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Alghalayini A, Hossain KR, Moghaddasi S, Turkewitz DR, D’Amario C, Wallach M, Valenzuela SM. In Vitro Enzymatic Studies Reveal pH and Temperature Sensitive Properties of the CLIC Proteins. Biomolecules 2023; 13:1394. [PMID: 37759794 PMCID: PMC10526857 DOI: 10.3390/biom13091394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Revised: 09/09/2023] [Accepted: 09/10/2023] [Indexed: 09/29/2023] Open
Abstract
Chloride intracellular ion channel (CLIC) proteins exist as both soluble and integral membrane proteins, with CLIC1 capable of shifting between two distinct structural conformations. New evidence has emerged indicating that members of the CLIC family act as moonlighting proteins, referring to the ability of a single protein to carry out multiple functions. In addition to their ion channel activity, CLIC family members possess oxidoreductase enzymatic activity and share significant structural and sequence homology, along with varying overlaps in their tissue distribution and cellular localization. In this study, the 2-hydroxyethyl disulfide (HEDS) assay system was used to characterize kinetic properties, as well as the temperature and pH profiles of three CLIC protein family members (CLIC1, CLIC3, CLIC4). We also assessed the effects of the drugs rapamycin and amphotericin B, on the three CLIC proteins' enzymatic activity in the HEDS assay. Our results demonstrate CLIC1 to be highly heat-sensitive, with optimal enzymatic activity observed at neutral pH7 and at a temperature of 37 °C, while CLIC3 had higher oxidoreductase activity in more acidic pH5 and was found to be relatively heat stable. CLIC4, like CLIC1, was temperature sensitive with optimal enzymatic activity observed at 37 °C; however, it showed optimal activity in more alkaline conditions of pH8. Our current study demonstrates individual differences in the enzymatic activity between the three CLIC proteins, suggesting each CLIC protein is likely regulated in discrete ways, involving changes in the subcellular milieu and microenvironment.
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Affiliation(s)
- Amani Alghalayini
- School of Life Sciences, University of Technology Sydney, Sydney, NSW 2007, Australia; (A.A.); (K.R.H.); (S.M.); (D.R.T.); (C.D.); (M.W.)
- ARC Research Hub for Integrated Device for End-User Analysis at Low-Levels (IDEAL), Faculty of Science, University of Technology Sydney, Sydney, NSW 2007, Australia
| | - Khondker Rufaka Hossain
- School of Life Sciences, University of Technology Sydney, Sydney, NSW 2007, Australia; (A.A.); (K.R.H.); (S.M.); (D.R.T.); (C.D.); (M.W.)
- ARC Research Hub for Integrated Device for End-User Analysis at Low-Levels (IDEAL), Faculty of Science, University of Technology Sydney, Sydney, NSW 2007, Australia
| | - Saba Moghaddasi
- School of Life Sciences, University of Technology Sydney, Sydney, NSW 2007, Australia; (A.A.); (K.R.H.); (S.M.); (D.R.T.); (C.D.); (M.W.)
| | - Daniel R. Turkewitz
- School of Life Sciences, University of Technology Sydney, Sydney, NSW 2007, Australia; (A.A.); (K.R.H.); (S.M.); (D.R.T.); (C.D.); (M.W.)
| | - Claudia D’Amario
- School of Life Sciences, University of Technology Sydney, Sydney, NSW 2007, Australia; (A.A.); (K.R.H.); (S.M.); (D.R.T.); (C.D.); (M.W.)
| | - Michael Wallach
- School of Life Sciences, University of Technology Sydney, Sydney, NSW 2007, Australia; (A.A.); (K.R.H.); (S.M.); (D.R.T.); (C.D.); (M.W.)
| | - Stella M. Valenzuela
- School of Life Sciences, University of Technology Sydney, Sydney, NSW 2007, Australia; (A.A.); (K.R.H.); (S.M.); (D.R.T.); (C.D.); (M.W.)
- ARC Research Hub for Integrated Device for End-User Analysis at Low-Levels (IDEAL), Faculty of Science, University of Technology Sydney, Sydney, NSW 2007, Australia
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Zhang L, Chen X, Yao S, Zheng L, Yang X, Wang Y, Li X, Wu E, Tuo B. Intracellular chloride channel 1 and tumor. Am J Cancer Res 2023; 13:3300-3314. [PMID: 37693147 PMCID: PMC10492100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2023] [Accepted: 07/08/2023] [Indexed: 09/12/2023] Open
Abstract
As the major intracellular anion, chloride plays an important role in maintaining intracellular and extracellular ion homeostasis, osmotic pressure, and cell volume. Intracellular chloride channel 1, which has the physiological role of forming membrane proteins in the lipid bilayer and playing ion channels, is a hot research topic in recent years. It has been found that CLIC1 does not only act as an ion channel but also participates in cell cycle regulation, apoptosis, and intracellular oxidation; thus, it participates in the proliferation, invasion, and migration of various tumor cells in various systems throughout the body. At the same time, CLIC1 is highly expressed in tumor cells and is associated with malignancy and a poor prognosis. This paper reviews the pathological mechanisms of CLIC1 in systemic diseases, which is important for the early diagnosis, treatment, and prognosis of systemic diseases associated with CLIC1 expression.
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Affiliation(s)
- Li Zhang
- Department of Gastroenterology, Digestive Disease Hospital, Affiliated Hospital of Zunyi Medical UniversityZunyi, Guizhou, China
| | - Xingyue Chen
- Department of Gastroenterology, Digestive Disease Hospital, Affiliated Hospital of Zunyi Medical UniversityZunyi, Guizhou, China
| | - Shun Yao
- Department of Gastroenterology, Digestive Disease Hospital, Affiliated Hospital of Zunyi Medical UniversityZunyi, Guizhou, China
| | - Liming Zheng
- Department of Gastroenterology, Digestive Disease Hospital, Affiliated Hospital of Zunyi Medical UniversityZunyi, Guizhou, China
| | - Xingyue Yang
- Department of Gastroenterology, Digestive Disease Hospital, Affiliated Hospital of Zunyi Medical UniversityZunyi, Guizhou, China
| | - Yongfeng Wang
- Department of Gastroenterology, Digestive Disease Hospital, Affiliated Hospital of Zunyi Medical UniversityZunyi, Guizhou, China
| | - Xin Li
- Department of Gastroenterology, Digestive Disease Hospital, Affiliated Hospital of Zunyi Medical UniversityZunyi, Guizhou, China
| | - Enqin Wu
- Department of Gastroenterology, Digestive Disease Hospital, Affiliated Hospital of Zunyi Medical UniversityZunyi, Guizhou, China
| | - Biguang Tuo
- Department of Gastroenterology, Digestive Disease Hospital, Affiliated Hospital of Zunyi Medical UniversityZunyi, Guizhou, China
- The Collaborative Innovation Center of Tissue Damage Repair and Regenerative Medicine of Zunyi Medical UniversityZunyi, Guizhou, China
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Liu D, De Schutter K, Far J, Staes A, Dewettinck K, Quinton L, Gevaert K, Smagghe G. RNAi of Mannosidase-Ia in the Colorado potato beetle and changes in the midgut and peritrophic membrane. PEST MANAGEMENT SCIENCE 2022; 78:5071-5079. [PMID: 36053804 DOI: 10.1002/ps.7145] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 08/03/2022] [Accepted: 08/23/2022] [Indexed: 06/15/2023]
Abstract
BACKGROUND In addition to its role in the digestive system, the peritrophic membrane (PM) provides a physical barrier protecting the intestine from abrasion and against pathogens. Because of its sensitivity to RNA interference (RNAi), the notorious pest insect, the Colorado potato beetle (CPB, Leptinotarsa decemlineata), has become a model insect for functional studies. Previously, RNAi-mediated silencing of Mannosidase-Ia (ManIa), a key enzyme in the transition from high-mannose glycan moieties to paucimannose N-glycans, was shown to disrupt the transition from larva to pupa and the metamorphosis into adult beetles. While these effects at the organismal level were interesting in a pest control context, the effects at the organ or tissue level and also immune effects have not been investigated yet. To fill this knowledge gap, we performed an analysis of the midgut and PM in ManIa-silenced insects. RESULTS As marked phenotype, the ManIaRNAi insects, the PM pore size was found to be decreased when compared to the control GFPRNAi insects. These smaller pores are related to the observation of thinner microvilli (Mv) on the epithelial cells of the midgut of ManIaRNAi insects. A midgut and PM proteome study and reverse transcription quantitative polymerase chain reaction (RT-qPCR) analysis with a selection of marker genes was performed to characterize the midgut cells and understand their response to the silencing of ManIa. In agreement with the loss of ManIa activity, an accumulation of high-mannose N-glycans was observed in the ManIa-silenced insects. As a pathogen-associated molecular pattern (PAMP), the presence of these glycan structures could trigger the activation of the immune pathways. CONCLUSION The observed decrease in PM pore size could be a response to prevent potential pathogens to access the midgut epithelium. This hypothesis is supported by the strong increase in transcription levels of the anti-fungal peptide drosomycin-like in ManIaRNAi insects, although further research is required to elucidate this possibility. The potential immune response in the midgut and the smaller pore size in the PM shed a light on the function of the PM as a physical barrier and provide evidence for the relation between the Mv and PM. © 2022 Society of Chemical Industry.
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Affiliation(s)
- Dongdong Liu
- Laboratory of Agrozoology, Department Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Kristof De Schutter
- Laboratory of Agrozoology, Department Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Johann Far
- Mass Spectrometry Laboratory, MolSys Research Unit, University of Liège, Liège, Belgium
| | - An Staes
- VIB Center for Medical Biotechnology, Ghent University, Ghent, Belgium
- Department of Biomolecular Medicine, Ghent University, Ghent, Belgium
| | - Koen Dewettinck
- Food Structure and Function Research Group, Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Loic Quinton
- Mass Spectrometry Laboratory, MolSys Research Unit, University of Liège, Liège, Belgium
| | - Kris Gevaert
- VIB Center for Medical Biotechnology, Ghent University, Ghent, Belgium
- Department of Biomolecular Medicine, Ghent University, Ghent, Belgium
| | - Guy Smagghe
- Laboratory of Agrozoology, Department Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
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Al Khamici H, Sanchez VC, Yan H, Cataisson C, Michalowski AM, Yang HH, Li L, Lee MP, Huang J, Yuspa SH. The oxidoreductase CLIC4 is required to maintain mitochondrial function and resistance to exogenous oxidants in breast cancer cells. J Biol Chem 2022; 298:102275. [PMID: 35863434 PMCID: PMC9418444 DOI: 10.1016/j.jbc.2022.102275] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Revised: 06/01/2022] [Accepted: 06/02/2022] [Indexed: 02/07/2023] Open
Abstract
The chloride intracellular channel-4 (CLIC4) is one of the six highly conserved proteins in the CLIC family that share high structural homology with GST-omega in the GST superfamily. While CLIC4 is a multifunctional protein that resides in multiple cellular compartments, the discovery of its enzymatic glutaredoxin-like activity in vitro suggested that it could function as an antioxidant. Here, we found that deleting CLIC4 from murine 6DT1 breast tumor cells using CRISPR enhanced the accumulation of reactive oxygen species (ROS) and sensitized cells to apoptosis in response to H2O2 as a ROS-inducing agent. In intact cells, H2O2 increased the expression of both CLIC4 mRNA and protein. In addition, increased superoxide production in 6DT1 cells lacking CLIC4 was associated with mitochondrial hyperactivity including increased mitochondrial membrane potential and mitochondrial organelle enlargement. In the absence of CLIC4, however, H2O2-induced apoptosis was associated with low expression and degradation of the antiapoptotic mitochondrial protein Bcl2 and the negative regulator of mitochondrial ROS, UCP2. Furthermore, transcriptomic profiling of H2O2-treated control and CLIC4-null cells revealed upregulation of genes associated with ROS-induced apoptosis and downregulation of genes that sustain mitochondrial functions. Accordingly, tumors that formed from transplantation of CLIC4-deficient 6DT1 cells were highly necrotic. These results highlight a critical role for CLIC4 in maintaining redox-homeostasis and mitochondrial functions in 6DT1 cells. Our findings also raise the possibility of targeting CLIC4 to increase cancer cell sensitivity to chemotherapeutic drugs that are based on elevating ROS in cancer cells.
