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León-Fuentes IM, Salgado-Gil MG, Novoa MS, Retamal MA. Connexins in Cancer, the Possible Role of Connexin46 as a Cancer Stem Cell-Determining Protein. Biomolecules 2023; 13:1460. [PMID: 37892142 PMCID: PMC10604234 DOI: 10.3390/biom13101460] [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] [Received: 08/17/2023] [Revised: 09/15/2023] [Accepted: 09/22/2023] [Indexed: 10/29/2023] Open
Abstract
Cancer is a widespread and incurable disease caused by genetic mutations, leading to uncontrolled cell proliferation and metastasis. Connexins (Cx) are transmembrane proteins that facilitate intercellular communication via hemichannels and gap junction channels. Among them, Cx46 is found mostly in the eye lens. However, in pathological conditions, Cx46 has been observed in various types of cancers, such as glioblastoma, melanoma, and breast cancer. It has been demonstrated that elevated Cx46 levels in breast cancer contribute to cellular resistance to hypoxia, and it is an enhancer of cancer aggressiveness supporting a pro-tumoral role. Accordingly, Cx46 is associated with an increase in cancer stem cell phenotype. These cells display radio- and chemoresistance, high proliferative abilities, self-renewal, and differentiation capacities. This review aims to consolidate the knowledge of the relationship between Cx46, its role in forming hemichannels and gap junctions, and its connection with cancer and cancer stem cells.
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Affiliation(s)
| | | | | | - Mauricio A. Retamal
- Programa de Comunicación Celular en Cáncer, Facultad de Medicina Clínica Alemana, Universidad del Desarrollo, República de Honduras 12740, Las Condes, Santiago 7610496, Chile; (I.M.L.-F.); (M.G.S.-G.); (M.S.N.)
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2
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Oliveira MC, Cordeiro RM, Bogaerts A. Effect of lipid oxidation on the channel properties of Cx26 hemichannels: A molecular dynamics study. Arch Biochem Biophys 2023; 746:109741. [PMID: 37689256 DOI: 10.1016/j.abb.2023.109741] [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] [Received: 05/23/2023] [Revised: 07/10/2023] [Accepted: 09/05/2023] [Indexed: 09/11/2023]
Abstract
Intercellular communication plays a crucial role in cancer, as well as other diseases, such as inflammation, tissue degeneration, and neurological disorders. One of the proteins responsible for this, are connexins (Cxs), which come together to form a hemichannel. When two hemichannels of opposite cells interact with each other, they form a gap junction (GJ) channel, connecting the intracellular space of these cells. They allow the passage of ions, reactive oxygen and nitrogen species (RONS), and signaling molecules from the interior of one cell to another cell, thus playing an essential role in cell growth, differentiation, and homeostasis. The importance of GJs for disease induction and therapy development is becoming more appreciated, especially in the context of oncology. Studies have shown that one of the mechanisms to control the formation and disruption of GJs is mediated by lipid oxidation pathways, but the underlying mechanisms are not well understood. In this study, we performed atomistic molecular dynamics simulations to evaluate how lipid oxidation influences the channel properties of Cx26 hemichannels, such as channel gating and permeability. Our results demonstrate that the Cx26 hemichannel is more compact in the presence of oxidized lipids, decreasing its pore diameter at the extracellular side and increasing it at the amino terminus domains, respectively. The permeability of the Cx26 hemichannel for water and RONS molecules is higher in the presence of oxidized lipids. The latter may facilitate the intracellular accumulation of RONS, possibly increasing oxidative stress in cells. A better understanding of this process will help to enhance the efficacy of oxidative stress-based cancer treatments.
