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Zhu K, Wang H, Ye K, Chen G, Zhang Z. Netrin-1 signaling pathway mechanisms in neurodegenerative diseases. Neural Regen Res 2025; 20:960-972. [PMID: 38989931 DOI: 10.4103/nrr.nrr-d-23-01573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Accepted: 03/16/2024] [Indexed: 07/12/2024] Open
Abstract
Netrin-1 and its receptors play crucial roles in inducing axonal growth and neuronal migration during neuronal development. Their profound impacts then extend into adulthood to encompass the maintenance of neuronal survival and synaptic function. Increasing amounts of evidence highlight several key points: (1) Diminished Netrin-1 levels exacerbate pathological progression in animal models of Alzheimer's disease and Parkinson's disease, and potentially, similar alterations occur in humans. (2) Genetic mutations of Netrin-1 receptors increase an individuals' susceptibility to neurodegenerative disorders. (3) Therapeutic approaches targeting Netrin-1 and its receptors offer the benefits of enhancing memory and motor function. (4) Netrin-1 and its receptors show genetic and epigenetic alterations in a variety of cancers. These findings provide compelling evidence that Netrin-1 and its receptors are crucial targets in neurodegenerative diseases. Through a comprehensive review of Netrin-1 signaling pathways, our objective is to uncover potential therapeutic avenues for neurodegenerative disorders.
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Affiliation(s)
- Kedong Zhu
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan, Hubei Province, China
| | - Hualong Wang
- Department of Neurology, The First Hospital of Hebei Medical University; Brain Aging and Cognitive Neuroscience Laboratory of Heibei Province, Shijiazhuang, Hebei Province, China
| | - Keqiang Ye
- Faculty of Life and Health Sciences, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong Province, China
| | - Guiqin Chen
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan, Hubei Province, China
| | - Zhaohui Zhang
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan, Hubei Province, China
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2
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Cai M, Zheng Q, Chen Y, Liu S, Zhu H, Bai B. Insights from the neural guidance factor Netrin-1 into neurodegeneration and other diseases. Front Mol Neurosci 2024; 17:1379726. [PMID: 38638604 PMCID: PMC11024333 DOI: 10.3389/fnmol.2024.1379726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Accepted: 03/22/2024] [Indexed: 04/20/2024] Open
Abstract
Netrin-1 was initially discovered as a neuronal growth cue for axonal guidance, and its functions have later been identified in inflammation, tumorigenesis, neurodegeneration, and other disorders. We have recently found its alterations in the brains with Alzheimer's disease, which might provide important clues to the mechanisms of some unique pathologies. To provide better understanding of this promising molecule, we here summarize research progresses in genetics, pathology, biochemistry, cell biology and other studies of Netrin-1 about its mechanistic roles and biomarker potentials with an emphasis on clinical neurodegenerative disorders in order to expand understanding of this promising molecular player in human diseases.
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Affiliation(s)
- Minqi Cai
- Department of Laboratory Medicine, Nanjing Drum Tower Hospital Clinical College of Jiangsu University, Nanjing, Jiangsu, China
| | - Qian Zheng
- Health Management Center, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, Jiangsu, China
| | - Yiqiang Chen
- Center for Precision Medicine, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, Jiangsu, China
| | - Siyuan Liu
- Center for Precision Medicine, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, Jiangsu, China
| | - Huimin Zhu
- Chemistry and Biomedicine Innovation Center, Medical School of Nanjing University, Nanjing, China
| | - Bing Bai
- Department of Laboratory Medicine, Nanjing Drum Tower Hospital Clinical College of Jiangsu University, Nanjing, Jiangsu, China
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3
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Pan S, Hale AT, Lemieux ME, Raval DK, Garton TP, Sadler B, Mahaney KB, Strahle JM. Iron homeostasis and post-hemorrhagic hydrocephalus: a review. Front Neurol 2024; 14:1287559. [PMID: 38283681 PMCID: PMC10811254 DOI: 10.3389/fneur.2023.1287559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2023] [Accepted: 11/21/2023] [Indexed: 01/30/2024] Open
Abstract
Iron physiology is regulated by a complex interplay of extracellular transport systems, coordinated transcriptional responses, and iron efflux mechanisms. Dysregulation of iron metabolism can result in defects in myelination, neurotransmitter synthesis, and neuronal maturation. In neonates, germinal matrix-intraventricular hemorrhage (GMH-IVH) causes iron overload as a result of blood breakdown in the ventricles and brain parenchyma which can lead to post-hemorrhagic hydrocephalus (PHH). However, the precise mechanisms by which GMH-IVH results in PHH remain elusive. Understanding the molecular determinants of iron homeostasis in the developing brain may lead to improved therapies. This manuscript reviews the various roles iron has in brain development, characterizes our understanding of iron transport in the developing brain, and describes potential mechanisms by which iron overload may cause PHH and brain injury. We also review novel preclinical treatments for IVH that specifically target iron. Understanding iron handling within the brain and central nervous system may provide a basis for preventative, targeted treatments for iron-mediated pathogenesis of GMH-IVH and PHH.
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Affiliation(s)
- Shelei Pan
- Department of Neurosurgery, Washington University School of Medicine, Washington University in St. Louis, St. Louis, MO, United States
| | - Andrew T. Hale
- Department of Neurosurgery, University of Alabama at Birmingham School of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States
| | - Mackenzie E. Lemieux
- Department of Neurosurgery, Washington University School of Medicine, Washington University in St. Louis, St. Louis, MO, United States
| | - Dhvanii K. Raval
- Department of Neurosurgery, Washington University School of Medicine, Washington University in St. Louis, St. Louis, MO, United States
| | - Thomas P. Garton
- Department of Neurology, Johns Hopkins University School of Medicine, Johns Hopkins University, Baltimore, MD, United States
| | - Brooke Sadler
- Department of Pediatrics, Washington University School of Medicine, Washington University in St. Louis, St. Louis, MO, United States
- Department of Hematology and Oncology, Washington University School of Medicine, Washington University in St. Louis, St. Louis, MO, United States
| | - Kelly B. Mahaney
- Department of Neurosurgery, Stanford University School of Medicine, Stanford University, Palo Alto, CA, United States
| | - Jennifer M. Strahle
- Department of Neurosurgery, Washington University School of Medicine, Washington University in St. Louis, St. Louis, MO, United States
- Department of Pediatrics, Washington University School of Medicine, Washington University in St. Louis, St. Louis, MO, United States
- Department of Orthopedic Surgery, Washington University School of Medicine, Washington University in St. Louis, St. Louis, MO, United States
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Sokol DK, Lahiri DK. APPlications of amyloid-β precursor protein metabolites in macrocephaly and autism spectrum disorder. Front Mol Neurosci 2023; 16:1201744. [PMID: 37799731 PMCID: PMC10548831 DOI: 10.3389/fnmol.2023.1201744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Accepted: 07/17/2023] [Indexed: 10/07/2023] Open
Abstract
Metabolites of the Amyloid-β precursor protein (APP) proteolysis may underlie brain overgrowth in Autism Spectrum Disorder (ASD). We have found elevated APP metabolites (total APP, secreted (s) APPα, and α-secretase adamalysins in the plasma and brain tissue of children with ASD). In this review, we highlight several lines of evidence supporting APP metabolites' potential contribution to macrocephaly in ASD. First, APP appears early in corticogenesis, placing APP in a prime position to accelerate growth in neurons and glia. APP metabolites are upregulated in neuroinflammation, another potential contributor to excessive brain growth in ASD. APP metabolites appear to directly affect translational signaling pathways, which have been linked to single gene forms of syndromic ASD (Fragile X Syndrome, PTEN, Tuberous Sclerosis Complex). Finally, APP metabolites, and microRNA, which regulates APP expression, may contribute to ASD brain overgrowth, particularly increased white matter, through ERK receptor activation on the PI3K/Akt/mTOR/Rho GTPase pathway, favoring myelination.
