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Alkafaas SS, Abdallah AM, Hassan MH, Hussien AM, Elkafas SS, Loutfy SA, Mikhail A, Murad OG, Elsalahaty MI, Hessien M, Elshazli RM, Alsaeed FA, Ahmed AE, Kamal HK, Hafez W, El-Saadony MT, El-Tarabily KA, Ghosh S. Molecular docking as a tool for the discovery of novel insight about the role of acid sphingomyelinase inhibitors in SARS- CoV-2 infectivity. BMC Public Health 2024; 24:395. [PMID: 38321448 PMCID: PMC10848368 DOI: 10.1186/s12889-024-17747-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Accepted: 01/11/2024] [Indexed: 02/08/2024] Open
Abstract
Recently, COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its variants, caused > 6 million deaths. Symptoms included respiratory strain and complications, leading to severe pneumonia. SARS-CoV-2 attaches to the ACE-2 receptor of the host cell membrane to enter. Targeting the SARS-CoV-2 entry may effectively inhibit infection. Acid sphingomyelinase (ASMase) is a lysosomal protein that catalyzes the conversion of sphingolipid (sphingomyelin) to ceramide. Ceramide molecules aggregate/assemble on the plasma membrane to form "platforms" that facilitate the viral intake into the cell. Impairing the ASMase activity will eventually disrupt viral entry into the cell. In this review, we identified the metabolism of sphingolipids, sphingolipids' role in cell signal transduction cascades, and viral infection mechanisms. Also, we outlined ASMase structure and underlying mechanisms inhibiting viral entry 40 with the aid of inhibitors of acid sphingomyelinase (FIASMAs). In silico molecular docking analyses of FIASMAs with inhibitors revealed that dilazep (S = - 12.58 kcal/mol), emetine (S = - 11.65 kcal/mol), pimozide (S = - 11.29 kcal/mol), carvedilol (S = - 11.28 kcal/mol), mebeverine (S = - 11.14 kcal/mol), cepharanthine (S = - 11.06 kcal/mol), hydroxyzin (S = - 10.96 kcal/mol), astemizole (S = - 10.81 kcal/mol), sertindole (S = - 10.55 kcal/mol), and bepridil (S = - 10.47 kcal/mol) have higher inhibition activity than the candidate drug amiodarone (S = - 10.43 kcal/mol), making them better options for inhibition.
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Affiliation(s)
- Samar Sami Alkafaas
- Molecular Cell Biology Unit, Division of Biochemistry, Department of Chemistry, Faculty of Science, Tanta University, Tanta, 31527, Egypt.
| | - Abanoub Mosaad Abdallah
- Narcotic Research Department, National Center for Social and Criminological Research (NCSCR), Giza, 11561, Egypt
| | - Mai H Hassan
- Molecular Cell Biology Unit, Division of Biochemistry, Department of Chemistry, Faculty of Science, Tanta University, Tanta, 31527, Egypt
| | - Aya Misbah Hussien
- Biotechnology department at Institute of Graduate Studies and Research, Alexandria University, Alexandria, Egypt
| | - Sara Samy Elkafas
- Production Engineering and Mechanical Design Department, Faculty of Engineering, Menofia University, Menofia, Egypt
- Faculty of Control System and Robotics, ITMO University, Saint-Petersburg, 197101, Russia
| | - Samah A Loutfy
- Virology and Immunology Unit, Cancer Biology Department, National Cancer Institute, Cairo University, Cairo, Egypt
- Nanotechnology Research Center, British University, Cairo, Egypt
| | - Abanoub Mikhail
- Department of Physics, Faculty of Science, Minia University, Minia, Egypt
- Faculty of Physics, ITMO University, Saint Petersburg, Russia
| | - Omnia G Murad
- Division of Biochemistry, Department of Chemistry, Faculty of Science, Tanta University, Tanta, 31527, Egypt
| | - Mohamed I Elsalahaty
- Division of Biochemistry, Department of Chemistry, Faculty of Science, Tanta University, Tanta, 31527, Egypt
| | - Mohamed Hessien
- Molecular Cell Biology Unit, Division of Biochemistry, Department of Chemistry, Faculty of Science, Tanta University, Tanta, 31527, Egypt
| | - Rami M Elshazli
- Biochemistry and Molecular Genetics Unit, Department of Basic Sciences, Faculty of Physical Therapy, Horus University - Egypt, New Damietta, 34517, Egypt
| | - Fatimah A Alsaeed
- Department of Biology, College of Science, King Khalid University, Muhayl, Saudi Arabia
| | - Ahmed Ezzat Ahmed
- Biology Department, College of Science, King Khalid University, Abha, 61413, Saudi Arabia
| | - Hani K Kamal
- Anatomy and Histology, Faculty of Pharmacy, King Abdulaziz University, Jeddah, 21589, Saudi Arabia
| | - Wael Hafez
- NMC Royal Hospital, 16Th Street, 35233, Khalifa City, Abu Dhabi, United Arab Emirates
- Medical Research Division, Department of Internal Medicine, The National Research Centre, 12622, 33 El Buhouth St, Ad Doqi, Dokki, Cairo Governorate, Egypt
| | - Mohamed T El-Saadony
- Department of Agricultural Microbiology, Faculty of Agriculture, Zagazig University, Zagazig, 44511, Egypt
| | - Khaled A El-Tarabily
- Department of Biology, College of Science, United Arab Emirates University, Al-Ain, 15551, United Arab Emirates
| | - Soumya Ghosh
- Department of Genetics, Faculty of Natural and Agricultural Sciences, University of the Free State, Bloemfontein, 9301, South Africa
- Natural & Medical Science Research Center, University of Nizwa, Nizwa, Oman
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2
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Rioux DJ, Prosser DC. A CIE change in our understanding of endocytic mechanisms. Front Cell Dev Biol 2023; 11:1334798. [PMID: 38192364 PMCID: PMC10773762 DOI: 10.3389/fcell.2023.1334798] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Accepted: 12/04/2023] [Indexed: 01/10/2024] Open
Abstract
The past six decades have seen major advances in our understanding of endocytosis, ranging from descriptive studies based on electron microscopy to biochemical and genetic characterization of factors required for vesicle formation. Most studies focus on clathrin as the major coat protein; indeed, clathrin-mediated endocytosis (CME) is the primary pathway for internalization. Clathrin-independent (CIE) pathways also exist, although mechanistic understanding of these pathways remains comparatively elusive. Here, we discuss how early studies of CME shaped our understanding of endocytosis and describe recent advances in CIE, including pathways in model organisms that are poised to provide key insights into endocytic regulation.
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Affiliation(s)
- Daniel J. Rioux
- Life Sciences, Virginia Commonwealth University, Richmond, VA, United States
- Department of Biology, Virginia Commonwealth University, Richmond, VA, United States
| | - Derek C. Prosser
- Department of Biology, Virginia Commonwealth University, Richmond, VA, United States
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3
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Abouelezz A, Almeida-Souza L. The mammalian endocytic cytoskeleton. Eur J Cell Biol 2022; 101:151222. [DOI: 10.1016/j.ejcb.2022.151222] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 03/31/2022] [Accepted: 04/01/2022] [Indexed: 12/27/2022] Open
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4
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Jeong SJ, Stitham J, Evans TD, Zhang X, Rodriguez-Velez A, Yeh YS, Tao J, Takabatake K, Epelman S, Lodhi IJ, Schilling JD, DeBosch BJ, Diwan A, Razani B. Trehalose causes low-grade lysosomal stress to activate TFEB and the autophagy-lysosome biogenesis response. Autophagy 2021; 17:3740-3752. [PMID: 33706671 DOI: 10.1080/15548627.2021.1896906] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The autophagy-lysosome system is an important cellular degradation pathway that recycles dysfunctional organelles and cytotoxic protein aggregates. A decline in this system is pathogenic in many human diseases including neurodegenerative disorders, fatty liver disease, and atherosclerosis. Thus there is intense interest in discovering therapeutics aimed at stimulating the autophagy-lysosome system. Trehalose is a natural disaccharide composed of two glucose molecules linked by a ɑ-1,1-glycosidic bond with the unique ability to induce cellular macroautophagy/autophagy and with reported efficacy on mitigating several diseases where autophagy is dysfunctional. Interestingly, the mechanism by which trehalose induces autophagy is unknown. One suggested mechanism is its ability to activate TFEB (transcription factor EB), the master transcriptional regulator of autophagy-lysosomal biogenesis. Here we describe a potential mechanism involving direct trehalose action on the lysosome. We find trehalose is endocytically taken up by cells and accumulates within the endolysosomal system. This leads to a low-grade lysosomal stress with mild elevation of lysosomal pH, which acts as a potent stimulus for TFEB activation and nuclear translocation. This process appears to involve inactivation of MTORC1, a known negative regulator of TFEB which is sensitive to perturbations in lysosomal pH. Taken together, our data show the trehalose can act as a weak inhibitor of the lysosome which serves as a trigger for TFEB activation. Our work not only sheds light on trehalose action but suggests that mild alternation of lysosomal pH can be a novel method of inducing the autophagy-lysosome system.Abbreviations: ASO: antisense oligonucleotide; AU: arbitrary units; BMDM: bone marrow-derived macrophages; CLFs: crude lysosomal fractions; CTSD: cathepsin D; LAMP: lysosomal associated membrane protein; LIPA/LAL: lipase A, lysosomal acid type; MAP1LC3: microtubule-associated protein 1 light chain 3; MFI: mean fluorescence intensity; MTORC1: mechanistic target of rapamycin kinase complex 1; pMAC: peritoneal macrophages; SLC2A8/GLUT8: solute carrier family 2, (facilitated glucose transporter), member 8; TFEB: transcription factor EB; TMR: tetramethylrhodamine; TREH: trehalase.
