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Siukstaite L, Imberty A, Römer W. Structural Diversities of Lectins Binding to the Glycosphingolipid Gb3. Front Mol Biosci 2021; 8:704685. [PMID: 34381814 PMCID: PMC8350385 DOI: 10.3389/fmolb.2021.704685] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Accepted: 07/08/2021] [Indexed: 12/18/2022] Open
Abstract
Glycolipids are present on the surfaces of all living cells and thereby represent targets for many protein receptors, such as lectins. Understanding the interactions between lectins and glycolipids is essential for investigating the functions of lectins and the dynamics of glycolipids in living membranes. This review focuses on lectins binding to the glycosphingolipid globotriaosylceramide (Gb3), an attractive host cell receptor, particularly for pathogens and pathogenic products. Shiga toxin (Stx), from Shigella dysenteriae or Escherichia coli, which is one of the most virulent bacterial toxins, binds and clusters Gb3, leading to local negative membrane curvature and the formation of tubular plasma membrane invaginations as the initial step for clathrin-independent endocytosis. After internalization, it is embracing the retrograde transport pathway. In comparison, the homotetrameric lectin LecA from Pseudomonas aeruginosa can also bind to Gb3, triggering the so-called lipid zipper mechanism, which results in membrane engulfment of the bacterium as an important step for its cellular uptake. Notably, both lectins bind to Gb3 but induce distinct plasma membrane domains and exploit mainly different transport pathways. Not only, several other Gb3-binding lectins have been described from bacterial origins, such as the adhesins SadP (from Streptococcus suis) and PapG (from E. coli), but also from animal, fungal, or plant origins. The variety of amino acid sequences and folds demonstrates the structural versatilities of Gb3-binding lectins and asks the question of the evolution of specificity and carbohydrate recognition in different kingdoms of life.
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Affiliation(s)
- Lina Siukstaite
- Faculty of Biology, University of Freiburg, Freiburg, Germany.,Signalling Research Centres BIOSS and CIBSS, University of Freiburg, Freiburg, Germany
| | - Anne Imberty
- CNRS, CERMAV, Université Grenoble Alpes, Grenoble, France
| | - Winfried Römer
- Faculty of Biology, University of Freiburg, Freiburg, Germany.,Signalling Research Centres BIOSS and CIBSS, University of Freiburg, Freiburg, Germany.,Freiburg Institute for Advanced Studies (FRIAS), University of Freiburg, Freiburg, Germany
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2
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Lingelem ABD, Kavaliauskiene S, Halsne R, Klokk TI, Surma MA, Klose C, Skotland T, Sandvig K. Diacylglycerol kinase and phospholipase D inhibitors alter the cellular lipidome and endosomal sorting towards the Golgi apparatus. Cell Mol Life Sci 2020; 78:985-1009. [PMID: 32447426 PMCID: PMC7897626 DOI: 10.1007/s00018-020-03551-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 05/12/2020] [Accepted: 05/13/2020] [Indexed: 12/13/2022]
Abstract
The membrane lipids diacylglycerol (DAG) and phosphatidic acid (PA) are important second messengers that can regulate membrane transport by recruiting proteins to the membrane and by altering biophysical membrane properties. DAG and PA are involved in the transport from the Golgi apparatus to endosomes, and we have here investigated whether changes in these lipids might be important for regulation of transport to the Golgi using the protein toxin ricin. Modulation of DAG and PA levels using DAG kinase (DGK) and phospholipase D (PLD) inhibitors gave a strong increase in retrograde ricin transport, but had little impact on ricin recycling or degradation. Inhibitor treatment strongly affected the endosome morphology, increasing endosomal tubulation and size. Furthermore, ricin was present in these tubular structures together with proteins known to regulate retrograde transport. Using siRNA to knock down different isoforms of PLD and DGK, we found that several isoforms of PLD and DGK are involved in regulating ricin transport to the Golgi. Finally, by performing lipidomic analysis we found that the DGK inhibitor gave a weak, but expected, increase in DAG levels, while the PLD inhibitor gave a strong and unexpected increase in DAG levels, showing that it is important to perform lipidomic analysis when using inhibitors of lipid metabolism.
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Affiliation(s)
- Anne Berit Dyve Lingelem
- Department of Molecular Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway.,Department of Forensic Biology, Oslo University Hospital, Oslo, Norway
| | - Simona Kavaliauskiene
- Department of Molecular Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
| | - Ruth Halsne
- Department of Molecular Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway.,Department of Forensic Biology, Oslo University Hospital, Oslo, Norway
| | - Tove Irene Klokk
- Department of Molecular Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway.,Regional Committees for Medical and Health Research Ethics, University of Oslo, Oslo, Norway
| | | | | | - Tore Skotland
- Department of Molecular Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
| | - Kirsten Sandvig
- Department of Molecular Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway. .,Department of Biosciences, University of Oslo, Oslo, Norway.
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3
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Targeting the Early Endosome-to-Golgi Transport of Shiga Toxins as a Therapeutic Strategy. Toxins (Basel) 2020; 12:toxins12050342. [PMID: 32456007 PMCID: PMC7290323 DOI: 10.3390/toxins12050342] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2020] [Revised: 05/19/2020] [Accepted: 05/20/2020] [Indexed: 02/07/2023] Open
Abstract
Shiga toxin (STx) produced by Shigella and closely related Shiga toxin 1 and 2 (STx1 and STx2) synthesized by Shiga toxin-producing Escherichia coli (STEC) are bacterial AB5 toxins. All three toxins target kidney cells and may cause life-threatening renal disease. While Shigella infections can be treated with antibiotics, resistance is increasing. Moreover, antibiotic therapy is contraindicated for STEC, and there are no definitive treatments for STEC-induced disease. To exert cellular toxicity, STx, STx1, and STx2 must undergo retrograde trafficking to reach their cytosolic target, ribosomes. Direct transport from early endosomes to the Golgi apparatus is an essential step that allows the toxins to bypass degradative late endosomes and lysosomes. The essentiality of this transport step also makes it an ideal target for the development of small-molecule inhibitors of toxin trafficking as potential therapeutics. Here, we review the recent advances in understanding the molecular mechanisms of the early endosome-to-Golgi transport of STx, STx1, and STx2, as well as the development of small-molecule inhibitors of toxin trafficking that act at the endosome/Golgi interface.
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4
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Kavaliauskiene S, Torgersen ML, Lingelem ABD, Klokk TI, Lintonen T, Simolin H, Ekroos K, Skotland T, Sandvig K. Cellular effects of fluorodeoxyglucose: Global changes in the lipidome and alteration in intracellular transport. Oncotarget 2018; 7:79885-79900. [PMID: 27829218 PMCID: PMC5346758 DOI: 10.18632/oncotarget.13089] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 10/21/2016] [Indexed: 11/29/2022] Open
Abstract
2-fluoro-2-deoxy-D-glucose (FDG), labeled with 18F radioisotope, is the most common imaging agent used for positron emission tomography (PET) in oncology. However, little is known about the cellular effects of FDG. Another glucose analogue, 2-deoxy-D-glucose (2DG), has been shown to affect many cellular functions, including intracellular transport and lipid metabolism, and has been found to improve the efficacy of cancer chemotherapeutic agents in vivo. Thus, in the present study, we have investigated cellular effects of FDG with the focus on changes in cellular lipids and intracellular transport. By quantifying more than 200 lipids from 17 different lipid classes in HEp-2 cells and by analyzing glycosphingolipids from MCF-7, HT-29 and HBMEC cells, we have discovered that FDG treatment inhibits glucosylceramide synthesis and thus reduces cellular levels of glycosphingolipids. In addition, in HEp-2 cells the levels and/or species composition of other lipid classes, namely diacylglycerols, phosphatidic acids and phosphatidylinositols, were found to change upon treatment with FDG. Furthermore, we show here that FDG inhibits retrograde Shiga toxin transport and is much more efficient in protecting cells against the toxin than 2DG. In summary, our data reveal novel effects of FDG on cellular transport and glycosphingolipid metabolism, which suggest a potential clinical application of FDG as an adjuvant for cancer chemotherapy.
