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Sharma R, Smolkin RM, Chowdhury P, Fernandez KC, Kim Y, Cols M, Alread W, Yen WF, Hu W, Wang ZM, Violante S, Chaligné R, Li MO, Cross JR, Chaudhuri J. Distinct metabolic requirements regulate B cell activation and germinal center responses. Nat Immunol 2023; 24:1358-1369. [PMID: 37365386 PMCID: PMC11262065 DOI: 10.1038/s41590-023-01540-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 05/18/2023] [Indexed: 06/28/2023]
Abstract
Following infection or vaccination, activated B cells at extrafollicular sites or within germinal centers (GCs) undergo vigorous clonal proliferation. Proliferating lymphocytes have been shown to undertake lactate dehydrogenase A (LDHA)-dependent aerobic glycolysis; however, the specific role of this metabolic pathway in a B cell transitioning from a naïve to a highly proliferative, activated state remains poorly defined. Here, we deleted LDHA in a stage-specific and cell-specific manner. We find that ablation of LDHA in a naïve B cell did not profoundly affect its ability to undergo a bacterial lipopolysaccharide-induced extrafollicular B cell response. On the other hand, LDHA-deleted naïve B cells had a severe defect in their capacities to form GCs and mount GC-dependent antibody responses. In addition, loss of LDHA in T cells severely compromised B cell-dependent immune responses. Strikingly, when LDHA was deleted in activated, as opposed to naïve, B cells, there were only minimal effects on the GC reaction and in the generation of high-affinity antibodies. These findings strongly suggest that naïve and activated B cells have distinct metabolic requirements that are further regulated by niche and cellular interactions.
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Affiliation(s)
- Rahul Sharma
- Immunology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Ryan M Smolkin
- Gerstner Sloan Kettering Graduate School of Biomedical Sciences, New York, NY, USA
| | - Priyanka Chowdhury
- Immunology and Microbial Pathogenesis Program, Weill Cornell Graduate School of Medical Sciences, New York, NY, USA
| | - Keith Conrad Fernandez
- Immunology and Microbial Pathogenesis Program, Weill Cornell Graduate School of Medical Sciences, New York, NY, USA
| | - Youngjun Kim
- Immunology and Microbial Pathogenesis Program, Weill Cornell Graduate School of Medical Sciences, New York, NY, USA
| | - Montserrat Cols
- Immunology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - William Alread
- Immunology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Wei-Feng Yen
- Immunology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Wei Hu
- Immunology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Zhong-Min Wang
- Gerstner Sloan Kettering Graduate School of Biomedical Sciences, New York, NY, USA
| | - Sara Violante
- Donald B. and Catherine C. Marron Cancer Metabolism Center, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Ronan Chaligné
- Computational and Systems Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Ming O Li
- Immunology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA
- Gerstner Sloan Kettering Graduate School of Biomedical Sciences, New York, NY, USA
- Immunology and Microbial Pathogenesis Program, Weill Cornell Graduate School of Medical Sciences, New York, NY, USA
| | - Justin R Cross
- Donald B. and Catherine C. Marron Cancer Metabolism Center, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Jayanta Chaudhuri
- Immunology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
- Gerstner Sloan Kettering Graduate School of Biomedical Sciences, New York, NY, USA.
- Immunology and Microbial Pathogenesis Program, Weill Cornell Graduate School of Medical Sciences, New York, NY, USA.
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Sphingolipids in Hematopoiesis: Exploring Their Role in Lineage Commitment. Cells 2021; 10:cells10102507. [PMID: 34685487 PMCID: PMC8534120 DOI: 10.3390/cells10102507] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 08/30/2021] [Accepted: 09/18/2021] [Indexed: 11/17/2022] Open
Abstract
Sphingolipids, associated enzymes, and the sphingolipid pathway are implicated in complex, multifaceted roles impacting several cell functions, such as cellular homeostasis, apoptosis, cell differentiation, and more through intrinsic and autocrine/paracrine mechanisms. Given this broad range of functions, it comes as no surprise that a large body of evidence points to important functions of sphingolipids in hematopoiesis. As the understanding of the processes that regulate hematopoiesis and of the specific characteristics that define each type of hematopoietic cells is being continuously refined, the understanding of the roles of sphingolipid metabolism in hematopoietic lineage commitment is also evolving. Recent findings indicate that sphingolipid alterations can modulate lineage commitment from stem cells all the way to megakaryocytic, erythroid, myeloid, and lymphoid cells. For instance, recent evidence points to the ability of de novo sphingolipids to regulate the stemness of hematopoietic stem cells while a substantial body of literature implicates various sphingolipids in specialized terminal differentiation, such as thrombopoiesis. This review provides a comprehensive discussion focused on the mechanisms that link sphingolipids to the commitment of hematopoietic cells to the different lineages, also highlighting yet to be resolved questions.