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Affiliation(s)
- Se-Jin Jeong
- Department of Medicine, Cardiovascular Division, Washington University School of Medicine, St. Louis, MO, USA
| | - Jeremiah Stitham
- Department of Medicine, Division of Endocrinology, Metabolism, Lipid Research, Washington University School of Medicine, St. Louis, MO, USA
| | - Trent D Evans
- Department of Medicine, Cardiovascular Division, Washington University School of Medicine, St. Louis, MO, USA
| | - Xiangyu Zhang
- Department of Medicine, Cardiovascular Division, Washington University School of Medicine, St. Louis, MO, USA
| | - Astrid Rodriguez-Velez
- Department of Medicine, Cardiovascular Division, Washington University School of Medicine, St. Louis, MO, USA
| | - Yu-Sheng Yeh
- Department of Medicine, Cardiovascular Division, Washington University School of Medicine, St. Louis, MO, USA
| | - Joan Tao
- Department of Medicine, Cardiovascular Division, Washington University School of Medicine, St. Louis, MO, USA
| | - Koki Takabatake
- Department of Medicine, Cardiovascular Division, Washington University School of Medicine, St. Louis, MO, USA
| | - Slava Epelman
- Peter Munk Cardiac Center, Ted Rogers Centre for Heart Failure Research and the Toronto General Hospital Research Institute, University of Toronto, Toronto, ON, Canada
| | - Irfan J Lodhi
- Department of Medicine, Division of Endocrinology, Metabolism, Lipid Research, Washington University School of Medicine, St. Louis, MO, USA
| | - Joel D Schilling
- Department of Medicine, Cardiovascular Division, Washington University School of Medicine, St. Louis, MO, USA.,Department of Pathology & Immunology, Washington University School of Medicine, St. Louis, MO, USA
| | - Brian J DeBosch
- Department of Pediatrics, Washington University School of Medicine, St. Louis, MO, USA
| | - Abhinav Diwan
- Department of Medicine, Cardiovascular Division, Washington University School of Medicine, St. Louis, MO, USA.,John Cochran VA Medical Center, St. Louis, MO, USA
| | - Babak Razani
- Department of Medicine, Cardiovascular Division, Washington University School of Medicine, St. Louis, MO, USA.,Department of Pathology & Immunology, Washington University School of Medicine, St. Louis, MO, USA.,John Cochran VA Medical Center, St. Louis, MO, USA
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5
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He L, Sayers EJ, Watson P, Jones AT. Contrasting roles for actin in the cellular uptake of cell penetrating peptide conjugates. Sci Rep 2018; 8:7318. [PMID: 29743505 PMCID: PMC5943252 DOI: 10.1038/s41598-018-25600-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Accepted: 04/25/2018] [Indexed: 12/13/2022] Open
Abstract
The increased need for macromolecular therapeutics, such as peptides, proteins and nucleotides, to reach intracellular targets necessitates more effective delivery vectors and a higher level of understanding of their mechanism of action. Cell penetrating peptides (CPPs) can transport a range of macromolecules into cells, either through direct plasma membrane translocation or endocytosis. All known endocytic pathways involve cell-cortex remodelling, a process shown to be regulated by reorganisation of the actin cytoskeleton. Here using flow cytometry, confocal microscopy and a variety of actin inhibitors we identify how actin disorganisation in different cell types differentially influences the cellular entry of three probes: the CPP octaarginine - Alexa488 conjugate (R8-Alexa488), octaarginine conjugated Enhanced Green Fluorescent Protein (EGFP-R8), and the fluid phase probe dextran. Disrupting actin organisation in A431 skin epithelial cells dramatically increases the uptake of EGFP-R8 and dextran, and contrasts strongly to inhibitory effects observed with transferrin and R8 attached to the fluorophore Alexa488. This demonstrates that uptake of the same CPP can occur via different endocytic processes depending on the conjugated fluorescent entity. Overall this study highlights how cargo influences cell uptake of this peptide and that the actin cytoskeleton may act as a gateway or barrier to endocytosis of drug delivery vectors.
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Affiliation(s)
- L He
- Cardiff School of Pharmacy and Pharmaceutical Sciences, Redwood Building, Cardiff University, Cardiff, Wales, CF10 3NB, UK
| | - E J Sayers
- Cardiff School of Pharmacy and Pharmaceutical Sciences, Redwood Building, Cardiff University, Cardiff, Wales, CF10 3NB, UK
| | - P Watson
- Cardiff School of Biosciences, The Sir Martin Evans Building, Cardiff University, Cardiff, Wales, CF10 3AX, UK.
| | - A T Jones
- Cardiff School of Pharmacy and Pharmaceutical Sciences, Redwood Building, Cardiff University, Cardiff, Wales, CF10 3NB, UK.
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6
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An imaging flow cytometry method to assess ricin trafficking in A549 human lung epithelial cells. Methods 2018; 134-135:41-49. [DOI: 10.1016/j.ymeth.2017.10.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Revised: 10/12/2017] [Accepted: 10/30/2017] [Indexed: 11/18/2022] Open
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7
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Novel mechanism of regulation of the 5-lipoxygenase/leukotriene B 4 pathway by high-density lipoprotein in macrophages. Sci Rep 2017; 7:12989. [PMID: 29021582 PMCID: PMC5636875 DOI: 10.1038/s41598-017-13154-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Accepted: 09/19/2017] [Indexed: 02/06/2023] Open
Abstract
High-density lipoprotein (HDL) interacts with various cells, particularly macrophages, in functional cell-HDL interactions. Here, we found that HDL protein quality and lipid quality play critical roles in HDL functions. HDL fractions from healthy volunteers (HDLHealthy) and patients with recurrent coronary atherosclerotic disease (HDLCAD) were prepared. To analyse functional HDL-macrophage interactions, macrophages were co-incubated with each HDL, and lipid mediator production was assessed by liquid chromatography/mass spectrometry-based metabololipidomics. HDLHealthy treatment attenuated the pro-inflammatory lipid mediator production, particularly that of leukotriene (LT) B4, and this treatment enhanced lipoxin (LX) B4 and resolvin (Rv) E2 production. HDLHealthy treatment enhanced the proteasome-mediated degradation of the LTB4-producing enzyme 5-lipoxygenase (LO) in activated macrophages; however, HDLCAD did not show these anti-inflammatory effects. HDLHealthy was engulfed by macrophages via clathrin-mediated endocytosis, which was a critical step in 5-LO/LTB4 regulation. We also found that HDLCAD showed higher levels of the LTB4-producing enzymes and thus promoted LTB4 production from HDLCAD. In addition, LTB4 attenuated HDL endocytosis, HDL-mediated 5-LO degradation in macrophages, and HDL-derived augmentation of macrophage phagocytosis. These results indicated that local LTB4 produced de novo from HDLCAD regulates HDL-macrophage functional interactions and plays critical roles in dysfunctional, inflammatory HDL characteristics.
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8
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Gal Y, Mazor O, Falach R, Sapoznikov A, Kronman C, Sabo T. Treatments for Pulmonary Ricin Intoxication: Current Aspects and Future Prospects. Toxins (Basel) 2017; 9:E311. [PMID: 28972558 PMCID: PMC5666358 DOI: 10.3390/toxins9100311] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Revised: 09/26/2017] [Accepted: 09/29/2017] [Indexed: 12/13/2022] Open
Abstract
Ricin, a plant-derived toxin originating from the seeds of Ricinus communis (castor beans), is one of the most lethal toxins known, particularly if inhaled. Ricin is considered a potential biological threat agent due to its high availability and ease of production. The clinical manifestation of pulmonary ricin intoxication in animal models is closely related to acute respiratory distress syndrome (ARDS), which involves pulmonary proinflammatory cytokine upregulation, massive neutrophil infiltration and severe edema. Currently, the only post-exposure measure that is effective against pulmonary ricinosis at clinically relevant time-points following intoxication in pre-clinical studies is passive immunization with anti-ricin neutralizing antibodies. The efficacy of this antitoxin treatment depends on antibody affinity and the time of treatment initiation within a limited therapeutic time window. Small-molecule compounds that interfere directly with the toxin or inhibit its intracellular trafficking may also be beneficial against ricinosis. Another approach relies on the co-administration of antitoxin antibodies with immunomodulatory drugs, thereby neutralizing the toxin while attenuating lung injury. Immunomodulators and other pharmacological-based treatment options should be tailored according to the particular pathogenesis pathways of pulmonary ricinosis. This review focuses on the current treatment options for pulmonary ricin intoxication using anti-ricin antibodies, disease-modifying countermeasures, anti-ricin small molecules and their various combinations.
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Affiliation(s)
- Yoav Gal
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona 76100, Israel.
| | - Ohad Mazor
- Department of Infectious Diseases, Israel Institute for Biological Research, Ness-Ziona 76100, Israel.
| | - Reut Falach
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona 76100, Israel.
| | - Anita Sapoznikov
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona 76100, Israel.
| | - Chanoch Kronman
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona 76100, Israel.
| | - Tamar Sabo
- Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona 76100, Israel.
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Soriano-Castell D, Chavero A, Rentero C, Bosch M, Vidal-Quadras M, Pol A, Enrich C, Tebar F. ROCK1 is a novel Rac1 effector to regulate tubular endocytic membrane formation during clathrin-independent endocytosis. Sci Rep 2017; 7:6866. [PMID: 28761175 PMCID: PMC5537229 DOI: 10.1038/s41598-017-07130-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Accepted: 06/23/2017] [Indexed: 01/10/2023] Open
Abstract
Clathrin-dependent and -independent pathways contribute for β1-integrin endocytosis. This study defines a tubular membrane clathrin-independent endocytic network, induced with the calmodulin inhibitor W13, for β1-integrin internalization. This pathway is dependent on increased phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) levels and dynamin activity at the plasma membrane. Exogenous addition of PI(4,5)P2 or phosphatidylinositol-4-phosphate 5-kinase (PIP5K) expression mimicked W13-generated-tubules which are inhibited by active Rac1. Therefore, the molecular mechanisms downstream of Rac1, that controls this plasma membrane tubulation, were analyzed biochemically and by the expression of different Rac1 mutants. The results indicate that phospholipase C and ROCK1 are the main Rac1 effectors that impair plasma membrane invagination and tubule formation, essentially by decreasing PI(4,5)P2 levels and promoting cortical actomyosin assembly respectively. Interestingly, among the plethora of proteins that participate in membrane remodeling, this study revealed that ROCK1, the well-known downstream RhoA effector, has an important role in Rac1 regulation of actomyosin at the cell cortex. This study provides new insights into Rac1 functioning on plasma membrane dynamics combining phosphatidylinositides and cytoskeleton regulation.
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Affiliation(s)
- David Soriano-Castell
- Departament de Biomedicina, Unitat de Biologia Cel·lular, Centre de Recerca Biomèdica CELLEX, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Facultat de Medicina, Universitat de Barcelona, Casanova 143, 08036, Barcelona, Spain
| | - Albert Chavero
- Departament de Biomedicina, Unitat de Biologia Cel·lular, Centre de Recerca Biomèdica CELLEX, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Facultat de Medicina, Universitat de Barcelona, Casanova 143, 08036, Barcelona, Spain
| | - Carles Rentero
- Departament de Biomedicina, Unitat de Biologia Cel·lular, Centre de Recerca Biomèdica CELLEX, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Facultat de Medicina, Universitat de Barcelona, Casanova 143, 08036, Barcelona, Spain
| | - Marta Bosch
- Departament de Biomedicina, Unitat de Biologia Cel·lular, Centre de Recerca Biomèdica CELLEX, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Facultat de Medicina, Universitat de Barcelona, Casanova 143, 08036, Barcelona, Spain
| | - Maite Vidal-Quadras
- Departament de Biomedicina, Unitat de Biologia Cel·lular, Centre de Recerca Biomèdica CELLEX, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Facultat de Medicina, Universitat de Barcelona, Casanova 143, 08036, Barcelona, Spain
| | - Albert Pol
- Departament de Biomedicina, Unitat de Biologia Cel·lular, Centre de Recerca Biomèdica CELLEX, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Facultat de Medicina, Universitat de Barcelona, Casanova 143, 08036, Barcelona, Spain.,Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010, Barcelona, Spain
| | - Carlos Enrich
- Departament de Biomedicina, Unitat de Biologia Cel·lular, Centre de Recerca Biomèdica CELLEX, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Facultat de Medicina, Universitat de Barcelona, Casanova 143, 08036, Barcelona, Spain
| | - Francesc Tebar
- Departament de Biomedicina, Unitat de Biologia Cel·lular, Centre de Recerca Biomèdica CELLEX, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Facultat de Medicina, Universitat de Barcelona, Casanova 143, 08036, Barcelona, Spain.
