101
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Underhill SM, Wheeler DS, Li M, Watts SD, Ingram SL, Amara SG. Amphetamine modulates excitatory neurotransmission through endocytosis of the glutamate transporter EAAT3 in dopamine neurons. Neuron 2014; 83:404-416. [PMID: 25033183 DOI: 10.1016/j.neuron.2014.05.043] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/27/2014] [Indexed: 12/15/2022]
Abstract
Amphetamines modify the brain and alter behavior through mechanisms generally attributed to their ability to regulate extracellular dopamine concentrations. However, the actions of amphetamine are also linked to adaptations in glutamatergic signaling. We report here that when amphetamine enters dopamine neurons through the dopamine transporter, it stimulates endocytosis of an excitatory amino acid transporter, EAAT3, in dopamine neurons. Consistent with this decrease in surface EAAT3, amphetamine potentiates excitatory synaptic responses in dopamine neurons. We also show that the process of internalization is dynamin- and Rho-mediated and requires a unique sequence in the cytosolic C terminus of EAAT3. Introduction of a peptide based on this motif into dopamine neurons blocks the effects of amphetamine on EAAT3 internalization and its action on excitatory responses. These data indicate that the internalization of EAAT3 triggered by amphetamine increases glutamatergic signaling and thus contributes to the effects of amphetamine on neurotransmission.
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Affiliation(s)
- Suzanne M Underhill
- Laboratory of Molecular and Cellular Neurobiology, NIH/NIMH, Bethesda, MD 20892, USA.
| | - David S Wheeler
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Minghua Li
- Department of Neurological Surgery, Oregon Health and Science University, Portland, OR 97239, USA
| | - Spencer D Watts
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Susan L Ingram
- Department of Neurological Surgery, Oregon Health and Science University, Portland, OR 97239, USA
| | - Susan G Amara
- Laboratory of Molecular and Cellular Neurobiology, NIH/NIMH, Bethesda, MD 20892, USA; Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA 15260, USA
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102
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Devarajan PV, Jain S, Dutta R. Infectious Diseases: Need for Targeted Drug Delivery. TARGETED DRUG DELIVERY : CONCEPTS AND DESIGN 2014. [PMCID: PMC7122176 DOI: 10.1007/978-3-319-11355-5_3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Infectious diseases are a leading cause of death worldwide, with the constant fear of global epidemics. It is indeed an irony that the reticuloendothelial system (RES), the body’s major defence system, is the primary site for intracellular infections which are more difficult to treat. Pro-inflammatory M1 macrophages play an important role in defence. However, ingenious pathogen survival mechanisms including phagolysosome destruction enable their persistence. Microbial biofilms present additional challenges. Low intracellular drug concentrations, drug efflux by efflux pumps and/or enzymatic degradation, emergence of multi-drug resistance (MDR), are serious limitations of conventional therapy. Targeted delivery using nanocarriers, and passive and active targeting strategies could provide quantum increase in intracellular drug concentration. Receptor mediated endocytosis using appropriate ligands is a viable approach. Liposomes and polymeric/lipidic nanoparticles, dendrimers micelles and micro/nanoemulsions could all be relied upon. Specialised targeting approaches are demonstrated for important diseases like tuberculosis, HIV and Malaria. Application of targeted delivery in the treatment of veterinary infections is exemplified and future possibilities indicated. The chapter thus provides an overview on important aspects of infectious diseases and the challenges therein, while stressing on the promise of targeted drug delivery in augmenting therapy of infectious diseases.
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Affiliation(s)
- Padma V. Devarajan
- grid.44871.3e0000000106680201Institute of Chemical Technology, Department of Pharmaceutical Sciences and Technology, Mumbai, India
| | - Sanyog Jain
- grid.419631.8000000008877852XNational Institute of Pharmaceutical Education and Research (NIPER), Centre for Pharmaceutical Nanotechnology, Department of Pharmaceutics, Mohali, Punjab India
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103
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Grove J, Metcalf DJ, Knight AE, Wavre-Shapton ST, Sun T, Protonotarios ED, Griffin LD, Lippincott-Schwartz J, Marsh M. Flat clathrin lattices: stable features of the plasma membrane. Mol Biol Cell 2014; 25:3581-94. [PMID: 25165141 PMCID: PMC4230618 DOI: 10.1091/mbc.e14-06-1154] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Clathrin-mediated endocytosis (CME) is a fundamental property of eukaryotic cells. Classical CME proceeds via the formation of clathrin-coated pits (CCPs) at the plasma membrane, which invaginate to form clathrin-coated vesicles, a process that is well understood. However, clathrin also assembles into flat clathrin lattices (FCLs); these structures remain poorly described, and their contribution to cell biology is unclear. We used quantitative imaging to provide the first comprehensive description of FCLs and explore their influence on plasma membrane organization. Ultrastructural analysis by electron and superresolution microscopy revealed two discrete populations of clathrin structures. CCPs were typified by their sphericity, small size, and homogeneity. FCLs were planar, large, and heterogeneous and present on both the dorsal and ventral surfaces of cells. Live microscopy demonstrated that CCPs are short lived and culminate in a peak of dynamin recruitment, consistent with classical CME. In contrast, FCLs were long lived, with sustained association with dynamin. We investigated the biological relevance of FCLs using the chemokine receptor CCR5 as a model system. Agonist activation leads to sustained recruitment of CCR5 to FCLs. Quantitative molecular imaging indicated that FCLs partitioned receptors at the cell surface. Our observations suggest that FCLs provide stable platforms for the recruitment of endocytic cargo.
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Affiliation(s)
- Joe Grove
- MRC Laboratory for Molecular Cell Biology, London WC1E 6BT, United Kingdom Institute of Immunity and Transplantation, University College London, London NW3 2PF, United Kingdom
| | - Daniel J Metcalf
- Biophysics and Diagnostics, National Physical Laboratory, Teddington TW11 0LW, United Kingdom
| | - Alex E Knight
- Biophysics and Diagnostics, National Physical Laboratory, Teddington TW11 0LW, United Kingdom
| | | | - Tony Sun
- MRC Laboratory for Molecular Cell Biology, London WC1E 6BT, United Kingdom
| | | | - Lewis D Griffin
- CoMPLEX, University College London, London WC1E 6BT, United Kingdom
| | - Jennifer Lippincott-Schwartz
- Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892
| | - Mark Marsh
- MRC Laboratory for Molecular Cell Biology, London WC1E 6BT, United Kingdom
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104
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Abstract
Of the many pathogens that infect humans and animals, a large number use cells of the host organism as protected sites for replication. To reach the relevant intracellular compartments, they take advantage of the endocytosis machinery and exploit the network of endocytic organelles for penetration into the cytosol or as sites of replication. In this review, we discuss the endocytic entry processes used by viruses and bacteria and compare the strategies used by these dissimilar classes of pathogens.
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Affiliation(s)
- Pascale Cossart
- Institut Pasteur, Unité des Interactions Bactéries-Cellules, Paris F-75015, France; INSERM U604, Paris F-75015, France; and INRA, USC2020, Paris F-75015, France
| | - Ari Helenius
- Institute of Biochemistry, ETH Zurich, 8093 Zurich, Switzerland
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105
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Croisé P, Estay-Ahumada C, Gasman S, Ory S. Rho GTPases, phosphoinositides, and actin: a tripartite framework for efficient vesicular trafficking. Small GTPases 2014; 5:e29469. [PMID: 24914539 DOI: 10.4161/sgtp.29469] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Rho GTPases are well known regulators of the actin cytoskeleton that act by binding and activating actin nucleators. They are therefore involved in many actin-based processes, including cell migration, cell polarity, and membrane trafficking. With the identification of phosphoinositide kinases and phosphatases as potential binding partners or effectors, Rho GTPases also appear to participate in the regulation of phosphoinositide metabolism. Since both actin dynamics and phosphoinositide turnover affect the efficiency and the fidelity of vesicle transport between cell compartments, Rho GTPases have emerged as critical players in membrane trafficking. Rho GTPase activity, actin remodeling, and phosphoinositide metabolism need to be coordinated in both space and time to ensure the progression of vesicles along membrane trafficking pathways. Although most molecular pathways are still unclear, in this review, we will highlight recent advances made in our understanding of how Rho-dependent signaling pathways organize actin dynamics and phosphoinositides and how phosphoinositides potentially provide negative feedback to Rho GTPases during endocytosis, exocytosis and membrane exchange between intracellular compartments.
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Affiliation(s)
- Pauline Croisé
- CNRS UPR 3212; Institut des Neurosciences Cellulaires et Intégratives; Université de Strasbourg; Strasbourg, France
| | - Catherine Estay-Ahumada
- CNRS UPR 3212; Institut des Neurosciences Cellulaires et Intégratives; Université de Strasbourg; Strasbourg, France
| | - Stéphane Gasman
- CNRS UPR 3212; Institut des Neurosciences Cellulaires et Intégratives; Université de Strasbourg; Strasbourg, France
| | - Stéphane Ory
- CNRS UPR 3212; Institut des Neurosciences Cellulaires et Intégratives; Université de Strasbourg; Strasbourg, France
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106
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Abstract
There are many pathways of endocytosis at the cell surface that apparently operate at the same time. With the advent of new molecular genetic and imaging tools, an understanding of the different ways by which a cell may endocytose cargo is increasing by leaps and bounds. In this review we explore pathways of endocytosis that occur in the absence of clathrin. These are referred to as clathrin-independent endocytosis (CIE). Here we primarily focus on those pathways that function at the small scale in which some have distinct coats (caveolae) and others function in the absence of specific coated intermediates. We follow the trafficking itineraries of the material endocytosed by these pathways and finally discuss the functional roles that these pathways play in cell and tissue physiology. It is likely that these pathways will play key roles in the regulation of plasma membrane area and tension and also control the availability of membrane during cell migration.
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Affiliation(s)
- Satyajit Mayor
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, and Institute for Stem Cell Biology and Regenerative Medicine, Bangalore 560065, India
| | - Robert G Parton
- The University of Queensland, Institute for Molecular Bioscience and Centre for Microscopy and Microanalysis, Queensland 4072, Brisbane, Australia
| | - Julie G Donaldson
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892
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107
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Lakshminarayan R, Wunder C, Becken U, Howes MT, Benzing C, Arumugam S, Sales S, Ariotti N, Chambon V, Lamaze C, Loew D, Shevchenko A, Gaus K, Parton RG, Johannes L. Galectin-3 drives glycosphingolipid-dependent biogenesis of clathrin-independent carriers. Nat Cell Biol 2014; 16:595-606. [PMID: 24837829 DOI: 10.1038/ncb2970] [Citation(s) in RCA: 215] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 04/15/2014] [Indexed: 12/17/2022]
Abstract
Several cell surface molecules including signalling receptors are internalized by clathrin-independent endocytosis. How this process is initiated, how cargo proteins are sorted and membranes are bent remains unknown. Here, we found that a carbohydrate-binding protein, galectin-3 (Gal3), triggered the glycosphingolipid (GSL)-dependent biogenesis of a morphologically distinct class of endocytic structures, termed clathrin-independent carriers (CLICs). Super-resolution and reconstitution studies showed that Gal3 required GSLs for clustering and membrane bending. Gal3 interacted with a defined set of cargo proteins. Cellular uptake of the CLIC cargo CD44 was dependent on Gal3, GSLs and branched N-glycosylation. Endocytosis of β1-integrin was also reliant on Gal3. Analysis of different galectins revealed a distinct profile of cargoes and uptake structures, suggesting the existence of different CLIC populations. We conclude that Gal3 functionally integrates carbohydrate specificity on cargo proteins with the capacity of GSLs to drive clathrin-independent plasma membrane bending as a first step of CLIC biogenesis.