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Affiliation(s)
- Simona Kavaliauskiene
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway.,Center for Cancer Biomedicine, Oslo University Hospital, Oslo, Norway.,Department of Biosciences, University of Oslo, Oslo, Norway
| | - Maria Lyngaas Torgersen
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway.,Center for Cancer Biomedicine, Oslo University Hospital, Oslo, Norway
| | - Anne Berit Dyve Lingelem
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway.,Center for Cancer Biomedicine, Oslo University Hospital, Oslo, Norway
| | - Tove Irene Klokk
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway.,Center for Cancer Biomedicine, Oslo University Hospital, Oslo, Norway
| | | | | | | | - Tore Skotland
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway.,Center for Cancer Biomedicine, Oslo University Hospital, Oslo, Norway
| | - Kirsten Sandvig
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway.,Center for Cancer Biomedicine, Oslo University Hospital, Oslo, Norway.,Department of Biosciences, University of Oslo, Oslo, Norway
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5
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Kavaliauskiene S, Dyve Lingelem AB, Skotland T, Sandvig K. Protection against Shiga Toxins. Toxins (Basel) 2017; 9:E44. [PMID: 28165371 PMCID: PMC5331424 DOI: 10.3390/toxins9020044] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Revised: 01/18/2017] [Accepted: 01/19/2017] [Indexed: 12/12/2022] Open
Abstract
Shiga toxins consist of an A-moiety and five B-moieties able to bind the neutral glycosphingolipid globotriaosylceramide (Gb3) on the cell surface. To intoxicate cells efficiently, the toxin A-moiety has to be cleaved by furin and transported retrogradely to the Golgi apparatus and to the endoplasmic reticulum. The enzymatically active part of the A-moiety is then translocated to the cytosol, where it inhibits protein synthesis and in some cell types induces apoptosis. Protection of cells can be provided either by inhibiting binding of the toxin to cells or by interfering with any of the subsequent steps required for its toxic effect. In this article we provide a brief overview of the interaction of Shiga toxins with cells, describe some compounds and conditions found to protect cells against Shiga toxins, and discuss whether they might also provide protection in animals and humans.
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Affiliation(s)
- Simona Kavaliauskiene
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, N-0379 Oslo, Norway.
- Center for Cancer Biomedicine, Faculty of Medicine, Oslo University Hospital, N-0379 Oslo, Norway.
| | - Anne Berit Dyve Lingelem
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, N-0379 Oslo, Norway.
- Center for Cancer Biomedicine, Faculty of Medicine, Oslo University Hospital, N-0379 Oslo, Norway.
| | - Tore Skotland
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, N-0379 Oslo, Norway.
- Center for Cancer Biomedicine, Faculty of Medicine, Oslo University Hospital, N-0379 Oslo, Norway.
| | - Kirsten Sandvig
- Department of Molecular Cell Biology, Institute for Cancer Research, Oslo University Hospital, N-0379 Oslo, Norway.
- Center for Cancer Biomedicine, Faculty of Medicine, Oslo University Hospital, N-0379 Oslo, Norway.
- Department of Biosciences, University of Oslo, N-0316 Oslo, Norway.
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6
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Klokk TI, Kavaliauskiene S, Sandvig K. Cross-linking of glycosphingolipids at the plasma membrane: consequences for intracellular signaling and traffic. Cell Mol Life Sci 2016; 73:1301-16. [PMID: 26407609 PMCID: PMC11108300 DOI: 10.1007/s00018-015-2049-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Revised: 09/16/2015] [Accepted: 09/17/2015] [Indexed: 12/11/2022]
Abstract
Glycosphingolipids (GSLs) are predominantly found in the outer leaflet of the plasma membrane, where they play a role in important processes such as cell adhesion, migration and signaling. However, by which mechanisms GSLs regulate these processes remains elusive. In this study, we therefore took advantage of the fact that some GSLs also serve as receptors for certain protein toxins, which rely on receptor binding for internalization and intoxication. Here, we demonstrate that Shiga and cholera toxins, which both possess multivalent GSL-binding capacity, induce dissociation of the cytosolic cPLA2α-AnxA1 complex in HeLa and HMEC-1 cells. The dissociation is mediated through an increase in cytosolic calcium levels and activation of the tyrosine kinase Syk. Ricin, a protein toxin that does not cross-link surface molecules, has no effect on the same complex. Importantly, we find that antibody-mediated cross-linking of Gb3 and GM1, the GSL receptors for Shiga and cholera toxin, respectively, also induces dissociation. These data demonstrate that cross-linking of GSLs at the plasma membrane mediates the intracellular signaling events resulting in dissociation of the complex. After dissociation, cPLA2α and AnxA1 are translocated to intracellular membranes where they are known to function in regulating membrane transport processes. In conclusion, we have characterized a novel mechanism for cell surface-induced initiation of intracellular signaling and transport events.
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Affiliation(s)
- Tove Irene Klokk
- Department of Molecular Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, 0379, Oslo, Norway.
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, 0316, Oslo, Norway.
| | - Simona Kavaliauskiene
- Department of Molecular Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, 0379, Oslo, Norway
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, 0316, Oslo, Norway
- Department of Biosciences, University of Oslo, 0316, Oslo, Norway
| | - Kirsten Sandvig
- Department of Molecular Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, 0379, Oslo, Norway
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, 0316, Oslo, Norway
- Department of Biosciences, University of Oslo, 0316, Oslo, Norway
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7
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Activation of the Classical Mitogen-Activated Protein Kinases Is Part of the Shiga Toxin-Induced Ribotoxic Stress Response and May Contribute to Shiga Toxin-Induced Inflammation. Infect Immun 2015; 84:138-48. [PMID: 26483408 DOI: 10.1128/iai.00977-15] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 10/12/2015] [Indexed: 12/20/2022] Open
Abstract
Infection with enterohemorrhagic Escherichia coli (EHEC) can result in severe disease, including hemorrhagic colitis and the hemolytic uremic syndrome. Shiga toxins (Stx) are the key EHEC virulence determinant contributing to severe disease. Despite inhibiting protein synthesis, Shiga toxins paradoxically induce the expression of proinflammatory cytokines from various cell types in vitro, including intestinal epithelial cells (IECs). This effect is mediated in large part by the ribotoxic stress response (RSR). The Shiga toxin-induced RSR is known to involve the activation of the stress-activated protein kinases (SAPKs) p38 and JNK. In some cell types, Stx also can induce the classical mitogen-activated protein kinases (MAPKs) or ERK1/2, but the mechanism(s) by which this activation occurs is unknown. In this study, we investigated the mechanism by which Stx activates ERK1/2s in IECs and the contribution of ERK1/2 activation to interleukin-8 (IL-8) expression. We demonstrate that Stx1 activates ERK1/2 in a biphasic manner: the first phase occurs in response to StxB1 subunit, while the second phase requires StxA1 subunit activity. We show that the A subunit-dependent ERK1/2 activation is mediated through ZAK-dependent signaling, and inhibition of ERK1/2 activation via the MEK1/2 inhibitors U0126 and PD98059 results in decreased Stx1-mediated IL-8 mRNA. Finally, we demonstrate that ERK1/2 are activated in vivo in the colon of Stx2-intoxicated infant rabbits, a model in which Stx2 induces a primarily neutrophilic inflammatory response. Together, our data support a role for ERK1/2 activation in the development of Stx-mediated intestinal inflammation.
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8
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Novel actions of 2-deoxy-D-glucose: protection against Shiga toxins and changes in cellular lipids. Biochem J 2015; 470:23-37. [PMID: 26251444 DOI: 10.1042/bj20141562] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 06/04/2015] [Indexed: 12/11/2022]
Abstract
2-Deoxy-D-glucose (2DG) is a structural analogue of glucose with well-established applications as an inhibitor of glycolysis and N-glycosylation. Importantly, 2DG has been shown to improve the efficacy of several cancer chemotherapeutic agents in vivo and thus it is in clinical studies in combination with chemotherapy and radiotherapy. However, although 2DG has been demonstrated to modulate many cellular functions, including autophagy, apoptosis and cell cycle control, little is known about the effects of 2DG on intracellular transport, which is of great importance when predicting the effects of 2DG on therapeutic agents. In addition to proteins, lipids play important roles in cellular signalling and in controlling cellular trafficking. We have, in the present study, investigated the effects of 2DG on cellular lipid composition and by use of protein toxins we have studied 2DG-mediated changes in intracellular trafficking. By quantifying more than 200 individual lipid species from 17 different lipid classes, we have found that 2DG treatment changes the levels and/or species composition of several lipids, such as phosphatidylinositol (PI), diacylglycerol (DAG), cholesteryl ester (CE), ceramide (Cer) and lysophospho-lipids. Moreover, 2DG becomes incorporated into the carbohydrate moiety of glycosphingolipids (GSLs). In addition, we have discovered that 2DG protects cells against Shiga toxins (Stxs) and inhibits release of the cytotoxic StxA1 moiety in the endoplasmic reticulum (ER). The data indicate that the 2DG-induced protection against Stx is independent of inhibition of glycolysis or N-glycosylation, but rather mediated via the depletion of Ca(2+) from cellular reservoirs by 2DG. In conclusion, our results reveal novel actions of 2DG on cellular lipids and Stx toxicity.
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9
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Geldanamycin Enhances Retrograde Transport of Shiga Toxin in HEp-2 Cells. PLoS One 2015; 10:e0129214. [PMID: 26017782 PMCID: PMC4445914 DOI: 10.1371/journal.pone.0129214] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Accepted: 05/06/2015] [Indexed: 12/22/2022] Open
Abstract
The heat shock protein 90 (Hsp90) inhibitor geldanamycin (GA) has been shown to alter endosomal sorting, diverting cargo destined for the recycling pathway into the lysosomal pathway. Here we investigated whether GA also affects the sorting of cargo into the retrograde pathway from endosomes to the Golgi apparatus. As a model cargo we used the bacterial toxin Shiga toxin, which exploits the retrograde pathway as an entry route to the cytosol. Indeed, GA treatment of HEp-2 cells strongly increased the Shiga toxin transport to the Golgi apparatus. The enhanced Golgi transport was not due to increased endocytic uptake of the toxin or perturbed recycling, suggesting that GA selectively enhances endosomal sorting into the retrograde pathway. Moreover, GA activated p38 and both inhibitors of p38 or its substrate MK2 partially counteracted the GA-induced increase in Shiga toxin transport. Thus, our data suggest that GA-induced p38 and MK2 activation participate in the increased Shiga toxin transport to the Golgi apparatus.
