1
|
Faraji P, Kühn H, Ahmadian S. Multiple Roles of Apolipoprotein E4 in Oxidative Lipid Metabolism and Ferroptosis During the Pathogenesis of Alzheimer's Disease. J Mol Neurosci 2024; 74:62. [PMID: 38958788 PMCID: PMC11222241 DOI: 10.1007/s12031-024-02224-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Accepted: 04/14/2024] [Indexed: 07/04/2024]
Abstract
Alzheimer's disease (AD) is the most prevalent neurodegenerative disease worldwide and has a great socio-economic impact. Modified oxidative lipid metabolism and dysregulated iron homeostasis have been implicated in the pathogenesis of this disorder, but the detailed pathophysiological mechanisms still remain unclear. Apolipoprotein E (APOE) is a lipid-binding protein that occurs in large quantities in human blood plasma, and a polymorphism of the APOE gene locus has been identified as risk factors for AD. The human genome involves three major APOE alleles (APOE2, APOE3, APOE4), which encode for three subtly distinct apolipoprotein E isoforms (APOE2, APOE3, APOE4). The canonic function of these apolipoproteins is lipid transport in blood and brain, but APOE4 allele carriers have a much higher risk for AD. In fact, about 60% of clinically diagnosed AD patients carry at least one APOE4 allele in their genomes. Although the APOE4 protein has been implicated in pathophysiological key processes of AD, such as extracellular beta-amyloid (Aβ) aggregation, mitochondrial dysfunction, neuroinflammation, formation of neurofibrillary tangles, modified oxidative lipid metabolism, and ferroptotic cell death, the underlying molecular mechanisms are still not well understood. As for all mammalian cells, iron plays a crucial role in neuronal functions and dysregulation of iron homeostasis has also been implicated in the pathogenesis of AD. Imbalances in iron homeostasis and impairment of the hydroperoxy lipid-reducing capacity induce cellular dysfunction leading to neuronal ferroptosis. In this review, we summarize the current knowledge on APOE4-related oxidative lipid metabolism and the potential role of ferroptosis in the pathogenesis of AD. Pharmacological interference with these processes might offer innovative strategies for therapeutic interventions.
Collapse
Affiliation(s)
- Parisa Faraji
- Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran
- Department of Biochemistry, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt Universität zu Berlin, Charitéplatz 1, 10117, Berlin, Germany
| | - Hartmut Kühn
- Department of Biochemistry, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt Universität zu Berlin, Charitéplatz 1, 10117, Berlin, Germany.
| | - Shahin Ahmadian
- Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran.
| |
Collapse
|
2
|
Li Y, Chang J, Chen X, Liu J, Zhao L. Advances in the Study of APOE and Innate Immunity in Alzheimer's Disease. J Alzheimers Dis 2023:JAD230179. [PMID: 37182889 DOI: 10.3233/jad-230179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Alzheimer's disease (AD) is a progressive degenerative disease of the nervous system (CNS) with an insidious onset. Clinically, it is characterized by a full range of dementia manifestations including memory impairment, aphasia, loss of speech, loss of use, loss of recognition, impairment of visuospatial skills, and impairment of executive function, as well as changes in personality and behavior. The exact cause of AD has not yet been identified. Nevertheless, modern research indicates that genetic factors contribute to 70% of human's risk of AD. Apolipoprotein (APOE) accounts for up to 90% of the genetic predisposition. APOE is a crucial gene that cannot be overstated. In addition, innate immunity plays a significant role in the etiology and treatment of AD. Understanding the different subtypes of APOE and their interconnections is of paramount importance. APOE and innate immunity, along with their relationship to AD, are primary research motivators for in-depth research and clinical trials. The exploration of novel technologies has led to an increasing trend in the study of AD at the cellular and molecular levels and continues to make more breakthroughs and progress. As of today, there is no effective treatment available for AD around the world. This paper aims to summarize and analyze the role of APOE and innate immunity, as well as development trends in recent years. It is anticipated that APOE and innate immunity will provide a breakthrough for humans to hinder AD progression in the near future.
Collapse
Affiliation(s)
- Yujiao Li
- First Teaching Hospital of Tianjin University of Traditional Chinese Medicine, Tianjin, China
- National Clinical Research Center for Chinese Medicine Acupuncture and Moxibustion, Tianjin, China
| | - Jun Chang
- First Teaching Hospital of Tianjin University of Traditional Chinese Medicine, Tianjin, China
- National Clinical Research Center for Chinese Medicine Acupuncture and Moxibustion, Tianjin, China
| | - Xi Chen
- First Teaching Hospital of Tianjin University of Traditional Chinese Medicine, Tianjin, China
- National Clinical Research Center for Chinese Medicine Acupuncture and Moxibustion, Tianjin, China
| | - Jianwei Liu
- Tianjin University of Traditional Chinese Medicine, Tianjin, China
| | - Lan Zhao
- First Teaching Hospital of Tianjin University of Traditional Chinese Medicine, Tianjin, China
- National Clinical Research Center for Chinese Medicine Acupuncture and Moxibustion, Tianjin, China
| |
Collapse
|
3
|
Ozsan McMillan I, Li JP, Wang L. Heparan sulfate proteoglycan in Alzheimer's disease: aberrant expression and functions in molecular pathways related to amyloid-β metabolism. Am J Physiol Cell Physiol 2023; 324:C893-C909. [PMID: 36878848 PMCID: PMC10069967 DOI: 10.1152/ajpcell.00247.2022] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 02/28/2023] [Accepted: 02/28/2023] [Indexed: 03/08/2023]
Abstract
Alzheimer's disease (AD) is the most common form of dementia. Currently, there is no effective treatment for AD, as its etiology remains poorly understood. Mounting evidence suggests that the accumulation and aggregation of amyloid-β peptides (Aβ), which constitute amyloid plaques in the brain, is critical for initiating and accelerating AD pathogenesis. Considerable efforts have been dedicated to shedding light on the molecular basis and fundamental origins of the impaired Aβ metabolism in AD. Heparan sulfate (HS), a linear polysaccharide of the glycosaminoglycan family, co-deposits with Aβ in plaques in the AD brain, directly binds and accelerates Aβ aggregation, and mediates Aβ internalization and cytotoxicity. Mouse model studies demonstrate that HS regulates Aβ clearance and neuroinflammation in vivo. Previous reviews have extensively explored these discoveries. Here, this review focuses on the recent advancements in understanding abnormal HS expression in the AD brain, the structural aspects of HS-Aβ interaction, and the molecules involved in modulating Aβ metabolism through HS interaction. Furthermore, this review presents a perspective on the potential effects of abnormal HS expression on Aβ metabolism and AD pathogenesis. In addition, the review highlights the importance of conducting further research to differentiate the spatiotemporal components of HS structure and function in the brain and AD pathogenesis.