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Affiliation(s)
- Heba Al Khamici
- Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Center, National Institutes of Health. Bethesda, Maryland, USA
| | - Vanesa C Sanchez
- Office of Science, Division of Nonclinical Science, Center for Tobacco Products, U.S. Food and Drug Administration, Silver Spring, Maryland, USA
| | - Hualong Yan
- Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Center, National Institutes of Health. Bethesda, Maryland, USA
| | - Christophe Cataisson
- Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Center, National Institutes of Health. Bethesda, Maryland, USA
| | - Aleksandra M Michalowski
- Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Center, National Institutes of Health. Bethesda, Maryland, USA
| | - Howard H Yang
- Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Center, National Institutes of Health. Bethesda, Maryland, USA
| | - Luowei Li
- Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Center, National Institutes of Health. Bethesda, Maryland, USA
| | - Maxwell P Lee
- Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Center, National Institutes of Health. Bethesda, Maryland, USA
| | - Jing Huang
- Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Center, National Institutes of Health. Bethesda, Maryland, USA
| | - Stuart H Yuspa
- Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Center, National Institutes of Health. Bethesda, Maryland, USA.
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Ponnalagu D, Singh H. Insights Into the Role of Mitochondrial Ion Channels in Inflammatory Response. Front Physiol 2020; 11:258. [PMID: 32327997 PMCID: PMC7160495 DOI: 10.3389/fphys.2020.00258] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 03/05/2020] [Indexed: 12/14/2022] Open
Abstract
Mitochondria are the source of many pro-inflammatory signals that cause the activation of the immune system and generate inflammatory responses. They are also potential targets of pro-inflammatory mediators, thus triggering a severe inflammatory response cycle. As mitochondria are a central hub for immune system activation, their dysfunction leads to many inflammatory disorders. Thus, strategies aiming at regulating mitochondrial dysfunction can be utilized as a therapeutic tool to cure inflammatory disorders. Two key factors that determine the structural and functional integrity of mitochondria are mitochondrial ion channels and transporters. They are not only important for maintaining the ionic homeostasis of the cell, but also play a role in regulating reactive oxygen species generation, ATP production, calcium homeostasis and apoptosis, which are common pro-inflammatory signals. The significance of the mitochondrial ion channels in inflammatory response is still not clearly understood and will need further investigation. In this article, we review the different mechanisms by which mitochondria can generate the inflammatory response as well as highlight how mitochondrial ion channels modulate these mechanisms and impact the inflammatory processes.
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Affiliation(s)
- Devasena Ponnalagu
- Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University, Wexner Medical Center, Columbus, OH, United States
| | - Harpreet Singh
- Department of Physiology and Cell Biology, Davis Heart and Lung Research Institute, The Ohio State University, Wexner Medical Center, Columbus, OH, United States
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6
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Huang MC, Chu IT, Wang ZF, Lin S, Chang TC, Chen CT. A G-Quadruplex Structure in the Promoter Region of CLIC4 Functions as a Regulatory Element for Gene Expression. Int J Mol Sci 2018; 19:ijms19092678. [PMID: 30201851 PMCID: PMC6165315 DOI: 10.3390/ijms19092678] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 09/05/2018] [Accepted: 09/06/2018] [Indexed: 12/25/2022] Open
Abstract
The differential transcriptional expression of CLIC4 between tumor cells and the surrounding stroma during cancer progression has been suggested to have a tumor-promoting effect. However, little is known about the transcriptional regulation of CLIC4. To better understand how this gene is regulated, the promoter region of CLIC4 was analyzed. We found that a high GC content near the transcriptional start site (TSS) might form an alternative G-quadruplex (G4) structure. Nuclear magnetic resonance spectroscopy (NMR) confirmed their formation in vitro. The reporter assay showed that one of the G4 structures exerted a regulatory role in gene transcription. When the G4-forming sequence was mutated to disrupt the G4 structure, the transcription activity dropped. To examine whether this G4 structure actually has an influence on gene transcription in the chromosome, we utilized the CRISPR/Cas9 system to edit the G4-forming sequence within the CLIC4 promoter in the cell genome. The pop-in/pop-out strategy was adopted to isolate the precisely-edited A375 cell clone. In CRISPR-modified A375 cell clones whose G4 was disrupted, there was a decrease in the endogenous CLIC4 messenger RNA (mRNA) expression level. In conclusion, we found that the G4 structure in the CLIC4 promoter might play an important role in regulating the level of transcription.
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Affiliation(s)
- Mu-Ching Huang
- Department of Biochemical Science and Technology, National Taiwan University, Taipei 106, Taiwan.
| | - I-Te Chu
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 115, Taiwan.
| | - Zi-Fu Wang
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 115, Taiwan.
| | - Steven Lin
- Institute of Biological Chemistry, Academia Sinica, Taipei 115, Taiwan.
| | - Ta-Chau Chang
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 115, Taiwan.
| | - Chin-Tin Chen
- Department of Biochemical Science and Technology, National Taiwan University, Taipei 106, Taiwan.
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Ferofontov A, Strulovich R, Marom M, Giladi M, Haitin Y. Inherent flexibility of CLIC6 revealed by crystallographic and solution studies. Sci Rep 2018; 8:6882. [PMID: 29720717 PMCID: PMC5931990 DOI: 10.1038/s41598-018-25231-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 04/16/2018] [Indexed: 12/22/2022] Open
Abstract
Chloride intracellular channels (CLICs) are a family of unique proteins, that were suggested to adopt both soluble and membrane-associated forms. Moreover, following this unusual metamorphic change, CLICs were shown to incorporate into membranes and mediate ion conduction in vitro, suggesting multimerization upon membrane insertion. Here, we present a 1.8 Å resolution crystal structure of the CLIC domain of mouse CLIC6 (mCLIC6). The structure reveals a monomeric arrangement and shows a high degree of structural conservation with other CLICs. Small-angle X-ray scattering (SAXS) analysis of mCLIC6 demonstrated that the overall solution structure is similar to the crystallographic conformation. Strikingly, further analysis of the SAXS data using ensemble optimization method unveiled additional elongated conformations, elucidating high structural plasticity as an inherent property of the protein. Moreover, structure-guided perturbation of the inter-domain interface by mutagenesis resulted in a population shift towards elongated conformations of mCLIC6. Additionally, we demonstrate that oxidative conditions induce an increase in mCLIC6 hydrophobicity along with mild oligomerization, which was enhanced by the presence of membrane mimetics. Together, these results provide mechanistic insights into the metamorphic nature of mCLIC6.
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Affiliation(s)
- Alisa Ferofontov
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, 6997801, Israel
| | - Roi Strulovich
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, 6997801, Israel
| | - Milit Marom
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, 6997801, Israel
| | - Moshe Giladi
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, 6997801, Israel
| | - Yoni Haitin
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, 6997801, Israel. .,Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, 6997801, Israel.
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8
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Argenzio E, Moolenaar WH. Emerging biological roles of Cl- intracellular channel proteins. J Cell Sci 2017; 129:4165-4174. [PMID: 27852828 DOI: 10.1242/jcs.189795] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Cl- intracellular channels (CLICs) are a family of six evolutionary conserved cytosolic proteins that exist in both soluble and membrane-associated forms; however, their functions have long been elusive. Soluble CLICs adopt a glutathione S-transferase (GST)-fold, can induce ion currents in artificial membranes and show oxidoreductase activity in vitro, but there is no convincing evidence of CLICs having such activities in vivo. Recent studies have revealed a role for CLIC proteins in Rho-regulated cortical actin dynamics as well as vesicular trafficking and integrin recycling, the latter of which are under the control of Rab GTPases. In this Commentary, we discuss the emerging roles of CLIC proteins in these processes and the lessons learned from gene-targeting studies. We also highlight outstanding questions regarding the molecular function(s) of these important but still poorly understood proteins.
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Affiliation(s)
- Elisabetta Argenzio
- Division of Cell Biology, The Netherlands Cancer Institute, Amsterdam 1066CX, The Netherlands
| | - Wouter H Moolenaar
- Division of Cell Biology, The Netherlands Cancer Institute, Amsterdam 1066CX, The Netherlands
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Abstract
Mitochondria are the "power house" of a cell continuously generating ATP to ensure its proper functioning. The constant production of ATP via oxidative phosphorylation demands a large electrochemical force that drives protons across the highly selective and low-permeable mitochondrial inner membrane. Besides the conventional role of generating ATP, mitochondria also play an active role in calcium signaling, generation of reactive oxygen species (ROS), stress responses, and regulation of cell-death pathways. Deficiencies in these functions result in several pathological disorders like aging, cancer, diabetes, neurodegenerative and cardiovascular diseases. A plethora of ion channels and transporters are present in the mitochondrial inner and outer membranes which work in concert to preserve the ionic equilibrium of a cell for the maintenance of cell integrity, in physiological as well as pathophysiological conditions. For, e.g., mitochondrial cation channels KATP and BKCa play a significant role in cardioprotection from ischemia-reperfusion injury. In addition to the cation channels, mitochondrial anion channels are equally essential, as they aid in maintaining electro-neutrality by regulating the cell volume and pH. This chapter focusses on the information on molecular identity, structure, function, and physiological relevance of mitochondrial chloride channels such as voltage dependent anion channels (VDACs), uncharacterized mitochondrial inner membrane anion channels (IMACs), chloride intracellular channels (CLIC) and the aspects of forthcoming chloride channels.
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Affiliation(s)
- Devasena Ponnalagu
- Department of Pharmacology and Physiology, Drexel University College of Medicine, 245 N. 15th Street, Room 8154, Mail Stop 488, Philadelphia, PA, 19102-1192, USA
| | - Harpreet Singh
- Department of Pharmacology and Physiology, Drexel University College of Medicine, 245 N. 15th Street, Room 8154, Mail Stop 488, Philadelphia, PA, 19102-1192, USA.
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10
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Carlson KSB, Nguyen L, Schwartz K, Lawrence DA, Schwartz BS. Neuroserpin Differentiates Between Forms of Tissue Type Plasminogen Activator via pH Dependent Deacylation. Front Cell Neurosci 2016; 10:154. [PMID: 27378851 PMCID: PMC4908126 DOI: 10.3389/fncel.2016.00154] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 05/27/2016] [Indexed: 11/17/2022] Open
Abstract
Tissue-type plasminogen activator (t-PA), initially characterized for its critical role in fibrinolysis, also has key functions in both physiologic and pathologic processes in the CNS. Neuroserpin (NSP) is a t-PA specific serine protease inhibitor (serpin) found almost exclusively in the CNS that regulates t-PA's proteolytic activity and protects against t-PA mediated seizure propagation and blood-brain barrier disruption. This report demonstrates that NSP inhibition of t-PA varies profoundly as a function of pH within the biologically relevant pH range for the CNS, and reflects the stability, rather than the formation of NSP: t-PA acyl-enzyme complexes. Moreover, NSP differentiates between the zymogen-like single chain form (single chain t-PA, sct-PA) and the mature protease form (two chain t-PA, tct-PA) of t-PA, demonstrating different pH profiles for protease inhibition, different pH ranges over which catalytic deacylation occurs, and different pH dependent profiles of deacylation rates for each form of t-PA. NSP's pH dependent inhibition of t-PA is not accounted for by differential acylation, and is specific for the NSP-t-PA serpin-protease pair. These results demonstrate a novel mechanism for the differential regulation of the two forms of t-PA in the CNS, and suggest a potential specific regulatory role for CNS pH in controlling t-PA proteolytic activity.
