1
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Mentrup T, Leinung N, Patel M, Fluhrer R, Schröder B. The role of SPP/SPPL intramembrane proteases in membrane protein homeostasis. FEBS J 2024; 291:25-44. [PMID: 37625440 DOI: 10.1111/febs.16941] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 07/03/2023] [Accepted: 08/23/2023] [Indexed: 08/27/2023]
Abstract
Signal peptide peptidase (SPP) and the four SPP-like proteases SPPL2a, SPPL2b, SPPL2c and SPPL3 constitute a family of aspartyl intramembrane proteases with homology to presenilins. The different members reside in distinct cellular localisations within the secretory pathway and the endo-lysosomal system. Despite individual cleavage characteristics, they all cleave single-span transmembrane proteins with a type II orientation exhibiting a cytosolic N-terminus. Though the identification of substrates is not complete, SPP/SPPL-mediated proteolysis appears to be rather selective. Therefore, according to our current understanding cleavage by SPP/SPPL proteases rather seems to serve a regulatory function than being a bulk proteolytic pathway. In the present review, we will summarise our state of knowledge on SPP/SPPL proteases and in particular highlight recently identified substrates and the functional and/or (patho)-physiological implications of these cleavage events. Based on this, we aim to provide an overview of the current open questions in the field. These are connected to the regulation of these proteases at the cellular level but also in context of disease and patho-physiological processes. Furthermore, the interplay with other proteostatic systems capable of degrading membrane proteins is beginning to emerge.
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Affiliation(s)
- Torben Mentrup
- Institute for Physiological Chemistry, Technische Universität Dresden, Germany
| | - Nadja Leinung
- Institute for Physiological Chemistry, Technische Universität Dresden, Germany
| | - Mehul Patel
- Institute for Physiological Chemistry, Technische Universität Dresden, Germany
| | - Regina Fluhrer
- Biochemistry and Molecular Biology, Institute of Theoretical Medicine, Faculty of Medicine, University of Augsburg, Germany
- Center for Interdisciplinary Health Research, University of Augsburg, Germany
| | - Bernd Schröder
- Institute for Physiological Chemistry, Technische Universität Dresden, Germany
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2
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Mentrup T, Stumpff-Niggemann AY, Leinung N, Schlosser C, Schubert K, Wehner R, Tunger A, Schatz V, Neubert P, Gradtke AC, Wolf J, Rose-John S, Saftig P, Dalpke A, Jantsch J, Schmitz M, Fluhrer R, Jacobsen ID, Schröder B. Phagosomal signalling of the C-type lectin receptor Dectin-1 is terminated by intramembrane proteolysis. Nat Commun 2022; 13:1880. [PMID: 35388002 PMCID: PMC8987071 DOI: 10.1038/s41467-022-29474-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Accepted: 03/14/2022] [Indexed: 11/23/2022] Open
Abstract
Sensing of pathogens by pattern recognition receptors (PRR) is critical to initiate protective host defence reactions. However, activation of the immune system has to be carefully titrated to avoid tissue damage necessitating mechanisms to control and terminate PRR signalling. Dectin-1 is a PRR for fungal β-glucans on immune cells that is rapidly internalised after ligand-binding. Here, we demonstrate that pathogen recognition by the Dectin-1a isoform results in the formation of a stable receptor fragment devoid of the ligand binding domain. This fragment persists in phagosomal membranes and contributes to signal transduction which is terminated by the intramembrane proteases Signal Peptide Peptidase-like (SPPL) 2a and 2b. Consequently, immune cells lacking SPPL2b demonstrate increased anti-fungal ROS production, killing capacity and cytokine responses. The identified mechanism allows to uncouple the PRR signalling response from delivery of the pathogen to degradative compartments and identifies intramembrane proteases as part of a regulatory circuit to control anti-fungal immune responses. Dectin-1 is a critical component of the innate sensing repertoire which is involved in pattern based recognition of fungal pathogens. Here the authors show that intramembrane proteolysis is involved in the regulation of the antifungal host response by termination of the phagosomal signalling of Dectin-1.
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Affiliation(s)
- Torben Mentrup
- Institute of Physiological Chemistry, Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | | | - Nadja Leinung
- Institute of Physiological Chemistry, Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Christine Schlosser
- Biochemistry and Molecular Biology, Institute of Theoretical Medicine, Medical Faculty, University of Augsburg, Augsburg, Germany
| | - Katja Schubert
- Research Group Microbial Immunology, Leibniz Institute for Natural Product Research and Infection Biology, Hans Knöll Institute, Jena, Germany
| | - Rebekka Wehner
- Institute of Immunology, Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany.,National Center for Tumor Diseases (NCT), Partner Site Dresden, Dresden, Germany.,German Cancer Consortium (DKTK), Partner Site Dresden, Dresden, and German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Antje Tunger
- Institute of Immunology, Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany.,National Center for Tumor Diseases (NCT), Partner Site Dresden, Dresden, Germany
| | - Valentin Schatz
- Institute of Clinical Microbiology and Hygiene, University Hospital of Regensburg and University of Regensburg, Regensburg, Germany
| | - Patrick Neubert
- Institute of Clinical Microbiology and Hygiene, University Hospital of Regensburg and University of Regensburg, Regensburg, Germany
| | - Ann-Christine Gradtke
- Institute of Physiological Chemistry, Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Janina Wolf
- Biochemical Institute, Christian-Albrechts-University of Kiel, Kiel, Germany
| | - Stefan Rose-John
- Biochemical Institute, Christian-Albrechts-University of Kiel, Kiel, Germany
| | - Paul Saftig
- Biochemical Institute, Christian-Albrechts-University of Kiel, Kiel, Germany
| | - Alexander Dalpke
- Institute of Medical Microbiology and Virology, University Hospital Carl Gustav Carus, Medical Faculty, Technische Universität Dresden, Dresden, Germany
| | - Jonathan Jantsch
- Institute of Clinical Microbiology and Hygiene, University Hospital of Regensburg and University of Regensburg, Regensburg, Germany
| | - Marc Schmitz
- Institute of Immunology, Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany.,National Center for Tumor Diseases (NCT), Partner Site Dresden, Dresden, Germany.,German Cancer Consortium (DKTK), Partner Site Dresden, Dresden, and German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Regina Fluhrer
- Biochemistry and Molecular Biology, Institute of Theoretical Medicine, Medical Faculty, University of Augsburg, Augsburg, Germany
| | - Ilse D Jacobsen
- Research Group Microbial Immunology, Leibniz Institute for Natural Product Research and Infection Biology, Hans Knöll Institute, Jena, Germany.,Institute of Microbiology, Friedrich Schiller University, Jena, Germany
| | - Bernd Schröder
- Institute of Physiological Chemistry, Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany.
