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Acosta FM, Riquelme MA, Gu S, Jiang JX. Evaluation of Connexin Hemichannel Activity In Vivo. Methods Mol Biol 2024; 2801:111-124. [PMID: 38578417 DOI: 10.1007/978-1-0716-3842-2_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/06/2024]
Abstract
Connexin hemichannels (Cx HCs) are hexameric structures at the cell plasma membrane, whose function as membrane transport proteins allows for the passive flow of small hydrophilic molecules and ions (≤1 kDa) between the cytosol and the extracellular environment. Activation of Cx HCs is highly dependent on pathological conditions. HC activity provokes changes in the microenvironment, inducing the dissemination of signaling molecules in both an autocrine and paracrine manner. Given the elicitation of a variety of signaling pathways, and assortment of Cx species and dispersion throughout the body, Cx HCs have been implicated in a range of processes such as cell proliferation, differentiation, cell death, and tissue modeling and remodeling. While studying the expression and localization of Cx HCs can be done using traditional laboratory techniques, such as immunoblot analysis, measuring the functionality/activity of the HCs requires a more explicit methodology and is essential for determining Cx-mediated physiological changes. The study of Cx HC function/activity has focused mainly on in vitro measurements through electrophysiological characterization or, more commonly, using HC-permeable dye uptake studies. Here, we describe the use of dye uptake to measure Cx HC activity in vivo using mechanically stimulated osteocytic Cx43 HCs with Evans blue dye as our model.
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Affiliation(s)
- Francisca M Acosta
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Manuel A Riquelme
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Sumin Gu
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Jean X Jiang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
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2
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Jones JC, Bodenstine TM. Connexins and Glucose Metabolism in Cancer. Int J Mol Sci 2022; 23:ijms231710172. [PMID: 36077565 PMCID: PMC9455984 DOI: 10.3390/ijms231710172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2022] [Revised: 08/26/2022] [Accepted: 08/30/2022] [Indexed: 11/16/2022] Open
Abstract
Connexins are a family of transmembrane proteins that regulate diverse cellular functions. Originally characterized for their ability to mediate direct intercellular communication through the formation of highly regulated membrane channels, their functions have been extended to the exchange of molecules with the extracellular environment, and the ability to modulate numerous channel-independent effects on processes such as motility and survival. Notably, connexins have been implicated in cancer biology for their context-dependent roles that can both promote or suppress cancer cell function. Moreover, connexins are able to mediate many aspects of cellular metabolism including the intercellular coupling of nutrients and signaling molecules. During cancer progression, changes to substrate utilization occur to support energy production and biomass accumulation. This results in metabolic plasticity that promotes cell survival and proliferation, and can impact therapeutic resistance. Significant progress has been made in our understanding of connexin and cancer biology, however, delineating the roles these multi-faceted proteins play in metabolic adaptation of cancer cells is just beginning. Glucose represents a major carbon substrate for energy production, nucleotide synthesis, carbohydrate modifications and generation of biosynthetic intermediates. While cancer cells often exhibit a dependence on glycolytic metabolism for survival, cellular reprogramming of metabolic pathways is common when blood perfusion is limited in growing tumors. These metabolic changes drive aggressive phenotypes through the acquisition of functional traits. Connections between glucose metabolism and connexin function in cancer cells and the surrounding stroma are now apparent, however much remains to be discovered regarding these relationships. This review discusses the existing evidence in this area and highlights directions for continued investigation.
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Taatjes DJ, Roth J. In focus in HCB. Histochem Cell Biol 2020; 153:129-133. [PMID: 32114634 DOI: 10.1007/s00418-020-01852-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- Douglas J Taatjes
- Department of Pathology and Laboratory Medicine, Larner College of Medicine, University of Vermont, Burlington, VT, 05405, USA.