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Affiliation(s)
- Karen-Sue B. Carlson
- Department of Biomolecular Chemistry, University of Wisconsin, MadisonWI, USA
- Medical Scientist Training Program, University of Wisconsin, MadisonWI, USA
| | - Lan Nguyen
- Departments of Biochemistry and Medicine, University of Illinois, UrbanaIL, USA
| | - Kat Schwartz
- Departments of Biochemistry and Medicine, University of Illinois, UrbanaIL, USA
| | - Daniel A. Lawrence
- Departments of Medicine and Molecular and Integrative Physiology, University of Michigan, Ann ArborMI, USA
| | - Bradford S. Schwartz
- Department of Biomolecular Chemistry, University of Wisconsin, MadisonWI, USA
- Departments of Biochemistry and Medicine, University of Illinois, UrbanaIL, USA
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11
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Ponnalagu D, Gururaja Rao S, Farber J, Xin W, Hussain AT, Shah K, Tanda S, Berryman M, Edwards JC, Singh H. Molecular identity of cardiac mitochondrial chloride intracellular channel proteins. Mitochondrion 2016; 27:6-14. [PMID: 26777142 DOI: 10.1016/j.mito.2016.01.001] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 12/08/2015] [Accepted: 01/07/2016] [Indexed: 01/08/2023]
Abstract
Emerging evidences demonstrate significance of chloride channels in cardiac function and cardioprotection from ischemia-reperfusion (IR) injury. Unlike mitochondrial potassium channels sensitive to calcium (BKCa) and ATP (KATP), molecular identity of majority of cardiac mitochondrial chloride channels located at the inner membrane is not known. In this study, we report the presence of unique dimorphic chloride intracellular channel (CLIC) proteins namely CLIC1, CLIC4 and CLIC5 as abundant CLICs in the rodent heart. Further, CLIC4, CLIC5, and an ortholog present in Drosophila (DmCLIC) localize to adult cardiac mitochondria. We found that CLIC4 is enriched in the outer mitochondrial membrane, whereas CLIC5 is present in the inner mitochondrial membrane. Also, CLIC5 plays a direct role in regulating mitochondrial reactive oxygen species (ROS) generation. Our study highlights that CLIC5 is localized to the cardiac mitochondria and directly modulates mitochondrial function.
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Affiliation(s)
- Devasena Ponnalagu
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA 19102, United States
| | - Shubha Gururaja Rao
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA 19102, United States
| | - Jason Farber
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA 19102, United States
| | - Wenyu Xin
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA 19102, United States
| | - Ahmed Tafsirul Hussain
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA 19102, United States
| | - Kajol Shah
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA 19102, United States
| | - Soichi Tanda
- Department of Biological Sciences, Ohio University, Athens, OH 45701, United States
| | - Mark Berryman
- Department of Biomedical Sciences, Ohio University, Athens, OH 45701, United States
| | - John C Edwards
- Division of Nephrology, St. Louis University, St. Louis, MO 63110, United States
| | - Harpreet Singh
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA 19102, United States.
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12
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Al-Momany A, Li L, Alexander RT, Ballermann BJ. Clustered PI(4,5)P₂ accumulation and ezrin phosphorylation in response to CLIC5A. J Cell Sci 2014; 127:5164-78. [PMID: 25344252 DOI: 10.1242/jcs.147744] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
CLIC5A (encoded by CLIC5) is a component of the ezrin-NHERF2-podocalyxin complex in renal glomerular podocyte foot processes. We explored the mechanism(s) by which CLIC5A regulates ezrin function. In COS-7 cells, CLIC5A augmented ezrin phosphorylation without changing ezrin abundance, increased the association of ezrin with the cytoskeletal fraction and enhanced actin polymerization and the formation of cell surface projections. CLIC5A caused the phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] reporter RFP-PH-PLC to translocate from the cytosol to discrete plasma membrane clusters at the cell surface, where it colocalized with CLIC5A. Transiently expressed HA-PIP5Kα colocalized with GFP-CLIC5A and was pulled from cell lysates by GST-CLIC5A, and silencing of endogenous PIP5Kα abrogated CLIC5A-dependent ERM phosphorylation. N- and C-terminal deletion mutants of CLIC5A, which failed to associate with the plasma membrane, failed to colocalize with PIP5Kα, did not alter the abundance of PI(4,5)P2 plasma membrane clusters and failed to enhance ezrin phosphorylation. Relative to wild-type mice, in CLIC5-deficient mice, the phosphorylation of glomerular ezrin was diminished and the cytoskeletal association of both ezrin and NHERF2 was reduced. Therefore, the mechanism of CLIC5A action involves clustered plasma membrane PI(4,5)P2 accumulation through an interaction of CLIC5A with PI(4,5)P2-generating kinases, in turn facilitating ezrin activation and actin-dependent cell surface remodeling.
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Affiliation(s)
- Abass Al-Momany
- Department of Physiology, University of Alberta, Edmonton, AL T6G 2V2, Canada
| | - Laiji Li
- Department of Medicine (Nephrology), University of Alberta, Edmonton, AL T6G 2V2, Canada
| | - R Todd Alexander
- Department of Pediatrics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AL T6G 2V2, Canada
| | - Barbara J Ballermann
- Department of Physiology, University of Alberta, Edmonton, AL T6G 2V2, Canada Department of Medicine (Nephrology), University of Alberta, Edmonton, AL T6G 2V2, Canada
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Padmakumar V, Masiuk KE, Luger D, Lee C, Coppola V, Tessarollo L, Hoover SB, Karavanova I, Buonanno A, Simpson RM, Yuspa SH. Detection of differential fetal and adult expression of chloride intracellular channel 4 (CLIC4) protein by analysis of a green fluorescent protein knock-in mouse line. BMC DEVELOPMENTAL BIOLOGY 2014; 14:24. [PMID: 24886590 PMCID: PMC4073518 DOI: 10.1186/1471-213x-14-24] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 05/13/2014] [Indexed: 01/17/2023]
Abstract
Background Chloride Intracellular Channel 4 (CLIC4) is one of seven members in the closely related CLIC protein family. CLIC4 is involved in multiple cellular processes including apoptosis, cellular differentiation, inflammation and endothelial tubulogenesis. Despite over a decade of research, no comprehensive in situ expression analysis of CLIC4 in a living organism has been reported. In order to fulfill this goal, we generated a knock-in mouse to express Green Fluorescent Protein (GFP) from the CLIC4 locus, thus substituting the GFP coding region for CLIC4. We used GFP protein expression to eliminate cross reaction with other CLIC family members. Results We analyzed CLIC4 expression during embryonic development and adult organs. During mid and late gestation, CLIC4 expression is modulated particularly in fetal brain, heart, thymus, liver and kidney as well as in developing brown adipose tissue and stratifying epidermis. In the adult mouse, CLIC4 is highly expressed globally in vascular endothelial cells as well as in liver, lung alveolar septae, pancreatic acini, spermatogonia, renal proximal tubules, cardiomyocytes and thymic epithelial cells. Neural expression included axonal tracks, olfactory bulb, Purkinje cell layer and dentate gyrus. Renal CLIC4 expression was most pronounced in proximal tubules, although altered renal function was not detected in the absence of CLIC4. Myeloid cells and B cells of the spleen are rich in CLIC4 expression as are CD4 and CD8 positive T cells. Conclusions In a comprehensive study detailing CLIC4 expression in situ in a mouse model that excludes cross reaction with other family members, we were able to document previously unreported expression for CLIC4 in developing fetus, particularly the brain. In addition, compartmentalized expression of CLIC4 in specific adult tissues and cells provides a focus to explore potential functions of this protein not addressed previously.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | - Stuart H Yuspa
- Laboratory of Cancer Biology and Genetics, National Cancer Institute, Bethesda, MD, USA.
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14
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Edwards JC, Bruno J, Key P, Cheng YW. Absence of chloride intracellular channel 4 (CLIC4) predisposes to acute kidney injury but has minimal impact on recovery. BMC Nephrol 2014; 15:54. [PMID: 24708746 PMCID: PMC4234247 DOI: 10.1186/1471-2369-15-54] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Accepted: 03/28/2014] [Indexed: 12/02/2022] Open
Abstract
Background CLIC4, a member of the CLIC family of proteins, was recently demonstrated to translocate to the nucleus in differentiating keratinocytes where it potentiates TGFβ-driven gene regulation. Since TGFβ signaling is known to play important roles in the fibrotic response to acute kidney injury, and since CLIC4 is abundantly expressed in kidney, we hypothesized that CLIC4 may play a role in the response to acute kidney injury. Methods Previously described Clic4 null mice were analyzed for the effect of absence of CLIC4 on growth, development and response to kidney injury. Kidney size, glomerular counts and density of peritubular capillaries of matched WT and Clic4 null mice were determined. Cohorts of WT and Clic4 null mice were subjected to the folic acid model of acute kidney injury. Extent of acute injury and long term functional recovery were assessed by plasma blood urea nitrogen (BUN); long term fibrosis/scarring was determined by histochemical assessment of kidney sections and by residual renal mass. Activation of the TGFβ signaling pathway was assessed by semi-quantitative western blots of phosphorylated SMADs 2 and 3. Results CLIC4 is abundantly expressed in the apical pole of renal proximal tubule cells, and in endothelial cells of glomerular and peritubular capillaries. CLIC4 null mice are small, have smaller kidneys with fewer glomeruli and less dense peritubular capillary networks, and have increased proteinuria. The Clic4 null mice show increased susceptibility to folic acid-induced acute kidney injury but no difference in recovery from acute injury, no nuclear redistribution of CLIC4 following injury, and no significant difference in activation of the TGFβ-signaling pathway as reflected in the level of phosphorylation of SMADs 2 and 3. Conclusions Absence of CLIC4 results in morphologic changes consistent with its known role in angiogenesis. These changes may be at least partially responsible for the increased susceptibility to acute kidney injury. However, the absence of CLIC4 has no significant impact on the extent of functional recovery or fibrosis following acute injury, indicating that CLIC4 does not play a major non-redundant role in the TGFβ signaling involved in response to acute kidney injury.
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Affiliation(s)
- John C Edwards
- Kidney Center and the Department of Internal Medicine, University of North Carolina, Chapel Hill NC, USA.
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15
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Argenzio E, Margadant C, Leyton-Puig D, Janssen H, Jalink K, Sonnenberg A, Moolenaar WH. CLIC4 regulates cell adhesion and β1 integrin trafficking. J Cell Sci 2014; 127:5189-203. [DOI: 10.1242/jcs.150623] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Chloride intracellular channel (CLIC) protein CLIC4 exists in both soluble and membrane-associated forms, and is implicated in diverse cellular processes, ranging from ion channel formation to intracellular membrane remodeling. CLIC4 is rapidly recruited to the plasma membrane by lysophosphatidic acid (LPA) and serum, suggesting a possible role for CLIC4 in exocytic-endocytic trafficking. However, the function and subcellular target(s) of CLIC4 remain elusive. Here we show that in HeLa and MDA-MB-231 cells, CLIC4 knockdown decreases cell-matrix adhesion, cell spreading and integrin signalling, while increasing cell motility. LPA stimulates the recruitment of CLIC4 to β1 integrins at the plasma membrane and in Rab35-positive endosomes. CLIC4 is required for both the internalization and the serum/LPA-induced recycling of β1 integrins, but not for EGF receptor trafficking. Furthermore, we show that CLIC4 suppresses Rab35 activity and antagonizes Rab35-dependent regulation of β1-integrin trafficking. Our results define CLIC4 as a regulator of Rab35 activity and serum/LPA-dependent integrin trafficking.