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Affiliation(s)
- Ramya Lakshminarayan
- 1] Institut Curie-Centre de Recherche, Endocytic Trafficking and Therapeutic Delivery group, 26 rue d'Ulm, 75248 Paris Cedex 05, France [2] CNRS UMR3666, 75005 Paris, France [3] INSERM U1143, 75005 Paris, France [4] [5]
| | - Christian Wunder
- 1] Institut Curie-Centre de Recherche, Endocytic Trafficking and Therapeutic Delivery group, 26 rue d'Ulm, 75248 Paris Cedex 05, France [2] CNRS UMR3666, 75005 Paris, France [3] INSERM U1143, 75005 Paris, France [4] [5]
| | - Ulrike Becken
- 1] Institut Curie-Centre de Recherche, Endocytic Trafficking and Therapeutic Delivery group, 26 rue d'Ulm, 75248 Paris Cedex 05, France [2] CNRS UMR3666, 75005 Paris, France [3] INSERM U1143, 75005 Paris, France [4] [5]
| | - Mark T Howes
- Institute for Molecular Bioscience, University of Queensland, St Lucia, Queensland 4072, Australia
| | - Carola Benzing
- Centre for Vascular Research, Australian Centre for Nanomedicine and ARC Centre of Excellence in Advanced Molecular Imaging, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Senthil Arumugam
- 1] Institut Curie-Centre de Recherche, Endocytic Trafficking and Therapeutic Delivery group, 26 rue d'Ulm, 75248 Paris Cedex 05, France [2] CNRS UMR3666, 75005 Paris, France [3] INSERM U1143, 75005 Paris, France
| | - Susanne Sales
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307 Dresden, Germany
| | - Nicholas Ariotti
- Institute for Molecular Bioscience, University of Queensland, St Lucia, Queensland 4072, Australia
| | - Valérie Chambon
- 1] Institut Curie-Centre de Recherche, Endocytic Trafficking and Therapeutic Delivery group, 26 rue d'Ulm, 75248 Paris Cedex 05, France [2] CNRS UMR3666, 75005 Paris, France [3] INSERM U1143, 75005 Paris, France [4]
| | - Christophe Lamaze
- 1] CNRS UMR3666, 75005 Paris, France [2] INSERM U1143, 75005 Paris, France [3] Institut Curie-Centre de Recherche, Membrane Dynamics and Mechanics of Intracellular Signaling group, 26 rue d'Ulm, 75248 Paris Cedex 05, France [4]
| | - Damarys Loew
- Institut Curie-Centre de Recherche, Proteomics and Mass Spectrometry Laboratory, 26 rue d'Ulm, 75248 Paris Cedex 05, France
| | - Andrej Shevchenko
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307 Dresden, Germany
| | - Katharina Gaus
- Centre for Vascular Research, Australian Centre for Nanomedicine and ARC Centre of Excellence in Advanced Molecular Imaging, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Robert G Parton
- Institute for Molecular Bioscience, University of Queensland, St Lucia, Queensland 4072, Australia
| | - Ludger Johannes
- 1] Institut Curie-Centre de Recherche, Endocytic Trafficking and Therapeutic Delivery group, 26 rue d'Ulm, 75248 Paris Cedex 05, France [2] CNRS UMR3666, 75005 Paris, France [3] INSERM U1143, 75005 Paris, France [4]
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108
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Chaudhary N, Gomez GA, Howes MT, Lo HP, McMahon KA, Rae JA, Schieber NL, Hill MM, Gaus K, Yap AS, Parton RG. Endocytic crosstalk: cavins, caveolins, and caveolae regulate clathrin-independent endocytosis. PLoS Biol 2014; 12:e1001832. [PMID: 24714042 PMCID: PMC3979662 DOI: 10.1371/journal.pbio.1001832] [Citation(s) in RCA: 110] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Accepted: 02/25/2014] [Indexed: 12/18/2022] Open
Abstract
Caveolar proteins and caveolae negatively regulate a second clathrin-independent endocytic CLIC/GEEC pathway; caveolin-1 affects membrane diffusion properties of raft-associated CLIC cargo, and the scaffolding domain of caveolin-1 is required and sufficient for endocytic inhibition. Several studies have suggested crosstalk between different clathrin-independent endocytic pathways. However, the molecular mechanisms and functional relevance of these interactions are unclear. Caveolins and cavins are crucial components of caveolae, specialized microdomains that also constitute an endocytic route. Here we show that specific caveolar proteins are independently acting negative regulators of clathrin-independent endocytosis. Cavin-1 and Cavin-3, but not Cavin-2 or Cavin-4, are potent inhibitors of the clathrin-independent carriers/GPI-AP enriched early endosomal compartment (CLIC/GEEC) endocytic pathway, in a process independent of caveola formation. Caveolin-1 (CAV1) and CAV3 also inhibit the CLIC/GEEC pathway upon over-expression. Expression of caveolar protein leads to reduction in formation of early CLIC/GEEC carriers, as detected by quantitative electron microscopy analysis. Furthermore, the CLIC/GEEC pathway is upregulated in cells lacking CAV1/Cavin-1 or with reduced expression of Cavin-1 and Cavin-3. Inhibition by caveolins can be mimicked by the isolated caveolin scaffolding domain and is associated with perturbed diffusion of lipid microdomain components, as revealed by fluorescence recovery after photobleaching (FRAP) studies. In the absence of cavins (and caveolae) CAV1 is itself endocytosed preferentially through the CLIC/GEEC pathway, but the pathway loses polarization and sorting attributes with consequences for membrane dynamics and endocytic polarization in migrating cells and adult muscle tissue. We also found that noncaveolar Cavin-1 can act as a modulator for the activity of the key regulator of the CLIC/GEEC pathway, Cdc42. This work provides new insights into the regulation of noncaveolar clathrin-independent endocytosis by specific caveolar proteins, illustrating multiple levels of crosstalk between these pathways. We show for the first time a role for specific cavins in regulating the CLIC/GEEC pathway, provide a new tool to study this pathway, identify caveola-independent functions of the cavins and propose a novel mechanism for inhibition of the CLIC/GEEC pathway by caveolin. Endocytosis is the process that allows cells to take up molecules from the environment. Several endocytic pathways exist in mammalian cells. While the best understood endocytic pathway uses clathrin, recent years have seen a great increase in our understanding of clathrin-independent endocytic pathways. Here we characterize the crosstalk between caveolae, flask-shaped specialized microdomains present at the plasma membrane, and a second clathrin-independent pathway, the CLIC/GEEC Cdc42-regulated endocytic pathway. These pathways are segregated in migrating cells with caveolae at the rear and CLIC/GEEC endocytosis at the leading edge. Here we find that specific caveolar proteins, caveolins and cavins, can also negatively regulate the CLIC/GEEC pathway. With the help of several techniques, including quantitative electron microscopy analysis and real-time live-cell imaging, we demonstrate that expression of caveolar proteins affects early carrier formation, causes cellular lipid changes, and changes the activity of the key regulator of the CLIC/GEEC pathway, Cdc42. The functional consequences of loss of caveolar proteins on the CLIC/GEEC pathway included inhibition of polarized cell migration and increased endocytosis in tissue explants.
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Affiliation(s)
- Natasha Chaudhary
- The University of Queensland, Institute for Molecular Bioscience, Queensland, Australia
| | - Guillermo A. Gomez
- The University of Queensland, Institute for Molecular Bioscience, Queensland, Australia
| | - Mark T. Howes
- The University of Queensland, Institute for Molecular Bioscience, Queensland, Australia
| | - Harriet P. Lo
- The University of Queensland, Institute for Molecular Bioscience, Queensland, Australia
| | - Kerrie-Ann McMahon
- The University of Queensland, Institute for Molecular Bioscience, Queensland, Australia
| | - James A. Rae
- The University of Queensland, Institute for Molecular Bioscience, Queensland, Australia
| | - Nicole L. Schieber
- The University of Queensland, Institute for Molecular Bioscience, Queensland, Australia
| | - Michelle M. Hill
- The University of Queensland, Diamantina Institute, Queensland, Australia
| | - Katharina Gaus
- The University of New South Wales, Centre for Vascular Research and Australian Centre for Nanomedicine, New South Wales, Australia
| | - Alpha S. Yap
- The University of Queensland, Institute for Molecular Bioscience, Queensland, Australia
| | - Robert G. Parton
- The University of Queensland, Institute for Molecular Bioscience, Queensland, Australia
- Centre for Microscopy and Microanalysis, Queensland, Australia
- * E-mail:
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109
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Dewerchin HL, Desmarets LM, Noppe Y, Nauwynck HJ. Myosins 1 and 6, myosin light chain kinase, actin and microtubules cooperate during antibody-mediated internalisation and trafficking of membrane-expressed viral antigens in feline infectious peritonitis virus infected monocytes. Vet Res 2014; 45:17. [PMID: 24517254 PMCID: PMC3937040 DOI: 10.1186/1297-9716-45-17] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Accepted: 01/29/2014] [Indexed: 12/20/2022] Open
Abstract
Monocytes infected with feline infectious peritonitis virus, a coronavirus, express viral proteins in their plasma membranes. Upon binding of antibodies, these proteins are quickly internalised through a new clathrin- and caveolae-independent internalisation pathway. By doing so, the infected monocytes can escape antibody-dependent cell lysis. In the present study, we investigated which kinases and cytoskeletal proteins are of importance during internalisation and subsequent intracellular transport. The experiments showed that myosin light chain kinase (MLCK) and myosin 1 are crucial for the initiation of the internalisation. With co-localisation stainings, it was found that MLCK and myosin 1 co-localise with antigens even before internalisation started. Myosin 6 co-localised with the internalising complexes during passage through the cortical actin, were it might play a role in moving or disintegrating actin filaments, to overcome the actin barrier. One minute after internalisation started, vesicles had passed the cortical actin, co-localised with microtubules and association with myosin 6 was lost. The vesicles were further transported over the microtubules and accumulated at the microtubule organising centre after 10 to 30 min. Intracellular trafficking over microtubules was mediated by MLCK, myosin 1 and a small actin tail. Since inhibiting MLCK with ML-7 was so efficient in blocking the internalisation pathway, this target can be used for the development of a new treatment for FIPV.
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Affiliation(s)
| | | | | | - Hans J Nauwynck
- Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium.
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110
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Sandvig K, Bergan J, Kavaliauskiene S, Skotland T. Lipid requirements for entry of protein toxins into cells. Prog Lipid Res 2014; 54:1-13. [PMID: 24462587 DOI: 10.1016/j.plipres.2014.01.001] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Revised: 01/15/2014] [Accepted: 01/15/2014] [Indexed: 01/05/2023]
Abstract
The plant toxin ricin and the bacterial toxin Shiga toxin both belong to a group of protein toxins having one moiety that binds to the cell surface, and another, enzymatically active moiety, that enters the cytosol and inhibits protein synthesis by inactivating ribosomes. Both toxins travel all the way from the cell surface to endosomes, the Golgi apparatus and the ER before the ribosome-inactivating moiety enters the cytosol. Shiga toxin binds to the neutral glycosphingolipid Gb3 at the cell surface and is therefore dependent on this lipid for transport into the cells, whereas ricin binds both glycoproteins and glycolipids with terminal galactose. The different steps of transport used by these toxins have specific requirements for lipid species, and with the recent developments in mass spectrometry analysis of lipids and microscopical and biochemical dissection of transport in cells, we are starting to see the complexity of endocytosis and intracellular transport. In this article we describe lipid requirements and the consequences of lipid changes for the entry and intoxication with ricin and Shiga toxin. These toxins can be a threat to human health, but can also be exploited for diagnosis and therapy, and have proven valuable as tools to study intracellular transport.
