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Bharadwaj S, Groza Y, Mierzwicka JM, Malý P. Current understanding on TREM-2 molecular biology and physiopathological functions. Int Immunopharmacol 2024; 134:112042. [PMID: 38703564 DOI: 10.1016/j.intimp.2024.112042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2024] [Revised: 04/05/2024] [Accepted: 04/05/2024] [Indexed: 05/06/2024]
Abstract
Triggering receptor expressed on myeloid cells 2 (TREM-2), a glycosylated receptor belonging to the immunoglobin superfamily and especially expressed in the myeloid cell lineage, is frequently explained as a reminiscent receptor for both adaptive and innate immunity regulation. TREM-2 is also acknowledged to influence NK cell differentiation via the PI3K and PLCγ signaling pathways, as well as the partial activation or direct inhibition of T cells. Additionally, TREM-2 overexpression is substantially linked to cell-specific functions, such as enhanced phagocytosis, reduced toll-like receptor (TLR)-mediated inflammatory cytokine production, increased transcription of anti-inflammatory cytokines, and reshaped T cell function. Whereas TREM-2-deficient cells exhibit diminished phagocytic function and enhanced proinflammatory cytokines production, proceeding to inflammatory injuries and an immunosuppressive environment for disease progression. Despite the growing literature supporting TREM-2+ cells in various diseases, such as neurodegenerative disorders and cancer, substantial facets of TREM-2-mediated signaling remain inadequately understood relevant to pathophysiology conditions. In this direction, herein, we have summarized the current knowledge on TREM-2 biology and cell-specific TREM-2 expression, particularly in the modulation of pivotal TREM-2-dependent functions under physiopathological conditions. Furthermore, molecular regulation and generic biological relevance of TREM-2 are also discussed, which might provide an alternative approach for preventing or reducing TREM-2-associated deformities. At last, we discussed the TREM-2 function in supporting an immunosuppressive cancer environment and as a potential drug target for cancer immunotherapy. Hence, summarized knowledge of TREM-2 might provide a window to overcome challenges in clinically effective therapies for TREM-2-induced diseases in humans.
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Affiliation(s)
- Shiv Bharadwaj
- Laboratory of Ligand Engineering, Institute of Biotechnology of the Czech Academy of Sciences, BIOCEV Research Center, Průmyslová 595, 252 50 Vestec, Czech Republic.
| | - Yaroslava Groza
- Laboratory of Ligand Engineering, Institute of Biotechnology of the Czech Academy of Sciences, BIOCEV Research Center, Průmyslová 595, 252 50 Vestec, Czech Republic
| | - Joanna M Mierzwicka
- Laboratory of Ligand Engineering, Institute of Biotechnology of the Czech Academy of Sciences, BIOCEV Research Center, Průmyslová 595, 252 50 Vestec, Czech Republic
| | - Petr Malý
- Laboratory of Ligand Engineering, Institute of Biotechnology of the Czech Academy of Sciences, BIOCEV Research Center, Průmyslová 595, 252 50 Vestec, Czech Republic.
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Shaw BC, Snider HC, Turner AK, Zajac DJ, Simpson JF, Estus S. An Alternatively Spliced TREM2 Isoform Lacking the Ligand Binding Domain is Expressed in Human Brain. J Alzheimers Dis 2022; 87:1647-1657. [DOI: 10.3233/jad-215602] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Background: Genetic variants in TREM2 are strongly associated with Alzheimer’s disease (AD) risk but alternative splicing in TREM2 transcripts has not been comprehensively described. Objective: Recognizing that alternative splice variants can result in reduced gene expression and/or altered function, we sought to fully characterize splice variation in TREM2. Methods: Human blood and anterior cingulate autopsy tissue from 61 donors were used for end-point and quantitative PCR and western blotting to identify and quantify novel TREM2 isoforms. Results: In addition to previously described transcripts lacking exon 3 or exon 4, or retaining part of intron 3, we identified novel isoforms lacking exon 2, along with isoforms lacking multiple exons. Isoforms lacking exon 2 were predominant at approximately 10% of TREM2 mRNA in the brain. Expression of TREM2 and frequency of exon 2 skipping did not differ between AD samples and non-AD controls (p = 0.1268 and p = 0.4909, respectively). Further, these novel splice isoforms were also observed across multiple tissues with similar frequency (range 5.3 –13.0% ). We found that the exon 2 skipped isoform D2-TREM2 is translated to protein and localizes similarly to full-length TREM2 protein, that both proteins are primarily retained in the Golgi complex, and that D2-TREM2 is expressed in AD and non-AD brain. Conclusion: Since the TREM2 ligand binding domain is encoded by exon 2, and skipping this exon retains reading frame while conserving localization, we hypothesize that D2-TREM2 acts as an inhibitor of TREM2 and targeting TREM2 splicing may be a novel therapeutic pathway for AD.
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Affiliation(s)
| | | | - Andrew K. Turner
- Department of Physiology and Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA
| | - Diana J. Zajac
- Department of Physiology and Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA
| | - James F. Simpson
- Department of Physiology and Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA
| | - Steven Estus
- Department of Physiology and Sanders-Brown Center on Aging, University of Kentucky, Lexington, KY, USA
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Shafi S, Singh A, Ibrahim AM, Alhajri N, Abu Izneid T, Pottoo FH. Role of triggering receptor expressed on myeloid cells 2 (TREM2) in neurodegenerative dementias. Eur J Neurosci 2021; 53:3294-3310. [PMID: 33786894 DOI: 10.1111/ejn.15215] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 03/22/2021] [Indexed: 01/04/2023]
Abstract
Neurodegeneration is a debilitating condition that causes nerve cell degeneration or death. Neurodegenerative diseases (NDDs) such as Alzheimer's disease (AD), Parkinson's disease (PD), frontotemporal dementia (FTD), and Lewy body dementia (LBD) are posing a larger population burden of dementia worldwide. Neurodegenerative dementia is one of the main challenges in public health with its main characteristics being permanent loss of memory, impairment in cognition, and impaired daily functions. The published literature about genetic studies of these disorders suggests genetic underpinning in the pathogenesis of neurodegenerative dementia. In the process of underlining the pathogenesis of NDD, growing evidence has related genetic variations in the triggering receptor expressed on myeloid cells 2 (TREM2). This review paper aims to provide a detailed information regarding the association of TREM2 and NDDs leading to dementia. A central consideration is AD that accounts for almost 50%-70% of all late-life dementias alone or in combination with other neurological disorders. Other prevalent neurodegenerative conditions that lead to dementia are also discussed. Such studies are important as they can give a comprehensive knowledge of TREM2's role in various NDDs, in order to maximize the potential for developing new therapeutic approaches.
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Affiliation(s)
- Sadat Shafi
- Pharmaceutical Medicine, Department of Pharmacology, School of Pharmaceutical Education and Research, Jamia Hamdard, New Delhi, India
| | - Archu Singh
- Department of Pharmaceutics, School of Pharmaceutical Education and Research, Jamia Hamdard, New Delhi, India
| | - Abdallah Mohammad Ibrahim
- Fundamentals of Nursing Department, College of Nursing, Imam Abdul Rahman Bin Faisal University, Dammam, Saudi Arabia
| | - Noora Alhajri
- Department of Epidemiology and Population Health, College of Medicine and Health Science, Khalifa University, Abu Dhabi, UAE
| | | | - Faheem Hyder Pottoo
- Department of Pharmacology, College of Clinical Pharmacy, Imam Abdulrahman Bin Faisal University, Damman, Saudi Arabia
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Chen H, Chen F, Zhang M, Chen Y, Cui L, Liang C. A Review of APOE Genotype-Dependent Autophagic Flux Regulation in Alzheimer's Disease. J Alzheimers Dis 2021; 84:535-555. [PMID: 34569952 DOI: 10.3233/jad-210602] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Autophagy is a basic physiological process maintaining cell renewal, the degradation of dysfunctional organelles, and the clearance of abnormal proteins and has recently been identified as a main mechanism underlying the onset and progression of Alzheimer's disease (AD). The APOE ɛ4 genotype is the strongest genetic determinant of AD pathogenesis and initiates autophagic flux at different times. This review synthesizes the current knowledge about the potential pathogenic effects of ApoE4 on autophagy and describes its associations with the biological hallmarks of autophagy and AD from a novel perspective. Via a remarkable variety of widely accepted signaling pathway markers, such as mTOR, TFEB, SIRT1, LC3, p62, LAMP1, LAMP2, CTSD, Rabs, and V-ATPase, ApoE isoforms differentially modulate autophagy initiation; membrane expansion, recruitment, and enclosure; autophagosome and lysosome fusion; and lysosomal degradation. Although the precise pathogenic mechanism varies for different genes and proteins, the dysregulation of autophagic flux is a key mechanism on which multiple pathogenic processes converge.
