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Giri RK. Molecular signatures in prion disease: altered death receptor pathways in a mouse model. J Transl Med 2024; 22:503. [PMID: 38802941 PMCID: PMC11129387 DOI: 10.1186/s12967-024-05121-x] [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: 12/02/2023] [Accepted: 03/20/2024] [Indexed: 05/29/2024] Open
Abstract
BACKGROUND Prion diseases are transmissible and fatal neurodegenerative diseases characterized by accumulation of misfolded prion protein isoform (PrPSc), astrocytosis, microgliosis, spongiosis, and neurodegeneration. Elevated levels of cell membrane associated PrPSc protein and inflammatory cytokines hint towards the activation of death receptor (DR) pathway/s in prion diseases. Activation of DRs regulate, either cell survival or apoptosis, autophagy and necroptosis based on the adaptors they interact. Very little is known about the DR pathways activation in prion disease. DR3 and DR5 that are expressed in normal mouse brain were never studied in prion disease, so also their ligands and any DR adaptors. This research gap is notable and investigated in the present study. METHODS C57BL/6J mice were infected with Rocky Mountain Laboratory scrapie mouse prion strain. The progression of prion disease was examined by observing morphological and behavioural abnormalities. The levels of PrP isoforms and GFAP were measured as the marker of PrPSc accumulation and astrocytosis respectively using antibody-based techniques that detect proteins on blot and brain section. The levels of DRs, their glycosylation and ectodomain shedding, and associated factors warrant their examination at protein level, hence western blot analysis was employed in this study. RESULTS Prion-infected mice developed motor deficits and neuropathology like PrPSc accumulation and astrocytosis similar to other prion diseases. Results from this research show higher expression of all DR ligands, TNFR1, Fas and p75NTR but decreased levels DR3 and DR5. The levels of DR adaptor proteins like TRADD and TRAF2 (primarily regulate pro-survival pathways) are reduced. FADD, which primarily regulate cell death, its level remains unchanged. RIPK1, which regulate pro-survival, apoptosis and necroptosis, its expression and proteolysis (inhibits necroptosis but activates apoptosis) are increased. CONCLUSIONS The findings from the present study provide evidence towards the involvement of DR3, DR5, DR6, TL1A, TRAIL, TRADD, TRAF2, FADD and RIPK1 for the first time in prion diseases. The knowledge obtained from this research discuss the possible impacts of these 16 differentially expressed DR factors on our understanding towards the multifaceted neuropathology of prion diseases and towards future explorations into potential targeted therapeutic interventions for prion disease specific neuropathology.
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Affiliation(s)
- Ranjit Kumar Giri
- Molecular and Cellular Neuroscience Division, National Brain Research Centre, Manesar, Gurgaon, Haryana, 122052, India.
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Huang X, Qi J, Su Y, Zhou Y, Wang Q, Huang T, Xue D, Zeng Y, Verkhratsky A, Zhou B, Chen H, Yi C. Endothelial DR6 in blood-brain barrier malfunction in Alzheimer's disease. Cell Death Dis 2024; 15:258. [PMID: 38609388 PMCID: PMC11014957 DOI: 10.1038/s41419-024-06639-0] [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] [Revised: 03/26/2024] [Accepted: 04/02/2024] [Indexed: 04/14/2024]
Abstract
The impairment of the blood-brain barrier (BBB) has been increasingly recognised as a critical element in the early pathogenesis of Alzheimer's disease (AD), prompting a focus on brain endothelial cells (BECs), which serve as the primary constituents of the BBB. Death receptor 6 (DR6) is highly expressed in brain vasculature and acts downstream of the Wnt/β-catenin pathway to promote BBB formation during development. Here, we found that brain endothelial DR6 levels were significantly reduced in a murine model of AD (APPswe/PS1dE9 mice) at the onset of amyloid-β (Aβ) accumulation. Toxic Aβ25-35 oligomer treatment recapitulated the reduced DR6 in cultured BECs. We further showed that suppressing DR6 resulted in BBB malfunction in the presence of Aβ25-35 oligomers. In contrast, overexpressing DR6 increased the level of BBB functional proteins through the activation of the Wnt/β-catenin and JNK pathways. More importantly, DR6 overexpression in BECs was sufficient to rescue BBB dysfunction in vitro. In conclusion, our findings provide new insight into the role of endothelial DR6 in AD pathogenesis, highlighting its potential as a therapeutic target to tackle BBB dysfunction in early-stage AD progression.
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Affiliation(s)
- Xiaomin Huang
- Research Centre, Seventh Affiliated Hospital of Sun Yat-sen University, Shenzhen, China
| | - Junhua Qi
- Research Centre, Seventh Affiliated Hospital of Sun Yat-sen University, Shenzhen, China
| | - Yixun Su
- Research Centre, Seventh Affiliated Hospital of Sun Yat-sen University, Shenzhen, China
| | - Ying Zhou
- The Brain Cognition and Brain Disease Institute, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, Guangdong, China
| | - Qi Wang
- Research Centre, Seventh Affiliated Hospital of Sun Yat-sen University, Shenzhen, China
| | - Taida Huang
- Research Centre, Seventh Affiliated Hospital of Sun Yat-sen University, Shenzhen, China
| | - Dongdong Xue
- Research Centre, Seventh Affiliated Hospital of Sun Yat-sen University, Shenzhen, China
| | - Yunxin Zeng
- Research Centre, Seventh Affiliated Hospital of Sun Yat-sen University, Shenzhen, China
| | - Alexei Verkhratsky
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK
- Achucarro Center for Neuroscience, IKERBASQUE, Bilbao, Spain
- Department of Stem Cell Biology, State Research Institute Centre for Innovative Medicine, Vilnius, Lithuania
- Department of Forensic Analytical Toxicology, School of Forensic Medicine, China Medical University, Shenyang, China
| | - Benjie Zhou
- Department of Pharmacy, The Seventh Affiliated Hospital of Sun Yat-sen University, Shenzhen, China.
- Shenzhen Key Laboratory of Chinese Medicine Active Substance Screening and Translational Research, Shenzhen, 518107, China.
| | - Hui Chen
- School of Life Sciences, Faculty of Science, University of Technology Sydney, Ultimo, NSW, 2007, Australia
| | - Chenju Yi
- Research Centre, Seventh Affiliated Hospital of Sun Yat-sen University, Shenzhen, China.
- Shenzhen Key Laboratory of Chinese Medicine Active Substance Screening and Translational Research, Shenzhen, 518107, China.
- Guangdong Provincial Key Laboratory of Brain Function and Disease, Guangzhou, China.
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Pádua MS, Guil-Guerrero JL, Prates JAM, Lopes PA. Insights on the Use of Transgenic Mice Models in Alzheimer's Disease Research. Int J Mol Sci 2024; 25:2805. [PMID: 38474051 DOI: 10.3390/ijms25052805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Revised: 02/26/2024] [Accepted: 02/27/2024] [Indexed: 03/14/2024] Open
Abstract
Alzheimer's disease (AD), the leading cause of dementia, presents a significant global health challenge with no known cure to date. Central to our understanding of AD pathogenesis is the β-amyloid cascade hypothesis, which underlies drug research and discovery efforts. Despite extensive studies, no animal models of AD have completely validated this hypothesis. Effective AD models are essential for accurately replicating key pathological features of the disease, notably the formation of β-amyloid plaques and neurofibrillary tangles. These pathological markers are primarily driven by mutations in the amyloid precursor protein (APP) and presenilin 1 (PS1) genes in familial AD (FAD) and by tau protein mutations for the tangle pathology. Transgenic mice models have been instrumental in AD research, heavily relying on the overexpression of mutated APP genes to simulate disease conditions. However, these models do not entirely replicate the human condition of AD. This review aims to provide a comprehensive evaluation of the historical and ongoing research efforts in AD, particularly through the use of transgenic mice models. It is focused on the benefits gathered from these transgenic mice models in understanding β-amyloid toxicity and the broader biological underpinnings of AD. Additionally, the review critically assesses the application of these models in the preclinical testing of new therapeutic interventions, highlighting the gap between animal models and human clinical realities. This analysis underscores the need for refinement in AD research methodologies to bridge this gap and enhance the translational value of preclinical studies.
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Affiliation(s)
- Mafalda Soares Pádua
- CIISA-Centro de Investigação Interdisciplinar em Sanidade Animal, Faculdade de Medicina Veterinária, Universidade de Lisboa, 1300-477 Lisbon, Portugal
- Laboratório Associado para Ciência Animal e Veterinária (AL4AnimalS), Faculdade de Medicina Veterinária, Universidade de Lisboa, 1300-477 Lisbon, Portugal
| | - José L Guil-Guerrero
- Departamento de Tecnología de Alimentos, Universidad de Almería, 04120 Almería, Spain
| | - José A M Prates
- CIISA-Centro de Investigação Interdisciplinar em Sanidade Animal, Faculdade de Medicina Veterinária, Universidade de Lisboa, 1300-477 Lisbon, Portugal
- Laboratório Associado para Ciência Animal e Veterinária (AL4AnimalS), Faculdade de Medicina Veterinária, Universidade de Lisboa, 1300-477 Lisbon, Portugal
| | - Paula Alexandra Lopes
- CIISA-Centro de Investigação Interdisciplinar em Sanidade Animal, Faculdade de Medicina Veterinária, Universidade de Lisboa, 1300-477 Lisbon, Portugal
- Laboratório Associado para Ciência Animal e Veterinária (AL4AnimalS), Faculdade de Medicina Veterinária, Universidade de Lisboa, 1300-477 Lisbon, Portugal
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4
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Dean B, Duce J, Li QX, Masters CL, Scarr E. Lower levels of soluble β-amyloid precursor protein, but not β-amyloid, in the frontal cortex in schizophrenia. Psychiatry Res 2024; 331:115656. [PMID: 38071879 DOI: 10.1016/j.psychres.2023.115656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Revised: 11/28/2023] [Accepted: 12/01/2023] [Indexed: 01/02/2024]
Abstract
We identified a sub-group (25%) of people with schizophrenia (muscarinic receptor deficit schizophrenia (MRDS)) that are characterised because of markedly lower levels of cortical muscarinic M1 receptors (CHRM1) compared to most people with the disorder (non-MRDS). Notably, bioinformatic analyses of our cortical gene expression data shows a disturbance in the homeostasis of a biochemical pathway that regulates levels of CHRM1. A step in this pathway is the processing of β-amyloid precursor protein (APP) and therefore we postulated there would be altered levels of APP in the frontal cortex from people with MRDS. Here we measure levels of CHRM1 using [3H]pirenzepine binding, soluble APP (sAPP) using Western blotting and amyloid beta peptides (Aβ1-40 and Aβ1-42) using ELISA in the frontal cortex (Brodmann's area 6: BA 6; MRDS = 14, non-MRDS = 14, controls = 14). We confirmed the MRDS cohort in this study had the expected low levels of [3H]pirenzepine binding. In addition, we showed that people with schizophrenia, independent of their sub-group status, had lower levels of sAPP compared to controls but did not have altered levels of Aβ1-40 or Aβ1-42. In conclusion, whilst changes in sAPP are not restricted to MRDS our data could indicate a role of APP, which is important in axonal and synaptic pruning, in the molecular pathology of the syndrome of schizophrenia.
