Sensitization Of TRPV1 Research Articles

The Contribution of the Ankyrin Repeat Domain of TRPV1 as a Thermal Module

The TRPV1 cation nonselective ion channel plays an essential role in thermosensation and perception of other noxious stimuli. TRPV1 can be activated by low extracellular pH, high temperature, or naturally occurring pungent molecules such as allicin, capsaicin, or resiniferatoxin. Its noxious thermal sensitivity makes it an important participant as a thermal sensor in mammals. However, details of the mechanism of channel activation by increases in temperature remain unclear. Here, we used a combination of approaches to try to understand the role of the ankyrin repeat domain (ARD) in channel behavior. First, a computational modeling approach by coarse-grained molecular dynamics simulation of the whole TRPV1 embedded in a phosphatidylcholine and phosphatidylethanolamine membrane provides insight into the dynamics of this channel domain. Global analysis of the structural ensemble shows that the ARD is a region that sustains high fluctuations during dynamics at different temperatures. We then performed biochemical and thermal stability studies of the purified ARD by the means of circular dichroism and tryptophan fluorescence and demonstrate that this region undergoes structural changes at similar temperatures that lead to TRPV1 activation. Our data suggest that the ARD is a dynamic module and that it may participate in controlling the temperature sensitivity of TRPV1.

Elucidating the functional evolution of heat sensors among Xenopus species adapted to different thermal niches by ancestral sequence reconstruction.

Ambient temperature fluctuations are detected via the thermosensory system which allows animals to seek preferable thermal conditions or escape from harmful temperatures. Evolutionary changes in thermal perception have thus potentially played crucial roles in niche selection. The genus Xenopus (clawed frog) is suitable for investigating the relationship between thermal perception and niche selection due to their diverse latitudinal and altitudinal distributions. Here we performed comparative analyses of the neuronal heat sensors TRPV1 and TRPA1 among closely related Xenopus species (X.borealis, X.muelleri, X.laevis, and X.tropicalis) to elucidate their functional evolution and to assess whether their functional differences correlate with thermal niche selection among the species. Comparison of TRPV1 among four extant Xenopus species and reconstruction of the ancestral TRPV1 revealed that TRPV1 responses to repeated heat stimulation were specifically altered in the lineage leading to X.tropicalis which inhabits warmer niches. Moreover, the thermal sensitivity of TRPA1 was lower in X.tropicalis than the other species, although the thermal sensitivity of TRPV1 and TRPA1 was not always lower in species that inhabit warmer niches than the species inhabit cooler niches. However, a clear correlation was found in species differences in TRPA1 activity. Heat-evoked activity of TRPA1 in X.borealis and X.laevis, which are adapted to cooler niches, was significantly higher than in X.tropicalis and X.muelleri which are adapted to warmer niches. These findings suggest that the functional properties of heat sensors changed during Xenopus evolution, potentially altering the preferred temperature ranges among species.

Multifunctional TRPV1 Ion Channels in Physiology and Pathology with Focus on the Brain, Vasculature, and Some Visceral Systems.

TRPV1 has been originally cloned as the heat and capsaicin receptor implicated in acute pain signalling, while further research has shifted the focus to its importance in chronic pain caused by inflammation and associated with this TRPV1 sensitization. However, accumulating evidence suggests that, apart from pain signalling, TRPV1 subserves many other unrelated to nociception functions in the nervous system. In the brain, TRPV1 can modulate synaptic transmission via both pre- and postsynaptic mechanisms and there is a functional crosstalk between GABA receptors and TRPV1. Other fundamental processes include TRPV1 role in plasticity, microglia-to-neuron communication, and brain development. Moreover, TRPV1 is widely expressed in the peripheral tissues, including the vasculature, gastrointestinal tract, urinary bladder, epithelial cells, and the cells of the immune system. TRPV1 can be activated by a large array of physical (heat, mechanical stimuli) and chemical factors (e.g., protons, capsaicin, resiniferatoxin, and endogenous ligands, such as endovanilloids). This causes two general cell effects, membrane depolarization and calcium influx, thus triggering depending on the cell-type diverse functional responses ranging from neuronal excitation to secretion and smooth muscle contraction. Here, we review recent research on the diverse TRPV1 functions with focus on the brain, vasculature, and some visceral systems as the basis of our better understanding of TRPV1 role in different human disorders.

