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Liu ZY, Li YQ, Wang DL, Wang Y, Qiu WT, Qiu YY, Zhang HL, You QL, Liu SM, Liang QN, Wu EJ, Hu BJ, Sun XD. Agrin-Lrp4 pathway in hippocampal astrocytes restrains development of temporal lobe epilepsy through adenosine signaling. Cell Biosci 2024; 14:66. [PMID: 38783336 PMCID: PMC11112884 DOI: 10.1186/s13578-024-01241-5] [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: 03/05/2024] [Accepted: 04/27/2024] [Indexed: 05/25/2024] Open
Abstract
BACKGROUND Human patients often experience an episode of serious seizure activity, such as status epilepticus (SE), prior to the onset of temporal lobe epilepsy (TLE), suggesting that SE can trigger the development of epilepsy. Yet, the underlying mechanisms are not fully understood. The low-density lipoprotein receptor related protein (Lrp4), a receptor for proteoglycan-agrin, has been indicated to modulate seizure susceptibility. However, whether agrin-Lrp4 pathway also plays a role in the development of SE-induced TLE is not clear. METHODS Lrp4f/f mice were crossed with hGFAP-Cre and Nex-Cre mice to generate brain conditional Lrp4 knockout mice (hGFAP-Lrp4-/-) and pyramidal neuron specific knockout mice (Nex-Lrp4-/-). Lrp4 was specifically knocked down in hippocampal astrocytes by injecting AAV virus carrying hGFAP-Cre into the hippocampus. The effects of agrin-Lrp4 pathway on the development of SE-induced TLE were evaluated on the chronic seizure model generated by injecting kainic acid (KA) into the amygdala. The spontaneous recurrent seizures (SRS) in mice were video monitored. RESULTS We found that Lrp4 deletion from the brain but not from the pyramidal neurons elevated the seizure threshold and reduced SRS numbers, with no change in the stage or duration of SRS. More importantly, knockdown of Lrp4 in the hippocampal astrocytes after SE induction decreased SRS numbers. In accord, direct injection of agrin into the lateral ventricle of control mice but not mice with Lrp4 deletion in hippocampal astrocytes also increased the SRS numbers. These results indicate a promoting effect of agrin-Lrp4 signaling in hippocampal astrocytes on the development of SE-induced TLE. Last, we observed that knockdown of Lrp4 in hippocampal astrocytes increased the extracellular adenosine levels in the hippocampus 2 weeks after SE induction. Blockade of adenosine A1 receptor in the hippocampus by DPCPX after SE induction diminished the effects of Lrp4 on the development of SE-induced TLE. CONCLUSION These results demonstrate a promoting role of agrin-Lrp4 signaling in hippocampal astrocytes in the development of SE-induced development of epilepsy through elevating adenosine levels. Targeting agrin-Lrp4 signaling may serve as a potential therapeutic intervention strategy to treat TLE.
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Affiliation(s)
- Zi-Yang Liu
- School of Basic Medical Sciences, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of GFNeurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Yuan-Quan Li
- School of Basic Medical Sciences, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of GFNeurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
- Department of Neurology of the Sixth Affiliated Hospital, Guangzhou Medical University, Guangzhou, China
| | - Die-Lin Wang
- Guangzhou Medical University-Guangzhou Institute of Biomedicine and Health (GMU-GIBH) Joint School of Life Sciences, Guangzhou Medical University, Guangzhou, China
| | - Ying Wang
- School of Basic Medical Sciences, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of GFNeurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Wan-Ting Qiu
- School of Basic Medical Sciences, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of GFNeurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
- Key Laboratory of Mental Health of the Ministry of Education, Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Guangdong-Hong Kong Joint Laboratory for Psychiatric Disorders, Guangdong Province Key Laboratory of Psychiatric Disorders, Guangdong Basic Research Center of Excellence for Integrated Traditional and Western Medicine for Qingzhi Diseases, Department of Neurobiology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China
| | - Yu-Yang Qiu
- School of Basic Medical Sciences, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of GFNeurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - He-Lin Zhang
- School of Basic Medical Sciences, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of GFNeurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Qiang-Long You
- School of Basic Medical Sciences, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of GFNeurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Shi-Min Liu
- School of Basic Medical Sciences, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of GFNeurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Qiu-Ni Liang
- School of Basic Medical Sciences, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of GFNeurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Er-Jian Wu
- School of Basic Medical Sciences, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of GFNeurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China
| | - Bing-Jie Hu
- School of Basic Medical Sciences, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of GFNeurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China.
| | - Xiang-Dong Sun
- School of Basic Medical Sciences, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Institute of Neuroscience and Department of GFNeurology of the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, China.
- Key Laboratory of Mental Health of the Ministry of Education, Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Guangdong-Hong Kong Joint Laboratory for Psychiatric Disorders, Guangdong Province Key Laboratory of Psychiatric Disorders, Guangdong Basic Research Center of Excellence for Integrated Traditional and Western Medicine for Qingzhi Diseases, Department of Neurobiology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, China.
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Hodgson L, Li Y, Iturria-Medina Y, Stratton JA, Wolf G, Krishnaswamy S, Bennett DA, Bzdok D. Supervised latent factor modeling isolates cell-type-specific transcriptomic modules that underlie Alzheimer's disease progression. Commun Biol 2024; 7:591. [PMID: 38760483 PMCID: PMC11101463 DOI: 10.1038/s42003-024-06273-8] [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: 12/18/2023] [Accepted: 05/01/2024] [Indexed: 05/19/2024] Open
Abstract
Late onset Alzheimer's disease (AD) is a progressive neurodegenerative disease, with brain changes beginning years before symptoms surface. AD is characterized by neuronal loss, the classic feature of the disease that underlies brain atrophy. However, GWAS reports and recent single-nucleus RNA sequencing (snRNA-seq) efforts have highlighted that glial cells, particularly microglia, claim a central role in AD pathophysiology. Here, we tailor pattern-learning algorithms to explore distinct gene programs by integrating the entire transcriptome, yielding distributed AD-predictive modules within the brain's major cell-types. We show that these learned modules are biologically meaningful through the identification of new and relevant enriched signaling cascades. The predictive nature of our modules, especially in microglia, allows us to infer each subject's progression along a disease pseudo-trajectory, confirmed by post-mortem pathological brain tissue markers. Additionally, we quantify the interplay between pairs of cell-type modules in the AD brain, and localized known AD risk genes to enriched module gene programs. Our collective findings advocate for a transition from cell-type-specificity to gene modules specificity to unlock the potential of unique gene programs, recasting the roles of recently reported genome-wide AD risk loci.
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Affiliation(s)
- Liam Hodgson
- School of Computer Science, McGill University, Montréal, QC, Canada
- Mila - Quebec Artificial Intelligence Institute, Montréal, QC, Canada
| | - Yue Li
- School of Computer Science, McGill University, Montréal, QC, Canada
| | - Yasser Iturria-Medina
- McConnell Brain Imaging Centre (BIC), MNI, Faculty of Medicine, McGill University, Montréal, Canada
- Neurology and Neurosurgery Department, Montreal Neurological Institute (MNI), Faculty of Medicine, McGill University, Montréal, Canada
- Ludmer Centre for Neuroinformatics and Mental Health, McGill University, Montréal, Canada
| | - Jo Anne Stratton
- Neurology and Neurosurgery Department, Montreal Neurological Institute (MNI), Faculty of Medicine, McGill University, Montréal, Canada
| | - Guy Wolf
- Mila - Quebec Artificial Intelligence Institute, Montréal, QC, Canada
- Department of Mathematics & Statistics, Université de Montréal, Montréal, Canada
| | - Smita Krishnaswamy
- Department of Computer Science, Department of Genetics, Yale University, New Haven, CT, USA
| | - David A Bennett
- Rush Alzheimer's Disease Center, Rush University Medical Center, Chicago, IL, USA
| | - Danilo Bzdok
- Mila - Quebec Artificial Intelligence Institute, Montréal, QC, Canada.
- Department of Biomedical Engineering, Faculty of Medicine, McGill University, Montréal, QC, Canada.
- The Neuro - Montréal Neurological Institute, McConnell Brain Imaging Centre, Faculty of Medicine, McGill University, Montréal, QC, Canada.
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3
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Mehrotra P, Jablonski J, Toftegard J, Zhang Y, Shahini S, Wang J, Hung CW, Ellis R, Kayal G, Rajabian N, Liu S, Roballo K, Udin SB, Andreadis ST, Personius KE. Skeletal muscle reprogramming enhances reinnervation after peripheral nerve injury. RESEARCH SQUARE 2024:rs.3.rs-3463557. [PMID: 38260278 PMCID: PMC10802751 DOI: 10.21203/rs.3.rs-3463557/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Peripheral Nerve Injuries (PNI) affect more than 20 million Americans and severely impact quality of life by causing long-term disability. The onset of PNI is characterized by nerve degeneration distal to the nerve injury resulting in long periods of skeletal muscle denervation. During this period, muscle fibers atrophy and frequently become incapable of "accepting" innervation because of the slow speed of axon regeneration post injury. We hypothesize that reprogramming the skeletal muscle to an embryonic-like state may preserve its reinnervation capability following PNI. To this end, we generated a mouse model in which NANOG, a pluripotency-associated transcription factor can be expressed locally upon delivery of doxycycline (Dox) in a polymeric vehicle. NANOG expression in the muscle upregulated the percentage of Pax7+ nuclei and expression of eMYHC along with other genes that are involved in muscle development. In a sciatic nerve transection model, NANOG expression led to upregulation of key genes associated with myogenesis, neurogenesis and neuromuscular junction (NMJ) formation, and downregulation of key muscle atrophy genes. Further, NANOG mice demonstrated extensive overlap between synaptic vesicles and NMJ acetylcholine receptors (AChRs) indicating restored innervation. Indeed, NANOG mice showed greater improvement in motor function as compared to wild-type (WT) animals, as evidenced by improved toe-spread reflex, EMG responses and isometric force production. In conclusion, we demonstrate that reprogramming the muscle can be an effective strategy to improve reinnervation and functional outcomes after PNI.
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Affiliation(s)
- Pihu Mehrotra
- Department of Chemical and Biological Engineering, University at Buffalo, Buffalo, NY 14260, USA
| | - James Jablonski
- Department of Department of Rehabilitation Science, University at Buffalo, Buffalo, NY 14214, USA
| | - John Toftegard
- Department of Biomedical Engineering, University at Buffalo, NY, Buffalo, NY 14260, USA
| | - Yali Zhang
- Department of Biostatistics and Bioinformatics, Roswell Park Comprehensive Cancer Center, Buffalo, NY 14203, USA
| | - Shahryar Shahini
- Department of Chemical and Biological Engineering, University at Buffalo, Buffalo, NY 14260, USA
| | - Jianmin Wang
- Department of Biostatistics and Bioinformatics, Roswell Park Comprehensive Cancer Center, Buffalo, NY 14203, USA
| | - Carey W Hung
- Biomedical Affairs and Research, Edward Via College of Osteopathic Medicine, Blacksburg, VA 24060, USA
| | - Reilly Ellis
- Biomedical Affairs and Research, Edward Via College of Osteopathic Medicine, Blacksburg, VA 24060, USA
| | - Gabriella Kayal
- Biomedical Affairs and Research, Edward Via College of Osteopathic Medicine, Blacksburg, VA 24060, USA
| | - Nika Rajabian
- Department of Chemical and Biological Engineering, University at Buffalo, Buffalo, NY 14260, USA
| | - Song Liu
- Department of Biostatistics and Bioinformatics, Roswell Park Comprehensive Cancer Center, Buffalo, NY 14203, USA
| | - Kelly Roballo
- Biomedical Affairs and Research, Edward Via College of Osteopathic Medicine, Blacksburg, VA 24060, USA
- Department of Biomedical Sciences and Pathobiology, Virginia Maryland College of Veterinary Medicine, Virginia Tech, Blacksburg, VA 24060, USA
| | - Susan B. Udin
- Department of Physiology and Biophysics, University at Buffalo, Amherst, NY 14203, USA
| | - Stelios T. Andreadis
- Department of Chemical and Biological Engineering, University at Buffalo, Buffalo, NY 14260, USA
- Department of Biomedical Engineering, University at Buffalo, NY, Buffalo, NY 14260, USA
- Center of Excellence in Bioinformatics and Life Sciences, Buffalo, NY 14203, USA
- Center for Cell, Gene and Tissue Engineering (CGTE), University at Buffalo, Buffalo, NY 14260, USA
| | - Kirkwood E. Personius
- Department of Department of Rehabilitation Science, University at Buffalo, Buffalo, NY 14214, USA
- Center for Cell, Gene and Tissue Engineering (CGTE), University at Buffalo, Buffalo, NY 14260, USA
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4
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Prömer J, Barresi C, Herbst R. From phosphorylation to phenotype - Recent key findings on kinase regulation, downstream signaling and disease surrounding the receptor tyrosine kinase MuSK. Cell Signal 2023; 104:110584. [PMID: 36608736 DOI: 10.1016/j.cellsig.2022.110584] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Revised: 12/16/2022] [Accepted: 12/31/2022] [Indexed: 01/04/2023]
Abstract
Muscle-specific kinase (MuSK) is the key regulator of neuromuscular junction development. MuSK acts via several distinct pathways and is responsible for pre- and postsynaptic differentiation. MuSK is unique among receptor tyrosine kinases as activation and signaling are particularly tightly regulated. Initiation of kinase activity requires Agrin, a heparan sulphate proteoglycan derived from motor neurons, the low-density lipoprotein receptor-related protein-4 (Lrp4) and the intracellular adaptor protein Dok-7. There is a great knowledge gap between MuSK activation and downstream signaling. Recent studies using omics techniques have addressed this knowledge gap, thereby greatly contributing to a better understanding of MuSK signaling. Impaired MuSK signaling causes severe muscle weakness as described in congenital myasthenic syndromes or myasthenia gravis but the underlying pathophysiology is often unclear. This review focuses on recent advances in deciphering MuSK activation and downstream signaling. We further highlight latest break-throughs in understanding and treatment of MuSK-related disorders and discuss the role of MuSK in non-muscle tissue.