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3
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Bhattacharya A, Qi L. ER-associated degradation in health and disease - from substrate to organism. J Cell Sci 2019; 132:132/23/jcs232850. [PMID: 31792042 DOI: 10.1242/jcs.232850] [Citation(s) in RCA: 62] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The recent literature has revolutionized our view on the vital importance of endoplasmic reticulum (ER)-associated degradation (ERAD) in health and disease. Suppressor/enhancer of Lin-12-like (Sel1L)-HMG-coA reductase degradation protein 1 (Hrd1)-mediated ERAD has emerged as a crucial determinant of normal physiology and as a sentinel against disease pathogenesis in the body, in a largely substrate- and cell type-specific manner. In this Review, we highlight three features of ERAD, constitutive versus inducible ERAD, quality versus quantity control of ERAD and ERAD-mediated regulation of nuclear gene transcription, through which ERAD exerts a profound impact on a number of physiological processes.
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Affiliation(s)
- Asmita Bhattacharya
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48105, USA.,Graduate Program of Genetics, Genomics and Development, Cornell University, Ithaca, NY 14853, USA
| | - Ling Qi
- Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI 48105, USA .,Division of Metabolism, Endocrinology & Diabetes, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI 48105, USA
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4
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Pothukuchi P, Agliarulo I, Russo D, Rizzo R, Russo F, Parashuraman S. Translation of genome to glycome: role of the Golgi apparatus. FEBS Lett 2019; 593:2390-2411. [PMID: 31330561 DOI: 10.1002/1873-3468.13541] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 07/12/2019] [Accepted: 07/15/2019] [Indexed: 12/16/2022]
Abstract
Glycans are one of the four biopolymers of the cell and they play important roles in cellular and organismal physiology. They consist of both linear and branched structures and are synthesized in a nontemplated manner in the secretory pathway of mammalian cells with the Golgi apparatus playing a key role in the process. In spite of the absence of a template, the glycans synthesized by a cell are not a random collection of possible glycan structures but a distribution of specific glycans in defined quantities that is unique to each cell type (Cell type here refers to distinct cell forms present in an organism that can be distinguished based on morphological, phenotypic and/or molecular criteria.) While information to produce cell type-specific glycans is encoded in the genome, how this information is translated into cell type-specific glycome (Glycome refers to the quantitative distribution of all glycan structures present in a given cell type.) is not completely understood. We summarize here the factors that are known to influence the fidelity of glycan biosynthesis and integrate them into known glycosylation pathways so as to rationalize the translation of genetic information to cell type-specific glycome.
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Affiliation(s)
- Prathyush Pothukuchi
- Institute of Biochemistry and Cellular Biology, National Research Council of Italy, Napoli, Italy
| | - Ilenia Agliarulo
- Institute of Biochemistry and Cellular Biology, National Research Council of Italy, Napoli, Italy
| | - Domenico Russo
- Institute of Biochemistry and Cellular Biology, National Research Council of Italy, Napoli, Italy
| | - Riccardo Rizzo
- Institute of Biochemistry and Cellular Biology, National Research Council of Italy, Napoli, Italy
| | - Francesco Russo
- Institute of Biochemistry and Cellular Biology, National Research Council of Italy, Napoli, Italy
| | - Seetharaman Parashuraman
- Institute of Biochemistry and Cellular Biology, National Research Council of Italy, Napoli, Italy
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5
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James B, Milstien S, Spiegel S. ORMDL3 and allergic asthma: From physiology to pathology. J Allergy Clin Immunol 2019; 144:634-640. [PMID: 31376405 DOI: 10.1016/j.jaci.2019.07.023] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 07/18/2019] [Accepted: 07/26/2019] [Indexed: 01/10/2023]
Abstract
There is a strong genetic component to asthma, and numerous genome-wide association studies have identified ORM1 (yeast)-like protein 3 (ORMDL3) as a gene associated with asthma susceptibility. However, how ORMDL3 contributes to asthma pathogenesis and its physiologic functions is not well understood and a matter of great debate. This rostrum describes recent advances and new insights in understanding of the multifaceted functions of ORMDL3 in patients with allergic asthma. We also suggest a potential unifying paradigm and discuss molecular mechanisms for the pathologic functions of ORMDL3 in asthma related to its evolutionarily conserved role in regulation of sphingolipid homeostasis. Finally, we briefly survey the utility of sphingolipid metabolites as potential biomarkers for allergic asthma.
