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Taylor A, Warner M, Mendoza C, Memmott C, LeCheminant T, Bailey S, Christensen C, Keller J, Suli A, Mizrachi D. Chimeric Claudins: A New Tool to Study Tight Junction Structure and Function. Int J Mol Sci 2021; 22:ijms22094947. [PMID: 34066630 PMCID: PMC8124314 DOI: 10.3390/ijms22094947] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 05/02/2021] [Accepted: 05/04/2021] [Indexed: 12/11/2022] Open
Abstract
The tight junction (TJ) is a structure composed of multiple proteins, both cytosolic and membranal, responsible for cell–cell adhesion in polarized endothelium and epithelium. The TJ is intimately connected to the cytoskeleton and plays a role in development and homeostasis. Among the TJ’s membrane proteins, claudins (CLDNs) are key to establishing blood–tissue barriers that protect organismal physiology. Recently, several crystal structures have been reported for detergent extracted recombinant CLDNs. These structural advances lack direct evidence to support quaternary structure of CLDNs. In this article, we have employed protein-engineering principles to create detergent-independent chimeric CLDNs, a combination of a 4-helix bundle soluble monomeric protein (PDB ID: 2jua) and the apical—50% of human CLDN1, the extracellular domain that is responsible for cell–cell adhesion. Maltose-binding protein-fused chimeric CLDNs (MBP-CCs) used in this study are soluble proteins that retain structural and functional aspects of native CLDNs. Here, we report the biophysical characterization of the structure and function of MBP-CCs. MBP-fused epithelial cadherin (MBP-eCAD) is used as a control and point of comparison of a well-characterized cell-adhesion molecule. Our synthetic strategy may benefit other families of 4-α-helix membrane proteins, including tetraspanins, connexins, pannexins, innexins, and more.
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Zhang JX, Qin MB, Ye Z, Peng P, Li SM, Song Q, Lin L, Liu SQ, Xie LH, Zhu Y, Huang JA. Association of tricellulin expression with poor colorectal cancer prognosis and metastasis. Oncol Rep 2020; 44:2174-2184. [PMID: 33000262 PMCID: PMC7551433 DOI: 10.3892/or.2020.7773] [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: 04/06/2020] [Accepted: 08/20/2020] [Indexed: 12/24/2022] Open
Abstract
Tricellulin is a tight-junction transmembrane protein that regulates cell-cell interactions. Altered tricellulin expression could promote tumor cell invasions and metastasis in human cancers. The present study assessed tricellulin expression in colorectal cancer tissues for any association with clinicopathological features of colorectal cancer patients and then investigated the underlying molecular events using quantitative proteomic analysis and in vitro experiments. Tissue samples from 98 colorectal cancer patients and 15 volunteers were collected for immunohistochemistry. Colorectal cell lines were used to overexpress or knockdown tricellulin expression in various assays. The data revealed that upregulated tricellulin expression was associated with lymph node and distant metastases and poor prognosis, while tricellulin overexpression promoted colorectal cancer cell migration and invasion in vitro. In contrast, tricellulin knockdown had positive effects on the tumor cells. Furthermore, TMT-LC-MS/MS and bioinformatics analyses revealed that tricellulin was involved in EMT and reduction of apoptosis through the NF-κB signaling pathway. These findings highlight for the first time the significance of tricellulin in colorectal cancer development and progression. Further study may validate tricellulin as a novel biomarker and target for colorectal cancer.
