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Cárdenas-García SP, Ijaz S, Pereda AE. The components of an electrical synapse as revealed by expansion microscopy of a single synaptic contact. eLife 2024; 13:e91931. [PMID: 38994821 PMCID: PMC11333041 DOI: 10.7554/elife.91931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 07/08/2024] [Indexed: 07/13/2024] Open
Abstract
Most nervous systems combine both transmitter-mediated and direct cell-cell communication, known as 'chemical' and 'electrical' synapses, respectively. Chemical synapses can be identified by their multiple structural components. Electrical synapses are, on the other hand, generally defined by the presence of a 'gap junction' (a cluster of intercellular channels) between two neuronal processes. However, while gap junctions provide the communicating mechanism, it is unknown whether electrical transmission requires the contribution of additional cellular structures. We investigated this question at identifiable single synaptic contacts on the zebrafish Mauthner cells, at which gap junctions coexist with specializations for neurotransmitter release and where the contact unequivocally defines the anatomical limits of a synapse. Expansion microscopy of these single contacts revealed a detailed map of the incidence and spatial distribution of proteins pertaining to various synaptic structures. Multiple gap junctions of variable size were identified by the presence of their molecular components. Remarkably, most of the synaptic contact's surface was occupied by interleaving gap junctions and components of adherens junctions, suggesting a close functional association between these two structures. In contrast, glutamate receptors were confined to small peripheral portions of the contact, indicating that most of the synaptic area functions as an electrical synapse. Thus, our results revealed the overarching organization of an electrical synapse that operates with not one, but multiple gap junctions, in close association with structural and signaling molecules known to be components of adherens junctions. The relationship between these intercellular structures will aid in establishing the boundaries of electrical synapses found throughout animal connectomes and provide insight into the structural organization and functional diversity of electrical synapses.
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Affiliation(s)
- Sandra P Cárdenas-García
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of MedicineBronxUnited States
| | - Sundas Ijaz
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of MedicineBronxUnited States
| | - Alberto E Pereda
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of MedicineBronxUnited States
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2
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Ribelayga CP, O’Brien J. When microscopy and electrophysiology meet connectomics-Steve Massey's contribution to unraveling the structure and function of the rod/cone gap junction. FRONTIERS IN OPHTHALMOLOGY 2023; 3:1305131. [PMID: 38983007 PMCID: PMC11182179 DOI: 10.3389/fopht.2023.1305131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Accepted: 10/31/2023] [Indexed: 07/11/2024]
Abstract
Electrical synapses, formed of gap junctions, are ubiquitous components of the central nervous system (CNS) that shape neuronal circuit connectivity and dynamics. In the retina, electrical synapses can create a circuit, control the signal-to-noise ratio in individual neurons, and support the coordinated neuronal firing of ganglion cells, hence, regulating signal processing at the network, single-cell, and dendritic level. We, the authors, and Steve Massey have had a long interest in gap junctions in retinal circuits, in general, and in the network of photoreceptors, in particular. Our combined efforts, based on a wide array of techniques of molecular biology, microscopy, and electrophysiology, have provided fundamental insights into the molecular structure and properties of the rod/cone gap junction. Yet, a full understanding of how rod/cone coupling controls circuit dynamics necessitates knowing its operating range. It is well established that rod/cone coupling can be greatly reduced or eliminated by bright-light adaptation or pharmacological treatment; however, the upper end of its dynamic range has long remained elusive. This held true until Steve Massey's recent interest for connectomics led to the development of a new strategy to assess this issue. The effort proved effective in establishing, with precision, the connectivity rules between rods and cones and estimating the theoretical upper limit of rod/cone electrical coupling. Comparing electrophysiological measurements and morphological data indicates that under pharmacological manipulation, rod/cone coupling can reach the theoretical maximum of its operating range, implying that, under these conditions, all the gap junction channels present at the junctions are open. As such, channel open probability is likely the main determinant of rod/cone coupling that can change momentarily in a time-of-day- and light-dependent manner. In this article we briefly review our current knowledge of the molecular structure of the rod/cone gap junction and of the mechanisms behind its modulation, and we highlight the recent work led by Steve Massey. Steve's contribution has been critical toward asserting the modulation depth of rod/cone coupling as well as elevating the rod/cone gap junction as one of the most suitable models to examine the role of electrical synapses and their plasticity in neural processing.
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Affiliation(s)
- Christophe P. Ribelayga
- Department of Vision Sciences, University of Houston College of Optometry, Houston, TX, United States
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3
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Cárdenas-García SP, Ijaz S, Pereda AE. The components of an electrical synapse as revealed by expansion microscopy of a single synaptic contact. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.25.550347. [PMID: 37546897 PMCID: PMC10402082 DOI: 10.1101/2023.07.25.550347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/08/2023]
Abstract
Most nervous systems combine both transmitter-mediated and direct cell-cell communication, known as 'chemical' and 'electrical' synapses, respectively. Chemical synapses can be identified by their multiple structural components. Electrical synapses are, on the other hand, generally defined by the presence of a 'gap junction' (a cluster of intercellular channels) between two neuronal processes. However, while gap junctions provide the communicating mechanism, it is unknown whether electrical transmission requires the contribution of additional cellular structures. We investigated this question at identifiable single synaptic contacts on the zebrafish Mauthner cells, at which gap junctions coexist with specializations for neurotransmitter release and where the contact defines the anatomical limits of a synapse. Expansion microscopy of these contacts revealed a detailed map of the incidence and spatial distribution of proteins pertaining to various synaptic structures. Multiple gap junctions of variable size were identified by the presence of their molecular components. Remarkably, most of the synaptic contact's surface was occupied by interleaving gap junctions and components of adherens junctions, suggesting a close functional association between these two structures. In contrast, glutamate receptors were confined to small peripheral portions of the contact, indicating that most of the synaptic area works as an electrical synapse. Thus, our results revealed the overarching organization of an electrical synapse that operates with not one, but multiple gap junctions, in close association with structural and signaling molecules known to be components of AJs. The relationship between these intercellular structures will aid in establishing the boundaries of electrical synapses found throughout animal connectomes and provide insight into the structural organization and functional diversity of electrical synapses.
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Affiliation(s)
- Sandra P. Cárdenas-García
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Sundas Ijaz
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Alberto E. Pereda
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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4
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Lee SN, Cho HJ, Jeong H, Ryu B, Lee HJ, Kim M, Yoo J, Woo JS, Lee HH. Cryo-EM structures of human Cx36/GJD2 neuronal gap junction channel. Nat Commun 2023; 14:1347. [PMID: 36906653 PMCID: PMC10008584 DOI: 10.1038/s41467-023-37040-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 02/28/2023] [Indexed: 03/13/2023] Open
Abstract
Connexin 36 (Cx36) is responsible for signal transmission in electrical synapses by forming interneuronal gap junctions. Despite the critical role of Cx36 in normal brain function, the molecular architecture of the Cx36 gap junction channel (GJC) is unknown. Here, we determine cryo-electron microscopy structures of Cx36 GJC at 2.2-3.6 Å resolutions, revealing a dynamic equilibrium between its closed and open states. In the closed state, channel pores are obstructed by lipids, while N-terminal helices (NTHs) are excluded from the pore. In the open state with pore-lining NTHs, the pore is more acidic than those in Cx26 and Cx46/50 GJCs, explaining its strong cation selectivity. The conformational change during channel opening also includes the α-to-π-helix transition of the first transmembrane helix, which weakens the protomer-protomer interaction. Our structural analyses provide high resolution information on the conformational flexibility of Cx36 GJC and suggest a potential role of lipids in the channel gating.