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Affiliation(s)
- Maria C Oliveira
- Plasma Lab for Applications in Sustainability and Medicine-Antwerp (PLASMANT), Department of Chemistry, University of Antwerp, Universiteitsplein 1, B-2610, Antwerp, Belgium.
| | - Rodrigo M Cordeiro
- Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Avenida dos Estados 5001, CEP 09210-580, Santo André, SP, Brazil
| | - Annemie Bogaerts
- Plasma Lab for Applications in Sustainability and Medicine-Antwerp (PLASMANT), Department of Chemistry, University of Antwerp, Universiteitsplein 1, B-2610, Antwerp, Belgium
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Fernández-Olivares A, Durán-Jara E, Verdugo DA, Fiori MC, Altenberg GA, Stehberg J, Alfaro I, Calderón JF, Retamal MA. Extracellular Cysteines Are Critical to Form Functional Cx46 Hemichannels. Int J Mol Sci 2022; 23:7252. [PMID: 35806258 PMCID: PMC9266770 DOI: 10.3390/ijms23137252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 06/16/2022] [Accepted: 06/18/2022] [Indexed: 12/10/2022] Open
Abstract
Connexin (Cxs) hemichannels participate in several physiological and pathological processes, but the molecular mechanisms that control their gating remain elusive. We aimed at determining the role of extracellular cysteines (Cys) in the gating and function of Cx46 hemichannels. We studied Cx46 and mutated all of its extracellular Cys to alanine (Ala) (one at a time) and studied the effects of the Cys mutations on Cx46 expression, localization, and hemichannel activity. Wild-type Cx46 and Cys mutants were expressed at comparable levels, with similar cellular localization. However, functional experiments showed that hemichannels formed by the Cys mutants did not open either in response to membrane depolarization or removal of extracellular divalent cations. Molecular-dynamics simulations showed that Cys mutants may show a possible alteration in the electrostatic potential of the hemichannel pore and an altered disposition of important residues that could contribute to the selectivity and voltage dependency in the hemichannels. Replacement of extracellular Cys resulted in "permanently closed hemichannels", which is congruent with the inhibition of the Cx46 hemichannel by lipid peroxides, through the oxidation of extracellular Cys. These results point to the modification of extracellular Cys as potential targets for the treatment of Cx46-hemichannel associated pathologies, such as cataracts and cancer, and may shed light into the gating mechanisms of other Cx hemichannels.
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Affiliation(s)
- Ainoa Fernández-Olivares
- Programa de Comunicación Celular en Cáncer, Facultad de Medicina Clínica Alemana, Universidad del Desarrollo, Santiago 7780272, Chile; (A.F.-O.); (I.A.)
| | - Eduardo Durán-Jara
- Centro de Medicina Regenerativa, Facultad de Medicina Clínica Alemana, Universidad del Desarrollo, Santiago 7780272, Chile;
| | - Daniel A. Verdugo
- Laboratorio de Neurobiología, Instituto de Ciencias Biomédicas, Facultad de Medicina y Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago 7780272, Chile; (D.A.V.); (J.S.)
| | - Mariana C. Fiori
- Department of Cell Physiology and Molecular Biophysics and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX 79430-6551, USA; (M.C.F.); (G.A.A.)
| | - Guillermo A. Altenberg
- Department of Cell Physiology and Molecular Biophysics and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX 79430-6551, USA; (M.C.F.); (G.A.A.)
| | - Jimmy Stehberg
- Laboratorio de Neurobiología, Instituto de Ciencias Biomédicas, Facultad de Medicina y Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago 7780272, Chile; (D.A.V.); (J.S.)
| | - Iván Alfaro
- Programa de Comunicación Celular en Cáncer, Facultad de Medicina Clínica Alemana, Universidad del Desarrollo, Santiago 7780272, Chile; (A.F.-O.); (I.A.)
- Centro Científico y Tecnológico de Excelencia Ciencia & Vida, Santiago 7690000, Chile
| | - Juan Francisco Calderón
- Centro de Genética y Genómica, Facultad de Medicina Clínica Alemana, Universidad del Desarrollo, Santiago 7780272, Chile
| | - Mauricio A. Retamal
- Programa de Comunicación Celular en Cáncer, Facultad de Medicina Clínica Alemana, Universidad del Desarrollo, Santiago 7780272, Chile; (A.F.-O.); (I.A.)
