51
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Laird DW. The gap junction proteome and its relationship to disease. Trends Cell Biol 2010; 20:92-101. [DOI: 10.1016/j.tcb.2009.11.001] [Citation(s) in RCA: 217] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2009] [Revised: 10/30/2009] [Accepted: 11/02/2009] [Indexed: 02/07/2023]
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52
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Meerschaert K, Tun MP, Remue E, De Ganck A, Boucherie C, Vanloo B, Degeest G, Vandekerckhove J, Zimmermann P, Bhardwaj N, Lu H, Cho W, Gettemans J. The PDZ2 domain of zonula occludens-1 and -2 is a phosphoinositide binding domain. Cell Mol Life Sci 2009; 66:3951-66. [PMID: 19784548 PMCID: PMC3724457 DOI: 10.1007/s00018-009-0156-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2009] [Revised: 09/02/2009] [Accepted: 09/04/2009] [Indexed: 02/02/2023]
Abstract
Zonula occludens proteins (ZO) are postsynaptic density protein-95 discs large-zonula occludens (PDZ) domain-containing proteins that play a fundamental role in the assembly of tight junctions and establishment of cell polarity. Here, we show that the second PDZ domain of ZO-1 and ZO-2 binds phosphoinositides (PtdInsP) and we identified critical residues involved in the interaction. Furthermore, peptide and PtdInsP binding of ZO PDZ2 domains are mutually exclusive. Although lipid binding does not seem to be required for plasma membrane localisation of ZO-1, phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P (2)) binding to the PDZ2 domain of ZO-2 regulates ZO-2 recruitment to nuclear speckles. Knockdown of ZO-2 expression disrupts speckle morphology, indicating that ZO-2 might play an active role in formation and stabilisation of these subnuclear structures. This study shows for the first time that ZO isoforms bind PtdInsPs and offers an alternative regulatory mechanism for the formation and stabilisation of protein complexes in the nucleus.
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Affiliation(s)
- Kris Meerschaert
- Department of Medical Protein Research, VIB, 9000 Ghent, Belgium
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Albert Baertsoenkaai 3, 9000 Ghent, Belgium
- Present Address: Ablynx nv, Technologiepark, 9052 Ghent/Zwijnaarde, Belgium
| | - Moe Phyu Tun
- Departments of Chemistry, University of Illinois, Chicago, IL 60607-7061 USA
| | - Eline Remue
- Department of Medical Protein Research, VIB, 9000 Ghent, Belgium
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Albert Baertsoenkaai 3, 9000 Ghent, Belgium
| | - Ariane De Ganck
- Department of Medical Protein Research, VIB, 9000 Ghent, Belgium
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Albert Baertsoenkaai 3, 9000 Ghent, Belgium
| | - Ciska Boucherie
- Department of Medical Protein Research, VIB, 9000 Ghent, Belgium
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Albert Baertsoenkaai 3, 9000 Ghent, Belgium
| | - Berlinda Vanloo
- Department of Medical Protein Research, VIB, 9000 Ghent, Belgium
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Albert Baertsoenkaai 3, 9000 Ghent, Belgium
| | | | - Joël Vandekerckhove
- Department of Medical Protein Research, VIB, 9000 Ghent, Belgium
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Albert Baertsoenkaai 3, 9000 Ghent, Belgium
| | | | - Nitin Bhardwaj
- Departments of Bioengineering, University of Illinois, Chicago, IL 60607-7061 USA
| | - Hui Lu
- Departments of Bioengineering, University of Illinois, Chicago, IL 60607-7061 USA
| | - Wonhwa Cho
- Departments of Chemistry, University of Illinois, Chicago, IL 60607-7061 USA
- Department of Chemistry (M/C 111), University of Illinois at Chicago, 845 West Taylor Street, Chicago, IL 60607-7061 USA
| | - Jan Gettemans
- Department of Medical Protein Research, VIB, 9000 Ghent, Belgium
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Albert Baertsoenkaai 3, 9000 Ghent, Belgium
- Department of Medical Protein Research, Faculty of Medicine and Health Sciences, Flanders Interuniversity Institute for Biotechnology, Ghent University, Albert Baertsoenkaai 3, 9000 Ghent, Belgium
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53
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Balla T. Green light to illuminate signal transduction events. Trends Cell Biol 2009; 19:575-86. [PMID: 19818623 DOI: 10.1016/j.tcb.2009.08.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2009] [Revised: 08/03/2009] [Accepted: 08/11/2009] [Indexed: 11/17/2022]
Abstract
When cells are exposed to hormones that act on cell surface receptors, information is processed through the plasma membrane into the cell interior via second messengers generated in the inner leaflet of the plasma membrane. Individual biochemical steps along this cascade have been characterized from ligand binding to receptors through to activation of guanine nucleotide binding proteins and their downstream effectors such as adenylate cyclase or phospholipase C. However, the complexity of temporal and spatial integration of these molecular events requires that they are studied in intact cells. The great expansion of fluorescent techniques and improved imaging technologies such as confocal and TIRF microscopy combined with genetically-engineered protein modules has provided a completely new approach to signal transduction research. Spatial definition of biochemical events followed with real-time temporal resolution has become a standard goal, and several new techniques are now breaking the resolution barrier of light microscopy.