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Affiliation(s)
- Huiyi Chen
- Guangdong Key Laboratory of Age-Related Cardiac and Cerebral Diseases, Affiliated Hospital of Guangdong Medical University, Zhanjiang, China
- Yuebei People's Hospital, Affiliated Hospital of Shantou University Medical College, Shaoguan, China
| | - Feng Chen
- Guangdong Key Laboratory of Age-Related Cardiac and Cerebral Diseases, Affiliated Hospital of Guangdong Medical University, Zhanjiang, China
| | - Miaoping Zhang
- Guangdong Key Laboratory of Age-Related Cardiac and Cerebral Diseases, Affiliated Hospital of Guangdong Medical University, Zhanjiang, China
| | - Yanting Chen
- Guangdong Key Laboratory of Age-Related Cardiac and Cerebral Diseases, Affiliated Hospital of Guangdong Medical University, Zhanjiang, China
| | - Lili Cui
- Guangdong Key Laboratory of Age-Related Cardiac and Cerebral Diseases, Affiliated Hospital of Guangdong Medical University, Zhanjiang, China
| | - Chunmei Liang
- Guangdong Key Laboratory of Age-Related Cardiac and Cerebral Diseases, Affiliated Hospital of Guangdong Medical University, Zhanjiang, China
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Ibach M, Mathews M, Linnartz-Gerlach B, Theil S, Kumar S, Feederle R, Brüstle O, Neumann H, Walter J. A reporter cell system for the triggering receptor expressed on myeloid cells 2 reveals differential effects of disease-associated variants on receptor signaling and activation by antibodies against the stalk region. Glia 2020; 69:1126-1139. [PMID: 33314333 DOI: 10.1002/glia.23953] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 12/01/2020] [Accepted: 12/02/2020] [Indexed: 12/31/2022]
Abstract
The triggering receptor expressed on myeloid cells 2 (TREM2) is an immune receptor expressed on myeloid-derived cell types. The extracellular immunoglobulin-like domain of TREM2 binds anionic ligands including Apolipoprotein E and Amyloid-β. The transmembrane domain interacts with its adaptor protein DAP12/TYROBP that is responsible for propagation of downstream signaling upon ligand interaction. Several sequence variants of TREM2 have been linked to different neurodegenerative diseases including Alzheimer's disease. Here, we generated HEK 293 Flp-In cell lines stably expressing human TREM2 and DAP12 using a bicistronic construct with a T2A linker sequence allowing initial expression of both proteins in stoichiometric amounts. Cell biological and biochemical analyses revealed transport of TREM2 to the cell surface, and canonical sequential proteolytic processing and shedding of TREM2 (sTREM2). The functionality of this cell system was demonstrated by detection of phosphorylated spleen tyrosine kinase (SYK) upon stimulation of TREM2 with the anionic membrane lipid phosphatidylserine or anti-TREM2 antibodies. Using this cell model, we demonstrated impaired signaling of disease associated TREM2 variants. We also identified a monoclonal antibody against the stalk region of TREM2 with agonistic activity. Activation of TREM2-DAP12 signaling with the monoclonal antibody and the partial loss of function of disease associated variants were recapitulated in induced pluripotent stem cell derived microglia. Thus, this reporter cell model represents a suitable experimental system to investigate signaling of TREM2 variants, and for the identification of ligands and compounds that modulate TREM2-DAP12 signaling. MAIN POINTS: Disease associated variants impair the signaling activity of TREM2 by distinct mechanisms. Targeting the stalk region of TREM2 with bivalent antibodies activates TREM2 signaling.
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Affiliation(s)
- Melanie Ibach
- Department of Neurology, University of Bonn, Bonn, Germany
| | | | - Bettina Linnartz-Gerlach
- Neural Regeneration, Institute of Reconstructive Neurobiology, University of Bonn Medical Faculty & University Hospital Bonn, Bonn, Germany
| | - Sandra Theil
- Department of Neurology, University of Bonn, Bonn, Germany
| | - Sathish Kumar
- Department of Neurology, University of Bonn, Bonn, Germany
| | - Regina Feederle
- Institute for Diabetes and Obesity, Monoclonal Antibody Core Facility, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany.,Core Facility Monoclonal Antibodies, German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
| | - Oliver Brüstle
- Life and Brain GmbH, Bonn, Germany.,Institute of Reconstructive Neurobiology, University of Bonn Medical Faculty & University Hospital Bonn, Bonn, Germany
| | - Harald Neumann
- Neural Regeneration, Institute of Reconstructive Neurobiology, University of Bonn Medical Faculty & University Hospital Bonn, Bonn, Germany
| | - Jochen Walter
- Department of Neurology, University of Bonn, Bonn, Germany
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Manich G, Gómez-López AR, Almolda B, Villacampa N, Recasens M, Shrivastava K, González B, Castellano B. Differential Roles of TREM2+ Microglia in Anterograde and Retrograde Axonal Injury Models. Front Cell Neurosci 2020; 14:567404. [PMID: 33328887 PMCID: PMC7715005 DOI: 10.3389/fncel.2020.567404] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 10/14/2020] [Indexed: 11/13/2022] Open
Abstract
Microglia are the main immune cells of the central nervous system (CNS), and they are devoted to the active surveillance of the CNS during homeostasis and disease. In the last years, the microglial receptor Triggering Receptor Expressed on Myeloid cells-2 (TREM2) has been defined to mediate several microglial functions, including phagocytosis, survival, proliferation, and migration, and to be a key regulator of a new common microglial signature induced under neurodegenerative conditions and aging, also known as disease-associated microglia (DAM). Although microglial TREM2 has been mainly studied in chronic neurodegenerative diseases, few studies address its regulation and functions in acute inflammatory injuries. In this context, the present work aims to study the regulation of TREM2 and its functions after reparative axonal injuries, using two-well established animal models of anterograde and retrograde neuronal degeneration: the perforant pathway transection (PPT) and the facial nerve axotomy (FNA). Our results indicate the appearance of a subpopulation of microglia expressing TREM2 after both anterograde and retrograde axonal injury. TREM2+ microglia were not directly related to proliferation, instead, they were associated with specific recognition and/or phagocytosis of myelin and degenerating neurons, as assessed by immunohistochemistry and flow cytometry. Characterization of TREM2+ microglia showed expression of CD16/32, CD68, and occasional Galectin-3. However, specific singularities within each model were observed in P2RY12 expression, which was only downregulated after PPT, and in ApoE, where de novo expression was detected only in TREM2+ microglia after FNA. Finally, we report that the pro-inflammatory or anti-inflammatory cytokine microenvironment, which may affect phagocytosis, did not directly modify the induction of TREM2+ subpopulation in any injury model, although it changed TREM2 levels due to modification of the microglial activation pattern. In conclusion, we describe a unique TREM2+ microglial subpopulation induced after axonal injury, which is directly associated with phagocytosis of specific cell remnants and show different phenotypes, depending on the microglial activation status and the degree of tissue injury.
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Affiliation(s)
- Gemma Manich
- Department of Cell Biology, Physiology, and Immunology, Institute of Neuroscience, Universitat Autònoma De Barcelona, Barcelona, Spain
| | - Ariadna Regina Gómez-López
- Department of Cell Biology, Physiology, and Immunology, Institute of Neuroscience, Universitat Autònoma De Barcelona, Barcelona, Spain
| | - Beatriz Almolda
- Department of Cell Biology, Physiology, and Immunology, Institute of Neuroscience, Universitat Autònoma De Barcelona, Barcelona, Spain
| | - Nàdia Villacampa
- Department of Cell Biology, Physiology, and Immunology, Institute of Neuroscience, Universitat Autònoma De Barcelona, Barcelona, Spain
| | - Mireia Recasens
- Department of Cell Biology, Physiology, and Immunology, Institute of Neuroscience, Universitat Autònoma De Barcelona, Barcelona, Spain
| | - Kalpana Shrivastava
- Department of Cell Biology, Physiology, and Immunology, Institute of Neuroscience, Universitat Autònoma De Barcelona, Barcelona, Spain
| | - Berta González
- Department of Cell Biology, Physiology, and Immunology, Institute of Neuroscience, Universitat Autònoma De Barcelona, Barcelona, Spain
| | - Bernardo Castellano
- Department of Cell Biology, Physiology, and Immunology, Institute of Neuroscience, Universitat Autònoma De Barcelona, Barcelona, Spain
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Deming Y, Li Z, Benitez BA, Cruchaga C. Triggering receptor expressed on myeloid cells 2 (TREM2): a potential therapeutic target for Alzheimer disease? Expert Opin Ther Targets 2018; 22:587-598. [PMID: 29889572 DOI: 10.1080/14728222.2018.1486823] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Abstract
INTRODUCTION There are currently no effective therapeutics for Alzheimer disease (AD). Clinical trials targeting amyloid beta thus far have shown very little benefit and only in the earliest stages of disease. These limitations have driven research to identify alternative therapeutic targets, one of the most promising is the triggering receptor expressed on myeloid cells 2 (TREM2). Areas covered: Here, we review the literature to-date and discuss the potentials and pitfalls for targeting TREM2 as a potential therapeutic for AD. We focus on research in animal and cell models for AD and central nervous system injury models which may help in understanding the role of TREM2 in disease. Expert opinion: Studies suggest TREM2 plays a key role in AD pathology; however, results have been conflicting about whether TREM2 is beneficial or harmful. More research is necessary before designing TREM2-targeting therapies. Successful therapeutics will most likely be administered early in disease.
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Affiliation(s)
- Yuetiva Deming
- a Department of Psychiatry , Washington University School of Medicine , St Louis , MO , USA
| | - Zeran Li
- a Department of Psychiatry , Washington University School of Medicine , St Louis , MO , USA
| | - Bruno A Benitez
- b Department of Medicine , Washington University School of Medicine , St Louis , MO , USA
| | - Carlos Cruchaga
- a Department of Psychiatry , Washington University School of Medicine , St Louis , MO , USA.,c Department of Developmental Biology , Washington University School of Medicine , St Louis , MO , USA.,d Knight Alzheimer's Disease Research Center , Washington University School of Medicine , St Louis , MO , USA.,e Hope Center for Neurological Disorders , Washington University School of Medicine , St Louis , MO , USA
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Raha AA, Henderson JW, Stott SRW, Vuono R, Foscarin S, Friedland RP, Zaman SH, Raha-Chowdhury R. Neuroprotective Effect of TREM-2 in Aging and Alzheimer's Disease Model. J Alzheimers Dis 2018; 55:199-217. [PMID: 27662313 DOI: 10.3233/jad-160663] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Neuroinflammation and activation of innate immunity are early events in neurodegenerative diseases including Alzheimer's disease (AD). Recently, a rare mutation in the gene Triggering receptor expressed on myeloid cells 2 (TREM2) has been associated with a substantial increase in the risk of developing late onset AD. To uncover the molecular mechanisms underlying this association, we investigated the RNA and protein expression of TREM2 in APP/PS1 transgenic mice. Our findings suggest that TREM2 not only plays a critical role in inflammation, but is also involved in neuronal cell survival and in neurogenesis. We have shown that TREM2 is a soluble protein transported by macrophages through ventricle walls and choroid plexus, and then enters the brain parenchyma via radial glial cells. TREM2 protein is essential for neuroplasticity and myelination. During the late stages of life, a lack of TREM2 protein may accelerate aging processes and neuronal cell loss and reduce microglial activity, ultimately leading to neuroinflammation. As inflammation plays a major role in neurodegenerative diseases, a lack of TREM2 could be a missing link between immunomodulation and neuroprotection.