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Affiliation(s)
- Deborah K. Sokol
- Department of Neurology, Section of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Debomoy K. Lahiri
- Department of Psychiatry, Indiana University School of Medicine, Indianapolis, IN, United States
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, United States
- Indiana Alzheimer Disease Research Center, Indiana University School of Medicine, Indianapolis, IN, United States
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Chau DDL, Ng LLH, Zhai Y, Lau KF. Amyloid precursor protein and its interacting proteins in neurodevelopment. Biochem Soc Trans 2023; 51:1647-1659. [PMID: 37387352 PMCID: PMC10629809 DOI: 10.1042/bst20221527] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Revised: 06/22/2023] [Accepted: 06/26/2023] [Indexed: 07/01/2023]
Abstract
Amyloid precursor protein (APP) is a key molecule in the pathogenesis of Alzheimer's disease (AD) as the pathogenic amyloid-β peptide is derived from it. Two closely related APP family proteins (APPs) have also been identified in mammals. Current knowledge, including genetic analyses of gain- and loss-of-function mutants, highlights the importance of APPs in various physiological functions. Notably, APPs consist of multiple extracellular and intracellular protein-binding regions/domains. Protein-protein interactions are crucial for many cellular processes. In past decades, many APPs interactors have been identified which assist the revelation of the putative roles of APPs. Importantly, some of these interactors have been shown to influence several APPs-mediated neuronal processes which are found defective in AD and other neurodegenerative disorders. Studying APPs-interactor complexes would not only advance our understanding of the physiological roles of APPs but also provide further insights into the association of these processes to neurodegeneration, which may lead to the development of novel therapies. In this mini-review, we summarize the roles of APPs-interactor complexes in neurodevelopmental processes including neurogenesis, neurite outgrowth, axonal guidance and synaptogenesis.
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Affiliation(s)
- Dennis Dik-Long Chau
- School of Life Sciences, Faculty of Science, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Laura Lok-Haang Ng
- School of Life Sciences, Faculty of Science, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Yuqi Zhai
- School of Life Sciences, Faculty of Science, The Chinese University of Hong Kong, Hong Kong SAR, China
| | - Kwok-Fai Lau
- School of Life Sciences, Faculty of Science, The Chinese University of Hong Kong, Hong Kong SAR, China
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Paşcalău R, Badea TC. Signaling - transcription interactions in mouse retinal ganglion cells early axon pathfinding -a literature review. FRONTIERS IN OPHTHALMOLOGY 2023; 3:1180142. [PMID: 38983012 PMCID: PMC11182120 DOI: 10.3389/fopht.2023.1180142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/05/2023] [Accepted: 04/21/2023] [Indexed: 07/11/2024]
Abstract
Sending an axon out of the eye and into the target brain nuclei is the defining feature of retinal ganglion cells (RGCs). The literature on RGC axon pathfinding is vast, but it focuses mostly on decision making events such as midline crossing at the optic chiasm or retinotopic mapping at the target nuclei. In comparison, the exit of RGC axons out of the eye is much less explored. The first checkpoint on the RGC axons' path is the optic cup - optic stalk junction (OC-OS). OC-OS development and the exit of the RGC pioneer axons out of the eye are coordinated spatially and temporally. By the time the optic nerve head domain is specified, the optic fissure margins are in contact and the fusion process is ongoing, the first RGCs are born in its proximity and send pioneer axons in the optic stalk. RGC differentiation continues in centrifugal waves. Later born RGC axons fasciculate with the more mature axons. Growth cones at the end of the axons respond to guidance cues to adopt a centripetal direction, maintain nerve fiber layer restriction and to leave the optic cup. Although there is extensive information on OC-OS development, we still have important unanswered questions regarding its contribution to the exit of the RGC axons out of the eye. We are still to distinguish the morphogens of the OC-OS from the axon guidance molecules which are expressed in the same place at the same time. The early RGC transcription programs responsible for axon emergence and pathfinding are also unknown. This review summarizes the molecular mechanisms for early RGC axon guidance by contextualizing mouse knock-out studies on OC-OS development with the recent transcriptomic studies on developing RGCs in an attempt to contribute to the understanding of human optic nerve developmental anomalies. The published data summarized here suggests that the developing optic nerve head provides a physical channel (the closing optic fissure) as well as molecular guidance cues for the pioneer RGC axons to exit the eye.
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Affiliation(s)
- Raluca Paşcalău
- Research and Development Institute, Transilvania University of Braşov, Braşov, Romania
- Ophthalmology Clinic, Cluj County Emergency Hospital, Cluj-Napoca, Romania
| | - Tudor Constantin Badea
- Research and Development Institute, Transilvania University of Braşov, Braşov, Romania
- National Center for Brain Research, Institutul de Cercetări pentru Inteligență Artificială, Romanian Academy, Bucharest, Romania
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Ma F, Akolkar H, Xu J, Liu Y, Popova D, Xie J, Youssef MM, Benosman R, Hart RP, Herrup K. The Amyloid Precursor Protein Modulates the Position and Length of the Axon Initial Segment. J Neurosci 2023; 43:1830-1844. [PMID: 36717226 PMCID: PMC10010458 DOI: 10.1523/jneurosci.0172-22.2023] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Revised: 01/23/2023] [Accepted: 01/24/2023] [Indexed: 01/31/2023] Open
Abstract
The amyloid precursor protein (APP) is linked to the genetics and pathogenesis of Alzheimer's disease (AD). It is the parent protein of the β-amyloid (Aβ) peptide, the main constituent of the amyloid plaques found in an AD brain. The pathways from APP to Aβ are intensively studied, yet the normal functions of APP itself have generated less interest. We report here that glutamate stimulation of neuronal activity leads to a rapid increase in App gene expression. In mouse and human neurons, elevated APP protein changes the structure of the axon initial segment (AIS) where action potentials are initiated. The AIS is shortened in length and shifts away from the cell body. The GCaMP8f Ca2+ reporter confirms the predicted decrease in neuronal activity. NMDA antagonists or knockdown of App block the glutamate effects. The actions of APP on the AIS are cell-autonomous; exogenous Aβ, either fibrillar or oligomeric, has no effect. In culture, APPSwe (a familial AD mutation) induces larger AIS changes than wild type APP. Ankyrin G and βIV-spectrin, scaffolding proteins of the AIS, both physically associate with APP, more so in AD brains. Finally, in humans with sporadic AD or in the R1.40 AD mouse model, both females and males, neurons have elevated levels of APP protein that invade the AIS. In vivo as in vitro, this increased APP is associated with a significant shortening of the AIS. The findings outline a new role for the APP and encourage a reconsideration of its relationship to AD.SIGNIFICANCE STATEMENT While the amyloid precursor protein (APP) has long been associated with Alzheimer's disease (AD), the normal functions of the full-length Type I membrane protein have been largely unexplored. We report here that the levels of APP protein increase with neuronal activity. In vivo and in vitro, modest amounts of excess APP alter the properties of the axon initial segment. The β-amyloid peptide derived from APP is without effect. Consistent with the observed changes in the axon initial segment which would be expected to decrease action potential firing, we show that APP expression depresses neuronal activity. In mouse AD models and human sporadic AD, APP physically associates with the scaffolding proteins of the axon initial segment, suggesting a relationship with AD dementia.