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10
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Bergan J, Skotland T, Lingelem ABD, Simm R, Spilsberg B, Lindbäck T, Sylvänne T, Simolin H, Ekroos K, Sandvig K. The ether lipid precursor hexadecylglycerol protects against Shiga toxins. Cell Mol Life Sci 2014; 71:4285-300. [PMID: 24740796 PMCID: PMC11113769 DOI: 10.1007/s00018-014-1624-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Revised: 03/12/2014] [Accepted: 04/01/2014] [Indexed: 11/24/2022]
Abstract
Shiga toxin-producing Escherichia coli bacteria cause hemorrhagic colitis and hemolytic uremic syndrome in humans. Currently, only supportive treatment is available for diagnosed patients. We show here that 24-h pretreatment with an ether lipid precursor, the alkylglycerol sn-1-O-hexadecylglycerol (HG), protects HEp-2 cells against Shiga toxin and Shiga toxin 2. Also the endothelial cell lines HMEC-1 and HBMEC are protected against Shiga toxins after HG pretreatment. In contrast, the corresponding acylglycerol, DL-α-palmitin, has no effect on Shiga toxicity. Although HG treatment provides a strong protection (~30 times higher IC₅₀) against Shiga toxin, only a moderate reduction in toxin binding was observed, suggesting that retrograde transport of the toxin from the plasma membrane to the cytosol is perturbed. Furthermore, endocytosis of Shiga toxin and retrograde sorting from endosomes to the Golgi apparatus remain intact, but transport from the Golgi to the endoplasmic reticulum is inhibited by HG treatment. As previously described, HG reduces the total level of all quantified glycosphingolipids to 50-70% of control, including the Shiga toxin receptor globotriaosylceramide (Gb3), in HEp-2 cells. In accordance with this, we find that interfering with Gb3 biosynthesis by siRNA-mediated knockdown of Gb3 synthase for 24 h causes a similar cytotoxic protection and only a moderate reduction in toxin binding (to 70% of control cells). Alkylglycerols, including HG, have been administered to humans for investigation of therapeutic roles in disorders where ether lipid biosynthesis is deficient, as well as in cancer therapy. Further studies may reveal if HG can also have a therapeutic potential in Shiga toxin-producing E. coli infections.
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Affiliation(s)
- Jonas Bergan
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Montebello, 0379 Oslo, Norway
- Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, Oslo, Norway
| | - Tore Skotland
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Montebello, 0379 Oslo, Norway
| | - Anne Berit Dyve Lingelem
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Montebello, 0379 Oslo, Norway
| | - Roger Simm
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Montebello, 0379 Oslo, Norway
| | - Bjørn Spilsberg
- Section of Bacteriology-Food and GMO, Norwegian Veterinary Institute, Oslo, Norway
| | - Toril Lindbäck
- Department of Food Safety and Infection Biology, Norwegian School of Veterinary Science, Oslo, Norway
| | | | | | | | - Kirsten Sandvig
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Montebello, 0379 Oslo, Norway
- Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, Oslo, Norway
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11
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Sandvig K, Skotland T, van Deurs B, Klokk TI. Retrograde transport of protein toxins through the Golgi apparatus. Histochem Cell Biol 2013; 140:317-26. [PMID: 23765164 DOI: 10.1007/s00418-013-1111-z] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/01/2013] [Indexed: 12/13/2022]
Abstract
A number of protein toxins from plants and bacteria take advantage of transport through the Golgi apparatus to gain entry into the cytosol where they exert their action. These toxins include the plant toxin ricin, the bacterial Shiga toxins, and cholera toxin. Such toxins bind to lipids or proteins at the cell surface, and they are endocytosed both by clathrin-dependent and clathrin-independent mechanisms. Sorting to the Golgi and retrograde transport to the endoplasmic reticulum (ER) are common to these toxins, but the exact mechanisms turn out to be toxin and cell-type dependent. In the ER, the enzymatically active part is released and then transported into the cytosol, exploiting components of the ER-associated degradation system. In this review, we will discuss transport of different protein toxins, but we will focus on factors involved in entry and sorting of ricin and Shiga toxin into and through the Golgi apparatus.
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Affiliation(s)
- Kirsten Sandvig
- Centre for Cancer Biomedicine, University of Oslo, Oslo, Norway.
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12
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Mukhopadhyay S, Linstedt AD. Retrograde trafficking of AB₅ toxins: mechanisms to therapeutics. J Mol Med (Berl) 2013; 91:1131-41. [PMID: 23665994 DOI: 10.1007/s00109-013-1048-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 04/23/2013] [Accepted: 04/24/2013] [Indexed: 01/28/2023]
Abstract
Bacterial AB5 toxins are a clinically relevant class of exotoxins that include several well-known members such as Shiga, cholera, and pertussis toxins. Infections with toxin-producing bacteria cause devastating human diseases that affect millions of individuals each year and have no definitive medical treatment. The molecular targets of AB5 toxins reside in the cytosol of infected cells, and the toxins reach the cytosol by trafficking through the retrograde membrane transport pathway that avoids degradative late endosomes and lysosomes. Focusing on Shiga toxin as the archetype member, we review recent advances in understanding the molecular mechanisms involved in the retrograde trafficking of AB5 toxins and highlight how these basic science advances are leading to the development of a promising new therapeutic approach based on inhibiting toxin transport.
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Affiliation(s)
- Somshuvra Mukhopadhyay
- Division of Pharmacology & Toxicology, College of Pharmacy and Institute for Cellular & Molecular Biology, The University of Texas at Austin, Austin, TX, 78712, USA
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13
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Amin R, Sharma S, Ratakonda S, Hassan HA. Extracellular nucleotides inhibit oxalate transport by human intestinal Caco-2-BBe cells through PKC-δ activation. Am J Physiol Cell Physiol 2013; 305:C78-89. [PMID: 23596171 DOI: 10.1152/ajpcell.00339.2012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Nephrolithiasis remains a major health problem in Western countries. Seventy to 80% of kidney stones are composed of calcium oxalate, and small changes in urinary oxalate affect risk of kidney stone formation. Intestinal oxalate secretion mediated by the anion exchanger SLC26A6 plays an essential role in preventing hyperoxaluria and calcium oxalate nephrolithiasis, indicating that understanding the mechanisms regulating intestinal oxalate transport is critical for management of hyperoxaluria. Purinergic signaling modulates several intestinal processes through pathways including PKC activation, which we previously found to inhibit Slc26a6 activity in mouse duodenal tissue. We therefore examined whether purinergic stimulation with ATP and UTP affects oxalate transport by human intestinal Caco-2-BBe (C2) cells. We measured [¹⁴C]oxalate uptake in the presence of an outward Cl⁻ gradient as an assay of Cl⁻/oxalate exchange activity, ≥50% of which is mediated by SLC26A6. We found that ATP and UTP significantly inhibited oxalate transport by C2 cells, an effect blocked by the PKC inhibitor Gö-6983. Utilizing pharmacological agonists and antagonists, as well as PKC-δ knockdown studies, we observed that ATP inhibits oxalate transport through the P2Y₂ receptor, PLC, and PKC-δ. Biotinylation studies showed that ATP inhibits oxalate transport by lowering SLC26A6 surface expression. These findings are of potential relevance to pathophysiology of inflammatory bowel disease-associated hyperoxaluria, where supraphysiological levels of ATP/UTP are expected and overexpression of the P2Y₂ receptor has been reported. We conclude that ATP and UTP inhibit oxalate transport by lowering SLC26A6 surface expression in C2 cells through signaling pathways including the P2Y₂ purinergic receptor, PLC, and PKC-δ.
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Affiliation(s)
- Ruhul Amin
- Department of Medicine, University of Chicago, Chicago, IL 60637, USA
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14
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Identification of a peptide-based neutralizer that potently inhibits both Shiga toxins 1 and 2 by targeting specific receptor-binding regions. Infect Immun 2013; 81:2133-8. [PMID: 23545297 DOI: 10.1128/iai.01256-12] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Shiga toxin (Stx) is a major virulence factor of enterohemorrhagic Escherichia coli that occasionally causes fatal systemic complications. We recently developed a tetravalent peptide (PPP-tet) that neutralizes the cytotoxicity of Stx2 using a multivalent peptide library approach. In this study, we used this technique to identify a series of tetravalent peptides that bound to Stx1, another major Stx family member, with high affinity by targeting one receptor-binding site of the B subunit. One peptide, MMA-tet, markedly inhibited Stx1 and Stx2 cytotoxicity with greater potency than PPP-tet. After forming a complex with Stx1 through its specific receptor-binding region, MMA-tet did not affect vesicular transport of the toxin to the endoplasmic reticulum but substantially rescued inhibition of the protein synthesis induced by Stx1. Oral application of MMA-tet protected mice from a fatal dose of an E. coli O157:H7 strain producing both toxins. MMA-tet may be a promising therapeutic agent against the infection.
