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Budhiraja S, McManus G, Baisiwala S, Perrault EN, Cho S, Saathoff M, Chen L, Park CH, Kazi HA, Dmello C, Lin P, James CD, Sonabend AM, Heiland DH, Ahmed AU. ARF4-mediated retrograde trafficking as a driver of chemoresistance in glioblastoma. Neuro Oncol 2024; 26:1421-1437. [PMID: 38506351 PMCID: PMC11300013 DOI: 10.1093/neuonc/noae059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Indexed: 03/21/2024] Open
Abstract
BACKGROUND Cellular functions hinge on the meticulous orchestration of protein transport, both spatially and temporally. Central to this process is retrograde trafficking, responsible for targeting proteins to the nucleus. Despite its link to many diseases, the implications of retrograde trafficking in glioblastoma (GBM) are still unclear. METHODS To identify genetic drivers of TMZ resistance, we conducted comprehensive CRISPR-knockout screening, revealing ADP-ribosylation factor 4 (ARF4), a regulator of retrograde trafficking, as a major contributor. RESULTS Suppressing ARF4 significantly enhanced TMZ sensitivity in GBM patient-derived xenograft (PDX) models, leading to improved survival rates (P < .01) in both primary and recurrent lines. We also observed that TMZ exposure stimulates ARF4-mediated retrograde trafficking. Proteomics analysis of GBM cells with varying levels of ARF4 unveiled the influence of this pathway on EGFR signaling, with increased nuclear trafficking of EGFR observed in cells with ARF4 overexpression and TMZ treatment. Additionally, spatially resolved RNA-sequencing of GBM patient tissues revealed substantial correlations between ARF4 and crucial nuclear EGFR (nEGFR) downstream targets, such as MYC, STAT1, and DNA-PK. Decreased activity of DNA-PK, a DNA repair protein downstream of nEGFR signaling that contributes to TMZ resistance, was observed in cells with suppressed ARF4 levels. Notably, treatment with DNA-PK inhibitor, KU-57788, in mice with a recurrent PDX line resulted in prolonged survival (P < .01), highlighting the promising therapeutic implications of targeting proteins reliant on ARF4-mediated retrograde trafficking. CONCLUSIONS Our findings demonstrate that ARF4-mediated retrograde trafficking contributes to the development of TMZ resistance, cementing this pathway as a viable strategy to overcome chemoresistance in GBM.
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Affiliation(s)
- Shreya Budhiraja
- Department of Neurological Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
- Northwestern Medicine Malnati Brain Tumor Institute of the Lurie Comprehensive Cancer Center, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Graysen McManus
- Department of Neurological Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | | | - Ella N Perrault
- Department of Neurological Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Sia Cho
- Department of Neurobiology, Northwestern University, Evanston, Illinois, USA
| | - Miranda Saathoff
- Department of Neurological Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Li Chen
- Department of Neurological Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Cheol H Park
- Department of Neurological Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Hasaan A Kazi
- Department of Neurological Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Crismita Dmello
- Department of Neurological Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Peiyu Lin
- Department of Neurological Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - C David James
- Department of Neurological Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
- Northwestern Medicine Malnati Brain Tumor Institute of the Lurie Comprehensive Cancer Center, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Adam M Sonabend
- Department of Neurological Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
- Northwestern Medicine Malnati Brain Tumor Institute of the Lurie Comprehensive Cancer Center, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Dieter H Heiland
- Department of Neurological Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
- Microenvironment and Immunology Research Laboratory, Medical Center - University of Freiburg, Freiburg, Germany
- Department of Neurosurgery, Medical Center - University of Freiburg, Freiburg, Germany
- Faculty of Medicine, University of Freiburg, Freiburg, Germany
- German Cancer Consortium (DKTK), Freiburg, Germany
| | - Atique U Ahmed
- Department of Neurological Surgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
- Northwestern Medicine Malnati Brain Tumor Institute of the Lurie Comprehensive Cancer Center, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
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Erazo-Oliveras A, Muñoz-Vega M, Salinas ML, Wang X, Chapkin RS. Dysregulation of cellular membrane homeostasis as a crucial modulator of cancer risk. FEBS J 2024; 291:1299-1352. [PMID: 36282100 PMCID: PMC10126207 DOI: 10.1111/febs.16665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2022] [Revised: 09/09/2022] [Accepted: 10/24/2022] [Indexed: 11/07/2022]
Abstract
Cellular membranes serve as an epicentre combining extracellular and cytosolic components with membranous effectors, which together support numerous fundamental cellular signalling pathways that mediate biological responses. To execute their functions, membrane proteins, lipids and carbohydrates arrange, in a highly coordinated manner, into well-defined assemblies displaying diverse biological and biophysical characteristics that modulate several signalling events. The loss of membrane homeostasis can trigger oncogenic signalling. More recently, it has been documented that select membrane active dietaries (MADs) can reshape biological membranes and subsequently decrease cancer risk. In this review, we emphasize the significance of membrane domain structure, organization and their signalling functionalities as well as how loss of membrane homeostasis can steer aberrant signalling. Moreover, we describe in detail the complexities associated with the examination of these membrane domains and their association with cancer. Finally, we summarize the current literature on MADs and their effects on cellular membranes, including various mechanisms of dietary chemoprevention/interception and the functional links between nutritional bioactives, membrane homeostasis and cancer biology.
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Affiliation(s)
- Alfredo Erazo-Oliveras
- Program in Integrative Nutrition and Complex Diseases; Texas A&M University; College Station, Texas, 77843; USA
- Department of Nutrition; Texas A&M University; College Station, Texas, 77843; USA
| | - Mónica Muñoz-Vega
- Program in Integrative Nutrition and Complex Diseases; Texas A&M University; College Station, Texas, 77843; USA
- Department of Nutrition; Texas A&M University; College Station, Texas, 77843; USA
| | - Michael L. Salinas
- Program in Integrative Nutrition and Complex Diseases; Texas A&M University; College Station, Texas, 77843; USA
- Department of Nutrition; Texas A&M University; College Station, Texas, 77843; USA
| | - Xiaoli Wang
- Program in Integrative Nutrition and Complex Diseases; Texas A&M University; College Station, Texas, 77843; USA
- Department of Nutrition; Texas A&M University; College Station, Texas, 77843; USA
| | - Robert S. Chapkin
- Program in Integrative Nutrition and Complex Diseases; Texas A&M University; College Station, Texas, 77843; USA
- Department of Nutrition; Texas A&M University; College Station, Texas, 77843; USA
- Center for Environmental Health Research; Texas A&M University; College Station, Texas, 77843; USA
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Diaz-Rohrer B, Castello-Serrano I, Chan SH, Wang HY, Shurer CR, Levental KR, Levental I. Rab3 mediates a pathway for endocytic sorting and plasma membrane recycling of ordered microdomains. Proc Natl Acad Sci U S A 2023; 120:e2207461120. [PMID: 36848577 PMCID: PMC10013782 DOI: 10.1073/pnas.2207461120] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Accepted: 01/31/2023] [Indexed: 03/01/2023] Open
Abstract
The composition of the plasma membrane (PM) must be tightly controlled despite constant, rapid endocytosis, which requires active, selective recycling of endocytosed membrane components. For many proteins, the mechanisms, pathways, and determinants of this PM recycling remain unknown. We report that association with ordered, lipid-driven membrane microdomains (known as rafts) is sufficient for PM localization of a subset of transmembrane proteins and that abrogation of raft association disrupts their trafficking and leads to degradation in lysosomes. Using orthogonal, genetically encoded probes with tunable raft partitioning, we screened for the trafficking machinery required for efficient recycling of engineered microdomain-associated cargo from endosomes to the PM. Using this screen, we identified the Rab3 family as an important mediator of PM localization of microdomain-associated proteins. Disruption of Rab3 reduced PM localization of raft probes and led to their accumulation in Rab7-positive endosomes, suggesting inefficient recycling. Abrogation of Rab3 function also mislocalized the endogenous raft-associated protein Linker for Activation of T cells (LAT), leading to its intracellular accumulation and reduced T cell activation. These findings reveal a key role for lipid-driven microdomains in endocytic traffic and suggest Rab3 as a mediator of microdomain recycling and PM composition.