Neurotrophic Proteins in Dentin and Their Effect on Trigeminal Sensory Neurons

IntroductionA plethora of bioactive molecules present during tooth formation become sequestered in the mineralized dentin matrix and can be released into the pulp tissue after demineralization from carious lesions. However, neurotrophic factors are differentially expressed and secreted during various stages of odontogenesis. Thus, the aims of this study were(1) to investigate their presence and relative abundance in crown and root dentin and(2) to evaluate the bioactivity of dentin-derived proteins on neuronal cells. MethodsDentin matrix proteins (DMPs) were isolated from matched roots and crowns of extracted healthy human third molars. The total protein amount as well as the concentration of growth factors and neurotrophic proteins were quantified. The impact on neuritogenesis was determined with mouse trigeminal neurons in vitro and by a hydrogel implant model in vivo. Transient receptor potential cation channel subfamily V member 1 (TRPV1) sensitization of DMP-conditioned neurons was evaluated by single-cell calcium imaging. ResultsThe relative concentration of neurotrophic molecules revealed that nerve growth factor is the most abundant neurotrophin with 3-fold increased expression in radicular dentin. Similarly, brain-derived neurotrophic factor and neurotrophin 3 are more abundant in radicular than coronal dentin. Conversely, glial cell line–derived neurotrophic factor is more abundant in coronal dentin, whereas neurotrophin 4 is equally distributed. Dentin matrix proteins promoted neurite outgrowth in vitro and axonal targeting in vivo, with a greater effect observed by radicular dentin extracts. Furthermore, DMPs sensitized TRPV1 responses in mouse trigeminal neurons with greater activity seen with extracts from root dentin. ConclusionsNeurotrophic factors are differentially distributed between coronal and radicular dentin with different effects of dentin-derived proteins on axonal growth and targeting as well as the sensitization of TRPV1. Thus, extracellular proteins from the dentin matrix are likely involved in neurogenic responses to caries and could be exploited in clinical regenerative endodontics to promote reinnervation and enhance tissue regeneration.

Mo1596 - Effect of Resolvin D1, D2 and E1 on Histamine-Induced Sensitization of TRPV1

Mo1596 - Effect of Resolvin D1, D2 and E1 on Histamine-Induced Sensitization of TRPV1

(105) mGlu2/3 differentially modulate TRPV1 sensitization in mouse and human sensory neurons

(105) mGlu2/3 differentially modulate TRPV1 sensitization in mouse and human sensory neurons

Ankyrin-rich membrane spanning protein as a novel modulator of transient receptor potential vanilloid 1-function in nociceptive neurons.

The ion channel TRPV1 is mainly expressed in small diameter dorsal root ganglion (DRG) neurons, which are involved in the sensation of acute noxious thermal and chemical stimuli. Direct modifications of the channel by diverse signalling events have been intensively investigated, but little is known about the composition of modulating macromolecular TRPV1 signalling complexes. Here, we hypothesize that the novel adaptor protein ankyrin-rich membrane spanning protein/kinase D interacting substrate (ARMS) interacts with TRPV1 and modulates its function in rodent DRG neurons. We used immunohistochemistry, electrophysiology, microfluorimetry and immunoprecipitation experiments to investigate TRPV1 and ARMS interactions in DRG neurons and transfected cells. We found that TRPV1 and ARMS are co-expressed in a subpopulation of DRG neurons. ARMS sensitizes TRPV1 towards capsaicin in transfected HEK 293 cells and in mouse DRG neurons in a PKA-dependent manner. Using a combination of functional imaging and immunocytochemistry, we show that the magnitude of the capsaicin response in DRG neurons depends not only on TRPV1 expression, but on the co-expression of ARMS alongside TRPV1. These data indicate that ARMS is an important component of the signalling complex regulating the sensitivity of TRPV1. The study identifies ARMS as an important component of the signalling complex regulating the sensitivity of excitatory ion channels (TRPV1) in peripheral sensory neurons (DRG neurons) and transfected cells.