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10
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Briceño MP, Nascimento LAC, Nogueira NP, Barenco PVC, Ferro EAV, Rezende-Oliveira K, Goulart LR, Alves PT, Barbosa BDF, Lima WR, Silva NM. Toxoplasma gondii Infection Promotes Epithelial Barrier Dysfunction of Caco-2 Cells. J Histochem Cytochem 2016; 64:459-69. [PMID: 27370796 DOI: 10.1369/0022155416656349] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Accepted: 06/01/2016] [Indexed: 12/12/2022] Open
Abstract
After oral infection, Toxoplasma gondii invades intestinal cells, induces breakdown of intestinal physiology and barrier functions, and causes intestinal pathology in some animal species. Although parasites' invasion into host cells is a known phenomenon, the effects of T. gondii infection in the intestinal barrier are still not well established. To evaluate morphological and physiological modifications on the colorectal adenocarcinoma-derived Caco-2 cell line during T. gondii infection, microvilli, tight junction integrity, and transepithelial electrical resistance (TEER) were investigated under infection. It was observed that the dextran uptake (endocytosis) and distribution were smaller in infected than in noninfected Caco-2 cells. The infection leads to the partial loss of microvilli at the cell surface. Claudin-1, zonula occludens-1 (ZO-1), and occludin expressions were colocalized by immunofluorescence and presented discontinuous net patterns in infected cells. Immunoblotting analysis at 24 hr postinfection revealed decreasing expression of occludin and ZO-1 proteins, whereas claudin-1 presented similar expression level compared with noninfected cells. T. gondii decreased TEER in Caco-2 cells 24 hr after infection. Our results suggest that T. gondii infection may lead to the loss of integrity of intestinal mucosa, resulting in impaired barrier function.
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Affiliation(s)
- Marisol Pallete Briceño
- Laboratory of Immunopathology, Institute of Biomedical Sciences (MPB, LACN, NPN, PVCB, WRL, NMS)
| | | | - Nathalia Pires Nogueira
- Laboratory of Immunopathology, Institute of Biomedical Sciences (MPB, LACN, NPN, PVCB, WRL, NMS)
| | | | - Eloisa Amália Vieira Ferro
- Laboratory of Immunopathology, Institute of Biomedical Sciences (MPB, LACN, NPN, PVCB, WRL, NMS),Laboratory of Immunophysiology of Reproduction, Institute of Biomedical Sciences, Federal University of Uberlândia, Uberlândia, Minas Gerais, Brazil (BFB, EAVF)
| | - Karine Rezende-Oliveira
- Laboratory of Biomedical Sciences, Federal University of Uberlândia, Ituiutaba, Minas Gerais, Brazil (KR-O)
| | - Luiz Ricardo Goulart
- Laboratory of Nanobiotechnology, Institute of Genetics and Biochemistry, Federal University of Uberlândia, Uberlândia, Minas Gerais, Brazil (LRG, PTA)
| | - Patrícia Terra Alves
- Laboratory of Immunopathology, Institute of Biomedical Sciences (MPB, LACN, NPN, PVCB, WRL, NMS),Laboratory of Nanobiotechnology, Institute of Genetics and Biochemistry, Federal University of Uberlândia, Uberlândia, Minas Gerais, Brazil (LRG, PTA)
| | - Bellisa de Freitas Barbosa
- Laboratory of Immunophysiology of Reproduction, Institute of Biomedical Sciences, Federal University of Uberlândia, Uberlândia, Minas Gerais, Brazil (BFB, EAVF)
| | - Wânia Rezende Lima
- Laboratory of Immunopathology, Institute of Biomedical Sciences (MPB, LACN, NPN, PVCB, WRL, NMS),Institute of Exact and Natural Sciences, Federal University of Mato Grosso, Rondonópolis, Mato Grosso, Brazil (WRL)
| | - Neide Maria Silva
- Laboratory of Immunopathology, Institute of Biomedical Sciences (MPB, LACN, NPN, PVCB, WRL, NMS)
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11
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Endocytic pathways and endosomal trafficking: a primer. Wien Med Wochenschr 2016; 166:196-204. [PMID: 26861668 DOI: 10.1007/s10354-016-0432-7] [Citation(s) in RCA: 149] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 01/05/2016] [Indexed: 01/05/2023]
Abstract
This brief overview of endocytic trafficking is written in honor of Renate Fuchs, who retires this year. In the mid-1980s, Renate pioneered studies on the ion-conducting properties of the recently discovered early and late endosomes and the mechanisms governing endosomal acidification. As described in this review, after uptake through one of many mechanistically distinct endocytic pathways, internalized proteins merge into a common early/sorting endosome. From there they again diverge along distinct sorting pathways, back to the cell surface, on to the trans-Golgi network or across polarized cells. Other transmembrane receptors are packaged into intraluminal vesicles of late endosomes/multivesicular bodies that eventually fuse with and deliver their content to lysosomes for degradation. Endosomal acidification, in part, determines sorting along this pathway. We describe other sorting machinery and mechanisms, as well as the rab proteins and phosphatidylinositol lipids that serve to dynamically define membrane compartments along the endocytic pathway.
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12
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Johannes L, Parton RG, Bassereau P, Mayor S. Building endocytic pits without clathrin. Nat Rev Mol Cell Biol 2015; 16:311-21. [PMID: 25857812 DOI: 10.1038/nrm3968] [Citation(s) in RCA: 145] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
How endocytic pits are built in clathrin- and caveolin-independent endocytosis still remains poorly understood. Recent insight suggests that different forms of clathrin-independent endocytosis might involve the actin-driven focusing of membrane constituents, the lectin-glycosphingolipid-dependent construction of endocytic nanoenvironments, and Bin-Amphiphysin-Rvs (BAR) domain proteins serving as scaffolding modules. We discuss the need for different types of internalization processes in the context of diverse cellular functions, the existence of clathrin-independent mechanisms of cargo recruitment and membrane bending from a biological and physical perspective, and finally propose a generic scheme for the formation of clathrin-independent endocytic pits.
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Affiliation(s)
- Ludger Johannes
- Institut Curie, PSL Research University, Endocytic Trafficking and Therapeutic Delivery Group, 26 rue d'Ulm, 75248 Paris Cedex 05, France; Centre National de la Recherche Scientifique UMR3666, 75005 Paris, France; and INSERM U1143, 75005 Paris, France
| | - Robert G Parton
- University of Queensland, Institute for Molecular Bioscience and Centre for Microscopy and Microanalysis, St Lucia QLD 4072, Australia
| | - Patricia Bassereau
- Institut Curie, PSL Research University, Membrane and Cell Functions Group, 26 rue d'Ulm, 75248 Paris Cedex 05, France; Centre National de la Recherche Scientifique UMR168, 75005 Paris, France; and Université Pierre et Marie Curie, 75252 Paris, France
| | - Satyajit Mayor
- National Centre for Biological Sciences, Cellular Organization and Signaling Group, and at Institute for Stem Cell Biology and Regenerative Medicine, UAS-GKVK Campus, 560 065 Bangalore, India
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Plačková P, Hřebabecký H, Šála M, Nencka R, Elbert T, Mertlíková-Kaiserová H. Transport mechanisms of a novel antileukemic and antiviral compound 9-norbornyl-6-chloropurine. J Enzyme Inhib Med Chem 2014; 30:57-62. [DOI: 10.3109/14756366.2013.879576] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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14
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Song K, Mize RR, Marrero L, Corti M, Kirk JM, Pincus SH. Antibody to ricin a chain hinders intracellular routing of toxin and protects cells even after toxin has been internalized. PLoS One 2013; 8:e62417. [PMID: 23638075 PMCID: PMC3634765 DOI: 10.1371/journal.pone.0062417] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Accepted: 03/25/2013] [Indexed: 11/18/2022] Open
Abstract
Background Mechanisms of antibody-mediated neutralization are of much interest. For plant and bacterial A-B toxins, A chain mediates toxicity and B chain binds target cells. It is generally accepted and taught that antibody (Ab) neutralizes by preventing toxin binding to cells. Yet for some toxins, ricin included, anti-A chain Abs afford greater protection than anti-B. The mechanism(s) whereby Abs to the A chain neutralize toxins are not understood. Methodology/Principal Findings We use quantitative confocal imaging, neutralization assays, and other techniques to study how anti-A chain Abs function to protect cells. Without Ab, ricin enters cells and penetrates to the endoplasmic reticulum within 15 min. Within 45–60 min, ricin entering and being expelled from cells reaches equilibrium. These results are consistent with previous observations, and support the validity of our novel methodology. The addition of neutralizing Ab causes ricin accumulation at the cell surface, delays internalization, and postpones retrograde transport of ricin. Ab binds ricin for >6hr as they traffic together through the cell. Ab protects cells even when administered hours after exposure. Conclusions/Key Findings We demonstrate the dynamic nature of the interaction between the host cell and toxin, and how Ab can alter the balance in favor of the cell. Ab blocks ricin’s entry into cells, hinders its intracellular routing, and can protect even after ricin is present in the target organelle, providing evidence that the major site of neutralization is intracellular. These data add toxins to the list of pathogenic agents that can be neutralized intracellularly and explain the in vivo efficacy of delayed administration of anti-toxin Abs. The results encourage the use of post-exposure passive Ab therapy, and show the importance of the A chain as a target of Abs.
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Affiliation(s)
- Kejing Song
- Research Institute for Children, Children’s Hospital, New Orleans, Louisiana, United States of America
| | - R. Ranney Mize
- Department of Cell Biology and Anatomy, Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States of America
| | - Luis Marrero
- Imaging Core, Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States of America
| | - Miriam Corti
- Research Institute for Children, Children’s Hospital, New Orleans, Louisiana, United States of America
| | - Jason M. Kirk
- Carl Zeiss Microimaging, Thornwood, New York, United States of America
| | - Seth H. Pincus
- Research Institute for Children, Children’s Hospital, New Orleans, Louisiana, United States of America
- Departments of Pediatrics and Microbiology, Immunology, and Parasitology, Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States of America
- * E-mail:
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Khan S, Jutzy JMS, Aspe JR, McGregor DW, Neidigh JW, Wall NR. Survivin is released from cancer cells via exosomes. Apoptosis 2011; 16:1-12. [PMID: 20717727 DOI: 10.1007/s10495-010-0534-4] [Citation(s) in RCA: 195] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Inhibitor of apoptosis (IAP) and Heat shock proteins (HSPs) provide assistance in protecting cells from stresses of hypoxia, imbalanced pH, and altered metabolic and redox states commonly found in the microenvironmental mixture of tumor and nontumor cells. HSPs are upregulated, cell-surface displayed and released extracellularly in some types of tumors, a finding that until now was not shared by members of the IAP family. The IAP Survivin has been implicated in apoptosis inhibition and the regulation of mitosis in cancer cells. Survivin exists in a number of subcellular locations such as the mitochondria, cytoplasm, nucleus, and most recently, the extracellular space. Our previous work showing that extracellular survivin was able to enhance cellular proliferation, survival and tumor cell invasion provides evidence that Survivin might be secreted via an unidentified exocytotic pathway. In the present study, we describe for the first time the exosome-release of Survivin to the extracellular space both basally and after proton irradiation-induced stress. To examine whether exosomes contributed to Survivin release from cancer cells, exosomes were purified from HeLa cervical carcinoma cells and exosome quantity and Survivin content were determined. We demonstrate that although proton irradiation does not influence the exosomal secretory rate, the Survivin content of exosomes isolated from HeLa cells treated with a sublethal dose of proton irradiation (3 Gy) is significantly higher than control. These data identify a novel secretory pathway by which Survivin can be actively released from cells in both the basal and stress-induced state.
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Affiliation(s)
- Salma Khan
- Center for Health Disparities Research and Molecular Medicine, Loma Linda University, 11085 Campus Street, Loma Linda, CA 92350, USA.