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Affiliation(s)
- Jin-Xiu Zhang
- Department of Gastroenterology, The Second Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi Zhuang Autonomous Region 530007, P.R. China
| | - Meng-Bin Qin
- Department of Gastroenterology, The Second Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi Zhuang Autonomous Region 530007, P.R. China
| | - Zhe Ye
- Department of Gastroenterology, The Second Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi Zhuang Autonomous Region 530007, P.R. China
| | - Peng Peng
- Department of Gastroenterology, The Second Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi Zhuang Autonomous Region 530007, P.R. China
| | - Si-Man Li
- Department of Gastroenterology, The Second Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi Zhuang Autonomous Region 530007, P.R. China
| | - Qian Song
- Department of Gastroenterology, The Second Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi Zhuang Autonomous Region 530007, P.R. China
| | - Lan Lin
- Department of Gastroenterology, The Second Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi Zhuang Autonomous Region 530007, P.R. China
| | - Shi-Quan Liu
- Department of Gastroenterology, The Second Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi Zhuang Autonomous Region 530007, P.R. China
| | - Li-Hua Xie
- Department of Gastroenterology, The Second Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi Zhuang Autonomous Region 530007, P.R. China
| | - Ye Zhu
- Department of Gastroenterology, The Second Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi Zhuang Autonomous Region 530007, P.R. China
| | - Jie-An Huang
- Department of Gastroenterology, The Second Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi Zhuang Autonomous Region 530007, P.R. China
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Piontek J, Krug SM, Protze J, Krause G, Fromm M. Molecular architecture and assembly of the tight junction backbone. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183279. [PMID: 32224152 DOI: 10.1016/j.bbamem.2020.183279] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Revised: 03/16/2020] [Accepted: 03/19/2020] [Indexed: 12/18/2022]
Abstract
The functional and structural concept of tight junctions has developed after discovery of claudin and TAMP proteins. Many of these proteins contribute to epi- and endothelial barrier but some, in contrast, form paracellular channels. Claudins form the backbone of tight junction (TJ) strands whereas other proteins regulate TJ dynamics. The current joined double-row model of TJ strands and channels is crucially based on the linear alignment of claudin-15 in the crystal. Molecular dynamics simulations, protein docking, mutagenesis, cellular TJ reconstitution, and electron microscopy studies largely support stability and functionality of the model. Here, we summarize in silico and in vitro data about TJ strand assembly including comparison of claudin crystal structures and alternative models. Sequence comparisons, experimental and structural data substantiate differentiation of classic and non-classic claudins differing in motifs related to strand assembly. Classic claudins seem to share a similar mechanism of strand formation. Interface variations likely contribute to TJ strand flexibility. Combined in vitro/in silico studies are expected to elucidate mechanistic keys determining TJ regulation.
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Affiliation(s)
- Jörg Piontek
- Institute of Clinical Physiology/Nutritional Medicine, Medical Department, Division of Gastroenterology, Infectiology, Rheumatology, Charité - Universitätsmedizin Berlin, 12203 Berlin, Germany
| | - Susanne M Krug
- Institute of Clinical Physiology/Nutritional Medicine, Medical Department, Division of Gastroenterology, Infectiology, Rheumatology, Charité - Universitätsmedizin Berlin, 12203 Berlin, Germany
| | - Jonas Protze
- Leibniz-Institut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany
| | - Gerd Krause
- Leibniz-Institut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany
| | - Michael Fromm
- Institute of Clinical Physiology/Nutritional Medicine, Medical Department, Division of Gastroenterology, Infectiology, Rheumatology, Charité - Universitätsmedizin Berlin, 12203 Berlin, Germany.
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Molecular organization, regulation and function of tricellular junctions. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183143. [DOI: 10.1016/j.bbamem.2019.183143] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 11/21/2019] [Accepted: 11/29/2019] [Indexed: 02/07/2023]
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Heinemann U, Schuetz A. Structural Features of Tight-Junction Proteins. Int J Mol Sci 2019; 20:E6020. [PMID: 31795346 PMCID: PMC6928914 DOI: 10.3390/ijms20236020] [Citation(s) in RCA: 88] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 11/25/2019] [Accepted: 11/26/2019] [Indexed: 12/14/2022] Open
Abstract
Tight junctions are complex supramolecular entities composed of integral membrane proteins, membrane-associated and soluble cytoplasmic proteins engaging in an intricate and dynamic system of protein-protein interactions. Three-dimensional structures of several tight-junction proteins or their isolated domains have been determined by X-ray crystallography, nuclear magnetic resonance spectroscopy, and cryo-electron microscopy. These structures provide direct insight into molecular interactions that contribute to the formation, integrity, or function of tight junctions. In addition, the known experimental structures have allowed the modeling of ligand-binding events involving tight-junction proteins. Here, we review the published structures of tight-junction proteins. We show that these proteins are composed of a limited set of structural motifs and highlight common types of interactions between tight-junction proteins and their ligands involving these motifs.
