1
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García-Morales A, Pulido NO, Balleza D. Relation between flexibility and intrinsically disorder regions in thermosensitive TRP channels reveal allosteric effects. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2024; 53:77-90. [PMID: 37777680 DOI: 10.1007/s00249-023-01682-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Revised: 08/06/2023] [Accepted: 08/20/2023] [Indexed: 10/02/2023]
Abstract
How a protein propagates the conformational changes throughout its structure remains largely unknown. In thermosensitive TRP channels, this allosteric communication is triggered by ligand interaction or in response to temperature changes. Because dynamic allostery suggests a dynamic role of disordered regions, in this work we set out to thoroughly evaluate these regions in six thermosensitive TRP channels. Thus, by contrasting the intrinsic flexibility of the transmembrane region as a function of the degree of disorder in those proteins, we discovered several residues that do not show a direct correlation in both parameters. This kind of structural discrepancy revealed residues that are either reported to be dynamic, functionally relevant or are involved in signal propagation and probably part of allosteric networks. These discrepant, potentially dynamic regions are not exclusive of TRP channels, as this same correlation was found in the Kv Shaker channel.
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Affiliation(s)
- Abigail García-Morales
- Unidad de Investigación y Desarrollo en Alimentos, Instituto Tecnológico de Veracruz, Tecnológico Nacional de México, Calz. Miguel Angel de Quevedo 2779 Col Formando Hogar, 91897, Veracruz, Ver, Mexico
| | - Nancy O Pulido
- Escuela de Ingeniería y Ciencias, Instituto Tecnológico y de Estudios Superiores de Monterrey, Cuernavaca, Mexico
| | - Daniel Balleza
- Unidad de Investigación y Desarrollo en Alimentos, Instituto Tecnológico de Veracruz, Tecnológico Nacional de México, Calz. Miguel Angel de Quevedo 2779 Col Formando Hogar, 91897, Veracruz, Ver, Mexico.
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2
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Ben-Abu Y, Tucker SJ, Contera S. Transcending Markov: non-Markovian rate processes of thermosensitive TRP ion channels. ROYAL SOCIETY OPEN SCIENCE 2023; 10:230984. [PMID: 37621668 PMCID: PMC10445021 DOI: 10.1098/rsos.230984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Accepted: 08/02/2023] [Indexed: 08/26/2023]
Abstract
The Markov state model (MSM) is a popular theoretical tool for describing the hierarchy of time scales involved in the function of many proteins especially ion channel gating. An MSM is a particular case of the general non-Markovian model, where the rate of transition from one state to another does not depend on the history of state occupancy within the system, i.e. it only includes reversible, non-dissipative processes. However, an MSM requires knowledge of the precise conformational state of the protein and is not predictive when those details are not known. In the case of ion channels, this simple description fails in real (non-equilibrium) situations, for example when local temperature changes, or when energy losses occur during channel gating. Here, we show it is possible to use non-Markovian equations (i.e. offer a general description that includes the MSM as a particular case) to develop a relatively simple analytical model that describes the non-equilibrium behaviour of the temperature-sensitive transient receptor potential (TRP) ion channels, TRPV1 and TRPM8. This model accurately predicts asymmetrical opening and closing rates, infinite processes and the creation of new states, as well as the effect of temperature changes throughout the process. This approach therefore overcomes the limitations of the MSM and allows us to go beyond a mere phenomenological description of the dynamics of ion channel gating towards a better understanding of the physics underlying these processes.
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Affiliation(s)
- Yuval Ben-Abu
- Physics Unit, Sapir Academic College, Sderot, Hof Ashkelon 79165, Israel
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Stephen J Tucker
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
- Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford OX1 3QU, UK
| | - Sonia Contera
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
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3
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Zhang H, Wang C, Zhang K, Kamau PM, Luo A, Tian L, Lai R. The role of TRPA1 channels in thermosensation. CELL INSIGHT 2022; 1:100059. [PMID: 37193355 PMCID: PMC10120293 DOI: 10.1016/j.cellin.2022.100059] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Revised: 10/05/2022] [Accepted: 10/05/2022] [Indexed: 05/18/2023]
Abstract
Transient receptor potential ankyrin 1 (TRPA1) is a polymodal nonselective cation channel sensitive to different physical and chemical stimuli. TRPA1 is associated with many important physiological functions in different species and thus is involved in different degrees of evolution. TRPA1 acts as a polymodal receptor for the perceiving of irritating chemicals, cold, heat, and mechanical sensations in various animal species. Numerous studies have supported many functions of TRPA1, but its temperature-sensing function remains controversial. Although TRPA1 is widely distributed in both invertebrates and vertebrates, and plays a crucial role in tempreture sensing, the role of TRPA1 thermosensation and molecular temperature sensitivity are species-specific. In this review, we summarize the temperature-sensing role of TRPA1 orthologues in terms of molecular, cellular, and behavioural levels.