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Affiliation(s)
- Seu-Na Lee
- Department of Life Sciences, Korea University, Seoul, 02841, Republic of Korea
| | - Hwa-Jin Cho
- Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul, 08826, Korea
| | - Hyeongseop Jeong
- Center for Research Equipment, Korea Basic Science Institute, Chungcheongbuk-do, 28119, Korea
| | - Bumhan Ryu
- Research Solution Center, Institute for Basic Science, Daejeon, 34126, Republic of Korea
| | - Hyuk-Joon Lee
- Department of Life Sciences, Korea University, Seoul, 02841, Republic of Korea
| | - Minsoo Kim
- Department of Physics, Sungkyunkwan University, Suwon, 16419, South Korea
| | - Jejoong Yoo
- Department of Physics, Sungkyunkwan University, Suwon, 16419, South Korea
| | - Jae-Sung Woo
- Department of Life Sciences, Korea University, Seoul, 02841, Republic of Korea.
| | - Hyung Ho Lee
- Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul, 08826, Korea.
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5
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Ishibashi M, Keung J, Morgans CW, Aicher SA, Carroll JR, Singer JH, Jia L, Li W, Fahrenfort I, Ribelayga CP, Massey SC. Analysis of rod/cone gap junctions from the reconstruction of mouse photoreceptor terminals. eLife 2022; 11:73039. [PMID: 35471186 PMCID: PMC9170248 DOI: 10.7554/elife.73039] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 04/25/2022] [Indexed: 12/14/2022] Open
Abstract
Electrical coupling, mediated by gap junctions, contributes to signal averaging, synchronization, and noise reduction in neuronal circuits. In addition, gap junctions may also provide alternative neuronal pathways. However, because they are small and especially difficult to image, gap junctions are often ignored in large-scale 3D reconstructions. Here, we reconstruct gap junctions between photoreceptors in the mouse retina using serial blockface-scanning electron microscopy, focused ion beam-scanning electron microscopy, and confocal microscopy for the gap junction protein Cx36. An exuberant spray of fine telodendria extends from each cone pedicle (including blue cones) to contact 40-50 nearby rod spherules at sites of Cx36 labeling, with approximately 50 Cx36 clusters per cone pedicle and 2-3 per rod spherule. We were unable to detect rod/rod or cone/cone coupling. Thus, rod/cone coupling accounts for nearly all gap junctions between photoreceptors. We estimate a mean of 86 Cx36 channels per rod/cone pair, which may provide a maximum conductance of ~1200 pS, if all gap junction channels were open. This is comparable to the maximum conductance previously measured between rod/cone pairs in the presence of a dopamine antagonist to activate Cx36, suggesting that the open probability of gap junction channels can approach 100% under certain conditions.
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Affiliation(s)
- Munenori Ishibashi
- Richard Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, University of Texas at Houston, Houston, United States
| | - Joyce Keung
- Richard Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, University of Texas at Houston, Houston, United States
| | - Catherine W Morgans
- Department of Chemical Physiology & Biochemistry, Oregon Health & Science University, Portland, United States
| | - Sue A Aicher
- Department of Chemical Physiology & Biochemistry, Oregon Health & Science University, Portland, United States
| | - James R Carroll
- Department of Chemical Physiology & Biochemistry, Oregon Health & Science University, Portland, United States
| | - Joshua H Singer
- Department of Biology, University of Maryland, College Park, College Park, United States
| | - Li Jia
- Retinal Neurophysiology Section, National Eye Institute, National Institutes of Health, Bethesda, United States
| | - Wei Li
- Retinal Neurophysiology Section, National Eye Institute, National Institutes of Health, Bethesda, United States
| | - Iris Fahrenfort
- Richard Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, University of Texas at Houston, Houston, United States
| | - Christophe P Ribelayga
- Richard Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, University of Texas at Houston, Houston, United States
| | - Stephen C Massey
- Richard Ruiz Department of Ophthalmology and Visual Science, McGovern Medical School, University of Texas at Houston, Houston, United States
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6
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Kraujalis T, Gudaitis L, Kraujaliene L, Snipas M, Palacios-Prado N, Verselis VK. The Amino Terminal Domain and Modulation of Connexin36 Gap Junction Channels by Intracellular Magnesium Ions. Front Physiol 2022; 13:839223. [PMID: 35264979 PMCID: PMC8899287 DOI: 10.3389/fphys.2022.839223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2021] [Accepted: 01/28/2022] [Indexed: 11/13/2022] Open
Abstract
Electrical synapses between neurons in the mammalian CNS are predominantly formed of the connexin36 (Cx36) gap junction (GJ) channel protein. Unique among GJs formed of a number of other members of the Cx gene family, Cx36 GJs possess a high sensitivity to intracellular Mg2+ that can robustly act to modulate the strength of electrical synaptic transmission. Although a putative Mg2+ binding site was previously identified to reside in the aqueous pore in the first extracellular (E1) loop domain, the involvement of the N-terminal (NT) domain in the atypical response of Cx36 GJs to pH was shown to depend on intracellular levels of Mg2+. In this study, we examined the impact of amino acid substitutions in the NT domain on Mg2+ modulation of Cx36 GJs, focusing on positions predicted to line the pore funnel, which constitutes the cytoplasmic entrance of the channel pore. We find that charge substitutions at the 8th, 13th, and 18th positions had pronounced effects on Mg2+ sensitivity, particularly at position 13 at which an A13K substitution completely abolished sensitivity to Mg2+. To assess potential mechanisms of Mg2+ action, we constructed and tested a series of mathematical models that took into account gating of the component hemichannels in a Cx36 GJ channel as well as Mg2+ binding to each hemichannel in open and/or closed states. Simultaneous model fitting of measurements of junctional conductance, gj, and transjunctional Mg2+ fluxes using a fluorescent Mg2+ indicator suggested that the most viable mechanism for Cx36 regulation by Mg2+ entails the binding of Mg2+ to and subsequent stabilization of the closed state in each hemichannel. Reduced permeability to Mg2+ was also evident, particularly for the A13K substitution, but homology modeling of all charge-substituted NT variants showed only a moderate correlation between a reduction in the negative electrostatic potential and a reduction in the permeability to Mg2+ ions. Given the reported role of the E1 domain in Mg2+ binding together with the impact of NT substitutions on gating and the apparent state-dependence of Mg2+ binding, this study suggests that the NT domain can be an integral part of Mg2+ modulation of Cx36 GJs likely through the coupling of conformational changes between NT and E1 domains.