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Affiliation(s)
- Brian Dean
- The Florey, Parkville, Victoria, Australia; The University of Melbourne of Melbourne Florey Department of Neuroscience and Mental Health, Parkville, Victoria, Australia.
| | - James Duce
- MSD Discovery Centre, 120 Moorgate, London, UK
| | - Qiao-Xin Li
- The Florey, Parkville, Victoria, Australia; The University of Melbourne of Melbourne Florey Department of Neuroscience and Mental Health, Parkville, Victoria, Australia
| | - Colin L Masters
- The Florey, Parkville, Victoria, Australia; The University of Melbourne of Melbourne Florey Department of Neuroscience and Mental Health, Parkville, Victoria, Australia
| | - Elizabeth Scarr
- The Department of Psychiatry, The University of Melbourne, Parkville, Victoria, Australia
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Ciccone L, Nencetti S, Rossello A, Orlandini E. Pomegranate: A Source of Multifunctional Bioactive Compounds Potentially Beneficial in Alzheimer's Disease. Pharmaceuticals (Basel) 2023; 16:1036. [PMID: 37513947 PMCID: PMC10385237 DOI: 10.3390/ph16071036] [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: 05/12/2023] [Revised: 07/07/2023] [Accepted: 07/20/2023] [Indexed: 07/30/2023] Open
Abstract
Pomegranate fruit (PF) is a fruit rich in nutraceuticals. Nonedible parts of the fruit, especially peels, contain high amounts of bioactive components that have been largely used in traditional medicine, such as the Chinese, Unani, and Ayurvedic ones, for treating several diseases. Polyphenols such as anthocyanins, tannins, flavonoids, phenolic acids, and lignans are the major bioactive molecules present in PF. Therefore, PF is considered a source of natural multifunctional agents that exert simultaneously antioxidant, anti-inflammatory, antitumor, antidiabetic, cardiovascular, and neuroprotective activities. Recently, several studies have reported that the nutraceuticals contained in PF (seed, peel, and juice) have a potential beneficial role in Alzheimer's disease (AD). Research suggests that the neuroprotective effect of PF is mostly due to its potent antioxidant and anti-inflammatory activities which contribute to attenuate the neuroinflammation associated with AD. Despite the numerous works conducted on PF, to date the mechanism by which PF acts in combatting AD is not completely known. Here, we summarize all the recent findings (in vitro and in vivo studies) related to the positive effects that PF and its bioactive components can have in the neurodegeneration processes occurring during AD. Moreover, considering the high biotransformation characteristics of the nutraceuticals present in PF, we propose to consider the chemical structure of its active metabolites as a source of inspiration to design new molecules with the same beneficial effects but less prone to be affected by the metabolic degradation process.
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Affiliation(s)
- Lidia Ciccone
- Department of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy
| | - Susanna Nencetti
- Department of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy
| | - Armando Rossello
- Department of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy
- Research Center "E. Piaggio", University of Pisa, 56122 Pisa, Italy
| | - Elisabetta Orlandini
- Research Center "E. Piaggio", University of Pisa, 56122 Pisa, Italy
- Department of Earth Sciences, University of Pisa, Via Santa Maria 53, 56126 Pisa, Italy
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Lee SH, Rezzonico MG, Friedman BA, Huntley MH, Meilandt WJ, Pandey S, Chen YJJ, Easton A, Modrusan Z, Hansen DV, Sheng M, Bohlen CJ. TREM2-independent oligodendrocyte, astrocyte, and T cell responses to tau and amyloid pathology in mouse models of Alzheimer disease. Cell Rep 2021; 37:110158. [DOI: 10.1016/j.celrep.2021.110158] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 09/11/2021] [Accepted: 12/01/2021] [Indexed: 01/04/2023] Open
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Zhang J, Zhao ZJ, Fu X, Niu H, Hu C, Dong Y, Cui MZ, Zhang F, Zeng L, Xu X. Proapoptotic Mitochondrial Carrier Homolog Protein PSAP Mediates Death Receptor 6 Induced Apoptosis. J Alzheimers Dis 2021; 74:1097-1106. [PMID: 32144986 DOI: 10.3233/jad-191086] [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] [Indexed: 11/15/2022]
Abstract
Presenilin-associated protein (PSAP) was originally identified as a mitochondrial proapoptotic protein. To further explore the apoptotic pathway that involves PSAP, our yeast two-hybrid screen revealed that PSAP interacts with a death receptor, DR6. DR6 is a relatively less common member of the death receptor family and has been shown to mediate the neurotoxicity of amyloid-β, mutant SOD1, and prion proteins and has also been implicated in the regulation of immune cell proliferation and differentiation. Our previous study showed that DR6 induces apoptosis via a unique mitochondria-dependent pathway different from the conventional death receptor-mediated extrinsic apoptotic pathways. Thus, the interaction of DR6 with PSAP established a direct molecular link between DR6 and mitochondrial apoptotic pathway. We investigated the possible role of PSAP in DR6-induced apoptosis. Interestingly, it was discovered that knockdown of PSAP strongly inhibited DR6-induced apoptosis. To further elucidate the mechanism by which PSAP mediates DR6-induced mitochondria-dependent apoptosis, our data demonstrated that knockdown of PSAP blocked DR6-induced Bax translocation and cytochrome c release from the mitochondria. Moreover, it was found that both PSAP and DR6 form complexes with Bax, but at different subcellular locations. The DR6-Bax complex was detected in the cytosolic fraction while the PSAP-Bax complex was detected in the mitochondrial fraction. The observation that knockdown of DR6 significantly reduced the amount of PSAP-Bax complex detected in mitochondria suggests a possibility that DR6-bound Bax is transferred to PSAP upon interaction with PSAP at the mitochondria, leading to cytochrome c release and eventually apoptosis.
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Affiliation(s)
- Jingtian Zhang
- Edmond H. Fischer Signal Transduction Laboratory, College of Life Sciences, Jilin University, Changchun, China
| | - Zhizhuang Joe Zhao
- Edmond H. Fischer Signal Transduction Laboratory, College of Life Sciences, Jilin University, Changchun, China.,Department of Pathology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Xueqi Fu
- Edmond H. Fischer Signal Transduction Laboratory, College of Life Sciences, Jilin University, Changchun, China
| | - Han Niu
- Edmond H. Fischer Signal Transduction Laboratory, College of Life Sciences, Jilin University, Changchun, China
| | - Chen Hu
- School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Yunzhou Dong
- Vascular Biology Program, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Mei-Zhen Cui
- Department of Biology, College of Arts and Sciences, University of Texas of the Permian Basin, Odessa, TX, USA
| | - Fuqiang Zhang
- Scientific Research Centre of China-Japan Union Hospital, Jilin University, Changchun, China
| | - Linlin Zeng
- Edmond H. Fischer Signal Transduction Laboratory, College of Life Sciences, Jilin University, Changchun, China
| | - Xuemin Xu
- Department of Biology, College of Arts and Sciences, University of Texas of the Permian Basin, Odessa, TX, USA
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8
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Lee SH, Meilandt WJ, Xie L, Gandham VD, Ngu H, Barck KH, Rezzonico MG, Imperio J, Lalehzadeh G, Huntley MA, Stark KL, Foreman O, Carano RA, Friedman BA, Sheng M, Easton A, Bohlen CJ, Hansen DV. Trem2 restrains the enhancement of tau accumulation and neurodegeneration by β-amyloid pathology. Neuron 2021; 109:1283-1301.e6. [DOI: 10.1016/j.neuron.2021.02.010] [Citation(s) in RCA: 70] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 01/07/2021] [Accepted: 02/08/2021] [Indexed: 12/15/2022]
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9
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Wu XL, Chen Y, Kong WC, Zhao ZQ. Amyloid precursor protein regulates 5-fluorouracil resistance in human hepatocellular carcinoma cells by inhibiting the mitochondrial apoptotic pathway. J Zhejiang Univ Sci B 2021; 21:234-245. [PMID: 32133800 DOI: 10.1631/jzus.b1900413] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Hepatocellular carcinoma (HCC) is a malignant tumor with high morbidity and mortality globally. It accounts for the majority of primary liver cancer cases. Amyloid precursor protein (APP), a cell membrane protein, plays a vital role in the pathogenesis of Alzheimer's disease, and has been found to be implicated in tumor growth and metastasis. Therefore, to understand the relationship between APP and 5-fluorouracil (5-FU) resistance in liver cancer, Cell Counting Kit-8, apoptosis and cell cycle assays, western blotting, and reverse transcription-quantitative polymerase chain reaction (qPCR) analysis were performed. The results demonstrated that APP expression in Bel7402-5-FU cells was significantly up-regulated, as compared with that in Bel7402 cells. Through successful construction of APP-silenced (siAPP) and overexpressed (OE) Bel7402 cell lines, data revealed that the Bel7402-APP751-OE cell line was insensitive, while the Bel7402-siAPP cell line was sensitive to 5-FU in comparison to the matched control group. Furthermore, APP overexpression decreased, while APP silencing increased 5-FU-induced apoptosis in Bel7402 cells. Mechanistically, APP overexpression and silencing can regulate the mitochondrial apoptotic pathway and the expression of apoptotic suppressor genes (B-cell lymphoma-2 (Bcl-2) and B-cell lymphoma-extra large (Bcl-xl)). Taken together, these results preliminarily revealed that APP overexpression contributes to the resistance of liver cancer cells to 5-FU, providing a new perspective for drug resistance.
