1
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García-Morales A, Balleza D. Non-canonical helical transitions and conformational switching are associated with characteristic flexibility and disorder indices in TRP and Kv channels. Channels (Austin) 2023; 17:2212349. [PMID: 37196183 DOI: 10.1080/19336950.2023.2212349] [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: 11/07/2022] [Revised: 04/21/2023] [Accepted: 05/02/2023] [Indexed: 05/19/2023] Open
Abstract
Structural evidence and much experimental data have demonstrated the presence of non-canonical helical substructures (π and 310) in regions of great functional relevance both in TRP as in Kv channels. Through an exhaustive compositional analysis of the sequences underlying these substructures, we find that each of them is associated with characteristic local flexibility profiles, which in turn are implicated in significant conformational rearrangements and interactions with specific ligands. We found that α-to-π helical transitions are associated with patterns of local rigidity whereas α-to-310 transitions are mainly leagued with high local flexibility profiles. We also study the relationship between flexibility and protein disorder in the transmembrane domain of these proteins. By contrasting these two parameters, we located regions showing a sort of structural discrepancy between these similar but not identical protein attributes. Notably, these regions are presumably implicated in important conformational rearrangements during the gating in those channels. In that sense, finding these regions where flexibility and disorder are not proportional allows us to detect regions with potential functional dynamism. From this point of view, we highlighted some conformational rearrangements that occur during ligand binding events, the compaction, and refolding of the outer pore loops in several TRP channels, as well as the well-known S4 motion in Kv channels.
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Affiliation(s)
| | - Daniel Balleza
- Unidad de Investigación y desarrollo en Alimentos, Instituto Tecnológico de Veracruz. Tecnológico Nacional de México, Veracruz, MEXICO
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2
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Borgström A, Peinelt C, Stokłosa P. TRPM4 in Cancer-A New Potential Drug Target. Biomolecules 2021; 11:biom11020229. [PMID: 33562811 PMCID: PMC7914809 DOI: 10.3390/biom11020229] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 01/22/2021] [Accepted: 01/28/2021] [Indexed: 12/11/2022] Open
Abstract
Transient receptor potential melastatin 4 (TRPM4) is widely expressed in various organs and associated with cardiovascular and immune diseases. Lately, the interest in studies on TRPM4 in cancer has increased. Thus far, TRPM4 has been investigated in diffuse large B-cell lymphoma, prostate, colorectal, liver, breast, urinary bladder, cervical, and endometrial cancer. In several types of cancer TRPM4 is overexpressed and contributes to cancer hallmark functions such as increased proliferation and migration and cell cycle shift. Hence, TRPM4 is a potential prognostic cancer marker and a promising anticancer drug target candidate. Currently, the underlying mechanism by which TRPM4 contributes to cancer hallmark functions is under investigation. TRPM4 is a Ca2+-activated monovalent cation channel, and its ion conductivity can decrease intracellular Ca2+ signaling. Furthermore, TRPM4 can interact with different partner proteins. However, the lack of potent and specific TRPM4 inhibitors has delayed the investigations of TRPM4. In this review, we summarize the potential mechanisms of action and discuss new small molecule TRPM4 inhibitors, as well as the TRPM4 antibody, M4P. Additionally, we provide an overview of TRPM4 in human cancer and discuss TRPM4 as a diagnostic marker and anticancer drug target.
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3
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Rivas J, Díaz N, Silva I, Morales D, Lavanderos B, Álvarez A, Saldías MP, Pulgar E, Cruz P, Maureira D, Flores G, Colombo A, Blanco C, Contreras HR, Jaña F, Gallegos I, Concha ML, Vergara-Jaque A, Poblete H, González W, Varela D, Trimmer JS, Cáceres M, Cerda O. KCTD5, a novel TRPM4-regulatory protein required for cell migration as a new predictor for breast cancer prognosis. FASEB J 2020; 34:7847-7865. [PMID: 32301552 DOI: 10.1096/fj.201901195rrr] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 03/03/2020] [Accepted: 03/26/2020] [Indexed: 12/23/2022]
Abstract
Transient receptor potential melastatin 4 (TRPM4) is a Ca2+ -activated nonselective cationic channel that regulates cell migration and contractility. Increased TRPM4 expression has been related to pathologies, in which cytoskeletal rearrangement and cell migration are altered, such as metastatic cancer. Here, we identify the K+ channel tetramerization domain 5 (KCTD5) protein, a putative adaptor of cullin3 E3 ubiquitin ligase, as a novel TRPM4-interacting protein. We demonstrate that KCTD5 is a positive regulator of TRPM4 activity by enhancing its Ca2+ sensitivity. We show that through its effects on TRPM4 that KCTD5 promotes cell migration and contractility. Finally, we observed that both TRPM4 and KCTD5 expression are increased in distinct patterns in different classes of breast cancer tumor samples. Together, these data support that TRPM4 activity can be regulated through expression levels of either TRPM4 or KCTD5, not only contributing to increased understanding of the molecular mechanisms involved on the regulation of these important ion channels, but also providing information that could inform treatments based on targeting these distinct molecules that define TRPM4 activity.
