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Boonen B, Voets T. A frozen portrait of a warm channel. Cell Calcium 2024; 123:102927. [PMID: 38959762 DOI: 10.1016/j.ceca.2024.102927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2024] [Accepted: 06/27/2024] [Indexed: 07/05/2024]
Abstract
In order to understand protein function, the field of structural biology makes extensive use of cryogenic electron microscopy (cryo-EM), a technique that enables structure determination at atomic resolution following embedding of protein particles in vitreous ice. Considering the profound effects of temperature on macromolecule function, an important-but often neglected-question is how the frozen particles relate to the actual protein conformations at physiological temperatures. In a recent study, Hu et al. compare structures of the cation channel TRPM4 "frozen" at 4 °C versus 37 °C, revealing how temperature critically affects the binding of activating Ca2+ ions and other channel modulators.
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Affiliation(s)
- Brett Boonen
- Laboratory of Ion Channel Research, VIB-KU Leuven Center for Brain and Disease Research & KU Leuven Department of Cellular and Molecular Medicine, Leuven, Belgium
| | - Thomas Voets
- Laboratory of Ion Channel Research, VIB-KU Leuven Center for Brain and Disease Research & KU Leuven Department of Cellular and Molecular Medicine, Leuven, Belgium.
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2
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Hu J, Park SJ, Walter T, Orozco IJ, O'Dea G, Ye X, Du J, Lü W. Physiological temperature drives TRPM4 ligand recognition and gating. Nature 2024; 630:509-515. [PMID: 38750366 PMCID: PMC11168932 DOI: 10.1038/s41586-024-07436-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Accepted: 04/17/2024] [Indexed: 06/14/2024]
Abstract
Temperature profoundly affects macromolecular function, particularly in proteins with temperature sensitivity1,2. However, its impact is often overlooked in biophysical studies that are typically performed at non-physiological temperatures, potentially leading to inaccurate mechanistic and pharmacological insights. Here we demonstrate temperature-dependent changes in the structure and function of TRPM4, a temperature-sensitive Ca2+-activated ion channel3-7. By studying TRPM4 prepared at physiological temperature using single-particle cryo-electron microscopy, we identified a 'warm' conformation that is distinct from those observed at lower temperatures. This conformation is driven by a temperature-dependent Ca2+-binding site in the intracellular domain, and is essential for TRPM4 function in physiological contexts. We demonstrated that ligands, exemplified by decavanadate (a positive modulator)8 and ATP (an inhibitor)9, bind to different locations of TRPM4 at physiological temperatures than at lower temperatures10,11, and that these sites have bona fide functional relevance. We elucidated the TRPM4 gating mechanism by capturing structural snapshots of its different functional states at physiological temperatures, revealing the channel opening that is not observed at lower temperatures. Our study provides an example of temperature-dependent ligand recognition and modulation of an ion channel, underscoring the importance of studying macromolecules at physiological temperatures. It also provides a potential molecular framework for deciphering how thermosensitive TRPM channels perceive temperature changes.
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Affiliation(s)
- Jinhong Hu
- Van Andel Institute, Grand Rapids, MI, USA
| | | | - Tyler Walter
- Van Andel Institute, Grand Rapids, MI, USA
- Zoetis, Kalamazoo, MI, USA
| | - Ian J Orozco
- Van Andel Institute, Grand Rapids, MI, USA
- AnaBios, San Diego, CA, USA
| | | | - Xinyu Ye
- Van Andel Institute, Grand Rapids, MI, USA
| | - Juan Du
- Van Andel Institute, Grand Rapids, MI, USA.
| | - Wei Lü
- Van Andel Institute, Grand Rapids, MI, USA.
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3
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Tarnovskaya SI, Kostareva AA, Zhorov BS. In silico analysis of TRPM4 variants of unknown clinical significance. PLoS One 2023; 18:e0295974. [PMID: 38100498 PMCID: PMC10723691 DOI: 10.1371/journal.pone.0295974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Accepted: 12/02/2023] [Indexed: 12/17/2023] Open
Abstract
BACKGROUND TRPM4 is a calcium-activated channel that selectively permeates monovalent cations. Genetic variants of the channel in cardiomyocytes are associated with various heart disorders, such as progressive familial heart block and Brugada syndrome. About97% of all known TRPM4 missense variants are classified as variants of unknown clinical significance (VUSs). The very large number of VUSs is a serious problem in diagnostics and treatment of inherited heart diseases. METHODS AND RESULTS We collected 233 benign or pathogenic missense variants in the superfamily of TRP channels from databases ClinVar, Humsavar and Ensembl Variation to compare performance of 22 algorithms that predict damaging variants. We found that ClinPred is the best-performing tool for TRP channels. We also used the paralogue annotation method to identify disease variants across the TRP family. In the set of 565 VUSs of hTRPM4, ClinPred predicted pathogenicity of 299 variants. Among these, 12 variants are also categorized as LP/P variants in at least one paralogue of hTRPM4. We further used the cryo-EM structure of hTRPM4 to find scores of contact pairs between parental (wild type) residues of VUSs for which ClinPred predicts a high probability of pathogenicity of variants for both contact partners. We propose that 68 respective missense VUSs are also likely pathogenic variants. CONCLUSIONS ClinPred outperformed other in-silico tools in predicting damaging variants of TRP channels. ClinPred, the paralogue annotation method, and analysis of residue contacts the hTRPM4 cryo-EM structure collectively suggest pathogenicity of 80 TRPM4 VUSs.
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Affiliation(s)
- Svetlana I. Tarnovskaya
- Almazov National Medical Research Centre, St. Petersburg, Russia
- Sechenov Institute of Evolutionary Physiology & Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
| | - Anna A. Kostareva
- Almazov National Medical Research Centre, St. Petersburg, Russia
- Department of Women’s and Children’s Health and Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Boris S. Zhorov
- Almazov National Medical Research Centre, St. Petersburg, Russia
- Sechenov Institute of Evolutionary Physiology & Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Canada
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4
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Vydra Bousova K, Zouharova M, Jiraskova K, Vetyskova V. Interaction of Calmodulin with TRPM: An Initiator of Channel Modulation. Int J Mol Sci 2023; 24:15162. [PMID: 37894842 PMCID: PMC10607381 DOI: 10.3390/ijms242015162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2023] [Revised: 10/05/2023] [Accepted: 10/11/2023] [Indexed: 10/29/2023] Open
Abstract
Transient receptor potential melastatin (TRPM) channels, a subfamily of the TRP superfamily, constitute a diverse group of ion channels involved in mediating crucial cellular processes like calcium homeostasis. These channels exhibit complex regulation, and one of the key regulatory mechanisms involves their interaction with calmodulin (CaM), a cytosol ubiquitous calcium-binding protein. The association between TRPM channels and CaM relies on the presence of specific CaM-binding domains in the channel structure. Upon CaM binding, the channel undergoes direct and/or allosteric structural changes and triggers down- or up-stream signaling pathways. According to current knowledge, ion channel members TRPM2, TRPM3, TRPM4, and TRPM6 are directly modulated by CaM, resulting in their activation or inhibition. This review specifically focuses on the interplay between TRPM channels and CaM and summarizes the current known effects of CaM interactions and modulations on TRPM channels in cellular physiology.
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5
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Aureliano M, Gumerova NI, Sciortino G, Garribba E, McLauchlan CC, Rompel A, Crans DC. Polyoxidovanadates' interactions with proteins: An overview. Coord Chem Rev 2022. [DOI: 10.1016/j.ccr.2021.214344] [Citation(s) in RCA: 52] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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6
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Kita DH, de Andrade GA, Missina JM, Postal K, Boell VK, Santana FS, Zattoni IF, da Silva Zanzarini I, Moure VR, de Moraes Rego FG, Picheth G, de Souza EM, Mitchell DA, Ambudkar SV, Nunes GG, Valdameri G. Polyoxovanadates as new P-glycoprotein inhibitors: insights into the mechanism of inhibition. FEBS Lett 2022; 596:381-399. [PMID: 34939198 PMCID: PMC9340886 DOI: 10.1002/1873-3468.14265] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Revised: 12/02/2021] [Accepted: 12/13/2021] [Indexed: 02/03/2023]
Abstract
A promising strategy to overcome multidrug resistance is the use of inhibitors of ABC drug transporters. For this reason, we evaluated the polyoxovanadates (POVs) [V10 O28 ]6- (V10 ), [H6 V14 O38 (PO4 )]5- (V14 ), [V15 O36 Cl]6- (V15 ) and [V18 O42 I]7- (V18 ) as inhibitors of three major multidrug resistance-linked ABC transporters: P-glycoprotein (P-gp), ABCG2 and MRP1. All of the POVs selectively inhibited P-gp. V10 and V18 were the two most promising compounds, with IC50 values of transport inhibition of 25.4 and 22.7 µm, respectively. Both compounds inhibited P-gp ATPase activity, with the same IC50 value of 1.26 µm. V10 and V18 triggered different conformational changes in the P-gp protein with time-dependent inhibition, which was confirmed using the synthesized salt of V10 with rhodamine B, RhoB-V10 . The hydrophilic nature of POVs supports the hypothesis that these compounds target an unusual ligand-binding site, opening new possibilities in the development of potent modulators of ABC transporters.