| | - Jürgen Roth
- University of Zurich, 8091, Zurich, Switzerland
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Flores JA, Haddad BG, Dolan KA, Myers JB, Yoshioka CC, Copperman J, Zuckerman DM, Reichow SL. Connexin-46/50 in a dynamic lipid environment resolved by CryoEM at 1.9 Å. Nat Commun 2020; 11:4331. [PMID: 32859914 PMCID: PMC7455559 DOI: 10.1038/s41467-020-18120-5] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 08/07/2020] [Indexed: 11/17/2022] Open
Abstract
Gap junctions establish direct pathways for cells to transfer metabolic and electrical messages. The local lipid environment is known to affect the structure, stability and intercellular channel activity of gap junctions; however, the molecular basis for these effects remains unknown. Here, we incorporate native connexin-46/50 (Cx46/50) intercellular channels into a dual lipid nanodisc system, mimicking a native cell-to-cell junction. Structural characterization by CryoEM reveals a lipid-induced stabilization to the channel, resulting in a 3D reconstruction at 1.9 Å resolution. Together with all-atom molecular dynamics simulations, it is shown that Cx46/50 in turn imparts long-range stabilization to the dynamic local lipid environment that is specific to the extracellular lipid leaflet. In addition, ~400 water molecules are resolved in the CryoEM map, localized throughout the intercellular permeation pathway and contributing to the channel architecture. These results illustrate how the aqueous-lipid environment is integrated with the architectural stability, structure and function of gap junction communication channels.
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Affiliation(s)
- Jonathan A Flores
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, 97239, USA
| | - Bassam G Haddad
- Department of Chemistry, Portland State University, Portland, OR, 97201, USA
| | - Kimberly A Dolan
- Department of Chemistry, Portland State University, Portland, OR, 97201, USA
- Biophysics Graduate Group, University of California, Berkeley, CA, 94720, USA
| | - Janette B Myers
- Department of Chemistry, Portland State University, Portland, OR, 97201, USA
| | - Craig C Yoshioka
- Department of Biomedical Engineering, Oregon Health and Science University, Portland, OR, 97239, USA
| | - Jeremy Copperman
- Department of Biomedical Engineering, Oregon Health and Science University, Portland, OR, 97239, USA
| | - Daniel M Zuckerman
- Department of Biomedical Engineering, Oregon Health and Science University, Portland, OR, 97239, USA
| | - Steve L Reichow
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, 97239, USA.
- Department of Chemistry, Portland State University, Portland, OR, 97201, USA.
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Retamal MA, Fiori MC, Fernandez-Olivares A, Linsambarth S, Peña F, Quintana D, Stehberg J, Altenberg GA. 4-Hydroxynonenal induces Cx46 hemichannel inhibition through its carbonylation. Biochim Biophys Acta Mol Cell Biol Lipids 2020; 1865:158705. [PMID: 32244060 DOI: 10.1016/j.bbalip.2020.158705] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Accepted: 03/28/2020] [Indexed: 12/22/2022]
Abstract
Hemichannels formed by connexins mediate the exchange of ions and signaling molecules between the cytoplasm and the extracellular milieu. Under physiological conditions hemichannels have a low open probability, but in certain pathologies their open probability increases, which can result in cell damage. Pathological conditions are characterized by the production of a number of proinflammatory molecules, including 4-hydroxynonenal (4-HNE), one of the most common lipid peroxides produced in response to inflammation and oxidative stress. The aim of this work was to evaluate whether 4-HNE modulates the activity of Cx46 hemichannels. We found that 4-HNE (100 μM) reduced the rate of 4',6-diamino-2-fenilindol (DAPI) uptake through hemichannels formed by recombinant human Cx46 fused to green fluorescent protein, an inhibition that was reversed partially by 10 mM dithiothreitol. Immunoblot analysis showed that the recombinant Cx46 expressed in HeLa cells becomes carbonylated after exposure to 4-HNE, and that 10 mM dithiothreitol reduced its carbonylation. We also found that Cx46 was carbonylated by 4-HNE in the lens of a selenite-induced cataract animal model. The exposure to 100 μM 4-HNE decreased hemichannel currents formed by recombinant rat Cx46 in Xenopus laevis oocytes. This inhibition also occurred in a mutant expressing only the extracellular loop cysteines, suggesting that other Cys are not responsible for the hemichannel inhibition by carbonylation. This work demonstrates for the first time that Cx46 is post-translationally modified by a lipid peroxide and that this modification reduces Cx46 hemichannel activity.