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Affiliation(s)
- Kirsten Sandvig
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway; Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; Department of Biosciences, University of Oslo, Oslo, Norway.
| | - Jonas Bergan
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway; Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway.
| | - Simona Kavaliauskiene
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway; Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway; Department of Biosciences, University of Oslo, Oslo, Norway.
| | - Tore Skotland
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway; Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway.
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111
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Abstract
Endocytosis is an essential process of eukaryotic cells that facilitates numerous cellular and organismal functions. The formation of vesicles from the plasma membrane serves the internalization of ligands and receptors and leads to their degradation or recycling. A number of distinct mechanisms have been described over the years, several of which are only partially characterized in terms of mechanism and function. These are often referred to as novel endocytic pathways. The pathways differ in their mode of uptake and in their intracellular destination. Here, an overview of the set of cellular proteins that facilitate the different pathways is provided. Further, the approaches to distinguish between the pathways by different modes of perturbation are critically discussed, emphasizing the use of genetic tools such as dominant negative mutant proteins.
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Affiliation(s)
- Lena Kühling
- Emmy Noether Group: Virus Endocytosis, Institutes of Molecular Virology and Medical Biochemistry, ZMBE, Westphalian Wilhelms University of Münster, Von-Esmarch-Str. 56, Münster, 48149, Germany
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112
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Lagache T, Lang G, Sauvonnet N, Olivo-Marin JC. Analysis of the spatial organization of molecules with robust statistics. PLoS One 2013; 8:e80914. [PMID: 24349021 PMCID: PMC3857798 DOI: 10.1371/journal.pone.0080914] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Accepted: 10/15/2013] [Indexed: 02/07/2023] Open
Abstract
One major question in molecular biology is whether the spatial distribution of observed molecules is random or organized in clusters. Indeed, this analysis gives information about molecules’ interactions and physical interplay with their environment. The standard tool for analyzing molecules’ distribution statistically is the Ripley’s K function, which tests spatial randomness through the computation of its critical quantiles. However, quantiles’ computation is very cumbersome, hindering its use. Here, we present an analytical expression of these quantiles, leading to a fast and robust statistical test, and we derive the characteristic clusters’ size from the maxima of the Ripley’s K function. Subsequently, we analyze the spatial organization of endocytic spots at the cell membrane and we report that clathrin spots are randomly distributed while clathrin-independent spots are organized in clusters with a radius of , which suggests distinct physical mechanisms and cellular functions for each pathway.
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Affiliation(s)
- Thibault Lagache
- Unité d’Analyse d’Images Quantitative, Institut Pasteur, Paris, France
- Unité de Recherche Associée 2582, Centre National de la Recherche Scientifique, Paris, France
- * E-mail: (TL); (JCOM)
| | - Gabriel Lang
- Unité Mixte de Recherche 518 Mathématiques et Informatique Appliquées, AgroParisTech and INRA, Paris, France
| | - Nathalie Sauvonnet
- Unité de Recherche Associée 2582, Centre National de la Recherche Scientifique, Paris, France
- Unité de Biologie des Interactions Cellulaires, Institut Pasteur, Paris, France
| | - Jean-Christophe Olivo-Marin
- Unité d’Analyse d’Images Quantitative, Institut Pasteur, Paris, France
- Unité de Recherche Associée 2582, Centre National de la Recherche Scientifique, Paris, France
- * E-mail: (TL); (JCOM)
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113
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Waysbort N, Russ D, Chain BM, Friedman N. Coupled IL-2-dependent extracellular feedbacks govern two distinct consecutive phases of CD4 T cell activation. THE JOURNAL OF IMMUNOLOGY 2013; 191:5822-30. [PMID: 24244020 DOI: 10.4049/jimmunol.1301575] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
T cells integrate cell-specific Ag receptor signaling with shared signals mediated by secreted cytokines, which often involve regulatory feedback loops. IL-2 signaling, for example, reduces the synthesis of IL-2 and increases the synthesis of IL-2Rα-chain, whereas both genes require TCR signaling for their activation. The ways by which T cells dynamically integrate these private and public signals during activation are not well understood. We combined robotics, multiparameter flow cytometry, and real-time quantitative PCR to analyze T cell activation at high temporal resolution over several days. Two distinct temporal phases of T cell activation were evident. First, Ag-dependent signals activated low IL-2Rα and high IL-2 production, independent of IL-2 signaling. Subsequently, secreted IL-2 acted as a shared resource driving high IL-2Rα expression, reduced IL-2 synthesis, and cell proliferation. This transition was independent of continued TCR signaling. Our data allowed the determination of the parameters of the IL-2-mediated extracellular positive and negative feedback circuits and demonstrated that the two loops are coupled and become activated at a similar level of IL-2 signaling. We propose that temporal separation of private and shared signals allows T cells to first integrate Ag-specific responses and subsequently share information leading to collective decision making.
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Affiliation(s)
- Nir Waysbort
- Department of Immunology, Weizmann Institute of Science, Rehovot 76100, Israel
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114
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Blouin CM. [Clathrin-independent endocytosis: free the way!]. Med Sci (Paris) 2013; 29:890-6. [PMID: 24148128 DOI: 10.1051/medsci/20132910017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Along the years, the interest paid to the study of endocytosis has never wavered as this process plays such an essential role in many cellular functions. Cell growth, adhesion and differentiation, regulation of signaling induced by membrane receptors or infection by viral particles are all dependent on the entry of molecules into the cell. Once the clathrin-dependent endocytosis well characterized, it has become apparent that other entry pathways also existed in the cell. This review is intended to provide an update on recent advances that establish with certainty the existence of endocytic pathways independent of clathrin and highlight their specific regulators.
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Affiliation(s)
- Cédric M Blouin
- Institut Curie, CNRS UMR144, Laboratoire Trafic, signalisation et ciblages intracellulaires, 26, rue d'Ulm, 75248 Paris Cedex 05, France
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Osorio-Espinoza A, Escamilla-Sánchez J, Aquino-Jarquin G, Arias-Montaño JA. Homologous desensitization of human histamine H₃ receptors expressed in CHO-K1 cells. Neuropharmacology 2013; 77:387-97. [PMID: 24161268 DOI: 10.1016/j.neuropharm.2013.09.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Revised: 09/06/2013] [Accepted: 09/09/2013] [Indexed: 11/18/2022]
Abstract
Histamine H₃ receptors (H₃Rs) modulate the function of the nervous system at the pre- and post-synaptic levels. In this work we aimed to determine whether, as other G protein-coupled receptors (GPCRs), H₃Rs desensitize in response to agonist exposure. By using CHO-K1 cells stably transfected with the human H₃R (hH3R) we show that functional responses (inhibition of forskolin-induced cAMP accumulation in intact cells and stimulation of [(35)S]-GTPγS binding to cell membranes) were markedly reduced after agonist exposure. For cAMP accumulation assays the effect was significant at 60 min with a maximum at 90 min. Agonist exposure resulted in decreased binding sites for the radioligand [(3)H]-N-methyl-histamine ([(3)H]-NMHA) to intact cells and modified the sub-cellular distribution of H₃Rs, as detected by sucrose density gradients and [(3)H]-NMHA binding to cell membranes, suggesting receptor internalization. The reduction in the inhibition of forskolin-stimulated cAMP formation observed after agonist pre-incubation was prevented by incubation in hypertonic medium or in ice-cold medium. Agonist-induced loss in binding sites was also prevented by hypertonic medium or incubation at 4 °C, but not by filipin III, indicating clathrin-dependent endocytosis. Immunodetection showed that CHO-K1 cells express GPCR kinases (GRKs) 2/3, and both the GRK general inhibitor ZnCl₂ and a small interfering RNA against GRK-2 reduced receptor desensitization. Taken together these results indicate that hH₃Rs experience homologous desensitization upon prolonged exposure to agonists, and that this process involves the action of GRK-2 and internalization via clathrin-coated vesicles.
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Affiliation(s)
- Angélica Osorio-Espinoza
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, Av. IPN 2508, Zacatenco, 07360 México, D.F., Mexico
| | - Juan Escamilla-Sánchez
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, Av. IPN 2508, Zacatenco, 07360 México, D.F., Mexico
| | - Guillermo Aquino-Jarquin
- Unidad de Investigación en Enfermedades Oncológicas, Hospital Infantil de México Federico Gómez, Dr. Márquez 162, Col. Doctores, 06720 México, D.F., Mexico
| | - José-Antonio Arias-Montaño
- Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, Av. IPN 2508, Zacatenco, 07360 México, D.F., Mexico.
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116
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González-Jamett AM, Momboisse F, Haro-Acuña V, Bevilacqua JA, Caviedes P, Cárdenas AM. Dynamin-2 function and dysfunction along the secretory pathway. Front Endocrinol (Lausanne) 2013; 4:126. [PMID: 24065954 PMCID: PMC3776141 DOI: 10.3389/fendo.2013.00126] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Accepted: 08/31/2013] [Indexed: 12/21/2022] Open
Abstract
Dynamin-2 is a ubiquitously expressed mechano-GTPase involved in different stages of the secretory pathway. Its most well-known function relates to the scission of nascent vesicles from the plasma membrane during endocytosis; however, it also participates in the formation of new vesicles from the Golgi network, vesicle trafficking, fusion processes and in the regulation of microtubule, and actin cytoskeleton dynamics. Over the last 8 years, more than 20 mutations in the dynamin-2 gene have been associated to two hereditary neuromuscular disorders: Charcot-Marie-Tooth neuropathy and centronuclear myopathy. Most of these mutations are grouped in the pleckstrin homology domain; however, there are no common mutations associated with both disorders, suggesting that they differently impact on dynamin-2 function in diverse tissues. In this review, we discuss the impact of these disease-related mutations on dynamin-2 function during vesicle trafficking and endocytotic processes.
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Affiliation(s)
- Arlek M. González-Jamett
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Fanny Momboisse
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Valentina Haro-Acuña
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Jorge A. Bevilacqua
- Programa de Anatomía y Biología del Desarrollo, ICBM, Facultad de Medicina, Departamento de Neurología y Neurocirugía, Hospital Clínico Universidad de Chile, Universidad de Chile, Santiago, Chile
| | - Pablo Caviedes
- Programa de Farmacología Molecular y Clínica, ICBM, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Ana María Cárdenas
- Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
- *Correspondence: Ana María Cárdenas, Facultad de Ciencias, Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Gran Bretaña 1111, Playa Ancha 2360102, Valparaíso, Chile e-mail:
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117
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Blouin CM, Lamaze C. Interferon gamma receptor: the beginning of the journey. Front Immunol 2013; 4:267. [PMID: 24027571 PMCID: PMC3760442 DOI: 10.3389/fimmu.2013.00267] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Accepted: 08/19/2013] [Indexed: 12/17/2022] Open
Abstract
Our view of endocytosis and membrane trafficking of transmembrane receptors has dramatically changed over the last 20 years. Several new endocytic routes have been discovered and mechanistically characterized in mammalian cells. Long considered as a passive means to terminate signaling through down-regulation of the number of activated receptors at the plasma membrane, it is now established that receptor endocytosis and endosomal sorting can be directly linked to the regulation of intracellular signaling pathways. The functional links between membrane trafficking of interferon receptors and JAK/STAT signaling have recently begun to be unraveled. These studies raise the exciting possibility that a certain level of signal specificity can be achieved through endocytosis and selective localization of the activated complexes within cellular membranes. The ongoing development of high-resolution cell imaging techniques with better spatial and temporal resolution gives new means of deciphering the inherent complexity of membrane trafficking and signaling. This should help to better comprehend the molecular mechanisms by which endocytosis and endosomal sorting of interferon receptors can orchestrate signaling selectivity within the JAK/STAT pathway that can be activated by as many as 60 different cytokines, growth factors, and hormones.