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Affiliation(s)
- Tadas Kraujalis
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
- Department of Applied Informatics, Kaunas University of Technology, Kaunas, Lithuania
- *Correspondence: Tadas Kraujalis,
| | - Lukas Gudaitis
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Lina Kraujaliene
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Mindaugas Snipas
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
- Department of Mathematical Modelling, Kaunas University of Technology, Kaunas, Lithuania
| | - Nicolás Palacios-Prado
- Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile
- Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaiso, Valparaíso, Chile
| | - Vytas K. Verselis
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, NY, United States
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Ogazon del Toro A, Jimenez L, Serrano Rubi M, Castillo A, Hinojosa L, Martinez Rendon J, Cereijido M, Ponce A. Prostaglandin E2 Enhances Gap Junctional Intercellular Communication in Clonal Epithelial Cells. Int J Mol Sci 2021; 22:5813. [PMID: 34071686 PMCID: PMC8198183 DOI: 10.3390/ijms22115813] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Revised: 03/30/2021] [Accepted: 03/30/2021] [Indexed: 12/12/2022] Open
Abstract
Prostaglandins are a group of lipids that produce diverse physiological and pathological effects. Among them, prostaglandin E2 (PGE2) stands out for the wide variety of functions in which it participates. To date, there is little information about the influence of PGE2 on gap junctional intercellular communication (GJIC) in any type of tissue, including epithelia. In this work, we set out to determine whether PGE2 influences GJIC in epithelial cells (MDCK cells). To this end, we performed dye (Lucifer yellow) transfer assays to compare GJIC of MDCK cells treated with PGE2 and untreated cells. Our results indicated that (1) PGE2 induces a statistically significant increase in GJIC from 100 nM and from 15 min after its addition to the medium, (2) such effect does not require the synthesis of new mRNA or proteins subunits but rather trafficking of subunits already synthesized, and (3) such effect is mediated by the E2 receptor, which, in turn, triggers a signaling pathway that includes activation of adenylyl cyclase and protein kinase A (PKA). These results widen the knowledge regarding modulation of gap junctional intercellular communication by prostaglandins.
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Affiliation(s)
| | | | | | | | | | | | | | - Arturo Ponce
- Department of Physiology, Biophysics and Neurosciences, CINVESTAV-IPN, CDMX, México C.P. 07360, Mexico; (A.O.d.T.); (L.J.); (M.S.R.); (A.C.); (L.H.); (J.M.R.); (M.C.)
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8
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Khan R, Jiang X, Hameed U, Shi Q. Role of Lipid Metabolism and Signaling in Mammalian Oocyte Maturation, Quality, and Acquisition of Competence. Front Cell Dev Biol 2021; 9:639704. [PMID: 33748128 PMCID: PMC7973101 DOI: 10.3389/fcell.2021.639704] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Accepted: 02/08/2021] [Indexed: 12/31/2022] Open
Abstract
It has been found that the quality of oocytes from obese women has been compromised and subsequent embryos displayed arrested development. The compromised quality may be either due to the poor or rich metabolic conditions such as imbalance or excession of lipids during oocyte development. Generally, lipids are mainly stored in the form of lipid droplets and are an important source of energy metabolism. Similarly, lipids are also essential signaling molecules involved in various biological cascades of oocyte maturation, growth and oocyte competence acquisition. To understand the role of lipids in controlling the oocyte development, we have comprehensively and concisely reviewed the literature and described the role of lipid metabolism in oocyte quality and maturation. Moreover, we have also presented a simplified model of fatty acid metabolism along with its implication on determining the oocyte quality and cryopreservation for fertilization.
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Affiliation(s)
- Ranjha Khan
- First Affiliated Hospital of USTC, Hefei National Laboratory for Physical Sciences at Microscale, The CAS Key Laboratory of Innate Immunity and Chronic Disease, School of Basic Medical Sciences, Division of Life Sciences and Medicine, CAS Center for Excellence in Molecular Cell Science, Collaborative Innovation Center of Genetics and Development, University of Science and Technology of China, Hefei, China
| | - Xiaohua Jiang
- First Affiliated Hospital of USTC, Hefei National Laboratory for Physical Sciences at Microscale, The CAS Key Laboratory of Innate Immunity and Chronic Disease, School of Basic Medical Sciences, Division of Life Sciences and Medicine, CAS Center for Excellence in Molecular Cell Science, Collaborative Innovation Center of Genetics and Development, University of Science and Technology of China, Hefei, China
| | - Uzma Hameed
- Institute of Industrial Biotechnology, Government College University, Lahore, Pakistan
| | - Qinghua Shi
- First Affiliated Hospital of USTC, Hefei National Laboratory for Physical Sciences at Microscale, The CAS Key Laboratory of Innate Immunity and Chronic Disease, School of Basic Medical Sciences, Division of Life Sciences and Medicine, CAS Center for Excellence in Molecular Cell Science, Collaborative Innovation Center of Genetics and Development, University of Science and Technology of China, Hefei, China
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9
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Alcamí P, Pereda AE. Beyond plasticity: the dynamic impact of electrical synapses on neural circuits. Nat Rev Neurosci 2019; 20:253-271. [DOI: 10.1038/s41583-019-0133-5] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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10
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Iyyathurai J, Wang N, D'hondt C, Jiang JX, Leybaert L, Bultynck G. The SH3-binding domain of Cx43 participates in loop/tail interactions critical for Cx43-hemichannel activity. Cell Mol Life Sci 2018; 75:2059-2073. [PMID: 29218600 PMCID: PMC6318120 DOI: 10.1007/s00018-017-2722-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 11/24/2017] [Accepted: 11/27/2017] [Indexed: 12/19/2022]
Abstract
Connexin 43 (Cx43) hemichannels establish local signaling networks via the release of ATP and other molecules, but their excessive opening may result in cell death. Hence, the activity of Cx43-hemichannels ought to be critically controlled. This involves interactions between the C-terminal tail (CT) and the cytoplasmic loop (CL), more particularly the L2 domain within CL. Previous work revealed an important role for the last nine amino acids of the Cx43 CT by targeting the L2 domain, as these nine amino acids were sufficient to restore the activity of CT-truncated Cx43-hemichannels. However, we discovered that deletion of the last 19 amino acids of the CT only partially lowered the binding to the L2 domain, indicating that a second L2-binding region is present in the CT. We here provide evidence that the SH3-binding domain is another CT region that targets the L2 domain. At the functional level, the SH3-binding domain was able to restore the activity of CT-truncated Cx43-hemichannels and alleviate the inhibition of full-length Cx43-hemichannels by high intracellular Ca2+ concentration ([Ca2+]i) as demonstrated by various approaches including patch clamp studies of unitary Cx43-hemichannel activity. Finally, we show that in full-length Cx43-hemichannels, deletion of either the SH3-binding domain or the CT9 region suppresses the hemichannel activity, while deletion of both domains completely annihilates the hemichannel activity. These results demonstrate that the Cx43 SH3-binding domain, in addition to the CT9 region, critically controls hemichannel activity at high [Ca2+]i, which may be involved in pathological hemichannel opening.
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Affiliation(s)
- Jegan Iyyathurai
- Laboratory of Molecular and Cellular Signaling, Department Cellular and Molecular Medicine, KU Leuven, Campus Gasthuisberg O/N-1 Bus 802, Herestraat 49, 3000, Louvain, Belgium
| | - Nan Wang
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, De Pintelaan 185, 9000, Ghent, Belgium
| | - Catheleyne D'hondt
- Laboratory of Molecular and Cellular Signaling, Department Cellular and Molecular Medicine, KU Leuven, Campus Gasthuisberg O/N-1 Bus 802, Herestraat 49, 3000, Louvain, Belgium
| | - Jean X Jiang
- Department of Biochemistry and Structural Biology, University of Texas Health Science Center, San Antonio, TX, USA
| | - Luc Leybaert
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, De Pintelaan 185, 9000, Ghent, Belgium
| | - Geert Bultynck
- Laboratory of Molecular and Cellular Signaling, Department Cellular and Molecular Medicine, KU Leuven, Campus Gasthuisberg O/N-1 Bus 802, Herestraat 49, 3000, Louvain, Belgium.