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16
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Chiang PC, Chou RH, Chien HF, Tsai T, Chen CT. Chloride intracellular channel 4 involves in the reduced invasiveness of cancer cells treated by photodynamic therapy. Lasers Surg Med 2013; 45:38-47. [DOI: 10.1002/lsm.22112] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/18/2012] [Indexed: 02/02/2023]
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17
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Suh KS, Malik M, Shukla A, Ryscavage A, Wright L, Jividen K, Crutchley JM, Dumont RA, Fernandez-Salas E, Webster JD, Simpson RM, Yuspa SH. CLIC4 is a tumor suppressor for cutaneous squamous cell cancer. Carcinogenesis 2012; 33:986-95. [PMID: 22387366 DOI: 10.1093/carcin/bgs115] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Chloride intracellular channel (CLIC) 4 is a member of a redox-regulated, metamorphic multifunctional protein family, first characterized as intracellular chloride channels. Current knowledge indicates that CLICs participate in signaling, cytoskeleton integrity and differentiation functions of multiple tissues. In metabolically stressed skin keratinocytes, cytoplasmic CLIC4 is S-nitrosylated and translocates to the nucleus where it enhances transforming growth factor-β (TGF-β) signaling by protecting phospho-Smad 2 and 3 from dephosphorylation. CLIC4 expression is diminished in multiple human epithelial cancers, and the protein is excluded from the nucleus. We now show that CLIC4 expression is reduced in chemically induced mouse skin papillomas, mouse and human squamous carcinomas and squamous cancer cell lines, and the protein is excluded from the nucleus. The extent of reduction in CLIC4 coincides with progression of squamous tumors from benign to malignant. Inhibiting antioxidant defense in tumor cells increases S-nitrosylation and nuclear translocation of CLIC4. Adenoviral-mediated reconstitution of nuclear CLIC4 in squamous cancer cells enhances TGF-β-dependent transcriptional activity and inhibits growth. Adenoviral targeting of CLIC4 to the nucleus of tumor cells in orthografts inhibits tumor growth, whereas elevation of CLIC4 in transgenic epidermis reduces de novo chemically induced skin tumor formation. In parallel, overexpression of exogenous CLIC4 in squamous tumor orthografts suppresses tumor growth and enhances TGF-β signaling. These results indicate that CLIC4 suppresses the growth of squamous cancers, that reduced CLIC4 expression and nuclear residence detected in cancer cells is associated with the altered redox state of tumor cells and the absence of detectable nuclear CLIC4 in cancers contributes to TGF-β resistance and enhances tumor development.
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Affiliation(s)
- K Stephen Suh
- Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
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18
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He G, Ma Y, Chou SY, Li H, Yang C, Chuang JZ, Sung CH, Ding A. Role of CLIC4 in the host innate responses to bacterial lipopolysaccharide. Eur J Immunol 2011; 41:1221-30. [PMID: 21469130 DOI: 10.1002/eji.201041266] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2010] [Revised: 01/11/2011] [Accepted: 02/15/2011] [Indexed: 11/08/2022]
Abstract
Chloride intracellular channel (CLIC) 4 has diverse functions in membrane trafficking, apoptosis, angiogenesis and cell differentiation. CLIC4 is abundantly expressed in macrophages, but its role in innate immune functions is unclear. Here, we show that primary murine macrophages express increased amounts of CLIC4 after exposure to bacterial lipopolysaccharide (LPS). Endogenous CLIC4 level was significantly elevated in the brain, heart, lung, kidney, liver and spleen after LPS injection of mice. Stable macrophage lines overexpressing CLIC4 produced more TNF, IL-6, IL-12 and CCL5 than mock transfectants when exposed to LPS. To explore the role of CLIC4 in vivo, we generated CLIC4-null mice. These mice were protected from LPS-induced death, and had reduced serum levels of inflammatory cytokines. Upon infection with Listeria monocytogenes, CLIC4-deficient mice were impaired in their ability to clear infection, and their macrophages responded to Listeria by producing less inflammatory cytokines and chemokines than the WT controls. When challenged with LPS in vitro, deletion of clic4 gene had little effect on MAPK and NF-κB activation, but led to a reduced accumulation of phosphorylated interferon response factor 3 (IRF3) within macrophages. Conversely, overexpression of CLIC4 enhanced LPS-mediated IRF3. Thus, these findings suggest that CLIC4 is an LPS-induced product that can serve as a positive regulator of LPS signaling.
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Affiliation(s)
- Guoan He
- Department of Microbiology and Immunology, Weill Cornell Medical College, NY 10065, USA
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19
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Chuang JZ, Chou SY, Sung CH. Chloride intracellular channel 4 is critical for the epithelial morphogenesis of RPE cells and retinal attachment. Mol Biol Cell 2010; 21:3017-28. [PMID: 20610659 PMCID: PMC2929995 DOI: 10.1091/mbc.e09-10-0907] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
A plasmid-based transfection method was used to cell-autonomously silence chloride intracellular channel 4 (CLIC4) in RPE in situ. These results show CLIC4 is critical for epithelial morphogenesis and retinal attachment. Novel candidate targets for retinal detachment therapy have also been identified. Retinal detachment is a sight-threatening condition. The molecular mechanism underlying the adhesion between the RPE and photoreceptors is poorly understood because the intimate interactions between these two cell types are impossible to model and study in vitro. In this article, we show that chloride intracellular channel 4 (CLIC4) is enriched at apical RPE microvilli, which are interdigitated with the photoreceptor outer segment. We used a novel plasmid-based transfection method to cell-autonomously suppress CLIC4 in RPE in situ. CLIC4 silenced RPE cells exhibited a significant loss of apical microvilli and basal infoldings, reduced retinal adhesion, and epithelial-mesenchymal transition. Ectopically expressing ezrin failed to rescue the morphological changes exerted by CLIC4 silencing. Neural retinas adjacent to the CLIC4-suppressed RPE cells display severe dysplasia. Finally, a high level of aquaporin 1 unexpectedly appeared at the apical surfaces of CLIC4-suppressed RPE cells, together with a concomitant loss of basal surface expression of monocarboxylate transporter MCT3. Our results suggested that CLIC4 plays an important role in RPE-photoreceptor adhesion, perhaps by modulating the activity of cell surface channels/transporters. We propose that these changes may be attributable to subretinal fluid accumulation in our novel retinal detachment animal model.
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Affiliation(s)
- Jen-Zen Chuang
- Department of Ophthalmology, Weill Medical College of Cornell University, New York, NY 10021, USA
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20
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Qiu MR, Jiang L, Matthaei KI, Schoenwaelder SM, Kuffner T, Mangin P, Joseph JE, Low J, Connor D, Valenzuela SM, Curmi PMG, Brown LJ, Mahaut-Smith M, Jackson SP, Breit SN. Generation and characterization of mice with null mutation of the chloride intracellular channel 1 gene. Genesis 2010; 48:127-36. [PMID: 20049953 DOI: 10.1002/dvg.20590] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
CLIC1 belongs to a family of highly conserved and widely expressed intracellular chloride ion channel proteins existing in both soluble and membrane integrated forms. To study the physiological and biological role of CLIC1 in vivo, we undertook conditional gene targeting to engineer Clic1 gene knock-out mice. This represents creation of the first gene knock-out of a vertebrate CLIC protein family member. We first generated a Clic1 Knock-in (Clic1(FN)) allele, followed by Clic1 knock-out (Clic1(-/-)) mice by crossing Clic1(FN) allele with TNAP-cre mice, resulting in germline gene deletion through Cre-mediated recombination. Mice heterozygous or homozygous for these alleles are viable and fertile and appear normal. However, Clic1(-) (/-) mice show a mild platelet dysfunction characterized by prolonged bleeding times and decreased platelet activation in response to adenosine diphosphate stimulation linked to P2Y(12) receptor signaling.
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Affiliation(s)
- Min Ru Qiu
- St. Vincent's Centre for Applied Medical Research, St. Vincent's Hospital and University of New South Wales, Sydney, New South Wales, Australia
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21
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Wegner B, Al-Momany A, Kulak SC, Kozlowski K, Obeidat M, Jahroudi N, Paes J, Berryman M, Ballermann BJ. CLIC5A, a component of the ezrin-podocalyxin complex in glomeruli, is a determinant of podocyte integrity. Am J Physiol Renal Physiol 2010; 298:F1492-503. [PMID: 20335315 DOI: 10.1152/ajprenal.00030.2010] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The chloride intracellular channel 5A (CLIC5A) protein, one of two isoforms produced by the CLIC5 gene, was isolated originally as part of a cytoskeletal protein complex containing ezrin from placental microvilli. Whether CLIC5A functions as a bona fide ion channel is controversial. We reported previously that a CLIC5 transcript is enriched approximately 800-fold in human renal glomeruli relative to most other tissues. Therefore, this study sought to explore CLIC5 expression and function in glomeruli. RT-PCR and Western blots show that CLIC5A is the predominant CLIC5 isoform expressed in glomeruli. Confocal immunofluorescence and immunogold electron microscopy reveal high levels of CLIC5A protein in glomerular endothelial cells and podocytes. In podocytes, CLIC5A localizes to the apical plasma membrane of foot processes, similar to the known distribution of podocalyxin and ezrin. Ezrin and podocalyxin colocalize with CLIC5A in glomeruli, and podocalyxin coimmunoprecipitates with CLIC5A from glomerular lysates. In glomeruli of jitterbug (jbg/jbg) mice, which lack the CLIC5A protein, ezrin and phospho-ERM levels in podocytes are markedly lower than in wild-type mice. Transmission electron microscopy reveals patchy broadening and effacement of podocyte foot processes as well as vacuolization of glomerular endothelial cells. These ultrastructural changes are associated with microalbuminuria at baseline and increased susceptibility to adriamycin-induced glomerular injury compared with wild-type mice. Together, the data suggest that CLIC5A is required for the development and/or maintenance of the proper glomerular endothelial cell and podocyte architecture. We postulate that the interaction between podocalyxin and subjacent filamentous actin, which requires ezrin, is compromised in podocytes of CLIC5A-deficient mice, leading to dysfunction under unfavorable genetic or environmental conditions.
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Affiliation(s)
- Binytha Wegner
- Department of Medicine, University of Alberta, Edmonton, Alberta, Canada
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22
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Two decades with dimorphic Chloride Intracellular Channels (CLICs). FEBS Lett 2010; 584:2112-21. [DOI: 10.1016/j.febslet.2010.03.013] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2009] [Revised: 03/08/2010] [Accepted: 03/08/2010] [Indexed: 01/11/2023]
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23
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Chloride channels of intracellular membranes. FEBS Lett 2010; 584:2102-11. [PMID: 20100480 DOI: 10.1016/j.febslet.2010.01.037] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2009] [Revised: 01/13/2010] [Accepted: 01/19/2010] [Indexed: 11/20/2022]
Abstract
Proteins implicated as intracellular chloride channels include the intracellular ClC proteins, the bestrophins, the cystic fibrosis transmembrane conductance regulator, the CLICs, and the recently described Golgi pH regulator. This paper examines current hypotheses regarding roles of intracellular chloride channels and reviews the evidence supporting a role in intracellular chloride transport for each of these proteins.
