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Chen D, Chen Y, Feng J, Huang W, Han Z, Liu Y, Lin Q, Li L, Lin Y. Guanine nucleotide exchange factor RABGEF1 facilitates TNF-induced necroptosis by targeting cIAP1. Biochem Biophys Res Commun 2024; 703:149669. [PMID: 38377943 DOI: 10.1016/j.bbrc.2024.149669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2024] [Revised: 02/04/2024] [Accepted: 02/09/2024] [Indexed: 02/22/2024]
Abstract
Necroptosis is a form of regulated cell death that depends on the receptor-interacting serine-threonine kinase 3 (RIPK3) and mixed lineage kinase domain-like (MLKL). The molecular mechanisms underlying distinct instances of necroptosis have only recently begun to emerge. In the present study, we characterized RABGEF1 as a positive regulator of RIPK1/RIPK3 activation in vitro. Based on the overexpression and knockdown experiments, we determined that RABGEF1 accelerated the phosphorylation of RIPK1 and promoted necrosome formation in L929 cells. The pro-necrotic effect of RABGEF1 is associated with its E3 ubiquitin ligase activity and guanine nucleotide exchange factor (GEF) activity. We further confirmed that RABGEF1 interacts with cIAP1 protein by inhibiting its function and plays a regulatory role in necroptosis, which can be abolished by treatment with the antagonist Smac mimetic (SM)-164. In conclusion, our study highlights a potential and novel role of RABGEF1 in promoting TNF-induced cell necrosis.
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Affiliation(s)
- Danni Chen
- The School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
| | - Yushi Chen
- The School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
| | - Jianting Feng
- The School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
| | - Wenyang Huang
- The School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
| | - Zeteng Han
- The School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
| | - Yuanyuan Liu
- The School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
| | - Qiaofa Lin
- The School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China
| | - Lisheng Li
- The School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China; Key Laboratory of Ministry of Education for Gastrointestinal Cancer, Fujian Medical University, 1 Xueyuan Road, Minhou, Fuzhou, China.
| | - Yingying Lin
- The School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China.
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Potuckova L, Draberova L, Halova I, Paulenda T, Draber P. Positive and Negative Regulatory Roles of C-Terminal Src Kinase (CSK) in FcεRI-Mediated Mast Cell Activation, Independent of the Transmembrane Adaptor PAG/CSK-Binding Protein. Front Immunol 2018; 9:1771. [PMID: 30116247 PMCID: PMC6082945 DOI: 10.3389/fimmu.2018.01771] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2018] [Accepted: 07/17/2018] [Indexed: 01/21/2023] Open
Abstract
C-terminal Src kinase (CSK) is a major negative regulator of Src family tyrosine kinases (SFKs) that play critical roles in immunoreceptor signaling. CSK is brought in contiguity to the plasma membrane-bound SFKs via binding to transmembrane adaptor PAG, also known as CSK-binding protein. The recent finding that PAG can function as a positive regulator of the high-affinity IgE receptor (FcεRI)-mediated mast cell signaling suggested that PAG and CSK have some non-overlapping regulatory functions in mast cell activation. To determine the regulatory roles of CSK in FcεRI signaling, we derived bone marrow-derived mast cells (BMMCs) with reduced or enhanced expression of CSK from wild-type (WT) or PAG knockout (KO) mice and analyzed their FcεRI-mediated activation events. We found that in contrast to PAG-KO cells, antigen-activated BMMCs with CSK knockdown (KD) exhibited significantly higher degranulation, calcium response, and tyrosine phosphorylation of FcεRI, SYK, and phospholipase C. Interestingly, FcεRI-mediated events in BMMCs with PAG-KO were restored upon CSK silencing. BMMCs with CSK-KD/PAG-KO resembled BMMCs with CSK-KD alone. Unexpectedly, cells with CSK-KD showed reduced kinase activity of LYN and decreased phosphorylation of transcription factor STAT5. This was accompanied by impaired production of proinflammatory cytokines and chemokines in antigen-activated cells. In line with this, BMMCs with CSK-KD exhibited enhanced phosphorylation of protein phosphatase SHP-1, which provides a negative feedback loop for regulating phosphorylation of STAT5 and LYN kinase activity. Furthermore, we found that in WT BMMCs SHP-1 forms complexes containing LYN, CSK, and STAT5. Altogether, our data demonstrate that in FcεRI-activated mast cells CSK is a negative regulator of degranulation and chemotaxis, but a positive regulator of adhesion to fibronectin and production of proinflammatory cytokines. Some of these pathways are not dependent on the presence of PAG.
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Affiliation(s)
- Lucie Potuckova
- Department of Signal Transduction, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czechia
| | - Lubica Draberova
- Department of Signal Transduction, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czechia
| | - Ivana Halova
- Department of Signal Transduction, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czechia
| | - Tomas Paulenda
- Department of Signal Transduction, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czechia
| | - Petr Draber
- Department of Signal Transduction, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czechia
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3
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Gao Y, Li Y, Zhang C, Zhao M, Deng C, Lan Q, Liu Z, Su N, Wang J, Xu F, Xu Y, Ping L, Chang L, Gao H, Wu J, Xue Y, Deng Z, Peng J, Xu P. Enhanced Purification of Ubiquitinated Proteins by Engineered Tandem Hybrid Ubiquitin-binding Domains (ThUBDs). Mol Cell Proteomics 2016; 15:1381-96. [PMID: 27037361 DOI: 10.1074/mcp.o115.051839] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Indexed: 11/06/2022] Open
Abstract
Ubiquitination is one of the most common post-translational modifications, regulating protein stability and function. However, the proteome-wide profiling of ubiquitinated proteins remains challenging due to their low abundance in cells. In this study, we systematically evaluated the affinity of ubiquitin-binding domains (UBDs) to different types of ubiquitin chains. By selecting UBDs with high affinity and evaluating various UBD combinations with different lengths and types, we constructed two artificial tandem hybrid UBDs (ThUBDs), including four UBDs made of DSK2p-derived ubiquitin-associated (UBA) and ubiquilin 2-derived UBA (ThUDQ2) and of DSK2p-derived UBA and RABGEF1-derived A20-ZnF (ThUDA20). ThUBD binds to ubiquitinated proteins, with markedly higher affinity than naturally occurring UBDs. Furthermore, it displays almost unbiased high affinity to all seven lysine-linked chains. Using ThUBD-based profiling with mass spectrometry, we identified 1092 and 7487 putative ubiquitinated proteins from yeast and mammalian cells, respectively, of which 362 and 1125 proteins had ubiquitin-modified sites. These results demonstrate that ThUBD is a refined and promising approach for enriching the ubiquitinated proteome while circumventing the need to overexpress tagged ubiquitin variants and use antibodies to recognize ubiquitin remnants, thus providing a readily accessible tool for the protein ubiquitination research community.