Collapse
Affiliation(s)
- Ilayda Ozsan McMillan
- Department of Molecular Pharmacology & Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States
- Byrd Alzheimer's Research Institute, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States
| | - Jin-Ping Li
- Department of Medical Biochemistry and Microbiology & The Biomedical Center, University of Uppsala, Uppsala, Sweden
- SciLifeLab Uppsala, University of Uppsala, Uppsala, Sweden
| | - Lianchun Wang
- Department of Molecular Pharmacology & Physiology, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States
- Byrd Alzheimer's Research Institute, Morsani College of Medicine, University of South Florida, Tampa, Florida, United States
| |
Collapse
|
4
|
Soluble TREM2 in body fluid in Alzheimer's disease and Parkinson's disease. Neurol Sci 2023:10.1007/s10072-023-06729-5. [PMID: 36913148 DOI: 10.1007/s10072-023-06729-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Accepted: 03/02/2023] [Indexed: 03/14/2023]
Abstract
BACKGROUND Previous studies showed conflicting results regarding soluble triggering receptor expressed on myeloid cells 2 (sTREM2) level alteration in body fluid in Alzheimer's disease (AD) and Parkinson's disease (PD). METHODS We applied the STATA 12.0 software to compute standard mean difference (SMD) and 95% confidence interval (CI). RESULTS The study showed elevated sTREM2 level in cerebrospinal fluid (CSF) in AD, mild cognitive impairment (MCI), and preclinical AD (pre-AD) patients, compared to healthy controls (HCs) with random effects models (AD: SMD 0.28, 95% CI 0.12 to 0.44, I2 = 77.6%, p < 0.001; MCI: SMD 0.29, 95% CI 0.09 to 0.48, I2 = 89.7%, p < 0.001; pre-AD: SMD 0.24, 95% CI 0.00 to 0.48, I2 = 80.8%, p < 0.001). The study showed no significant difference in sTREM2 level in plasma between AD patients and HCs with a random effects model (SMD 0.06, 95% CI - 0.16 to 0.28, I2 = 65.6%, p = 0.008). The study showed no significant difference in sTREM2 level in CSF or plasma between PD patients and HCs with random effects models (CSF: SMD 0.33, 95% CI - 0.02 to 0.67, I2 = 85.6%, p < 0.001; plasma: SMD 0.37, 95% CI - 0.17 to 0.92, I2 = 77.8%, p = 0.011). CONCLUSIONS In conclusion, the study highlighted the CSF sTREM2 as a promising biomarker in the different clinical stages of AD. More studies were essential to explore the CSF and plasmatic concentrations of sTREM2 alteration in PD.
Collapse
|
5
|
Neumann P, Lenz DE, Streit WJ, Bechmann I. Is microglial dystrophy a form of cellular senescence? An analysis of senescence markers in the aged human brain. Glia 2023; 71:377-390. [PMID: 36286188 DOI: 10.1002/glia.24282] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 09/27/2022] [Accepted: 09/30/2022] [Indexed: 01/08/2023]
Abstract
Aging can cause morphological transformation in human microglia indicative of cell senescence, termed microglial dystrophy. However, cellular senescence is characterized by additional changes, such as an irregular cell cycle arrest, and a variety of metabolic and molecular changes including a senescence-associated secretory phenotype, dysfunction of degradation mechanisms, and altered DNA damage response. Here, we tested whether dystrophic microglia display customary markers of cell senescence by performing double and triple staining in sections of the temporal lobe and brain stem from 14 humans. We found that markers related to oxidative damage, such as upregulation of 8-hydroxy-2'-deoxyguanosine (8-OHdG), hemeoxygenase-1 (HO-1), and y-H2AX, as well as inclusion of lipofuscin, do not or only exceptionally colocalize with dystrophic microglia. Further, we did not observe a decline in lamin B1 around nuclear laminae in either dystrophic or ramified microglia within the same microscopic field. Only ferritin expression, which is known to increase with aging in CNS microglia, was frequently observed in dystrophic, but rarely in ramified microglial cells. We conclude that neither dystrophic nor ramified microglia in human brain exhibit significant expression of conventional senescence markers associated with oxidative stress, and that ferritin is the dominant immunophenotypic change related to microglial aging. We suggest that multiple pathogenic mechanisms other than those driving cellular senescence contribute to dystrophic transformation of microglia.
Collapse
Affiliation(s)
| | - Dana E Lenz
- Institute of Anatomy, Universität Leipzig, Leipzig, Germany
| | - Wolfgang J Streit
- Department of Neuroscience, University of Florida College of Medicine, Gainesville, Florida, USA
| | - Ingo Bechmann
- Institute of Anatomy, Universität Leipzig, Leipzig, Germany
| |
Collapse
|
6
|
Zhang C, Chen S. Role of TREM2 in the Development of Neurodegenerative Diseases After Traumatic Brain Injury. Mol Neurobiol 2022; 60:342-354. [PMID: 36264434 DOI: 10.1007/s12035-022-03094-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 10/14/2022] [Indexed: 11/28/2022]
Abstract
Traumatic brain injury (TBI) has been found as the primary cause of morbidity and disability worldwide, which has posed a significant social and economic burden. The first stage of TBI produces brain edema, axonal damage, and hypoxia, thus having an effect on the blood-brain barrier function, promoting inflammatory responses, and increasing oxidative stress. Patients with TBI are more likely to develop post-traumatic epilepsy, behavioral issues, as well as mental illnesses. The long-term effects arising from TBI have aroused rising attention over the past few years. Microglia in the brain can express the triggering receptor expressed on myeloid cells 2 (TREM2), which is a single transmembrane receptor pertaining to the immunoglobulin superfamily. The receptor has been correlated with a number of neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, and other relevant diseases. In this review, it is demonstrated that TREM2 is promising to serve as a neuroprotective factor for neurodegenerative disorders following TBI by modulating the function of microglial cells. Accordingly, it has potential avenues for TREM2-related therapies to improve long-term recovery after TBI.