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Shahidi-Noghabi S, Van Damme EJM, De Vos WH, Smagghe G. Internalization of Sambucus nigra agglutinins I and II in insect midgut CF-203 cells. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2011; 76:211-222. [PMID: 21254203 DOI: 10.1002/arch.20405] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Accepted: 10/02/2010] [Indexed: 05/30/2023]
Abstract
In this project, the uptake mechanisms and localization of two lectins from Sambucus nigra, further referred to as S. nigra agglutinin (SNA)-I and SNA-II, into insect midgut CF-203 cells were studied. SNA-I is a chimeric lectin belonging to the class of ribosome-inactivating proteins, whereas SNA-II is a hololectin devoid of enzymatic activity. Internalization of the fluorescein isothiocyanate-labeled lectin was investigated using confocal microscopy. Both lectins were internalized into the cytoplasm of CF-203 cells at similar rates. Preexposure of the insect midgut cells to specific inhibitors of clathrin- and caveolae-mediated endocytosis resulted in an inhibition of lectin uptake in CF-203 cells and caspase-induced cytotoxicity caused by SNA-I and SNA-II, confirming the involvement of both endocytosis pathways. Further studies demonstrated that the uptake mechanism(s) for both lectins required phosphoinositide 3-kinases, but did not depend on the actin cytoskeleton. Since the hololectin SNA-II apparently uses a similar endocytosis pathway as the chimerolectin SNA-I, it can be concluded that the endocytosis process mainly relies on the carbohydrate-binding activity of the lectins under investigation. © 2011 Wiley Periodicals, Inc.
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Affiliation(s)
- Shahnaz Shahidi-Noghabi
- Laboratory of Agrozoology, Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
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Abstract
Macropinocytosis is a regulated form of endocytosis that mediates the non-selective uptake of solute molecules, nutrients and antigens. It is an actin-dependent process initiated from surface membrane ruffles that give rise to large endocytic vacuoles called macropinosomes. Macropinocytosis is important in a range of physiological processes; it is highly active in macrophages and dendritic cells where it is a major pathway for the capture of antigens, it is relevant to cell migration and tumour metastasis and it represents a portal of cell entry exploited by a range of pathogens. The molecular basis for the formation and maturation of macropinosomes has only recently begun to be defined. Here, we review the general characteristics of macropinocytosis, describe some of the regulators of this pathway, which have been identified to date and highlight strategies to explore the relevance of this endocytosis pathway in vivo.
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18
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Lin AEJ, Guttman JA. Hijacking the endocytic machinery by microbial pathogens. PROTOPLASMA 2010; 244:75-90. [PMID: 20574860 DOI: 10.1007/s00709-010-0164-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Accepted: 05/19/2010] [Indexed: 05/24/2023]
Abstract
Understanding the mechanisms that microbes exploit to invade host cells and cause disease is crucial if we are to eliminate their threat. Although pathogens use a variety of microbial factors to trigger entry into non-phagocytic cells, their targeting of the host cell process of endocytosis has emerged as a common theme. To accomplish this, microbes often rewire the normal course of particle internalization, frequently usurping theoretical maximal sizes to permit entry and reconfiguring molecular components that were once thought to be required for vesicle formation. Here, we discuss recent advances in our understanding of how toxins, viruses, bacteria, and fungi manipulate the host cell endocytic machinery to generate diseases. Additionally, we will reveal the advantages of using these organisms to expand our general knowledge of endocytic mechanisms in eukaryotic cells.
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Affiliation(s)
- Ann En-Ju Lin
- Department of Biological Sciences, Shrum Science Centre, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada
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19
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Wu G, Li Z. Rapid clearance of circulating protein by early chicken embryo blood cells. ACTA ACUST UNITED AC 2009; 212:2176-82. [PMID: 19561207 DOI: 10.1242/jeb.031377] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
It has been speculated that free amino acids digested from proteins in bird eggs are transported to the circulation for the nourishment of the embryo. In the present study, we found that early chicken embryo protein in the serum might be utilized efficiently as a nutrient. Proteins injected into the blood of embryonic day 3 (E3) embryos were partially degraded and rapidly cleared. The rapid clearance of the injected proteins might be the result of efficient pinocytosis by blood cells, which then efficiently digested the intracellular proteins. An evaluation of the fluorescence intensity of injected fluorescein isothiocyanate-labeled bovine serum albumin (FITC-BSA) indicated that about half was taken up by the blood cells 80 min after injection. About 4 h after injection, most of the FITC-BSA was digested and the products were released into the serum, which implies that circulating blood cells may serve as a digestive system in early chick embryos. However, the endocytic activity of blood cells decreased after E5, and BSA may reside in the circulation with a longer half-life after E5. These results imply that blood cells would serve as a digestive system only in early embryos. In summary, the mechanism revealed here gives the early embryo the ability to make use of protein as a nutrient without prior digestion outside the embryo.
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Affiliation(s)
- Guojin Wu
- Department of Biochemistry and Molecular Biology, College of Biology Science, China Agricultural University, No. 2, Yuanmingyuan West Road, Beijing 100193, China
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20
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Hansen CG, Nichols BJ. Molecular mechanisms of clathrin-independent endocytosis. J Cell Sci 2009; 122:1713-21. [PMID: 19461071 DOI: 10.1242/jcs.033951] [Citation(s) in RCA: 208] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
There is good evidence that, in addition to the canonical clathrin-associated endocytic machinery, mammalian cells possess multiple sets of proteins that are capable of mediating the formation of endocytic vesicles. The identity, mechanistic properties and function of these clathrin-independent endocytic pathways are currently under investigation. This Commentary briefly recounts how the field of clathrin-independent endocytosis has developed to date. It then highlights recent progress in identifying key proteins that might define alternative types of endocytosis. These proteins include CtBP (also known as BARS), flotillins (also known as reggies) and GRAF1. We argue that a combination of information about pathway-specific proteins and the ultrastructure of endocytic invaginations provides a means of beginning to classify endocytic pathways.
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21
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Extracellular, cell-permeable survivin inhibits apoptosis while promoting proliferative and metastatic potential. Br J Cancer 2009; 100:1073-86. [PMID: 19293795 PMCID: PMC2669990 DOI: 10.1038/sj.bjc.6604978] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
The tumour microenvironment is believed to be involved in development, growth, metastasis, and therapy resistance of many cancers. Here we show survivin, a member of the inhibitor of apoptosis protein (IAP) family, implicated in apoptosis inhibition and the regulation of mitosis in cancer cells, exists in a novel extracellular pool in tumour cells. Furthermore, we have constructed stable cell lines that provide the extracellular pool with either wild-type survivin (Surv-WT) or the previously described dominant-negative mutant survivin (Surv-T34A), which has proven pro-apoptotic effects in cancer cells but not in normal proliferating cells. Cancer cells grown in conditioned medium (CM) taken from Surv-WT cells absorbed survivin and experienced enhanced protection against genotoxic stresses. These cells also exhibited an increased replicative and metastatic potential, suggesting that survivin in the tumour microenvironment may be directly associated with malignant progression, further supporting survivin's function in tumourigenesis. Alternatively, cancer cells grown in CM taken from the Surv-T34A cells began to apoptose through a caspase-2- and caspase-9-dependent pathway that was further enhanced by the addition of other chemo- and radiotherapeutic modalities. Together our findings suggest a novel microenvironmental function for survivin in the control of cancer aggressiveness and spread, and should result in the genesis of additional cancer treatment modalities.
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22
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Abstract
The functionality of receptor and channel proteins depends directly upon their expression level on the plasma membrane. Therefore, the ability to selectively adjust the surface level of a particular receptor or channel protein is pivotal to many cellular signalling events. The internalization and recycling pathway plays a major role in the regulation of protein surface level, and thus has been a focus of research for many years. Although several endocytic pathways have been identified, most of our knowledge has come from the clathrin-dependent pathway, while the other pathways remain much less well defined. Considering that clathrin-independent internalization may account for as much as 50% of the total endocytic activity in the cell, the lack of such knowledge constitutes a major gap in our efforts to understand how different internalization pathways are utilized and co-ordinated. Recent studies have provided valuable insights into this area, yet many more questions still remain. In this review, we will give a panoramic introduction to the current knowledge of various internalization and recycling pathways, with an emphasis on the latest findings that have broadened our view of the clathrin-independent pathways. We will also dedicate one section to the emerging studies of the clathrin-independent internalization pathways in neuronal cells.
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Affiliation(s)
- Qiang Gong
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
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23
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Abstract
The extent to which the many different pathways of endocytosis share underlying molecular mechanisms is currently unknown. In this issue of Developmental Cell, Yarar et al. (2007) report that SNX9, a protein that binds phosphatidylinositides, dynamin, and N-WASP, coordinates actin assembly with several distinct endocytic processes.
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Affiliation(s)
- Michael G Roth
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
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Casartelli M, Corti P, Cermenati G, Grimaldi A, Fiandra L, Santo N, Pennacchio F, Giordana B. Absorption of horseradish peroxidase in Bombyx mori larval midgut. JOURNAL OF INSECT PHYSIOLOGY 2007; 53:517-25. [PMID: 17391693 DOI: 10.1016/j.jinsphys.2007.02.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2006] [Revised: 02/07/2007] [Accepted: 02/07/2007] [Indexed: 05/14/2023]
Abstract
Increasing experimental evidence indicates that ingested proteins can in part reach the haemocoel undegraded, but information on the mechanisms involved in protein transport across the insect gut is very limited, in spite of the implications that this may have on the development of novel delivery strategies of insecticide proteins targeting haemocoelic receptors. Here we contribute to this field of study, by focusing on horseradish peroxidase (HRP) transport through Bombyx mori larval midgut, isolated and perfused in vitro. The protein crossed the intestinal barrier in a time-dependent manner and the influx was linearly related to time between 30 and 90 min of incubation. HRP absorption was strongly affected by temperature and inhibition of cell metabolism: protein influx at 4 degrees C was reduced to 27% of that measured at 25 degrees C and was similarly inhibited by the metabolic inhibitor DNP. Transmission electron microscopy analysis of midgut columnar cells exposed to HRP showed the presence of the protein both in vesicular structures inside the cytoplasm and in the space between two adjacent absorptive cells, indicating the occurrence of both a transcellular and a paracellular permeation route. The analysis of HRP influx as a function of increasing protein concentration in the lumen supported this morphological indication. The J(max) relative to the HRP transcellular transport component was 121+/-24 pmol/cm(2)/h and the K(d) of the passage through the paracellular route was 1.9+/-0.3 microl/cm(2)/h. The paracellular electrical resistance decreased in midguts exposed to HRP, indicating that its passage through this pathway was likely due to an alteration exerted on the junctional complex by the protein itself. The role of the cytoskeleton in HRP transport was investigated by assessing the impact of drugs affecting microtubules and actin filaments.
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Affiliation(s)
- Morena Casartelli
- Dipartimento di Biologia, Università degli Studi di Milano, via Celoria 26, 20133 Milan, Italy.
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Worthington ZEV, Carbonetti NH. Evading the proteasome: absence of lysine residues contributes to pertussis toxin activity by evasion of proteasome degradation. Infect Immun 2007; 75:2946-53. [PMID: 17420233 PMCID: PMC1932868 DOI: 10.1128/iai.02011-06] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pertussis toxin (PT) is an important virulence factor produced by Bordetella pertussis. PT holotoxin comprises one enzymatically active A subunit (S1), associated with a pentamer of B subunits. PT is an ADP-ribosyltransferase that modifies several mammalian heterotrimeric G proteins. Some bacterial toxins are believed to undergo retrograde intracellular transport through the Golgi apparatus to the endoplasmic reticulum (ER). The ER-associated degradation (ERAD) pathway involves the removal of misfolded proteins from the ER and degradation upon their return to the cytosol; this pathway may be exploited by PT and other toxins. In the cytosol, ERAD substrates are ubiquitinated at lysine residues, targeting them to the proteasome for degradation. We hypothesize that S1 avoids ubiquitination and proteasome degradation due to its lack of lysine residues. We predicted that the addition of lysine residues would reduce PT toxicity by allowing ubiquitination and degradation to occur. Variant forms of PT were engineered, replacing one, two, or three arginines with lysines in a variety of locations on S1. Several variants were identified with wild-type in vitro enzymatic activity but reduced cellular activity, consistent with our hypothesis. Significant recovery of the cellular activity of these variants was observed when CHO cells were pretreated with a proteasome inhibitor. We concluded that the replacement of arginine residues with lysine in the S1 subunit of PT renders the toxin subject to proteasomal degradation, suggesting that wild-type PT avoids proteasome degradation due to an absence of lysine residues.