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Affiliation(s)
- Cédric M. Blouin
- Laboratoire Trafic, Signalisation et Ciblage Intracellulaires, Institut Curie – Centre de Recherche, Paris, France
- CNRS UMR144, Paris, France
| | - Christophe Lamaze
- Laboratoire Trafic, Signalisation et Ciblage Intracellulaires, Institut Curie – Centre de Recherche, Paris, France
- CNRS UMR144, Paris, France
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118
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Cleyrat C, Darehshouri A, Anderson KL, Page C, Lidke DS, Volkmann N, Hanein D, Wilson BS. The architectural relationship of components controlling mast cell endocytosis. J Cell Sci 2013; 126:4913-25. [PMID: 23986485 DOI: 10.1242/jcs.128876] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Eukaryotic cells use multiple routes for receptor internalization. Here, we examine the topographical relationships of clathrin-dependent and clathrin-independent endocytic structures on the plasma membranes of leukemia-derived mast cells. The high affinity IgE receptor (FcεRI) utilizes both pathways, whereas transferrin receptor serves as a marker for the classical clathrin-mediated endocytosis pathway. Both receptors were tracked by live-cell imaging in the presence or absence of inhibitors that established their differential dependence on specific endocytic adaptor proteins. The topology of antigen-bound FcεRI, clathrin, dynamin, Arf6 and Eps15-positive structures were analyzed by 2D and 3D immunoelectron microscopy techniques, revealing their remarkable spatial relationships and unique geometry. We conclude that the mast cell plasma membrane has multiple specialized domains for endocytosis. Their close proximity might reflect shared components, such as lipids and adaptor proteins, that facilitate inward membrane curvature. Intersections between these specialized domains might represent sorting stations that direct cargo to specific endocytic pathways.
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Affiliation(s)
- Cédric Cleyrat
- Department of Pathology University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA
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119
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Maldonado-Báez L, Williamson C, Donaldson JG. Clathrin-independent endocytosis: a cargo-centric view. Exp Cell Res 2013; 319:2759-69. [PMID: 23954817 DOI: 10.1016/j.yexcr.2013.08.008] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Revised: 08/06/2013] [Accepted: 08/07/2013] [Indexed: 12/12/2022]
Abstract
Clathrin-independent endocytosis occurs in all cells and interest in this mode of cellular entry has grown. Although this form of endocytosis was first described for entry of bacterial toxins, here we focus our attention on the endogenous cell surface "cargo" proteins that enter cells by this mechanism. The cargo proteins entering by this mechanism are varied and include nutrient transporters, ion channels, cell adhesion molecules and proteins associated with the immune system. Despite the apparent lack of selection at the cell surface, we provide some examples of specific sorting of these cargo proteins after entry, leading to distinct itineraries and cellular fates.
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Affiliation(s)
- Lymarie Maldonado-Báez
- Cell Biology & Physiology Center, National Heart, Lung and Blood Institute, NIH, Bethesda, MD 20892, USA
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120
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Augmented adenovirus transduction of murine T lymphocytes utilizing a bi-specific protein targeting murine interleukin 2 receptor. Cancer Gene Ther 2013; 20:445-52. [PMID: 23928733 DOI: 10.1038/cgt.2013.39] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Accepted: 05/18/2013] [Indexed: 11/08/2022]
Abstract
Adenoviruses are currently used in a variety of bench and bedside applications. However, their employment in gene delivery to lymphocyte lineages is hampered by the lack of coxsackie virus and adenovirus receptor (CAR) on the cell surface. Exploitation of an alternative receptor on the surface of T lymphocytes can allow for utilization of adenovirus in a variety of T lymphocyte-based diseases and therapies. Here, we describe how resistance to infection can be overcome by the utilization of a bi-specific fusion protein, soluble CAR murine interleukin 2 (sCAR-mIL-2), that retargets adenovirus to the murine IL-2 receptor (IL-2R). Infection of a murine T-cell line, CTLL-2, with a sCAR-mIL-2/Adenovirus conjugate provided a ninefold increase in both green fluorescence protein-positive cells and luciferase expression. In addition, this increase in infection was also seen in isolated primary murine T lymphocytes. In this context, the sCAR-mIL-2 adapter provided a fourfold gene transduction increase in activated primary murine T lymphocytes. Our results show that recombinant sCAR-mIL-2 fusion protein promotes IL-2R-targeted gene transfer to murine T lymphocytes and that alternative targeting can abrogate their native resistance to infection.
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121
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Basquin C, Sauvonnet N. Phosphoinositide 3-kinase at the crossroad between endocytosis and signaling of cytokine receptors. Commun Integr Biol 2013; 6:e24243. [PMID: 23986799 PMCID: PMC3737753 DOI: 10.4161/cib.24243] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Accepted: 03/05/2013] [Indexed: 12/24/2022] Open
Abstract
Class I phosphoinositide 3-kinase (PI3K) is a lipid kinase playing key roles in many signaling pathways regulating cell survival and growth. Besides its important role in signal transduction, PI3K is also involved in actin and membrane reorganization such as protrusion, adhesion, phagocytosis and macropinocytosis. Receptor-mediated endocytosis is initiated by plasma membrane reorganization creating buds that then mature to small vesicles. Whereas most of endocytic mechanisms involve actin polymerization, PI3K requirement has not been clearly investigated. Our study identifies class I PI3K as a key player in clathrin-independent endocytosis of the interleukin 2 receptor (IL-2R) in contrast to the clathrin-dependent entry of transferrin (Tf). IL-2R is a cytokine receptor, inducing several signaling cascades such as PI3K, that are essential for the immune response. We have shown previously that IL-2R can be internalized with or without IL-2 and this process requires dynamin, actin and their regulators cortactin, N-WASP, Rac1 and the kinases Pak. Our recent work reveals that PI3K regulates Rac1 during IL-2R uptake in two ways: via its catalytic activity (p110) and via its regulatory factor (p85). Indeed, the catalytic activity of PI3K is required for both constitutive and IL-2 induced uptake of cytokine receptors, in lymphocytes as well as in epithelial cells. Interestingly, Vav2, a Rac1 GTPase exchange factor (GEF) induced upon PI3K activation, is specifically involved and recruited during IL-2R uptake. The second action of PI3K is via its regulatory subunit, p85, which binds activated Rac1 and IL-2R; this interaction being enhanced upon IL-2 treatment. Thus, PI3K regulates both the activation of Rac1 and its recruitment during IL-2R endocytosis. Finally, our results identify a link between cytokine receptors signaling and clathrin-independent endocytosis.
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Affiliation(s)
- Cyril Basquin
- Institut Pasteur; Unité de Biologie des Interactions Cellulaires; Paris, France ; CNRS URA 2582; Dynamique des Interactions Cellulaires; Paris, France
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Delmas D, Aires V, Colin DJ, Limagne E, Scagliarini A, Cotte AK, Ghiringhelli F. Importance of lipid microdomains, rafts, in absorption, delivery, and biological effects of resveratrol. Ann N Y Acad Sci 2013; 1290:90-7. [DOI: 10.1111/nyas.12177] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Dominique Delmas
- University of Burgundy; Dijon France
- Chemotherapy, Lipid Metabolism and Antitumoral Immune Response Team; INSERM Research Center U866; Dijon France
| | - Virginie Aires
- University of Burgundy; Dijon France
- Chemotherapy, Lipid Metabolism and Antitumoral Immune Response Team; INSERM Research Center U866; Dijon France
| | - Didier J. Colin
- Center for Biomedical Imaging (CIBM)-microPET Imaging Laboratory; University of Geneva; Geneva Switzerland
| | - Emeric Limagne
- University of Burgundy; Dijon France
- Chemotherapy, Lipid Metabolism and Antitumoral Immune Response Team; INSERM Research Center U866; Dijon France
| | - Alessandra Scagliarini
- University of Burgundy; Dijon France
- Chemotherapy, Lipid Metabolism and Antitumoral Immune Response Team; INSERM Research Center U866; Dijon France
| | - Alexia K. Cotte
- University of Burgundy; Dijon France
- Chemotherapy, Lipid Metabolism and Antitumoral Immune Response Team; INSERM Research Center U866; Dijon France
| | - François Ghiringhelli
- University of Burgundy; Dijon France
- Chemotherapy, Lipid Metabolism and Antitumoral Immune Response Team; INSERM Research Center U866; Dijon France
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Prosser DC, Wendland B. Conserved roles for yeast Rho1 and mammalian RhoA GTPases in clathrin-independent endocytosis. Small GTPases 2013; 3:229-35. [PMID: 23238351 PMCID: PMC3520887 DOI: 10.4161/sgtp.21631] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Eukaryotic cells use numerous endocytic pathways for nutrient uptake, protein turnover and response to the extracellular environment. While clathrin-mediated endocytosis (CME) has been extensively studied in yeast and mammalian cells, recent studies in higher eukaryotes have described multiple clathrin-independent endocytic pathways that depend upon Rho family GTPases and their effector proteins. In contrast, yeast cells have been thought to rely solely on CME. In a recent study, we used CME-defective yeast cells lacking clathrin-binding endocytic adaptor proteins in a genetic screen to identify novel factors involved in endocytosis. This approach revealed the existence of a clathrin-independent endocytic pathway involving the GTPase Rho1, which is the yeast homolog of RhoA. Further characterization of the yeast Rho1-mediated endocytic pathway suggested that the Rho1 pathway requires additional proteins that appear to play conserved roles in RhoA-dependent, clathrin-independent endocytic pathways in mammalian cells. Here, we discuss the parallels between the yeast Rho1-dependent and mammalian RhoA-dependent endocytic pathways, as well as the applications of yeast as a model for studying clathrin-independent endocytosis in higher eukaryotes.
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Affiliation(s)
- Derek C Prosser
- Department of Biology, The John Hopkins University, Baltimore, MD, USA.
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Clostridium difficile binary toxin CDT induces clustering of the lipolysis-stimulated lipoprotein receptor into lipid rafts. mBio 2013; 4:e00244-13. [PMID: 23631918 PMCID: PMC3648903 DOI: 10.1128/mbio.00244-13] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Clostridium difficile is the leading cause of antibiotics-associated diarrhea and pseudomembranous colitis. Hypervirulent C. difficile strains produce the binary actin-ADP-ribosylating toxin CDT (C. difficile transferase), in addition to the Rho-glucosylating toxins A and B. We recently identified the lipolysis-stimulated lipoprotein receptor (LSR) as the host receptor that mediates uptake of CDT into target cells. Here we investigated in H1-HeLa cells, which ectopically express LSR, the influence of CDT on the plasma membrane distribution of the receptor. We found by fluorescence microscopy that the binding component of CDT (CDTb) induces clustering of LSR into subcompartments of the plasma membrane. Detergent extraction of cells treated with CDTb, followed by sucrose gradient fractionation, uncovered accumulation of LSR in detergent-resistant membranes (DRMs) that contained typical marker proteins of lipid rafts. Membrane cholesterol depletion with methyl-β-cyclodextrin inhibited the association of LSR with DRMs upon addition of CDTb. The receptor-binding domain of CDTb also triggered LSR clustering into DRMs. CDTb-triggered clustering of LSR into DRMs could be confirmed in Caco-2 cells. Our data suggest that CDT forces its receptor to cluster into lipid rafts and that oligomerization of the B component might enhance but is not essential for this process. C. difficile binary toxin CDT is a member of the iota-like, actin ADP-ribosylating toxin family. The mechanism that mediates endocytic uptake of these toxins still remains elusive. Previous studies highlighted the importance of lipid rafts for oligomerization of the binding component of these toxins and for cell entry. Recently, the host cell receptor for this toxin family, namely, the lipolysis-stimulated lipoprotein receptor (LSR), has been identified. Our study now demonstrates that the binding component of CDT (CDTb) induces clustering of LSR into lipid rafts. Importantly, LSR clustering is efficiently induced also by the receptor-binding domain of CDTb, suggesting that oligomerization of the B component of CDT is not the main trigger of this process. The current work extends our knowledge on the cooperative play between iota-like toxins and their receptor.