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Affiliation(s)
- Xiao-Long Wu
- Department of Oncology, 900 Hospital of the Joint Logistics Team, Fuzhou 350025, China
| | - Ying Chen
- Department of Oncology, 900 Hospital of the Joint Logistics Team, Fuzhou 350025, China
| | - Wen-Cui Kong
- Department of Oncology, 900 Hospital of the Joint Logistics Team, Fuzhou 350025, China
| | - Zhong-Quan Zhao
- Department of Oncology, 900 Hospital of the Joint Logistics Team, Fuzhou 350025, China
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10
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Whiteley AM, Prado MA, de Poot SAH, Paulo JA, Ashton M, Dominguez S, Weber M, Ngu H, Szpyt J, Jedrychowski MP, Easton A, Gygi SP, Kurz T, Monteiro MJ, Brown EJ, Finley D. Global proteomics of Ubqln2-based murine models of ALS. J Biol Chem 2020; 296:100153. [PMID: 33277362 PMCID: PMC7873701 DOI: 10.1074/jbc.ra120.015960] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Revised: 11/21/2020] [Accepted: 12/04/2020] [Indexed: 12/12/2022] Open
Abstract
Familial neurodegenerative diseases commonly involve mutations that result in either aberrant proteins or dysfunctional components of the proteolytic machinery that act on aberrant proteins. UBQLN2 is a ubiquitin receptor of the UBL/UBA family that binds the proteasome through its ubiquitin-like domain and is thought to deliver ubiquitinated proteins to proteasomes for degradation. UBQLN2 mutations result in familial amyotrophic lateral sclerosis (ALS)/frontotemporal dementia in humans through an unknown mechanism. Quantitative multiplexed proteomics was used to provide for the first time an unbiased and global analysis of the role of Ubqln2 in controlling the composition of the proteome. We studied several murine models of Ubqln2-linked ALS and also generated Ubqln2 null mutant mice. We identified impacts of Ubqln2 on diverse physiological pathways, most notably serotonergic signaling. Interestingly, we observed an upregulation of proteasome subunits, suggesting a compensatory response to diminished proteasome output. Among the specific proteins whose abundance is linked to UBQLN2 function, the strongest hits were the ubiquitin ligase TRIM32 and two retroelement-derived proteins, PEG10 and CXX1B. Cycloheximide chase studies using induced human neurons and HEK293 cells suggested that PEG10 and TRIM32 are direct clients. Although UBQLN2 directs the degradation of multiple proteins via the proteasome, it surprisingly conferred strong protection from degradation on the Gag-like protein CXX1B, which is expressed from the same family of retroelement genes as PEG10. In summary, this study charts the proteomic landscape of ALS-related Ubqln2 mutants and identifies candidate client proteins that are altered in vivo in disease models and whose degradation is promoted by UBQLN2.
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Affiliation(s)
| | - Miguel A Prado
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA
| | | | - Joao A Paulo
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA
| | - Marissa Ashton
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA
| | - Sara Dominguez
- Department of Neuroscience, Genentech Inc, South San Francisco, California, USA
| | - Martin Weber
- Department of Neuroscience, Genentech Inc, South San Francisco, California, USA
| | - Hai Ngu
- Department of Pathology, Genentech Inc, South San Francisco, California, USA
| | - John Szpyt
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA
| | - Mark P Jedrychowski
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA
| | - Amy Easton
- Department of Neuroscience, Genentech Inc, South San Francisco, California, USA
| | - Steven P Gygi
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA
| | - Thimo Kurz
- Henry Wellcome Lab of Cell Biology, College of Medical, Veterinary and Life Sciences, Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow, United Kingdom
| | - Mervyn J Monteiro
- Center for Biomedical Engineering and Technology, Department of Anatomy and Neurobiology, University of Maryland Medical School, Baltimore, Maryland, USA
| | - Eric J Brown
- Department of Immunology and Infectious Diseases, Genentech Inc, South San Francisco, California, USA
| | - Daniel Finley
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA.
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11
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Mishra V, Re DB, Le Verche V, Alvarez MJ, Vasciaveo A, Jacquier A, Doulias PT, Greco TM, Nizzardo M, Papadimitriou D, Nagata T, Rinchetti P, Perez-Torres EJ, Politi KA, Ikiz B, Clare K, Than ME, Corti S, Ischiropoulos H, Lotti F, Califano A, Przedborski S. Systematic elucidation of neuron-astrocyte interaction in models of amyotrophic lateral sclerosis using multi-modal integrated bioinformatics workflow. Nat Commun 2020; 11:5579. [PMID: 33149111 PMCID: PMC7642391 DOI: 10.1038/s41467-020-19177-y] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 10/02/2020] [Indexed: 12/31/2022] Open
Abstract
Cell-to-cell communications are critical determinants of pathophysiological phenotypes, but methodologies for their systematic elucidation are lacking. Herein, we propose an approach for the Systematic Elucidation and Assessment of Regulatory Cell-to-cell Interaction Networks (SEARCHIN) to identify ligand-mediated interactions between distinct cellular compartments. To test this approach, we selected a model of amyotrophic lateral sclerosis (ALS), in which astrocytes expressing mutant superoxide dismutase-1 (mutSOD1) kill wild-type motor neurons (MNs) by an unknown mechanism. Our integrative analysis that combines proteomics and regulatory network analysis infers the interaction between astrocyte-released amyloid precursor protein (APP) and death receptor-6 (DR6) on MNs as the top predicted ligand-receptor pair. The inferred deleterious role of APP and DR6 is confirmed in vitro in models of ALS. Moreover, the DR6 knockdown in MNs of transgenic mutSOD1 mice attenuates the ALS-like phenotype. Our results support the usefulness of integrative, systems biology approach to gain insights into complex neurobiological disease processes as in ALS and posit that the proposed methodology is not restricted to this biological context and could be used in a variety of other non-cell-autonomous communication mechanisms.
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Affiliation(s)
- Vartika Mishra
- Departments of Pathology and Cell Biology, Columbia University, New York, NY, 10032, USA
- Center for Motor Neuron Biology and Diseases, Columbia University, New York, NY, 10032, USA
- Spark Therapeutics, 3737 Market Street, Philadelphia, PA, 19104, USA
| | - Diane B Re
- Center for Motor Neuron Biology and Diseases, Columbia University, New York, NY, 10032, USA
- Department of Environmental Health Sciences, Columbia University, New York, NY, 10032, USA
| | - Virginia Le Verche
- Departments of Pathology and Cell Biology, Columbia University, New York, NY, 10032, USA
- Center for Motor Neuron Biology and Diseases, Columbia University, New York, NY, 10032, USA
- Center for Gene Therapy, City of Hope, 1500 E. Duarte Road, Duarte, CA, 91010, USA
| | - Mariano J Alvarez
- Department of Systems Biology, Columbia University, New York, NY, 10032, USA
- DarwinHealth Inc., New York, NY, 10032, USA
| | - Alessandro Vasciaveo
- Department of Systems Biology, Columbia University, New York, NY, 10032, USA
- Herbert Irving Comprehensive Cancer Center, Columbia University, New York, NY, USA
| | - Arnaud Jacquier
- Departments of Pathology and Cell Biology, Columbia University, New York, NY, 10032, USA
- Center for Motor Neuron Biology and Diseases, Columbia University, New York, NY, 10032, USA
- Institut NeuroMyoGène, CNRS UMR 5310 - INSERM U1217 - Université de Lyon - Université Claude Bernard Lyon 1, Lyon, France
| | - Paschalis-Tomas Doulias
- Department of Pediatrics, Children's Hospital of Philadelphia Research Institute and the University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Todd M Greco
- Department of Pediatrics, Children's Hospital of Philadelphia Research Institute and the University of Pennsylvania, Philadelphia, PA, 19104, USA
- Department of Molecular Biology, Princeton University, Princeton, USA
| | - Monica Nizzardo
- Departments of Pathology and Cell Biology, Columbia University, New York, NY, 10032, USA
- Center for Motor Neuron Biology and Diseases, Columbia University, New York, NY, 10032, USA
- Dino Ferrari Center, Department of Pathophysiology and Transplantation, University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, 20122, Italy
| | - Dimitra Papadimitriou
- Departments of Pathology and Cell Biology, Columbia University, New York, NY, 10032, USA
- Center for Motor Neuron Biology and Diseases, Columbia University, New York, NY, 10032, USA
- Henry Dunant Hospital, BRFAA, Athens, Greece
| | - Tetsuya Nagata
- Departments of Pathology and Cell Biology, Columbia University, New York, NY, 10032, USA
- Center for Motor Neuron Biology and Diseases, Columbia University, New York, NY, 10032, USA
- Department of Neurology and Neurological Science, Tokyo Medical and Dental University, Tokyo, Japan
| | - Paola Rinchetti
- Departments of Pathology and Cell Biology, Columbia University, New York, NY, 10032, USA
- Center for Motor Neuron Biology and Diseases, Columbia University, New York, NY, 10032, USA
- Dino Ferrari Center, Department of Pathophysiology and Transplantation, University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, 20122, Italy
| | - Eduardo J Perez-Torres
- Departments of Pathology and Cell Biology, Columbia University, New York, NY, 10032, USA
- Center for Motor Neuron Biology and Diseases, Columbia University, New York, NY, 10032, USA
| | - Kristin A Politi
- Departments of Pathology and Cell Biology, Columbia University, New York, NY, 10032, USA
- Center for Motor Neuron Biology and Diseases, Columbia University, New York, NY, 10032, USA
| | - Burcin Ikiz
- Departments of Pathology and Cell Biology, Columbia University, New York, NY, 10032, USA
- Center for Motor Neuron Biology and Diseases, Columbia University, New York, NY, 10032, USA
| | - Kevin Clare
- Departments of Pathology and Cell Biology, Columbia University, New York, NY, 10032, USA
- Center for Motor Neuron Biology and Diseases, Columbia University, New York, NY, 10032, USA
- New York Medical College, Valhalla, NY, 10595, USA
| | - Manuel E Than
- Protein Crystallography Group, Leibniz Institute on Aging - Fritz Lipmann Institute (FLI), Beutenbergstr. 11, 07745, Jena, Germany
| | - Stefania Corti
- Dino Ferrari Center, Department of Pathophysiology and Transplantation, University of Milan, Neurology Unit, IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Milan, 20122, Italy
| | - Harry Ischiropoulos
- Department of Pediatrics, Children's Hospital of Philadelphia Research Institute and the University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Francesco Lotti
- Departments of Pathology and Cell Biology, Columbia University, New York, NY, 10032, USA
- Center for Motor Neuron Biology and Diseases, Columbia University, New York, NY, 10032, USA
| | - Andrea Califano
- Center for Motor Neuron Biology and Diseases, Columbia University, New York, NY, 10032, USA.
- Department of Systems Biology, Columbia University, New York, NY, 10032, USA.
- Herbert Irving Comprehensive Cancer Center, Columbia University, New York, NY, USA.
- J.P. Sulzberger Columbia Genome Center, Columbia University, New York, NY, USA.
- Department of Biomedical Informatics, Columbia University, New York, NY, USA.
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA.
| | - Serge Przedborski
- Departments of Pathology and Cell Biology, Columbia University, New York, NY, 10032, USA.
- Center for Motor Neuron Biology and Diseases, Columbia University, New York, NY, 10032, USA.
- Departments of Neurology and Neuroscience, Columbia University, New York, NY, 10032, USA.