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Affiliation(s)
- Briana James
- Department of Biochemistry and Molecular Biology and the Massey Cancer Center, Virginia Commonwealth University School of Medicine, Richmond, Va
| | - Sheldon Milstien
- Department of Biochemistry and Molecular Biology and the Massey Cancer Center, Virginia Commonwealth University School of Medicine, Richmond, Va
| | - Sarah Spiegel
- Department of Biochemistry and Molecular Biology and the Massey Cancer Center, Virginia Commonwealth University School of Medicine, Richmond, Va.
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Schlafen2 mutation unravels a role for chronic ER stress in the loss of T cell quiescence. Oncotarget 2018; 7:39396-39407. [PMID: 27276683 PMCID: PMC5129940 DOI: 10.18632/oncotarget.9818] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2016] [Accepted: 05/22/2016] [Indexed: 11/29/2022] Open
Abstract
Immunologically naïve lymphocytes are kept in a quiescent state until antigen engagement. These quiescent immune cells are characterized by small cell size, lack of spontaneous proliferation and low metabolic rate. Lymphocyte quiescence is actively enforced condition which ensures the preservation of proper differentiation and proliferation capabilities of naïve and memory lymphocytes. Previously we described a chemically induced mutation in Schlafen2 (Slfn2), termed elektra, which breaks quiescence and compromises immunity. However, the mechanism by which Slfn2 maintains quiescence remains unknown. Here we demonstrate that elektra T cells display chronic ER stress under steady state conditions. Modulation of ER stress response by depletion of either UPR mediators XBP1 or CHOP, improved viability and partially corrected the developmental abnormalities and proliferation capabilities of elektra T cells. Altogether, our results demonstrate a functional connection between Slfn2 induced quiescence in T cells and ER homeostasis, clarifying a novel mechanism by which immune cell quiescence is maintained.
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7
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Liu Z, Xia Y, Li B, Xu H, Wang C, Liu Y, Li Y, Li C, Gao N, Li L. Induction of ER stress-mediated apoptosis by ceramide via disruption of ER Ca(2+) homeostasis in human adenoid cystic carcinoma cells. Cell Biosci 2014; 4:71. [PMID: 25937892 PMCID: PMC4417540 DOI: 10.1186/2045-3701-4-71] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Accepted: 11/15/2014] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND Ceramides are a class of sphingolipids that form the structural component of the cell membrane and also act as second messengers in cell signaling pathways. Emerging results suggest that ceramide induces growth arrest and apoptosis in various human cancer cells. However, the mechanisms underlying its antitumor activity are yet to be identified. Endoplasmic reticulum stress (ER stress), a cellular adaptive response, is believed to initially compensate for damage but can eventually trigger cell death if the stimulus is severe or prolonged. In this study, we investigated whether ceramide induces cell death in human salivary adenoid cystic carcinoma (ACCs) through activation of the apoptotic ER stress. RESULTS RT-PCR, real-time PCR and western blot demonstrated that exogenous ceramide treatment up-regulated GRP78 and p-eIF2α expression and XBP1 splicing. Moreover, the ceramide synthase inhibitor FB1 abolished ceramide-induced ER stress. Up-regulation of the ER stress-associated apoptosis promoting transcription factor CHOP and p-JNK suggested that the antitumor activity of ceramide is owing to activation of apoptotic ER stress. Mechanistically, [Ca(2+)]ER depletion and SERCA inhibition by ceramide treatment suggested that it induces ER stress by disrupting [Ca(2+)]ER homeostasis. The chemical chaperone TUDCA inhibited ceramide-induced ER stress and cell death. In addition, the downstream metabolite of ceramide, S1P, cannot activate ER stress. CONCLUSIONS These results demonstrated that exogenous ceramide induces cancer cell death through a mechanism involving severe ER stress triggered by the disruption of ER Ca(2+) homeostasis.
