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Liu NJ, Hou LP, Bao JJ, Wang LJ, Chen XY. Sphingolipid metabolism, transport, and functions in plants: Recent progress and future perspectives. PLANT COMMUNICATIONS 2021; 2:100214. [PMID: 34746760 PMCID: PMC8553973 DOI: 10.1016/j.xplc.2021.100214] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2021] [Revised: 05/12/2021] [Accepted: 06/26/2021] [Indexed: 05/08/2023]
Abstract
Sphingolipids, which comprise membrane systems together with other lipids, are ubiquitous in cellular organisms. They show a high degree of diversity across plant species and vary in their structures, properties, and functions. Benefiting from the development of lipidomic techniques, over 300 plant sphingolipids have been identified. Generally divided into free long-chain bases (LCBs), ceramides, glycosylceramides (GlcCers) and glycosyl inositol phosphoceramides (GIPCs), plant sphingolipids exhibit organized aggregation within lipid membranes to form raft domains with sterols. Accumulating evidence has revealed that sphingolipids obey certain trafficking and distribution rules and confer unique properties to membranes. Functional studies using sphingolipid biosynthetic mutants demonstrate that sphingolipids participate in plant developmental regulation, stimulus sensing, and stress responses. Here, we present an updated metabolism/degradation map and summarize the structures of plant sphingolipids, review recent progress in understanding the functions of sphingolipids in plant development and stress responses, and review sphingolipid distribution and trafficking in plant cells. We also highlight some important challenges and issues that we may face during the process of studying sphingolipids.
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Affiliation(s)
- Ning-Jing Liu
- State Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences/Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Fenglin Road 300, Shanghai 200032, China
- Corresponding author
| | - Li-Pan Hou
- State Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences/Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Fenglin Road 300, Shanghai 200032, China
- University of Chinese Academy of Sciences, Shanghai 200032, China
| | - Jing-Jing Bao
- State Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences/Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Fenglin Road 300, Shanghai 200032, China
- University of Chinese Academy of Sciences, Shanghai 200032, China
| | - Ling-Jian Wang
- State Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences/Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Fenglin Road 300, Shanghai 200032, China
| | - Xiao-Ya Chen
- State Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences/Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Fenglin Road 300, Shanghai 200032, China
- University of Chinese Academy of Sciences, Shanghai 200032, China
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Calcium levels in the Golgi complex regulate clustering and apical sorting of GPI-APs in polarized epithelial cells. Proc Natl Acad Sci U S A 2021; 118:2014709118. [PMID: 34389665 DOI: 10.1073/pnas.2014709118] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Glycosylphosphatidylinositol-anchored proteins (GPI-APs) are lipid-associated luminal secretory cargoes selectively sorted to the apical surface of the epithelia where they reside and play diverse vital functions. Cholesterol-dependent clustering of GPI-APs in the Golgi is the key step driving their apical sorting and their further plasma membrane organization and activity; however, the specific machinery involved in this Golgi event is still poorly understood. In this study, we show that the formation of GPI-AP homoclusters (made of single GPI-AP species) in the Golgi relies directly on the levels of calcium within cisternae. We further demonstrate that the TGN calcium/manganese pump, SPCA1, which regulates the calcium concentration within the Golgi, and Cab45, a calcium-binding luminal Golgi resident protein, are essential for the formation of GPI-AP homoclusters in the Golgi and for their subsequent apical sorting. Down-regulation of SPCA1 or Cab45 in polarized epithelial cells impairs the oligomerization of GPI-APs in the Golgi complex and leads to their missorting to the basolateral surface. Overall, our data reveal an unexpected role for calcium in the mechanism of GPI-AP apical sorting in polarized epithelial cells and identify the molecular machinery involved in the clustering of GPI-APs in the Golgi.
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Lebreton S, Paladino S, Zurzolo C. Clustering in the Golgi apparatus governs sorting and function of GPI‐APs in polarized epithelial cells. FEBS Lett 2019; 593:2351-2365. [DOI: 10.1002/1873-3468.13573] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 07/29/2019] [Accepted: 08/05/2019] [Indexed: 01/25/2023]
Affiliation(s)
- Stéphanie Lebreton
- Unité de Trafic Membranaire et Pathogénèse Institut Pasteur Paris France
| | - Simona Paladino
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche Università degli Studi di Napoli Federico II Naples Italy
| | - Chiara Zurzolo
- Unité de Trafic Membranaire et Pathogénèse Institut Pasteur Paris France
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Kokkonen N, Khosrowabadi E, Hassinen A, Harrus D, Glumoff T, Kietzmann T, Kellokumpu S. Abnormal Golgi pH Homeostasis in Cancer Cells Impairs Apical Targeting of Carcinoembryonic Antigen by Inhibiting Its Glycosyl-Phosphatidylinositol Anchor-Mediated Association with Lipid Rafts. Antioxid Redox Signal 2019; 30:5-21. [PMID: 29304557 PMCID: PMC6276271 DOI: 10.1089/ars.2017.7389] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
AIMS Carcinoembryonic antigen (CEACAM5, CEA) is a known tumor marker for colorectal cancer that localizes in a polarized manner to the apical surface in normal colon epithelial cells whereas in cancer cells it is present at both the apical and basolateral surfaces of the cells. Since the Golgi apparatus sorts and transports most proteins to these cell surface domains, we set out here to investigate whether any of the factors commonly associated with tumorigenesis, including hypoxia, generation of reactive oxygen species (ROS), altered redox homeostasis, or an altered Golgi pH, are responsible for mistargeting of CEA to the basolateral surface in cancer cells. RESULTS Using polarized nontumorigenic Madin-Darby canine kidney (MDCK) cells and CaCo-2 colorectal cancer cells as targets, we show that apical delivery of CEA is not affected by hypoxia, ROS, nor changes in the Golgi redox state. Instead, we find that an elevated Golgi pH induces basolateral targeting of CEA and increases its TX-100 solubility, indicating impaired association of CEA with lipid rafts. Moreover, disruption of lipid rafts by methyl-β-cyclodextrin induced accumulation of the CEA protein at the basolateral surface in MDCK cells. Experiments with the glycosylphosphatidylinositol (GPI)-anchorless CEA mutant and CEA-specific GPI-anchored enhanced green fluorescent protein (EGFP-GPI) fusion protein revealed that the GPI-anchor was critical for the pH-dependent apical delivery of the CEA in MDCK cells. Innovation and Conclusion: The findings indicate that an abnormal Golgi pH homeostasis in cancer cells is an important factor that causes mistargeting of CEA to the basolateral surface of cancer cells via inhibiting its GPI-anchor-mediated association with lipid rafts.
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Affiliation(s)
- Nina Kokkonen
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - Elham Khosrowabadi
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - Antti Hassinen
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - Deborah Harrus
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - Tuomo Glumoff
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - Thomas Kietzmann
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - Sakari Kellokumpu
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
- Address correspondence to: Dr. Sakari Kellokumpu, Faculty of Biochemistry and Molecular Medicine, University of Oulu, PO Box 5400, Oulu FI-90014, Finland
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Lebreton S, Zurzolo C, Paladino S. Organization of GPI-anchored proteins at the cell surface and its physiopathological relevance. Crit Rev Biochem Mol Biol 2018; 53:403-419. [PMID: 30040489 DOI: 10.1080/10409238.2018.1485627] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Glycosylphosphatidylinositol (GPI)-anchored proteins (GPI-APs) are a class of proteins attached to the extracellular leaflet of the plasma membrane via a post-translational modification, the glycolipid anchor. The presence of both glycolipid anchor and protein portion confers them unique features. GPI-APs are expressed in all eukaryotes, from fungi to plants and animals. They display very diverse functions ranging from enzymatic activity, signaling, cell adhesion, cell wall metabolism, neuritogenesis, and immune response. Likewise other plasma membrane proteins, the spatio-temporal organization of GPI-APs is critical for their biological activities in physiological conditions. In this review, we will summarize the latest findings on plasma membrane organization of GPI-APs and the mechanism of its regulation in different cell types. We will also examine the involvement of specific GPI-APs namely the prion protein PrPC, the Folate Receptor alpha and the urokinase plasminogen activator receptor in human diseases focusing on neurodegenerative diseases and cancer.