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Affiliation(s)
- Mauricio A Retamal
- Universidad del Desarrollo, Centro de Fisiología Celular e Integrativa, Facultad de Medicina Clínica Alemana, Santiago, Chile; Universidad del Desarrollo, Programa de Comunicación Celular en Cáncer, Facultad de Medicina Clínica Alemana, Santiago, Chile.
| | - Mariana C Fiori
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX 79430-6551, USA
| | - Ainoa Fernandez-Olivares
- Universidad del Desarrollo, Centro de Fisiología Celular e Integrativa, Facultad de Medicina Clínica Alemana, Santiago, Chile; Universidad del Desarrollo, Programa de Comunicación Celular en Cáncer, Facultad de Medicina Clínica Alemana, Santiago, Chile
| | - Sergio Linsambarth
- Laboratorio de Neurobiología, Instituto de Ciencias Biomédicas, Facultad de Medicina y Facultad de Ciencias de la vida, Universidad Andres Bello, Santiago, Chile
| | - Francisca Peña
- Laboratorio de Neurobiología, Instituto de Ciencias Biomédicas, Facultad de Medicina y Facultad de Ciencias de la vida, Universidad Andres Bello, Santiago, Chile
| | - Daisy Quintana
- Laboratorio de Neurobiología, Instituto de Ciencias Biomédicas, Facultad de Medicina y Facultad de Ciencias de la vida, Universidad Andres Bello, Santiago, Chile
| | - Jimmy Stehberg
- Laboratorio de Neurobiología, Instituto de Ciencias Biomédicas, Facultad de Medicina y Facultad de Ciencias de la vida, Universidad Andres Bello, Santiago, Chile
| | - Guillermo A Altenberg
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX 79430-6551, USA
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PUFAs supplementation affects the renal expression of pannexin 1 and connexins in diabetic kidney of rats. Histochem Cell Biol 2019; 153:165-175. [PMID: 31858211 DOI: 10.1007/s00418-019-01838-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/14/2019] [Indexed: 12/26/2022]
Abstract
In diabetic nephropathy (DN), intercellular communication is disrupted. Connexins (Cx) have a crucial role in that process. Dietary ratios and supplementation with polyunsaturated fatty acids (PUFAs) can alleviate diabetic complications and cause alterations in Cx levels. Although pannexins (Panx) share similarities with members of the Cx family, their function in diabetic nephropathy has still not been fully determined. We studied the influence of PUFA supplementation on the immunoexpression of Px1 and Cx family members in diabetic kidneys of rats. Four groups of rats in experimental DM1 model were supplemented with different dietary n-6/n-3 ratios; ≈7 in control (C) and diabetic groups (STZ), ≈ 60 in the STZ + N6 group and ≈ 1 (containing 16% EPA and 19% DHA) in the STZ + N3 group. Immunoexpression of Cx40, Cx43, Cx45 and Panx1 was evaluated in the renal tissue of diabetic rats using immunohistochemistry. Diabetes significantly decreased the protein expression of Cx40 and Cx43 and increased Panx1 protein expression in the renal cortex (p < 0.05-p < 0.01). There was a significant impact of diet on Cx and Panx1 immunoexpression. Dietary supplementation with a high n-6/n-3 ratio downregulated the protein expression of Cx45 and Panx1 in diabetic rats (p < 0.05-p < 0.01), while Cx43 immunoexpression was increased in diabetic rats fed with high and low n-6/n-3 ratios (p < 0.01-p < 0.001). Hyperglycaemic conditions in DN interfere with cell-to-cell communication and disturb the connection between cells and their immediate environment due to variations in connexin and pannexin immunoexpression. These variations can be regulated by PUFA dietary intake, suggesting their beneficial effect and possible therapeutic option.