Collapse
Affiliation(s)
- Chunhao Zhang
- Department of Neurosurgery, Shanghai Sixth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200233, People's Republic of China
| | - Shiwen Chen
- Department of Neurosurgery, Shanghai Sixth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200233, People's Republic of China.
| |
Collapse
|
7
|
Yang J, Fu Z, Zhang X, Xiong M, Meng L, Zhang Z. TREM2 ectodomain and its soluble form in Alzheimer's disease. J Neuroinflammation 2020; 17:204. [PMID: 32635934 PMCID: PMC7341574 DOI: 10.1186/s12974-020-01878-2] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Accepted: 06/23/2020] [Indexed: 12/14/2022] Open
Abstract
Triggering receptor expressed on myeloid cells 2 (TREM2) is a receptor mainly expressed on the surface of microglia. It mediates multiple pathophysiological processes in various diseases. Recently, TREM2 has been found to play a role in the development of Alzheimer's disease (AD). TREM2 is a transmembrane protein that is specifically expressed on microglia in the brain. It contains a long ectodomain that directly interacts with the extracellular environment to regulate microglial function. The ectodomain of TREM2 is processed by a disintegrin and metalloprotease, resulting in the release of a soluble form of TREM2 (sTREM2). Recent studies have demonstrated that sTREM2 is a bioactive molecule capable of binding ligands, activating microglia, and regulating immune responses during the AD continuum. Clinical studies revealed that sTREM2 level is elevated in cerebrospinal fluid (CSF) of AD patients, and the sTREM2 level is positively correlated with the levels of classical CSF biomarkers, namely t-tau and p-tau, indicating that it is a reliable predictor of the early stages of AD. Herein, we summarize the key results on the generation, structure, and function of sTREM2 to provide new insights into TREM2-related mechanisms underlying AD pathogenesis and to promote the development of TREM2-based therapeutic strategy.
Collapse
Affiliation(s)
- Jiaolong Yang
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan, 430060, China
| | - Zhihui Fu
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan, 430060, China
| | - Xingyu Zhang
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan, 430060, China
| | - Min Xiong
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan, 430060, China
| | - Lanxia Meng
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan, 430060, China
| | - Zhentao Zhang
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan, 430060, China.
| |
Collapse
|
8
|
Lessard CB, Malnik SL, Zhou Y, Ladd TB, Cruz PE, Ran Y, Mahan TE, Chakrabaty P, Holtzman DM, Ulrich JD, Colonna M, Golde TE. High-affinity interactions and signal transduction between Aβ oligomers and TREM2. EMBO Mol Med 2019; 10:emmm.201809027. [PMID: 30341064 PMCID: PMC6220267 DOI: 10.15252/emmm.201809027] [Citation(s) in RCA: 80] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Rare coding variants in the triggering receptor expressed on myeloid cells 2 (TREM2) are associated with increased risk for Alzheimer's disease (AD), but how they confer this risk remains uncertain. We assessed binding of TREM2, AD‐associated TREM2 variants to various forms of Aβ and APOE in multiple assays. TREM2 interacts directly with various forms of Aβ, with highest affinity interactions observed between TREM2 and soluble Aβ42 oligomers. High‐affinity binding of TREM2 to Aβ oligomers is characterized by very slow dissociation. Pre‐incubation with Aβ is shown to block the interaction of APOE. In cellular assays, AD‐associated variants of TREM2 reduced the amount of Aβ42 internalized, and in NFAT assay, the R47H and R62H variants decreased NFAT signaling activity in response to Aβ42. These studies demonstrate i) a high‐affinity interaction between TREM2 and Aβ oligomers that can block interaction with another TREM2 ligand and ii) that AD‐associated TREM2 variants bind Aβ with equivalent affinity but show loss of function in terms of signaling and Aβ internalization.
Collapse
Affiliation(s)
- Christian B Lessard
- Center for Translational Research in Neurodegenerative Disease, Department of Neuroscience, University of Florida, Gainesville, FL, USA
| | - Samuel L Malnik
- Center for Translational Research in Neurodegenerative Disease, Department of Neuroscience, University of Florida, Gainesville, FL, USA
| | - Yingyue Zhou
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA
| | - Thomas B Ladd
- Center for Translational Research in Neurodegenerative Disease, Department of Neuroscience, University of Florida, Gainesville, FL, USA
| | - Pedro E Cruz
- Center for Translational Research in Neurodegenerative Disease, Department of Neuroscience, University of Florida, Gainesville, FL, USA
| | - Yong Ran
- Center for Translational Research in Neurodegenerative Disease, Department of Neuroscience, University of Florida, Gainesville, FL, USA
| | - Thomas E Mahan
- Department of Neurology, Hope Center for Neurological Disorders, Knight ADRC, Washington University School of Medicine, St. Louis, MO, USA
| | - Paramita Chakrabaty
- Center for Translational Research in Neurodegenerative Disease, Department of Neuroscience, University of Florida, Gainesville, FL, USA.,McKnight Brain Institute, University of Florida, Gainesville, FL, USA
| | - David M Holtzman
- Department of Neurology, Hope Center for Neurological Disorders, Knight ADRC, Washington University School of Medicine, St. Louis, MO, USA
| | - Jason D Ulrich
- Department of Neurology, Hope Center for Neurological Disorders, Knight ADRC, Washington University School of Medicine, St. Louis, MO, USA
| | - Marco Colonna
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA
| | - Todd E Golde
- Center for Translational Research in Neurodegenerative Disease, Department of Neuroscience, University of Florida, Gainesville, FL, USA .,McKnight Brain Institute, University of Florida, Gainesville, FL, USA
| |
Collapse
|
9
|
Dubey H, Gulati K, Ray A. Recent studies on cellular and molecular mechanisms in Alzheimer’s disease: focus on epigenetic factors and histone deacetylase. Rev Neurosci 2018; 29:241-260. [DOI: 10.1515/revneuro-2017-0049] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Accepted: 08/28/2017] [Indexed: 01/06/2023]
Abstract
AbstractAlzheimer’s disease (AD) is one of the most common neurodegenerative disorders mainly affecting elderly people. It is characterized by progressive loss of memory and cognitive function. More than 95% of AD cases are related to sporadic or late-onset AD (LOAD). The etiology of LOAD is still unclear. It has been reported that environmental factors and epigenetic alterations play a significant role in AD pathogenesis. Furthermore, recently, genome-wide association studies (GWAS) identified 10 novel risk genes:ABCA7,APOE,BIN1,CD2AP,CD33,CLU,CR1,MS4A6A,MS4A4E, andPICALM, which play an important role for LOAD. In this review, the therapeutic approaches of AD by epigenetic modifications have been discussed. Nowadays, HDAC inhibitors have clinically proven its activity for epigenetic modifications. Furthermore, we try to establish the relationship between HDAC inhibitors and above mentioned LOAD risk genes. Finally, we are hoping that this review may open new area of research for AD treatment.
