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Liu X, Qin H, Liu Y, Ma J, Li Y, He Y, Zhu H, Mao L. The biological functions and pathological mechanisms of CASK in various diseases. Heliyon 2024; 10:e28863. [PMID: 38638974 PMCID: PMC11024568 DOI: 10.1016/j.heliyon.2024.e28863] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 03/21/2024] [Accepted: 03/26/2024] [Indexed: 04/20/2024] Open
Abstract
Background As a scaffold protein, calcium/calmodulin-dependent serine protein kinase (CASK) has been extensively studied in a variety of tissues throughout the body. The Cask gene is ubiquitous in several tissues, such as the neurons, islets, heart, kidneys and sperm, and is mostly localised in the cytoplasm adjacent to the basement membrane. CASK binds to a variety of proteins through its domains to exerting its biological activity. Scope of review Here, we discuss the role of CASK in multiple tissues throughout the body. The role of different CASK domains in regulating neuronal development, neurotransmitter release and synaptic vesicle secretion was emphasised; the regulatory mechanism of CASK on the function of pancreatic islet β cells was analysed; the role of CASK in cardiac physiology, kidney and sperm development was discussed; and the role of CASK in different tumours was compared. Finally, we clarify the importance of the Cask gene in the body, and how deletion or mutation of the Cask gene can have adverse consequences. Major conclusions CASK is a conserved gene with similar roles in various tissues. The function of the Cask gene in the nervous system is mainly involved in the development of the nervous system and the release of neurotransmitters. In the endocrine system, an involvement of CASK has been reported in the process of insulin vesicle transport. CASK is also involved in cardiomyocyte ion channel regulation, kidney and sperm development, and tumour proliferation. CASK is an indispensable gene for the whole body, and CASK mutations can cause foetal malformations or death at birth. In this review, we summarise the biological functions and pathological mechanisms of CASK in various systems, thereby providing a basis for further in-depth studies of CASK functions.
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Affiliation(s)
- Xingjing Liu
- Department of Endocrinology, The Affiliated Huaian No.1 People’s Hospital of Nanjing Medical University, Huaian, Jiangsu Province, China
| | - Haonan Qin
- Department of Orthopedics, The Affiliated Huaian No.1 People’s Hospital of Nanjing Medical University, Huaian, Jiangsu Province, China
| | - Yuanyuan Liu
- Department of Endocrinology, The Affiliated Huaian No.1 People’s Hospital of Nanjing Medical University, Huaian, Jiangsu Province, China
| | - Jingjing Ma
- Department of Endocrinology, The Affiliated Huaian No.1 People’s Hospital of Nanjing Medical University, Huaian, Jiangsu Province, China
| | - Yiming Li
- Department of Endocrinology, The Affiliated Huaian No.1 People’s Hospital of Nanjing Medical University, Huaian, Jiangsu Province, China
| | - Yu He
- Department of Endocrinology, The Affiliated Huaian No.1 People’s Hospital of Nanjing Medical University, Huaian, Jiangsu Province, China
| | - Huimin Zhu
- Department of Electrophysiology, The Affiliated Huaian No.1 People’s Hospital of Nanjing Medical University, Huaian, Jiangsu Province, China
| | - Li Mao
- Department of Endocrinology, The Affiliated Huaian No.1 People’s Hospital of Nanjing Medical University, Huaian, Jiangsu Province, China
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Bahouth SW, Nooh MM, Mancarella S. Involvement of SAP97 anchored multiprotein complexes in regulating cardiorenal signaling and trafficking networks. Biochem Pharmacol 2023; 208:115406. [PMID: 36596415 DOI: 10.1016/j.bcp.2022.115406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 12/26/2022] [Accepted: 12/28/2022] [Indexed: 01/02/2023]
Abstract
SAP97 is a member of the MAGUK family of proteins, but unlike other MAGUK proteins that are selectively expressed in the CNS, SAP97 is also expressed in peripheral organs, like the heart and kidneys. SAP97 has several protein binding cassettes, and this review will describe their involvement in creating SAP97-anchored multiprotein networks. SAP97-anchored networks localized at the inner leaflet of the cell membrane play a major role in trafficking and targeting of membrane G protein-coupled receptors (GPCR), channels, and structural proteins. SAP97 plays a major role in compartmentalizing voltage gated sodium and potassium channels to specific cellular compartments of heart cells. SAP97 undergoes extensive alternative splicing. These splice variants give rise to different SAP97 isoforms that alter its cellular localization, networking, signaling and trafficking effects. Regarding GPCR, SAP97 binds to the β1-adrenergic receptor and recruits AKAP5/PKA and PDE4D8 to create a multiprotein complex that regulates trafficking and signaling of cardiac β1-AR. In the kidneys, SAP97 anchored networks played a role in trafficking of aquaporin-2 water channels. Cardiac specific ablation of SAP97 (SAP97-cKO) resulted in cardiac hypertrophy and failure in aging mice. Similarly, instituting transverse aortic constriction (TAC) in young SAP97 c-KO mice exacerbated TAC-induced cardiac remodeling and dysfunction. These findings highlight a critical role for SAP97 in the pathophysiology of a number of cardiac and renal diseases, suggesting that SAP97 is a relevant target for drug discovery.