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Affiliation(s)
- Animesh Alexander Raha
- John Van Geest Centre for Brain Repair, Department of Clinical Neuroscience, University of Cambridge, Cambridge, UK
| | - James W Henderson
- John Van Geest Centre for Brain Repair, Department of Clinical Neuroscience, University of Cambridge, Cambridge, UK
| | - Simon R W Stott
- John Van Geest Centre for Brain Repair, Department of Clinical Neuroscience, University of Cambridge, Cambridge, UK
| | - Romina Vuono
- John Van Geest Centre for Brain Repair, Department of Clinical Neuroscience, University of Cambridge, Cambridge, UK
| | - Simona Foscarin
- John Van Geest Centre for Brain Repair, Department of Clinical Neuroscience, University of Cambridge, Cambridge, UK
| | | | - Shahid H Zaman
- Cambridge Intellectual & Developmental Disabilities Research Group, Department of Psychiatry, University of Cambridge, Cambridge, UK
| | - Ruma Raha-Chowdhury
- John Van Geest Centre for Brain Repair, Department of Clinical Neuroscience, University of Cambridge, Cambridge, UK
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Jay TR, von Saucken VE, Landreth GE. TREM2 in Neurodegenerative Diseases. Mol Neurodegener 2017; 12:56. [PMID: 28768545 PMCID: PMC5541421 DOI: 10.1186/s13024-017-0197-5] [Citation(s) in RCA: 252] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 07/20/2017] [Indexed: 12/12/2022] Open
Abstract
TREM2 variants have been identified as risk factors for Alzheimer's disease (AD) and other neurodegenerative diseases (NDDs). Because TREM2 encodes a receptor exclusively expressed on immune cells, identification of these variants conclusively demonstrates that the immune response can play an active role in the pathogenesis of NDDs. These TREM2 variants also confer the highest risk for developing Alzheimer's disease of any risk factor identified in nearly two decades, suggesting that understanding more about TREM2 function could provide key insights into NDD pathology and provide avenues for novel immune-related NDD biomarkers and therapeutics. The expression, signaling and function of TREM2 in NDDs have been extensively investigated in an effort to understand the role of immune function in disease pathogenesis and progression. We provide a comprehensive review of our current understanding of TREM2 biology, including new insights into the regulation of TREM2 expression, and TREM2 signaling and function across NDDs. While many open questions remain, the current body of literature provides clarity on several issues. While it is still often cited that TREM2 expression is decreased by pro-inflammatory stimuli, it is now clear that this is true in vitro, but inflammatory stimuli in vivo almost universally increase TREM2 expression. Likewise, while TREM2 function is classically described as promoting an anti-inflammatory phenotype, more than half of published studies demonstrate a pro-inflammatory role for TREM2, suggesting that its role in inflammation is much more complex. Finally, these components of TREM2 biology are applied to a discussion of how TREM2 impacts NDD pathologies and the latest assessment of how these findings might be applied to immune-directed clinical biomarkers and therapeutics.
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Affiliation(s)
- Taylor R. Jay
- Department of Neurosciences, Case Western Reserve University, School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106 USA
| | - Victoria E. von Saucken
- Department of Neurosciences, Case Western Reserve University, School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106 USA
- Stark Neurosciences Research Institute, Indiana University School of Medicine, 320 W 15th Street, Indianapolis, IN 46202 USA
| | - Gary E. Landreth
- Department of Neurosciences, Case Western Reserve University, School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106 USA
- Stark Neurosciences Research Institute, Indiana University School of Medicine, 320 W 15th Street, Indianapolis, IN 46202 USA
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Yeh FL, Hansen DV, Sheng M. TREM2, Microglia, and Neurodegenerative Diseases. Trends Mol Med 2017; 23:512-533. [DOI: 10.1016/j.molmed.2017.03.008] [Citation(s) in RCA: 180] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2016] [Revised: 02/15/2017] [Accepted: 03/26/2017] [Indexed: 01/17/2023]
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11
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Jendresen C, Årskog V, Daws MR, Nilsson LNG. The Alzheimer's disease risk factors apolipoprotein E and TREM2 are linked in a receptor signaling pathway. J Neuroinflammation 2017; 14:59. [PMID: 28320424 PMCID: PMC5360024 DOI: 10.1186/s12974-017-0835-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 03/07/2017] [Indexed: 11/19/2022] Open
Abstract
Background Triggering receptor expressed on myeloid cells 2 (TREM2) and apolipoprotein E (APOE) are genetically linked to Alzheimer’s disease. Here, we investigated whether human ApoE mediates signal transduction through human and murine TREM2 and sought to identify a TREM2-binding domain in human ApoE. Methods To investigate cell signaling through TREM2, a cell line was used which expressed an NFAT-inducible β-galactosidase reporter and human or murine TREM2, fused to CD8 transmembrane and CD3ζ intracellular signaling domains. ELISA-based binding assays were used to determine binding affinities of human ApoE isoforms to human TREM2 and to identify a TREM2-binding domain in ApoE. Results ApoE was found to be an agonist to human TREM2 with EC50 in the low nM range, and to murine TREM2 with reduced potency. In the reporter cells, TREM2 expression was lower than in nontransgenic mouse brain. Human ApoE isoforms ε2, ε3, and ε4 bound to human TREM2 with Kd in the low nM range. The binding was displaced by an ApoE-mimetic peptide (amino acids 130–149). Conclusions An ApoE-mediated dose-dependent signal transduction through TREM2 in reporter cells was demonstrated, and a TREM2-binding region in ApoE was identified. The relevance of an ApoE-TREM2 receptor signaling pathway to Alzheimer’s disease is discussed. Electronic supplementary material The online version of this article (doi:10.1186/s12974-017-0835-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Charlotte Jendresen
- Department of Pharmacology, Institute of Clinical Medicine, University of Oslo and Oslo University Hospital, Postboks 1057 Blindern, 0316, Oslo, Norway
| | - Vibeke Årskog
- Department of Pharmacology, Institute of Clinical Medicine, University of Oslo and Oslo University Hospital, Postboks 1057 Blindern, 0316, Oslo, Norway
| | - Michael R Daws
- Division of Anatomy, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Lars N G Nilsson
- Department of Pharmacology, Institute of Clinical Medicine, University of Oslo and Oslo University Hospital, Postboks 1057 Blindern, 0316, Oslo, Norway.
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12
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Owens R, Grabert K, Davies CL, Alfieri A, Antel JP, Healy LM, McColl BW. Divergent Neuroinflammatory Regulation of Microglial TREM Expression and Involvement of NF-κB. Front Cell Neurosci 2017; 11:56. [PMID: 28303091 PMCID: PMC5332401 DOI: 10.3389/fncel.2017.00056] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Accepted: 02/15/2017] [Indexed: 12/28/2022] Open
Abstract
The triggering receptor expressed on myeloid cells (TREM) family of proteins are cell surface receptors with important roles in regulation of myeloid cell inflammatory activity. In the central nervous system, TREM2 is implicated in further roles in microglial homeostasis, neuroinflammation and neurodegeneration. Different TREM receptors appear to have contrasting roles in controlling myeloid immune activity therefore the relative and co-ordinated regulation of their expression is important to understand but is currently poorly understood. We sought to determine how microglial TREM expression is affected under neuroinflammatory conditions in vitro and in vivo. Our data show that microglial Trem1 and Trem2 gene expression are regulated in an opposing manner by lipopolysaccharide (LPS) in vitro in both adult murine and human microglia. LPS caused a significant induction of Trem1 and a contrasting suppression of Trem2 expression. We also observed similar divergent Trem1 and Trem2 responses in vivo in response to acute brain inflammation and acute cerebral ischaemia. Our data show that inhibition of NF-κB activation prevents the LPS-induced alterations in both Trem1 and Trem2 expression in vitro indicating NF-κB as a common signaling intermediate controlling these divergent responses. Distinct patterns of microglial Trem1 induction and Trem2 suppression to different Toll-like receptor (TLR) ligands were also evident, notably with Trem1 induction restricted to those ligands activating TLRs signaling via TRIF. Our data show co-ordinated but divergent regulation of microglial TREM receptor expression with a central role for NF-κB. Neuroinflammatory conditions that alter the balance in TREM expression could therefore be an important influence on microglial inflammatory and homeostatic activity with implications for neuroinflammatory and neurodegenerative disease.