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Bergan J, Dyve Lingelem AB, Simm R, Skotland T, Sandvig K. Shiga toxins. Toxicon 2012; 60:1085-107. [PMID: 22960449 DOI: 10.1016/j.toxicon.2012.07.016] [Citation(s) in RCA: 148] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Revised: 06/19/2012] [Accepted: 07/25/2012] [Indexed: 02/03/2023]
Abstract
Shiga toxins are virulence factors produced by the bacteria Shigella dysenteriae and certain strains of Escherichia coli. There is currently no available treatment for disease caused by these toxin-producing bacteria, and understanding the biology of the Shiga toxins might be instrumental in addressing this issue. In target cells, the toxins efficiently inhibit protein synthesis by inactivating ribosomes, and they may induce signaling leading to apoptosis. To reach their cytoplasmic target, Shiga toxins are endocytosed and transported by a retrograde pathway to the endoplasmic reticulum, before the enzymatically active moiety is translocated to the cytosol. The toxins thereby serve as powerful tools to investigate mechanisms of intracellular transport. Although Shiga toxins are a serious threat to human health, the toxins may be exploited for medical purposes such as cancer therapy or imaging.
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Affiliation(s)
- Jonas Bergan
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Norway
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16
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Annexin A1 and A2: roles in retrograde trafficking of Shiga toxin. PLoS One 2012; 7:e40429. [PMID: 22792315 PMCID: PMC3391278 DOI: 10.1371/journal.pone.0040429] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2012] [Accepted: 06/06/2012] [Indexed: 01/05/2023] Open
Abstract
Annexins constitute a family of calcium and membrane binding proteins. As annexin A1 and A2 have previously been linked to various membrane trafficking events, we initiated this study to investigate the role of these annexins in the uptake and intracellular transport of the bacterial Shiga toxin (Stx) and the plant toxin ricin. Once endocytosed, both toxins are retrogradely transported from endosomes to the Golgi apparatus and the endoplasmic reticulum before being targeted to the cytosol where they inhibit protein synthesis. This study was performed to obtain new information both about toxin transport and the function of annexin A1 and annexin A2. Our data show that depletion of annexin A1 or A2 alters the retrograde transport of Stx but not ricin, without affecting toxin binding or internalization. Knockdown of annexin A1 increases Golgi transport of Stx, whereas knockdown of annexin A2 slightly decreases the same transport step. Interestingly, annexin A1 was found in proximity to cytoplasmic phospholipase A2 (cPLA2), and the basal as well as the increased Golgi transport of Stx upon annexin A1 knockdown is dependent on cPLA2 activity. In conclusion, annexin A1 and A2 have different roles in Stx transport to the trans-Golgi network. The most prominent role is played by annexin A1 which normally works as a negative regulator of retrograde transport from the endosomes to the Golgi network, most likely by complex formation and inhibition of cPLA2.
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The B subunits of Shiga-like toxins induce regulated VWF secretion in a phospholipase D1-dependent manner. Blood 2012; 120:1143-9. [PMID: 22718838 DOI: 10.1182/blood-2012-01-408096] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Shiga toxin (Stx) causes diarrhea-associated hemolytic uremic syndrome by damaging renal microvascular endothelium. The pentameric B subunits of Stx types 1 and 2 (Stx1B and Stx2B) are sufficient to stimulate acute VWF secretion from endothelial cells, but Stx1B and Stx2B exert distinct effects on Ca(2+) and cAMP pathways. Therefore, we investigated other signaling components in StxB-induced VWF exocytosis. Incubation of HUVECs with StxB transiently increased phospholipase D (PLD) activity. Inhibition of PLD activity or shRNA-mediated PLD1 knockdown abolished StxB-induced VWF secretion. In addition, treatment with StxB triggered actin polymerization, enhanced endothelial monolayer permeability, and activated RhoA. PLD activation and VWF secretion induced by Stx1B were abolished on protein kinase Cα (PKCα) inhibition or gene silencing but were only moderately reduced by Rho or Rho kinase inhibitors. Conversely, PLD activation and VWF exocytosis induced by Stx2B were reduced by Rho/Rho kinase inhibitors and dominant-negative RhoA, whereas attenuation of PKCα did not affect either process. Another PLD1 activator, ADP-ribosylation factor 6, was involved in VWF secretion induced by Stx1B or Stx2B, but not histamine. These data indicate that Stx1B and Stx2B induce acute VWF secretion in a PLD1-dependent manner but do so by differentially modulating PKCα, RhoA, and ADP-ribosylation factor 6.
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Contreras X, Mzoughi O, Gaston F, Peterlin MB, Bahraoui E. Protein kinase C-delta regulates HIV-1 replication at an early post-entry step in macrophages. Retrovirology 2012; 9:37. [PMID: 22554282 PMCID: PMC3432598 DOI: 10.1186/1742-4690-9-37] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2011] [Accepted: 03/15/2012] [Indexed: 11/17/2022] Open
Abstract
Background Macrophages, which are CD4 and CCR5 positive, can sustain HIV-1 replication for long periods of time. Thus, these cells play critical roles in the transmission, dissemination and persistence of viral infection. Of note, current antiviral therapies do not target macrophages efficiently. Previously, it was demonstrated that interactions between CCR5 and gp120 stimulate PKC. However, the PKC isozymes involved were not identified. Results In this study, we identified PKC-delta as a major cellular cofactor for HIV-1 replication in macrophages. Indeed, PKC-delta was stimulated following the interaction between the virus and its target cell. Moreover, inhibition of PKC-delta blocked the replication of R5-tropic viruses in primary human macrophages. However, this inhibition did not have significant effects on receptor and co-receptor expression or fusion. Additionally, it did not affect the formation of the early reverse transcription product containing R/U5 sequences, but did inhibit the synthesis of subsequent cDNAs. Importantly, the inhibition of PKC-delta altered the redistribution of actin, a cellular cofactor whose requirement for the completion of reverse transcription was previously established. It also prevented the association of the reverse transcription complex with the cytoskeleton. Conclusion This work highlights the importance of PKC-delta during early steps of the replicative cycle of HIV-1 in human macrophages.
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Affiliation(s)
- Xavier Contreras
- Université Paul Sabatier, EA 3038, 118 Route de Narbonne, Toulouse 31062, France.
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19
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Abstract
Shiga toxins and ricin are potent inhibitors of protein synthesis. In addition to causing inhibition of protein synthesis, these toxins activate proinflammatory signaling cascades that may contribute to the severe diseases associated with toxin exposure. Treatment of cells with Shiga toxins and ricin have been shown to activate a number of signaling pathways including those associated with the ribotoxic stress response, Nuclear factor kappa B activation, inflammasome activation, the unfolded protein response, mTOR signaling, hemostasis, and retrograde trafficking. In this chapter, we review our current understanding of these signaling pathways as they pertain to intoxication by Shiga toxins and ricin.
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Sugawara T, Nakatsu D, Kii H, Maiya N, Adachi A, Yamamoto A, Kano F, Murata M. PKCδ and ε regulate the morphological integrity of the ER–Golgi intermediate compartment (ERGIC) but not the anterograde and retrograde transports via the Golgi apparatus. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1823:861-75. [DOI: 10.1016/j.bbamcr.2012.01.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 01/13/2012] [Accepted: 01/17/2012] [Indexed: 02/03/2023]
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Lengfeld J, Wang Q, Zohlman A, Salvarezza S, Morgan S, Ren J, Kato K, Rodriguez-Boulan E, Liu B. Protein kinase C δ regulates the release of collagen type I from vascular smooth muscle cells via regulation of Cdc42. Mol Biol Cell 2012; 23:1955-63. [PMID: 22456512 PMCID: PMC3350558 DOI: 10.1091/mbc.e11-06-0531] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Both gene knockout and chemical inhibition show that PKCδ is critical for efficient secretion of type I collagen by arterial smooth muscle cells. The data suggest that PKCδ regulates trafficking of collagen I by controlling its exit from the trans-Golgi network through a mechanism involving Cdc42. Collagen type I is the most abundant component of extracellular matrix in the arterial wall. Mice knocked out for the protein kinase C δ gene (PKCδ KO) show a marked reduction of collagen I in the arterial wall. The lack of PKCδ diminished the ability of arterial smooth muscle cells (SMCs) to secrete collagen I without significantly altering the intracellular collagen content. Moreover, the unsecreted collagen I molecules accumulate in large perinuclear puncta. These perinuclear structures colocalize with the trans-Golgi network (TGN) marker TGN38 and to a lesser degree with cis-Golgi marker (GM130) but not with early endosomal marker (EEA1). Associated with diminished collagen I secretion, PKCδ KO SMCs exhibit a significant reduction in levels of cell division cycle 42 (Cdc42) protein and mRNA. Restoring PKCδ expression partially rescues Cdc42 expression and collagen I secretion in PKCδ KO SMCs. Inhibition of Cdc42 expression or activity with small interfering RNA or secramine A in PKCδ WT SMCs eliminates collagen I secretion. Conversely, restoring Cdc42 expression in PKCδ KO SMCs enables collagen I secretion. Taken together, our data demonstrate that PKCδ mediates collagen I secretion from SMCs, likely through a Cdc42-dependent mechanism.