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Affiliation(s)
- José Rivas
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Santiago, Chile.,Departamento de Ciencias de la Salud, Universidad de Aysén, Coyhaique, Chile
| | - Nicolás Díaz
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Santiago, Chile
| | - Ian Silva
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Santiago, Chile
| | - Danna Morales
- Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Santiago, Chile.,Program of Physiology and Biophysics, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Boris Lavanderos
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Santiago, Chile
| | - Alhejandra Álvarez
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Santiago, Chile
| | - María Paz Saldías
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Santiago, Chile
| | - Eduardo Pulgar
- Program of Anatomy and Developmental Biology, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Pablo Cruz
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Santiago, Chile
| | - Diego Maureira
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Santiago, Chile
| | - Guillermo Flores
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Alicia Colombo
- Departamento de Oncología Básico Clínica, Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Departamento de Anatomía Patológica, Hospital Clínico Universidad de Chile, Universidad de Chile, Santiago, Chile
| | - Constanza Blanco
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Santiago, Chile
| | - Héctor R Contreras
- Departamento de Oncología Básico Clínica, Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - Fabián Jaña
- Departamento de Ciencias de la Salud, Universidad de Aysén, Coyhaique, Chile.,The Wound Repair, Treatment and Health (WoRTH) Initiative, Santiago, Chile
| | - Ivan Gallegos
- Departamento de Oncología Básico Clínica, Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Departamento de Anatomía Patológica, Hospital Clínico Universidad de Chile, Universidad de Chile, Santiago, Chile
| | - Miguel L Concha
- Program of Anatomy and Developmental Biology, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Biomedical Neuroscience Institute, Santiago, Chile.,Center for Geroscience, Brain Health and Metabolism, Santiago, Chile.,Millennium Nucleus on Physics of Active Matter, Santiago, Chile
| | - Ariela Vergara-Jaque
- Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Santiago, Chile.,Multidisciplinary Scientific Nucleus, Universidad de Talca, Talca, Chile.,Center for Bioinformatics and Molecular Simulations (CBSM), Faculty of Engineering, Universidad de Talca, Talca, Chile
| | - Horacio Poblete
- Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Santiago, Chile.,Multidisciplinary Scientific Nucleus, Universidad de Talca, Talca, Chile.,Center for Bioinformatics and Molecular Simulations (CBSM), Faculty of Engineering, Universidad de Talca, Talca, Chile
| | - Wendy González
- Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Santiago, Chile.,Center for Bioinformatics and Molecular Simulations (CBSM), Faculty of Engineering, Universidad de Talca, Talca, Chile
| | - Diego Varela
- Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Santiago, Chile.,Program of Physiology and Biophysics, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile
| | - James S Trimmer
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA
| | - Mónica Cáceres
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Santiago, Chile.,The Wound Repair, Treatment and Health (WoRTH) Initiative, Santiago, Chile
| | - Oscar Cerda
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Santiago, Chile.,The Wound Repair, Treatment and Health (WoRTH) Initiative, Santiago, Chile
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4
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Pergakis M, Badjatia N, Chaturvedi S, Cronin CA, Kimberly WT, Sheth KN, Simard JM. BIIB093 (IV glibenclamide): an investigational compound for the prevention and treatment of severe cerebral edema. Expert Opin Investig Drugs 2019; 28:1031-1040. [PMID: 31623469 DOI: 10.1080/13543784.2019.1681967] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Introduction: Brain swelling due to edema formation is a major cause of neurological deterioration and death in patients with large hemispheric infarction (LHI) and severe traumatic brain injury (TBI), especially contusion-TBI. Preclinical studies have shown that SUR1-TRPM4 channels play a critical role in edema formation and brain swelling in LHI and TBI. Glibenclamide, a sulfonylurea drug and potent inhibitor of SUR1-TRPM4, was reformulated for intravenous injection, known as BIIB093.Areas covered: We discuss the findings from Phase 2 clinical trials of BIIB093 in patients with LHI (GAMES-Pilot and GAMES-RP) and from a small Phase 2 clinical trial in patients with TBI. For the GAMES trials, we review data on objective biological variables, adjudicated edema-related endpoints, functional outcomes, and mortality which, despite missing the primary endpoint, supported the initiation of a Phase 3 trial in LHI (CHARM). For the TBI trial, we review data on MRI measures of edema and the initiation of a Phase 2 trial in contusion-TBI (ASTRAL).Expert opinion: Emerging clinical data show that BIIB093 has the potential to transform our management of patients with LHI, contusion-TBI and other conditions in which swelling leads to neurological deterioration and death.
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Affiliation(s)
- Melissa Pergakis
- Department of Neurology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Neeraj Badjatia
- Department of Neurology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Seemant Chaturvedi
- Department of Neurology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Carolyn A Cronin
- Department of Neurology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - W Taylor Kimberly
- Division of Neurocritical Care and Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
| | - Kevin N Sheth
- Division of Neurocritical Care, Department of Neurology, Yale University School of Medicine, New Haven, CT, USA
| | - J Marc Simard
- Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, MD, USA
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5
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Blanco C, Morales D, Mogollones I, Vergara‐Jaque A, Vargas C, Álvarez A, Riquelme D, Leiva‐Salcedo E, González W, Morales D, Maureira D, Aldunate I, Cáceres M, Varela D, Cerda O. EB1‐ and EB2‐dependent anterograde trafficking of TRPM4 regulates focal adhesion turnover and cell invasion. FASEB J 2019; 33:9434-9452. [DOI: 10.1096/fj.201900136r] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Constanza Blanco
- Program of Cellular and Molecular Biology Universidad de Chile Santiago Chile
- Millennium Nucleus of Ion Channels‐Associated Diseases (MiNICAD) Santiago Chile
| | - Danna Morales
- Program of Physiology and Biophysics Institute of Biomedical Sciences Faculty of Medicine Universidad de Chile Santiago Chile
- Millennium Nucleus of Ion Channels‐Associated Diseases (MiNICAD) Santiago Chile
| | - Ignacio Mogollones
- Program of Cellular and Molecular Biology Universidad de Chile Santiago Chile
- Millennium Nucleus of Ion Channels‐Associated Diseases (MiNICAD) Santiago Chile
| | - Ariela Vergara‐Jaque
- Program of Physiology and Biophysics Institute of Biomedical Sciences Faculty of Medicine Universidad de Chile Santiago Chile
- Multidisciplinary Scientific Nucleus Universidad de Talca Talca Chile
- Center for Bioinformatics and Molecular Simulation Universidad de Talca Talca Chile
| | - Carla Vargas
- Program of Cellular and Molecular Biology Universidad de Chile Santiago Chile
- Millennium Nucleus of Ion Channels‐Associated Diseases (MiNICAD) Santiago Chile
| | - Alhejandra Álvarez
- Program of Cellular and Molecular Biology Universidad de Chile Santiago Chile
- Millennium Nucleus of Ion Channels‐Associated Diseases (MiNICAD) Santiago Chile
| | - Denise Riquelme
- Department of Biology Faculty of Chemistry and Biology Universidad de Santiago de Chile Santiago Chile
| | - Elías Leiva‐Salcedo