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Affiliation(s)
- Stéphanie Lebreton
- a Unité de Trafic Membranaire et Pathogénèse, Institut Pasteur , Paris , France
| | - Chiara Zurzolo
- a Unité de Trafic Membranaire et Pathogénèse, Institut Pasteur , Paris , France
| | - Simona Paladino
- b Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università di Napoli Federico II , Napoli , Italy.,c CEINGE Biotecnologie Avanzate , Napoli , Italy
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6
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Zurzolo C, Simons K. Glycosylphosphatidylinositol-anchored proteins: Membrane organization and transport. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:632-9. [DOI: 10.1016/j.bbamem.2015.12.018] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2015] [Revised: 12/12/2015] [Accepted: 12/15/2015] [Indexed: 11/17/2022]
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Muñiz M, Riezman H. Trafficking of glycosylphosphatidylinositol anchored proteins from the endoplasmic reticulum to the cell surface. J Lipid Res 2015; 57:352-60. [PMID: 26450970 DOI: 10.1194/jlr.r062760] [Citation(s) in RCA: 74] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Indexed: 11/20/2022] Open
Abstract
In eukaryotes, many cell surface proteins are attached to the plasma membrane via a glycolipid glycosylphosphatidylinositol (GPI) anchor. GPI-anchored proteins (GPI-APs) receive the GPI anchor as a conserved posttranslational modification in the lumen of the endoplasmic reticulum (ER). After anchor attachment, the GPI anchor is structurally remodeled to function as a transport signal that actively triggers the delivery of GPI-APs from the ER to the plasma membrane, via the Golgi apparatus. The structure and composition of the GPI anchor confer a special mode of interaction with membranes of GPI-APs within the lumen of secretory organelles that lead them to be differentially trafficked from other secretory membrane proteins. In this review, we examine the mechanisms by which GPI-APs are selectively transported through the secretory pathway, with special focus on the recent progress made in their actively regulated export from the ER and the trans-Golgi network.
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Affiliation(s)
- Manuel Muñiz
- Departamento de Biología Celular, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain Universidad de Sevilla and Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain
| | - Howard Riezman
- National Centre of Competence in Research (NCCR) Chemical Biology, Department of Biochemistry, University of Geneva, Geneva, Switzerland
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8
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Paladino S, Lebreton S, Zurzolo C. Trafficking and Membrane Organization of GPI-Anchored Proteins in Health and Diseases. CURRENT TOPICS IN MEMBRANES 2015; 75:269-303. [PMID: 26015286 DOI: 10.1016/bs.ctm.2015.03.006] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Glycosylphosphatidylinositol (GPI)-anchored proteins (GPI-APs) are a class of lipid-anchored proteins attached to the membranes by a glycolipid anchor that is added, as posttranslation modification, in the endoplasmic reticulum. GPI-APs are expressed at the cell surface of eukaryotes where they play diverse vital functions. Like all plasma membrane proteins, GPI-APs must be correctly sorted along the different steps of the secretory pathway to their final destination. The presence of both a glycolipid anchor and a protein portion confers special trafficking features to GPI-APs. Here, we discuss the recent advances in the field of GPI-AP trafficking, focusing on the mechanisms regulating their biosynthetic pathway and plasma membrane organization. We also discuss how alterations of these mechanisms can result in different diseases. Finally, we will examine the strict relationship between the trafficking and function of GPI-APs in epithelial cells.
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Affiliation(s)
- Simona Paladino
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università Federico II, Napoli, Italy; CEINGE Biotecnologie Avanzate, Napoli, Italy
| | - Stéphanie Lebreton
- Unité de Trafic Membranaire et Pathogénèse, Institut Pasteur, Paris, France
| | - Chiara Zurzolo
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università Federico II, Napoli, Italy; Unité de Trafic Membranaire et Pathogénèse, Institut Pasteur, Paris, France
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Moscatelli A, Gagliardi A, Maneta-Peyret L, Bini L, Stroppa N, Onelli E, Landi C, Scali M, Idilli AI, Moreau P. Characterisation of detergent-insoluble membranes in pollen tubes of Nicotiana tabacum (L.). Biol Open 2015; 4:378-99. [PMID: 25701665 PMCID: PMC4359744 DOI: 10.1242/bio.201410249] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Pollen tubes are the vehicle for sperm cell delivery to the embryo sac during fertilisation of Angiosperms. They provide an intriguing model for unravelling mechanisms of growing to extremes. The asymmetric distribution of lipids and proteins in the pollen tube plasma membrane modulates ion fluxes and actin dynamics and is maintained by a delicate equilibrium between exocytosis and endocytosis. The structural constraints regulating polarised secretion and asymmetric protein distribution on the plasma membrane are mostly unknown. To address this problem, we investigated whether ordered membrane microdomains, namely membrane rafts, might contribute to sperm cell delivery. Detergent insoluble membranes, rich in sterols and sphingolipids, were isolated from tobacco pollen tubes. MALDI TOF/MS analysis revealed that actin, prohibitins and proteins involved in methylation reactions and in phosphoinositide pattern regulation are specifically present in pollen tube detergent insoluble membranes. Tubulins, voltage-dependent anion channels and proteins involved in membrane trafficking and signalling were also present. This paper reports the first evidence of membrane rafts in Angiosperm pollen tubes, opening new perspectives on the coordination of signal transduction, cytoskeleton dynamics and polarised secretion.
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Affiliation(s)
- Alessandra Moscatelli
- Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milan, Italy
| | - Assunta Gagliardi
- Laboratorio di Proteomica Funzionale, Dipartimento di Scienze della Vita, Università degli Studi di Siena, Via Aldo Moro 2, 53100 Siena, Italy
| | - Lilly Maneta-Peyret
- Laboratoire de Biogenèse Membranaire, Université Bordeaux Segalen, 71 Avenue Edouard Bourlaux, 33883 Villenave d'Ornon, France
| | - Luca Bini
- Laboratorio di Proteomica Funzionale, Dipartimento di Scienze della Vita, Università degli Studi di Siena, Via Aldo Moro 2, 53100 Siena, Italy
| | - Nadia Stroppa
- Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milan, Italy
| | - Elisabetta Onelli
- Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milan, Italy
| | - Claudia Landi
- Laboratorio di Proteomica Funzionale, Dipartimento di Scienze della Vita, Università degli Studi di Siena, Via Aldo Moro 2, 53100 Siena, Italy
| | - Monica Scali
- Dipartimento di Scienze della Vita, Università degli Studi di Siena, Via P. A. Mattioli 4, 53100 Siena, Italy
| | - Aurora Irene Idilli
- Dipartimento di Bioscienze, Università degli Studi di Milano, Via Celoria 26, 20133 Milan, Italy Present address: Institute of Biophysics, National Research Council and FBK, 38123 Trento, Italy
| | - Patrick Moreau
- Laboratoire de Biogenèse Membranaire, Université Bordeaux Segalen, 71 Avenue Edouard Bourlaux, 33883 Villenave d'Ornon, France
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10
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Paladino S, Lebreton S, Tivodar S, Formiggini F, Ossato G, Gratton E, Tramier M, Coppey-Moisan M, Zurzolo C. Golgi sorting regulates organization and activity of GPI proteins at apical membranes. Nat Chem Biol 2014; 10:350-357. [PMID: 24681536 PMCID: PMC4027978 DOI: 10.1038/nchembio.1495] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Accepted: 02/19/2014] [Indexed: 01/01/2023]
Abstract
Here we combined classical biochemistry with new biophysical approaches to study the organization of glycosylphosphatidylinositol (GPI)-anchored proteins (GPI-APs) with high spatial and temporal resolution at the plasma membrane of polarized epithelial cells. We show that in polarized MDCK cells, after sorting in the Golgi, each GPI-AP reaches the apical surface in homoclusters. Golgi-derived homoclusters are required for their subsequent plasma membrane organization into cholesterol-dependent heteroclusters. By contrast, in nonpolarized MDCK cells, GPI-APs are delivered to the surface as monomers in an unpolarized manner and are not able to form heteroclusters. We further demonstrate that this GPI-AP organization is regulated by the content of cholesterol in the Golgi apparatus and is required to maintain the functional state of the protein at the apical membrane. Thus, in contrast to fibroblasts, in polarized epithelial cells, a selective cholesterol-dependent sorting mechanism in the Golgi regulates both the organization and function of GPI-APs at the apical surface.
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Affiliation(s)
- Simona Paladino
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università degli Studi di Napoli Federico II, Napoli, Italy
- CEINGE Biotecnologie Avanzate, Napoli, Italy
| | - Stéphanie Lebreton
- Unité de Trafic Membranaire et Pathogénèse, Institut Pasteur, Paris, France
| | - Simona Tivodar
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università degli Studi di Napoli Federico II, Napoli, Italy
| | | | - Giulia Ossato
- Laboratory for Fluorescence Dynamics, University of California, Irvine, California
| | - Enrico Gratton
- Laboratory for Fluorescence Dynamics, University of California, Irvine, California
| | - Marc Tramier
- Institut de génétique et dévelopement de Rennes, UMR 6290
| | - Maïté Coppey-Moisan
- Complexes macromoléculaires en cellules vivantes, Institut Jacques Monod, UMR 7592 CNRS, University Paris-Diderot, France
| | - Chiara Zurzolo
- Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Università degli Studi di Napoli Federico II, Napoli, Italy
- Unité de Trafic Membranaire et Pathogénèse, Institut Pasteur, Paris, France
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11
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Walch L. Emerging role of the scaffolding protein Dlg1 in vesicle trafficking. Traffic 2014; 14:964-73. [PMID: 23829493 DOI: 10.1111/tra.12089] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Revised: 07/02/2013] [Accepted: 07/06/2013] [Indexed: 01/23/2023]
Abstract
Discs large 1 (Dlg1) is a modular scaffolding protein implicated in the control of cell polarity through assembly of specific multiprotein complexes, including receptors, ion channels and signaling proteins, at specialized zones of the plasma membrane. Recent data have shown that in addition to these well-known interaction partners, Dlg1 may also recruit components of the vesicle trafficking machinery either to the plasma membrane or to transport vesicles. Here, we discuss Dlg1 function in vesicle formation, targeting, tethering and fusion, in both the exocytotic and endocytotic pathways. These pathways contribute to cell functions as major and diverse as glutamatergic activity in the neurons, membrane homeostasis in Schwann cell myelination, insulin stimulation of glucose transport in adipocytes, or endothelial secretion of the hemostatic protein, von Willebrand factor (VWF).