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12
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Peters van Ton AM, Verbeek MM, Alkema W, Pickkers P, Abdo WF. Downregulation of synapse-associated protein expression and loss of homeostatic microglial control in cerebrospinal fluid of infectious patients with delirium and patients with Alzheimer's disease. Brain Behav Immun 2020; 89:656-667. [PMID: 32592865 DOI: 10.1016/j.bbi.2020.06.027] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 06/18/2020] [Accepted: 06/18/2020] [Indexed: 12/16/2022] Open
Abstract
Delirium is a complex and multifactorial condition associated with long-term cognitive decline. Due to the strong links between systemic inflammation, delirium and dementia we hypothesized that responses within the brain in patients who develop delirium could show biochemical overlap with patients with Alzheimer's disease (AD). In this observational study we analyzed protein expression signatures in cerebrospinal fluid (CSF) from 15 patients with infectious delirium and compared these to 29 patients with AD, 30 infectious patients without delirium and 15 non-infectious controls free of neurological disease. A proximity extension assay was performed measuring a total of 184 inflammatory and neurology-related proteins. Eight inflammatory proteins (4%), including the key neuron-microglia communication marker CX3CL1 (fractalkine), were significantly upregulated in both delirium and AD, compared to infectious patients without delirium. Likewise, 23 proteins (13%) showed downregulation in both delirium and AD, relative to infectious patients without delirium, which interestingly included CD200R1, another neuron-microglia communication marker, as well as a cluster of proteins related to synapse formation and function. Synaptopathy is an early event in AD and correlates strongly with cognitive dysfunction. These results were partially mediated by aging, which is an important predisposing risk factor among many others for both conditions. Within this study we report the first in vivo human evidence suggesting that synapse pathology and loss of homeostatic microglial control is involved in the pathophysiology of both infectious delirium and AD and thus may provide a link for the association between infections, delirium and long-term cognitive decline.
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Affiliation(s)
- A M Peters van Ton
- Radboudumc, Radboud Institute for Molecular Life Sciences, Department of Intensive Care Medicine, Nijmegen, The Netherlands; Radboudumc, Radboud Center for Infectious Diseases, Nijmegen, The Netherlands
| | - M M Verbeek
- Radboudumc, Donders Center of Medical Neurosciences, Department of Neurology, Nijmegen, The Netherlands; Radboudumc, Department of Laboratory Medicine, Nijmegen, The Netherlands
| | - W Alkema
- Radboudumc, Radboud Institute for Molecular Life Sciences, Center for Molecular and Biomolecular Informatics, Nijmegen, The Netherlands
| | - P Pickkers
- Radboudumc, Radboud Institute for Molecular Life Sciences, Department of Intensive Care Medicine, Nijmegen, The Netherlands; Radboudumc, Radboud Center for Infectious Diseases, Nijmegen, The Netherlands
| | - W F Abdo
- Radboudumc, Radboud Institute for Molecular Life Sciences, Department of Intensive Care Medicine, Nijmegen, The Netherlands; Radboudumc, Radboud Center for Infectious Diseases, Nijmegen, The Netherlands.
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13
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Trem2 Deletion Reduces Late-Stage Amyloid Plaque Accumulation, Elevates the Aβ42:Aβ40 Ratio, and Exacerbates Axonal Dystrophy and Dendritic Spine Loss in the PS2APP Alzheimer's Mouse Model. J Neurosci 2020; 40:1956-1974. [PMID: 31980586 PMCID: PMC7046459 DOI: 10.1523/jneurosci.1871-19.2019] [Citation(s) in RCA: 93] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 12/08/2019] [Accepted: 12/23/2019] [Indexed: 01/17/2023] Open
Abstract
TREM2 is an Alzheimer's disease (AD) risk gene expressed in microglia. To study the role of Trem2 in a mouse model of β-amyloidosis, we compared PS2APP transgenic mice versus PS2APP mice lacking Trem2 (PS2APP;Trem2ko) at ages ranging from 4 to 22 months. Microgliosis was impaired in PS2APP;Trem2ko mice, with Trem2-deficient microglia showing compromised expression of proliferation/Wnt-related genes and marked accumulation of ApoE. TREM2 is an Alzheimer's disease (AD) risk gene expressed in microglia. To study the role of Trem2 in a mouse model of β-amyloidosis, we compared PS2APP transgenic mice versus PS2APP mice lacking Trem2 (PS2APP;Trem2ko) at ages ranging from 4 to 22 months. Microgliosis was impaired in PS2APP;Trem2ko mice, with Trem2-deficient microglia showing compromised expression of proliferation/Wnt-related genes and marked accumulation of ApoE. Plaque abundance was elevated in PS2APP;Trem2ko females at 6–7 months; but by 12 or 19–22 months of age, it was notably diminished in female and male PS2APP;Trem2ko mice, respectively. Across all ages, plaque morphology was more diffuse in PS2APP;Trem2ko brains, and the Aβ42:Aβ40 ratio was elevated. The amount of soluble, fibrillar Aβ oligomers also increased in PS2APP;Trem2ko hippocampi. Associated with these changes, axonal dystrophy was exacerbated from 6 to 7 months onward in PS2APP;Trem2ko mice, notwithstanding the reduced plaque load at later ages. PS2APP;Trem2ko mice also exhibited more dendritic spine loss around plaque and more neurofilament light chain in CSF. Thus, aggravated neuritic dystrophy is a more consistent outcome of Trem2 deficiency than amyloid plaque load, suggesting that the microglial packing of Aβ into dense plaque is an important neuroprotective activity. SIGNIFICANCE STATEMENT Genetic studies indicate that TREM2 gene mutations confer increased Alzheimer's disease (AD) risk. We studied the effects of Trem2 deletion in the PS2APP mouse AD model, in which overproduction of Aβ peptide leads to amyloid plaque formation and associated neuritic dystrophy. Interestingly, neuritic dystrophies were intensified in the brains of Trem2-deficient mice, despite these mice displaying reduced plaque accumulation at later ages (12–22 months). Microglial clustering around plaques was impaired, plaques were more diffuse, and the Aβ42:Aβ40 ratio and amount of soluble, fibrillar Aβ oligomers were elevated in Trem2-deficient brains. These results suggest that the Trem2-dependent compaction of Aβ into dense plaques is a protective microglial activity, limiting the exposure of neurons to toxic Aβ species.
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14
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Meilandt WJ, Maloney JA, Imperio J, Lalehzadeh G, Earr T, Crowell S, Bainbridge TW, Lu Y, Ernst JA, Fuji RN, Atwal JK. Characterization of the selective in vitro and in vivo binding properties of crenezumab to oligomeric Aβ. ALZHEIMERS RESEARCH & THERAPY 2019; 11:97. [PMID: 31787113 PMCID: PMC6886224 DOI: 10.1186/s13195-019-0553-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Accepted: 11/06/2019] [Indexed: 02/01/2023]
Abstract
Background Accumulation of amyloid β (Aβ) in the brain is proposed as a cause of Alzheimer’s disease (AD), with Aβ oligomers hypothesized to be the primary mediators of neurotoxicity. Crenezumab is a humanized immunoglobulin G4 monoclonal antibody that has been shown to bind to synthetic monomeric and aggregated Aβ in vitro; however, less is known about the binding characteristic in vivo. In this study, we evaluated the binding patterns of crenezumab to synthetic and native forms of Aβ both in vitro and in vivo. Methods Crenezumab was used to immunoprecipitate Aβ from synthetic Aβ preparations or brain homogenates from a PS2APP mouse model of AD to determine the forms of Aβ that crenezumab interacts with. Following systemic dosing in PS2APP or nontransgenic control mice, immunohistochemistry was used to localize crenezumab and assess its relative distribution in the brain, compared with amyloid plaques and markers of neuritic dystrophies (BACE1; LAMP1). Pharmacodynamic correlations were performed to investigate the relationship between peripheral and central target engagement. Results In vitro, crenezumab immunoprecipitated Aβ oligomers from both synthetic Aβ preparations and endogenous brain homogenates from PS2APP mice. In vivo studies in the PS2APP mouse showed that crenezumab localizes to regions surrounding the periphery of amyloid plaques in addition to the hippocampal mossy fibers. These regions around the plaques are reported to be enriched in oligomeric Aβ, actively incorporate soluble Aβ, and contribute to Aβ-induced neurotoxicity and axonal dystrophy. In addition, crenezumab did not appear to bind to the dense core region of plaques or vascular amyloid. Conclusions Crenezumab binds to multiple forms of amyloid β (Aβ), particularly oligomeric forms, and localizes to brain areas rich in Aβ oligomers, including the halo around plaques and hippocampal mossy fibers, but not to vascular Aβ. These insights highlight a unique mechanism of action for crenezumab of engaging Aβ oligomers.
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Affiliation(s)
- William J Meilandt
- Department of Neuroscience, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA
| | - Janice A Maloney
- Department of Neuroscience, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA
| | - Jose Imperio
- Department of Neuroscience, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA
| | - Guita Lalehzadeh
- Department of Neuroscience, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA
| | - Tim Earr
- Department of Neuroscience, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA
| | - Susan Crowell
- Department of Preclinical and Translational Pharmacokinetics/Pharmacodynamics, Genentech, Inc., 1 DNA Way, South San Francisco, CA, USA
| | - Travis W Bainbridge
- Department of Protein Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, CA, USA
| | - Yanmei Lu
- Department of Biochemical and Cellular Pharmacology, Genentech, Inc., 1 DNA Way, South San Francisco, CA, USA
| | - James A Ernst
- Department of Protein Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, CA, USA
| | - Reina N Fuji
- Department of Safety Assessment Pathology, Genentech, Inc., 1 DNA Way, South San Francisco, CA, USA
| | - Jasvinder K Atwal
- Department of Neuroscience, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA.
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15
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Yong Y, Gamage K, Cheng I, Barford K, Spano A, Winckler B, Deppmann C. p75NTR and DR6 Regulate Distinct Phases of Axon Degeneration Demarcated by Spheroid Rupture. J Neurosci 2019; 39:9503-9520. [PMID: 31628183 PMCID: PMC6880466 DOI: 10.1523/jneurosci.1867-19.2019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 09/11/2019] [Accepted: 10/13/2019] [Indexed: 12/19/2022] Open
Abstract
The regressive events associated with trophic deprivation are critical for sculpting a functional nervous system. After nerve growth factor withdrawal, sympathetic axons derived from male and female neonatal mice maintain their structural integrity for ∼18 h (latent phase) followed by a rapid and near unison disassembly of axons over the next 3 h (catastrophic phase). Here we examine the molecular basis by which axons transition from latent to catastrophic phases of degeneration following trophic withdrawal. Before catastrophic degeneration, we observed an increase in intra-axonal calcium. This calcium flux is accompanied by p75 neurotrophic factor receptor-Rho-actin-dependent expansion of calcium-rich axonal spheroids that eventually rupture, releasing their contents to the extracellular space. Conditioned media derived from degenerating axons are capable of hastening transition into the catastrophic phase of degeneration. We also found that death receptor 6, but not p75 neurotrophic factor receptor, is required for transition into the catastrophic phase in response to conditioned media but not for the intra-axonal calcium flux, spheroid formation, or rupture that occur toward the end of latency. Our results support the existence of an interaxonal degenerative signal that promotes catastrophic degeneration among trophically deprived axons.SIGNIFICANCE STATEMENT Developmental pruning shares several morphological similarities to both disease- and injury-induced degeneration, including spheroid formation. The function and underlying mechanisms governing axonal spheroid formation, however, remain unclear. In this study, we report that axons coordinate each other's degeneration during development via axonal spheroid rupture. Before irreversible breakdown of the axon in response to trophic withdrawal, p75 neurotrophic factor receptor-RhoA signaling governs the formation and growth of spheroids. These spheroids then rupture, allowing exchange of contents ≤10 kDa between the intracellular and extracellular space to drive death receptor 6 and calpain-dependent catastrophic degeneration. This finding informs not only our understanding of regressive events during development but may also provide a rationale for designing new treatments toward myriad neurodegenerative disorders.