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MESH Headings
- Humans
- ATP Binding Cassette Transporter, Subfamily G, Member 2/antagonists & inhibitors
- ATP Binding Cassette Transporter, Subfamily G, Member 2/metabolism
- ATP Binding Cassette Transporter, Subfamily G, Member 2/genetics
- ATP Binding Cassette Transporter, Subfamily G, Member 2/chemistry
- Multidrug Resistance-Associated Proteins/antagonists & inhibitors
- Multidrug Resistance-Associated Proteins/metabolism
- ATP Binding Cassette Transporter, Subfamily B, Member 1/antagonists & inhibitors
- ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism
- ATP Binding Cassette Transporter, Subfamily B, Member 1/chemistry
- Neoplasm Proteins/antagonists & inhibitors
- Neoplasm Proteins/metabolism
- Neoplasm Proteins/genetics
- Tungsten Compounds/pharmacology
- Tungsten Compounds/chemistry
- ATP Binding Cassette Transporter, Subfamily B/antagonists & inhibitors
- ATP Binding Cassette Transporter, Subfamily B/metabolism
- ATP Binding Cassette Transporter, Subfamily B/chemistry
- ATP Binding Cassette Transporter, Subfamily B/genetics
- Drug Resistance, Multiple/drug effects
- Animals
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Affiliation(s)
- Diogo Henrique Kita
- Pharmaceutical Sciences Graduate Program, Laboratory of Cancer Drug Resistance, Federal University of Paraná, Curitiba, PR, Brazil
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Gisele Alves de Andrade
- Pharmaceutical Sciences Graduate Program, Laboratory of Cancer Drug Resistance, Federal University of Paraná, Curitiba, PR, Brazil
| | | | - Kahoana Postal
- Department of Chemistry, Federal University of Paraná, Curitiba, PR, Brazil
| | | | | | - Ingrid Fatima Zattoni
- Pharmaceutical Sciences Graduate Program, Laboratory of Cancer Drug Resistance, Federal University of Paraná, Curitiba, PR, Brazil
| | - Isadora da Silva Zanzarini
- Pharmaceutical Sciences Graduate Program, Laboratory of Cancer Drug Resistance, Federal University of Paraná, Curitiba, PR, Brazil
| | - Vivian Rotuno Moure
- Pharmaceutical Sciences Graduate Program, Laboratory of Cancer Drug Resistance, Federal University of Paraná, Curitiba, PR, Brazil
- Department of Clinical Analysis, Federal University of Paraná, Curitiba, PR, Brazil
| | | | - Geraldo Picheth
- Department of Clinical Analysis, Federal University of Paraná, Curitiba, PR, Brazil
| | - Emanuel Maltempi de Souza
- Department of Biochemistry and Molecular Biology, Federal University of Paraná, Curitiba, PR, Brazil
| | - David A. Mitchell
- Department of Biochemistry and Molecular Biology, Federal University of Paraná, Curitiba, PR, Brazil
| | - Suresh V. Ambudkar
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA
| | | | - Glaucio Valdameri
- Pharmaceutical Sciences Graduate Program, Laboratory of Cancer Drug Resistance, Federal University of Paraná, Curitiba, PR, Brazil
- Department of Clinical Analysis, Federal University of Paraná, Curitiba, PR, Brazil
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7
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Kovács ZM, Dienes C, Hézső T, Almássy J, Magyar J, Bányász T, Nánási PP, Horváth B, Szentandrássy N. Pharmacological Modulation and (Patho)Physiological Roles of TRPM4 Channel—Part 1: Modulation of TRPM4. Pharmaceuticals (Basel) 2022; 15:ph15010081. [PMID: 35056138 PMCID: PMC8781449 DOI: 10.3390/ph15010081] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 01/06/2022] [Indexed: 02/06/2023] Open
Abstract
Transient receptor potential melastatin 4 is a unique member of the TRPM protein family and, similarly to TRPM5, is Ca2+-sensitive and permeable to monovalent but not divalent cations. It is widely expressed in many organs and is involved in several functions by regulating the membrane potential and Ca2+ homeostasis in both excitable and non-excitable cells. This part of the review discusses the pharmacological modulation of TRPM4 by listing, comparing, and describing both endogenous and exogenous activators and inhibitors of the ion channel. Moreover, other strategies used to study TRPM4 functions are listed and described. These strategies include siRNA-mediated silencing of TRPM4, dominant-negative TRPM4 variants, and anti-TRPM4 antibodies. TRPM4 is receiving more and more attention and is likely to be the topic of research in the future.
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Affiliation(s)
- Zsigmond Máté Kovács
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.M.K.); (C.D.); (T.H.); (J.A.); (J.M.); (T.B.); (P.P.N.); (B.H.)
- Doctoral School of Molecular Medicine, University of Debrecen, 4032 Debrecen, Hungary
| | - Csaba Dienes
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.M.K.); (C.D.); (T.H.); (J.A.); (J.M.); (T.B.); (P.P.N.); (B.H.)
- Doctoral School of Molecular Medicine, University of Debrecen, 4032 Debrecen, Hungary
| | - Tamás Hézső
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.M.K.); (C.D.); (T.H.); (J.A.); (J.M.); (T.B.); (P.P.N.); (B.H.)
- Doctoral School of Molecular Medicine, University of Debrecen, 4032 Debrecen, Hungary
| | - János Almássy
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.M.K.); (C.D.); (T.H.); (J.A.); (J.M.); (T.B.); (P.P.N.); (B.H.)
| | - János Magyar
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.M.K.); (C.D.); (T.H.); (J.A.); (J.M.); (T.B.); (P.P.N.); (B.H.)
- Division of Sport Physiology, Department of Physiology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary
| | - Tamás Bányász
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.M.K.); (C.D.); (T.H.); (J.A.); (J.M.); (T.B.); (P.P.N.); (B.H.)
| | - Péter P. Nánási
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.M.K.); (C.D.); (T.H.); (J.A.); (J.M.); (T.B.); (P.P.N.); (B.H.)
- Department of Dental Physiology and Pharmacology, Faculty of Dentistry, University of Debrecen, 4032 Debrecen, Hungary
| | - Balázs Horváth
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.M.K.); (C.D.); (T.H.); (J.A.); (J.M.); (T.B.); (P.P.N.); (B.H.)
- Faculty of Pharmacy, University of Debrecen, 4032 Debrecen, Hungary
| | - Norbert Szentandrássy
- Department of Physiology, Faculty of Medicine, University of Debrecen, 4032 Debrecen, Hungary; (Z.M.K.); (C.D.); (T.H.); (J.A.); (J.M.); (T.B.); (P.P.N.); (B.H.)
- Department of Basic Medical Sciences, Faculty of Dentistry, University of Debrecen, 4032 Debrecen, Hungary
- Correspondence:
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8
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Arullampalam P, Preti B, Ross-Kaschitza D, Lochner M, Rougier JS, Abriel H. Species-Specific Effects of Cation Channel TRPM4 Small-Molecule Inhibitors. Front Pharmacol 2021; 12:712354. [PMID: 34335274 PMCID: PMC8321095 DOI: 10.3389/fphar.2021.712354] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 06/30/2021] [Indexed: 12/14/2022] Open
Abstract
Background: The Transient Receptor Potential Melastatin member 4 (TRPM4) gene encodes a calcium-activated non-selective cation channel expressed in several tissues. Mutations in TRPM4 have been reported in patients with different types of cardiac conduction defects. It is also linked to immune response and cancers, but the associated molecular mechanisms are still unclear. Thus far, 9-phenanthrol is the most common pharmacological compound used to investigate TRPM4 function. We recently identified two promising aryloxyacyl-anthranilic acid compounds (abbreviated CBA and NBA) inhibiting TRPM4. However, all aforementioned compounds were screened using assays expressing human TRPM4, whereas the efficacy of mouse TRPM4 has not been assessed. Mouse models are essential to investigate ion channel physiology and chemical compound efficacy. Aim: In this study, we performed comparative electrophysiology experiments to assess the effect of these TRPM4 inhibitors on human and mouse TRPM4 channels heterologously expressed in TsA-201 cells. Methods and Results: We identified striking species-dependent differences in TRPM4 responses. NBA inhibited both human and mouse TRPM4 currents when applied intracellularly and extracellularly using excised membrane patches. CBA inhibited human TRPM4, both intracellularly and extracellularly. Unexpectedly, the application of CBA had no inhibiting effect on mouse TRPM4 current when perfused on the extracellular side. Instead, its increased mouse TRPM4 current at negative holding potentials. In addition, CBA on the intracellular side altered the outward rectification component of the mouse TRPM4 current. Application of 9-phenanthrol, both intracellularly and extracellularly, inhibited human TRPM4. For mouse TRPM4, 9-phenanthrol perfusion led to opposite effects depending on the site of application. With intracellular 9-phenanthrol, we observed a tendency towards potentiation of mouse TRPM4 outward current at positive holding potentials. Conclusion: Altogether, these results suggest that pharmacological compounds screened using “humanised assays” should be extensively characterised before application in vivo mouse models.
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Affiliation(s)
- Prakash Arullampalam
- Swiss National Centre of Competence in Research (NCCR) TransCure, Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - Barbara Preti
- Swiss National Centre of Competence in Research (NCCR) TransCure, Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - Daniela Ross-Kaschitza
- Swiss National Centre of Competence in Research (NCCR) TransCure, Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - Martin Lochner
- Swiss National Centre of Competence in Research (NCCR) TransCure, Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - Jean-Sébastien Rougier
- Swiss National Centre of Competence in Research (NCCR) TransCure, Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - Hugues Abriel
- Swiss National Centre of Competence in Research (NCCR) TransCure, Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
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9
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Ruan Z, Haley E, Orozco IJ, Sabat M, Myers R, Roth R, Du J, Lü W. Structures of the TRPM5 channel elucidate mechanisms of activation and inhibition. Nat Struct Mol Biol 2021; 28:604-613. [PMID: 34168372 PMCID: PMC8767786 DOI: 10.1038/s41594-021-00607-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Accepted: 05/12/2021] [Indexed: 02/06/2023]
Abstract
The Ca2+-activated TRPM5 channel plays essential roles in taste perception and insulin secretion. However, the mechanism by which Ca2+ regulates TRPM5 activity remains elusive. We report cryo-EM structures of the zebrafish TRPM5 in an apo closed state, a Ca2+-bound open state, and an antagonist-bound inhibited state. We define two novel ligand binding sites: a Ca2+ site (CaICD) in the intracellular domain and an antagonist site in the transmembrane domain (TMD). The CaICD site is unique to TRPM5 and has two roles: modulating the voltage dependence and promoting Ca2+ binding to the CaTMD site, which is conserved throughout TRPM channels. Conformational changes initialized from both Ca2+ sites cooperatively open the ion-conducting pore. The antagonist NDNA wedges into the space between the S1-S4 domain and pore domain, stabilizing the transmembrane domain in an apo-like closed state. Our results lay the foundation for understanding the voltage-dependent TRPM channels and developing new therapeutic agents.