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Affiliation(s)
- Suleiman W Bahouth
- Department of Pharmacology, Addiction Science and Toxicology, The University of Tennessee-Health Sciences Center, Memphis, TN, United States.
| | - Mohammed M Nooh
- Department of Biochemistry, Faculty of Pharmacy Cairo University, Cairo, Egypt and Biochemistry Department, Faculty of Pharmacy, October 6 University, Giza, Egypt
| | - Salvatore Mancarella
- Department of Physiology, The University of Tennessee-Health Sciences Center, Memphis, TN, United States
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Rajeev P, Singh N, Kechkar A, Butler C, Ramanan N, Sibarita JB, Jose M, Nair D. Nanoscale regulation of Ca2+ dependent phase transitions and real-time dynamics of SAP97/hDLG. Nat Commun 2022; 13:4236. [PMID: 35869063 PMCID: PMC9307800 DOI: 10.1038/s41467-022-31912-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Accepted: 07/08/2022] [Indexed: 11/20/2022] Open
Abstract
Synapse associated protein-97/Human Disk Large (SAP97/hDLG) is a conserved, alternatively spliced, modular, scaffolding protein critical in regulating the molecular organization of cell-cell junctions in vertebrates. We confirm that the molecular determinants of first order phase transition of SAP97/hDLG is controlled by morpho-functional changes in its nanoscale organization. Furthermore, the nanoscale molecular signatures of these signalling islands and phase transitions are altered in response to changes in cytosolic Ca2+. Additionally, exchange kinetics of alternatively spliced isoforms of the intrinsically disordered region in SAP97/hDLG C-terminus shows differential sensitivities to Ca2+ bound Calmodulin, affirming that the molecular signatures of local phase transitions of SAP97/hDLG depends on their nanoscale heterogeneity and compositionality of isoforms. SAP97/hDLG is a ubiquitous, alternatively spliced, and conserved modular scaffolding protein involved in the organization cell junctions and excitatory synapses. Here, authors confirm that SAP97/hDLG condenses in to nanosized molecular domains in both heterologous cells and hippocampal pyramidal neurons. Authors demonstrate that in vivo and in vitro condensation, molecular signatures of nanoscale condensates and exchange kinetics of SAP97/hDLG is modulated by the local availability of alternatively spliced isoforms. Additionally, SAP97/hDLG isoforms exhibits a differential sensitivity to Ca2+ bound Calmodulin, resulting in altered properties of nanocondensates and their real-time regulation
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Ortega-Olvera JM, Winkler R, Quintanilla-Vega B, Shibayama M, Chávez-Munguía B, Martín-Tapia D, Alarcón L, González-Mariscal L. The organophosphate pesticide methamidophos opens the blood-testis barrier and covalently binds to ZO-2 in mice. Toxicol Appl Pharmacol 2018; 360:257-272. [PMID: 30291936 DOI: 10.1016/j.taap.2018.10.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Revised: 09/21/2018] [Accepted: 10/01/2018] [Indexed: 12/12/2022]
Abstract
Methamidophos (MET) is an organophosphate (OP) pesticide widely used in agriculture in developing countries. MET causes adverse effects in male reproductive function in humans and experimental animals, but the underlying mechanisms remain largely unknown. We explored the effect of MET on mice testes (5 mg/kg/day/4 days), finding that this pesticide opens the blood-testis barrier and perturbs spermatogenesis, generating the appearance of immature germ cells in the epididymis. In the seminiferous tubules, MET treatment changed the level of expression or modified the stage-specific localization of tight junction (TJ) proteins ZO-1, ZO-2, occludin, and