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Affiliation(s)
- Jakob Prömer
- Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria
| | - Cinzia Barresi
- Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria
| | - Ruth Herbst
- Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria.
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5
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Jiang PP, Peng SS, Pankratova S, Luo P, Zhou P, Chen Y. Proteins Involved in Synaptic Plasticity Are Downregulated in the Cerebrospinal Fluid of Infants With Clinical Sepsis Complicated by Neuroinflammation. Front Cell Neurosci 2022; 16:887212. [PMID: 35634471 PMCID: PMC9130476 DOI: 10.3389/fncel.2022.887212] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 04/20/2022] [Indexed: 12/04/2022] Open
Abstract
Newborn infants are prone to sepsis and related inflammation of different organs. Neuroinflammation has been associated with long-term adverse neuronal (neuropsychiatric/neurodegenerative) outcomes, including attention deficit hyperactivity disorder (ADHD) or even Alzheimer's disease. Despite a vast number of findings on sepsis-induced inflammatory responses in the central nervous system (CNS), how neuroinflammation affects brain development remains largely elusive. In this study, neonates with clinical sepsis and screened for meningitis were included and classified by the neuroinflammation status based on cerebrospinal fluid (CSF) parameters (INF vs. NOINF). CSF samples collected from clinical screening were subjected to proteomics analysis. Proteins with differential abundance were subjected to enrichment analysis to reveal affected biological pathways. INF and NOINF infants had similar demographic data and hematological and biochemical parameters in blood and CSF. The CSF proteomes were essentially different between the two groups. All 65 proteins with differential abundance showed lower abundance in the INF group and functionally covered pivotal developmental processes, including axonal and synaptic function and extracellular homeostasis. CSF proteins, PTPRZ1 and IGFBP4, were correlated with C-reactive protein (CRP) and ratios of immature/total neutrophils in blood. In general, a substantial change in the CSF protein profile was found under neuroinflammation, and these changes are related to systemic conditions. The results suggest that changes in CSF proteins may be involved in sepsis-affected neurodevelopment, such as disturbances in circuit formation, which has the potential to predispose neonates to long-term adverse outcomes.
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Affiliation(s)
- Ping-Ping Jiang
- Department of Veterinary and Animal Sciences, University of Copenhagen, Copenhagen, Denmark
- School of Public Health, Sun Yat-sen University, Guangzhou, China
| | - Shan-Shan Peng
- School of Public Health, Sun Yat-sen University, Guangzhou, China
| | - Stanislava Pankratova
- Department of Veterinary and Animal Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Ping Luo
- School of Public Health, Sun Yat-sen University, Guangzhou, China
| | - Ping Zhou
- Department of Neonatology, Bao'an Women and Children's Hospital, Jinan University, Shenzhen, China
| | - You Chen
- Department of Neonatology, Bao'an Women and Children's Hospital, Jinan University, Shenzhen, China
- *Correspondence: You Chen
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6
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Houlton J, Zubkova OV, Clarkson AN. Recovery of Post-Stroke Spatial Memory and Thalamocortical Connectivity Following Novel Glycomimetic and rhBDNF Treatment. Int J Mol Sci 2022; 23:ijms23094817. [PMID: 35563207 PMCID: PMC9101131 DOI: 10.3390/ijms23094817] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2022] [Revised: 04/22/2022] [Accepted: 04/25/2022] [Indexed: 12/10/2022] Open
Abstract
Stroke-induced cognitive impairments remain of significant concern, with very few treatment options available. The involvement of glycosaminoglycans in neuroregenerative processes is becoming better understood and recent advancements in technology have allowed for cost-effective synthesis of novel glycomimetics. The current study evaluated the therapeutic potential of two novel glycomimetics, compound A and G, when administered systemically five-days post-photothrombotic stroke to the PFC. As glycosaminoglycans are thought to facilitate growth factor function, we also investigated the combination of our glycomimetics with intracerebral, recombinant human brain-derived neurotrophic factor (rhBDNF). C56BL/6J mice received sham or stroke surgery and experimental treatment (day-5), before undergoing the object location recognition task (OLRT). Four-weeks post-surgery, animals received prelimbic injections of the retrograde tracer cholera toxin B (CTB), before tissue was collected for quantification of thalamo-PFC connectivity and reactive astrogliosis. Compound A or G treatment alone modulated a degree of reactive astrogliosis yet did not influence spatial memory performance. Contrastingly, compound G+rhBDNF treatment significantly improved spatial memory, dampened reactive astrogliosis and limited stroke-induced loss of connectivity between the PFC and midline thalamus. As rhBDNF treatment had negligible effects, these findings support compound A acted synergistically to enhance rhBDNF to restrict secondary degeneration and facilitate functional recovery after PFC stroke.
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Affiliation(s)
- Josh Houlton
- Department of Anatomy, Brain Health Research Centre and Brain Research New Zealand, University of Otago, Dunedin 9054, New Zealand;
| | - Olga V. Zubkova
- The Ferrier Research Institute, Gracefield Research Centre, Victoria University of Wellington, 69 Gracefield Road, Lower Hutt 5040, New Zealand;
| | - Andrew N. Clarkson
- Department of Anatomy, Brain Health Research Centre and Brain Research New Zealand, University of Otago, Dunedin 9054, New Zealand;
- Correspondence: ; Tel./Fax: +64-3-279-7326
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7
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Zhang Q, Zhang J, Ye J, Li X, Liu H, Ma X, Wang C, He K, Zhang W, Yuan J, Zhao Y, Xu H, Liu Q. Nuclear speckle specific hnRNP D-like prevents age- and AD-related cognitive decline by modulating RNA splicing. Mol Neurodegener 2021; 16:66. [PMID: 34551807 PMCID: PMC8456587 DOI: 10.1186/s13024-021-00485-w] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Accepted: 08/12/2021] [Indexed: 01/21/2023] Open
Abstract
BACKGROUND Aberrant alternative splicing plays critical role in aging and age-related diseases. Heterogeneous nuclear ribonucleoproteins (hnRNPs) reportedly regulate RNA splicing process. Whether and how hnRNPs contribute to age-related neurodegenerative diseases, especially Alzheimer's disease (AD), remain elusive. METHODS Immunoblotting and immunostaining were performed to determine expression patterns and cellular/subcellular localization of the long isoform of hnRNP D-like (L-DL), which is a hnRNP family member, in mouse hippocampus. Downregulation of L-DL in WT mice was achieved by AAV-mediated shRNA delivery, followed by memory-related behavioural tests. L-DL interactome was analysed by affinity-precipitation and mass spectrometry. Alternative RNA splicing was measured by RNA-seq and analyzed by bioinformatics-based approaches. Downregulation and upregulation of L-DL in APP/PS1 mice were performed using AAV-mediated transduction. RESULTS We show that L-DL is specifically localized to nuclear speckles. L-DL levels are decreased in the hippocampus of aged mouse brains and downregulation of L-DL impairs cognition in mice. L-DL serves as a structural component to recruit other speckle proteins, and regulates cytoskeleton- and synapse-related gene expression by altering RNA splicing. Mechanistically, these splicing changes are modulated via L-DL-mediated interaction of SF3B3, a core component of U2 snRNP, and U2AF65, a U2 spliceosome protein that guides U2 snRNP's binding to RNA. In addition, L-DL levels are decreased in APP/PS1 mouse brains. While downregulation of L-DL deteriorates memory deficits and overexpression of L-DL improves cognitive function in AD mice, by regulating the alternative splicing and expression of synaptic gene CAMKV. CONCLUSIONS Our findings define a molecular mechanism by which hnRNP L-DL regulates alternative RNA splicing, and establish a direct role for L-DL in AD-related synaptic dysfunction and memory decline.
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Affiliation(s)
- Qingyang Zhang
- Institute on Aging and Brain Disorders, The First Affiliated Hospital of USTC, Hefei National Laboratory for Physical Sciences at the Microscale, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230026, China
| | - Juan Zhang
- Institute on Aging and Brain Disorders, The First Affiliated Hospital of USTC, Hefei National Laboratory for Physical Sciences at the Microscale, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230026, China.,Anhui Province Key Laboratory of Biomedical Aging Research, University of Science and Technology of China, Hefei, 230026, China
| | - Jin Ye
- School of Life Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230026, China
| | - Xiaohui Li
- Institute on Aging and Brain Disorders, The First Affiliated Hospital of USTC, Hefei National Laboratory for Physical Sciences at the Microscale, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230026, China.,Anhui Province Key Laboratory of Biomedical Aging Research, University of Science and Technology of China, Hefei, 230026, China
| | - Hongda Liu
- Institute on Aging and Brain Disorders, The First Affiliated Hospital of USTC, Hefei National Laboratory for Physical Sciences at the Microscale, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230026, China
| | - Xiaolin Ma
- Institute on Aging and Brain Disorders, The First Affiliated Hospital of USTC, Hefei National Laboratory for Physical Sciences at the Microscale, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230026, China
| | - Chao Wang
- School of Life Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230026, China
| | - Keqiang He
- Department of Anesthesiology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230001, China
| | - Wei Zhang
- Department of Anesthesiology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230001, China
| | - Ji Yuan
- Department of Anesthesiology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230001, China
| | - Yingjun Zhao
- The First Affiliated Hospital of Xiamen University, Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Xiamen University, Xiamen, 361000, China
| | - Huaxi Xu
- The First Affiliated Hospital of Xiamen University, Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, Institute of Neuroscience, Xiamen University, Xiamen, 361000, China.
| | - Qiang Liu
- Institute on Aging and Brain Disorders, The First Affiliated Hospital of USTC, Hefei National Laboratory for Physical Sciences at the Microscale, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230026, China. .,Anhui Province Key Laboratory of Biomedical Aging Research, University of Science and Technology of China, Hefei, 230026, China. .,Center for Excellence in Animal Evolution and Genetics, Chinese Academy of Sciences, Kunming, 650201, China.
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8
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Vergoossen DLE, Keo A, Mahfouz A, Huijbers MG. Timing and localization of myasthenia gravis-related gene expression. Eur J Neurosci 2021; 54:5574-5585. [PMID: 34228850 PMCID: PMC8457065 DOI: 10.1111/ejn.15382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 06/01/2021] [Accepted: 07/01/2021] [Indexed: 11/29/2022]
Abstract
Myasthenia gravis (MG) is an acquired autoimmune disorder caused by autoantibodies binding acetylcholine receptors (AChR), muscle‐specific kinase (MuSK), agrin or low‐density lipoprotein receptor‐related protein 4 (Lrp4). These autoantibodies inhibit neuromuscular transmission by blocking the function of these proteins and thereby cause fluctuating skeletal muscle weakness. Several reports suggest that these autoantibodies might also affect the central nervous system (CNS) in MG patients. A comprehensive overview of the timing and localization of the expression of MG‐related antigens in other organs is currently lacking. To investigate the spatio‐temporal expression of MG‐related genes outside skeletal muscle, we used in silico tools to assess public expression databases. Acetylcholine esterase, nicotinic AChR α1 subunit, agrin, collagen Q, downstream of kinase‐7, Lrp4, MuSK and rapsyn were included as MG‐related genes because of their well‐known involvement in either congenital or autoimmune MG. We investigated expression of MG‐related genes in (1) all human tissues using GTEx data, (2) specific brain regions, (3) neurodevelopmental stages, and (4) cell types using datasets from the Allen Institute for Brain Sciences. MG‐related genes show heterogenous spatio‐temporal expression patterns in the human body as well as in the CNS. For each of these genes, several (new) tissues, brain areas and cortical cell types with (relatively) high expression were identified suggesting a potential role for these genes outside skeletal muscle. The possible presence of MG‐related antigens outside skeletal muscle suggests that autoimmune MG, congenital MG or treatments targeting the same proteins may affect MG‐related protein function in other organs.
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Affiliation(s)
- Dana L E Vergoossen
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Arlin Keo
- Leiden Computational Biology Center, Leiden University Medical Center, Leiden, The Netherlands.,Delft Bioinformatics Lab, Delft University of Technology, Delft, The Netherlands
| | - Ahmed Mahfouz
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands.,Leiden Computational Biology Center, Leiden University Medical Center, Leiden, The Netherlands.,Delft Bioinformatics Lab, Delft University of Technology, Delft, The Netherlands
| | - Maartje G Huijbers
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands.,Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands
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Zhang P, Yang L, Li G, Jin Y, Wu D, Wang QM, Huang P. Agrin Involvement in Synaptogenesis Induced by Exercise in a Rat Model of Experimental Stroke. Neurorehabil Neural Repair 2020; 34:1124-1137. [PMID: 33135566 DOI: 10.1177/1545968320969939] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
BACKGROUND Agrin is a proteoglycan that aggregates nicotinic acetylcholine receptors (AChRs) on neuromuscular junctions and takes part in synaptogenesis in the development of the central nervous system. However, its effects on neural repair and synaptogenesis after stroke are still unclear. OBJECTIVE This study aimed to investigate the effects of agrin on neural repair and synaptogenesis after stroke and the effects of exercise on this process in vivo and in vitro. METHODS Exercise with gradually increased intensity was initiated at 1 day after middle cerebral artery occlusion (MCAO) for a maximum of 14 days. Neurological deficit scores and foot fault tests were used to assess the behavioral recovery. Western blotting, immunofluorescence, and electron microscopic images were used to detect the expression of agrin, synaptogenesis-related proteins, and synaptic density in vivo. In vitro, the ischemic neuron model was established via oxygen-glucose deprivation (OGD). The lentivirus overexpressed agrin and CREB inhibitor were used to investigate the mechanism by which agrin promoted synaptogenesis. RESULTS Exercise promoted behavioral recovery and this beneficial role was linked to the upregulated expression of agrin and increased synaptic density. Overexpressed agrin promoted synaptogenesis in OGD neuron, CREB inhibitor downregulated the expression of agrin and hampered synaptogenesis in cultured neurons. CONCLUSIONS These results indicated that exercise poststroke improved the recovery of behavioral function after stroke. Synaptogenesis was an important and beneficial factor, and agrin played a critical role in this process and could be a potential therapeutic target for the treatment of stroke and other nervous system diseases.