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Affiliation(s)
- Zhe Liu
- Department of Head and Neck Oncology, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China ; State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China
| | - Yichao Xia
- Department of Head and Neck Oncology, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China ; State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China
| | - Bo Li
- Department of Head and Neck Oncology, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China ; State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China
| | - Hui Xu
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China
| | - Chenxing Wang
- Department of Head and Neck Oncology, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China ; State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China
| | - Ying Liu
- Department of Head and Neck Oncology, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China ; State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China
| | - Yi Li
- Department of Head and Neck Oncology, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China ; State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China
| | - Chunjie Li
- Department of Head and Neck Oncology, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China ; State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China
| | - Ning Gao
- Department of Head and Neck Oncology, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China ; State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China
| | - Longjiang Li
- Department of Head and Neck Oncology, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China ; State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, PR China
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8
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Drori A, Messerle M, Brune W, Tirosh B. Lack of XBP-1 impedes murine cytomegalovirus gene expression. PLoS One 2014; 9:e110942. [PMID: 25333725 PMCID: PMC4205010 DOI: 10.1371/journal.pone.0110942] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Accepted: 09/26/2014] [Indexed: 11/17/2022] Open
Abstract
The unfolded protein response (UPR) is an endoplasmic reticulum (ER)-to-nucleus signaling cascade induced in response to ER stress. The UPR aims at restoring homeostasis, but can also induce apoptosis if stress persists. Infection by human and murine cytomegaloviruses (CMVs) provokes ER stress and induces the UPR. However, both CMVs manipulate the UPR to promote its prosurvival activity and delay apoptosis. The underlying mechanisms remain largely unknown. Recently, we demonstrated that MCMV and HCMV encode a late protein to target IRE1 for degradation. However, the importance of its downstream effector, X Box binding protein 1 (XBP-1), has not been directly studied. Here we show that deletion of XBP-1 prior to or early after infection confers a transient delay in viral propagation in fibroblasts that can be overcome by increasing the viral dose. A similar phenotype was demonstrated in peritoneal macrophages. In vivo, acute infection by MCMV is reduced in the absence of XBP-1. Our data indicate that removal of XBP-1 confers a kinetic delay in early stages of MCMV infection and suggest that the late targeting of IRE1 is aimed at inhibiting activities other than the splicing of XBP-1 mRNA.
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Affiliation(s)
- Adi Drori
- Institute for Drug Research, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Martin Messerle
- Department of Virology, Hannover Medical School, Hannover, Germany
| | - Wolfram Brune
- Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany
| | - Boaz Tirosh
- Institute for Drug Research, The Hebrew University of Jerusalem, Jerusalem, Israel
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9
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Hasegawa H, Forte C, Barber I, Turnbaugh S, Stoops J, Shen M, Lim AC. Modulation of in vivo IgG crystallization in the secretory pathway by heavy chain isotype class switching and N-linked glycosylation. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:1325-38. [DOI: 10.1016/j.bbamcr.2014.03.024] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Revised: 03/17/2014] [Accepted: 03/26/2014] [Indexed: 10/25/2022]
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10
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Dufort FJ, Gumina MR, Ta NL, Tao Y, Heyse SA, Scott DA, Richardson AD, Seyfried TN, Chiles TC. Glucose-dependent de novo lipogenesis in B lymphocytes: a requirement for atp-citrate lyase in lipopolysaccharide-induced differentiation. J Biol Chem 2014; 289:7011-7024. [PMID: 24469453 DOI: 10.1074/jbc.m114.551051] [Citation(s) in RCA: 114] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Bacterially derived lipopolysaccharide (LPS) stimulates naive B lymphocytes to differentiate into immunoglobulin (Ig)-secreting plasma cells. Differentiation of B lymphocytes is characterized by a proliferative phase followed by expansion of the intracellular membrane secretory network to support Ig production. A key question in lymphocyte biology is how naive B cells reprogram metabolism to support de novo lipogenesis necessary for proliferation and expansion of the endomembrane network in response to LPS. We report that extracellularly acquired glucose is metabolized, in part, to support de novo lipogenesis in response to LPS stimulation of splenic B lymphocytes. LPS stimulation leads to increased levels of endogenous ATP-citrate lyase (ACLY), and this is accompanied by increased ACLY enzymatic activity. ACLY produces cytosolic acetyl-CoA from mitochondrially derived citrate. Inhibition of ACLY activity in LPS-stimulated B cells with the selective inhibitor 2-hydroxy-N-arylbenzenesulfonamide (compound-9; C-9) blocks glucose incorporation into de novo lipid biosynthesis, including cholesterol, free fatty acids, and neutral and acidic phospholipids. Moreover, inhibition of ACLY activity in splenic B cells results in inhibition of proliferation and defective endomembrane expansion and reduced expression of CD138 and Blimp-1, markers for plasma-like B cell differentiation. ACLY activity is also required for LPS-induced IgM production in CH12 B lymphoma cells. These data demonstrate that ACLY mediates glucose-dependent de novo lipogenesis in response to LPS signaling and identify a role for ACLY in several phenotypic changes that define plasma cell differentiation.