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Affiliation(s)
- Hao Zhang
- Key Laboratory of Animal Models and Human Disease Mechanisms, Key Laboratory of Bioactive Peptides of Yunnan Province, Engineering Laboratory of Bioactive Peptides, National & Local Joint Engineering Center of Natural Bioactive Peptides, KIZ-CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, National Resource Center for Non-Human Primates, Kunming Primate Research Center, and National Research Facility for Phenotypic & Genetic Analysis of Model Animals (Primate Facility), Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, 650107, Yunnan, China
| | - Chengsan Wang
- Key Laboratory of Animal Models and Human Disease Mechanisms, Key Laboratory of Bioactive Peptides of Yunnan Province, Engineering Laboratory of Bioactive Peptides, National & Local Joint Engineering Center of Natural Bioactive Peptides, KIZ-CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, National Resource Center for Non-Human Primates, Kunming Primate Research Center, and National Research Facility for Phenotypic & Genetic Analysis of Model Animals (Primate Facility), Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, 650107, Yunnan, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Keyi Zhang
- University of Chinese Academy of Sciences, Beijing, 100049, China
- School of Molecular Medicine, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, 310000, China
| | - Peter Muiruri Kamau
- Key Laboratory of Animal Models and Human Disease Mechanisms, Key Laboratory of Bioactive Peptides of Yunnan Province, Engineering Laboratory of Bioactive Peptides, National & Local Joint Engineering Center of Natural Bioactive Peptides, KIZ-CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, National Resource Center for Non-Human Primates, Kunming Primate Research Center, and National Research Facility for Phenotypic & Genetic Analysis of Model Animals (Primate Facility), Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, 650107, Yunnan, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
- Sino-African Joint Research Center, Kunming Institute of Zoology, Chinese, Academy of Sciences, Kunming, Yunnan, 650223, China
| | - Anna Luo
- Key Laboratory of Animal Models and Human Disease Mechanisms, Key Laboratory of Bioactive Peptides of Yunnan Province, Engineering Laboratory of Bioactive Peptides, National & Local Joint Engineering Center of Natural Bioactive Peptides, KIZ-CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, National Resource Center for Non-Human Primates, Kunming Primate Research Center, and National Research Facility for Phenotypic & Genetic Analysis of Model Animals (Primate Facility), Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, 650107, Yunnan, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Lifeng Tian
- University of Chinese Academy of Sciences, Beijing, 100049, China
- School of Molecular Medicine, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou, 310000, China
| | - Ren Lai
- Key Laboratory of Animal Models and Human Disease Mechanisms, Key Laboratory of Bioactive Peptides of Yunnan Province, Engineering Laboratory of Bioactive Peptides, National & Local Joint Engineering Center of Natural Bioactive Peptides, KIZ-CUHK Joint Laboratory of Bioresources and Molecular Research in Common Diseases, National Resource Center for Non-Human Primates, Kunming Primate Research Center, and National Research Facility for Phenotypic & Genetic Analysis of Model Animals (Primate Facility), Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, 650107, Yunnan, China
- Sino-African Joint Research Center, Kunming Institute of Zoology, Chinese, Academy of Sciences, Kunming, Yunnan, 650223, China
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4
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York JM, Zakon HH. OUP accepted manuscript. Genome Biol Evol 2022; 14:6519823. [PMID: 35106545 PMCID: PMC8857925 DOI: 10.1093/gbe/evac009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/15/2022] [Indexed: 11/14/2022] Open
Abstract
Animals rely on their sensory systems to inform them of ecologically relevant environmental variation. In the Southern Ocean, the thermal environment has remained between −1.9 and 5 °C for 15 Myr, yet we have no knowledge of how an Antarctic marine organism might sense their thermal habitat as we have yet to discover a thermosensitive ion channel that gates (opens/closes) below 10 °C. Here, we investigate the evolutionary dynamics of transient receptor potential (TRP) channels, which are the primary thermosensors in animals, within cryonotothenioid fishes—the dominant fish fauna of the Southern Ocean. We found cryonotothenioids have a similar complement of TRP channels as other teleosts (∼28 genes). Previous work has shown that thermosensitive gating in a given channel is species specific, and multiple channels act together to sense the thermal environment. Therefore, we combined evidence of changes in selective pressure, gene gain/loss dynamics, and the first sensory ganglion transcriptome in this clade to identify the best candidate TRP channels that might have a functional dynamic range relevant for frigid Antarctic temperatures. We concluded that TRPV1a, TRPA1b, and TRPM4 are the likeliest putative thermosensors, and found evidence of diversifying selection at sites across these proteins. We also put forward hypotheses for molecular mechanisms of other cryonotothenioid adaptations, such as reduced skeletal calcium deposition, sensing oxidative stress, and unusual magnesium homeostasis. By completing a comprehensive and unbiased survey of these genes, we lay the groundwork for functional characterization and answering long-standing thermodynamic questions of thermosensitive gating and protein adaptation to low temperatures.
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Affiliation(s)
- Julia M York
- Department of Integrative Biology, University of Texas at Austin, USA
- Corresponding author: E-mail:
| | - Harold H Zakon
- Department of Integrative Biology, University of Texas at Austin, USA
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5
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Peng C, Yang Z, Liu Z, Wang S, Yu H, Cui C, Hu Y, Xing Q, Hu J, Huang X, Bao Z. A Systematical Survey on the TRP Channels Provides New Insight into Its Functional Diversity in Zhikong Scallop ( Chlamys farreri). Int J Mol Sci 2021; 22:ijms222011075. [PMID: 34681735 PMCID: PMC8539334 DOI: 10.3390/ijms222011075] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2021] [Revised: 10/08/2021] [Accepted: 10/11/2021] [Indexed: 12/25/2022] Open
Abstract
Transient receptor potential (TRP) channel plays a significant role in mediating various sensory physiological functions. It is widely present in the vertebrate and invertebrate genomes and can be activated by multiple compounds, messenger molecules, temperature, and mechanical stimulation. Mollusks are the second largest phylum of the animal kingdom and are sensitive to environmental factors. However, the molecular underpinnings through which mollusks sense and respond to environmental stimulus are unknown. In this study, we systematically identified and characterized 17 TRP channels (C.FA TRPs, seven subfamilies) in the genome of the Zhikong scallop (Chlamys farreri). All C.FA TRPs had six transmembrane structures (TM1–TM6). The sequences and structural features of C.FA TRPs are highly conserved with TRP channels of other species. Spatiotemporal expression profiling suggested that some C.FA TRPs participated in the early embryonic development of scallops and the sensory process of adult tissues. Notably, the expression of C.FA TRPM3 continuously increased during developmental stages and was highest among all C.FA TRPs. C.FA TRPC-α was specifically expressed in eyes, which may be involved in light transmission of scallop eyes. Under high temperature stress, C.FA TRPA1 and C.FA TRPA1-homolog upregulated significantly, which indicated that the TRPA subfamily is the thermoTRPs channel of scallops. Our results provided the first systematic study of TRP channels in scallops, and the findings will provide a valuable resource for a better understanding of TRP evolution and function in mollusks.