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Affiliation(s)
- Pengyue Zhang
- Yunnan University of Traditional Chinese Medicine, Kunming, China.,Kunming University of Science and Technology, Kunming, China
| | - Liqiang Yang
- Kunming University of Science and Technology, Kunming, China
| | - Guangxiang Li
- Kunming University of Science and Technology, Kunming, China
| | - Yaju Jin
- Yunnan University of Traditional Chinese Medicine, Kunming, China
| | - Danli Wu
- Yunnan University of Traditional Chinese Medicine, Kunming, China
| | - Qing Mei Wang
- Spaulding Rehabilitation Hospital, Charlestown, MA, USA
| | - Peidong Huang
- Yunnan University of Traditional Chinese Medicine, Kunming, China
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10
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Liu D, Zhao Y, Qi Y, Gao Y, Tu D, Wang Y, Gao HM, Zhou H. Benzo(a)pyrene exposure induced neuronal loss, plaque deposition, and cognitive decline in APP/PS1 mice. J Neuroinflammation 2020; 17:258. [PMID: 32867800 PMCID: PMC7461337 DOI: 10.1186/s12974-020-01925-y] [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: 09/29/2019] [Accepted: 08/13/2020] [Indexed: 12/15/2022] Open
Abstract
Background Exposure to benzo(a)pyrene (BaP) was associated with cognitive impairments and some Alzheimer’s disease (AD)-like pathological changes. However, it is largely unknown whether BaP exposure participates in the disease progression of AD. Objectives To investigate the effect of BaP exposure on AD progression and its underlying mechanisms. Methods BaP or vehicle was administered to 4-month-old APPswe/PS1dE9 transgenic (APP/PS1) mice and wildtype (WT) mice for 2 months. Learning and memory ability and exploratory behaviors were evaluated 1 month after the initiation/termination of BaP exposure. AD-like pathological and biochemical alterations were examined 1 month after 2-month BaP exposure. Levels of soluble beta-amyloid (Aβ) oligomers and the number of Aβ plaques in the cortex and the hippocampus were quantified. Gene expression profiling was used to evaluate alternation of genes/pathways associated with AD onset and progression. Immunohistochemistry and Western blot were used to demonstrate neuronal loss and neuroinflammation in the cortex and the hippocampus. Treatment of primary neuron-glia cultures with aged Aβ (a mixture of monomers, oligomers, and fibrils) and/or BaP was used to investigate mechanisms by which BaP enhanced Aβ-induced neurodegeneration. Results BaP exposure induced progressive decline in spatial learning/memory and exploratory behaviors in APP/PS1 mice and WT mice, and APP/PS1 mice showed severer behavioral deficits than WT mice. Moreover, BaP exposure promoted neuronal loss, Aβ burden and Aβ plaque formation in APP/PS1 mice, but not in WT mice. Gene expression profiling showed most robust alteration in genes and pathways related to inflammation and immunoregulatory process, Aβ secretion and degradation, and synaptic formation in WT and APP/PS1 mice after BaP exposure. Consistently, the cortex and the hippocampus of WT and APP/PS1 mice displayed activation of microglia and astroglia and upregulation of inducible nitric oxide synthase (iNOS), glial fibrillary acidic protein (GFAP), and NADPH oxidase (three widely used neuroinflammatory markers) after BaP exposure. Furthermore, BaP exposure aggravated neurodegeneration induced by aged Aβ peptide in primary neuron-glia cultures through enhancing NADPH oxidase-derived oxidative stress. Conclusion Our study showed that chronic exposure to environmental pollutant BaP induced, accelerated, and exacerbated the progression of AD, in which elevated neuroinflammation and NADPH oxidase-derived oxidative insults were key pathogenic events.
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Affiliation(s)
- Dan Liu
- Department of Occupational and Environmental Health Sciences, Peking University, Beijing, 100191, China.,Population Health Sciences, German Centre for Neurodegenerative Diseases (DZNE), Bonn, Germany
| | - Yujia Zhao
- Department of Occupational and Environmental Health Sciences, Peking University, Beijing, 100191, China
| | - Yuze Qi
- Department of Occupational and Environmental Health Sciences, Peking University, Beijing, 100191, China
| | - Yun Gao
- MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Center, Institute for Brain Sciences, Nanjing University, 12 Xuefu Road, Nanjing, 210061, Jiangsu Province, China
| | - Dezhen Tu
- MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Center, Institute for Brain Sciences, Nanjing University, 12 Xuefu Road, Nanjing, 210061, Jiangsu Province, China
| | - Yinxi Wang
- Department of Occupational and Environmental Health Sciences, Peking University, Beijing, 100191, China
| | - Hui-Ming Gao
- MOE Key Laboratory of Model Animal for Disease Study, Model Animal Research Center, Institute for Brain Sciences, Nanjing University, 12 Xuefu Road, Nanjing, 210061, Jiangsu Province, China.
| | - Hui Zhou
- Department of Occupational and Environmental Health Sciences, Peking University, Beijing, 100191, China.
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11
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A Role of Low-Density Lipoprotein Receptor-Related Protein 4 (LRP4) in Astrocytic Aβ Clearance. J Neurosci 2020; 40:5347-5361. [PMID: 32457076 DOI: 10.1523/jneurosci.0250-20.2020] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 05/10/2020] [Accepted: 05/16/2020] [Indexed: 01/28/2023] Open
Abstract
Amyloid-β (Aβ) deposition occurs years before cognitive symptoms appear and is considered a cause of Alzheimer's disease (AD). The imbalance of Aβ production and clearance leads to Aβ accumulation and Aβ deposition. Increasing evidence indicates an important role of astrocytes, the most abundant cell type among glial cells in the brain, in Aβ clearance. We explored the role of low-density lipoprotein receptor-related protein 4 (LRP4), a member of the LDLR family, in AD pathology. We show that Lrp4 is specifically expressed in astrocytes and its levels in astrocytes were higher than those of Ldlr and Lrp1, both of which have been implicated in Aβ uptake. LRP4 was reduced in postmortem brain tissues of AD patients. Genetic deletion of the Lrp4 gene augmented Aβ plaques in 5xFAD male mice, an AD mouse model, and exacerbated the deficits in neurotransmission, synchrony between the hippocampus and PFC, and cognition. Mechanistically, LRP4 promotes Aβ uptake by astrocytes likely by interacting with ApoE. Together, our study demonstrates that astrocytic LRP4 plays an important role in Aβ pathology and cognitive function.SIGNIFICANCE STATEMENT This study investigates how astrocytes, a type of non-nerve cells in the brain, may contribute to Alzheimer's disease (AD) development. We demonstrate that the low-density lipoprotein receptor-related protein 4 (LRP4) is reduced in the brain of AD patients. Mimicking the reduced levels in an AD mouse model exacerbates cognitive impairment and increases amyloid aggregates that are known to damage the brain. We show that LRP4 could promote the clearance of amyloid protein by astrocytes. Our results reveal a previously unappreciated role of LRP4 in AD development.
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12
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Bekooij T, Gilhuis H, Dawson L, Niks E. Dysautonomia as the Presenting Symptom in Anti-Muscle-Specific Kinase Antibody Myasthenia Gravis. J Neuromuscul Dis 2020; 7:47-50. [DOI: 10.3233/jnd-190411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- T.J.S. Bekooij
- Department of Neurology, Haaglanden Medical Centre Westeinde, The Hague, The Netherlands
| | - H.J. Gilhuis
- Department of Neurology, Reinier de Graaf Hospital, Delft, The Netherlands
| | - L. Dawson
- Department of Neurology, Reinier de Graaf Hospital, Delft, The Netherlands
| | - E.H. Niks
- Department of Neurology, Leiden University Medical Centre, The Netherlands
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13
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Handara G, Kröger S. Alternative Splicing and the Intracellular Domain Mediate TM-agrin's Ability to Differentially Regulate the Density of Excitatory and Inhibitory Synapse-like Specializations in Developing CNS Neurons. Neuroscience 2019; 419:60-71. [PMID: 31672640 DOI: 10.1016/j.neuroscience.2019.09.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Revised: 09/09/2019] [Accepted: 09/10/2019] [Indexed: 01/26/2023]
Abstract
Agrin is a multi-domain protein best known for its essential function during formation of the neuromuscular junction. Alternative mRNA splicing at sites named y and z in the C-terminal part of agrin regulates its interaction with a receptor complex consisting of the agrin-binding low-density lipoprotein receptor-related protein 4 (Lrp4) and the muscle-specific kinase (MuSK). Isoforms with inserts at both splice sites bind to Lrp4, activate MuSK and are synaptogenic at the neuromuscular junction. Agrin is also expressed as a transmembrane protein in the central nervous system (CNS) but its function during interneuronal synapse formation is unclear. Recently we demonstrated that transfection of a full-length cDNA coding for transmembrane agrin (TM-agrin) in cultured embryonic cortical neurons induced an Lrp4-dependent but MuSK-independent increase in dendritic glutamatergic synapses and an Lrp4- and MuSK-independent reduction of inhibitory synapses. Here we show that presynaptic specializations were similarly affected by TM-agrin overexpression. In addition, we mapped the regions within TM-agrin responsible for TM-agrin's effects on dendritic aggregates of synapse-associated proteins. We show that the presence of a four amino acid insert at splice site y is essential for the increase in the density of puncta containing the postsynaptic density protein 95 kDa. This effect was independent of splice site z. The reduction of the gephyrin puncta density was independent of the entire extracellular part of TM-agrin but required a highly conserved serine residue in the intracellular domain of TM-agrin. These results provide further evidence for a function of TM-agrin during CNS synaptogenesis and demonstrate that different domains and alternative splicing of TM-agrin differentially affect excitatory and inhibitory synapse formation in cultured embryonic CNS neurons.
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Affiliation(s)
- Gerry Handara
- Department of Physiological Genomics, Biomedical Center, Ludwig-Maximilians-University, Großhaderner Str. 9, D-82152 Planegg-Martinsried, Germany; Institute for Stem Cell Research, German Research Center for Environmental Health, Helmholtz Centre Munich, Ingolstädter Landstraße 1, D-85764 Neuherberg, Germany
| | - Stephan Kröger
- Department of Physiological Genomics, Biomedical Center, Ludwig-Maximilians-University, Großhaderner Str. 9, D-82152 Planegg-Martinsried, Germany.
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14
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Rudell JB, Maselli RA, Yarov-Yarovoy V, Ferns MJ. Pathogenic effects of agrin V1727F mutation are isoform specific and decrease its expression and affinity for HSPGs and LRP4. Hum Mol Genet 2019; 28:2648-2658. [PMID: 30994901 PMCID: PMC6687949 DOI: 10.1093/hmg/ddz081] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 03/27/2019] [Accepted: 04/15/2019] [Indexed: 12/17/2022] Open
Abstract
Agrin is a large extracellular matrix protein whose isoforms differ in their tissue distribution and function. Motoneuron-derived y+z+ agrin regulates the formation of the neuromuscular junction (NMJ), while y-z- agrin is widely expressed and has diverse functions. Previously we identified a missense mutation (V1727F) in the second laminin globular (LG2) domain of agrin that causes severe congenital myasthenic syndrome. Here, we define pathogenic effects of the agrin V1727F mutation that account for the profound dysfunction of the NMJ. First, by expressing agrin variants in heterologous cells, we show that the V1727F mutation reduces the secretion of y+z+ agrin compared to wild type, whereas it has no effect on the secretion of y-z- agrin. Second, we find that the V1727F mutation significantly impairs binding of y+z+ agrin to both heparin and the low-density lipoprotein receptor-related protein 4 (LRP4) coreceptor. Third, molecular modeling of the LG2 domain suggests that the V1727F mutation primarily disrupts the y splice insert, and consistent with this we find that it partially occludes the contribution of the y splice insert to agrin binding to heparin and LRP4. Together, these findings identify several pathogenic effects of the V1727F mutation that reduce its expression and ability to bind heparan sulfate proteoglycan and LRP4 coreceptors involved in the muscle-specific kinase signaling pathway. These defects primarily impair the function of neural y+z+ agrin and combine to cause a severe CMS phenotype, whereas y-z- agrin function in other tissues appears preserved.
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Affiliation(s)
- John B Rudell
- Department of Physiology and Membrane Biology, University of California Davis, Davis, CA, USA
| | - Ricardo A Maselli
- Department of Neurology, University of California Davis, Davis, CA, USA
| | - Vladimir Yarov-Yarovoy
- Department of Physiology and Membrane Biology, University of California Davis, Davis, CA, USA
| | - Michael J Ferns
- Department of Physiology and Membrane Biology, University of California Davis, Davis, CA, USA
- Department of Anesthesiology and Pain Medicine, University of California Davis, Davis, CA, USA
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15
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Houlton J, Abumaria N, Hinkley SFR, Clarkson AN. Therapeutic Potential of Neurotrophins for Repair After Brain Injury: A Helping Hand From Biomaterials. Front Neurosci 2019; 13:790. [PMID: 31427916 PMCID: PMC6688532 DOI: 10.3389/fnins.2019.00790] [Citation(s) in RCA: 63] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 07/15/2019] [Indexed: 12/17/2022] Open
Abstract
Stroke remains the leading cause of long-term disability with limited options available to aid in recovery. Significant effort has been made to try and minimize neuronal damage following stroke with use of neuroprotective agents, however, these treatments have yet to show clinical efficacy. Regenerative interventions have since become of huge interest as they provide the potential to restore damaged neural tissue without being limited by a narrow therapeutic window. Neurotrophins, such as brain-derived neurotrophic factor (BDNF), and their high affinity receptors are actively produced throughout the brain and are involved in regulating neuronal activity and normal day-to-day function. Furthermore, neurotrophins are known to play a significant role in both protection and recovery of function following neurodegenerative diseases such as stroke and traumatic brain injury (TBI). Unfortunately, exogenous administration of these neurotrophins is limited by a lack of blood-brain-barrier (BBB) permeability, poor half-life, and rapid degradation. Therefore, we have focused this review on approaches that provide a direct and sustained neurotrophic support using pharmacological therapies and mimetics, physical activity, and potential drug delivery systems, including discussion around advantages and limitations for use of each of these systems. Finally, we discuss future directions of biomaterial drug-delivery systems, including the incorporation of heparan sulfate (HS) in conjunction with neurotrophin-based interventions.