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Affiliation(s)
- Yuan Gao
- From the ‡State Key Laboratory of Proteomics, National Engineering Research Center for Protein Drugs, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Beijing Institute of Radiation Medicine, Beijing 102206,China
| | - Yanchang Li
- From the ‡State Key Laboratory of Proteomics, National Engineering Research Center for Protein Drugs, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Beijing Institute of Radiation Medicine, Beijing 102206,China
| | - Chengpu Zhang
- From the ‡State Key Laboratory of Proteomics, National Engineering Research Center for Protein Drugs, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Beijing Institute of Radiation Medicine, Beijing 102206,China
| | - Mingzhi Zhao
- From the ‡State Key Laboratory of Proteomics, National Engineering Research Center for Protein Drugs, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Beijing Institute of Radiation Medicine, Beijing 102206,China
| | - Chen Deng
- From the ‡State Key Laboratory of Proteomics, National Engineering Research Center for Protein Drugs, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Beijing Institute of Radiation Medicine, Beijing 102206,China
| | - Qiuyan Lan
- the ¶School of Basic Medical Science, Key Laboratory of Combinatorial Biosynthesis and Drug Discovery of Ministry of Education, School of Pharmaceutical Sciences, Wuhan University, Wuhan 430071, China
| | - Zexian Liu
- the ‖Department of Biomedical Engineering, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China; and
| | - Na Su
- From the ‡State Key Laboratory of Proteomics, National Engineering Research Center for Protein Drugs, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Beijing Institute of Radiation Medicine, Beijing 102206,China
| | - Jingwei Wang
- the ¶School of Basic Medical Science, Key Laboratory of Combinatorial Biosynthesis and Drug Discovery of Ministry of Education, School of Pharmaceutical Sciences, Wuhan University, Wuhan 430071, China
| | - Feng Xu
- From the ‡State Key Laboratory of Proteomics, National Engineering Research Center for Protein Drugs, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Beijing Institute of Radiation Medicine, Beijing 102206,China
| | - Yongru Xu
- From the ‡State Key Laboratory of Proteomics, National Engineering Research Center for Protein Drugs, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Beijing Institute of Radiation Medicine, Beijing 102206,China
| | - Lingyan Ping
- the ¶School of Basic Medical Science, Key Laboratory of Combinatorial Biosynthesis and Drug Discovery of Ministry of Education, School of Pharmaceutical Sciences, Wuhan University, Wuhan 430071, China
| | - Lei Chang
- From the ‡State Key Laboratory of Proteomics, National Engineering Research Center for Protein Drugs, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Beijing Institute of Radiation Medicine, Beijing 102206,China
| | - Huiying Gao
- From the ‡State Key Laboratory of Proteomics, National Engineering Research Center for Protein Drugs, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Beijing Institute of Radiation Medicine, Beijing 102206,China
| | - Junzhu Wu
- the ¶School of Basic Medical Science, Key Laboratory of Combinatorial Biosynthesis and Drug Discovery of Ministry of Education, School of Pharmaceutical Sciences, Wuhan University, Wuhan 430071, China
| | - Yu Xue
- the ‖Department of Biomedical Engineering, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China; and
| | - Zixin Deng
- the ¶School of Basic Medical Science, Key Laboratory of Combinatorial Biosynthesis and Drug Discovery of Ministry of Education, School of Pharmaceutical Sciences, Wuhan University, Wuhan 430071, China
| | - Junmin Peng
- the **Departments of Structural Biology and Developmental Neurobiology, St. Jude Proteomics Facility, St. Jude Children's Research Hospital, Memphis, Tennessee 38105
| | - Ping Xu
- From the ‡State Key Laboratory of Proteomics, National Engineering Research Center for Protein Drugs, Beijing Proteome Research Center, National Center for Protein Sciences Beijing, Beijing Institute of Radiation Medicine, Beijing 102206,China; the ¶School of Basic Medical Science, Key Laboratory of Combinatorial Biosynthesis and Drug Discovery of Ministry of Education, School of Pharmaceutical Sciences, Wuhan University, Wuhan 430071, China;
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Rasmussen RE, Erstad SM, Ramos-Martinez EM, Fimognari L, De Porcellinis AJ, Sakuragi Y. An easy and efficient permeabilization protocol for in vivo enzyme activity assays in cyanobacteria. Microb Cell Fact 2016; 15:186. [PMID: 27825349 PMCID: PMC5101802 DOI: 10.1186/s12934-016-0587-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 10/29/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Cyanobacteria are photosynthetic bacteria that thrive in diverse ecosystems and play major roles in the global carbon cycle. The abilities of cyanobacteria to fix atmospheric CO2 and to allocate the fixed carbons to chemicals and biofuels have attracted growing attentions as sustainable microbial cell factories. Better understanding of the activities of enzymes involved in the central carbon metabolism would lead to increasing product yields. Currently cell-free lysates are the most widely used method for determination of intracellular enzyme activities. However, due to thick cell walls, lysis of cyanobacterial cells is inefficient and often laborious. In some cases radioisotope-labeled substrates can be fed directly to intact cells; however, label-free assays are often favored due to safety and practical reasons. RESULTS Here we show an easy and highly efficient method for permeabilization of the cyanobacteria Synechococcus sp. PCC 7002 and Synechocystis sp. PCC 6803, and determination of two intracellular enzymes, ribulose-1,5-bisphosphate carboxylase/decarboxylase (Rubisco) and glucose-6-phosphate dehydrogenase (G6PDH), that play pivotal roles in the central carbon metabolism in cyanobacteria. Incubation of the cyanobacterial cells in the commercially available B-PER reagent for 10 min permeabilized the cells, as confirmed by the SYTOX Green staining. There was no significant change in the cell shape and no major loss of intracellular proteins was observed during the treatment. When used directly in the assays, the permeabilized cells exhibited the enzyme activities that are comparable or even higher than those detected for cell-free lysates. Moreover, the permeabilized cells could be stored at -20 °C without losing the enzyme activities. The permeabilization process and subsequent activity assays were successfully adapted to the 96-well plate system. CONCLUSIONS An easy, efficient and scalable permeabilization protocol was established for cyanobacteria. The permeabilized cells can be directly applied for measurement of G6PDH and Rubisco activities without using radioisotopes and the protocol may be readily adapted to studies of other cyanobacterial species and other intracellular enzymes. The permeabilization and enzyme assays can be performed in 96-well plates in a high-throughput manner.
