Alternative titles; symbols
HGNC Approved Gene Symbol: TRPM8
Cytogenetic location: 2q37.1 Genomic coordinates (GRCh38) : 2:233,917,373-234,019,522 (from NCBI)
TRPM8 belongs to the melastatin (TRPM1; 603576)-related transient receptor (TRPM) channel family. TRPMs are Ca(2+)-permeable cation channels localized predominantly to the plasma membrane. The structural machinery of TRPM channels includes intracellular N and C termini, 6 transmembrane segments, and a pore region between segments 5 and 6. The N-terminal domain has a conserved region, and the C-terminal domain contains a TRP motif, a coiled-coil region, and, in some TRPM channels, an enzymatic domain. TRPM8 is activated by a broad range of modulator compounds, including cold and cooling compounds, such as menthol (review by Farooqi et al., 2011).
Using subtractive hybridization to generate a prostate-specific cDNA library, followed by 5-prime and 3-prime RACE, Tsavaler et al. (2001) obtained a cDNA encoding TRPM8, which they called TRPP8. The predicted 1,104-amino acid TRPP8 protein lacks a signal peptide, but it contains 7 C-terminal transmembrane alpha helices and a large N-terminal hydrophilic domain with 8 potential N-linked glycosylation sites. The authors noted that TRPP8 is most closely related to TRPC7 (TRPM2; 603749), followed by melastatin (TRPM1), with which it shares approximately 34% identity. Western blot analysis showed expression of a 130-kD TRPP8 protein, close to the predicted value. Northern blot and dot blot analyses revealed expression of 5.2- and 6.2-kb TRPP8 transcripts only in normal prostate and a melanoma cell line. In addition to normal prostate and the melanoma cell line, RT-PCR analysis detected expression of TRPP8 in testis, a colorectal adenocarcinoma cell line, and a prostate carcinoma cell line. In situ hybridization analysis demonstrated moderate expression of TRPP8 in epithelial cells of normal prostate. Stronger expression was detected in epithelium of benign prostate hyperplasia and in prostate carcinomas. Expression was also detected in several other neoplastic tissues. Tsavaler et al. (2001) proposed that TRPP8, in contrast to the putative tumor suppressor melastatin, may be an oncogene given its high expression in melanomas.
Peier et al. (2002) cloned and characterized the mouse Trpm8 gene, a distant relative of vanilloid receptor-1 (VR1; 602076). The predicted 1,104-amino acid Trpm8 protein is 93% identical to human TRPM8, and its closest relative is TRPM2, which is 42% identical. TRPM8 belongs to the 'long' or melastatin subfamily of TRP channels, a group characterized by a lack of ankyrin domains in their N termini. TRP channels typically contain 6 transmembrane (TM) domains, and a Kyte-Doolittle plot suggested the presence of 8 distinct hydrophobic peaks in the Trpm8 sequence, representing 6 to 8 predicted TM domains. Overall, the predicted TM domains are within amino acids 695 to 1,024. Outside of this region, the only predicted secondary structures are coiled-coil domains present in both the N- and C-terminal portions of the protein.
Using expression cloning of a rat trigeminal nerve cDNA library in a human embryonic kidney cell line and screening for changes in intracellular calcium on exposure to room-temperature menthol, McKemy et al. (2002) identified a cDNA encoding Trpm8, which they called Cmr1 (cold-menthol receptor-1). The deduced 1,104-amino acid protein is 92% identical to human TRPM8. Northern blot analysis detected transcripts of 6.0 and 4.5 kb in rat dorsal root ganglia and trigeminal neurons. In situ hybridization analysis demonstrated expression in small-diameter, but not larger-diameter, sensory neurons, similar in size to VR1-expressing cells.
By genomic sequence analysis, Tsavaler et al. (2001) determined that the TRPM8 gene contains 24 exons and spans 95 kb.
Cryoelectron Microscopy
Yin et al. (2018) determined the cryoelectron microscopy structure of full-length TRPM8 from the collared flycatcher (Ficedula albicollis) at an overall resolution of about 4.1 angstroms. The TRPM8 structure revealed a 3-layered architecture. The amino-terminal domain with a fold distinct among known TRP structures, together with the carboxyl-terminal region, forms a large 2-layered cytosolic ring that extensively interacts with the transmembrane channel layer. The structure suggests that the menthol-binding site is located within the voltage-sensor-like domain and thus provides a structural glimpse of the design principle of the molecular transducer for cold and menthol sensation.