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Affiliation(s)
- Fay J Dufort
- Department of Biology, Boston College, Chestnut Hill, Massachusetts 02467
| | - Maria R Gumina
- Department of Biology, Boston College, Chestnut Hill, Massachusetts 02467
| | - Nathan L Ta
- Department of Biology, Boston College, Chestnut Hill, Massachusetts 02467
| | - Yongzhen Tao
- Sanford-Burnham Medical Research Institute La Jolla, California 92037
| | - Shannon A Heyse
- Department of Biology, Boston College, Chestnut Hill, Massachusetts 02467
| | - David A Scott
- Sanford-Burnham Medical Research Institute La Jolla, California 92037
| | - Adam D Richardson
- Sanford-Burnham Medical Research Institute La Jolla, California 92037
| | - Thomas N Seyfried
- Department of Biology, Boston College, Chestnut Hill, Massachusetts 02467
| | - Thomas C Chiles
- Department of Biology, Boston College, Chestnut Hill, Massachusetts 02467.
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11
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Benhamron S, Hadar R, Iwawaky T, So JS, Lee AH, Tirosh B. Regulated IRE1-dependent decay participates in curtailing immunoglobulin secretion from plasma cells. Eur J Immunol 2013; 44:867-76. [PMID: 24242955 DOI: 10.1002/eji.201343953] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 10/21/2013] [Accepted: 11/12/2013] [Indexed: 01/22/2023]
Abstract
Inositol-requiring enzyme 1 (IRE1) is a kinase and ribonuclease that executes the splicing of X box binding protein 1 (XBP-1) mRNA in response to the accumulation of unfolded protein in the ER, a signal cascade termed the unfolded protein response. Recently, IRE1 has been implicated in mRNA and miRNA cleavage and degradation, a pathway termed regulated IRE1-dependent decay (RIDD). Deletion of XBP-1 in the liver and pancreas strongly enhances RIDD by upregulating IRE1 protein levels and enhancing its ribo-nuclease activity. Because XBP-1 is essential for generating plasma cells with developed secretory capacity, we sought to evaluate the contribution of RIDD to this regulation. Mice were conditionally deleted for XBP-1 and/or IRE1 in their B-cell lineage. Similarly to the liver, deletion of XBP-1 induces IRE1 expression in LPS-treated B cells. In vitro, IRE1 cleaves the mRNA of secretory μ chains, which explains the reduction in secretory μ mRNA and its synthesis in XBP-1 KO plasma cells. In accordance, the IgM response is partially restored in XBP-1/IRE1 double KO mice relative to XBP-1 KO mice. Interestingly, the IgG1 response is reduced to a similar level in XBP-1 KO, IRE1 KO, and their double knockout animals. Our data demonstrate a specific contribution by RIDD in curtailing immunoglobulin synthesis and secretion.
