmacological dissection of PLC/PKC signaling Key Findings::
- TRPV1 antagonists dilate skeletal muscle arterioles in vitro and in vivo, increase coronary perfusion, transiently decrease blood pressure
- Stretch-induced activation requires phospholipase C/PKC signaling combined with temperature
- TRPV1 drives the rapid component of myogenic tone in heart and skeletal muscle arteries; TRPM4 contributes remaining tone
- TRPV1 disruption slows tone development and impairs vasodilation following brief arterial constrictionConclusion:: TRPV1 is the primary stretch sensor for rapid myogenic tone in cardiac and skeletal muscle arterioles; its activation is temperature- and signaling-pathway-dependent. Limitations:: Rodent; does not address ME/CFS; temperature dependence means findings are context-sensitive. ME/CFS relevance:: If TRPV1 is sensitized (as in inflamed or pro-nociceptive states documented in ME/CFS), myogenic tone would be elevated at rest and exaggerated during exercise, impairing normal exercise-induced vasodilation and contributing to post-exertional muscle ischaemia. Certainty Assessment::
- *Quality:* High (Journal of Physiology; same Ahern group; direct follow-up with mechanistic depth)
- *Sample:* Multiple knockout + pharmacological cohorts
- *Replication:* Same group as Phan 2020; cross-validates findings
- *Score:* 0.726 Rivera-Mancilla et al. 2024 — TRP Channels in Human Dermal Arteries
Full Citation:: Rivera-Mancilla E, Al-Hassany L, Marynissen H, Bamps D, Garrelds IM, Cornette J, Danser AHJ, Villalón CM, de Hoon JN, MaassenVanDenBrink A. Functional Analysis of TRPA1, TRPM3, and TRPV1 Channels in Human Dermal Arteries and Their Role in Vascular Modulation. Pharmaceuticals. 2024;17(2):156. (Rivera-Mancilla et al. 2024) DOI:: 10.3390/ph17020156 PMID:: 38399371 Study Design:: Ex vivo pharmacology; isolated human dermal artery segments from surgical patients; wire myography; TRP agonists/antagonists; CGRP, NOS, COX and K-channel pathway dissection Key Findings::
- Pregnenolone sulfate (PregS, TRPM3 agonist) induces relaxation in human dermal arteries via CGRP-independent mechanisms; blocked by isosakuranetin (TRPM3 antagonist)
- Capsaicin-induced relaxation not blocked by CGRP receptor antagonists, NOS inhibitors, COX inhibitors, or K-channel blockers — standard vasodilation pathways not involved
- Cinnamaldehyde (TRPA1) similarly did not activate the tested relaxation pathways
- *TRPV1 vasoconstriction was not tested or observed in this preparation*Conclusion:: In human dermal arteries, TRPM3 mediates vascular relaxation via non-CGRP pathways. TRPV1 vasodilation pathways tested were inconclusive. Does not contradict TRPV1 vasoconstriction in resistance arterioles (different tissue, different receptor-effector coupling). Limitations:: Dermal arteries (not skeletal muscle or cardiac resistance arterioles); focused on relaxation, not constriction; patient-derived tissue has uncontrolled variability. ME/CFS relevance:: Confirms TRPM3 vascular activity in human tissue. Tissue specificity is critical: dermal findings cannot be generalized to the skeletal muscle arterioles where Phan 2020/2022 demonstrated TRPV1 vasoconstriction. Certainty Assessment::
- *Quality:* Medium (Pharmaceuticals MDPI; ex vivo human tissue; Erasmus/KU Leuven groups)
- *Sample:* Human dermal arteries from surgical patients (n not specified per arm)
- *Replication:* Not independently replicated; single study
- *Score:* 0.657 Ren et al. 2024 — Oligomeric Rearrangement as Channel Activity Regulator
Full Citation:: Ren Y, Yang X, Shen Y. Oligomeric rearrangement may regulate channel activity. Biophys Rep. 2024;10(5):293–296. (Ren, Yang, and Shen 2024) DOI:: 10.52601/bpr.2023.230018 PMID:: 39539288 Study Design:: Perspective/commentary; no primary data Key Findings::
- Proposes oligomeric stoichiometry switching as a general gating mechanism across channel families
- Highlights TRPV3 pentamer (Lansky 2023) and CALHM channel data as evidence
- Argues this mechanism could be widespread and represent a novel therapeutic target categoryConclusion:: Oligomeric transitions are not unique to TRPV3; could represent a general regulatory principle. Conceptual framework for considering whether other TRP channels (including TRPM3, TRPV1) undergo similar transitions under pathological conditions. Limitations:: Commentary only — no primary data; highly speculative extrapolation from TRPV3 data; primary evidence base is Lansky 2023. Certainty Assessment::
- *Quality:* Low-Medium (Biophys Rep; perspective format; no primary data)
- *Sample:* N/A (commentary)
- *Replication:* N/A
- *Score:* 0.558 Delmas & Coste 2020 — SnapShot: Orofacial Sensation (TRP Family Reference)
Full Citation:: Delmas P, Coste B. SnapShot: Orofacial Sensation. Cell. 2020;183(1):284–284.e1. (Delmas and Coste 2020) DOI:: 10.1016/j.cell.2020.08.014 PMID:: 33007264 Study Design:: Cell SnapShot (visual one-page reference summary; no primary data) Key Findings::
- Provides overview of TRP channel family members in trigeminal/orofacial sensory system
- Covers: TRPV1 (heat \>43°C, capsaicin, acidosis, inflammation), TRPA1 (cold \<17°C, irritants, ROS), TRPM8 (cool \<25°C, menthol), TRPV3/TRPV4 (warm), TRPM3 (noxious heat, steroids), TRPC4/TRPC5 (mechanosensation)
- Includes receptor-channel overview for all major sensory modalitiesConclusion:: Authoritative reference summary for TRP channel family physiological roles from Cell. Useful for contextualizing where each TRP channel sits in the sensory-vascular landscape. Limitations:: Reference format only — no primary data, no statistical analysis; limited to orofacial context (not systemic vascular roles). Certainty Assessment::
- *Quality:* High journal (Cell) for a reference format; content is review/synthesis
- *Sample:* N/A
- *Score:* 0.60