- Department of Biology Faculty of Chemistry and Biology Universidad de Santiago de Chile Santiago Chile
| | - Wendy González
- Millennium Nucleus of Ion Channels‐Associated Diseases (MiNICAD) Santiago Chile
- Center for Bioinformatics and Molecular Simulation Universidad de Talca Talca Chile
| | - Diego Morales
- Program of Cellular and Molecular Biology Universidad de Chile Santiago Chile
- Millennium Nucleus of Ion Channels‐Associated Diseases (MiNICAD) Santiago Chile
| | - Diego Maureira
- Program of Cellular and Molecular Biology Universidad de Chile Santiago Chile
- Millennium Nucleus of Ion Channels‐Associated Diseases (MiNICAD) Santiago Chile
| | - Ismael Aldunate
- Program of Cellular and Molecular Biology Universidad de Chile Santiago Chile
| | - Mónica Cáceres
- Program of Cellular and Molecular Biology Universidad de Chile Santiago Chile
- Millennium Nucleus of Ion Channels‐Associated Diseases (MiNICAD) Santiago Chile
- The Wound Repair Treatment, and Health (WoRTH) Initiative Santiago Chile
| | - Diego Varela
- Program of Physiology and Biophysics Institute of Biomedical Sciences Faculty of Medicine Universidad de Chile Santiago Chile
- Millennium Nucleus of Ion Channels‐Associated Diseases (MiNICAD) Santiago Chile
| | - Oscar Cerda
- Program of Cellular and Molecular Biology Universidad de Chile Santiago Chile
- Millennium Nucleus of Ion Channels‐Associated Diseases (MiNICAD) Santiago Chile
- The Wound Repair Treatment, and Health (WoRTH) Initiative Santiago Chile
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6
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Purification of Functional Human TRP Channels Recombinantly Produced in Yeast. Cells 2019; 8:cells8020148. [PMID: 30754715 PMCID: PMC6406451 DOI: 10.3390/cells8020148] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Revised: 01/27/2019] [Accepted: 02/03/2019] [Indexed: 01/16/2023] Open
Abstract
(1) Background: Human transient receptor potential (TRP) channels constitute a large family of ion-conducting membrane proteins that allow the sensation of environmental cues. As the dysfunction of TRP channels contributes to the pathogenesis of many widespread diseases, including cardiac disorders, these proteins also represent important pharmacological targets. TRP channels are typically produced using expensive and laborious mammalian or insect cell-based systems. (2) Methods: We demonstrate an alternative platform exploiting the yeast Saccharomyces cerevisiae capable of delivering high yields of functional human TRP channels. We produce 11 full-length human TRP members originating from four different subfamilies, purify a selected subset of these to a high homogeneity and confirm retained functionality using TRPM8 as a model target. (3) Results: Our findings demonstrate the potential of the described production system for future functional, structural and pharmacological studies of human TRP channels.
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7
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Kullmann FA, Beckel JM, McDonnell B, Gauthier C, Lynn AM, Wolf-Johnston A, Kanai A, Zabbarova IV, Ikeda Y, de Groat WC, Birder LA. Involvement of TRPM4 in detrusor overactivity following spinal cord transection in mice. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2018; 391:1191-1202. [PMID: 30054681 PMCID: PMC6186176 DOI: 10.1007/s00210-018-1542-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Accepted: 07/17/2018] [Indexed: 12/31/2022]
Abstract
Transient receptor potential cation channel subfamily M member 4 (TRPM4) has been shown to play a key role in detrusor contractility under physiological conditions. In this study, we investigated the potential role of TRPM4 in detrusor overactivity following spinal cord transection (SCT) in mice. TRPM4 expression and function were evaluated in bladder tissue with or without the mucosa from spinal intact (SI) and SCT female mice (T8-T9 vertebra; 1-28 days post SCT) using PCR, western blot, immunohistochemistry, and muscle strip contractility techniques. TRPM4 was expressed in the urothelium (UT) and detrusor smooth muscle (DSM) and was upregulated after SCT. Expression levels peaked 3-7 days post SCT in both the UT and DSM. Pharmacological block of TRPM4 with the antagonist, 9-Phenanthrol (30 μM) greatly reduced spontaneous phasic activity that developed after SCT, regardless of the presence or absence of the mucosa. Detrusor overactivity following spinal cord injury leads to incontinence and/or renal impairment and represents a major health problem for which current treatments are not satisfactory. Augmented TRPM4 expression in the bladder after chronic SCT supports the hypothesis that TRPM4 channels play a role in DSM overactivity following SCT. Inhibition of TRPM4 may be beneficial for improving detrusor overactivity in SCI.
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Affiliation(s)
- F Aura Kullmann
- Department of Medicine/Renal and Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA.
| | - Jonathan M Beckel
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
| | - Bronagh McDonnell
- Department of Medicine/Renal and Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
| | - Christian Gauthier
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, 15260, USA
| | - Andrew M Lynn
- Department of Medicine/Renal and Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
| | - Amanda Wolf-Johnston
- Department of Medicine/Renal and Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
| | - Anthony Kanai
- Department of Medicine/Renal and Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
| | - Irina V Zabbarova
- Department of Medicine/Renal and Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
| | - Youko Ikeda
- Department of Medicine/Renal and Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
| | - William C de Groat
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
| | - Lori A Birder
- Department of Medicine/Renal and Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
- Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
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8
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Bianchi B, Ozhathil LC, Medeiros-Domingo A, Gollob MH, Abriel H. Four TRPM4 Cation Channel Mutations Found in Cardiac Conduction Diseases Lead to Altered Protein Stability. Front Physiol 2018; 9:177. [PMID: 29568272 PMCID: PMC5852105 DOI: 10.3389/fphys.2018.00177] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 02/20/2018] [Indexed: 12/20/2022] Open
Abstract
Transient receptor potential melastatin member 4 (TRPM4), a non-selective cation channel, mediates cell membrane depolarization in immune response, insulin secretion, neurological disorders, and cancer. Pathological variants in TRPM4 gene have been linked to several cardiac phenotypes such as complete heart block (CHB), ventricular tachycardia, and Brugada syndrome (BrS). Despite recent findings regarding the functional implications of TRPM4 in cardiac diseases, the molecular and cellular mechanisms leading to altered conduction are poorly understood. In the present study, we identify and characterize four novel TRPM4 variants found in patients with CHB or ventricular fibrillation. Three of them, p.A101T, p.S1044C and a double variant p.A101T/P1204L, led to a decreased expression and function of the channel. On the contrary, the variant p.Q854R showed an increase in TRPM4 current. Recent evidence indicates that altered degradation rate of mutant proteins represents a pathogenic mechanism underlying genetic diseases. In consequence, protein turnover of WT-TRPM4 and TRPM4 variants overexpressed in HEK293 cells was analyzed using cycloheximide, an inhibitor of protein biosynthesis. Upon addition of cycloheximide, WT-TRPM4 decayed with a half-life of ~20 h, while loss-of-expression variants showed a ~30% increase in degradation rate, with a half-life close to 12 h. Together, the gain-of-expression variant showed a higher stability and a doubled half-life compared to WT-TRPM4. In conclusion, decreased or increased protein expression of several TRPM4 variants linked to cardiac conduction disorders or ventricular arrhythmias were found to be caused by altered TRPM4 half-life compared to the WT form.