Collapse
|
10
|
Glial Draper Rescues Aβ Toxicity in a Drosophila Model of Alzheimer's Disease. J Neurosci 2017; 37:11881-11893. [PMID: 29109235 DOI: 10.1523/jneurosci.0862-17.2017] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Revised: 10/19/2017] [Accepted: 10/23/2017] [Indexed: 12/24/2022] Open
Abstract
Pathological hallmarks of Alzheimer's disease (AD) include amyloid-β (Aβ) plaques, neurofibrillary tangles, and reactive gliosis. Glial cells offer protection against AD by engulfing extracellular Aβ peptides, but the repertoire of molecules required for glial recognition and destruction of Aβ are still unclear. Here, we show that the highly conserved glial engulfment receptor Draper/MEGF10 provides neuroprotection in an AD model of Drosophila (both sexes). Neuronal expression of human Aβ42arc in adult flies results in robust Aβ accumulation, neurodegeneration, locomotor dysfunction, and reduced lifespan. Notably, all of these phenotypes are more severe in draper mutant animals, whereas enhanced expression of glial Draper reverses Aβ accumulation, as well as behavioral phenotypes. We also show that the signal transducer and activator of transcription (Stat92E), c-Jun N-terminal kinase (JNK)/AP-1 signaling, and expression of matrix metalloproteinase-1 (Mmp1) are activated downstream of Draper in glia in response to Aβ42arc exposure. Furthermore, Aβ42-induced upregulation of the phagolysosomal markers Atg8 and p62 was notably reduced in draper mutant flies. Based on our findings, we propose that glia clear neurotoxic Aβ peptides in the AD model Drosophila brain through a Draper/STAT92E/JNK cascade that may be coupled to protein degradation pathways such as autophagy or more traditional phagolysosomal destruction methods.SIGNIFICANCE STATEMENT Alzheimer's disease (AD) and similar dementias are common incurable neurodegenerative disorders in the aging population. As the primary immune responders in the brain, glial cells are implicated as key players in the onset and progression of AD and related disorders. Here we show that the glial engulfment receptor Draper is protective in a Drosophila model of AD, reducing levels of amyloid β (Aβ) peptides, reversing locomotor defects, and extending lifespan. We further show that protein degradation pathways are induced downstream of Draper in AD model flies, supporting a model in which glia engulf and destroy Aβ peptides to reduce amyloid-associated toxicity.
Collapse
|
11
|
Murta V, Ferrari C. Peripheral Inflammation and Demyelinating Diseases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 949:263-285. [PMID: 27714694 DOI: 10.1007/978-3-319-40764-7_13] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
In recent decades, several neurodegenerative diseases have been shown to be exacerbated by systemic inflammatory processes. There is a wide range of literature that demonstrates a clear but complex relationship between the central nervous system (CNS) and the immunological system, both under naïve or pathological conditions. In diseased brains, peripheral inflammation can transform "primed" microglia into an "active" state, which can trigger stronger pathological responses. Demyelinating diseases are a group of neurodegenerative diseases characterized by inflammatory lesions associated with demyelination, which in turn induces axonal damage, neurodegeneration, and progressive loss of function. Among them, the most important are multiple sclerosis (MS) and neuromyelitis optica (NMO). In this review, we will analyze the effect of specific peripheral inflammatory stimuli in the progression of demyelinating diseases and discuss their animal models. In most cases, peripheral immune stimuli are exacerbating.
Collapse
Affiliation(s)
- Verónica Murta
- Laboratorio de Neuropatología Molecular, Instituto de Biología Celular y Neurociencias, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Carina Ferrari
- Instituto de Ciencias Básicas y Medicina Experimental, Instituto Universitario del Hospital Italiano, Buenos Aires, Argentina.
| |
Collapse
|
12
|
Kober DL, Brett TJ. TREM2-Ligand Interactions in Health and Disease. J Mol Biol 2017; 429:1607-1629. [PMID: 28432014 DOI: 10.1016/j.jmb.2017.04.004] [Citation(s) in RCA: 137] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 04/06/2017] [Accepted: 04/10/2017] [Indexed: 01/04/2023]
Abstract
The protein triggering receptor expressed on myeloid cells-2 (TREM2) is an immunomodulatory receptor with a central role in myeloid cell activation and survival. In recent years, the importance of TREM2 has been highlighted by the identification of coding variants that increase risk for Alzheimer's disease and other neurodegenerative diseases. Animal studies have further shown the importance of TREM2 in neurodegenerative and other inflammatory disease models including chronic obstructive pulmonary disease, multiple sclerosis, and stroke. A mechanistic understanding of TREM2 function remains elusive, however, due in part to the absence of conclusive information regarding the identity of endogenous TREM2 ligands. While many TREM2 ligands have been proposed, their physiological role and mechanism of engagement remain to be determined. In this review, we highlight the suggested roles of TREM2 in these diseases and the recent advances in our understanding of TREM2 and discuss putative TREM2-ligand interactions and their potential roles in signaling during health and disease. We develop a model based on the TREM2 structure to explain how different TREM2 ligands might interact with the receptor and how disease risk variants may alter ligand interactions. Finally, we propose future experimental directions to establish the role and importance of these different interactions on TREM2 function.
Collapse
Affiliation(s)
- Daniel L Kober
- Molecular Microbiology and Microbial Pathogenesis Program, Washington University School of Medicine, St. Louis, MO 63110, USA; Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Tom J Brett
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA.
| |
Collapse
|
13
|
Naj AC, Schellenberg GD. Genomic variants, genes, and pathways of Alzheimer's disease: An overview. Am J Med Genet B Neuropsychiatr Genet 2017; 174:5-26. [PMID: 27943641 PMCID: PMC6179157 DOI: 10.1002/ajmg.b.32499] [Citation(s) in RCA: 125] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 09/19/2016] [Indexed: 12/19/2022]
Abstract
Alzheimer's disease (AD) (MIM: 104300) is a highly heritable disease with great complexity in its genetic contributors, and represents the most common form of dementia. With the gradual aging of the world's population, leading to increased prevalence of AD, and the substantial cost of care for those afflicted, identifying the genetic causes of disease represents a critical effort in identifying therapeutic targets. Here we provide a comprehensive review of genomic studies of AD, from the earliest linkage studies identifying monogenic contributors to early-onset forms of AD to the genome-wide and rare variant association studies of recent years that are being used to characterize the mosaic of genetic contributors to late-onset AD (LOAD), and which have identified approximately ∼20 genes with common variants contributing to LOAD risk. In addition, we explore studies employing alternative approaches to identify genetic contributors to AD, including studies of AD-related phenotypes and multi-variant association studies such as pathway analyses. Finally, we introduce studies of next-generation sequencing, which have recently helped identify multiple low-frequency and rare variant contributors to AD, and discuss on-going efforts with next-generation sequencing studies to develop statistically well- powered and comprehensive genomic studies of AD. Through this review, we help uncover the many insights the genetics of AD have provided into the pathways and pathophysiology of AD. © 2016 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Adam C Naj
- Department of Biostatistics and Epidemiology/Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
| | - Gerard D Schellenberg
- Department of Pathology and Laboratory Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania
| |
Collapse
|
14
|
Kober DL, Alexander-Brett JM, Karch CM, Cruchaga C, Colonna M, Holtzman MJ, Brett TJ. Neurodegenerative disease mutations in TREM2 reveal a functional surface and distinct loss-of-function mechanisms. eLife 2016; 5:e20391. [PMID: 27995897 PMCID: PMC5173322 DOI: 10.7554/elife.20391] [Citation(s) in RCA: 127] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Accepted: 11/28/2016] [Indexed: 01/09/2023] Open
Abstract
Genetic variations in the myeloid immune receptor TREM2 are linked to several neurodegenerative diseases. To determine how TREM2 variants contribute to these diseases, we performed structural and functional studies of wild-type and variant proteins. Our 3.1 Å TREM2 crystal structure revealed that mutations found in Nasu-Hakola disease are buried whereas Alzheimer's disease risk variants are found on the surface, suggesting that these mutations have distinct effects on TREM2 function. Biophysical and cellular methods indicate that Nasu-Hakola mutations impact protein stability and decrease folded TREM2 surface expression, whereas Alzheimer's risk variants impact binding to a TREM2 ligand. Additionally, the Alzheimer's risk variants appear to epitope map a functional surface on TREM2 that is unique within the larger TREM family. These findings provide a guide to structural and functional differences among genetic variants of TREM2, indicating that therapies targeting the TREM2 pathway should be tailored to these genetic and functional differences with patient-specific medicine approaches for neurodegenerative disorders.