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Affiliation(s)
- Zoë E V Worthington
- Department of Microbiology and Immunology, University of Maryland School of Medicine, 660 W. Redwood Street, Baltimore, MD 21201, USA.
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Ganeshan R, Nowotarski K, Di A, Nelson DJ, Kirk KL. CFTR surface expression and chloride currents are decreased by inhibitors of N-WASP and actin polymerization. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1773:192-200. [PMID: 17084917 PMCID: PMC1828603 DOI: 10.1016/j.bbamcr.2006.09.031] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2006] [Revised: 08/14/2006] [Accepted: 09/26/2006] [Indexed: 01/25/2023]
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) undergoes rapid turnover at the plasma membrane in various cell types. The ubiquitously expressed N-WASP promotes actin polymerization and regulates endocytic trafficking of other proteins in response to signaling molecules such as Rho-GTPases. In the present study we investigated the effects of wiskostatin, an N-WASP inhibitor, on the surface expression and activity of CFTR. We demonstrate, using surface biotinylation methods, that the steady-state surface CFTR pool in stably transfected BHK cells was dramatically decreased following wiskostatin treatment with a corresponding increase in the amount of intracellular CFTR. Similar effects were observed for latrunculin B, a specific actin-disrupting reagent. Both reagents strongly inhibited macroscopic CFTR-mediated Cl(-) currents in two cell types including HT29-Cl19A colonic epithelial cells. As previously reported, CFTR internalization from the cell surface was strongly inhibited by a cyclic-AMP cocktail. This effect of cyclic-AMP was only partially blunted in the presence of wiskostatin, which raises the possibility that these two factors modulate different steps in CFTR traffic. In kinetic studies wiskostatin appeared to accelerate the initial rate of CFTR endocytosis as well as inhibit its recycling back to the cell surface over longer time periods. Our studies implicate a role for N-WASP-mediated actin polymerization in regulating CFTR surface expression and channel activity.
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Affiliation(s)
- Radhika Ganeshan
- Department of Physiology and Biophysics, Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, 1918 University Blvd., MCLM 985, Birmingham, AL 35294, USA
| | - Krzysztof Nowotarski
- Department of Physiology and Biophysics, Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, 1918 University Blvd., MCLM 985, Birmingham, AL 35294, USA
| | - Anke Di
- Department of Neurobiology, Pharmacology and Physiology, The University of Chicago, 947 East 58th St., MC 0926, Chicago, IL 60637, USA
| | - Deborah J. Nelson
- Department of Neurobiology, Pharmacology and Physiology, The University of Chicago, 947 East 58th St., MC 0926, Chicago, IL 60637, USA
| | - Kevin L. Kirk
- Department of Physiology and Biophysics, Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, 1918 University Blvd., MCLM 985, Birmingham, AL 35294, USA
- *Author for correspondence Kevin L. Kirk, Ph.D., Department of Physiology and Biophysics, Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, 1918 University Blvd., MCLM 985, Birmingham, AL 35294, USA, Tel (205) 934-3122; FAX (205) 934-5787; e-mail:
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Spooner R, Watson P, Marsden C, Smith D, Moore K, Cook J, Lord J, Roberts L. Protein disulphide-isomerase reduces ricin to its A and B chains in the endoplasmic reticulum. Biochem J 2004; 383:285-93. [PMID: 15225124 PMCID: PMC1134069 DOI: 10.1042/bj20040742] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2004] [Accepted: 06/30/2004] [Indexed: 11/17/2022]
Abstract
Cells expressing ricin B chain within the secretory pathway are significantly more resistant to intoxication by ricin holotoxin but not to other cytotoxins that exploit similar endocytic routes to the cytosol. Furthermore, cells expressing the related B chain of abrin are protected against both incoming abrin and ricin. These phenotypes can be correlated with the abilities of the respective B chains to form disulphide-linked A-B holotoxins, since abrin B chain forms heterodimers with either abrin or ricin A chains, whereas ricin B chain forms heterodimers with ricin A chain only. In the ricin B-expressing cells, this newly made lectin disappears with biphasic kinetics comprising a retention phase followed by slow turnover and disposal after disengagement from calnexin cycle components. Interference with ricin cytotoxicity occurs during the early retention phase when ricin B chain is associated with PDI (protein disulphide-isomerase). The data show that retrotranslocation of incoming toxin is impeded by PDI-catalysed formation of heterodimers between endogenous B and A chains derived from reduced holotoxin, thus proving that reduction of ricin occurs in the endoplasmic reticulum. In contrast with other toxins, ricin does not appear to require either proteolytic cleavage or unfolding for PDI-catalysed reduction.
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Key Words
- endoplasmic reticulum-associated protein degradation (erad)
- oxidoreductase
- protein disulphide-isomerase
- retrograde transport
- ricin
- toxin
- ata, abrin isoform f a chain
- atb, abrin b chain
- bfa, brefeldin a
- bmh, bis-maleimidohexane
- cnx, calnexin
- cst, castanospermine
- cta, cholera toxin a
- dmem, dulbecco's modified eagle's medium
- dmm, deoxymannojirimycin
- dtt, dithiothreitol
- endo h, endoglycosidase h
- er, endoplasmic reticulum
- fcs, foetal calf serum
- nem, n-ethylmaleimide
- pdi, protein disulphide-isomerase
- pe, pseudomonas exotoxin a
- rta, ricin toxin a chain
- rtb, ricin toxin b chain
- sfm, serum-free medium
- slt, shiga-like toxin 1
- tn, tunicamycin
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Affiliation(s)
- Robert A. Spooner
- Molecular Cell Biology, Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, U.K
| | - Peter D. Watson
- Molecular Cell Biology, Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, U.K
| | - Catherine J. Marsden
- Molecular Cell Biology, Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, U.K
| | - Daniel C. Smith
- Molecular Cell Biology, Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, U.K
| | - Katherine A. H. Moore
- Molecular Cell Biology, Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, U.K
| | - Jonathon P. Cook
- Molecular Cell Biology, Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, U.K
| | - J. Michael Lord
- Molecular Cell Biology, Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, U.K
| | - Lynne M. Roberts
- Molecular Cell Biology, Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, U.K
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Schnatwinkel C, Christoforidis S, Lindsay MR, Uttenweiler-Joseph S, Wilm M, Parton RG, Zerial M. The Rab5 effector Rabankyrin-5 regulates and coordinates different endocytic mechanisms. PLoS Biol 2004; 2:E261. [PMID: 15328530 PMCID: PMC514490 DOI: 10.1371/journal.pbio.0020261] [Citation(s) in RCA: 220] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2003] [Accepted: 06/11/2004] [Indexed: 01/07/2023] Open
Abstract
The small GTPase Rab5 is a key regulator of clathrin-mediated endocytosis. On early endosomes, within a spatially restricted domain enriched in phosphatydilinositol-3-phosphate [PI(3)P], Rab5 coordinates a complex network of effectors that functionally cooperate in membrane tethering, fusion, and organelle motility. Here we discovered a novel PI(3)P-binding Rab5 effector, Rabankyrin-5, which localises to early endosomes and stimulates their fusion activity. In addition to early endosomes, however, Rabankyrin-5 localises to large vacuolar structures that correspond to macropinosomes in epithelial cells and fibroblasts. Overexpression of Rabankyrin-5 increases the number of macropinosomes and stimulates fluid-phase uptake, whereas its downregulation inhibits these processes. In polarised epithelial cells, this function is primarily restricted to the apical membrane. Rabankyrin-5 localises to large pinocytic structures underneath the apical surface of kidney proximal tubule cells, and its overexpression in polarised Madin-Darby canine kidney cells stimulates apical but not basolateral, non-clathrin-mediated pinocytosis. In demonstrating a regulatory role in endosome fusion and (macro)pinocytosis, our studies suggest that Rab5 regulates and coordinates different endocytic mechanisms through its effector Rabankyrin-5. Furthermore, its active role in apical pinocytosis in epithelial cells suggests an important function of Rabankyrin-5 in the physiology of polarised cells.
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Affiliation(s)
| | - Savvas Christoforidis
- 2Laboratory of Biological Chemistry, Medical SchoolUniversity of Ioannina, IoanninaGreece
| | - Margaret R Lindsay
- 3Institute for Molecular Bioscience, Centre for Microscopy and MicroanalysisSchool of Biomedical Sciences, University of Queensland, Brisbane, QueenslandAustralia
| | | | - Matthias Wilm
- 4European Molecular Biology LaboratoryHeidelbergGermany
| | - Robert G Parton
- 3Institute for Molecular Bioscience, Centre for Microscopy and MicroanalysisSchool of Biomedical Sciences, University of Queensland, Brisbane, QueenslandAustralia
| | - Marino Zerial
- 1Max-Planck Institute of Molecular Cell Biology and GeneticsDresdenGermany
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29
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Gonçalves C, Mennesson E, Fuchs R, Gorvel JP, Midoux P, Pichon C. Macropinocytosis of Polyplexes and Recycling of Plasmid via the Clathrin-Dependent Pathway Impair the Transfection Efficiency of Human Hepatocarcinoma Cells. Mol Ther 2004; 10:373-85. [PMID: 15294184 DOI: 10.1016/j.ymthe.2004.05.023] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2004] [Accepted: 05/13/2004] [Indexed: 11/19/2022] Open
Abstract
Knowledge of the entry mechanism and intracellular routing of polyplexes is of major importance for designing efficient gene delivery systems. We therefore investigated the internalization and trafficking of polyplexes in HepG2 cells. pDNA encoding the luciferase was complexed with histidylated polylysine (His-pLK), a polymer that requires acidic pH for pDNA endosomal release. Fluoresceinylated polyplexes (F-His-pLK or F-pDNA) were internalized by clathrin-dependent and -independent pathways. The latter most likely occurred by macropinocytosis since it was stimulated by phorbol myristate and blocked by dimethylamiloride. Intracellular routing of the plasmid was analyzed by confocal microscopy and flow cytometry. These data revealed that: (i) one part of the plasmid was present in vesicles that were not labeled with any known organelle-specific marker, (ii) the other part was in transferrin receptor-positive vesicles, and (iii) the plasmid was not transferred to late endosomes/lysosomes. Using luciferase activity as a readout for gene expression, we found that it was strongly reduced when macropinocytosis was stimulated, whereas macropinocytosis inhibitors had no effect. However, blocking clathrin-dependent internalization by chlorpromazine completely prevented gene expression. These findings demonstrate that: (i) macropinocytosis of polyplexes and (ii) plasmid recycling impair the transfection efficiency and (iii) clathrin-dependent endocytosis is the most productive route for transfection of HepG2 cells.