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Affiliation(s)
- Udo Heinemann
- Macromolecular Structure and Interaction Laboratory, Max Delbrück Center for Molecular Medicine, 13125 Berlin, Germany
| | - Anja Schuetz
- Protein Production & Characterization Platform, Max Delbrück Center for Molecular Medicine, 13125 Berlin, Germany
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Applications of catalyzed cytoplasmic disulfide bond formation. Biochem Soc Trans 2019; 47:1223-1231. [DOI: 10.1042/bst20190088] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Revised: 09/09/2019] [Accepted: 09/20/2019] [Indexed: 12/14/2022]
Abstract
Abstract
Disulfide bond formation is an essential post-translational modification required for many proteins to attain their native, functional structure. The formation of disulfide bonds, otherwise known as oxidative protein folding, occurs in the endoplasmic reticulum and mitochondrial inter-membrane space in eukaryotes and the periplasm of prokaryotes. While there are differences in the molecular mechanisms of oxidative folding in different compartments, it can essentially be broken down into two steps, disulfide formation and disulfide isomerization. For both steps, catalysts exist in all compartments where native disulfide bond formation occurs. Due to the importance of disulfide bonds for a plethora of proteins, considerable effort has been made to generate cell factories which can make them more efficiently and cheaper. Recently synthetic biology has been used to transfer catalysts of native disulfide bond formation into the cytoplasm of prokaryotes such as Escherichia coli. While these engineered systems cannot yet rival natural systems in the range and complexity of disulfide-bonded proteins that can be made, a growing range of proteins have been made successfully and yields of homogenously folded eukaryotic proteins exceeding g/l yields have been obtained. This review will briefly give an overview of such systems, the uses reported to date and areas of future potential development, including combining with engineered systems for cytoplasmic glycosylation.
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Apoptotic Fragmentation of Tricellulin. Int J Mol Sci 2019; 20:ijms20194882. [PMID: 31581480 PMCID: PMC6801678 DOI: 10.3390/ijms20194882] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 09/25/2019] [Accepted: 09/26/2019] [Indexed: 01/02/2023] Open
Abstract
Apoptotic extrusion of cells from epithelial cell layers is of central importance for epithelial homeostasis. As a prerequisite cell-cell contacts between apoptotic cells and their neighbors have to be dissociated. Tricellular tight junctions (tTJs) represent specialized structures that seal polarized epithelial cells at sites where three cells meet and are characterized by the specific expression of tricellulin and angulins. Here, we specifically addressed the fate of tricellulin in apoptotic cells. METHODS Apoptosis was induced by staurosporine or camptothecin in MDCKII and RT-112 cells. The fate of tricellulin was analyzed by Western blotting and immunofluorescence microscopy. Caspase activity was inhibited by Z-VAD-FMK or Z-DEVD-FMK. RESULTS Induction of apoptosis induces the degradation of tricellulin with time. Aspartate residues 487 and 441 were identified as caspase cleavage-sites in the C-terminal coiled-coil domain of human tricellulin. Fragmentation of tricellulin was inhibited in the presence of caspase inhibitors or when Asp487 or Asp441 were mutated to asparagine. Deletion of the tricellulin C-terminal amino acids prevented binding to lipolysis-stimulated lipoprotein receptor (LSR)/angulin-1 and thus should impair specific localization of tricellulin to tTJs. CONCLUSIONS Tricellulin is a substrate of caspases and its cleavage in consequence contributes to the dissolution of tTJs during apoptosis.
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