claudin-3. In contrast, claudin-11 was barely altered. MET also modified the shape of claudin-11, and ZO-2 at the cell border, from a zigzag to a more linear pattern. In addition, MET diminished the expression of ZO-2 in spermatids present in seminiferous tubules, induced the phosphorylation of ZO-2 and occludin in testes and reduced the interaction between these proteins assessed by co-immunoprecipitation. MET formed covalent bonds with ZO-2 in serine, tyrosine and lysine residues. The covalent modifications formed on ZO-2 at putative phosphorylation sites might interfere with ZO-2 interaction with regulatory molecules and other TJ proteins. MET bonds formed at ZO-2 ubiquitination sites likely interfere with ZO-2 degradation and TJ sealing, based on results obtained in cultured epithelial cells transfected with ZO-2 mutated at a MET target lysine residue. Our results shed light on MET male reproductive toxicity and are important to improve regulations regarding the use of OP pesticides and to protect the health of agricultural workers.
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Affiliation(s)
| | - Robert Winkler
- Department of Biotechnology and Biochemistry, Cinvestav, Irapuato 36824, Mexico; Max Planck Institute for Chemical Ecology, Jena 07745, Germany
| | | | - Mineko Shibayama
- Department of Infectomics and Molecular Pathogenesis, Cinvestav, Mexico City 07360, Mexico
| | - Bibiana Chávez-Munguía
- Department of Infectomics and Molecular Pathogenesis, Cinvestav, Mexico City 07360, Mexico
| | - Dolores Martín-Tapia
- Department of Physiology, Biophysics and Neuroscience, Cinvestav, Mexico City 07360, Mexico
| | - Lourdes Alarcón
- Department of Physiology, Biophysics and Neuroscience, Cinvestav, Mexico City 07360, Mexico
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Del Pino I, Koch D, Schemm R, Qualmann B, Betz H, Paarmann I. Proteomic analysis of glycine receptor β subunit (GlyRβ)-interacting proteins: evidence for syndapin I regulating synaptic glycine receptors. J Biol Chem 2014; 289:11396-11409. [PMID: 24509844 DOI: 10.1074/jbc.m113.504860] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Glycine receptors (GlyRs) mediate inhibitory neurotransmission in spinal cord and brainstem. They are clustered at inhibitory postsynapses via a tight interaction of their β subunits (GlyRβ) with the scaffolding protein gephyrin. In an attempt to isolate additional proteins interacting with GlyRβ, we performed pulldown experiments with rat brain extracts using a glutathione S-transferase fusion protein encompassing amino acids 378-455 of the large intracellular loop of GlyRβ as bait. This identified syndapin I (SdpI) as a novel interaction partner of GlyRβ that coimmunoprecipitates with native GlyRs from brainstem extracts. Both SdpI and SdpII bound efficiently to the intracellular loop of GlyRβ in vitro and colocalized with GlyRβ upon coexpression in COS-7 cells. The SdpI-binding site was mapped to a proline-rich sequence of 22 amino acids within the intracellular loop of GlyRβ. Deletion and point mutation analysis disclosed that SdpI binding to GlyRβ is Src homology 3 domain-dependent. In cultured rat spinal cord neurons, SdpI immunoreactivity was found to partially colocalize with marker proteins of inhibitory and excitatory synapses. When SdpI was acutely knocked down in cultured spinal cord neurons by viral miRNA expression, postsynaptic GlyR clusters were significantly reduced in both size and number. Similar changes in GlyR cluster properties were found in spinal cultures from SdpI-deficient mice. Our results are consistent with a role of SdpI in the trafficking and/or cytoskeletal anchoring of synaptic GlyRs.