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Affiliation(s)
- Rosie Owens
- The Royal (Dick) School of Veterinary Studies, University of Edinburgh Midlothian, UK
| | - Kathleen Grabert
- The Royal (Dick) School of Veterinary Studies, University of Edinburgh Midlothian, UK
| | - Claire L Davies
- The Royal (Dick) School of Veterinary Studies, University of Edinburgh Midlothian, UK
| | - Alessio Alfieri
- The Royal (Dick) School of Veterinary Studies, University of Edinburgh Midlothian, UK
| | - Jack P Antel
- Neuroimmunology Unit, Montreal Neurological Institute, McGill University Montreal, QC, Canada
| | - Luke M Healy
- Neuroimmunology Unit, Montreal Neurological Institute, McGill University Montreal, QC, Canada
| | - Barry W McColl
- The Royal (Dick) School of Veterinary Studies, University of Edinburgh Midlothian, UK
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13
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Yin J, Liu X, He Q, Zhou L, Yuan Z, Zhao S. Vps35-dependent recycling of Trem2 regulates microglial function. Traffic 2016; 17:1286-1296. [PMID: 27717139 DOI: 10.1111/tra.12451] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Revised: 09/21/2016] [Accepted: 09/21/2016] [Indexed: 01/03/2023]
Abstract
Triggering receptor expressed on myeloid cells 2 (Trem2), an immune-modulatory receptor, is preferentially expressed in microglia of central nervous system. Trem2 might be involved in the development of Alzheimer's disease (AD) through regulating the inflammatory responses and phagocytosis of microglia. However, the intracellular trafficking of Trem2 remains unclear. In this study, we showed that Trem2 in the plasma membrane underwent endocytosis and recycling. Trem2 is internalized in a clathrin-dependent manner and then recycled back to the plasma membrane through vacuolar protein sorting 35 (Vps35), the key component of cargo recognition core of retromer complex, but not Rab11. When Vps35 is knocked down, Trem2 accumulated in the lysosomes but was not degraded. More importantly, Vps35 deficiency leads to excessive lipopolysaccharide (LPS)-induced inducible nitric oxide synthase (iNOS) expression and IL-6 production, which can be abolished by Trem2 overexpression. Furthermore, R47H Trem2, an AD-associated mutant, failed to interact with Vps35 and became unstable compared with wild-type Trem2. Our study suggests that Vps35/retromer is responsible for recycling of Trem2 in the regulation of microglial function such as proinflammatory responses, whereas R47H mutation impairs Trem2 trafficking, which might contribute to AD.
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Affiliation(s)
- Jie Yin
- State Key Laboratory of Brain and Cognitive Sciences, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,Sino-Danish College, University of Chinese Academy of Sciences, Beijing, China
| | - Xiaocui Liu
- Qingdao Mental Health Center, Qingdao, China
| | - Qing He
- State Key Laboratory of Brain and Cognitive Sciences, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,Sino-Danish College, University of Chinese Academy of Sciences, Beijing, China
| | - Lujun Zhou
- State Key Laboratory of Brain and Cognitive Sciences, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,Sino-Danish College, University of Chinese Academy of Sciences, Beijing, China
| | - Zengqiang Yuan
- State Key Laboratory of Brain and Cognitive Sciences, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.,Center of Alzheimer's Disease, Beijing Institute for Brain Disorders, Beijing, China
| | - Siqi Zhao
- State Key Laboratory of Brain and Cognitive Sciences, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
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14
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Smith AR, Smith RG, Condliffe D, Hannon E, Schalkwyk L, Mill J, Lunnon K. Increased DNA methylation near TREM2 is consistently seen in the superior temporal gyrus in Alzheimer's disease brain. Neurobiol Aging 2016; 47:35-40. [PMID: 27522519 DOI: 10.1016/j.neurobiolaging.2016.07.008] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 06/16/2016] [Accepted: 07/07/2016] [Indexed: 11/24/2022]
Abstract
Although mutations within the TREM2 gene have been robustly associated with Alzheimer's disease, it is not known whether alterations in the regulation of this gene are also involved in pathogenesis. Here, we present data demonstrating increased DNA methylation in the superior temporal gyrus in Alzheimer's disease brain at a CpG site located 289 bp upstream of the transcription start site of the TREM2 gene in 3 independent study cohorts using 2 different technologies (Illumina Infinium 450K methylation beadchip and pyrosequencing). A meta-analysis across all 3 cohorts reveals consistent AD-associated hypermethylation (p = 3.47E-08). This study highlights that extending genetic studies of TREM2 in AD to investigate epigenetic changes may nominate additional mechanisms by which disruption to this gene increases risk.
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Affiliation(s)
- Adam R Smith
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, RILD, University of Exeter, Devon, UK
| | - Rebecca G Smith
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, RILD, University of Exeter, Devon, UK
| | - Daniel Condliffe
- School of Biological and Chemical Sciences, Queen Mary University of London, London, UK
| | - Eilis Hannon
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, RILD, University of Exeter, Devon, UK
| | - Leonard Schalkwyk
- School of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, UK
| | - Jonathan Mill
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, RILD, University of Exeter, Devon, UK; Social, Genetic and Developmental Psychiatry (SGDP) Centre, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - Katie Lunnon
- Institute of Biomedical and Clinical Science, University of Exeter Medical School, RILD, University of Exeter, Devon, UK.
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15
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Li C, Shah SZA, Zhao D, Yang L. Role of the Retromer Complex in Neurodegenerative Diseases. Front Aging Neurosci 2016; 8:42. [PMID: 26973516 PMCID: PMC4772447 DOI: 10.3389/fnagi.2016.00042] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Accepted: 02/15/2016] [Indexed: 11/13/2022] Open
Abstract
The retromer complex is a protein complex that plays a central role in endosomal trafficking. Retromer dysfunction has been linked to a growing number of neurological disorders. The process of intracellular trafficking and recycling is crucial for maintaining normal intracellular homeostasis, which is partly achieved through the activity of the retromer complex. The retromer complex plays a primary role in sorting endosomal cargo back to the cell surface for reuse, to the trans-Golgi network (TGN), or alternatively to specialized endomembrane compartments, in which the cargo is not subjected to lysosomal-mediated degradation. In most cases, the retromer acts as a core that interacts with associated proteins, including sorting nexin family member 27 (SNX27), members of the vacuolar protein sorting 10 (VPS10) receptor family, the major endosomal actin polymerization-promoting complex known as Wiskott-Aldrich syndrome protein and scar homolog (WASH), and other proteins. Some of the molecules carried by the retromer complex are risk factors for neurodegenerative diseases. Defects such as haplo-insufficiency or mutations in one or several units of the retromer complex lead to various pathologies. Here, we summarize the molecular architecture of the retromer complex and the roles of this system in intracellular trafficking related the pathogenesis of neurodegenerative diseases.
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Affiliation(s)
- Chaosi Li
- National Animal Transmissible Spongiform Encephalopathy Laboratory, Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University Beijing, China
| | - Syed Zahid Ali Shah
- National Animal Transmissible Spongiform Encephalopathy Laboratory, Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University Beijing, China
| | - Deming Zhao
- National Animal Transmissible Spongiform Encephalopathy Laboratory, Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University Beijing, China
| | - Lifeng Yang
- National Animal Transmissible Spongiform Encephalopathy Laboratory, Key Laboratory of Animal Epidemiology and Zoonosis of Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University Beijing, China
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16
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Thomas KA, King RG, Sestero CM, Justement LB. TREM-like transcript 2 is stored in human neutrophil primary granules and is up-regulated in response to inflammatory mediators. J Leukoc Biol 2016; 100:177-84. [PMID: 26753760 DOI: 10.1189/jlb.3ab1115-507r] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2015] [Accepted: 12/28/2015] [Indexed: 12/12/2022] Open
Abstract
The triggering receptor expressed on myeloid cell locus encodes a family of receptors that is emerging as an important class of molecules involved in modulating the innate immune response and inflammation. Of the 4 conserved members, including triggering receptor expressed on myeloid cells 1 and 2 and triggering receptor expressed on myeloid cell-like transcripts 1 and 2, relatively little is known about triggering receptor expressed on myeloid cell-like transcript 2 expression and function, particularly in humans. In this study, experiments were performed to determine if triggering receptor expressed on myeloid cell-like transcript 2 expression is conserved between mouse and human, demonstrating that human triggering receptor expressed on myeloid cell-like transcript 2 is expressed on cells of the lymphoid, as well as myeloid/granuloid lineages, similar to murine triggering receptor expressed on myeloid cell-like transcript 2. Consistent with studies in the mouse, triggering receptor expressed on myeloid cell-like transcript 2 expression is up-regulated in response to inflammatory mediators on human neutrophils. Importantly, it was shown that triggering receptor expressed on myeloid cell-like transcript 2, in resting human neutrophils, is predominantly localized to intracellular vesicles, including secretory vesicles and primary granules; with the majority of triggering receptor expressed on myeloid cell-like transcript 2 stored in primary granules. In contrast to other primary granule proteins, triggering receptor expressed on myeloid cell-like transcript 2 is not expelled on neutrophil extracellular traps but is retained in the plasma membrane following primary granule exocytosis. In summary, these findings establish that triggering receptor expressed on myeloid cell-like transcript 2 expression is conserved between species and is likely to be important in regulating neutrophil antimicrobial function following primary granule exocytosis.
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Affiliation(s)
- Kimberly A Thomas
- Department of Pathology and Laboratory Medicine, University of California, Los Angeles, California, USA
| | - R Glenn King
- Department of Microbiology, University of Alabama at Birmingham, Alabama, USA; and
| | | | - Louis B Justement
- Department of Microbiology, University of Alabama at Birmingham, Alabama, USA; and
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17
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Walter J. The Triggering Receptor Expressed on Myeloid Cells 2: A Molecular Link of Neuroinflammation and Neurodegenerative Diseases. J Biol Chem 2015; 291:4334-41. [PMID: 26694609 DOI: 10.1074/jbc.r115.704981] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The triggering receptor expressed on myeloid cells (TREM) 2 is a member of the immunoglobulin superfamily of receptors and mediates signaling in immune cells via engagement of its co-receptor DNAX-activating protein of 12 kDa (DAP12). Homozygous mutations in TREM2 or DAP12 cause Nasu-Hakola disease, which is characterized by bone abnormalities and dementia. Recently, a variant of TREM2 has also been associated with an increased risk for Alzheimer disease. The selective expression of TREM2 on immune cells and its association with different forms of dementia indicate a contribution of this receptor in common pathways of neurodegeneration.