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Affiliation(s)
- Beatrice Bianchi
- Swiss National Centre of Competence in Research (NCCR) TransCure, Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | - Lijo Cherian Ozhathil
- Swiss National Centre of Competence in Research (NCCR) TransCure, Institute of Biochemistry and Molecular Medicine, University of Bern, Bern, Switzerland
| | | | - Michael H Gollob
- Department of Medicine, Peter Munk Cardiac Centre, Toronto General Hospital, University of Toronto, Toronto, ON, Canada
| | - 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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Direct versus indirect actions of ghrelin on hypothalamic NPY neurons. PLoS One 2017; 12:e0184261. [PMID: 28877214 PMCID: PMC5587286 DOI: 10.1371/journal.pone.0184261] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Accepted: 08/21/2017] [Indexed: 12/19/2022] Open
Abstract
Objectives Assess direct versus indirect action(s) of ghrelin on hypothalamic NPY neurons. Materials and methods Electrophysiology was used to measure ion channel activity in NPY-GFP neurons in slice preparations. Ca2+ imaging was used to monitor ghrelin activation of isolated NPY GFP-labeled neurons. Immunohistochemistry was used to localize Trpm4, SUR1 and Kir6.2 in the hypothalamus. Results Acylated ghrelin depolarized the membrane potential (MP) of NPY-GFP neurons in brain slices. Depolarization resulted from a decreased input resistance (IR) in ~70% of neurons (15/22) or an increased IR in the remainder (7/22), consistent with the opening or closing of ion channels, respectively. Although tetrodotoxin (TTX) blockade of presynaptic action potentials reduced ghrelin-induced changes in MP and IR, ghrelin still significantly depolarized the MP and decreased IR in TTX-treated neurons, suggesting that ghrelin directly opens cation channel(s) in NPY neurons. In isolated NPY-GFP neurons, ghrelin produced a sustained rise of [Ca2+]c, with an EC50 ~110 pM. Pharmacologic studies confirmed that the direct action of ghrelin was through occupation of the growth hormone secretagogue receptor, GHS-R, and demonstrated the importance of the adenylate cyclase/cAMP/protein kinase A (PKA) and phospholipase C/inositol triphosphate (PLC/IP3) pathways as activators of 5' AMP-activated protein kinase (AMPK). Activation of isolated neurons was not affected by CNQX or TTX, but reducing [Na+]o suppressed activation, suggesting a role for Na+-permeable cation channels. SUR1 and two channel partners, Kir6.2 and Trpm4, were identified immunologically in NPY-GFP neurons in situ. The actions of SUR1 and Trpm4 modulators were informative: like ghrelin, diazoxide, a SUR1 agonist, elevated [Ca2+]c and glibenclamide, a SUR1 antagonist, partially suppressed ghrelin action, while 9-phenanthrol and flufenamic acid, selective Trpm4 antagonists, blocked ghrelin actions on isolated neurons. Ghrelin activation was unaffected by nifedipine and ω-conotoxin, inhibitors of L- and N-type Ca2+ channels, respectively, while Ni2+, mibefradil, and TTA-P2 completely or partially inhibited ghrelin action, implicating T-type Ca2+ channels. Activation was also sensitive to a spider toxin, SNX-482, at concentrations selective for R-type Ca2+ channels. Nanomolar concentrations of GABA markedly inhibited ghrelin-activation of isolated NPY-GFP neurons, consistent with chronic suppression of ghrelin action in vivo. Conclusions NPY neurons express all the molecular machinery needed to respond directly to ghrelin. Consistent with recent studies, ghrelin stimulates presynaptic inputs that activate NPY-GFP neurons in situ. Ghrelin can also directly activate a depolarizing conductance. Results with isolated NPY-GFP neurons suggest the ghrelin-activated, depolarizing current is a Na+ conductance with the pharmacologic properties of SUR1/Trpm4 non-selective cation channels. In the isolated neuron model, the opening of SUR1/Trpm4 channels activates T- and SNX482-sensitive R-type voltage dependent Ca2+ channels, which could contribute to NPY neuronal activity in situ.
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10
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Boyce AKJ, Epp AL, Nagarajan A, Swayne LA. Transcriptional and post-translational regulation of pannexins. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:72-82. [PMID: 28279657 DOI: 10.1016/j.bbamem.2017.03.004] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Revised: 03/02/2017] [Accepted: 03/03/2017] [Indexed: 12/21/2022]
Abstract
Pannexins are a 3-membered family of proteins that form large pore ion and metabolite channels in vertebrates. The impact of pannexins on vertebrate biology is intricately tied to where and when they are expressed, and how they are modified, once produced. The purpose of this review is therefore to outline our current understanding of transcriptional and post-translational regulation of pannexins. First, we briefly summarize their discovery and characteristics. Next, we describe several aspects of transcriptional regulation, including cell and tissue-specific expression, dynamic expression over development and disease, as well as new insights into the underlying molecular machinery involved. Following this, we delve into the role of post-translational modifications in the regulation of trafficking and channel properties, highlighting important work on glycosylation, phosphorylation, S-nitrosylation and proteolytic cleavage. Embedded throughout, we also highlight important knowledge gaps and avenues of future research. This article is part of a Special Issue entitled: Gap Junction Proteins edited by Jean Claude Herve.