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Yamaki K, Terashi M, Yamamoto S, Fujiwara R, Inoue JI, Shimizu K, Yanagita S, Doi Y, Kimura KI, Kotani K, Sugihara M, Koyama Y. Immunoglobulin a suppresses B cell receptor-mediated activation of mouse B cells with differential inhibition of signaling molecules. Immunopharmacol Immunotoxicol 2021; 44:76-86. [PMID: 34844505 DOI: 10.1080/08923973.2021.2006216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
CONTEXT We previously reported that monoclonal mouse immunoglobulin (Ig) A, OA-4, attenuates sensitization in mice by suppressing B cell activation. OBJECTIVE Here, it is demonstrated for the first time that mouse IgA inhibits mouse B cell activation in vitro under natural conditions (i.e. in the absence of chemical, physical, and genetic modifications of IgA and B cells). MATERIALS AND METHODS Mouse splenocytes were stimulated with anti-B cell receptor (BCR) antibody or lipopolysaccharide (LPS) in the presence or absence of OA-4. Splenic B cell proliferation and the activation of several intracellular signaling molecules were measured. RESULTS Anti-BCR antibody-induced proliferation was markedly inhibited by OA-4 or the commercially available mouse IgA S107, whereas LPS-induced proliferation was weakly attenuated by a high concentration of OA-4. Moreover, OA-4 markedly decreased the anti-BCR antibody-induced phosphorylation of p44/42 mitogen-activated protein kinase (ERK) and CD22 and decreased phosphorylated phospholipase (PLC) γ2 and intracellular Ca2+ levels moderately, whereas protein kinase B (Akt) phosphorylation was not affected by OA-4. The MAPK/ERK kinase-ERK and phosphoinositide 3-kinase-Akt pathways were found to play a role in the proliferation of splenocytes induced by anti-BCR antibody based on experiments with their inhibitors. In contrast to that in splenic B cells, ERK phosphorylation induced by anti-BCR antibody in A20 cells was not inhibited by OA-4. The modulatory effects of IgA were different among the cell types and signaling pathways. CONCLUSION IgA is a potential immunoregulatory drug utilizing new mechanisms that affect splenic B cells but not A20 lymphomas.
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Affiliation(s)
- Kouya Yamaki
- Laboratory of Pharmacology, Kobe Pharmaceutical University, Kobe, Japan
| | - Masato Terashi
- Laboratory of Pharmacology, Kobe Pharmaceutical University, Kobe, Japan
| | - Saori Yamamoto
- Laboratory of Pharmacology, Kobe Pharmaceutical University, Kobe, Japan
| | - Rei Fujiwara
- Laboratory of Pharmacology, Kobe Pharmaceutical University, Kobe, Japan
| | - Jun-Ichi Inoue
- Laboratory of Pharmacology, Kobe Pharmaceutical University, Kobe, Japan
| | - Kishi Shimizu
- Laboratory of Pharmacology, Kobe Pharmaceutical University, Kobe, Japan
| | - Sakura Yanagita
- Laboratory of Pharmacology, Kobe Pharmaceutical University, Kobe, Japan
| | - Yuma Doi
- Laboratory of Pharmacology, Kobe Pharmaceutical University, Kobe, Japan
| | - Kei-Ichiro Kimura
- Laboratory of Pharmacology, Kobe Pharmaceutical University, Kobe, Japan
| | - Kayo Kotani
- Laboratory of Pharmacology, Kobe Pharmaceutical University, Kobe, Japan
| | - Mai Sugihara
- Laboratory of Pharmacology, Kobe Pharmaceutical University, Kobe, Japan
| | - Yutaka Koyama
- Laboratory of Pharmacology, Kobe Pharmaceutical University, Kobe, Japan
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Mentrup T, Schröder B. Signal peptide peptidase-like 2 proteases: Regulatory switches or proteasome of the membrane? BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2021; 1869:119163. [PMID: 34673079 DOI: 10.1016/j.bbamcr.2021.119163] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Revised: 10/07/2021] [Accepted: 10/11/2021] [Indexed: 12/30/2022]
Abstract
Signal peptide peptidase-like 2 (SPPL) proteases constitute a subfamily of SPP/SPPL intramembrane proteases which are homologues of the presenilins, the catalytic core of the γ-secretase complex. The three SPPL2 proteases SPPL2a, SPPL2b and SPPL2c proteolyse single-span, type II-oriented transmembrane proteins and/or tail-anchored proteins within their hydrophobic transmembrane segments. We review recent progress in defining substrate spectra and in vivo functions of these proteases. Characterisation of the respective knockout mice has implicated SPPL2 proteases in immune cell differentiation and function, prevention of atherosclerotic plaque development and spermatogenesis. Mechanisms how substrates are selected by these enzymes are still incompletely understood. We will discuss current views on how selective SPPL2-mediated cleavage is or whether these proteases may exhibit a generalised role in the turnover of membrane proteins. This has been suggested previously for the mechanistically related γ-secretase for which the term "proteasome of the membrane" has been coined based on its broad substrate spectrum. With regard to individual substrates, potential signalling functions of the resulting cytosolic cleavage fragments remain a controversial aspect. However, it has been clearly shown that SPPL2 proteases can influence cellular signalling and membrane trafficking by controlling levels of their membrane-bound substrate proteins which highlights these enzymes as regulatory switches. Based on this, regulatory mechanisms controlling activity of SPPL2 proteases would need to be postulated, which are just beginning to emerge. These different questions, which are relevant for other families of intramembrane proteases in a similar way, will be critically discussed based on the current state of knowledge.