Abstract PR062

Background & Objectives: Nerve growth factor (NGF) induced-transient receptor potential vanilloid type 1 (TRPV1) sensitization augments sympathetic nerve response, which may be detrimental to the ischemic myocardium[1]. We have previously demonstrated that intrathecal morphine preconditioning (ITMP) could reduce myocardial ischemia-reperfusion (I/R) injury [2], while the mechanisms need to be elucidated. This study was designed to investigate the effects of ITMP on spinal NGF-TRPV1 sensitization following myocardial I/R injury and the involvement of μ-opioid receptor. Materials & Methods: All rats were subjected to 30 min ischemia followed by 120 min reperfusion, except the rats in SHAM group. ITMP was produced by three cycles of 5 min intrathecal injection of morphine and 5 min intermission before myocardial ischemia. The μ-opioid receptor (MOR) antagonist CTOP was intrathecally injected 10 min prior to ITMP. The severity of arrhythmia was scored and myocardial infarct size (IS) was measured as the percentage of area at risk (IS/AAR). The co-expression of TRPV1 and MOR in dorsal root ganglion (DRG) was detected by double immunofluorescence assay. The protein levels of NGF and TRPV1 in DRG and spinal cord were detected by western blot and immunohistochemistry methods, respectively. Results: The myocardial infarct size and the incidence of arrhythmia induced by myocardial I/R injury were significantly reduced by IPC and ITMP. However, the cardioprotective effects of ITMP were abolished by CTOP. According to the immunofluorescence results, TRPV1 and MOR were co-expressed in rat DRG neurons, and their expression were obviously elevated after myocardial I/R injury. Both IPC and ITMP markedly inhibited the expression of TRPV1 in DRG neurons while had little effects on the expression of MOR. Moreover, the rise of NGF level in rat DRG as well as the expressions of NGF and TRPV1 in spinal dorsal horn induced by myocardial I/R injury were suppressed by IPC and ITMP. Nevertheless, the effects of ITMP on the expressions of NGF and TRPV1 were also blocked by CTOP.Conclusion: ITMP may exert cardioprotection by inhibiting the expressions of NGF and TRPV1 in DRG and spinal cord via activation of the spinal μ-opioid receptor, and thus prevent NGF-induced TRPV1 sensitization. This work was supported by the National Natural Science Foundation of China (81471145)

Bradykinin Induces TRPV1 Exocytotic Recruitment in Peptidergic Nociceptors.

Transient receptor potential vanilloid I (TRPV1) sensitization in peripheral nociceptors is a prominent phenomenon that occurs in inflammatory pain conditions. Pro-algesic agents can potentiate TRPV1 activity in nociceptors through both stimulation of its channel gating and mobilization of channels to the neuronal surface in a context dependent manner. A recent study reported that ATP-induced TRPV1 sensitization in peptidergic nociceptors involves the exocytotic release of channels trafficked by large dense core vesicles (LDCVs) that cargo alpha-calcitonin gene related peptide alpha (αCGRP). We hypothesized that, similar to ATP, bradykinin may also use different mechanisms to sensitize TRPV1 channels in peptidergic and non-peptidergic nociceptors. We found that bradykinin notably enhances the excitability of peptidergic nociceptors, and sensitizes TRPV1, primarily through the bradykinin receptor 2 pathway. Notably, bradykinin sensitization of TRPV1 in peptidergic nociceptors was significantly blocked by inhibiting Ca2+-dependent neuronal exocytosis. In addition, silencing αCGRP gene expression, but not substance P, drastically reduced bradykinin-induced TRPV1 sensitization in peptidergic nociceptors. Taken together, these findings indicate that bradykinin-induced sensitization of TRPV1 in peptidergic nociceptors is partially mediated by the exocytotic mobilization of new channels trafficked by αCGRP-loaded LDCVs to the neuronal membrane. Our findings further imply a central role of αCGRP peptidergic nociceptors in peripheral algesic sensitization, and substantiate that inhibition of LDCVs exocytosis is a valuable therapeutic strategy to treat pain, as it concurrently reduces the release of pro-inflammatory peptides and the membrane recruitment of thermoTRP channels.