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Affiliation(s)
- Tamas Balla
- Section on Molecular Signal Transduction, Program on Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
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54
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Tuomi S, Mai A, Nevo J, Laine JO, Vilkki V, Ohman TJ, Gahmberg CG, Parker PJ, Ivaska J. PKCepsilon regulation of an alpha5 integrin-ZO-1 complex controls lamellae formation in migrating cancer cells. Sci Signal 2009; 2:ra32. [PMID: 19567915 DOI: 10.1126/scisignal.2000135] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Disruption of intercellular adhesions, increased abundance of alpha(5)beta(1) integrin, and activation of protein kinase Cepsilon (PKCepsilon) correlate with invasion and unfavorable prognosis in lung cancer. However, it remains elusive how these distinct factors contribute to the invasive behavior of cancer cells. Persistent cell motility requires the formation of stable lamellae at the leading edge of a migrating cell. Here, we report that the tight junction protein zonula occludens-1 (ZO-1) preferentially interacts with alpha(5)beta(1) integrin at the lamellae of migrating cells. Disruption of ZO-1 binding to an internal PDZ-binding motif in the alpha(5) cytoplasmic tail prevented the polarized localization of ZO-1 and alpha(5) at the leading edge. Furthermore, silencing of alpha(5) integrin inhibited migration and invasion of lung cancer cells, and silencing of ZO-1 resulted in increased Rac activity and reduced directional cell motility. The formation of the alpha(5)-ZO-1 complex was dependent on PKCepsilon: Phosphorylation of ZO-1 at serine-168 regulated the subcellular localization of ZO-1 and thus controlled its association with alpha(5) integrin. In conclusion, PKCepsilon activation drives the formation of a spatially restricted, promigratory alpha(5)-ZO-1 complex at the leading edge of lung cancer cells.
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Affiliation(s)
- Saara Tuomi
- Medical Biotechnology, VTT Technical Research Centre of Finland and University of Turku, FIN-20520 Turku, Finland
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55
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Hao JJ, Liu Y, Kruhlak M, Debell KE, Rellahan BL, Shaw S. Phospholipase C-mediated hydrolysis of PIP2 releases ERM proteins from lymphocyte membrane. ACTA ACUST UNITED AC 2009; 184:451-62. [PMID: 19204146 PMCID: PMC2646552 DOI: 10.1083/jcb.200807047] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mechanisms controlling the disassembly of ezrin/radixin/moesin (ERM) proteins, which link the cytoskeleton to the plasma membrane, are incompletely understood. In lymphocytes, chemokine (e.g., SDF-1) stimulation inactivates ERM proteins, causing their release from the plasma membrane and dephosphorylation. SDF-1–mediated inactivation of ERM proteins is blocked by phospholipase C (PLC) inhibitors. Conversely, reduction of phosphatidylinositol 4,5-bisphosphate (PIP2) levels by activation of PLC, expression of active PLC mutants, or acute targeting of phosphoinositide 5-phosphatase to the plasma membrane promotes release and dephosphorylation of moesin and ezrin. Although expression of phosphomimetic moesin (T558D) or ezrin (T567D) mutants enhances membrane association, activation of PLC still relocalizes them to the cytosol. Similarly, in vitro binding of ERM proteins to the cytoplasmic tail of CD44 is also dependent on PIP2. These results demonstrate a new role of PLCs in rapid cytoskeletal remodeling and an additional key role of PIP2 in ERM protein biology, namely hydrolysis-mediated ERM inactivation.