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Affiliation(s)
| | - Kanchana Gamage
- Department of Cell Biology
- Amgen, Massachusetts & Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, Massachusetts 02138
| | - Irene Cheng
- Department of Biology
- Neuroscience Graduate Program
| | | | | | | | - Christopher Deppmann
- Department of Biology,
- Neuroscience Graduate Program
- Department of Cell Biology
- Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia 22903, and
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16
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García-González L, Pilat D, Baranger K, Rivera S. Emerging Alternative Proteinases in APP Metabolism and Alzheimer's Disease Pathogenesis: A Focus on MT1-MMP and MT5-MMP. Front Aging Neurosci 2019; 11:244. [PMID: 31607898 PMCID: PMC6769103 DOI: 10.3389/fnagi.2019.00244] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2019] [Accepted: 08/20/2019] [Indexed: 12/12/2022] Open
Abstract
Processing of amyloid beta precursor protein (APP) into amyloid-beta peptide (Aβ) by β-secretase and γ-secretase complex is at the heart of the pathogenesis of Alzheimer’s disease (AD). Targeting this proteolytic pathway effectively reduces/prevents pathology and cognitive decline in preclinical experimental models of the disease, but therapeutic strategies based on secretase activity modifying drugs have so far failed in clinical trials. Although this may raise some doubts on the relevance of β- and γ-secretases as targets, new APP-cleaving enzymes, including meprin-β, legumain (δ-secretase), rhomboid-like protein-4 (RHBDL4), caspases and membrane-type matrix metalloproteinases (MT-MMPs/η-secretases) have confirmed that APP processing remains a solid mechanism in AD pathophysiology. This review will discuss recent findings on the roles of all these proteinases in the nervous system, and in particular on the roles of MT-MMPs, which are at the crossroads of pathological events involving not only amyloidogenesis, but also inflammation and synaptic dysfunctions. Assessing the potential of these emerging proteinases in the Alzheimer’s field opens up new research prospects to improve our knowledge of fundamental mechanisms of the disease and help us establish new therapeutic strategies.
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Affiliation(s)
| | - Dominika Pilat
- Aix-Marseille Univ, CNRS, INP, Inst Neurophysiopathol, Marseille, France
| | - Kévin Baranger
- Aix-Marseille Univ, CNRS, INP, Inst Neurophysiopathol, Marseille, France
| | - Santiago Rivera
- Aix-Marseille Univ, CNRS, INP, Inst Neurophysiopathol, Marseille, France
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17
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Bellozi PMQ, Gomes GF, da Silva MCM, Lima IVDA, Batista CRÁ, Carneiro Junior WDO, Dória JG, Vieira ÉLM, Vieira RP, de Freitas RP, Ferreira CN, Candelario-Jalil E, Wyss-Coray T, Ribeiro FM, de Oliveira ACP. A positive allosteric modulator of mGluR5 promotes neuroprotective effects in mouse models of Alzheimer's disease. Neuropharmacology 2019; 160:107785. [PMID: 31541651 DOI: 10.1016/j.neuropharm.2019.107785] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 09/06/2019] [Accepted: 09/17/2019] [Indexed: 12/26/2022]
Abstract
Alzheimer's Disease (AD) is the most prevalent neurodegenerative disorder. Despite advances in the understanding of its pathophysiology, none of the available therapies prevents disease progression. Excess glutamate plays an important role in excitotoxicity by activating ionotropic receptors. However, the mechanisms modulating neuronal cell survival/death via metabotropic glutamate receptors (mGluRs) are not completely understood. Recent data indicates that CDPPB, a positive allosteric modulator of mGluR5, has neuroprotective effects. Thus, this work aimed to investigate CDPPB treatment effects on amyloid-β (Aβ) induced pathological alterations in vitro and in vivo and in a transgenic mouse model of AD (T41 mice). Aβ induced cell death in primary cultures of hippocampal neurons, which was prevented by CDPPB. Male C57BL/6 mice underwent stereotaxic surgery for unilateral intra-hippocampal Aβ injection, which induced memory deficits, neurodegeneration, neuronal viability reduction and decrease of doublecortin-positive cells, a marker of immature neurons and neuronal proliferation. Treatment with CDPPB for 8 days reversed neurodegeneration and doublecortin-positive cells loss and recovered memory function. Fourteen months old T41 mice presented cognitive deficits, neuronal viability reduction, gliosis and Aβ accumulation. Treatment with CDPPB for 28 days increased neuronal viability (32.2% increase in NeuN+ cells) and reduced gliosis in CA1 region (Iba-1+ area by 31.3% and GFAP+ area by 37.5%) in transgenic animals, without inducing hepatotoxicity. However, it did not reverse cognitive deficit. Despite a four-week treatment did not prevent memory loss in aged transgenic mice, CDPPB is protective against Aβ stimulus. Therefore, this drug represents a potential candidate for further investigations as AD treatment.
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Affiliation(s)
| | - Giovanni Freitas Gomes
- Department of Pharmacology, Universidade Federal de Minas Gerais, Belo Horizonte, 31270-901, Brazil
| | | | | | | | | | - Juliana Guimarães Dória
- Department of Biochemistry and Immunology, Universidade Federal de Minas Gerais, Belo Horizonte, 31270-901, Brazil
| | | | - Rafael Pinto Vieira
- Department of Biochemistry and Immunology, Universidade Federal de Minas Gerais, Belo Horizonte, 31270-901, Brazil
| | | | - Claudia Natália Ferreira
- Clinical Pathology Sector of COLTEC, Universidade Federal de Minas Gerais, Belo Horizonte, 31270-901, Brazil
| | | | - Tony Wyss-Coray
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Fabíola Mara Ribeiro
- Department of Biochemistry and Immunology, Universidade Federal de Minas Gerais, Belo Horizonte, 31270-901, Brazil
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Penserga T, Kudumala SR, Poulos R, Godenschwege TA. A Role for Drosophila Amyloid Precursor Protein in Retrograde Trafficking of L1-Type Cell Adhesion Molecule Neuroglian. Front Cell Neurosci 2019; 13:322. [PMID: 31354437 PMCID: PMC6640005 DOI: 10.3389/fncel.2019.00322] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Accepted: 07/01/2019] [Indexed: 11/21/2022] Open
Abstract
The role of the Amyloid Precursor Protein (APP) in the pathology of Alzheimer’s disease (AD) has been well studied. However, the normal function of APP in the nervous system is poorly understood. Here, we characterized the role of the Drosophila homolog (APPL) in the adult giant fiber (GF) neurons. We find that endogenous APPL is transported from the synapse to the soma in the adult. Live-imaging revealed that retrograde moving APPL vesicles co-traffic with L1-type cell adhesion molecule Neuroglian (Nrg). In APPL null mutants, stationary Nrg vesicles were increased along the axon, and the number of Nrg vesicles moving in retrograde but not anterograde direction was reduced. In contrast, trafficking of endo-lysosomal vesicles, which did not co-localize with APPL in GF axons, was not affected. This suggests that APPL loss of function does not generally disrupt axonal transport but that APPL has a selective role in the effectiveness of retrograde transport of proteins it co-traffics with. While the GF terminals of APPL loss of function animals exhibited pruning defects, APPL gain of function had no disruptive effect on GF morphology and function, or on retrograde axonal transport of Nrg. However, cell-autonomous developmental expression of a secretion-deficient form of APPL (APPL-SD), lacking the α-, β-, and, γ-secretase cleavage sites, resulted in progressive retraction of the GF terminals. Conditional expression of APPL-SD in mature GFs caused accumulation of Nrg in normal sized synaptic terminals, which was associated with severely reduced retrograde flux of Nrg labeled vesicles in the axons. Albeit β-secretase null mutants developed GF terminals they also exhibited Nrg accumulations. This suggests that cleavage defective APPL has a toxic effect on retrograde trafficking and that β-secretase cleavage has a function in Nrg sorting in endosomal compartments at the synapse. In summary, our results suggest a role for APPL and its proteolytic cleavage sites in retrograde trafficking, thus our findings are of relevance to the understanding of the endogenous role of APP as well as to the development of therapeutic treatments of Alzheimer’s disease.
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Affiliation(s)
- Tyrone Penserga
- Department of Biological Sciences, Florida Atlantic University, Jupiter, FL, United States
| | - Sirisha Rani Kudumala
- Department of Biological Sciences, Florida Atlantic University, Jupiter, FL, United States
| | - Richelle Poulos
- Department of Biological Sciences, Florida Atlantic University, Jupiter, FL, United States
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19
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Faw TD, Lerch JK, Thaxton TT, Deibert RJ, Fisher LC, Basso DM. Unique Sensory and Motor Behavior in Thy1-GFP-M Mice before and after Spinal Cord Injury. J Neurotrauma 2018; 35:2167-2182. [PMID: 29385890 DOI: 10.1089/neu.2017.5395] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Sensorimotor recovery after spinal cord injury (SCI) is of utmost importance to injured individuals and will rely on improved understanding of SCI pathology and recovery. Novel transgenic mouse lines facilitate discovery, but must be understood to be effective. The purpose of this study was to characterize the sensory and motor behavior of a common transgenic mouse line (Thy1-GFP-M) before and after SCI. Thy1-GFP-M positive (TG+) mice and their transgene negative littermates (TG-) were acquired from two sources (in-house colony, n = 32, Jackson Laboratories, n = 4). C57BL/6J wild-type (WT) mice (Jackson Laboratories, n = 10) were strain controls. Moderate-severe T9 contusion (SCI) or transection (TX) occurred in TG+ (SCI, n = 25, TX, n = 5), TG- (SCI, n = 5), and WT (SCI, n = 10) mice. To determine responsiveness to rehabilitation, a cohort of TG+ mice with SCI (n = 4) had flat treadmill (TM) training 42-49 days post-injury (dpi). To characterize recovery, we performed Basso Mouse Scale, Grid Walk, von Frey Hair, and Plantar Heat Testing before and out to day 42 post-SCI. Open field locomotion was significantly better in the Thy1 SCI groups (TG+ and TG-) compared with WT by 7 dpi (p < 0.01) and was maintained through 42 dpi (p < 0.01). These unexpected locomotor gains were not apparent during grid walking, indicating severe impairment of precise motor control. Thy1 derived mice were hypersensitive to mechanical stimuli at baseline (p < 0.05). After SCI, mechanical hyposensitivity emerged in Thy1 derived groups (p < 0.001), while thermal hyperalgesia occurred in all groups (p < 0.001). Importantly, consistent findings across TG+ and TG- groups suggest that the effects are mediated by the genetic background rather than transgene manipulation itself. Surprisingly, TM training restored mechanical and thermal sensation to baseline levels in TG+ mice with SCI. This behavioral profile and responsiveness to chronic training will be important to consider when choosing models to study the mechanisms underlying sensorimotor recovery after SCI.