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Affiliation(s)
- Sandrine Benhamron
- Institute for Drug Research, The School of Pharmacy, The Hebrew University, Jerusalem, Israel
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12
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Stahl S, Burkhart JM, Hinte F, Tirosh B, Mohr H, Zahedi RP, Sickmann A, Ruzsics Z, Budt M, Brune W. Cytomegalovirus downregulates IRE1 to repress the unfolded protein response. PLoS Pathog 2013; 9:e1003544. [PMID: 23950715 PMCID: PMC3738497 DOI: 10.1371/journal.ppat.1003544] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Accepted: 06/21/2013] [Indexed: 02/07/2023] Open
Abstract
During viral infection, a massive demand for viral glycoproteins can overwhelm the capacity of the protein folding and quality control machinery, leading to an accumulation of unfolded proteins in the endoplasmic reticulum (ER). To restore ER homeostasis, cells initiate the unfolded protein response (UPR) by activating three ER-to-nucleus signaling pathways, of which the inositol-requiring enzyme 1 (IRE1)-dependent pathway is the most conserved. To reduce ER stress, the UPR decreases protein synthesis, increases degradation of unfolded proteins, and upregulates chaperone expression to enhance protein folding. Cytomegaloviruses, as other viral pathogens, modulate the UPR to their own advantage. However, the molecular mechanisms and the viral proteins responsible for UPR modulation remained to be identified. In this study, we investigated the modulation of IRE1 signaling by murine cytomegalovirus (MCMV) and found that IRE1-mediated mRNA splicing and expression of the X-box binding protein 1 (XBP1) is repressed in infected cells. By affinity purification, we identified the viral M50 protein as an IRE1-interacting protein. M50 expression in transfected or MCMV-infected cells induced a substantial downregulation of IRE1 protein levels. The N-terminal conserved region of M50 was found to be required for interaction with and downregulation of IRE1. Moreover, UL50, the human cytomegalovirus (HCMV) homolog of M50, affected IRE1 in the same way. Thus we concluded that IRE1 downregulation represents a previously undescribed viral strategy to curb the UPR. Viruses abuse the cell's protein synthesis and folding machinery to produce large amounts of viral proteins. This enforced synthesis overloads the cell's capacity and leads to an accumulation of unfolded proteins in the endoplasmic reticulum (ER) resulting in ER stress, which can compromise cell viability. To restore ER homeostasis, cells initiate the unfolded protein response (UPR) to reduce protein synthesis, increase degradation of unfolded proteins, and upregulate chaperone expression for enhanced protein folding. The most conserved branch of the UPR is the signaling pathway activated by the ER stress sensor IRE1. It upregulates ER-associated degradation (ERAD), thereby antagonizing ER stress. Some of the counter-regulatory mechanisms of the UPR are detrimental for viral replication and are, therefore, moderated by viruses. In this study we identified the first viral IRE1 inhibitor: The murine cytomegalovirus M50 protein, which interacts with IRE1 and induces its degradation. By this means, M50 inhibits IRE1 signaling and prevents ERAD upregulation. Interestingly, the M50 homolog in human cytomegalovirus, UL50, also downregulated IRE1 revealing a previously unknown mechanism of viral host cell manipulation.
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Affiliation(s)
- Sebastian Stahl
- Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany
- Division of Viral Infections, Robert Koch Institute, Berlin, Germany
| | - Julia M. Burkhart
- Department of Bioanalytics, ISAS – Leibniz Institute for Analytical Sciences, Dortmund, Germany
| | - Florian Hinte
- Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany
| | - Boaz Tirosh
- Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University, Jerusalem, Israel
| | - Hermine Mohr
- Max von Pettenkofer Institute, Ludwig-Maximilians-Universität München, Munich, Germany
| | - René P. Zahedi
- Department of Bioanalytics, ISAS – Leibniz Institute for Analytical Sciences, Dortmund, Germany
| | - Albert Sickmann
- Department of Bioanalytics, ISAS – Leibniz Institute for Analytical Sciences, Dortmund, Germany
- Medical Proteome Center (MPC), Ruhr-Universität, Bochum, Germany
| | - Zsolt Ruzsics
- Max von Pettenkofer Institute, Ludwig-Maximilians-Universität München, Munich, Germany
- DZIF German Center for Infection Research, Munich, Germany
| | - Matthias Budt
- Division of Viral Infections, Robert Koch Institute, Berlin, Germany
| | - Wolfram Brune
- Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany
- Division of Viral Infections, Robert Koch Institute, Berlin, Germany
- DZIF German Center for Infection Research, Hamburg, Germany
- * E-mail:
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13
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Brewer JW. Phospholipids: "greasing the wheels" of humoral immunity. BIOCHIMICA ET BIOPHYSICA ACTA 2013; 1831:642-51. [PMID: 23051607 PMCID: PMC3562403 DOI: 10.1016/j.bbalip.2012.09.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2012] [Revised: 09/27/2012] [Accepted: 09/28/2012] [Indexed: 12/14/2022]
Abstract
Phospholipids are major structural components of all cellular membranes. In addition, certain phospholipids execute regulatory activities that affect cell behavior, function and fate in critically important physiological settings. The influence of phospholipids is especially obvious in the adaptive immune system, where these macromolecules mediate both intrinsic and extrinsic effects on B and T lymphocytes. This review article highlights the action of lysophospholipid sphingosine-1-phosphate as a lymphocyte chemoattractant, the function of phosphatidylinositol phosphates as signaling conduits in lymphocytes and the role of phospholipids as raw materials for membrane assembly and organelle biogenesis in activated B lymphocytes. Special emphasis is placed on the means by which these three processes push humoral immune responses forward. This article is part of a Special Issue entitled Phospholipids and Phospholipid Metabolism.