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Affiliation(s)
- Andrew K J Boyce
- Division of Medical Sciences and Island Medical Program, University of Victoria, Victoria V8P 5C2, Canada
| | - Anna L Epp
- Division of Medical Sciences and Island Medical Program, University of Victoria, Victoria V8P 5C2, Canada
| | - Archana Nagarajan
- Division of Medical Sciences and Island Medical Program, University of Victoria, Victoria V8P 5C2, Canada
| | - Leigh Anne Swayne
- Division of Medical Sciences and Island Medical Program, University of Victoria, Victoria V8P 5C2, Canada; Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver V6T 1Z3, Canada.
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11
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Huang ZG, Liu HW, Yan ZZ, Wang S, Wang LY, Ding JP. The glycosylation of the extracellular loop of β2 subunits diversifies functional phenotypes of BK Channels. Channels (Austin) 2016; 11:156-166. [PMID: 27690717 DOI: 10.1080/19336950.2016.1243631] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
Large-conductance Ca2+- and voltage-activated potassium (MaxiK or BK) channels are composed of a pore-forming α subunit (Slo) and 4 types of auxiliary β subunits or just a pore-forming α subunit. Although multiple N-linked glycosylation sites in the extracellular loop of β subunits have been identified, very little is known about how glycosylation influences the structure and function of BK channels. Using a combination of site-directed mutagenesis, western blot and patch-clamp recordings, we demonstrated that 3 sites in the extracellular loop of β2 subunit are N-glycosylated (N-X-T/S at N88, N96 and N119). Glycosylation of these sites strongly and differentially regulate gating kinetics, outward rectification, toxin sensitivity and physical association between the α and β2 subunits. We constructed a model and used molecular dynamics (MD) to simulate how the glycosylation facilitates the association of α/β2 subunits and modulates the dimension of the extracellular cavum above the pore of the channel, ultimately to modify biophysical and pharmacological properties of BK channels. Our results suggest that N-glycosylation of β2 subunits plays crucial roles in imparting functional heterogeneity of BK channels, and is potentially involved in the pathological phenotypes of carbohydrate metabolic diseases.
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Affiliation(s)
- Zhi-Gang Huang
- a Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology , Huazhong University of Science and Technology , Wuhan , Hubei , China.,b Wuhan Foreign Languages School , Wuhan , Hubei , China
| | - Hao-Wen Liu
- a Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology , Huazhong University of Science and Technology , Wuhan , Hubei , China
| | - Zhen-Zhen Yan
- a Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology , Huazhong University of Science and Technology , Wuhan , Hubei , China
| | - Sheng Wang
- a Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology , Huazhong University of Science and Technology , Wuhan , Hubei , China
| | - Lu-Yang Wang
- c Program in Neurosciences and Mental Health, SickKids Research Institute and Department of Physiology , University of Toronto , Toronto , Ontario , Canada
| | - Jiu-Ping Ding
- a Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology , Huazhong University of Science and Technology , Wuhan , Hubei , China
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12
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Effects of N-Glycosylation of the human cation channel TRPA1 on agonist-sensitivity. Biosci Rep 2016; 36:BSR20160149. [PMID: 27582506 PMCID: PMC5052711 DOI: 10.1042/bsr20160149] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 08/30/2016] [Indexed: 12/30/2022] Open
Abstract
Determining the functional significance of post-translational modifications advances our understanding of many broadly-expressed proteins, and particularly ion channels. The enzymes that catalyze these modifications are often expressed in a cell-type specific manner, resulting in considerable structural diversity among post-translationally modified proteins that are expressed across a variety of cell types. TRP channels exhibit notably variable behavior between cell types in vitro and in vivo , and they are frequently modified with N-glycans that contribute to protein function. TRPA1 possesses two putative N-linked glycosylation sites at N747 and N753 that have not yet been studied in detail. Here, we show that both of these sites can be modified with an N-glycan and that the glycan at position N747 modulates agonist-sensitivity of TRPA1 in vitro Additionally, we found that N-glycosylation also modulates cooperative effects of temperature and the agonist cinnamaldehyde on TRPA1 channel activation. Collectively, these findings suggest a dynamic role played by the N-glycosylation of human TRPA1. They also provide further evidence of the versatility of N-glycans and will assist in efforts to fully understand the complex regulation of TRPA1 activity.
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13
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Thayer DA, Yang SB, Jan YN, Jan LY. N-linked glycosylation of Kv1.2 voltage-gated potassium channel facilitates cell surface expression and enhances the stability of internalized channels. J Physiol 2016; 594:6701-6713. [PMID: 27377235 DOI: 10.1113/jp272394] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2016] [Accepted: 06/09/2016] [Indexed: 01/20/2023] Open
Abstract
KEY POINTS Kv1.2 and related voltage-gated potassium channels have a highly conserved N-linked glycosylation site in the first extracellular loop, with complex glycosylation in COS-7 cells similar to endogenous Kv1.2 glycosylation in hippocampal neurons. COS-7 cells expressing Kv1.2 show a crucial role of this N-linked glycosylation in the forward trafficking of Kv1.2 to the cell membrane. Although both wild-type and non-glycosylated mutant Kv1.2 channels that have reached the cell membrane are internalized at a comparable rate, mutant channels are degraded at a faster rate. Treatment of wild-type Kv1.2 channels on the cell surface with glycosidase to remove sialic acids also results in the faster degradation of internalized channels. Glycosylation of Kv1.2 is important with respect to facilitating trafficking to the cell membrane and enhancing the stability of channels that have reached the cell membrane. ABSTRACT Studies in cultured hippocampal neurons and the COS-7 cell line demonstrate important roles for N-linked glycosylation of Kv1.2 channels in forward trafficking and protein degradation. Kv1.2 channels can contain complex N-linked glycans, which facilitate cell surface expression of the channels. Additionally, the protein stability of cell surface-expressed Kv1.2 channels is affected by glycosylation via differences in the degradation of internalized channels. The present study reveals the importance of N-linked complex glycosylation in boosting Kv1.2 channel density. Notably, sialic acids at the terminal sugar branches play an important role in dampening the degradation of Kv1.2 internalized from the cell membrane to promote its stability.