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Littler DR, Harrop SJ, Goodchild SC, Phang JM, Mynott AV, Jiang L, Valenzuela SM, Mazzanti M, Brown LJ, Breit SN, Curmi PMG. The enigma of the CLIC proteins: Ion channels, redox proteins, enzymes, scaffolding proteins? FEBS Lett 2010; 584:2093-101. [PMID: 20085760 DOI: 10.1016/j.febslet.2010.01.027] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Revised: 01/13/2010] [Accepted: 01/13/2010] [Indexed: 12/13/2022]
Abstract
Chloride intracellular channel proteins (CLICs) are distinct from most ion channels in that they have both soluble and integral membrane forms. CLICs are highly conserved in chordates, with six vertebrate paralogues. CLIC-like proteins are found in other metazoans. CLICs form channels in artificial bilayers in a process favoured by oxidising conditions and low pH. They are structurally plastic, with CLIC1 adopting two distinct soluble conformations. Phylogenetic and structural data indicate that CLICs are likely to have enzymatic function. The physiological role of CLICs appears to be maintenance of intracellular membranes, which is associated with tubulogenesis but may involve other substructures.
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Affiliation(s)
- Dene R Littler
- School of Physics, University of New South Wales, Sydney, NSW 2052, Australia
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25
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SCAMP5, NBEA and AMISYN: three candidate genes for autism involved in secretion of large dense-core vesicles. Hum Mol Genet 2010; 19:1368-78. [DOI: 10.1093/hmg/ddq013] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
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26
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Xiong X, Huang S, Zhang H, Li J, Shen J, Xiong J, Lin Y, Jiang L, Wang X, Liang S. Enrichment and proteomic analysis of plasma membrane from rat dorsal root ganglions. Proteome Sci 2009; 7:41. [PMID: 19889238 PMCID: PMC2780401 DOI: 10.1186/1477-5956-7-41] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2009] [Accepted: 11/05/2009] [Indexed: 12/04/2022] Open
Abstract
Background Dorsal root ganglion (DRG) neurons are primary sensory neurons that conduct neuronal impulses related to pain, touch and temperature senses. Plasma membrane (PM) of DRG cells plays important roles in their functions. PM proteins are main performers of the functions. However, mainly due to the very low amount of DRG that leads to the difficulties in PM sample collection, few proteomic analyses on the PM have been reported and it is a subject that demands further investigation. Results By using aqueous polymer two-phase partition in combination with high salt and high pH washing, PMs were efficiently enriched, demonstrated by western blot analysis. A total of 954 non-redundant proteins were identified from the plasma membrane-enriched preparation with CapLC-MS/MS analysis subsequent to protein separation by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) or shotgun digestion. 205 (21.5%) of the identified proteins were unambiguously assigned as PM proteins, including a large number of signal proteins, receptors, ion channel and transporters. Conclusion The aqueous polymer two-phase partition is a simple, rapid and relatively inexpensive method. It is well suitable for the purification of PMs from small amount of tissues. Therefore, it is reasonable for the DRG PM to be enriched by using aqueous two-phase partition as a preferred method. Proteomic analysis showed that DRG PM was rich in proteins involved in the fundamental biological processes including material exchange, energy transformation and information transmission, etc. These data would help to our further understanding of the fundamental DRG functions.
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Affiliation(s)
- Xia Xiong
- Hunan Normal University, Changsha, PR China.
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27
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Ponsioen B, van Zeijl L, Langeslag M, Berryman M, Littler D, Jalink K, Moolenaar WH. Spatiotemporal regulation of chloride intracellular channel protein CLIC4 by RhoA. Mol Biol Cell 2009; 20:4664-72. [PMID: 19776349 DOI: 10.1091/mbc.e09-06-0529] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Chloride intracellular channel (CLIC) 4 is a soluble protein structurally related to omega-type glutathione-S-transferases (GSTs) and implicated in various biological processes, ranging from chloride channel formation to vascular tubulogenesis. However, its function(s) and regulation remain unclear. Here, we show that cytosolic CLIC4 undergoes rapid but transient translocation to discrete domains at the plasma membrane upon stimulation of G(13)-coupled, RhoA-activating receptors, such as those for lysophosphatidic acid, thrombin, and sphingosine-1-phosphate. CLIC4 recruitment is strictly dependent on Galpha(13)-mediated RhoA activation and F-actin integrity, but not on Rho kinase activity; it is constitutively induced upon enforced RhoA-GTP accumulation. Membrane-targeted CLIC4 does not seem to enter the plasma membrane or modulate transmembrane chloride currents. Mutational analysis reveals that CLIC4 translocation depends on at least six conserved residues, including reactive Cys35, whose equivalents are critical for the enzymatic function of GSTs. We conclude that CLIC4 is regulated by RhoA to be targeted to the plasma membrane, where it may function not as an inducible chloride channel but rather by displaying Cys-dependent transferase activity toward a yet unknown substrate.
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Affiliation(s)
- Bas Ponsioen
- Division of Cell Biology and Center for Biomedical Genetics, The Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands
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28
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Singh H, Ashley RH. CLIC4 (p64H1) and its putative transmembrane domain form poorly selective, redox-regulated ion channels. Mol Membr Biol 2009; 24:41-52. [PMID: 17453412 DOI: 10.1080/09687860600927907] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Despite being synthesized in the cytosol without a leader sequence, the soluble 253-residue mammalian protein CLIC4 (Chloride Intracellular Channel 4, or p64H1), a structural homologue of Omega-type glutathione-S-transferase, autoinserts into membranes to form an integral membrane protein with ion channel activity. A predicted transmembrane domain (TMD) near the N-terminus of CLIC4 could mediate membrane insertion, and contribute to oligomeric pores, with minimal reorganization of the soluble protein structure. We tested this idea by reconstituting recombinant CLIC4 in planar bilayers containing phosphatidyethanolamine, phosphatidylserine and cholesterol, recording ion channels with a maximum conductance of approximately 15 pS in KCl under both oxidizing and reducing conditions. The channels discriminated poorly between anions and cations, incompatible with the current "CLIC" nomenclature, and their conductance was modified by the trans (external or luminal) redox potential, as previously observed for CLIC1. We then reconstituted a truncated version of the protein, limited to the first 61 residues containing the predicted TMD. This included a single trans cysteine residue in the putative pore-forming subunits, at the external entrance to the pore. The truncated protein formed non-selective channels with a reduced conductance, but they retained their trans-redox sensitivity, and could still be blocked or inactivated by trans (not cis) thiol-reative dithiobisnitrobenzoic acid. We suggest that oligomers containing the putative TMD are essential components of the CLIC4 pore. However, the pore is inherently non-selective, and any ionic selectivity in CLIC4 (and other membrane CLICs) may be attributable to other regions of the protein, including the channel vestibules.
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Affiliation(s)
- Harpreet Singh
- Biomedical Sciences, College of Medicine, University of Edinburgh, Edinburgh, UK
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29
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Fanucchi S, Adamson RJ, Dirr HW. Formation of an Unfolding Intermediate State of Soluble Chloride Intracellular Channel Protein CLIC1 at Acidic pH. Biochemistry 2008; 47:11674-81. [DOI: 10.1021/bi801147r] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sylvia Fanucchi
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Roslin J. Adamson
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Heini W. Dirr
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
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Al-Ghoul M, Brück TB, Lauer-Fields JL, Asirvatham VS, Zapata C, Kerr RG, Fields GB. Comparative proteomic analysis of matched primary and metastatic melanoma cell lines. J Proteome Res 2008; 7:4107-18. [PMID: 18698805 DOI: 10.1021/pr800174k] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Identification of the biochemical pathways involved in the transformation from primary to metastatic melanoma is an area under intense investigation. A 2DE proteomics approach has been applied herein to the matched patient primary and metastatic melanoma cell lines WM-115 and WM-266-4, respectively, to better understand the processes that underlie tumor progression. Image analysis between samples aligned 470 common gel spots. Quantitative gel analysis indicated 115 gel spots of greater intensity in the metastatic line compared with the primary one, leading to the identification of 131 proteins via database searching of nano-LC-ESI-Q-TOF-MS/MS data. This more than tripled the number of proteins previously shown to be of higher abundance during melanoma progression. Also observed were 22 gel spots to be of lesser intensity in the metastatic line with respect to the primary one. Of these gel spots 15 proteins could be identified. Numerous proteins from both groups had not been reported previously to participate in melanoma progression. Further analysis of one protein, cyclophilin A, confirmed that this protein is expressed at higher levels in metastatic melanoma compared with primary melanoma and normal fibroblasts. Overall, this study expands our knowledge of protein modulation during melanoma stages, and suggests new targets for inhibitor development.
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Affiliation(s)
- Mohammad Al-Ghoul
- Department of Chemistry and Biochemistry, Florida Atlantic University, Boca Raton, FL 33431, USA
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CLIC4 interacts with histamine H3 receptor and enhances the receptor cell surface expression. Biochem Biophys Res Commun 2008; 369:603-8. [DOI: 10.1016/j.bbrc.2008.02.071] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2008] [Accepted: 02/13/2008] [Indexed: 11/23/2022]
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Suh KS, Malik M, Shukla A, Yuspa SH. CLIC4, skin homeostasis and cutaneous cancer: surprising connections. Mol Carcinog 2007; 46:599-604. [PMID: 17443730 DOI: 10.1002/mc.20324] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Chloride intracellular channel 4 (CLIC4) is a putative chloride channel for intracellular organelles. CLIC4 has biological activities in addition to or because of its channel activity. In keratinocytes, CLIC4 resides in the mitochondria and cytoplasm, and CLIC4 gene expression is regulated by p53, TNF-alpha, and c-Myc. Cytoplasmic CLIC4 translocates to the nucleus in response to cellular stress conditions including DNA damage, metabolic inhibition, senescence, and exposure to certain trophic factors such as TNF-alpha and LPS. Nuclear translocation is associated with growth arrest or apoptosis, depending on the level of expression. In the nucleus CLIC4 interacts with several nuclear proteins as demonstrated by yeast two-hybrid screening and co-immunoprecipitation. Nuclear CLIC4 appears to act on the TGF-beta pathway, and TGF-beta also causes CLIC4 nuclear translocation. In human and mouse cancer cell lines, CLIC4 levels are reduced, and CLIC4 is excluded from the nucleus. CLIC4 soluble or membrane-inserted status is dependent on redox state, and redox alterations in cancer cells could underly the defect in nuclear translocation. CLIC4 is reduced and excluded from the nucleus of many human epithelial neoplasms. Paradoxically, CLIC4 is reciprocally upregulated in tumor stroma in conjunction with the expression of alpha-smooth muscle actin in the fibroblast to myofibroblast transition. Overexpression of CLIC4 in cancer cells inhibits tumor growth in vivo. Conversely, overexpression of CLIC4 in tumor stromal cells stimulates tumor growth in vivo. Thus, CLIC4 participates in normal and pathological processes and may serve as a useful target for therapies in disturbances of homeostasis and neoplastic transformation.