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Affiliation(s)
- Justin Lengfeld
- Division of Peripheral Vascular Surgery, Department of Surgery, University of Wisconsin-Madison, Madison, WI 53705, USA
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Dyve Lingelem AB, Bergan J, Sandvig K. Inhibitors of intravesicular acidification protect against Shiga toxin in a pH-independent manner. Traffic 2011; 13:443-54. [PMID: 22132807 DOI: 10.1111/j.1600-0854.2011.01319.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Revised: 11/28/2011] [Accepted: 12/01/2011] [Indexed: 01/01/2023]
Abstract
Shiga toxin inhibits protein synthesis after being transported from the cell surface to endosomes and retrogradely through the Golgi apparatus to the endoplasmic reticulum (ER) and into the cytosol. In this study, we have abolished proton gradients across internal membranes in different ways and investigated the effect on the various transport steps of Shiga toxin. Although inhibitors of the proton pump such as bafilomycin A1 and concanamycin A as well as some ionophores and chloroquine all protect against Shiga toxin, they mediate protection by inhibiting different transport steps. For instance, chloroquine protects the cells, although the toxin is transported to the ER. Importantly, our data indicate that proton pump activity is required for efficient endosome-to-Golgi transport of Shiga toxin, although acidification as such does not seem to be required.
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Affiliation(s)
- Anne Berit Dyve Lingelem
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, 0379 Oslo, Norway
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23
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Paul S, Dansithong W, Jog SP, Holt I, Mittal S, Brook JD, Morris GE, Comai L, Reddy S. Expanded CUG repeats Dysregulate RNA splicing by altering the stoichiometry of the muscleblind 1 complex. J Biol Chem 2011; 286:38427-38438. [PMID: 21900255 PMCID: PMC3207417 DOI: 10.1074/jbc.m111.255224] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Revised: 08/29/2011] [Indexed: 01/27/2023] Open
Abstract
To understand the role of the splice regulator muscleblind 1 (MBNL1) in the development of RNA splice defects in myotonic dystrophy I (DM1), we purified RNA-independent MBNL1 complexes from normal human myoblasts and examined the behavior of these complexes in DM1 myoblasts. Antibodies recognizing MBNL1 variants (MBNL1(CUG)), which can sequester in the toxic CUG RNA foci that develop in DM1 nuclei, were used to purify MBNL1(CUG) complexes from normal myoblasts. In normal myoblasts, MBNL1(CUG) bind 10 proteins involved in remodeling ribonucleoprotein complexes including hnRNP H, H2, H3, F, A2/B1, K, L, DDX5, DDX17, and DHX9. Of these proteins, only MBNL1(CUG) colocalizes extensively with DM1 CUG foci (>80% of foci) with its partners being present in <10% of foci. Importantly, the stoichiometry of MBNL1(CUG) complexes is altered in DM1 myoblasts, demonstrating an increase in the steady state levels of nine of its partner proteins. These changes are recapitulated by the expression of expanded CUG repeat RNA in Cos7 cells. Altered stoichiometry of MBNL1(CUG) complexes results from aberrant protein synthesis or stability and is unlinked to PKCα function. Modeling these changes in normal myoblasts demonstrates that increased levels of hnRNP H, H2, H3, F, and DDX5 independently dysregulate splicing in overlapping RNA subsets. Thus expression of expanded CUG repeats alters the stoichiometry of MBNL1(CUG) complexes to allow both the reinforcement and expansion of RNA processing defects.
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Affiliation(s)
- Sharan Paul
- Department of Biochemistry and Molecular Biology, University of Southern California, Los Angeles, California 90033
| | - Warunee Dansithong
- Department of Biochemistry and Molecular Biology, University of Southern California, Los Angeles, California 90033
| | - Sonali P Jog
- Department of Biochemistry and Molecular Biology, University of Southern California, Los Angeles, California 90033
| | - Ian Holt
- Wolfson Centre for Inherited Neuromuscular Disease, Robert Jones and Agnes Hunt Orthopedic Hospital, Oswestry SY10 7AG, United Kingdom; Institute for Science and Technology in Medicine, Keele University, Keele ST5 5BG, United Kingdom
| | - Saloni Mittal
- Institute of Genetics, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, United Kingdom
| | - J David Brook
- Institute of Genetics, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH, United Kingdom
| | - Glenn E Morris
- Wolfson Centre for Inherited Neuromuscular Disease, Robert Jones and Agnes Hunt Orthopedic Hospital, Oswestry SY10 7AG, United Kingdom; Institute for Science and Technology in Medicine, Keele University, Keele ST5 5BG, United Kingdom
| | - Lucio Comai
- Department Molecular Microbiology and Immunology, Institute for Genetic Medicine, University of Southern California, Los Angeles, California 90033.
| | - Sita Reddy
- Department of Biochemistry and Molecular Biology, University of Southern California, Los Angeles, California 90033.
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Shiga toxin (Stx)1B and Stx2B induce von Willebrand factor secretion from human umbilical vein endothelial cells through different signaling pathways. Blood 2011; 118:3392-8. [PMID: 21816831 DOI: 10.1182/blood-2011-06-363648] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Diarrhea-associated hemolytic uremic syndrome (D(+)HUS) is caused by the ingestion of Escherichia coli that produce Shiga toxin (Stx), which is composed of a cytotoxic A subunit and pentameric B subunits that bind globotriaosylceramide on susceptible cells. Stx occurs in 2 types, Stx1 and Stx2. B subunits of either type stimulate von Willebrand factor (VWF) secretion from human umbilical vein endothelial cells (HUVECs), and Stx2B can cause thrombotic microangiopathy in Adamts13(-/-) mice. We have now determined that Stx1B and Stx2B activate different signaling pathways in HUVECs. VWF secretion induced by Stx1B is associated with a transient rise in intracellular Ca(2+) level that is blocked by chelation with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester, removal of extracellular Ca(2+), the phospholipase C inhibitor U73122, the protein kinase inhibitor staurosporine, or small interfering RNA knockdown of protein kinase Cα. In contrast, Stx2B-induced VWF secretion is associated with activation of protein kinase A (PKA) and is blocked by the PKA inhibitor H89 or small interfering RNA knockdown of PKA. Stx2B does not increase cAMP levels and may activate PKA by a cAMP-independent mechanism. The activation of distinct signaling pathways may be relevant to understanding why E coli that express Stx2 are more likely to cause D(+)HUS than are E coli expressing only Stx1.
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Wang H, Xiao L, Kazanietz MG. p23/Tmp21 associates with protein kinase Cdelta (PKCdelta) and modulates its apoptotic function. J Biol Chem 2011; 286:15821-31. [PMID: 21454541 DOI: 10.1074/jbc.m111.227991] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
There is emerging evidence that C1 domains, motifs originally identified in PKC isozymes and responsible for binding of phorbol esters and diacylglycerol, interact with the Golgi/endoplasmic reticulum protein p23 (Tmp21). In this study, we investigated whether PKCδ, a kinase widely implicated in apoptosis and inhibition of cell cycle progression, associates with p23 and determined the potential functional implications of this interaction. Using a yeast two-hybrid approach, we found that the PKCδ C1b domain associates with p23 and identified two key residues (Asp(245) and Met(266)) implicated in this interaction. Interestingly, silencing p23 from LNCaP prostate cancer cells using RNAi markedly enhanced PKCδ-dependent apoptosis and activation of PKCδ downstream effectors ROCK and JNK by phorbol 12-myristate 13-acetate. Moreover, translocation of PKCδ to the plasma membrane by phorbol 12-myristate 13-acetate was enhanced in p23-depleted LNCaP cells. Notably, a PKCδ mutant that failed to interact with p23 triggered a strong apoptotic response when expressed in LNCaP cells. In summary, our data compellingly support the concept that C1 domains have dual roles both in lipid and protein associations and provide strong evidence that p23 acts as an anchoring protein that retains PKCδ at the perinuclear region, thus limiting the availability of this kinase for activation in response to stimuli.
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Affiliation(s)
- HongBin Wang
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6160, USA.