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Affiliation(s)
- Randi Engelberth Rasmussen
- Department of Plant and Environmental Sciences, Copenhagen Plant Science Center, University of Copenhagen, Frederiksberg, Denmark
| | - Simon Matthé Erstad
- Department of Plant and Environmental Sciences, Copenhagen Plant Science Center, University of Copenhagen, Frederiksberg, Denmark
| | - Erick Miguel Ramos-Martinez
- Department of Plant and Environmental Sciences, Copenhagen Plant Science Center, University of Copenhagen, Frederiksberg, Denmark
| | - Lorenzo Fimognari
- Department of Plant and Environmental Sciences, Copenhagen Plant Science Center, University of Copenhagen, Frederiksberg, Denmark
| | - Alice Jara De Porcellinis
- Department of Plant and Environmental Sciences, Copenhagen Plant Science Center, University of Copenhagen, Frederiksberg, Denmark
| | - Yumiko Sakuragi
- Department of Plant and Environmental Sciences, Copenhagen Plant Science Center, University of Copenhagen, Frederiksberg, Denmark.
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Marichal T, Gaudenzio N, El Abbas S, Sibilano R, Zurek O, Starkl P, Reber LL, Pirottin D, Kim J, Chambon P, Roers A, Antoine N, Kawakami Y, Kawakami T, Bureau F, Tam SY, Tsai M, Galli SJ. Guanine nucleotide exchange factor RABGEF1 regulates keratinocyte-intrinsic signaling to maintain skin homeostasis. J Clin Invest 2016; 126:4497-4515. [PMID: 27820702 DOI: 10.1172/jci86359] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Accepted: 09/29/2016] [Indexed: 01/07/2023] Open
Abstract
Epidermal keratinocytes form a structural and immune barrier that is essential for skin homeostasis. However, the mechanisms that regulate epidermal barrier function are incompletely understood. Here we have found that keratinocyte-specific deletion of the gene encoding RAB guanine nucleotide exchange factor 1 (RABGEF1, also known as RABEX-5) severely impairs epidermal barrier function in mice and induces an allergic cutaneous and systemic phenotype. RABGEF1-deficient keratinocytes exhibited aberrant activation of the intrinsic IL-1R/MYD88/NF-κB signaling pathway and MYD88-dependent abnormalities in expression of structural proteins that contribute to skin barrier function. Moreover, ablation of MYD88 signaling in RABGEF1-deficient keratinocytes or deletion of Il1r1 restored skin homeostasis and prevented development of skin inflammation. We further demonstrated that epidermal RABGEF1 expression is reduced in skin lesions of humans diagnosed with either atopic dermatitis or allergic contact dermatitis as well as in an inducible mouse model of allergic dermatitis. Our findings reveal a key role for RABGEF1 in dampening keratinocyte-intrinsic MYD88 signaling and sustaining epidermal barrier function in mice, and suggest that dysregulation of RABGEF1 expression may contribute to epidermal barrier dysfunction in allergic skin disorders in mice and humans. Thus, RABGEF1-mediated regulation of IL-1R/MYD88 signaling might represent a potential therapeutic target.
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6
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Rabex-5 is a lenalidomide target molecule that negatively regulates TLR-induced type 1 IFN production. Proc Natl Acad Sci U S A 2016; 113:10625-30. [PMID: 27601648 DOI: 10.1073/pnas.1611751113] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Immunomodulatory drugs (IMiDs) are a family of compounds derived from thalidomide. Binding of the IMiD molecule to the Lon protease Cereblon initiates the degradation of substrates via the ubiquitin proteasome pathway. Here, we show that Cereblon forms a complex with Rabex-5, a regulator of immune homeostasis. Treatment with lenalidomide prevented the association of Cereblon with Rabex-5. Conversely, mutation of the IMiD binding site increased Cereblon-Rabex-5 coimmunoprecipitation. The thalidomide binding region of Cereblon therefore regulates the formation of this complex. Knockdown of Rabex-5 in the THP-1 macrophage cell line up-regulated Toll-like receptor (TLR)-induced cytokine and type 1 IFN production via a STAT1/IRF activating pathway. Thus, we identify Rabex-5 as a IMiD target molecule that functions to restrain TLR activated auto-immune promoting pathways. We propose that release of Rabex-5 from complex with Cereblon enables the suppression of immune responses, contributing to the antiinflammatory properties of IMiDs.
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7
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Tam SY, Lilla JN, Chen CC, Kalesnikoff J, Tsai M. RabGEF1/Rabex-5 Regulates TrkA-Mediated Neurite Outgrowth and NMDA-Induced Signaling Activation in NGF-Differentiated PC12 Cells. PLoS One 2015; 10:e0142935. [PMID: 26588713 PMCID: PMC4654474 DOI: 10.1371/journal.pone.0142935] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 10/28/2015] [Indexed: 01/15/2023] Open
Abstract
Nerve growth factor (NGF) binds to its cognate receptor TrkA and induces neuronal differentiation by activating distinct downstream signal transduction events. RabGEF1 (also known as Rabex-5) is a guanine nucleotide exchange factor for Rab5, which regulates early endosome fusion and vesicular trafficking in endocytic pathways. Here, we used the antisense (AS) expression approach to induce an NGF-dependent sustained knockdown of RabGEF1 protein expression in stable PC12 transfectants. We show that RabGEF1 is a negative regulator of NGF-induced neurite outgrowth and modulates other cellular and signaling processes that are activated by the interaction of NGF with TrkA receptors, such as cell cycle progression, cessation of proliferation, and activation of NGF-mediated downstream signaling responses. Moreover, RabGEF1 can bind to Rac1, and the activation of Rac1 upon NGF treatment is significantly enhanced in AS transfectants, suggesting that RabGEF1 is a negative regulator of NGF-induced Rac1 activation in PC12 cells. Furthermore, we show that RabGEF1 can also interact with NMDA receptors by binding to the NR2B subunit and its associated binding partner SynGAP, and negatively regulates activation of nitric oxide synthase activity induced by NMDA receptor stimulation in NGF-differentiated PC12 cells. Our data suggest that RabGEF1 is a negative regulator of TrkA-dependent neuronal differentiation and of NMDA receptor-mediated signaling activation in NGF-differentiated PC12 cells.