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Affiliation(s)
- Kwang S Suh
- Laboratory of Cancer Biology and Genetics, Center for Cancer Research National Cancer Institute, Bethesda, Maryland 20892, USA
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Komori N, Takemori N, Kim HK, Singh A, Hwang SH, Foreman RD, Chung K, Chung JM, Matsumoto H. Proteomics study of neuropathic and nonneuropathic dorsal root ganglia: altered protein regulation following segmental spinal nerve ligation injury. Physiol Genomics 2007; 29:215-30. [PMID: 17213366 DOI: 10.1152/physiolgenomics.00255.2006] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Peripheral nerve injury is often followed by the development of severe neuropathic pain. Nerve degeneration accompanied by inflammatory mediators is thought to play a role in generation of neuropathic pain. Neuronal cell death follows axonal degeneration, devastating a vast number of molecules in injured neurons and the neighboring cells. Because we have little understanding of the cellular and molecular mechanisms underlying neuronal cell death triggered by nerve injury, we conducted a proteomics study of rat 4th and 5th lumbar (L4 and L5) dorsal root ganglion (DRG) after L5 spinal nerve ligation. DRG proteins were displayed on two-dimensional gels and analyzed through quantitative densitometry, statistical validation of the quantitative data, and peptide mass fingerprinting for protein identification. Among approximately 1,300 protein spots detected on each gel, we discovered 67 proteins that were tightly regulated by nerve ligation. We find that the injury to primary sensory neurons turned on multiple cellular mechanisms critical for the structural and functional integrity of neurons and for the defense against oxidative damage. Our data indicate that the regulation of metabolic enzymes was carefully orchestrated to meet the altered energy requirement of the DRG cells. Our data also demonstrate that ligation of the L5 spinal nerve led to the upregulation in the L4 DRG of the proteins that are highly expressed in embryonic sensory neurons. To understand the molecular mechanisms underlying neuropathic pain, we need to comprehend such dynamic aspect of protein modulations that follow nerve injury.
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Affiliation(s)
- Naoka Komori
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73190, USA.
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Suh KS, Crutchley JM, Koochek A, Ryscavage A, Bhat K, Tanaka T, Oshima A, Fitzgerald P, Yuspa SH. Reciprocal Modifications of CLIC4 in Tumor Epithelium and Stroma Mark Malignant Progression of Multiple Human Cancers. Clin Cancer Res 2007; 13:121-31. [PMID: 17200346 DOI: 10.1158/1078-0432.ccr-06-1562] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE CLIC4, a member of a family of intracellular chloride channels, is regulated by p53, c-Myc, and tumor necrosis factor-alpha. Regulation by factors involved in cancer pathogenesis, together with the previously shown proapoptotic activity of CLIC4, suggests that the protein may have a tumor suppressor function. To address this possibility, we characterized the expression profile, subcellular localization, and gene integrity of CLIC4 in human cancers and determined the functional consequences of CLIC4 expression in tumor epithelium and stromal cells. EXPERIMENTAL DESIGN CLIC4 expression profiles were analyzed by genomics, proteomics, bioinformatics, and tissue microarrays. CLIC4 expression, as a consequence of crosstalk between stroma and epithelium, was tested in vitro by coculture of breast epithelial tumor cells and normal fibroblasts, and the functional consequences of CLIC4 expression was tested in vivo in xenografts of human breast tumor cell lines reconstituted with CLIC4 or mixed with fibroblasts that overexpress CLIC4 transgenically. RESULTS In cDNA arrays of matched human normal and tumor tissues, CLIC4 expression was reduced in renal, ovarian, and breast cancers. However, CLIC4 protein levels were variable in tumor lysate arrays. Transcript sequences of CLIC4 from the human expressed sequence tag database and manual sequencing of cDNA from 60 human cancer cell lines (NCI60) failed to reveal deletion or mutations in the CLIC4 gene. On matched tissue arrays, CLIC4 was predominantly nuclear in normal human epithelial tissues but not cancers. With advancing malignant progression, CLIC4 staining became undetectable in tumor cells, but expression increased in stromal cells coincident with up-regulation of alpha-smooth muscle actin, suggesting that CLIC4 is up-regulated in myofibroblasts. Coculture of cancer cells and fibroblasts induced the expression of both CLIC4 and alpha-smooth muscle actin in fibroblasts adjacent to tumor nests. Introduction of CLIC4 or nuclear targeted CLIC4 via adenovirus into human breast cancer xenografts inhibited tumor growth, whereas overexpression of CLIC4 in stromal cells of xenografts enhanced tumor growth. CONCLUSION Loss of CLIC4 in tumor cells and gain in tumor stroma is common to many human cancers and marks malignant progression. Up-regulation of CLIC4 in tumor stroma is coincident with myofibroblast conversion, generally a poor prognostic indicator. Reactivation and restoration of CLIC4 in tumor cells or the converse in tumor stromal cells could provide a novel approach to inhibit tumor growth.
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Affiliation(s)
- Kwang S Suh
- Laboratory of Cellular Carcinogenesis and Tumor Promotion, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA
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Edwards JC, Cohen C, Xu W, Schlesinger PH. c-Src control of chloride channel support for osteoclast HCl transport and bone resorption. J Biol Chem 2006; 281:28011-22. [PMID: 16831863 PMCID: PMC1808340 DOI: 10.1074/jbc.m605865200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Bone degradation by osteoclasts depends upon active transport of hydrogen ions to solubilize bone mineral. This transport is supported by the parallel actions of a proton ATPase and a chloride channel located in the osteoclast ruffled membrane. We have previously identified a novel chloride channel, p62, which appears to be the avian counterpart to CLIC-5b and is expressed coincident with the appearance of acid secretion as avian osteoclasts differentiate in culture. In this article, we show that suppression of CLIC-5b in differentiating avian osteoclasts results in decreased acidification by vesicles derived from these cells and decreased ability of the cells to resorb bone. Acidification is rescued by the presence of valinomycin, consistent with a selective loss of chloride channel but not proton pump activity. Osteoclast bone resorption is known to be dependent on the expression of the tyrosine kinase, c-Src. We show that CLIC-5b from osteoclasts has affinity for both Src SH2 and SH3 domains. We find that suppression of expression of Src in developing osteoclasts results in decreased vesicular acidification, which is rescued by valinomycin, consistent with the loss of chloride conductance in the proton pump-containing vesicles. Suppression of c-Src causes no change in the steady state level of CLIC-5b expression, but does result in failure of proton pump and CLIC-5b to colocalize in cultured osteoclast precursors. We conclude that suppression of c-Src interferes with osteoclast bone resorption by disrupting functional co-localization of proton pump and CLIC-5b.
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Affiliation(s)
- John C. Edwards
- From the UNC Kidney Center and the Department of Medicine, School of Medicine, University of North Carolina, Chapel Hill, North Carolina 27599, the
- Department of Medicine, St. Louis University School of Medicine, St. Louis, Missouri 63104, and the
| | - Christopher Cohen
- Department of Physiology and Cell Biology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Weibing Xu
- Department of Physiology and Cell Biology, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Paul H. Schlesinger
- Department of Physiology and Cell Biology, Washington University School of Medicine, St. Louis, Missouri 63110
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Berry KL, Hobert O. Mapping Functional Domains of Chloride Intracellular Channel (CLIC) Proteins in Vivo. J Mol Biol 2006; 359:1316-33. [PMID: 16737711 DOI: 10.1016/j.jmb.2006.04.046] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2006] [Revised: 04/06/2006] [Accepted: 04/20/2006] [Indexed: 10/24/2022]
Abstract
Chloride intracellular channel (CLIC) proteins are small proteins distantly related to the omega family of glutathione S-transferases (GSTs). CLIC proteins are expressed in a wide variety of tissues in multicellular organisms and are targeted to specific cellular membranes. Members of this family are capable in vitro of changing conformation from a globular, soluble state to a membrane-inserted state in which they provide chloride conductance. The structural basis for in vivo CLIC protein function, however, is not well understood. We have mapped the functional domains of CLIC family members using an in vivo assay for membrane localization and function of CLIC proteins in the nematode Caenorhabditis elegans. A<70 amino acid N-terminal domain is a key determinant of membrane localization and function of invertebrate CLIC proteins. This domain, which we term the ''PTM'' domain, named after an amphipathic putative transmembrane helix contained within it, directs distinct C. elegans CLIC homologs to distinct subcellular membranes. We find that within the PTM region, the cysteine residues required for GST-type activity are unnecessary for invertebrate CLIC function, but that specific residues within the proposed transmembrane helix are necessary for correct targeting and protein function. We find that among all tested invertebrate CLIC proteins, function appears to be completely conserved despite striking differences in the charged residues contained within the amphipathic helix. This indicates that these residues do not contribute to anion selectivity as previously suggested. We find that outside the PTM region, the remaining three-quarters of CLIC protein sequence is functionally equivalent not only among vertebrate and invertebrate CLIC proteins, but also among the more distantly related GST-omega and GST-sigma proteins. The PTM region thus provides both targeting information and CLIC functional specificity, possibly adapting GST-type proteins to function as ion channels.
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Affiliation(s)
- Katherine L Berry
- Department of Biochemistry and Molecular Biophysics Howard Hughes Medical Institute, Columbia University Medical Center, New York, NY 10032, USA
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Abstract
Neurons and related cell types often contain two major classes of neurosecretory vesicles, synaptic vesicles (SVs) and dense-core granules (DCGs), which store and release distinct cargo. SVs store and release classic neurotransmitters, which facilitate propagation of action potentials across the synaptic cleft, whereas DCGs transport, store, and release hormones, proteins, and neuropeptides, which facilitate neuronal survival, synaptic transmission, and learning. Over the past few years, there has been a major surge in our understanding of many of the key molecular mechanisms underlying cargo release from SVs and DCGs. This surge has been driven largely by the use of fluorescence microscopy (especially total internal reflection fluorescence microscopy) to visualize SVs or DCGs in living cells. This review highlights some of the recent insights into cargo release from neurosecretory vesicles provided by fluorescence microscopy, with emphasis on DCGs.
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Affiliation(s)
- Bethe A Scalettar
- Department of Physics, Lewis & Clark College, Portland, OR 97219, USA.
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Bohman S, Matsumoto T, Suh K, Dimberg A, Jakobsson L, Yuspa S, Claesson-Welsh L. Proteomic analysis of vascular endothelial growth factor-induced endothelial cell differentiation reveals a role for chloride intracellular channel 4 (CLIC4) in tubular morphogenesis. J Biol Chem 2005; 280:42397-404. [PMID: 16239224 DOI: 10.1074/jbc.m506724200] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Formation of new vessels from pre-existing capillaries demands extensive reprogramming of endothelial cells through transcriptional and post-transcriptional events. We show that 120 protein spots in a two-dimensional isoelectric focusing/electrophoretic analysis were affected during vascular endothelial growth factor-A-induced endothelial cell tubular morphogenesis in vitro, as a result of changes in charge or expression level of the corresponding proteins. For about 22% of the spots, the protein products could be identified, of which several previously have been implicated in cytoskeletal reorganization and angiogenesis. One such protein was heat shock protein 27, a chaperone involved in beta-actin rearrangement that was identified as regulated in degree of serine phosphorylation. We also identified regulation of chloride intracellular channel 4 (CLIC4), the expression of which decreased during tubular morphogenesis. CLIC4 was expressed at high levels in resting vessels, whereas expression was modulated during pathological angiogenesis such as in tumor vessels. The subcellular localization of CLIC4 in endothelial cells was dependent on whether cells were engaged in proliferation or tube formation. Antisense- and small interfering RNA-mediated suppression of CLIC4 expression led to arrest in tubular morphogenesis. Our data implicate CLIC4 in formation of a vessel lumen.