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Affiliation(s)
- Cheng Peng
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266000, China; (C.P.); (Z.Y.); (Z.L.); (S.W.); (H.Y.); (C.C.); (Y.H.); (Q.X.); (J.H.); (Z.B.)
| | - Zujing Yang
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266000, China; (C.P.); (Z.Y.); (Z.L.); (S.W.); (H.Y.); (C.C.); (Y.H.); (Q.X.); (J.H.); (Z.B.)
| | - Zhi Liu
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266000, China; (C.P.); (Z.Y.); (Z.L.); (S.W.); (H.Y.); (C.C.); (Y.H.); (Q.X.); (J.H.); (Z.B.)
| | - Shenhai Wang
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266000, China; (C.P.); (Z.Y.); (Z.L.); (S.W.); (H.Y.); (C.C.); (Y.H.); (Q.X.); (J.H.); (Z.B.)
| | - Haitao Yu
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266000, China; (C.P.); (Z.Y.); (Z.L.); (S.W.); (H.Y.); (C.C.); (Y.H.); (Q.X.); (J.H.); (Z.B.)
| | - Chang Cui
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266000, China; (C.P.); (Z.Y.); (Z.L.); (S.W.); (H.Y.); (C.C.); (Y.H.); (Q.X.); (J.H.); (Z.B.)
| | - Yuqing Hu
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266000, China; (C.P.); (Z.Y.); (Z.L.); (S.W.); (H.Y.); (C.C.); (Y.H.); (Q.X.); (J.H.); (Z.B.)
| | - Qiang Xing
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266000, China; (C.P.); (Z.Y.); (Z.L.); (S.W.); (H.Y.); (C.C.); (Y.H.); (Q.X.); (J.H.); (Z.B.)
- Laboratory for Marine Fisheries Science and Food Production Processes, Pilot Qingdao National Laboratory for Marine Science and Technology, Qingdao 266000, China
| | - Jingjie Hu
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266000, China; (C.P.); (Z.Y.); (Z.L.); (S.W.); (H.Y.); (C.C.); (Y.H.); (Q.X.); (J.H.); (Z.B.)
- Laboratory of Tropical Marine Germplasm Resources and Breeding Engineering, SANYA Oceanographic Institution of the Ocean University of CHINA (SOI-OUC), Sanya 572000, China
| | - Xiaoting Huang
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266000, China; (C.P.); (Z.Y.); (Z.L.); (S.W.); (H.Y.); (C.C.); (Y.H.); (Q.X.); (J.H.); (Z.B.)
- Laboratory for Marine Fisheries Science and Food Production Processes, Pilot Qingdao National Laboratory for Marine Science and Technology, Qingdao 266000, China
- Correspondence:
| | - Zhenmin Bao
- MOE Key Laboratory of Marine Genetics and Breeding, College of Marine Life Sciences, Ocean University of China, Qingdao 266000, China; (C.P.); (Z.Y.); (Z.L.); (S.W.); (H.Y.); (C.C.); (Y.H.); (Q.X.); (J.H.); (Z.B.)
- Laboratory for Marine Fisheries Science and Food Production Processes, Pilot Qingdao National Laboratory for Marine Science and Technology, Qingdao 266000, China
- Laboratory of Tropical Marine Germplasm Resources and Breeding Engineering, SANYA Oceanographic Institution of the Ocean University of CHINA (SOI-OUC), Sanya 572000, China
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6
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Cao E. Structural mechanisms of transient receptor potential ion channels. J Gen Physiol 2021; 152:133640. [PMID: 31972006 PMCID: PMC7054860 DOI: 10.1085/jgp.201811998] [Citation(s) in RCA: 52] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Accepted: 01/03/2020] [Indexed: 12/26/2022] Open
Abstract
Transient receptor potential (TRP) ion channels are evolutionarily ancient sensory proteins that detect and integrate a wide range of physical and chemical stimuli. TRP channels are fundamental for numerous biological processes and are therefore associated with a multitude of inherited and acquired human disorders. In contrast to many other major ion channel families, high-resolution structures of TRP channels were not available before 2013. Remarkably, however, the subsequent “resolution revolution” in cryo-EM has led to an explosion of TRP structures in the last few years. These structures have confirmed that TRP channels assemble as tetramers and resemble voltage-gated ion channels in their overall architecture. But beyond the relatively conserved transmembrane core embedded within the lipid bilayer, each TRP subtype appears to be endowed with a unique set of soluble domains that may confer diverse regulatory mechanisms. Importantly, TRP channel structures have revealed sites and mechanisms of action of numerous synthetic and natural compounds, as well as those for endogenous ligands such as lipids, Ca2+, and calmodulin. Here, I discuss these recent findings with a particular focus on the conserved transmembrane region and how these structures may help to rationally target this important class of ion channels for the treatment of numerous human conditions.