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Affiliation(s)
- See-Ying Tam
- Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America
- * E-mail:
| | - Jennifer N. Lilla
- Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Ching-Cheng Chen
- Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Janet Kalesnikoff
- Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Mindy Tsai
- Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America
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8
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Cruse G, Beaven MA, Music SC, Bradding P, Gilfillan AM, Metcalfe DD. The CD20 homologue MS4A4 directs trafficking of KIT toward clathrin-independent endocytosis pathways and thus regulates receptor signaling and recycling. Mol Biol Cell 2015; 26:1711-27. [PMID: 25717186 PMCID: PMC4436782 DOI: 10.1091/mbc.e14-07-1221] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Accepted: 02/18/2015] [Indexed: 01/29/2023] Open
Abstract
MS4A4 traffics through endocytic recycling pathways and stabilizes surface KIT expression by regulating endocytosis and recycling. Silencing MS4A4 reduces KIT recruitment to lipid raft microdomains and PLCg1 signaling while promoting AKT signaling, cell migration, and proliferation. This study is the first to describe functions for human MS4A4. MS4A family members differentially regulate the cell cycle, and aberrant, or loss of, expression of MS4A family proteins has been observed in colon and lung cancer. However, the precise functions of MS4A family proteins and their mechanistic interactions remain unsolved. Here we report that MS4A4 facilitates trafficking of the receptor tyrosine kinase KIT through endocytic recycling rather than degradation pathways by a mechanism that involves recruitment of KIT to caveolin-1–enriched microdomains. Silencing of MS4A4 in human mast cells altered ligand-induced KIT endocytosis pathways and reduced receptor recycling to the cell surface, thus promoting KIT signaling in the endosomes while reducing that in the plasma membrane, as exemplified by Akt and PLCγ1 phosphorylation, respectively. The altered endocytic trafficking of KIT also resulted in an increase in SCF-induced mast cell proliferation and migration, which may reflect altered signaling in these cells. Our data reveal a novel function for MS4A family proteins in regulating trafficking and signaling, which could have implications in both proliferative and immunological diseases.
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Affiliation(s)
- Glenn Cruse
- Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892
| | - Michael A Beaven
- Laboratory of Molecular Immunology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Stephen C Music
- Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892
| | - Peter Bradding
- Department of Infection, Immunity and Inflammation, Institute for Lung Health, University of Leicester, Glenfield Hospital, Leicester LE3 9QP, United Kingdom
| | - Alasdair M Gilfillan
- Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892
| | - Dean D Metcalfe
- Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892
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Abstract
Mast cells are key effector and immunoregulatory cells in IgE-associated immune responses, including allergic disorders. IgE antibodies bind to the high-affinity IgE receptor, FcεRI, expressed on the surface of mast cells; antigen-induced cross-linking of FcεRI-bound IgE molecules activates the mast cell to release an array of proinflammatory and immunomodulatory mediators. Because mast cells often respond to very low levels of antigen in vivo, the level of FcεRI expressed on the surface of these cells is an important factor in determining the responsiveness of these cells to antigen. FcεRI surface expression is regulated by a number of processes, including FcεRI stabilization, FcεRI recycling, and antigen-induced internalization. Although members of the Rab family of small GTPases and the ubiquitin ligase, Cbl, have recently emerged as major regulators of many of the membrane trafficking events that govern FcεRI expression levels, the mechanisms and intracellular pathways that regulate FcεRI trafficking remain poorly defined. This chapter outlines a number of flow cytometry-based assays that can be used to investigate cell surface FcεRI expression and dynamics (stabilization, recycling, and internalization) on bone marrow-derived mast cells (BMCMCs), the most commonly used model system for studying mast cells in vitro. Given the importance of FcεRI levels to mast cell responsiveness and function, the characterization of FcεRI expression and dynamics on different mast cell populations is critical when trying to compare IgE-dependent processes between different mast cell populations.
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Affiliation(s)
- Eon J Rios
- Department of Epithelial Biology, Stanford University, Palo Alto, CA, USA
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10
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Azouz NP, Zur N, Efergan A, Ohbayashi N, Fukuda M, Amihai D, Hammel I, Rothenberg ME, Sagi-Eisenberg R. Rab5 Is a Novel Regulator of Mast Cell Secretory Granules: Impact on Size, Cargo, and Exocytosis. THE JOURNAL OF IMMUNOLOGY 2014; 192:4043-53. [DOI: 10.4049/jimmunol.1302196] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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11
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Reber LL, Frossard N. Targeting mast cells in inflammatory diseases. Pharmacol Ther 2014; 142:416-35. [PMID: 24486828 DOI: 10.1016/j.pharmthera.2014.01.004] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Accepted: 01/24/2014] [Indexed: 12/24/2022]
Abstract
Although mast cells have long been known to play a critical role in anaphylaxis and other allergic diseases, they also participate in some innate immune responses and may even have some protective functions. Data from the study of mast cell-deficient mice have facilitated our understanding of some of the molecular mechanisms driving mast cell functions during both innate and adaptive immune responses. This review presents an overview of the biology of mast cells and their potential involvement in various inflammatory diseases. We then discuss some of the current pharmacological approaches used to target mast cells and their products in several diseases associated with mast cell activation.
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Affiliation(s)
- Laurent L Reber
- Department of Pathology, Stanford University School of Medicine, Stanford, CA, USA.
| | - Nelly Frossard
- Laboratoire d'Innovation Thérapeutique, UMR 7200 CNRS-Université de Strasbourg, Faculté de Pharmacie, France
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12
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Oka T, Rios EJ, Tsai M, Kalesnikoff J, Galli SJ. Rapid desensitization induces internalization of antigen-specific IgE on mouse mast cells. J Allergy Clin Immunol 2013; 132:922-32.e1-16. [PMID: 23810240 DOI: 10.1016/j.jaci.2013.05.004] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Revised: 04/19/2013] [Accepted: 05/13/2013] [Indexed: 12/24/2022]
Abstract
BACKGROUND Rapid desensitization transiently prevents severe allergic reactions, allowing administration of life-saving therapies in previously sensitized patients. However, the mechanisms underlying successful rapid desensitization are not fully understood. OBJECTIVES We sought to investigate whether the mast cell (MC) is an important target of rapid desensitization in mice sensitized to exhibit IgE-dependent passive systemic anaphylaxis in vivo and to investigate the antigen specificity and underlying mechanisms of rapid desensitization in our mouse model. METHODS C57BL/6 mice (in vivo) or primary isolated C57BL/6 mouse peritoneal mast cells (PMCs; in vitro) were passively sensitized with antigen-specific anti-2,4-dinitrophenyl IgE, anti-ovalbumin IgE, or both. MCs were exposed over a short period of time to increasing amounts of antigen (2,4-dinitrophenyl-human serum albumin or ovalbumin) in the presence of extracellular calcium in vitro or by means of intravenous administration to sensitized mice in vivo before challenging the mice with or exposing the PMCs to optimal amounts of specific or irrelevant antigen. RESULTS Rapidly exposing mice or PMCs to progressively increasing amounts of specific antigen inhibited the development of antigen-induced hypothermia in sensitized mice in vivo and inhibited antigen-induced PMC degranulation and prostaglandin D2 synthesis in vitro. Such MC hyporesponsiveness was induced antigen-specifically and was associated with a significant reduction in antigen-specific IgE levels on MC surfaces. CONCLUSIONS Rapidly exposing MCs to progressively increasing amounts of antigen can both enhance the internalization of antigen-specific IgE on the MC surface and also desensitize these cells in an antigen-specific manner in vivo and in vitro.