Collapse
Affiliation(s)
- Daniel L Kober
- Molecular Microbiology and Microbial Pathogenesis Program, Washington University School of Medicine, St. Louis, United States
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Washington University School of Medicine, St. Louis, United States
| | - Jennifer M Alexander-Brett
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Washington University School of Medicine, St. Louis, United States
| | - Celeste M Karch
- Department of Psychiatry, Washington University School of Medicine, St. Louis, United States
| | - Carlos Cruchaga
- Department of Psychiatry, Washington University School of Medicine, St. Louis, United States
| | - Marco Colonna
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, United States
| | - Michael J Holtzman
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Washington University School of Medicine, St. Louis, United States
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, United States
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, United States
| | - Thomas J Brett
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Washington University School of Medicine, St. Louis, United States
| |
Collapse
|
15
|
Han J, Wang M, Ren M, Lou H. Contributions of triggering-receptor-expressed-on-myeloid-cells-2 to neurological diseases. Int J Neurosci 2016; 127:368-375. [PMID: 27871212 DOI: 10.1080/00207454.2016.1264072] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Jie Han
- Department of Pharmacology, School of Medicine, Shandong University, Jinan 250012, China
- Department of Radiation Oncology, Shandong Cancer Hospital and Institute affiliated to Shandong University, Jinan 250012, China
| | - Miaomiao Wang
- Department of Hematology, Qilu Hospital, Shandong University, Jinan 250012, China
| | - Manru Ren
- Department of Pharmacology, School of Medicine, Shandong University, Jinan 250012, China
| | - Haiyan Lou
- Department of Pharmacology, School of Medicine, Shandong University, Jinan 250012, China
| |
Collapse
|
16
|
Andreasson KI, Bachstetter AD, Colonna M, Ginhoux F, Holmes C, Lamb B, Landreth G, Lee DC, Low D, Lynch MA, Monsonego A, O’Banion MK, Pekny M, Puschmann T, Russek-Blum N, Sandusky LA, Selenica MLB, Takata K, Teeling J, Town T, Van Eldik LJ, Russek-Blum N, Monsonego A, Low D, Takata K, Ginhoux F, Town T, O’Banion MK, Lamb B, Colonna M, Landreth G, Andreasson KI, Sandusky LA, Selenica MLB, Lee DC, Holmes C, Teeling J, Lynch MA, Van Eldik LJ, Bachstetter AD, Pekny M, Puschmann T. Targeting innate immunity for neurodegenerative disorders of the central nervous system. J Neurochem 2016; 138:653-93. [PMID: 27248001 PMCID: PMC5433264 DOI: 10.1111/jnc.13667] [Citation(s) in RCA: 94] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 04/01/2016] [Accepted: 04/30/2016] [Indexed: 12/21/2022]
Abstract
Neuroinflammation is critically involved in numerous neurodegenerative diseases, and key signaling steps of innate immune activation hence represent promising therapeutic targets. This mini review series originated from the 4th Venusberg Meeting on Neuroinflammation held in Bonn, Germany, 7-9th May 2015, presenting updates on innate immunity in acute brain injury and chronic neurodegenerative disorders, such as traumatic brain injury and Alzheimer disease, on the role of astrocytes and microglia, as well as technical developments that may help elucidate neuroinflammatory mechanisms and establish clinical relevance. In this meeting report, a brief overview of physiological and pathological microglia morphology is followed by a synopsis on PGE2 receptors, insights into the role of arginine metabolism and further relevant aspects of neuroinflammation in various clinical settings, and concluded by a presentation of technical challenges and solutions when working with microglia and astrocyte cultures. Microglial ontogeny and induced pluripotent stem cell-derived microglia, advances of TREM2 signaling, and the cytokine paradox in Alzheimer's disease are further contributions to this article. Neuroinflammation is critically involved in numerous neurodegenerative diseases, and key signaling steps of innate immune activation hence represent promising therapeutic targets. This mini review series originated from the 4th Venusberg Meeting on Neuroinflammation held in Bonn, Germany, 7-9th May 2015, presenting updates on innate immunity in acute brain injury and chronic neurodegenerative disorders, such as traumatic brain injury and Alzheimer's disease, on the role of astrocytes and microglia, as well as technical developments that may help elucidate neuroinflammatory mechanisms and establish clinical relevance. In this meeting report, a brief overview on physiological and pathological microglia morphology is followed by a synopsis on PGE2 receptors, insights into the role of arginine metabolism and further relevant aspects of neuroinflammation in various clinical settings, and concluded by a presentation of technical challenges and solutions when working with microglia cultures. Microglial ontogeny and induced pluripotent stem cell-derived microglia, advances of TREM2 signaling, and the cytokine paradox in Alzheimer's disease are further contributions to this article.