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11
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Raškevičius V, Jotautis V, Rimkutė L, Marandykina A, Kazokaitė M, Kairys V, Skeberdis VA. Molecular basis for potentiation of Cx36 gap junction channel conductance by n-alcohols and general anesthetics. Biosci Rep 2018; 38:BSR20171323. [PMID: 29298877 PMCID: PMC5803492 DOI: 10.1042/bsr20171323] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Revised: 12/22/2017] [Accepted: 01/01/2018] [Indexed: 01/01/2023] Open
Abstract
In our recent study, we have demonstrated that short carbon chain n-alcohols (up to octanol) stimulated while long carbon chain n-alcohols inhibited the conductance of connexin (Cx) 36 (Cx36) gap junction (GJ) channels. In contrast, GJ channels composed of other types of Cxs all were inhibited by n-alcohols independent of their carbon chain length. To identify the putative structural domains of Cx36, responsible for the dual effect of n-alcohols, we performed structural modeling of Cx36 protein docking with hexanol and isoflurane that stimulated as well as nonanol and carbenoxolone that inhibited the conductance of Cx36 GJs and revealed their multiple common docking sites and a single pocket accessible only to hexanol and isoflurane. The pocket is located in the vicinity of three unique cysteine residues, namely C264 in the fourth, and C92 and C87 in the second transmembrane domain of the neighboring Cx36 subunits. To examine the hypothesis that disulphide bonding might be involved in the stimulatory effect of hexanol and isoflurane, we generated cysteine substitutions in Cx36 and demonstrated by a dual whole-cell patch-clamp technique that in HeLa (human cervix carcinoma cell line) and N2A (mouse neuroblastoma cell line) cells these mutations reversed the stimulatory effect of hexanol and isoflurane to inhibitory one, typical of other Cxs that lack respective cysteines and a specific docking pocket for these compounds. Our findings suggest that the stimulatory effect of hexanol and isoflurane on Cx36 GJ conductance could be achieved by re-shuffling of the inter-subunit disulphide bond between C264 and C92 to the intra-subunit one between C264 and C87.
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Affiliation(s)
- Vytautas Raškevičius
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas LT-50162, Lithuania
| | - Vaidas Jotautis
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas LT-50162, Lithuania
| | - Lina Rimkutė
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas LT-50162, Lithuania
| | - Alina Marandykina
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas LT-50162, Lithuania
| | - Mintautė Kazokaitė
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas LT-50162, Lithuania
| | - Visvaldas Kairys
- Institute of Biotechnology, Vilnius University, Vilnius LT-10257, Lithuania
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12
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Leybaert L, Lampe PD, Dhein S, Kwak BR, Ferdinandy P, Beyer EC, Laird DW, Naus CC, Green CR, Schulz R. Connexins in Cardiovascular and Neurovascular Health and Disease: Pharmacological Implications. Pharmacol Rev 2017; 69:396-478. [PMID: 28931622 PMCID: PMC5612248 DOI: 10.1124/pr.115.012062] [Citation(s) in RCA: 171] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Connexins are ubiquitous channel forming proteins that assemble as plasma membrane hemichannels and as intercellular gap junction channels that directly connect cells. In the heart, gap junction channels electrically connect myocytes and specialized conductive tissues to coordinate the atrial and ventricular contraction/relaxation cycles and pump function. In blood vessels, these channels facilitate long-distance endothelial cell communication, synchronize smooth muscle cell contraction, and support endothelial-smooth muscle cell communication. In the central nervous system they form cellular syncytia and coordinate neural function. Gap junction channels are normally open and hemichannels are normally closed, but pathologic conditions may restrict gap junction communication and promote hemichannel opening, thereby disturbing a delicate cellular communication balance. Until recently, most connexin-targeting agents exhibited little specificity and several off-target effects. Recent work with peptide-based approaches has demonstrated improved specificity and opened avenues for a more rational approach toward independently modulating the function of gap junctions and hemichannels. We here review the role of connexins and their channels in cardiovascular and neurovascular health and disease, focusing on crucial regulatory aspects and identification of potential targets to modify their function. We conclude that peptide-based investigations have raised several new opportunities for interfering with connexins and their channels that may soon allow preservation of gap junction communication, inhibition of hemichannel opening, and mitigation of inflammatory signaling.
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Affiliation(s)
- Luc Leybaert
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Paul D Lampe
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Stefan Dhein
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Brenda R Kwak
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Peter Ferdinandy
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Eric C Beyer
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Dale W Laird
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Christian C Naus
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Colin R Green
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
| | - Rainer Schulz
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium (L.L.); Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, Washington (P.D.L.); Institute for Pharmacology, University of Leipzig, Leipzig, Germany (S.D.); Department of Pathology and Immunology, Department of Medical Specialization-Cardiology, University of Geneva, Geneva, Switzerland (B.R.K.); Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary (P.F.); Pharmahungary Group, Szeged, Hungary (P.F.); Department of Pediatrics, University of Chicago, Chicago, Illinois (E.C.B.); Department of Anatomy and Cell Biology, University of Western Ontario, Dental Science Building, London, Ontario, Canada (D.W.L.); Cellular and Physiological Sciences, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada (C.C.N.); Department of Ophthalmology and The New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand (C.R.G.); and Physiologisches Institut, Justus-Liebig-Universität Giessen, Giessen, Germany (R.S.)
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Khajeh M, Rahbarghazi R, Nouri M, Darabi M. Potential role of polyunsaturated fatty acids, with particular regard to the signaling pathways of arachidonic acid and its derivatives in the process of maturation of the oocytes: Contemporary review. Biomed Pharmacother 2017; 94:458-467. [PMID: 28779707 DOI: 10.1016/j.biopha.2017.07.140] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 07/25/2017] [Accepted: 07/27/2017] [Indexed: 01/20/2023] Open
Abstract
Oocyte meiotic maturation is one of the significant physiological requirements for ovulation and fertility. It is believed that Cyclic Adenosine Monophosphate, protein kinase A and protein kinase C pathways along with eicosanoids, particularly prostaglandin E2, and steroids are the key factors regulating mammalian oocyte maturation. The aim of the current study was to highlight the molecular events triggered by arachidonic acid during oocyte meiotic arrest and resumption at the time of gonadotrophin surge. It should be noted that arachidonic acid release is tightly regulated by Follicle-stimulating and Luteinizing hormones during oocyte development.
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Affiliation(s)
- Masoumeh Khajeh
- Department of Biochemistry and Clinical Laboratories, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran; Stem Cell Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Reza Rahbarghazi
- Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz, Iran; Stem Cell Research Center, Tabriz University of Medical Sciences, Tabriz, Iran; Department of Applied Cell Sciences, Faculty of Advanced Medical Sciences, Tabriz University of Medical Sciences, Tabriz, Iran.
| | - Mohammad Nouri
- Department of Biochemistry and Clinical Laboratories, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran; Stem Cell Research Center, Tabriz University of Medical Sciences, Tabriz, Iran; Women's Reproductive Health Research Center, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Masoud Darabi
- Department of Biochemistry and Clinical Laboratories, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran; Stem Cell Research Center, Tabriz University of Medical Sciences, Tabriz, Iran.
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14
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Miller AC, Pereda AE. The electrical synapse: Molecular complexities at the gap and beyond. Dev Neurobiol 2017; 77:562-574. [PMID: 28170151 DOI: 10.1002/dneu.22484] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 01/04/2017] [Accepted: 01/04/2017] [Indexed: 12/21/2022]
Abstract
Gap junctions underlie electrical synaptic transmission between neurons. Generally perceived as simple intercellular channels, "electrical synapses" have demonstrated to be more functionally sophisticated and structurally complex than initially anticipated. Electrical synapses represent an assembly of multiple molecules, consisting of channels, adhesion complexes, scaffolds, regulatory machinery, and trafficking proteins, all required for their proper function and plasticity. Additionally, while electrical synapses are often viewed as strictly symmetric structures, emerging evidence has shown that some components forming electrical synapses can be differentially distributed at each side of the junction. We propose that the molecular complexity and asymmetric distribution of proteins at the electrical synapse provides rich potential for functional diversity. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 562-574, 2017.