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Cx46 hemichannel modulation by nitric oxide: Role of the fourth transmembrane helix cysteine and its possible involvement in cataract formation. Nitric Oxide 2019; 86:54-62. [DOI: 10.1016/j.niox.2019.02.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 02/08/2019] [Accepted: 02/20/2019] [Indexed: 01/09/2023]
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Ni H, Narsingani K, Zhang H, Giles WR. Can principles of the surface potential be combined with knowledge of natural products to reduce atrial rhythm disturbances? Acta Physiol (Oxf) 2018; 222. [PMID: 28719150 DOI: 10.1111/apha.12918] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- H. Ni
- Biological Physics Group; School of Physics & Astronomy; The University of Manchester; Manchester UK
| | - K. Narsingani
- Faculties of Kinesiology & Medicine; University of Calgary; Calgary AB Canada
| | - H. Zhang
- Biological Physics Group; School of Physics & Astronomy; The University of Manchester; Manchester UK
| | - W. R. Giles
- Faculties of Kinesiology & Medicine; University of Calgary; Calgary AB Canada
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Salari S, Silverå Ejneby M, Brask J, Elinder F. Isopimaric acid - a multi-targeting ion channel modulator reducing excitability and arrhythmicity in a spontaneously beating mouse atrial cell line. Acta Physiol (Oxf) 2018; 222. [PMID: 28514017 DOI: 10.1111/apha.12895] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Revised: 03/08/2017] [Accepted: 05/12/2017] [Indexed: 11/28/2022]
Abstract
AIM Atrial fibrillation is the most common persistent cardiac arrhythmia, and it is not well controlled by present drugs. Because some resin acids open voltage-gated potassium channels and reduce neuronal excitability, we explored the effects of the resin acid isopimaric acid (IPA) on action potentials and ion currents in cardiomyocytes. METHODS Spontaneously beating mouse atrial HL-1 cells were investigated with the whole-cell patch-clamp technique. RESULTS 1-25 μmol L-1 IPA reduced the action potential frequency by up to 50%. The effect of IPA on six different voltage-gated ion channels was investigated; most voltage-dependent parameters of ion channel gating were shifted in the negative direction along the voltage axis, consistent with a hypothesis that a lipophilic and negatively charged compound binds to the lipid membrane close to the positively charged voltage sensor of the ion channels. The major finding was that IPA inactivated sodium channels and L- and T-type calcium channels and activated the rapidly activating potassium channel and the transient outward potassium channel. Computer simulations of IPA effects on all of the ion currents were consistent with a reduced excitability, and they also showed that effects on the Na channel played the largest role to reduce the action potential frequency. Finally, induced arrhythmia in the HL-1 cells was reversed by IPA. CONCLUSION Low concentrations of IPA reduced the action potential frequency and restored regular firing by altering the voltage dependencies of several voltage-gated ion channels. These findings can form the basis for a new pharmacological strategy to treat atrial fibrillation.
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Affiliation(s)
- S. Salari
- Department of Clinical and Experimental Medicine; Linköping University; Linköping Sweden
| | - M. Silverå Ejneby
- Department of Clinical and Experimental Medicine; Linköping University; Linköping Sweden
| | - J. Brask
- Department of Clinical and Experimental Medicine; Linköping University; Linköping Sweden
| | - F. Elinder
- Department of Clinical and Experimental Medicine; Linköping University; Linköping Sweden
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Willebrords J, Maes M, Crespo Yanguas S, Vinken M. Inhibitors of connexin and pannexin channels as potential therapeutics. Pharmacol Ther 2017; 180:144-160. [PMID: 28720428 PMCID: PMC5802387 DOI: 10.1016/j.pharmthera.2017.07.001] [Citation(s) in RCA: 106] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
While gap junctions support the exchange of a number of molecules between neighboring cells, connexin hemichannels provide communication between the cytosol and the extracellular environment of an individual cell. The latter equally holds true for channels composed of pannexin proteins, which display an architecture reminiscent of connexin hemichannels. In physiological conditions, gap junctions are usually open, while connexin hemichannels and, to a lesser extent, pannexin channels are typically closed, yet they can be activated by a number of pathological triggers. Several agents are available to inhibit channels built up by connexin and pannexin proteins, including alcoholic substances, glycyrrhetinic acid, anesthetics and fatty acids. These compounds not always strictly distinguish between gap junctions, connexin hemichannels and pannexin channels, and may have effects on other targets as well. An exception lies with mimetic peptides, which reproduce specific amino acid sequences in connexin or pannexin primary protein structure. In this paper, a state-of-the-art overview is provided on inhibitors of cellular channels consisting of connexins and pannexins with specific focus on their mode-of-action and therapeutic potential.