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Affiliation(s)
- Torben Mentrup
- Institute for Physiological Chemistry, Technische Universität Dresden, Fiedlerstraße 42, D-01307 Dresden, Germany
| | - Bernd Schröder
- Institute for Physiological Chemistry, Technische Universität Dresden, Fiedlerstraße 42, D-01307 Dresden, Germany.
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5
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Gradtke AC, Mentrup T, Lehmann CHK, Cabrera-Cabrera F, Desel C, Okakpu D, Assmann M, Dalpke A, Schaible UE, Dudziak D, Schröder B. Deficiency of the Intramembrane Protease SPPL2a Alters Antimycobacterial Cytokine Responses of Dendritic Cells. THE JOURNAL OF IMMUNOLOGY 2021; 206:164-180. [PMID: 33239420 DOI: 10.4049/jimmunol.2000151] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Accepted: 10/30/2020] [Indexed: 12/30/2022]
Abstract
Signal peptide peptidase-like 2a (SPPL2a) is an aspartyl intramembrane protease essential for degradation of the invariant chain CD74. In humans, absence of SPPL2a leads to Mendelian susceptibility to mycobacterial disease, which is attributed to a loss of the dendritic cell (DC) subset conventional DC2. In this study, we confirm depletion of conventional DC2 in lymphatic tissues of SPPL2a-/- mice and demonstrate dependence on CD74 using SPPL2a-/- CD74-/- mice. Upon contact with mycobacteria, SPPL2a-/- bone marrow-derived DCs show enhanced secretion of IL-1β, whereas production of IL-10 and IFN-β is reduced. These effects correlated with modulated responses upon selective stimulation of the pattern recognition receptors TLR4 and Dectin-1. In SPPL2a-/- bone marrow-derived DCs, Dectin-1 is redistributed to endosomal compartments. Thus, SPPL2a deficiency alters pattern recognition receptor pathways in a CD74-dependent way, shifting the balance from anti- to proinflammatory cytokines in antimycobacterial responses. We propose that in addition to the DC reduction, this altered DC functionality contributes to Mendelian susceptibility to mycobacterial disease upon SPPL2a deficiency.
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Affiliation(s)
- Ann-Christine Gradtke
- Institute of Physiological Chemistry, Technische Universität Dresden, D-01307 Dresden, Germany
| | - Torben Mentrup
- Institute of Physiological Chemistry, Technische Universität Dresden, D-01307 Dresden, Germany
| | - Christian H K Lehmann
- Laboratory of Dendritic Cell Biology, Department of Dermatology, Friedrich-Alexander University Erlangen-Nürnberg, University Hospital Erlangen, D-91052 Erlangen, Germany.,Medical Immunology Campus Erlangen, D-91054 Erlangen, Germany.,Deutsches Zentrum Immuntherapie, D-91054 Erlangen, Germany.,Comprehensive Cancer Center Erlangen-European Metropolitan Area of Nuremberg, D-91054 Erlangen, Germany
| | - Florencia Cabrera-Cabrera
- Institute of Physiological Chemistry, Technische Universität Dresden, D-01307 Dresden, Germany.,Biochemical Institute, Christian-Albrechts-University Kiel, D-24118 Kiel, Germany
| | - Christine Desel
- Biochemical Institute, Christian-Albrechts-University Kiel, D-24118 Kiel, Germany
| | - Darian Okakpu
- Institute of Physiological Chemistry, Technische Universität Dresden, D-01307 Dresden, Germany
| | - Maike Assmann
- Priority Program Infections, Division of Cellular Microbiology, Research Center Borstel, Leibniz Lung Center, and German Center for Infection Research, partner site Borstel, D-23845 Borstel, Germany; and
| | - Alexander Dalpke
- Institute of Medical Microbiology and Hygiene, Technische Universität Dresden, D-01307 Dresden, Germany
| | - Ulrich E Schaible
- Priority Program Infections, Division of Cellular Microbiology, Research Center Borstel, Leibniz Lung Center, and German Center for Infection Research, partner site Borstel, D-23845 Borstel, Germany; and
| | - Diana Dudziak
- Laboratory of Dendritic Cell Biology, Department of Dermatology, Friedrich-Alexander University Erlangen-Nürnberg, University Hospital Erlangen, D-91052 Erlangen, Germany.,Medical Immunology Campus Erlangen, D-91054 Erlangen, Germany.,Deutsches Zentrum Immuntherapie, D-91054 Erlangen, Germany.,Comprehensive Cancer Center Erlangen-European Metropolitan Area of Nuremberg, D-91054 Erlangen, Germany
| | - Bernd Schröder
- Institute of Physiological Chemistry, Technische Universität Dresden, D-01307 Dresden, Germany;
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Podleśny-Drabiniok A, Marcora E, Goate AM. Microglial Phagocytosis: A Disease-Associated Process Emerging from Alzheimer’s Disease Genetics. Trends Neurosci 2020; 43:965-979. [DOI: 10.1016/j.tins.2020.10.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 09/02/2020] [Accepted: 10/05/2020] [Indexed: 01/02/2023]
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7
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Antagonism of Macrophage Migration Inhibitory Factory (MIF) after Traumatic Brain Injury Ameliorates Astrocytosis and Peripheral Lymphocyte Activation and Expansion. Int J Mol Sci 2020; 21:ijms21207448. [PMID: 33050322 PMCID: PMC7589344 DOI: 10.3390/ijms21207448] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 09/10/2020] [Accepted: 09/23/2020] [Indexed: 12/22/2022] Open
Abstract
Traumatic brain injury (TBI) precedes the onset of epilepsy in up to 15–20% of symptomatic epilepsies and up to 5% of all epilepsy. Treatment of acquired epilepsies, including post-traumatic epilepsy (PTE), presents clinical challenges, including frequent resistance to anti-epileptic therapies. Considering that over 1.6 million Americans present with a TBI each year, PTE is an urgent clinical problem. Neuroinflammation is thought to play a major causative role in many of the post-traumatic syndromes, including PTE. Increasing evidence suggests that neuroinflammation facilitates and potentially contributes to seizure induction and propagation. The inflammatory cytokine, macrophage migration inhibitory factor (MIF), is elevated after TBI and higher levels of MIF correlate with worse post-traumatic outcomes. MIF was recently demonstrated to directly alter the firing dynamics of CA1 pyramidal neurons in the hippocampus, a structure critically involved in many types of seizures. We hypothesized that antagonizing MIF after TBI would be anti-inflammatory, anti-neuroinflammatory and neuroprotective. The results show that administering the MIF antagonist ISO1 at 30 min after TBI prevented astrocytosis but was not neuroprotective in the peri-lesion cortex. The results also show that ISO1 inhibited the TBI-induced increase in γδT cells in the gut, and the percent of B cells infiltrating into the brain. The ISO1 treatment also increased this population of B cells in the spleen. These findings are discussed with an eye towards their therapeutic potential for post-traumatic syndromes, including PTE.