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26
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Lemjabbar-Alaoui H, Sidhu SS, Mengistab A, Gallup M, Basbaum C. TACE/ADAM-17 phosphorylation by PKC-epsilon mediates premalignant changes in tobacco smoke-exposed lung cells. PLoS One 2011; 6:e17489. [PMID: 21423656 PMCID: PMC3057966 DOI: 10.1371/journal.pone.0017489] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2010] [Accepted: 02/05/2011] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND Tobacco smoke predisposes humans and animals to develop lung tumors, but the molecular events responsible for this are poorly understood. We recently showed that signaling mechanisms triggered by smoke in lung cells could lead to the activation of a growth factor signaling pathway, thereby promoting hyperproliferation of lung epithelial cells. Hyperproliferation is considered a premalignant change in the lung, in that increased rates of DNA synthesis are associated with an increased number of DNA copying errors, events that are exacerbated in the presence of tobacco smoke carcinogens. Despite the existence of DNA repair mechanisms, a small percentage of these errors go unrepaired and can lead to tumorigenic mutations. The results of our previous study showed that an early event following smoke exposure was the generation of oxygen radicals through the activation of NADPH oxidase. Although it was clear that these radicals transduced signals through the epidermal growth factor receptor (EGFR), and that this was mediated by TACE-dependent cleavage of amphiregulin, it remained uncertain how oxygen radicals were able to activate TACE. PRINCIPAL FINDINGS In the present study, we demonstrate for the first time that phosphorylation of TACE at serine/threonine residues by tobacco smoke induces amphiregulin release and EGFR activation. TACE phosphorylation is triggered in smoke-exposed lung cells by the ROS-induced activation of PKC through the action of SRC kinase. Furthermore, we identified PKCε as the PKC isoform involved in smoke-induced TACE activation and hyperproliferation of lung cells. CONCLUSIONS Our data elucidate new signaling paradigms by which tobacco smoke promotes TACE activation and hyperproliferation of lung cells.
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Affiliation(s)
- Hassan Lemjabbar-Alaoui
- Thoracic Oncology Laboratory, Department of Surgery, Comprehensive Cancer Center, University of California San Francisco, San Francisco, California, United States of America.
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Parent N, Scherer M, Liebisch G, Schmitz G, Bertrand R. Protein kinase C-δ isoform mediates lysosome labilization in DNA damage-induced apoptosis. Int J Oncol 2010; 38:313-24. [PMID: 21174057 DOI: 10.3892/ijo.2010.881] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2010] [Accepted: 11/05/2010] [Indexed: 11/05/2022] Open
Abstract
A lysosomal pathway, characterized by the partial rupture or labilization of lysosomal membranes (LLM) and cathepsin release into the cytosol, is evoked during the early events of 20-S-camptothecin lactone (CPT)-induced apoptosis in human cancer cells, including human histiocytic lymphoma U-937 cells. These lysosomal events begin rapidly and simultaneously with mitochondrial permeabilization and caspase activation within 3 h after drug treatment. Recently, in a comparative proteomics analysis performed on highly-enriched lysosomal extracts, we identified proteins whose translocation to lysosomes correlated with LLM induction after CPT treatment, including protein kinase C-δ (PKC-δ). In this study, we show that the PKC-δ translocation to lysosomes is required for LLM, as silencing its expression with RNA interference or suppressing its activity with the inhibitor, rottlerin, prevents CPT-induced LLM. PKC-δ translocation to lysosomes is associated with lysosomal acidic sphingomyelinase (ASM) phosphorylation and activation, which in turn leads to an increase in ceramide (CER) content in lysosomes. The accumulation of endogenous CER in lysosomes is a critical event for CPT-induced LLM as suppressing PKC-δ or ASM activity reduces both the CPT-mediated CER generation in lysosomes and CPT-induced LLM. These findings reveal a novel mechanism by which PKC-δ mediates ASM phosphorylation/activation and CER accumulation in lysosomes in CPT-induced LLM, rapidly activating the lysosomal pathway of apoptosis after CPT treatment.
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Affiliation(s)
- Nicolas Parent
- Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Hôpital Notre-Dame and Institut du Cancer de Montréal, Montreal, QC H2L 4M1, Canada
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Endocytosis and retrograde transport of Shiga toxin. Toxicon 2010; 56:1181-5. [DOI: 10.1016/j.toxicon.2009.11.021] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2009] [Accepted: 11/17/2009] [Indexed: 01/22/2023]
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29
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Torgersen ML, Engedal N, Pedersen AMG, Husebye H, Espevik T, Sandvig K. Toll-like receptor 4 facilitates binding of Shiga toxin to colon carcinoma and primary umbilical vein endothelial cells. ACTA ACUST UNITED AC 2010; 61:63-75. [DOI: 10.1111/j.1574-695x.2010.00749.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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30
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Park SH, Choi HJ, Yang H, Do KH, Kim J, Moon Y. Repression of Peroxisome Proliferator-Activated Receptor γ by Mucosal Ribotoxic Insult-Activated CCAAT/Enhancer-Binding Protein Homologous Protein. THE JOURNAL OF IMMUNOLOGY 2010; 185:5522-30. [DOI: 10.4049/jimmunol.1001315] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Shiga toxin increases formation of clathrin-coated pits through Syk kinase. PLoS One 2010; 5:e10944. [PMID: 20668539 PMCID: PMC2910670 DOI: 10.1371/journal.pone.0010944] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2010] [Accepted: 05/13/2010] [Indexed: 11/19/2022] Open
Abstract
Clathrin-dependent endocytosis is a main entry mechanism for the glycolipid-binding Shiga toxin (Stx), although clathrin-independent pathways are also involved. Binding of Stx to its receptor Gb3 not only is essential for Stx retrograde transport to the endoplasmic reticulum and toxicity but also activates signaling through the tyrosine kinase Syk. We previously described that Syk activity is important for Stx entry, but it remained unclear how this kinase modulates endocytosis of Stx. Here we characterized the effects of Stx and Syk on clathrin-coated pit formation. We found that acute treatment with Stx results in an increase in the number of clathrin-coated profiles as determined by electron microscopy and on the number of structures containing the endocytic AP-2 adaptor at the plasma membrane determined by live-cell spinning disk confocal imaging. These responses to Stx require functional Syk activity. We propose that a signaling pathway mediated by Syk and modulated by Stx leads to an increased number of endocytic clathrin-coated structures, thus providing a possible mechanism by which Stx enhances its own endocytosis.
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32
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Protein toxins from plants and bacteria: Probes for intracellular transport and tools in medicine. FEBS Lett 2010; 584:2626-34. [DOI: 10.1016/j.febslet.2010.04.008] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2010] [Accepted: 04/07/2010] [Indexed: 01/07/2023]
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Abstract
Shiga toxins comprise a family of structurally and functionally related protein toxins expressed by Shigella dysenteriae serotype 1 and multiple serotypes of Escherichia coli. While the capacity of Shiga toxins to inhibit protein synthesis by catalytic inactivation of eukaryotic ribosomes has been well described, it is also apparent that Shiga toxins trigger apoptosis in many cell types. This review presents evidence that Shiga toxins induce apoptosis of epithelial, endothelial, leukocytic, lymphoid and neuronal cells. Apoptotic signaling pathways activated by the toxins are reviewed with an emphasis on signaling mechanisms that are shared among different cell types. Data suggesting that Shiga toxins induce apoptosis through the endoplasmic reticulum stress response and clinical evidence demonstrating apoptosis in humans infected with Shiga toxin-producing bacteria are briefly discussed. The potential for use of Shiga toxins to induce apoptosis in cancer cells is briefly reviewed.
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Affiliation(s)
- Vernon L Tesh
- Department of Microbial & Molecular Pathogenesis, College of Medicine, Texas A&M University System Health Science Center, 407 Reynolds Medical Building, College Station, TX 77843-1114, USA.
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34
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Pust S, Dyve AB, Torgersen ML, van Deurs B, Sandvig K. Interplay between toxin transport and flotillin localization. PLoS One 2010; 5:e8844. [PMID: 20107503 PMCID: PMC2809741 DOI: 10.1371/journal.pone.0008844] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2009] [Accepted: 01/06/2010] [Indexed: 11/18/2022] Open
Abstract
The flotillin proteins are localized in lipid domains at the plasma membrane as well as in intracellular compartments. In the present study, we examined the importance of flotillin-1 and flotillin-2 for the uptake and transport of the bacterial Shiga toxin (Stx) and the plant toxin ricin and we investigated whether toxin binding and uptake were associated with flotillin relocalization. We observed a toxin-induced redistribution of the flotillins, which seemed to be regulated in a p38-dependent manner. Our experiments provide no evidence for a changed endocytic uptake of Stx or ricin in cells silenced for flotillin-1 or -2. However, the Golgi-dependent sulfation of both toxins was significantly reduced in flotillin knockdown cells. Interestingly, when the transport of ricin to the ER was investigated, we obtained an increased mannosylation of ricin in flotillin-1 and flotillin-2 knockdown cells. The toxicity of both toxins was twofold increased in flotillin-depleted cells. Since BFA (Brefeldin A) inhibits the toxicity even in flotillin knockdown cells, the retrograde toxin transport is apparently still Golgi-dependent. Thus, flotillin proteins regulate and facilitate the retrograde transport of Stx and ricin.
