12 results on '"Dick J. H. van den Boomen"'
Search Results
2. Ubiquitin-mediated regulation of sterol homeostasis
- Author
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Dick J. H. van den Boomen, Norbert Volkmar, and Paul J. Lehner
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Ubiquitin-Protein Ligases ,Familial hypercholesterolemia ,Biology ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Ubiquitin ,medicine ,Animals ,Homeostasis ,Humans ,Transcription factor ,030304 developmental biology ,0303 health sciences ,Cholesterol ,Sterol homeostasis ,Cell Biology ,medicine.disease ,Cell biology ,Sterols ,Metabolic pathway ,chemistry ,Proteolysis ,HMG-CoA reductase ,biology.protein ,Hydroxymethylglutaryl CoA Reductases ,lipids (amino acids, peptides, and proteins) ,030217 neurology & neurosurgery - Abstract
Cholesterol is an essential component of mammalian membranes, and its homeostasis is strictly regulated, with imbalances causing atherosclerosis, Niemann Pick disease, and familial hypercholesterolemia. Cellular cholesterol supply is mediated by LDL-cholesterol import and de novo cholesterol biosynthesis, and both pathways are adjusted to cellular demand by the cholesterol-sensitive SREBP2 transcription factor. Cholesterol homeostasis is modulated by a wide variety of metabolic pathways and the ubiquitination machinery, in particular E3 ubiquitin ligases. In this article, we review recent progress in understanding the role of E3 ubiquitin ligases in the metabolic control of cellular sterol homeostasis.
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- 2020
3. Plasma membrane profiling defines an expanded class of cell surface proteins selectively targeted for degradation by HCMV US2 in cooperation with UL141.
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Jye-Lin Hsu, Dick J H van den Boomen, Peter Tomasec, Michael P Weekes, Robin Antrobus, Richard J Stanton, Eva Ruckova, Daniel Sugrue, Gavin S Wilkie, Andrew J Davison, Gavin W G Wilkinson, and Paul J Lehner
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Immunologic diseases. Allergy ,RC581-607 ,Biology (General) ,QH301-705.5 - Abstract
Human cytomegalovirus (HCMV) US2, US3, US6 and US11 act in concert to prevent immune recognition of virally infected cells by CD8+ T-lymphocytes through downregulation of MHC class I molecules (MHC-I). Here we show that US2 function goes far beyond MHC-I degradation. A systematic proteomic study using Plasma Membrane Profiling revealed US2 was unique in downregulating additional cellular targets, including: five distinct integrin α-chains, CD112, the interleukin-12 receptor, PTPRJ and thrombomodulin. US2 recruited the cellular E3 ligase TRC8 to direct the proteasomal degradation of all its targets, reminiscent of its degradation of MHC-I. Whereas integrin α-chains were selectively degraded, their integrin β1 binding partner accumulated in the ER. Consequently integrin signaling, cell adhesion and migration were strongly suppressed. US2 was necessary and sufficient for degradation of the majority of its substrates, but remarkably, the HCMV NK cell evasion function UL141 requisitioned US2 to enhance downregulation of the NK cell ligand CD112. UL141 retained CD112 in the ER from where US2 promoted its TRC8-dependent retrotranslocation and degradation. These findings redefine US2 as a multifunctional degradation hub which, through recruitment of the cellular E3 ligase TRC8, modulates diverse immune pathways involved in antigen presentation, NK cell activation, migration and coagulation; and highlight US2's impact on HCMV pathogenesis.