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Affiliation(s)
- Jochen Walter
- From the Department of Neurology, University of Bonn, 53127 Bonn, Germany
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18
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Aredo B, Li T, Chen X, Zhang K, Wang CXZ, Gou D, Zhao B, He Y, Ufret-Vincenty RL. A chimeric Cfh transgene leads to increased retinal oxidative stress, inflammation, and accumulation of activated subretinal microglia in mice. Invest Ophthalmol Vis Sci 2015; 56:3427-40. [PMID: 26030099 DOI: 10.1167/iovs.14-16089] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
PURPOSE Variants of complement factor H (Cfh) affecting short consensus repeats (SCRs) 6 to 8 increase the risk of age-related macular degeneration. Our aim was to explore the effect of expressing a Cfh variant on the in vivo susceptibility of the retina and RPE to oxidative stress and inflammation, using chimeric Cfh transgenic mice (chCfhTg). METHODS The chCfhTg and age-matched C57BL/6J (B6) mice were subjected to oxidative stress by either normal aging, or by exposure to a combination of oral hydroquinone (0.8% HQ) and increased light. Eyes were collected for immunohistochemistry of RPE-choroid flat mounts and of retinal sections, ELISA, electron microscopy, and RPE/microglia gene expression analysis. RESULTS Aging mice to 2 years led to an increased accumulation of basal laminar deposits, subretinal microglia/macrophages (MG/MΦ) staining for CD16 and for malondialdehyde (MDA), and MDA-modified proteins in the retina in chCfhTg compared to B6 mice. The chCfhTg mice maintained on HQ diet and increased light showed greater deposition of basal laminar deposits, more accumulation of fundus spots suggestive of MG/MΦ, and increased deposition of C3d in the sub-RPE space, compared to controls. In addition, chCfhTg mice demonstrated upregulation of NLRP3, IP-10, CD68, and TREM-2 in the RNA isolates from RPE/MG/MΦ. CONCLUSIONS Expression of a Cfh transgene introducing a variant in SCRs 6 to 8 was sufficient to lead to increased retinal/RPE susceptibility to oxidative stress, a proinflammatory MG/MΦ phenotype, and a proinflammatory RPE/MG/MΦ gene expression profile in a transgenic mouse model. Our data suggest that altered interactions of Cfh with MDA-modified proteins may be relevant in explaining the effects of the Cfh variant.
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Affiliation(s)
- Bogale Aredo
- Department of Ophthalmology UT Southwestern Medical Center, Dallas, Texas, United States
| | - Tao Li
- Department of Ophthalmology UT Southwestern Medical Center, Dallas, Texas, United States 2Department of Ophthalmology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People's Republic of China
| | - Xiao Chen
- Department of Ophthalmology UT Southwestern Medical Center, Dallas, Texas, United States
| | - Kaiyan Zhang
- Department of Ophthalmology UT Southwestern Medical Center, Dallas, Texas, United States
| | - Cynthia Xin-Zhao Wang
- Department of Ophthalmology UT Southwestern Medical Center, Dallas, Texas, United States
| | - Darlene Gou
- Department of Ophthalmology UT Southwestern Medical Center, Dallas, Texas, United States
| | - Biren Zhao
- Department of Ophthalmology UT Southwestern Medical Center, Dallas, Texas, United States
| | - Yuguang He
- Department of Ophthalmology UT Southwestern Medical Center, Dallas, Texas, United States
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19
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Zhong L, Chen XF, Zhang ZL, Wang Z, Shi XZ, Xu K, Zhang YW, Xu H, Bu G. DAP12 Stabilizes the C-terminal Fragment of the Triggering Receptor Expressed on Myeloid Cells-2 (TREM2) and Protects against LPS-induced Pro-inflammatory Response. J Biol Chem 2015; 290:15866-15877. [PMID: 25957402 DOI: 10.1074/jbc.m115.645986] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2015] [Indexed: 11/06/2022] Open
Abstract
Triggering receptor expressed on myeloid cells 2 (TREM2) is a DAP12-associated receptor expressed in microglia, macrophages, and other myeloid-derived cells. Previous studies have suggested that TREM2/DAP12 signaling pathway reduces inflammatory responses and promotes phagocytosis of apoptotic neurons. Recently, TREM2 has been identified as a risk gene for Alzheimer disease (AD). Here, we show that DAP12 stabilizes the C-terminal fragment of TREM2 (TREM2-CTF), a substrate for γ-secretase. Co-expression of DAP12 with TREM2 selectively increased the level of TREM2-CTF with little effects on that of full-length TREM2. The interaction between DAP12 and TREM2 is essential for TREM2-CTF stabilization as a mutant form of DAP12 with disrupted interaction with TREM2 failed to exhibit such an effect. Silencing of either Trem2 or Dap12 gene significantly exacerbated pro-inflammatory responses induced by lipopolysaccharides (LPS). Importantly, overexpression of either full-length TREM2 or TREM2-CTF reduced LPS-induced inflammatory responses. Taken together, our results support a role of DAP12 in stabilizing TREM2-CTF, thereby protecting against excessive pro-inflammatory responses.
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Affiliation(s)
- Li Zhong
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Medical College, Xiamen University, Xiamen 361102, PR China
| | - Xiao-Fen Chen
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Medical College, Xiamen University, Xiamen 361102, PR China.
| | - Zhen-Lian Zhang
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Medical College, Xiamen University, Xiamen 361102, PR China
| | - Zhe Wang
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Medical College, Xiamen University, Xiamen 361102, PR China
| | - Xin-Zhen Shi
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Medical College, Xiamen University, Xiamen 361102, PR China
| | - Kai Xu
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Medical College, Xiamen University, Xiamen 361102, PR China
| | - Yun-Wu Zhang
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Medical College, Xiamen University, Xiamen 361102, PR China
| | - Huaxi Xu
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Medical College, Xiamen University, Xiamen 361102, PR China; Degenerative Disease Research Program, Center for Neuroscience, Aging, and Stem Cell Research, Sanford-Burnham Medical Research Institute, La Jolla, California 92037
| | - Guojun Bu
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Medical College, Xiamen University, Xiamen 361102, PR China; Department of Neuroscience, Mayo Clinic, Jacksonville, Florida 32224.
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20
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Xing J, Titus AR, Humphrey MB. The TREM2-DAP12 signaling pathway in Nasu-Hakola disease: a molecular genetics perspective. ACTA ACUST UNITED AC 2015; 5:89-100. [PMID: 26478868 PMCID: PMC4605443 DOI: 10.2147/rrbc.s58057] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Nasu–Hakola disease or polycystic lipomembranous osteodysplasia with sclerosing leukoencephalopathy (PLOSL) is a rare recessively inherited disease that is associated with early dementia and bone cysts with fractures. Here, we review the genetic causes of PLOSL with loss-of-function mutations or deletions in one of two genes, TYROBP and TREM2, encoding for two proteins DNAX-activating protein 12 (DAP12) and triggering receptor expressed on myeloid cells-2 (TREM2). TREM2 and DAP12 form an immunoreceptor signaling complex that mediates myeloid cell, including microglia and osteoclasts, development, activation, and function. Functionally, TREM2-DAP12 mediates osteoclast multi-nucleation, migration, and resorption. In microglia, TREM2-DAP12 participates in recognition and apoptosis of neuronal debris and amyloid deposits. Review of the complex immunoregulatory roles of TREM2-DAP12 in the innate immune system, where it can both promote and inhibit pro-inflammatory responses, is given. Little is known about the function of TREM2-DAP12 in normal brain homeostasis or in pathological central nervous system diseases. Based on the state of the field, genetic testing now aids in diagnosis of PLOSL, but therapeutics and interventions are still under development.
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Affiliation(s)
- Junjie Xing
- Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA ; Department of Microbiology and immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Amanda R Titus
- Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Mary Beth Humphrey
- Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA ; Department of Microbiology and immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA ; Department of veteran's Affairs, Oklahoma City, OK, USA
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21
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Kleinberger G, Yamanishi Y, Suárez-Calvet M, Czirr E, Lohmann E, Cuyvers E, Struyfs H, Pettkus N, Wenninger-Weinzierl A, Mazaheri F, Tahirovic S, Lleó A, Alcolea D, Fortea J, Willem M, Lammich S, Molinuevo JL, Sánchez-Valle R, Antonell A, Ramirez A, Heneka MT, Sleegers K, van der Zee J, Martin JJ, Engelborghs S, Demirtas-Tatlidede A, Zetterberg H, Van Broeckhoven C, Gurvit H, Wyss-Coray T, Hardy J, Colonna M, Haass C. TREM2 mutations implicated in neurodegeneration impair cell surface transport and phagocytosis. Sci Transl Med 2015; 6:243ra86. [PMID: 24990881 DOI: 10.1126/scitranslmed.3009093] [Citation(s) in RCA: 528] [Impact Index Per Article: 58.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Genetic variants in the triggering receptor expressed on myeloid cells 2 (TREM2) have been linked to Nasu-Hakola disease, Alzheimer's disease (AD), Parkinson's disease, amyotrophic lateral sclerosis, frontotemporal dementia (FTD), and FTD-like syndrome without bone involvement. TREM2 is an innate immune receptor preferentially expressed by microglia and is involved in inflammation and phagocytosis. Whether and how TREM2 missense mutations affect TREM2 function is unclear. We report that missense mutations associated with FTD and FTD-like syndrome reduce TREM2 maturation, abolish shedding by ADAM proteases, and impair the phagocytic activity of TREM2-expressing cells. As a consequence of reduced shedding, TREM2 is virtually absent in the cerebrospinal fluid (CSF) and plasma of a patient with FTD-like syndrome. A decrease in soluble TREM2 was also observed in the CSF of patients with AD and FTD, further suggesting that reduced TREM2 function may contribute to increased risk for two neurodegenerative disorders.