- Centro Científico y Tecnológico de Excelencia Ciencia & Vida, Santiago 7690000, Chile
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina Clínica Alemana, Universidad del Desarrollo, Santiago 7690000, Chile
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Retamal MA, Altenberg GA. Role and Posttranslational Regulation of Cx46 Hemichannels and Gap Junction Channels in the Eye Lens. Front Physiol 2022; 13:864948. [PMID: 35431975 PMCID: PMC9006113 DOI: 10.3389/fphys.2022.864948] [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: 01/29/2022] [Accepted: 03/14/2022] [Indexed: 12/31/2022] Open
Abstract
Connexins are a family of proteins that can form two distinct types of channels: hemichannels and gap junction channels. Hemichannels are composed of six connexin subunits and when open allow for exchanges between the cytoplasm and the extracellular milieu. Gap junction channels are formed by head-to-head docking of two hemichannels in series, each one from one of two adjacent cells. These channels allow for exchanges between the cytoplasms of contacting cells. The lens is a transparent structure located in the eye that focuses light on the retina. The transparency of the lens depends on its lack of blood irrigation and the absence of organelles in its cells. To survive such complex metabolic scenario, lens cells express Cx43, Cx46 and Cx50, three connexins isoforms that form hemichannels and gap junction channels that allow for metabolic cooperation between lens cells. This review focuses on the roles of Cx46 hemichannels and gap junction channels in the lens under physiological conditions and in the formation of cataracts, with emphasis on the modulation by posttranslational modifications.
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Affiliation(s)
- Mauricio A. Retamal
- Universidad del Desarrollo, Centro de Fisiología Celular e Integrativa, Clínica Alemana Facultad de Medicina, Santiago, Chile
- Universidad del Desarrollo, Programa de Comunicación Celular en Cáncer, Clínica Alemana Facultad de Medicina, Santiago, Chile
- Department of Cell Physiology and Molecular Biophysics, and Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, United States
- *Correspondence: Mauricio A. Retamal, ; Guillermo A. Altenberg,
| | - Guillermo A. Altenberg
- Department of Cell Physiology and Molecular Biophysics, and Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, United States
- *Correspondence: Mauricio A. Retamal, ; Guillermo A. Altenberg,
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Retamal MA. Carbon Monoxide Modulates Connexin Function through a Lipid Peroxidation-Dependent Process: A Hypothesis. Front Physiol 2016; 7:259. [PMID: 27445849 PMCID: PMC4923120 DOI: 10.3389/fphys.2016.00259] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 06/13/2016] [Indexed: 12/13/2022] Open
Abstract
Hemichannels are ion channels composed of six connexins (Cxs), and they have the peculiarity to be permeable not only to ions, but also to molecules such as ATP and glutamate. Under physiological conditions they present a low open probability, which is sufficient to enable them to participate in several physiological functions. However, massive and/or prolonged hemichannel opening induces or accelerates cell death. Therefore, the study of the molecular mechanisms that control hemichannel activity appears to be essential for understanding several physiological and pathological processes. Carbon monoxide (CO) is a gaseous transmitter that modulates many cellular processes, some of them through modulation of ion channel activity. CO exerts its biological actions through the activation of guanylate cyclase and/or inducing direct carbonylation of proline, threonine, lysine, and arginine. It is well accepted that guanylate cyclase dependent pathway and direct carbonylation, are not sensitive to reducing agents. However, it is important to point out that CO—through a lipid peroxide dependent process—can also induce a secondary carbonylation in cysteine groups, which is sensitive to reducing agents. Recently, in our laboratory we demonstrated that the application of CO donors to the bath solution inhibited Cx46 hemichannel currents in Xenopus laevis oocytes, a phenomenon that was fully reverted by reducing agents. Therefore, a plausible mechanism of CO-induced Cx46 hemichannel inhibition is through Cx46-lipid oxidation. In this work, I will present current evidence and some preliminary results that support the following hypothesis: Carbon monoxide inhibits Cx46 HCs through a lipid peroxidation-dependent process. The main goal of this paper is to broaden the scientific community interest in studying the relationship between CO-Fatty acids and hemichannels, which will pave the way to more research directed to the understanding of the molecular mechanism(s) that control the opening and closing of hemichannels in both physiological and pathological conditions.