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Affiliation(s)
- Erhu Cao
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT
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7
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Kim M, Sisco NJ, Hilton JK, Montano CM, Castro MA, Cherry BR, Levitus M, Van Horn WD. Evidence that the TRPV1 S1-S4 membrane domain contributes to thermosensing. Nat Commun 2020; 11:4169. [PMID: 32820172 PMCID: PMC7441067 DOI: 10.1038/s41467-020-18026-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 07/30/2020] [Indexed: 01/14/2023] Open
Abstract
Sensing and responding to temperature is crucial in biology. The TRPV1 ion channel is a well-studied heat-sensing receptor that is also activated by vanilloid compounds, including capsaicin. Despite significant interest, the molecular underpinnings of thermosensing have remained elusive. The TRPV1 S1-S4 membrane domain couples chemical ligand binding to the pore domain during channel gating. Here we show that the S1-S4 domain also significantly contributes to thermosensing and couples to heat-activated gating. Evaluation of the isolated human TRPV1 S1-S4 domain by solution NMR, far-UV CD, and intrinsic fluorescence shows that this domain undergoes a non-denaturing temperature-dependent transition with a high thermosensitivity. Further NMR characterization of the temperature-dependent conformational changes suggests the contribution of the S1-S4 domain to thermosensing shares features with known coupling mechanisms between this domain with ligand and pH activation. Taken together, this study shows that the TRPV1 S1-S4 domain contributes to TRPV1 temperature-dependent activation.
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Affiliation(s)
- Minjoo Kim
- School of Molecular Sciences, Arizona State University, 551 E. University Drive, Tempe, AZ, 85287, USA
- The Biodesign Institute Virginia G. Piper Center for Personalized Diagnostics, Arizona State University, Tempe, AZ, 85287, USA
| | - Nicholas J Sisco
- School of Molecular Sciences, Arizona State University, 551 E. University Drive, Tempe, AZ, 85287, USA
- The Biodesign Institute Virginia G. Piper Center for Personalized Diagnostics, Arizona State University, Tempe, AZ, 85287, USA
| | - Jacob K Hilton
- School of Molecular Sciences, Arizona State University, 551 E. University Drive, Tempe, AZ, 85287, USA
- The Biodesign Institute Virginia G. Piper Center for Personalized Diagnostics, Arizona State University, Tempe, AZ, 85287, USA
| | - Camila M Montano
- The Biodesign Institute Virginia G. Piper Center for Personalized Diagnostics, Arizona State University, Tempe, AZ, 85287, USA
| | - Manuel A Castro
- School of Molecular Sciences, Arizona State University, 551 E. University Drive, Tempe, AZ, 85287, USA
| | - Brian R Cherry
- The Magnetic Resonance Research Center, Arizona State University, Tempe, AZ, 85287, USA
| | - Marcia Levitus
- School of Molecular Sciences, Arizona State University, 551 E. University Drive, Tempe, AZ, 85287, USA
- The Biodesign Institute Center for Single Molecule Biophysics, Arizona State University, Tempe, AZ, 85287, USA
| | - Wade D Van Horn
- School of Molecular Sciences, Arizona State University, 551 E. University Drive, Tempe, AZ, 85287, USA.
- The Biodesign Institute Virginia G. Piper Center for Personalized Diagnostics, Arizona State University, Tempe, AZ, 85287, USA.
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8
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Du G, Tian Y, Yao Z, Vu S, Zheng J, Chai L, Wang K, Yang S. A specialized pore turret in the mammalian cation channel TRPV1 is responsible for distinct and species-specific heat activation thresholds. J Biol Chem 2020; 295:9641-9649. [PMID: 32461255 DOI: 10.1074/jbc.ra120.013037] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 05/20/2020] [Indexed: 11/06/2022] Open
Abstract
The transient receptor potential vanilloid 1 (TRPV1) channel is a heat-activated cation channel that plays a crucial role in ambient temperature detection and thermal homeostasis. Although several structural features of TRPV1 have been shown to be involved in heat-induced activation of the gating process, the physiological significance of only a few of these key elements has been evaluated in an evolutionary context. Here, using transient expression in HEK293 cells, electrophysiological recordings, and molecular modeling, we show that the pore turret contains both structural and functional determinants that set the heat activation thresholds of distinct TRPV1 orthologs in mammals whose body temperatures fluctuate widely. We found that TRPV1 from the bat Carollia brevicauda exhibits a lower threshold temperature of channel activation than does its human ortholog and three bat-specific amino acid substitutions located in the pore turret are sufficient to determine this threshold temperature. Furthermore, the structure of the TRPV1 pore turret appears to be of physiological and evolutionary significance for differentiating the heat-activated threshold among species-specific TRPV1 orthologs. These findings support a role for the TRPV1 pore turret in tuning the heat-activated threshold, and they suggest that its evolution was driven by adaption to specific physiological traits among mammals exposed to variable temperatures.