Yin et al. (2019) used cryoelectron microscopy to determine the structures of TRMP8 in complex with the synthetic cooling compound icilin, phosphatidylinositol 4,5-bisphosphate (PIP2), and calcium as well as in complex with the menthol analog WS12 and PIP2. The structure revealed the binding sites for cooling agonists and PIP2 and TRMP8. Notably, PIP2 binds to TRPM8 in 2 different modes, which illustrate the mechanism of allosteric coupling between PIP2 and agonists. The TRPM8 agonist-binding site is located at the voltage sensor-like domain (VSLD) cavity, which enables the cooling agents to directly control the TRP domain to open the intracellular gate. Second, PIP2 binding in TRPM8 engages subdomains from both the transmembrane domain and the cytoplasmic domain at an interlayer nexus. Yin et al. (2019) concluded that PIP2 facilitates cooling agent sensing allosterically and mediates structural rearrangements during channel gating, which account for the stringent PIP2 dependence in TRPM8 channels.
Diver et al. (2019) presented cryoelectron microscopy structures of TRPM8 in ligand-free, antagonist-bound, or calcium-bound forms, revealing how robust conformational changes give rise to 2 nonconducting states, closed and desensitized. The authors described a malleable ligand-binding pocket that accommodates drugs of diverse chemical structures and delineated the ion permeation pathway, including the contribution of lipids to pore architecture. Furthermore, they showed that direct calcium binding mediates stimulus-evoked desensitization, clarifying this important mechanism of sensory adaptation. Diver et al. (2019) observed large rearrangements within the S4-S5 linker that reposition the S1-S4 and pore domains relative to the TRP helix, leading them to propose a distinct model for modulation of TRPM8 and possibly other TRP channels.
Peier et al. (2002) identified several human ESTs (e.g., GenBank 8750489), many of which had been isolated from various cancer tissues, that contain fragments of the TRPM8 gene. Antonarakis (2002) mapped these ESTs to chromosome 2q37.
McKemy et al. (2002) found that, in addition to menthol, rat Cmr1 was responsive to icilin, cold (with a range from 8 to 28 degrees C), and eucalyptol (the main constituent of oil of Eucalyptus), with low or no responses to menthone, camphor, cyclohexanol, or capsaicin, the agonist for VR1, which is related to the TRP family. Expression of both Cmr1 and Vr1 endowed cells to respond to distinct temperature thresholds, cool and hot (more than 43 degrees C), respectively. McKemy et al. (2002) suggested this coexpression may explain the paradox that noxious cold is sometimes perceived as burning pain. The authors also proposed that in other contexts, such as prostate and tumors, an endogenous menthol-like ligand may modulate the TRPM8 channel.
Peier et al. (2002) showed that mouse Trpm8 is specifically expressed in a subset of pain- and temperature-sensing neurons. Cells overexpressing the Trpm8 channel could be activated by cold temperatures and by a cooling agent, menthol. The authors concluded that the identification of a cold-sensing TRP channel in a distinct subpopulation of sensory neurons implicated an expanded role for this family of ion channels in somatic sensory detection.
Voets et al. (2004) demonstrated that temperature sensing is tightly linked to voltage-dependent gating in the cold-sensitive channel TRPM8 and the heat-sensitive channel TRPV1 (602076). Both channels are activated upon depolarization, and changes in temperature result in graded shifts of their voltage-dependent activation curves. The chemical agonists menthol (TRPM8) and capsaicin (TRPV1) function as gating modifiers, shifting activation curves towards physiologic membrane potentials. Kinetic analysis of gating at different temperatures indicated that temperature sensitivity in TRPM8 and TRPV1 arises from a 10-fold difference in the activation energies associated with voltage-dependent opening and closing. Voets et al. (2004) concluded that their results suggested a simple unifying principle that explains both cold and heat sensitivity in TRP channels, namely, that membrane voltage contributes to the fine-tuning of cold and heat sensitivity in sensory cells.
Parra et al. (2010) showed that Trpm8 mediated cold sensation in mouse cornea and influenced the rate of tearing.
Using protein interaction assays and imaging techniques, Gkika et al. (2015) found that human TCAF1 (616251) and TCAF2 (616252) interacted directly with TRPM8 and chaperoned it to the cell surface. TCAF1 enhanced cold stimuli-induced TRPM8 channel activation, whereas TCAF2 silenced it. Knockdown of TCAF1, but not TCAF2, via small interfering RNA reduced the abundance of TRPM8 at the cell surface. Domain analysis revealed that a PI3K (see 602839) domain in TCAF1 accounted for most, but not all, of the differences in the effects of TCAF1 and TCAF2 on TRPM8 channel activity. Single-channel recording revealed that TCAF1 had a complex effect on the kinetics of TRPM8 channel activation.