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Affiliation(s)
- Laurence Walch
- INSERM U698, Université Paris 7, Hemostasis, Bio-engineering and Cardiovascular Remodeling, CHU X. Bichat, Paris, France.
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12
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Rac1 participates in thermally induced alterations of the cytoskeleton, cell morphology and lipid rafts, and regulates the expression of heat shock proteins in B16F10 melanoma cells. PLoS One 2014; 9:e89136. [PMID: 24586549 PMCID: PMC3930703 DOI: 10.1371/journal.pone.0089136] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 01/17/2014] [Indexed: 11/19/2022] Open
Abstract
Eukaryotic cells exhibit a characteristic response to hyperthermic treatment, involving morphological and cytoskeletal alterations and the induction of heat shock protein synthesis. Small GTPases of the Ras superfamily are known to serve as molecular switches which mediate responses to extracellular stimuli. We addressed here how small GTPase Rac1 integrates signals from heat stress and simultaneously induces various cellular changes in mammalian cells. As evidence that Rac1 is implicated in the heat shock response, we first demonstrated that both mild (41.5°C) and severe (43°C) heat shock induced membrane translocation of Rac1. Following inhibition of the activation or palmitoylation of Rac1, the size of its plasma membrane-bound pool was significantly decreased while the heat shock-induced alterations in the cytoskeleton and cell morphology were prevented. We earlier documented that the size distribution pattern of cholesterol-rich rafts is temperature dependent and hypothesized that this is coupled to the triggering mechanism of stress sensing and signaling. Interestingly, when plasma membrane localization of Rac1 was inhibited, a different and temperature independent average domain size was detected. In addition, inhibition of the activation or palmitoylation of Rac1 resulted in a strongly decreased expression of the genes of major heat shock proteins hsp25 and hsp70 under both mild and severe heat stress conditions.
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Galmes R, Delaunay JL, Maurice M, Aït-Slimane T. Oligomerization is required for normal endocytosis/transcytosis of a GPI-anchored protein in polarized hepatic cells. J Cell Sci 2013; 126:3409-16. [PMID: 23750006 DOI: 10.1242/jcs.126250] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Targeting of glycosyl-phosphatidylinositol (GPI)-anchored proteins (GPI-APs) in polarized epithelial cells depends on their association with detergent-resistant membrane microdomains called rafts. In MDCK cells, GPI-APs associate with rafts in the trans-Golgi network and are directly delivered to the apical membrane. It has been shown that oligomerization is required for their stabilization in rafts and their apical targeting. In hepatocytes, GPI-APs are first delivered to the basolateral membrane and secondarily reach the apical membrane by transcytosis. We investigated whether oligomerization is required for raft association and apical sorting of GPI-APs in polarized HepG2 cells, and at which step of the pathway oligomerization occurs. Model proteins were wild-type GFP-GPI and a double cysteine GFP-GPI mutant, in which GFP dimerization was impaired. Unlike wild-type GFP-GPI, which was efficiently endocytosed and transcytosed to the apical surface, the double cysteine mutant was basolaterally internalized, but massively accumulated in early endosomes, and reached the bile canaliculi with delayed kinetics. The double cysteine mutant was less resistant to Triton X-100 extraction, and formed fewer high molecular weight complexes. We conclude from these results that, in hepatocytes, oligomerization plays a key role in targeting GPI-APs to the apical membrane, by increasing their affinity for rafts and allowing their transcytosis.
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Affiliation(s)
- Romain Galmes
- INSERM, UMR_S938, Centre de Recherche Saint-Antoine, Paris, France
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14
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Youker RT, Bruns JR, Costa SA, Rbaibi Y, Lanni F, Kashlan OB, Teng H, Weisz OA. Multiple motifs regulate apical sorting of p75 via a mechanism that involves dimerization and higher-order oligomerization. Mol Biol Cell 2013; 24:1996-2007. [PMID: 23637462 PMCID: PMC3681702 DOI: 10.1091/mbc.e13-02-0078] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The sorting signals that direct proteins to the apical surface of polarized epithelial cells are complex and can include posttranslational modifications, such as N- and O-linked glycosylation. Efficient apical sorting of the neurotrophin receptor p75 is dependent on its O-glycosylated membrane proximal stalk, but how this domain mediates targeting is unknown. Protein oligomerization or clustering has been suggested as a common step in the segregation of all apical proteins. Like many apical proteins, p75 forms dimers, and we hypothesized that formation of higher-order clusters mediated by p75 dimerization and interactions of the stalk facilitate its apical sorting. Using fluorescence fluctuation techniques (photon-counting histogram and number and brightness analyses) to study p75 oligomerization status in vivo, we found that wild-type p75-green fluorescent protein forms clusters in the trans-Golgi network (TGN) but not at the plasma membrane. Disruption of either the dimerization motif or the stalk domain impaired both clustering and polarized delivery. Manipulation of O-glycan processing or depletion of multiple galectins expressed in Madin-Darby canine kidney cells had no effect on p75 sorting, suggesting that the stalk domain functions as a structural prop to position other determinants in the lumenal domain of p75 for oligomerization. Additionally, a p75 mutant with intact dimerization and stalk motifs but with a dominant basolateral sorting determinant (Δ250 mutant) did not form oligomers, consistent with a requirement for clustering in apical sorting. Artificially enhancing dimerization restored clustering to the Δ250 mutant but was insufficient to reroute this mutant to the apical surface. Together these studies demonstrate that clustering in the TGN is required for normal biosynthetic apical sorting of p75 but is not by itself sufficient to reroute a protein to the apical surface in the presence of a strong basolateral sorting determinant. Our studies shed new light on the hierarchy of polarized sorting signals and on the mechanisms by which newly synthesized proteins are segregated in the TGN for eventual apical delivery.
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Affiliation(s)
- Robert T Youker
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
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15
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Masaki T. Polarization and myelination in myelinating glia. ISRN NEUROLOGY 2012; 2012:769412. [PMID: 23326681 PMCID: PMC3544266 DOI: 10.5402/2012/769412] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Accepted: 11/13/2012] [Indexed: 01/13/2023]
Abstract
Myelinating glia, oligodendrocytes in central nervous system and Schwann cells in peripheral nervous system, form myelin sheath, a multilayered membrane system around axons enabling salutatory nerve impulse conduction and maintaining axonal integrity. Myelin sheath is a polarized structure localized in the axonal side and therefore is supposed to be formed based on the preceding polarization of myelinating glia. Thus, myelination process is closely associated with polarization of myelinating glia. However, cell polarization has been less extensively studied in myelinating glia than other cell types such as epithelial cells. The ultimate goal of this paper is to provide insights for the field of myelination research by applying the information obtained in polarity study in other cell types, especially epithelial cells, to cell polarization of myelinating glia. Thus, in this paper, the main aspects of cell polarization study in general are summarized. Then, they will be compared with polarization in oligodendrocytes. Finally, the achievements obtained in polarization study for epithelial cells, oligodendrocytes, and other types of cells will be translated into polarization/myelination process by Schwann cells. Then, based on this model, the perspectives in the study of Schwann cell polarization/myelination will be discussed.
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Affiliation(s)
- Toshihiro Masaki
- Department of Medical Science, Teikyo University of Science, 2-2-1 Senju-Sakuragi, Adachi-ku, Tokyo 120-0045, Japan
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16
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Deponte M, Hoppe HC, Lee MC, Maier AG, Richard D, Rug M, Spielmann T, Przyborski JM. Wherever I may roam: Protein and membrane trafficking in P. falciparum-infected red blood cells. Mol Biochem Parasitol 2012; 186:95-116. [DOI: 10.1016/j.molbiopara.2012.09.007] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Revised: 09/21/2012] [Accepted: 09/24/2012] [Indexed: 11/27/2022]
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17
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In vivo incorporation of an azide-labeled sugar analog to detect mammalian glycosylphosphatidylinositol molecules isolated from the cell surface. Carbohydr Res 2012; 362:62-9. [PMID: 23085221 DOI: 10.1016/j.carres.2012.09.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Revised: 09/11/2012] [Accepted: 09/13/2012] [Indexed: 11/22/2022]
Abstract
N-Acetylgalactosamine (GalNAc) linked to the first mannose of glycosylphosphatidylinositol (GPI) core has been previously reported to be heterogeneously present on some mammalian GPI-anchored proteins. Here we present a method for profiling GalNAc-containing GPI-anchored proteins in mammalian cells by metabolic labeling with tetraacetylated N-azidoacetylgalactosamine (GalNAz) followed by biotinylation of the incorporated sugar analog. We have labeled both endogenous and recombinant GPI-anchored proteins with GalNAz, and demonstrated that the azide-activated sugar gets incorporated into the GPI glycan, likely as an unsubstituted side branch of the core structure. GalNAz was detected only on GPI molecules attached to proteins, and not on GPI precursors, indicating that GalNAc modification takes place after the GPI anchor is transferred to protein. We have highlighted the utility of this cell labeling approach by demonstrating the ability to examine specific GalNAc-containing GPI-anchored proteins isolated non-destructively from separate membrane domains (apical and basolateral) in polarized epithelial cells. This study represents the first demonstration of site-specific in vivo labeling of a GPI moiety with a synthetic sugar analog.