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Affiliation(s)
- Isabel Del Pino
- Department of Neurochemistry, Max-Planck-Institute for Brain Research, D-60438 Frankfurt/Main
| | - Dennis Koch
- Institute for Biochemistry I, Jena University Hospital, Friedrich Schiller University Jena, D-07743 Jena
| | - Rudolf Schemm
- Department for Theoretical and Computational Biophysics, Max-Planck-Institute for Biophysical Chemistry, D-37077 Göttingen, and
| | - Britta Qualmann
- Institute for Biochemistry I, Jena University Hospital, Friedrich Schiller University Jena, D-07743 Jena
| | - Heinrich Betz
- Department of Neurochemistry, Max-Planck-Institute for Brain Research, D-60438 Frankfurt/Main,; Max-Planck Institute for Medical Research, 69120 Heidelberg, Germany.
| | - Ingo Paarmann
- Department of Neurochemistry, Max-Planck-Institute for Brain Research, D-60438 Frankfurt/Main,.
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Hervé JC, Derangeon M, Sarrouilhe D, Bourmeyster N. Influence of the scaffolding protein Zonula Occludens (ZOs) on membrane channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:595-604. [DOI: 10.1016/j.bbamem.2013.07.006] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 07/02/2013] [Accepted: 07/04/2013] [Indexed: 01/20/2023]
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Gorny X, Mikhaylova M, Seeger C, Reddy PP, Reissner C, Schott BH, Helena Danielson U, Kreutz MR, Seidenbecher C. AKAP79/150 interacts with the neuronal calcium-binding protein caldendrin. J Neurochem 2012; 122:714-26. [PMID: 22693956 DOI: 10.1111/j.1471-4159.2012.07828.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The A kinase-anchoring protein AKAP79/150 is a postsynaptic scaffold molecule and a key regulator of signaling events. At the postsynapse it coordinates phosphorylation and dephosphorylation of receptors via anchoring kinases and phosphatases near their substrates. Interactions between AKAP79 and two Ca(2+) -binding proteins caldendrin and calmodulin have been investigated here. Calmodulin is a known interaction partner of AKAP79/150 that has been shown to regulate activity of the kinase PKC in a Ca(2+) -dependent manner. Pull-down experiments and surface plasmon resonance biosensor analyses have been used here to demonstrate that AKAP79 can also interact with caldendrin, a neuronal calcium-binding protein implicated in regulation of Ca(2+) -influx and release. We demonstrate that calmodulin and caldendrin compete for a partially overlapping binding site on AKAP79 and that their binding is differentially dependent on calcium. Therefore, this competition is regulated by calcium levels. Moreover, both proteins have different binding characteristics suggesting that the two proteins might play complementary roles. The postsynaptic enrichment, the complex binding mechanism, and the competition with calmodulin, makes caldendrin an interesting novel player in the signaling toolkit of the AKAP interactome.
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Affiliation(s)
- Xenia Gorny
- Leibniz Institute for Neurobiology, Magdeburg, Germany
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9
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González-Mariscal L, Quirós M, Díaz-Coránguez M. ZO proteins and redox-dependent processes. Antioxid Redox Signal 2011; 15:1235-53. [PMID: 21294657 DOI: 10.1089/ars.2011.3913] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
SIGNIFICANCE ZO-1, ZO-2, and ZO-3 are scaffold proteins of the tight junction (TJ) that belong to the MAGUK protein family characterized for exhibiting PDZ, SH3, and GuK domains. ZO proteins are present only in multicellular organisms, being the placozoa the first to have them. ZO proteins associate among themselves and with other integral and adaptor proteins of the TJ, of the ZA and of gap junctions, as with numerous signaling proteins and the actin cytoskeleton. ZO proteins are also present at the nucleus of proliferating cells. RECENT ADVANCES Oxidative stress disassembles the TJs of endothelial and epithelial cells. CRITICAL ISSUES Oxidative stress alters ZO proteins expression and localization, in conditions like hypoxia, bacterial and viral infections, vitamin deficiencies, age-related diseases, diabetes and inflammation, alcohol and tobacco consumption. FUTURE DIRECTIONS Molecules present in the signaling pathways triggered by oxidative stress can be targets for therapeutic intervention.
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Affiliation(s)
- Lorenza González-Mariscal
- Department of Physiology, Biophysics and Neuroscience, Center for Research and Advanced Studies (Cinvestav), Mexico DF, México.