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Affiliation(s)
- Guangxu Du
- Department of Pharmacology, Qingdao University School of Pharmacy, Qingdao, Shandong, China
| | - Yuhua Tian
- Department of Pharmacology, Qingdao University School of Pharmacy, Qingdao, Shandong, China
| | - Zhihao Yao
- Department of Pharmacology, Qingdao University School of Pharmacy, Qingdao, Shandong, China.,Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of the Yunnan Province Kunming Institute of Zoology, Kunming, Yunnan China
| | - Simon Vu
- University of California Davis, School of Medicine, Davis, California, USA
| | - Jie Zheng
- University of California Davis, School of Medicine, Davis, California, USA
| | - Longhui Chai
- College of Wildlife and Protected Area, Northeast Forestry University, Harbin, China
| | - KeWei Wang
- Department of Pharmacology, Qingdao University School of Pharmacy, Qingdao, Shandong, China
| | - Shilong Yang
- College of Wildlife and Protected Area, Northeast Forestry University, Harbin, China
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9
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Pang WC, Ramli ANM, Hamid AAA. Comparative modelling studies of fruit bromelain using molecular dynamics simulation. J Mol Model 2020; 26:142. [PMID: 32417971 DOI: 10.1007/s00894-020-04398-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Accepted: 04/28/2020] [Indexed: 12/25/2022]
Abstract
Fruit bromelain is a cysteine protease accumulated in pineapple fruits. This proteolytic enzyme has received high demand for industrial and therapeutic applications. In this study, fruit bromelain sequences QIM61759, QIM61760 and QIM61761 were retrieved from the National Center for Biotechnology Information (NCBI) Genbank Database. The tertiary structure of fruit bromelain QIM61759, QIM61760 and QIM61761 was generated by using MODELLER. The result revealed that the local stereochemical quality of the generated models was improved by using multiple templates during modelling process. Moreover, by comparing with the available papain model, structural analysis provides an insight on how pro-peptide functions as a scaffold in fruit bromelain folding and contributing to inactivation of mature protein. The structural analysis also disclosed the similarities and differences between these models. Lastly, thermal stability of fruit bromelain was studied. Molecular dynamics simulation of fruit bromelain structures at several selected temperatures demonstrated how fruit bromelain responds to elevation of temperature.
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Affiliation(s)
- Wei Cheng Pang
- Faculty of Industrial Science & Technology, Universiti Malaysia Pahang, Lebuhraya Tun Razak, 26300 Gambang, Kuantan, Pahang Darul Makmur, Malaysia
| | - Aizi Nor Mazila Ramli
- Faculty of Industrial Science & Technology, Universiti Malaysia Pahang, Lebuhraya Tun Razak, 26300 Gambang, Kuantan, Pahang Darul Makmur, Malaysia. .,Bio Aromatic Research Centre of Excellence, Universiti Malaysia Pahang, Lebuhraya Tun Razak, 26300 Gambang, Kuantan, Pahang Darul Makmur, Malaysia.
| | - Azzmer Azzar Abdul Hamid
- Department of Biotechnology, Kulliyyah of Science, International Islamic University Malaysia (IIUM), Bandar Indera Mahkota, 25200, Kuantan, Pahang, Malaysia.,Research Unit for Bioinformatics and Computational Biology (RUBIC), Kulliyyah of Science, International Islamic University Malaysia (IIUM), Bandar Indera Mahkota, 25200, Kuantan, Pahang, Malaysia
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10
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Chu Y, Cohen BE, Chuang HH. A single TRPV1 amino acid controls species sensitivity to capsaicin. Sci Rep 2020; 10:8038. [PMID: 32415171 PMCID: PMC7229161 DOI: 10.1038/s41598-020-64584-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Accepted: 04/11/2020] [Indexed: 11/09/2022] Open
Abstract
Chili peppers produce capsaicin (a vanilloid) that activates the transient receptor potential cation channel subfamily V member 1 (TRPV1) on sensory neurons to alter their membrane potential and induce pain. To identify residues responsible for differential TRPV1 capsaicin sensitivity among species, we used intracellular Ca2+ imaging to characterize chimeras composed of capsaicin-sensitive rat TRPV1 (rTRPV1) and capsaicin-insensitive chicken TRPV1 (cTRPV1) exposed to a series of capsaicinoids. We found that chimeras containing rat E570-V686 swapped into chicken receptors displayed capsaicin sensitivity, and that simply changing the alanine at position 578 in the S4-S5 helix of the chicken receptor to a glutamic acid was sufficient to endow it with capsaicin sensitivity in the micromolar range. Moreover, introduction of lysine, glutamine or proline at residue A578 also elicited capsaicin sensitivity in cTRPV1. Similarly, replacing corresponding rTRPV1 residue E570 with lysine or glutamine retained capsaicin sensitivity. The hydrophilic capsaicin analog Cap-EA activated a cTRPV1-A578E mutant, suggesting that A578 may participate in vanilloid binding. The hydrophilic vanilloid agonist zingerone did not activate any A578 mutants with capsaicin sensitivity, suggesting that the vanilloid group alone is not sufficient for receptor activation. Our study demonstrates that a subtle modification of TRPV1 in different species globally alters capsaicin responses.