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Affiliation(s)
- Sascha Pust
- Centre for Cancer Biomedicine, University of Oslo, Oslo, Norway
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
| | - Anne Berit Dyve
- Centre for Cancer Biomedicine, University of Oslo, Oslo, Norway
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
| | - Maria L. Torgersen
- Centre for Cancer Biomedicine, University of Oslo, Oslo, Norway
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
| | - Bo van Deurs
- Structural Cell Biology Unit, Department of Cellular and Molecular Medicine, The Panum Institute, University of Copenhagen, Copenhagen, Denmark
| | - Kirsten Sandvig
- Centre for Cancer Biomedicine, University of Oslo, Oslo, Norway
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
- * E-mail:
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35
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Johannes L, Römer W. Shiga toxins--from cell biology to biomedical applications. Nat Rev Microbiol 2009; 8:105-16. [PMID: 20023663 DOI: 10.1038/nrmicro2279] [Citation(s) in RCA: 352] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Shiga toxin-producing Escherichia coli is an emergent pathogen that can induce haemolytic uraemic syndrome. The toxin has received considerable attention not only from microbiologists but also in the field of cell biology, where it has become a powerful tool to study intracellular trafficking. In this Review, we summarize the Shiga toxin family members and their structures, receptors, trafficking pathways and cellular targets. We discuss how Shiga toxin affects cells not only by inhibiting protein biosynthesis but also through the induction of signalling cascades that lead to apoptosis. Finally, we discuss how Shiga toxins might be exploited in cancer therapy and immunotherapy.
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Affiliation(s)
- Ludger Johannes
- Institut Curie - Centre de Recherche and CNRS UMR144, Traffic, Signalling and Delivery Laboratory, 26 rue d'Ulm, 75248 Paris Cedex 05, France.
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Saenz JB, Li J, Haslam DB. The MAP kinase-activated protein kinase 2 (MK2) contributes to the Shiga toxin-induced inflammatory response. Cell Microbiol 2009; 12:516-29. [PMID: 19951368 DOI: 10.1111/j.1462-5822.2009.01414.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Infection with Shiga toxin (STx)-producing bacteria can progress to a toxemic, extraintestinal injury cascade known as haemolytic uremic syndrome (HUS), the leading cause of acute renal failure in children. Mounting evidence suggests that STx activates stress response pathways in susceptible cells and has implicated the p38 mitogen-activated protein kinase (MAPK) pathway. More importantly, some of the pathology associated with HUS is believed to be a result of a STx-induced inflammatory response. From a siRNA screen of the human kinome adapted to a high-throughput format, we found that knock-down of the MAPK-activated protein kinase 2 (MK2), a downstream target of the p38 MAPK, protected against Shiga toxicity. Further characterization of the in vitro role of MK2 revealed that STx activates the p38-MK2 stress response pathway in both p38- and MK2-dependent manners in two distinct cell lines. MK2 activation was specific to damage to the ribosome by an enzymatically active toxin and did not result from translational inhibition per se. Genetic and chemical inhibition of MK2 significantly decreased the inflammatory response to STx. These findings suggest that MK2 inhibition might play a valuable role in decreasing the immuopathological component of STx-mediated disease.
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Affiliation(s)
- Jose B Saenz
- Department of Pediatrics, Washington University School of Medicine, St. Louis, MO 63110, USA
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Choi HJ, Yang H, Park SH, Moon Y. HuR/ELAVL1 RNA binding protein modulates interleukin-8 induction by muco-active ribotoxin deoxynivalenol. Toxicol Appl Pharmacol 2009; 240:46-54. [DOI: 10.1016/j.taap.2009.06.023] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Revised: 05/28/2009] [Accepted: 06/26/2009] [Indexed: 10/20/2022]
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Dyve AB, Bergan J, Utskarpen A, Sandvig K. Sorting nexin 8 regulates endosome-to-Golgi transport. Biochem Biophys Res Commun 2009; 390:109-14. [PMID: 19782049 DOI: 10.1016/j.bbrc.2009.09.076] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2009] [Accepted: 09/20/2009] [Indexed: 11/25/2022]
Abstract
Sorting nexin 8 (SNX8) belongs to the sorting nexin protein family, whose members are involved in endocytosis and endosomal sorting and signaling. The function of SNX8 has so far been unknown. Here, we have investigated the role of SNX8 in intracellular transport of the bacterial toxin Shiga toxin (Stx) and the plant toxin ricin. After being endocytosed, these toxins are transported retrogradely from endosomes, via the Golgi apparatus and the endoplasmic reticulum (ER), into the cytosol, where they exert their toxic effect. Interestingly, our experiments show that SNX8 regulates the transport of Stx and ricin differently; siRNA-mediated knockdown of SNX8 significantly increased the Stx transport to the trans-Golgi network (TGN), whereas ricin transport was slightly inhibited. We also found that SNX8 colocalizes with early endosome antigen 1 (EEA1) and with retromer components, suggesting an endosomal localization of SNX8 and supporting our finding that SNX8 is involved in endosomal sorting.
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Affiliation(s)
- Anne Berit Dyve
- Faculty Division The Norwegian Radium Hospital, Centre for Cancer Biomedicine, University of Oslo, 0316 Oslo, Norway
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39
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Entry of Shiga toxin into cells. Toxicol Lett 2009. [DOI: 10.1016/j.toxlet.2009.06.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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40
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Hehnly H, Longhini KM, Chen JL, Stamnes M. Retrograde Shiga toxin trafficking is regulated by ARHGAP21 and Cdc42. Mol Biol Cell 2009; 20:4303-12. [PMID: 19692570 DOI: 10.1091/mbc.e09-02-0155] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Shiga-toxin-producing Escherichia coli remain a food-borne health threat. Shiga toxin is endocytosed by intestinal epithelial cells and transported retrogradely through the secretory pathway. It is ultimately translocated to the cytosol where it inhibits protein translation. We found that Shiga toxin transport through the secretory pathway was dependent on the cytoskeleton. Recent studies reveal that Shiga toxin activates signaling pathways that affect microtubule reassembly and dynein-dependent motility. We propose that Shiga toxin alters cytoskeletal dynamics in a way that facilitates its transport through the secretory pathway. We have now found that Rho GTPases regulate the endocytosis and retrograde motility of Shiga toxin. The expression of RhoA mutants inhibited endocytosis of Shiga toxin. Constitutively active Cdc42 or knockdown of the Cdc42-specific GAP, ARHGAP21, inhibited the transport of Shiga toxin to the juxtanuclear Golgi apparatus. The ability of Shiga toxin to stimulate microtubule-based transferrin transport also required Cdc42 and ARHGAP21 function. Shiga toxin addition greatly decreases the levels of active Cdc42-GTP in an ARHGAP21-dependent manner. We conclude that ARHGAP21 and Cdc42-based signaling regulates the dynein-dependent retrograde transport of Shiga toxin to the Golgi apparatus.
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Affiliation(s)
- Heidi Hehnly
- Department of Molecular Physiology and Biophysics, Roy J. and Lucille A. Carver College of Medicine, The University of Iowa, Iowa City, IA 52242, USA
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41
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Raa H, Grimmer S, Schwudke D, Bergan J, Wälchli S, Skotland T, Shevchenko A, Sandvig K. Glycosphingolipid requirements for endosome-to-Golgi transport of Shiga toxin. Traffic 2009; 10:868-82. [PMID: 19453975 DOI: 10.1111/j.1600-0854.2009.00919.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Shiga toxin binds to globotriaosylceramide (Gb3) receptors on the target cell surface. To enter the cytosol, Shiga toxin is dependent on endocytic uptake, retrograde transport to the Golgi apparatus and further to the endoplasmic reticulum before translocation of the enzymatically active moiety to the cytosol. Here, we have investigated the importance of newly synthesized glycosphingolipids for the uptake and intracellular transport of Shiga toxin in HEp-2 cells. Inhibition of glycosphingolipid synthesis by treatment with either PDMP or Fumonisin B(1) for 24-48 h strongly reduced the transport of Gb3-bound Shiga toxin from endosomes to the Golgi apparatus. This was associated with a change in localization of sorting nexins 1 and 2, and accompanied by a protection against the toxin. In contrast, there was no effect on transport or toxicity of the plant toxin ricin. High-resolution mass spectrometry revealed a 2-fold reduction in Gb3 at conditions giving a 10-fold inhibition of Shiga toxin transport to the Golgi. Furthermore, mass spectrometry showed that the treatment with PDMP (DL-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol) and Fumonisin B(1) among other changes of the lipidome, affected the relative content of the different glycosphingolipid species. The largest depletion was observed for the hexosylceramide species with the N-amidated fatty acid 16:0, whereas hexosylceramide species with 24:1 were less affected. Quantitative lipid profiling with mass spectrometry demonstrated that PDMP did not influence the content of sphingomyelins, phospholipids and plasmalogens. In contrast, Fumonisin B(1) affected the amount and composition of sphingomyelin and glycolipids and altered the profiles of phospholipids and plasmalogens.