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Affiliation(s)
- Adam C Miller
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon
| | - Alberto E Pereda
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York
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15
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Puebla C, Retamal MA, Acuña R, Sáez JC. Regulation of Connexin-Based Channels by Fatty Acids. Front Physiol 2017; 8:11. [PMID: 28174541 PMCID: PMC5258758 DOI: 10.3389/fphys.2017.00011] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Accepted: 01/06/2017] [Indexed: 01/29/2023] Open
Abstract
In this mini-review, we briefly summarize the current knowledge about the effects of fatty acids (FAs) on connexin-based channels, as well as discuss the limited information about the impact FAs may have on pannexins (Panxs). FAs regulate diverse cellular functions, some of which are explained by changes in the activity of channels constituted by connexins (Cxs) or Panxs, which are known to play critical roles in maintaining the functional integrity of diverse organs and tissues. Cxs are transmembrane proteins that oligomerize into hexamers to form hemichannels (HCs), which in turn can assemble into dodecamers to form gap junction channels (GJCs). While GJCs communicate the cytoplasm of contacting cells, HCs serve as pathways for the exchange of ions and small molecules between the intra and extracellular milieu. Panxs, as well as Cx HCs, form channels at the plasma membrane that enable the interchange of molecules between the intra and extracellular spaces. Both Cx- and Panx-based channels are controlled by several post-translational modifications. However, the mechanism of action of FAs on these channels has not been described in detail. It has been shown however that FAs frequently decrease GJC-mediated cell-cell communication. The opposite effect also has been described for HC or Panx-dependent intercellular communication, where, the acute FA effect can be reversed upon washout. Additionally, changes in GJCs mediated by FAs have been associated with post-translational modifications (e.g., phosphorylation), and seem to be directly related to chemical properties of FAs (e.g., length of carbon chain and/or degree of saturation), but this possible link remains poorly understood.
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Affiliation(s)
- Carlos Puebla
- Instituto de Ciencias Biomédicas, Facultad de Ciencias de la Salud, Universidad Autónoma de ChileSantiago, Chile; Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del DesarrolloSantiago, Chile
| | - Mauricio A Retamal
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo Santiago, Chile
| | - Rodrigo Acuña
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo Santiago, Chile
| | - Juan C Sáez
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de ChileSantiago, Chile; Centro Interdisciplinario de Neurociencias de Valparaíso, Intituto Milenio, Universidad de ValparaísoValparaíso, Chile
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16
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Manjarrez-Marmolejo J, Franco-Pérez J. Gap Junction Blockers: An Overview of their Effects on Induced Seizures in Animal Models. Curr Neuropharmacol 2017; 14:759-71. [PMID: 27262601 PMCID: PMC5050393 DOI: 10.2174/1570159x14666160603115942] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 02/26/2016] [Accepted: 04/21/2016] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Gap junctions are clusters of intercellular channels allowing the bidirectional pass of ions directly into the cytoplasm of adjacent cells. Electrical coupling mediated by gap junctions plays a role in the generation of highly synchronized electrical activity. The hypersynchronous neuronal activity is a distinctive characteristic of convulsive events. Therefore, it has been postulated that enhanced gap junctional communication is an underlying mechanism involved in the generation and maintenance of seizures. There are some chemical compounds characterized as gap junction blockers because of their ability to disrupt the gap junctional intercellular communication. OBJECTIVE Hence, the aim of this review is to analyze the available data concerning the effects of gap junction blockers specifically in seizure models. RESULTS Carbenoxolone, quinine, mefloquine, quinidine, anandamide, oleamide, heptanol, octanol, meclofenamic acid, niflumic acid, flufenamic acid, glycyrrhetinic acid and retinoic acid have all been evaluated on animal seizure models. In vitro, these compounds share anticonvulsant effects typically characterized by the reduction of both amplitude and frequency of the epileptiform activity induced in brain slices. In vivo, gap junction blockers modify the behavioral parameters related to seizures induced by 4-aminopyridine, pentylenetetrazole, pilocarpine, penicillin and maximal electroshock. CONCLUSION Although more studies are still required, these molecules could be a promising avenue in the search for new pharmaceutical alternatives for the treatment of epilepsy.
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Affiliation(s)
| | - Javier Franco-Pérez
- Laboratory of Physiology of Reticular Formation, National Institute of Neurology and Neurosurgery, M.V.S. Insurgentes Sur 3877, Col. La Fama, C.P. 14269, Mexico D.F., Mexico
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Snipas M, Kraujalis T, Paulauskas N, Maciunas K, Bukauskas FF. Stochastic Model of Gap Junctions Exhibiting Rectification and Multiple Closed States of Slow Gates. Biophys J 2016; 110:1322-33. [PMID: 27028642 DOI: 10.1016/j.bpj.2016.01.035] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Revised: 01/03/2016] [Accepted: 01/27/2016] [Indexed: 12/26/2022] Open
Abstract
Gap-junction (GJ) channels formed from connexin (Cx) proteins provide direct pathways for electrical and metabolic cell-cell communication. Earlier, we developed a stochastic 16-state model (S16SM) of voltage gating of the GJ channel containing two pairs of fast and slow gates, each operating between open (o) and closed (c) states. However, experimental data suggest that gates may in fact contain two or more closed states. We developed a model in which the slow gate operates according to a linear reaction scheme, o↔c1↔c2, where c1 and c2 are initial-closed and deep-closed states that both close the channel fully, whereas the fast gate operates between the open state and the closed state and exhibits a residual conductance. Thus, we developed a stochastic 36-state model (S36SM) of GJ channel gating that is sensitive to transjunctional voltage (Vj). To accelerate simulation and eliminate noise in simulated junctional conductance (gj) records, we transformed an S36SM into a Markov chain 36-state model (MC36SM) of GJ channel gating. This model provides an explanation for well-established experimental data, such as delayed gj recovery after Vj gating, hysteresis of gj-Vj dependence, and the low ratio of functional channels to the total number of GJ channels clustered in junctional plaques, and it has the potential to describe chemically mediated gating, which cannot be reflected using an S16SM. The MC36SM, when combined with global optimization algorithms, can be used for automated estimation of gating parameters including probabilities of c1↔c2 transitions from experimental gj-time and gj-Vj dependencies.
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Affiliation(s)
- Mindaugas Snipas
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania; Department of Mathematical Modelling, Kaunas University of Technology, Kaunas, Lithuania
| | - Tadas Kraujalis
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Nerijus Paulauskas
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Kestutis Maciunas
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania
| | - Feliksas F Bukauskas
- Institute of Cardiology, Lithuanian University of Health Sciences, Kaunas, Lithuania; Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, New York.