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Affiliation(s)
- Desiree A Thayer
- Howard Hughes Medical Institute, Departments of Physiology, Biochemistry and Biophysics, Kavli Institute for Fundamental Neuroscience, Weill Institute for Neurosciences, University of California-San Francisco, San Francisco, CA, USA.,Amunix, Mountain View, CA, USA
| | - Shi-Bing Yang
- Howard Hughes Medical Institute, Departments of Physiology, Biochemistry and Biophysics, Kavli Institute for Fundamental Neuroscience, Weill Institute for Neurosciences, University of California-San Francisco, San Francisco, CA, USA.,Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Yuh Nung Jan
- Howard Hughes Medical Institute, Departments of Physiology, Biochemistry and Biophysics, Kavli Institute for Fundamental Neuroscience, Weill Institute for Neurosciences, University of California-San Francisco, San Francisco, CA, USA
| | - Lily Y Jan
- Howard Hughes Medical Institute, Departments of Physiology, Biochemistry and Biophysics, Kavli Institute for Fundamental Neuroscience, Weill Institute for Neurosciences, University of California-San Francisco, San Francisco, CA, USA
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14
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Ohya S, Kito H, Hatano N, Muraki K. Recent advances in therapeutic strategies that focus on the regulation of ion channel expression. Pharmacol Ther 2016; 160:11-43. [PMID: 26896566 DOI: 10.1016/j.pharmthera.2016.02.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
A number of different ion channel types are involved in cell signaling networks, and homeostatic regulatory mechanisms contribute to the control of ion channel expression. Profiling of global gene expression using microarray technology has recently provided novel insights into the molecular mechanisms underlying the homeostatic and pathological control of ion channel expression. It has demonstrated that the dysregulation of ion channel expression is associated with the pathogenesis of neural, cardiovascular, and immune diseases as well as cancers. In addition to the transcriptional, translational, and post-translational regulation of ion channels, potentially important evidence on the mechanisms controlling ion channel expression has recently been accumulated. The regulation of alternative pre-mRNA splicing is therefore a novel therapeutic strategy for the treatment of dominant-negative splicing disorders. Epigenetic modification plays a key role in various pathological conditions through the regulation of pluripotency genes. Inhibitors of pre-mRNA splicing and histone deacetyalase/methyltransferase have potential as potent therapeutic drugs for cancers and autoimmune and inflammatory diseases. Moreover, membrane-anchoring proteins, lysosomal and proteasomal degradation-related molecules, auxiliary subunits, and pharmacological agents alter the protein folding, membrane trafficking, and post-translational modifications of ion channels, and are linked to expression-defect channelopathies. In this review, we focused on recent insights into the transcriptional, spliceosomal, epigenetic, and proteasomal regulation of ion channel expression: Ca(2+) channels (TRPC/TRPV/TRPM/TRPA/Orai), K(+) channels (voltage-gated, KV/Ca(2+)-activated, KCa/two-pore domain, K2P/inward-rectifier, Kir), and Ca(2+)-activated Cl(-) channels (TMEM16A/TMEM16B). Furthermore, this review highlights expression of these ion channels in expression-defect channelopathies.
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Affiliation(s)
- Susumu Ohya
- Department of Pharmacology, Division of Pathological Sciences, Kyoto Pharmaceutical University, Kyoto 607-8414, Japan.
| | - Hiroaki Kito
- Department of Pharmacology, Division of Pathological Sciences, Kyoto Pharmaceutical University, Kyoto 607-8414, Japan
| | - Noriyuki Hatano
- Laboratory of Cellular Pharmacology, School of Pharmacy, Aichi-Gakuin University, Nagoya 464-8650, Japan
| | - Katsuhiko Muraki
- Laboratory of Cellular Pharmacology, School of Pharmacy, Aichi-Gakuin University, Nagoya 464-8650, Japan.
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15
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Cho CH, Lee YS, Kim E, Hwang EM, Park JY. Physiological functions of the TRPM4 channels via protein interactions. BMB Rep 2015; 48:1-5. [PMID: 25441424 PMCID: PMC4345635 DOI: 10.5483/bmbrep.2015.48.1.252] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Indexed: 11/23/2022] Open
Abstract
Transient Receptor Potential, Melastatin-related, member 4 (TRPM4) channels are Ca2+-activated Ca2+-impermeable cation channels. These channels are expressed in various types of mammalian tissues including the brain and are implicated in many diverse physiological and pathophysiological conditions. In the past several years, the trafficking processes and regulatory mechanism of these channels and their interacting proteins have been uncovered. Here in this minireview, we summarize the current understanding of the trafficking mechanism of TRPM4 channels on the plasma membrane as well as heteromeric complex formation via protein interactions. We also describe physiological implications of protein-TRPM4 interactions and suggest TRPM4 channels as therapeutic targets in many related diseases. [BMB Reports 2015; 48(1): 1-5]
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Affiliation(s)
- Chang-Hoon Cho
- School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul 136-703, Korea
| | - Young-Sun Lee
- Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul 136-791; Department of Physiology, Institute of Health Science and Medical Research Center for Neural Dysfunction, Gyeongsang National University School of Medicine, Jinju 660-751, Korea
| | - Eunju Kim
- School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul 136-703; Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul 136-791, Korea
| | - Eun Mi Hwang
- Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul 136-791; Neuroscience Program, University of Science and Technology (UST), Daejeon 305-350, Korea
| | - Jae-Yong Park
- School of Biosystem and Biomedical Science, College of Health Science, Korea University, Seoul 136-703, Korea
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16
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Guinamard R, Bouvagnet P, Hof T, Liu H, Simard C, Sallé L. TRPM4 in cardiac electrical activity. Cardiovasc Res 2015; 108:21-30. [PMID: 26272755 DOI: 10.1093/cvr/cvv213] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 07/31/2015] [Indexed: 11/12/2022] Open
Abstract
TRPM4 forms a non-selective cation channel activated by internal Ca(2+). Its functional expression was demonstrated in cardiomyocytes of several mammalian species including humans, but the channel is also present in many other tissues. The recent characterization of the TRPM4 inhibitor 9-phenanthrol, and the availability of transgenic mice have helped to clarify the role of TRPM4 in cardiac electrical activity, including diastolic depolarization from the sino-atrial node cells in mouse, rat, and rabbit, as well as action potential duration in mouse cardiomyocytes. In rat and mouse, pharmacological inhibition of TRPM4 prevents cardiac ischaemia-reperfusion injuries and decreases the occurrence of arrhythmias. Several studies have identified TRPM4 mutations in patients with inherited cardiac diseases including conduction blocks and Brugada syndrome. This review identifies TRPM4 as a significant actor in cardiac electrophysiology.