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Fujita M, Kinoshita T. GPI-anchor remodeling: Potential functions of GPI-anchors in intracellular trafficking and membrane dynamics. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1821:1050-8. [DOI: 10.1016/j.bbalip.2012.01.004] [Citation(s) in RCA: 164] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2011] [Revised: 12/28/2011] [Accepted: 01/04/2012] [Indexed: 01/08/2023]
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19
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Yano H, Yamamoto-Hino M, Awano W, Aoki-Kinoshita KF, Tsuda-Sakurai K, Okano H, Goto S. Identification of proteasome components required for apical localization of Chaoptin using functional genomics. J Neurogenet 2012; 26:53-63. [PMID: 22417167 DOI: 10.3109/01677063.2012.661497] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Abstract: the distinct localization of membrane proteins with regard to cell polarity is crucial for the structure and function of various organs in multicellular organisms. However, the molecules and mechanisms that regulate protein localization to particular subcellular domains are still largely unknown. To identify the genes involved in regulation of protein localization, the authors performed a large-scale screen using a Drosophila RNA interference (RNAi) library, by which Drosophila genes could be knocked down in a tissue- and stage-specific manner. Drosophila photoreceptor cells have a morphologically distinct apicobasal polarity, along which Chaoptin (Chp), a glycosylphosphatidylinositol (GPI)-anchored membrane protein, and the Na (+) , K(+) -ATPase are localized to the apical and basolateral domains, respectively. By examining the subcellular localization of these proteins, the authors identified 106 genes whose knockdown resulted in mislocalization of Chp and Na(+) , K(+) -ATPase. Gene ontology analysis revealed that the knockdown of proteasome components resulted in mislocalization of Chp to the basolateral plasma membrane. These results suggest that the proteasome is involved, directly or indirectly, in selective localization of Chp to the apical plasma membrane of Drosophila photoreceptor cells.
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Affiliation(s)
- Hiroyuki Yano
- Research Group of Glycobiology and Glycotechnology , Tokyo , Japan
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20
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Zhou G, Liang FX, Romih R, Wang Z, Liao Y, Ghiso J, Luque-Garcia JL, Neubert TA, Kreibich G, Alonso MA, Schaeren-Wiemers N, Sun TT. MAL facilitates the incorporation of exocytic uroplakin-delivering vesicles into the apical membrane of urothelial umbrella cells. Mol Biol Cell 2012; 23:1354-66. [PMID: 22323295 PMCID: PMC3315800 DOI: 10.1091/mbc.e11-09-0823] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
MAL, suggested to play a key role in the apical sorting of membrane proteins, is not involved in the apical sorting of uroplakins. Instead, it plays an important role in facilitating the incorporation of the uroplakin-delivering exocytic vesicles into the apical surface of terminally differentiated urothelial umbrella cells. The apical surface of mammalian bladder urothelium is covered by large (500–1000 nm) two-dimensional (2D) crystals of hexagonally packed 16-nm uroplakin particles (urothelial plaques), which play a role in permeability barrier function and uropathogenic bacterial binding. How the uroplakin proteins are delivered to the luminal surface is unknown. We show here that myelin-and-lymphocyte protein (MAL), a 17-kDa tetraspan protein suggested to be important for the apical sorting of membrane proteins, is coexpressed with uroplakins in differentiated urothelial cell layers. MAL depletion in Madin–Darby canine kidney cells did not affect, however, the apical sorting of uroplakins, but it decreased the rate by which uroplakins were inserted into the apical surface. Moreover, MAL knockout in vivo led to the accumulation of fusiform vesicles in mouse urothelial superficial umbrella cells, whereas MAL transgenic overexpression in vivo led to enhanced exocytosis and compensatory endocytosis, resulting in the accumulation of the uroplakin-degrading multivesicular bodies. Finally, although MAL and uroplakins cofloat in detergent-resistant raft fractions, they are associated with distinct plaque and hinge membrane subdomains, respectively. These data suggest a model in which 1) MAL does not play a role in the apical sorting of uroplakins; 2) the propensity of uroplakins to polymerize forming 16-nm particles and later large 2D crystals that behave as detergent-resistant (giant) rafts may drive their apical targeting; 3) the exclusion of MAL from the expanding 2D crystals of uroplakins explains the selective association of MAL with the hinge areas in the uroplakin-delivering fusiform vesicles, as well as at the apical surface; and 4) the hinge-associated MAL may play a role in facilitating the incorporation of the exocytic uroplakin vesicles into the corresponding hinge areas of the urothelial apical surface.
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Affiliation(s)
- Ge Zhou
- Department of Cell Biology, NYU Cancer Institute, NYU Langone Medical Center, New York University, New York, NY 10016, USA
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21
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Surma MA, Klose C, Simons K. Lipid-dependent protein sorting at the trans-Golgi network. Biochim Biophys Acta Mol Cell Biol Lipids 2011; 1821:1059-67. [PMID: 22230596 DOI: 10.1016/j.bbalip.2011.12.008] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2011] [Revised: 12/02/2011] [Accepted: 12/03/2011] [Indexed: 12/14/2022]
Abstract
In eukaryotic cells, the trans-Golgi network serves as a sorting station for post-Golgi traffic. In addition to coat- and adaptor-mediated mechanisms, studies in mammalian epithelial cells and yeast have provided evidence for lipid-dependent protein sorting as a major delivery mechanism for cargo sorting to the cell surface. The mechanism for lipid-mediated sorting is the generation of raft platforms of sphingolipids, sterols and specific sets of cargo proteins by phase segregation in the TGN. Here, we review the evidence for such lipid-raft-based sorting at the TGN, as well as their involvement in the formation of TGN-to-PM transport carriers. This article is part of a Special Issue entitled Lipids and Vesicular Transport.
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Affiliation(s)
- Michal A Surma
- Max Planck Institute for Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307 Dresden, Germany
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22
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Imjeti NS, Lebreton S, Paladino S, de la Fuente E, Gonzalez A, Zurzolo C. N-Glycosylation instead of cholesterol mediates oligomerization and apical sorting of GPI-APs in FRT cells. Mol Biol Cell 2011; 22:4621-34. [PMID: 21998201 PMCID: PMC3226479 DOI: 10.1091/mbc.e11-04-0320] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
In contrast to MDCK cells, in FRT cells oligomerization and apical sorting of GPI-APs are mediated by N-glycosylation independent of cholesterol and raft association. Sorting of glycosylphosphatidyl-inositol–anchored proteins (GPI-APs) in polarized epithelial cells is not fully understood. Oligomerization in the Golgi complex has emerged as the crucial event driving apical segregation of GPI-APs in two different kind of epithelial cells, Madin–Darby canine kidney (MDCK) and Fisher rat thyroid (FRT) cells, but whether the mechanism is conserved is unknown. In MDCK cells cholesterol promotes GPI-AP oligomerization, as well as apical sorting of GPI-APs. Here we show that FRT cells lack this cholesterol-driven oligomerization as apical sorting mechanism. In these cells both apical and basolateral GPI-APs display restricted diffusion in the Golgi likely due to a cholesterol-enriched membrane environment. It is striking that N-glycosylation is the critical event for oligomerization and apical sorting of GPI-APs in FRT cells but not in MDCK cells. Our data indicate that at least two mechanisms exist to determine oligomerization in the Golgi leading to apical sorting of GPI-APs. One depends on cholesterol, and the other depends on N-glycosylation and is insensitive to cholesterol addition or depletion.