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Affiliation(s)
- Barbara Diaz-Rohrer
- Department of Molecular Physiology and Biological Physics, Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA22904
| | - Ivan Castello-Serrano
- Department of Molecular Physiology and Biological Physics, Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA22904
| | - Sze Ham Chan
- Department of Molecular Physiology and Biological Physics, Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA22904
| | - Hong-Yin Wang
- Department of Molecular Physiology and Biological Physics, Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA22904
| | - Carolyn R. Shurer
- Department of Molecular Physiology and Biological Physics, Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA22904
| | - Kandice R. Levental
- Department of Molecular Physiology and Biological Physics, Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA22904
| | - Ilya Levental
- Department of Molecular Physiology and Biological Physics, Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, VA22904
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Chip-Based Sensing of the Intercellular Transfer of Cell Surface Proteins: Regulation by the Metabolic State. Biomedicines 2021; 9:biomedicines9101452. [PMID: 34680568 PMCID: PMC8533487 DOI: 10.3390/biomedicines9101452] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 10/05/2021] [Accepted: 10/07/2021] [Indexed: 01/08/2023] Open
Abstract
Glycosylphosphatidylinositol (GPI)-anchored proteins (GPI-APs) are anchored at the surface of mammalian blood and tissue cells through a carboxy-terminal GPI glycolipid. Eventually, they are released into incubation medium in vitro and blood in vivo and subsequently inserted into neighboring cells, potentially leading to inappropriate surface expression or lysis. To obtain first insight into the potential (patho)physiological relevance of intercellular GPI-AP transfer and its biochemical characterization, a cell-free chip- and microfluidic channel-based sensing system was introduced. For this, rat or human adipocyte or erythrocyte plasma membranes (PM) were covalently captured by the TiO2 chip surface operating as the acceptor PM. To measure transfer between PM, donor erythrocyte or adipocyte PM were injected into the channels of a flow chamber, incubated, and washed out, and the type and amount of proteins which had been transferred to acceptor PM evaluated with specific antibodies. Antibody binding was detected as phase shift of horizontal surface acoustic waves propagating over the chip surface. Time- and temperature-dependent transfer, which did not rely on fusion of donor and acceptor PM, was detected for GPI-APs, but not typical transmembrane proteins. Transfer of GPI-APs was found to be prevented by α-toxin, which binds to the glycan core of GPI anchors, and serum proteins in concentration-dependent fashion. Blockade of transfer, which was restored by synthetic phosphoinositolglycans mimicking the glycan core of GPI anchors, led to accumulation in the chip channels of full-length GPI-APs in association with phospholipids and cholesterol in non-membrane structures. Strikingly, efficacy of transfer between adipocytes and erythrocytes was determined by the metabolic state (genotype and feeding state) of the rats, which were used as source for the PM and sera, with upregulation in obese and diabetic rats and counterbalance by serum proteins. The novel chip-based sensing system for GPI-AP transfer may be useful for the prediction and stratification of metabolic diseases as well as elucidation of the putative role of intercellular transfer of cell surface proteins, such as GPI-APs, in (patho)physiological mechanisms.
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5
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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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6
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Rudnik S, Damme M. The lysosomal membrane-export of metabolites and beyond. FEBS J 2021; 288:4168-4182. [PMID: 33067905 DOI: 10.1111/febs.15602] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 10/01/2020] [Accepted: 10/15/2020] [Indexed: 01/01/2023]
Abstract
Lysosomes are degradative organelles in eukaryotic cells mediating the hydrolytic catabolism of various macromolecules to small basic building blocks. These low-molecular-weight metabolites are transported across the lysosomal membrane and reused in the cytoplasm and other organelles for biosynthetic pathways. Even though in the past 20 years our understanding of the lysosomal membrane regarding various transporters, other integral and peripheral membrane proteins, the lipid composition, but also its turnover has dramatically improved, there are still many unresolved questions concerning key aspects of the function of the lysosomal membrane. These include a possible function of lysosomes as a cellular storage compartment, yet unidentified transporters mediating the export such as various amino acids, mechanisms mediating the transport of lysosomal membrane proteins from the Golgi apparatus to lysosomes, and the turnover of lysosomal membrane proteins. Here, we review the current knowledge about the lysosomal membrane and identify some of the open questions that need to be solved in the future for a comprehensive and complete understanding of how lysosomes communicate with other organelles, cellular processes, and pathways.
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Affiliation(s)
- Sönke Rudnik
- Institut für Biochemie, Christian-Albrechts-Universität zu Kiel, Kiel, Germany
| | - Markus Damme
- Institut für Biochemie, Christian-Albrechts-Universität zu Kiel, Kiel, Germany
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7
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A New Take on Prion Protein Dynamics in Cellular Trafficking. Int J Mol Sci 2020; 21:ijms21207763. [PMID: 33092231 PMCID: PMC7589859 DOI: 10.3390/ijms21207763] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Revised: 10/14/2020] [Accepted: 10/14/2020] [Indexed: 12/12/2022] Open
Abstract
The mobility of cellular prion protein (PrPC) in specific cell membrane domains and among distinct cell compartments dictates its molecular interactions and directs its cell function. PrPC works in concert with several partners to organize signaling platforms implicated in various cellular processes. The scaffold property of PrPC is able to gather a molecular repertoire to create heterogeneous membrane domains that favor endocytic events. Dynamic trafficking of PrPC through multiple pathways, in a well-orchestrated mechanism of intra and extracellular vesicular transport, defines its functional plasticity, and also assists the conversion and spreading of its infectious isoform associated with neurodegenerative diseases. In this review, we highlight how PrPC traffics across intra- and extracellular compartments and the consequences of this dynamic transport in governing cell functions and contributing to prion disease pathogenesis.
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8
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Vidal M. Exosomes and GPI-anchored proteins: Judicious pairs for investigating biomarkers from body fluids. Adv Drug Deliv Rev 2020; 161-162:110-123. [PMID: 32828789 DOI: 10.1016/j.addr.2020.08.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 07/27/2020] [Accepted: 08/14/2020] [Indexed: 12/16/2022]
Abstract
Exosomes are 50-100 nm membranous vesicles actively released by cells which can be indicative of a diseased cell status. They contain various kinds of molecule - proteins, mRNA, miRNA, lipids - that are actively being studied as potential biomarkers. Hereafter I put forward several arguments in favor of the potential use of glycosylphosphatidylinositol-anchored proteins (GPI-APs) as biomarkers especially of cancerous diseases. I will briefly update readers on the exosome field and review various features of GPI-APs, before further discussing the advantages of this class of proteins as potential exosomal biomarkers. I will finish with a few examples of exosomal GPI-APs that have already been demonstrated to be good prognostic markers, as well as innovative approaches developed to quantify these exosomal biomarkers.
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9
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Kaźmierczak Z, Szostak-Paluch K, Przybyło M, Langner M, Witkiewicz W, Jędruchniewicz N, Dąbrowska K. Endocytosis in cellular uptake of drug delivery vectors: Molecular aspects in drug development. Bioorg Med Chem 2020; 28:115556. [PMID: 32828419 DOI: 10.1016/j.bmc.2020.115556] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 05/05/2020] [Accepted: 05/06/2020] [Indexed: 12/16/2022]
Abstract
Drug delivery vectors are widely applied to increase drug efficacy while reducing the side effects and potential toxicity of a drug. They allow for patient-tailored therapy, dose titration, and therapeutic drug monitoring. A major part of drug delivery systems makes use of large nanocarriers: liposomes or virus-like particles (VLPs). These systems allow for a relatively large amount of cargo with good stability of vectors, and they offer multiple options for targeting vectors in vivo. Here we discuss endocytic pathways that are available for drug delivery by large nanocarriers. We focus on molecular aspects of the process, including an overview of potential molecular targets for studies of drug delivery vectors and for future solutions allowing targeted drug delivery.
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Affiliation(s)
- Zuzanna Kaźmierczak
- Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wrocław, Poland
| | - Kamila Szostak-Paluch
- Research and Development Center, Regional Specialized Hospital, Wrocław, Poland; Wrocław University of Science and Technology, Faculty of Fundamental Technical Problems, Department of Biomedical Engineering, Wrocław, Poland
| | - Magdalena Przybyło
- Wrocław University of Science and Technology, Faculty of Fundamental Technical Problems, Department of Biomedical Engineering, Wrocław, Poland; Lipid Systems sp z o.o., Wrocław, Poland
| | - Marek Langner
- Wrocław University of Science and Technology, Faculty of Fundamental Technical Problems, Department of Biomedical Engineering, Wrocław, Poland; Lipid Systems sp z o.o., Wrocław, Poland
| | - Wojciech Witkiewicz
- Research and Development Center, Regional Specialized Hospital, Wrocław, Poland
| | | | - Krystyna Dąbrowska
- Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wrocław, Poland; Research and Development Center, Regional Specialized Hospital, Wrocław, Poland.
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11
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Bourgeat L, Serghei A, Lesieur C. Experimental Protein Molecular Dynamics: Broadband Dielectric Spectroscopy coupled with nanoconfinement. Sci Rep 2019; 9:17988. [PMID: 31784681 PMCID: PMC6884508 DOI: 10.1038/s41598-019-54562-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Accepted: 11/05/2019] [Indexed: 11/09/2022] Open
Abstract
Protein dynamics covers multiple spatiotemporal scale processes, among which slow motions, not much understood even though they are underlying protein folding and protein functions. Protein slow motions are associated with structural heterogeneity, short-lived and poorly populated conformations, hard to detect individually. In addition, they involve collective motions of many atoms, not easily tracked by simulation and experimental devices. Here we propose a biophysical approach, coupling geometrical nanoconfinement and broadband dielectric spectroscopy (BDS), which distinguishes protein conformations by their respective molecular dynamics. In particular, protein-unfolding intermediates, usually poorly populated in macroscopic solutions are detected. The protein dynamics is observed under unusual conditions (sample nanoconfinement and dehydration) highlighting the robustness of protein structure and protein dynamics to a variety of conditions consistent with protein sustainability. The protein dielectric signals evolve with the temperature of thermal treatments indicating sensitivity to atomic and molecular interaction changes triggered by the protein thermal unfolding. As dipole fluctuations depend on both collective large-scale motions and local motions, the approach offers a prospect to track in-depth unfolding events.
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Affiliation(s)
- Laëtitia Bourgeat
- AMPERE, CNRS, Univ. Lyon, 69622, Lyon, France
- IMP, CNRS, Univ. Lyon, 69622, Lyon, France
| | | | - Claire Lesieur
- AMPERE, CNRS, Univ. Lyon, 69622, Lyon, France.