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125
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Endocytosis of gene delivery vectors: from clathrin-dependent to lipid raft-mediated endocytosis. Mol Ther 2013; 21:1118-30. [PMID: 23587924 DOI: 10.1038/mt.2013.54] [Citation(s) in RCA: 226] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The ideal nonviral vector delivers its nucleic acid cargo to a specific intracellular target. Vectors enter cells mainly through endocytosis and are distributed to various intracellular organelles. Recent advances in microscopy, lipidomics, and proteomics confirm that the cell membrane is composed of clusters of lipids, organized in the form of lipid raft domains, together with non-raft domains that comprise a generally disordered lipid milieu. The binding of a nonviral vector to either region can determine the pathway for its endocytic uptake and subsequent intracellular itinerary. Given this model of the cell membrane structure, endocytic pathways should be reclassified in relation to lipid rafts. In this review, we attempt to assess the currently recognized endocytic pathways in mammalian cells. The endocytic pathways are classified in relation to the membrane regions that make up the primary endocytic vesicles. This review covers the well-recognized clathrin-mediated endocytosis (CME), phagocytosis, and macropinocytosis in addition to the less addressed pathways that take place in lipid rafts. These include caveolae-mediated, flotillin-dependent, GTPase regulator associated with focal adhesion kinase-1 (GRAF1)-dependent, adenosine diphosphate-ribosylation factor 6 (Arf6)-dependent, and RhoA-dependent endocytic pathways. We summarize the regulators associated with each uptake pathway and methods for interfering with these regulators are discussed. The fate of endocytic vesicles resulting from each endocytic uptake pathway is highlighted.
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Bhattacharyya S, Mulherkar N, Chandran K. Endocytic pathways involved in filovirus entry: advances, implications and future directions. Viruses 2013; 4:3647-64. [PMID: 23342373 PMCID: PMC3528284 DOI: 10.3390/v4123647] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Detailed knowledge of the host-virus interactions that accompany filovirus entry into cells is expected to identify determinants of viral virulence and host range, and to yield targets for the development of antiviral therapeutics. While it is generally agreed that filovirus entry into the host cytoplasm requires viral internalization into acidic endosomal compartments and proteolytic cleavage of the envelope glycoprotein by endo/lysosomal cysteine proteases, our understanding of the specific endocytic pathways co-opted by filoviruses remains limited. This review addresses the current knowledge on cellular endocytic pathways implicated in filovirus entry, highlights the consensus as well as controversies, and discusses important remaining questions.
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Affiliation(s)
- Suchita Bhattacharyya
- Department of Atomic Energy-Centre for Excellence in Basic Sciences, University of Mumbai, Health Centre Building, Vidyanagari, Kalina, Santacruz East, Mumbai 400098, India; E-Mail:
| | - Nirupama Mulherkar
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, 1300 Morris Park Ave, Bronx, NY 10461, USA; E-Mail:
| | - Kartik Chandran
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, 1300 Morris Park Ave, Bronx, NY 10461, USA; E-Mail:
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-718-430-8851
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Rankin CR, Hilgarth RS, Leoni G, Kwon M, Den Beste KA, Parkos CA, Nusrat A. Annexin A2 regulates β1 integrin internalization and intestinal epithelial cell migration. J Biol Chem 2013; 288:15229-39. [PMID: 23558678 DOI: 10.1074/jbc.m112.440909] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The gastrointestinal epithelium functions as an important barrier that separates luminal contents from the underlying tissue compartment and is vital in maintaining mucosal homeostasis. Mucosal wounds in inflammatory disorders compromise the critical epithelial barrier. In response to injury, intestinal epithelial cells (IECs) rapidly migrate to reseal wounds. We have previously observed that a membrane-associated, actin binding protein, annexin A2 (AnxA2), is up-regulated in migrating IECs and plays an important role in promoting wound closure. To identify the mechanisms by which AnxA2 promotes IEC movement and wound closure, we used a loss of function approach. AnxA2-specific shRNA was utilized to generate IECs with stable down-regulation of AnxA2. Loss of AnxA2 inhibited IEC migration while promoting enhanced cell-matrix adhesion. These functional effects were associated with increased levels of β1 integrin protein, which is reported to play an important role in mediating the cell-matrix adhesive properties of epithelial cells. Because cell migration requires dynamic turnover of integrin-based adhesions, we tested whether AnxA2 modulates internalization of cell surface β1 integrin required for forward cell movement. Indeed, pulse-chase biotinylation experiments in IECs lacking AnxA2 demonstrated a significant increase in cell surface β1 integrin that was accompanied by decreased β1 integrin internalization and degradation. These findings support an important role of AnxA2 in controlling dynamics of β1 integrin at the cell surface that in turn is required for the active turnover of cell-matrix associations, cell migration, and wound closure.
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Affiliation(s)
- Carl R Rankin
- Department of Pathology and Laboratory Medicine, Epithelial Pathobiology and Mucosal Inflammation Research Unit, Emory University, Atlanta, Georgia 30306, USA
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Chi X, Wang S, Huang Y, Stamnes M, Chen JL. Roles of rho GTPases in intracellular transport and cellular transformation. Int J Mol Sci 2013; 14:7089-108. [PMID: 23538840 PMCID: PMC3645678 DOI: 10.3390/ijms14047089] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Revised: 03/04/2013] [Accepted: 03/12/2013] [Indexed: 01/21/2023] Open
Abstract
Rho family GTPases belong to the Ras GTPase superfamily and transduce intracellular signals known to regulate a variety of cellular processes, including cell polarity, morphogenesis, migration, apoptosis, vesicle trafficking, viral transport and cellular transformation. The three best-characterized Rho family members are Cdc42, RhoA and Rac1. Cdc42 regulates endocytosis, the transport between the endoplasmic reticulum and Golgi apparatus, post-Golgi transport and exocytosis. Cdc42 influences trafficking through interaction with Wiskott-Aldrich syndrome protein (N-WASP) and the Arp2/3 complex, leading to changes in actin dynamics. Rac1 mediates endocytic and exocytic vesicle trafficking by interaction with its effectors, PI3kinase, synaptojanin 2, IQGAP1 and phospholipase D1. RhoA participates in the regulation of endocytosis through controlling its downstream target, Rho kinase. Interestingly, these GTPases play important roles at different stages of viral protein and genome transport in infected host cells. Importantly, dysregulation of Cdc42, Rac1 and RhoA leads to numerous disorders, including malignant transformation. In some cases, hyperactivation of Rho GTPases is required for cellular transformation. In this article, we review a number of findings related to Rho GTPase function in intracellular transport and cellular transformation.
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Affiliation(s)
- Xiaojuan Chi
- College of Animal Science, Fujian Agriculture and Forestry University, Fuzhou 350002, China; E-Mails: (X.C.); (Y.H.)
| | - Song Wang
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences (CAS), Beijing 100101, China; E-Mail:
| | - Yifan Huang
- College of Animal Science, Fujian Agriculture and Forestry University, Fuzhou 350002, China; E-Mails: (X.C.); (Y.H.)
| | - Mark Stamnes
- Department of Molecular Physiology and Biophysics, Roy J. and Lucille A. Carver College of Medicine, The University of Iowa, Iowa City, IA 52242, USA; E-Mail:
| | - Ji-Long Chen
- College of Animal Science, Fujian Agriculture and Forestry University, Fuzhou 350002, China; E-Mails: (X.C.); (Y.H.)
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences (CAS), Beijing 100101, China; E-Mail:
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +86-10-6480-7300; Fax: +86-10-6480-7980
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129
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Harper CB, Popoff MR, McCluskey A, Robinson PJ, Meunier FA. Targeting membrane trafficking in infection prophylaxis: dynamin inhibitors. Trends Cell Biol 2013; 23:90-101. [DOI: 10.1016/j.tcb.2012.10.007] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Revised: 10/11/2012] [Accepted: 10/11/2012] [Indexed: 12/01/2022]
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130
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Pan W, Stone KP, Hsuchou H, Manda VK, Zhang Y, Kastin AJ. Cytokine signaling modulates blood-brain barrier function. Curr Pharm Des 2013; 17:3729-40. [PMID: 21834767 DOI: 10.2174/138161211798220918] [Citation(s) in RCA: 158] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 08/30/2011] [Accepted: 09/26/2011] [Indexed: 02/06/2023]
Abstract
The blood-brain barrier (BBB) provides a vast interface for cytokines to affect CNS function. The BBB is a target for therapeutic intervention. It is essential, therefore, to understand how cytokines interact with each other at the level of the BBB and how secondary signals modulate CNS functions beyond the BBB. The interactions between cytokines and lipids, however, have not been fully addressed at the level of the BBB. Here, we summarize current understanding of the localization of cytokine receptors and transporters in specific membrane microdomains, particularly lipid rafts, on the luminal (apical) surface of the microvascular endothelial cells composing the BBB. We then illustrate the clinical context of cytokine effects on the BBB by neuroendocrine regulation and amplification of inflammatory signals. Two unusual aspects discussed are signaling crosstalk by different classes of cytokines and genetic regulation of drug efflux transporters. We also introduce a novel area of focus on how cytokines may act through nuclear hormone receptors to modulate efflux transporters and other targets. A specific example discussed is the ATP-binding cassette transporter-1 (ABCA-1) that regulates lipid metabolism. Overall, cytokine signaling at the level of the BBB is a crucial feature of the dynamic regulation that can rapidly change BBB function and affect brain health and disease.
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Affiliation(s)
- Weihong Pan
- Blood-Brain Barrier Group, Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA 70808, USA
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131
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Santos MDS, Naal RMZG, Baird B, Holowka D. Inhibitors of PI(4,5)P2 synthesis reveal dynamic regulation of IgE receptor signaling by phosphoinositides in RBL mast cells. Mol Pharmacol 2013; 83:793-804. [PMID: 23313938 DOI: 10.1124/mol.112.082834] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) is a versatile phospholipid that participates in many membrane-associated signaling processes. PI(4,5)P2 production at the plasma membrane (PM) depends on levels of its precursor, phosphatidylinositol 4-phosphate (PI4P), synthesized principally by two intracellular enzymes, PI4-kinases IIIα and IIIb; the former is preferentially inhibited by phenylarsine oxide (PAO). We found that PAO and quercetin, another lipid kinase inhibitor, rapidly inhibit Ca(2+) responses to antigen in IgE-sensitized rat basophilic leukemia mast cells. Quercetin also rapidly inhibits store-operated Ca(2+) influx stimulated by thapsigargin. In addition, quercetin and PAO effectively inhibit antigen-stimulated ruffling and spreading in these cells, and they inhibit endocytosis of crosslinked IgE receptor complexes, evidently by inhibiting pinching off of endocytic vesicles containing the clustered IgE receptors. A minimal model to account for these diverse effects is inhibition of PI(4,5)P2 synthesis by PAO and quercetin. To characterize the direct effects of these agents on PI(4,5)P2 synthesis, we monitored the reappearance of the PI(4,5)P2-specific PH domain PH-phospholipase C δ-EGFP at the PM after Ca(2+) ionophore (A23187)-induced PI(4,5)P2 hydrolysis, followed by Ca(2+) chelation with excess EGTA. Resynthesized PI(4,5)P2 initially appears as micron-sized patches near the PM. Addition of quercetin subsequent to A23187-induced PI(4,5)P2 hydrolysis reduces PI(4,5)P2 resynthesis in PM-associated patches, and PAO reduces PI(4,5)P2 at the PM while enhancing PI(4,5)P2 accumulation at the Golgi complex. Taken together, these results provide evidence that PI4P generated by PI4-kinase IIIα is dynamically coupled to PI(4,5)P2 pools at the PM that are important for downstream signaling processes activated by IgE receptors.