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Affiliation(s)
- Tatsuya Oka
- Department of Pathology, Stanford University School of Medicine, Stanford, Calif
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13
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Abstract
Stimulation of the receptor tyrosine kinase KIT by Stem Cell Factor (SCF) triggers activation of RAS and its downstream effectors. Proper KIT activation is essential for the maturation, survival and proliferation of mast cells. In addition, SCF activation of KIT is critical for recruiting mast cells to sites of infection or injury, where they release a mix of pro-inflammatory substances. RIN3, a RAS effector and RAB5-directed guanine nucleotide exchange factor (GEF), is highly expressed and enriched in human mast cells. SCF treatment of mast cells increased the amount of GTP-bound RAB5, and the degree of RAB5 activation correlated with the expression level of RIN3. At the same time, SCF caused the dissociation of a pre-formed complex of RIN3 with BIN2, a membrane bending protein implicated in endocytosis. Silencing of RIN3 increased the rate of SCF-induced KIT internalization, while persistent RIN3 over-expression led to KIT down regulation. These observations strongly support a role for RIN3 in coordinating the early steps of KIT endocytosis. Importantly, RIN3 also functioned as an inhibitor of mast cell migration toward SCF. Finally, we demonstrate that elevated RIN3 levels sensitize mastocytosis cells to treatment with a KIT tyrosine kinase inhibitor, suggesting the value of a two-pronged inhibitor approach for this difficult to treat malignancy. These findings directly connect KIT activation with a mast cell-specific RAS effector that regulates the cellular response to SCF and provide new insight for the development of more effective mastocytosis treatments.
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Affiliation(s)
- Christine Janson
- Molecular Biology Institute, Jonsson Comprehensive Cancer Center, Department of Biological Chemistry, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Noriyuki Kasahara
- Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - George C. Prendergast
- Lankenau Institute for Medical Research, Wynnewood, Pennsylvania, United of States of America
| | - John Colicelli
- Molecular Biology Institute, Jonsson Comprehensive Cancer Center, Department of Biological Chemistry, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail:
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14
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Aikawa Y, Hirakawa H, Lee S. Spatiotemporal regulation of the ubiquitinated cargo-binding activity of Rabex-5 in the endocytic pathway. J Biol Chem 2012; 287:40586-97. [PMID: 23048039 DOI: 10.1074/jbc.m112.411793] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
BACKGROUND The regulatory mechanism underlying the interaction of the Rabex-5 MIU domain with ubiquitinated cargos remains unclear. RESULTS Rabex-5 guanine nucleotide exchange factor (GEF) mutants affected interactions of ubiquitinated cargos. CONCLUSION GDP/GTP exchange in the GEF domain controls the MIU domain interactions with the ubiquitinated cargos. SIGNIFICANCE Rabex-5 GEF activity acts as an intramolecular switch for spatiotemporal trafficking of the ubiquitinated cargos. Ubiquitin (Ub)-dependent endocytosis of membrane proteins requires precise molecular recognition of ubiquitinated cargo by Ub-binding proteins (UBPs). Many UBPs are often themselves monoubiquitinated, a mechanism referred to as coupled monoubiquitination, which prevents them from binding in trans to the ubiquitinated cargo. However, the spatiotemporal regulatory mechanism underlying the interaction of UBPs with the ubiquitinated cargo, via their Ub-binding domains (UBDs) remains unclear. Previously, we reported the interaction of Rabex-5, a UBP and guanine nucleotide exchange factor (GEF) for Rab5, with ubiquitinated neural cell adhesion molecule L1, via its motif interacting with Ub (MIU) domain. This interaction is critical for the internalization and sorting of the ubiquitinated L1 into endosomal/lysosomal compartments. The present study demonstrated that the interaction of Rabex-5 with Rab5 depends specifically on interaction of the MIU domain with the ubiquitinated L1 to drive its internalization. Notably, impaired GEF mutants and the Rabex-5(E213A) mutant increased the flexibility of the hinge region in the HB-VPS9 tandem domain, which significantly affected their interactions with the ubiquitinated L1. In addition, GEF mutants increased the catalytic efficiency, which resulted in a reduced interaction with the ubiquitinated L1. Furthermore, the coupled monoubiquitination status of Rabex-5 was found to be significantly associated with interaction of Rabex-5 and the ubiquitinated L1. Collectively, our study reveals a novel mechanism, wherein the GEF activity of Rabex-5 acts as an intramolecular switch orchestrating ubiquitinated cargo-binding activity and coupled monoubiquitination to permit the spatiotemporal dynamic exchange of the ubiquitinated cargos.
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Affiliation(s)
- Yoshikatsu Aikawa
- Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha University, 1-3 Miyakodani, Kyotanabe, Kyoto 610-0394, Japan.
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15
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Kageyama-Yahara N, Suehiro Y, Yamamoto T, Kadowaki M. Rab5a regulates surface expression of FcεRI and functional activation in mast cells. Biol Pharm Bull 2011; 34:760-3. [PMID: 21532169 DOI: 10.1248/bpb.34.760] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Surface expression levels of high-affinity immunoglobulin E (IgE) receptors (FcεRI) on mast cells are regulated by constitutive internalization from the plasma membrane, which is thought to be an important determinant of FcεRI-mediated signaling potential. However, molecular mechanism of FcεRI trafficking has remained poorly understood. Rab proteins are small guanosine 5'-triphosphatases (GTPases) involved in the regulation of membrane traffic. In particular, Rab5 has been shown to regulate transport in the early endocytic pathway, whereas it is not known whether the FcεRI surface expression levels are regulated by Rab5. In this study, we investigated the role of individual Rab5 isoforms in mast cells by small interfering RNA knockdown method. Our results demonstrate that Rab5a knockdown enhanced FcεRI-dependent mast cell activation and upregulated FcεRI surface expression in its steady state. In contrast, Rab5c knockdown caused suppression of the activation. These findings revealed modulatory and individual roles of Rab5 isoforms in mast cell functions.
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Affiliation(s)
- Natsuko Kageyama-Yahara
- Division of Gastrointestinal Pathophysiology, Department of Bioscience, Institute of Natural Medicine, University of Toyama, Toyama, Japan.