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Affiliation(s)
- Christine Gonçalves
- Centre de Biophysique Moléculaire, UPR4301 CNRS, Rue Charles Sadron, 45071 Orléans, Cedex 2, France
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30
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Abstract
Internalization of receptors, lipids, pathogens, and other cargo at the plasma membrane involves several different pathways and requires coordinated interactions between a variety of protein and lipid molecules. The actin cytoskeleton is an integral part of the cell cortex, and there is growing evidence that F-actin plays a direct role in these endocytic events. Genetic studies in yeast have firmly established a functional connection between actin and endocytosis. Identification of several proteins that may function at the interface between actin and the endocytic machinery has provided further evidence for this association in both yeast and mammalian cells. Several of these proteins are directly involved in regulating actin assembly and could thus harness forces produced during actin polymerization to facilitate specific steps in the endocytic process. Recent microscopy studies in mammalian cells provide powerful evidence that localized recruitment and polymerization of actin occurs at endocytic sites. In this review, we focus on progress made in elucidating the functions of the actin cytoskeleton in endocytosis.
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Affiliation(s)
- Asa E Y Engqvist-Goldstein
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3202, USA
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31
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Abstract
Macropinocytosis is a form of endocytosis that accompanies cell surface ruffling. It is distinct in many ways from the better characterized micropinocytosis, which includes clathrin-coated vesicle endocytosis and small uncoated vesicles. Because macropinosomes are relatively large, they provide an efficient route for non-selective endocytosis of solute macromolecules. This route may facilitate MHC-class-II-restricted antigen presentation by dendritic cells. Because the ruffling that leads to macropinocytosis is regulated, it has been exploited by some pathogenic bacteria as a novel route for entry into cells.
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Affiliation(s)
- J A Swanson
- Dept of Cell Biology, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA
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32
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Hamasaki M, Araki N, Hatae T. Association of early endosomal autoantigen 1 with macropinocytosis in EGF-stimulated a431 cells. ACTA ACUST UNITED AC 2004; 277:298-306. [PMID: 15052657 DOI: 10.1002/ar.a.20027] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Association of early endosomal autoantigen 1 (EEA1) with macropinosomes was examined in EGF-stimulated A431 cells by dual labeling with immunofluorescence of anti-EEA1 and FITC-dextran (FDx), a fluid-phase endocytic marker. Addition of EGF to A431 cells drastically enhanced macropinosome formation. Newly formed macropinosomes labeled with 5-min pulse of FDx were located at the cell periphery and labeled weakly for EEA1. After a 5-min chase, these macropinosomes aggregated and frequently fused with each other. Immunofluorescence showed that EEA1 appeared on the membrane of FDx-labeled macropinosomes at that time, suggesting that EEA1 functioned in homotypic macropinosome fusion. With longer chase (30-60 min), macropinosomes decreased in number and size, indicating that FDx was largely exocytosed via recycling compartments. A small amount of FDx-labeled macropinosomes remained in the perinuclear region even at 60 min after pulse labeling. They were EEA1-positive but negative for cathepsin D, a lysosomal enzyme. This indicates that macropinosomes do not mature to late endosomes or fuse with lysosomes. Instead, EEA1 continuously mediates homotypic fusion as long as the macropinosomes persist.
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Affiliation(s)
- Masao Hamasaki
- Department of Histology and Cell Biology, School of Medicine, Kagawa University, Kagawa, Japan
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33
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Abstract
In this review we describe the potential roles of the actin cytoskeleton in receptor-mediated endocytosis in mammalian cells and summarize the efforts of recent years in establishing a relationship between these two cellular functions. With molecules such as dynamin, syndapin, HIP1R, Abp1, synaptojanin, N-WASP, intersectin, and cortactin a set of molecular links is now available and it is likely that their further characterization will reveal the basic principles of a functional interconnection between the membrane cytoskeleton and the vesicle-budding machinery. We will therefore discuss proteins involved in endocytic clathrin coat formation and accessory factors to control and regulate coated vesicle formation but we will also focus on actin cytoskeletal components such as the Arp2/3 complex, spectrin, profilin, and motor proteins involved in actin dynamics and organization. Additionally, we will discuss how phosphoinositides, such as PI(4,5)P2, small GTPases thought to control the actin cytoskeleton, such as Rho, Rac, and Cdc42, or membrane trafficking, such as Rab GTPases and ARF proteins, and different kinases may participate in the functional connection of actin and endocytosis. We will compare the concepts and different molecular mechanisms involved in mammalian cells with yeast as well as with specialized cells, such as epithelial cells and neurons, because different model organisms often offer complementary advantages for further studies in this thriving field of current cell biological research.
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Affiliation(s)
- Britta Qualmann
- Department of Neurochemistry and Molecular Biology, Leibniz Institute for Neurobiology, Magdeburg, Germany
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34
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Abstract
In this study we have examined the pathway by which papillomaviruses infect cells, using bovine papillomavirus (BPV) virions and mouse C127 cells as the model system. By confocal microscopy, the entry of BPV virions, BPV virus-like particles (VLPs), and HPV16 VLPs were very similar. In dually exposed cells, HPV-16 VLPs and BPV virions colocalized intracellularly. BPV VLPs colocalized with AP-2, a clathrin adapter molecular and a marker of the clathrin-dependent endocytic pathway; and also with transferrin receptor, a marker of early endosomes; and Lamp-2, a marker of late endosomes and lysosomes. BPV infection was detected within 12 h of virion cell-surface binding, as measured by an RT-PCR assay. Infection was prevented by several pharmacologic inhibitors, including chlorpromazine, which blocks clathrin-dependent endocytosis and the lysosomotropic agent, bafilomycin A. By contrast, two inhibitors of caveolae-dependent uptake, filipin and nystatin, did not prevent BPV infection. We conclude that papillomaviruses infect cells via clathrin-dependent receptor-mediated endocytosis. Surprisingly, the kinetics of internalization were unusually slow for this mechanism, with the t(1/2) of entry of BPV-1 being approximately 4 h versus 5-15 min for a typical ligand.
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Affiliation(s)
- Patricia M Day
- Laboratory of Cellular Oncology, Division of Basic Sciences, National Cancer Institute, National Institutes of Health, Building 36, Room 1D-32, Bethesda, MD 20892, USA
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35
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Sun P, Yamamoto H, Suetsugu S, Miki H, Takenawa T, Endo T. Small GTPase Rah/Rab34 is associated with membrane ruffles and macropinosomes and promotes macropinosome formation. J Biol Chem 2003; 278:4063-71. [PMID: 12446704 DOI: 10.1074/jbc.m208699200] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Macropinocytosis is an efficient process for the uptake of nutrients and solute macromolecules into cells from the external environment. Macropinosomes, which are surrounded by actin, are formed from the cell surface membrane ruffles and migrate toward the cell center. We have cloned the entire coding sequence of a member of the Rab family small GTPases, Rah/Rab34. It lacked a consensus sequence for GTP-binding/GTPase domain. Although wild-type Rah exhibited extremely low GTPase activity in vitro, it exerted appreciable GTPase activity in vivo. In fibroblasts, Rah was colocalized with actin to the membrane ruffles and membranes of relatively large vesicles adjacent to the ruffles. These vesicles were identified as macropinosomes on the basis of several criteria. Rah and Rab5 coexisted in some, but not all, macropinosomes. Rah was predominantly associated with nascent macropinosomes, whereas Rab5 was present in endosomes at later stages. The number of macropinosomes in the cells overexpressing Rah increased about 2-fold. The formation of macropinosomes by the treatment of platelet-derived growth factor or phorbol ester was also facilitated by Rah but suppressed by a dominant-negative Rah. Rah-promoted macropinosome formation was retarded by dominant-negative mutants of Rac1 and WAVE2, which are essential for membrane ruffling. These results imply that Rah is required for efficient macropinosome formation from the membrane ruffles.
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Affiliation(s)
- Peng Sun
- Department of Biology, Faculty of Science, and Graduate School of Science and Technology, Chiba University, Yayoicho, Inageku, Japan
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36
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Naslavsky N, Weigert R, Donaldson JG. Convergence of non-clathrin- and clathrin-derived endosomes involves Arf6 inactivation and changes in phosphoinositides. Mol Biol Cell 2003; 14:417-31. [PMID: 12589044 PMCID: PMC149982 DOI: 10.1091/mbc.02-04-0053] [Citation(s) in RCA: 225] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The trafficking of two plasma membrane (PM) proteins that lack clathrin internalization sequences, major histocompatibility complex class I (MHCI), and interleukin 2 receptor alpha subunit (Tac) was compared with that of PM proteins internalized via clathrin. MHCI and Tac were internalized into endosomes that were distinct from those containing clathrin cargo. At later times, a fraction of these internalized membranes were observed in Arf6-associated, tubular recycling endosomes whereas another fraction acquired early endosomal autoantigen 1 (EEA1) before fusion with the "classical" early endosomes containing the clathrin-dependent cargo, LDL. After convergence, cargo molecules from both pathways eventually arrived, in a Rab7-dependent manner, at late endosomes and were degraded. Expression of a constitutively active mutant of Arf6, Q67L, caused MHCI and Tac to accumulate in enlarged PIP(2)-enriched vacuoles, devoid of EEA1 and inhibited their fusion with clathrin cargo-containing endosomes and hence blocked degradation. By contrast, trafficking and degradation of clathrin-cargo was not affected. A similar block in transport of MHCI and Tac was reversibly induced by a PI3-kinase inhibitor, implying that inactivation of Arf6 and acquisition of PI3P are required for convergence of endosomes arising from these two pathways.
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Affiliation(s)
- Naava Naslavsky
- Laboratory of Cell Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, USA
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37
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Abstract
Ricin is a heterodimeric protein produced in the seeds of the castor oil plant (Ricinus communis). It is exquisitely potent to mammalian cells, being able to fatally disrupt protein synthesis by attacking the Achilles heel of the ribosome. For this enzyme to reach its substrate, it must not only negotiate the endomembrane system but it must also cross an internal membrane and avoid complete degradation without compromising its activity in any way. Cell entry by ricin involves a series of steps: (i) binding, via the ricin B chain (RTB), to a range of cell surface glycolipids or glycoproteins having beta-1,4-linked galactose residues; (ii) uptake into the cell by endocytosis; (iii) entry of the toxin into early endosomes; (iv) transfer, by vesicular transport, of ricin from early endosomes to the trans-Golgi network; (v) retrograde vesicular transport through the Golgi complex to reach the endoplasmic reticulum; (vi) reduction of the disulphide bond connecting the ricin A chain (RTA) and the RTB; (vii) partial unfolding of the RTA to render it translocationally-competent to cross the endoplasmic reticulum (ER) membrane via the Sec61p translocon in a manner similar to that followed by misfolded ER proteins that, once recognised, are targeted to the ER-associated protein degradation (ERAD) machinery; (viii) avoiding, at least in part, ubiquitination that would lead to rapid degradation by cytosolic proteasomes immediately after membrane translocation when it is still partially unfolded; (ix) refolding into its protease-resistant, biologically active conformation; and (x) interaction with the ribosome to catalyse the depurination reaction. It is clear that ricin can take advantage of many target cell molecules, pathways and processes. It has been reported that a single molecule of ricin reaching the cytosol can kill that cell as a consequence of protein synthesis inhibition. The ready availability of ricin, coupled to its extreme potency when administered intravenously or if inhaled, has identified this protein toxin as a potential biological warfare agent. Therapeutically, its cytotoxicity has encouraged the use of ricin in 'magic bullets' to specifically target and destroy cancer cells, and the unusual intracellular trafficking properties of ricin potentially permit its development as a vaccine vector. Combining our understanding of the ricin structure with ways to cripple its unwanted properties (its enzymatic activity and promotion of vascular leak whilst retaining protein stability and important immunodominant epitopes), will also be crucial in the development of a long awaited protective vaccine against this toxin.