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8
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Mentrup T, Cabrera-Cabrera F, Fluhrer R, Schröder B. Physiological functions of SPP/SPPL intramembrane proteases. Cell Mol Life Sci 2020; 77:2959-2979. [PMID: 32052089 PMCID: PMC7366577 DOI: 10.1007/s00018-020-03470-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Revised: 01/09/2020] [Accepted: 01/22/2020] [Indexed: 01/07/2023]
Abstract
Intramembrane proteolysis describes the cleavage of substrate proteins within their hydrophobic transmembrane segments. Several families of intramembrane proteases have been identified including the aspartyl proteases Signal peptide peptidase (SPP) and its homologues, the SPP-like (SPPL) proteases SPPL2a, SPPL2b, SPPL2c and SPPL3. As presenilin homologues, they employ a similar catalytic mechanism as the well-studied γ-secretase. However, SPP/SPPL proteases cleave transmembrane proteins with a type II topology. The characterisation of SPP/SPPL-deficient mouse models has highlighted a still growing spectrum of biological functions and also promoted the substrate discovery of these proteases. In this review, we will summarise the current hypotheses how phenotypes of these mouse models are linked to the molecular function of the enzymes. At the cellular level, SPP/SPPL-mediated cleavage events rather provide specific regulatory switches than unspecific bulk proteolysis. By this means, a plethora of different cell biological pathways is influenced including signal transduction, membrane trafficking and protein glycosylation.
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Affiliation(s)
- Torben Mentrup
- Institute for Physiological Chemistry, Medizinisch-Theoretisches Zentrum MTZ, Technische Universität Dresden, Fiedlerstraße 42, 01307, Dresden, Germany
| | - Florencia Cabrera-Cabrera
- Institute for Physiological Chemistry, Medizinisch-Theoretisches Zentrum MTZ, Technische Universität Dresden, Fiedlerstraße 42, 01307, Dresden, Germany
| | - Regina Fluhrer
- Biochemistry and Molecular Biology, Faculty of Medicine, University of Augsburg, Universitätsstraße 2, 86135, Augsburg, Germany
- Biomedizinisches Centrum (BMC), Ludwig Maximilians University of Munich, Feodor-Lynen-Strasse 17, 81377, Munich, Germany
- DZNE-German Center for Neurodegenerative Diseases, Munich, Feodor-Lynen-Strasse 17, 81377, Munich, Germany
| | - Bernd Schröder
- Institute for Physiological Chemistry, Medizinisch-Theoretisches Zentrum MTZ, Technische Universität Dresden, Fiedlerstraße 42, 01307, Dresden, Germany.
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9
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Zhou Y, Zhang Y, Han J, Yang M, Zhu J, Jin T. Transitional B cells involved in autoimmunity and their impact on neuroimmunological diseases. J Transl Med 2020; 18:131. [PMID: 32183811 PMCID: PMC7079408 DOI: 10.1186/s12967-020-02289-w] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Accepted: 02/28/2020] [Indexed: 02/08/2023] Open
Abstract
Transitional B cells (TrB cells) represent a crucial link between immature B cells in the bone marrow and mature peripheral B cells. Although TrB cells represent one of the regulatory B cell subpopulations in healthy individuals, the frequency of CD24hiCD38hi TrB cells in circulation may be altered in individuals with autoimmune diseases, such as multiple sclerosis, neuromyelitisoptica spectrum disorders, systemic lupus erythematosus, Sjögren’s syndrome, rheumatoid arthritis, systemic sclerosis, and juvenile dermatomyositis. Although TrB cells play regulatory roles under inflammatory conditions, consequences of their functional impairment vary across autoimmune diseases. Since the origin, development, and function of TrB cells, especially in humans, remain unclear and controversial, this review aimed to discuss the characteristics of TrB cells at steady state and explore their role in various immune diseases, including autoimmune rheumatic diseases and neuroimmunological diseases.
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Affiliation(s)
- Yang Zhou
- Department of Neurology and Neuroscience Center, The First Hospital of Jilin University, Xinmin Street 71#, Changchun, 130021, China
| | - Ying Zhang
- Department of Neurology and Neuroscience Center, The First Hospital of Jilin University, Xinmin Street 71#, Changchun, 130021, China
| | - Jinming Han
- Department of Neurology and Neuroscience Center, The First Hospital of Jilin University, Xinmin Street 71#, Changchun, 130021, China
| | - Mengge Yang
- Department of Neurology and Neuroscience Center, The First Hospital of Jilin University, Xinmin Street 71#, Changchun, 130021, China
| | - Jie Zhu
- Department of Neurology and Neuroscience Center, The First Hospital of Jilin University, Xinmin Street 71#, Changchun, 130021, China.,Department of Neurobiology, Care Sciences and Society, Karolinska Institute, Stockholm, Sweden
| | - Tao Jin
- Department of Neurology and Neuroscience Center, The First Hospital of Jilin University, Xinmin Street 71#, Changchun, 130021, China.