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Affiliation(s)
- Fulin Ma
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
| | - Himanshu Akolkar
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | - Jianquan Xu
- Departments of Medicine and Bioengineering, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | - Yang Liu
- Departments of Medicine and Bioengineering, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | - Dina Popova
- Human Genetics Institute, Rutgers University, Piscataway, NJ 08854
| | - Jiaan Xie
- Departments of Medicine and Bioengineering, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
| | - Mark M Youssef
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ 08854
| | - Ryad Benosman
- Robotics Institute, Carnegie Mellon University, Pittsburgh, PA 15213
| | - Ronald P Hart
- Human Genetics Institute, Rutgers University, Piscataway, NJ 08854
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ 08854
| | - Karl Herrup
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
- Departments of Medicine and Bioengineering, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261
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Martinsson I, Quintino L, Garcia MG, Konings SC, Torres-Garcia L, Svanbergsson A, Stange O, England R, Deierborg T, Li JY, Lundberg C, Gouras GK. Aβ/Amyloid Precursor Protein-Induced Hyperexcitability and Dysregulation of Homeostatic Synaptic Plasticity in Neuron Models of Alzheimer’s Disease. Front Aging Neurosci 2022; 14:946297. [PMID: 35928998 PMCID: PMC9344931 DOI: 10.3389/fnagi.2022.946297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 06/16/2022] [Indexed: 11/13/2022] Open
Abstract
Alzheimer’s disease (AD) is increasingly seen as a disease of synapses and diverse evidence has implicated the amyloid-β peptide (Aβ) in synapse damage. The molecular and cellular mechanism(s) by which Aβ and/or its precursor protein, the amyloid precursor protein (APP) can affect synapses remains unclear. Interestingly, early hyperexcitability has been described in human AD and mouse models of AD, which precedes later hypoactivity. Here we show that neurons in culture with either elevated levels of Aβ or with human APP mutated to prevent Aβ generation can both induce hyperactivity as detected by elevated calcium transient frequency and amplitude. Since homeostatic synaptic plasticity (HSP) mechanisms normally maintain a setpoint of activity, we examined whether HSP was altered in AD transgenic neurons. Using methods known to induce HSP, we demonstrate that APP protein levels are regulated by chronic modulation of activity and that AD transgenic neurons have an impaired adaptation of calcium transients to global changes in activity. Further, AD transgenic compared to WT neurons failed to adjust the length of their axon initial segments (AIS), an adaptation known to alter excitability. Thus, we show that both APP and Aβ influence neuronal activity and that mechanisms of HSP are disrupted in primary neuron models of AD.
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Affiliation(s)
- Isak Martinsson
- Experimental Dementia Research Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
- Experimental Neuroinflammation Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
- *Correspondence: Isak Martinsson,
| | - Luis Quintino
- CNS Gene Therapy, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Megg G. Garcia
- Experimental Dementia Research Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
- Experimental Neuroinflammation Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Sabine C. Konings
- Experimental Dementia Research Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Laura Torres-Garcia
- Experimental Dementia Research Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
- Neural Plasticity and Repair, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Alexander Svanbergsson
- Neural Plasticity and Repair, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Oliver Stange
- Experimental Dementia Research Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Rebecca England
- Experimental Dementia Research Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Tomas Deierborg
- Experimental Neuroinflammation Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Jia-Yi Li
- Neural Plasticity and Repair, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Cecilia Lundberg
- CNS Gene Therapy, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Gunnar K. Gouras
- Experimental Dementia Research Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
- Gunnar K. Gouras,
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Ju T, Sun L, Fan Y, Wang T, Liu Y, Liu D, Liu T, Zhao C, Wang W, Chi L. Decreased Netrin-1 in Mild Cognitive Impairment and Alzheimer’s Disease Patients. Front Aging Neurosci 2022; 13:762649. [PMID: 35250531 PMCID: PMC8888826 DOI: 10.3389/fnagi.2021.762649] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2021] [Accepted: 12/27/2021] [Indexed: 12/14/2022] Open
Abstract
Background and Objective Inflammatory mediators are closely associated with the pathogenesis of Alzheimer’s disease (AD) and mild cognitive impairment (MCI). Netrin-1 is an axon guidance protein and despite its capacity to function as a neuroimmune guidance signal, its role in AD or MCI is poorly understood. In addition, the association among netrin-1, cognitive impairment and serum inflammatory cytokines such as interleukin-17 (IL-17) and tumor necrosis (TNF-α) remains unclear. The aim of this study was to determine serum levels of IL-17, TNF-α and netrin-1in a cohort of AD and MCI patients, and to study the relationship between these cytokines and cognitive status, as well as to assess the possible relationships between netrin-1 levels and inflammatory molecules. Methods Serum concentrations of netrin-1, TNF-α and IL-17 were determined in 20 AD patients, 22 MCI patients and 22 healthy controls using an enzyme-linked immunosorbent assay (ELISA). In addition, neuropsychological evaluations and psychometric assessments were performed in all subjects. Results Serum netrin-1 levels were decreased in AD and MCI patients and were positively correlated with Mini Mental State Examination (MMSE) scores. In contrast, serum TNF-α and IL-17 levels were elevated in AD and MCI cohorts and negatively correlated with MMSE scores. Serum netrin-1 levels were inversely related with TNF-α and IL-17 levels in AD, but not MCI, patients. Conclusion Based on the findings reported here, netrin-1 may serve as a marker for the early recognition of dementia and predict cognitive impairment.
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Affiliation(s)
- Ting Ju
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Lina Sun
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Yuwei Fan
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Tianhang Wang
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Yanchen Liu
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Dan Liu
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Tianyi Liu
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Chang Zhao
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin, China
- Intensive Care Unit, Jiangyin People’s Hospital, Wuxi, China
| | - Wenxin Wang
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin, China
- Department of Neurology, Shenzhen Samii Medical Center, Shenzhen, China
| | - Lijun Chi
- Department of Neurology, The First Affiliated Hospital of Harbin Medical University, Harbin, China
- *Correspondence: Lijun Chi,
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Zhou Z, Bai J, Zhong S, Zhang R, Kang K, Zhang X, Xu Y, Zhao C, Zhao M. Downregulation of PIK3CB Involved in Alzheimer's Disease via Apoptosis, Axon Guidance, and FoxO Signaling Pathway. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2022; 2022:1260161. [PMID: 35096262 PMCID: PMC8794666 DOI: 10.1155/2022/1260161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 01/08/2022] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To investigate the molecular function of phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit beta (PIK3CB) underlying Alzheimer's disease (AD). METHODS RNA sequencing data were used to filtrate differentially expressed genes (DEGs) in AD/nondementia control and PIK3CB-low/high groups. An unbiased coexpression network was established to evaluate module-trait relationships by using weight gene correlation network analysis (WGCNA). Global regulatory network was constructed to predict the protein-protein interaction. Further cross-talking pathways of PIK3CB were identified by functional enrichment analysis. RESULTS The mean expression of PIK3CB in AD patients was significantly lower than those in nondementia controls. We identified 2,385 DEGs from 16,790 background genes in AD/control and PIK3CB-low/high groups. Five coexpression modules were established using WGCNA, which participated in apoptosis, axon guidance, long-term potentiation (LTP), regulation of actin cytoskeleton, synaptic vesicle cycle, FoxO, mitogen-activated protein kinase (MAPK), and vascular endothelial growth factor (VEGF) signaling pathways. DEGs with strong relation to AD and low PIK3CB expression were extracted to construct a global regulatory network, in which cross-talking pathways of PIK3CB were identified, such as apoptosis, axon guidance, and FoxO signaling pathway. The occurrence of AD could be accurately predicted by low PIK3CB based on the area under the curve of 71.7%. CONCLUSIONS These findings highlight downregulated PIK3CB as a potential causative factor of AD, possibly mediated via apoptosis, axon guidance, and FoxO signaling pathway.