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Affiliation(s)
- Zheng Ruan
- Van Andel Institute, 333 Bostwick Ave., N.E., Grand Rapids, MI 49503
| | - Emery Haley
- Van Andel Institute, 333 Bostwick Ave., N.E., Grand Rapids, MI 49503
| | - Ian J. Orozco
- Van Andel Institute, 333 Bostwick Ave., N.E., Grand Rapids, MI 49503
| | - Mark Sabat
- Takeda California Inc, 9625 Towne Centre Dr, San Diego, CA 92121
| | - Richard Myers
- Takeda California Inc, 9625 Towne Centre Dr, San Diego, CA 92121
| | - Rebecca Roth
- Van Andel Institute, 333 Bostwick Ave., N.E., Grand Rapids, MI 49503
| | - Juan Du
- Van Andel Institute, 333 Bostwick Ave., N.E., Grand Rapids, MI 49503,CORRESPONDING AUTHOR: Correspondence and requests for materials should be addressed to J. D. () TEL: (616) 234-5358, FAX: 616-234-5170 or W. L. (). TEL: (616) 234-5022, FAX: 616-234-5170
| | - Wei Lü
- Van Andel Institute, 333 Bostwick Ave., N.E., Grand Rapids, MI 49503,CORRESPONDING AUTHOR: Correspondence and requests for materials should be addressed to J. D. () TEL: (616) 234-5358, FAX: 616-234-5170 or W. L. (). TEL: (616) 234-5022, FAX: 616-234-5170
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10
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Shi R, Fu Y, Zhao D, Boczek T, Wang W, Guo F. Cell death modulation by transient receptor potential melastatin channels TRPM2 and TRPM7 and their underlying molecular mechanisms. Biochem Pharmacol 2021; 190:114664. [PMID: 34175300 DOI: 10.1016/j.bcp.2021.114664] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 06/21/2021] [Accepted: 06/22/2021] [Indexed: 10/21/2022]
Abstract
Transient receptor potential melastatin (TRPM) channels are members of the transient receptor potential (TRP) channels, a family of evolutionarily conserved integral membrane proteins. TRPM channels are nonselective cation channels, mediating the influx of various ions including Ca2+, Na+ and Zn2+. The function of TRPM channels is vital for cell proliferation, cell development and cell death. Cell death is a key procedure during embryonic development, organism homeostasis, aging and disease. The category of cell death modalities, beyond the traditionally defined concepts of necrosis, autophagy, and apoptosis, were extended with the discovery of pyroptosis, necroptosis and ferroptosis. As upstream signaling regulators of cell death, TRPM channels have been involved inrelevant pathologies. In this review, we introduced several cell death modalities, then summarized the contribution of TRPM channels (especially TRPM2 and TRPM7) to different cell death modalities and discussed the underlying regulatory mechanisms. Our work highlighted the possibility of TRPM channels as potential therapeutic targets in cell death-related diseases.
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Affiliation(s)
- Ruixue Shi
- Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110122, China
| | - Yu Fu
- Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110122, China
| | - Dongyi Zhao
- The University of Tokyo, Department of Pharmaceutical Science, 1130033, Japan
| | - Tomasz Boczek
- Department of Molecular Neurochemistry, Medical University of Lodz, 92215, Poland.
| | - Wuyang Wang
- Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou 221004, China.
| | - Feng Guo
- Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110122, China.
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11
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Riquelme D, Peralta FA, Navarro FD, Moreno C, Leiva-Salcedo E. I CAN (TRPM4) Contributes to the Intrinsic Excitability of Prefrontal Cortex Layer 2/3 Pyramidal Neurons. Int J Mol Sci 2021; 22:ijms22105268. [PMID: 34067824 PMCID: PMC8157065 DOI: 10.3390/ijms22105268] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Revised: 05/11/2021] [Accepted: 05/14/2021] [Indexed: 01/17/2023] Open
Abstract
Pyramidal neurons in the medial prefrontal cortical layer 2/3 are an essential contributor to the cellular basis of working memory; thus, changes in their intrinsic excitability critically affect medial prefrontal cortex (mPFC) functional properties. Transient Receptor Potential Melastatin 4 (TRPM4), a calcium-activated nonselective cation channel (CAN), regulates the membrane potential in a calcium-dependent manner. In this study, we uncovered the role of TRPM4 in regulating the intrinsic excitability plasticity of pyramidal neurons in the mouse mPFC layer of 2/3 using a combination of conventional and nystatin perforated whole-cell recordings. Interestingly, we found that TRPM4 is open at resting membrane potential, and its inhibition increases input resistance and hyperpolarizes membrane potential. After high-frequency stimulation, pyramidal neurons increase a calcium-activated non-selective cation current, increase the action potential firing, and the amplitude of the afterdepolarization, these effects depend on intracellular calcium. Furthermore, pharmacological inhibition or genetic silencing of TRPM4 reduces the firing rate and the afterdepolarization after high frequency stimulation. Together, these results show that TRPM4 plays a significant role in the excitability of mPFC layer 2/3 pyramidal neurons by modulating neuronal excitability in a calcium-dependent manner.
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12
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Feng J, Zong P, Yan J, Yue Z, Li X, Smith C, Ai X, Yue L. Upregulation of transient receptor potential melastatin 4 (TRPM4) in ventricular fibroblasts from heart failure patients. Pflugers Arch 2021; 473:521-531. [PMID: 33594499 PMCID: PMC8857941 DOI: 10.1007/s00424-021-02525-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 01/22/2021] [Accepted: 01/26/2021] [Indexed: 12/19/2022]
Abstract
The transient receptor potential melastatin 4 (TRPM4) is a Ca2+-activated nonselective monovalent cation channel belonging to the TRP channel superfamily. TRPM4 is widely expressed in various tissues and most abundantly expressed in the heart. TRPM4 plays a critical role in cardiac conduction. Patients carrying a gain-of-function or loss-of-function mutation of TRPM4 display impaired cardiac conduction. Knockout or over-expression of TRPM4 in mice recapitulates conduction defects in patients. Moreover, recent studies have indicated that TRPM4 plays a role in hypertrophy and heart failure. Whereas the role of TRPM4 mediated by cardiac myocytes has been well investigated, little is known about TRPM4 and its role in cardiac fibroblasts. Here we show that in human left ventricular fibroblasts, TRPM4 exhibits typical Ca2+-activation characteristics, linear current-voltage (I-V) relation, and monovalent permeability. TRPM4 currents recorded in fibroblasts from heart failure patients (HF) are more than 2-fold bigger than those from control individuals (CTL). The enhanced functional TRPM4 in HF is not resulted from changed channel properties, as TRPM4 currents from both HF and CTL fibroblasts demonstrate similar sensitivity to intracellular calcium activation and extracellular 9-phenanthrol (9-phen) blockade. Consistent with enhanced TRPM4 activity, the protein level of TRPM4 is about 2-fold higher in HF than that of CTL hearts. Moreover, TRPM4 current in CTL fibroblasts is increased after 24 hours of TGFβ1 treatment, implying that TRPM4 in vivo may be upregulated by fibrogenesis promotor TGFβ1. The upregulated TRPM4 in HF fibroblasts suggests that TRPM4 may play a role in cardiac fibrogenesis under various pathological conditions.
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Affiliation(s)
- Jianlin Feng
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut School of Medicine (UConn Health), Farmington, CT, 06030, USA
| | - Pengyu Zong
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut School of Medicine (UConn Health), Farmington, CT, 06030, USA
| | - Jiajie Yan
- Department of Physiology and Biophysics, Rush University Medical Center, Chicago, IL, 60612, USA
| | - Zhichao Yue
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut School of Medicine (UConn Health), Farmington, CT, 06030, USA
| | - Xin Li
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut School of Medicine (UConn Health), Farmington, CT, 06030, USA
| | - Chevaughn Smith
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut School of Medicine (UConn Health), Farmington, CT, 06030, USA
| | - Xun Ai
- Department of Physiology and Biophysics, Rush University Medical Center, Chicago, IL, 60612, USA
| | - Lixia Yue
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut School of Medicine (UConn Health), Farmington, CT, 06030, USA.
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13
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Quelhas P, Baltazar G, Cairrao E. The Neurovascular Unit: Focus on the Regulation of Arterial Smooth Muscle Cells. Curr Neurovasc Res 2020; 16:502-515. [PMID: 31738142 DOI: 10.2174/1567202616666191026122642] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2019] [Revised: 09/01/2019] [Accepted: 09/20/2019] [Indexed: 02/08/2023]
Abstract
The neurovascular unit is a physiological unit present in the brain, which is constituted by elements of the nervous system (neurons and astrocytes) and the vascular system (endothelial and mural cells). This unit is responsible for the homeostasis and regulation of cerebral blood flow. There are two major types of mural cells in the brain, pericytes and smooth muscle cells. At the arterial level, smooth muscle cells are the main components that wrap around the outside of cerebral blood vessels and the major contributors to basal tone maintenance, blood pressure and blood flow distribution. They present several mechanisms by which they regulate both vasodilation and vasoconstriction of cerebral blood vessels and their regulation becomes even more important in situations of injury or pathology. In this review, we discuss the main regulatory mechanisms of brain smooth muscle cells and their contributions to the correct brain homeostasis.
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Affiliation(s)
- Patrícia Quelhas
- CICS-UBI - Centro de Investigacao em Ciencias da Saude, University of Beira Interior, 6200-506 Covilha, Portugal
| | - Graça Baltazar
- CICS-UBI - Centro de Investigacao em Ciencias da Saude, University of Beira Interior, 6200-506 Covilha, Portugal
| | - Elisa Cairrao
- CICS-UBI - Centro de Investigacao em Ciencias da Saude, University of Beira Interior, 6200-506 Covilha, Portugal
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14
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Thakore P, Earley S. Transient Receptor Potential Channels and Endothelial Cell Calcium Signaling. Compr Physiol 2019; 9:1249-1277. [PMID: 31187891 DOI: 10.1002/cphy.c180034] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The vascular endothelium is a broadly distributed and highly specialized organ. The endothelium has a number of functions including the control of blood vessels diameter through the production and release of potent vasoactive substances or direct electrical communication with underlying smooth muscle cells, regulates the permeability of the vascular barrier, stimulates the formation of new blood vessels, and influences inflammatory and thrombotic processes. Endothelial cells that make up the endothelium express a variety of cell-surface receptors and ion channels on the plasma membrane that are capable of detecting circulating hormones, neurotransmitters, oxygen tension, and shear stress across the vascular wall. Changes in these stimuli activate signaling cascades that initiate an appropriate physiological response. Increases in the global intracellular Ca2+ concentration and localized Ca2+ signals that occur within specialized subcellular microdomains are fundamentally important components of many signaling pathways in the endothelium. The transient receptor potential (TRP) channels are a superfamily of cation-permeable ion channels that act as a primary means of increasing cytosolic Ca2+ in endothelial cells. Consequently, TRP channels are vitally important for the major functions of the endothelium. In this review, we provide an in-depth discussion of Ca2+ -permeable TRP channels in the endothelium and their role in vascular regulation. © 2019 American Physiological Society. Compr Physiol 9:1249-1277, 2019.