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- 2015
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- View/download PDF
4. A trimeric Rab7 GEF controls NPC1-dependent lysosomal cholesterol export
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Ilana Berlin, Agata Sienkiewicz, Paul J. Lehner, Dick J. H. van den Boomen, Marlieke L.M. Jongsma, Daphne M. van Elsland, J. Paul Luzio, Jacques Neefjes, van den Boomen, Dick JH [0000-0001-6474-3661], Luzio, J Paul [0000-0003-3912-9760], Neefjes, Jacques JC [0000-0001-6763-2211], Lehner, Paul J [0000-0001-9383-1054], Apollo - University of Cambridge Repository, van den Boomen, Dick J. H. [0000-0001-6474-3661], Luzio, J. Paul [0000-0003-3912-9760], Neefjes, Jacques J. C. [0000-0001-6763-2211], and Lehner, Paul J. [0000-0001-9383-1054]
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0301 basic medicine ,Hydroxymethylglutaryl-CoA Synthase ,49/47 ,General Physics and Astronomy ,Endogeny ,Membrane trafficking ,Small GTPases ,631/80/313/2011 ,chemistry.chemical_compound ,0302 clinical medicine ,Guanine Nucleotide Exchange Factors ,Homeostasis ,14/19 ,lcsh:Science ,Late endosome ,0303 health sciences ,Multidisciplinary ,631/80/313 ,030302 biochemistry & molecular biology ,Intracellular Signaling Peptides and Proteins ,3. Good health ,Cell biology ,13/31 ,Sterols ,Cholesterol ,631/45/287/1197 ,lipids (amino acids, peptides, and proteins) ,Protein Binding ,Endosome ,Science ,Protein subunit ,Endosomes ,Models, Biological ,General Biochemistry, Genetics and Molecular Biology ,Article ,03 medical and health sciences ,631/80/313/1624 ,Niemann-Pick C1 Protein ,Humans ,030304 developmental biology ,Fluorescent Dyes ,Genome, Human ,82/58 ,HEK 293 cells ,rab7 GTP-Binding Proteins ,Transporter ,Biological Transport ,General Chemistry ,Cholesterol, LDL ,030104 developmental biology ,HEK293 Cells ,chemistry ,Cholesterol import ,rab GTP-Binding Proteins ,Multiprotein Complexes ,LDL receptor ,lcsh:Q ,NPC1 ,CRISPR-Cas Systems ,Protein Multimerization ,Lysosomes ,030217 neurology & neurosurgery ,HeLa Cells - Abstract
Cholesterol import in mammalian cells is mediated by the LDL receptor pathway. Here, we perform a genome-wide CRISPR screen using an endogenous cholesterol reporter and identify >100 genes involved in LDL-cholesterol import. We characterise C18orf8 as a core subunit of the mammalian Mon1-Ccz1 guanidine exchange factor (GEF) for Rab7, required for complex stability and function. C18orf8-deficient cells lack Rab7 activation and show severe defects in late endosome morphology and endosomal LDL trafficking, resulting in cellular cholesterol deficiency. Unexpectedly, free cholesterol accumulates within swollen lysosomes, suggesting a critical defect in lysosomal cholesterol export. We find that active Rab7 interacts with the NPC1 cholesterol transporter and licenses lysosomal cholesterol export. This process is abolished in C18orf8-, Ccz1- and Mon1A/B-deficient cells and restored by a constitutively active Rab7. The trimeric Mon1-Ccz1-C18orf8 (MCC) GEF therefore plays a central role in cellular cholesterol homeostasis coordinating Rab7 activation, endosomal LDL trafficking and NPC1-dependent lysosomal cholesterol export., Lysosomes play an important role in cellular LDL-cholesterol uptake. Here, the authors perform a genome-wide genetic screen for cholesterol regulators and identify C18orf8 as a conserved subunit of a trimeric Rab7 GEF that controls LDL trafficking and NPC1-dependent lysosomal cholesterol export.
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- 2019
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- View/download PDF
5. The sterol-responsive RNF145 E3 ubiquitin ligase mediates the degradation of HMG-CoA reductase together with gp78 and Hrd1
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Dick J. H. van den Boomen, James A. Nathan, Anna S Dickson, Richard T. Timms, Paul J. Lehner, Norbert Volkmar, Sam A. Menzies, Volkmar, Norbert [0000-0003-0766-5606], Nathan, James A [0000-0002-0248-1632], Lehner, Paul J [0000-0001-9383-1054], and Apollo - University of Cambridge Repository