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Affiliation(s)
- Timothy D Faw
- 1 Neuroscience Graduate Program, The Ohio State University , Columbus, Ohio.,2 School of Health and Rehabilitation Sciences, The Ohio State University , Columbus, Ohio.,3 Center for Brain and Spinal Cord Repair, The Ohio State University , Columbus, Ohio
| | - Jessica K Lerch
- 3 Center for Brain and Spinal Cord Repair, The Ohio State University , Columbus, Ohio.,4 Department of Neuroscience, The Ohio State University , Columbus, Ohio
| | - Tyler T Thaxton
- 2 School of Health and Rehabilitation Sciences, The Ohio State University , Columbus, Ohio.,3 Center for Brain and Spinal Cord Repair, The Ohio State University , Columbus, Ohio
| | - Rochelle J Deibert
- 2 School of Health and Rehabilitation Sciences, The Ohio State University , Columbus, Ohio.,3 Center for Brain and Spinal Cord Repair, The Ohio State University , Columbus, Ohio
| | - Lesley C Fisher
- 2 School of Health and Rehabilitation Sciences, The Ohio State University , Columbus, Ohio.,3 Center for Brain and Spinal Cord Repair, The Ohio State University , Columbus, Ohio
| | - D Michele Basso
- 2 School of Health and Rehabilitation Sciences, The Ohio State University , Columbus, Ohio.,3 Center for Brain and Spinal Cord Repair, The Ohio State University , Columbus, Ohio
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20
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Le Pichon CE, Meilandt WJ, Dominguez S, Solanoy H, Lin H, Ngu H, Gogineni A, Sengupta Ghosh A, Jiang Z, Lee SH, Maloney J, Gandham VD, Pozniak CD, Wang B, Lee S, Siu M, Patel S, Modrusan Z, Liu X, Rudhard Y, Baca M, Gustafson A, Kaminker J, Carano RAD, Huang EJ, Foreman O, Weimer R, Scearce-Levie K, Lewcock JW. Loss of dual leucine zipper kinase signaling is protective in animal models of neurodegenerative disease. Sci Transl Med 2018; 9:9/403/eaag0394. [PMID: 28814543 DOI: 10.1126/scitranslmed.aag0394] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 11/23/2016] [Accepted: 03/27/2017] [Indexed: 12/16/2022]
Abstract
Hallmarks of chronic neurodegenerative disease include progressive synaptic loss and neuronal cell death, yet the cellular pathways that underlie these processes remain largely undefined. We provide evidence that dual leucine zipper kinase (DLK) is an essential regulator of the progressive neurodegeneration that occurs in amyotrophic lateral sclerosis and Alzheimer's disease. We demonstrate that DLK/c-Jun N-terminal kinase signaling was increased in mouse models and human patients with these disorders and that genetic deletion of DLK protected against axon degeneration, neuronal loss, and functional decline in vivo. Furthermore, pharmacological inhibition of DLK activity was sufficient to attenuate the neuronal stress response and to provide functional benefit even in the presence of ongoing disease. These findings demonstrate that pathological activation of DLK is a conserved mechanism that regulates neurodegeneration and suggest that DLK inhibition may be a potential approach to treat multiple neurodegenerative diseases.
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Affiliation(s)
- Claire E Le Pichon
- Department of Neuroscience, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - William J Meilandt
- Department of Neuroscience, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA.
| | - Sara Dominguez
- Department of Neuroscience, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Hilda Solanoy
- Department of Neuroscience, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Han Lin
- Department of Neuroscience, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Hai Ngu
- Department of Pathology, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Alvin Gogineni
- Department of Biomedical Imaging, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | | | - Zhiyu Jiang
- Department of Neuroscience, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Seung-Hye Lee
- Department of Neuroscience, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Janice Maloney
- Department of Neuroscience, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Vineela D Gandham
- Department of Biomedical Imaging, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Christine D Pozniak
- Department of Neuroscience, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Bei Wang
- Department of Neuroscience, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Sebum Lee
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Michael Siu
- Department of Discovery Chemistry, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Snahel Patel
- Department of Discovery Chemistry, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Zora Modrusan
- Department of Molecular Biology, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Xingrong Liu
- Department of Drug Metabolism and Pharmacokinetics, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - York Rudhard
- In Vitro Pharmacology, Evotec AG, Manfred Eigen Campus, 22419 Hamburg, Germany
| | - Miriam Baca
- Department of Pathology, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Amy Gustafson
- Department of Biochemical and Cellular Pharmacology, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Josh Kaminker
- Department of Bioinformatics, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Richard A D Carano
- Department of Biomedical Imaging, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Eric J Huang
- Department of Pathology, University of California, San Francisco, San Francisco, CA 94143, USA.,Pathology Service 113B, San Francisco Veterans Affairs Medical Center, San Francisco, CA 94121, USA
| | - Oded Foreman
- Department of Pathology, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Robby Weimer
- Department of Biomedical Imaging, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Kimberly Scearce-Levie
- Department of Neuroscience, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA
| | - Joseph W Lewcock
- Department of Neuroscience, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA.
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21
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Fricker M, Tolkovsky AM, Borutaite V, Coleman M, Brown GC. Neuronal Cell Death. Physiol Rev 2018; 98:813-880. [PMID: 29488822 PMCID: PMC5966715 DOI: 10.1152/physrev.00011.2017] [Citation(s) in RCA: 654] [Impact Index Per Article: 109.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Revised: 05/23/2017] [Accepted: 07/10/2017] [Indexed: 02/07/2023] Open
Abstract
Neuronal cell death occurs extensively during development and pathology, where it is especially important because of the limited capacity of adult neurons to proliferate or be replaced. The concept of cell death used to be simple as there were just two or three types, so we just had to work out which type was involved in our particular pathology and then block it. However, we now know that there are at least a dozen ways for neurons to die, that blocking a particular mechanism of cell death may not prevent the cell from dying, and that non-neuronal cells also contribute to neuronal death. We review here the mechanisms of neuronal death by intrinsic and extrinsic apoptosis, oncosis, necroptosis, parthanatos, ferroptosis, sarmoptosis, autophagic cell death, autosis, autolysis, paraptosis, pyroptosis, phagoptosis, and mitochondrial permeability transition. We next explore the mechanisms of neuronal death during development, and those induced by axotomy, aberrant cell-cycle reentry, glutamate (excitoxicity and oxytosis), loss of connected neurons, aggregated proteins and the unfolded protein response, oxidants, inflammation, and microglia. We then reassess which forms of cell death occur in stroke and Alzheimer's disease, two of the most important pathologies involving neuronal cell death. We also discuss why it has been so difficult to pinpoint the type of neuronal death involved, if and why the mechanism of neuronal death matters, the molecular overlap and interplay between death subroutines, and the therapeutic implications of these multiple overlapping forms of neuronal death.
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Affiliation(s)
- Michael Fricker
- Hunter Medical Research Institute, University of Newcastle, Callaghan, New South Wales , Australia ; Department of Clinical Neurosciences, University of Cambridge , Cambridge , United Kingdom ; Neuroscience Institute, Lithuanian University of Health Sciences , Kaunas , Lithuania ; and Department of Biochemistry, University of Cambridge , Cambridge , United Kingdom
| | - Aviva M Tolkovsky
- Hunter Medical Research Institute, University of Newcastle, Callaghan, New South Wales , Australia ; Department of Clinical Neurosciences, University of Cambridge , Cambridge , United Kingdom ; Neuroscience Institute, Lithuanian University of Health Sciences , Kaunas , Lithuania ; and Department of Biochemistry, University of Cambridge , Cambridge , United Kingdom
| | - Vilmante Borutaite
- Hunter Medical Research Institute, University of Newcastle, Callaghan, New South Wales , Australia ; Department of Clinical Neurosciences, University of Cambridge , Cambridge , United Kingdom ; Neuroscience Institute, Lithuanian University of Health Sciences , Kaunas , Lithuania ; and Department of Biochemistry, University of Cambridge , Cambridge , United Kingdom
| | - Michael Coleman
- Hunter Medical Research Institute, University of Newcastle, Callaghan, New South Wales , Australia ; Department of Clinical Neurosciences, University of Cambridge , Cambridge , United Kingdom ; Neuroscience Institute, Lithuanian University of Health Sciences , Kaunas , Lithuania ; and Department of Biochemistry, University of Cambridge , Cambridge , United Kingdom
| | - Guy C Brown
- Hunter Medical Research Institute, University of Newcastle, Callaghan, New South Wales , Australia ; Department of Clinical Neurosciences, University of Cambridge , Cambridge , United Kingdom ; Neuroscience Institute, Lithuanian University of Health Sciences , Kaunas , Lithuania ; and Department of Biochemistry, University of Cambridge , Cambridge , United Kingdom
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22
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Braidy N, Essa MM, Poljak A, Selvaraju S, Al-Adawi S, Manivasagm T, Thenmozhi AJ, Ooi L, Sachdev P, Guillemin GJ. Consumption of pomegranates improves synaptic function in a transgenic mice model of Alzheimer's disease. Oncotarget 2018; 7:64589-64604. [PMID: 27486879 PMCID: PMC5323101 DOI: 10.18632/oncotarget.10905] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 06/17/2016] [Indexed: 01/18/2023] Open
Abstract
Alzheimer's Disease (AD) is a progressive neurodegenerative disorder characterized by extracellular plaques containing abnormal Amyloid Beta (Aβ) aggregates, intracellular neurofibrillary tangles containing hyperphosphorylated tau protein, microglia-dominated neuroinflammation, and impairments in synaptic plasticity underlying cognitive deficits. Therapeutic strategies for the treatment of AD are currently limited. In this study, we investigated the effects of dietary supplementation of 4% pomegranate extract to a standard chow diet on neuroinflammation, and synaptic plasticity in APPsw/Tg2576 mice brain. Treatment with a custom mixed diet (pellets) containing 4% pomegranate for 15 months ameliorated the loss of synaptic structure proteins, namely PSD-95, Munc18-1, and SNAP25, synaptophysin, phosphorylation of Calcium/Calmodulin Dependent Protein Kinase IIα (p-CaMKIIα/ CaMKIIα), and phosphorylation of Cyclic AMP-Response Element Binding Protein (pCREB/CREB), inhibited neuroinflammatory activity, and enhanced autophagy, and activation of the phophoinositide-3-kinase-Akt-mammalian target of rapamycin signaling pathway. These neuroprotective effects were associated with reduced β-site cleavage of Amyloid Precursor Protein in APPsw/Tg2576 mice. Therefore, long-term supplementation with pomegranates can attenuate AD pathology by reducing inflammation, and altering APP-dependent processes.