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Affiliation(s)
- Pratish Thakore
- Department of Pharmacology, Center for Cardiovascular Research, University of Nevada, Reno School of Medicine, Reno, Nevada, USA
| | - Scott Earley
- Department of Pharmacology, Center for Cardiovascular Research, University of Nevada, Reno School of Medicine, Reno, Nevada, USA
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15
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Picardo MCD, Sugimura YK, Dorst KE, Kallurkar PS, Akins VT, Ma X, Teruyama R, Guinamard R, Kam K, Saha MS, Del Negro CA. Trpm4 ion channels in pre-Bötzinger complex interneurons are essential for breathing motor pattern but not rhythm. PLoS Biol 2019; 17:e2006094. [PMID: 30789900 PMCID: PMC6400419 DOI: 10.1371/journal.pbio.2006094] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Revised: 03/05/2019] [Accepted: 02/05/2019] [Indexed: 12/21/2022] Open
Abstract
Inspiratory breathing movements depend on pre-Bötzinger complex (preBötC) interneurons that express calcium (Ca2+)-activated nonselective cationic current (ICAN) to generate robust neural bursts. Hypothesized to be rhythmogenic, reducing ICAN is predicted to slow down or stop breathing; its contributions to motor pattern would be reflected in the magnitude of movements (output). We tested the role(s) of ICAN using reverse genetic techniques to diminish its putative ion channels Trpm4 or Trpc3 in preBötC neurons in vivo. Adult mice transduced with Trpm4-targeted short hairpin RNA (shRNA) progressively decreased the tidal volume of breaths yet surprisingly increased breathing frequency, often followed by gasping and fatal respiratory failure. Mice transduced with Trpc3-targeted shRNA survived with no changes in breathing. Patch-clamp and field recordings from the preBötC in mouse slices also showed an increase in the frequency and a decrease in the magnitude of preBötC neural bursts in the presence of Trpm4 antagonist 9-phenanthrol, whereas the Trpc3 antagonist pyrazole-3 (pyr-3) showed inconsistent effects on magnitude and no effect on frequency. These data suggest that Trpm4 mediates ICAN, whose influence on frequency contradicts a direct role in rhythm generation. We conclude that Trpm4-mediated ICAN is indispensable for motor output but not the rhythmogenic core mechanism of the breathing central pattern generator.
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Affiliation(s)
- Maria Cristina D. Picardo
- Department of Applied Science, Integrated Science Center, William & Mary, Williamsburg, Virginia, United States of America
| | - Yae K. Sugimura
- Department of Applied Science, Integrated Science Center, William & Mary, Williamsburg, Virginia, United States of America
| | - Kaitlyn E. Dorst
- Department of Applied Science, Integrated Science Center, William & Mary, Williamsburg, Virginia, United States of America
| | - Prajkta S. Kallurkar
- Department of Applied Science, Integrated Science Center, William & Mary, Williamsburg, Virginia, United States of America
| | - Victoria T. Akins
- Department of Applied Science, Integrated Science Center, William & Mary, Williamsburg, Virginia, United States of America
| | - Xingru Ma
- Department of Applied Science, Integrated Science Center, William & Mary, Williamsburg, Virginia, United States of America
| | - Ryoichi Teruyama
- Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, United States of America
| | - Romain Guinamard
- Signalisation, Electrophysiologie et Imagerie des Lésions d’Ischémie-Reperfusion Myocardique, Normandie Université, UNICAEN, Caen, France
| | - Kaiwen Kam
- Department of Cell Biology and Anatomy, Chicago Medical School, Rosalind Franklin University, Chicago, Illinois, United States of America
| | - Margaret S. Saha
- Department of Biology, Integrated Science Center, William & Mary, Williamsburg, Virginia, United States of America
| | - Christopher A. Del Negro
- Department of Applied Science, Integrated Science Center, William & Mary, Williamsburg, Virginia, United States of America
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16
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Bijelic A, Rompel A. Polyoxometalates: more than a phasing tool in protein crystallography. CHEMTEXTS 2018; 4:10. [PMID: 30596006 PMCID: PMC6294228 DOI: 10.1007/s40828-018-0064-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 08/06/2018] [Indexed: 01/18/2023]
Abstract
Protein crystallography is the most widely used method for determining the molecular structure of proteins and obtaining structural information on protein–ligand complexes at the atomic level. As the structure determines the functions and properties of a protein, crystallography is of immense importance for nearly all research fields related to biochemistry. However, protein crystallography suffers from some major drawbacks, whereby the unpredictability of the crystallization process represents the main bottleneck. Crystallization is still more or less a ‘trial and error’ based procedure, and therefore, very time and resource consuming. Many strategies have been developed in the past decades to improve or enable the crystallization of proteins, whereby the use of so-called additives, which are mostly small molecules that make proteins more amenable to crystallization, is one of the most convenient and successful methods. Most of the commonly used additives are, however, restricted to particular crystallization conditions or groups of proteins. Therefore, a more universal additive addressing a wider range of proteins and being applicable to a broad spectrum of crystallization conditions would represent a significant advance in the field of protein crystallography. In recent years, polyoxometalates (POMs) emerged as a promising group of crystallization additives due to their unique structures and properties. In this regard, the tellurium-centered Anderson–Evans polyoxotungstate [TeW6O24]6− (TEW) showed its high potential as crystallization additive. In this lecture text, the development of POMs as tools in protein crystallography are discussed with a special focus on the so far most successful cluster TEW.
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Affiliation(s)
- Aleksandar Bijelic
- Universität Wien, Fakultät für Chemie, Institut für Biophysikalische Chemie, Althanstraße 14, 1090 Vienna, Austria
| | - Annette Rompel
- Universität Wien, Fakultät für Chemie, Institut für Biophysikalische Chemie, Althanstraße 14, 1090 Vienna, Austria
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17
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Tan CH, McNaughton PA. TRPM2 and warmth sensation. Pflugers Arch 2018; 470:787-798. [PMID: 29552700 PMCID: PMC5942353 DOI: 10.1007/s00424-018-2139-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 03/08/2018] [Accepted: 03/09/2018] [Indexed: 01/08/2023]
Abstract
The abilities to detect warmth and heat are critical for the survival of all animals, both in order to be able to identify suitable thermal environments for the many different activities essential for life and to avoid damage caused by extremes of temperature. Several ion channels belonging to the TRP family are activated by non-noxious warmth or by heat and are therefore plausible candidates for thermal detectors, but identifying those that actually regulate warmth and heat detection in intact animals has proven problematic. TRPM2 has recently emerged as a likely candidate for the detector of non-noxious warmth, as it is expressed in sensory neurons, and mice show deficits in the detection of warmth when TRPM2 is genetically deleted. TRPM2 is a chanzyme, containing a thermally activated TRP ion channel domain attached to a C-terminal motif, derived from a mitochondrial ADP ribose pyrophosphatase, that confers on the channel sensitivity to ADP ribose and reactive oxygen species such as hydrogen peroxide. Several open questions remain. Male mammals prefer cooler environments than female, but the molecular basis of this sex difference is unknown. TRPM2 plays a role in regulating body temperature, but are other warmth-detecting mechanisms also involved? TRPM2 is expressed in autonomic neurons, but does it confer a sensory function in addition to the well-known motor functions of autonomic neurons? TRPM2 is thought to play important roles in the immune system, in pain and in insulin secretion, but the mechanisms are unclear. TRPM2 has to date received less attention than many other members of the TRP family but is rapidly assuming importance both in normal physiology and as a key target in disease pathology.
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Affiliation(s)
- Chun-Hsiang Tan
- Department of Neurology, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan
- Graduate Institute of Clinical Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Peter A McNaughton
- Wolfson Centre for Age-Related Diseases, Institute of Psychiatry, Psychology and Neuroscience, Guy's Campus, King's College London, London, SE1 1UL, UK.
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18
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Autzen HE, Myasnikov AG, Campbell MG, Asarnow D, Julius D, Cheng Y. Structure of the human TRPM4 ion channel in a lipid nanodisc. Science 2017; 359:228-232. [PMID: 29217581 DOI: 10.1126/science.aar4510] [Citation(s) in RCA: 180] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Accepted: 11/27/2017] [Indexed: 12/11/2022]
Abstract
Transient receptor potential (TRP) melastatin 4 (TRPM4) is a widely expressed cation channel associated with a variety of cardiovascular disorders. TRPM4 is activated by increased intracellular calcium in a voltage-dependent manner but, unlike many other TRP channels, is permeable to monovalent cations only. Here we present two structures of full-length human TRPM4 embedded in lipid nanodiscs at ~3-angstrom resolution, as determined by single-particle cryo-electron microscopy. These structures, with and without calcium bound, reveal a general architecture for this major subfamily of TRP channels and a well-defined calcium-binding site within the intracellular side of the S1-S4 domain. The structures correspond to two distinct closed states. Calcium binding induces conformational changes that likely prime the channel for voltage-dependent opening.
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Affiliation(s)
- Henriette E Autzen
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143, USA.,Department of Molecular Biology and Genetics, University of Aarhus, 8000 Aarhus, Denmark
| | - Alexander G Myasnikov
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143, USA
| | - Melody G Campbell
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143, USA
| | - Daniel Asarnow
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143, USA
| | - David Julius
- Department of Physiology, University of California, San Francisco, CA 94143, USA
| | - Yifan Cheng
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143, USA.,Howard Hughes Medical Institute, University of California, San Francisco, CA 94143, USA
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19
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Electron cryo-microscopy structure of a human TRPM4 channel. Nature 2017; 552:200-204. [DOI: 10.1038/nature24674] [Citation(s) in RCA: 112] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Accepted: 10/23/2017] [Indexed: 12/18/2022]
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20
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Leiva-Salcedo E, Riquelme D, Cerda O, Stutzin A. TRPM4 activation by chemically- and oxygen deprivation-induced ischemia and reperfusion triggers neuronal death. Channels (Austin) 2017; 11:624-635. [PMID: 28876976 DOI: 10.1080/19336950.2017.1375072] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Cerebral ischemia-reperfusion injury triggers a deleterious process ending in neuronal death. This process has two components, a glutamate-dependent and a glutamate-independent mechanism. In the glutamate-independent mechanism, neurons undergo a slow depolarization eventually leading to neuronal death. However, little is known about the molecules that take part in this process. Here we show by using mice cortical neurons in culture and ischemia-reperfusion protocols that TRPM4 is fundamental for the glutamate-independent neuronal damage. Thus, by blocking excitotoxicity, we reveal a slow activating, glibenclamide- and 9-phenanthrol-sensitive current, which is activated within 5 min upon ischemia-reperfusion onset. TRPM4 shRNA-based silenced neurons show a reduced ischemia-reperfusion induced current and depolarization. Neurons were protected from neuronal death up to 3 hours after the ischemia-reperfusion challenge. The activation of TRPM4 during ischemia-reperfusion injury involves the increase in both, intracellular calcium and H2O2, which may act together to produce a sustained activation of the channel.