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Affiliation(s)
- Zhike Zhou
- Department of Geriatrics, The First Affiliated Hospital, China Medical University, Shenyang, 110001 Liaoning, China
| | - Jun Bai
- Cancer Systems Biology Center, The China-Japan Union Hospital, Jilin University, Changchun, 130033 Jilin, China
| | - Shanshan Zhong
- Department of Neurology, The First Affiliated Hospital, China Medical University, Shenyang, 110001 Liaoning, China
| | - Rongwei Zhang
- Department of Geriatrics, The First Affiliated Hospital, China Medical University, Shenyang, 110001 Liaoning, China
| | - Kexin Kang
- Department of Geriatrics, The First Affiliated Hospital, China Medical University, Shenyang, 110001 Liaoning, China
| | - Xiaoqian Zhang
- Department of Neurology, The First Affiliated Hospital, China Medical University, Shenyang, 110001 Liaoning, China
| | - Ying Xu
- Cancer Systems Biology Center, The China-Japan Union Hospital, Jilin University, Changchun, 130033 Jilin, China
- Computational Systems Biology Lab, Department of Biochemistry and Molecular Biology and Institute of Bioinformatics, The University of Georgia, USA
| | - Chuansheng Zhao
- Department of Neurology, The First Affiliated Hospital, China Medical University, Shenyang, 110001 Liaoning, China
| | - Mei Zhao
- Department of Cardiology, The Shengjing Affiliated Hospital, China Medical University, Shenyang, 110004 Liaoning, China
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Fahed D, Chettab A, Mathe D, Denis M, Traverse-Glehen A, Karlin L, Perrial E, Dumontet C. Netrin-1 expression and targeting in multiple myeloma. Leuk Lymphoma 2021; 63:395-403. [PMID: 34585999 DOI: 10.1080/10428194.2021.1984459] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Deleted in colorectal cancer (DCC) and uncoordinated-5 (UNC5) receptors, play a key role in tumor progression of several solid tumors by inducing apoptosis when unbound to their ligand netrin-1. Netrin 1 is currently being evaluated as a therapeutic target. These receptors, known as dependence receptors, and their ligands, have not yet been extensively explored in hematological malignancies. Here, we performed a screening of various human myeloma cell lines and bone marrow samples from multiple myeloma patients for netrin-1 and its receptors to determine the expression of netrin 1 and its receptors in multiple myeloma as well as to assess the potential anti-myeloma activity of a novel anti-netrin-1 treatment (NP137). Our results showed heterogeneous expression of netrin-1 and its receptors DCC and UNC5H2(B) in six human myeloma lines. Additionally, immunohistochemistry and flow cytometry showed expression of these molecules in a majority of myeloma patient samples. In vitro NP137 did not induce apoptosis of myeloma cell lines yet enhanced the cytotoxicity of bortezomib and dexamethasone. In vivo, NP137 treatment of SCID mice with established RPMI8226 myeloma tumors led to a reduction of tumor size compared to controls. Ex vivo, NP137 lowered the plasma cells percentage in bone marrow aspirates in a fraction of the patient samples analyzed. These results suggest that netrin signaling could constitute a novel therapeutic target in multiple myeloma.
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Affiliation(s)
- David Fahed
- Anticancer Antibodies Team, CRCL, CNRS UMR5286, CLB, UCBL, Lyon, France
| | | | | | | | | | | | - Emeline Perrial
- Anticancer Antibodies Team, CRCL, CNRS UMR5286, CLB, UCBL, Lyon, France
| | - Charles Dumontet
- Anticancer Antibodies Team, CRCL, CNRS UMR5286, CLB, UCBL, Lyon, France.,Antineo, Lyon, France.,Hospices Civils de Lyon, Lyon, France
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12
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Steubler V, Erdinger S, Back MK, Ludewig S, Fässler D, Richter M, Han K, Slomianka L, Amrein I, von Engelhardt J, Wolfer DP, Korte M, Müller UC. Loss of all three APP family members during development impairs synaptic function and plasticity, disrupts learning, and causes an autism-like phenotype. EMBO J 2021; 40:e107471. [PMID: 34008862 PMCID: PMC8204861 DOI: 10.15252/embj.2020107471] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 03/29/2021] [Accepted: 04/01/2021] [Indexed: 12/15/2022] Open
Abstract
The key role of APP for Alzheimer pathogenesis is well established. However, perinatal lethality of germline knockout mice lacking the entire APP family has so far precluded the analysis of its physiological functions for the developing and adult brain. Here, we generated conditional APP/APLP1/APLP2 triple KO (cTKO) mice lacking the APP family in excitatory forebrain neurons from embryonic day 11.5 onwards. NexCre cTKO mice showed altered brain morphology with agenesis of the corpus callosum and disrupted hippocampal lamination. Further, NexCre cTKOs revealed reduced basal synaptic transmission and drastically reduced long-term potentiation that was associated with reduced dendritic length and reduced spine density of pyramidal cells. With regard to behavior, lack of the APP family leads not only to severe impairments in a panel of tests for learning and memory, but also to an autism-like phenotype including repetitive rearing and climbing, impaired social communication, and deficits in social interaction. Together, our study identifies essential functions of the APP family during development, for normal hippocampal function and circuits important for learning and social behavior.
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Affiliation(s)
- Vicky Steubler
- Department of Functional GenomicsInstitute of Pharmacy and Molecular BiotechnologyHeidelberg UniversityHeidelbergGermany
| | - Susanne Erdinger
- Department of Functional GenomicsInstitute of Pharmacy and Molecular BiotechnologyHeidelberg UniversityHeidelbergGermany
| | - Michaela K Back
- Institute of PathophysiologyFocus Program Translational Neuroscience (FTN)University Medical Center of the Johannes Gutenberg University MainzMainzGermany
| | - Susann Ludewig
- Division of Cellular NeurobiologyZoological Institute, TU BraunschweigBraunschweigGermany
- Helmholtz Centre for Infection Research, Neuroinflammation and Neurodegeneration GroupBraunschweigGermany
| | - Dominique Fässler
- Department of Functional GenomicsInstitute of Pharmacy and Molecular BiotechnologyHeidelberg UniversityHeidelbergGermany
| | - Max Richter
- Department of Functional GenomicsInstitute of Pharmacy and Molecular BiotechnologyHeidelberg UniversityHeidelbergGermany
| | - Kang Han
- Department of Functional GenomicsInstitute of Pharmacy and Molecular BiotechnologyHeidelberg UniversityHeidelbergGermany
| | - Lutz Slomianka
- Institute of Anatomy and Zurich Center for Integrative Human PhysiologyUniversity of ZurichZurichSwitzerland
| | - Irmgard Amrein
- Institute of Anatomy and Zurich Center for Integrative Human PhysiologyUniversity of ZurichZurichSwitzerland
| | - Jakob von Engelhardt
- Institute of PathophysiologyFocus Program Translational Neuroscience (FTN)University Medical Center of the Johannes Gutenberg University MainzMainzGermany
| | - David P Wolfer
- Institute of Anatomy and Zurich Center for Integrative Human PhysiologyUniversity of ZurichZurichSwitzerland
- Institute of Human Movement SciencesETH ZurichZurichSwitzerland
| | - Martin Korte
- Division of Cellular NeurobiologyZoological Institute, TU BraunschweigBraunschweigGermany
- Helmholtz Centre for Infection Research, Neuroinflammation and Neurodegeneration GroupBraunschweigGermany
| | - Ulrike C Müller
- Department of Functional GenomicsInstitute of Pharmacy and Molecular BiotechnologyHeidelberg UniversityHeidelbergGermany
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13
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Chen G, Kang SS, Wang Z, Ahn EH, Xia Y, Liu X, Sandoval IM, Manfredsson FP, Zhang Z, Ye K. Netrin-1 receptor UNC5C cleavage by active δ-secretase enhances neurodegeneration, promoting Alzheimer's disease pathologies. SCIENCE ADVANCES 2021; 7:7/16/eabe4499. [PMID: 33863723 PMCID: PMC8051868 DOI: 10.1126/sciadv.abe4499] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Accepted: 02/26/2021] [Indexed: 05/22/2023]
Abstract
Netrin-1, a family member of laminin-related secreted proteins, mediates axon guidance and cell migration during neural development. T835M mutation in netrin receptor UNC5C predisposes to the late-onset Alzheimer's disease (AD) and increases neuronal cell death. However, it remains unclear how this receptor is molecularly regulated in AD. Here, we show that δ-secretase selectively cleaves UNC5C and escalates its proapoptotic activity, facilitating neurodegeneration in AD. Netrin deficiency activates δ-secretase that specifically cuts UNC5C at N467 and N547 residues and enhances subsequent caspase-3 activation, additively augmenting neuronal cell death. Blockade of δ-secretase cleavage of UNC5C diminishes T835M mutant's proapoptotic activity. Viral expression of δ-secretase-truncated UNC5C fragments into APP/PS1 mice strongly accelerates AD pathologies, impairing learning and memory. Conversely, deletion of UNC5C from netrin-1-depleted mice attenuates AD pathologies and rescues cognitive disorders. Hence, δ-secretase truncates UNC5C and elevates its neurotoxicity, contributing to AD pathogenesis.