- Institut Rhônalpin des systèmes complexes, IXXI-ENS-Lyon, 69007, Lyon, France.
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McCauliff LA, Langan A, Li R, Ilnytska O, Bose D, Waghalter M, Lai K, Kahn PC, Storch J. Intracellular cholesterol trafficking is dependent upon NPC2 interaction with lysobisphosphatidic acid. eLife 2019; 8:50832. [PMID: 31580258 PMCID: PMC6855803 DOI: 10.7554/elife.50832] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2019] [Accepted: 10/02/2019] [Indexed: 12/12/2022] Open
Abstract
Unesterified cholesterol accumulation in the late endosomal/lysosomal (LE/LY) compartment is the cellular hallmark of Niemann-Pick C (NPC) disease, caused by defects in the genes encoding NPC1 or NPC2. We previously reported the dramatic stimulation of NPC2 cholesterol transport rates to and from model membranes by the LE/LY phospholipid lysobisphosphatidic acid (LBPA). It had been previously shown that enrichment of NPC1-deficient cells with LBPA results in cholesterol clearance. Here we demonstrate that LBPA enrichment in human NPC2-deficient cells, either directly or via its biosynthetic precursor phosphtidylglycerol (PG), is entirely ineffective, indicating an obligate functional interaction between NPC2 and LBPA in cholesterol trafficking. We further demonstrate that NPC2 interacts directly with LBPA and identify the NPC2 hydrophobic knob domain as the site of interaction. Together these studies reveal a heretofore unknown step of intracellular cholesterol trafficking which is critically dependent upon the interaction of LBPA with functional NPC2 protein. Cholesterol is a type of fat that is essential for many processes in the body, such as repairing damaged cells and producing certain hormones. Normally, cholesterol enters cells from the bloodstream and is then moved to the parts of the cell that need it via a process known as ‘trafficking’. When cholesterol trafficking goes wrong, abnormally large amounts of cholesterol and other fats accumulate within the cell. Over time, these fatty deposits become toxic to cells and eventually damage the affected tissues. Niemann-Pick type C disease (NPC) is a severe genetic disorder affecting cholesterol trafficking. It is characterized by cholesterol build-up in multiple tissues, including the brain, which ultimately causes degeneration and death of nerve cells. Two proteins, NPC1 and NPC2, are involved in NPC disease. Both proteins normally help move cholesterol out of important trafficking compartments (known as the endosomal and lysosomal compartments) to other areas of the cell where it is needed. Patients with the disease can have mutations in either the gene for NPC1 or the gene for NPC2. This means that cells from NPC1 patients do not make enough functional NPC1 protein (but contain working NPC2), and vice versa. Previous studies had shown that giving cells with NPC1 mutations large amounts of the small molecule lysobisphosphatidic acid (LBPA for short) could compensate for the loss of NPC1, and stop the toxic build-up of cholesterol. McCauliff, Langan, Li et al. therefore wanted to explore exactly how LBPA was doing this. They had shown that LBPA dramatically increased the ability of purified NPC2 protein to transport cholesterol, and wondered if the effect of LBPA in the cells without NPC1 depended on NPC2. They predicted that boosting LBPA levels would not work in cells lacking NPC2. Biochemical experiments using purified protein showed that LBPA and NPC2 did indeed interact directly with each other. Systematically changing different building blocks of NPC2 revealed that a single region of the protein is sensitive to LBPA, and when this region was altered, LBPA could no longer interact with NPC2. Since LBPA is naturally produced by cells, they then stimulated cells grown in the laboratory to generate more LBPA using its precursor phosphatidylglycerol. They used cells from patients with mutations in either NPC1 or NPC2 and demonstrated that LBPA’s ability to reverse the accumulation of cholesterol was dependent on its interaction with NPC2. Thus, increasing LBPA levels in cells from patients with NPC1 mutations was beneficial, but had no effect on cells from patients with NPC2 mutations. These results shed new light not only on how cells transport cholesterol, but also on potential methods to combat disorders of cellular cholesterol trafficking. In the future, LBPA could be developed as a genetically tailored, patient-specific therapy for diseases like NPC.
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Affiliation(s)
- Leslie A McCauliff
- Department of Nutritional Sciences, Rutgers University, New Brunswick, United States.,Rutgers Center for Lipid Research, Rutgers University, New Brunswick, United States
| | - Annette Langan
- Department of Nutritional Sciences, Rutgers University, New Brunswick, United States.,Rutgers Center for Lipid Research, Rutgers University, New Brunswick, United States
| | - Ran Li
- Department of Nutritional Sciences, Rutgers University, New Brunswick, United States.,Rutgers Center for Lipid Research, Rutgers University, New Brunswick, United States
| | - Olga Ilnytska
- Department of Nutritional Sciences, Rutgers University, New Brunswick, United States.,Rutgers Center for Lipid Research, Rutgers University, New Brunswick, United States
| | - Debosreeta Bose
- Department of Nutritional Sciences, Rutgers University, New Brunswick, United States.,Rutgers Center for Lipid Research, Rutgers University, New Brunswick, United States
| | - Miriam Waghalter
- Department of Nutritional Sciences, Rutgers University, New Brunswick, United States
| | - Kimberly Lai
- Department of Nutritional Sciences, Rutgers University, New Brunswick, United States
| | - Peter C Kahn
- Department of Biochemistry and Microbiology, Rutgers University, New Brunswick, United States
| | - Judith Storch
- Department of Nutritional Sciences, Rutgers University, New Brunswick, United States.,Rutgers Center for Lipid Research, Rutgers University, New Brunswick, United States
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13
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Vidal M. Exosomes: Revisiting their role as "garbage bags". Traffic 2019; 20:815-828. [PMID: 31418976 DOI: 10.1111/tra.12687] [Citation(s) in RCA: 98] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Accepted: 08/14/2019] [Indexed: 12/17/2022]
Abstract
In recent years, the term "extracellular vesicle" (EV) has been used to define different types of vesicles released by various cells. It includes plasma membrane-derived vesicles (ectosomes/microvesicles) and endosome-derived vesicles (exosomes). Although it remains difficult to evaluate the compartment of origin of the two kinds of vesicles once released, it is critical to discriminate these vesicles because their mode of biogenesis is probably directly related to their physiologic function and/or to the physio-pathologic state of the producing cell. The purpose of this review is to specifically consider exosome secretion and its consequences in terms of a material loss for producing cells, rather than on the effects of exosomes once they are taken up by recipient cells. I especially describe one putative basic function of exosomes, that is, to convey material out of cells for off-site degradation by recipient cells. As illustrated by some examples, these components could be evacuated from cells for various reasons, for example, to promote "differentiation" or enhance homeostatic responses. This basic function might explain why so many diseases have made use of the exosomal pathway during pathogenesis.
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Affiliation(s)
- Michel Vidal
- LPHI - Université de Montpellier, CNRS, Montpellier, France
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14
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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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15
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Kalappurakkal JM, Anilkumar AA, Patra C, van Zanten TS, Sheetz MP, Mayor S. Integrin Mechano-chemical Signaling Generates Plasma Membrane Nanodomains that Promote Cell Spreading. Cell 2019; 177:1738-1756.e23. [PMID: 31104842 PMCID: PMC6879320 DOI: 10.1016/j.cell.2019.04.037] [Citation(s) in RCA: 84] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Revised: 11/15/2018] [Accepted: 04/17/2019] [Indexed: 01/19/2023]
Abstract
Glycosylphosphatidylinositol-anchored proteins (GPI-APs) are a major class of lipid-anchored plasma membrane proteins. GPI-APs form nanoclusters generated by cortical acto-myosin activity. While our understanding of the physical principles governing this process is emerging, the molecular machinery and functional relevance of GPI-AP nanoclustering are unknown. Here, we first show that a membrane receptor signaling pathway directs nanocluster formation. Arg-Gly-Asp motif-containing ligands bound to the β1-integrin receptor activate src and focal adhesion kinases, resulting in RhoA signaling. This cascade triggers actin-nucleation via specific formins, which, along with myosin activity, drive the nanoclustering of membrane proteins with actin-binding domains. Concurrently, talin-mediated activation of the mechano-transducer vinculin is required for the coupling of the acto-myosin machinery to inner-leaflet lipids, thereby generating GPI-AP nanoclusters. Second, we show that these nanoclusters are functional; disruption of their formation either in GPI-anchor remodeling mutants or in vinculin mutants impairs cell spreading and migration, hallmarks of integrin function.
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Affiliation(s)
- Joseph Mathew Kalappurakkal
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bellary Road, Bangalore, India
| | - Anupama Ambika Anilkumar
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bellary Road, Bangalore, India; St. Johns Research Institute, Bangalore, India
| | - Chandrima Patra
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bellary Road, Bangalore, India
| | - Thomas S van Zanten
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bellary Road, Bangalore, India
| | - Michael P Sheetz
- Mechanobiology Institute, National University of Singapore, Singapore, Singapore
| | - Satyajit Mayor
- National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bellary Road, Bangalore, India; Institute for Stem Cell Biology and Regenerative Medicine, Bellary Road, Bangalore, India.