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Affiliation(s)
- Ying Chu
- Institute of Molecular Biology, Academia Sinica, Taipei, 11529, Taiwan.
| | - Bruce E Cohen
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Huai-Hu Chuang
- Institute of Molecular Biology, Academia Sinica, Taipei, 11529, Taiwan
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11
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A paradigm of thermal adaptation in penguins and elephants by tuning cold activation in TRPM8. Proc Natl Acad Sci U S A 2020; 117:8633-8638. [PMID: 32220960 PMCID: PMC7165450 DOI: 10.1073/pnas.1922714117] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Sensing temperature is critical for the survival of all living beings. Here, we show that during cold-induced activation of the archetypical temperature-sensitive TRPM8 ion channel, there are hydrophobic residues in the pore domain stabilized in the exposed state. Tuning hydrophobicity of these residues specifically alters cold response in TRPM8. Furthermore, TRPM8 orthologs in vertebrates evolved to employ such a mechanism, which physiologically tunes cold tolerance for better thermal adaptation. Our findings not only advance the understanding of the cold-induced activation mechanism of TRPM8 but also bring insights to the molecular evolution strategy for ambient-temperature adaptation in vertebrates. To adapt to habitat temperature, vertebrates have developed sophisticated physiological and ecological mechanisms through evolution. Transient receptor potential melastatin 8 (TRPM8) serves as the primary sensor for cold. However, how cold activates TRPM8 and how this sensor is tuned for thermal adaptation remain largely unknown. Here we established a molecular framework of how cold is sensed in TRPM8 with a combination of patch-clamp recording, unnatural amino acid imaging, and structural modeling. We first observed that the maximum cold activation of TRPM8 in eight different vertebrates (i.e., African elephant and emperor penguin) with distinct side-chain hydrophobicity (SCH) in the pore domain (PD) is tuned to match their habitat temperature. We further showed that altering SCH for residues in the PD with solvent-accessibility changes leads to specific tuning of the cold response in TRPM8. We also observed that knockin mice expressing the penguin’s TRPM8 exhibited remarkable tolerance to cold. Together, our findings suggest a paradigm of thermal adaptation in vertebrates, where the evolutionary tuning of the cold activation in the TRPM8 ion channel through altering SCH and solvent accessibility in its PD largely contributes to the setting of the cold-sensitive/tolerant phenotype.
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12
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Garami A, Shimansky YP, Rumbus Z, Vizin RCL, Farkas N, Hegyi J, Szakacs Z, Solymar M, Csenkey A, Chiche DA, Kapil R, Kyle DJ, Van Horn WD, Hegyi P, Romanovsky AA. Hyperthermia induced by transient receptor potential vanilloid-1 (TRPV1) antagonists in human clinical trials: Insights from mathematical modeling and meta-analysis. Pharmacol Ther 2020; 208:107474. [PMID: 31926897 DOI: 10.1016/j.pharmthera.2020.107474] [Citation(s) in RCA: 81] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 12/23/2019] [Indexed: 02/06/2023]
Abstract
Antagonists of the transient receptor potential vanilloid-1 (TRPV1) channel alter body temperature (Tb) in laboratory animals and humans: most cause hyperthermia; some produce hypothermia; and yet others have no effect. TRPV1 can be activated by capsaicin (CAP), protons (low pH), and heat. First-generation (polymodal) TRPV1 antagonists potently block all three TRPV1 activation modes. Second-generation (mode-selective) TRPV1 antagonists potently block channel activation by CAP, but exert different effects (e.g., potentiation, no effect, or low-potency inhibition) in the proton mode, heat mode, or both. Based on our earlier studies in rats, only one mode of TRPV1 activation - by protons - is involved in thermoregulatory responses to TRPV1 antagonists. In rats, compounds that potently block, potentiate, or have no effect on proton activation cause hyperthermia, hypothermia, or no effect on Tb, respectively. A Tb response occurs when a TRPV1 antagonist blocks (in case of hyperthermia) or potentiates (hypothermia) the tonic TRPV1 activation by protons somewhere in the trunk, perhaps in muscles, and - via the acido-antithermogenic and acido-antivasoconstrictor reflexes - modulates thermogenesis and skin vasoconstriction. In this work, we used a mathematical model to analyze Tb data from human clinical trials of TRPV1 antagonists. The analysis suggests that, in humans, the hyperthermic effect depends on the antagonist's potency to block TRPV1 activation not only by protons, but also by heat, while the CAP activation mode is uninvolved. Whereas in rats TRPV1 drives thermoeffectors by mediating pH signals from the trunk, but not Tb signals, our analysis suggests that TRPV1 mediates both pH and thermal signals driving thermoregulation in humans. Hence, in humans (but not in rats), TRPV1 is likely to serve as a thermosensor of the thermoregulation system. We also conducted a meta-analysis of Tb data from human trials and found that polymodal TRPV1 antagonists (ABT-102, AZD1386, and V116517) increase Tb, whereas the mode-selective blocker NEO6860 does not. Several strategies of harnessing the thermoregulatory effects of TRPV1 antagonists in humans are discussed.
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Affiliation(s)
- Andras Garami
- Department of Thermophysiology, Institute for Translational Medicine, Medical School, University of Pecs, Pecs, Hungary.