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Affiliation(s)
- Guiqin Chen
- Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan 430060, Hubei Province, China
| | - Seong Su Kang
- Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Zhihao Wang
- Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Eun Hee Ahn
- Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Yiyuan Xia
- Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Xia Liu
- Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Ivette M Sandoval
- Parkinson's Disease Research Unit, Department of Neurobiology, Barrow Neurological Institute, 350 West Thomas Road, Phoenix, AZ 85013, USA
| | - Fredric P Manfredsson
- Parkinson's Disease Research Unit, Department of Neurobiology, Barrow Neurological Institute, 350 West Thomas Road, Phoenix, AZ 85013, USA
| | - Zhaohui Zhang
- Department of Neurology, Renmin Hospital of Wuhan University, Wuhan 430060, Hubei Province, China.
| | - Keqiang Ye
- Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA.
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14
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Hoogmartens J, Cacace R, Van Broeckhoven C. Insight into the genetic etiology of Alzheimer's disease: A comprehensive review of the role of rare variants. ALZHEIMER'S & DEMENTIA (AMSTERDAM, NETHERLANDS) 2021; 13:e12155. [PMID: 33665345 PMCID: PMC7896636 DOI: 10.1002/dad2.12155] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 12/22/2020] [Accepted: 12/29/2020] [Indexed: 12/12/2022]
Abstract
Early-onset Alzheimer's disease (EOAD) is generally known as a dominant disease due to highly penetrant pathogenic mutations in the amyloid precursor protein, presenilin 1 and 2. However, they explain only a fraction of EOAD patients (5% to 10%). Furthermore, only 10% to 15% of EOAD families present with clear autosomal dominant inheritance. Studies showed that only 35% to 60% of EOAD patients have at least one affected first-degree relative. Parent-offspring concordance in EOAD was estimated to be <10%, indicating that full penetrant dominant alleles are not the sole players in EOAD. We aim to summarize current knowledge of rare variants underlying familial and seemingly sporadic Alzheimer's disease (AD) patients. Genetic findings indicate that in addition to the amyloid beta pathway, other pathways are of importance in AD pathophysiology. We discuss the difficulties in interpreting the influence of rare variants on disease onset and we underline the value of carefully selected ethnicity-matched cohorts in AD genetic research.
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Affiliation(s)
- Julie Hoogmartens
- Neurodegenerative Brain DiseasesVIB Center for Molecular NeurologyAntwerpBelgium
- Department of Biomedical SciencesUniversity of AntwerpAntwerpBelgium
| | - Rita Cacace
- Neurodegenerative Brain DiseasesVIB Center for Molecular NeurologyAntwerpBelgium
- Department of Biomedical SciencesUniversity of AntwerpAntwerpBelgium
| | - Christine Van Broeckhoven
- Neurodegenerative Brain DiseasesVIB Center for Molecular NeurologyAntwerpBelgium
- Department of Biomedical SciencesUniversity of AntwerpAntwerpBelgium
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15
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Zang Y, Chaudhari K, Bashaw GJ. New insights into the molecular mechanisms of axon guidance receptor regulation and signaling. Curr Top Dev Biol 2021; 142:147-196. [PMID: 33706917 DOI: 10.1016/bs.ctdb.2020.11.008] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
As the nervous system develops, newly differentiated neurons need to extend their axons toward their synaptic targets to form functional neural circuits. During this highly dynamic process of axon pathfinding, guidance receptors expressed at the tips of motile axons interact with soluble guidance cues or membrane tethered molecules present in the environment to be either attracted toward or repelled away from the source of these cues. As competing cues are often present at the same location and during the same developmental period, guidance receptors need to be both spatially and temporally regulated in order for the navigating axons to make appropriate guidance decisions. This regulation is exerted by a diverse array of molecular mechanisms that have come into focus over the past several decades and these mechanisms ensure that the correct complement of surface receptors is present on the growth cone, a fan-shaped expansion at the tip of the axon. This dynamic, highly motile structure is defined by a lamellipodial network lining the periphery of the growth cone interspersed with finger-like filopodial projections that serve to explore the surrounding environment. Once axon guidance receptors are deployed at the right place and time at the growth cone surface, they respond to their respective ligands by initiating a complex set of signaling events that serve to rearrange the growth cone membrane and the actin and microtubule cytoskeleton to affect axon growth and guidance. In this review, we highlight recent advances that shed light on the rich complexity of mechanisms that regulate axon guidance receptor distribution, activation and downstream signaling.
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Affiliation(s)
- Yixin Zang
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Karina Chaudhari
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Greg J Bashaw
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States.
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16
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Wang H, Yang J, Schneider JA, De Jager PL, Bennett DA, Zhang HY. Genome-wide interaction analysis of pathological hallmarks in Alzheimer's disease. Neurobiol Aging 2020; 93:61-68. [PMID: 32450446 PMCID: PMC9795865 DOI: 10.1016/j.neurobiolaging.2020.04.025] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Revised: 04/21/2020] [Accepted: 04/22/2020] [Indexed: 12/31/2022]
Abstract
Genome-wide association studies have identified many loci associated with Alzheimer's dementia. However, these variants only explain part of the heritability of Alzheimer's disease (AD). As genetic epistasis can be a major contributor to the "missing heritability" of AD, we conducted genome-wide epistasis screening for AD pathologies in 2 independent cohorts. First, we performed a genome-wide epistasis study of AD-related brain pathologies (Nmax = 1318) in ROS/MAP. Candidate interactions were validated using cerebrospinal fluid biomarkers of AD in ADNI (Nmax = 1128). Further functional analysis tested the association of candidate interactions with neuroimaging phenotypes. For tau and amyloid-β pathology, we identified 2803 and 464 candidate SNP-SNP interactions, respectively. Associations of candidate SNP-SNP interactions with brain volume and white matter changes from neuroimages provides additional insights into their molecular functions. Transcriptional analysis supported possible gene-gene interactions identified by statistical screening through their co-expression in the brain. In summary, we outlined an exhaustive epistasis analysis to identify novel genetic interactions with potential roles in AD pathologies. We further delved into the functional relevance of candidate interactions by association with neuroimaging phenotypes and analysis of co-expression between corresponding gene pairs.
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Affiliation(s)
- Hui Wang
- Hubei Key Laboratory of Agricultural Bioinformatics, College of Informatics, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Jingyun Yang
- Rush Alzheimer’s Disease Center, Rush University Medical Center, Chicago, Illinois, USA,Department of Neurological Sciences, Rush University Medical Center, Chicago, Illinois, USA
| | - Julie A. Schneider
- Rush Alzheimer’s Disease Center, Rush University Medical Center, Chicago, Illinois, USA,Department of Neurological Sciences, Rush University Medical Center, Chicago, Illinois, USA,Department of Pathology, Rush University Medical Center, Chicago, Illinois, USA
| | - Philip L De Jager
- Center for Translational and Computational Neuroimmunology, Columbia University Medical Center, New York, New York, USA,Cell Circuits Program, Broad Institute, Cambridge, Massachusetts, USA
| | - David A. Bennett
- Rush Alzheimer’s Disease Center, Rush University Medical Center, Chicago, Illinois, USA,Department of Neurological Sciences, Rush University Medical Center, Chicago, Illinois, USA,Corresponding to Hong-Yu Zhang, Huazhong Agricultural University, No.1 Shizishan Street, Hongshan District, Wuhan, Hubei 430070, China, Tel: +86-27-87285085, , David A. Bennett, Rush Medical College, 600 S Paulina St, Chicago, IL 60612, USA, Tel: +1-312-942-4463,
| | - Hong-Yu Zhang
- Hubei Key Laboratory of Agricultural Bioinformatics, College of Informatics, Huazhong Agricultural University, Wuhan, Hubei, China,Corresponding to Hong-Yu Zhang, Huazhong Agricultural University, No.1 Shizishan Street, Hongshan District, Wuhan, Hubei 430070, China, Tel: +86-27-87285085, , David A. Bennett, Rush Medical College, 600 S Paulina St, Chicago, IL 60612, USA, Tel: +1-312-942-4463,
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17
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Abstract
The spinal cord receives, relays and processes sensory information from the periphery and integrates this information with descending inputs from supraspinal centres to elicit precise and appropriate behavioural responses and orchestrate body movements. Understanding how the spinal cord circuits that achieve this integration are wired during development is the focus of much research interest. Several families of proteins have well-established roles in guiding developing spinal cord axons, and recent findings have identified new axon guidance molecules. Nevertheless, an integrated view of spinal cord network development is lacking, and many current models have neglected the cellular and functional diversity of spinal cord circuits. Recent advances challenge the existing spinal cord axon guidance dogmas and have provided a more complex, but more faithful, picture of the ontogenesis of vertebrate spinal cord circuits.