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16
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Vorberg IM. All the Same? The Secret Life of Prion Strains within Their Target Cells. Viruses 2019; 11:v11040334. [PMID: 30970585 DOI: 10.3390/v11040334] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Revised: 04/02/2019] [Accepted: 04/05/2019] [Indexed: 01/23/2023] Open
Abstract
Prions are infectious β-sheet-rich protein aggregates composed of misfolded prion protein (PrPSc) that do not possess coding nucleic acid. Prions replicate by recruiting and converting normal cellular PrPC into infectious isoforms. In the same host species, prion strains target distinct brain regions and cause different disease phenotypes. Prion strains are associated with biophysically distinct PrPSc conformers, suggesting that strain properties are enciphered within alternative PrPSc quaternary structures. So far it is unknown how prion strains target specific cells and initiate productive infections. Deeper mechanistic insight into the prion life cycle came from cell lines permissive to a range of different prion strains. Still, it is unknown why certain cell lines are refractory to infection by one strain but permissive to another. While pharmacologic and genetic manipulations revealed subcellular compartments involved in prion replication, little is known about strain-specific requirements for endocytic trafficking pathways. This review summarizes our knowledge on how prions replicate within their target cells and on strain-specific differences in prion cell biology.
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Affiliation(s)
- Ina M Vorberg
- German Center for Neurodegenerative Diseases (DZNE e.V.), Sigmund-Freud-Strasse 27, 53127 Bonn, Germany.
- Rheinische Friedrich-Wilhelms-Universität Bonn, 53127 Bonn, Germany.
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17
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Kathuria R, Chattopadhyay K. Vibrio choleraecytolysin: Multiple facets of the membrane interaction mechanism of aβ-barrel pore-forming toxin. IUBMB Life 2018; 70:260-266. [DOI: 10.1002/iub.1725] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2018] [Accepted: 02/05/2018] [Indexed: 12/22/2022]
Affiliation(s)
- Reema Kathuria
- Centre for Protein Science, Design and Engineering, Department of Biological Sciences; Indian Institute of Science Education and Research Mohali; Manauli, Mohali Punjab India
| | - Kausik Chattopadhyay
- Centre for Protein Science, Design and Engineering, Department of Biological Sciences; Indian Institute of Science Education and Research Mohali; Manauli, Mohali Punjab India
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18
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Arumugam S, Kaur A. The Lipids of the Early Endosomes: Making Multimodality Work. Chembiochem 2017; 18:1053-1060. [PMID: 28374483 DOI: 10.1002/cbic.201700046] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Indexed: 01/21/2023]
Abstract
Early endosomes are dynamic intracellular compartments that fuse with incoming endocytic carrier vesicles and associated cargoes from the plasma membrane. It has been long known that the chemical structures of lipids confer striking properties and rich biochemistry on bilayers. Although the organisational principles of the plasma membrane are relatively better understood, understanding endosomal membranes has been challenging. It has become increasingly apparent that endosomal membranes, because of their lipid compositions and interactions, use distinct lipid chemistries. We discuss the biochemical and biophysical phenomena in play at the early endosomal membrane. We focus on cholesterol, phosphoinositides, and phosphatidylserine and their clear roles in endosome functions. We discuss the various principles and mechanisms underpinning how these lipids are implicated at the functional level in the working of endosomes, and we summarise early endosomes as a multimodal organelle employing distinct lipid-specific mechanisms.
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Affiliation(s)
- Senthil Arumugam
- European Molecular Biology Laboratory Australia Node for Single Molecule Science and ARC Centre of Excellence in Advanced Molecular Imaging, School of Medical Sciences, University of New South Wales, Sydney, 2052, New South Wales, Australia
| | - Amandeep Kaur
- European Molecular Biology Laboratory Australia Node for Single Molecule Science and ARC Centre of Excellence in Advanced Molecular Imaging, School of Medical Sciences, University of New South Wales, Sydney, 2052, New South Wales, Australia
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19
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Tangsongcharoen C, Jupatanakul N, Promdonkoy B, Dimopoulos G, Boonserm P. Molecular analysis of Culex quinquefasciatus larvae responses to Lysinibacillus sphaericus Bin toxin. PLoS One 2017; 12:e0175473. [PMID: 28406958 PMCID: PMC5391067 DOI: 10.1371/journal.pone.0175473] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Accepted: 03/26/2017] [Indexed: 12/22/2022] Open
Abstract
Lysinibacillus sphaericus produces the mosquito larvicidal binary toxin consisting of BinA and BinB, which are both required for toxicity against Culex and Anopheles larvae. The molecular mechanisms behind Bin toxin-induced damage remain unexplored. We used whole-genome microarray-based transcriptome analysis to better understand how Culex larvae respond to Bin toxin treatment at the molecular level. Our analyses of Culex quinquefasciatus larvae transcriptome changes at 6, 12, and 18 h after Bin toxin treatment revealed a wide range of transcript signatures, including genes linked to the cytoskeleton, metabolism, immunity, and cellular stress, with a greater number of down-regulated genes than up-regulated genes. Bin toxin appears to mainly repress the expression of genes involved in metabolism, the mitochondrial electron transport chain, and the protein transporter of the outer/inner mitochondrial membrane. The induced genes encode proteins linked to mitochondrial-mediated apoptosis and cellular detoxification including autophagic processes and lysosomal compartments. This study is, to our knowledge, the first microarray analysis of Bin toxin-induced transcriptional responses in Culex larvae, providing a basis for an in-depth understanding of the molecular nature of Bin toxin-induced damage.
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Affiliation(s)
- Chontida Tangsongcharoen
- Institute of Molecular Biosciences, Mahidol University, Salaya, Phuttamonthon, Nakhon Pathom, Thailand
| | - Natapong Jupatanakul
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Boonhiang Promdonkoy
- National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Khlong Nueng, Khlong Luang, Pathum Thani, Thailand
| | - George Dimopoulos
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Panadda Boonserm
- Institute of Molecular Biosciences, Mahidol University, Salaya, Phuttamonthon, Nakhon Pathom, Thailand
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20
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Trubiani O, Guarnieri S, Orciani M, Salvolini E, Di Primio R. Sphingolipid Microdomains Mediate CD38 Internalization: Topography of the Endocytosis. Int J Immunopathol Pharmacol 2016; 17:293-300. [PMID: 15461863 DOI: 10.1177/039463200401700309] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Plasma membranes of several cell types contain specialized microdomains (or lipid rafts) enriched in sphingolipids, cholesterol, sphingomyelin, and glycosyl-phosphatidylinositol-anchored proteins. These membrane domains are characterized by detergent insolubility at low temperatures and low buoyant density. Human CD38 is the prototype of a gene family encoding surface molecules endowed with multiple functional activities. The endocytosis of the human CD38 molecule has been investigated in normal lymphocytes and in a number of leukemia- and lymphoma-derived cell lines demonstrating that internalization after CD38 ligation is a reproducible event involving only a fraction of the whole amount of the surface molecule. This study reports the results obtained by conventional, confocal, and electron microscopy on the effects induced by the engagement of the molecule with agonistic mAb, reproducing the signals mediated by its natural ligand. The results demonstrate that the endocytosis induced as consequence of CD38 ligation is preceded by a thorough rearrangement of the cell surface with formation of glycosphingolipid- and cholesterol-rich plasma membrane microdomains. These data suggest that specialized raft microdomains might be the plasma membrane structure through which CD38 translocates at intracellular level. The CD38/lipid interactions during the coated pit formation trigger a process that generate membrane curvature, considered as the first step of CD38 endocytosis. Moreover, ultrastructural studies show that early CD38+ endosomes are pleiomorphic and contain cisternal and vesicular regions. Late endosomes exhibit a complex organisation, containing uncoupled CD38-ligand multivesicular- or multilamellar-regions.
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Affiliation(s)
- O Trubiani
- Dipartimento di Scienze Odontostomatologiche, University of Chieti, Italy
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21
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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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22
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Chapter Six - The Ubiquitin Network in the Control of EGFR Endocytosis and Signaling. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2016; 141:225-76. [DOI: 10.1016/bs.pmbts.2016.03.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
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23
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Kettle E, Page SL, Morgan GP, Malladi CS, Wong CL, Boadle RA, Marsh BJ, Robinson PJ, Chircop M. A Cholesterol-Dependent Endocytic Mechanism Generates Midbody Tubules During Cytokinesis. Traffic 2015; 16:1174-92. [DOI: 10.1111/tra.12328] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 08/24/2015] [Accepted: 08/24/2015] [Indexed: 11/28/2022]
Affiliation(s)
- Emma Kettle
- Children's Medical Research Institute; The University of Sydney; 214 Hawkesbury Road Westmead NSW 2145 Australia
| | - Scott L. Page
- Children's Medical Research Institute; The University of Sydney; 214 Hawkesbury Road Westmead NSW 2145 Australia
| | - Garry P. Morgan
- Institute for Molecular Biosciences, Queensland Bioscience Precinct; The University of Queensland; Brisbane Queensland 4072 Australia
| | - Chandra S. Malladi
- Department of Molecular Physiology, School of Medicine; University of Western Sydney; Penrith NSW 2751 Australia
| | - Chin L. Wong
- Children's Medical Research Institute; The University of Sydney; 214 Hawkesbury Road Westmead NSW 2145 Australia
| | - Ross A. Boadle
- Westmead Millennium Institute for Medical Research; 176 Hawkesbury Road Westmead NSW 2145 Australia
| | - Brad J. Marsh
- Institute for Molecular Biosciences, Queensland Bioscience Precinct; The University of Queensland; Brisbane Queensland 4072 Australia
| | - Phillip J. Robinson
- Children's Medical Research Institute; The University of Sydney; 214 Hawkesbury Road Westmead NSW 2145 Australia
| | - Megan Chircop
- Children's Medical Research Institute; The University of Sydney; 214 Hawkesbury Road Westmead NSW 2145 Australia
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24
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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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25
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Puig B, Altmeppen H, Glatzel M. The GPI-anchoring of PrP: implications in sorting and pathogenesis. Prion 2015; 8:11-8. [PMID: 24509692 DOI: 10.4161/pri.27892] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The cellular prion protein (PrP(C)) is an N-glycosylated GPI-anchored protein usually present in lipid rafts with numerous putative functions. When it changes its conformation to a pathological isoform (then referred to as PrP(Sc)), it is an essential part of the prion, the agent causing fatal and transmissible neurodegenerative prion diseases. There is growing evidence that toxicity and neuronal damage on the one hand and propagation/infectivity on the other hand are two distinct processes of the disease and that the GPI-anchor attachment of PrP(C) and PrP(Sc) plays an important role in protein localization and in neurotoxicity. Here we review how the signal sequence of the GPI-anchor matters in PrP(C) localization, how an altered cellular localization of PrP(C) or differences in GPI-anchor composition can affect prion infection, and we discuss through which mechanisms changes on the anchorage of PrP(C) can modify the disease process.