Photosensitization in Porphyrias and Photodynamic Therapy Involves TRPA1 and TRPV1

Photosensitization, an exaggerated sensitivity to harmless light, occurs genetically in rare diseases, such as porphyrias, and in photodynamic therapy where short-term toxicity is intended. A common feature is the experience of pain from bright light. In human subjects, skin exposure to 405 nm light induced moderate pain, which was intensified by pretreatment with aminolevulinic acid. In heterologous expression systems and cultured sensory neurons, exposure to blue light activated TRPA1 and, to a lesser extent, TRPV1 channels in the absence of additional photosensitization. Pretreatment with aminolevulinic acid or with protoporphyrin IX dramatically increased the light sensitivity of both TRPA1 and TRPV1 via generation of reactive oxygen species. Artificial lipid bilayers equipped with purified human TRPA1 showed substantial single-channel activity only in the presence of protoporphyrin IX and blue light. Photosensitivity and photosensitization could be demonstrated in freshly isolated mouse tissues and led to TRP channel-dependent release of proinflammatory neuropeptides upon illumination. With antagonists in clinical development, these findings may help to alleviate pain during photodynamic therapy and also allow for disease modification in porphyria patients. Cutaneous porphyria patients suffer from burning pain upon exposure to sunlight and other patients undergoing photodynamic therapy experience similar pain, which can limit the therapeutic efforts. This study elucidates the underlying molecular transduction mechanism and identifies potential targets of therapy. Ultraviolet and blue light generates singlet oxygen, which oxidizes and activates the ion channels TRPA1 and TRPV1. The disease and the therapeutic options could be reproduced in models ranging from isolated ion channels to human subjects, applying protoporphyrin IX or its precursor aminolevulinic acid. There is an unmet medical need, and our results suggest a therapeutic use of the pertinent antagonists in clinical development.

The Complement System Component C5a Produces Thermal Hyperalgesia via Macrophage-to-Nociceptor Signaling That Requires NGF and TRPV1.

The complement cascade is a principal component of innate immunity. Recent studies have underscored the importance of C5a and other components of the complement system in inflammatory and neuropathic pain, although the underlying mechanisms are largely unknown. In particular, it is unclear how the complement system communicates with nociceptors and which ion channels and receptors are involved. Here we demonstrate that inflammatory thermal and mechanical hyperalgesia induced by complete Freund's adjuvant was accompanied by C5a upregulation and was markedly reduced by C5a receptor (C5aR1) knock-out or treatment with the C5aR1 antagonist PMX53. Direct administration of C5a into the mouse hindpaw produced strong thermal hyperalgesia, an effect that was absent in TRPV1 knock-out mice, and was blocked by the TRPV1 antagonist AMG9810. Immunohistochemistry of mouse plantar skin showed prominent expression of C5aR1 in macrophages. Additionally, C5a evoked strong Ca(2+) mobilization in macrophages. Macrophage depletion in transgenic macrophage Fas-induced apoptosis mice abolished C5a-dependent thermal hyperalgesia. Examination of inflammatory mediators following C5a injection revealed a rapid upregulation of NGF, a mediator known to sensitize TRPV1. Preinjection of an NGF-neutralizing antibody or Trk inhibitor GNF-5837 prevented C5a-induced thermal hyperalgesia. Notably, NGF-induced thermal hyperalgesia was unaffected by macrophage depletion. Collectively, these results suggest that complement fragment C5a induces thermal hyperalgesia by triggering macrophage-dependent signaling that involves mobilization of NGF and NGF-dependent sensitization of TRPV1. Our findings highlight the importance of macrophage-to-neuron signaling in pain processing and identify C5a, NGF, and TRPV1 as key players in this cross-cellular communication. This study provides mechanistic insight into how the complement system, a key component of innate immunity, regulates the development of pain hypersensitivity. We demonstrate a crucial role of the C5a receptor, C5aR1, in the development of inflammatory thermal and mechanical sensitization. By focusing on the mechanisms of C5a-induced thermal hyperalgesia, we show that this process requires recruitment of macrophages and initiation of macrophage-to-nociceptor signaling. At the molecular level, we demonstrate that this signaling depends on NGF and is mediated by the heat-sensitive nociceptive channel TRPV1. This deeper understanding of how immune cells and neurons interact to regulate pain processing is expected to facilitate mechanism-based approaches in the development of new analgesics.