Collapse
Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | - Niva Russek-Blum
- The Dead Sea and Arava Science Center, Central Arava Branch, Yair Station, Hazeva, Israel
| | - Alon Monsonego
- The Shraga Segal Dept. of Microbiology, Immunology and Genetics, The Faculty of Health Sciences: The National Institute of Biotechnology in the Negev, and Zlotowski Center for Neuroscience, Ben-Gurion University, Beer-Sheva 84105, Israel
| | - Donovan Low
- Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Singapore
| | - Kazuyuki Takata
- Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Singapore
- Department of Clinical and Translational Physiology, Kyoto Pharmaceutical University, Kyoto, Japan
| | - Florent Ginhoux
- Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Singapore
| | - Terrence Town
- Departments of Physiology and Biophysics, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089,
| | - M. Kerry O’Banion
- Departments of Neuroscience and Neurology, Del Monte Neuromedicine Institute, University of Rochester School of Medicine & Dentistry, Rochester, NY 14642,
| | - Bruce Lamb
- Department of Neurosciences, Cleveland Clinic, Cleveland, OH 44106
| | - Marco Colonna
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110
| | - Gary Landreth
- Department of Neurosciences, Case Western Reserve University 44106
| | - Katrin I. Andreasson
- Department of Neurology and Neurological Sciences, Stanford Neuroscience Institute, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Leslie A. Sandusky
- USF Health Byrd Alzheimer’s Institute, Tampa, FL 33613
- College of Pharmacy & Pharmaceutical Sciences, Tampa, FL 33613
| | - Maj-Linda B. Selenica
- USF Health Byrd Alzheimer’s Institute, Tampa, FL 33613
- College of Pharmacy & Pharmaceutical Sciences, Tampa, FL 33613
| | - Daniel C. Lee
- USF Health Byrd Alzheimer’s Institute, Tampa, FL 33613
- College of Pharmacy & Pharmaceutical Sciences, Tampa, FL 33613
| | - Clive Holmes
- Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton General Hospital, Tremona Road, Southampton, SO16 7YD, United Kingdom
| | - Jessica Teeling
- Centre for Biological Sciences, University of Southampton, Southampton General Hospital, Tremona Road, Southampton, SO16 7YD, United Kingdom
| | | | | | | | - Milos Pekny
- Center for Brain Repair and Rehabilitation, Department of Clinical Neuroscience and Rehabilitation, Institute of Neuroscience and Physiology, Sahlgrenska Academy at the University of Gothenburg, SE-405 30 Gothenburg, Sweden
- Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia
- Hunter Medical Research Institute, University of Newcastle, New South Wales, Australia
| | - Till Puschmann
- Center for Brain Repair and Rehabilitation, Department of Clinical Neuroscience and Rehabilitation, Institute of Neuroscience and Physiology, Sahlgrenska Academy at the University of Gothenburg, SE-405 30 Gothenburg, Sweden
| |
Collapse
|
17
|
Roussos P, Katsel P, Fam P, Tan W, Purohit DP, Haroutunian V. The triggering receptor expressed on myeloid cells 2 (TREM2) is associated with enhanced inflammation, neuropathological lesions and increased risk for Alzheimer's dementia. Alzheimers Dement 2015; 11:1163-70. [PMID: 25499537 PMCID: PMC4461564 DOI: 10.1016/j.jalz.2014.10.013] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Revised: 09/25/2014] [Accepted: 10/27/2014] [Indexed: 12/31/2022]
Abstract
INTRODUCTION The objective of this study was to elucidate the relationship between the triggering receptor expressed on myeloid cells 2 (TREM2) risk variant, neuropathological lesions, alterations in gene and protein expression, and the severity of neuroinflammation. METHODS The genetic association study of the R47 H TREM2 variant with Alzheimer's disease (AD), neuropathology, and changes in TREM2 and TYRO protein tyrosine kinase-binding protein (TYROBP) gene and protein expression, and neuroinflammatory markers. RESULTS The TREM2 variant is associated with: (i) AD (odds ratio: 4.76; P = .014); (ii) increased density of amyloid plaques and neurofibrillary tangles in multiple brain regions; (iii) increased TREM2 (P = .041) and TYROBP (P = .006) gene expression; (iv) decreased TREM2 protein levels (P = .016); and (v) upregulation of proinflammatory cytokines (regulated on activation, normal T cell expressed and secreted [RANTES] and interferon [IFN] gamma) (P = .003) and nominal downregulation of protective markers (α2-macroglobulin, interleukin 4 or IL-4, and ApoA1) (P = .018). DISCUSSION These findings link the TREM2 missense mutation with specific molecular abnormalities and increases in neuropathological lesions in the human brain.
Collapse
Affiliation(s)
- Panos Roussos
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Department of Genetics and Genomic Science and Institute for Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Mental Illness Research, Education, and Clinical Center (VISN 3), James J. Peters VA Medical Center, Bronx, NY, USA
| | - Pavel Katsel
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Peter Fam
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Weilun Tan
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Dushyant P Purohit
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Department of Pathology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Vahram Haroutunian
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Mental Illness Research, Education, and Clinical Center (VISN 3), James J. Peters VA Medical Center, Bronx, NY, USA; Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
| |
Collapse
|
18
|
Yaghmoor F, Noorsaeed A, Alsaggaf S, Aljohani W, Scholtzova H, Boutajangout A, Wisniewski T. The Role of TREM2 in Alzheimer's Disease and Other Neurological Disorders. JOURNAL OF ALZHEIMER'S DISEASE & PARKINSONISM 2014; 4:160. [PMID: 25664220 PMCID: PMC4317331 DOI: 10.4172/2161-0460.1000160] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Alzheimer's disease (AD) is the leading cause of dementia worldwide. Late-onset AD (LOAD), is the most common form of Alzheimer's disease, representing about >95% of cases and early-onset AD represents <5% of cases. Several risk factors have been discovered that are associated with AD, with advancing age being the most prominent. Other environmental risk factors include diabetes mellitus, level of physical activity, educational status, hypertension and head injury. The most well known genetic risk factor for LOAD is inheritance of the apolipoprotein (apo) E4 allele. Recently, rare variants of TREM2 have been reported as a significant risk factor for LOAD, comparable to inheritance of apoE4. In this review we will focus on the role(s) of TREM2 in AD as well as in other neurodegenerative disorders.
Collapse
Affiliation(s)
- Faris Yaghmoor
- Departments of Neurology, New York University School of Medicine, Alexandria ERSP, 450 East 29th Street, New York, NY 10016, USA
| | - Ahmed Noorsaeed
- Pathology, New York University School of Medicine, Alexandria ERSP, 450 East 29th Street, New York, NY 10016, USA
| | - Samar Alsaggaf
- Departments of Neurology, New York University School of Medicine, Alexandria ERSP, 450 East 29th Street, New York, NY 10016, USA
| | - Waleed Aljohani
- Departments of Neurology, New York University School of Medicine, Alexandria ERSP, 450 East 29th Street, New York, NY 10016, USA
| | - Henrieta Scholtzova
- Departments of Neurology, New York University School of Medicine, Alexandria ERSP, 450 East 29th Street, New York, NY 10016, USA
| | - Allal Boutajangout
- Departments of Neurology, New York University School of Medicine, Alexandria ERSP, 450 East 29th Street, New York, NY 10016, USA
- Psychiatry, New York University School of Medicine, Alexandria ERSP, 450 East 29th Street, New York, NY 10016, USA
- Physiology and Neuroscience, New York University School of Medicine, Alexandria ERSP, 450 East 29th Street, New York, NY10016, USA
- King Abdulaziz University, School of Medicine, Jeddah, Saudi Arabia
| | - Thomas Wisniewski
- Departments of Neurology, New York University School of Medicine, Alexandria ERSP, 450 East 29th Street, New York, NY 10016, USA
- Pathology, New York University School of Medicine, Alexandria ERSP, 450 East 29th Street, New York, NY 10016, USA
- Psychiatry, New York University School of Medicine, Alexandria ERSP, 450 East 29th Street, New York, NY 10016, USA
| |
Collapse
|
19
|
Genua M, Rutella S, Correale C, Danese S. The triggering receptor expressed on myeloid cells (TREM) in inflammatory bowel disease pathogenesis. J Transl Med 2014; 12:293. [PMID: 25347935 PMCID: PMC4231187 DOI: 10.1186/s12967-014-0293-z] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Accepted: 10/09/2014] [Indexed: 01/29/2023] Open
Abstract
The Triggering Receptors Expressed on Myeloid cells (TREM) are a family of cell-surface molecules that control inflammation, bone homeostasis, neurological development and blood coagulation. TREM-1 and TREM-2, the best-characterized receptors so far, play divergent roles in several infectious diseases. In the intestine, TREM-1 is highly expressed by macrophages, contributing to inflammatory bowel disease (IBD) pathogenesis. Contrary to current understanding, TREM-2 also promotes inflammation in IBD by fueling dendritic cell functions. This review will focus specifically on recent insights into the role of TREM proteins in IBD development, and discuss opportunities for novel treatment approaches.