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18
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Amsalem O, Van Geit W, Muller E, Markram H, Segev I. From Neuron Biophysics to Orientation Selectivity in Electrically Coupled Networks of Neocortical L2/3 Large Basket Cells. Cereb Cortex 2016; 26:3655-3668. [PMID: 27288316 PMCID: PMC4961030 DOI: 10.1093/cercor/bhw166] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In the neocortex, inhibitory interneurons of the same subtype are electrically coupled with each other via dendritic gap junctions (GJs). The impact of multiple GJs on the biophysical properties of interneurons and thus on their input processing is unclear. The present experimentally based theoretical study examined GJs in L2/3 large basket cells (L2/3 LBCs) with 3 goals in mind: (1) To evaluate the errors due to GJs in estimating the cable properties of individual L2/3 LBCs and suggest ways to correct these errors when modeling these cells and the networks they form; (2) to bracket the GJ conductance value (0.05-0.25 nS) and membrane resistivity (10 000-40 000 Ω cm(2)) of L2/3 LBCs; these estimates are tightly constrained by in vitro input resistance (131 ± 18.5 MΩ) and the coupling coefficient (1-3.5%) of these cells; and (3) to explore the functional implications of GJs, and show that GJs: (i) dynamically modulate the effective time window for synaptic integration; (ii) improve the axon's capability to encode rapid changes in synaptic inputs; and (iii) reduce the orientation selectivity, linearity index, and phase difference of L2/3 LBCs. Our study provides new insights into the role of GJs and calls for caution when using in vitro measurements for modeling electrically coupled neuronal networks.
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Affiliation(s)
| | - Werner Van Geit
- Blue Brain Project, École polytechnique fédérale de Lausanne (EPFL) Biotech Campus, 1202 Geneva, Switzerland
| | - Eilif Muller
- Blue Brain Project, École polytechnique fédérale de Lausanne (EPFL) Biotech Campus, 1202 Geneva, Switzerland
| | - Henry Markram
- Blue Brain Project, École polytechnique fédérale de Lausanne (EPFL) Biotech Campus, 1202 Geneva, Switzerland
| | - Idan Segev
- Department of Neurobiology.,Edmond and Lily Safra Center for Brain Sciences, The Hebrew University, 9190401 Jerusalem, Israel
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Szoboszlay M, Lőrincz A, Lanore F, Vervaeke K, Silver RA, Nusser Z. Functional Properties of Dendritic Gap Junctions in Cerebellar Golgi Cells. Neuron 2016; 90:1043-56. [PMID: 27133465 PMCID: PMC4893164 DOI: 10.1016/j.neuron.2016.03.029] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Revised: 03/03/2016] [Accepted: 03/22/2016] [Indexed: 12/13/2022]
Abstract
The strength and variability of electrical synaptic connections between GABAergic interneurons are key determinants of spike synchrony within neuronal networks. However, little is known about how electrical coupling strength is determined due to the inaccessibility of gap junctions on the dendritic tree. We investigated the properties of gap junctions in cerebellar interneurons by combining paired somato-somatic and somato-dendritic recordings, anatomical reconstructions, immunohistochemistry, electron microscopy, and modeling. By fitting detailed compartmental models of Golgi cells to their somato-dendritic voltage responses, we determined their passive electrical properties and the mean gap junction conductance (0.9 nS). Connexin36 immunofluorescence and freeze-fracture replica immunogold labeling revealed a large variability in gap junction size and that only 18% of the 340 channels are open in each plaque. Our results establish that the number of gap junctions per connection is the main determinant of both the strength and variability in electrical coupling between Golgi cells.
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Affiliation(s)
- Miklos Szoboszlay
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine of the Hungarian Academy of Sciences, Budapest 1083, Hungary; János Szentágothai School of Neurosciences, Semmelweis University, Budapest 1085, Hungary
| | - Andrea Lőrincz
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine of the Hungarian Academy of Sciences, Budapest 1083, Hungary
| | - Frederic Lanore
- Department of Neuroscience, Physiology, and Pharmacology, University College London, London WC1E 6BT, UK
| | - Koen Vervaeke
- Department of Neuroscience, Physiology, and Pharmacology, University College London, London WC1E 6BT, UK
| | - R Angus Silver
- Department of Neuroscience, Physiology, and Pharmacology, University College London, London WC1E 6BT, UK.
| | - Zoltan Nusser
- Laboratory of Cellular Neurophysiology, Institute of Experimental Medicine of the Hungarian Academy of Sciences, Budapest 1083, Hungary.
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Maciunas K, Snipas M, Paulauskas N, Bukauskas FF. Reverberation of excitation in neuronal networks interconnected through voltage-gated gap junction channels. ACTA ACUST UNITED AC 2016; 147:273-88. [PMID: 26880752 PMCID: PMC4772373 DOI: 10.1085/jgp.201511488] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 01/05/2016] [Indexed: 11/20/2022]
Abstract
Voltage-dependent gap junction gating contributes to reverberation in neuronal circuits. We combined Hodgkin–Huxley equations and gating models of gap junction (GJ) channels to simulate the spread of excitation in two-dimensional networks composed of neurons interconnected by voltage-gated GJs. Each GJ channel contains two fast and slow gates, each exhibiting current–voltage (I-V) rectification and gating properties that depend on transjunctional voltage (Vj). The data obtained show how junctional conductance (gj), which is necessary for synchronization of the neuronal network, depends on its size and the intrinsic firing rate of neurons. A phase shift between action potentials (APs) of neighboring neurons creates bipolar, short-lasting Vj spikes of approximately ±100 mV that induce Vj gating, leading to a small decay of gj, which can accumulate into larger decays during bursting activity of neurons. We show that I-V rectification of GJs in local regions of the two-dimensional network of neurons can lead to unidirectional AP transfer and consequently to reverberation of excitation. This reverberation can be initiated by a single electrical pulse and terminated by a low-amplitude pulse applied in a specific window of reverberation cycle. Thus, the model accounts for the influence of dynamically modulatable electrical synapses in shaping the function of a neuronal network and the formation of reverberation, which, as proposed earlier, may be important for the development of short-term memory and its consolidation into long-term memory.
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Affiliation(s)
- Kestutis Maciunas
- Institute of Cardiology, Lithuanian University of Health Sciences, 50009 Kaunas, Lithuania
| | - Mindaugas Snipas
- Institute of Cardiology, Lithuanian University of Health Sciences, 50009 Kaunas, Lithuania Department of Mathematical Modelling, Kaunas University of Technology, 51368 Kaunas, Lithuania
| | - Nerijus Paulauskas
- Institute of Cardiology, Lithuanian University of Health Sciences, 50009 Kaunas, Lithuania
| | - Feliksas F Bukauskas
- Institute of Cardiology, Lithuanian University of Health Sciences, 50009 Kaunas, Lithuania Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, NY 10461
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21
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Puebla C, Cisterna BA, Salas DP, Delgado-López F, Lampe PD, Sáez JC. Linoleic acid permeabilizes gastric epithelial cells by increasing connexin 43 levels in the cell membrane via a GPR40- and Akt-dependent mechanism. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:439-48. [PMID: 26869446 DOI: 10.1016/j.bbalip.2016.02.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Revised: 01/25/2016] [Accepted: 02/06/2016] [Indexed: 02/08/2023]
Abstract
Linoleic acid (LA) is known to activate G-protein coupled receptors and connexin hemichannels (Cx HCs) but possible interlinks between these two responses remain unexplored. Here, we evaluated the mechanism of action of LA on the membrane permeability mediated by Cx HCs in MKN28 cells. These cells were found to express connexins, GPR40, GPR120, and CD36 receptors. The Cx HC activity of these cells increased after 5 min of treatment with LA or GW9508, an agonist of GPR40/GPR120; or exposure to extracellular divalent cation-free solution (DCFS), known to increase the open probability of Cx HCs, yields an immediate increase in Cx HC activity of similar intensity and additive with LA-induced change. Treatment with a CD36 blocker or transfection with siRNA-GPR120 maintains the LA-induced Cx HC activity. However, cells transfected with siRNA-GPR40 did not show LA-induced Cx HC activity but activity was increased upon exposure to DCFS, confirming the presence of activatable Cx HCs in the cell membrane. Treatment with AKTi (Akt inhibitor) abrogated the LA-induced Cx HC activity. In HeLa cells transfected with Cx43 (HeLa-Cx43), LA induced phosphorylation of surface Cx43 at serine 373 (S373), site for Akt phosphorylation. HeLa-Cx43 but not HeLa-Cx43 cells with a S373A mutation showed a LA-induced Cx HC activity directly related to an increase in cell surface Cx43 levels. Thus, the increase in membrane permeability induced by LA is mediated by an intracellular signaling pathway activated by GPR40 that leads to an increase in membrane levels of Cx43 phosphorylated at serine 373 via Akt.