259 Neuronal Sensitization of TRPV1 by Histamine Mediated by Histamine 1 Receptor in an Unique Cohort of PI-IBS Patients

259 Neuronal Sensitization of TRPV1 by Histamine Mediated by Histamine 1 Receptor in an Unique Cohort of PI-IBS Patients

Extracellular Sodium is Required for Temperature-Dependent Gating in TRPV1 Channels

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 other stimuli suggest that the channel has a unique opening transition that is allosterically modulated by independent stimulus-sensing domains. On the contrary, recently obtained near-atomic resolution structures of TRPV1 in different states suggest that different agonists promote distinct open states, by differentially modulating the inner pore gate or the selectivity filter. Finally, it has been proposed that the opening of the pore may confer the channel with high temperature-sensitivity. Here we show that extracellular sodium ions tune both temperature-dependent activation and inactivation in TRPV1 channels to maintain sensitivity to noxious stimuli at physiological temperatures. Exploration of temperature-dependent activation over a wide range of temperatures in the presence of distinct modulators demonstrates that the gating mechanism involves temperature-sensitive and -insensitive transitions that are allosterically coupled and differentially modified by sodium, pH, vanilloids and tarantula toxins. We observe that the channels exhibit non-maximal open probability and temperature-independent gating in the absence of external sodium or in the presence of double knot tarantula toxin DkTx, indicating that the opening transition is temperature-independent and supporting the modular allosteric view of this channel protein. This unique gating mechanism provides a framework for understanding how the temperature sensitivity of TRPV1 is tuned by a wide array of regulators.

A-kinase anchoring protein 79/150 coordinates metabotropic glutamate receptor sensitization of peripheral sensory neurons.

Glutamate serves as the primary excitatory neurotransmitter in the nervous system. Previous studies have identified a role for glutamate and group I metabotropic receptors as targets for study in peripheral inflammatory pain. However, the coordination of signaling events that transpire from receptor activation to afferent neuronal sensitization has not been explored. Herein, we identify that scaffolding protein A-kinase anchoring protein 79/150 (AKAP150) coordinates increased peripheral thermal sensitivity after group I metabotropic receptor (mGluR5) activation. In both acute and persistent models of thermal somatosensory behavior, we report that mGluR5 sensitization requires AKAP150 expression. Furthermore, electrophysiological approaches designed to record afferent neuronal activity reveal that mGluR5 sensitization also requires functional AKAP150 expression. In dissociated primary afferent neurons, mGluR5 activation increases TRPV1 responses in an AKAP-dependent manner through a mechanism that induces AKAP association with TRPV1. Experimental results presented herein identify a mechanism of receptor-driven scaffolding association with ion channel targets. Importantly, this mechanism could prove significant in the search for therapeutic targets that repress episodes of acute pain from becoming chronic in nature.

505 Impaired Esophageal Mucosa Integrity in Refractory Reflux Disease Patients on Proton Pump Inhibitors. A Role for Residual Acid Reflux?

was assayed by immunoprecipitation and western blotting. To further investigate if PAR2 activation sensitized acid-induced ATP release through TRPV1 and ASICs, pretreatment with IRTX or amiloride for 45 min before trypsin (4 mg/ml, 60 min) was administered. Results: Acid stimulated the release of ATP from HEEC (217 ± 58 % Control, P<0.0001). This was reduced by 60% after pretreatment with IRTX (P<0.0001) and by 79% after amiloride pretreatment (P<0.0001). TRPV1 siRNA transfection also decreased acid-induced ATP release (54%, P<0.01). Pretreatment of HEECs with trypsin, tryptase or the PAR-2 agonist further increased acid-induced ATP release (Table). Trypsin or tryptase led to the phosphorylation of TRPV1, indicating TRPV1 sensitization. Acid-induced ATP release sensitized by trypsin was partially blocked by IRTX and amiloride (39% and 50%, respectively, P<0.0001). Conclusions: Acid-induced ATP release was augmented by TRPV1 and ASICs through PAR2 activation. These findings suggest that the pathophysiology of heartburn sensation or esophageal hypersensitivity may be associated with the activation of PAR-2, TRPV1 and ASICs. Effects of trypsin, tryptase or PAR-2 agonist on acid-induced ATP release in HEEC

504 PAR-2 Activation Enhances Acid-Induced ATP Release Through TRPV1 and ASICs Sensitization in Human Esophageal Epithelial Cells

504 PAR-2 Activation Enhances Acid-Induced ATP Release Through TRPV1 and ASICs Sensitization in Human Esophageal Epithelial Cells

Pain: Turning down the heat in pain.

The GABA receptor subunit GABAB1 inhibits sensitization of the heat-activated transient receptor potential cation channel TRPV1 in peripheral nociceptors.