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10
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Macrophage Migration Inhibitory Factor Alters Functional Properties of CA1 Hippocampal Neurons in Mouse Brain Slices. Int J Mol Sci 2019; 21:ijms21010276. [PMID: 31906137 PMCID: PMC6981710 DOI: 10.3390/ijms21010276] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 12/23/2019] [Accepted: 12/24/2019] [Indexed: 02/06/2023] Open
Abstract
Neuroinflammation is implicated in a host of neurological insults, such as traumatic brain injury (TBI), ischemic stroke, Alzheimer's disease, Parkinson's disease, and epilepsy. The immune response to central nervous system (CNS) injury involves sequelae including the release of numerous cytokines and chemokines. Macrophage migration inhibitory factor (MIF), is one such cytokine that is elevated following CNS injury, and is associated with the prognosis of TBI, and ischemic stroke. MIF has been identified in astrocytes and neurons, and some of the trophic actions of MIF have been related to its direct and indirect actions on astrocytes. However, the potential modulation of CNS neuronal function by MIF has not yet been explored. This study tests the hypothesis that MIF can directly influence hippocampal neuronal function. MIF was microinjected into the hippocampus and the genetically encoded calcium indicator, GCaMP6f, was used to measure Ca2+ events in acute adult mouse brain hippocampal slices. Results demonstrated that a single injection of 200 ng MIF into the hippocampus significantly increased baseline calcium signals in CA1 pyramidal neuron somata, and altered calcium responses to N-methyl-d-aspartate (NMDA) + D-serine in pyramidal cell apical dendrites located in the stratum radiatum. These data are the first to show direct effects of MIF on hippocampal neurons and on NMDA receptor function. Considering that MIF is elevated after brain insults such as TBI, the data suggest that, in addition to the previously described role of MIF in astrocyte reactivity, elevated MIF can have significant effects on neuronal function in the hippocampus.
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11
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Velcicky J, Mathison CJN, Nikulin V, Pflieger D, Epple R, Azimioara M, Cow C, Michellys PY, Rigollier P, Beisner DR, Bodendorf U, Guerini D, Liu B, Wen B, Zaharevitz S, Brandl T. Discovery of Orally Active Hydroxyethylamine Based SPPL2a Inhibitors. ACS Med Chem Lett 2019; 10:887-892. [PMID: 31223443 DOI: 10.1021/acsmedchemlett.9b00044] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Accepted: 05/16/2019] [Indexed: 01/12/2023] Open
Abstract
SPPL2a (Signal Peptide Peptidase Like 2a) is an intramembrane aspartyl protease engaged in the function of B-cells and dendritic cells. Despite being an attractive target for modulation of the immune system, selective SPPL2a inhibitors are barely described in the literature. Recently, we have disclosed a selective, small molecular weight agent SPL-707 which confirmed that pharmacological inhibition of SPPL2a leads to the accumulation of its substrate CD74/p8 and as a consequence to a reduction in the number of B-cells as well as myeloid dendritic cells in mice. In this paper we describe the discovery of novel hydroxyethylamine based SPPL2a inhibitors. Starting from a rather lipophilic screening hit, several iterative optimization cycles allowed for its transformation into a highly potent and selective compound 15 (SPL-410) which inhibited in vivo CD74/p8 fragment processing in mice at 10 mg/kg oral dose.
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Affiliation(s)
| | - Casey J. N. Mathison
- The Genomics Institute of the Novartis Research Foundation, 10675 John Jay Hopkins Drive, San Diego, California 92121, United States
| | - Victor Nikulin
- The Genomics Institute of the Novartis Research Foundation, 10675 John Jay Hopkins Drive, San Diego, California 92121, United States
| | | | - Robert Epple
- The Genomics Institute of the Novartis Research Foundation, 10675 John Jay Hopkins Drive, San Diego, California 92121, United States
| | - Mihai Azimioara
- The Genomics Institute of the Novartis Research Foundation, 10675 John Jay Hopkins Drive, San Diego, California 92121, United States
| | - Christopher Cow
- The Genomics Institute of the Novartis Research Foundation, 10675 John Jay Hopkins Drive, San Diego, California 92121, United States
| | - Pierre-Yves Michellys
- The Genomics Institute of the Novartis Research Foundation, 10675 John Jay Hopkins Drive, San Diego, California 92121, United States
| | | | - Daniel R. Beisner
- The Genomics Institute of the Novartis Research Foundation, 10675 John Jay Hopkins Drive, San Diego, California 92121, United States
| | | | | | - Bo Liu
- The Genomics Institute of the Novartis Research Foundation, 10675 John Jay Hopkins Drive, San Diego, California 92121, United States
| | - Ben Wen
- The Genomics Institute of the Novartis Research Foundation, 10675 John Jay Hopkins Drive, San Diego, California 92121, United States
| | - Samantha Zaharevitz
- The Genomics Institute of the Novartis Research Foundation, 10675 John Jay Hopkins Drive, San Diego, California 92121, United States
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Martínez-Barricarte R, Kong XF, Casanova JL. Measurement of CD74 N-terminal Fragment Accumulation in Cells Treated with SPPL2a Inhibitor. Bio Protoc 2019; 9:e3254. [PMID: 33654779 DOI: 10.21769/bioprotoc.3254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Revised: 04/29/2019] [Accepted: 05/27/2019] [Indexed: 11/02/2022] Open
Abstract
The recent discovery of human signal peptide peptidase-like 2a (SPPL2a) deficiency in humans revealed the toxicity associated with the accumulation of one of its substrates, CD74 N-terminal fragment (CD74-NTF), for certain type of dendritic cells (cDC2). We developed a two-step protocol for monitoring the accumulation of this molecule in different subsets of PBMCs and immortalized B cells, in which SPPL2a is chemically inhibited and CD74-NTF levels are then assessed by flow cytometry or western blotting. The chemical inhibition of SPPL2a has been described elsewhere, but this is the first time that this inhibition has been reported as a protocol.