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Affiliation(s)
- Gernot Kleinberger
- Adolf-Butenandt Institute, Biochemistry, Ludwig-Maximilians University Munich, 80336 Munich, Germany. Munich Cluster for Systems Neurology (SyNergy), 80336 Munich, Germany
| | - Yoshinori Yamanishi
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Marc Suárez-Calvet
- Adolf-Butenandt Institute, Biochemistry, Ludwig-Maximilians University Munich, 80336 Munich, Germany. Department of Neurology, Institut d'Investigacions Biomèdiques, Hospital de la Santa Creu i Sant Pau, Universitat Autònoma de Barcelona, 08025 Barcelona, Spain. Center for Networked Biomedical Research for Neurodegenerative Diseases, CIBERNED, 28031 Madrid, Spain
| | - Eva Czirr
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA. Center for Tissue Regeneration, Repair and Restoration, Veterans Administration Palo Alto Health Care System, Palo Alto, CA 94304, USA
| | - Ebba Lohmann
- Behavioral Neurology and Movement Disorders Unit, Department of Neurology, Istanbul Faculty of Medicine, Istanbul University, 34093 Istanbul, Turkey. Department of Neurodegenerative Diseases, Hertie Institute for Clinical Brain Research, University of Tübingen, 72076 Tübingen, Germany. German Center for Neurodegenerative Diseases (DZNE), Tübingen, 72076 Tübingen, Germany
| | - Elise Cuyvers
- Neurodegenerative Brain Diseases Group, Department of Molecular Genetics, VIB, 2610 Antwerp, Belgium. Laboratory of Neurogenetics, Institute Born-Bunge, University of Antwerp, 2610 Antwerp, Belgium
| | - Hanne Struyfs
- Reference Center for Biological Markers of Dementia, Laboratory of Neurochemistry and Behavior, Institute Born-Bunge, University of Antwerp, 2610 Antwerp, Belgium
| | - Nadine Pettkus
- Adolf-Butenandt Institute, Biochemistry, Ludwig-Maximilians University Munich, 80336 Munich, Germany
| | | | - Fargol Mazaheri
- German Center for Neurodegenerative Diseases (DZNE), Munich, 80336 Munich, Germany
| | - Sabina Tahirovic
- German Center for Neurodegenerative Diseases (DZNE), Munich, 80336 Munich, Germany
| | - Alberto Lleó
- Department of Neurology, Institut d'Investigacions Biomèdiques, Hospital de la Santa Creu i Sant Pau, Universitat Autònoma de Barcelona, 08025 Barcelona, Spain. Center for Networked Biomedical Research for Neurodegenerative Diseases, CIBERNED, 28031 Madrid, Spain
| | - Daniel Alcolea
- Department of Neurology, Institut d'Investigacions Biomèdiques, Hospital de la Santa Creu i Sant Pau, Universitat Autònoma de Barcelona, 08025 Barcelona, Spain. Center for Networked Biomedical Research for Neurodegenerative Diseases, CIBERNED, 28031 Madrid, Spain
| | - Juan Fortea
- Department of Neurology, Institut d'Investigacions Biomèdiques, Hospital de la Santa Creu i Sant Pau, Universitat Autònoma de Barcelona, 08025 Barcelona, Spain. Center for Networked Biomedical Research for Neurodegenerative Diseases, CIBERNED, 28031 Madrid, Spain
| | - Michael Willem
- Adolf-Butenandt Institute, Biochemistry, Ludwig-Maximilians University Munich, 80336 Munich, Germany
| | - Sven Lammich
- Adolf-Butenandt Institute, Biochemistry, Ludwig-Maximilians University Munich, 80336 Munich, Germany
| | - José L Molinuevo
- Alzheimer's Disease and Other Cognitive Disorders Unit, Neurology Service, ICN Hospital Clinic i Universitari, 08036 Barcelona, Spain
| | - Raquel Sánchez-Valle
- Alzheimer's Disease and Other Cognitive Disorders Unit, Neurology Service, ICN Hospital Clinic i Universitari, 08036 Barcelona, Spain
| | - Anna Antonell
- Alzheimer's Disease and Other Cognitive Disorders Unit, Neurology Service, ICN Hospital Clinic i Universitari, 08036 Barcelona, Spain
| | - Alfredo Ramirez
- Department of Psychiatry and Psychotherapy, University of Bonn, 53127 Bonn, Germany. Institute of Human Genetics, University of Bonn, 53127 Bonn, Germany
| | - Michael T Heneka
- Universitätsklinikum Bonn, Neurology, 53127 Bonn, Germany. German Center for Neurodegenerative Diseases (DZNE), 53127 Bonn, Germany
| | - Kristel Sleegers
- Neurodegenerative Brain Diseases Group, Department of Molecular Genetics, VIB, 2610 Antwerp, Belgium. Laboratory of Neurogenetics, Institute Born-Bunge, University of Antwerp, 2610 Antwerp, Belgium
| | - Julie van der Zee
- Neurodegenerative Brain Diseases Group, Department of Molecular Genetics, VIB, 2610 Antwerp, Belgium. Laboratory of Neurogenetics, Institute Born-Bunge, University of Antwerp, 2610 Antwerp, Belgium
| | - Jean-Jacques Martin
- Antwerp Biobank, Institute Born-Bunge, University of Antwerp, 2610 Antwerp, Belgium
| | - Sebastiaan Engelborghs
- Reference Center for Biological Markers of Dementia, Laboratory of Neurochemistry and Behavior, Institute Born-Bunge, University of Antwerp, 2610 Antwerp, Belgium. Department of Neurology and Memory Clinic, Hospital Network Antwerp (ZNA), Middelheim and Hoge Beuken, 2020 Antwerp, Belgium
| | - Asli Demirtas-Tatlidede
- Behavioral Neurology and Movement Disorders Unit, Department of Neurology, Istanbul Faculty of Medicine, Istanbul University, 34093 Istanbul, Turkey
| | - Henrik Zetterberg
- Institute of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, The Sahlgrenska Academy at the University of Gothenburg, S-431 80 Mölndal, Sweden. Reta Lila Weston Laboratories and Department of Molecular Neuroscience, UCL Institute of Neurology, London WC1N 3BG, UK
| | - Christine Van Broeckhoven
- Neurodegenerative Brain Diseases Group, Department of Molecular Genetics, VIB, 2610 Antwerp, Belgium. Laboratory of Neurogenetics, Institute Born-Bunge, University of Antwerp, 2610 Antwerp, Belgium
| | - Hakan Gurvit
- Behavioral Neurology and Movement Disorders Unit, Department of Neurology, Istanbul Faculty of Medicine, Istanbul University, 34093 Istanbul, Turkey
| | - Tony Wyss-Coray
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA. Center for Tissue Regeneration, Repair and Restoration, Veterans Administration Palo Alto Health Care System, Palo Alto, CA 94304, USA. Neuroscience IDP Program, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - John Hardy
- Reta Lila Weston Laboratories and Department of Molecular Neuroscience, UCL Institute of Neurology, London WC1N 3BG, UK
| | - Marco Colonna
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Christian Haass
- Adolf-Butenandt Institute, Biochemistry, Ludwig-Maximilians University Munich, 80336 Munich, Germany. Munich Cluster for Systems Neurology (SyNergy), 80336 Munich, Germany. German Center for Neurodegenerative Diseases (DZNE), Munich, 80336 Munich, Germany.
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Lue LF, Schmitz CT, Serrano G, Sue LI, Beach TG, Walker DG. TREM2 Protein Expression Changes Correlate with Alzheimer's Disease Neurodegenerative Pathologies in Post-Mortem Temporal Cortices. Brain Pathol 2014; 25:469-80. [PMID: 25186950 PMCID: PMC4427527 DOI: 10.1111/bpa.12190] [Citation(s) in RCA: 114] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2014] [Accepted: 08/11/2014] [Indexed: 12/16/2022] Open
Abstract
Triggering receptor expressed by myeloid cells 2 (TREM2), a member of the immunoglobulin superfamily, has anti-inflammatory phagocytic function in myeloid cells. Several studies have shown that TREM2 gene variant rs75932628-T increased the risks for Alzheimer's disease (AD), Parkinson's disease, frontotemporal dementia and amyotrophic lateral sclerosis. It has been suggested that the risks could be resulted from the loss of TREM2 function caused by the mutation. Indeed, new evidence showed that several mutations in the immunoglobulin-like V-region led to low cell surface expression of TREM2 and reduced phagocytic function. Because of the emerging importance in understanding TREM2 expression and functions in human neurodegenerative diseases, we conducted biochemical and morphological studies of TREM2 expression in human post-mortem temporal cortical samples from AD and normal cases. Increased expression of TREM2 protein was found to significantly correlate with increases of phosphorylated-tau and active caspase 3, a marker of apoptosis, and also loss of the presynaptic protein SNAP25. Strong intensities of TREM2 immunoreactivity were observed in the microglia associated with amyloid plaques and in neuritic pathology-enriched areas. Based on the findings that TREM2 expression correlated with neurodegenerative markers, further investigation on whether there is abnormality of TREM2 functions in AD brains with nonmutated TREM2 is needed.