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Affiliation(s)
- Marcela de Souza Santos
- Departamento de Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, SãoPaulo, Brazil
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132
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Basquin C, Malardé V, Mellor P, Anderson DH, Meas-Yedid V, Olivo-Marin JC, Dautry-Varsat A, Sauvonnet N. The signalling factor PI 3-kinase is a specific regulator of the clathrin-independent dynamin-dependent endocytosis of IL-2 receptors. J Cell Sci 2013; 126:1099-108. [DOI: 10.1242/jcs.110932] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Receptor-mediated endocytosis is an essential process used by eukaryotic cells to internalise many molecules. Several clathrin-independent endocytic routes exist but the molecular mechanism of each pathway remains to be uncovered. This study focuses on a clathrin-independent, dynamin-dependent pathway used by interleukin 2 receptors (IL-2R), essential players of the immune response. Rac1 and its targets the p21-activated kinases (Pak) are specific regulators of this pathway, acting on cortactin and actin polymerization. Here, our study reveals a dual and specific role of phosphatidylinositol 3-kinase (PI 3-kinase) in IL-2R endocytosis. Firstly, the inhibition of the catalytic activity of PI 3-kinase strongly affects IL-2R endocytosis, in contrast to transferrin (Tf) uptake, a marker of the clathrin-mediated pathway. Moreover, Vav2, a GTPase exchange factor (GEF) induced upon PI 3-kinase activation, is specifically involved in IL-2R entry. The second action of PI 3-kinase is via its regulatory subunit, p85α, which binds to and recruits Rac1 during IL-2R internalisation. Indeed, the overexpression of a p85α mutant missing the Rac1 binding motif, leads to the specific inhibition of IL-2R endocytosis. The inhibitory effect of this p85α mutant could be rescued by the overexpression of either Rac1 or the active form of Pak, indicating that p85α acts upstream of the Rac1-Pak cascade. Finally, biochemical and fluorescent microscopy techniques reveal an interaction between p85α, Rac1 and IL-2R that is enhanced by IL-2. In summary our results point out a key role of class I PI 3-kinase in IL-2R endocytosis that creates a link with IL-2 signalling.
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133
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Shankar J, Kojic LD, St-Pierre P, Wang PTC, Fu M, Joshi B, Nabi IR. Raft endocytosis of autocrine motility factor regulates mitochondrial dynamics via rac1 signaling and the gp78 ubiquitin ligase. J Cell Sci 2013; 126:3295-304. [DOI: 10.1242/jcs.120162] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Gp78 is a cell surface receptor that also functions as an E3 ubiquitin ligase in the endoplasmic reticulum-associated degradation (ERAD) pathway. The Gp78 ligand, the glycolytic enzyme phosphoglucose isomerase (also called autocrine motility factor or AMF), functions as a cytokine upon secretion by tumor cells. AMF is internalized via a PI3K- and dynamin-dependent raft endocytic pathway to the smooth endoplasmic reticulum (ER), however the relationship between AMF and Gp78 ubiquitin ligase activity remains unclear. AMF uptake to the smooth ER is inhibited by the dynamin inhibitor, dynasore, reduced in Gp78 knockdown cells and induces the dynamin-dependent downregulation of its cell surface receptor. AMF uptake is Rac1-dependent, inhibited by expression of dominant-negative Rac1 and the Rac1 inhibitor NSC23766, and therefore distinct from Cdc42 and RhoA-dependent raft endocytic pathways. AMF stimulates Rac1 activation, that is reduced by dynasore treatment and absent in Gp78-knockdown cells and therefore requires Gp78-mediated endocytosis. AMF also prevents Gp78-induced degradation of the mitochondrial fusion proteins, Mitofusin 1 and 2 in a dynamin, Rac1 and PI3K-dependent manner. Gp78 induces mitochondrial clustering and fission in a ubiquitin ligase-dependent manner that is also reversed by AMF. The raft-dependent endocytosis of AMF therefore promotes Rac1/PI3K signaling that feeds back to promote AMF endocytosis and also inhibits the ability of Gp78 to target the mitofusins for degradation, thereby preventing Gp78-dependent mitochondrial fission. Through regulation of an ER-localized ubiquitin ligase, the raft-dependent endocytosis of AMF represents an extracellular regulator of mitochondrial fusion and dynamics.
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134
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Muro S. Challenges in design and characterization of ligand-targeted drug delivery systems. J Control Release 2012; 164:125-37. [PMID: 22709588 PMCID: PMC3481020 DOI: 10.1016/j.jconrel.2012.05.052] [Citation(s) in RCA: 173] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2011] [Revised: 05/19/2012] [Accepted: 05/26/2012] [Indexed: 01/11/2023]
Abstract
Targeting of therapeutic agents to molecular markers expressed on the surface of cells requiring clinical intervention holds promise to improve specificity of delivery, enhancing therapeutic effects while decreasing potential damage to healthy tissues. Drug targeting to cellular receptors involved in endocytic transport facilitates intracellular delivery, a requirement for a number of therapeutic goals. However, after several decades of experimental design, there is still considerable controversy on the practical outcome of drug targeting strategies. The plethora of factors contributing to the relative efficacy of targeting makes the success of these approaches hardly predictable. Lack of fully specific targets, along with selection of targets with spatial and temporal expression well aligned to interventional requirements, pose difficulties to this process. Selection of adequate sub-molecular target epitopes determines accessibility for anchoring of drug conjugates and bulkier drug carriers, as well as proper signaling for uptake within the cell. Targeting design must adapt to physiological variables of blood flow, disease status, and tissue architecture by accommodating physicochemical parameters such as carrier composition, functionalization, geometry, and avidity. In many cases, opposite features need to meet a balance, e.g., sustained circulation versus efficient targeting, penetration through tissues versus uptake within cells, internalization within endocytic compartment to avoid efflux pumps versus accessibility to molecular targets within the cytosol, etc. Detailed characterization of these complex physiological factors and design parameters, along with a deep understanding of the mechanisms governing the interaction of targeted drugs and carriers with the biological environment, are necessary steps toward achieving efficient drug targeting systems.
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Affiliation(s)
- Silvia Muro
- Fischell Department of Bioengineering, School of Engineering, University of Maryland College Park, College Park, MD 20742, USA.
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135
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Japanese encephalitis virus infects neuronal cells through a clathrin-independent endocytic mechanism. J Virol 2012; 87:148-62. [PMID: 23055570 DOI: 10.1128/jvi.01399-12] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Japanese encephalitis virus (JEV) is a mosquito-borne pathogenic flavivirus responsible for acute viral encephalitis in humans. The cellular entry of JEV is poorly characterized in terms of molecular requirements and pathways. Here we present a systematic study of the internalization mechanism of JEV in fibroblasts and neuroblastoma cells. To verify the roles of distinct pathways of cell entry, we used fluorescently labeled virus particles, a combination of pharmacological inhibitors, RNA interference (RNAi), and dominant-negative (DN) mutants of regulatory proteins involved in endocytosis. Our study demonstrates that JEV infects fibroblasts in a clathrin-dependent manner, but it deploys a clathrin-independent mechanism to infect neuronal cells. The clathrin-independent pathway requires dynamin and plasma membrane cholesterol. Virus binding to neuronal cells leads to rapid actin rearrangements and an intact and dynamic actin cytoskeleton, and the small GTPase RhoA plays an important role in viral entry. Immunofluorescence analysis of viral colocalization with endocytic markers showed that JEV traffics through Rab5-positive early endosomes and that release of the viral nucleocapsid occurs at the level of the early and not the late endosomes.
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136
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Tortorella LL, Pipalia NH, Mukherjee S, Pastan I, Fitzgerald D, Maxfield FR. Efficiency of immunotoxin cytotoxicity is modulated by the intracellular itinerary. PLoS One 2012; 7:e47320. [PMID: 23056628 PMCID: PMC3467225 DOI: 10.1371/journal.pone.0047320] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Accepted: 09/14/2012] [Indexed: 01/13/2023] Open
Abstract
Pseudomonas exotoxin-based immunotoxins, including LMB-2 (antiTac(F(v))-PE38), are proposed to traffic to the trans-Golgi network (TGN) and move by a retrograde pathway to the endoplasmic reticulum, where they undergo translocation to the cytoplasm, a step that is essential for cytotoxicity. The retrograde transport pathways used by LMB-2 are not completely understood, so it is unclear if transit through specific organelles is critical for maximal cytotoxic activity. In this study, we used Chinese hamster ovary (CHO) cell lines that express chimeric constructs of CD25, the Tac antigen, attached to the cytoplasmic domain of the TGN-targeted transmembrane proteins, TGN38 and furin. These chimeras are both targeted to the TGN, but the itineraries they follow are quite different. LMB-2 was incubated with the two cell lines, and the efficiency of cell killing was determined using cell viability and cytotoxicity assays. LMB-2 that is targeted through the endocytic recycling compartment to the TGN via Tac-TGN38 kills the cells more efficiently than immunotoxins delivered through the late endosomes by Tac-furin. Although the processing to the 37 kDa active fragment was more efficient in Tac-furin cells than in Tac-TGN38 cells, this was not associated with enhanced cytotoxicity - presumably because the toxin was also degraded more rapidly in these cells. These data indicate that trafficking through specific organelles is an important factor modulating toxicity by LMB-2.
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Affiliation(s)
- Lori L. Tortorella
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, United States of America
| | - Nina H. Pipalia
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, United States of America
| | - Sushmita Mukherjee
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, United States of America
| | - Ira Pastan
- Laboratory of Molecular Biology, National Cancer Institute, Bethesda, Maryland, United States of America
| | - David Fitzgerald
- Laboratory of Molecular Biology, National Cancer Institute, Bethesda, Maryland, United States of America
| | - Frederick R. Maxfield
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, United States of America
- * E-mail:
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137
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Davies BSJ, Goulbourne CN, Barnes RH, Turlo KA, Gin P, Vaughan S, Vaux DJ, Bensadoun A, Beigneux AP, Fong LG, Young SG. Assessing mechanisms of GPIHBP1 and lipoprotein lipase movement across endothelial cells. J Lipid Res 2012; 53:2690-7. [PMID: 23008484 DOI: 10.1194/jlr.m031559] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lipoprotein lipase (LPL) is secreted into the interstitial spaces by adipocytes and myocytes but then must be transported to the capillary lumen by GPIHBP1, a glycosylphosphatidylinositol-anchored protein of capillary endothelial cells. The mechanism by which GPIHBP1 and LPL move across endothelial cells remains unclear. We asked whether the transport of GPIHBP1 and LPL across endothelial cells was uni- or bidirectional. We also asked whether GPIHBP1 and LPL are transported across cells in vesicles and whether this transport process requires caveolin-1. The movement of GPIHBP1 and LPL across cultured endothelial cells was bidirectional. Also, GPIHBP1 moved bidirectionally across capillary endothelial cells in live mice. The transport of LPL across endothelial cells was inhibited by dynasore and genistein, consistent with a vesicular transport process. Also, transmission electron microscopy (EM) and dual-axis EM tomography revealed GPIHBP1 and LPL in invaginations of the plasma membrane and in vesicles. The movement of GPIHBP1 across capillary endothelial cells was efficient in the absence of caveolin-1, and there was no defect in the internalization of LPL by caveolin-1-deficient endothelial cells in culture. Our studies show that GPIHBP1 and LPL move bidirectionally across endothelial cells in vesicles and that transport is efficient even when caveolin-1 is absent.