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26
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Jaensch N, Corrêa IR, Watanabe R. Stable cell surface expression of GPI-anchored proteins, but not intracellular transport, depends on their fatty acid structure. Traffic 2014; 15:1305-29. [PMID: 25196094 DOI: 10.1111/tra.12224] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 09/02/2014] [Accepted: 09/02/2014] [Indexed: 11/28/2022]
Abstract
Glycosylphosphatidylinositol-anchored proteins (GPI-APs) are a class of lipid anchored proteins expressed on the cell surface of eukaryotes. The potential interaction of GPI-APs with ordered lipid domains enriched in cholesterol and sphingolipids has been proposed to function in the intracellular transport of these lipid anchored proteins. Here, we examined the biological importance of two saturated fatty acids present in the phosphatidylinositol moiety of GPI-APs. These fatty acids are introduced by the action of lipid remodeling enzymes and required for the GPI-AP association within ordered lipid domains. We found that the fatty acid remodeling is not required for either efficient Golgi-to-plasma membrane transport or selective endocytosis via GPI-enriched early endosomal compartment (GEEC)/ clathrin-independent carrier (CLIC) pathway, whereas cholesterol depletion significantly affects both pathways independent of their fatty acid structure. Therefore, the mechanism of cholesterol dependence does not appear to be related to the interaction with ordered lipid domains mediated by two saturated fatty acids. Furthermore, cholesterol extraction drastically releases the unremodeled GPI-APs carrying an unsaturated fatty acid from the cell surface, but not remodeled GPI-APs carrying two saturated fatty acids. This underscores the essential role of lipid remodeling to ensure a stable membrane association of GPI-APs particularly under potential membrane lipid perturbation.
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Affiliation(s)
- Nina Jaensch
- Department of Biochemistry, University of Geneva Sciences II, CH1-1211 Geneva, Switzerland
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27
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Cytomegalovirus immune evasion by perturbation of endosomal trafficking. Cell Mol Immunol 2014; 12:154-69. [PMID: 25263490 PMCID: PMC4654299 DOI: 10.1038/cmi.2014.85] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 08/15/2014] [Accepted: 08/16/2014] [Indexed: 12/30/2022] Open
Abstract
Cytomegaloviruses (CMVs), members of the herpesvirus family, have evolved a variety of mechanisms to evade the immune response to survive in infected hosts and to establish latent infection. They effectively hide infected cells from the effector mechanisms of adaptive immunity by eliminating cellular proteins (major histocompatibility Class I and Class II molecules) from the cell surface that display viral antigens to CD8 and CD4 T lymphocytes. CMVs also successfully escape recognition and elimination of infected cells by natural killer (NK) cells, effector cells of innate immunity, either by mimicking NK cell inhibitory ligands or by downregulating NK cell-activating ligands. To accomplish these immunoevasion functions, CMVs encode several proteins that function in the biosynthetic pathway by inhibiting the assembly and trafficking of cellular proteins that participate in immune recognition and thereby, block their appearance at the cell surface. However, elimination of these proteins from the cell surface can also be achieved by perturbation of their endosomal route and subsequent relocation from the cell surface into intracellular compartments. Namely, the physiological route of every cellular protein, including immune recognition molecules, is characterized by specific features that determine its residence time at the cell surface. In this review, we summarize the current understanding of endocytic trafficking of immune recognition molecules and perturbations of the endosomal system during infection with CMVs and other members of the herpesvirus family that contribute to their immune evasion mechanisms.
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28
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Diaz-Rohrer B, Levental KR, Levental I. Rafting through traffic: Membrane domains in cellular logistics. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:3003-3013. [PMID: 25130318 DOI: 10.1016/j.bbamem.2014.07.029] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Revised: 07/28/2014] [Accepted: 07/31/2014] [Indexed: 01/03/2023]
Abstract
The intricate and tightly regulated organization of eukaryotic cells into spatially and functionally distinct membrane-bound compartments is a defining feature of complex organisms. These compartments are defined by their lipid and protein compositions, with their limiting membrane as the functional interface to the rest of the cell. Thus, proper segregation of membrane proteins and lipids is necessary for the maintenance of organelle identity, and this segregation must be maintained despite extensive, rapid membrane exchange between compartments. Sorting processes of high efficiency and fidelity are required to avoid potentially deleterious mis-targeting and maintain cellular function. Although much molecular machinery associated with membrane traffic (i.e. membrane budding/fusion/fission) has been characterized both structurally and biochemically, the mechanistic details underlying the tightly regulated distribution of membranes between subcellular locations remain to be elucidated. This review presents evidence for the role of ordered lateral membrane domains known as lipid rafts in both biosynthetic sorting in the late secretory pathway, as well as endocytosis and recycling to/from the plasma membrane. Although such evidence is extensive and the involvement of membrane domains in sorting is definitive, specific mechanistic details for raft-dependent sorting processes remain elusive.
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Affiliation(s)
- Blanca Diaz-Rohrer
- University of Texas Health Science Center at Houston, 6431 Fannin St, Houston, TX 77030, USA
| | - Kandice R Levental
- University of Texas Health Science Center at Houston, 6431 Fannin St, Houston, TX 77030, USA
| | - Ilya Levental
- University of Texas Health Science Center at Houston, 6431 Fannin St, Houston, TX 77030, USA; Cancer Prevention and Research Institute of Texas, USA.
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29
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Oupický D, Li J. Bioreducible polycations in nucleic acid delivery: past, present, and future trends. Macromol Biosci 2014; 14:908-22. [PMID: 24678057 PMCID: PMC4410047 DOI: 10.1002/mabi.201400061] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 02/19/2014] [Indexed: 12/16/2022]
Abstract
Polycations that are degradable by reduction of disulfide bonds are developed for applications in delivery of nucleic acids. This Feature Article surveys methods of synthesis of bioreducible polycations and discusses current understanding of the mechanism of action of bioreducible polyplexes. Emphasis is placed on the relationship between the biological redox environment and toxicity, trafficking, transfection activity, and in vivo behavior of bioreducible polycations and polyplexes.
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Affiliation(s)
- David Oupický
- Department of Pharmaceutical Sciences, Center for Drug Delivery and Nanomedicine, University of Nebraska Medical Center, Durham Research Center, 985830 Nebraska Medical Center, Omaha, NE 68198-5830, USA.
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30
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Muñiz M, Zurzolo C. Sorting of GPI-anchored proteins from yeast to mammals--common pathways at different sites? J Cell Sci 2014; 127:2793-801. [PMID: 24906797 DOI: 10.1242/jcs.148056] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Glycosylphosphatidylinositol (GPI)-anchored proteins (GPI-APs) are luminal secretory cargos that are attached by a post-translational glycolipid modification, the GPI anchor, to the external leaflet of the plasma membrane. GPI-APs are conserved among eukaryotes and possess many diverse and vital functions for which the GPI membrane attachment appears to be essential. The presence of the GPI anchor and its subsequent modifications along the secretory pathway confer to the anchored proteins unique trafficking properties that make GPI-APs an exceptional system to study mechanisms of sorting. In this Commentary, we discuss the recent advances in the field of GPI-AP sorting focusing on the mechanisms operating at the level of the exit from the ER and from the trans-Golgi network (TGN), which take place, respectively, in yeast and in polarized mammalian cells. By considering the similarities and differences between these two sorting events, we present unifying principles that appear to work at different sorting stations and in different organisms.