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Affiliation(s)
- Joseph W Brewer
- Department of Microbiology and Immunology, College of Medicine, University of South Alabama, 5851 USA Drive North Mobile, AL 36688, USA.
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Borklu Yucel E, Ulgen KO. Assessment of crosstalks between the Snf1 kinase complex and sphingolipid metabolism in S. cerevisiae via systems biology approaches. MOLECULAR BIOSYSTEMS 2013; 9:2914-31. [DOI: 10.1039/c3mb70248k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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15
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Tidhar R, Ben-Dor S, Wang E, Kelly S, Merrill AH, Futerman AH. Acyl chain specificity of ceramide synthases is determined within a region of 150 residues in the Tram-Lag-CLN8 (TLC) domain. J Biol Chem 2012; 287:3197-206. [PMID: 22144673 PMCID: PMC3270974 DOI: 10.1074/jbc.m111.280271] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Revised: 11/26/2011] [Indexed: 12/15/2022] Open
Abstract
In mammals, ceramides are synthesized by a family of six ceramide synthases (CerS), transmembrane proteins located in the endoplasmic reticulum, where each use fatty acyl-CoAs of defined chain length for ceramide synthesis. Little is known about the molecular features of the CerS that determine acyl-CoA selectivity. We now explore CerS structure-function relationships by constructing chimeric proteins combining sequences from CerS2, which uses C22-CoA for ceramide synthesis, and CerS5, which uses C16-CoA. CerS2 and -5 are 41% identical and 63% similar. Chimeras containing approximately half of CerS5 (from the N terminus) and half of CerS2 (from the C terminus) were catalytically inactive. However, the first 158 residues of CerS5 could be replaced with the equivalent region of CerS2 without affecting specificity of CerS5 toward C16-CoA; likewise, the putative sixth transmembrane domain (at the C terminus) of CerS5 could be replaced with the corresponding sequence of CerS2 without affecting CerS5 specificity. Remarkably, a chimeric CerS5/2 protein containing the first 158 residues and the last 83 residues of CerS2 displayed specificity toward C16-CoA, and a chimeric CerS2/5 protein containing the first 150 residues and the last 79 residues of CerS5 displayed specificity toward C22-CoA, demonstrating that a minimal region of 150 residues is sufficient for retaining CerS specificity.
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Affiliation(s)
- Rotem Tidhar
- From the Departments of Biological Chemistry and
| | - Shifra Ben-Dor
- Biological Services, Weizmann Institute of Science, Rehovot 76100, Israel and
| | - Elaine Wang
- the School of Biology and Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332-0230
| | - Samuel Kelly
- the School of Biology and Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332-0230
| | - Alfred H. Merrill
- the School of Biology and Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332-0230
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16
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UPR-Mediated Membrane Biogenesis in B Cells. Biochem Res Int 2011; 2012:738471. [PMID: 22110962 PMCID: PMC3206326 DOI: 10.1155/2012/738471] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Accepted: 08/25/2011] [Indexed: 02/04/2023] Open
Abstract
The unfolded protein
response (UPR) can coordinate the regulation of
gene transcription and protein translation to
balance the load of client proteins with the
protein folding and degradative capacities of
the ER. Increasing evidence also implicates the
UPR in the regulation of lipid synthesis and
membrane biogenesis. The differentiation of
B lymphocytes into antibody-secreting cells is
marked by significant expansion of the ER, the
site for antibody synthesis and assembly. In
activated B cells, the demand for membrane
protein and lipid components leads to activation
of the UPR transcriptional activator XBP1(S)
which, in turn, initiates a cascade of
biochemical events that enhance supplies of
phospholipid precursors and build machinery for
the synthesis, maturation, and transport of
secretory proteins. The alterations in lipid
metabolism that occur during this developmental
transition and the impact of membrane
phospholipid restriction on B cell secretory
characteristics are discussed in this
paper.