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Affiliation(s)
- Naga Salaija Imjeti
- Institut Pasteur, Unité de Traffic Membranaire et Pathogenèse, 75015 Paris, France
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23
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Puig B, Altmeppen HC, Thurm D, Geissen M, Conrad C, Braulke T, Glatzel M. N-glycans and glycosylphosphatidylinositol-anchor act on polarized sorting of mouse PrP(C) in Madin-Darby canine kidney cells. PLoS One 2011; 6:e24624. [PMID: 21931781 PMCID: PMC3169634 DOI: 10.1371/journal.pone.0024624] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Accepted: 08/14/2011] [Indexed: 11/18/2022] Open
Abstract
The cellular prion protein (PrP(C)) plays a fundamental role in prion disease. PrP(C) is a glycosylphosphatidylinositol (GPI)-anchored protein with two variably occupied N-glycosylation sites. In general, GPI-anchor and N-glycosylation direct proteins to apical membranes in polarized cells whereas the majority of mouse PrP(C) is found in basolateral membranes in polarized Madin-Darby canine kidney (MDCK) cells. In this study we have mutated the first, the second, and both N-glycosylation sites of PrP(C) and also replaced the GPI-anchor of PrP(C) by the Thy-1 GPI-anchor in order to investigate the role of these signals in sorting of PrP(C) in MDCK cells. Cell surface biotinylation experiments and confocal microscopy showed that lack of one N-linked oligosaccharide leads to loss of polarized sorting of PrP(C). Exchange of the PrP(C) GPI-anchor for the one of Thy-1 redirects PrP(C) to the apical membrane. In conclusion, both N-glycosylation and GPI-anchor act on polarized sorting of PrP(C), with the GPI-anchor being dominant over N-glycans.
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Affiliation(s)
- Berta Puig
- Institute of Neuropathology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Hermann C. Altmeppen
- Institute of Neuropathology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Dana Thurm
- Institute of Neuropathology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Markus Geissen
- Institute of Neuropathology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Catharina Conrad
- Institute of Neuropathology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Thomas Braulke
- Department of Biochemistry, Children's Hospital University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Markus Glatzel
- Institute of Neuropathology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- * E-mail:
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24
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Sohail A, Marco M, Zhao H, Shi Q, Merriman S, Mobashery S, Fridman R. Characterization of the dimerization interface of membrane type 4 (MT4)-matrix metalloproteinase. J Biol Chem 2011; 286:33178-89. [PMID: 21828052 DOI: 10.1074/jbc.m111.253369] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
MT4-MMP (MMP17) belongs to a unique subset of membrane type-matrix metalloproteinases that are anchored to the cell surface via a glycosylphosphatidylinositol moiety. However, little is known about its biochemical properties. Here, we report that MT4-MMP is displayed on the cell surface as a mixed population of monomeric, dimeric, and oligomeric forms. Sucrose gradient fractionation demonstrated that these forms of MT4-MMP are all present in lipid rafts. Mutational and computational analyses revealed that Cys(564), which is present within the stem region, mediates MT4-MMP homodimerization by forming a disulfide bond. Substitution of Cys(564) results in a more rapid MT4-MMP turnover, when compared with the wild-type enzyme, consistent with a role for dimerization in protein stability. Expression of MT4-MMP in Madin-Darby canine kidney cells enhanced cell migration and invasion of Matrigel, a process that requires catalytic activity. However, a serine substitution at Cys(564) did not reduce MT4-MMP-stimulated cell invasion of Matrigel suggesting that homodimerization is not required for this process. Deglycosylation studies showed that MT4-MMP is modified by N-glycosylation. Moreover, inhibition of N-glycosylation by tunicamycin diminished the extent of MT4-MMP dimerization suggesting that N-glycans may confer stability to the dimeric form. Taken together, the data presented here provide a new insight into the characteristics of MT4-MMP and highlight the common and distinct properties of the glycosylphosphatidylinositol-anchored membrane type-matrix metalloproteinases.
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Affiliation(s)
- Anjum Sohail
- Department of Pathology and the Karmanos Cancer Institute, Wayne State University, Detroit, Michigan 48201, USA
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25
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Structural remodeling, trafficking and functions of glycosylphosphatidylinositol-anchored proteins. Prog Lipid Res 2011; 50:411-24. [PMID: 21658410 DOI: 10.1016/j.plipres.2011.05.002] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Glycosylphosphatidylinositol (GPI) is a glycolipid that is covalently attached to proteins as a post-translational modification. Such modification leads to the anchoring of the protein to the outer leaflet of the plasma membrane. Proteins that are decorated with GPIs have unique properties in terms of their physical nature. In particular, these proteins tend to accumulate in lipid rafts, which are critical for the functions and trafficking of GPI-anchored proteins (GPI-APs). Recent studies mainly using mutant cells revealed that various structural remodeling reactions occur to GPIs present in GPI-APs as they are transported from the endoplasmic reticulum to the cell surface. This review examines the recent progress describing the mechanisms of structural remodeling of mammalian GPI-anchors, such as inositol deacylation, glycan remodeling and fatty acid remodeling, with particular focus on their trafficking and functions, as well as the pathogenesis involving GPI-APs and their deficiency.
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26
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Abstract
Infection by prions involves conversion of a host-encoded cell surface protein (PrP(C)) to a disease-related isoform (PrP(Sc)). PrP(C) carries two glycosylation sites variably occupied by complex N-glycans, which have been suggested by previous studies to influence the susceptibility to these diseases and to determine characteristics of prion strains. We used the Rov cell system, which is susceptible to sheep prions, to generate a series of PrP(C) glycosylation mutants with mutations at one or both attachment sites. We examined their subcellular trafficking and ability to convert into PrP(Sc) and to sustain stable prion propagation in the absence of wild-type PrP. The susceptibility to infection of mutants monoglycosylated at either site differed dramatically depending on the amino acid substitution. Aglycosylated double mutants showed overaccumulation in the Golgi compartment and failed to be infected. Introduction of an ectopic glycosylation site near the N terminus fully restored cell surface expression of PrP but not convertibility into PrP(Sc), while PrP(C) with three glycosylation sites conferred cell permissiveness to infection similarly to the wild type. In contrast, predominantly aglycosylated molecules with nonmutated N-glycosylation sequons, produced in cells expressing glycosylphosphatidylinositol-anchorless PrP(C), were able to form infectious PrP(Sc). Together our findings suggest that glycosylation is important for efficient trafficking of anchored PrP to the cell surface and sustained prion propagation. However, properly trafficked glycosylation mutants were not necessarily prone to conversion, thus making it difficult in such studies to discern whether the amino acid changes or glycan chain removal most influences the permissiveness to prion infection.
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Sbai O, Devi TS, Melone MAB, Feron F, Khrestchatisky M, Singh LP, Perrone L. RAGE-TXNIP axis is required for S100B-promoted Schwann cell migration, fibronectin expression and cytokine secretion. J Cell Sci 2010; 123:4332-9. [PMID: 21098642 DOI: 10.1242/jcs.074674] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
During peripheral nerve injury, Schwann cells (SCs) adopt a migratory phenotype and remodel the extracellular matrix and provide a supportive activity for neuron regeneration. SCs synthesize neurotrophic factors and cytokines that are crucial for the repair of the injured nerve. The receptor for advanced glycation end products (RAGE) and its ligand S100B, which are secreted by SCs, are required for the repair of the injured peripheral nerve in vivo. However, the precise intracellular pathways involved have not been completely elucidated. Here, we show that RAGE-induced S100B secretion involves the recruitment of S100B in lipid rafts and caveolae. Moreover, we demonstrate for the first time that RAGE induces the expression of thioredoxin interacting protein (TXNIP) in SCs and the injured sciatic nerve in vivo. TXNIP is involved in the activation of p38 MAPK, CREB and NFκB in SCs. TXNIP silencing partially inhibits RAGE-induced SC migration and completely abolishes RAGE-induced fibronectin and IL-1β expression. Our results support a model in which TXNIP mediates in part RAGE-induced SC migration and is required for the expression of provisional ECM and pro-inflammatory IL-1β. We provide new insight on the role of the SC RAGE-TXNIP axis in the repair of injured peripheral nerves.
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Affiliation(s)
- Oualid Sbai
- NICN, CNRS UMR 6184, Faculté de Médecine, Université Aix-Marseille, 13344 Marseille Cedex 15, France
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Nelson WJ. Remodeling epithelial cell organization: transitions between front-rear and apical-basal polarity. Cold Spring Harb Perspect Biol 2010; 1:a000513. [PMID: 20066074 DOI: 10.1101/cshperspect.a000513] [Citation(s) in RCA: 213] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Polarized epithelial cells have a distinctive apical-basal axis of polarity for vectorial transport of ions and solutes across the epithelium. In contrast, migratory mesenchymal cells have a front-rear axis of polarity. During development, mesenchymal cells convert to epithelia by coalescing into aggregates that undergo epithelial differentiation. Signaling networks and protein complexes comprising Rho family GTPases, polarity complexes (Crumbs, PAR, and Scribble), and their downstream effectors, including the cytoskeleton and the endocytic and exocytic vesicle trafficking pathways, together regulate the distributions of plasma membrane and cytoskeletal proteins between front-rear and apical-basal polarity. The challenge is to understand how these regulators and effectors are adapted to regulate symmetry breaking processes that generate cell polarities that are specialized for different cellular activities and functions.
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Affiliation(s)
- W James Nelson
- Department of Biology, Stanford University, Stanford, California 94305, USA.