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Affiliation(s)
- Carlos Puebla
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.
| | - Bruno A Cisterna
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile; Instituto Milenio, Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Daniela P Salas
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Fernando Delgado-López
- Laboratorios de Biomedicina, Departamento de Ciencias Preclínicas, Facultad de Medicina, Universidad Católica del Maule, Talca, Chile
| | - Paul D Lampe
- Translational Research Program, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, United States
| | - Juan C Sáez
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile; Instituto Milenio, Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile.
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22
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Rimkutė L, Jotautis V, Marandykina A, Sveikatienė R, Antanavičiūtė I, Skeberdis VA. The role of neural connexins in HeLa cell mobility and intercellular communication through tunneling tubes. BMC Cell Biol 2016; 17:3. [PMID: 26758208 PMCID: PMC4710989 DOI: 10.1186/s12860-016-0080-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Accepted: 01/08/2016] [Indexed: 01/12/2023] Open
Abstract
Background Membranous tunneling tubes (TTs) are a recently discovered new form of communication between remote cells allowing their electrical synchronization, migration, and transfer of cellular materials. TTs have been identified in the brain and share similarities with neuronal processes. TTs can be open-ended, close-ended or contain functional gap junctions at the membrane interface. Gap junctions are formed of two unapposed hemichannels composed of six connexin (Cx) subunits. There are evidences that Cxs also play channel-independent role in cell adhesion, migration, division, differentiation, formation of neuronal networks and tumorigenicity. These properties of Cxs and TTs may synergetically determine the cellular and intercellular processes. Therefore, we examined the impact of Cxs expressed in the nervous system (Cx36, Cx40, Cx43, Cx45, and Cx47) on: 1) cell mobility; 2) formation and properties of TTs; and 3) transfer of siRNA between remote cells through TTs. Results We have identified two types of TTs between HeLa cells: F-actin rich only and containing F-actin and α-tubulin. The morphology of TTs was not influenced by expression of examined connexins; however, Cx36-EGFP-expressing cells formed more TTs while cells expressing Cx43-EGFP, Cx45, and Cx47 formed fewer TTs between each other compared with wt and Cx40-CFP-expressing cells. Also, Cx36-EGFP and Cx40-CFP-expressing HeLa cells were more mobile compared with wt and other Cxs-expressing cells. TTs containing Cx40-CFP, Cx43-EGFP, or Cx47 gap junctions were capable of transmitting double-stranded small interfering RNA; however, Cx36-EGFP and Cx45 were not permeable to it. In addition, we show that Cx43-EGFP-expressing HeLa cells and laryngeal squamous cell carcinoma cells can couple to the mesenchymal stem cells through TTs. Conclusions Different Cxs may modulate the mobility of cells and formation of TTs in an opposite manner; siRNA transfer through the GJ-containing TTs is Cx isoform-dependent. Electronic supplementary material The online version of this article (doi:10.1186/s12860-016-0080-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Lina Rimkutė
- Institute of Cardiology, Lithuanian University of Health Sciences, 17 Sukilėlių Ave., 50009, Kaunas, Lithuania.
| | - Vaidas Jotautis
- Institute of Cardiology, Lithuanian University of Health Sciences, 17 Sukilėlių Ave., 50009, Kaunas, Lithuania.
| | - Alina Marandykina
- Institute of Cardiology, Lithuanian University of Health Sciences, 17 Sukilėlių Ave., 50009, Kaunas, Lithuania.
| | - Renata Sveikatienė
- Institute of Cardiology, Lithuanian University of Health Sciences, 17 Sukilėlių Ave., 50009, Kaunas, Lithuania.
| | - Ieva Antanavičiūtė
- Institute of Cardiology, Lithuanian University of Health Sciences, 17 Sukilėlių Ave., 50009, Kaunas, Lithuania.
| | - Vytenis Arvydas Skeberdis
- Institute of Cardiology, Lithuanian University of Health Sciences, 17 Sukilėlių Ave., 50009, Kaunas, Lithuania.
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23
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Jing Y, Guo S, Zhang X, Sun A, Tao F, Ju H, Qian H. Effects of small interfering RNA interference of connexin 37 on subcutaneous gastric tumours in mice. Mol Med Rep 2014; 10:2955-60. [PMID: 25310476 DOI: 10.3892/mmr.2014.2609] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Accepted: 05/09/2014] [Indexed: 11/06/2022] Open
Abstract
The present study aimed to investigate the effects of small interfering (si)RNA interference of connexin 37 (Cx37) on subcutaneous gastric tumours in mice. Constructed lentiviruses carrying siRNA against Cx37 significantly knocked down Cx37 mRNA and protein expression in vitro. A total of 60 mice with gastric cancer were randomly divided into the Cx37 siRNA group, the mock‑siRNA group and the control group. Cx37 siRNA, mock‑siRNA and saline were separately injected (with the lentiviruses transfected into the gastric cancer cells). Following six weeks, the Cx37 mRNA expression, Cx37 protein expression and tumor apoptosis were detected using semiquantitative reverse transcription‑polymerase chain reaction, western blot analysis and terminal deoxynucleotidyl transferase‑mediated dUTP nick end labelling, respectively. Six weeks following lentiviral transfection, the Cx37 mRNA levels in the Cx37 siRNA group, mock‑siRNA group and saline group decreased to 42, 63 and 67%, respectively (P<0.05). The mock‑siRNA group demonstrated no significant change in Cx37 levels compared with the control group. Western blot analysis revealed lower Cx37 protein levels in the Cx37‑RNAi group than in the other groups (0.21±0.07 vs. 0.65±0.06 vs. 0.54±0.07), and that the apoptotic index of the Cx37‑RNAi group was higher than those of the mock‑siRNA and control groups (19.7±5.1 vs. 9.8±6.4 vs. 10.5±7.2%, 11.1±6.9; P<0.05). In conclusion, it was demonstrated that Cx37 siRNA is correlated with gastric cancer. Interference of Cx37 effectively reduces Cx37 mRNA and protein expression and promotes tumour apoptosis.