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Affiliation(s)
- Romain Guinamard
- Groupe Signalisation, Electrophysiologie et Imagerie des Lésions d'Ischémie-Reperfusion Myocardique, EA4650, Université de Caen Basse-Normandie, Sciences D, Esplanade de la Paix, CS 14032, 14032 Caen Cedex 5, France
| | | | - Thomas Hof
- Groupe Signalisation, Electrophysiologie et Imagerie des Lésions d'Ischémie-Reperfusion Myocardique, EA4650, Université de Caen Basse-Normandie, Sciences D, Esplanade de la Paix, CS 14032, 14032 Caen Cedex 5, France
| | - Hui Liu
- Department of Anatomy, Hainan Medical College, Haikou, Hainan 571101, China
| | - Christophe Simard
- Groupe Signalisation, Electrophysiologie et Imagerie des Lésions d'Ischémie-Reperfusion Myocardique, EA4650, Université de Caen Basse-Normandie, Sciences D, Esplanade de la Paix, CS 14032, 14032 Caen Cedex 5, France
| | - Laurent Sallé
- Groupe Signalisation, Electrophysiologie et Imagerie des Lésions d'Ischémie-Reperfusion Myocardique, EA4650, Université de Caen Basse-Normandie, Sciences D, Esplanade de la Paix, CS 14032, 14032 Caen Cedex 5, France
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17
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Wojciechowski D, Fischer M, Fahlke C. Tryptophan Scanning Mutagenesis Identifies the Molecular Determinants of Distinct Barttin Functions. J Biol Chem 2015; 290:18732-43. [PMID: 26063802 DOI: 10.1074/jbc.m114.625376] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Indexed: 01/05/2023] Open
Abstract
CLC-K chloride channels are expressed in the kidney and in the inner ear and require the accessory subunit barttin for proper function and membrane insertion. Barttin exerts multiple functions on CLC-proteins: it modifies protein stability and intracellular trafficking as well as channel activity, ion conduction, and gating. So far, the molecular determinants of these distinct barttin functions have remained elusive. Here we performed serial perturbation mutagenesis to identify the sequence determinants of barttin function. Barttin consists of two transmembrane helices followed by a long intracellular carboxyl terminus, and earlier work demonstrated that the transmembrane core of barttin suffices for most effects on the α-subunit. We individually substituted every amino acid of the predicted transmembrane core (amino acids 9-26 and 35-55) with tryptophan, co-expressed mutant barttin with hClC-Ka or V166E rClC-K1, and characterized CLC-K/barttin channels by patch clamp techniques, biochemistry, and confocal microscopy. The majority of mutations left the chaperone function of barttin, i.e. the effects on endoplasmic reticulum exit and surface membrane insertion, unaffected. In contrast, tryptophan insertion at multiple positions resulted in impaired activity of hClC-Ka/barttin and changes in gating of V166E rClC-K1/barttin. These results demonstrate that mutations in a cluster of hydrophobic residues within transmembrane domain 1 affect barttin-CLC-K interaction and impair gating modification by the accessory subunit. Whereas tight interaction is necessary for functional modification, even impaired association of barttin and CLC-K suffices for normal intracellular trafficking. Our findings allow definition of a likely interaction surface and clarify the mechanisms underlying CLC-K channel modification by barttin.
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Affiliation(s)
- Daniel Wojciechowski
- From the Institut für Neurophysiologie, Medizinische Hochschule Hannover, 30625 Hannover, Germany and
| | - Martin Fischer
- From the Institut für Neurophysiologie, Medizinische Hochschule Hannover, 30625 Hannover, Germany and
| | - Christoph Fahlke
- Institute of Complex Systems-Zelluläre Biophysik (ICS-4), Forschungszentrum Jülich, 52428 Jülich Germany
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18
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Muthusamy S, Malhotra P, Hosameddin M, Dudeja AK, Borthakur S, Saksena S, Gill RK, Dudeja PK, Alrefai WA. N-glycosylation is essential for ileal ASBT function and protection against proteases. Am J Physiol Cell Physiol 2015; 308:C964-71. [PMID: 25855079 DOI: 10.1152/ajpcell.00023.2015] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 04/07/2015] [Indexed: 12/22/2022]
Abstract
The bile acid transporter ASBT is a glycoprotein responsible for active absorption of bile acids. Inhibiting ASBT function and bile acid absorption is an attractive approach to lower plasma cholesterol and improve glucose imbalance in diabetic patients. Deglycosylation of ASBT was shown to decrease its function. However, the exact roles of N-glycosylation of ASBT, and how it affects its function, is not known. Current studies investigated the roles of N-glycosylation in ASBT protein stability and protection against proteases utilizing HEK-293 cells stably transfected with ASBT-V5 fusion protein. ASBT-V5 protein was detected as two bands with molecular mass of ~41 and ~35 kDa. Inhibition of glycosylation by tunicamycin significantly decreased ASBT activity and shifted ASBT bands to ~30 kDa, representing a deglycosylated protein. Treatment of total cellular lysates with PNGase F or Endo H glycosidases showed that the upper 41-kDa band represents a fully mature N-acetylglucosamine-rich glycoprotein and the lower 35-kDa band represents a mannose-rich core glycoprotein. Studies with the glycosylation deficient ASBT mutant (N10Q) showed that the N-glycosylation is not essential for ASBT targeting to plasma membrane. However, mature glycosylation significantly increased the half-life and protected ASBT protein from digestion with trypsin. Incubating the cells with high glucose (25 mM) for 48 h increased mature glycosylated ASBT along with an increase in its function. These results unravel novel roles for N-glycosylation of ASBT and suggest that high levels of glucose alter the composition of the glycan and may contribute to the increase in ASBT function in diabetes mellitus.