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29
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Weisz OA, Rodriguez-Boulan E. Apical trafficking in epithelial cells: signals, clusters and motors. J Cell Sci 2010; 122:4253-66. [PMID: 19923269 DOI: 10.1242/jcs.032615] [Citation(s) in RCA: 228] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
In the early days of epithelial cell biology, researchers working with kidney and/or intestinal epithelial cell lines and with hepatocytes described the biosynthetic and recycling routes followed by apical and basolateral plasma membrane (PM) proteins. They identified the trans-Golgi network and recycling endosomes as the compartments that carried out apical-basolateral sorting. They described complex apical sorting signals that promoted association with lipid rafts, and simpler basolateral sorting signals resembling clathrin-coated-pit endocytic motifs. They also noticed that different epithelial cell types routed their apical PM proteins very differently, using either a vectorial (direct) route or a transcytotic (indirect) route. Although these original observations have generally held up, recent studies have revealed interesting complexities in the routes taken by apically destined proteins and have extended our understanding of the machinery required to sustain these elaborate sorting pathways. Here, we critically review the current status of apical trafficking mechanisms and discuss a model in which clustering is required to recruit apical trafficking machineries. Uncovering the mechanisms responsible for polarized trafficking and their epithelial-specific variations will help understand how epithelial functional diversity is generated and the pathogenesis of many human diseases.
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Affiliation(s)
- Ora A Weisz
- Department of Medicine and Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, PA 15261, USA.
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30
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Doppel and PrPC co-immunoprecipitate in detergent-resistant membrane domains of epithelial FRT cells. Biochem J 2009; 425:341-51. [PMID: 19888917 PMCID: PMC2825736 DOI: 10.1042/bj20091050] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Dpl (doppel) is a paralogue of the PrPC (cellular prion protein), whose misfolded conformer (the scrapie prion protein, PrPSc) is responsible for the onset of TSEs (transmissible spongiform encephalopathies) or prion diseases. It has been shown that the ectopic expression of Dpl in the brains of some lines of PrP-knockout mice provokes cerebellar ataxia, which can be rescued by the reintroduction of the PrP gene, suggesting a functional interaction between the two proteins. It is, however, still unclear where, and under which conditions, this event may occur. In the present study we addressed this issue by analysing the intracellular localization and the interaction between Dpl and PrPC in FRT (Fischer rat thyroid) cells stably expressing the two proteins separately or together. We show that both proteins localize prevalently on the basolateral surface of FRT cells, in both singly and doubly transfected clones. Interestingly we found that they associate with DRMs (detergent-resistant membranes) or lipid rafts, from where they can be co-immunoprecipitated in a cholesterol-dependent fashion. Although the interaction between Dpl and PrPC has been suggested before, our results provide the first clear evidence that this interaction occurs in rafts and is dependent on the integrity of these membrane microdomains. Furthermore, both Dpl and PrPC could be immunoprecipitated with flotillin-2, a raft protein involved in endocytosis and cell signalling events, suggesting that they share the same lipid environment.
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31
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Kolotuev I, Apaydin A, Labouesse M. Secretion of Hedgehog-related peptides and WNT during Caenorhabditis elegans development. Traffic 2009; 10:803-10. [PMID: 19210682 DOI: 10.1111/j.1600-0854.2008.00871.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
There is growing awareness that endocytic trafficking plays a critical role in cell-cell communication during animal development. We are beginning to understand how endocytosis can initiate, modulate or terminate signaling. In contrast, our knowledge of the mechanisms involved in secreting signaling peptides remains more limited, particularly when it comes to secretion at the apical surface in epithelial cells. In this study, we review the mechanisms that control secretion in Caenorhabditis elegans, focusing on the role of Patched family members and the V0 complex of the vacuolar-adenosine triphosphatase (V-ATPase) in secreting Hedgehog-related peptides and of MIG-14/Wls and the retromer complex in secreting EGL-20/WNT.
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Affiliation(s)
- Irina Kolotuev
- IGBMC, CNRS/INSERM/ULP, 1 rue Laurent Fries, BP.10142, 67400 Illkirch, France
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32
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Abstract
Lipid rafts are nanoscopic assemblies of sphingolipids, cholesterol, and specific membrane proteins that contribute to lateral heterogeneity in eukaryotic membranes. Separation of artificial membranes into liquid-ordered (Lo) and liquid-disordered phases is regarded as a common model for this compartmentalization. However, tight lipid packing in Lo phases seems to conflict with efficient partitioning of raft-associated transmembrane (TM) proteins. To assess membrane order as a component of raft organization, we performed fluorescence spectroscopy and microscopy with the membrane probes Laurdan and C-laurdan. First, we assessed lipid packing in model membranes of various compositions and found cholesterol and acyl chain dependence of membrane order. Then we probed cell membranes by using two novel systems that exhibit inducible phase separation: giant plasma membrane vesicles [Baumgart et al. (2007) Proc Natl Acad Sci USA 104:3165-3170] and plasma membrane spheres. Notably, only the latter support selective inclusion of raft TM proteins with the ganglioside GM1 into one phase. We measured comparable small differences in order between the separated phases of both biomembranes. Lateral packing in the ordered phase of giant plasma membrane vesicles resembled the Lo domain of model membranes, whereas the GM1 phase in plasma membrane spheres exhibited considerably lower order, consistent with different partitioning of lipid and TM protein markers. Thus, lipid-mediated coalescence of the GM1 raft domain seems to be distinct from the formation of a Lo phase, suggesting additional interactions between proteins and lipids to be effective.
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Abstract
Tissue patterning during development relies on cell communication by secreted proteins and receptors that engage in complex signaling crosstalk to induce distinct cell behaviors in a context-dependent fashion. Here I summarize recent insights into basic mechanisms that control the distribution and activities of transforming growth factor beta, Wnt, Hedgehog, and Notch proteins, by regulating trafficking decisions during secretion and endocytosis.
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Affiliation(s)
- Daniel B Constam
- Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL) CH 1015 Lausanne, Switzerland USA.
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Kolotuev I, Apaydin A, Labouesse M. Secretion of Hedgehog-Related Peptides and WNT DuringCaenorhabditis elegansDevelopment. Traffic 2009. [DOI: 10.1111/j.1600-0854.2009.00871.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Sarnataro D, Caputo A, Casanova P, Puri C, Paladino S, Tivodar SS, Campana V, Tacchetti C, Zurzolo C. Lipid rafts and clathrin cooperate in the internalization of PrP in epithelial FRT cells. PLoS One 2009; 4:e5829. [PMID: 19503793 PMCID: PMC2688078 DOI: 10.1371/journal.pone.0005829] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2009] [Accepted: 04/27/2009] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The cellular prion protein (PrP(C)) plays a key role in the pathogenesis of Transmissible Spongiform Encephalopathies in which the protein undergoes post-translational conversion to the infectious form (PrP(Sc)). Although endocytosis appears to be required for this conversion, the mechanism of PrP(C) internalization is still debated, as caveolae/raft- and clathrin-dependent processes have all been reported to be involved. METHODOLOGY/PRINCIPAL FINDINGS We have investigated the mechanism of PrP(C) endocytosis in Fischer Rat Thyroid (FRT) cells, which lack caveolin-1 (cav-1) and caveolae, and in FRT/cav-1 cells which form functional caveolae. We show that PrP(C) internalization requires activated Cdc-42 and is sensitive to cholesterol depletion but not to cav-1 expression suggesting a role for rafts but not for caveolae in PrP(C) endocytosis. PrP(C) internalization is also affected by knock down of clathrin and by the expression of dominant negative Eps15 and Dynamin 2 mutants, indicating the involvement of a clathrin-dependent pathway. Notably, PrP(C) co-immunoprecipitates with clathrin and remains associated with detergent-insoluble microdomains during internalization thus indicating that PrP(C) can enter the cell via multiple pathways and that rafts and clathrin cooperate in its internalization. CONCLUSIONS/SIGNIFICANCE These findings are of particular interest if we consider that the internalization route/s undertaken by PrP(C) can be crucial for the ability of different prion strains to infect and to replicate in different cell lines.