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Affiliation(s)
- Jian-Jiang Hao
- Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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56
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Epithelial cell–cell junctions and plasma membrane domains. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:820-31. [DOI: 10.1016/j.bbamem.2008.07.015] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2008] [Revised: 07/10/2008] [Accepted: 07/21/2008] [Indexed: 12/16/2022]
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57
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Johnstone S, Isakson B, Locke D. Biological and biophysical properties of vascular connexin channels. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2009; 278:69-118. [PMID: 19815177 PMCID: PMC2878191 DOI: 10.1016/s1937-6448(09)78002-5] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Intercellular channels formed by connexin proteins play a pivotal role in the direct movement of ions and larger cytoplasmic solutes between vascular endothelial cells, between vascular smooth muscle cells, and between endothelial and smooth muscle cells. Multiple genetic and epigenetic factors modulate connexin expression levels and/or channel function, including cell-type-independent and cell-type-specific transcription factors, posttranslational modifications, and localized membrane targeting. Additionally, differences in protein-protein interactions, including those between connexins, significantly contribute to both vascular homeostasis and disease progression. The biophysical properties of the connexin channels identified in the vasculature, those formed by Cx37, Cx40, Cx43 and/or Cx45 proteins, are discussed in this chapter in the physiological and pathophysiological context of vessel function.
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Affiliation(s)
- Scott Johnstone
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 29908
| | - Brant Isakson
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 29908
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, VA 29908
| | - Darren Locke
- Department of Pharmacology and Physiology, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, NJ 07103
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58
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Adjobo-Hermans MJW, Goedhart J, Gadella TWJ. Regulation of PLCβ1a membrane anchoring by its substrate phosphatidylinositol (4,5)-bisphosphate. J Cell Sci 2008; 121:3770-7. [DOI: 10.1242/jcs.029785] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Basic knowledge as to the subcellular location and dynamics of PLCβ isozymes is scant. Here, we report on the subcellular location of GFP-PLCβ1a and the use of total internal reflection fluorescence (TIRF) microscopy to examine the dynamics of GFP-PLCβ1a at the plasma membrane upon stimulation of Gq-coupled receptors. Using this technique, we observed PLCβ1a dissociation from the plasma membrane upon addition of agonist. An increase in intracellular calcium and a decrease in PtdIns(4,5)P2 both coincided with a translocation of PLCβ1a from the plasma membrane into the cytosol. In order to differentiate between calcium and PtdIns(4,5)P2, rapamycin-induced heterodimerization of FRB and FKBP12 fused to 5-phosphatase IV was used to instantaneously convert PtdIns(4,5)P2 into PtdIns(4)P. Addition of rapamycin caused PLCβ1a to dissociate from the plasma membrane, indicating that removal of PtdIns(4,5)P2 is sufficient to cause translocation of PLCβ1a from the plasma membrane. In conclusion, PLCβ1a localization is regulated by its own substrate.