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Affiliation(s)
- Saminathan Muthusamy
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Pooja Malhotra
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Mobashir Hosameddin
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Amish K Dudeja
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Sujata Borthakur
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Seema Saksena
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Ravinder K Gill
- Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Pradeep K Dudeja
- Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois; and Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
| | - Waddah A Alrefai
- Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois; and Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
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19
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Post-Translational Modifications of TRP Channels. Cells 2014; 3:258-87. [PMID: 24717323 PMCID: PMC4092855 DOI: 10.3390/cells3020258] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Revised: 03/25/2014] [Accepted: 03/27/2014] [Indexed: 01/07/2023] Open
Abstract
Transient receptor potential (TRP) channels constitute an ancient family of cation channels that have been found in many eukaryotic organisms from yeast to human. TRP channels exert a multitude of physiological functions ranging from Ca2+ homeostasis in the kidney to pain reception and vision. These channels are activated by a wide range of stimuli and undergo covalent post-translational modifications that affect and modulate their subcellular targeting, their biophysical properties, or channel gating. These modifications include N-linked glycosylation, protein phosphorylation, and covalent attachment of chemicals that reversibly bind to specific cysteine residues. The latter modification represents an unusual activation mechanism of ligand-gated ion channels that is in contrast to the lock-and-key paradigm of receptor activation by its agonists. In this review, we summarize the post-translational modifications identified on TRP channels and, when available, explain their physiological role.
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20
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Guinamard R, Hof T, Del Negro CA. The TRPM4 channel inhibitor 9-phenanthrol. Br J Pharmacol 2014; 171:1600-13. [PMID: 24433510 PMCID: PMC3966741 DOI: 10.1111/bph.12582] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Revised: 12/17/2013] [Accepted: 01/08/2014] [Indexed: 01/06/2023] Open
Abstract
The phenanthrene-derivative 9-phenanthrol is a recently identified inhibitor of the transient receptor potential melastatin (TRPM) 4 channel, a Ca(2+) -activated non-selective cation channel whose mechanism of action remains to be determined. Subsequent studies performed on other ion channels confirm the specificity of the drug for TRPM4. In addition, 9-phenanthrol modulates a variety of physiological processes through TRPM4 current inhibition and thus exerts beneficial effects in several pathological conditions. 9-Phenanthrol modulates smooth muscle contraction in bladder and cerebral arteries, affects spontaneous activity in neurons and in the heart, and reduces lipopolysaccharide-induced cell death. Among promising potential applications, 9-phenanthrol exerts cardioprotective effects against ischaemia-reperfusion injuries and reduces ischaemic stroke injuries. In addition to reviewing the biophysical effects of 9-phenanthrol, here we present information about its appropriate use in physiological studies and possible clinical applications.
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Affiliation(s)
- R Guinamard
- EA 4650, Groupe Signalisation, Electrophysiologie et Imagerie des Lésions d'Ischémie-Reperfusion Myocardique, UCBN, Normandie UniversitéCaen, France
- Department of Applied Science, The College of William and MaryWilliamsburg, VA, USA
| | - T Hof
- EA 4650, Groupe Signalisation, Electrophysiologie et Imagerie des Lésions d'Ischémie-Reperfusion Myocardique, UCBN, Normandie UniversitéCaen, France
| | - C A Del Negro
- Department of Applied Science, The College of William and MaryWilliamsburg, VA, USA
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21
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Syam N, Rougier JS, Abriel H. Glycosylation of TRPM4 and TRPM5 channels: molecular determinants and functional aspects. Front Cell Neurosci 2014; 8:52. [PMID: 24605085 PMCID: PMC3932411 DOI: 10.3389/fncel.2014.00052] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Accepted: 02/06/2014] [Indexed: 11/30/2022] Open
Abstract
The transient receptor potential channel, TRPM4, and its closest homolog, TRPM5, are non-selective cation channels that are activated by an increase in intracellular calcium. They are expressed in many cell types, including neurons and myocytes. Although the electrophysiological and pharmacological properties of these two channels have been previously studied, less is known about their regulation, in particular their post-translational modifications. We, and others, have reported that wild-type (WT) TRPM4 channels expressed in HEK293 cells, migrated on SDS-PAGE gel as doublets, similar to other ion channels and membrane proteins. In the present study, we provide evidence that TRPM4 and TRPM5 are each N-linked glycosylated at a unique residue, Asn992 and Asn932, respectively. N-linked glycosylated TRPM4 is also found in native cardiac cells. Biochemical experiments using HEK293 cells over-expressing WT TRPM4/5 or N992Q/N932Q mutants demonstrated that the abolishment of N-linked glycosylation did not alter the number of channels at the plasma membrane. In parallel, electrophysiological experiments demonstrated a decrease in the current density of both mutant channels, as compared to their respective controls, either due to the Asn to Gln mutations themselves or abolition of glycosylation. To discriminate between these possibilities, HEK293 cells expressing TRPM4 WT were treated with tunicamycin, an inhibitor of glycosylation. In contrast to N-glycosylation signal abolishment by mutagenesis, tunicamycin treatment led to an increase in the TRPM4-mediated current. Altogether, these results demonstrate that TRPM4 and TRPM5 are both N-linked glycosylated at a unique site and also suggest that TRPM4/5 glycosylation seems not to be involved in channel trafficking, but mainly in their functional regulation.
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Affiliation(s)
- Ninda Syam
- Department of Clinical Research, and Swiss National Centre of Competence in Research (NCCR) TransCure, University of Bern Bern, Switzerland
| | - Jean-Sébastien Rougier
- Department of Clinical Research, and Swiss National Centre of Competence in Research (NCCR) TransCure, University of Bern Bern, Switzerland
| | - Hugues Abriel
- Department of Clinical Research, and Swiss National Centre of Competence in Research (NCCR) TransCure, University of Bern Bern, Switzerland
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22
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