Janssens et al. (2016) showed that murine dorsal root ganglion neurons exhibited Trpm8-dependent responses to both menthol and allyl isothiocyanate (AITC), also known as mustard oil. Kinetic analysis of Trpm8 channel gating revealed that the presence of menthol slowed the kinetics of current relaxation, whereas the presence of AITC accelerated gating kinetics upon depolarization. These observations suggested that menthol stabilizes the open channel, whereas AITC destabilizes the closed channel. The authors classified these ligands as type I (menthol-like) and type II (AITC-like) agonists. Type I and type II agonists had distinct effects on Trpm8 currents and Trpm8-mediated calcium signals in excitable cells: menthol induced more prominent activation of inward Trpm8 current during action potential repolarization, leading to a greater calcium ion influx, and AITC induced a greater Trpm8 current in the action potential upstroke phase. Combined treatment with menthol and AITC resulted in faster channel activation kinetics but did not alter the time course for deactivation, suggesting that type I and type II agonists can act simultaneously and independently.
In a rat model of chronic neuropathic pain following nerve damage, Proudfoot et al. (2006) found that Trpm8 activation in a subpopulation of sensory afferents reversed injury-induced hypersensitivity and induced analgesia. Topical and intrathecal application of menthol and icilin, both Trpm8 activators, or modest cooling produced behavioral analgesia in the animals. Trpm8 expression was increased in a subset of sensory neurons after nerve injury. The analgesic effect was centrally mediated and relied on group II/III metabotropic glutamate receptors (see, e.g., GRM2; 604099) which likely exert inhibitory control over nociceptive inputs.
Bautista et al. (2007) showed that cultured sensory neurons and intact sensory nerve fibers from Trpm8-deficient mice exhibited profoundly diminished responses to cold. These animals also showed clear behavioral deficits in their ability to discriminate between cold and warm surfaces, or to respond to evaporative cooling. At the same time Trpm8 mutant mice were not completely insensitive to cold, as they avoided contact with surfaces below 10 degrees C, albeit with reduced efficiency. Thus, Bautista et al. (2007) concluded that their findings demonstrated an essential and predominant role for TRPM8 in thermosensation over a wide range of cold temperatures, validating the hypothesis that TRP channels are the principal sensors of thermal stimuli in the peripheral nervous system.
Independently, Dhaka et al. (2007) and Colburn et al. (2007) showed that Trpm8 deletion significantly increased the ability of mice to tolerate cold.
Liu et al. (2013) found that L-menthol, the predominant analgesic menthol isomer used in medicinal preparations, effectively attenuated pain behaviors evoked by chemical stimuli, heat, or inflammation in wildtype mice. Mice lacking Trpm8 received no analgesic effect from L-menthol treatment in any of these acute pain models, although other analgesics, including acetaminophen, remained effective. A similar loss of L-menthol-induced analgesia was observed in mice treated with a selective Trpm8 inhibitor. Treatment with WS12, a menthol derivative and selective Trpm8 agonist, induced Trpm8-dependent analgesia of acute and inflammatory pain in wildtype mice. Naloxone treatment blocked both L-menthol- and WS12-induced analgesia, suggesting that Trpm8-induced analgesia relies on activation of endogenous opioid receptors. Liu et al. (2013) concluded that TRPM8 is the primary mediator of menthol-induced analgesia of acute and inflammatory pain.
Antonarakis, S. E. Personal Communication. Baltimore, Md. 3/25/2002.