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Affiliation(s)
- Yuanming Jing
- Department of Gastrointestinal Surgery, Shaoxing People's Hospital, Shaoxing Hospital of Zhejiang University, Shaoxing, Zhejiang 312000, P.R. China
| | - Suxia Guo
- Department of Cardiology, The Affiliated People's Hospital of Nanjing Medical University in Wuxi and People's Hospital of Wuxi City, Wuxi, Jiangsu 214023, P.R. China
| | - Xiaoping Zhang
- Department of Gastrointestinal Surgery, Shaoxing People's Hospital, Shaoxing Hospital of Zhejiang University, Shaoxing, Zhejiang 312000, P.R. China
| | - Aijing Sun
- Department of Gastrointestinal Surgery, Shaoxing People's Hospital, Shaoxing Hospital of Zhejiang University, Shaoxing, Zhejiang 312000, P.R. China
| | - Feng Tao
- Department of Gastrointestinal Surgery, Shaoxing People's Hospital, Shaoxing Hospital of Zhejiang University, Shaoxing, Zhejiang 312000, P.R. China
| | - Haixing Ju
- Department of Colorectal Surgery, Zhejiang Provincial Tumor Hospital, Hangzhou, Zhejiang 310022, P.R. China
| | - Haixin Qian
- Department of General Surgery, The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu 215006, P.R. China
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24
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Palacios-Prado N, Chapuis S, Panjkovich A, Fregeac J, Nagy JI, Bukauskas FF. Molecular determinants of magnesium-dependent synaptic plasticity at electrical synapses formed by connexin36. Nat Commun 2014; 5:4667. [PMID: 25135336 PMCID: PMC4142521 DOI: 10.1038/ncomms5667] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Accepted: 07/11/2014] [Indexed: 01/28/2023] Open
Abstract
Neuronal gap junction (GJ) channels composed of connexin36 (Cx36) play an important role in neuronal synchronization and network dynamics. Here we show that Cx36-containing electrical synapses between inhibitory neurons of the thalamic reticular nucleus are bidirectionally modulated by changes in intracellular free magnesium concentration ([Mg(2+)]i). Chimeragenesis demonstrates that the first extracellular loop of Cx36 contains a Mg(2+)-sensitive domain, and site-directed mutagenesis shows that the pore-lining residue D47 is critical in determining high Mg(2+)-sensitivity. Single-channel analysis of Mg(2+)-sensitive chimeras and mutants reveals that [Mg(2+)]i controls the strength of electrical coupling mostly via gating mechanisms. In addition, asymmetric transjunctional [Mg(2+)]i induces strong instantaneous rectification, providing a novel mechanism for electrical rectification in homotypic Cx36 GJs. We suggest that Mg(2+)-dependent synaptic plasticity of Cx36-containing electrical synapses could underlie neuronal circuit reconfiguration via changes in brain energy metabolism that affects neuronal levels of intracellular ATP and [Mg(2+)]i.
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Affiliation(s)
- Nicolás Palacios-Prado
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, NY 10461, USA
- Grass Laboratory, Marine Biological Laboratory, Woods Hole, MA 02543, USA
| | - Sandrine Chapuis
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, NY 10461, USA
| | - Alejandro Panjkovich
- European Molecular Biology Laboratory, Hamburg Outstation, 22603 Hamburg, Germany
| | - Julien Fregeac
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, NY 10461, USA
| | - James I. Nagy
- Department of Physiology, University of Manitoba, Winnipeg, Manitoba R3E 0J9, Canada
| | - Feliksas F. Bukauskas
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, NY 10461, USA
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25
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Hansen DB, Ye ZC, Calloe K, Braunstein TH, Hofgaard JP, Ransom BR, Nielsen MS, MacAulay N. Activation, permeability, and inhibition of astrocytic and neuronal large pore (hemi)channels. J Biol Chem 2014; 289:26058-26073. [PMID: 25086040 DOI: 10.1074/jbc.m114.582155] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Astrocytes and neurons express several large pore (hemi)channels that may open in response to various stimuli, allowing fluorescent dyes, ions, and cytoplasmic molecules such as ATP and glutamate to permeate. Several of these large pore (hemi)channels have similar characteristics with regard to activation, permeability, and inhibitor sensitivity. Consequently, their behaviors and roles in astrocytic and neuronal (patho)physiology remain undefined. We took advantage of the Xenopus laevis expression system to determine the individual characteristics of several large pore channels in isolation. Expression of connexins Cx26, Cx30, Cx36, or Cx43, the pannexins Px1 or Px2, or the purinergic receptor P2X7 yielded functional (hemi)channels with isoform-specific characteristics. Connexin hemichannels had distinct sensitivity to alterations of extracellular Ca(2+) and their permeability to dyes and small atomic ions (conductance) were not proportional. Px1 and Px2 exhibited conductance at positive membrane potentials, but only Px1 displayed detectable fluorescent dye uptake. P2X7, in the absence of Px1, was permeable to fluorescent dyes in an agonist-dependent manner. The large pore channels displayed overlapping sensitivity to the inhibitors Brilliant Blue, gadolinium, and carbenoxolone. These results demonstrated isoform-specific characteristics among the large pore membrane channels; an open (hemi)channel is not a nonselective channel. With these isoform-specific properties in mind, we characterized the divalent cation-sensitive permeation pathway in primary cultured astrocytes. We observed no activation of membrane conductance or Cx43-mediated dye uptake in astrocytes nor in Cx43-expressing C6 cells. Our data underscore that although Cx43-mediated transport is observed in overexpressing cell systems, such transport may not be detectable in native cells under comparable experimental conditions.
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Affiliation(s)
- Daniel Bloch Hansen
- Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen N, Denmark
| | - Zu-Cheng Ye
- Department of Neurology, University of Washington, Seattle, Washington 98195
| | - Kirstine Calloe
- Department of Veterinary Clinical and Animal Science, Faculty of Health and Medical Sciences, University of Copenhagen, 1870 Frederiksberg, Denmark, and
| | - Thomas Hartig Braunstein
- Danish National Research Foundation Centre for Cardiac Arrhythmia and Department of Biomedicine, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Johannes Pauli Hofgaard
- Danish National Research Foundation Centre for Cardiac Arrhythmia and Department of Biomedicine, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Bruce R Ransom
- Department of Neurology, University of Washington, Seattle, Washington 98195
| | - Morten Schak Nielsen
- Danish National Research Foundation Centre for Cardiac Arrhythmia and Department of Biomedicine, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Nanna MacAulay
- Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, 2200 Copenhagen N, Denmark,.
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26
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Farnsworth NL, Benninger RKP. New insights into the role of connexins in pancreatic islet function and diabetes. FEBS Lett 2014; 588:1278-87. [PMID: 24583073 DOI: 10.1016/j.febslet.2014.02.035] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2013] [Revised: 02/13/2014] [Accepted: 02/19/2014] [Indexed: 12/22/2022]
Abstract
Multi-cellular systems require complex signaling mechanisms for proper tissue function, to mediate signaling between cells in close proximity and at distances. This holds true for the islets of Langerhans, which are multicellular micro-organs located in the pancreas responsible for glycemic control, through secretion of insulin and other hormones. Coupling of electrical and metabolic signaling between islet β-cells is required for proper insulin secretion and effective glycemic control. β-cell specific coupling is established through gap junctions composed of connexin36, which results in coordinated insulin release across the islet. Islet connexins have been implicated in both Type-1 and Type-2 diabetes; however a clear link remains to be determined. The goal of this review is to discuss recent discoveries regarding the role of connexins in regulating insulin secretion, the regulation of connexins within the islet, and recent studies which support a role for connexins in diabetes. Further studies which investigate the regulation of connexins in the islet and their role in diabetes may lead to novel diabetes therapies which regulate islet function and β-cell survival through modulation of gap junction coupling.
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Affiliation(s)
- Nikki L Farnsworth
- Barbara Davis center for childhood diabetes, University of Colorado, Anschutz Medical Campus, Aurora, CO 80045, United States
| | - Richard K P Benninger
- Barbara Davis center for childhood diabetes, University of Colorado, Anschutz Medical Campus, Aurora, CO 80045, United States; Department of Bioengineering, University of Colorado, Anschutz Medical Campus, Aurora, CO 80045, United States.
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