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Affiliation(s)
- Michael J Lord
- Department of Biological Sciences, University of Warwick, Coventry, UK
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38
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Szaszi K, Paulsen A, Szabo EZ, Numata M, Grinstein S, Orlowski J. Clathrin-mediated endocytosis and recycling of the neuron-specific Na+/H+ exchanger NHE5 isoform. Regulation by phosphatidylinositol 3'-kinase and the actin cytoskeleton. J Biol Chem 2002; 277:42623-32. [PMID: 12205089 DOI: 10.1074/jbc.m206629200] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Mammalian Na+/H+ exchangers (NHEs) are a family of integral membrane proteins that play central roles in sodium, acid-base, and cell volume homeostasis. The recently cloned NHE5 isoform is expressed predominantly in brain, but its functional and cellular properties are poorly understood. To facilitate its characterization, an epitope-tagged construct of NHE5 was ectopically expressed in nonneuronal and neuronal cells. In NHE-deficient Chinese hamster ovary AP-1 cells, NHE5 localized at the plasmalemma, but a significant fraction accumulated intracellularly in vesicles that concentrated in a juxtanuclear region. Similarly, in nerve growth factor-differentiated neuroendocrine PC12 cells and primary hippocampal neurons, immunolabeling of NHE5 was detected in endomembrane vesicles in the perinuclear region of the cell body but also along the processes. More detailed characterization in AP-1 cells using organelle-specific markers showed that NHE5 co-localized with internalized transferrin, a marker of recycling endosomes. Transient transfection of a dominant negative mutant of dynamin-1, which inhibits clathrin-mediated endocytosis, blocked uptake of transferrin as well as internalization of NHE5. Likewise, wortmannin inhibition of phosphatidylinositol 3'-kinase, a lipid kinase implicated in endosomal traffic, induced coalescence of vesicles containing NHE5 and caused a pronounced inhibition of plasmalemmal Na+/H+ exchange. By contrast, disruption of the F-actin cytoskeleton with cytochalasin D increased cell surface NHE5 activity and abundance. These observations demonstrate that NHE5 is localized to the recycling endosomal pathway and is dynamically regulated by phosphatidylinositol 3'-kinase and by the state of F-actin assembly.
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Affiliation(s)
- Katalin Szaszi
- Department of Physiology, McGill University, Montreal, Quebec H3G 1Y6, Canada
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39
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Moisenovic M, Tonevitsky A, Agapov I, Niwa H, Schewe H, Bereiter-Hahn J. Differences in endocytosis and intracellular sorting of ricin and viscumin in 3T3 cells. Eur J Cell Biol 2002; 81:529-38. [PMID: 12437187 DOI: 10.1078/0171-9335-00263] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ricin and viscumin are heterodimeric protein toxins. Their A-chain is enzymatically active and removes an adenine residue from the 28S rRNA, the B-chain has lectin activity and binds to terminal galactose residues of cell surface receptors. The toxins reveal a high degree of identity in their amino acid sequences. Nevertheless, uptake into 3T3 cells occurs via different receptors and endocytotic pathways. This has been revealed by enzyme linked based analysis of ricin competition with viscumin, and by fluorochrome-labeled toxins (viscumin-FITC, ricin-Alexa 568), which were added simultaneously or separately to living cells. Then the uptake was followed by confocal laser scanning microscopy. Ricin immediately is delivered to the tubular and vesicular structures of endosomes in the perinuclear area while viscumin becomes endocytosed into small vesicles preferentially in the cell periphery. After about 60 min both these toxins may be found in tubo-vesicular structures of endosomes where the sorting process can directly be observed. The fact that this sorting takes place is a strong argument for the assumption that the toxins are bound to membrane proteins, either to their original receptors or to other proteins inside the endosomal compartment exhibiting terminal galactose residues. The toxins are biologically fully active as has been proven by binding and by toxicity experiments, thus the differences in targeting do not arise from labeling.
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Affiliation(s)
- Mihail Moisenovic
- Department of Cell Physiology and Immunology, Biological Faculty, MV Lomonosov Moscow State University, Russia
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40
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Grimmer S, van Deurs B, Sandvig K. Membrane ruffling and macropinocytosis in A431 cells require cholesterol. J Cell Sci 2002; 115:2953-62. [PMID: 12082155 DOI: 10.1242/jcs.115.14.2953] [Citation(s) in RCA: 184] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cholesterol is important for the formation of caveolea and deeply invaginated clathrin-coated pits. We have now investigated whether formation of macropinosomes is dependent on the presence of cholesterol in the plasma membrane. Macropinocytosis in A431 cells was induced by the phorbol ester 12-O-tetradecanoylphorbol 13-acetate, a potent activator of protein kinase C (PKC). When cells were pretreated with methyl-β-cyclodextrin to extract cholesterol, the phorbol ester was unable to induce the increased endocytosis of ricin otherwise seen, although PKC could still be activated. Electron microscopy revealed that extraction of cholesterol inhibited the formation of membrane ruffles and macropinosomes at the plasma membrane. Furthermore, cholesterol depletion inhibited the phorbol ester-induced reorganization of filamentous actin at the cell periphery, a prerequisite for the formation of membrane ruffles that close into macropinosomes. Under normal conditions the small GTPase Rac1 is activated by the phorbol ester and subsequently localized to the plasma membrane, where it induces the reorganization of actin filaments required for formation of membrane ruffles. Cholesterol depletion did not inhibit the activation of Rac1. However,confocal microscopy showed that extraction of cholesterol prevented the phorbol ester-stimulated localization of Rac1 to the plasma membrane. Thus,our results demonstrate that cholesterol is required for the membrane localization of activated Rac1, actin reorganization, membrane ruffling and macropinocytosis.
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Affiliation(s)
- Stine Grimmer
- Institute for Cancer Research, The Norwegian Radium Hospital, Montebello, 0310 Oslo, Norway
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41
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Abstract
Whether the endocytic uptake of a given molecule is mediated through clathrin-coated pits or not is a classical criterion used to characterize its endocytic pathway(s). Hence, clathrin-dependent endocytosis has been associated with highly selective and efficient uptake, whereas clathrin-independent endocytosis appeared to be confined to bulk uptake of fluid-phase markers. This scholastic view has recently been challenged using newly developed molecular tools that allow for the first time a functional and mechanistic analysis of these less well-characterized clathrin-independent pathways, including caveolar uptake and macropinocytosis. Furthermore, several studies point to a critical role of lateral lipid asymmetry--lipid rafts/microdomains--in membrane sorting. We will discuss the potential role of these structures in endocytosis and the possibility that differential sorting at the plasma membrane predisposes the ensuing intracellular fate of a given molecule as well as its physiological function.
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Affiliation(s)
- Ludger Johannes
- Institut Curie, UMR144 CNRS, Traffic and Signaling Laboratory, 26 rue d'Ulm, 75005 Paris Cedex 05, France.
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42
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Abstract
A convergence of cellular, genetic and biochemical studies supports the hypothesis that the actin cytoskeleton is coupled to endocytic processes, but the roles played by actin filaments during endocytosis are not yet clear. Recent studies have identified several proteins that may functionally link the endocytic machinery with actin filament dynamics. Three of these proteins, Abp1p, Pan1p and cortactin, are activators of actin assembly nucleated by the Arp2/3 complex, a key regulator of actin assembly in vivo. Two others, intersectin and syndapin, bind N-WASp, a potent activator of actin assembly via the Arp2/3 complex. All of these proteins also bind components of the endocytic machinery, and thus, could coordinately regulate actin assembly and trafficking events. Hip1R, an F-actin-binding protein that associates with clathrin-coated vesicles, may physically link endocytic vesicles to actin filaments. The GTPase dynamin is implicated in modulating actin filaments at specialized actin-rich structures of the cell cortex, suggesting that dynamin may regulate the organization of cortical actin filaments as well as regulate actin dynamics during endocytosis. Finally, myosin VI may generate actin-dependent forces for membrane invagination or vesicle movement during the early stages of endocytosis.
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Affiliation(s)
- Dorothy A Schafer
- Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, Missouri 63119, USA.
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43
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Torgersen ML, Skretting G, van Deurs B, Sandvig K. Internalization of cholera toxin by different endocytic mechanisms. J Cell Sci 2001; 114:3737-47. [PMID: 11707525 DOI: 10.1242/jcs.114.20.3737] [Citation(s) in RCA: 273] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The mechanism of cholera toxin (CT) internalization has been investigated using Caco-2 cells transfected with caveolin to induce formation of caveolae, HeLa cells with inducible synthesis of mutant dynamin (K44A) and BHK cells in which antisense mRNA to clathrin heavy chain can be induced. Here we show that endocytosis and the ability of CT to increase the level of cAMP were unaltered in caveolin-transfected cells grown either in a non-polarized or polarized manner. Treatment of Caco-2 cells with filipin reduced CT-uptake by less than 20%, suggesting that caveolae do not play a major role in the uptake. Extraction of cholesterol by methyl-β-cyclodextrin, which removes caveolae and inhibits uptake from clathrin-coated pits, gave 30-40% reduction of CT-endocytosis. Also, CT-uptake in HeLa K44A cells was reduced by 50-70% after induction of mutant dynamin, which inhibits both caveolae- and clathrin-dependent endocytosis. These cells contain few caveolae, and nystatin and filipin had no effect on CT-uptake, indicating major involvement of clathrin-coated pits in CT-internalization. Similarly, in BHK cells, where clathrin-dependent endocytosis is blocked by induction of antisense clathrin heavy chain, the CT-uptake was reduced by 50% in induced cells. In conclusion, a large fraction of CT can be endocytosed by clathrin-dependent as well as by caveolae- and clathrin-independent endocytosis in different cell types.
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Affiliation(s)
- M L Torgersen
- Institute for Cancer Research, the Norwegian Radium Hospital, Montebello, 0310 Oslo, Norway
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44
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Day PJ, Owens SR, Wesche J, Olsnes S, Roberts LM, Lord JM. An interaction between ricin and calreticulin that may have implications for toxin trafficking. J Biol Chem 2001; 276:7202-8. [PMID: 11113144 DOI: 10.1074/jbc.m009499200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Here we demonstrate that ricin is able to interact with the molecular chaperone calreticulin both in vitro and in vivo. The interaction occurred with ricin holotoxin, but not with free ricin A chain; and it was prevented in the presence of lactose, suggesting that it was mediated by the lectin activity of the ricin B chain. This lectin is galactose-specific, and metabolic labeling with [(3)H]galactose or treating galactose oxidase-modified calreticulin with sodium [(3)H]borohydride indicated that Vero cell calreticulin possesses a terminally galactosylated oligosaccharide. Brefeldin A treatment indicated that the intracellular interaction occurred initially in a post-Golgi stack compartment, possibly the trans-Golgi network, whereas the reductive separation of ricin subunits occurred in an earlier part of the secretory pathway, most probably the endoplasmic reticulum (ER). Intoxicating Vero cells with ricin whose A chain had been modified to include either a tyrosine sulfation site or the sulfation site plus available N-glycosylation sites, in the presence of Na(2)35SO(4), confirmed that calreticulin interacted with endocytosed ricin that had already undergone retrograde transport to both the Golgi and the ER. Although we cannot exclude the possibility that the interaction between ricin and calreticulin is an indirect one, the data presented are consistent with the idea that calreticulin may function as a recycling carrier for retrograde transport of ricin from the Golgi to the ER.
