Review
Current View of Ligand and Lipid Recognition by the Menthol Receptor TRPM8

https://doi.org/10.1016/j.tibs.2020.05.008Get rights and content

Highlights

  • The transient receptor potential (TRP) channel superfamily members TRPM8 and TRPV1 are two well-known somatosensory receptors that can be activated by both thermal stimuli and natural chemicals.

  • TRPM8 is the cold and menthol receptor while TRPV1 is the heat and capsaicin receptor in humans.

  • Recent cryoelectron microscopy (cryo-EM) studies of TRPM8 have revealed remarkable structural features that underlie its distinguishing functions in cooling-compound sensing, making it unique compared with TRPV1 and other TRP channel members.

  • These studies also revealed how phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2], which is required for TRPM8 function, binds to a membrane interfacial cavity where functionally important subdomains are localized and synergizes with cooling agonist binding for channel activation.

Transient receptor potential (TRP) melastatin member 8 (TRPM8), which is a calcium-permeable ion channel, functions as the primary molecular sensor of cold and menthol in humans. Recent cryoelectron microscopy (cryo-EM) studies of TRPM8 have shown distinct structural features in its architecture and domain assembly compared with the capsaicin receptor TRP vanilloid member 1 (TRPV1). Moreover, ligand-bound TRPM8 structures have uncovered unforeseen binding sites for both cooling agonists and membrane lipid phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2]. These complex structures unveil the molecular basis of cooling agonist sensing by TRPM8 and the allosteric role of PI(4,5)P2 in agonist binding for TRPM8 activation. Here, we review the recent advances in TRPM8 structural biology and investigate the molecular principles governing the distinguishing role of TRPM8 as the evolutionarily conserved menthol receptor.

Section snippets

The Molecular Sensors of Menthol and Capsaicin in Humans

The TRP ion channel superfamily comprises calcium-permeable ion channels that serve diverse sensory physiological roles involved in vision, taste, touch, hearing, osmo- and thermosensation etc. [1., 2., 3.]. Among all TRP channels, TRPM8 and TRPV1 are two unique ion channels because they are responsible for not only cold and heat temperature sensation, respectively, but also chemically induced cooling or burning sensations [4., 5., 6., 7., 8.].

TRPM8, also known as the cold and menthol (see

Structure Determination of the TRPM8 and TRPV1 Channels

From an evolutionary standpoint, TRPM8 and TRPV1 show different degrees of conservation in the channels’ sensitivity to their own natural agonists. For instance, TRPM8 shows conserved sensitivity to the naturally occurring cooling agonist menthol across various species, including the less cold-sensitive hibernator animals [32,33]. By contrast, mammalian TRPV1 is sensitive to capsaicin, while avian and zebrafish TRPV1 are not [34,35,74]. Moreover, the vanilloid sensitivity of TRPV1 can be

Overall Architectures of the TRPM8 and TRPV1 Channels

TRPM8 and TRPV1 form homotetramers comprising a transmembrane channel domain (TMD) and a cytoplasmic domain (CD) (Figure 1A) [41,43]. Analogous to the voltage-gated cation channels, the TMDs of TRPM8 and TRPV1 can be divided into a voltage-sensor-like domain (VSLD) composed of the transmembrane helical segments S1 to S4 and a pore domain formed by the S5 and S6 helices and a pore helix (PH) (Figure 1B–D). The TMDs of the homotetrameric channels are arranged in a domain-swapped configuration

Distinct Binding Sites for Cooling Agonists and Vanilloids

Cryo-EM studies have revealed that the cooling agonists and the vanilloid compounds bind to distinct locations in the TMDs of the TRPM8 and TRPV1 channels, respectively (Figure 2A) [40,42,44]. The vanilloid-binding pocket in the TRPV1 channel was uncovered when the rat TRPV1 structures in complex with DkTx/RTx and capsaicin were captured in amphipol and nanodiscs [40,42]. It is located above the S4–S5 linker and embraced by S3 and S4 in the VSLD from the same subunit and S6 from the neighboring

Molecular Basis of Ligand Recognition by TRPM8

Structures of TRPM8 in complex with various agonists and antagonists allowed many interesting questions about the ligand recognition by TRPM8 to be addressed. First, how does the VSLD cavity accommodate a wide variety of structurally and chemically distinct, both naturally occurring and synthetic, compounds? Close-up comparisons of the VSLD cavity from different ligand-bound TRPM8 structures show that residues lining the binding site can adopt different rotamer conformations (Figure 3A) [44,45