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Affiliation(s)
- Josh Houlton
- Brain Health Research Centre, Department of Anatomy, University of Otago, Dunedin, New Zealand
| | - Nashat Abumaria
- State Key Laboratory of Medical Neurobiology, MOE Frontiers Center for Brain Science, Institute of Brain Science, Fudan University, Shanghai, China
- Department of Laboratory Animal Science, Shanghai Medical College, Fudan University, Shanghai, China
| | - Simon F. R. Hinkley
- The Ferrier Research Institute, Victoria University of Wellington, Petone, New Zealand
| | - Andrew N. Clarkson
- Brain Health Research Centre, Department of Anatomy, University of Otago, Dunedin, New Zealand
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16
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The role of agrin, Lrp4 and MuSK during dendritic arborization and synaptogenesis in cultured embryonic CNS neurons. Dev Biol 2019; 445:54-67. [DOI: 10.1016/j.ydbio.2018.10.017] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 10/22/2018] [Accepted: 10/22/2018] [Indexed: 01/06/2023]
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17
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Cardoso AL, Fernandes A, Aguilar-Pimentel JA, de Angelis MH, Guedes JR, Brito MA, Ortolano S, Pani G, Athanasopoulou S, Gonos ES, Schosserer M, Grillari J, Peterson P, Tuna BG, Dogan S, Meyer A, van Os R, Trendelenburg AU. Towards frailty biomarkers: Candidates from genes and pathways regulated in aging and age-related diseases. Ageing Res Rev 2018; 47:214-277. [PMID: 30071357 DOI: 10.1016/j.arr.2018.07.004] [Citation(s) in RCA: 281] [Impact Index Per Article: 46.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Revised: 07/08/2018] [Accepted: 07/10/2018] [Indexed: 12/12/2022]
Abstract
OBJECTIVE Use of the frailty index to measure an accumulation of deficits has been proven a valuable method for identifying elderly people at risk for increased vulnerability, disease, injury, and mortality. However, complementary molecular frailty biomarkers or ideally biomarker panels have not yet been identified. We conducted a systematic search to identify biomarker candidates for a frailty biomarker panel. METHODS Gene expression databases were searched (http://genomics.senescence.info/genes including GenAge, AnAge, LongevityMap, CellAge, DrugAge, Digital Aging Atlas) to identify genes regulated in aging, longevity, and age-related diseases with a focus on secreted factors or molecules detectable in body fluids as potential frailty biomarkers. Factors broadly expressed, related to several "hallmark of aging" pathways as well as used or predicted as biomarkers in other disease settings, particularly age-related pathologies, were identified. This set of biomarkers was further expanded according to the expertise and experience of the authors. In the next step, biomarkers were assigned to six "hallmark of aging" pathways, namely (1) inflammation, (2) mitochondria and apoptosis, (3) calcium homeostasis, (4) fibrosis, (5) NMJ (neuromuscular junction) and neurons, (6) cytoskeleton and hormones, or (7) other principles and an extensive literature search was performed for each candidate to explore their potential and priority as frailty biomarkers. RESULTS A total of 44 markers were evaluated in the seven categories listed above, and 19 were awarded a high priority score, 22 identified as medium priority and three were low priority. In each category high and medium priority markers were identified. CONCLUSION Biomarker panels for frailty would be of high value and better than single markers. Based on our search we would propose a core panel of frailty biomarkers consisting of (1) CXCL10 (C-X-C motif chemokine ligand 10), IL-6 (interleukin 6), CX3CL1 (C-X3-C motif chemokine ligand 1), (2) GDF15 (growth differentiation factor 15), FNDC5 (fibronectin type III domain containing 5), vimentin (VIM), (3) regucalcin (RGN/SMP30), calreticulin, (4) PLAU (plasminogen activator, urokinase), AGT (angiotensinogen), (5) BDNF (brain derived neurotrophic factor), progranulin (PGRN), (6) α-klotho (KL), FGF23 (fibroblast growth factor 23), FGF21, leptin (LEP), (7) miRNA (micro Ribonucleic acid) panel (to be further defined), AHCY (adenosylhomocysteinase) and KRT18 (keratin 18). An expanded panel would also include (1) pentraxin (PTX3), sVCAM/ICAM (soluble vascular cell adhesion molecule 1/Intercellular adhesion molecule 1), defensin α, (2) APP (amyloid beta precursor protein), LDH (lactate dehydrogenase), (3) S100B (S100 calcium binding protein B), (4) TGFβ (transforming growth factor beta), PAI-1 (plasminogen activator inhibitor 1), TGM2 (transglutaminase 2), (5) sRAGE (soluble receptor for advanced glycosylation end products), HMGB1 (high mobility group box 1), C3/C1Q (complement factor 3/1Q), ST2 (Interleukin 1 receptor like 1), agrin (AGRN), (6) IGF-1 (insulin-like growth factor 1), resistin (RETN), adiponectin (ADIPOQ), ghrelin (GHRL), growth hormone (GH), (7) microparticle panel (to be further defined), GpnmB (glycoprotein nonmetastatic melanoma protein B) and lactoferrin (LTF). We believe that these predicted panels need to be experimentally explored in animal models and frail cohorts in order to ascertain their diagnostic, prognostic and therapeutic potential.
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18
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Synaptogenesis Is Modulated by Heparan Sulfate in Caenorhabditis elegans. Genetics 2018; 209:195-208. [PMID: 29559501 PMCID: PMC5937176 DOI: 10.1534/genetics.118.300837] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Accepted: 03/06/2018] [Indexed: 01/06/2023] Open
Abstract
The nervous system regulates complex behaviors through a network of neurons interconnected by synapses. How specific synaptic connections are genetically determined is still unclear. Male mating is the most complex behavior in Caenorhabditis elegans It is composed of sequential steps that are governed by > 3000 chemical connections. Here, we show that heparan sulfates (HS) play a role in the formation and function of the male neural network. HS, sulfated in position 3 by the HS modification enzyme HST-3.1/HS 3-O-sulfotransferase and attached to the HS proteoglycan glypicans LON-2/glypican and GPN-1/glypican, functions cell-autonomously and nonautonomously for response to hermaphrodite contact during mating. Loss of 3-O sulfation resulted in the presynaptic accumulation of RAB-3, a molecule that localizes to synaptic vesicles, and disrupted the formation of synapses in a component of the mating circuits. We also show that the neural cell adhesion protein NRX-1/neurexin promotes and the neural cell adhesion protein NLG-1/neuroligin inhibits the formation of the same set of synapses in a parallel pathway. Thus, neural cell adhesion proteins and extracellular matrix components act together in the formation of synaptic connections.
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19
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Xi J, Yan C, Liu WW, Qiao K, Lin J, Tian X, Wu H, Lu J, Wong LJ, Beeson D, Zhao C. Novel SEA and LG2 Agrin mutations causing congenital Myasthenic syndrome. Orphanet J Rare Dis 2017; 12:182. [PMID: 29258548 PMCID: PMC5735900 DOI: 10.1186/s13023-017-0732-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Accepted: 12/04/2017] [Indexed: 11/17/2022] Open
Abstract
Background Congenital myasthenic syndrome caused by mutations in AGRN, a gene encoding a protein with a crucial function at the neuromuscular junction, is a rare disorder. There are few studies in this area. We here present two cases with novel mutations of AGRN of which we further investigated possible pathogenesis. Results Patient 1 had general limb weakness with fluctuation and deterioration in the afternoon and in hot weather. Patient 2 had early-onset weakness of lower extremities with suspected fluctuation in the early stages, which then progressed to the upper limbs. Both distal and proximal muscles were involved. Repetitive stimulation on EMG in both patients showed decrement in proximal and distal limbs. Patient 2 showed a marked response to salbutamol while Patient 1 did not. By targeted exome sequencing, two novel homozygous missense variants, p.L1176P and p.R1698C, in the SEA and LG2 domain of agrin were identified respectively. Further functional analysis revealed instability of the protein and impaired clustering of the acetylcholine receptor (AChR) by both mutations. Conclusions The mutations identified in AGRN in our study may cause congenital myasthenic syndrome by damaging protein stability and interfering with AChR clustering. These results broaden the understandings on the phenotype, genotype and pathogenesis of this rare disorder. Electronic supplementary material The online version of this article (10.1186/s13023-017-0732-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jianying Xi
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Chong Yan
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Wei-Wei Liu
- Neurosciences Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, OX3 9DS, UK
| | - Kai Qiao
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Jie Lin
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Xia Tian
- Baylor Genetics Laboratories, Houston, Texas, USA
| | - Hui Wu
- Department of Neurology, Jing'an District Center Hospital of Shanghai, Shanghai, China
| | - Jiahong Lu
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Lee-Jun Wong
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
| | - David Beeson
- Neurosciences Group, Nuffield Department of Clinical Neurosciences, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, OX3 9DS, UK.
| | - Chongbo Zhao
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China.,Department of Neurology, Jing'an District Center Hospital of Shanghai, Shanghai, China
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20
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Karakatsani A, Marichal N, Urban S, Kalamakis G, Ghanem A, Schick A, Zhang Y, Conzelmann KK, Rüegg MA, Berninger B, Ruiz de Almodovar C, Gascón S, Kröger S. Neuronal LRP4 regulates synapse formation in the developing CNS. Development 2017; 144:4604-4615. [PMID: 29061639 DOI: 10.1242/dev.150110] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Accepted: 10/11/2017] [Indexed: 01/19/2023]
Abstract
The low-density lipoprotein receptor-related protein 4 (LRP4) is essential in muscle fibers for the establishment of the neuromuscular junction. Here, we show that LRP4 is also expressed by embryonic cortical and hippocampal neurons, and that downregulation of LRP4 in these neurons causes a reduction in density of synapses and number of primary dendrites. Accordingly, overexpression of LRP4 in cultured neurons had the opposite effect inducing more but shorter primary dendrites with an increased number of spines. Transsynaptic tracing mediated by rabies virus revealed a reduced number of neurons presynaptic to the cortical neurons in which LRP4 was knocked down. Moreover, neuron-specific knockdown of LRP4 by in utero electroporation of LRP4 miRNA in vivo also resulted in neurons with fewer primary dendrites and a lower density of spines in the developing cortex and hippocampus. Collectively, our results demonstrate an essential and novel role of neuronal LRP4 in dendritic development and synaptogenesis in the CNS.
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Affiliation(s)
- Andromachi Karakatsani
- Department of Physiological Genomics, Ludwig-Maximilians-University, Grosshaderner Str. 9, D-82152 Planegg-Martinsried, Germany.,Biochemistry Center (BZH), Heidelberg University, 69120 Heidelberg, Germany.,Interdisciplinary Center for Neurosciences, Heidelberg University, 69120 Heidelberg, Germany
| | - Nicolás Marichal
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University Mainz, Hanns-Dieter-Hüsch Weg 19, D-55128 Mainz, Germany.,Focus Program Translational Neurosciences Mainz, Johannes Gutenberg University Mainz, Langenbeckstrasse 1, D-55131 Mainz, Germany
| | - Severino Urban
- Biochemistry Center (BZH), Heidelberg University, 69120 Heidelberg, Germany.,Interdisciplinary Center for Neurosciences, Heidelberg University, 69120 Heidelberg, Germany
| | - Georgios Kalamakis
- Division of Molecular Neurobiology, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
| | - Alexander Ghanem
- Max von Pettenkofer Institute and Gene Center, Ludwig-Maximilians-University, D-81377, Munich, Germany
| | - Anna Schick
- Department of Physiological Genomics, Ludwig-Maximilians-University, Grosshaderner Str. 9, D-82152 Planegg-Martinsried, Germany
| | - Yina Zhang
- Department of Physiological Genomics, Ludwig-Maximilians-University, Grosshaderner Str. 9, D-82152 Planegg-Martinsried, Germany
| | - Karl-Klaus Conzelmann
- Max von Pettenkofer Institute and Gene Center, Ludwig-Maximilians-University, D-81377, Munich, Germany
| | - Markus A Rüegg
- Biozentrum, University of Basel, 4056 Basel, Switzerland
| | - Benedikt Berninger
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University Mainz, Hanns-Dieter-Hüsch Weg 19, D-55128 Mainz, Germany.,Focus Program Translational Neurosciences Mainz, Johannes Gutenberg University Mainz, Langenbeckstrasse 1, D-55131 Mainz, Germany
| | - Carmen Ruiz de Almodovar
- Biochemistry Center (BZH), Heidelberg University, 69120 Heidelberg, Germany.,Interdisciplinary Center for Neurosciences, Heidelberg University, 69120 Heidelberg, Germany
| | - Sergio Gascón
- Department of Physiological Genomics, Ludwig-Maximilians-University, Grosshaderner Str. 9, D-82152 Planegg-Martinsried, Germany .,Institute for Stem Cell Research, Helmholtz Center Munich at the Biomedical Center (BMC), Grosshaderner Strasse 9, D-82152 Planegg-Martinsried, Germany.,Toxicology and Pharmacology Department, Faculty of Veterinary Medicine, Complutense University, Ave. Puerta de Hierro s/n, 28040 Madrid, Spain
| | - Stephan Kröger
- Department of Physiological Genomics, Ludwig-Maximilians-University, Grosshaderner Str. 9, D-82152 Planegg-Martinsried, Germany
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21
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MacDonald R, Barbat-Artigas S, Cho C, Peng H, Shang J, Moustaine A, Carbonetto S, Robitaille R, Chalifour LE, Paudel H. A Novel Egr-1-Agrin Pathway and Potential Implications for Regulation of Synaptic Physiology and Homeostasis at the Neuromuscular Junction. Front Aging Neurosci 2017; 9:258. [PMID: 28824419 PMCID: PMC5541023 DOI: 10.3389/fnagi.2017.00258] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 07/19/2017] [Indexed: 12/11/2022] Open
Abstract
Synaptic transmission requires intricate coordination of the components involved in processing of incoming signals, formation and stabilization of synaptic machinery, neurotransmission and in all related signaling pathways. Changes to any of these components cause synaptic imbalance and disruption of neuronal circuitry. Extensive studies at the neuromuscular junction (NMJ) have greatly aided in the current understanding of synapses and served to elucidate the underlying physiology as well as associated adaptive and homeostatic processes. The heparan sulfate proteoglycan agrin is a vital component of the NMJ, mediating synaptic formation and maintenance in both brain and muscle, but very little is known about direct control of its expression. Here, we investigated the relationship between agrin and transcription factor early growth response-1 (Egr-1), as Egr-1 regulates the expression of many genes involved in synaptic homeostasis and plasticity. Using chromatin immunoprecipitation (ChIP), cell culture with cell lines derived from brain and muscle, and animal models, we show that Egr-1 binds to the AGRN gene locus and suppresses its expression. When compared with wild type (WT), mice deficient in Egr-1 (Egr-1−/−) display a marked increase in AGRN mRNA and agrin full-length and cleavage fragment protein levels, including the 22 kDa, C-terminal fragment in brain and muscle tissue homogenate. Because agrin is a crucial component of the NMJ, we explored possible physiological implications of the Egr-1-agrin relationship. In the diaphragm, Egr-1−/− mice display increased NMJ motor endplate density, individual area and area of innervation. In addition to increased density, soleus NMJs also display an increase in fragmented and faint endplates in Egr-1−/− vs. WT mice. Moreover, the soleus NMJ electrophysiology of Egr-1−/− mice revealed increased quantal content and motor testing showed decreased movement and limb muscle strength compared with WT. This study provides evidence for the potential involvement of a novel Egr-1-agrin pathway in synaptic homeostatic and compensatory mechanisms at the NMJ. Synaptic homeostasis is greatly affected by the process of aging. These and other data suggest that changes in Egr-1 expression may directly or indirectly promote age-related pathologies.