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Affiliation(s)
- Brandon S J Davies
- Department of Medicine, University of California, Los Angeles, CA 90095, USA.
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138
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Dutta D, Williamson CD, Cole NB, Donaldson JG. Pitstop 2 is a potent inhibitor of clathrin-independent endocytosis. PLoS One 2012; 7:e45799. [PMID: 23029248 PMCID: PMC3448704 DOI: 10.1371/journal.pone.0045799] [Citation(s) in RCA: 156] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Accepted: 08/24/2012] [Indexed: 12/13/2022] Open
Abstract
Clathrin independent endocytosis (CIE) is a form of endocytosis present in all cells that mediates the entry of nutrients, macromolecules and membrane proteins into cells. When compared to clathrin-dependent endocytosis (CDE), however, much less is known about the machinery involved in forming CIE endosomes. One way to distinguish CIE from CDE has been to deplete cells of coat proteins involved in CDE such as clathrin or the dynamin GTPase, leading to a block of CDE but not CIE. A drawback of such genetic manipulations is that depletion of proteins important for mediating CDE over a period of days can have complex indirect effects on cellular function. The identification of chemical compounds that specifically and rapidly block CDE or CIE would facilitate the determination of whether a process involved CDE or CIE. To date, all of those compounds have targeted CDE. Dynasore and the dynoles specifically target and block dynamin activity thus inhibiting CDE but not most forms of CIE. Recently, a new compound called pitstop 2 was identified as an inhibitor of the interaction of amphiphysin with the amino terminal domain of clathrin, and shown to inhibit CDE in cells. Here we show that pitstop 2 is also a potent inhibitor of CIE. The effects of pitstop 2 are not restricted to inhibition of clathrin since knockdown of clathrin fails to rescue the inhibition of endocytosis of CIE proteins by the drug. Thus pitstop 2 has additional cellular targets besides the amino terminal domain of clathrin and thus cannot be used to distinguish CIE from CDE.
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Affiliation(s)
- Dipannita Dutta
- Laboratory of Cell Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Chad D. Williamson
- Laboratory of Cell Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Nelson B. Cole
- Laboratory of Cell Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Julie G. Donaldson
- Laboratory of Cell Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
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139
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Gauthier NC, Masters TA, Sheetz MP. Mechanical feedback between membrane tension and dynamics. Trends Cell Biol 2012; 22:527-35. [PMID: 22921414 DOI: 10.1016/j.tcb.2012.07.005] [Citation(s) in RCA: 295] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Revised: 07/05/2012] [Accepted: 07/10/2012] [Indexed: 01/05/2023]
Abstract
The plasma membrane represents a physical inelastic barrier with a given area that adheres to the underlying cytoskeleton. The tension in the membrane physically affects cell functions and recent studies have highlighted that this physical signal orchestrates complex aspects of trafficking and motility. Despite its undeniable importance, little is known about the mechanisms by which membrane tension regulates cell functions or stimulates signals. The maintenance of membrane tension is also a matter of debate, particularly the nature of the membrane reservoir and trafficking pathways that buffer tension. In this review we discuss the importance of membrane area and of tension as a master integrator of cell functions, particularly for membrane traffic.
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Affiliation(s)
- Nils C Gauthier
- Mechanobiology Institute, National University of Singapore, 5A Engineering Drive 1, Singapore 117411.
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140
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Iversen TG, Frerker N, Sandvig K. Uptake of ricinB-quantum dot nanoparticles by a macropinocytosis-like mechanism. J Nanobiotechnology 2012; 10:33. [PMID: 22849338 PMCID: PMC3466139 DOI: 10.1186/1477-3155-10-33] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2012] [Accepted: 07/23/2012] [Indexed: 12/23/2022] Open
Abstract
Background There is a huge effort in developing ligand-mediated targeting of nanoparticles to diseased cells and tissue. The plant toxin ricin has been shown to enter cells by utilizing both dynamin-dependent and -independent endocytic pathways. Thus, it is a representative ligand for addressing the important issue of whether even a relatively small ligand-nanoparticle conjugate can gain access to the same endocytic pathways as the free ligand. Results Here we present a systematic study concerning the internalization mechanism of ricinB:Quantum dot (QD) nanoparticle conjugates in HeLa cells. Contrary to uptake of ricin itself, we found that internalization of ricinB:QDs was inhibited in HeLa cells expressing dominant-negative dynamin. Both clathrin-, Rho-dependent uptake as well as a specific form of macropinocytosis involve dynamin. However, the ricinB:QD uptake was not affected by siRNA-mediated knockdown of clathrin or inhibition of Rho-dependent uptake caused by treating cells with the Clostridium C3 transferase. RicinB:QD uptake was significantly reduced by cholesterol depletion with methyl-β-cyclodextrin and by inhibitors of actin polymerization such as cytochalasin D. Finally, we found that uptake of ricinB:QDs was blocked by the amiloride analog EIPA, an inhibitor of macropinocytosis. Upon entry, the ricinB:QDs co-localized with dextran, a marker for fluid-phase uptake. Thus, internalization of ricinB:QDs in HeLa cells critically relies on a dynamin-dependent macropinocytosis-like mechanism. Conclusions Our results demonstrate that internalization of a ligand-nanoparticle conjugate can be dependent on other endocytic mechanisms than those used by the free ligand, highlighting the challenges of using ligand-mediated targeting of nanoparticles-based drug delivery vehicles to cells of diseased tissues.
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Affiliation(s)
- Tore Geir Iversen
- Centre for Cancer Biomedicine, Faculty Division Norwegian Radium Hospital, University of Oslo, Oslo, Norway.
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141
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On the cellular processing of non-viral nanomedicines for nucleic acid delivery: Mechanisms and methods. J Control Release 2012; 161:566-81. [DOI: 10.1016/j.jconrel.2012.05.020] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Revised: 05/11/2012] [Accepted: 05/11/2012] [Indexed: 11/24/2022]
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142
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Irmak MK, Oztas Y, Oztas E. Integration of maternal genome into the neonate genome through breast milk mRNA transcripts and reverse transcriptase. Theor Biol Med Model 2012; 9:20. [PMID: 22676860 PMCID: PMC3413567 DOI: 10.1186/1742-4682-9-20] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Accepted: 05/25/2012] [Indexed: 12/30/2022] Open
Abstract
Human milk samples contain microvesicles similar to the retroviruses. These microvesicles contain mRNA transcripts and possess reverse transcriptase activity. They contain about 14,000 transcripts representing the milk transcriptome. Microvesicles are also enriched with proteins related to "caveolar-mediated endocytosis signaling" pathway. It has recently been reported that microvesicles could be transferred to other cells by endocytosis and their RNA content can be translated and be functional in their new location. A significant percentage of the mammalian genome appears to be the product of reverse transcription, containing sequences whose characteristics point to RNA as a template precursor. These are mobile elements that move by way of transposition and are called retrotransposons. We thought that retrotransposons may stem from about 14,000 transcriptome of breast milk microvesicles, and reviewed the literature.The enhanced acceptance of maternal allografts in children who were breast-fed and tolerance to the maternal MHC antigens after breastfeeding may stem from RNAs of the breast milk microvesicles that can be taken up by the breastfed infant and receiving maternal genomic information. We conclude that milk microvesicles may transfer genetic signals from mother to neonate during breastfeeding. Moreover, transfer of wild type RNA from a healthy wet-nurse to the suckling neonate through the milk microvesicles and its subsequent reverse transcription and integration into the neonate genome could result in permanent correction of the clinical manifestations in genetic diseases.
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Affiliation(s)
- M Kemal Irmak
- High Council of Science, Gulhane Military Medical Academy, Ankara, Turkey.
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143
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Cai B, Caplan S, Naslavsky N. cPLA2α and EHD1 interact and regulate the vesiculation of cholesterol-rich, GPI-anchored, protein-containing endosomes. Mol Biol Cell 2012; 23:1874-88. [PMID: 22456504 PMCID: PMC3350552 DOI: 10.1091/mbc.e11-10-0881] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
cPLA2 hydrolyzes phospholipids and regulates membrane curvature and/or tubulation. Despite disparate roles for cPLA2 at the Golgi and early endosomes, its function in the regulation of membranes containing GPI-anchored proteins is not known. A role for cPLA2α and EHD1 is identified in the vesiculation of cholesterol-rich, GPI-AP–containing membranes. The lipid modifier phospholipase A2 catalyzes the hydrolysis of phospholipids to inverted-cone–shaped lysophospholipids that contribute to membrane curvature and/or tubulation. Conflicting findings exist regarding the function of cytosolic phospholipase A2 (cPLA2) and its role in membrane regulation at the Golgi and early endosomes. However, no studies addressed the role of cPLA2 in the regulation of cholesterol-rich membranes that contain glycosylphosphatidylinositol-anchored proteins (GPI-APs). Our studies support a role for cPLA2α in the vesiculation of GPI-AP–containing membranes, using endogenous CD59 as a model for GPI-APs. On cPLA2α depletion, CD59-containing endosomes became hypertubular. Moreover, accumulation of lysophospholipids induced by a lysophospholipid acyltransferase inhibitor extensively vesiculated CD59-containing endosomes. However, overexpression of cPLA2α did not increase the endosomal vesiculation, implying a requirement for additional factors. Indeed, depletion of the “pinchase” EHD1, a C-terminal Eps15 homology domain (EHD) ATPase, also induced hypertubulation of CD59-containing endosomes. Furthermore, EHD1 and cPLA2α demonstrated in situ proximity (<40 nm) and interacted in vivo. The results presented here provide evidence that the lipid modifier cPLA2α and EHD1 are involved in the vesiculation of CD59-containing endosomes. We speculate that cPLA2α induces membrane curvature and allows EHD1, possibly in the context of a complex, to sever the curved membranes into vesicles.
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Affiliation(s)
- Bishuang Cai
- Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, NE 68198, USA
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144
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Sigismund S, Confalonieri S, Ciliberto A, Polo S, Scita G, Di Fiore PP. Endocytosis and signaling: cell logistics shape the eukaryotic cell plan. Physiol Rev 2012; 92:273-366. [PMID: 22298658 DOI: 10.1152/physrev.00005.2011] [Citation(s) in RCA: 236] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Our understanding of endocytosis has evolved remarkably in little more than a decade. This is the result not only of advances in our knowledge of its molecular and biological workings, but also of a true paradigm shift in our understanding of what really constitutes endocytosis and of its role in homeostasis. Although endocytosis was initially discovered and studied as a relatively simple process to transport molecules across the plasma membrane, it was subsequently found to be inextricably linked with almost all aspects of cellular signaling. This led to the notion that endocytosis is actually the master organizer of cellular signaling, providing the cell with understandable messages that have been resolved in space and time. In essence, endocytosis provides the communications and supply routes (the logistics) of the cell. Although this may seem revolutionary, it is still likely to be only a small part of the entire story. A wealth of new evidence is uncovering the surprisingly pervasive nature of endocytosis in essentially all aspects of cellular regulation. In addition, many newly discovered functions of endocytic proteins are not immediately interpretable within the classical view of endocytosis. A possible framework, to rationalize all this new knowledge, requires us to "upgrade" our vision of endocytosis. By combining the analysis of biochemical, biological, and evolutionary evidence, we propose herein that endocytosis constitutes one of the major enabling conditions that in the history of life permitted the development of a higher level of organization, leading to the actuation of the eukaryotic cell plan.