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16
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Abstract
Rab22 is a small GTPase that is localized on early endosomes and regulates early endosomal sorting. This study reports that Rab22 promotes NGF signaling–dependent neurite outgrowth and gene expression in PC12 cells by sorting NGF and the activated/phosphorylated receptor (pTrkA) into signaling endosomes to sustain signal transduction in the cell. Rab22 is a small GTPase that is localized on early endosomes and regulates early endosomal sorting. This study reports that Rab22 promotes nerve growth factor (NGF) signaling-dependent neurite outgrowth and gene expression in PC12 cells by sorting NGF and the activated/phosphorylated receptor (pTrkA) into signaling endosomes to sustain signal transduction in the cell. NGF binding induces the endocytosis of pTrkA into Rab22-containing endosomes. Knockdown of Rab22 via small hairpin RNA (shRNA) blocks NGF-induced pTrkA endocytosis into the endosomes and gene expression (VGF) and neurite outgrowth. Overexpression of human Rab22 can rescue the inhibitory effects of the Rab22 shRNA, suggesting a specific Rab22 function in NGF signal transduction, rather than off-target effects. Furthermore, the Rab22 effector, Rabex-5, is necessary for NGF-induced neurite outgrowth and gene expression, as evidenced by the inhibitory effect of shRNA-mediated knockdown of Rabex-5. Disruption of the Rab22–Rabex-5 interaction via overexpression of the Rab22-binding domain of Rabex-5 in the cell also blocks NGF-induced neurite outgrowth, suggesting a critical role of Rab22–Rabex-5 interaction in the biogenesis of NGF-signaling endosomes to sustain the signal for neurite outgrowth. These data provide the first evidence for an early endosomal Rab GTPase as a positive regulator of NGF signal transduction and cell differentiation.
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Affiliation(s)
- Liang Wang
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
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17
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Abstract
Elevated IgE levels and increased IgE sensitization to allergens are central features of allergic asthma. IgE binds to the high-affinity Fcε receptor I (FcεRI) on mast cells, basophils, and dendritic cells and mediates the activation of these cells upon antigen-induced cross-linking of IgE-bound FcεRI. FcεRI activation proceeds through a network of signaling molecules and adaptor proteins and is negatively regulated by a number of cell surface and intracellular proteins. Therapeutic neutralization of serum IgE in moderate-to-severe allergic asthmatics reduces the frequency of asthma exacerbations through a reduction in cell surface FcεRI expression that results in decreased FcεRI activation, leading to improved asthma control. Our increasing understanding of IgE receptor signaling may lead to the development of novel therapeutics for the treatment of asthma.
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Affiliation(s)
- Lawren C Wu
- Department of Immunology, Genentech, Incorporated, South San Francisco, California 94080, USA.
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18
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Jin C, Shelburne CP, Li G, Potts EN, Riebe KJ, Sempowski GD, Foster WM, Abraham SN. Particulate allergens potentiate allergic asthma in mice through sustained IgE-mediated mast cell activation. J Clin Invest 2011; 121:941-55. [PMID: 21285515 PMCID: PMC3049384 DOI: 10.1172/jci43584] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2010] [Accepted: 12/01/2010] [Indexed: 11/17/2022] Open
Abstract
Allergic asthma is characterized by airway hyperresponsiveness, inflammation, and a cellular infiltrate dominated by eosinophils. Numerous epidemiological studies have related the exacerbation of allergic asthma with an increase in ambient inhalable particulate matter from air pollutants. This is because inhalable particles efficiently deliver airborne allergens deep into the airways, where they can aggravate allergic asthma symptoms. However, the cellular mechanisms by which inhalable particulate allergens (pAgs) potentiate asthmatic symptoms remain unknown, in part because most in vivo and in vitro studies exploring the pathogenesis of allergic asthma use soluble allergens (sAgs). Using a mouse model of allergic asthma, we found that, compared with their sAg counterparts, pAgs triggered markedly heightened airway hyperresponsiveness and pulmonary eosinophilia in allergen-sensitized mice. Mast cells (MCs) were implicated in this divergent response, as the differences in airway inflammatory responses provoked by the physical nature of the allergens were attenuated in MC-deficient mice. The pAgs were found to mediate MC-dependent responses by enhancing retention of pAg/IgE/FcεRI complexes within lipid raft–enriched, CD63(+) endocytic compartments, which prolonged IgE/FcεRI-initiated signaling and resulted in heightened cytokine responses. These results reveal how the physical attributes of allergens can co-opt MC endocytic circuitry and signaling responses to aggravate pathological responses of allergic asthma in mice.
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Affiliation(s)
- Cong Jin
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27514, USA
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19
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Tsai M, Chen CC, Mukai K, Song CH, Thompson LJ, Ziegler SF, Tam SY, Galli SJ. Thymic stromal lymphopoietin contributes to myeloid hyperplasia and increased immunoglobulins, but not epidermal hyperplasia, in RabGEF1-deficient mice. THE AMERICAN JOURNAL OF PATHOLOGY 2010; 177:2411-20. [PMID: 20829437 DOI: 10.2353/ajpath.2010.100181] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Mice overexpressing the proallergic cytokine thymic stromal lymphopoietin (TSLP) in the skin develop a pathology resembling atopic dermatitis. RabGEF1, a guanine nucleotide exchange factor for Rab5 GTPase, is a negative regulator of IgE-dependent mast cell activation, and Rabgef1-/- and TSLP transgenic mice share many similar phenotypic characteristics, including elevated serum IgE levels and severe skin inflammation, with infiltrates of both lymphocytes and eosinophils. We report here that Rabgef1-/- mice also develop splenomegaly, lymphadenopathy, myeloid hyperplasia, and high levels of TSLP. Rabgef1-/-TSLPR-/- mice, which lack TSLP/TSLP receptor (TSLPR) signaling, had levels of blood neutrophils, spleen myeloid cells, and serum IL-4, IgG1, and IgE levels that were significantly reduced compared with those in Rabgef1-/-TSLPR+/+ mice. However, Rabgef1-/-TSLPR-/- mice, like Rag1- or eosinophil-deficient Rabgef1-/- mice, developed cutaneous inflammation and epidermal hyperplasia. Therefore, in Rabgef1-/- mice, TSLP/TSLPR interactions are not required for the development of epidermal hyperplasia but contribute to the striking myeloid hyperplasia and overproduction of immunoglobulins observed in these animals. Our study shows that RabGEF1 can negatively regulate TSLP production in vivo and that excessive production of TSLP contributes to many of the phenotypic abnormalities in Rabgef1-/- mice. However, the marked epidermal hyperplasia, cutaneous inflammation, and increased numbers of dermal mast cells associated with RabGEF1 deficiency can develop via a TSLPR-independent pathway, as well as in the absence of Rag1 or eosinophils.