Collapse
Affiliation(s)
- Marco Genua
- IBD Center, Humanitas Clinical and Research Hospital, Rozzano, Italy.
| | - Sergio Rutella
- Division of Translational Medicine, Research Branch, Sidra Medical & Research Center, Doha, Qatar.
| | - Carmen Correale
- IBD Center, Humanitas Clinical and Research Hospital, Rozzano, Italy.
| | - Silvio Danese
- IBD Center, Humanitas Clinical and Research Hospital, Rozzano, Italy.
| |
Collapse
|
20
|
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.
Collapse
|
21
|
Benilova I, Gallardo R, Ungureanu AA, Castillo Cano V, Snellinx A, Ramakers M, Bartic C, Rousseau F, Schymkowitz J, De Strooper B. The Alzheimer disease protective mutation A2T modulates kinetic and thermodynamic properties of amyloid-β (Aβ) aggregation. J Biol Chem 2014; 289:30977-89. [PMID: 25253695 DOI: 10.1074/jbc.m114.599027] [Citation(s) in RCA: 118] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Missense mutations in alanine 673 of the amyloid precursor protein (APP), which corresponds to the second alanine of the amyloid β (Aβ) sequence, have dramatic impact on the risk for Alzheimer disease; A2V is causative, and A2T is protective. Assuming a crucial role of amyloid-Aβ in neurodegeneration, we hypothesized that both A2V and A2T mutations cause distinct changes in Aβ properties that may at least partially explain these completely different phenotypes. Using human APP-overexpressing primary neurons, we observed significantly decreased Aβ production in the A2T mutant along with an enhanced Aβ generation in the A2V mutant confirming earlier data from non-neuronal cell lines. More importantly, thioflavin T fluorescence assays revealed that the mutations, while having little effect on Aβ42 peptide aggregation, dramatically change the properties of the Aβ40 pool with A2V accelerating and A2T delaying aggregation of the Aβ peptides. In line with the kinetic data, Aβ A2T demonstrated an increase in the solubility at equilibrium, an effect that was also observed in all mixtures of the A2T mutant with the wild type Aβ40. We propose that in addition to the reduced β-secretase cleavage of APP, the impaired propensity to aggregate may be part of the protective effect conferred by A2T substitution. The interpretation of the protective effect of this mutation is thus much more complicated than proposed previously.
Collapse
Affiliation(s)
- Iryna Benilova
- From the VIB Center for the Biology of Disease, the Center for Human Genetics and Leuven Institute for Neurodegenerative Diseases, University of Leuven
| | - Rodrigo Gallardo
- the VIB Switch Laboratory, the Switch Laboratory, Department of Cellular and Molecular Medicine
| | - Andreea-Alexandra Ungureanu
- Laboratory of Solid State Physics and Magnetism, University of Leuven, 3000 Leuven, and Imec, 3001 Leuven, Belgium
| | - Virginia Castillo Cano
- the VIB Switch Laboratory, the Switch Laboratory, Department of Cellular and Molecular Medicine
| | - An Snellinx
- From the VIB Center for the Biology of Disease, the Center for Human Genetics and Leuven Institute for Neurodegenerative Diseases, University of Leuven
| | - Meine Ramakers
- the VIB Switch Laboratory, the Switch Laboratory, Department of Cellular and Molecular Medicine
| | - Carmen Bartic
- Laboratory of Solid State Physics and Magnetism, University of Leuven, 3000 Leuven, and Imec, 3001 Leuven, Belgium
| | - Frederic Rousseau
- the VIB Switch Laboratory, the Switch Laboratory, Department of Cellular and Molecular Medicine
| | - Joost Schymkowitz
- the VIB Switch Laboratory, the Switch Laboratory, Department of Cellular and Molecular Medicine
| | - Bart De Strooper
- From the VIB Center for the Biology of Disease, the Center for Human Genetics and Leuven Institute for Neurodegenerative Diseases, University of Leuven,
| |
Collapse
|
22
|
Streit WJ, Xue QS. Human CNS immune senescence and neurodegeneration. Curr Opin Immunol 2014; 29:93-6. [PMID: 24908174 DOI: 10.1016/j.coi.2014.05.005] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 05/10/2014] [Accepted: 05/13/2014] [Indexed: 02/07/2023]
Abstract
Microglial cells comprising the brain's immune system are essential for ensuring neuroprotection in the normal and pathological CNS. On the basis of histopathological observations in human brain, we believe that the ability of microglia to provide neuroprotection deteriorates as our brains get older and that such CNS immune senescence is a major factor contributing to the development of aging-related neurodegenerative diseases, notably Alzheimer's disease. The idea is consistent with the fact that immune senescence occurs naturally in the periphery, rendering the elderly people more susceptible to infections and cancers. There is an analogous situation in the brain, except that here the main impact comes down to diminished neuroprotection and resultant neurodegeneration.