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Affiliation(s)
- Manuel Muñiz
- Department of Cell Biology, University of Seville, Avda. Reina Mercedes s/n 41012 Seville, Spain
| | - Chiara Zurzolo
- Institut Pasteur, Unité de Trafic Membranaire et Pathogénèse, 75724 Paris CEDEX 15, France
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31
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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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32
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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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33
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Rouvinski A, Karniely S, Kounin M, Moussa S, Goldberg MD, Warburg G, Lyakhovetsky R, Papy-Garcia D, Kutzsche J, Korth C, Carlson GA, Godsave SF, Peters PJ, Luhr K, Kristensson K, Taraboulos A. Live imaging of prions reveals nascent PrPSc in cell-surface, raft-associated amyloid strings and webs. ACTA ACUST UNITED AC 2014; 204:423-41. [PMID: 24493590 PMCID: PMC3912534 DOI: 10.1083/jcb.201308028] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mammalian prions refold host glycosylphosphatidylinositol-anchored PrP(C) into β-sheet-rich PrP(Sc). PrP(Sc) is rapidly truncated into a C-terminal PrP27-30 core that is stable for days in endolysosomes. The nature of cell-associated prions, their attachment to membranes and rafts, and their subcellular locations are poorly understood; live prion visualization has not previously been achieved. A key obstacle has been the inaccessibility of PrP27-30 epitopes. We overcame this hurdle by focusing on nascent full-length PrP(Sc) rather than on its truncated PrP27-30 product. We show that N-terminal PrP(Sc) epitopes are exposed in their physiological context and visualize, for the first time, PrP(Sc) in living cells. PrP(Sc) resides for hours in unexpected cell-surface, slow moving strings and webs, sheltered from endocytosis. Prion strings observed by light and scanning electron microscopy were thin, micrometer-long structures. They were firmly cell associated, resisted phosphatidylinositol-specific phospholipase C, aligned with raft markers, fluoresced with thioflavin, and were rapidly abolished by anti-prion glycans. Prion strings and webs are the first demonstration of membrane-anchored PrP(Sc) amyloids.
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Affiliation(s)
- Alexander Rouvinski
- Department of Microbiology and Molecular Genetics, Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
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34
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Ganguly S, Mukherjee A, Mazumdar B, Ghosh AN, Banerjee KK. The β-prism lectin domain of Vibrio cholerae hemolysin promotes self-assembly of the β-pore-forming toxin by a carbohydrate-independent mechanism. J Biol Chem 2013; 289:4001-8. [PMID: 24356964 DOI: 10.1074/jbc.m113.522284] [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: 11/06/2022] Open
Abstract
Vibrio cholerae cytolysin/hemolysin (VCC) is an amphipathic 65-kDa β-pore-forming toxin with a C-terminal β-prism lectin domain. Because deletion or point mutation of the lectin domain seriously compromises hemolytic activity, it is thought that carbohydrate-dependent interactions play a critical role in membrane targeting of VCC. To delineate the contributions of the cytolysin and lectin domains in pore formation, we used wild-type VCC, 50-kDa VCC (VCC(50)) without the lectin domain, and mutant VCC(D617A) with no carbohydrate-binding activity. VCC and its two variants with no carbohydrate-binding activity moved to the erythrocyte stroma with apparent association constants on the order of 10(7) M(-1). However, loss of the lectin domain severely reduced the efficiency of self-association of the VCC monomer with the β-barrel heptamer in the synthetic lipid bilayer from ∼83 to 27%. Notably, inactivation of the carbohydrate-binding activity by the D617A mutation marginally reduced oligomerization to ∼77%. Oligomerization of VCC(50) was temperature-insensitive; by contrast, VCC self-assembly increased with increasing temperature, suggesting that the process is driven by entropy and opposed by enthalpy. Asialofetuin, the β1-galactosyl-terminated glycoprotein inhibitor of VCC-induced hemolysis, promoted oligomerization of 65-kDa VCC to a species that resembled the membrane-inserted heptamer in stoichiometry and morphology but had reduced global amphipathicity. In conclusion, we propose (i) that the β-prism lectin domain facilitated toxin assembly by producing entropy during relocation in the heptamer and (ii) that glycoconjugates inhibited VCC by promoting its assembly to a water-soluble, less amphipathic oligomer variant with reduced ability to penetrate the bilayer.
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35
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Hilgemann DW, Fine M, Linder ME, Jennings BC, Lin MJ. Massive endocytosis triggered by surface membrane palmitoylation under mitochondrial control in BHK fibroblasts. eLife 2013; 2:e01293. [PMID: 24282236 PMCID: PMC3839538 DOI: 10.7554/elife.01293] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Large Ca transients cause massive endocytosis (MEND) in BHK fibroblasts by nonclassical mechanisms. We present evidence that MEND depends on mitochondrial permeability transition pore (PTP) openings, followed by coenzyme A (CoA) release, acyl CoA synthesis, and membrane protein palmitoylation. MEND is blocked by inhibiting mitochondrial Ca uptake or PTP openings, depleting fatty acids, blocking acyl CoA synthesis, metabolizing CoA, or inhibiting palmitoylation. It is triggered by depolarizing mitochondria or promoting PTP openings. After mitochondrial MEND blockade, MEND is restored by cytoplasmic acyl CoA or CoA. MEND is blocked by siRNA knockdown of the plasmalemmal acyl transferase, DHHC5. When acyl CoA is abundant, transient H2O2 oxidative stress or PKC activation initiates MEND, but the immediate presence of H2O2 prevents MEND. The PTP inhibitor, NIM811, significantly increases plasmalemma in normally growing cells. Thus, the MEND pathway may contribute to constitutive as well as pathological plasmalemma turnover in dependence on mitochondrial stress signaling. DOI: http://dx.doi.org/10.7554/eLife.01293.001.
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Affiliation(s)
- Donald W Hilgemann
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, United States
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36
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Takamura A, Sakai N, Shinpoo M, Noguchi A, Takahashi T, Matsuda S, Yamamoto M, Narita A, Ohno K, Ohashi T, Ida H, Eto Y. The useful preliminary diagnosis of Niemann-Pick disease type C by filipin test in blood smear. Mol Genet Metab 2013; 110:401-4. [PMID: 24001525 DOI: 10.1016/j.ymgme.2013.08.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Accepted: 08/10/2013] [Indexed: 11/28/2022]
Abstract
Niemann-Pick disease type C (NP-C) is an autosomal recessive lysosomal lipid storage disorder characterized with accumulation of cholesterol in endosomes and lysosomes. The diagnosis of NP-C is difficult due to its heterogeneous group of diseases. Biochemical diagnosis of NP-C is conducted by cholesterol staining with cultured skin fibroblasts and confirmed by the analysis of genetic mutations of NPC1 or NPC2 gene. Here, we report an easier biochemical diagnostic method with blood smear by filipin staining.
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Affiliation(s)
- Ayumi Takamura
- Advanced Clinical Research Center, Institute for Neurological Disorders, Fukushima and Kanagawa, Japan.
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37
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Degiacomi MT, Iacovache I, Pernot L, Chami M, Kudryashev M, Stahlberg H, van der Goot FG, Dal Peraro M. Molecular assembly of the aerolysin pore reveals a swirling membrane-insertion mechanism. Nat Chem Biol 2013; 9:623-9. [PMID: 23912165 DOI: 10.1038/nchembio.1312] [Citation(s) in RCA: 151] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2013] [Accepted: 06/25/2013] [Indexed: 12/24/2022]
Abstract
Aerolysin is the founding member of a superfamily of β-pore-forming toxins whose pore structure is unknown. We have combined X-ray crystallography, cryo-EM, molecular dynamics and computational modeling to determine the structures of aerolysin mutants in their monomeric and heptameric forms, trapped at various stages of the pore formation process. A dynamic modeling approach based on swarm intelligence was applied, whereby the intrinsic flexibility of aerolysin extracted from new X-ray structures was used to fully exploit the cryo-EM spatial restraints. Using this integrated strategy, we obtained a radically new arrangement of the prepore conformation and a near-atomistic structure of the aerolysin pore, which is fully consistent with all of the biochemical data available so far. Upon transition from the prepore to pore, the aerolysin heptamer shows a unique concerted swirling movement, accompanied by a vertical collapse of the complex, ultimately leading to the insertion of a transmembrane β-barrel.
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Affiliation(s)
- Matteo T Degiacomi
- 1] Institute of Bioengineering, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland. [2] [3]
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38
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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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39
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Amiya E, Watanabe M, Takeda N, Saito T, Shiga T, Hosoya Y, Nakao T, Imai Y, Manabe I, Nagai R, Komuro I, Maemura K. Angiotensin II impairs endothelial nitric-oxide synthase bioavailability under free cholesterol-enriched conditions via intracellular free cholesterol-rich membrane microdomains. J Biol Chem 2013; 288:14497-14509. [PMID: 23548909 DOI: 10.1074/jbc.m112.448522] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Vascular endothelial function is impaired in hypercholesterolemia partly because of injury by modified LDL. In addition to modified LDL, free cholesterol (FC) is thought to play an important role in the development of endothelial dysfunction, although the precise mechanisms remain to be elucidated. The aim of this study was to clarify the mechanisms of endothelial dysfunction induced by an FC-rich environment. Loading cultured human aortic endothelial cells with FC induced the formation of vesicular structures composed of FC-rich membranes. Raft proteins such as phospho-caveolin-1 (Tyr-14) and small GTPase Rac were accumulated toward FC-rich membranes around vesicular structures. In the presence of these vesicles, angiotensin II-induced production of reactive oxygen species (ROS) was considerably enhanced. This ROS shifted endothelial NOS (eNOS) toward vesicle membranes and vesicles with a FC-rich domain trafficked toward perinuclear late endosomes/lysosomes, which resulted in the deterioration of eNOS Ser-1177 phosphorylation and NO production. Angiotensin II-induced ROS decreased the bioavailability of eNOS under the FC-enriched condition.