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Affiliation(s)
- Ryen MacDonald
- Lady Davis Institute for Medical Research, Jewish General HospitalMontreal, QC, Canada.,Integrated Program in Neuroscience, McGill UniversityMontreal, QC, Canada
| | | | - Chulmin Cho
- Lady Davis Institute for Medical Research, Jewish General HospitalMontreal, QC, Canada.,Integrated Program in Neuroscience, McGill UniversityMontreal, QC, Canada
| | - Huashan Peng
- Center for Research in NeuroscienceMontreal, QC, Canada
| | - Jijun Shang
- Lady Davis Institute for Medical Research, Jewish General HospitalMontreal, QC, Canada
| | - Ayman Moustaine
- Département de neurosciences, Université de MontréalMontreal, QC, Canada
| | - Salvatore Carbonetto
- Integrated Program in Neuroscience, McGill UniversityMontreal, QC, Canada.,Center for Research in NeuroscienceMontreal, QC, Canada.,Department of Medicine, McGill UniversityMontreal, QC, Canada
| | - Richard Robitaille
- Département de neurosciences, Université de MontréalMontreal, QC, Canada
| | - Lorraine E Chalifour
- Lady Davis Institute for Medical Research, Jewish General HospitalMontreal, QC, Canada.,Department of Medicine, McGill UniversityMontreal, QC, Canada
| | - Hemant Paudel
- Lady Davis Institute for Medical Research, Jewish General HospitalMontreal, QC, Canada.,Integrated Program in Neuroscience, McGill UniversityMontreal, QC, Canada.,Department of Medicine, McGill UniversityMontreal, QC, Canada
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22
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Hypertension-induced synapse loss and impairment in synaptic plasticity in the mouse hippocampus mimics the aging phenotype: implications for the pathogenesis of vascular cognitive impairment. GeroScience 2017; 39:385-406. [PMID: 28664509 DOI: 10.1007/s11357-017-9981-y] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Accepted: 05/30/2017] [Indexed: 12/22/2022] Open
Abstract
Strong epidemiological and experimental evidence indicates that hypertension has detrimental effects on the cerebral microcirculation and thereby promotes accelerated brain aging. Hypertension is an independent risk factor for both vascular cognitive impairment (VCI) and Alzheimer's disease (AD). However, the pathophysiological link between hypertension-induced cerebromicrovascular injury (e.g., blood-brain barrier disruption, increased microvascular oxidative stress, and inflammation) and cognitive decline remains elusive. The present study was designed to characterize neuronal functional and morphological alterations induced by chronic hypertension and compare them to those induced by aging. To achieve that goal, we induced hypertension in young C57BL/6 mice by chronic (4 weeks) infusion of angiotensin II. We found that long-term potentiation (LTP) of performant path synapses following high-frequency stimulation of afferent fibers was decreased in hippocampal slices obtained from hypertensive mice, mimicking the aging phenotype. Hypertension and advanced age were associated with comparable decline in synaptic density in the stratum radiatum of the mouse hippocampus. Hypertension, similar to aging, was associated with changes in mRNA expression of several genes involved in regulation of neuronal function, including down-regulation of Bdnf, Homer1, and Dlg4, which may have a role in impaired synaptic plasticity. Collectively, hypertension impairs synaptic plasticity, reduces synaptic density, and promotes dysregulation of genes involved in synaptic function in the mouse hippocampus mimicking the aging phenotype. These hypertension-induced neuronal alterations may impair establishment of memories in the hippocampus and contribute to the pathogenesis and clinical manifestation of both vascular cognitive impairment (VCI) and Alzheimer's disease (AD).
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23
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De Luca C, Papa M. Matrix Metalloproteinases, Neural Extracellular Matrix, and Central Nervous System Pathology. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2017; 148:167-202. [PMID: 28662822 DOI: 10.1016/bs.pmbts.2017.04.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The functionality and stability of the central nervous system (CNS) pabulum, called neural extracellular matrix (nECM), is paramount for the maintenance of a healthy network. The loosening or the damage of the scaffold disrupts synaptic transmission with the consequent imbalance of the neurotransmitters, reactive cells invasion, astrocytosis, new matrix deposition, digestion of the previous structure and ultimately, maladaptive plasticity with the loss of neuronal viability. nECM is constantly affected by CNS disorders, particularly in chronic modifying such as neurodegenerative disease, or in acute/subacute with chronic sequelae, like cerebrovascular and inflammatory pathology. Matrix metalloproteinases (MMPs) are the main interfering agent of nECM, guiding the balance of degradation and new deposition of proteins such as proteoglycans and glycoproteins, or glycosaminoglycans, such as hyaluronic acid. Activation of these enzymes is modulated by their physiologic inhibitors, the tissue inhibitors of MMPs or via other proteases inhibitors, as well as genetic or epigenetic up- or downregulation through molecular interaction or receptor activation. The appropriate understanding of the pathways underlying nECM modifications in CNS pathology is probably one of the pivotal future directions to identify the healthy brain network and subsequently design new therapies to interfere with the progression of the CNS disease and eventually find appropriate therapies.
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Affiliation(s)
- Ciro De Luca
- Laboratory of Neuronal Networks, University of Campania "Luigi Vanvitelli", Naples, Italy
| | - Michele Papa
- Laboratory of Neuronal Networks, University of Campania "Luigi Vanvitelli", Naples, Italy; SYSBIO, Centre for Systems Biology, University of Milano-Bicocca, Milano, Italy.
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24
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Sun XD, Li L, Liu F, Huang ZH, Bean JC, Jiao HF, Barik A, Kim SM, Wu H, Shen C, Tian Y, Lin TW, Bates R, Sathyamurthy A, Chen YJ, Yin DM, Xiong L, Lin HP, Hu JX, Li BM, Gao TM, Xiong WC, Mei L. Lrp4 in astrocytes modulates glutamatergic transmission. Nat Neurosci 2016; 19:1010-8. [PMID: 27294513 PMCID: PMC4961622 DOI: 10.1038/nn.4326] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Accepted: 05/08/2016] [Indexed: 02/06/2023]
Abstract
Neurotransmission requires precise control of neurotransmitter release from axon terminals. This process is regulated by glial cells; however, underlying mechanisms are not fully understood. Here we report that glutamate release in the brain is impaired in mice lacking low density lipoprotein receptor-related protein 4 (Lrp4), a protein critical for neuromuscular junction formation. Electrophysiological studies indicate compromised release probability in astrocyte-specific Lrp4 knockout mice. Lrp4 mutant astrocytes suppress glutamate transmission by enhancing the release of ATP, whose levels are elevated in the hippocampus of Lrp4 mutant mice. Consequently, the mutant mice are impaired in locomotor activity and spatial memory and are resistant to seizure induction. These impairments could be ameliorated by adenosine A1 receptor antagonist. The results reveal a critical role of Lrp4, in response to agrin, in modulating astrocytic ATP release and synaptic transmission. Our study provides insight into the interaction between neurons and astrocytes for synaptic homeostasis and/or plasticity.
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Affiliation(s)
- Xiang-Dong Sun
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Georgia, USA
| | - Lei Li
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Georgia, USA
| | - Fang Liu
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Georgia, USA
| | - Zhi-Hui Huang
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Georgia, USA
| | - Jonathan C Bean
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Georgia, USA
| | - Hui-Feng Jiao
- Center for Neuropsychiatric Diseases, Institute of Life Science, Nanchang University, Nanchang, China
| | - Arnab Barik
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Georgia, USA
| | - Seon-Myung Kim
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Georgia, USA
| | - Haitao Wu
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Georgia, USA
| | - Chengyong Shen
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Georgia, USA
| | - Yun Tian
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Georgia, USA
| | - Thiri W Lin
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Georgia, USA
| | - Ryan Bates
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Georgia, USA
| | - Anupama Sathyamurthy
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Georgia, USA
| | - Yong-Jun Chen
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Georgia, USA
| | - Dong-Min Yin
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Georgia, USA
| | - Lei Xiong
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Georgia, USA
| | - Hui-Ping Lin
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Georgia, USA
| | - Jin-Xia Hu
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Georgia, USA
| | - Bao-Ming Li
- Center for Neuropsychiatric Diseases, Institute of Life Science, Nanchang University, Nanchang, China.,Jiangxi Medical School, Nanchang University, Nanchang, China
| | - Tian-Ming Gao
- State Key Laboratory of Organ Failure Research, Key Laboratory of Psychiatric Disorders of Guangdong Province, Department of Neurobiology, Southern Medical University, Guangzhou, China
| | - Wen-Cheng Xiong
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Georgia, USA.,Charlie Norwood Virginia Medical Center, Augusta, Georgia, USA
| | - Lin Mei
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Georgia, USA.,Center for Neuropsychiatric Diseases, Institute of Life Science, Nanchang University, Nanchang, China.,Jiangxi Medical School, Nanchang University, Nanchang, China.,Charlie Norwood Virginia Medical Center, Augusta, Georgia, USA
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25
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Abstract
Heparan sulfate proteoglycans (HSPGs) have long been implicated in a wide range of cell-cell signaling and cell-matrix interactions, both in vitro and in vivo in invertebrate models. Although many of the genes that encode HSPG core proteins and the biosynthetic enzymes that generate and modify HSPG sugar chains have not yet been analyzed by genetics in vertebrates, recent studies have shown that HSPGs do indeed mediate a wide range of functions in early vertebrate development, for example during left-right patterning and in cardiovascular and neural development. Here, we provide a comprehensive overview of the various roles of HSPGs in these systems and explore the concept of an instructive heparan sulfate sugar code for modulating vertebrate development. Summary: This Review article examines the role of heparan sulfate proteoglycans in vertebrate development and explores the concept of an instructive 'sugar code' for modulating development.
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Affiliation(s)
- Fabienne E Poulain
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA
| | - H Joseph Yost
- University of Utah, Department of Neurobiology and Anatomy, Department of Pediatrics, Salt Lake City, UT 84132, USA
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26
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Stoyanova II, Hofmeijer J, van Putten MJAM, le Feber J. Acyl Ghrelin Improves Synapse Recovery in an In Vitro Model of Postanoxic Encephalopathy. Mol Neurobiol 2015; 53:6136-6143. [PMID: 26541885 PMCID: PMC5085991 DOI: 10.1007/s12035-015-9502-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2015] [Accepted: 10/19/2015] [Indexed: 11/04/2022]
Abstract
Comatose patients after cardiac arrest have a poor prognosis. Approximately half never awakes as a result of severe diffuse postanoxic encephalopathy. Several neuroprotective agents have been tested, however without significant effect. In the present study, we used cultured neuronal networks as a model system to study the general synaptic damage caused by temporary severe hypoxia and the possibility to restrict it by ghrelin treatment. Briefly, we applied hypoxia (pO2 lowered from 150 to 20 mmHg) during 6 h in 55 cultures. Three hours after restoration of normoxia, half of the cultures were treated with ghrelin for 24 h, while the other, non-supplemented, were used as a control. All cultures were processed immunocytochemically for detection of the synaptic marker synaptophysin. We observed that hypoxia led to drastic decline of the number of synapses, followed by some recovery after return to normoxia, but still below the prehypoxic level. Additionally, synaptic vulnerability was selective: large- and small-sized neurons were more susceptible to synaptic damage than the medium-sized ones. Ghrelin treatment significantly increased the synapse density, as compared with the non-treated controls or with the prehypoxic period. The effect was detected in all neuronal subtypes. In conclusion, exogenous ghrelin has a robust impact on the recovery of cortical synapses after hypoxia. It raises the possibility that ghrelin or its analogs may have a therapeutic potential for treatment of postanoxic encephalopathy.