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Affiliation(s)
- Lih-Fen Lue
- Laboratory of Neuroregeneration, Banner Sun Health Research Institute, Sun City, AZ
| | | | - Geidy Serrano
- W. H. Civin Laboratory for Neuropathology, Banner Sun Health Research Institute, Sun City, AZ
| | - Lucia I Sue
- W. H. Civin Laboratory for Neuropathology, Banner Sun Health Research Institute, Sun City, AZ
| | - Thomas G Beach
- W. H. Civin Laboratory for Neuropathology, Banner Sun Health Research Institute, Sun City, AZ
| | - Douglas G Walker
- Laboratory of Neuroinflammation, Banner Sun Health Research Institute, Sun City, AZ
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23
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What happens to microglial TREM2 in Alzheimer's disease: Immunoregulatory turned into immunopathogenic? Neuroscience 2014; 302:138-50. [PMID: 25281879 DOI: 10.1016/j.neuroscience.2014.09.050] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Revised: 09/23/2014] [Accepted: 09/23/2014] [Indexed: 12/12/2022]
Abstract
Microglia play major roles in initiation, coordination and execution of innate immunity in the brain. In the adult brain, these include maintenance of homeostasis, neuron and tissue repair, and eliminating infectious agents, apoptotic cells, and misfolded proteins. Some of these activities are accompanied by inflammatory reactions; and others are performed with no inflammatory effects. Under normal conditions, triggering receptor expressed on myeloid cells 2 (TREM2) belongs to the second category. It pairs with the adaptor protein DNAX-activating protein of 12kDa (DAP12) to induce phagocytosis of apoptotic neurons without inflammatory responses, and to regulate Toll-like receptor-mediated inflammatory responses, and microglial activation. Although ligands for TREM2 are largely unknown, the mitochondrial heat shock protein 60, expressed on cell surface of apoptotic neurons, is a specific ligand that activates TREM2-mediated phagocytosis by microglia. TREM2 also phagocytoses amyloid beta peptide in cultured cells. Several TREM2 mutations have been identified recently that increase the risk of Alzheimer's disease, Frontotemporal dementia, Parkinson's disease, and amyotrophic lateral sclerosis. Some of these mutations cause impaired proteolysis of full-length TREM2 at the plasma membrane to different degrees. The defects in the intramembrane cleavage result in dysfunction of phagocytosis signaling. The association of TREM2 mutations with neurodegenerative disease also calls for the understanding of the biology and pathological role of non-mutated TREM2 on human brains and microglia. This review provides a summary of current literature in TREM2 and DAP12 from several aspects, and proposes a theory that loss of TREM2 functions might contribute to the immunopathogenic role of microglia in Alzheimer's disease.
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24
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Hu X, Liou AKF, Leak RK, Xu M, An C, Suenaga J, Shi Y, Gao Y, Zheng P, Chen J. Neurobiology of microglial action in CNS injuries: receptor-mediated signaling mechanisms and functional roles. Prog Neurobiol 2014; 119-120:60-84. [PMID: 24923657 PMCID: PMC4121732 DOI: 10.1016/j.pneurobio.2014.06.002] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Revised: 05/31/2014] [Accepted: 06/03/2014] [Indexed: 12/28/2022]
Abstract
Microglia are the first line of immune defense against central nervous system (CNS) injuries and disorders. These highly plastic cells play dualistic roles in neuronal injury and recovery and are known for their ability to assume diverse phenotypes. A broad range of surface receptors are expressed on microglia and mediate microglial 'On' or 'Off' responses to signals from other host cells as well as invading microorganisms. The integrated actions of these receptors result in tightly regulated biological functions, including cell mobility, phagocytosis, the induction of acquired immunity, and trophic factor/inflammatory mediator release. Over the last few years, significant advances have been made toward deciphering the signaling mechanisms related to these receptors and their specific cellular functions. In this review, we describe the current state of knowledge of the surface receptors involved in microglial activation, with an emphasis on their engagement of distinct functional programs and their roles in CNS injuries. It will become evident from this review that microglial homeostasis is carefully maintained by multiple counterbalanced strategies, including, but not limited to, 'On' and 'Off' receptor signaling. Specific regulation of theses microglial receptors may be a promising therapeutic strategy against CNS injuries.
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Affiliation(s)
- Xiaoming Hu
- Center of Cerebrovascular Disease Research, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA; State Key Laboratory of Medical Neurobiology and Institute of Brain Sciences, Fudan University, Shanghai, China; Geriatric Research, Educational and Clinical Center, Veterans Affairs Pittsburgh Health Care System, Pittsburgh, PA 15240, USA.
| | - Anthony K F Liou
- Center of Cerebrovascular Disease Research, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - Rehana K Leak
- Division of Pharmaceutical Sciences, Duquesne University, Pittsburgh, PA 15282, USA
| | - Mingyue Xu
- State Key Laboratory of Medical Neurobiology and Institute of Brain Sciences, Fudan University, Shanghai, China
| | - Chengrui An
- State Key Laboratory of Medical Neurobiology and Institute of Brain Sciences, Fudan University, Shanghai, China
| | - Jun Suenaga
- Center of Cerebrovascular Disease Research, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - Yejie Shi
- Center of Cerebrovascular Disease Research, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - Yanqin Gao
- State Key Laboratory of Medical Neurobiology and Institute of Brain Sciences, Fudan University, Shanghai, China
| | - Ping Zheng
- State Key Laboratory of Medical Neurobiology and Institute of Brain Sciences, Fudan University, Shanghai, China
| | - Jun Chen
- Center of Cerebrovascular Disease Research, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA; State Key Laboratory of Medical Neurobiology and Institute of Brain Sciences, Fudan University, Shanghai, China; Geriatric Research, Educational and Clinical Center, Veterans Affairs Pittsburgh Health Care System, Pittsburgh, PA 15240, USA.
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25
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Microglial beclin 1 regulates retromer trafficking and phagocytosis and is impaired in Alzheimer's disease. Neuron 2013; 79:873-86. [PMID: 24012002 DOI: 10.1016/j.neuron.2013.06.046] [Citation(s) in RCA: 283] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/27/2013] [Indexed: 01/13/2023]
Abstract
Phagocytosis controls CNS homeostasis by facilitating the removal of unwanted cellular debris. Accordingly, impairments in different receptors or proteins involved in phagocytosis result in enhanced inflammation and neurodegeneration. While various studies have identified extrinsic factors that modulate phagocytosis in health and disease, key intracellular regulators are less understood. Here we show that the autophagy protein beclin 1 is required for efficient phagocytosis in vitro and in mouse brains. Furthermore, we show that beclin 1-mediated impairments in phagocytosis are associated with dysfunctional recruitment of retromer to phagosomal membranes, reduced retromer levels, and impaired recycling of phagocytic receptors CD36 and Trem2. Interestingly, microglia isolated from human Alzheimer's disease (AD) brains show significantly reduced beclin 1 and retromer protein levels. These findings position beclin 1 as a link between autophagy, retromer trafficking, and receptor-mediated phagocytosis and provide insight into mechanisms by which phagocytosis is regulated and how it may become impaired in AD.
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26
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Wunderlich P, Glebov K, Kemmerling N, Tien NT, Neumann H, Walter J. Sequential proteolytic processing of the triggering receptor expressed on myeloid cells-2 (TREM2) protein by ectodomain shedding and γ-secretase-dependent intramembranous cleavage. J Biol Chem 2013; 288:33027-36. [PMID: 24078628 DOI: 10.1074/jbc.m113.517540] [Citation(s) in RCA: 205] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Triggering receptor expressed on myeloid cells-2 (TREM2) and its signaling adaptor protein TYROBP/DAP12 play important roles in signal transduction in dendritic cells, osteoclasts, tissue macrophages, and microglia. Recently, TREM2 variants have been shown to be linked to late onset Alzheimer disease. Here, we demonstrate that TREM2 undergoes sequential proteolytic processing by ectodomain shedding and intramembrane proteolysis. The C-terminal fragment (CTF) of TREM2 generated by ectodomain shedding is cleaved by γ-secretase. Importantly, pharmacologic and genetic γ-secretase inhibition resulted in accumulation of TREM2 CTF at the plasma membrane that also interacts with the signaling adaptor protein DAP12. Thus, the accumulated TREM2 CTF thereby might limit the interaction of DAP12 with the functional full-length receptor, resulting in decreased DAP12 phosphorylation and impaired metabolism of phosphatidylinositol 4,5-bisphosphate. Together, these data demonstrate γ-secretase-mediated intramembranous proteolysis of TREM2 and functionally link two Alzheimer disease-associated proteins in one signaling pathway.
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Affiliation(s)
- Patrick Wunderlich
- From the Department of Neurology, University of Bonn, 53127 Bonn, Germany and
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27
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Kim H, Walczak P, Kerr C, Galpoththawela C, Gilad AA, Muja N, Bulte JWM. Immunomodulation by transplanted human embryonic stem cell-derived oligodendroglial progenitors in experimental autoimmune encephalomyelitis. Stem Cells 2013; 30:2820-9. [PMID: 22949039 DOI: 10.1002/stem.1218] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Accepted: 08/09/2012] [Indexed: 12/18/2022]
Abstract
Transplantation of embryonic stem cells and their neural derivatives can lead to amelioration of the disease symptoms of experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis (MS). Oligodendroglial progenitors (OPs), derived from human embryonic stem cells (hESC, HES-1), were labeled with superparamagnetic iron oxide and transduced with luciferase. At 7 days following induction of EAE in C57/BL6 mice, 1 × 10(6) cells were transplanted in the ventricles of C57/BL6 mice and noninvasively monitored by magnetic resonance and bioluminescence imaging. Cells were found to remain within the cerebroventricular system and did not survive for more than 10 days. However, EAE mice that received hESC-OPs showed a significant improvement in neurological disability scores (0.9 ± 0.2; n = 12) compared to that of control animals (3.3 ± 0.4; n = 12) at day 15 post-transplantation. Histopathologically, transplanted hESC-OPs generated TREM2-positive CD45 cells, increased TIMP-1 expression, confined inflammatory cells within the subarachnoid space, and gave rise to higher numbers of Foxp3-positive regulatory T cells in the spinal cord and spleen. Our results suggest that transplantation of hESC-OPs can alter the pathogenesis of EAE through immunomodulation, potentially providing new avenues for stem cell-based treatment of MS.