Collapse
Affiliation(s)
- Wolfgang J Streit
- Department of Neuroscience, University of Florida College of Medicine and McKnight Brain Institute, Gainesville, FL 32610, USA.
| | - Qing-Shan Xue
- Department of Neuroscience, University of Florida College of Medicine and McKnight Brain Institute, Gainesville, FL 32610, USA
| |
Collapse
|
23
|
Preparation, crystallization, and preliminary crystallographic analysis of wild-type and mutant human TREM-2 ectodomains linked to neurodegenerative and inflammatory diseases. Protein Expr Purif 2014; 96:32-8. [PMID: 24508568 DOI: 10.1016/j.pep.2014.01.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Revised: 01/28/2014] [Accepted: 01/29/2014] [Indexed: 11/22/2022]
Abstract
TREM-2 (triggering receptor expressed on myeloid cells-2) is an innate immune receptor expressed on dendritic cells, macrophages, osteoclasts, and microglia. Recent genetic studies have reported the occurrence of point mutations in TREM-2 that correlate with a dramatically increased risk for the development of neurodegenerative diseases, including Alzheimer's disease, frontotemporal dementia, and Parkinson's disease. Structural and biophysical studies of wild-type and mutant TREM-2 ectodomains are required to understand the functional consequences of these mutations. In order to facilitate these studies, we undertook the production and crystallization of these proteins. Here we demonstrate that, unlike many single Ig domain proteins, TREM-2 could not be readily refolded from bacterially-expressed inclusion bodies. Instead, we developed a mammalian-cell based expression system for the successful production of wild-type and mutant TREM-2 proteins in milligram quantities and a single-chromatography-step purification scheme that produced diffraction-quality crystals. These crystals diffract to a resolution of 3.3 Å and produce data sufficient for structure determination. We describe herein the procedures to produce wild-type and mutant human TREM-2 Ig domains in sufficient quantities for structural and biophysical studies. Such studies are crucial to understand the functional consequences of TREM-2 point mutations linked to the development of neurodegenerative diseases and, ultimately, to develop patient-specific molecular therapies to treat them.
Collapse
|
24
|
Boutajangout A, Wisniewski T. The innate immune system in Alzheimer's disease. Int J Cell Biol 2013; 2013:576383. [PMID: 24223593 PMCID: PMC3809371 DOI: 10.1155/2013/576383] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Accepted: 09/09/2013] [Indexed: 11/17/2022] Open
Abstract
Alzheimer's disease (AD) is the leading cause for dementia in the world. It is characterized by two biochemically distinct types of protein aggregates: amyloid β (A β ) peptide in the forms of parenchymal amyloid plaques and congophilic amyloid angiopathy (CAA) and aggregated tau protein in the form of intraneuronal neurofibrillary tangles (NFT). Several risk factors have been discovered that are associated with AD. The most well-known genetic risk factor for late-onset AD is apolipoprotein E4 (ApoE4) (Potter and Wisniewski (2012), and Verghese et al. (2011)). Recently, it has been reported by two groups independently that a rare functional variant (R47H) of TREM2 is associated with the late-onset risk of AD. TREM2 is expressed on myeloid cells including microglia, macrophages, and dendritic cells, as well as osteoclasts. Microglia are a major part of the innate immune system in the CNS and are also involved in stimulating adaptive immunity. Microglia express several Toll-like receptors (TLRs) and are the resident macrophages of the central nervous system (CNS). In this review, we will focus on the recent advances regarding the role of TREM2, as well as the effects of TLRs 4 and 9 on AD.
Collapse
Affiliation(s)
- Allal Boutajangout
- Department of Neurology, New York University School of Medicine, Alexandria East River Science Park, 450 East 29th Street, Room 802, New York City, NY 10016, USA
- Psychiatry Department, New York University School of Medicine, Alexandria East River Science Park, 450 East 29th Street, Room 802, New York City, NY 10016, USA
- Physiology and Neuroscience Department, New York University School of Medicine, Alexandria East River Science Park, 450 East 29th Street, Room 802, New York City, NY 10016, USA
- King Abdulaziz University, School of Medicine, Jeddah, KAU 21589, Saudi Arabia
| | - Thomas Wisniewski
- Department of Neurology, New York University School of Medicine, Alexandria East River Science Park, 450 East 29th Street, Room 802, New York City, NY 10016, USA
- Psychiatry Department, New York University School of Medicine, Alexandria East River Science Park, 450 East 29th Street, Room 802, New York City, NY 10016, USA
- Pathology, New York University School of Medicine, Alexandria East River Science Park, 450 East 29th Street, Room 802, New York City, NY 10016, USA
| |
Collapse
|
25
|
Zhao Y, Lukiw WJ. TREM2 signaling, miRNA-34a and the extinction of phagocytosis. Front Cell Neurosci 2013; 7:131. [PMID: 24009555 PMCID: PMC3756624 DOI: 10.3389/fncel.2013.00131] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Accepted: 08/02/2013] [Indexed: 01/22/2023] Open
Affiliation(s)
- Yuhai Zhao
- Departments of Neurology, Neuroscience, and Ophthalmology, LSU Neuroscience Center, Louisiana State University Health Sciences Center New Orleans, LA, USA
| | | |
Collapse
|
26
|
Morris GP, Clark IA, Zinn R, Vissel B. Microglia: a new frontier for synaptic plasticity, learning and memory, and neurodegenerative disease research. Neurobiol Learn Mem 2013; 105:40-53. [PMID: 23850597 DOI: 10.1016/j.nlm.2013.07.002] [Citation(s) in RCA: 171] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 07/03/2013] [Indexed: 12/25/2022]
Abstract
We focus on emerging roles for microglia in synaptic plasticity, cognition and disease. We outline evidence that ramified microglia, traditionally thought to be functionally "resting" (i.e. quiescent) in the normal brain, in fact are highly dynamic and plastic. Ramified microglia continually and rapidly extend processes, contact synapses in an activity and experience dependent manner, and play a functionally dynamic role in synaptic plasticity, possibly through release of cytokines and growth factors. Ramified microglial also contribute to structural plasticity through the elimination of synapses via phagocytic mechanisms, which is necessary for normal cognition. Microglia have numerous mechanisms to monitor neuronal activity and numerous mechanisms also exist to prevent them transitioning to an activated state, which involves retraction of their surveying processes. Based on the evidence, we suggest that maintaining the ramified state of microglia is essential for normal synaptic and structural plasticity that supports cognition. Further, we propose that change of their ramified morphology and function, as occurs in inflammation associated with numerous neurological disorders such as Alzheimer's and Parkinson's disease, disrupts their intricate and essential synaptic functions. In turn altered microglia function could cause synaptic dysfunction and excess synapse loss early in disease, initiating a range of pathologies that follow. We conclude that the future of learning and memory research depends on an understanding of the role of non-neuronal cells and that this should include using sophisticated molecular, cellular, physiological and behavioural approaches combined with imaging to causally link the role of microglia to brain function and disease including Alzheimer's and Parkinson's disease and other neuropsychiatric disorders.
Collapse
Affiliation(s)
- Gary P Morris
- Neurodegenerative Disorders, Garvan Institute of Medical Research, Neuroscience Department, Sydney, Australia; Faculty of Medicine, University of New South Wales, Sydney, Australia.
| | | | | | | |
Collapse
|
27
|
Progress in Alzheimer's disease research circa 2013: Is the glass half empty or half full? Alzheimers Res Ther 2013; 5:26. [PMID: 23731836 PMCID: PMC3706787 DOI: 10.1186/alzrt180] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
|