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Affiliation(s)
- P J Day
- Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom
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45
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Abstract
The cytoskeleton is required for multiple cellular events including endocytosis and the transfer of cargo within the endocytic system. Polarized epithelial cells are capable of endocytosis at either of their distinct apical or basolateral plasma membrane domains. Actin plays a role in internalization at both cell surfaces. Microtubules and actin are required for efficient transcytosis and delivery of proteins to late endosomes and lysosomes. Microtubules are also important in apical recycling pathways and, in some polarized cell types, basolateral recycling requires actin. The microtubule motor proteins dynein and kinesin and the class I unconventional myosin motors play a role in many of these trafficking steps. This review examines the endocytic pathways of polarized epithelial cells and focuses on the emerging roles of the actin cytoskeleton in these processes.
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Affiliation(s)
- G Apodaca
- Renal-Electrolyte Division of the Department of Medicine, Laboratory of Epithelial Biology, and Department of Cell Biology and Physiology, University of Pittsburgh, PA 15261, USA.
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46
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Segal G, Lee W, Arora PD, McKee M, Downey G, McCulloch CA. Involvement of actin filaments and integrins in the binding step in collagen phagocytosis by human fibroblasts. J Cell Sci 2001; 114:119-129. [PMID: 11112696 DOI: 10.1242/jcs.114.1.119] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
In physiological conditions, collagen degradation by fibroblasts occurs primarily via phagocytosis, an intracellular pathway that is thought to require collagen receptors and actin assembly for fibril internalization and degradation. Currently it is unclear which specific steps of collagen phagocytosis in fibroblasts involve actin filament assembly. As studies of phagocytosis in fibroblasts are complicated by the relatively slow rate of particle internalization compared to professional phagocytes, we have examined the role of collagen receptors and actin only in the initial collagen binding step. Prior to the binding of collagen-coated fluorescent beads by human gingival fibroblasts, a cell type that is avidly phagocytic in vitro, cells were treated with cytochalasin D (actin filament barbed-end capping) or swinholide A (actin dimer sequestering and severing) or latrunculin B (actin monomer sequestering). Bead binding and immunostaining of (alpha)(2)(beta)(1) and (alpha)(3)(beta)(1) integrin collagen receptors were measured by flow cytometry. After 1–3 hours of coincubation with beads, cytochalasin D or swinholide A eliminated actin filaments stained by rhodamine-phalloidin and inhibited collagen bead binding (reductions of 25% and 50%, respectively), possibly because of cell rounding and restricted interactions with beads. In contrast, latrunculin enhanced binding dose-dependently over controls (twofold at 1 microM) and induced the formation of brightly staining aggregates of actin and the retention of long cytoplasmic extensions. Latrunculin also reduced surface (beta)(1), (alpha)(2) and (alpha)(3) integrin staining up to 40% in bead-free and bead-loaded cells, indicating that latrunculin enhanced collagen receptor internalization. As determined by fluorescence recovery after photobleaching, latrunculin increased the mobility of surface-bound (beta)(1) integrin. The stimulatory effect of latrunculin on collagen bead binding was reduced to control levels by treatment with a (beta)(1) integrin inactivating antibody while a (beta)(1) integrin blocking antibody abrogated both bead binding and the latrunculin-induced stimulation. Immunoblotting of bead-associated proteins showed that latrunculin completely eliminated binding of (beta)-actin to collagen beads but did not affect (beta)(1) integrin binding. These data indicate that latrunculin-induced sequestration of actin monomers facilitates the disengagement of actin from (beta)(1) integrin receptors, increases collagen bead binding and enhances collagen receptor mobility. We suggest that these alterations increase the probability of adhesive bead-to-cell interactions.
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Affiliation(s)
- G Segal
- CIHR Group in Periodontal Physiology, Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada
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Ricci V, Galmiche A, Doye A, Necchi V, Solcia E, Boquet P. High cell sensitivity to Helicobacter pylori VacA toxin depends on a GPI-anchored protein and is not blocked by inhibition of the clathrin-mediated pathway of endocytosis. Mol Biol Cell 2000; 11:3897-909. [PMID: 11071915 PMCID: PMC15045 DOI: 10.1091/mbc.11.11.3897] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Helicobacter pylori vacuolating toxin (VacA) causes vacuolation in a variety of cultured cell lines, sensitivity to VacA differing greatly, however, among the different cell types. We found that the high sensitivity of HEp-2 cells to VacA was impaired by treating the cells with phosphatidylinositol-specific phospholipase C (PI-PLC) which removes glycosylphosphatidylinositol (GPI)-anchored proteins from the cell surface. Incubation of cells with a cholesterol-sequestering agent, that impairs both structure and function of sphingolipid-cholesterol-rich membrane microdomains ("lipid rafts"), also impaired VacA-induced cell vacuolation. Overexpression into HEp-2 cells of proteins inhibiting clathrin-dependent endocytosis (i.e., a dominant-negative mutant of Eps15, the five tandem Src-homology-3 domains of intersectin, and the K44A dominant-negative mutant of dynamin II) did not affect vacuolation induced by VacA. Nevertheless, F-actin depolymerization, known to block the different types of endocytic mechanisms, strongly impaired VacA vacuolating activity. Taken together, our data suggest that the high cell sensitivity to VacA depends on the presence of one or several GPI-anchored protein(s), intact membrane lipid rafts, and an uptake mechanism via a clathrin-independent endocytic pathway.
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Affiliation(s)
- V Ricci
- INSERM U452, Faculté de Médecine, 28 Avenue de Valombrose, 06107 Nice Cedex 2, France
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48
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Dharmawardhane S, Schürmann A, Sells MA, Chernoff J, Schmid SL, Bokoch GM. Regulation of macropinocytosis by p21-activated kinase-1. Mol Biol Cell 2000; 11:3341-52. [PMID: 11029040 PMCID: PMC14996 DOI: 10.1091/mbc.11.10.3341] [Citation(s) in RCA: 237] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The process of macropinocytosis is an essential aspect of normal cell function, contributing to both growth and motile processes of cells. p21-activated kinases (PAKs) are targets for activated Rac and Cdc42 guanosine 5'-triphosphatases and have been shown to regulate the actin-myosin cytoskeleton. In fibroblasts PAK1 localizes to areas of membrane ruffling, as well as to amiloride-sensitive pinocytic vesicles. Expression of a PAK1 kinase autoinhibitory domain blocked both platelet-derived growth factor- and RacQ61L-stimulated uptake of 70-kDa dextran particles, whereas an inactive version of this domain did not, indicating that PAK kinase activity is required for normal growth factor-induced macropinocytosis. The mechanisms by which PAK modulate macropinocytosis were examined in NIH3T3 cell lines expressing various PAK1 constructs under the control of a tetracycline-responsive transactivator. Cells expressing PAK1 (H83,86L), a mutant that dramatically stimulates formation of dorsal membrane ruffles, exhibited increased macropinocytic uptake of 70-kDa dextran particles in the absence of additional stimulation. This effect was not antagonized by coexpression of dominant-negative Rac1-T17N. In the presence of platelet-derived growth factor, both PAK1 (H83,86L) and a highly kinase active PAK1 (T423E) mutant dramatically enhanced the uptake of 70-kDa dextran. Neither wild-type PAK1 nor vector controls exhibited enhanced macropinocytosis, nor did PAK1 (H83,86L) affect clathrin-dependent endocytic mechanisms. Active versions of PAK1 enhanced both growth factor-stimulated 70-kDa dextran uptake and efflux, suggesting that PAK1 activity modulated pinocytic vesicle cycling. These data indicate that PAK1 plays an important regulatory role in the process of macropinocytosis, perhaps related to the requirement for PAK in directed cell motility.
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Affiliation(s)
- S Dharmawardhane
- Department of Immunology, The Scripps Research Institute, La Jolla, California 92037, USA
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49
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Guérin I, de Chastellier C. Disruption of the actin filament network affects delivery of endocytic contents marker to phagosomes with early endosome characteristics: the case of phagosomes with pathogenic mycobacteria. Eur J Cell Biol 2000; 79:735-49. [PMID: 11089922 DOI: 10.1078/0171-9335-00092] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Phagosomes containing live virulent mycobacteria undergo fusion with early endosomes, but they are unable to mature normally. Accordingly, they do not fuse with lysosomes. Although M. avium-containing phagosomes retain fusion and intermingling characteristics of early endosomes indefinitely, fusions with early endosomes are increasingly restricted as bacteria multiply. In addition, when endocytic tracers, such as horseradish peroxidase (HRP), are added to M. avium-infected macrophages at 1 or up to 15 days after infection, an atypical time course of acquisition of the tracer by the phagosomes is observed, i.e., a 10 to 20 min lag, instead of immediate acquisition as is typical for early endosomes (and phagosomes with early endosome characteristics). These events coincide with a marked disorganization of the actin filament network in M. avium-infected macrophages. In the present study, we have therefore addressed the following question: Do actin filaments play a role in fusion and intermingling of contents between early endosomes and immature phagosomes that undergo homotypic fusion with early endosomes? We examined the time course of acquisition of subsequently internalized endocytic marker (HRP) by early endosome-like preexisting phagosomes, i.e. 2 hour-old phagosomes with either hydrophobic latex particles, virulent or avirulent M. avium, after depolymerization of the actin filament network with cytochalasin D or after repolymerization of the actin filament network with jasplakinolide, in cases where the network had been depolymerized (macrophages infected with M. avium, at 1 or up to 7 days after infection). By direct morphological observation at the electron microscope level and by a kinetic approach, we show here that depolymerization of the actin filament network with cytochalasin D delays acquisition of HRP whereas repolymerization restores immediate acquisition of the marker. We conclude that the actin filament network is involved in fusion and intermingling of endocytic contents between early endosomes and early endosome-like phagosomes, and that disruption of this network by M. avium is the cause for the atypical acquisition of content marker by phagosomes containing these pathogenic mycobacteria.
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Affiliation(s)
- I Guérin
- Inserm U411, UFR de Médecine Necker, Paris, France
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50
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Pol A, Lu A, Pons M, Peiró S, Enrich C. Epidermal growth factor-mediated caveolin recruitment to early endosomes and MAPK activation. Role of cholesterol and actin cytoskeleton. J Biol Chem 2000; 275:30566-72. [PMID: 10889188 DOI: 10.1074/jbc.m001131200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The endocytic compartment of eukaryotic cells is a complex intracellular structure involved in sorting, processing, and degradation of a great variety of internalized molecules. Recently, the uptake through caveolae has emerged as an alternative internalization pathway, which seems to be directly related with some signal transduction pathways. However, the mechanisms, molecules, and structures regulating the transport of caveolin from the cell surface into the endocytic compartment are largely unknown. In this study, normal quiescent fibroblasts (normal rat kidney (NRK)) were used to demonstrate that epidermal growth factor causes partial redistribution of caveolin from the cell surface into a cellubrevin early endocytic compartment. Treatment of NRK cells with cytochalasin D or latrunculin A inhibits this pathway and the concomitant activation of Mek and mitotic-activated protein (MAP) kinase; however, if cells were pre-treated with filipin, cytochalasin D does not inhibit the phosphorylation of MAP kinase induced by epidermal growth factor. From these results we conclude that in NRK cells the intact actin cytoskeleton is necessary for the EGF-mediated transport of caveolin from the cell surface into the early endocytic compartment and the activation of MAP kinase pathway.
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Affiliation(s)
- A Pol
- Departament de Biologia Cel.lular, Institut d'Investigacions Biomèdiques August Pi Sunyer (IDIBAPS) Facultat de Medicina, Universitat de Barcelona, Casanova 143, 08036-Barcelona, Spain
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