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Goldfinger M, Shmuel M, Benhamron S, Tirosh B. Protein synthesis in plasma cells is regulated by crosstalk between endoplasmic reticulum stress and mTOR signaling. Eur J Immunol 2010; 41:491-502. [PMID: 21268018 DOI: 10.1002/eji.201040677] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Revised: 10/04/2010] [Accepted: 11/19/2010] [Indexed: 01/22/2023]
Abstract
Plasma cells (PCs) secrete copious levels of immunoglobulins. To achieve this, their endoplasmic reticulum (ER) undergoes expansion in a process that requires continuous ER stress and activation of the unfolded protein response. It is important that protein synthesis, the driver of ER stress, is regulated in a manner that does not induce apoptosis. We followed protein synthesis in murine splenic B cells activated in vitro with LPS. Total protein synthesis levels increased and then steeply decreased when the cells acquired a secretory phenotype. We explored the involvement of two mechanisms in controlling protein synthesis levels, namely ER stress-mediated phosphorylation of eukaryote initiation factor 2α (eIF2α) and the mammalian target of rapamycin (mTOR) pathway, which attenuate or activate mRNA translation, respectively. We show that induction of ER stress in activated B cells counter-intuitively led to dephosphorylation of eIF2α. Despite the reduction in phosphorylated eIF2α, expression of activating transcription factor 4, an effector of hyper eIF2α phosphorylation, was induced. In addition, ER stress attenuated the mTOR pathway, which ultimately reduced protein synthesis. Finally, B cells engineered to overactivate the mTOR pathway exhibited higher apoptosis in the course of LPS stimulation. We conclude that protein synthesis in PCs is controlled by an ER stress-mediated mTOR regulation, which is needed for optimal cell viability.
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Affiliation(s)
- Meidan Goldfinger
- Institute for Drug Research, The School of Pharmacy, The Hebrew University, Jerusalem, Israel
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García-Álvarez I, Egido-Gabás M, Romero-Ramírez L, Doncel-Pérez E, Nieto-Sampedro M, Casas J, Fernández-Mayoralas A. Lipid and ganglioside alterations in tumor cells treated with antimitotic oleyl glycoside. MOLECULAR BIOSYSTEMS 2010; 7:129-38. [PMID: 21057675 DOI: 10.1039/c0mb00125b] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Oleyl 2-acetamido-2-deoxy-α-D-glucopyranoside (1) was previously shown to exhibit antimitotic activity on glioma (C6) and melanoma (A375) cell lines. Preliminary studies about its mechanism of action using (1)H MAS NMR suggested that 1 may be altering the metabolism of lipids. We have now studied the effect of 1 on the fatty acid, sphingolipid and ganglioside content in a line of carcinomic human alveolar epithelial cells (A549) using UPLC-MS. Oleic acid and NB-DNJ were used as positive controls for inhibition of fatty acid and ganglioside synthesis, respectively. Compound 1 (10 μM) was more efficient than oleic acid in reducing fatty acid levels of A549 cells, producing a decrease in the range of 40-15%, depending on the acyl chain length and the number of insaturations. In addition, glycoside 1 caused a reduction on ganglioside content of A549 tumor cell line and accumulation of lactosylceramide, the common metabolic precursor for ganglioside biosynthesis. Alteration of ganglioside metabolism was also observed with two galactosylated derivatives of 1, which caused a more pronounced increase in lactosylceramide levels. Compound 1 at higher concentrations (above 30 μM) produced drastic alterations in glycosphingolipid metabolism, leading to cell metabolic profiles very different from those obtained at 10 μM. These biochemical changes were ascribed to activation of endoplasmic reticulum stress pathways.
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19
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Prolonged endoplasmic reticulum stress promotes mislocalization of immunoglobulins to the cytoplasm. Mol Immunol 2010; 47:1719-27. [DOI: 10.1016/j.molimm.2010.03.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2010] [Accepted: 03/04/2010] [Indexed: 02/01/2023]
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