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Affiliation(s)
- Daniela Sarnataro
- Dipartimento di Biologia e Patologia Cellulare e Molecolare, Università degli Studi di Napoli “Federico II”, Napoli, Italy
| | - Anna Caputo
- Dipartimento di Biologia e Patologia Cellulare e Molecolare, Università degli Studi di Napoli “Federico II”, Napoli, Italy
- Unité de Trafic Membranaire et Pathogénèse, Institut Pasteur, Paris, France
| | - Philippe Casanova
- Unité de Trafic Membranaire et Pathogénèse, Institut Pasteur, Paris, France
| | - Claudia Puri
- FIRC Institute of Molecular Oncology Foundation (IFOM), Milano, Italy
| | - Simona Paladino
- Dipartimento di Biologia e Patologia Cellulare e Molecolare, Università degli Studi di Napoli “Federico II”, Napoli, Italy
- CEINGE Biotecnologie Avanzate s.c.a.r.l., Napoli, Italy
| | - Simona S. Tivodar
- Dipartimento di Biologia e Patologia Cellulare e Molecolare, Università degli Studi di Napoli “Federico II”, Napoli, Italy
| | - Vincenza Campana
- Dipartimento di Biologia e Patologia Cellulare e Molecolare, Università degli Studi di Napoli “Federico II”, Napoli, Italy
- Unité de Trafic Membranaire et Pathogénèse, Institut Pasteur, Paris, France
| | - Carlo Tacchetti
- FIRC Institute of Molecular Oncology Foundation (IFOM), Milano, Italy
- MicroscoBio Research Center, Università di Genova, Genova, Italy
- Dipartimento di Medicina Sperimentale, Università di Genova, Genova, Italy
| | - Chiara Zurzolo
- Dipartimento di Biologia e Patologia Cellulare e Molecolare, Università degli Studi di Napoli “Federico II”, Napoli, Italy
- Unité de Trafic Membranaire et Pathogénèse, Institut Pasteur, Paris, France
- * E-mail:
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Luton F, Hexham MJ, Zhang M, Mostov KE. Identification of a cytoplasmic signal for apical transcytosis. Traffic 2009; 10:1128-42. [PMID: 19522755 DOI: 10.1111/j.1600-0854.2009.00941.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Polarized epithelial cells contain apical and basolateral surfaces with distinct protein compositions. To establish and maintain this asymmetry, newly made plasma membrane proteins are sorted in the trans Golgi network for delivery to apical or basolateral surfaces. Signals for basolateral sorting are generally located in the cytoplasmic domain of the protein, whereas signals for apical sorting can be in any part of the protein and can depend on N-linked glycosylation of the protein. Signals for constitutive transcytosis to the apical surface have not been reported. In this study, we used the polymeric immunoglobulin receptor (pIgR), which is biosynthetically delivered to the basolateral surface. There the pIgR can bind a ligand and, with or without bound ligand, the pIgR can then be transcytosed to the apical surface. We found that the glycosylation of the pIgR did not affect the biosynthetic transport of the pIgR. However, glycosylation had an effect on pIgR apical transcytosis. Importantly, analysis of the cytoplasmic tail of the pIgR suggested that a short peptide segment was sufficient to transcytose the pIgR or a neutral reporter from the basolateral to the apical surface. This apical transcytosis sorting signal was not involved in polarized biosynthetic traffic of the pIgR.
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Affiliation(s)
- Frédéric Luton
- Department of Anatomy, and Biochemistry and Biophysics, and Cardiovascular Research Institute, University of California, San Francisco, CA 94158-2140, USA
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Myelin, DIGs, and membrane rafts in the central nervous system. Prostaglandins Other Lipid Mediat 2009; 91:118-29. [PMID: 19379822 DOI: 10.1016/j.prostaglandins.2009.04.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Revised: 04/08/2009] [Accepted: 04/09/2009] [Indexed: 11/21/2022]
Abstract
Over the past 40 years our understanding of the organization of cell membranes has changed dramatically. Membranes are no longer viewed as a homogenous sea of phospholipids studded with randomly positioned islands of proteins. Our current view of the membrane involves the formation of small lipid clusters, comprised mainly of cholesterol and sphingolipids, known as membrane rafts. These lipid clusters apparently include and exclude specific proteins leading to the hypothesis that these domains (1) regulate cellular polarity and compartmentalization through trafficking and sorting, (2) provide platforms for cellular signaling and adhesion, and (3) function as cellular gate keepers. Tremendous controversy surrounds the concept of membrane rafts primarily because these small, highly dynamic entities are too small to be observed with traditional microscopic methods and the most utilized approach for raft analysis relies on poorly quantified, inconsistent biochemical extractions. New analytical approaches are being developed and applied to the study of membrane rafts and these techniques provide great promise for furthering our understanding of these enigmatic domains. In this review we will provide a brief summary of the current understanding of membrane rafts, utilizing the CNS myelin literature for illustrative purposes, and present caveats that should be considered when studying these domains.
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Paladino S, Lebreton S, Tivodar S, Campana V, Tempre R, Zurzolo C. Different GPI-attachment signals affect the oligomerisation of GPI-anchored proteins and their apical sorting. J Cell Sci 2009; 121:4001-7. [PMID: 19056670 DOI: 10.1242/jcs.036038] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
To understand the mechanism involved in the apical sorting of glycosylphosphatidylinositol (GPI)-anchored proteins (GPI-APs) we fused to the C-terminus of GFP the GPI-anchor-attachment signal of the folate receptor (FR) or of the prion protein (PrP), two native GPI-anchored proteins that are sorted apically or basolaterally, respectively, in MDCK cells. We investigated the behaviour of the resulting fusion proteins GFP-FR and GFP-PrP by analysing three parameters: their association with DRMs, their oligomerisation and their apical sorting. Strikingly, we found that different GPI-attachment signals differently modulate the ability of the resulting GFP-fusion protein to oligomerise and to be apically sorted. This is probably owing to differences in the GPI anchor and/or in the surrounding lipid microenvironment. Accordingly, we show that addition of cholesterol to the cells is necessary and sufficient to drive the oligomerisation and consequent apical sorting of GFP-PrP, which under control conditions does not oligomerise and is basolaterally sorted.
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Affiliation(s)
- Simona Paladino
- Dipartimento di Biologia e Patologia Cellulare e Molecolare, Università degli Studi di Napoli Federico II
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Identification of rhoptry trafficking determinants and evidence for a novel sorting mechanism in the malaria parasite Plasmodium falciparum. PLoS Pathog 2009; 5:e1000328. [PMID: 19266084 PMCID: PMC2648313 DOI: 10.1371/journal.ppat.1000328] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2008] [Accepted: 02/04/2009] [Indexed: 01/15/2023] Open
Abstract
The rhoptry of the malaria parasite Plasmodium falciparum is an unusual secretory organelle that is thought to be related to secretory lysosomes in higher eukaryotes. Rhoptries contain an extensive collection of proteins that participate in host cell invasion and in the formation of the parasitophorous vacuole, but little is known about sorting signals required for rhoptry protein targeting. Using green fluorescent protein chimeras and in vitro pull-down assays, we performed an analysis of the signals required for trafficking of the rhoptry protein RAP1. We provide evidence that RAP1 is escorted to the rhoptry via an interaction with the glycosylphosphatidyl inositol-anchored rhoptry protein RAMA. Once within the rhoptry, RAP1 contains distinct signals for localisation within a sub-compartment of the organelle and subsequent transfer to the parasitophorous vacuole after invasion. This is the first detailed description of rhoptry trafficking signals in Plasmodium.
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Catino MA, Paladino S, Tivodar S, Pocard T, Zurzolo C. N- andO-Glycans Are Not Directly Involved in the Oligomerization and Apical Sorting of GPI Proteins. Traffic 2008; 9:2141-50. [DOI: 10.1111/j.1600-0854.2008.00826.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Christensen HM, Harris DA. A deleted prion protein that is neurotoxic in vivo is localized normally in cultured cells. J Neurochem 2008; 108:44-56. [PMID: 19046329 DOI: 10.1111/j.1471-4159.2008.05719.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The prion protein (PrP) possesses sequence-specific domains that endow the molecule with neuroprotective and neurotoxic activities, and that may contribute to the pathogenesis of prion diseases. To further define critical neurotoxic determinants within PrP, we previously generated Tg(DeltaCR) mice that express a form of PrP harboring a deletion of 21 amino acids within the central domain of the protein [Li et al., EMBO J. 26 (2007), 548]. These animals exhibit a neonatal lethal phenotype that is dose-dependently rescued by co-expression of wild-type PrP. In this study, we examined the localization and cell biological properties of the PrP(DeltaCR) protein in cultured cells to further understand the mechanism of PrP(DeltaCR) neurotoxicity. We found that the distribution of PrP(DeltaCR) was identical to that of wild-type PrP in multiple cell lines of both neuronal and non-neuronal origin, and that co-expression of the two proteins did not alter the localization of either one. Both proteins were found in lipid rafts, and both were localized to the apical surface in polarized epithelial cells. Taken together, our results suggest that PrP(DeltaCR) toxicity is not a result of mislocalization or aggregation of the protein, and more likely stems from altered binding interactions leading to the activation of deleterious signaling pathways.
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Affiliation(s)
- Heather M Christensen
- Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, Missouri 63110, USA
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Vagin O, Kraut JA, Sachs G. Role of N-glycosylation in trafficking of apical membrane proteins in epithelia. Am J Physiol Renal Physiol 2008; 296:F459-69. [PMID: 18971212 DOI: 10.1152/ajprenal.90340.2008] [Citation(s) in RCA: 154] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Polarized distribution of plasma membrane transporters and receptors in epithelia is essential for vectorial functions of epithelia. This polarity is maintained by sorting of membrane proteins into apical or basolateral transport containers in the trans-Golgi network and/or endosomes followed by their delivery to the appropriate plasma membrane domains. Sorting depends on the recognition of sorting signals in proteins by specific sorting machinery. In the present review, we summarize experimental evidence for and against the hypothesis that N-glycans attached to the membrane proteins can act as apical sorting signals. Furthermore, we discuss the roles of N-glycans in the apical sorting event per se and their contribution to folding and quality control of glycoproteins in the endoplasmic reticulum or retention of glycoproteins in the plasma membrane. Finally, we review existing hypotheses on the mechanism of apical sorting and discuss the potential roles of the lectins, VIP36 and galectin-3, as putative apical sorting receptors.