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Affiliation(s)
- Merel J. W. Adjobo-Hermans
- Swammerdam Institute for Life Sciences, Section of Molecular Cytology, Centre for Advanced Microscopy, University of Amsterdam, Kruislaan 316, NL-1098 SM, Amsterdam, The Netherlands
| | - Joachim Goedhart
- Swammerdam Institute for Life Sciences, Section of Molecular Cytology, Centre for Advanced Microscopy, University of Amsterdam, Kruislaan 316, NL-1098 SM, Amsterdam, The Netherlands
| | - Theodorus W. J. Gadella
- Swammerdam Institute for Life Sciences, Section of Molecular Cytology, Centre for Advanced Microscopy, University of Amsterdam, Kruislaan 316, NL-1098 SM, Amsterdam, The Netherlands
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59
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Acute internalization of gap junctions in vascular endothelial cells in response to inflammatory mediator-induced G-protein coupled receptor activation. FEBS Lett 2008; 582:4039-46. [PMID: 18992245 DOI: 10.1016/j.febslet.2008.10.043] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2008] [Revised: 10/22/2008] [Accepted: 10/24/2008] [Indexed: 11/21/2022]
Abstract
During the inflammatory response, activation of G-protein coupled receptors (GPCRs) by inflammatory mediators rapidly leads to inhibition of gap junction intercellular communication (GJIC); however, the steps that lead to this inhibition are not known. Combining high-resolution fluorescence microscopy and functional assays, we found that activation of the GPCRs PAR-1 and ET(A/B) by their natural inflammatory mediator agonists, thrombin and endothelin-1, resulted in rapid and acute internalization of gap junctions (GJs) that coincided with the inhibition of GJIC followed by increased vascular permeability. The endocytosis protein clathrin and the scaffold protein ZO-1 appeared to be involved in GJ internalization, and ZO-1 was partially displaced from GJs during the internalization process. These findings demonstrate that GJ internalization is an efficient mechanism for modulating GJIC in inflammatory response.
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60
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Hunter AW, Gourdie RG. The second PDZ domain of zonula occludens-1 is dispensable for targeting to connexin 43 gap junctions. ACTA ACUST UNITED AC 2008; 15:55-63. [PMID: 18649178 DOI: 10.1080/15419060802014370] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Zonula occludens (ZO)-1 is emerging as a central player in the control of gap junction (GJ) dynamics. Previously the authors reported that ZO-1 localizes preferentially to the periphery of Cx43 GJs. How ZO-1 arrives at GJ edges is unknown, but this targeting might involve we established interaction between the Cx43 C-terminus and the PDZ2 domain of ZO-1. Here the show that despite blocking the canonical PDZ2-mediated interaction by fusion of GFP to the C-terminus of Cx43, ZO-1 continued to target to domains juxtaposed with the edges of GJs comprised solely of tagged Cx43. This edge-association was not abolished by deletion of PDZ2 from ZO-1, as mutant ZO-1 also targeted to the periphery of GJs composed of either tagged or untagged Cx43. Additionally, ZO-2 was found colocalized with ZO-1 at GJ edges. These data demonstrate that ZO-1 targets to GJ edges independently of several known PDZ2-mediated interactions, including ZO-1 homodimerization, heterodimerization with ZO-2, and direct ZO-1 binding to the C-terminal residues of Cx43.
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Affiliation(s)
- Andrew W Hunter
- Department of Cell Biology and Anatomy, Cardiovascular Developmental Biology Center, Medical University of South Carolina, Charleston, South Carolina 29425, USA.
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61
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Lim BK, Xiong D, Dorner A, Youn TJ, Yung A, Liu TI, Gu Y, Dalton ND, Wright AT, Evans SM, Chen J, Peterson KL, McCulloch AD, Yajima T, Knowlton KU. Coxsackievirus and adenovirus receptor (CAR) mediates atrioventricular-node function and connexin 45 localization in the murine heart. J Clin Invest 2008; 118:2758-70. [PMID: 18636119 DOI: 10.1172/jci34777] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2007] [Accepted: 06/04/2008] [Indexed: 12/31/2022] Open
Abstract
The coxsackievirus and adenovirus receptor (CAR) is a transmembrane protein that belongs to the family of adhesion molecules. In the postnatal heart, it is localized predominantly at the intercalated disc, where its function is not known. Here, we demonstrate that a first degree or complete block of atrioventricular (AV) conduction developed in the absence of CAR in the adult mouse heart and that prolongation of AV conduction occurred in the embryonic heart of the global CAR-KO mouse. In the cardiac-specific CAR-KO (CAR-cKO) mouse, we observed the loss of connexin 45 localization to the cell-cell junctions of the AV node but preservation of connexin 40 and 43 in contracting myocardial cells and connexin 30.2 in the AV node. There was also a marked decrease in beta-catenin and zonula occludens-1 (ZO-1) localization to the intercalated discs of CAR-cKO mouse hearts at 8 weeks before the mice developed cardiomyopathy at 21 weeks of age. We also found that CAR formed a complex with connexin 45 via its PSD-95/DigA/ZO-1-binding (PDZ-binding) motifs. We conclude that CAR expression is required for normal AV-node conduction and cardiac function. Furthermore, localization of connexin 45 at the AV-node cell-cell junction and of beta-catenin and ZO-1 at the ventricular intercalated disc are dependent on CAR.