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Affiliation(s)
- Heechul Kim
- Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205-2195, USA
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28
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Chertoff M, Shrivastava K, Gonzalez B, Acarin L, Giménez-Llort L. Differential modulation of TREM2 protein during postnatal brain development in mice. PLoS One 2013; 8:e72083. [PMID: 23977213 PMCID: PMC3747061 DOI: 10.1371/journal.pone.0072083] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Accepted: 07/04/2013] [Indexed: 01/25/2023] Open
Abstract
During postnatal development, microglia, the resident innate immune cells of the central nervous system are constantly monitoring the brain parenchyma, cleaning the cell debris, the synaptic contacts overproduced and also maintaining the brain homeostasis. In this context, the postnatal microglia need some control over the innate immune response. One such molecule recently described to be involved in modulation of immune response is TREM2 (triggering receptor expressed on myeloid cells 2). Although some studies have observed TREM2 mRNA in postnatal brain, the regional pattern of the TREM2 protein has not been described. We therefore characterized the distribution of TREM2 protein in mice brain from Postnatal day (P) 1 to 14 by immunostaining. In our study, TREM2 protein was expressed only in microglia/macrophages and is developmentally downregulated in a region-dependent manner. Its expression persisted in white matter, mainly in caudal corpus callosum, and the neurogenic subventricular zone for a longer time than in grey matter. Additionally, the phenotypes of the TREM2+ microglia also differ; expressing CD16/32, MHCII and CD86 (antigen presentation markers) and CD68 (phagocytic marker) in different regions as well as with different intensity till P7. The mannose receptor (CD206) colocalized with TREM2 only at P1–P3 in the subventricular zone and cingulum, while others persisted at low intensities till P7. Furthermore, the spatiotemporal expression pattern and characterization of TREM2 indicate towards its other plausible roles in phagocytosis, progenitor’s fate determination or microglia phenotype modulation during postnatal development. Hence, the increase of TREM2 observed in pathologies may recapitulate their function during postnatal development, as a better understanding of this period may open new pathway for future therapies.
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Affiliation(s)
- Mariela Chertoff
- Department of Cell Biology, Physiology and Immunology, Universitat Autonoma Barcelona, Barcelona, Spain
- Institute of Neuroscience, Universitat Autonoma Barcelona, Barcelona, Spain
- * E-mail:
| | - Kalpana Shrivastava
- Department of Cell Biology, Physiology and Immunology, Universitat Autonoma Barcelona, Barcelona, Spain
- Institute of Neuroscience, Universitat Autonoma Barcelona, Barcelona, Spain
| | - Berta Gonzalez
- Department of Cell Biology, Physiology and Immunology, Universitat Autonoma Barcelona, Barcelona, Spain
- Institute of Neuroscience, Universitat Autonoma Barcelona, Barcelona, Spain
| | - Laia Acarin
- Department of Cell Biology, Physiology and Immunology, Universitat Autonoma Barcelona, Barcelona, Spain
- Institute of Neuroscience, Universitat Autonoma Barcelona, Barcelona, Spain
| | - Lydia Giménez-Llort
- Department of Psychiatry and Forensic Medicine, Universitat Autonoma Barcelona, Barcelona, Spain
- Institute of Neuroscience, Universitat Autonoma Barcelona, Barcelona, Spain
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29
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Harry GJ, Kraft AD. Microglia in the developing brain: a potential target with lifetime effects. Neurotoxicology 2012; 33:191-206. [PMID: 22322212 DOI: 10.1016/j.neuro.2012.01.012] [Citation(s) in RCA: 179] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Revised: 01/24/2012] [Accepted: 01/25/2012] [Indexed: 12/15/2022]
Abstract
Microglia are a heterogenous group of monocyte-derived cells serving multiple roles within the brain, many of which are associated with immune and macrophage like properties. These cells are known to serve a critical role during brain injury and to maintain homeostasis; yet, their defined roles during development have yet to be elucidated. Microglial actions appear to influence events associated with neuronal proliferation and differentiation during development, as well as, contribute to processes associated with the removal of dying neurons or cellular debris and management of synaptic connections. These long-lived cells display changes during injury and with aging that are critical to the maintenance of the neuronal environment over the lifespan of the organism. These processes may be altered by changes in the colonization of the brain or by inflammatory events during development. This review addresses the role of microglia during brain development, both structurally and functionally, as well as the inherent vulnerability of the developing nervous system. A framework is presented considering microglia as a critical nervous system-specific cell that can influence multiple aspects of brain development (e.g., vascularization, synaptogenesis, and myelination) and have a long term impact on the functional vulnerability of the nervous system to a subsequent insult, whether environmental, physical, age-related, or disease-related.
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Affiliation(s)
- G Jean Harry
- National Toxicology Program Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA.
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30
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Satoh JI, Tabunoki H, Ishida T, Yagishita S, Jinnai K, Futamura N, Kobayashi M, Toyoshima I, Yoshioka T, Enomoto K, Arai N, Arima K. Immunohistochemical characterization of microglia in Nasu-Hakola disease brains. Neuropathology 2010; 31:363-75. [DOI: 10.1111/j.1440-1789.2010.01174.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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31
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Thrash JC, Torbett BE, Carson MJ. Developmental regulation of TREM2 and DAP12 expression in the murine CNS: implications for Nasu-Hakola disease. Neurochem Res 2008; 34:38-45. [PMID: 18404378 DOI: 10.1007/s11064-008-9657-1] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2008] [Accepted: 03/07/2008] [Indexed: 11/25/2022]
Abstract
Trem2 is an orphan, DAP12 associated receptor constitutively expressed in vivo by subsets of microglia in the healthy adult murine CNS and in vitro by subsets of oligodendrocytes in neonatal mixed glial cultures. Loss of a functional Trem2 signaling pathway is the genetic cause of Nasu-Hakola disease. Whether the early onset cognitive dementia and myelin-pallor associated with this disorder are due to deficits in functional Trem2 signaling in microglia and/or oligodendrocytes is still being debated. Here, we find that Trem2/DAP12 expression is detected in embryonic day 14 CNS mRNA. Using dual immunohistochemistry/in situ hybridization, we find that both Trem2 and DAP12 expression always co-localized with markers of microglia/macrophages. However, Trem2/DAP12 positive microglia are found in very close apposition with CNP+ oligodendrocytes prior to myelination (post-natal day 1). In addition, CNS expression of TREM2 and DAP12 are not detected in PU.1KO which lack microglia and macrophages. Our data provide continuing support for Nasu-Hakola disease being identified as a cognitive disorder caused by a primary dysfunction of CNS microglia.
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Affiliation(s)
- J Cameron Thrash
- Division of Biomedical Sciences, Center for Glial-Neuronal Interactions, University of California Riverside, 900 University Ave, Riverside, CA, 92521, USA
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32
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Piccio L, Buonsanti C, Mariani M, Cella M, Gilfillan S, Cross AH, Colonna M, Panina-Bordignon P. Blockade of TREM-2 exacerbates experimental autoimmune encephalomyelitis. Eur J Immunol 2007; 37:1290-301. [PMID: 17407101 DOI: 10.1002/eji.200636837] [Citation(s) in RCA: 200] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Triggering receptor expressed on myeloid cells (TREM-2) is a membrane receptor associated with DAP12 that is expressed primarily in myeloid cells, including dendritic cells and microglia, and promotes fusion of osteoclast precursors into multinucleated cells. A rare autosomal recessive condition, Nasu-Hakola disease (NHD) is associated with loss-of-function mutations in DAP12 and TREM-2. The brain pathology observed in NHD patients suggests that disruption of the TREM-2/DAP12 pathway leads to neurodegeneration with demyelination and axonal loss. In this study, we have characterized TREM-2 protein expression on microglia using a newly produced monoclonal antibody directed against the mouse TREM-2 receptor. We report that TREM-2 expression is up-regulated in the spinal cord during both the early inflammatory and chronic phases of myelin oligodendrocyte glycoprotein (MOG)(35-55)peptide-induced experimental autoimmune encaphalomyelitis (EAE). We also demonstrate that TREM-2 is highly expressed on microglial cells in the central nervous system (CNS) during EAE and that blockade of TREM-2 during the effector phase of EAE results in disease exacerbation with more diffuse CNS inflammatory infiltrates and demyelination in the brain parenchyma. These results demonstrate a critical role for TREM-2 during inflammatory responses in the CNS.
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MESH Headings
- Animals
- Blotting, Northern
- Brain/immunology
- Brain/metabolism
- Brain/pathology
- Encephalomyelitis, Autoimmune, Experimental/immunology
- Encephalomyelitis, Autoimmune, Experimental/metabolism
- Encephalomyelitis, Autoimmune, Experimental/pathology
- Fluorescent Antibody Technique
- Macrophages/immunology
- Macrophages/metabolism
- Membrane Glycoproteins/immunology
- Membrane Glycoproteins/metabolism
- Mice
- Microglia/metabolism
- RNA, Messenger/analysis
- Receptors, Immunologic/immunology
- Receptors, Immunologic/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Spinal Cord/immunology
- Spinal Cord/metabolism
- Spinal Cord/pathology
- Up-Regulation
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