Structural Basis of the PI(4,5)P2 Dependence in TRPM8 Function

PI(4,5)P2 is an important signaling phospholipid in the plasma membrane. It has been shown to be a critical regulator of many TRP channels, which include the TRPV, TRPM, and TRPC subfamilies [57,58]. For TRPV1, two seemingly opposite regulatory effects of PI(4,5)P2, both activating and inhibitory, on channel gating have been reported [59., 60., 61.]. The cryo-EM structure of TRPV1 reconstituted in nanodiscs reveals PtdIns binding in the same cleft as for vanilloids, from which the inhibitory

Regulatory Roles of the CD in the TRPM and TRPV Channels

The CDs constitute a great proportion of the TRPM8 and TRPV1 channel structures, but their functional roles remain mostly unclear. For TRPM8, it has been shown that the channel is inhibited by G protein-coupled bradykinin receptor B2 (B2R), leading to pain and inflammation [67,68]. A recent study revealed direct Gαq gating of TRPM8 via binding to R364 and R368 in MHR1/2 and to R470 in MHR3 in the CD (Figure 5A) [69]. Neutralization of these basic residues abolished TRPM8 inhibition by Gαq and

Concluding Remarks

The cryo-EM studies of TRPM8 have shown distinguishing structural features in its channel architecture and domain assembly [43., 44., 45.]. Ligand-bound TRPM8 complex structures have revealed a discrete binding site in the VSLD cavity shared by cooling agonists and antagonists as well as a membrane interfacial cavity for PI(4,5)P2 binding, which is strategically located to synergize with the agonist binding for channel activation. In comparison with the vanilloid receptor TRPV1, structural

Acknowledgments

This work was supported by the National Institutes of Health (R35NS097241 to S-Y.L.). We are grateful to Gabriel C. Lander and Mengyu Wu for their impressive efforts during our collaborative work on the TRPM8FA-Apo structure. We also thank Huanghe Yang and Son C. Le for the collaboration on the functional characterization of TRPM8 and Mario J. Borgnia and Allen L. Hsu for their support in cryo-EM screening and data collection. We thank the former Lee laboratory members Lejla Zubcevic and

Glossary

310-Helix
a less common motif of protein secondary structure compared with the α-helix. The main chain hydrogen bonding is formed between amino acids that are three residues apart in sequence. Due to the distorted hydrogen-binding network, both π-helices and 310-helices are structurally flexible and energetically costly and play critical roles in the functions and gating of many ion channels, including TRP channels.
Agonist
a chemical substance that binds to receptors or ion channels and activates

References (74)

  • V. Matos-Cruz

    Molecular prerequisites for diminished cold sensitivity in ground squirrels and hamsters

    Cell Rep.

    (2017)
  • S.-E. Jordt et al.

    Molecular basis for species-specific sensitivity to “hot” chili peppers

    Cell

    (2002)
  • F.J.P. Kühn

    Contribution of the S5-pore-S6 domain to the gating characteristics of the cation channels TRPM2 and TRPM8

    J. Biol. Chem.

    (2010)
  • L. Zubcevic et al.

    The role of π-helices in TRP channel gating

    Curr. Opin. Struct. Biol.

    (2019)
  • W. Zheng

    Direct binding between pre-S1 and TRP-like domains in TRPP channels mediates gating and functional regulation by PIP2

    Cell Rep.

    (2018)
  • A. Pedretti

    Comparative modeling of the quaternary structure for the human TRPM8 channel and analysis of its binding features

    Biochim. Biophys. Acta

    (2009)
  • E. Cao

    TRPV1 channels are intrinsically heat sensitive and negatively regulated by phosphoinositide lipids

    Neuron

    (2013)
  • E.N. Senning

    Regulation of TRPV1 ion channel by phosphoinositide (4,5)-bisphosphate: the role of membrane asymmetry

    J. Biol. Chem.

    (2014)
  • X. Zhang

    Direct Gαq gating is the sole mechanism for TRPM8 inhibition caused by bradykinin receptor activation

    Cell Rep.

    (2019)
  • I.S. Ramsey

    An introduction to TRP channels

    Annu. Rev. Physiol.

    (2006)
  • K. Venkatachalam et al.

    TRP channels

    Annu. Rev. Biochem.

    (2007)
  • A. Patapoutian

    ThermoTRP channels and beyond: mechanisms of temperature sensation

    Nat. Rev. Neurosci.