| | - Yury P Shimansky
- Department of Neurobiology, Barrow Neurological Institute, Dignity Health, Phoenix, AZ, USA
| | - Zoltan Rumbus
- Department of Thermophysiology, Institute for Translational Medicine, Medical School, University of Pecs, Pecs, Hungary
| | - Robson C L Vizin
- Thermoregulation and Systemic Inflammation Laboratory (FeverLab), Trauma Research, St. Joseph's Hospital and Medical Center, Dignity Health, Phoenix, AZ, USA
| | - Nelli Farkas
- Institute for Translational Medicine, Medical School and Szentagothai Research Centre, University of Pecs, Pecs, Hungary
| | - Judit Hegyi
- Institute for Translational Medicine, Medical School and Szentagothai Research Centre, University of Pecs, Pecs, Hungary
| | - Zsolt Szakacs
- Institute for Translational Medicine, Medical School and Szentagothai Research Centre, University of Pecs, Pecs, Hungary
| | - Margit Solymar
- Department of Thermophysiology, Institute for Translational Medicine, Medical School, University of Pecs, Pecs, Hungary
| | - Alexandra Csenkey
- Department of Thermophysiology, Institute for Translational Medicine, Medical School, University of Pecs, Pecs, Hungary
| | | | | | | | - Wade D Van Horn
- School of Molecular Sciences, Arizona State University, Tempe, AZ, USA
| | - Peter Hegyi
- Institute for Translational Medicine, Medical School and Szentagothai Research Centre, University of Pecs, Pecs, Hungary; Department of Translational Medicine, First Department of Medicine, Medical School, University of Pecs, Pecs, Hungary
| | - Andrej A Romanovsky
- Thermoregulation and Systemic Inflammation Laboratory (FeverLab), Trauma Research, St. Joseph's Hospital and Medical Center, Dignity Health, Phoenix, AZ, USA; School of Molecular Sciences, Arizona State University, Tempe, AZ, USA; Zharko Pharma Inc., Olympia, WA, USA.
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13
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Macikova L, Vyklicka L, Barvik I, Sobolevsky AI, Vlachova V. Cytoplasmic Inter-Subunit Interface Controls Use-Dependence of Thermal Activation of TRPV3 Channel. Int J Mol Sci 2019; 20:E3990. [PMID: 31426314 PMCID: PMC6719031 DOI: 10.3390/ijms20163990] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Revised: 08/12/2019] [Accepted: 08/13/2019] [Indexed: 02/07/2023] Open
Abstract
The vanilloid transient receptor potential channel TRPV3 is a putative molecular thermosensor widely considered to be involved in cutaneous sensation, skin homeostasis, nociception, and pruritus. Repeated stimulation of TRPV3 by high temperatures above 50 °C progressively increases its responses and shifts the activation threshold to physiological temperatures. This use-dependence does not occur in the related heat-sensitive TRPV1 channel in which responses decrease, and the activation threshold is retained above 40 °C during activations. By combining structure-based mutagenesis, electrophysiology, and molecular modeling, we showed that chimeric replacement of the residues from the TRPV3 cytoplasmic inter-subunit interface (N251-E257) with the homologous residues of TRPV1 resulted in channels that, similarly to TRPV1, exhibited a lowered thermal threshold, were sensitized, and failed to close completely after intense stimulation. Crosslinking of this interface by the engineered disulfide bridge between substituted cysteines F259C and V385C (or, to a lesser extent, Y382C) locked the channel in an open state. On the other hand, mutation of a single residue within this region (E736) resulted in heat resistant channels. We propose that alterations in the cytoplasmic inter-subunit interface produce shifts in the channel gating equilibrium and that this domain is critical for the use-dependence of the heat sensitivity of TRPV3.
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Affiliation(s)
- Lucie Macikova
- Department of Cellular Neurophysiology, Institute of Physiology Czech Academy of Sciences, 142 20 Prague, Czech Republic
- Department of Physiology, Faculty of Science, Charles University, 128 00 Prague, Czech Republic
| | - Lenka Vyklicka
- Department of Cellular Neurophysiology, Institute of Physiology Czech Academy of Sciences, 142 20 Prague, Czech Republic
| | - Ivan Barvik
- Division of Biomolecular Physics, Institute of Physics, Faculty of Mathematics and Physics, Charles University, 121 16 Prague, Czech Republic
| | - Alexander I Sobolevsky
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Viktorie Vlachova
- Department of Cellular Neurophysiology, Institute of Physiology Czech Academy of Sciences, 142 20 Prague, Czech Republic.
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14
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Hilton JK, Kim M, Van Horn WD. Structural and Evolutionary Insights Point to Allosteric Regulation of TRP Ion Channels. Acc Chem Res 2019; 52:1643-1652. [PMID: 31149807 DOI: 10.1021/acs.accounts.9b00075] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The familiar pungent taste of spicy food, the refreshing taste of mint, and many other physiological phenomena are mediated by transient receptor potential (TRP) ion channels. TRP channels are a superfamily of ion channels that are sensitive to diverse chemical and physical stimuli and play diverse roles in biology. In addition to chemical regulation, some family members also sense common physical stimuli, such as temperature or pressure. Since their discovery and cloning in the 1990s and 2000s, understanding the molecular mechanisms governing TRP channel function and polymodal regulation has been a consistent but challenging goal. Until recently, a general lack of high-resolution TRP channel structures had significantly limited a molecular understanding of their function. In the past few years, a flood of TRP channel structures have been released, made possible primarily by advances in cryo-electron microscopy (cryo-EM). The boon of many structures has unleashed unparalleled insight into TRP channel architecture. Substantive comparative studies between TRP structures provide snapshots of distinct states such as ligand-free, stabilized by chemical agonists, or antagonists, partially illuminating how a given channel opens and closes. However, the now ∼75 TRP channel structures have ushered in surprising outcomes, including a lack of an apparent general mechanism underlying channel opening and closing among family members. Similarly, the structures reveal a surprising diversity in which chemical ligands bind TRP channels. Several TRP channels are activated by temperature changes in addition to ligand binding. Unraveling mechanisms of thermosensation has proven an elusive challenge to the field. Although some studies point to thermosensitive domains in the transmembrane region of the channels, results have sometimes been contradictory and difficult to interpret; in some cases, a domain that proves essential for thermal sensitivity in one context can be entirely removed from the channel without affecting thermosensation in another context. These results are not amenable to simple interpretations and point to allosteric networks of regulation within the channel structure. TRP channels have evolved to be fine-tuned for the needs of a species in its environmental niche, a fact that has been both a benefit and burden in unlocking their molecular features. Functional evolutionary divergence has presented challenges for studying TRP channels, as orthologs from different species can give conflicting experimental results. However, this diversity can also be examined comparatively to decipher the basis for functional differences. As with structural biology, untangling the similarities and differences resulting from evolutionary pressure between species has been a rich source of data guiding the field. This Account will contextualize the existing biochemical and functional data with an eye to evolutionary data and couple these insights with emerging structural biology to better understand the molecular mechanisms behind chemical and physical regulation of TRP channels.