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Affiliation(s)
- Hilde Raa
- Centre for Cancer Biomedicine, Faculty Division Norwegian Radium Hospital, University of Oslo, 0316 Oslo, Norway
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42
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Wälchli S, Aasheim HC, Skånland SS, Spilsberg B, Torgersen ML, Rosendal KR, Sandvig K. Characterization of clathrin and Syk interaction upon Shiga toxin binding. Cell Signal 2009; 21:1161-8. [PMID: 19289168 DOI: 10.1016/j.cellsig.2009.03.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Accepted: 03/05/2009] [Indexed: 11/19/2022]
Abstract
Shiga toxin (Stx) is a bacterial toxin that binds to its receptor Gb3 at the plasma membrane. It is taken up by endocytosis and transported retrogradely via the Golgi apparatus to the endoplasmic reticulum. The toxin is then translocated to the cytosol where it exerts its toxic effect. We have previously shown that phosphorylation of clathrin heavy chain (CHC) is an early event following Stx binding to HeLa cells, and that this requires the activity of the tyrosine kinase Syk. Here, we have investigated this event in more detail in the B lymphoid cell line Ramos, which expresses high endogenous levels of both Syk and Gb3. We report that efficient endocytosis of Stx in Ramos cells requires Syk activity and that Syk is recruited to the uptake site of Stx. Furthermore, in response to Stx treatment, CHC and Syk were rapidly phosphorylated in a Src family kinase dependent manner at Y1477 and Y352, respectively. We show that these phosphorylated residues act as binding sites for the direct interaction between Syk and CHC. Interestingly, Syk-CHC complex formation could be induced by both Stx and B cell receptor stimulation.
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Affiliation(s)
- Sébastien Wälchli
- Department of Biochemistry, Institute for Cancer Research, Faculty Division: The Norwegian Radium Hospital, Montebello, Oslo, Norway.
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Phosphorylation of Fli1 at threonine 312 by protein kinase C delta promotes its interaction with p300/CREB-binding protein-associated factor and subsequent acetylation in response to transforming growth factor beta. Mol Cell Biol 2009; 29:1882-94. [PMID: 19158279 DOI: 10.1128/mcb.01320-08] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Previous studies have shown that transforming growth factor beta (TGF-beta)-induced collagen gene expression involves acetylation-dependent dissociation from the human alpha2(I) collagen (COL1A2) promoter of the transcriptional repressor Fli1. The goal of this study was to elucidate the regulatory steps preceding the acetylation of Fli1. We first showed that TGF-beta induces Fli1 phosphorylation on a threonine residue(s). The major phosphorylation site was localized to threonine 312 located in the DNA binding domain of Fli1. Using several independent approaches, we demonstrated that Fli1 is directly phosphorylated by protein kinase C delta (PKC delta). Additional experiments showed that in response to TGF-beta, PKC delta is recruited to the collagen promoter to phosphorylate Fli1 and that this step is a prerequisite for the subsequent interaction of Fli1 with p300/CREB-binding protein-associated factor (PCAF) and an acetylation event. The phosphorylation of endogenous Fli1 preceded its acetylation in response to TGF-beta stimulation, and the blockade of PKC delta abrogated both the phosphorylation and acetylation of Fli1 in dermal fibroblasts. Promoter studies showed that a phosphorylation-deficient mutant of Fli1 exhibited an increased inhibitory effect on the COL1A2 gene, which could not be reversed by the forced expression of PCAF or PKC delta. These data strongly suggest that the phosphorylation-acetylation cascade triggered by PKC delta represents the primary mechanism whereby TGF-beta regulates the transcriptional activity of Fli1 in the context of the collagen promoter.
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Skånland SS, Wälchli S, Sandvig K. β-arrestins attenuate p38-mediated endosome to Golgi transport. Cell Microbiol 2009; 11:796-807. [PMID: 19159388 DOI: 10.1111/j.1462-5822.2009.01292.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Shiga toxin (Stx) is after endocytosis transported via early endosomes to the Golgi apparatus and endoplasmic reticulum. It is then translocated to the cytosol where it exerts its toxic effect. We recently reported that p38 is required for endosome to Golgi transport of Stx. In the present study, we investigated whether β-arrestins are effectors of this pathway. β-arrestin knockdown led to enhanced Stx transport. A similar phenotype was achieved upon p38 activation. We demonstrate that p38 and β-arrestin act on the same pathway. β-arrestin colocalized with internalized Stx and, interestingly, was recruited to endosomes upon p38 activation. After Stx treatment, p38 and β-arrestin formed a transient complex. From these data we propose that β-arrestin negatively regulates Stx transport via an interaction with activated p38 and attenuation of its signalling. Interestingly, also mannose 6-phosphate receptor transport was regulated by p38 and β-arrestin. β-arrestins therefore seem to regulate an endosome to Golgi pathway used by multiple cargo proteins.
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Affiliation(s)
- Sigrid S Skånland
- Centre for Cancer Biomedicine, Faculty Division Norwegian Radium Hospital, University of Oslo, Oslo, Norway
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Abstract
Retrograde transport, in which proteins and lipids are shuttled between endosomes and biosynthetic/secretory compartments such as the Golgi apparatus, is crucial for a diverse range of cellular functions. Mechanistic studies that explore the molecular machinery involved in this retrograde trafficking route are shedding light on the functions of transport proteins and are providing fresh insights into possible new therapeutic directions.
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Affiliation(s)
- Ludger Johannes
- CNRS UMR144, Centre de Recherche, Traffic, Signaling, and Delivery Laboratory, 75248 Paris Cedex 05, France.
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46
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Tekle C, Deurs BV, Sandvig K, Iversen TG. Cellular trafficking of quantum dot-ligand bioconjugates and their induction of changes in normal routing of unconjugated ligands. NANO LETTERS 2008; 8:1858-1865. [PMID: 18570482 DOI: 10.1021/nl0803848] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Can quantum dots (Qdots) act as relevant intracellular probes to investigate routing of ligands in live cells? The intracellular trafficking of Qdots that were coupled to the plant toxin ricin, Shiga toxin, or the ligand transferrin (Tf) was studied by confocal fluorescence microscopy. The Tf:Qdots were internalized by clathrin-dependent endocytosis as fast as Tf, but their recycling was blocked. Unlike Shiga toxin, the Shiga:Qdot bioconjugate was not routed to the Golgi apparatus. The internalized ricin:Qdot bioconjugates localized to the same endosomes as ricin itself but could not be visualized in the Golgi apparatus. Importantly, we find that the endosomal accumulation of ricin:Qdots affects endosome-to-Golgi transport of both ricin and Shiga toxin: Transport of ricin was reduced whereas transport of Shiga toxin was increased. In conclusion, the data reveal that, although coupling of Qdots to a ligand does not necessarily change the endocytic pathway normally used by the ligands studied, it appears that the ligand-coupled Qdot nanoparticles can be arrested within endosomes and somehow perturb the normal endosomal sorting in cells. Thus, the results demonstrate that Qdots may have severe consequences on cell physiology.
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Affiliation(s)
- Christina Tekle
- Centre for Cancer Biomedicine, Faculty Division, Norwegian Radium Hospital, University of Oslo, 0316 Oslo, Norway
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47
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Pavelka M, Neumüller J, Ellinger A. Retrograde traffic in the biosynthetic-secretory route. Histochem Cell Biol 2008; 129:277-88. [PMID: 18270728 PMCID: PMC2248610 DOI: 10.1007/s00418-008-0383-1] [Citation(s) in RCA: 20] [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] [Accepted: 01/09/2008] [Indexed: 02/04/2023]
Abstract
In the biosynthetic-secretory route from the rough endoplasmic reticulum, across the pre-Golgi intermediate compartments, the Golgi apparatus stacks, trans Golgi network, and post-Golgi organelles, anterograde transport is accompanied and counterbalanced by retrograde traffic of both membranes and contents. In the physiologic dynamics of cells, retrograde flow is necessary for retrieval of molecules that escaped from their compartments of function, for keeping the compartments' balances, and maintenance of the functional integrities of organelles and compartments along the secretory route, for repeated use of molecules, and molecule repair. Internalized molecules may be transported in retrograde direction along certain sections of the secretory route, and compartments and machineries of the secretory pathway may be misused by toxins. An important example is the toxin of Shigella dysenteriae, which has been shown to travel from the cell surface across endosomes, and the Golgi apparatus en route to the endoplasmic reticulum, and the cytosol, where it exerts its deleterious effects. Most importantly in medical research, knowledge about the retrograde cellular pathways is increasingly being utilized for the development of strategies for targeted delivery of drugs to the interior of cells. Multiple details about the molecular transport machineries involved in retrograde traffic are known; a high number of the molecular constituents have been characterized, and the complicated fine structural architectures of the compartments involved become more and more visible. However, multiple contradictions exist, and already established traffic models again are in question by contradictory results obtained with diverse cell systems, and/or different techniques. Additional problems arise by the fact that the conditions used in the experimental protocols frequently do not reflect the physiologic situations of the cells. Regular and pathologic situations often are intermingled, and experimental treatments by themselves change cell organizations. This review addresses physiologic and pathologic situations, tries to correlate results obtained by different cell biologic techniques, and asks questions, which may be the basis and starting point for further investigations.
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Affiliation(s)
- Margit Pavelka
- Department of Cell Biology and Ultrastructure Research, Center for Anatomy and Cell Biology, Medical University of Vienna, Schwarzspanierstrasse 17, Vienna, Austria.
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