    (2003)
  • M.J. Caterina

    The capsaicin receptor: a heat-activated ion channel in the pain pathway

    Nature

    (1997)
  • D.D. McKemy

    Identification of a cold receptor reveals a general role for TRP channels in thermosensation

    Nature

    (2002)
  • D.M. Bautista

    The menthol receptor TRPM8 is the principal detector of environmental cold

    Nature

    (2007)
  • S. Ma

    Menthol derivative WS-12 selectively activates transient receptor potential melastatin-8 (TRPM8) ion channels

    Pak. J. Pharm. Sci.

    (2008)
  • E.T. Wei et al.

    AG-3-5: a chemical producing sensations of cold

    J. Pharm. Pharmacol.

    (1983)
  • B. Liu et al.

    Functional control of cold- and menthol-sensitive TRPM8 ion channels by phosphatidylinositol 4,5-bisphosphate

    J. Neurosci.

    (2005)
  • T. Rohacs

    PI(4,5)P2 regulates the activation and desensitization of TRPM8 channels through the TRP domain

    Nat. Neurosci.

    (2005)
  • E. Zakharian

    Gating of transient receptor potential melastatin 8 (TRPM8) channels activated by cold and chemical agonists in planar lipid bilayers

    J. Neurosci.

    (2010)
  • D. Julius

    TRP channels and pain

    Annu. Rev. Cell Dev. Biol.

    (2013)
  • T. Voets

    The principle of temperature-dependent gating in cold- and heat-sensitive TRP channels

    Nature

    (2004)
  • T. Voets

    TRPM8 voltage sensor mutants reveal a mechanism for integrating thermal and chemical stimuli

    Nat. Chem. Biol.

    (2007)
  • D.E. Clapham et al.

    A thermodynamic framework for understanding temperature sensing by transient receptor potential (TRP) channels

    Proc. Natl. Acad. Sci. U. S. A.

    (2011)
  • L. Almaraz

    Trpm8

    Handb. Exp. Pharmacol.

    (2014)
  • M.D. Andrews

    Discovery of a selective TRPM8 antagonist with clinical efficacy in cold-related pain

    ACS Med. Chem. Lett.

    (2015)
  • A.D. Weyer et al.

    Development of TRPM8 antagonists to treat chronic pain and migraine

    Pharmaceuticals (Basel)

    (2017)

    • Cited by (17)

    • Use the force, fluke: Ligand-independent gating of Schistosoma mansoni ion channel TRPM<inf>PZQ</inf>

      2023, International Journal for Parasitology

    • Membrane lipids and transporter function

      2021, Biochimica et Biophysica Acta - Molecular Basis of Disease
      Citation Excerpt :

      Bacterial voltage-gated sodium channels (NaChBac) are likely evolutionary ancestors of mammalian voltage-gated sodium channels [67] and also contain multiple tightly bound lipids at the transmembrane domain [68]. Transient receptor channel TRPM8 has been studied in detail and is a channel requiring PIP2 for action. [69]. Taken together, as cryo-EM technology nurtures a rapidly expanding list of transport and other membrane protein structures [70,71], the information of tightly bound lipids to such transporters is rapidly growing as well.

    • Sample preparation of the human TRPA1 ion channel for cryo-EM studies

      2021, Methods in Enzymology
      Citation Excerpt :

      As with many membrane proteins, TRP channels form both specific and non-specific interactions with membrane lipids. The specific interactions between various TRP channels and lipids/lipid-like molecules have been well-studied in recent publications (Gao, Cao, Julius, & Cheng, 2016; Yin et al., 2019; Yin & Lee, 2020; Zubcevic, Herzik, et al., 2018; Zubcevic, Hsu, Borgnia, & Lee, 2019). During detergent solubilization and subsequent size-exclusion chromatography, most of the protein-bound lipids are stripped away.

    • Essential Oils of Mentha arvensis and Cinnamomum cassia Exhibit Distinct Antibacterial Activity at Different Temperatures In Vitro and on Chicken Skin

      2023, Foods

    • Design and Synthesis of Emissive and Switchable Photo-Active Molecules

      2023, Design and Synthesis of Emissive and Switchable Photo-Active Molecules

    • Localization of TRP channels in healthy oral mucosa from human donors

      2022, eNeuro
    View all citing articles on Scopus
    View full text
    © 2020 Elsevier Ltd. All rights reserved.