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10
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Lye MF, Fanning AS, Su Y, Anderson JM, Lavie A. Insights into regulated ligand binding sites from the structure of ZO-1 Src homology 3-guanylate kinase module. J Biol Chem 2010; 285:13907-17. [PMID: 20200156 DOI: 10.1074/jbc.m109.093674] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tight junctions are dynamic components of epithelial and endothelial cells that regulate the paracellular transport of ions, solutes, and immune cells. The assembly and permeability of these junctions is dependent on the zonula occludens (ZO) proteins, members of the membrane-associated guanylate kinase homolog (MAGUK) protein family, which are characterized by a core Src homology 3 (SH3)-GUK module that coordinates multiple protein-protein interactions. The structure of the ZO-1 SH3-GUK domain confirms that the interdependent folding of the SH3 and GUK domains is a conserved feature of MAGUKs, but differences in the orientation of the GUK domains in three different MAGUKs reveal interdomain flexibility of the core unit. Using pull-down assays, we show that an effector loop, the U6 region in ZO-1, forms a novel intramolecular interaction with the core module. This interaction is divalent cation-dependent and overlaps with the binding site for the regulatory molecule calmodulin on the GUK domain. These findings provide insight into the previously observed ability of the U6 region to regulate TJ assembly in vivo and the structural basis for the complex protein interactions of the MAGUK family.
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Affiliation(s)
- Ming F Lye
- Department of Biochemistry and Molecular Genetics, University of Illinois, Chicago, Illinois 60607, USA
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Rich RL, Myszka DG. Grading the commercial optical biosensor literature-Class of 2008: 'The Mighty Binders'. J Mol Recognit 2010; 23:1-64. [PMID: 20017116 DOI: 10.1002/jmr.1004] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Optical biosensor technology continues to be the method of choice for label-free, real-time interaction analysis. But when it comes to improving the quality of the biosensor literature, education should be fundamental. Of the 1413 articles published in 2008, less than 30% would pass the requirements for high-school chemistry. To teach by example, we spotlight 10 papers that illustrate how to implement the technology properly. Then we grade every paper published in 2008 on a scale from A to F and outline what features make a biosensor article fabulous, middling or abysmal. To help improve the quality of published data, we focus on a few experimental, analysis and presentation mistakes that are alarmingly common. With the literature as a guide, we want to ensure that no user is left behind.
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Affiliation(s)
- Rebecca L Rich
- Center for Biomolecular Interaction Analysis, University of Utah, Salt Lake City, UT 84132, USA
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12
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Van Elzen R, Ghesquière B, Timmerman E, Vandamme S, Moens L, Gevaert K, Dewilde S. Integrated Proteomic Analysis Reveals a Substantial Enrichment of Protein Trafficking Processes in Hippocampus Tissue after Hypoxic Stress. J Proteome Res 2009; 9:204-15. [DOI: 10.1021/pr900517m] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Roos Van Elzen
- Department of Biomedical Sciences, University of Antwerp, B-2610 Antwerp, Belgium, Department of Medical Protein Research, VIB, B-9000 Ghent, Belgium, Department of Biochemistry, Ghent University, B-9000 Ghent, Belgium, and Department of Biology, University of Antwerp, B-2610 Antwerp, Belgium
| | - Bart Ghesquière
- Department of Biomedical Sciences, University of Antwerp, B-2610 Antwerp, Belgium, Department of Medical Protein Research, VIB, B-9000 Ghent, Belgium, Department of Biochemistry, Ghent University, B-9000 Ghent, Belgium, and Department of Biology, University of Antwerp, B-2610 Antwerp, Belgium
| | - Evy Timmerman
- Department of Biomedical Sciences, University of Antwerp, B-2610 Antwerp, Belgium, Department of Medical Protein Research, VIB, B-9000 Ghent, Belgium, Department of Biochemistry, Ghent University, B-9000 Ghent, Belgium, and Department of Biology, University of Antwerp, B-2610 Antwerp, Belgium
| | - Stefaan Vandamme
- Department of Biomedical Sciences, University of Antwerp, B-2610 Antwerp, Belgium, Department of Medical Protein Research, VIB, B-9000 Ghent, Belgium, Department of Biochemistry, Ghent University, B-9000 Ghent, Belgium, and Department of Biology, University of Antwerp, B-2610 Antwerp, Belgium