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Affiliation(s)
- Nady Braidy
- Centre for Healthy Brain Ageing, School of Psychiatry, Faculty of Medicine, University of New South Wales, Sydney, Australia
| | - Musthafa Mohamed Essa
- Department of Food Science and Nutrition, College of Agricultural and Marine Sciences, Sultan Qaboos University, Al Khoudh, Oman.,Ageing and Dementia Research Group, Sultan Qaboos University, Al Khoudh, Oman
| | - Anne Poljak
- Centre for Healthy Brain Ageing, School of Psychiatry, Faculty of Medicine, University of New South Wales, Sydney, Australia.,College of Medicine and Health Sciences, Sultan Qaboos University, Al Khoudh, Oman
| | - Subash Selvaraju
- Department of Food Science and Nutrition, College of Agricultural and Marine Sciences, Sultan Qaboos University, Al Khoudh, Oman.,Ageing and Dementia Research Group, Sultan Qaboos University, Al Khoudh, Oman
| | - Samir Al-Adawi
- Department of Food Science and Nutrition, College of Agricultural and Marine Sciences, Sultan Qaboos University, Al Khoudh, Oman.,College of Medicine and Health Sciences, Sultan Qaboos University, Al Khoudh, Oman
| | | | | | - Lezanne Ooi
- Illawarra Health and Medical Research Institute, University of Wollongong, NSW, Australia
| | - Perminder Sachdev
- Centre for Healthy Brain Ageing, School of Psychiatry, Faculty of Medicine, University of New South Wales, Sydney, Australia.,Neuropsychiatric Institute, The Prince of Wales Hospital, Sydney, Australia
| | - Gilles J Guillemin
- Neuroinflammation Group, MND and Neurodegenerative Diseases Research Centre, Macquarie University, NSW, Australia
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23
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Colombo A, Hsia HE, Wang M, Kuhn PH, Brill MS, Canevazzi P, Feederle R, Taveggia C, Misgeld T, Lichtenthaler SF. Non-cell-autonomous function of DR6 in Schwann cell proliferation. EMBO J 2018; 37:embj.201797390. [PMID: 29459438 DOI: 10.15252/embj.201797390] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Revised: 12/20/2017] [Accepted: 01/16/2018] [Indexed: 12/21/2022] Open
Abstract
Death receptor 6 (DR6) is an orphan member of the TNF receptor superfamily and controls cell death and differentiation in a cell-autonomous manner in different cell types. Here, we report an additional non-cell-autonomous function for DR6 in the peripheral nervous system (PNS). DR6-knockout (DR6 KO) mice showed precocious myelination in the PNS Using an in vitro myelination assay, we demonstrate that neuronal DR6 acts in trans on Schwann cells (SCs) and reduces SC proliferation and myelination independently of its cytoplasmic death domain. Mechanistically, DR6 was found to be cleaved in neurons by "a disintegrin and metalloprotease 10" (ADAM10), releasing the soluble DR6 ectodomain (sDR6). Notably, in the in vitro myelination assay, sDR6 was sufficient to rescue the DR6 KO phenotype. Thus, in addition to the cell-autonomous receptor function of full-length DR6, the proteolytically released sDR6 can unexpectedly also act as a paracrine signaling factor in the PNS in a non-cell-autonomous manner during SC proliferation and myelination. This new mode of DR6 signaling will be relevant in future attempts to target DR6 in disease settings.
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Affiliation(s)
- Alessio Colombo
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
| | - Hung-En Hsia
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany.,Neuroproteomics, Klinikum rechts der Isar, and Institute for Advanced Study, Technical University Munich, Munich, Germany
| | - Mengzhe Wang
- Institute of Neuronal Cell Biology, Technical University of Munich, Munich, Germany
| | - Peer-Hendrik Kuhn
- Neuroproteomics, Klinikum rechts der Isar, and Institute for Advanced Study, Technical University Munich, Munich, Germany
| | - Monika S Brill
- Institute of Neuronal Cell Biology, Technical University of Munich, Munich, Germany
| | - Paolo Canevazzi
- Division of Neuroscience, INSPE at San Raffaele Scientific Institute, Milan, Italy
| | - Regina Feederle
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany.,Institute for Diabetes and Obesity, Monoclonal Antibody Research Group, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Munich, Germany.,Munich Center for Systems Neurology (SyNergy), Munich, Germany
| | - Carla Taveggia
- Division of Neuroscience, INSPE at San Raffaele Scientific Institute, Milan, Italy
| | - Thomas Misgeld
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany.,Institute of Neuronal Cell Biology, Technical University of Munich, Munich, Germany.,Munich Center for Systems Neurology (SyNergy), Munich, Germany.,Center for Integrated Protein Sciences (CIPSM), Munich, Germany
| | - Stefan F Lichtenthaler
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany .,Neuroproteomics, Klinikum rechts der Isar, and Institute for Advanced Study, Technical University Munich, Munich, Germany.,Munich Center for Systems Neurology (SyNergy), Munich, Germany
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24
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Hollville E, Deshmukh M. Physiological functions of non-apoptotic caspase activity in the nervous system. Semin Cell Dev Biol 2017; 82:127-136. [PMID: 29199140 DOI: 10.1016/j.semcdb.2017.11.037] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 11/22/2017] [Accepted: 11/29/2017] [Indexed: 12/15/2022]
Abstract
Caspases are cysteine proteases that play important and well-defined roles in apoptosis and inflammation. Increasing evidence point to alternative functions of caspases where restricted and localized caspase activation within neurons allows for a variety of non-apoptotic and non-inflammatory processes required for brain development and function. In this review, we highlight sublethal caspase functions in axon and dendrite pruning, neurite outgrowth and dendrite branches formation, as well as in long-term depression and synaptic plasticity. Importantly, as non-apoptotic activity of caspases is often confined in space and time in neurons, we also discuss the mechanisms that restrict caspase activity in order to maintain the neuronal networks in a healthy and functional state.
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Affiliation(s)
| | - Mohanish Deshmukh
- Neuroscience Center, UNC Chapel Hill, Chapel Hill, NC, USA; Department of Cell Biology and Physiology, UNC Chapel Hill, Chapel Hill, NC, USA.
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25
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Prostaglandin J2 promotes O-GlcNAcylation raising APP processing by α- and β-secretases: relevance to Alzheimer's disease. Neurobiol Aging 2017; 62:130-145. [PMID: 29149631 DOI: 10.1016/j.neurobiolaging.2017.10.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2017] [Revised: 09/26/2017] [Accepted: 10/11/2017] [Indexed: 12/19/2022]
Abstract
Regulation of the amyloid precursor protein (APP) processing by α- and β-secretases is of special interest to Alzheimer's disease (AD), as these proteases prevent or mediate amyloid beta formation, respectively. Neuroinflammation is also implicated in AD. Our data demonstrate that the endogenous mediator of inflammation prostaglandin J2 (PGJ2) promotes full-length APP (FL-APP) processing by α- and β-secretases. The decrease in FL-APP was independent of proteasomal, lysosomal, calpain, caspase, and γ-secretase activities. Moreover, PGJ2-treatment promoted cleavage of secreted APP, specifically sAPPα and sAPPβ, generated by α and β-secretase, respectively. Notably, PGJ2-treatment induced caspase-dependent cleavage of sAPPβ. Mechanistically, PGJ2-treatment selectively diminished mature (O- and N-glycosylated) but not immature (N-glycosylated only) FL-APP. PGJ2-treatment also increased the overall levels of protein O-GlcNAcylation, which occurs within the nucleocytoplasmic compartment. It is known that APP undergoes O-GlcNAcylation and that the latter protects proteins from proteasomal degradation. Our results suggest that by increasing protein O-GlcNAcylation levels, PGJ2 renders mature APP less prone to proteasomal degradation, thus shunting APP toward processing by α- and β-secretases.
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26
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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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27
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Not just amyloid: physiological functions of the amyloid precursor protein family. Nat Rev Neurosci 2017; 18:281-298. [PMID: 28360418 DOI: 10.1038/nrn.2017.29] [Citation(s) in RCA: 381] [Impact Index Per Article: 54.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Amyloid precursor protein (APP) gives rise to the amyloid-β peptide and thus has a key role in the pathogenesis of Alzheimer disease. By contrast, the physiological functions of APP and the closely related APP-like proteins (APLPs) remain less well understood. Studying these physiological functions has been challenging and has required a careful long-term strategy, including the analysis of different App-knockout and Aplp-knockout mice. In this Review, we summarize these findings, focusing on the in vivo roles of APP family members and their processing products for CNS development, synapse formation and function, brain injury and neuroprotection, as well as ageing. In addition, we discuss the implications of APP physiology for therapeutic approaches.
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28
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BACE1 across species: a comparison of the in vivo consequences of BACE1 deletion in mice and rats. Sci Rep 2017; 7:44249. [PMID: 28281673 PMCID: PMC5345047 DOI: 10.1038/srep44249] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 02/06/2017] [Indexed: 01/18/2023] Open
Abstract
Assessing BACE1 (β-site APP cleaving enzyme 1) knockout mice for general health and neurological function may be useful in predicting risks associated with prolonged pharmacological BACE1 inhibition, a treatment approach currently being developed for Alzheimer’s disease. To determine whether BACE1 deletion-associated effects in mice generalize to another species, we developed a novel Bace1−/− rat line using zinc-finger nuclease technology and compared Bace1−/− mice and rats with their Bace1+/+ counterparts. Lack of BACE1 was confirmed in Bace1−/− animals from both species. Removal of BACE1 affected startle magnitude, balance beam performance, pain response, and nerve myelination in both species. While both mice and rats lacking BACE1 have shown increased mortality, the increase was smaller and restricted to early developmental stages for rats. Bace1−/− mice and rats further differed in body weight, spontaneous locomotor activity, and prepulse inhibition of startle. While the effects of species and genetic background on these phenotypes remain difficult to distinguish, our findings suggest that BACE1’s role in myelination and some sensorimotor functions is consistent between mice and rats and may be conserved in other species. Other phenotypes differ between these models, suggesting that some effects of BACE1 inhibition vary with the biological context (e.g. species or background strain).