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Affiliation(s)
- Sara Sigismund
- IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, Milan, Italy
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145
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Tkachenko E, Tse D, Sideleva O, Deharvengt SJ, Luciano MR, Xu Y, McGarry CL, Chidlow J, Pilch PF, Sessa WC, Toomre DK, Stan RV. Caveolae, fenestrae and transendothelial channels retain PV1 on the surface of endothelial cells. PLoS One 2012; 7:e32655. [PMID: 22403691 PMCID: PMC3293851 DOI: 10.1371/journal.pone.0032655] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Accepted: 01/28/2012] [Indexed: 11/21/2022] Open
Abstract
PV1 protein is an essential component of stomatal and fenestral diaphragms, which are formed at the plasma membrane of endothelial cells (ECs), on structures such as caveolae, fenestrae and transendothelial channels. Knockout of PV1 in mice results in in utero and perinatal mortality. To be able to interpret the complex PV1 knockout phenotype, it is critical to determine whether the formation of diaphragms is the only cellular role of PV1. We addressed this question by measuring the effect of complete and partial removal of structures capable of forming diaphragms on PV1 protein level. Removal of caveolae in mice by knocking out caveolin-1 or cavin-1 resulted in a dramatic reduction of PV1 protein level in lungs but not kidneys. The magnitude of PV1 reduction correlated with the abundance of structures capable of forming diaphragms in the microvasculature of these organs. The absence of caveolae in the lung ECs did not affect the transcription or translation of PV1, but it caused a sharp increase in PV1 protein internalization rate via a clathrin- and dynamin-independent pathway followed by degradation in lysosomes. Thus, PV1 is retained on the cell surface of ECs by structures capable of forming diaphragms, but undergoes rapid internalization and degradation in the absence of these structures, suggesting that formation of diaphragms is the only role of PV1.
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Affiliation(s)
- Eugene Tkachenko
- Department of Medicine, University of California, San Diego, California, United States of America
| | - Dan Tse
- Department of Pathology, Dartmouth Medical School, Lebanon, New Hampshire, United States of America
- Heart and Vascular Research Center, Dartmouth Medical School, Lebanon, New Hampshire, United States of America
| | - Olga Sideleva
- Department of Pathology, Dartmouth Medical School, Lebanon, New Hampshire, United States of America
| | - Sophie J. Deharvengt
- Department of Pathology, Dartmouth Medical School, Lebanon, New Hampshire, United States of America
| | - Marcus R. Luciano
- Department of Pathology, Dartmouth Medical School, Lebanon, New Hampshire, United States of America
| | - Yan Xu
- Department of Pathology, Dartmouth Medical School, Lebanon, New Hampshire, United States of America
| | - Caitlin L. McGarry
- Department of Pathology, Dartmouth Medical School, Lebanon, New Hampshire, United States of America
- Heart and Vascular Research Center, Dartmouth Medical School, Lebanon, New Hampshire, United States of America
| | - John Chidlow
- Department of Pharmacology, Yale University, New Haven, Connecticut, United States of America
| | - Paul F. Pilch
- Department of Biochemistry, Boston University, Boston, Massachusetts, United States of America
| | - William C. Sessa
- Department of Pharmacology, Yale University, New Haven, Connecticut, United States of America
| | - Derek K. Toomre
- Department of Cell Biology, Yale University, New Haven, Connecticut, United States of America
| | - Radu V. Stan
- Department of Pathology, Dartmouth Medical School, Lebanon, New Hampshire, United States of America
- Department of Microbiology and Immunology, Dartmouth Medical School, Lebanon, New Hampshire, United States of America
- Heart and Vascular Research Center, Dartmouth Medical School, Lebanon, New Hampshire, United States of America
- Norris Cotton Cancer Center, Dartmouth Medical School, Lebanon, New Hampshire, United States of America
- * E-mail:
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146
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Mediouni S, Watkins JD, Pierres M, Bole A, Loret EP, Baillat G. A monoclonal antibody directed against a conformational epitope of the HIV-1 trans-activator (Tat) protein neutralizes cross-clade. J Biol Chem 2012; 287:11942-50. [PMID: 22362765 DOI: 10.1074/jbc.m111.319863] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The identification of a neutralizing mAb against extracellular HIV-1 transactivator of transcription (Tat) is important for the development of an efficient HIV-1 treatment. Tat plays an essential role in HIV-1 pathogenesis, not only for HIV-1 replication but also as an extracellular toxin able to disrupt the immune system. We showed previously that immunization of rabbits with Tat Oyi, a variant cloned from an African woman who did not develop AIDS following HIV-1 infection, raised antibodies able to recognize different Tat variants. We carried out mice immunization with Tat Oyi and selected a mAb named 7G12, which had the capacity to cross-recognize heterologous Tat variants by a common three-dimensional epitope. These results highlighted that Tat variants were able to acquire a structure, in contrast to a number of studies showing Tat as an unfolded protein. mAb 7G12 also had the capacity to neutralize the biological activities of these Tat variants by blocking the cellular uptake of extracellular Tat. This is the first study using Tat Oyi to produce a mAb able to neutralize effectively activities of extracellular Tats from different HIV-1 subtypes. This mAb has an important potential in therapeutic passive immunization and could help HIV-1 infected patients to restore their immunity.
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Affiliation(s)
- Sonia Mediouni
- Equipe de Recherche Technologique 2011, Université de la Méditerranée, Faculté de Pharmacie, 27 BD Jean Moulin, 13385 Marseille Cedex 5, France
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147
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Gonnord P, Blouin CM, Lamaze C. Membrane trafficking and signaling: two sides of the same coin. Semin Cell Dev Biol 2011; 23:154-64. [PMID: 22085846 DOI: 10.1016/j.semcdb.2011.11.002] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Accepted: 11/02/2011] [Indexed: 02/07/2023]
Abstract
Recent findings on clathrin-dependent and non clathrin-dependent endocytic routes are currently changing our classical view of endocytosis. Originally seen as a way for the cell to internalize membrane, receptors or various soluble molecules, this process is in fact directly linked to complex signaling pathways. Here, we review new insights in endocytosis and present latest development in imaging techniques that allow us to visualize and follow the dynamics of membrane-associated signaling events at the plasma membrane and other intracellular compartments. The immune synapse is taken as an illustration of the importance of membrane reorganization and proteins clustering to initiate and maintain signaling. Future challenges include understanding the crosslink between traffic and signaling and how all compartmentalized signals are integrated inside the cell at a higher level.
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Affiliation(s)
- Pauline Gonnord
- Laboratory of Cellular and Molecular Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
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148
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Prosser DC, Drivas TG, Maldonado-Báez L, Wendland B. Existence of a novel clathrin-independent endocytic pathway in yeast that depends on Rho1 and formin. ACTA ACUST UNITED AC 2011; 195:657-71. [PMID: 22065638 PMCID: PMC3257529 DOI: 10.1083/jcb.201104045] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Much like mammalian cells, yeast contain a Rho-dependent pathway for endocytosis in addition to canonical clathrin-dependent endocytosis. Yeast is a powerful model organism for dissecting the temporal stages and choreography of the complex protein machinery during endocytosis. The only known mechanism for endocytosis in yeast is clathrin-mediated endocytosis, even though clathrin-independent endocytic pathways have been described in other eukaryotes. Here, we provide evidence for a clathrin-independent endocytic pathway in yeast. In cells lacking the clathrin-binding adaptor proteins Ent1, Ent2, Yap1801, and Yap1802, we identify a second endocytic pathway that depends on the GTPase Rho1, the downstream formin Bni1, and the Bni1 cofactors Bud6 and Spa2. This second pathway does not require components of the better-studied endocytic pathway, including clathrin and Arp2/3 complex activators. Thus, our results reveal the existence of a second pathway for endocytosis in yeast, which suggests similarities with the RhoA-dependent endocytic pathways of mammalian cells.
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Affiliation(s)
- Derek C Prosser
- Department of Biology, The Johns Hopkins University, Baltimore, MD 21218, USA
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149
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Oda K, Yumoto R, Nagai J, Katayama H, Takano M. Mechanism underlying insulin uptake in alveolar epithelial cell line RLE-6TN. Eur J Pharmacol 2011; 672:62-9. [PMID: 22004610 DOI: 10.1016/j.ejphar.2011.10.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Revised: 09/28/2011] [Accepted: 10/02/2011] [Indexed: 10/16/2022]
Abstract
For the development of efficient pulmonary delivery systems for protein and peptide drugs, it is important to understand their transport mechanisms in alveolar epithelial cells. In this study, the uptake mechanism for FITC-insulin in cultured alveolar epithelial cell line RLE-6TN was elucidated. FITC-insulin uptake by RLE-6TN cells was time-dependent, temperature-sensitive, and concentration-dependent. The uptake was inhibited by metabolic inhibitors, cytochalasin D, clathrin-mediated endocytosis inhibitors, and dynasore, an inhibitor of dynamin GTPase. On the other hand, no inhibitory effect was observed with caveolae-mediated endocytosis inhibitors and a macropinocytosis inhibitor. Intracellular FITC-insulin was found to be partly transported to the basal side of the epithelial cell monolayers. In addition, colocalization of FITC-insulin and LysoTracker Red was observed on confocal laser scanning microscopy, indicating that FITC-insulin was partly targeted to lysosomes. In accordance with these findings, SDS-PAGE/fluoroimage analysis showed that intact FITC-insulin in the cells was eliminated with time. The possible receptor involved in FITC-insulin uptake by RLE-6TN cells was examined by using siRNA. Transfection of the cells with megalin or insulin receptor siRNA successfully reduced the corresponding mRNA expression. FITC-insulin uptake decreased on the transfection with insulin receptor siRNA, but not that with megalin siRNA. These results suggest that insulin is taken up through endocytosis in RLE-6TN cells, and after the endocytosis, the intracellular insulin is partly degraded in lysosomes and partly transported to the basal side. Insulin receptor, but not megalin, may be involved at least partly in insulin endocytosis in RLE-6TN cells.
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Affiliation(s)
- Keisuke Oda
- Department of Pharmaceutics and Therapeutics, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan
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150
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Guimarães de Araújo ME, Huber LA, Stasyk T. Latex beads internalization and quantitative proteomics join forces to decipher the endosomal proteome. Expert Rev Proteomics 2011; 8:303-7. [PMID: 21679111 DOI: 10.1586/epr.11.27] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The proteome analysis of endocytic compartments has been constrained by the limited purity of the organelle fractions obtained by current biochemical methods. Duclos and coworkers have developed a novel method to isolate highly purified endosomal organelles based on small latex beads internalization followed by gradient centrifugation and successfully combined it with a redundant peptide counting method to compare the relative abundance of proteins in organelles. The presence of bona fide markers in their respective subcellular organelles and the identification of several new endosomal-associated proteins, attested the applicability of their combinatory approach. Future applications of this strategy may deliver a comprehensive endosomal proteome chart: from the identification of the key players to the determination of time and signaling-dependent proteome changes. As a long-term perspective, such an approach may unveil new clues to the molecular mechanisms underlining human diseases associated with endosomal biogenesis defects.
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