GABA Blocks Pathological but Not Acute TRPV1 Pain Signals

Sensitization of the capsaicin receptor TRPV1 is central to the initiation of pathological forms of pain, and multiple signaling cascades are known to enhance TRPV1 activity under inflammatory conditions. How might detrimental escalation of TRPV1 activity be counteracted? Using a genetic-proteomic approach, we identify the GABAB1 receptor subunit as bona fide inhibitor of TRPV1 sensitization in the context of diverse inflammatory settings. We find that the endogenous GABAB agonist, GABA, is released from nociceptive nerve terminals, suggesting an autocrine feedback mechanism limiting TRPV1 sensitization. The effect of GABAB on TRPV1 is independent of canonical G protein signaling and rather relies on close juxtaposition of the GABAB1 receptor subunit and TRPV1. Activating the GABAB1 receptor subunit does not attenuate normal functioning of the capsaicin receptor but exclusively reverts its sensitized state. Thus, harnessing this mechanism for anti-pain therapy may prevent adverse effects associated with currently available TRPV1 blockers.

Modeling pain in vitro using nociceptor neurons reprogrammed from fibroblasts.

Reprogramming somatic cells from one cell fate to another can generate specific neurons suitable for disease modeling. To maximize the utility of patient-derived neurons, they must model not only disease-relevant cell classes but also the diversity of neuronal subtypes found in vivo and the pathophysiological changes that underlie specific clinical diseases. Here, we identify five transcription factors that reprogram mouse and human fibroblasts into noxious stimulus-detecting (nociceptor) neurons that recapitulate the expression of quintessential nociceptor-specific functional receptors and channels found in adult mouse nociceptor neurons as well as native subtype diversity. Moreover, the derived nociceptor neurons exhibit TrpV1 sensitization to the inflammatory mediator prostaglandin E2 and the chemotherapeutic drug oxaliplatin, modeling the inherent mechanisms underlying inflammatory pain hypersensitivity and painful chemotherapy-induced neuropathy. Using fibroblasts from patients with familial dysautonomia (hereditary sensory and autonomic neuropathy type III), we show that the technique can reveal novel aspects of human disease phenotypes in vitro.

Peripheral Group I Metabotropic Glutamate Receptor Activation Leads to Muscle Mechanical Hyperalgesia Through TRPV1 Phosphorylation in the Rat

Elevated glutamate levels within injured muscle play important roles in muscle pain and hyperalgesia. In this study, we hypothesized that protein kinase C (PKC)–dependent TRPV1 phosphorylation contributes to the muscle mechanical hyperalgesia following activation of Group I metabotropic glutamate receptors (mGlu1/5). Mechanical hyperalgesia induced by (R,S)-3,5-dihydroxyphenylglycine (DHPG), an mGlu1/5 agonist, in the masseter muscle was attenuated by AMG9810, a specific TRPV1 antagonist. AMG9810 also suppressed mechanical hyperalgesia evoked by pharmacologic activation of PKC. DHPG-induced mechanical hyperalgesia was suppressed by pretreatment with a decoy peptide that disrupted interactions between TRPV1 and A-kinase–anchoring protein (AKAP), which facilitates phosphorylation of TRPV1. In dissociated trigeminal ganglia, DHPG upregulated serine phosphorylation of TRPV1 (S800), during which DHPG-induced mechanical hyperalgesia was prominent. The TRPV1 phosphorylation at S800 was suppressed by a PKC inhibitor. Electrophysiologic measurements in trigeminal ganglion neurons demonstrated that TRPV1 sensitivity was enhanced by pretreatment with DHPG, and this was prevented by a PKC inhibitor, but not by a protein kinase A inhibitor. These results suggest that mGlu1/5 activation in masseter afferents invokes phosphorylation of TRPV1 serine residues including S800, and that phosphorylation-induced sensitization of TRPV1 is involved in masseter mechanical hyperalgesia. These data support a role of TRPV1 as an integrator of glutamate receptor signaling in muscle nociceptors. PerspectiveThis article demonstrates that activation of mGlu1/5 leads to phosphorylation of a specific TRPV1 residue via PKC and AKAP150 in trigeminal sensory neurons and that functional interactions between glutamate receptors and TRPV1 mediate mechanical hyperalgesia in the muscle tissue.