| | - Luc Moens
- Department of Biomedical Sciences, University of Antwerp, B-2610 Antwerp, Belgium, Department of Medical Protein Research, VIB, B-9000 Ghent, Belgium, Department of Biochemistry, Ghent University, B-9000 Ghent, Belgium, and Department of Biology, University of Antwerp, B-2610 Antwerp, Belgium
| | - Kris Gevaert
- Department of Biomedical Sciences, University of Antwerp, B-2610 Antwerp, Belgium, Department of Medical Protein Research, VIB, B-9000 Ghent, Belgium, Department of Biochemistry, Ghent University, B-9000 Ghent, Belgium, and Department of Biology, University of Antwerp, B-2610 Antwerp, Belgium
| | - Sylvia Dewilde
- Department of Biomedical Sciences, University of Antwerp, B-2610 Antwerp, Belgium, Department of Medical Protein Research, VIB, B-9000 Ghent, Belgium, Department of Biochemistry, Ghent University, B-9000 Ghent, Belgium, and Department of Biology, University of Antwerp, B-2610 Antwerp, Belgium
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Fanning AS, Anderson JM. Zonula occludens-1 and -2 are cytosolic scaffolds that regulate the assembly of cellular junctions. Ann N Y Acad Sci 2009; 1165:113-20. [PMID: 19538295 DOI: 10.1111/j.1749-6632.2009.04440.x] [Citation(s) in RCA: 293] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The integrity of the tight junction barrier in epithelial and endothelial cells is critical to human health, but we still lack a detailed mechanistic knowledge of how the barrier is formed during development or responds to pathological and pharmacological insults. This limits our understanding of barrier dysfunction in disease and slows the development of therapeutic strategies. Recent studies confirm the long-maintained but previously unsupported view that the zonula occludens (ZO) proteins ZO-1 and ZO-2 are critical determinants of barrier formation. However, ZO proteins can also be components of adherens junctions, and recent studies suggest that ZO proteins may also promote the assembly and function of these junctions during epithelial morphogenesis. We review these studies and outline several recent observations that suggest that one role of ZO proteins is to regulate cytoskeletal dynamics at cell junctions. Finally, we propose a model by which the functional activities of ZO proteins in the adherens junction and tight junction are differentiated by a novel regulatory motif known as the U6 or acidic motif.
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Affiliation(s)
- Alan S Fanning
- The Department of Cell and Molecular Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7545, USA.
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Newman RA, Prehoda KE. Intramolecular interactions between the SRC homology 3 and guanylate kinase domains of discs large regulate its function in asymmetric cell division. J Biol Chem 2009; 284:12924-32. [PMID: 19261607 DOI: 10.1074/jbc.m809304200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Membrane-associated guanylate kinases (MAGUKs) regulate the formation and function of molecular assemblies at specialized regions of the membrane. Allosteric regulation of an intramolecular interaction between the Src homology 3 (SH3) and guanylate kinase (GK) domains of MAGUKs is thought to play a central role in regulating MAGUK function. Here we show that a mutant of the Drosophila MAGUK Discs large (Dlg), dlg(sw), encodes a form of Dlg that disrupts the intramolecular association while leaving the SH3 and GK domains intact, providing an excellent model system to assess the role of the SH3-GK intramolecular interaction in MAGUK function. Analysis of asymmetric cell division of maternal-zygotic dlg(sw) embryonic neuroblasts demonstrates that the intramolecular interaction is not required for Dlg localization but is necessary for cell fate determinant segregation to the basal cortex and mitotic spindle alignment with the cortical polarity axis. These defects ultimately result in improper patterning of the embryonic central nervous system. Furthermore, we demonstrate that the sw mutation of Dlg results in unregulated complex assembly as assessed by GukHolder association with the SH3-GK versus PDZ-SH3-GK modules of Dlg(sw). From these studies, we conclude that allosteric regulation of the SH3-GK intramolecular interaction is required for regulation of MAGUK function in asymmetric cell division, possibly through regulation of complex assembly.
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Affiliation(s)
- Rhonda A Newman
- Department of Chemistry and Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
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