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Affiliation(s)
- Elías Leiva-Salcedo
- a Departamento de Biología , Facultad de Química y Biología, Universidad de Santiago de Chile , Santiago , Chile
| | - Denise Riquelme
- a Departamento de Biología , Facultad de Química y Biología, Universidad de Santiago de Chile , Santiago , Chile
| | - Oscar Cerda
- b Programa de Biología Celular y Molecular , Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile , Santiago , Chile.,c Millennium Nucleus of Ion Channels-Associated Diseases (MiNICAD) , Universidad de Chile , Santiago , Chile
| | - Andrés Stutzin
- d Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile , Santiago , Chile
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21
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Tykocki NR, Boerman EM, Jackson WF. Smooth Muscle Ion Channels and Regulation of Vascular Tone in Resistance Arteries and Arterioles. Compr Physiol 2017; 7:485-581. [PMID: 28333380 DOI: 10.1002/cphy.c160011] [Citation(s) in RCA: 222] [Impact Index Per Article: 31.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Vascular tone of resistance arteries and arterioles determines peripheral vascular resistance, contributing to the regulation of blood pressure and blood flow to, and within the body's tissues and organs. Ion channels in the plasma membrane and endoplasmic reticulum of vascular smooth muscle cells (SMCs) in these blood vessels importantly contribute to the regulation of intracellular Ca2+ concentration, the primary determinant of SMC contractile activity and vascular tone. Ion channels provide the main source of activator Ca2+ that determines vascular tone, and strongly contribute to setting and regulating membrane potential, which, in turn, regulates the open-state-probability of voltage gated Ca2+ channels (VGCCs), the primary source of Ca2+ in resistance artery and arteriolar SMCs. Ion channel function is also modulated by vasoconstrictors and vasodilators, contributing to all aspects of the regulation of vascular tone. This review will focus on the physiology of VGCCs, voltage-gated K+ (KV) channels, large-conductance Ca2+-activated K+ (BKCa) channels, strong-inward-rectifier K+ (KIR) channels, ATP-sensitive K+ (KATP) channels, ryanodine receptors (RyRs), inositol 1,4,5-trisphosphate receptors (IP3Rs), and a variety of transient receptor potential (TRP) channels that contribute to pressure-induced myogenic tone in resistance arteries and arterioles, the modulation of the function of these ion channels by vasoconstrictors and vasodilators, their role in the functional regulation of tissue blood flow and their dysfunction in diseases such as hypertension, obesity, and diabetes. © 2017 American Physiological Society. Compr Physiol 7:485-581, 2017.
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Affiliation(s)
- Nathan R Tykocki
- Department of Pharmacology, University of Vermont, Burlington, Vermont, USA
| | - Erika M Boerman
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri, USA
| | - William F Jackson
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan, USA
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22
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Respiratory Rhythm Generation: The Whole Is Greater Than the Sum of the Parts. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1015:147-161. [DOI: 10.1007/978-3-319-62817-2_9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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23
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Morales-Lázaro SL, Lemus L, Rosenbaum T. Regulation of thermoTRPs by lipids. Temperature (Austin) 2016; 4:24-40. [PMID: 28349093 DOI: 10.1080/23328940.2016.1254136] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Revised: 10/21/2016] [Accepted: 10/24/2016] [Indexed: 12/30/2022] Open
Abstract
The family of Transient Receptor Potential (TRP) ion channels is constituted by 7 subfamilies among which are those that respond to temperature, the thermoTRPs. These channels are versatile molecules of a polymodal nature that have been shown to be modulated in various fashions by molecules of a lipidic nature. Some of these molecules interact directly with the channels on specific regions of their structures and some of these promote changes in membrane fluidity or modify their gating properties in response to their agonists. Here, we have discussed how some of these lipids regulate the activity of thermoTRPs and included some of the available evidence for the molecular mechanisms underlying their effects on these channels.
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Affiliation(s)
- Sara L Morales-Lázaro
- Department of Cognitive Neuroscience, Instituto de Fisiología Celular, Circuito exterior s/n, Universidad Nacional Autónoma de México , Coyoacan, México City, Mexico
| | - Luis Lemus
- Department of Cognitive Neuroscience, Instituto de Fisiología Celular, Circuito exterior s/n, Universidad Nacional Autónoma de México , Coyoacan, México City, Mexico
| | - Tamara Rosenbaum
- Department of Cognitive Neuroscience, Instituto de Fisiología Celular, Circuito exterior s/n, Universidad Nacional Autónoma de México , Coyoacan, México City, Mexico
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24
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Holzmann C, Kappel S, Kilch T, Jochum MM, Urban SK, Jung V, Stöckle M, Rother K, Greiner M, Peinelt C. Transient receptor potential melastatin 4 channel contributes to migration of androgen-insensitive prostate cancer cells. Oncotarget 2016; 6:41783-93. [PMID: 26496025 PMCID: PMC4747188 DOI: 10.18632/oncotarget.6157] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Accepted: 09/30/2015] [Indexed: 11/25/2022] Open
Abstract
Impaired Ca2+ signaling in prostate cancer contributes to several cancer hallmarks, such as enhanced proliferation and migration and a decreased ability to induce apoptosis. Na+ influx via transient receptor potential melastatin 4 channel (TRPM4) can reduce store-operated Ca2+ entry (SOCE) by decreasing the driving force for Ca2+. In patients with prostate cancer, gene expression of TRPM4 is elevated. Recently, TRPM4 was identified as a cancer driver gene in androgen-insensitive prostate cancer. We investigated TRPM4 protein expression in cancer tissue samples from 20 patients with prostate cancer. We found elevated TRPM4 protein levels in prostatic intraepithelial neoplasia (PIN) and prostate cancer tissue compared to healthy tissue. In primary human prostate epithelial cells (hPEC) from healthy tissue and in the androgen-insensitive prostate cancer cell lines DU145 and PC3, TRPM4 mediated large Na+ currents. We demonstrated significantly increased SOCE after siRNA targeting of TRPM4 in hPEC and DU145 cells. In addition, knockdown of TRPM4 reduced migration but not proliferation of DU145 and PC3 cells. Taken together, our data identify TRPM4 as a regulator of SOCE in hPEC and DU145 cells, demonstrate a role for TRPM4 in cancer cell migration and suggest that TRPM4 is a promising potential therapeutic target.
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Affiliation(s)
- Christian Holzmann
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, Germany
| | - Sven Kappel
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, Germany.,Center of Human and Molecular Biology, Saarland University, Homburg, Germany
| | - Tatiana Kilch
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, Germany.,Center of Human and Molecular Biology, Saarland University, Homburg, Germany
| | - Marcus Martin Jochum
- Center of Human and Molecular Biology, Saarland University, Homburg, Germany.,Clinics of Urology and Pediatric Urology, Saarland University, Homburg, Germany
| | - Sabine Katharina Urban
- Center of Human and Molecular Biology, Saarland University, Homburg, Germany.,Department of Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Volker Jung
- Clinics of Urology and Pediatric Urology, Saarland University, Homburg, Germany
| | - Michael Stöckle
- Clinics of Urology and Pediatric Urology, Saarland University, Homburg, Germany
| | - Karen Rother
- Center of Human and Molecular Biology, Saarland University, Homburg, Germany.,Department of Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Markus Greiner
- Center of Human and Molecular Biology, Saarland University, Homburg, Germany.,Department of Medical Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Christine Peinelt
- Biophysics, Center for Integrative Physiology and Molecular Medicine, School of Medicine, Saarland University, Homburg, Germany.,Center of Human and Molecular Biology, Saarland University, Homburg, Germany
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25
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Leitner MG, Michel N, Behrendt M, Dierich M, Dembla S, Wilke BU, Konrad M, Lindner M, Oberwinkler J, Oliver D. Direct modulation of TRPM4 and TRPM3 channels by the phospholipase C inhibitor U73122. Br J Pharmacol 2016; 173:2555-69. [PMID: 27328745 DOI: 10.1111/bph.13538] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Revised: 06/10/2016] [Accepted: 06/15/2016] [Indexed: 02/01/2023] Open
Abstract
BACKGROUND AND PURPOSE Signalling through phospholipase C (PLC) controls many cellular processes. Much information on the relevance of this important pathway has been derived from pharmacological inhibition of the enzymatic activity of PLC. We found that the most frequently employed PLC inhibitor, U73122, activates endogenous ionic currents in widely used cell lines. Given the extensive use of U73122 in research, we set out to identify these U73122-sensitive ion channels. EXPERIMENTAL APPROACH We performed detailed biophysical analysis of the U73122-induced currents in frequently used cell lines. KEY RESULTS At concentrations required to inhibit PLC, U73122 modulated the activity of transient receptor potential melastatin (TRPM) channels through covalent modification. U73122 was shown to be a potent agonist of ubiquitously expressed TRPM4 channels and activated endogenous TRPM4 channels in CHO cells independently of PLC and of the downstream second messengers PI(4,5)P2 and Ca(2+) . U73122 also potentiated Ca(2) (+) -dependent TRPM4 currents in human Jurkat T-cells, endogenous TRPM4 in HEK293T cells and recombinant human TRPM4. In contrast to TRPM4, TRPM3 channels were inhibited whereas the closely related TRPM5 channels were insensitive to U73122, showing that U73122 exhibits high specificity within the TRPM channel family. CONCLUSIONS AND IMPLICATIONS Given the widespread expression of TRPM4 and TRPM3 channels, these actions of U73122 must be considered when interpreting its effects on cell function. U73122 may also be useful for identifying and characterizing TRPM channels in native tissue, thus facilitating the analysis of their physiology.