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Affiliation(s)
- Byung-Kwan Lim
- Department of Medicine, University of California San Diego, Division of Cardiology, La Jolla, California 92093-0613, USA
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62
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Interaction between connexin35 and zonula occludens-1 and its potential role in the regulation of electrical synapses. Proc Natl Acad Sci U S A 2008; 105:12545-50. [PMID: 18719117 DOI: 10.1073/pnas.0804793105] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Although regulation of chemical transmission is known to involve the interaction of receptors with scaffold proteins, little is known about the existence of protein-protein interactions in regulating gap junction-mediated electrical synapses. The scaffold protein zonula-occludens-1 (ZO-1), a member of the MAGUK family of proteins, was reported to interact with several connexins (Cxs). We show here that ZO-1 extensively colocalizes with Cx35 at identifiable "mixed" (electrical and chemical) contacts on goldfish Mauthner cells, a model synapse for the study of vertebrate electrical transmission where it is possible to correlate physiological properties with molecular composition. Further, our analysis indicates that these proteins directly interact at goldfish electrical synapses. In contrast to Cx43, which interacts with ZO-1 via the PDZ2 domain, Cx35 interacts with ZO-1 via the PDZ1 domain, and this association is of lower affinity. The properties of the ZO-1/Cx35 association suggest the existence of a more dynamic relation between these two proteins, possibly including a role of ZO-1 in regulating gap junctional conductance at these highly modifiable electrical synapses. The interaction of ZO-1 with conserved regions of the C termini of Cx35/Cx36 orthologs may have a common function at electrical synapses of mammals and other vertebrates.
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63
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Derangeon M, Bourmeyster N, Plaisance I, Pinet-Charvet C, Chen Q, Duthe F, Popoff MR, Sarrouilhe D, Hervé JC. RhoA GTPase and F-actin dynamically regulate the permeability of Cx43-made channels in rat cardiac myocytes. J Biol Chem 2008; 283:30754-65. [PMID: 18667438 DOI: 10.1074/jbc.m801556200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Gap junctions are clusters of transmembrane channels allowing a passive diffusion of ions and small molecules between adjacent cells. Connexin43, the main channel-forming protein expressed in ventricular myocytes, can associate with zonula occludens-1, a scaffolding protein linked to the actin cytoskeleton and to signal transduction molecules. The possible influence of Rho GTPases, major regulators of cellular junctions and of the actin cytoskeleton, in the modulation of gap junctional intercellular communication (GJIC) was examined. The activation of RhoA by cytoxic necrotizing factor 1 markedly enhanced GJIC, whereas its specific inhibition by the Clostridium botulinum C3 exoenzyme significantly reduced it. RhoA activity affects GJIC without major cellular redistribution of junctional plaques or changes in the Cx43 phosphorylation pattern. As these GTPases frequently act via the cortical cytoskeleton, the importance of F-actin in the modulation of GJIC was investigated by means of agents interfering with actin polymerization. Cytoskeleton stabilization by phalloidin slowed down the kinetics of channel rundown in the absence of ATP, whereas its disruption by cytochalasin D rapidly and markedly reduced GJIC despite ATP presence. Cytoskeleton stabilization by phalloidin markedly reduced the consequences of RhoA activation or inactivation. This mechanism appears to be the first described capable to both up- or down-regulate GJIC through RhoA activation or, conversely, inhibition. The inhibition of Rho downstream kinase effectors had no effect on GJIC. The present results provide further insight into the gating and regulation of junctional channels and identify a new downstream target for the small G-protein RhoA.