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Affiliation(s)
- Mauricio A Retamal
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo Santiago, Chile
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Retamal MA, León-Paravic CG, Ezquer M, Ezquer F, Rio RD, Pupo A, Martínez AD, González C. Carbon monoxide: A new player in the redox regulation of connexin hemichannels. IUBMB Life 2015; 67:428-37. [DOI: 10.1002/iub.1388] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2015] [Accepted: 05/05/2015] [Indexed: 01/23/2023]
Affiliation(s)
- Mauricio A. Retamal
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina; Clínica Alemana Universidad del Desarrollo; Santiago Chile
| | - Carmen G. León-Paravic
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina; Clínica Alemana Universidad del Desarrollo; Santiago Chile
| | - Marcelo Ezquer
- Centro de Medicina Regenerativa, Facultad de Medicina; Clínica Alemana Universidad del Desarrollo; Santiago Chile
| | - Fernando Ezquer
- Centro de Medicina Regenerativa, Facultad de Medicina; Clínica Alemana Universidad del Desarrollo; Santiago Chile
| | - Rodrigo Del Rio
- Centro de Investigación Biomédica; Universidad Autónoma de Chile; Santiago Chile
| | - Amaury Pupo
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias; Instituto de Neurociencia; Universidad de Valparaíso; Valparaíso Chile
| | - Agustín D. Martínez
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias; Instituto de Neurociencia; Universidad de Valparaíso; Valparaíso Chile
| | - Carlos González
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias; Instituto de Neurociencia; Universidad de Valparaíso; Valparaíso Chile
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León-Paravic CG, Figueroa VA, Guzmán DJ, Valderrama CF, Vallejos AA, Fiori MC, Altenberg GA, Reuss L, Retamal MA. Carbon monoxide (CO) is a novel inhibitor of connexin hemichannels. J Biol Chem 2014; 289:36150-7. [PMID: 25384983 PMCID: PMC4276878 DOI: 10.1074/jbc.m114.602243] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Revised: 11/07/2014] [Indexed: 12/13/2022] Open
Abstract
Hemichannels (HCs) are hexamers of connexins that can form gap-junction channels at points of cell contacts or "free HCs" at non-contacting regions. HCs are involved in paracrine and autocrine cell signaling, and under pathological conditions may induce and/or accelerate cell death. Therefore, studies of HC regulation are of great significance. Nitric oxide affects the activity of Cx43 and Cx46 HCs, whereas carbon monoxide (CO), another gaseous transmitter, modulates the activity of several ion channels, but its effect on HCs has not been explored. We studied the effect of CO donors (CORMs) on Cx46 HCs expressed in Xenopus laevis oocytes using two-electrode voltage clamp and on Cx43 and Cx46 expressed in HeLa cells using a dye-uptake technique. CORM-2 inhibited Cx46 HC currents in a concentration-dependent manner. The C-terminal domain and intracellular Cys were not necessary for the inhibition. The effect of CORM-2 was not prevented by guanylyl-cyclase, protein kinase G, or thioredoxin inhibitors, and was not due to endocytosis of HCs. However, the effect of CORM-2 was reversed by reducing agents that act extracellularly. Additionally, CO inhibited dye uptake of HeLa cells expressing Cx43 or Cx46, and MCF-7 cells, which endogenously express Cx43 and Cx46. Because CORM-2 carbonylates Cx46 in vitro and induces conformational changes, a direct effect of that CO on Cx46 is possible. The inhibition of HCs could help to understand some of the biological actions of CO in physiological and pathological conditions.