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Affiliation(s)
- Michael G Leitner
- Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps-University Marburg, Marburg, Germany
| | - Niklas Michel
- Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps-University Marburg, Marburg, Germany
| | - Marc Behrendt
- Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps-University Marburg, Marburg, Germany
| | - Marlen Dierich
- Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps-University Marburg, Marburg, Germany
| | - Sandeep Dembla
- Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps-University Marburg, Marburg, Germany
| | - Bettina U Wilke
- Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps-University Marburg, Marburg, Germany
| | - Maik Konrad
- Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps-University Marburg, Marburg, Germany
| | - Moritz Lindner
- Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps-University Marburg, Marburg, Germany.,Department of Ophthalmology, University of Bonn, Bonn, Germany
| | - Johannes Oberwinkler
- Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps-University Marburg, Marburg, Germany
| | - Dominik Oliver
- Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps-University Marburg, Marburg, Germany
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Constantine M, Liew CK, Lo V, Macmillan A, Cranfield CG, Sunde M, Whan R, Graham RM, Martinac B. Heterologously-expressed and Liposome-reconstituted Human Transient Receptor Potential Melastatin 4 Channel (TRPM4) is a Functional Tetramer. Sci Rep 2016; 6:19352. [PMID: 26785754 PMCID: PMC4726259 DOI: 10.1038/srep19352] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 12/11/2015] [Indexed: 11/24/2022] Open
Abstract
Mutation, irregular expression and sustained activation of the Transient Receptor Potential Channel, type Melastatin 4 (TRPM4), have been linked to various cardiovascular diseases. However, much remains unknown about the structure of this important ion channel. Here, we have purified a heterologously expressed TRPM4-eGFP fusion protein and investigated the oligomeric state of TRPM4-eGFP in detergent micelles using crosslinking, native gel electrophoresis, multi-angle laser light scattering and electron microscopy. Our data indicate that TRPM4 is tetrameric, like other TRP channels studied to date. Furthermore, the functionality of liposome reconstituted TRPM4-eGFP was examined using electrophysiology. Single-channel recordings from TRPM4-eGFP proteoliposomes showed inhibition of the channel using Flufenamic acid, a well-established inhibitor of TRPM4, suggesting that the channels are functional upon reconstitution. Our characterisation of the oligomeric structure of TRPM4 and the ability to reconstitute functional channels in liposomes should facilitate future studies into the structure, function and pharmacology of this therapeutically relevant channel.
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Affiliation(s)
- Maryrose Constantine
- Victor Chang Cardiac Research Institute, Lowy Packer Building, NSW 2010
- St Vincent’s Clinical School, University of New South Wales, Sydney, NSW 2010, Australia
| | - Chu Kong Liew
- Victor Chang Cardiac Research Institute, Lowy Packer Building, NSW 2010
| | - Victor Lo
- School of Medical Sciences, The Bosch Institute, The University of Sydney, NSW 2006
| | - Alex Macmillan
- Biomedical Imaging Facility, Lowy Cancer Research Centre, The University of New South Wales, Kensington, NSW 2052, Australia
| | | | - Margaret Sunde
- School of Medical Sciences, The Bosch Institute, The University of Sydney, NSW 2006
| | - Renee Whan
- Biomedical Imaging Facility, Lowy Cancer Research Centre, The University of New South Wales, Kensington, NSW 2052, Australia
| | - Robert M. Graham
- Victor Chang Cardiac Research Institute, Lowy Packer Building, NSW 2010
- St Vincent’s Clinical School, University of New South Wales, Sydney, NSW 2010, Australia
| | - Boris Martinac
- Victor Chang Cardiac Research Institute, Lowy Packer Building, NSW 2010
- St Vincent’s Clinical School, University of New South Wales, Sydney, NSW 2010, Australia
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Praetorius HA. Being dedicated. Am J Physiol Renal Physiol 2015; 309:F835. [DOI: 10.1152/ajprenal.00398.2015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Flannery RJ, Kleene NK, Kleene SJ. A TRPM4-dependent current in murine renal primary cilia. Am J Physiol Renal Physiol 2015; 309:F697-707. [PMID: 26290373 PMCID: PMC4609916 DOI: 10.1152/ajprenal.00294.2015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 08/13/2015] [Indexed: 12/13/2022] Open
Abstract
Defects in primary cilia lead to a variety of human diseases. One of these, polycystic kidney disease, can be caused by defects in a Ca²⁺-gated ion channel (TRPP2) found on the cilium. Other ciliary functions also contribute to cystogenesis, and defects in apical Ca²⁺ homeostasis have been implicated. By recording directly from the native cilia of mIMCD-3 cells, a murine cell line of renal epithelial origin, we have identified a second Ca²⁺-gated channel in the ciliary membrane: the transient receptor potential cation channel, subfamily M, member 4 (TRPM4). In excised primary cilia, TRPM4 was found to have a low sensitivity to Ca²⁺, with an EC₅₀ of 646 μM at +100 mV. It was inhibited by MgATP and by 9-phenanthrol. The channel was not permeable to Ca²⁺ or Cl⁻ and had a permeability ratio PK/PNa of 1.42. Reducing the expression of Trpm4 mRNA with short hairpin (sh) RNA reduced the TRPM4 current by 87% and shortened primary cilia by 43%. When phospholipase C was inhibited, the sensitivity to cytoplasmic Ca²⁺ greatly increased (EC₅₀ = 26 μM at +100 mV), which is consistent with previous reports that phosphatidylinositol 4,5-bisphosphate (PIP2) modulates the channel. MgATP did not restore the channel to a preinactivation state, suggesting that the enzyme or substrate necessary for making PIP2 is not abundant in primary cilia of mIMCD-3 cells. The function of TRPM4 in renal primary cilia is not yet known, but it is likely to influence the apical Ca²⁺ dynamics of the cell, perhaps in tandem with TRPP2.
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Affiliation(s)
- Richard J Flannery
- Department of Molecular and Cellular Physiology, University of Cincinnati, Cincinnati, Ohio
| | - Nancy K Kleene
- Department of Molecular and Cellular Physiology, University of Cincinnati, Cincinnati, Ohio
| | - Steven J Kleene
- Department of Molecular and Cellular Physiology, University of Cincinnati, Cincinnati, Ohio
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Burris SK, Wang Q, Bulley S, Neeb ZP, Jaggar JH. 9-Phenanthrol inhibits recombinant and arterial myocyte TMEM16A channels. Br J Pharmacol 2015; 172:2459-68. [PMID: 25573456 DOI: 10.1111/bph.13077] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2013] [Revised: 12/19/2014] [Accepted: 12/23/2014] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND AND PURPOSE In arterial smooth muscle cells (myocytes), intravascular pressure stimulates membrane depolarization and vasoconstriction (the myogenic response). Ion channels proposed to mediate pressure-induced depolarization include several transient receptor potential (TRP) channels, including TRPM4, and transmembrane protein 16A (TMEM16A), a Ca(2+) -activated Cl(-) channel (CaCC). 9-Phenanthrol, a putative selective TRPM4 channel inhibitor, abolishes myogenic tone in cerebral arteries, suggesting that either TRPM4 is essential for pressure-induced depolarization, upstream of activation of other ion channels or that 9-phenanthrol is non-selective. Here, we tested the hypothesis that 9-phenanthrol is also a TMEM16A channel blocker, an ion channel for which few inhibitors have been identified. EXPERIMENTAL APPROACH Patch clamp electrophysiology was used to measure rat cerebral artery myocyte and human recombinant TMEM16A (rTMEM16A) currents or currents generated by recombinant bestrophin-1, another Ca(2+) -activated Cl(-) channel, expressed in HEK293 cells. KEY RESULTS 9-Phenanthrol blocked myocyte TMEM16A currents activated by either intracellular Ca(2+) or Eact , a TMEM16A channel activator. In contrast, 9-phenanthrol did not alter recombinant bestrophin-1 currents. 9-Phenanthrol reduced arterial myocyte TMEM16A currents with an IC50 of ∼12 μM. Cell-attached patch recordings indicated that 9-phenanthrol reduced single rTMEM16A channel open probability and mean open time, and increased mean closed time without affecting the amplitude. CONCLUSIONS AND IMPLICATIONS These data identify 9-phenanthrol as a novel TMEM16A channel blocker and provide an explanation for the previous observation that 9-phenanthrol abolishes myogenic tone when both TRPM4 and TMEM16A channels contribute to this response. 9-Phenanthrol may be a promising candidate from which to develop TMEM16A channel-specific inhibitors.
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Affiliation(s)
- Sarah K Burris
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN, USA
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Sakuraba M, Murata J, Teruyama R, Kamiya K, Yamaguchi J, Okano H, Uchiyama Y, Ikeda K. Spatiotemporal expression of TRPM4 in the mouse cochlea. J Neurosci Res 2014; 92:1409-18. [PMID: 24840118 DOI: 10.1002/jnr.23410] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Revised: 02/26/2014] [Accepted: 04/14/2014] [Indexed: 11/11/2022]
Abstract
The present study was conducted to elucidate the presence of the transient receptor potential cation channel subfamily M member 4, TRPM4, in the mouse inner ear. TRPM4 immunoreactivity (IR) was found in the cell body of inner hair cells (IHCs) in the organ of Corti in the apical side of marginal cells of the stria vascularis, in the apical portion of the dark cells of the vestibule, and in a subset of the type II neurons in the spiral ganglion. Subsequently, changes in the distribution and expression of TRPM4 in the inner ear during embryonic and postnatal developments were also evaluated. Immunohistochemical localization demonstrated that the emergence of the TRPM4-IR in IHCs occurs shortly before the onset of hearing, whereas that in the marginal cells happens earlier, at the time of birth, coinciding with the onset of endolymph formation. Furthermore, semiquantitative real-time PCR assay showed that expressions of TRPM4 in the organ of Corti and in the stria vascularis increased dramatically at the onset of hearing. Because TRPM4 is a Ca(2+) -activated monovalent-selective cation channel, these findings imply that TRPM4 contributes to potassium ion transport, essential for the signal transduction in IHCs and the formation of endolymph by marginal cells.
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Affiliation(s)
- Mayumi Sakuraba
- Department of Otorhinolaryngology, Juntendo University Graduate School of Medicine, Tokyo, Japan
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Abstract
TRPM5 is a Ca(2+)-activated cation channel that mediates signaling in taste and other chemosensory cells. Within taste cells, TRPM5 is the final element in a signaling cascade that starts with the activation of G protein-coupled receptors by bitter, sweet, or umami taste molecules and that requires the enzyme PLCβ2. PLCβ2 breaks down PIP2 into DAG and IP3, and the ensuing release of Ca(2+) from intracellular stores activates TRPM5. Since its initial discovery in the taste system, TRPM5 has been found to be distributed in sparse chemosensory cells located throughout the digestive track, in the respiratory system, and in the olfactory system. It is also found in pancreatic islets, where it contributes to insulin secretion. This review highlights recent work on the mechanisms of the activation of the TRPM5 channel and its regulation by voltage, phosphoinositides, temperature, and pH. The distribution of the channel in the body and its functional contribution to various sensory and nonsensory processes are discussed.