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Affiliation(s)
- Mickaël Derangeon
- Institut de Physiologie et Biologie Cellulaires, Université de Poitiers, F-86022 Poitiers, France
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64
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Chen J, Pan L, Wei Z, Zhao Y, Zhang M. Domain-swapped dimerization of ZO-1 PDZ2 generates specific and regulatory connexin43-binding sites. EMBO J 2008; 27:2113-23. [PMID: 18636092 DOI: 10.1038/emboj.2008.138] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2008] [Accepted: 06/25/2008] [Indexed: 12/19/2022] Open
Abstract
PDZ domain scaffold proteins are capable of assembling macromolecular protein complexes in diverse cellular processes through PDZ-mediated binding to a short peptide fragment at the carboxyl tail of target proteins. How each PDZ domain specifically recognizes its target protein(s) remains a major conceptual question, as at least a few out of the several hundred PDZ domains in each eukaryotic genome share overlapping binding properties with any given target protein. Here, we show that the domain-swapped dimerization of zonula occludens-1 PDZ2 generates a distinct interface that functions together with the well-separated canonical carboxyl tail-binding pocket in each PDZ unit in binding to connexin43 (Cx43). We further demonstrate that the charge-charge interaction network formed by residues in the PDZ dimer interface and upstream residues of the Cx43 peptide not only provides the unprecedented interaction specificity for the complex but may also function as a phosphorylation-mediated regulatory switch for the dynamics of the Cx43 gap junctions. Finally, we provide evidence that such domain-swapped dimer assembly also occurs in other PDZ domain scaffold proteins. Therefore, our findings present a new paradigm for understanding how some PDZ domain proteins specifically bind to and regulate the functions of their target proteins.
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Affiliation(s)
- Jia Chen
- Department of Biochemistry, Molecular Neuroscience Center, Hong Kong University of Science and Technology, Kowloon, Hong Kong
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65
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Hofgaard JP, Banach K, Mollerup S, Jørgensen HK, Olesen SP, Holstein-Rathlou NH, Nielsen MS. Phosphatidylinositol-bisphosphate regulates intercellular coupling in cardiac myocytes. Pflugers Arch 2008; 457:303-13. [PMID: 18536930 DOI: 10.1007/s00424-008-0538-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2008] [Revised: 05/15/2008] [Accepted: 05/19/2008] [Indexed: 11/26/2022]
Abstract
Changes in the lipid composition of cardiac myocytes have been reported during cardiac hypertrophy, cardiomyopathy, and infarction. Because a recent study indicates a relation between low phosphatidylinositol-bisphosphate (PIP(2)) levels and reduced intercellular coupling, we tested the hypothesis that agonist-induced changes in PIP(2) can result in a reduction of the functional coupling of cardiomyocytes and, consequently, in changes in conduction velocity. Intercellular coupling was measured by Lucifer Yellow dye transfer in cultured neonatal rat cardiomyocytes. Conduction velocity was measured in cardiomyocytes grown on microelectrode arrays. Intercellular coupling was reduced by angiotensin II (43.7 +/- 9.3%, N = 11) and noradrenaline (58.0 +/- 10.7%, N = 11). To test if reduced intercellular coupling after agonist stimulation was caused by PIP(2)-depletion, myocytes were stimulated by angiotensin II (57.3 +/- 5.7%, N = 14) and then allowed to recover in medium with or without wortmannin (an inhibitor of PIP(2) synthesis). Intercellular coupling fully recovered in control medium (102.1 +/- 8.9%, N = 10), whereas no recovery occurred in the presence of wortmannin (69.3 +/- 7.8%, N = 12). Inhibition of PKC, calmodulin, or arachidonic acid production did not affect the response to either angiotensin II or noradrenaline. Furthermore, decreasing or increasing PIP(2) also decreased and increased intercellular coupling, respectively. This supports the role of PIP(2) in the regulation of intercellular coupling. In beating myocytes, conduction velocity was reduced by angiotensin II stimulation, and recovery after wash out was prevented by inhibition of PIP(2) production. Reductions in PIP(2) inhibit intercellular coupling in cardiomyocytes, and stimulation by physiologically relevant agonists reduces intercellular coupling by this mechanism. The reduction in intercellular coupling lowered conduction velocity.