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Affiliation(s)
- Carmen G León-Paravic
- From the Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile 7690000 and
| | - Vania A Figueroa
- From the Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile 7690000 and
| | - Diego J Guzmán
- From the Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile 7690000 and
| | - Carlos F Valderrama
- From the Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile 7690000 and
| | - Antonio A Vallejos
- From the Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile 7690000 and
| | - Mariana C Fiori
- the Department of Cell Physiology and Molecular Biophysics, and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas 79430
| | - Guillermo A Altenberg
- the Department of Cell Physiology and Molecular Biophysics, and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas 79430
| | - Luis Reuss
- the Department of Cell Physiology and Molecular Biophysics, and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas 79430
| | - Mauricio A Retamal
- From the Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile 7690000 and the Department of Cell Physiology and Molecular Biophysics, and Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas 79430
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Eugenin EA, Basilio D, Sáez JC, Orellana JA, Raine CS, Bukauskas F, Bennett MVL, Berman JW. The role of gap junction channels during physiologic and pathologic conditions of the human central nervous system. J Neuroimmune Pharmacol 2012; 7:499-518. [PMID: 22438035 PMCID: PMC3638201 DOI: 10.1007/s11481-012-9352-5] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2012] [Accepted: 02/28/2012] [Indexed: 12/15/2022]
Abstract
Gap junctions (GJs) are expressed in most cell types of the nervous system, including neuronal stem cells, neurons, astrocytes, oligodendrocytes, cells of the blood brain barrier (endothelial cells and astrocytes) and under inflammatory conditions in microglia/macrophages. GJs connect cells by the docking of two hemichannels, one from each cell with each hemichannel being formed by 6 proteins named connexins (Cx). Unapposed hemichannels (uHC) also can be open on the surface of the cells allowing the release of different intracellular factors to the extracellular space. GJs provide a mechanism of cell-to-cell communication between adjacent cells that enables the direct exchange of intracellular messengers, such as calcium, nucleotides, IP(3), and diverse metabolites, as well as electrical signals that ultimately coordinate tissue homeostasis, proliferation, differentiation, metabolism, cell survival and death. Despite their essential functions in physiological conditions, relatively little is known about the role of GJs and uHC in human diseases, especially within the nervous system. The focus of this review is to summarize recent findings related to the role of GJs and uHC in physiologic and pathologic conditions of the central nervous system.
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Affiliation(s)
- Eliseo A Eugenin
- Department of Pathology, F727, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, USA.
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Retamal MA, Evangelista-Martínez F, León-Paravic CG, Altenberg GA, Reuss L. Biphasic effect of linoleic acid on connexin 46 hemichannels. Pflugers Arch 2011; 461:635-43. [PMID: 21360038 PMCID: PMC3108795 DOI: 10.1007/s00424-011-0936-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Revised: 02/01/2011] [Accepted: 02/04/2011] [Indexed: 01/05/2023]
Abstract
Connexins form hemichannels at undocked plasma membranes and gap-junction channels (GJCs) at intercellular contacting zones. Under physiological conditions, hemichannels have low open probabilities, but their activation under pathological conditions, such as ischemia, induces and/or accelerates cell death. Connexin 46 (Cx46) is a major connexin of the lens, and mutations of this connexin induce cataracts. Here, we report the effects of linoleic acid (LA) on the electrical properties of Cx46 GJCs and hemichannels expressed in Xenopus laevis oocytes. LA has a biphasic effect, increasing hemichannel current at 0.1 μM and decreasing it at concentrations of 100 μM or higher. The effects of extracellular and microinjected LA conjugated to coenzyme A (LA-CoA) suggest that the current activation site is accessible from the intracellular but not extracellular compartment, whereas the current inhibitory site is either located in a region of the hemichannel pore inaccessible to intracellular LA-CoA, or requires crossing of LA through an organelle membrane. Experiments with other fatty acids demonstrated that the block of hemichannels depends on the presence of a hydrogenated double bond at position 9 and is directly proportional to the number of double bonds. Experiments in paired oocytes expressing Cx46 showed that LA does not affect GJCs. The block by unsaturated fatty acids reported here opens the possibility that increases in the concentration of these lipids in the lens induce cataract formation by blocking Cx46 hemichannels.
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Affiliation(s)
- Mauricio A Retamal
- Laboratorio de Fisiología, Clínica Alemana-Universidad del Desarrollo, Santiago, Chile.
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Cell membrane permeabilization via connexin hemichannels in living and dying cells. Exp Cell Res 2010; 316:2377-89. [DOI: 10.1016/j.yexcr.2010.05.026] [Citation(s) in RCA: 143] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Revised: 05/20/2010] [Accepted: 05/21/2010] [Indexed: 12/31/2022]
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