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Affiliation(s)
- Emily R Liman
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, 3641 Watt Way, Los Angeles, CA, 90089, USA,
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Abstract
TRPM4 is a Ca(2+)-activated nonselective cation channel. The channel is activated by an increase of intracellular Ca(2+) and is regulated by several factors including temperature and Pi(4,5)P2. TRPM4 allows Na(+) entry into the cell upon activation, but is completely impermeable to Ca(2+). Unlike TRPM5, its closest relative in the transient receptor potential family, TRPM4 proteins are widely expressed in the body. Currents with properties that are reminiscent of TRPM4 have been described in a variety of tissues since the advent of the patch clamp technology, but their physiological role is only beginning to be clarified with the increasing characterization of knockout mouse models for TRPM4. Furthermore, mutations in the TRPM4 gene have been associated with cardiac conduction disorders in human patients. This review aims to overview the currently available data on the functional properties of TRPM4 and the current understanding of its physiological role in healthy and diseased tissue.
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Affiliation(s)
- Ilka Mathar
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, Katholieke Universiteit Leuven, Herestraat 49, bus 802, 3000, Leuven, Belgium
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Kruse M, Pongs O. TRPM4 channels in the cardiovascular system. Curr Opin Pharmacol 2013; 15:68-73. [PMID: 24721656 DOI: 10.1016/j.coph.2013.12.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Revised: 12/03/2013] [Accepted: 12/05/2013] [Indexed: 02/08/2023]
Abstract
The non-selective Transient Receptor Potential Melastatin 4 (TRPM4) cation channel is abundantly expressed in cardiac cells, being involved in several aspects of cardiac rhythmicity, including cardiac conduction, pace making and action-potential repolarization. Dominantly inherited mutations in the TRPM4 gene are associated with the cardiac bundle-branch disorder progressive familial heart block type I (PFHBI) and isolated cardiac conduction disease (ICCD) giving rise to atrio-ventricular conduction block (AVB), right bundle branch block, bradycardia, and the Brugada syndrome. The mutant phenotypes closely resemble those associated with mutations in the SCN5A gene, encoding the voltage-gated Na(+) channel NaV1.5. These observations and the unexpected partnership with sulfonylurea-receptors (SURs) makes the TRPM4 channel a promising novel target for treatment of cardiac disorders.
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Affiliation(s)
- Martin Kruse
- Department of Physiology and Biophysics, University of Washington, Seattle, WA, USA
| | - Olaf Pongs
- Institute of Physiology, Universitätsklinikum des Saarlandes, Homburg, Germany.
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34
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Gonzales AL, Earley S. Regulation of cerebral artery smooth muscle membrane potential by Ca²⁺-activated cation channels. Microcirculation 2013; 20:337-47. [PMID: 23116477 DOI: 10.1111/micc.12023] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2012] [Accepted: 10/26/2012] [Indexed: 12/24/2022]
Abstract
Arterial tone is dependent on the depolarizing and hyperpolarizing currents regulating membrane potential and governing the influx of Ca²⁺ needed for smooth muscle contraction. Several ion channels have been proposed to contribute to membrane depolarization, but the underlying molecular mechanisms are not fully understood. In this review, we will discuss the historical and physiological significance of the Ca²⁺-activated cation channel, TRPM4, in regulating membrane potential of cerebral artery smooth muscle cells. As a member of the recently described transient receptor potential super family of ion channels, TRPM4 possesses the biophysical properties and upstream cellular signaling and regulatory pathways that establish it as a major physiological player in smooth muscle membrane depolarization.
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Affiliation(s)
- Albert L Gonzales
- Vascular Physiology Research Group, Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA
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Abstract
TRP channels constitute a large superfamily of cation channel forming proteins, all related to the gene product of the transient receptor potential (trp) locus in Drosophila. In mammals, 28 different TRP channel genes have been identified, which exhibit a large variety of functional properties and play diverse cellular and physiological roles. In this article, we provide a brief and systematic summary of expression, function, and (patho)physiological role of the mammalian TRP channels.
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Affiliation(s)
- Maarten Gees
- Laboratory Ion Channel Research and TRP Research Platform Leuven (TRPLe), KU Leuven, Campus Gasthuisberg, Leuven, Belgium
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Simon F, Varela D, Cabello-Verrugio C. Oxidative stress-modulated TRPM ion channels in cell dysfunction and pathological conditions in humans. Cell Signal 2013; 25:1614-24. [PMID: 23602937 DOI: 10.1016/j.cellsig.2013.03.023] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Revised: 03/25/2013] [Accepted: 03/28/2013] [Indexed: 10/27/2022]
Abstract
The transient receptor potential melastatin (TRPM) protein family is an extensive group of ion channels expressed in several types of mammalian cells. Many studies have shown that these channels are crucial for performing several physiological functions. Additionally, a large body of evidence indicates that these channels are also involved in numerous human diseases, known as channelopathies. A characteristic event frequently observed during pathological states is the raising in intracellular oxidative agents over reducing molecules, shifting the redox balance and inducing oxidative stress. In particular, three members of the TRPM subfamily, TRPM2, TRPM4 and TRPM7, share the remarkable feature that their activities are modulated by oxidative stress. Because of the increase in oxidative stress, these TRPM channels function aberrantly, promoting the onset and development of diseases. Increases, absences, or modifications in the function of these redox-modulated TRPM channels are associated with cell dysfunction and human pathologies. Therefore, the effect of oxidative stress on ion channels becomes an essential part of the pathogenic mechanism. Thus, oxidative stress-modulated ion channels are more susceptible to generating pathological states than oxidant-independent channels. This review examines the most relevant findings regarding the participation of the oxidative stress-modulated TRPM ion channels, TRPM2, TRPM4, and TRPM7, in human diseases. In addition, the potential roles of these channels as therapeutic tools and targets for drug design are discussed.
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Affiliation(s)
- Felipe Simon
- Departamento de Ciencias Biológicas, Facultad de Ciencias Biológicas and Facultad de Medicina, Universidad Andres Bello, Avenida Republica 239, 8370146, Santiago, Chile.
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TRPM4 channels in smooth muscle function. Pflugers Arch 2013; 465:1223-31. [PMID: 23443854 DOI: 10.1007/s00424-013-1250-z] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 02/08/2013] [Accepted: 02/09/2013] [Indexed: 01/03/2023]
Abstract
The melastatin (M) transient receptor potential (TRP) channel TRPM4 is selective for monovalent cations and is activated by high levels of intracellular Ca(2+). TRPM4 is broadly distributed and may be involved in numerous functions, including electrical conduction in the heart, respiratory rhythm, immune response, and secretion of insulin by pancreatic β-cells. The significance of TRPM4 in smooth muscle cell function is reviewed here. Several studies indicate that TRPM4 channels are critically important for pressure-induced cerebral arterial myocyte depolarization and myogenic vasoconstriction as well as autoregulation of cerebral blood flow. Regulation of TRPM4 activity in arterial smooth muscle cells is complex and involves release of Ca(2+) from the sarcoplasmic reticulum through inositol 1,4,5-trisphosphate receptors and translocation of TRPM4 channels to the plasma membrane in response to protein kinase Cδ. TRPM4 is also present in colonic, urinary bladder, aortic, interlobar pulmonary and renal artery, airway, and corpus cavernosum smooth muscle cells, but its significance and regulation in these tissues is less well characterized.
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Abriel H, Syam N, Sottas V, Amarouch MY, Rougier JS. TRPM4 channels in the cardiovascular system: Physiology, pathophysiology, and pharmacology. Biochem Pharmacol 2012; 84:873-81. [DOI: 10.1016/j.bcp.2012.06.021] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Revised: 06/15/2012] [Accepted: 06/19/2012] [Indexed: 12/11/2022]
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Simard JM, Woo SK, Schwartzbauer GT, Gerzanich V. Sulfonylurea receptor 1 in central nervous system injury: a focused review. J Cereb Blood Flow Metab 2012; 32:1699-717. [PMID: 22714048 PMCID: PMC3434627 DOI: 10.1038/jcbfm.2012.91] [Citation(s) in RCA: 147] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Revised: 05/03/2012] [Accepted: 05/09/2012] [Indexed: 01/13/2023]
Abstract
The sulfonylurea receptor 1 (Sur1)-regulated NC(Ca-ATP) channel is a nonselective cation channel that is regulated by intracellular calcium and adenosine triphosphate. The channel is not constitutively expressed, but is transcriptionally upregulated de novo in all cells of the neurovascular unit, in many forms of central nervous system (CNS) injury, including cerebral ischemia, traumatic brain injury (TBI), spinal cord injury (SCI), and subarachnoid hemorrhage (SAH). The channel is linked to microvascular dysfunction that manifests as edema formation and delayed secondary hemorrhage. Also implicated in oncotic cell swelling and oncotic (necrotic) cell death, the channel is a major molecular mechanism of 'accidental necrotic cell death' in the CNS. In animal models of SCI, pharmacological inhibition of Sur1 by glibenclamide, as well as gene suppression of Abcc8, prevents delayed capillary fragmentation and tissue necrosis. In models of stroke and TBI, glibenclamide ameliorates edema, secondary hemorrhage, and tissue damage. In a model of SAH, glibenclamide attenuates the inflammatory response due to extravasated blood. Clinical trials of an intravenous formulation of glibenclamide in TBI and stroke underscore the importance of recent advances in understanding the role of the Sur1-regulated NC(Ca-ATP) channel in acute ischemic, traumatic, and inflammatory injury to the CNS.
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Affiliation(s)
- J Marc Simard
- Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, Maryland 21201-1595, USA.
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The Ca2+-Activated Monovalent Cation-Selective Channels TRPM4 and TRPM5. METHODS IN PHARMACOLOGY AND TOXICOLOGY 2012. [DOI: 10.1007/978-1-62703-077-9_6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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Aureliano M. Recent perspectives into biochemistry of decavanadate. World J Biol Chem 2011; 2:215-25. [PMID: 22031844 PMCID: PMC3202125 DOI: 10.4331/wjbc.v2.i10.215] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Revised: 09/07/2011] [Accepted: 09/14/2011] [Indexed: 02/05/2023] Open
Abstract
The number of papers about decavanadate has doubled in the past decade. In the present review, new insights into decavanadate biochemistry, cell biology, and antidiabetic and antitumor activities are described. Decameric vanadate species (V10) clearly differs from monomeric vanadate (V1), and affects differently calcium pumps, and structure and function of myosin and actin. Only decavanadate inhibits calcium accumulation by calcium pump ATPase, and strongly inhibits actomyosin ATPase activity (IC50 = 1.4 μmol/L, V10), whereas no such effects are detected with V1 up to 150 μmol/L; prevents actin polymerization (IC50 of 68 μmol/L, whereas no effects detected with up to 2 mmol/L V1); and interacts with actin in a way that induces cysteine oxidation and vanadate reduction to vanadyl. Moreover, in vivo decavanadate toxicity studies have revealed that acute exposure to polyoxovanadate induces different changes in antioxidant enzymes and oxidative stress parameters, in comparison with vanadate. In vitro studies have clearly demonstrated that mitochondrial oxygen consumption is strongly affected by decavanadate (IC50, 0.1 μmol/L); perhaps the most relevant biological effect. Finally, decavanadate (100 μmol/L) increases rat adipocyte glucose accumulation more potently than several vanadium complexes. Preliminary studies suggest that decavanadate does not have similar effects in human adipocytes. Although decavanadate can be a useful biochemical tool, further studies must be carried out before it can be confirmed that decavanadate and its complexes can be used as anticancer or antidiabetic agents.