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29
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Physiological role for amyloid precursor protein in adult experience-dependent plasticity. Proc Natl Acad Sci U S A 2016; 113:7912-7. [PMID: 27354516 DOI: 10.1073/pnas.1604299113] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Changes in neural circuits after experience-dependent plasticity are brought about by the formation of new circuits via axonal growth and pruning. Here, using a combination of electrophysiology, adeno-associated virus-delivered fluorescent proteins, analysis of mutant mice, and two-photon microscopy, we follow long-range horizontally projecting axons in primary somatosensory cortex before and after selective whisker plucking. Whisker plucking induces axonal growth and pruning of horizontal projecting axons from neurons located in the surrounding intact whisker representations. We report that amyloid precursor protein is crucial for axonal pruning and contributes in a cell autonomous way.
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30
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Unsain N, Barker PA. New Views on the Misconstrued: Executioner Caspases and Their Diverse Non-apoptotic Roles. Neuron 2016; 88:461-74. [PMID: 26539888 DOI: 10.1016/j.neuron.2015.08.029] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Initially characterized for their roles in apoptosis, executioner caspases have emerged as important regulators of an array of cellular activities. This is especially true in the nervous system, where sublethal caspase activity has been implicated in axonal pathfinding and branching, axonal degeneration, dendrite pruning, regeneration, long-term depression, and metaplasticity. Here we examine the roles of sublethal executioner caspase activity in nervous system development and maintenance, consider the mechanisms that locally activate and restrain these potential killers, and discuss how their activity be subverted in neurodegenerative disease.
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Affiliation(s)
- Nicolas Unsain
- Laboratorio de Neurobiología, Instituto de Investigación Médica Mercedes y Martín Ferreyra, Instituto Nacional de Investigación Médica Córdoba-Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional de Córdoba, Friuli 2434, Córdoba (5016), Argentina
| | - Philip A Barker
- Irving K. Barber School of Arts and Sciences, University of British Columbia, Kelowna, BC V1V 1V7, Canada.
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31
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The crystal structure of DR6 in complex with the amyloid precursor protein provides insight into death receptor activation. Genes Dev 2015; 29:785-90. [PMID: 25838500 PMCID: PMC4403255 DOI: 10.1101/gad.257675.114] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 03/09/2015] [Indexed: 11/25/2022]
Abstract
Death receptor 6 (DR6) was recently shown to bind amyloid precursor protein (APP) via the protein extracellular regions, stimulate axonal pruning, and inhibit synapse formation. Xu et al. report the crystal structure of the DR6 ectodomain in complex with the E2 domain of APP and show that it supports a model for APP-induced dimerization and activation of cell surface DR6. The amyloid precursor protein (APP) has garnered considerable attention due to its genetic links to Alzheimer's disease. Death receptor 6 (DR6) was recently shown to bind APP via the protein extracellular regions, stimulate axonal pruning, and inhibit synapse formation. Here, we report the crystal structure of the DR6 ectodomain in complex with the E2 domain of APP and show that it supports a model for APP-induced dimerization and activation of cell surface DR6.
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32
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Gershoni-Emek N, Chein M, Gluska S, Perlson E. Amyotrophic lateral sclerosis as a spatiotemporal mislocalization disease: location, location, location. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 315:23-71. [PMID: 25708461 DOI: 10.1016/bs.ircmb.2014.11.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Spatiotemporal localization of signals is a fundamental feature impacting cell survival and proper function. The cell needs to respond in an accurate manner in both space and time to both intra- and intercellular environment cues. The regulation of this comprehensive process involves the cytoskeleton and the trafficking machinery, as well as local protein synthesis and ligand-receptor mechanisms. Alterations in such mechanisms can lead to cell dysfunction and disease. Motor neurons that can extend over tens of centimeters are a classic example for the importance of such events. Changes in spatiotemporal localization mechanisms are thought to play a role in motor neuron degeneration that occurs in amyotrophic lateral sclerosis (ALS). In this review we will discuss these mechanisms and argue that possible misregulated factors can lead to motor neuron degeneration in ALS.
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Affiliation(s)
- Noga Gershoni-Emek
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; The Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Michael Chein
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; The Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Shani Gluska
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; The Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Eran Perlson
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel; The Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
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33
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The multifaceted nature of amyloid precursor protein and its proteolytic fragments: friends and foes. Acta Neuropathol 2015; 129:1-19. [PMID: 25287911 DOI: 10.1007/s00401-014-1347-2] [Citation(s) in RCA: 154] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2014] [Revised: 09/26/2014] [Accepted: 09/26/2014] [Indexed: 12/29/2022]
Abstract
The amyloid precursor protein (APP) has occupied a central position in Alzheimer's disease (AD) pathophysiology, in large part due to the seminal role of amyloid-β peptide (Aβ), a proteolytic fragment derived from APP. Although the contribution of Aβ to AD pathogenesis is accepted by many in the research community, recent studies have unveiled a more complicated picture of APP's involvement in neurodegeneration in that other APP-derived fragments have been shown to exert pathological influences on neuronal function. However, not all APP-derived peptides are neurotoxic, and some even harbor neuroprotective effects. In this review, we will explore this complex picture by first discussing the pleiotropic effects of the major APP-derived peptides cleaved by multiple proteases, including soluble APP peptides (sAPPα, sAPPβ), various C- and N-terminal fragments, p3, and APP intracellular domain fragments. In addition, we will highlight two interesting sequences within APP that likely contribute to this duality in APP function. First, it has been found that caspase-mediated cleavage of APP in the cytosolic region may release a cytotoxic peptide, C31, which plays a role in synapse loss and neuronal death. Second, recent studies have implicated the -YENPTY- motif in the cytoplasmic region as a domain that modulates several APP activities through phosphorylation and dephosphorylation of the first tyrosine residue. Thus, this review summarizes the current understanding of various APP proteolytic products and the interplay among them to gain deeper insights into the possible mechanisms underlying neurodegeneration and AD pathophysiology.
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Xu Y, Wang D, Luo Y, Li W, Shan Y, Tan X, Zhu C. Beta amyloid-induced upregulation of death receptor 6 accelerates the toxic effect of N-terminal fragment of amyloid precursor protein. Neurobiol Aging 2014; 36:157-68. [PMID: 25150572 DOI: 10.1016/j.neurobiolaging.2014.07.027] [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: 10/23/2013] [Revised: 06/29/2014] [Accepted: 07/21/2014] [Indexed: 12/18/2022]
Abstract
Amyloid precursor protein (APP) plays essential roles in the development of the Alzheimer's disease. Although full-length APP has been thoroughly studied, the role of the cleavage fragments especially the N-terminal fragments (N-APPs) in Alzheimer's disease pathogenesis was still elusive. In this study, we demonstrated that application of recombinant APP₁₈₋₂₈₆ could enhance beta amyloid (Aβ)-induced neuronal injuries which were related to the activation of apoptosis proteins. Aβ treatment could induce a slight increase of N-APPs release. In addition, expression of death receptor 6 (DR6) was increased in Aβ-treated neurons and APP transgenic mice. Moreover, the effect of APP₁₈₋₂₈₆ on Aβ-induced injuries could be suppressed by the application of recombinant DR6₄₁₋₃₄₁ and DR6 antibody. Furthermore, pull-down assay revealed that APP₁₈₋₂₈₆ could bind both exogenous and endogenous DR6. Aβ promoted APP₁₈₋₂₈₆ targeting to neuron which was accompanied with the increase of DR6 expression, whereas downregulation of DR6 by interference RNA could alleviate the binding of N-APPs to neuron and also suppressed Aβ-dependent toxic effect with N-APPs. These results suggested that APP N-terminal fragments might play neurotoxic roles in Aβ-induced neuronal injuries through cell surface DR6.
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Affiliation(s)
- Yuxia Xu
- State Key Laboratory of Medical Neurobiology, Department of Neurobiology and Institutes of Brain Science, School of Basic Medical Science, Fudan University, Shanghai, China
| | - Dandan Wang
- State Key Laboratory of Medical Neurobiology, Department of Neurobiology and Institutes of Brain Science, School of Basic Medical Science, Fudan University, Shanghai, China
| | - Ying Luo
- Department of Chemistry and Institute of Biomedical Sciences, Fudan University, Shanghai, China
| | - Wei Li
- Department of Chemistry and Institute of Biomedical Sciences, Fudan University, Shanghai, China
| | - Ye Shan
- State Key Laboratory of Medical Neurobiology, Department of Neurobiology and Institutes of Brain Science, School of Basic Medical Science, Fudan University, Shanghai, China
| | - Xiangshi Tan
- Department of Chemistry and Institute of Biomedical Sciences, Fudan University, Shanghai, China
| | - Cuiqing Zhu
- State Key Laboratory of Medical Neurobiology, Department of Neurobiology and Institutes of Brain Science, School of Basic Medical Science, Fudan University, Shanghai, China.
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Genetic analysis reveals that amyloid precursor protein and death receptor 6 function in the same pathway to control axonal pruning independent of β-secretase. J Neurosci 2014; 34:6438-47. [PMID: 24806670 DOI: 10.1523/jneurosci.3522-13.2014] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
In the developing brain, initial neuronal projections are formed through extensive growth and branching of developing axons, but many branches are later pruned to sculpt the mature pattern of connections. Despite its widespread occurrence, the mechanisms controlling pruning remain incompletely characterized. Based on pharmacological and biochemical analysis in vitro and initial genetic analysis in vivo, prior studies implicated a pathway involving binding of the Amyloid Precursor Protein (APP) to Death Receptor 6 (DR6) and activation of a downstream caspase cascade in axonal pruning. Here, we further test their involvement in pruning in vivo and their mechanism of action through extensive genetic and biochemical analysis. Genetic deletion of DR6 was previously shown to impair pruning of retinal axons in vivo. We show that genetic deletion of APP similarly impairs pruning of retinal axons in vivo and provide evidence that APP and DR6 act cell autonomously and in the same pathway to control pruning. Prior analysis had suggested that β-secretase cleavage of APP and binding of an N-terminal fragment of APP to DR6 is required for their actions, but further genetic and biochemical analysis reveals that β-secretase activity is not required and that high-affinity binding to DR6 requires a more C-terminal portion of the APP ectodomain. These results provide direct support for the model that APP and DR6 function cell autonomously and in the same pathway to control pruning in vivo and raise the possibility of alternate mechanisms for how APP and DR6 control pruning.
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