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Affiliation(s)
- Olga Vagin
- Department of Physiology, David Geffen School of Medicine at University of California, Bldg. 113, Rm. 324, 11301 Wilshire Blvd., Los Angeles, California 90073, USA.
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Coordinated protein sorting, targeting and distribution in polarized cells. Nat Rev Mol Cell Biol 2008; 9:833-45. [PMID: 18946473 DOI: 10.1038/nrm2525] [Citation(s) in RCA: 396] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The polarized distribution of functions in polarized cells requires the coordinated interaction of three machineries that modify the basic mechanisms of intracellular protein trafficking and distribution. First, intrinsic protein-sorting signals and cellular decoding machineries regulate protein trafficking to plasma membrane domains; second, intracellular signalling complexes define the plasma membrane domains to which proteins are delivered; and third, proteins that are involved in cell-cell and cell-substrate adhesion orientate the three-dimensional distribution of intracellular signalling complexes and, accordingly, the direction of membrane traffic. The integration of these mechanisms into a complex and dynamic network is crucial for normal tissue function and is often defective in disease states.
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Zhao H, Sohail A, Sun Q, Shi Q, Kim S, Mobashery S, Fridman R. Identification and role of the homodimerization interface of the glycosylphosphatidylinositol-anchored membrane type 6 matrix metalloproteinase (MMP25). J Biol Chem 2008; 283:35023-32. [PMID: 18936094 DOI: 10.1074/jbc.m806553200] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The membrane type (MT) 6 matrix metalloproteinase (MMP) (MMP25) is a glycosylphosphatidylinositol-anchored matrix metalloproteinase (MMP) that is highly expressed in leukocytes and in some cancer tissues. We previously showed that natural MT6-MMP is expressed on the cell surface as a major reduction-sensitive form of M(r) 120, likely representing enzyme homodimers held by disulfide bridges. Among the membrane type-MMPs, the stem region of MT6-MMP contains three cysteine residues at positions 530, 532, and 534 which may contribute to dimerization. A systematic site-directed mutagenesis study of the Cys residues in the stem region shows that Cys(532) is involved in MT6-MMP dimerization by forming an intermolecular disulfide bond. The mutagenesis data also suggest that Cys(530) and Cys(534) form an intramolecular disulfide bond. The experimental observations on cysteines were also investigated by computational studies of the stem peptide, which validate these proposals. Dimerization is not essential for transport of MT6-MMP to the cell surface, partitioning into lipid rafts or cleavage of alpha-1-proteinase inhibitor. However, monomeric forms of MT6-MMP exhibited enhanced autolysis and metalloprotease-dependent degradation. Collectively, these studies establish the stem region of MT6-MMP as the dimerization interface, an event whose outcome imparts protease stability to the protein.
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Affiliation(s)
- Huiren Zhao
- Department of Pathology, Wayne State University and Proteases and Cancer Program, Barbara Ann Karmanos Cancer Institute, Detroit, Michigan 48201, USA
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MT4-(MMP17) and MT6-MMP (MMP25), A unique set of membrane-anchored matrix metalloproteinases: properties and expression in cancer. Cancer Metastasis Rev 2008; 27:289-302. [PMID: 18286233 DOI: 10.1007/s10555-008-9129-8] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The process of cancer progression involves the action of multiple proteolytic systems, among which the family of matrix metalloproteinases (MMPs) play a pivotal role. The MMPs evolved to accomplish their proteolytic tasks in multiple cellular and tissue microenvironments including lipid rafts by incorporation and deletions of specific structural domains. The membrane type-MMPs (MT-MMPs) incorporated membrane anchoring domains that display these proteases at the cell surface, and thus they are optimal pericellular proteolytic machines. Two members of the MT-MMP subfamily, MMP-17 (MT4-MMP) and MMP-25 (MT6-MMP), are anchored to the plasma membrane via a glycosyl-phosphatidyl inositol (GPI) anchor, which confers these enzymes a unique set of regulatory and functional mechanisms that separates them from the rest of the MMP family. Discovered almost a decade ago, the body of work on GPI-MT-MMPs today is still surprisingly limited when compared to other MT-MMPs. However, new evidence shows that the GPI-MT-MMPs are highly expressed in human cancer, where they are associated with progression. Accumulating biochemical and functional evidence also highlights their distinct properties. In this review, we summarize the structural, biochemical, and biological properties of GPI-MT-MMPs and present an overview of their expression and role in cancer. We further discuss the potential implications of GPI-anchoring for enzyme function. Finally, we comment on the new scientific challenges that lie ahead to better understand the function and role in cancer of these intriguing but yet unique MMPs.
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Abstract
Heterogeneities in cell membranes due to the ordering of lipids and proteins are thought to play an important role in enabling protein and lipid trafficking throughout the secretory pathway and in maintaining cell polarization. Protein-coated vesicles provide a major mechanism for intracellular transport of select cargo, which may be sorted into lipid microdomains; however, the mechanisms and physical constraints for lipid sorting by protein coats are relatively unexplored. We studied the influence of membrane-tethered protein coats on the sorting, morphology, and phase behavior of liquid-ordered lipid domains in a model system of giant unilamellar vesicles composed of dioleoylphosphatidylcholine, sphingomyelin, and cholesterol. We created protein-coated membranes by forming giant unilamellar vesicles containing a small amount of biotinylated lipid, thereby creating binding sites for streptavidin and avidin proteins in solution. We found that individual tethered proteins colocalize with the liquid-disordered phase, whereas ordered protein domains on the membrane surface colocalize with the liquid-ordered phase. These observations may be explained by considering the thermodynamics of this coupled system, which maximizes its entropy by cosegregating ordered protein and lipid domains. In addition, protein ordering inhibits lipid domain rearrangement and modifies the morphology and miscibility transition temperature of the membrane, most dramatically near the critical point in the membrane phase diagram. This observation suggests that liquid-ordered domains are stabilized by contact with ordered protein domains; it also hints at an approach to the stabilization of lipid microdomains by cross-linked protein clusters or ordered protein coats.
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Fujita M, Jigami Y. Lipid remodeling of GPI-anchored proteins and its function. Biochim Biophys Acta Gen Subj 2008; 1780:410-20. [PMID: 17913366 DOI: 10.1016/j.bbagen.2007.08.009] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2007] [Revised: 08/10/2007] [Accepted: 08/14/2007] [Indexed: 02/07/2023]
Abstract
Many proteins are attached to the cell surface via a conserved post-translational modification, the glycosylphosphatidylinositol (GPI) anchor. GPI-anchored proteins are functionally diverse, but one of their most striking features is their association with lipid microdomains, which consist mainly of sphingolipids and sterols. GPI-anchored proteins modulate various biological functions when they are incorporated into these specialized domains. The biosynthesis of GPI and its attachment to proteins occurs in the endoplasmic reticulum. The lipid moieties of GPI-anchored proteins are further modified during their transport to the cell surface, and these remodeling processes are essential for the association of proteins with lipid microdomains. Recently, several genes required for GPI lipid remodeling have been identified in yeast and mammalian cells. In this review, we describe the pathways for lipid remodeling of GPI-anchored proteins in yeast and mammalian cells, and discuss how lipid remodeling affects the association of GPI-anchored proteins with microdomains in cellular events.
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Affiliation(s)
- Morihisa Fujita
- Research Institute for Cell Engineering, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8566, Japan
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Lázaro-Diéguez F, Colonna C, Cortegano M, Calvo M, Martínez SE, Egea G. Variable actin dynamics requirement for the exit of different cargo from thetrans-Golgi network. FEBS Lett 2007; 581:3875-81. [PMID: 17651738 DOI: 10.1016/j.febslet.2007.07.015] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2007] [Revised: 07/06/2007] [Accepted: 07/08/2007] [Indexed: 01/16/2023]
Abstract
Efficient post-Golgi trafficking depends on microtubules, but actin filaments and actin-associated proteins are also postulated. Here we examined, by inverse fluorescence recovery after photobleaching, the role of actin dynamics in the exit from the TGN of fluorescent-tagged apical or basolateral and raft or non-raft-associated cargoes. Either the actin-stabilizing jasplakinolide or the actin-depolymerising latrunculin B variably but significantly inhibited post-Golgi traffic of non-raft associated apical p75NTR and basolateral VSV-G cargoes. The TGN-exit of the apical-destined VSV-G mutant was impaired only by latrunculin B. Strikingly, the raft-associated GPI-anchor protein was not affected by either actin toxin. Results indicate that actin dynamics participates in the TGN egress of both apical- and basolateral-targeted proteins but is not needed for apical raft-associated cargo.
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Affiliation(s)
- Francisco Lázaro-Diéguez
- Departament de Biologia Cellular i Anatomia Patològica, Facultat de Medicina, Universitat de Barcelona, C/Casanova 143, E-08036 Barcelona, Spain
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