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Affiliation(s)
- Rubén Martínez-Barricarte
- St. Giles Laboratory of Human Genetics of Infectious Diseases, Rockefeller Branch, The Rockefeller University, New York City, NY, USA
| | - Xiao-Fei Kong
- St. Giles Laboratory of Human Genetics of Infectious Diseases, Rockefeller Branch, The Rockefeller University, New York City, NY, USA
| | - Jean-Laurent Casanova
- St. Giles Laboratory of Human Genetics of Infectious Diseases, Rockefeller Branch, The Rockefeller University, New York City, NY, USA.,Laboratory of Human Genetics of Infectious Diseases, Necker Branch, INSERM U1163, Necker Hospital for Sick Children, Paris, France.,Paris Descartes University, Imagine Institute, Paris, France.,Howard Hughes Medical Institute, New York, USA.,Pediatric Hematology and Immunology Unit, Necker Hospital for Sick Children, AP-HP, Paris, France
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13
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Penticuff JC, Woolbright BL, Sielecki TM, Weir SJ, Taylor JA. MIF family proteins in genitourinary cancer: tumorigenic roles and therapeutic potential. Nat Rev Urol 2019; 16:318-328. [DOI: 10.1038/s41585-019-0171-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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14
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Mentrup T, Theodorou K, Cabrera-Cabrera F, Helbig AO, Happ K, Gijbels M, Gradtke AC, Rabe B, Fukumori A, Steiner H, Tholey A, Fluhrer R, Donners M, Schröder B. Atherogenic LOX-1 signaling is controlled by SPPL2-mediated intramembrane proteolysis. J Exp Med 2019; 216:807-830. [PMID: 30819724 PMCID: PMC6446863 DOI: 10.1084/jem.20171438] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 08/21/2018] [Accepted: 10/17/2018] [Indexed: 11/27/2022] Open
Abstract
The intramembrane proteases SPPL2a/b control pro-atherogenic signaling of membrane-bound proteolytic fragments derived from the oxLDL receptor LOX-1. In mice deficient for these proteases, plaque development and fibrosis is enhanced. This highlights SPPL2a/b as crucial players of a novel athero-protective mechanism, which is conserved in humans. The lectin-like oxidized LDL receptor 1 (LOX-1) is a key player in the development of atherosclerosis. LOX-1 promotes endothelial activation and dysfunction by mediating uptake of oxidized LDL and inducing pro-atherogenic signaling. However, little is known about modulators of LOX-1–mediated responses. Here, we show that the function of LOX-1 is controlled proteolytically. Ectodomain shedding by the metalloprotease ADAM10 and lysosomal degradation generate membrane-bound N-terminal fragments (NTFs), which we identified as novel substrates of the intramembrane proteases signal peptide peptidase–like 2a and b (SPPL2a/b). SPPL2a/b control cellular LOX-1 NTF levels which, following self-association via their transmembrane domain, can activate MAP kinases in a ligand-independent manner. This leads to an up-regulation of several pro-atherogenic and pro-fibrotic targets including ICAM-1 and the connective tissue growth factor CTGF. Consequently, SPPL2a/b-deficient mice, which accumulate LOX-1 NTFs, develop larger and more advanced atherosclerotic plaques than controls. This identifies intramembrane proteolysis by SPPL2a/b as a novel atheroprotective mechanism via negative regulation of LOX-1 signaling.
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Affiliation(s)
- Torben Mentrup
- Institute of Physiological Chemistry, Technische Universität Dresden, Dresden, Germany.,Biochemical Institute, Christian Albrechts University of Kiel, Kiel, Germany
| | - Kosta Theodorou
- Department of Pathology, Cardiovascular Research Institute, Maastricht University, Maastricht, Netherlands
| | - Florencia Cabrera-Cabrera
- Institute of Physiological Chemistry, Technische Universität Dresden, Dresden, Germany.,Biochemical Institute, Christian Albrechts University of Kiel, Kiel, Germany
| | - Andreas O Helbig
- Systematic Proteome Research and Bioanalytics, Institute for Experimental Medicine, Christian Albrechts University of Kiel, Kiel, Germany
| | - Kathrin Happ
- Biochemical Institute, Christian Albrechts University of Kiel, Kiel, Germany
| | - Marion Gijbels
- Department of Pathology, Cardiovascular Research Institute, Maastricht University, Maastricht, Netherlands.,Department of Molecular Genetics, Cardiovascular Research Institute, Maastricht University, Maastricht, Netherlands.,Amsterdam Cardiovascular Sciences, Department of Medical Biochemistry, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | - Ann-Christine Gradtke
- Institute of Physiological Chemistry, Technische Universität Dresden, Dresden, Germany.,Biochemical Institute, Christian Albrechts University of Kiel, Kiel, Germany
| | - Björn Rabe
- Biochemical Institute, Christian Albrechts University of Kiel, Kiel, Germany
| | - Akio Fukumori
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
| | - Harald Steiner
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany.,Biomedical Center, Metabolic Biochemistry, Ludwig Maximilians University of Munich, Munich, Germany
| | - Andreas Tholey
- Systematic Proteome Research and Bioanalytics, Institute for Experimental Medicine, Christian Albrechts University of Kiel, Kiel, Germany
| | - Regina Fluhrer
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany.,Biomedical Center, Metabolic Biochemistry, Ludwig Maximilians University of Munich, Munich, Germany
| | - Marjo Donners
- Department of Pathology, Cardiovascular Research Institute, Maastricht University, Maastricht, Netherlands
| | - Bernd Schröder
- Institute of Physiological Chemistry, Technische Universität Dresden, Dresden, Germany .,Biochemical Institute, Christian Albrechts University of Kiel, Kiel, Germany
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15
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Rijvers L, Melief M, van der Vuurst de Vries RM, Stéphant M, van Langelaar J, Wierenga‐Wolf AF, Hogervorst JM, Geurts‐Moespot AJ, Sweep FCGJ, Hintzen RQ, van Luijn MM. The macrophage migration inhibitory factor pathway in human B cells is tightly controlled and dysregulated in multiple sclerosis. Eur J Immunol 2018; 48:1861-1871. [PMID: 30160778 PMCID: PMC6282801 DOI: 10.1002/eji.201847623] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 07/04/2018] [Accepted: 08/21/2018] [Indexed: 12/31/2022]
Abstract
In MS, B cells survive peripheral tolerance checkpoints to mediate local inflammation, but the underlying molecular mechanisms are relatively underexplored. In mice, the MIF pathway controls B-cell development and the induction of EAE. Here, we found that MIF and MIF receptor CD74 are downregulated, while MIF receptor CXCR4 is upregulated in B cells from early onset MS patients. B cells were identified as the main immune subset in blood expressing MIF. Blocking of MIF and CD74 signaling in B cells triggered CXCR4 expression, and vice versa, with separate effects on their proinflammatory activity, proliferation, and sensitivity to Fas-mediated apoptosis. This study reveals a new reciprocal negative regulation loop between CD74 and CXCR4 in human B cells. The disturbance of this loop during MS onset provides further insights into how pathogenic B cells survive peripheral tolerance checkpoints to mediate disease activity in MS.