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Affiliation(s)
- Svante Bohman
- Department of Genetics and Pathology, Uppsala University, Dag Hammarskjölds väg 20, S-751 85 Uppsala, Sweden
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Littler DR, Assaad NN, Harrop SJ, Brown LJ, Pankhurst GJ, Luciani P, Aguilar MI, Mazzanti M, Berryman MA, Breit SN, Curmi PMG. Crystal structure of the soluble form of the redox-regulated chloride ion channel protein CLIC4. FEBS J 2005; 272:4996-5007. [PMID: 16176272 DOI: 10.1111/j.1742-4658.2005.04909.x] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The structure of CLIC4, a member of the CLIC family of putative intracellular chloride ion channel proteins, has been determined at 1.8 Angstroms resolution by X-ray crystallography. The protein is monomeric and it is structurally similar to CLIC1, belonging to the GST fold class. Differences between the structures of CLIC1 and CLIC4 are localized to helix 2 in the glutaredoxin-like N-terminal domain, which has previously been shown to undergo a dramatic structural change in CLIC1 upon oxidation. The structural differences in this region correlate with the sequence differences, where the CLIC1 sequence appears to be atypical of the family. Purified, recombinant, wild-type CLIC4 is shown to bind to artificial lipid bilayers, induce a chloride efflux current when associated with artificial liposomes and produce an ion channel in artificial bilayers with a conductance of 30 pS. Membrane binding is enhanced by oxidation of CLIC4 while no channels were observed via tip-dip electrophysiology in the presence of a reducing agent. Thus, recombinant CLIC4 appears to be able to form a redox-regulated ion channel in the absence of any partner proteins.
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Affiliation(s)
- Dene R Littler
- School of Physics, University of New South Wales, Sydney, Australia
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Suh KS, Mutoh M, Gerdes M, Crutchley JM, Mutoh T, Edwards LE, Dumont RA, Sodha P, Cheng C, Glick, A, Yuspa SH. Antisense Suppression of the Chloride Intracellular Channel Family Induces Apoptosis, Enhances Tumor Necrosis Factor α-Induced Apoptosis, and Inhibits Tumor Growth. Cancer Res 2005. [DOI: 10.1158/0008-5472.562.65.2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
mtCLIC/CLIC4 is a p53 and tumor necrosis factor α (TNFα) regulated intracellular chloride channel protein that localizes to cytoplasm and organelles and induces apoptosis when overexpressed in several cell types of mouse and human origin. CLIC4 is elevated during TNFα-induced apoptosis in human osteosarcoma cell lines. In contrast, inhibition of NFκB results in an increase in TNFα-mediated apoptosis with a decrease in CLIC4 protein levels. Cell lines expressing an inducible CLIC4-antisense construct that also reduces the expression of several other chloride intracellular channel (CLIC) family proteins were established in the human osteosarcoma lines SaOS and U2OS cells and a malignant derivative of the mouse squamous papilloma line SP1. Reduction of CLIC family proteins by antisense expression caused apoptosis in these cells. Moreover, CLIC4-antisense induction increased TNFα-mediated apoptosis in both the SaOS and U2OS derivative cell lines without altering TNFα-induced NFκB activity. Reducing CLIC proteins in tumor grafts of SP1 cells expressing a tetracycline-regulated CLIC4-antisense substantially inhibited tumor growth and induced tumor apoptosis. Administration of TNFα i.p. modestly enhanced the antitumor effect of CLIC reduction in vivo. These results suggest that CLIC proteins could serve as drug targets for cancer therapy, and reduction of CLIC proteins could enhance the activity of other anticancer drugs.
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Affiliation(s)
- Kwang S. Suh
- Laboratory of Cellular Carcinogenesis and Tumor Promotion, National Cancer Institute, Bethesda, Maryland
| | - Michihiro Mutoh
- Laboratory of Cellular Carcinogenesis and Tumor Promotion, National Cancer Institute, Bethesda, Maryland
| | - Michael Gerdes
- Laboratory of Cellular Carcinogenesis and Tumor Promotion, National Cancer Institute, Bethesda, Maryland
| | - John M. Crutchley
- Laboratory of Cellular Carcinogenesis and Tumor Promotion, National Cancer Institute, Bethesda, Maryland
| | - Tomoko Mutoh
- Laboratory of Cellular Carcinogenesis and Tumor Promotion, National Cancer Institute, Bethesda, Maryland
| | - Lindsay E. Edwards
- Laboratory of Cellular Carcinogenesis and Tumor Promotion, National Cancer Institute, Bethesda, Maryland
| | - Rebecca A. Dumont
- Laboratory of Cellular Carcinogenesis and Tumor Promotion, National Cancer Institute, Bethesda, Maryland
| | - Pooja Sodha
- Laboratory of Cellular Carcinogenesis and Tumor Promotion, National Cancer Institute, Bethesda, Maryland
| | - Christina Cheng
- Laboratory of Cellular Carcinogenesis and Tumor Promotion, National Cancer Institute, Bethesda, Maryland
| | - Adam Glick,
- Laboratory of Cellular Carcinogenesis and Tumor Promotion, National Cancer Institute, Bethesda, Maryland
| | - Stuart H. Yuspa
- Laboratory of Cellular Carcinogenesis and Tumor Promotion, National Cancer Institute, Bethesda, Maryland
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Board PG, Coggan M, Watson S, Gage PW, Dulhunty AF. CLIC-2 modulates cardiac ryanodine receptor Ca2+ release channels. Int J Biochem Cell Biol 2004; 36:1599-612. [PMID: 15147738 DOI: 10.1016/j.biocel.2004.01.026] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2003] [Accepted: 01/14/2004] [Indexed: 10/26/2022]
Abstract
We have examined the biochemical and functional properties of the recently identified, uncharacterised CLIC-2 protein. Sequence alignments showed that CLIC-2 has a high degree of sequence similarity with CLIC-1 and some similarity to the omega class of glutathione transferases (GSTO). A homology model of CLIC-2 based on the crystal structure of CLIC-1 suggests that CLIC-2 belongs to the GST structural family but, unlike the GSTs, CLIC-2 exists as a monomer. It also has an unusual enzyme activity profile. While the CXXC active site motif is conserved between CLIC-2 and the glutaredoxins, no thiol transferase activity was detected. In contrast, low glutathione peroxidase activity was recorded. CLIC-2 was found to be widely distributed in tissues including heart and skeletal muscle. Functional studies showed that CLIC-2 inhibited cardiac ryanodine receptor Ca2+ release channels in lipid bilayers when added to the cytoplasmic side of the channels and inhibited Ca2+ release from cardiac sarcoplasmic reticulum vesicles. The inhibition of RyR channels was reversed by removing CLIC-2 from the solution or by adding an anti-CLIC-2 antibody. The results suggest that one function of CLIC-2 might be to limit Ca2+ release from internal stores in cells.
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Affiliation(s)
- Philip G Board
- Division of Molecular Bioscience, John Curtin School of Medical Research, The Australian National University, P.O. Box 334, Canberra, ACT 2601, Australia.
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Myers K, Somanath PR, Berryman M, Vijayaraghavan S. Identification of chloride intracellular channel proteins in spermatozoa. FEBS Lett 2004; 566:136-40. [PMID: 15147883 DOI: 10.1016/j.febslet.2004.04.017] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2004] [Revised: 04/02/2004] [Accepted: 04/07/2004] [Indexed: 10/26/2022]
Abstract
We have identified for the first time the presence of chloride intracellular channel (CLIC) proteins in bovine epididymal spermatozoa. CLIC1 was discovered during microsequencing of proteins that co-purified with protein phosphatase 1, PP1gamma2, in sperm extracts. In addition to CLIC1, Western blot showed that two additional CLIC family members, CLIC4 and CLIC5, are also present in spermatozoa. CLIC fusion proteins, GST-CLIC1, GST-CLIC4 and GST-CLIC5, were all able to bind to PP1gamma2 in sperm extracts during pull-down assays. Immunofluorescence microscopy revealed that each of the three isoforms occupies a distinct location within the cell. Given that PP1gamma2 is a key enzyme regulating sperm motility, PP1gamma2-binding proteins, such as the CLIC proteins, are likely to play significant roles in sperm function.
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Affiliation(s)
- Kimberley Myers
- Department of Biological Sciences, Kent State University, Kent, OH 44242, USA
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Suh KS, Mutoh M, Nagashima K, Fernandez-Salas E, Edwards LE, Hayes DD, Crutchley JM, Marin KG, Dumont RA, Levy JM, Cheng C, Garfield S, Yuspa SH. The Organellular Chloride Channel Protein CLIC4/mtCLIC Translocates to the Nucleus in Response to Cellular Stress and Accelerates Apoptosis. J Biol Chem 2004; 279:4632-41. [PMID: 14610078 DOI: 10.1074/jbc.m311632200] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
CLIC4/mtCLIC, a chloride intracellular channel protein, localizes to the mitochondria and cytoplasm of keratinocytes and participates in the apoptotic response to stress. We now show that multiple stress inducers cause the translocation of cytoplasmic CLIC4 to the nucleus. Immunogold electron microscopy and confocal analyses indicate that nuclear CLIC4 is detected prior to the apoptotic phenotype. CLIC4 associates with the Ran, NTF2, and Importin-alpha nuclear import complexes in immunoprecipitates of lysates from cells treated with apoptotic/stress-inducing agents. Deletion or mutation of the nuclear localization signal in the C terminus of CLIC4 eliminates nuclear translocation, whereas N terminus deletion enhances nuclear localization. Targeting CLIC4 to the nucleus via adenoviral transduction accelerates apoptosis when compared with cytoplasmic CLIC4, and only nuclear-targeted CLIC4 causes apoptosis in Apaf null mouse fibroblasts or in Bcl-2-overexpressing keratinocytes. These results indicate that CLIC4 nuclear translocation is an integral part of the cellular response to stress and may contribute to the initiation of nuclear alterations that are associated with apoptosis.
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Affiliation(s)
- Kwang S Suh
- Laboratory of Cellular Carcinogenesis and Tumor Promotion, Center for Cancer Research, NCI, National Institutes of Health (NIH), Bethesda, Maryland 20892, USA
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Lo WK, Wen XJ, Zhou CJ. Microtubule configuration and membranous vesicle transport in elongating fiber cells of the rat lens. Exp Eye Res 2003; 77:615-26. [PMID: 14550404 DOI: 10.1016/s0014-4835(03)00176-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
This study examines the microtubule configuration and its close association with the Golgi complex and Golgi-derived membranous vesicles in elongating fiber cells of the rat lens. Since fiber cells elongate tremendously during lens differentiation, we hypothesize that a microtubule-based motor system exists in the elongating fiber cells for transporting important membrane proteins and organelles to the target regions for cell growth. The newly synthesized membrane proteins are known to be transported from the trans-Golgi network in the form of vesicles to the target plasma membrane. By thin-section TEM, we observed a large number of vesicles of various sizes and shapes randomly distributed throughout the cytoplasm of elongating fiber cells. Both Golgi complex and vesicles exhibited characteristic normal structural features seen in other cell types and thus represented real vesicular organelles in the fiber cells. A large number of microtubules were regularly arranged into bundles parallel to the long axis of fiber cells as examined in both longitudinal and cross-section views. Many of these microtubules were closely associated or in intimate contact with the Golgi complex and vesicles in elongating fiber cells. The microtubule polarity assay revealed that microtubules exhibited a unidirectional polarity for the entire length of fiber cells as examined in both anterior and posterior cortical fiber segments. Namely, the minus end of microtubules was towards the anterior lens pole while the plus end was headed towards the posterior pole. This suggests that multiple molecular motors such as kinesin and dynein are needed for carrying the vesicles to both lens poles, since conventional kinesin is known to transport vesicular organelles towards the plus end whereas cytoplasmic dynein carries them towards the minus end of microtubules. By immunoblot analysis, we indeed detected the presence of both kinesin (120 kD) and dynein (70 kD) in homogenate prepared from lens cortical fibers. Moreover, immunogold TEM demonstrated that the aquaporin 0 (formally MIP26) antibody was localized on the membranous vesicles as well as plasma membranes of the cortical fiber cells. This study suggests that a microtubule-based motor system exists in the lens and plays an important role in transporting membrane proteins such as aquaporin 0 in the vesicles during fiber cell differentiation and elongation.