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Affiliation(s)
- Irina I Stoyanova
- Department of Clinical Neurophysiology, Faculty of Science and Technology, University of Twente, Building Carré 3714, P.O. Box 217, 7500 AE, Enschede, The Netherlands.
| | - Jeannette Hofmeijer
- Department of Clinical Neurophysiology, Faculty of Science and Technology, University of Twente, Building Carré 3714, P.O. Box 217, 7500 AE, Enschede, The Netherlands.,Department of Neurology, Rijnstate Hospital, Arnhem, The Netherlands
| | - Michel J A M van Putten
- Department of Clinical Neurophysiology, Faculty of Science and Technology, University of Twente, Building Carré 3714, P.O. Box 217, 7500 AE, Enschede, The Netherlands.,Department of Clinical Neurophysiology, Medisch Spectrum Twente, Enschede, The Netherlands
| | - Joost le Feber
- Department of Clinical Neurophysiology, Faculty of Science and Technology, University of Twente, Building Carré 3714, P.O. Box 217, 7500 AE, Enschede, The Netherlands.,Department of Biomedical Signals and Systems, EWI, University of Twente, Enschede, The Netherlands
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27
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Zhang BGX, Quigley AF, Bourke JL, Nowell CJ, Myers DE, Choong PFM, Kapsa RMI. Combination of agrin and laminin increase acetylcholine receptor clustering and enhance functional neuromuscular junction formation In vitro. Dev Neurobiol 2015; 76:551-65. [PMID: 26251299 DOI: 10.1002/dneu.22331] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Revised: 06/23/2015] [Accepted: 08/01/2015] [Indexed: 01/07/2023]
Abstract
Clustering of acetylcholine receptors (AChR) at the postsynaptic membrane is a crucial step in the development of neuromuscular junctions (NMJ). During development and after denervation, aneural AChR clusters form on the sarcolemma. Recent studies suggest that these receptors are critical for guiding and initiating synaptogenesis. The aim of this study is to investigate the effect of agrin and laminin-1; agents with known AChR clustering activity; on NMJ formation and muscle maturation. Primary myoblasts were differentiated in vitro on collagen, laminin or collagen and laminin-coated surfaces in the presence or absence of agrin and laminin. The pretreated cells were then subject to innervation by PC12 cells. The number of neuromuscular junctions was assessed by immunocytochemical co-localization of AChR clusters and the presynaptic marker synaptophysin. Functional neuromuscular junctions were quantitated by analysis of the level of spontaneous as well as neuromuscular blocker responsive contractile activity and muscle maturation was assessed by the degree of myotube striation. Agrin alone did not prime muscle for innervation while a combination of agrin and laminin pretreatment increased the number of neuromuscular junctions formed and enhanced acetylcholine based neurotransmission and myotube striation. This study has direct clinical relevance for treatment of denervation injuries and creating functional neuromuscular constructs for muscle tissue repair.
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Affiliation(s)
- Bill G X Zhang
- Department of Orthopaedics, St. Vincent's Hospital Melbourne and the University of Melbourne, Fitzroy, VIC, 3065, Australia.,Department of Surgery, St. Vincent's Hospital Melbourne and the University of Melbourne, Fitzroy, VIC, 3065, Australia
| | - Anita F Quigley
- Department of Medicine, the University of Melbourne, St Vincent's Hospital Melbourne, Fitzroy, VIC, 3065, Australia.,ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, University of Wollongong, Wollongong, NSW, 2522, Australia
| | - Justin L Bourke
- Department of Medicine, the University of Melbourne, St Vincent's Hospital Melbourne, Fitzroy, VIC, 3065, Australia
| | - Cameron J Nowell
- Walter and Eliza Hall Institute, Parkville, VIC, 3052, Australia
| | - Damian E Myers
- Department of Orthopaedics, St. Vincent's Hospital Melbourne and the University of Melbourne, Fitzroy, VIC, 3065, Australia.,Department of Surgery, St. Vincent's Hospital Melbourne and the University of Melbourne, Fitzroy, VIC, 3065, Australia
| | - Peter F M Choong
- Department of Orthopaedics, St. Vincent's Hospital Melbourne and the University of Melbourne, Fitzroy, VIC, 3065, Australia.,Department of Surgery, St. Vincent's Hospital Melbourne and the University of Melbourne, Fitzroy, VIC, 3065, Australia
| | - Robert M I Kapsa
- ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, University of Wollongong, Wollongong, NSW, 2522, Australia
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28
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Eldridge S, Nalesso G, Ismail H, Vicente-Greco K, Kabouridis P, Ramachandran M, Niemeier A, Herz J, Pitzalis C, Perretti M, Dell'Accio F. Agrin mediates chondrocyte homeostasis and requires both LRP4 and α-dystroglycan to enhance cartilage formation in vitro and in vivo. Ann Rheum Dis 2015; 75:1228-35. [PMID: 26290588 PMCID: PMC4760904 DOI: 10.1136/annrheumdis-2015-207316] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 07/14/2015] [Indexed: 12/31/2022]
Abstract
Objectives Osteoarthritis (OA) is a leading cause of disability for which there is no cure. The identification of molecules supporting cartilage homeostasis and regeneration is therefore a major pursuit in musculoskeletal medicine. Agrin is a heparan sulfate proteoglycan which, through binding to low-density lipoprotein receptor-related protein 4 (LRP4), is required for neuromuscular synapse formation. In other tissues, it connects the cytoskeleton to the basement membrane through binding to α-dystroglycan. Prompted by an unexpected expression pattern, we investigated the role and receptor usage of agrin in cartilage. Methods Agrin expression pattern was investigated in human osteoarthritic cartilage and following destabilisation of the medial meniscus in mice. Extracellular matrix (ECM) formation and chondrocyte differentiation was studied in gain and loss of function experiments in vitro in three-dimensional cultures and gain of function in vivo, using an ectopic cartilage formation assay in nude mice. Receptor usage was investigated by disrupting LRP4 and α-dystroglycan by siRNA and blocking antibodies respectively. Results Agrin was detected in normal cartilage but was progressively lost in OA. In vitro, agrin knockdown resulted in reduced glycosaminoglycan content, downregulation of the cartilage transcription factor SOX9 and other cartilage-specific ECM molecules. Conversely, exogenous agrin supported cartilage differentiation in vitro and ectopic cartilage formation in vivo. In the context of cartilage differentiation, agrin used an unusual receptor repertoire requiring both LRP4 and α-dystroglycan. Conclusions We have discovered that agrin strongly promotes chondrocyte differentiation and cartilage formation in vivo. Our results identify agrin as a novel potent anabolic growth factor with strong therapeutic potential in cartilage regeneration.
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Affiliation(s)
- Suzanne Eldridge
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Giovanna Nalesso
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Habib Ismail
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | | | - Panos Kabouridis
- The Francis Crick Institute (Mill Hill Laboratory), The Ridgeway, London, UK
| | - Manoj Ramachandran
- Department of Trauma and Orthopaedic Surgery, Royal London Hospital, London, UK
| | - Andreas Niemeier
- Department of Orthopaedics and IBMII: Molecular Cell Biology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Joachim Herz
- Department of Molecular Genetics, Center for Translational Neurodegeneration Research, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Costantino Pitzalis
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Mauro Perretti
- Centre for Biochemical Pharmacology, William Harvey Research Institute, London, UK
| | - Francesco Dell'Accio
- Centre for Experimental Medicine and Rheumatology, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
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29
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Smith PD, Coulson-Thomas VJ, Foscarin S, Kwok JCF, Fawcett JW. "GAG-ing with the neuron": The role of glycosaminoglycan patterning in the central nervous system. Exp Neurol 2015; 274:100-14. [PMID: 26277685 DOI: 10.1016/j.expneurol.2015.08.004] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2015] [Revised: 07/17/2015] [Accepted: 08/06/2015] [Indexed: 01/17/2023]
Abstract
Proteoglycans (PGs) are a diverse family of proteins that consist of one or more glycosaminoglycan (GAG) chains, covalently linked to a core protein. PGs are major components of the extracellular matrix (ECM) and play critical roles in development, normal function and damage-response of the central nervous system (CNS). GAGs are classified based on their disaccharide subunits, into the following major groups: chondroitin sulfate (CS), heparan sulfate (HS), heparin (HEP), dermatan sulfate (DS), keratan sulfate (KS) and hyaluronic acid (HA). All except HA are modified by sulfation, giving GAG chains specific charged structures and binding properties. While significant neuroscience research has focused on the role of one PG family member, chondroitin sulfate proteoglycan (CSPG), there is ample evidence in support of a role for the other PGs in regulating CNS function in normal and pathological conditions. This review discusses the role of all the identified PG family members (CS, HS, HEP, DS, KS and HA) in normal CNS function and in the context of pathology. Understanding the pleiotropic roles of these molecules in the CNS may open the door to novel therapeutic strategies for a number of neurological conditions.
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Affiliation(s)
- Patrice D Smith
- John van Geest Centre for Brain Repair, University of Cambridge, Forvie Site, Robinson Way, Cambridge, UK; Department of Neuroscience, Carleton University, Ottawa, ON, Canada.
| | - Vivien J Coulson-Thomas
- John van Geest Centre for Brain Repair, University of Cambridge, Forvie Site, Robinson Way, Cambridge, UK
| | - Simona Foscarin
- John van Geest Centre for Brain Repair, University of Cambridge, Forvie Site, Robinson Way, Cambridge, UK
| | - Jessica C F Kwok
- John van Geest Centre for Brain Repair, University of Cambridge, Forvie Site, Robinson Way, Cambridge, UK
| | - James W Fawcett
- John van Geest Centre for Brain Repair, University of Cambridge, Forvie Site, Robinson Way, Cambridge, UK.
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30
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The role of neuronal versus astrocyte-derived heparan sulfate proteoglycans in brain development and injury. Biochem Soc Trans 2015; 42:1263-9. [PMID: 25233401 DOI: 10.1042/bst20140166] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Astrocytes modulate many aspects of neuronal function, including synapse formation and the response to injury. Heparan sulfate proteoglycans (HSPGs) mediate some of the effects of astrocytes on synaptic function, and participate in the astrocyte-mediated brain injury response. HSPGs are a highly conserved class of proteoglycans, with variable heparan sulfate (HS) chains that play a major role in determining the function of these proteins, such as binding to growth factors and receptors. Expression of both the core proteins and their HS chains can vary depending on cellular origin, thus the functional impact of HSPGs may be determined by the cell type in which they are expressed. In the brain, HSPGs are expressed by both neurons and astrocytes; however, the specific contribution of neuronal HSPGs compared with astrocyte-derived HSPGs to development and the injury response is largely unknown. The present review examines the current evidence regarding the roles of HSPGs in the brain, describes the cellular origins of HSPGs, and interrogates the roles of HSPGs from astrocytes and neurons in synaptogenesis and injury. The importance of considering cell-type-specific expression of HSPGs when studying brain function is discussed.
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31
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Del Campo Milan M, Zuroff L, Jimenez CR, Scheltens P, Teunissen CE. Can agrin cerebrospinal fluid concentration be used as an early biomarker for Alzheimer's disease? ALZHEIMER'S & DEMENTIA (AMSTERDAM, NETHERLANDS) 2015; 1:75-80. [PMID: 27239494 PMCID: PMC4876904 DOI: 10.1016/j.dadm.2014.11.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The need for effective treatments halting Alzheimer's disease (AD) urges the discovery of the earliest possible biomarkers. Agrin is increased in the early stages of AD and is involved in amyloid-β (Aβ) fibrillation and synaptogenesis. We investigated the potential of agrin as an early AD cerebrospinal fluid (CSF) biomarker. We analyzed the agrin CSF concentration in nondemented controls (n = 20) and those with mild (n = 20) and severe (n = 20) AD. The levels of agrin CSF were not significantly divergent among the different patient groups and did not correlate with the concentration of Aβ42, total tau, phosphorylated tau, or the Mini Mental State Examination scores. However, agrin strongly correlated with age in those with dementia. The results indicate that agrin cannot be used as an early AD CSF biomarker using the current immunoassay. However, our population was relatively young; thus, the correlation between agrin and age suggests that stronger differences in agrin concentrations might be found in older groups with more heterogeneous AD pathologic features.
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Affiliation(s)
- Marta Del Campo Milan
- Neurochemistry Laboratory and Biobank, Department of Clinical Chemistry, VU University Medical Center, Amsterdam, The Netherlands
- Alzheimer Center, VU University Medical Center, Amsterdam, The Netherlands
| | - Leah Zuroff
- Neurochemistry Laboratory and Biobank, Department of Clinical Chemistry, VU University Medical Center, Amsterdam, The Netherlands
- Alzheimer Center, VU University Medical Center, Amsterdam, The Netherlands
| | - Connie R. Jimenez
- OncoProteomics Laboratory, Department Medical Oncology, VU University Medical Center, Amsterdam, The Netherlands
| | - Philip Scheltens
- Alzheimer Center, VU University Medical Center, Amsterdam, The Netherlands
| | - Charlotte E. Teunissen
- Neurochemistry Laboratory and Biobank, Department of Clinical Chemistry, VU University Medical Center, Amsterdam, The Netherlands
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Zhang Y, Lin S, Karakatsani A, Rüegg MA, Kröger S. Differential regulation of AChR clustering in the polar and equatorial region of murine muscle spindles. Eur J Neurosci 2014; 41:69-78. [PMID: 25377642 DOI: 10.1111/ejn.12768] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 09/29/2014] [Accepted: 10/02/2014] [Indexed: 12/16/2022]
Abstract
Intrafusal fibers of muscle spindles are innervated in the central region by afferent sensory axons and at both polar regions by efferent γ-motoneurons. We previously demonstrated that both neuron-muscle contact sites contain cholinergic synapse-like specialisation, including aggregates of the nicotinic acetylcholine receptor (AChR). In this study we tested the hypothesis that agrin and its receptor complex (consisting of LRP4 and the tyrosine kinase MuSK) are involved in the aggregation of AChRs in muscle spindles, similar to their role at the neuromuscular junction. We show that agrin, MuSK and LRP4 are concentrated at the contact site between the intrafusal fibers and the sensory- and γ-motoneuron, respectively, and that they are expressed in the cell bodies of proprioceptive neurons in dorsal root ganglia. Moreover, agrin and LRP4, but not MuSK, are expressed in γ-motoneuron cell bodies in the ventral horn of the spinal cord. In agrin- and in MuSK-deficient mice, AChR aggregates are absent from the polar regions. In contrast, the subcellular concentration of AChRs in the central region where the sensory neuron contacts the intrafusal muscle fiber is apparently unaffected. Skeletal muscle-specific expression of miniagrin in agrin(-/-) mice in vivo is sufficient to restore the formation of γ-motoneuron endplates. These results show that agrin and MuSK are major determinants during the formation of γ-motoneuron endplates but appear dispensable for the aggregation of AChRs at the central region. Our results therefore suggest different molecular mechanisms for AChR clustering within two domains of intrafusal fibers.