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Affiliation(s)
- Eisuke Amiya
- Department of Cardiovascular Medicine, Graduate School of Medicine, the University of Tokyo, Tokyo 113-8655, Japan
| | - Masafumi Watanabe
- Department of Cardiovascular Medicine, Graduate School of Medicine, the University of Tokyo, Tokyo 113-8655, Japan
| | - Norihiko Takeda
- Department of Cardiovascular Medicine, Graduate School of Medicine, the University of Tokyo, Tokyo 113-8655, Japan
| | - Tetsuya Saito
- Department of Cardiovascular Medicine, Graduate School of Medicine, the University of Tokyo, Tokyo 113-8655, Japan
| | - Taro Shiga
- Department of Cardiovascular Medicine, Graduate School of Medicine, the University of Tokyo, Tokyo 113-8655, Japan
| | - Yumiko Hosoya
- Department of Cardiovascular Medicine, Graduate School of Medicine, the University of Tokyo, Tokyo 113-8655, Japan
| | - Tomoko Nakao
- Department of Cardiovascular Medicine, Graduate School of Medicine, the University of Tokyo, Tokyo 113-8655, Japan
| | - Yasushi Imai
- Department of Cardiovascular Medicine, Graduate School of Medicine, the University of Tokyo, Tokyo 113-8655, Japan
| | - Ichiro Manabe
- Department of Cardiovascular Medicine, Graduate School of Medicine, the University of Tokyo, Tokyo 113-8655, Japan
| | - Ryozo Nagai
- Department of Cardiovascular Medicine, Graduate School of Medicine, the University of Tokyo, Tokyo 113-8655, Japan; Jichi Medical University, Shimotsuke 329-0498, Japan
| | - Issei Komuro
- Department of Cardiovascular Medicine, Graduate School of Medicine, the University of Tokyo, Tokyo 113-8655, Japan; Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan
| | - Koji Maemura
- Department of Cardiovascular Medicine, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki 852-8102, Japan.
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40
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Siljamäki E, Rintanen N, Kirsi M, Upla P, Wang W, Karjalainen M, Ikonen E, Marjomäki V. Cholesterol dependence of collagen and echovirus 1 trafficking along the novel α2β1 integrin internalization pathway. PLoS One 2013; 8:e55465. [PMID: 23393580 PMCID: PMC3564754 DOI: 10.1371/journal.pone.0055465] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Accepted: 12/23/2012] [Indexed: 12/29/2022] Open
Abstract
We have previously shown that soluble collagen and a human pathogen, echovirus 1 (EV1) cluster α2β1 integrin on the plasma membrane and cause their internalization into cytoplasmic endosomes. Here we show that cholesterol plays a major role not only in the uptake of α2β1 integrin and its ligands but also in the formation of α2 integrin-specific multivesicular bodies (α2-MVBs) and virus infection. EV1 infection and α2β1 integrin internalization were totally halted by low amounts of the cholesterol-aggregating drugs filipin or nystatin. Inhibition of cholesterol synthesis and accumulation of lanosterol after ketoconazole treatment inhibited uptake of collagen, virus and clustered integrin, and prevented formation of multivesicular bodies and virus infection. Loading of lipid starved cells with cholesterol increased infection to some extent but could not completely restore EV1 infection to control levels. Cold Triton X-100 treatment did not solubilize the α2-MVBs suggesting, together with cholesterol labeling, that the cytoplasmic endosomes were enriched in detergent-resistant lipids in contrast to αV integrin labeled control endosomes in the clathrin pathway. Cholesterol aggregation leading to increased ion permeability caused a significant reduction in EV1 uncoating in endosomes as judged by sucrose gradient centrifugation and by neutral red-based uncoating assay. In contrast, the replication step was not dependent on cholesterol in contrast to the reports on several other viruses. In conclusion, our results showed that the integrin internalization pathway is dependent on cholesterol for uptake of collagen, EV1 and integrin, for maturation of endosomal structures and for promoting EV1 uncoating. The results thus provide novel information for developing anti-viral strategies and more insight into collagen and integrin trafficking.
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Affiliation(s)
- Elina Siljamäki
- Department of Biological and Environmental Science/Nanoscience Center, University of Jyväskylä, Jyväskylä, Finland
| | - Nina Rintanen
- Department of Biological and Environmental Science/Nanoscience Center, University of Jyväskylä, Jyväskylä, Finland
| | - Maija Kirsi
- Department of Biological and Environmental Science/Nanoscience Center, University of Jyväskylä, Jyväskylä, Finland
| | - Paula Upla
- Department of Biological and Environmental Science/Nanoscience Center, University of Jyväskylä, Jyväskylä, Finland
| | - Wei Wang
- Institute of Biomedicine, University of Helsinki, Helsinki, Finland
- Minerva Foundation Institute for Medical Research, Helsinki, Finland
| | - Mikko Karjalainen
- Department of Biological and Environmental Science/Nanoscience Center, University of Jyväskylä, Jyväskylä, Finland
| | - Elina Ikonen
- Institute of Biomedicine, University of Helsinki, Helsinki, Finland
- Minerva Foundation Institute for Medical Research, Helsinki, Finland
| | - Varpu Marjomäki
- Department of Biological and Environmental Science/Nanoscience Center, University of Jyväskylä, Jyväskylä, Finland
- * E-mail:
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41
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Mencarelli C, Martinez–Martinez P. Ceramide function in the brain: when a slight tilt is enough. Cell Mol Life Sci 2013; 70:181-203. [PMID: 22729185 PMCID: PMC3535405 DOI: 10.1007/s00018-012-1038-x] [Citation(s) in RCA: 176] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Revised: 05/16/2012] [Accepted: 05/21/2012] [Indexed: 12/14/2022]
Abstract
Ceramide, the precursor of all complex sphingolipids, is a potent signaling molecule that mediates key events of cellular pathophysiology. In the nervous system, the sphingolipid metabolism has an important impact. Neurons are polarized cells and their normal functions, such as neuronal connectivity and synaptic transmission, rely on selective trafficking of molecules across plasma membrane. Sphingolipids are abundant on neural cellular membranes and represent potent regulators of brain homeostasis. Ceramide intracellular levels are fine-tuned and alteration of the sphingolipid-ceramide profile contributes to the development of age-related, neurological and neuroinflammatory diseases. The purpose of this review is to guide the reader towards a better understanding of the sphingolipid-ceramide pathway system. First, ceramide biology is presented including structure, physical properties and metabolism. Second, we describe the function of ceramide as a lipid second messenger in cell physiology. Finally, we highlight the relevance of sphingolipids and ceramide in the progression of different neurodegenerative diseases.
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Affiliation(s)
- Chiara Mencarelli
- Department of Neuroscience, School for Mental Health and Neuroscience, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands
| | - Pilar Martinez–Martinez
- Department of Neuroscience, School for Mental Health and Neuroscience, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands
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42
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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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43
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Zagorac GB, Mahmutefendić H, Tomaš MI, Kučić N, Le Bouteiller P, Lučin P. Early endosomal rerouting of major histocompatibility class I conformers. J Cell Physiol 2012; 227:2953-64. [PMID: 21959869 DOI: 10.1002/jcp.23042] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Major histocompatibility class I (MHC-I) molecules are present at the cell surface both as fully conformed trimolecular complexes composed of heavy chain (HC), beta-2-microglobulin (β2m) and peptide, and various open forms, devoid of peptide and/or β2m (open MHC-I conformers). Fully conformed MHC-I complexes and open MHC-I conformers can be distinguished by well characterized monoclonal antibody reagents that recognize their conformational difference in the extracellular domain. In the present study, we used these tools in order to test whether conformational difference in the extracellular domain determines endocytic and endosomal route of plasma membrane (PM) proteins. We analyzed PM localization, internalization, endosomal trafficking, and recycling of human and murine MHC-I proteins on various cell lines. We have shown that fully conformed MHC-I and open MHC-I conformers segregate at the PM and during endosomal trafficking resulting in the exclusion of open MHC-I conformers from the recycling route. This segregation is associated with their partitioning into the membranes of different compositions. As a result, the open MHC-I conformers internalized with higher rate than fully conformed counterparts. Thus, our data suggest the existence of conformation-based protein sorting mechanism in the endosomal system.
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44
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Abstract
All bacterial toxins, which globally are hydrophilic proteins, interact first with their target cells by recognizing a surface receptor, which is either a lipid or a lipid derivative, or another compound but in a lipid environment. Intracellular active toxins follow various trafficking pathways, the sorting of which is greatly dependent on the nature of the receptor, notably lipidic receptor or receptor embedded into a distinct environment such as lipid microdomains. Numerous other toxins act locally on cell membrane. Indeed, phospholipase activity is a common mechanism shared by several membrane-damaging toxins. In addition, many toxins active intracellularly or on cell membrane modulate host cell phospholipid pathways. Unusually, a few bacterial toxins require a lipid post-translational modification to be active. Thereby, lipids are obligate partners of bacterial toxins.