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Affiliation(s)
- Liza Rijvers
- Department of ImmunologyErasmus MCUniversity Medical CenterRotterdamThe Netherlands
- MS Center ErasMSErasmus MCUniversity Medical CenterRotterdamThe Netherlands
| | - Marie‐José Melief
- Department of ImmunologyErasmus MCUniversity Medical CenterRotterdamThe Netherlands
- MS Center ErasMSErasmus MCUniversity Medical CenterRotterdamThe Netherlands
| | - Roos M. van der Vuurst de Vries
- Department of NeurologyErasmus MCUniversity Medical CenterRotterdamThe Netherlands
- MS Center ErasMSErasmus MCUniversity Medical CenterRotterdamThe Netherlands
| | - Maeva Stéphant
- Department of ImmunologyErasmus MCUniversity Medical CenterRotterdamThe Netherlands
- MS Center ErasMSErasmus MCUniversity Medical CenterRotterdamThe Netherlands
| | - Jamie van Langelaar
- Department of ImmunologyErasmus MCUniversity Medical CenterRotterdamThe Netherlands
- MS Center ErasMSErasmus MCUniversity Medical CenterRotterdamThe Netherlands
| | - Annet F. Wierenga‐Wolf
- Department of ImmunologyErasmus MCUniversity Medical CenterRotterdamThe Netherlands
- MS Center ErasMSErasmus MCUniversity Medical CenterRotterdamThe Netherlands
| | - Jeanet M. Hogervorst
- Department of ImmunologyErasmus MCUniversity Medical CenterRotterdamThe Netherlands
- MS Center ErasMSErasmus MCUniversity Medical CenterRotterdamThe Netherlands
| | | | - Fred C. G. J. Sweep
- Department of Laboratory MedicineRadboud University Medical CenterNijmegenThe Netherlands
| | - Rogier Q. Hintzen
- Department of ImmunologyErasmus MCUniversity Medical CenterRotterdamThe Netherlands
- Department of NeurologyErasmus MCUniversity Medical CenterRotterdamThe Netherlands
- MS Center ErasMSErasmus MCUniversity Medical CenterRotterdamThe Netherlands
| | - Marvin M. van Luijn
- Department of ImmunologyErasmus MCUniversity Medical CenterRotterdamThe Netherlands
- MS Center ErasMSErasmus MCUniversity Medical CenterRotterdamThe Netherlands
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16
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Drake JR. The immunobiology of ubiquitin-dependent B cell receptor functions. Mol Immunol 2018; 101:146-154. [PMID: 29940407 DOI: 10.1016/j.molimm.2018.05.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Revised: 04/29/2018] [Accepted: 05/24/2018] [Indexed: 02/01/2023]
Abstract
MHC class II-restricted antigen presentation by dendritic cells is necessary for activation of naïve CD4 T cells, whereas class II-restricted antigen presentation by B lymphocytes and macrophages is important for the recruitment of CD4+ helper and regulatory T cells. Antigen presentation by B cells is also important for induction of T cell tolerance. B cells are unique among these three types of MHC class II-expressing antigen presenting cells (APC) as they constitutively express high levels of cell surface class II molecules and express a clonally restricted antigen specific receptor, the B cell receptor (BCR). Here, I review our current understanding of three major steps that underlie the processing and presentation of BCR-bound cognate antigen: (1) endocytosis of antigen-BCR (Ag-BCR) complexes, (2) Ag-BCR trafficking to intracellular antigen processing compartments and (3) generation of antigenic peptide-MHC class II complexes, with a particular focus on the role of BCR ubiquitination in each. I will highlight potential topics for future research and briefly discuss the impact of the cell biology of BCR-mediated antigen processing on the response of the B cell and T cell to the cell-cell interactions mediated by B cell-expressed peptide-class II complexes.
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Affiliation(s)
- James R Drake
- Albany Medical College, Department of Immunology and Microbial Disease, 47 New Scotland Ave., MC-151, Albany, NY 12208-3479, United States.
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17
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Velcicky J, Bodendorf U, Rigollier P, Epple R, Beisner DR, Guerini D, Smith P, Liu B, Feifel R, Wipfli P, Aichholz R, Couttet P, Dix I, Widmer T, Wen B, Brandl T. Discovery of the First Potent, Selective, and Orally Bioavailable Signal Peptide Peptidase-Like 2a (SPPL2a) Inhibitor Displaying Pronounced Immunomodulatory Effects In Vivo. J Med Chem 2018; 61:865-880. [DOI: 10.1021/acs.jmedchem.7b01371] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
| | | | | | - Robert Epple
- The Genomics Institute of the Novartis Research Foundation, 10675 John Jay Hopkins Drive, San Diego, California 92121, United States
| | - Daniel R. Beisner
- The Genomics Institute of the Novartis Research Foundation, 10675 John Jay Hopkins Drive, San Diego, California 92121, United States
| | | | | | - Bo Liu
- The Genomics Institute of the Novartis Research Foundation, 10675 John Jay Hopkins Drive, San Diego, California 92121, United States
| | | | | | | | | | | | - Toni Widmer
- Chemical
and Pharmaceutical Profiling, Global Drug Development, Novartis Pharma AG, CH-4002 Basel, Switzerland
| | - Ben Wen
- The Genomics Institute of the Novartis Research Foundation, 10675 John Jay Hopkins Drive, San Diego, California 92121, United States
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18
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Mentrup T, Fluhrer R, Schröder B. Latest emerging functions of SPP/SPPL intramembrane proteases. Eur J Cell Biol 2017; 96:372-382. [DOI: 10.1016/j.ejcb.2017.03.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Revised: 02/28/2017] [Accepted: 03/02/2017] [Indexed: 10/20/2022] Open
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19
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Signal peptide peptidase and SPP-like proteases - Possible therapeutic targets? BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2017. [PMID: 28624439 DOI: 10.1016/j.bbamcr.2017.06.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Signal peptide peptidase (SPP) and the four homologous SPP-like proteases SPPL2a, SPPL2b, SPPL2c and SPPL3 are GxGD-type intramembrane-cleaving proteases (I-CLIPs). In addition to divergent subcellular localisations, distinct differences in the mechanistic properties and substrate requirements of individual family members have been unravelled. SPP/SPPL proteases employ a catalytic mechanism related to that of the γ-secretase complex. Nevertheless, differential targeting of SPP/SPPL proteases and γ-secretase by inhibitors has been demonstrated. Furthermore, also within the SPP/SPPL family significant differences in the sensitivity to currently available inhibitory compounds have been reported. Though far from complete, our knowledge on pathophysiological functions of SPP/SPPL proteases, in particular based on studies in mice, has been significantly increased over the last years. Based on this, inhibition of distinct SPP/SPPL proteases has been proposed as a novel therapeutic concept e.g. for the treatment of autoimmunity and viral or protozoal infections, as we will discuss in this review. This article is part of a Special Issue entitled: Proteolysis as a Regulatory Event in Pathophysiology edited by Stefan Rose-John.