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18
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Meijers R, Smock RG, Zhang Y, Wang JH. Netrin Synergizes Signaling and Adhesion through DCC. Trends Biochem Sci 2019; 45:6-12. [PMID: 31704057 DOI: 10.1016/j.tibs.2019.10.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 10/09/2019] [Accepted: 10/14/2019] [Indexed: 01/08/2023]
Abstract
Netrin is a prototypical axon guidance cue. Structural studies have revealed how netrin interacts with the deleted in colorectal cancer (DCC) receptor, other receptors, and co-factors for signaling. Recently, genetic studies suggested that netrin is involved in neuronal haptotaxis, which requires a reversible adhesion process. Structural data indicate that netrin can also mediate trans-adhesion between apposing cells decorated with its receptors on the condition that the auxiliary guidance cue draxin is present. Here, we propose that netrin is involved in conditional adhesion, a reversible and localized process that can contribute to cell adhesion and migration. We suggest that netrin-mediated adhesion and signaling are linked, and that local environmental factors in the ventricular zone, the floor plate, or other tissues coordinate its function.
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Affiliation(s)
- Rob Meijers
- European Molecular Biology Laboratory (EMBL), Hamburg Outstation, Notkestrasse 85, D-22607 Hamburg, Germany.
| | - Robert G Smock
- European Molecular Biology Laboratory (EMBL), Hamburg Outstation, Notkestrasse 85, D-22607 Hamburg, Germany
| | - Yan Zhang
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871 China
| | - Jia-Huai Wang
- State Key Laboratory of Membrane Biology, College of Life Sciences, Peking University, Beijing 100871 China; Department of Medical Oncology and Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA.
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19
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Lee WS, Lee WH, Bae YC, Suk K. Axon Guidance Molecules Guiding Neuroinflammation. Exp Neurobiol 2019; 28:311-319. [PMID: 31308791 PMCID: PMC6614065 DOI: 10.5607/en.2019.28.3.311] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 05/08/2019] [Accepted: 05/09/2019] [Indexed: 12/19/2022] Open
Abstract
Axon guidance molecules (AGMs), such as Netrins, Semaphorins, and Ephrins, have long been known to regulate axonal growth in the developing nervous system. Interestingly, the chemotactic properties of AGMs are also important in the postnatal period, such as in the regulation of immune and inflammatory responses. In particular, AGMs play pivotal roles in inflammation of the nervous system, by either stimulating or inhibiting inflammatory responses, depending on specific ligand-receptor combinations. Understanding such regulatory functions of AGMs in neuroinflammation may allow finding new molecular targets to treat neurodegenerative diseases, in which neuroinflammation underlies aetiology and progression.
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Affiliation(s)
- Won Suk Lee
- Department of Pharmacology, School of Medicine, Kyungpook National University, Daegu 41944, Korea.,Brain Science and Engineering Institute, Kyungpook National University, Daegu 41944, Korea
| | - Won-Ha Lee
- BK21 Plus KNU Creative BioResearch Group, School of Life Sciences, Kyungpook National University, Daegu 41566, Korea
| | - Yong Chul Bae
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu 41940, Korea
| | - Kyoungho Suk
- Department of Pharmacology, School of Medicine, Kyungpook National University, Daegu 41944, Korea.,Brain Science and Engineering Institute, Kyungpook National University, Daegu 41944, Korea
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20
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Tang BL. Amyloid Precursor Protein (APP) and GABAergic Neurotransmission. Cells 2019; 8:E550. [PMID: 31174368 PMCID: PMC6627941 DOI: 10.3390/cells8060550] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 05/25/2019] [Accepted: 06/06/2019] [Indexed: 12/16/2022] Open
Abstract
The amyloid precursor protein (APP) is the parent polypeptide from which amyloid-beta (Aβ) peptides, key etiological agents of Alzheimer's disease (AD), are generated by sequential proteolytic processing involving β- and γ-secretases. APP mutations underlie familial, early-onset AD, and the involvement of APP in AD pathology has been extensively studied. However, APP has important physiological roles in the mammalian brain, particularly its modulation of synaptic functions and neuronal survival. Recent works have now shown that APP could directly modulate γ-aminobutyric acid (GABA) neurotransmission in two broad ways. Firstly, APP is shown to interact with and modulate the levels and activity of the neuron-specific Potassium-Chloride (K+-Cl-) cotransporter KCC2/SLC12A5. The latter is key to the maintenance of neuronal chloride (Cl-) levels and the GABA reversal potential (EGABA), and is therefore important for postsynaptic GABAergic inhibition through the ionotropic GABAA receptors. Secondly, APP binds to the sushi domain of metabotropic GABAB receptor 1a (GABABR1a). In this regard, APP complexes and is co-transported with GABAB receptor dimers bearing GABABR1a to the axonal presynaptic plasma membrane. On the other hand, secreted (s)APP generated by secretase cleavages could act as a GABABR1a-binding ligand that modulates presynaptic vesicle release. The discovery of these novel roles and activities of APP in GABAergic neurotransmission underlies the physiological importance of APP in postnatal brain function.
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Affiliation(s)
- Bor Luen Tang
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597, Singapore.
- NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore 117597, Singapore.
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21
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Sokol DK, Maloney B, Westmark CJ, Lahiri DK. Novel Contribution of Secreted Amyloid-β Precursor Protein to White Matter Brain Enlargement in Autism Spectrum Disorder. Front Psychiatry 2019; 10:165. [PMID: 31024350 PMCID: PMC6469489 DOI: 10.3389/fpsyt.2019.00165] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 03/06/2019] [Indexed: 12/27/2022] Open
Abstract
The most replicated neuroanatomical finding in autism is the tendency toward brain overgrowth, especially in younger children. Research shows that both gray and white matter are enlarged. Proposed mechanisms underlying brain enlargement include abnormal inflammatory and neurotrophic signals that lead to excessive, aberrant dendritic connectivity via disrupted pruning and cell adhesion, and enlargement of white matter due to excessive gliogenesis and increased myelination. Amyloid-β protein precursor (βAPP) and its metabolites, more commonly associated with Alzheimer's disease (AD), are also dysregulated in autism plasma and brain tissue samples. This review highlights findings that demonstrate how one βAPP metabolite, secreted APPα, and the ADAM family α-secretases, may lead to increased brain matter, with emphasis on increased white matter as seen in autism. sAPPα and the ADAM family α-secretases contribute to the anabolic, non-amyloidogenic pathway, which is in contrast to the amyloid (catabolic) pathway known to contribute to Alzheimer disease. The non-amyloidogenic pathway could produce brain enlargement via genetic mechanisms affecting mRNA translation and polygenic factors that converge on molecular pathways (mitogen-activated protein kinase/MAPK and mechanistic target of rapamycin/mTOR), promoting neuroinflammation. A novel mechanism linking the non-amyloidogenic pathway to white matter enlargement is proposed: α-secretase and/or sAPPα, activated by ERK receptor signaling activates P13K/AKt/mTOR and then Rho GTPases favoring myelination via oligodendrocyte progenitor cell (OPC) activation of cofilin. Applying known pathways in AD to autism should allow further understanding and provide options for new drug targets.