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RNF145 ,QH301-705.5 ,Ubiquitin-Protein Ligases ,Science ,Reductase ,Research Communication ,Mice ,03 medical and health sciences ,chemistry.chemical_compound ,gp78 ,0302 clinical medicine ,Ubiquitin ,cell biology ,Animals ,Humans ,human ,Biology (General) ,030304 developmental biology ,chemistry.chemical_classification ,HMGCR ,0303 health sciences ,DNA ligase ,biology ,Cholesterol ,Ubiquitination ,Membrane Proteins ,cholesterol ,Sterol ,3. Good health ,Cell biology ,Ubiquitin ligase ,Receptors, Autocrine Motility Factor ,ER associated degradation ,Enzyme ,chemistry ,E3 ubiquitin ligase ,Proteolysis ,Ubiquitin-Conjugating Enzymes ,HMG-CoA reductase ,biology.protein ,Medicine ,Hydroxymethylglutaryl CoA Reductases ,lipids (amino acids, peptides, and proteins) ,CRISPR-Cas Systems ,030217 neurology & neurosurgery - Abstract
Mammalian HMG-CoA reductase (HMGCR), the rate-limiting enzyme of the cholesterol biosynthetic pathway and the therapeutic target of statins, is post-transcriptionally regulated by sterol-accelerated degradation. Under cholesterol-replete conditions, HMGCR is ubiquitinated and degraded, but the identity of the E3 ubiquitin ligase(s) responsible for mammalian HMGCR turnover remains controversial. Using systematic, unbiased CRISPR/Cas9 genome-wide screens with a sterol-sensitive endogenous HMGCR reporter, we comprehensively map the E3 ligase landscape required for sterol-accelerated HMGCR degradation. We find that RNF145 and gp78 independently co-ordinate HMGCR ubiquitination and degradation. RNF145, a sterol-responsive ER-resident E3 ligase, is unstable but accumulates following sterol depletion. Sterol addition triggers RNF145 recruitment to HMGCR via Insigs, promoting HMGCR ubiquitination and proteasome-mediated degradation. In the absence of both RNF145 and gp78, Hrd1, a third UBE2G2-dependent E3 ligase, partially regulates HMGCR activity. Our findings reveal a critical role for the sterol-responsive RNF145 in HMGCR regulation and elucidate the complexity of sterol-accelerated HMGCR degradation. Editorial note: This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter)., eLife digest Cholesterol is a fatty molecule that is essential for our health; for example, it is a component of the outer membrane that surrounds every cell in our body. Yet, it also has a reputation for clogging arteries and causing heart attacks and strokes. Our organism can adjust the amount of cholesterol it creates through an enzyme called HMGCR, which is found in all cells. Switching off HMGCR, for instance by taking drugs called statins, reduces the amount of cholesterol made by cells. To regulate the activity of HMGCR, the body uses proteins known as E3 ubiquitin ligases, which can label the enzyme for destruction. However, the identity of the ligases that target HMGCR is a matter of intense debate. Here, Menzies, Volkmar et al. addressed this issue by using an approach called a genome-wide CRISPR forward genetic screen. First, HMGCR was marked inside the cells with a fluorescent tag to watch how its levels change in response to different amounts of cholesterol. Then, each gene in the cell was deleted, and the effects recorded. This allowed Menzies, Volkmar et al. to find the genes responsible for the rapid destruction of HMGCR. The experiments revealed that the E3 ubiquitin ligases RNF145 and gp78 are independently responsible for the degradation of the majority of HMGCR, with a third ligase, Hrd1, getting involved if the first two are absent. In particular, RNF145 builds up when a cell is starved of cholesterol, but it immediately marks HMGCR for destruction once cholesterol becomes more abundant. This ligase can therefore both sense and respond to the amount of cholesterol in a cell, making it a perfect candidate for regulating HMGCR based on what the body needs. Identifying the proteins that adjust the levels of HMGCR sheds light on how a cell controls the amount of cholesterol it creates. This knowledge could be relevant in the fight against the health problems associated with this molecule.
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- 2018
6. Author response: The sterol-responsive RNF145 E3 ubiquitin ligase mediates the degradation of HMG-CoA reductase together with gp78 and Hrd1
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James A. Nathan, Anna S Dickson, Richard T. Timms, Paul J. Lehner, Dick J. H. van den Boomen, Norbert Volkmar, and Sam A. Menzies
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biology ,Biochemistry ,Chemistry ,HMG-CoA reductase ,biology.protein ,Degradation (geology) ,Sterol ,Ubiquitin ligase - Published
- 2018
7. Multiple E2 ubiquitin-conjugating enzymes regulate human cytomegalovirus US2-mediated immunoreceptor downregulation