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Affiliation(s)
- Yina Zhang
- Department of Physiological Genomics, Ludwig-Maximilians-University, Pettenkoferstrasse 12, D-80336, Munich, Germany; Helmholtz Center Munich, Neuherberg, Germany
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Levy AD, Omar MH, Koleske AJ. Extracellular matrix control of dendritic spine and synapse structure and plasticity in adulthood. Front Neuroanat 2014; 8:116. [PMID: 25368556 PMCID: PMC4202714 DOI: 10.3389/fnana.2014.00116] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Accepted: 09/29/2014] [Indexed: 12/20/2022] Open
Abstract
Dendritic spines are the receptive contacts at most excitatory synapses in the central nervous system. Spines are dynamic in the developing brain, changing shape as they mature as well as appearing and disappearing as they make and break connections. Spines become much more stable in adulthood, and spine structure must be actively maintained to support established circuit function. At the same time, adult spines must retain some plasticity so their structure can be modified by activity and experience. As such, the regulation of spine stability and remodeling in the adult animal is critical for normal function, and disruption of these processes is associated with a variety of late onset diseases including schizophrenia and Alzheimer's disease. The extracellular matrix (ECM), composed of a meshwork of proteins and proteoglycans, is a critical regulator of spine and synapse stability and plasticity. While the role of ECM receptors in spine regulation has been extensively studied, considerably less research has focused directly on the role of specific ECM ligands. Here, we review the evidence for a role of several brain ECM ligands and remodeling proteases in the regulation of dendritic spine and synapse formation, plasticity, and stability in adults.
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Affiliation(s)
- Aaron D Levy
- Interdepartmental Neuroscience Program, Yale University New Haven, CT, USA ; Department of Molecular Biophysics and Biochemistry, Yale University New Haven, CT, USA
| | - Mitchell H Omar
- Interdepartmental Neuroscience Program, Yale University New Haven, CT, USA ; Department of Molecular Biophysics and Biochemistry, Yale University New Haven, CT, USA
| | - Anthony J Koleske
- Interdepartmental Neuroscience Program, Yale University New Haven, CT, USA ; Department of Molecular Biophysics and Biochemistry, Yale University New Haven, CT, USA ; Department of Neurobiology, Yale University New Haven, CT, USA
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The presence of dysautonomia in different subgroups of myasthenia gravis patients. J Neurol 2014; 261:2119-27. [DOI: 10.1007/s00415-014-7465-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Revised: 08/05/2014] [Accepted: 08/05/2014] [Indexed: 10/24/2022]
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Steiner E, Enzmann GU, Lyck R, Lin S, Rüegg MA, Kröger S, Engelhardt B. The heparan sulfate proteoglycan agrin contributes to barrier properties of mouse brain endothelial cells by stabilizing adherens junctions. Cell Tissue Res 2014; 358:465-79. [PMID: 25107608 PMCID: PMC4210653 DOI: 10.1007/s00441-014-1969-7] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 07/17/2014] [Indexed: 01/13/2023]
Abstract
Barrier characteristics of brain endothelial cells forming the blood–brain barrier (BBB) are tightly regulated by cellular and acellular components of the neurovascular unit. During embryogenesis, the accumulation of the heparan sulfate proteoglycan agrin in the basement membranes ensheathing brain vessels correlates with BBB maturation. In contrast, loss of agrin deposition in the vasculature of brain tumors is accompanied by the loss of endothelial junctional proteins. We therefore wondered whether agrin had a direct effect on the barrier characteristics of brain endothelial cells. Agrin increased junctional localization of vascular endothelial (VE)-cadherin, β-catenin, and zonula occludens-1 (ZO-1) but not of claudin-5 and occludin in the brain endothelioma cell line bEnd5 without affecting the expression levels of these proteins. This was accompanied by an agrin-induced reduction of the paracellular permeability of bEnd5 monolayers. In vivo, the lack of agrin also led to reduced junctional localization of VE-cadherin in brain microvascular endothelial cells. Taken together, our data support the notion that agrin contributes to barrier characteristics of brain endothelium by stabilizing the adherens junction proteins VE-cadherin and β-catenin and the junctional protein ZO-1 to brain endothelial junctions.
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Affiliation(s)
- Esther Steiner
- Theodor Kocher Institute, University of Bern, Freiestrasse 1, 3012, Bern, Switzerland
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Kerrisk ME, Cingolani LA, Koleske AJ. ECM receptors in neuronal structure, synaptic plasticity, and behavior. PROGRESS IN BRAIN RESEARCH 2014; 214:101-31. [PMID: 25410355 DOI: 10.1016/b978-0-444-63486-3.00005-0] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
During central nervous system development, extracellular matrix (ECM) receptors and their ligands play key roles as guidance molecules, informing neurons where and when to send axonal and dendritic projections, establish connections, and form synapses between pre- and postsynaptic cells. Once stable synapses are formed, many ECM receptors transition in function to control the maintenance of stable connections between neurons and regulate synaptic plasticity. These receptors bind to and are activated by ECM ligands. In turn, ECM receptor activation modulates downstream signaling cascades that control cytoskeletal dynamics and synaptic activity to regulate neuronal structure and function and thereby impact animal behavior. The activities of cell adhesion receptors that mediate interactions between pre- and postsynaptic partners are also strongly influenced by ECM composition. This chapter highlights a number of ECM receptors, their roles in the control of synapse structure and function, and the impact of these receptors on synaptic plasticity and animal behavior.
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Affiliation(s)
- Meghan E Kerrisk
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA
| | - Lorenzo A Cingolani
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Anthony J Koleske
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, USA; Department of Neurobiology, Yale University, New Haven, CT, USA; Interdepartmental Neuroscience Program, Yale University, New Haven, CT, USA; Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University, New Haven, CT, USA.
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Morawski M, Filippov M, Tzinia A, Tsilibary E, Vargova L. ECM in brain aging and dementia. PROGRESS IN BRAIN RESEARCH 2014; 214:207-27. [PMID: 25410360 DOI: 10.1016/b978-0-444-63486-3.00010-4] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
An essential component of the brain extracellular space is the extracellular matrix contributing to the spatial assembly of cells by binding cell-surface adhesion molecules, supporting cell migration, differentiation, and tissue development. The most interesting and complex functions of the central nervous system are the abilities to encode new information (learning) and to store this information (memory). The creation of perineuronal nets, consisting mostly of chondroitin sulfate proteoglycans, stabilizes the synapses and memory trails and forms protective shields against neurodegenerative processes but terminates plasticity and the potential for recovery of the tissue. Age-related changes in the extracellular matrix composition and the extracellular space volume and permissivity are major determinants of the onset and development of the most common neurodegenerative disorder, Alzheimer's disease. In this regard, heparan sulfate proteoglycans, involved in amyloid clearance from the brain, play an important role in Alzheimer's disease and other types of neurodegeneration. Additional key players in the modification of the extracellular matrix are matrix metalloproteinases. Recent studies show that the extracellular matrix and matrix metalloproteinases are important regulators of plasticity, learning, and memory and might be involved in different neurological disorders like epilepsy, schizophrenia, addiction, and dementia. The identification of molecules and mechanisms that modulate these processes is crucial for the understanding of brain function and dysfunction and for the design of new therapeutic approaches targeting the molecular mechanism underlying these neurological disorders.
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Affiliation(s)
- Markus Morawski
- University of Leipzig, EU-ESF Transnational Junior Research Group "MESCAMP", Paul Flechsig Institute for Brain Research, Leipzig, Germany.
| | - Mikhail Filippov
- German Center for Neurodegenerative Diseases (DZNE), Magdeburg, Germany
| | - Athina Tzinia
- NCSR "Demokritos", Institute of Biosciences and Applications, Athens, Greece
| | - Effie Tsilibary
- NCSR "Demokritos", Institute of Biosciences and Applications, Athens, Greece
| | - Lydia Vargova
- Charles University, 2nd Faculty of Medicine, Department of Neuroscience, Prague, Czech Republic; Institute of Experimental Medicine AS CR, v.v.i., Department of Neuroscience, Prague, Czech Republic
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Soleman S, Filippov MA, Dityatev A, Fawcett JW. Targeting the neural extracellular matrix in neurological disorders. Neuroscience 2013; 253:194-213. [PMID: 24012743 DOI: 10.1016/j.neuroscience.2013.08.050] [Citation(s) in RCA: 167] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 08/06/2013] [Accepted: 08/26/2013] [Indexed: 01/15/2023]
Abstract
The extracellular matrix (ECM) is known to regulate important processes in neuronal cell development, activity and growth. It is associated with the structural stabilization of neuronal processes and synaptic contacts during the maturation of the central nervous system. The remodeling of the ECM during both development and after central nervous system injury has been shown to affect neuronal guidance, synaptic plasticity and their regenerative responses. Particular interest has focused on the inhibitory role of chondroitin sulfate proteoglycans (CSPGs) and their formation into dense lattice-like structures, termed perineuronal nets (PNNs), which enwrap sub-populations of neurons and restrict plasticity. Recent studies in mammalian systems have implicated CSPGs and PNNs in regulating and restricting structural plasticity. The enzymatic degradation of CSPGs or destabilization of PNNs has been shown to enhance neuronal activity and plasticity after central nervous system injury. This review focuses on the role of the ECM, CSPGs and PNNs; and how developmental and pharmacological manipulation of these structures have enhanced neuronal plasticity and aided functional recovery in regeneration, stroke, and amblyopia. In addition to CSPGs, this review also points to the functions and potential therapeutic value of these and several other key ECM molecules in epileptogenesis and dementia.
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Affiliation(s)
- S Soleman
- Cambridge Centre for Brain Repair, Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom
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Mitsui S, Osako Y, Yuri K. Mental retardation-related protease, motopsin (prss12), binds to the BRICHOS domain of the integral membrane protein 2a. Cell Biol Int 2013; 38:117-23. [PMID: 23955961 DOI: 10.1002/cbin.10164] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Accepted: 08/02/2013] [Indexed: 11/06/2022]
Abstract
Motopsin (prss12), a mosaic serine protease secreted by neuronal cells, is believed to be important for cognitive function, as the loss of its function causes severe nonsyndromic mental retardation. To understand the molecular role of motopsin, we identified the integral membrane protein 2a (Itm2a) as a motopsin-interacting protein using a yeast two-hybrid system. A pull-down assay showed that the BRICHOS domain of Itm2a was essential for this interaction. Motopsin and Itm2a co-localized in COS cells and in cultured neurons when transiently expressed in these cells. Both proteins were co-immunoprecipitated from lysates of these transfected COS cells. Itm2a was strongly detected in a brain lysate prepared between postnatal day 0 and 10, during which period motopsin protein was also enriched in the brain. Immunohistochemistry detected Itm2a as patchy spots along endothelial cells of brain capillaries (which also expressed myosin II regulatory light chain [RLC]), and on glial fibrillary acidic protein (GFAP)-positive processes in the developing cerebral cortex. The data raise the possibility that secreted motopsin interacts with endothelial cells in the developing brain.
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Affiliation(s)
- Shinichi Mitsui
- Department of Rehabilitation Sciences, Gunma University Graduate School of Health Sciences, Showa, Maebashi, 371-8514, Japan
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Choi HY, Liu Y, Tennert C, Sugiura Y, Karakatsani A, Kröger S, Johnson EB, Hammer RE, Lin W, Herz J. APP interacts with LRP4 and agrin to coordinate the development of the neuromuscular junction in mice. eLife 2013; 2:e00220. [PMID: 23986861 PMCID: PMC3748711 DOI: 10.7554/elife.00220] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Accepted: 07/18/2013] [Indexed: 12/22/2022] Open
Abstract
ApoE, ApoE receptors and APP cooperate in the pathogenesis of Alzheimer’s disease. Intriguingly, the ApoE receptor LRP4 and APP are also required for normal formation and function of the neuromuscular junction (NMJ). In this study, we show that APP interacts with LRP4, an obligate co-receptor for muscle-specific tyrosine kinase (MuSK). Agrin, a ligand for LRP4, also binds to APP and co-operatively enhances the interaction of APP with LRP4. In cultured myotubes, APP synergistically increases agrin-induced acetylcholine receptor (AChR) clustering. Deletion of the transmembrane domain of LRP4 (LRP4 ECD) results in growth retardation of the NMJ, and these defects are markedly enhanced in APP−/−;LRP4ECD/ECD mice. Double mutant NMJs are significantly reduced in size and number, resulting in perinatal lethality. Our findings reveal novel roles for APP in regulating neuromuscular synapse formation through hetero-oligomeric interaction with LRP4 and agrin and thereby provide new insights into the molecular mechanisms that govern NMJ formation and maintenance. DOI:http://dx.doi.org/10.7554/eLife.00220.001 One of the hallmarks of Alzheimer’s disease is the formation of plaques in the brain by a protein called β-amyloid. This protein is generated by the cleavage of a precursor protein, and mutations in the gene that encodes amyloid precursor protein greatly increase the risk of developing a familial, early-onset form of Alzheimer’s disease in middle age. Individuals with a particular variant of a lipoprotein called ApoE (ApoE4) are also more likely to develop Alzheimer’s disease at a younger age than the rest of the population. Due to its prevalence—approximately 20% of the world’s population are carriers of at least one allele—ApoE4 is the single-most important risk factor for the late-onset form of Alzheimer’s disease. Amyloid precursor protein and the receptors for ApoE—in particular one called LRP4—are also essential for the development of the specialized synapse that forms between motor neurons and muscles. However, the mechanisms by which they, individually or together, contribute to the formation of these neuromuscular junctions are incompletely understood. Now, Choi et al. have shown that amyloid precursor protein and LRP4 interact at the developing neuromuscular junction. A protein called agrin, which is produced by motor neurons and which must bind to LRP4 to induce neuromuscular junction formation, also binds directly to amyloid precursor protein. This latter interaction leads to the formation of a complex between LRP4 and amyloid precursor protein that robustly promotes the formation of the neuromuscular junction. Mutations that remove the part of LRP4 that anchors it to the cell membrane weaken this complex and thus reduce the development of neuromuscular junctions in mice, especially if the animals also lack amyloid precursor protein. These three proteins thus seem to influence the development and maintenance of neuromuscular junctions by regulating the activity of a fourth protein, called MuSK, which is present on the surface of muscle cells. Activation of MuSK by agrin bound to LRP4 promotes the clustering of acetylcholine receptors in the membrane, which is a crucial step in the formation of the neuromuscular junction. Intriguingly, Choi et al. have now shown that amyloid precursor protein can, by interacting directly with LRP4, also activate MuSK even in the absence of agrin, albeit only to a small extent. The work of Choi et al. suggests that the complex formed between agrin, amyloid precursor protein and LRP4 helps to focus the activation of MuSK, and thus the clustering of acetylcholine receptors, to the site of the developing neuromuscular junction. Since all four proteins are also found in the central nervous system, similar processes might well be at work during the development and maintenance of synapses in the brain. Further studies of these interactions, both at the neuromuscular junction and in the brain, should shed new light on both normal synapse formation and the synaptic dysfunction that is seen in Alzheimer’s disease. DOI:http://dx.doi.org/10.7554/eLife.00220.002
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Affiliation(s)
- Hong Y Choi
- Department of Molecular Genetics , University of Texas Southwestern Medical Center , Dallas , United States
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Mitsui S, Hidaka C, Furihata M, Osako Y, Yuri K. A mental retardation gene, motopsin/prss12, modulates cell morphology by interaction with seizure-related gene 6. Biochem Biophys Res Commun 2013; 436:638-44. [DOI: 10.1016/j.bbrc.2013.04.112] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Accepted: 04/27/2013] [Indexed: 10/26/2022]
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Abstract
Muscle-specific kinase (MuSK) is essential for each step in neuromuscular synapse formation. Before innervation, MuSK initiates postsynaptic differentiation, priming the muscle for synapse formation. Approaching motor axons recognize the primed, or prepatterned, region of muscle, causing motor axons to stop growing and differentiate into specialized nerve terminals. MuSK controls presynaptic differentiation by causing the clustering of Lrp4, which functions as a direct retrograde signal for presynaptic differentiation. Developing synapses are stabilized by neuronal Agrin, which is released by motor nerve terminals and binds to Lrp4, a member of the low-density lipoprotein receptor family, stimulating further association between Lrp4 and MuSK and increasing MuSK kinase activity. In addition, MuSK phosphorylation is stimulated by an inside-out ligand, docking protein-7 (Dok-7), which is recruited to tyrosine-phosphorylated MuSK and increases MuSK kinase activity. Mutations in MuSK and in genes that function in the MuSK signaling pathway, including Dok-7, cause congenital myasthenia, and autoantibodies to MuSK, Lrp4, and acetylcholine receptors are responsible for myasthenia gravis.