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20
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Schneppenheim J, Loock AC, Hüttl S, Schweizer M, Lüllmann-Rauch R, Oberg HH, Arnold P, Lehmann CHK, Dudziak D, Kabelitz D, Lucius R, Lennon-Duménil AM, Saftig P, Schröder B. The Influence of MHC Class II on B Cell Defects Induced by Invariant Chain/CD74 N-Terminal Fragments. THE JOURNAL OF IMMUNOLOGY 2017; 199:172-185. [DOI: 10.4049/jimmunol.1601533] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 05/01/2017] [Indexed: 01/24/2023]
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21
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Invariant Chain Complexes and Clusters as Platforms for MIF Signaling. Cells 2017; 6:cells6010006. [PMID: 28208600 PMCID: PMC5371871 DOI: 10.3390/cells6010006] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Revised: 02/05/2017] [Accepted: 02/07/2017] [Indexed: 12/24/2022] Open
Abstract
Invariant chain (Ii/CD74) has been identified as a surface receptor for migration inhibitory factor (MIF). Most cells that express Ii also synthesize major histocompatibility complex class II (MHC II) molecules, which depend on Ii as a chaperone and a targeting factor. The assembly of nonameric complexes consisting of one Ii trimer and three MHC II molecules (each of which is a heterodimer) has been regarded as a prerequisite for efficient delivery to the cell surface. Due to rapid endocytosis, however, only low levels of Ii-MHC II complexes are displayed on the cell surface of professional antigen presenting cells and very little free Ii trimers. The association of Ii and MHC II has been reported to block the interaction with MIF, thus questioning the role of surface Ii as a receptor for MIF on MHC II-expressing cells. Recent work offers a potential solution to this conundrum: Many Ii-complexes at the cell surface appear to be under-saturated with MHC II, leaving unoccupied Ii subunits as potential binding sites for MIF. Some of this work also sheds light on novel aspects of signal transduction by Ii-bound MIF in B-lymphocytes: membrane raft association of Ii-MHC II complexes enables MIF to target Ii-MHC II to antigen-clustered B-cell-receptors (BCR) and to foster BCR-driven signaling and intracellular trafficking.
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22
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Schröder B, Saftig P. Intramembrane proteolysis within lysosomes. Ageing Res Rev 2016; 32:51-64. [PMID: 27143694 DOI: 10.1016/j.arr.2016.04.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Revised: 04/01/2016] [Accepted: 04/26/2016] [Indexed: 11/26/2022]
Abstract
Regulated intramembrane proteolysis is of pivotal importance in a diverse set of developmental and physiological processes. Altered intramembrane substrate turnover may be associated with neurodegeneration, cancer and impaired immune function. In this review we will focus on the intramembrane proteases which have been localized in the lysosomal membrane. Members of the γ-secretase complex and γ-secretase activity are found in the lysosomal membrane and are discussed to contribute to intracellular amyloid β production. Mutant or deficient γ-secretase may cause disturbed lysosomal function. The signal peptide peptidase-like (SPPL) protease 2a is a lysosomal membrane component and cleaves CD74, the invariant chain of the MHC II complex, as well as FasL, TNF, ITM2B and TMEM106, type II transmembrane proteins involved in the regulation of immunity and neurodegeneration. Therefore, it can be concluded, that not only proteolysis within the lysosomal lumen but also within lysosomal membranes regulates important cellular functions and contributes essentially to proteostasis of membrane proteins what may become increasingly compromised in the aged individual.
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23
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The biological function and significance of CD74 in immune diseases. Inflamm Res 2016; 66:209-216. [DOI: 10.1007/s00011-016-0995-1] [Citation(s) in RCA: 88] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Accepted: 09/30/2016] [Indexed: 12/25/2022] Open
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24
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Substrate determinants of signal peptide peptidase-like 2a (SPPL2a)-mediated intramembrane proteolysis of the invariant chain CD74. Biochem J 2016; 473:1405-22. [DOI: 10.1042/bcj20160156] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Accepted: 03/16/2016] [Indexed: 11/17/2022]
Abstract
Intramembrane proteolysis of CD74 by SPPL2a is essential for B- and dendritic cells. We show that CD74 is proteolysed in the luminal third of the transmembrane segment and identify determinants within its transmembrane and luminal membrane-proximal domain facilitating this cleavage.
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25
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Schröder B. The multifaceted roles of the invariant chain CD74--More than just a chaperone. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:1269-81. [PMID: 27033518 DOI: 10.1016/j.bbamcr.2016.03.026] [Citation(s) in RCA: 140] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Revised: 03/22/2016] [Accepted: 03/23/2016] [Indexed: 01/13/2023]
Abstract
The invariant chain (CD74) is well known for its essential role in antigen presentation by mediating assembly and subcellular trafficking of the MHCII complex. Beyond this, CD74 has also been implicated in a number of processes independent of MHCII. These include the regulation of endosomal trafficking, cell migration and cellular signalling as surface receptor of the pro-inflammatory cytokine macrophage migration inhibitory factor (MIF). In several forms of cancer, CD74 is up-regulated and associated with enhanced proliferation and metastatic potential. In this review, an overview of the diverse biological functions of the CD74 protein is provided with a particular focus on how these may be regulated. In particular, proteolysis of CD74 will be discussed as a central mechanism to control the actions of this important protein at different levels.
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Affiliation(s)
- Bernd Schröder
- Biochemical Institute, Christian Albrechts University of Kiel, Otto-Hahn-Platz 9, D-24118 Kiel, Germany.
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