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Affiliation(s)
- Deborah K. Sokol
- Pediatrics Section, Department of Neurology, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Bryan Maloney
- Indiana Alzheimers Disease Center, Department of Psychiatry, Stark Neuroscience Research Institute, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Cara J. Westmark
- Department of Neurology, University of Wisconsin, Madison, WI, United States
| | - Debomoy K. Lahiri
- Indiana Alzheimers Disease Center, Department of Psychiatry, Stark Neuroscience Research Institute, Indiana University School of Medicine, Indianapolis, IN, United States
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN, United States
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22
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Park MK, Lee JW, Lee JC, Hwang SJ, Roh HW, Hong CH, Son SJ. NLRP1 and NTN1, Deregulated Blood Differentially Methylated Regions in Mild Cognitive Impairment Patients. J Mol Neurosci 2018; 66:561-571. [DOI: 10.1007/s12031-018-1180-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Accepted: 09/21/2018] [Indexed: 12/31/2022]
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23
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Medoro A, Bartollino S, Mignogna D, Passarella D, Porcile C, Pagano A, Florio T, Nizzari M, Guerra G, Di Marco R, Intrieri M, Raimo G, Russo C. Complexity and Selectivity of γ-Secretase Cleavage on Multiple Substrates: Consequences in Alzheimer's Disease and Cancer. J Alzheimers Dis 2018; 61:1-15. [PMID: 29103038 DOI: 10.3233/jad-170628] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The processing of the amyloid-β protein precursor (AβPP) by β- and γ-secretases is a pivotal event in the genesis of Alzheimer's disease (AD). Besides familial mutations on the AβPP gene, or upon its overexpression, familial forms of AD are often caused by mutations or deletions in presenilin 1 (PSEN1) and 2 (PSEN2) genes: the catalytic components of the proteolytic enzyme γ-secretase (GS). The "amyloid hypothesis", modified over time, states that the aberrant processing of AβPP by GS induces the formation of specific neurotoxic soluble amyloid-β (Aβ) peptides which, in turn, cause neurodegeneration. This theory, however, has recently evidenced significant limitations and, in particular, the following issues are debated: 1) the concept and significance of presenilin's "gain of function" versus "loss of function"; and 2) the presence of several and various GS substrates, which interact with AβPP and may influence Aβ formation. The latter consideration is suggestive: despite the increasing number of GS substrates so far identified, their reciprocal interaction with AβPP itself, even in the AD field, is significantly unexplored. On the other hand, GS is also an important pharmacological target in the cancer field; inhibitors or GS activity are investigated in clinical trials for treating different tumors. Furthermore, the function of AβPP and PSENs in brain development and in neuronal migration is well known. In this review, we focused on a specific subset of GS substrates that directly interact with AβPP and are involved in its proteolysis and signaling, by evaluating their role in neurodegeneration and in cell motility or proliferation, as a possible connection between AD and cancer.
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Affiliation(s)
- Alessandro Medoro
- Department of Medicine and Health Sciences "V. Tiberio", University of Molise, Campobasso, Italy
| | - Silvia Bartollino
- Department of Medicine and Health Sciences "V. Tiberio", University of Molise, Campobasso, Italy
| | - Donatella Mignogna
- Department of Medicine and Health Sciences "V. Tiberio", University of Molise, Campobasso, Italy
| | - Daniela Passarella
- Department of Medicine and Health Sciences "V. Tiberio", University of Molise, Campobasso, Italy
| | - Carola Porcile
- Department of Medicine and Health Sciences "V. Tiberio", University of Molise, Campobasso, Italy
| | - Aldo Pagano
- Department of Experimental Medicine, University of Genoa and Ospedale Policlinico San Martino, IRCCS per l'Oncologia, Genoa, Italy
| | - Tullio Florio
- Department of Internal Medicine and Centre of Excellence for Biomedical Research, University of Genoa, Genoa, Italy
| | - Mario Nizzari
- Department of Internal Medicine and Centre of Excellence for Biomedical Research, University of Genoa, Genoa, Italy
| | - Germano Guerra
- Department of Medicine and Health Sciences "V. Tiberio", University of Molise, Campobasso, Italy
| | - Roberto Di Marco
- Department of Medicine and Health Sciences "V. Tiberio", University of Molise, Campobasso, Italy
| | - Mariano Intrieri
- Department of Medicine and Health Sciences "V. Tiberio", University of Molise, Campobasso, Italy
| | - Gennaro Raimo
- Department of Medicine and Health Sciences "V. Tiberio", University of Molise, Campobasso, Italy
| | - Claudio Russo
- Department of Medicine and Health Sciences "V. Tiberio", University of Molise, Campobasso, Italy
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Dai MH, Zheng H, Zeng LD, Zhang Y. The genes associated with early-onset Alzheimer's disease. Oncotarget 2018; 9:15132-15143. [PMID: 29599933 PMCID: PMC5871104 DOI: 10.18632/oncotarget.23738] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Accepted: 10/14/2017] [Indexed: 01/31/2023] Open
Abstract
Alzheimer's disease (AD) is a progressive neurodegenerative disorder that accounts for the most cases of dementia, which is characterized by the deposition of dense plaques of amyloid beta (Aβ) plaques and neurofibrillary tangles consisting of hyperphosphorylated tau. The two main types of AD can be classified as early-onset AD (EOAD, onset < 65 years) and late-onset AD (LOAD, onset ≥ 65 years). Evidence from family and twin studies indicate that genetic factors are estimated to play a role in at least 80% of AD cases. The first milestone with linkage analysis revealed the mutations in APP, PSEN1, and PSEN2 genes that cause EOAD. But pathogenic mutations in these three genes can only explain a small fraction of EOAD families. The additional disease-causing genes have not yet been identified. This review provides an overview of the genetic basis of EOAD and the relationship between the functions of these risk genes and the neuropathologic features of AD. A better understanding of genetic mechanisms underlying EOAD pathogenesis and the potentially molecular mechanisms of neurodegeneration will lead to the development of effective diagnosis and treatment strategies for this devastating disease.
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Affiliation(s)
- Meng-Hui Dai
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
| | - Hui Zheng
- Department of Radiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
| | - Ling-Dan Zeng
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
| | - Yan Zhang
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
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Sosa LJ, Cáceres A, Dupraz S, Oksdath M, Quiroga S, Lorenzo A. The physiological role of the amyloid precursor protein as an adhesion molecule in the developing nervous system. J Neurochem 2017; 143:11-29. [PMID: 28677143 DOI: 10.1111/jnc.14122] [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: 12/30/2016] [Revised: 06/28/2017] [Accepted: 06/29/2017] [Indexed: 12/12/2022]
Abstract
The amyloid precursor protein (APP) is a type I transmembrane glycoprotein better known for its participation in the physiopathology of Alzheimer disease as the source of the beta amyloid fragment. However, the physiological functions of the full length protein and its proteolytic fragments have remained elusive. APP was first described as a cell-surface receptor; nevertheless, increasing evidence highlighted APP as a cell adhesion molecule. In this review, we will focus on the current knowledge of the physiological role of APP as a cell adhesion molecule and its involvement in key events of neuronal development, such as migration, neurite outgrowth, growth cone pathfinding, and synaptogenesis. Finally, since APP is over-expressed in Down syndrome individuals because of the extra copy of chromosome 21, in the last section of the review, we discuss the potential contribution of APP to the neuronal and synaptic defects described in this genetic condition. Read the Editorial Highlight for this article on page 9. Cover Image for this issue: doi. 10.1111/jnc.13817.