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Frans H.J. Claas, Anouk B. C. Schuren, Emmanuel J. H. J. Wiertz, Michael L. van de Weijer, Paul J. Lehner, Dick J. H. van den Boomen, Arend Mulder, and Robert Jan Lebbink
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0301 basic medicine ,Down-Regulation ,Cytomegalovirus ,ER-associated protein degradation ,Receptors, Cell Surface ,Ubiquitin-conjugating enzyme ,Endoplasmic-reticulum-associated protein degradation ,Protein degradation ,Models, Biological ,US2 ,03 medical and health sciences ,0302 clinical medicine ,Viral Envelope Proteins ,Ubiquitin ,Downregulation and upregulation ,E2 ,Humans ,CRISPR ,Genetic Testing ,Receptors, Immunologic ,biology ,Endoplasmic reticulum ,Histocompatibility Antigens Class I ,U937 Cells ,Cell Biology ,ERAD ,Molecular biology ,Up-Regulation ,Ubiquitin ligase ,Cell biology ,030104 developmental biology ,Proteolysis ,Ubiquitin-Conjugating Enzymes ,biology.protein ,CRISPR-Cas Systems ,030217 neurology & neurosurgery ,Research Article - Abstract
Misfolded endoplasmic reticulum (ER) proteins are dislocated towards the cytosol and degraded by the ubiquitin-proteasome system in a process called ER-associated protein degradation (ERAD). During infection with human cytomegalovirus (HCMV), the viral US2 protein targets HLA class I molecules (HLA-I) for degradation via ERAD to avoid elimination by the immune system. US2-mediated degradation of HLA-I serves as a paradigm of ERAD and has facilitated the identification of TRC8 (also known as RNF139) as an E3 ubiquitin ligase. No specific E2 enzymes had previously been described for cooperation with TRC8. In this study, we used a lentiviral CRISPR/Cas9 library targeting all known human E2 enzymes to assess their involvement in US2-mediated HLA-I downregulation. We identified multiple E2 enzymes involved in this process, of which UBE2G2 was crucial for the degradation of various immunoreceptors. UBE2J2, on the other hand, counteracted US2- induced ERAD by downregulating TRC8 expression. These findings indicate the complexity of cellular quality control mechanisms, which are elegantly exploited by HCMV to elude the immune system.
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- 2017
8. TMEM129 is a Derlin-1 associated ERAD E3 ligase essential for virus-induced degradation of MHC-I
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James A. Nathan, Gordon Dougan, Dick J. H. van den Boomen, Paul J. Lehner, Richard T. Timms, Guinevere L. Grice, Karsten Skødt, and Helen R. Stagg
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Genes, Viral ,Ubiquitin-Protein Ligases ,viruses ,Molecular Sequence Data ,Down-Regulation ,Herpesvirus 1, Human ,Haploidy ,Endoplasmic-reticulum-associated protein degradation ,Ubiquitin-conjugating enzyme ,Endoplasmic Reticulum ,Gene product ,Viral Proteins ,Cytosol ,Ubiquitin ,MHC class I ,Humans ,Amino Acid Sequence ,Genetic Testing ,Multidisciplinary ,integumentary system ,biology ,Protein Stability ,Endoplasmic reticulum ,Histocompatibility Antigens Class I ,Ubiquitination ,Membrane Proteins ,Proteins ,RNA-Binding Proteins ,Endoplasmic Reticulum-Associated Degradation ,Biological Sciences ,Ubiquitin ligase ,Biochemistry ,Proteolysis ,Ubiquitin-Conjugating Enzymes ,Biocatalysis ,biology.protein ,Protein Binding ,Genetic screen - Abstract
The US11 gene product of human cytomegalovirus promotes viral immune evasion by hijacking the endoplasmic reticulum (ER)-associated degradation (ERAD) pathway. US11 initiates dislocation of newly translocated MHC I from the ER to the cytosol for proteasome-mediated degradation. Despite the critical role for ubiquitin in this degradation pathway, the responsible E3 ligase is unknown. In a forward genetic screen for host ERAD components hijacked by US11 in near-haploid KBM7 cells, we identified TMEM129, an uncharacterized polytopic membrane protein. TMEM129 is essential and rate-limiting for US11-mediated MHC-I degradation and acts as a novel ER resident E3 ubiquitin ligase. TMEM129 contains an unusual cysteine-only RING with intrinsic E3 ligase activity and is recruited to US11 via Derlin-1. Together with its E2 conjugase Ube2J2, TMEM129 is responsible for the ubiquitination, dislocation, and subsequent degradation of US11-associated MHC-I. US11 engages two degradation pathways: a Derlin-1/TMEM129-dependent pathway required for MHC-I degradation and a SEL1L/HRD1-dependent pathway required for "free" US11 degradation. Our data show that TMEM129 is a novel ERAD E3 ligase and the central component of a novel mammalian ERAD complex.