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Affiliation(s)
- Joost Willebrords
- Department of In Vitro Toxicology and Dermato-cosmetology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Laarbeeklaan 103, Brussels, Belgium
| | - Michaël Maes
- Department of In Vitro Toxicology and Dermato-cosmetology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Laarbeeklaan 103, Brussels, Belgium
| | - Sara Crespo Yanguas
- Department of In Vitro Toxicology and Dermato-cosmetology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Laarbeeklaan 103, Brussels, Belgium
| | - Mathieu Vinken
- Department of In Vitro Toxicology and Dermato-cosmetology, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Laarbeeklaan 103, Brussels, Belgium.
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Gleisner MA, Navarrete M, Hofmann F, Salazar-Onfray F, Tittarelli A. Mind the Gaps in Tumor Immunity: Impact of Connexin-Mediated Intercellular Connections. Front Immunol 2017; 8:1067. [PMID: 28919895 PMCID: PMC5585150 DOI: 10.3389/fimmu.2017.01067] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Accepted: 08/16/2017] [Indexed: 12/22/2022] Open
Abstract
Gap junctions (GJs)-mediated intercellular communications (GJICs) are connexin (Cx)-formed plasma membrane channels that allow for the passage of small molecules between adjacent cells, and are involved in several physiopathological processes, including immune responses against cancer. In general, tumor cells are poorly coupled through GJs, mainly due to low Cx expression or reduced channel activity, suggesting that Cxs may have tumor suppressor roles. However, more recent data indicate that Cxs and/or GJICs may also in some cases promote tumor progression. This dual role of Cx channels in tumor outcome may be due, at least partially, to the fact that GJs not only interconnect cells from the same type, such as cancer cells, but also promote the intercellular communication of tumor cells with different types of cells from their microenvironment, and such diverse intercellular interactions have distinctive impact on tumor development. For example, whereas GJ-mediated interactions among tumor cells and microglia have been implicated in promotion of tumor growth, tumor cells delivery to dendritic cells of antigenic peptides through GJs have been associated with enhanced immune-mediated tumor elimination. In this review, we provide an updated overview on the role of GJICs in tumor immunity, focusing on the pro-tumor and antitumor effect of GJs occurring among tumor and immune cells. Accumulated data suggest that GJICs may act as tumor suppressors or enhancers depending on whether tumor cells interact predominantly with antitumor immune cells or with stromal cells. The complex modulation of immune-tumor cell GJICs should be taken into consideration in order to potentiate current cancer immunotherapies.
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Affiliation(s)
- María Alejandra Gleisner
- Disciplinary Program of Immunology, Faculty of Medicine, Institute of Biomedical Sciences, Universidad de Chile, Santiago, Chile.,Faculty of Medicine, Millennium Institute on Immunology and Immunotherapy, Universidad de Chile, Santiago, Chile
| | - Mariela Navarrete
- Disciplinary Program of Immunology, Faculty of Medicine, Institute of Biomedical Sciences, Universidad de Chile, Santiago, Chile.,Faculty of Medicine, Millennium Institute on Immunology and Immunotherapy, Universidad de Chile, Santiago, Chile
| | - Francisca Hofmann
- Disciplinary Program of Immunology, Faculty of Medicine, Institute of Biomedical Sciences, Universidad de Chile, Santiago, Chile.,Faculty of Medicine, Millennium Institute on Immunology and Immunotherapy, Universidad de Chile, Santiago, Chile
| | - Flavio Salazar-Onfray
- Disciplinary Program of Immunology, Faculty of Medicine, Institute of Biomedical Sciences, Universidad de Chile, Santiago, Chile.,Faculty of Medicine, Millennium Institute on Immunology and Immunotherapy, Universidad de Chile, Santiago, Chile
| | - Andrés Tittarelli
- Disciplinary Program of Immunology, Faculty of Medicine, Institute of Biomedical Sciences, Universidad de Chile, Santiago, Chile.,Faculty of Medicine, Millennium Institute on Immunology and Immunotherapy, Universidad de Chile, Santiago, Chile
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