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Affiliation(s)
- Jacob K. Hilton
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, United States
- The Biodesign Institute Centers for Personalized Diagnostics and Mechanisms of Evolution, Arizona State University, Tempe, Arizona 85281, United States
| | - Minjoo Kim
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, United States
- The Biodesign Institute Centers for Personalized Diagnostics and Mechanisms of Evolution, Arizona State University, Tempe, Arizona 85281, United States
| | - Wade D. Van Horn
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287, United States
- The Biodesign Institute Centers for Personalized Diagnostics and Mechanisms of Evolution, Arizona State University, Tempe, Arizona 85281, United States
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15
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Zheng W, Wen H. Heat activation mechanism of TRPV1: New insights from molecular dynamics simulation. Temperature (Austin) 2019; 6:120-131. [PMID: 31286023 DOI: 10.1080/23328940.2019.1578634] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Revised: 12/30/2018] [Accepted: 01/30/2019] [Indexed: 02/07/2023] Open
Abstract
As a member of the transient receptor potential (TRP) channels superfamily, the TRPV1 channel undergoes a closed-to-open gating transition in response to various physical and chemical stimuli including heat. Thanks to recent progress in cryo-electron microscopy, high-resolution structures are becoming available for various TRP channels including TRPV1. This has enabled us to study the molecular mechanism of TRPV1 channel gating by using molecular simulation. Here we review recent progress in molecular simulations of TRPV1 channel by us and others, with focus on our molecular dynamics (MD) simulations of TRPV1 at different temperatures. While no consensus has been reached on the heat activation mechanism of TRPV1, the simulations have offered specific predictions and models for future experimental studies to test.
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Affiliation(s)
- Wenjun Zheng
- Department of Physics, State University of New York at Buffalo, Buffalo, NY, USA
| | - Han Wen
- Department of Physics, State University of New York at Buffalo, Buffalo, NY, USA
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16
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Sánchez-Moreno A, Guevara-Hernández E, Contreras-Cervera R, Rangel-Yescas G, Ladrón-de-Guevara E, Rosenbaum T, Islas LD. Irreversible temperature gating in trpv1 sheds light on channel activation. eLife 2018; 7:36372. [PMID: 29869983 PMCID: PMC5999395 DOI: 10.7554/elife.36372] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2018] [Accepted: 05/26/2018] [Indexed: 02/06/2023] Open
Abstract
Temperature-activated TRP channels or thermoTRPs are among the only proteins that can directly convert temperature changes into changes in channel open probability. In spite of a wealth of functional and structural information, the mechanism of temperature activation remains unknown. We have carefully characterized the repeated activation of TRPV1 by thermal stimuli and discovered a previously unknown inactivation process, which is irreversible. We propose that this form of gating in TRPV1 channels is a consequence of the heat absorption process that leads to channel opening.
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Affiliation(s)
| | - Eduardo Guevara-Hernández
- Departamento de Fisiología, Facultad de Medicina, México City, México.,Instituto de Fisiología Celular, México City, México
| | | | | | | | | | - León D Islas
- Departamento de Fisiología, Facultad de Medicina, México City, México
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17
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Expression and Purification of the Pain Receptor TRPV1 for Spectroscopic Analysis. Sci Rep 2017; 7:9861. [PMID: 28852163 PMCID: PMC5575240 DOI: 10.1038/s41598-017-10426-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 08/08/2017] [Indexed: 02/08/2023] Open
Abstract
The transient receptor potential vanilloid 1 (TRPV1) channel is an essential component of the cellular mechanism through which noxious stimuli evoke pain. Functional and structural characterizations of TRPV1 shed light on vanilloid activation, yet the mechanisms for temperature and proton gating remain largely unknown. Spectroscopic approaches are needed to understand the mechanisms by which TRPV1 translates diverse stimuli into channel opening. Here, we have engineered a minimal cysteine-less rat TRPV1 construct (eTRPV1) that can be stably purified and reconstituted for spectroscopic studies. Biophysical analyses of TRPV1 constructs reveal that the S5-pore helix loop influences protein stability and vanilloid and proton responses, but not thermal sensitivity. Cysteine mutants retain function and stability for double electron-electron resonance (DEER) and electron paramagnetic resonance (EPR) spectroscopies. DEER measurements in the closed state demonstrate that eTRPV1 reports distances in the extracellular vestibule, equivalent to those observed in the apo TRPV1 structure. EPR measurements show a distinct pattern of mobilities and spectral features, in detergent and liposomes, for residues at the pore domain that agree with their location in the TRPV1 structure. Our results set the stage for a systematic characterization of TRPV1 using spectroscopic approaches to reveal conformational changes compatible with thermal- and ligand-dependent gating.
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