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Cui H, Freeman C, Jacobson GA, Small DH. Proteoglycans in the central nervous system: role in development, neural repair, and Alzheimer's disease. IUBMB Life 2013; 65:108-20. [PMID: 23297096 DOI: 10.1002/iub.1118] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Accepted: 11/20/2012] [Indexed: 12/25/2022]
Abstract
Proteoglycans (PGs) are major components of the cell surface and extracellular matrix and play critical roles in development and maintenance of the central nervous system (CNS). PGs are a family of proteins, all of which contain a core protein to which glycosaminoglycan side chains are covalently attached. PGs possess diverse physiological roles, particularly in neural development, and are also implicated in the pathogenesis of neurodegenerative diseases such as Alzheimer's disease (AD). The main functions of PGs in the CNS are reviewed as are the roles of PGs in brain injury and in the development or treatment of AD.
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Affiliation(s)
- Hao Cui
- Menzies Research Institute Tasmania, University of Tasmania, Hobart, Tasmania, Australia
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Zhang C, Ojiaku P, Cole GJ. Forebrain and hindbrain development in zebrafish is sensitive to ethanol exposure involving agrin, Fgf, and sonic hedgehog function. BIRTH DEFECTS RESEARCH. PART A, CLINICAL AND MOLECULAR TERATOLOGY 2013; 97:8-27. [PMID: 23184466 PMCID: PMC4230296 DOI: 10.1002/bdra.23099] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Revised: 10/05/2012] [Accepted: 10/11/2012] [Indexed: 01/14/2023]
Abstract
BACKGROUND Ethanol is a teratogen that affects numerous developmental processes in the nervous system, which includes development and survival of GABAergic and glutamatergic neurons. Possible molecular mechanisms accounting for ethanol's effects on nervous system development include perturbed fibroblast growth factor (Fgf) and Sonic hedgehog (Shh) signaling. In zebrafish, forebrain GABAergic neuron development is dependent on Fgf19 and Shh signaling. The present study was conducted to test the hypothesis that ethanol affects GABAergic and glutamatergic neuron development by disrupting Fgf, Shh, and agrin function. METHODS Zebrafish embryos were exposed to varying concentrations of ethanol during a range of developmental stages, in the absence or presence of morpholino oligonucleotides (MOs) that disrupt agrin or Shh function. In situ hybridization was used to analyze glutamic acid decarboxylase (GAD1) gene expression, as well as markers of glutamatergic neurons. RESULTS Acute ethanol exposure results in marked reduction in GAD1 gene expression in forebrain and hindbrain, and reduction of glutamatergic neuronal markers in hindbrain. Subthreshold ethanol exposure, combined with agrin or Shh MO treatment, produces a similar diminution in expression of markers for GABAergic and glutamatergic neurons. Consistent with the ethanol effects on Fgf and Shh pathways, Fgf19, Fgf8, or Shh mRNA overexpression rescues ethanol-induced decreases in GAD1 and Atonal1a gene expression. CONCLUSIONS These studies demonstrate that GABAergic and glutamatergic neuron development in zebrafish forebrain or cerebellum is sensitive to ethanol exposure, and provides additional evidence that a signaling pathway involving agrin, Fgfs and Shh may be a critical target of ethanol exposure during zebrafish embryogenesis.
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Affiliation(s)
- Chengjin Zhang
- Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, NC 27707
| | - Princess Ojiaku
- Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, NC 27707
- Department of Biology, North Carolina Central University, Durham, NC 27707
| | - Gregory J. Cole
- Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, NC 27707
- Department of Biology, North Carolina Central University, Durham, NC 27707
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Zong Y, Jin R. Structural mechanisms of the agrin-LRP4-MuSK signaling pathway in neuromuscular junction differentiation. Cell Mol Life Sci 2012. [PMID: 23178848 DOI: 10.1007/s00018-012-1209-9] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The neuromuscular junction (NMJ) is the most extensively studied model of neuronal synaptogenesis. Acetylcholine receptor (AChR) clustering on the postsynaptic membrane is a cardinal event in the differentiation of NMJs. AChR clustering and postsynaptic differentiation is orchestrated by sophisticated interactions among three proteins: the neuron-secreted proteoglycan agrin, the co-receptor LRP4, and the muscle-specific receptor tyrosine kinase MuSK. LRP4 and MuSK act as scaffolds for multiple binding partners, resulting in a complex and dynamic network of interacting proteins that is required for AChR clustering. In this review, we discuss the structural basis for NMJ postsynaptic differentiation mediated by the agrin-LRP4-MuSK signaling pathway.
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Affiliation(s)
- Yinong Zong
- Center for Neuroscience, Aging, and Stem Cell Research, Sanford-Burnham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla, CA, 92037, USA
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Target-derived matricryptins organize cerebellar synapse formation through α3β1 integrins. Cell Rep 2012; 2:223-30. [PMID: 22884367 DOI: 10.1016/j.celrep.2012.07.001] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Revised: 04/05/2012] [Accepted: 07/02/2012] [Indexed: 02/04/2023] Open
Abstract
Trans-synaptic organizing cues must be passed between synaptic partners for synapses to properly form. Much of our understanding of this process stems from studies at the neuromuscular junction, where target-derived growth factors, extracellular matrix (ECM) molecules, and matricryptins (proteolytically released fragments of ECM molecules) are all essential for the formation and maintenance of motor nerve terminals. While growth factors and ECM molecules also contribute to the formation of brain synapses, it remains unclear whether synaptic roles exist for matricryptins in the mammalian brain. We report that collagen XVIII and its matricryptin endostatin are generated by cerebellar Purkinje cells and are necessary for the organization of climbing fiber terminals in these neurons. Moreover, endostatin is sufficient to induce climbing fiber terminal formation in vitro by binding and signaling through α3β1 integrins. Taken together, these studies reveal roles for both matricryptins and integrins in the organization of brain synapses.
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Wlodarczyk J, Mukhina I, Kaczmarek L, Dityatev A. Extracellular matrix molecules, their receptors, and secreted proteases in synaptic plasticity. Dev Neurobiol 2012; 71:1040-53. [PMID: 21793226 DOI: 10.1002/dneu.20958] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Neural cells secrete diverse molecules, which accumulate in the extracellular space and form the extracellular matrix (ECM). Interactions between cells and the ECM are well recognized to play the crucial role in cell migration and guidance of growing axons, whereas formation of mature neural ECM in the form of perineuronal nets is believed to restrict certain forms of developmental plasticity. On the other hand, major components of perineuronal nets and other ECM molecules support induction of functional plasticity, the most studied form of which is long-term potentiation. Here, we review the underlying mechanisms by which ECM molecules, their receptors and remodeling proteases regulate the induction and maintenance of synaptic modifications. In particular, we highlight that activity-dependent secretion and activation of proteases leads to a local cleavage of the ECM and release of signaling proteolytic fragments. These molecules regulate transmitter receptor trafficking, actin cytoskeleton, growth of dendritic spines, and formation of dendritic filopodia.
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Steiner E, Enzmann GU, Lin S, Ghavampour S, Hannocks MJ, Zuber B, Rüegg MA, Sorokin L, Engelhardt B. Loss of astrocyte polarization upon transient focal brain ischemia as a possible mechanism to counteract early edema formation. Glia 2012; 60:1646-59. [DOI: 10.1002/glia.22383] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2012] [Accepted: 06/07/2012] [Indexed: 11/10/2022]
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Maselli RA, Fernandez JM, Arredondo J, Navarro C, Ngo M, Beeson D, Cagney Ó, Williams DC, Wollmann RL, Yarov-Yarovoy V, Ferns MJ. LG2 agrin mutation causing severe congenital myasthenic syndrome mimics functional characteristics of non-neural (z-) agrin. Hum Genet 2012; 131:1123-35. [PMID: 22205389 PMCID: PMC4795461 DOI: 10.1007/s00439-011-1132-4] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Accepted: 12/11/2011] [Indexed: 10/14/2022]
Abstract
We describe a severe form of congenital myasthenic syndrome (CMS) caused by two heteroallelic mutations: a nonsense and a missense mutation in the gene encoding agrin (AGRN). The identified mutations, Q353X and V1727F, are located at the N-terminal and at the second laminin G-like (LG2) domain of agrin, respectively. A motor-point muscle biopsy demonstrated severe disruption of the architecture of the neuromuscular junction (NMJ), including: dispersion and fragmentation of endplate areas with normal expression of acetylcholinesterase; simplification of postsynaptic membranes; pronounced reduction of the axon terminal size; widening of the primary synaptic cleft; and, collection of membranous debris material in the primary synaptic cleft and in the subsynaptic cytoplasm. Expression studies in heterologous cells revealed that the Q353X mutation abolished expression of full-length agrin. Moreover, the V1727F mutation decreased agrin-induced clustering of the acetylcholine receptor (AChR) in cultured C2 muscle cells by >100-fold, and phosphorylation of the MuSK receptor and AChR beta subunit by ~tenfold. Surprisingly, the V1727F mutant also displayed increased binding to α-dystroglycan but decreased binding to a neural (z+) agrin-specific antibody. Our findings demonstrate that agrin mutations can associate with a severe form of CMS and cause profound distortion of the architecture and function of the NMJ. The impaired ability of V1727F agrin to activate MuSK and cluster AChRs, together with its increased affinity to α-dystroglycan, mimics non-neural (z-) agrin and are important determinants of the pathogenesis of the disease.
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MESH Headings
- Acetylcholinesterase/metabolism
- Adult
- Agrin/chemistry
- Agrin/genetics
- Agrin/metabolism
- Base Sequence
- Cell Line
- Codon, Nonsense
- Dystroglycans/metabolism
- Female
- HEK293 Cells
- Humans
- Male
- Models, Molecular
- Muscle Fibers, Skeletal/metabolism
- Muscle Fibers, Skeletal/pathology
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/pathology
- Muscle, Skeletal/physiopathology
- Mutation, Missense
- Myasthenic Syndromes, Congenital/genetics
- Myasthenic Syndromes, Congenital/metabolism
- Neuromuscular Junction/metabolism
- Neuromuscular Junction/pathology
- Pedigree
- Receptors, Cholinergic/genetics
- Receptors, Cholinergic/metabolism
- Sequence Analysis, DNA
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Affiliation(s)
- Ricardo A. Maselli
- Department of Neurology, University of California Davis, Davis, California, 95616 USA
| | - Jose M. Fernandez
- Service of Clinical Neurophysiology. University Hospital of Vigo, Vigo (Pontevedra), Spain
| | - Juan Arredondo
- Department of Neurology, University of California Davis, Davis, California, 95616 USA
| | - Carmen Navarro
- Department of Pathology, University Hospital of Vigo and CIBERER (Centro de Investigacion Biomedica en Red en Enfermedades Raras), Vigo (Pontevedra), Spain
| | - Maian Ngo
- Department of Neurology, University of California Davis, Davis, California, 95616 USA
| | - David Beeson
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK
| | - Órla Cagney
- Department of Neurology, University of California Davis, Davis, California, 95616 USA
| | - D. Colette Williams
- Veterinary Medical Teaching Hospital, University of California Davis, Davis, California, 95616, USA
| | - Robert L. Wollmann
- Department of Pathology, University of Chicago, Chicago, Illinois, 60637, USA
| | - Vladimir Yarov-Yarovoy
- Department of Physiology and Membrane Biology, University of California Davis, Davis, California 95616, USA
| | - Michael J Ferns
- Department of Physiology and Membrane Biology, University of California Davis, Davis, California 95616, USA
- Department of Anesthesiology, University of California Davis, Davis, California 95616, USA
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Mukhina IV, Korotchenko SA, Dityatev AE. Extracellular matrix molecules, their receptors, and extracellular proteases as synaptic plasticity modulators. NEUROCHEM J+ 2012. [DOI: 10.1134/s1819712412020055] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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