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Affiliation(s)
- Mindy Tsai
- Stanford University School of Medicine, Department of Pathology, L-235, 300 Pasteur Drive, Stanford, CA 94305-5324, USA.
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20
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Xu L, Lubkov V, Taylor LJ, Bar-Sagi D. Feedback regulation of Ras signaling by Rabex-5-mediated ubiquitination. Curr Biol 2010; 20:1372-7. [PMID: 20655225 DOI: 10.1016/j.cub.2010.06.051] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2010] [Revised: 06/05/2010] [Accepted: 06/07/2010] [Indexed: 10/19/2022]
Abstract
Ras proteins play a central role in transducing signals that control cell proliferation, differentiation, motility, and survival. The location-specific signaling activity of Ras has been previously shown to be regulated by ubiquitination [1]. However, the molecular machinery that controls Ras ubiquitination has not been defined. Here we demonstrate through biochemical and functional analyses that Rabex-5 (also known as RabGEF1) [2, 3] functions as an E3 ligase for Ras. Rabex-5-mediated Ras ubiquitination promotes Ras endosomal localization and leads to the suppression of ERK activation. Moreover, the Ras effector RIN1 [4, 5] is required for Rabex-5-dependent Ras ubiquitination, suggesting a feedback mechanism by which Ras activation can be coupled to ubiquitination. These findings define new elements in the regulatory circuitry that link Ras compartmentalization to signaling output.
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Affiliation(s)
- Lizhong Xu
- Department of Biochemistry, New York University School of Medicine, New York, NY 10016, USA
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21
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Ubiquitination and endocytosis of the high affinity receptor for IgE. Mol Immunol 2010; 47:2427-34. [PMID: 20638130 DOI: 10.1016/j.molimm.2010.06.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Revised: 05/31/2010] [Accepted: 06/09/2010] [Indexed: 01/17/2023]
Abstract
The high affinity receptor for IgE (FcvarepsilonRI) is constitutivelly expressed on the surface of mast cells and basophils as a multimeric complex. Upon antigen ligation to FcvarepsilonRI-bound IgE molecules, the receptor complex transduces intracellular signals leading to the release of preformed and newly synthesised pro-inflammatory mediators. FcvarepsilonRI engagement also generates negative intracellular signals involving the coordinated action of adapters, phosphatases and ubiquitin ligases that limits the intensity and duration of positive signals. Relevant to this, antigen-induced FcvarepsilonRI ubiquitination has become recognized as an important signal for the internalization and delivery of engaged receptor complexes to lysosomes for degradation. In this article, we review recent advances in our understanding of molecular mechanisms that guarantee the clearance of antigen-stimulated FcvarepsilonRI complexes from the cell surface. A particular emphasis will be given on how lipid rafts and the ubiquitin pathway cooperate to ensure receptor internalization and sorting along the endocytic compartments. A brief discussion regarding how ubiquitination regulates the endocytosis of Fc receptors other than FcvarepsilonRI will be included.
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22
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Zhu H, Qian H, Li G. Delayed onset of positive feedback activation of Rab5 by Rabex-5 and Rabaptin-5 in endocytosis. PLoS One 2010; 5:e9226. [PMID: 20169068 PMCID: PMC2821916 DOI: 10.1371/journal.pone.0009226] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2008] [Accepted: 01/26/2010] [Indexed: 12/01/2022] Open
Abstract
Background Rabex-5 is a guanine nucleotide exchange factor (GEF) that specifically activates Rab5, i.e., converting Rab5-GDP to Rab5-GTP, through two distinct pathways to promote endosome fusion and endocytosis. The direct pathway involves a pool of membrane-associated Rabex-5 that targets to the membrane via an early endosomal targeting (EET) domain. The indirect pathway, on the other hand, involves a cytosolic pool of Rabex-5/Rabaptin-5 complex. The complex is recruited to the membrane via Rabaptin-5 binding to Rab5-GTP, suggesting a positive feedback mechanism. The relationship of these two pathways for Rab5 activation in the cell is unclear. Methodology/Principal Findings We dissect the relative contribution of each pathway to Rab5 activation via mathematical modeling and kinetic analysis in the cell. These studies show that the indirect pathway constitutes a positive feedback loop for converting Rab5-GDP to Rab5-GTP on the endosomal membrane and allows sensitive regulation of endosome fusion activity by the levels of Rab5 and Rabex-5 in the cell. The onset of this positive feedback effect, however, contains a threshold, which requires above endogenous levels of Rab5 or Rabex-5 in the cell. We term this novel phenomenon “delayed response”. The presence of the direct pathway reduces the delay by increasing the basal level of Rab5-GTP, thus facilitates the function of the Rabex-5/Rabaptin-5-mediated positive feedback loop. Conclusion Our data support the mathematical model. With the model's guidance, the data reveal the affinity of Rabex-5/Rabaptin-5/Rab5-GTP interaction in the cell, which is quantitatively related to the Rabex-5 concentration for the onset of the indirect positive feedback pathway. The presence of the direct pathway and increased Rab5 concentration can reduce the Rabex-5 concentration required for the onset of the positive feedback loop. Thus the direct and indirect pathways cooperate in the regulation of early endosome fusion.
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Affiliation(s)
- Huaiping Zhu
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - Hong Qian
- Department of Applied Mathematics, University of Washington, Seattle, Washington, United States of America
| | - Guangpu Li
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
- * E-mail:
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23
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Zhu H, Liang Z, Li G. Rabex-5 is a Rab22 effector and mediates a Rab22-Rab5 signaling cascade in endocytosis. Mol Biol Cell 2009; 20:4720-9. [PMID: 19759177 DOI: 10.1091/mbc.e09-06-0453] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Rabex-5 targets to early endosomes and functions as a guanine nucleotide exchange factor for Rab5. Membrane targeting is critical for Rabex-5 to activate Rab5 on early endosomes in the cell. Here, we report the identification of Rab22 as a binding site on early endosomes for direct recruitment of Rabex-5 and activation of Rab5, establishing a Rab22-Rab5 signaling relay to promote early endosome fusion. Rab22 in guanosine 5'-O-(3-thio)triphosphate-loaded form, but not guanosine diphosphate-loaded form, binds to the early endosomal targeting domain (residues 81-230) of Rabex-5 in pull-down assays. Rabex-5 targets to Rab22-containing early endosomes, and Rab22 knockdown by short hairpin RNA abrogates the membrane targeting of Rabex-5 in the cell. In addition, coexpression of Rab22 and Rab5 shows synergistic enlargement of early endosomes, and this synergy is dependent on Rabex-5, providing further support for the collaboration of the two Rab GTPases in regulation of endosome dynamics. This novel Rab22-Rabex-5-Rab5 cascade is functionally important for the endocytosis and degradation of epidermal growth factor.