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- 2014
9. MHC class I molecules are preferentially ubiquitinated on endoplasmic reticulum luminal residues during HRD1 ubiquitin E3 ligase-mediated dislocation
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Robin Antrobus, Helen Bye, Paul J. Lehner, Emmanuel J. H. J. Wiertz, Dick J. H. van den Boomen, and Marian L. Burr
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Adenosine Triphosphatases ,Multidisciplinary ,Base Sequence ,biology ,Ubiquitin ,Ubiquitin-Protein Ligases ,Endoplasmic reticulum ,Histocompatibility Antigens Class I ,Ubiquitination ,Nuclear Proteins ,Transporter associated with antigen processing ,Biological Sciences ,Endoplasmic-reticulum-associated protein degradation ,Ubiquitin-conjugating enzyme ,Endoplasmic Reticulum ,Ubiquitin ligase ,Cell biology ,Biochemistry ,MHC class I ,biology.protein ,Humans ,Integral membrane protein ,HeLa Cells - Abstract
Misfolded MHC class I heavy chains (MHC I HCs) are targeted for endoplasmic reticulum (ER)-associated degradation (ERAD) by the ubiquitin E3 ligase HRD1, and E2 ubiquitin conjugating enzyme UBE2J1, and represent one of the few known endogenous ERAD substrates. The mechanism by which misfolded proteins are dislocated across the ER membrane into the cytosol is unclear. Here, we investigate the requirements for MHC I ubiquitination and degradation and show that endogenous misfolded MHC I HCs are recognized in the ER lumen by EDEM1 in a glycan-dependent manner and targeted to the core SEL1L/HRD1/UBE2J1 complex. A soluble MHC I HC lacking its transmembrane domain and cytosolic tail uses the same ERAD components and is degraded as efficiently as wild-type MHC I. Unexpectedly, HRD1-dependent polyubiquitination is preferentially targeted to the ER luminal domain of full-length MHC I HCs, despite the presence of an exposed cytosolic C-terminal tail. MHC I luminal domain ubiquitination occurs before p97 ATPase-mediated extraction from the ER membrane and can be targeted to nonlysine, as well as lysine, residues. A subset of integral membrane proteins, therefore, requires an early dislocation event to expose part of their luminal domain to the cytosol, before HRD1-mediated polyubiquitination and dislocation.
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- 2013
10. Temporal proteomic analysis of HIV infection reveals remodelling of the host phosphoproteome by lentiviral Vif variants
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Paul J. Lehner, Nicholas J Matheson, James C Williamson, Dick J. H. van den Boomen, Kim Wals, Robin Antrobus, Edward J. D. Greenwood, Greenwood, Edward [0000-0002-5224-0263], Matheson, Nicholas [0000-0002-3318-1851], Van Den Boomen, Dick [0000-0001-6474-3661], Williamson, James [0000-0002-2009-189X], Lehner, Paul [0000-0001-9383-1054], and Apollo - University of Cambridge Repository
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0301 basic medicine ,Time Factors ,Proteome ,QH301-705.5 ,Science ,viruses ,infectious disease ,Phosphatase ,Hyperphosphorylation ,HIV Infections ,Proteomics ,Tandem mass tag ,General Biochemistry, Genetics and Molecular Biology ,03 medical and health sciences ,proteomics ,lentivirus ,vif Gene Products, Human Immunodeficiency Virus ,Humans ,human ,Biology (General) ,Cells, Cultured ,Microbiology and Infectious Disease ,General Immunology and Microbiology ,biology ,Kinase ,phosphorylation ,General Neuroscience ,microbiology ,HIV ,General Medicine ,Protein phosphatase 2 ,Phosphoproteins ,biology.organism_classification ,Virology ,Vif ,3. Good health ,Cell biology ,PP2A ,030104 developmental biology ,Host-Pathogen Interactions ,Lentivirus ,Medicine ,Phosphorylation ,Research Article - Abstract
Viruses manipulate host factors to enhance their replication and evade cellular restriction. We used multiplex tandem mass tag (TMT)-based whole cell proteomics to perform a comprehensive time course analysis of >6500 viral and cellular proteins during HIV infection. To enable specific functional predictions, we categorized cellular proteins regulated by HIV according to their patterns of temporal expression. We focussed on proteins depleted with similar kinetics to APOBEC3C, and found the viral accessory protein Vif to be necessary and sufficient for CUL5-dependent proteasomal degradation of all members of the B56 family of regulatory subunits of the key cellular phosphatase PP2A (PPP2R5A-E). Quantitative phosphoproteomic analysis of HIV-infected cells confirmed Vif-dependent hyperphosphorylation of >200 cellular proteins, particularly substrates of the aurora kinases. The ability of Vif to target PPP2R5 subunits is found in primate and non-primate lentiviral lineages, and remodeling of the cellular phosphoproteome is therefore a second ancient and conserved Vif function. DOI: http://dx.doi.org/10.7554/eLife.18296.001, eLife