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MESH Headings
- Androstadienes/pharmacology
- Angiotensin II/metabolism
- Animals
- Animals, Newborn
- Arachidonic Acid/pharmacology
- Calcium/metabolism
- Cell Communication/drug effects
- Cells, Cultured
- Dose-Response Relationship, Drug
- GTP-Binding Protein alpha Subunits, Gq-G11/metabolism
- Gap Junctions/drug effects
- Gap Junctions/metabolism
- Myocardial Contraction/drug effects
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/metabolism
- Norepinephrine/metabolism
- Phosphatidylinositol Phosphates/metabolism
- Protein Kinase C/metabolism
- Protein Kinase Inhibitors/pharmacology
- Rats
- Rats, Wistar
- Receptor, Angiotensin, Type 1/metabolism
- Receptors, Adrenergic, beta-1/metabolism
- Signal Transduction/drug effects
- Time Factors
- Wortmannin
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Affiliation(s)
- Johannes P Hofgaard
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
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66
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Marín-Vicente C, Nicolás FE, Gómez-Fernández JC, Corbalán-García S. The PtdIns(4,5)P2 ligand itself influences the localization of PKCalpha in the plasma membrane of intact living cells. J Mol Biol 2007; 377:1038-52. [PMID: 18304574 DOI: 10.1016/j.jmb.2007.12.011] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2007] [Revised: 11/30/2007] [Accepted: 12/04/2007] [Indexed: 11/28/2022]
Abstract
Rapamycin-triggered heterodimerization strategy is becoming an excellent tool for rapidly modifying phosphatidylinositol(4,5)-bisphosphate [PtdIns(4,5)P2] levels at the plasma membrane and for studying their influence in different processes. In this work, we studied the effect of modulation of the PtdIns(4,5)P2 concentration on protein kinase C (PKC) alpha membrane localization in intact living cells. We showed that an increase in the PtdIns(4,5)P2 concentration enlarges the permanence of PKCalpha in the plasma membrane when PC12 cells are stimulated with ATP, independently of the diacylglycerol generated. The depletion of this phosphoinositide decreases both the percentage of protein able to translocate to the plasma membrane and its permanence there. Our results demonstrate that the polybasic cluster located in the C2 domain of PKCalpha is responsible for this phosphoinositide-protein interaction. Furthermore, the C2 domain acts as a dominant interfering module in the neural differentiation process of PC12 cells, a fact that was also supported by the inhibitory effect obtained by knocking down PKCalpha with small interfering RNA duplexes. Taken together, these data demonstrate that PtdIns(4,5)P2 itself targets PKCalpha to the plasma membrane through the polybasic cluster located in the C2 domain, with this interaction being critical in the signaling network involved in neural differentiation.
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Affiliation(s)
- Consuelo Marín-Vicente
- Dpto. de Bioquímica y Biología Molecular (A), Facultad de Veterinaria, Universidad de Murcia, Apdo. 4021, E-30100 Murcia, Spain
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Gamper N, Shapiro MS. Regulation of ion transport proteins by membrane phosphoinositides. Nat Rev Neurosci 2007; 8:921-34. [DOI: 10.1038/nrn2257] [Citation(s) in RCA: 192] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Fanning AS, Lye MF, Anderson JM, Lavie A. Domain swapping within PDZ2 is responsible for dimerization of ZO proteins. J Biol Chem 2007; 282:37710-6. [PMID: 17928286 DOI: 10.1074/jbc.m707255200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ZO-1 is a multidomain protein involved in cell-cell junctions and contains three PDZ domains, which are necessary for its function in vivo. PDZ domains play a central role in assembling diverse protein complexes through their ability to recognize short peptide motifs on other proteins. We determined the structure of the second of the three PDZ domains of ZO-1, which is known to promote dimerization as well as bind to C-terminal sequences on connexins. The dimer is stabilized by extensive symmetrical domain swapping of beta-strands, which is unlike any other known mechanism of PDZ dimerization. The canonical peptide-binding groove remains intact in both subunits of the PDZ2 dimer and is created by elements contributed from both monomers. This unique structure reveals an additional example of how PDZ domains dimerize and has multiple implications for both peptide binding and oligomerization in vivo.
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Affiliation(s)
- Alan S Fanning
- Department of Cell and Molecular Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7545, USA
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