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Affiliation(s)
- Woo-Kuen Lo
- Department of Anatomy and Neurobiology, Morehouse School of Medicine, 720 Westview Drive, SW, Atlanta, GA 30310, USA.
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Arnould T, Mercy L, Houbion A, Vankoningsloo S, Renard P, Pascal T, Ninane N, Demazy C, Raes M. mtCLIC is up-regulated and maintains a mitochondrial membrane potential in mtDNA-depleted L929 cells. FASEB J 2003; 17:2145-7. [PMID: 12958156 DOI: 10.1096/fj.03-0075fje] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
To explain why mitochondrial DNA (mtDNA)-depleted or rho0 cells still keep a mitochondrial membrane potential (Delta(psi)m) in the absence of respiration, several hypotheses have been proposed. The principal and well accepted one involves a reverse of action for ANT combined to F1-ATPase activity. However, the existence of other putative electrogenic channels has been speculated. Here, using mRNA differential display reverse transcriptase-polymerase chain reaction on L929 mtDNA-depleted cells, we identified mtCLIC as a differentially expressed gene in cells deprived from mitochondrial ATP production. Mitochondrial chloride intracellular channel (mtCLIC), a member of a recently discovered and expanding family of chloride intracellular channels, is up-regulated in mtDNA-depleted and rho0 cells. We showed that its expression is dependent on CREB and p53 and is sensitive to calcium and tumor necrosis factor alpha. Interestingly, up- or down-regulation of mtCLIC protein expression changes Delta(psi)m whereas the chloride channel inhibitor NPPB reduces the Delta(psi)m in mtDNA-depleted L929 cells, measured with the fluorescent probe rhodamine 123. Finally, we demonstrated that purified mitochondria from mtDNA-depleted cells incorporate, in a NPPB-sensitive manner, more 36chloride than parental mitochondria. These findings suggest that mtCLIC could be involved in mitochondrial membrane potential generation in mtDNA-depleted cells, a feature required to prevent apoptosis and to drive continuous protein import into mitochondria.
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Affiliation(s)
- T Arnould
- Laboratoire de Biochimie et Biologie Cellulaire, University of Namur (F.U.N.D.P), 61 rue de Bruxelles, 5000 Namur, Belgium.
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46
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Friedli M, Guipponi M, Bertrand S, Bertrand D, Neerman-Arbez M, Scott HS, Antonarakis SE, Reymond A. Identification of a novel member of the CLIC family, CLIC6, mapping to 21q22.12. Gene 2003; 320:31-40. [PMID: 14597386 DOI: 10.1016/s0378-1119(03)00830-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Five members of the newly identified chloride intracellular channel (CLIC) gene family of intracellular chloride channels (CLIC1-CLIC5) have previously been described in humans. Here we report the molecular cloning and initial characterisation of two splice forms of a novel member of this family, CLIC6, mapping to human chromosome 21. Two essential features distinguish CLIC6 from other members of the family. The CLIC6 protein is significantly longer and the CLIC6 gene contains a GC rich segment, which encodes a 10 amino acid motif repeated 14 times in the amino-terminus. Surprisingly, the repeat is conserved in the lagomorphs, but not in the rodents lineage. The putative bovine orthologue of CLIC5, p64, also exhibits a repeated motif, which is different from that of CLIC6. Attempts to functionally characterise CLIC6 by voltage clamp failed to show any chloride channel activity. Hence, the exact function of this protein remains unknown.
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MESH Headings
- Alternative Splicing
- Amino Acid Sequence
- Animals
- COS Cells
- Cell Line
- Chloride Channels/genetics
- Chlorocebus aethiops
- Chromosome Mapping
- Chromosomes, Human, Pair 21/genetics
- Cloning, Molecular
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- Female
- Gene Expression
- Green Fluorescent Proteins
- Humans
- Luminescent Proteins/genetics
- Luminescent Proteins/metabolism
- Membrane Potentials/physiology
- Mice
- Mice, Inbred BALB C
- Mice, Inbred C57BL
- Mice, Inbred CBA
- Mice, Inbred Strains
- Microscopy, Fluorescence
- Molecular Sequence Data
- Oocytes/metabolism
- Oocytes/physiology
- Recombinant Fusion Proteins/genetics
- Recombinant Fusion Proteins/metabolism
- Repetitive Sequences, Nucleic Acid/genetics
- Sequence Alignment
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Transfection
- Xenopus
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Affiliation(s)
- Marc Friedli
- Division of Medical Genetics, Centre Médical Universitaire, University of Geneva Medical School, 1 rue Michel-Servet, CH-1211 Geneva 4, Switzerland
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Berryman MA, Goldenring JR. CLIC4 is enriched at cell-cell junctions and colocalizes with AKAP350 at the centrosome and midbody of cultured mammalian cells. ACTA ACUST UNITED AC 2003; 56:159-72. [PMID: 14569596 DOI: 10.1002/cm.10141] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
CLIC4 is a member of the chloride intracellular channel (CLIC) protein family whose principal cellular functions are poorly understood. Recently, we demonstrated that several CLIC proteins, including CLIC4, interact with AKAP350. AKAP350 is concentrated at the Golgi apparatus, centrosome, and midbody and acts as a scaffolding protein for several protein kinases and phosphatases. In this report, we show that endogenous CLIC4 and AKAP350 colocalize at the centrosome and midbody of cultured cells by immunofluorescence microscopy. Unlike AKAP350, CLIC4 is not enriched in the Golgi apparatus but is enriched in mitochondria, actin-based structures at the cell cortex, and the nuclear matrix, indicating that CLIC4-AKAP350 interactions are regulated at specific subcellular sites in vivo. In addition to the centrosome and midbody, CLIC4 colocalizes with AKAP350 and the tight junction protein ZO-1 in the apical region of polarized epithelial cells, suggesting that CLIC4 may play a role in maintaining apical-basolateral membrane polarity during mitosis and cytokinesis. Biochemical studies show that CLIC4 behaves mainly as a soluble cytosolic protein and can associate with proteins of the microtubule cytoskeleton. The localization of CLIC4 to the cortical actin cytoskeleton and its association with AKAP350 at the centrosome and midbody suggests that CLIC4 may be important for regulating cytoskeletal organization during the cell cycle. These findings lead to the conclusion that CLIC4 and possibly other CLIC proteins have alternate cellular functions that are distinct from their proposed roles as chloride channels.
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Affiliation(s)
- Mark A Berryman
- Department of Biomedical Sciences, Molecular and Cellular Biology Program, Ohio University College of Osteopathic Medicine, Athens, OH 45701, USA.
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48
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Ueki T, Yamaguchi N, Michibata H. Chloride channel in vanadocytes of a vanadium-rich ascidian Ascidia sydneiensis samea. Comp Biochem Physiol B Biochem Mol Biol 2003; 136:91-8. [PMID: 12941642 DOI: 10.1016/s1096-4959(03)00175-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Ascidians, so-called sea squirts, can accumulate high levels of vanadium in the vacuoles of signet ring cells, which are one type of ascidian blood cell and are also called vanadocytes. In addition to containing high concentrations of vanadium in the +3 oxidation state, the proton concentrations in vanadocyte vacuoles are extremely high. In order to elucidate the entire mechanism of the accumulation and reduction of vanadium by ascidian vanadocytes, it is necessary to clarify the participation of anions, which might be involved as counter ions in the active accumulation of both vanadium and protons. We examined the chloride channel, since chloride ions are necessary for the acidification of intracellular vesicles and coexist with H(+)-ATPase. We cloned a cDNA encoding a chloride channel from blood cells of a vanadium-rich ascidian, Ascidia sydneiensis samea. It encoded a 787-amino-acid protein, which showed striking similarity to mammalian ClC3/4/5-type chloride channels. Using a whole-mount in situ hybridization method that we developed for ascidian blood cells, the chloride channel was revealed to be transcribed in vanadocytes, suggesting its participation in the process of vanadium accumulation.
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Affiliation(s)
- Tatsuya Ueki
- Marine Biological Laboratory, Graduate School of Science, Hiroshima University, Mukaishima-cho 2445, Hiroshima 722-0073, Japan
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Ashley RH. Challenging accepted ion channel biology: p64 and the CLIC family of putative intracellular anion channel proteins (Review). Mol Membr Biol 2003; 20:1-11. [PMID: 12745921 DOI: 10.1080/09687680210042746] [Citation(s) in RCA: 102] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Parchorin, p64 and the related chloride intracellular channel (CLIC) proteins are widely expressed in multicellular organisms and have emerged as candidates for novel, auto-inserting, self-assembling intracellular anion channels involved in a wide variety of fundamental cellular events including regulated secretion, cell division and apoptosis. Although the mammalian phosphoproteins p64 and parchorin (49 and 65K, respectively) have only been indirectly implicated in anion channel activity, two CLIC proteins (CLIC1 and CLIC4, 27 and 29K, respectively) appear to be essential molecular components of anion channels, and CLIC1 can form anion channels in planar lipid bilayers in the absence of other cellular proteins. However, these putative ion channel proteins are controversial because they exist in both soluble and membrane forms, with at least one transmembrane domain. Even more surprisingly, soluble CLICs share the same glutaredoxin fold as soluble omega class glutathione-S-transferases. Working out how these ubiquitous, soluble proteins unfold, insert into membranes and then refold to form integral membrane proteins, and how cells control this potentially dangerous process and make use of the associated ion channels, are challenging prospects. Critical to this future work is the need for better characterization of membrane topology, careful functional analysis of reconstituted and native channels, including their conductances and selectivities, and detailed structure/function studies including targeted mutagenesis to investigate the structure of the putative pore, the role of protein phosphorylation and the role of conserved cysteine residues.
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Affiliation(s)
- R H Ashley
- Department of Biomedical Sciences, University of Edinburgh, UK.
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50
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Washburn CL, Bean JE, Silverman MA, Pellegrino MJ, Yates PA, Allen RG. Regulation of peptidergic vesicle mobility by secretagogues. Traffic 2002; 3:801-9. [PMID: 12383346 DOI: 10.1034/j.1600-0854.2002.31105.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Neuropeptides are released into the extracellular space from large secretory granules. In order to reach their release sites, these granules are translocated on microtubules and thought to interact with filamentous actin as they approach the cell membrane. We have used a green fluorescent protein-tagged neuropeptide prohormone (prepro-orphanin FQ) to visualize vesicle trafficking dynamics in NS20Y cells and cultures of primary hippocampal neurons. We found that the majority of secretory granules were mobile and accumulated at both the tips of neurites as well as other apparently specialized cellular sites. We also used live-cell imaging to test the notion that peptidergic vesicle mobility was regulated by secretagogues. We show that treatment with forskolin appeared to increase vesicle rates of speed, while depolarization with high K+ had no effect, even though both treatments stimulated neuropeptide secretion. In cultured hippocampal neurons the green fluorescent protein-tagged secretory vesicles were routed to both dendrites and axons, indicating that peptidergic vesicle transport was not polarized. Basal peptidergic vesicle mobility rates in hippocampal neurons were the same as those in NS20Y cells. Taken together, these studies suggest that secretory vesicle mobility is regulated by specific classes of secretagogues and that neuropeptide containing secretory vesicles may be released from dendritic structures.
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Affiliation(s)
- C L Washburn
- Center for Research on Occupational and Environmental Toxicology, The Vollum Institute Portland, OR 97201, USA
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