digest About 100 years since it was first transmitted to humans, the Human Immunodeficiency Virus (HIV) infects almost 40 million people worldwide and causes more than a million AIDS-related deaths every year. It is therefore critical to understand how HIV has been able to multiply and spread, and why infection with HIV causes AIDS. In the evolutionary “arms race” between viruses like HIV and the cells they infect, viruses try to enhance their ability to multiply, and cells try to resist. These interactions emphasise the processes that are most important for cells and viruses, and suggest new ways to treat HIV and other viral infections. Proteomics is the large-scale study of molecules known as proteins, the critical building blocks of both cells and viruses. Greenwood, Matheson et al. use proteomics to measure how the abundance of proteins in human cells change during HIV infection, and identify new interactions between the virus and its host. The experiments distinguish more than 6500 proteins, and reveal that an HIV protein called Vif destroys several key components of a cellular protein called PP2A. Previous studies have demonstrated that PP2A plays a critical role in regulating the activities of numerous other proteins and processes in cells. Greenwood, Matheson et al. further show that other HIV-related viruses that infect monkeys, apes and even sheep can also counteract PP2A, suggesting that this interaction has been important during host and virus evolution. The next steps following on from this work are to find out why HIV attacks PP2A, and whether drugs that interfere with this interaction may help to treat HIV infection. A future challenge will be to investigate how HIV interacts with other cellular proteins highlighted by the proteomics approach. DOI: http://dx.doi.org/10.7554/eLife.18296.002
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- 2016
11. Author response: Temporal proteomic analysis of HIV infection reveals remodelling of the host phosphoproteome by lentiviral Vif variants
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Nicholas J Matheson, James C Williamson, Paul J. Lehner, Robin Antrobus, Kim Wals, Dick J. H. van den Boomen, and Edward J. D. Greenwood
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Host (biology) ,Human immunodeficiency virus (HIV) ,medicine ,Biology ,medicine.disease_cause ,Virology - Published
- 2016
12. L-plastin phosphorylation: A novel target for the immunosuppressive drug dexamethasone in primary human T cells
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Dick J. H. van den Boomen, Christoph Stober, Guido H. Wabnitz, Felix Michalke, Yvonne Samstag, Beate Jahraus, and Henning Kirchgessner
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T-Lymphocytes ,medicine.medical_treatment ,CD3 ,Blotting, Western ,Immunology ,Cell Separation ,macromolecular substances ,Biology ,Lymphocyte Activation ,Dexamethasone ,Immunological synapse ,medicine ,Humans ,Immunology and Allergy ,Phosphorylation ,Receptor ,Membrane Glycoproteins ,Microfilament Proteins ,T-cell receptor ,Immunosuppression ,Flow Cytometry ,Actin cytoskeleton ,Cell biology ,biology.protein ,bacteria ,Immunosuppressive Agents ,Glucocorticoid ,medicine.drug - Abstract
Activation of naïve T cells requires costimulation via TCR/CD3 plus accessory receptors, which enables the dynamic rearrangement of the actin cytoskeleton and immune synapse maturation. Signaling events induced following costimulation may thus be valuable targets for therapeutic immunosuppression. Phosphorylation of the actin-bundling protein L-plastin represents such a costimulatory signal in primary human T cells. Phosphorylated L-plastin has a higher affinity toward F-actin. However, the importance of the L-plastin phosphorylation for actin cytoskeleton regulation upon antigen recognition remained unclear. Here, we demonstrate that phosphorylation of L-plastin is important for immune synapse maturation. Thus, expression of nonphosphorylatable L-plastin in untransformed human peripheral blood T cells leads to reduced accumulation of LFA-1 in the immune synapse and to a diminished F-actin increase upon T-cell activation. Interestingly, L-plastin phosphorylation is inhibited by the glucocorticoid dexamethasone. In line with this finding, dexamethasone treatment leads to a reduced F-actin content in stimulated T cells and prevents maturation of the immune synapse. This inhibitory effect of dexamethasone could be reverted by expression of a phospho-mimicking L-plastin mutant. In conclusion, our data introduce costimulation-induced L-plastin phosphorylation as an important event for immune synapse formation and its inhibition by dexamethasone as a novel mode of function of this immunosuppressive glucocorticoid.
- Published
- 2011
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