Bautista, D. M., Siemens, J., Glazer, J. M., Tsuruda, P. R., Basbaum, A. I., Stucky, C. L., Jordt, S.-E., Julius, D. The menthol receptor TRPM8 is the principal detector of environmental cold. Nature 448: 204-208, 2007. [PubMed: 17538622] [Full Text: https://doi.org/10.1038/nature05910]
Colburn, R. W., Lubin, M. L., Stone, D. J., Jr., Wang, Y., Lawrence, D., D'Andrea, M. R., Brandt, M. R., Liu, Y., Flores, C. M., Qin, N. Attenuated cold sensitivity in TRPM8 null mice. Neuron 54: 379-386, 2007. [PubMed: 17481392] [Full Text: https://doi.org/10.1016/j.neuron.2007.04.017]
Dhaka, A., Murray, A. N., Mathur, J., Earley, T. J., Petrus, M. J., Patapoutian, A. TRPM8 is required for cold sensation in mice. Neuron 54: 371-378, 2007. [PubMed: 17481391] [Full Text: https://doi.org/10.1016/j.neuron.2007.02.024]
Diver, M. M., Cheng, Y., Julius, D. Structural insights into TRPM8 inhibition and desensitization. Science 365: 1434-1440, 2019. [PubMed: 31488702] [Full Text: https://doi.org/10.1126/science.aax6672]
Farooqi, A. A., Javeed, M. K., Javed, Z., Riaz, A. M., Mukhtar, S., Minhaj, S., Abbas, S., Bhatti, S. TRPM channels: same ballpark, different players, and different rules in immunogenetics. Immunogenetics 63: 773-787, 2011. [PubMed: 21932052] [Full Text: https://doi.org/10.1007/s00251-011-0570-4]
Gkika, D., Lemonnier, L., Shapovalov, G., Gordienko, D., Poux, C., Bernardini, M., Bokhobza, A., Bidaux, G., Degerny, C., Verreman, K., Guarmit, B., Benahmed, M., de Launoit, Y., Bindels, R. J. M., Fiorio Pla, A., Prevarskaya, N. TRP channel-associated factors are a novel protein family that regulates TRPM8 trafficking and activity. J. Cell Biol. 208: 89-107, 2015. [PubMed: 25559186] [Full Text: https://doi.org/10.1083/jcb.201402076]
Janssens, A., Gees, M., Toth, B. I., Ghosh, D., Mulier, M., Vennekens, R., Vriens, J., Talavera, K., Voets, T. Definition of two agonist types at the mammalian cold-activated channel TRPM8. eLife 5: e17240, 2016. Note: Electronic Article. [PubMed: 27449282] [Full Text: https://doi.org/10.7554/eLife.17240]
Liu, B., Fan, L., Balakrishna, S., Sui, A., Morris, J. B., Jordt, S.-E. TRPM8 is the principal mediator of menthol-induced analgesia of acute and inflammatory pain. Pain 154: 2169-2177, 2013. [PubMed: 23820004] [Full Text: https://doi.org/10.1016/j.pain.2013.06.043]
McKemy, D. D., Neuhausser, W. M., Julius, D. Identification of a cold receptor reveals a general role for TRP channels in thermosensation. Nature 416: 52-58, 2002. [PubMed: 11882888] [Full Text: https://doi.org/10.1038/nature719]
Parra, A., Madrid, R., Echevarria, D., del Olmo, S., Morenilla-Palao, C., Acosta, M. C., Gallar, J., Dhaka, A., Viana, F., Belmonte, C. Ocular surface wetness is regulated by TRPM8-dependent cold thermoreceptors of the cornea. Nature Med. 16: 1396-1399, 2010. [PubMed: 21076394] [Full Text: https://doi.org/10.1038/nm.2264]
Peier, A. M., Moqrich, A., Hergarden, A. C., Reeve, A. J., Andersson, D. A., Story, G. M., Earley, T. J., Dragoni, I., McIntyre, P., Bevan, S., Patapoutian, A. A TRP channel that senses cold stimuli and menthol. Cell 108: 705-715, 2002. [PubMed: 11893340] [Full Text: https://doi.org/10.1016/s0092-8674(02)00652-9]
Proudfoot, C. J., Garry, E. M., Cottrell, D. F., Rosie, R., Anderson, H., Robertson, D. C., Fleetwood-Walker, S. M., Mitchell, R. Analgesia mediated by the TRPM8 cold receptor in chronic neuropathic pain. Curr. Biol. 16: 1591-1605, 2006. [PubMed: 16920620] [Full Text: https://doi.org/10.1016/j.cub.2006.07.061]
Tsavaler, L., Shapero, M. H., Morkowski, S., Laus, R. Trp-p8, a novel prostate-specific gene, is up-regulated in prostate cancer and other malignancies and shares high homology with transient receptor potential calcium channel proteins. Cancer Res. 61: 3760-3769, 2001. [PubMed: 11325849]
Voets, T., Droogmans, G., Wissenbach, U., Janssens, A., Flockerzi, V., Nilius, B. The principle of temperature-dependent gating in cold- and heat-sensitive TRP channels. Nature 430: 748-754, 2004. [PubMed: 15306801] [Full Text: https://doi.org/10.1038/nature02732]
Yin, Y., Le, S. C., Hsu, A. L., Borgnia, M. J., Yang, H., Lee, S.-Y. Structural basis of cooling agent and lipid sensing by the cold-activated TRPM8 channel. Science 363: eaav9334, 2019. Note: Electronic Article. [PubMed: 30733385] [Full Text: https://doi.org/10.1126/science.aav9334]
Yin, Y., Wu, M., Zubcevic, L., Borschel, W. F., Lander, G. C., Lee, S.-Y. Structure of the cold- and menthol-sensing ion channel TRPM8. Science 359: 237-241, 2018. [PubMed: 29217583] [Full Text: https://doi.org/10.1126/science.aan4325]