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Affiliation(s)
- Blandine Geny
- Unité des Bactéries Anaérobies et Toxines, Institut Pasteur, 28 rue du Dr Roux, 75724 Paris cedex 15, France
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45
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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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46
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Maccarrone M, Bernardi G, Agrò AF, Centonze D. Cannabinoid receptor signalling in neurodegenerative diseases: a potential role for membrane fluidity disturbance. Br J Pharmacol 2011; 163:1379-90. [PMID: 21323908 PMCID: PMC3165948 DOI: 10.1111/j.1476-5381.2011.01277.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2010] [Revised: 01/13/2011] [Accepted: 01/24/2011] [Indexed: 11/30/2022] Open
Abstract
Type-1 cannabinoid receptor (CB(1)) is the most abundant G-protein-coupled receptor (GPCR) in the brain. CB(1) and its endogenous agonists, the so-called 'endocannabinoids (eCBs)', belong to an ancient neurosignalling system that plays important functions in neurodegenerative and neuroinflammatory disorders like Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and multiple sclerosis. For this reason, research on the therapeutic potential of drugs modulating the endogenous tone of eCBs is very intense. Several GPCRs reside within subdomains of the plasma membranes that contain high concentrations of cholesterol: the lipid rafts. Here, the hypothesis that changes in membrane fluidity alter function of the endocannabinoid system, as well as progression of particular neurodegenerative diseases, is described. To this end, the impact of membrane cholesterol on membrane properties and hence on neurodegenerative diseases, as well as on CB(1) signalling in vitro and on CB(1) -dependent neurotransmission within the striatum, is discussed. Overall, present evidence points to the membrane environment as a critical regulator of signal transduction triggered by CB(1) , and calls for further studies aimed at better clarifying the contribution of membrane lipids to eCBs signalling. The results of these investigations might be exploited also for the development of novel therapeutics able to combat disorders associated with abnormal activity of CB(1).
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Affiliation(s)
- M Maccarrone
- Department of Biomedical Sciences, University of Teramo, Teramo 64100, Italy.
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47
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Regulation of carcinoembryonic antigen release from colorectal cancer cells. Mol Biol Rep 2011; 39:3695-704. [PMID: 21725636 DOI: 10.1007/s11033-011-1144-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Accepted: 06/24/2011] [Indexed: 01/13/2023]
Abstract
Clinical and experimental evidence suggest that circulating carcinoembryonic antigen (CEA) released from tumor cells has an instrumental role in colorectal cancer-liver metastasis. However, the precise mechanism of the regulation of the CEA release from cancer cells is not known. We investigated if the rate of CEA and another GPI-anchored protein, alkaline phosphatase (AP) release is correlated with cellular glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) expression. We also evaluated the effects of phosphatidic acid (PA), a compound known to inhibit GPI-PLD activity, on the CEA and AP release from colon cancer cells. The expression of CEA, GPI-PLD, and AP in five colon carcinoma cells (LS180, Caco2, SW742, SW1116, and HT29/219) was verified by immunoblot and real-time RT-PCR analysis. The amounts of CEA and AP released into cell culture media were determined using ELISA and a colorimetric assay, respectively. We examined the effects of PA (20-100 μM) on CEA and AP release from LS180 cells. All five cancer cell lines analyzed expressed GPI-PLD protein. While there was a positive relationship between AP release and the levels of GPI-PLD transcript expression, we found no direct correlation between CEA released from cancer cells and the GPI-PLD mRNA expression level. However, the rate of CEA release was positively associated with the level of CEA transcript expression. In comparison to controls, the release of GPI-anchored CEA and AP, but not CA19-9 was inhibited significantly by both crude and pure phosphatidic acid (by 56 and 54.5%, respectively). Using PA for inhibiting CEA release from cancer cells may have therapeutic application in preventing CRC-liver metastasis.
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Refaei M, Leventis R, Silvius JR. Assessment of the roles of ordered lipid microdomains in post-endocytic trafficking of glycosyl-phosphatidylinositol-anchored proteins in mammalian fibroblasts. Traffic 2011; 12:1012-24. [PMID: 21696526 DOI: 10.1111/j.1600-0854.2011.01206.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have used artificial phosphatidylethanolamine-polyethylene glycol (PE-PEG)-anchored proteins, incorporated into living mammalian cells, to evaluate previously proposed roles for ordered lipid 'raft' domains in the post-endocytic trafficking of glycosylphosphatidylinositol (GPI)-anchored proteins in CHO and BHK cells. In CHO cells, endocytosed PE-PEG protein conjugates colocalized strongly with the internalized GPI-anchored folate receptor, concentrating in the endosomal recycling compartment, regardless of the structure of the hydrocarbon chains of the PE-PEG 'anchor'. However, internalized PE-PEG protein conjugates with long-chain saturated anchors recycled to the plasma membrane at a slow rate comparable to that measured for the GPI-anchored folate receptor, whereas conjugates with short-chain or unsaturated anchors recycled at a faster rate similar to that observed for the transferrin receptor. These findings support the proposal (Mayor et al. Cholesterol-dependent retention of GPI-anchored proteins in endosomes. EMBO J 1998;17:4628-4638) that the slow recycling of GPI proteins in CHO cells rests on their affinity for ordered lipid domains. In BHK cells, internalized PE-PEG protein conjugates with either saturated or unsaturated 'anchors' colocalized strongly with simultaneously endocytosed folate receptor and, like the folate receptor, gradually accumulated in late endosomes/lysosomes. These latter findings do not support previous suggestions that the sorting of GPI proteins to late endosomes in BHK cells depends on their association with lipid rafts.
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Affiliation(s)
- Mohammad Refaei
- Department of Biochemistry, McGill University, Montréal, Québec, Canada
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Location, location, location: is membrane partitioning everything when it comes to innate immune activation? Mediators Inflamm 2011; 2011:186093. [PMID: 21765613 PMCID: PMC3134105 DOI: 10.1155/2011/186093] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2010] [Accepted: 03/27/2011] [Indexed: 01/25/2023] Open
Abstract
In the last twenty years, the general view of the plasma membrane has changed from a homogeneous arrangement of lipids to a mosaic of microdomains. It is currently thought that islands of highly ordered saturated lipids and cholesterol, which are laterally mobile, exist in the plane of the plasma membrane. Lipid rafts are thought to provide a means to explain the spatial segregation of certain signalling pathways emanating from the cell surface. They seem to provide the necessary microenvironment in order for certain specialised signalling events to take place, such as the innate immune recognition. The innate immune system seems to employ germ-lined encoded receptors, called pattern recognition receptors (PRRs), in order to detect pathogens. One family of such receptors are the Toll-like receptors (TLRs), which are the central “sensing” apparatus of the innate immune system. In recent years, it has become apparent that TLRs are recruited into membrane microdomains in response to ligands. These nanoscale assemblies of sphingolipid, cholesterol, and TLRs stabilize and coalesce, forming signalling platforms, which transduce signals that lead to innate immune activation. In the current paper, we will investigate all past and current literature concerning recruitment of extracellular and intracellular TLRs into lipid rafts and how this membrane organization modulates innate immune responses.
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Cheng F, Cappai R, Ciccotosto GD, Svensson G, Multhaup G, Fransson LÅ, Mani K. Suppression of amyloid beta A11 antibody immunoreactivity by vitamin C: possible role of heparan sulfate oligosaccharides derived from glypican-1 by ascorbate-induced, nitric oxide (NO)-catalyzed degradation. J Biol Chem 2011; 286:27559-72. [PMID: 21642435 DOI: 10.1074/jbc.m111.243345] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Amyloid β (Aβ) is generated from the copper- and heparan sulfate (HS)-binding amyloid precursor protein (APP) by proteolytic processing. APP supports S-nitrosylation of the HS proteoglycan glypican-1 (Gpc-1). In the presence of ascorbate, there is NO-catalyzed release of anhydromannose (anMan)-containing oligosaccharides from Gpc-1-nitrosothiol. We investigated whether these oligosaccharides interact with Aβ during APP processing and plaque formation. anMan immunoreactivity was detected in amyloid plaques of Alzheimer (AD) and APP transgenic (Tg2576) mouse brains by immunofluorescence microscopy. APP/APP degradation products detected by antibodies to the C terminus of APP, but not Aβ oligomers detected by the anti-Aβ A11 antibody, colocalized with anMan immunoreactivity in Tg2576 fibroblasts. A 50-55-kDa anionic, sodium dodecyl sulfate-stable, anMan- and Aβ-immunoreactive species was obtained from Tg2576 fibroblasts using immunoprecipitation with anti-APP (C terminus). anMan-containing HS oligo- and disaccharide preparations modulated or suppressed A11 immunoreactivity and oligomerization of Aβ42 peptide in an in vitro assay. A11 immunoreactivity increased in Tg2576 fibroblasts when Gpc-1 autoprocessing was inhibited by 3-β[2(diethylamino)ethoxy]androst-5-en-17-one (U18666A) and decreased when Gpc-1 autoprocessing was stimulated by ascorbate. Neither overexpression of Gpc-1 in Tg2576 fibroblasts nor addition of copper ion and NO donor to hippocampal slices from 3xTg-AD mice affected A11 immunoreactivity levels. However, A11 immunoreactivity was greatly suppressed by the subsequent addition of ascorbate. We speculate that temporary interaction between the Aβ domain and small, anMan-containing oligosaccharides may preclude formation of toxic Aβ oligomers. A portion of the oligosaccharides are co-secreted with the Aβ peptides and deposited in plaques. These results support the notion that an inadequate supply of vitamin C could contribute to late onset AD in humans.
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Affiliation(s)
- Fang Cheng
- Department of Experimental Medical Science, Division of Neuroscience, Glycobiology Group, Lund University, Biomedical Center A13, SE-221 84 Lund, Sweden
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