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Guinamard R, Sallé L, Simard C. The non-selective monovalent cationic channels TRPM4 and TRPM5. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 704:147-71. [PMID: 21290294 DOI: 10.1007/978-94-007-0265-3_8] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Transient Receptor Potential (TRP) proteins are non-selective cationic channels with a consistent Ca(2+)-permeability, except for TRPM4 and TRPM5 that are not permeable to this ion. However, Ca(2+) is a major regulator of their activity since both channels are activated by a rise in internal Ca(2+). Thus TRPM4 and TRPM5 are responsible for most of the Ca(2+)-activated non-selective cationic currents (NSC(Ca)) recorded in a large variety of tissues. Their activation induces cell-membrane depolarization that modifies the driving force for ions as well as activity of voltage gated channels and thereby strongly impacts cell physiology. In the last few years, the ubiquitously expressed TRPM4 channel has been implicated in insulin secretion, the immune response, constriction of cerebral arteries, the activity of inspiratory neurons and cardiac dysfunction. Conversely, TRPM5 whose expression is more restricted, has until now been mainly implicated in taste transduction.
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Affiliation(s)
- Romain Guinamard
- Groupe Cœur et Ischémie, EA 3212, Université de Caen, Sciences D, F-14032, Caen Cedex, France,
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Abstract
Natural product ligands have contributed significantly to the deorphanisation of TRP ion channels. Furthermore, natural product ligands continue to provide valuable leads for the identification of ligands acting at "orphan" TRP channels. Additional naturally occurring modulators at TRP channels can be expected to be discovered in future, aiding in our understanding of not only their pharmacology and physiology, but also the therapeutic potential of this fascinating family of ion channels.
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Zholos A, Johnson C, Burdyga T, Melanaphy D. TRPM channels in the vasculature. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 704:707-29. [PMID: 21290323 DOI: 10.1007/978-94-007-0265-3_37] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Recent studies show that mammalian melastatin TRPM nonselective cation channels (TRPM1-8), members of the largest and most diverse TRP subfamily, are widely expressed in the endothelium and vascular smooth muscles. When activated, these channels similarly to other TRPs permit the entry of sodium, calcium and magnesium, thus causing membrane depolarisation. Although membrane depolarisation reduces the driving force for calcium entry via TRPMs as well as other pathways for calcium entry, in smooth muscle myocytes expressing voltage-gated Ca(2+) channels the predominant functional effect is an increase in intracellular Ca(2+) concentration and myocyte contraction. This review focuses on several best documented aspects of vascular functions of TRPMs, including the role of TRPM2 in oxidant stress, regulation of endothelial permeability and cell death, the connection between TRPM4 and myogenic response, significance of TRPM7 for magnesium homeostasis, vessel injury and hypertension, and emerging evidence that the cold and menthol receptor TRPM8 is involved in the regulation of vascular tone.
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Affiliation(s)
- Alexander Zholos
- Centre for Vision and Vascular Science, School of Medicine, Dentistry and Biomedical Sciences, Royal Victoria Hospital, Queen's University of Belfast, Belfast BT12 6BA, UK.
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Guinamard R, Demion M, Launay P. Physiological roles of the TRPM4 channel extracted from background currents. Physiology (Bethesda) 2010; 25:155-64. [PMID: 20551229 DOI: 10.1152/physiol.00004.2010] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Calcium-activated nonselective cationic currents have been known for 30 years, but their physiological implications have remained unresolved until the recent cloning of the TRPM4 ion channel. Since then, TRPM4 has been identified as a key modulator of numerous calcium-dependent mechanisms such as the immune response, insulin secretion, cerebral artery constriction, respiratory rhythm, and cardiac conduction.
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Earley S. Vanilloid and melastatin transient receptor potential channels in vascular smooth muscle. Microcirculation 2010; 17:237-49. [PMID: 20536737 DOI: 10.1111/j.1549-8719.2010.00026.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The mammalian transient receptor potential (TRP) superfamily consists of six subfamilies that are defined by structural homology: TRPC (conventional or canonical), TRPV (vanilloid), TRPM (melastatin), TRPA (ankyrin), TRPP (polycystin), and TRPML (mucoliptin). This review focuses on channels belonging to the vanilloid (V) and melastatin (M) TRP subfamilies. The TRPV subfamily consists of six members (TRPV1-6) and the TRPM subfamily has eight (TRPM1-8). The basic biophysical properties of these channels are briefly described. All of these channels except TRPV5, TRPV6, and TRPM1 are reportedly present in arterial smooth muscle from various segments of the vasculature. Studies demonstrating involvement of TRPV1, TRPV2, TRPV4, TRPM4, TRPM7, and TRPM8 in regulation of arterial smooth muscle function are reviewed. The functions of TRPV3, TRPM2, TRPM3, and TRPM6 channels in arterial myocytes have not been reported.
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Affiliation(s)
- Scott Earley
- Vascular Physiology Research Group, Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA.
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Zholos A. Pharmacology of transient receptor potential melastatin channels in the vasculature. Br J Pharmacol 2010; 159:1559-71. [PMID: 20233227 DOI: 10.1111/j.1476-5381.2010.00649.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Mammalian transient receptor potential melastatin (TRPM) non-selective cation channels, the largest TRP subfamily, are widely expressed in excitable and non-excitable cells where they perform diverse functions ranging from detection of cold, taste, osmolarity, redox state and pH to control of Mg(2+) homeostasis and cell proliferation or death. Recently, TRPM gene expression has been identified in vascular smooth muscles with dominance of the TRPM8 channel. There has been in parallel considerable progress in decoding the functional roles of several TRPMs in the vasculature. This research on native cells is aided by the knowledge of the activation mechanisms and pharmacological properties of heterologously expressed TRPM subtypes. This paper summarizes the present state of knowledge of vascular TRPM channels and outlines several anticipated directions of future research in this area.
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Affiliation(s)
- Alexander Zholos
- Centre for Vision and Vascular Science, Queen's University of Belfast, UK.
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Cloning and characterization of rat transient receptor potential-melastatin 4 (TRPM4). Biochem Biophys Res Commun 2009; 391:806-11. [PMID: 19945433 DOI: 10.1016/j.bbrc.2009.11.142] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2009] [Accepted: 11/24/2009] [Indexed: 11/21/2022]
Abstract
Transient receptor potential-melastatin 4 (TRPM4) is a Ca(2+)-activated, but Ca(2+)-impermeable, cation channel. Increasing [Ca(2+)](i) induce current activation and reduction through TRPM4 channels. Several TRPM4 isoforms are expressed in mice and humans, but rat TRPM4 (rTRPM4) has not been previously identified. Here, we identified, cloned, and characterized two rTRPM4 isoforms, rTRPM4a and rTRPM4b, using 5'-RACE-PCR. rTRPM4b channel activity increased with [Ca(2+)](i) in a dose-dependent manner. However, the rTRPM4b Ca(2+)-dependent activity at negative potentials differed from that of human TRPM4b (hTRPM4b), even though both represent full-length proteins. Additionally, rTRPM4b showed a slightly different single-channel current amplitude and open time distribution than hTRPM4b. However, rTRPM4a, which lacks the N-terminal region of rTRPM4b, and hTRPM4a had no similar functional channel activities. Furthermore, we characterized splicing regions, tissue distribution, and cellular localization of these isoforms. Unlike rTRPM4a, rTRPM4b was localized to the membrane at high levels, suggesting that rTRPM4b is the functionally active channel.
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Abstract
Currently, efforts have been directed towards using decavanadate as a tool for the understanding of several biochemical processes such as muscle contraction, calcium homeostasis, in vivo changes of oxidative stress markers, mitochondrial oxygen consumption, mitochondrial membrane depolarization, actin polymerization and glucose uptake, among others. In addition, studies have been conducted in order to make vanadium available and safe for clinical use, for instance with decavanadate compounds that present interesting pharmacological properties, eventually useful for the treatment of diabetes. Here, recent contributions of decavanadate to the effects of vanadium in biological systems, not only in vitro, but also in vivo, are analysed.
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Affiliation(s)
- Manuel Aureliano
- Faculty of Sciences and Technology, University of Algarve, Portugal.
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Ramos S, Duarte RO, Moura JJG, Aureliano M. Decavanadate interactions with actin: cysteine oxidation and vanadyl formation. Dalton Trans 2009:7985-94. [PMID: 19771361 DOI: 10.1039/b906255f] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Incubation of actin with decavanadate induces cysteine oxidation and oxidovanadium(IV) formation. The studies were performed combining kinetic with spectroscopic (NMR and EPR) methodologies. Although decavanadate is converted to labile oxovanadates, the rate of deoligomerization can be very slow (half-life time of 5.4 h, at 25 degrees C, with a first order kinetics), which effectively allows decavanadate to exist for some time under experimental conditions. It was observed that decavanadate inhibits F-actin-stimulated myosin ATPase activity with an IC(50) of 0.8 microM V(10) species, whereas 50 microM of vanadate or oxidovanadium(IV) only inhibits enzyme activity up to 25%. Moreover, from these three vanadium forms, only decavanadate induces the oxidation of the so called "fast" cysteines (or exposed cysteine, Cys-374) when the enzyme is in the polymerized and active form, F-actin, with an IC(50) of 1 microM V(10) species. Decavanadate exposition to F- and G-actin (monomeric form) promotes vanadate reduction since a typical EPR oxidovanadium(IV) spectrum was observed. Upon observation that V(10) reduces to oxidovanadium(IV), it is proposed that this cation interacts with G-actin (K(d) of 7.48 +/- 1.11 microM), and with F-actin (K(d) = 43.05 +/- 5.34 microM) with 1:1 and 4:1 stoichiometries, respectively, as observed by EPR upon protein titration with oxidovanadium(IV). The interaction of oxidovanadium(IV) with the protein may occur close to the ATP binding site of actin, eventually with lysine-336 and 3 water molecules.
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