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Affiliation(s)
- Huaiping Zhu
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
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24
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Galvis A, Giambini H, Villasana Z, Barbieri MA. Functional determinants of ras interference 1 mutants required for their inhbitory activity on endocytosis. Exp Cell Res 2008; 315:820-35. [PMID: 19118546 DOI: 10.1016/j.yexcr.2008.12.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2008] [Revised: 12/04/2008] [Accepted: 12/09/2008] [Indexed: 01/11/2023]
Abstract
In this study, we initiated experiments to address the structure-function relationship of Rin1. A total of ten substitute mutations were created, and their effects on Rin1 function were examined. Of the ten mutants, four of them (P541A, E574A, Y577F, T580A) were defective in Rab5 binding, while two other Rin1 mutants (D537A, Y561F) partially interacted with Rab5. Mutations in several other residues (Y506F, Y523F, T572A, Y578F) resulted in partial loss of Rab5 function. Biochemical studies showed that six of them (D537A, P541A, Y561F, E574A, Y577F, T580A) were unable to activate Rab5 in an in vitro assay. In addition, Rin1: D537A and Rin1: Y561F mutants showed dominant inhibition of Rab5 function. Consistent with the biochemical studies, we observed that these two Rin1 mutants have lost their ability to stimulate the endocytosis of EGF, form enlarged Rab5-positive endosomes, or support in vitro endosome fusion. Based on these data, our results showed that mutations in the Vps9 domain of Rin1 lead to a loss-of-function phenotype, indicating a specific structure-function relationship between Rab5 and Rin1.
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Affiliation(s)
- Adriana Galvis
- Department of Biological Sciences, Florida International University 11220 SW 8(th) Street, Miami, FL 33199, USA
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25
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Abstract
Mast cells can function as effector and immunoregulatory cells in immunoglobulin E-associated allergic disorders, as well as in certain innate and adaptive immune responses. This review focuses on exciting new developments in the field of mast cell biology published in the past year. We highlight advances in the understanding of FcvarepsilonRI-mediated signaling and mast cell-activation events, as well as in the use of genetic models to study mast cell function in vivo. Finally, we discuss newly identified functions for mast cells or individual mast cell products, such as proteases and interleukin 10, in host defense, cardiovascular disease and tumor biology and in settings in which mast cells have anti-inflammatory or immunosuppressive functions.
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Affiliation(s)
- Janet Kalesnikoff
- Department of Pathology, Stanford University School of Medicine, Stanford, California 94305, USA.
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Contributions of F-BAR and SH2 domains of Fes protein tyrosine kinase for coupling to the FcepsilonRI pathway in mast cells. Mol Cell Biol 2008; 29:389-401. [PMID: 19001085 DOI: 10.1128/mcb.00904-08] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
This study investigates the roles of Fer-CIP4 homology (FCH)-Bin/amphiphysin/Rvs (F-BAR) and SH2 domains of Fes protein tyrosine kinase in regulating its activation and signaling downstream of the high-affinity immunoglobulin G (IgE) receptor (FcepsilonRI) in mast cells. Homology modeling of the Fes F-BAR domain revealed conservation of some basic residues implicated in phosphoinositide binding (R113/K114). The Fes F-BAR can bind phosphoinositides and induce tubulation of liposomes in vitro. Mutation of R113/K114 to uncharged residues (RK/QQ) caused a significant reduction in phosphoinositide binding in vitro and a more diffuse cytoplasmic localization in transfected COS-7 cells. RBL-2H3 mast cells expressing full-length Fes carrying the RK/QQ mutation show defects in FcepsilonRI-induced Fes tyrosine phosphorylation and degranulation compared to cells expressing wild-type Fes. This correlated with reduced localization to Lyn kinase-containing membrane fractions for the RK/QQ mutant compared to wild-type Fes in mast cells. The Fes SH2 domain also contributes to Fes signaling in mast cells, via interactions with the phosphorylated FcepsilonRI beta chain and the actin regulatory protein HS1. We show that Fes phosphorylates C-terminal tyrosine residues in HS1 implicated in actin stabilization. Thus, coordinated actions of the F-BAR and SH2 domains of Fes allow for coupling to FcepsilonRI signaling and potential regulation the actin reorganization in mast cells.
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27
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Mattera R, Bonifacino JS. Ubiquitin binding and conjugation regulate the recruitment of Rabex-5 to early endosomes. EMBO J 2008; 27:2484-94. [PMID: 18772883 DOI: 10.1038/emboj.2008.177] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2008] [Accepted: 08/12/2008] [Indexed: 01/17/2023] Open
Abstract
Rab GTPases and ubiquitination are critical regulators of transmembrane cargo sorting in endocytic and lysosomal targeting pathways. The endosomal protein Rabex-5 intersects these two layers of regulation by being both a guanine nucleotide exchange factor (GEF) for Rab5 and a substrate for ubiquitin (Ub) binding and conjugation. The ability of trafficking machinery components to bind ubiquitinated proteins is known to have a function in cargo sorting. Here, we demonstrate that Ub binding is essential for the recruitment of Rabex-5 from the cytosol to endosomes, independently of its GEF activity and of Rab5. We also show that monoubiquitinated Rabex-5 is enriched in the cytosol. These observations are consistent with a model whereby a cycle of Ub binding and monoubiquitination regulates the association of Rabex-5 with endosomes.
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Affiliation(s)
- Rafael Mattera
- Cell Biology and Metabolism Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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28
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Abstract
Rab5 is a small GTPase that regulates early endocytic events and is activated by RabGEF1/Rabex-5. Rabaptin-5, a Rab5 interacting protein, was identified as a protein critical for potentiating RabGEF1/Rabex-5's activation of Rab5. Using Rabaptin-5 shRNA knockdown, we show that Rabaptin-5 is dispensable for Rab5-dependent processes in intact mast cells, including high affinity IgE receptor (FcepsilonRI) internalization and endosome fusion. However, Rabaptin-5 deficiency markedly diminished expression of FcepsilonRI and beta1 integrin on the mast cell surface by diminishing receptor surface stability. This in turn reduced the ability of mast cells to bind IgE and significantly diminished both mast cell sensitivity to antigen (Ag)-induced mediator release and Ag-induced mast cell adhesion and migration. These findings show that, although dispensable for canonical Rab5 processes in mast cells, Rabaptin-5 importantly contributes to mast cell IgE-dependent immunologic function by enhancing mast cell receptor surface stability.
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