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Affiliation(s)
- Lucas J Sosa
- Departamento de Química Biológica Ranwell Caputto, Facultad de Ciencias Químicas, CIQUIBIC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Alfredo Cáceres
- Laboratorio Neurobiología, Instituto Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina.,Instituto Universitario Ciencias Biomédicas Córdoba, Córdoba, Argentina
| | - Sebastián Dupraz
- Axonal Growth and Regeneration, German Center for Neurodegenarative Diseases, Bonn, Germany
| | - Mariana Oksdath
- Departamento de Química Biológica Ranwell Caputto, Facultad de Ciencias Químicas, CIQUIBIC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Santiago Quiroga
- Departamento de Química Biológica Ranwell Caputto, Facultad de Ciencias Químicas, CIQUIBIC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Alfredo Lorenzo
- Laboratorio de Neuropatología Experimental, Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina
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26
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Molecular characterization of Netrin-1 and APP receptor binding: New leads to block the progression of senile plaques in Alzheimer's disease. Biochem Biophys Res Commun 2017; 488:466-470. [PMID: 28501620 DOI: 10.1016/j.bbrc.2017.05.056] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2017] [Accepted: 05/09/2017] [Indexed: 01/20/2023]
Abstract
Alzheimer's disease is a growing concern in the context of the increasing lifespan of the populations. The work presented here is part of the fight against this threat. It supports a therapeutic approach to reduce the incidence of Alzheimer's disease, taking advantage of the specific binding of several domains of Netrin-1 to the β-amyloid precursor protein. This basic knowledge shall then be used to predict, design or characterize lead compounds that may in turn inhibit/delay Alzheimer's disease's progression, extending the therapeutic offer of the other leads already being investigated in this line. The present work is focused on the interaction of the various portions of APP with the three domains of Netrin-1, the so-called LamNT, EGF-like and NTR domains respectively. It reveals in detail which portions of APP and Netrin-1 are specifically involved in these interactions, using ELISA technique in combination with protein-protein binding simulations. So far unsuspected interaction sites located in Netrin-1 EGF-like and NTR domains open possibilities for new therapeutic approaches in which these sites will be specifically targeted.
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27
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Wang B, Li H, Mutlu SA, Bowser DA, Moore MJ, Wang MC, Zheng H. The Amyloid Precursor Protein Is a Conserved Receptor for Slit to Mediate Axon Guidance. eNeuro 2017; 4:ENEURO.0185-17.2017. [PMID: 28785723 PMCID: PMC5534435 DOI: 10.1523/eneuro.0185-17.2017] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Accepted: 05/29/2017] [Indexed: 02/03/2023] Open
Abstract
The amyloid precursor protein (APP) is a receptor-like membrane protein. Although APP processing and β-amyloid production play a central role in Alzheimer's disease (AD) pathogenesis, the physiological function of APP remains elusive. Here, we identify APP as a novel receptor for Slit that mediates axon guidance and neural circuit formation. APP deficiency abolishes the Slit repulsive effect in a 3D olfactory explant culture, consistent with its callosal projection deficit in vivo and reminiscent of Slit loss. Inactivation of APP ortholog APL-1 in Caenorhabditis elegans results in pioneer axon mistargeting and genetic analysis places APL-1 in the SLT-1 (Slit)/SAX-3 (Robo) repulsive pathway. Slit binds to APP through the E1 domain, which triggers APP ectodomain shedding and recruitment of the intracellular FE65 and Pak1 complex and associated Rac1 GTPase activation. Our study establishes APP as a novel receptor for Slit ligand mediating axon guidance and neural circuit formation.
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Affiliation(s)
- Baiping Wang
- Huffington Center on Aging and Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030
| | - Hongmei Li
- Huffington Center on Aging and Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030
| | - Sena A. Mutlu
- Program in Developmental Biology, Baylor College of Medicine, Houston, TX 77030
| | - Devon A. Bowser
- Interdisciplinary Bioinnovation PhD Program, Tulane University, New Orleans, LA 70118
| | - Michael J. Moore
- Department of Biomedical Engineering, Tulane University, New Orleans, LA 70118
| | - Meng C. Wang
- Huffington Center on Aging and Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030
| | - Hui Zheng
- Huffington Center on Aging and Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030
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28
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Not just amyloid: physiological functions of the amyloid precursor protein family. Nat Rev Neurosci 2017; 18:281-298. [PMID: 28360418 DOI: 10.1038/nrn.2017.29] [Citation(s) in RCA: 387] [Impact Index Per Article: 55.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Amyloid precursor protein (APP) gives rise to the amyloid-β peptide and thus has a key role in the pathogenesis of Alzheimer disease. By contrast, the physiological functions of APP and the closely related APP-like proteins (APLPs) remain less well understood. Studying these physiological functions has been challenging and has required a careful long-term strategy, including the analysis of different App-knockout and Aplp-knockout mice. In this Review, we summarize these findings, focusing on the in vivo roles of APP family members and their processing products for CNS development, synapse formation and function, brain injury and neuroprotection, as well as ageing. In addition, we discuss the implications of APP physiology for therapeutic approaches.
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29
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Spilman PR, Corset V, Gorostiza O, Poksay KS, Galvan V, Zhang J, Rao R, Peters-Libeu C, Vincelette J, McGeehan A, Dvorak-Ewell M, Beyer J, Campagna J, Bankiewicz K, Mehlen P, John V, Bredesen DE. Netrin-1 Interrupts Amyloid-β Amplification, Increases sAβPPα in vitro and in vivo, and Improves Cognition in a Mouse Model of Alzheimer's Disease. J Alzheimers Dis 2017; 52:223-42. [PMID: 27060954 DOI: 10.3233/jad-151046] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Recent studies have shown that inoculation of susceptible mice with amyloid-β (Aβ) peptides accelerates Aβ deposition in the brain, supporting the idea that Aβ may be self-amplifying; however, the exact mechanism is not understood. Here we provide evidence that Aβ may self-amplify, in part, by inhibiting α-secretase ADAM10 (a disintegrin and metalloprotease) cleavage of full-length Aβ precursor protein (FL AβPP) and therefore allow greater β-secretase processing, and that Aβ itself is a substrate for ADAM10. Exposure of primary neuronal cultures from PDAβPP mice to exogenous rat Aβ1- 40 resulted in increased de novo human Aβ1-42 production and exposure of cells to Aβ decreased production of ADAM10 cleavage product soluble AβPPα (sAβPPα). In a cell-free assay, Aβ decreased ADAM10 cleavage of the chimeric substrate MBP-AβPPC125 and Aβ itself was apparently cleaved by the enzyme. The axonal guidance and trophic factor netrin-1, however, reduced the Aβ1- 40-induced Aβ1-42 increase, increased sAβPPα, and reversed the Aβ-induced sAβPPα decrease in vitro. In vivo, induction of netrin-1 expression in PDAβPPSwe/Ind transgenic mice resulted in reductions in both Aβ1-42 and Aβ1- 40, and ICV delivery of netrin-1 to PDAβPPSwe/Ind mice increased sAβPPα, decreased Aβ, and improved working memory. Finally, to support further study of netrin-1's potential as a therapeutic for Alzheimer's disease, pilot gene therapy studies were performed and a netrin mimetic peptide synthesized and tested that, like netrin, can increase sAβPPα and decrease Aβ1-42in vitro. Taken together, these data provide mechanistic insights into Aβ self-amplification and the ability of netrin-1 to disrupt it.
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Affiliation(s)
- Patricia R Spilman
- Buck Institute for Research on Aging, Novato, CA, USA.,Drug Discovery Laboratory, Department of Neurology & Easton Center for AD Research, University of California, Los Angeles, CA, USA
| | - Veronique Corset
- Buck Institute for Research on Aging, Novato, CA, USA.,Apoptosis, Cancer and Development Laboratory, University of Lyon Cancer Center, Centre Léon Bérard, Lyon, France
| | | | | | | | - Junli Zhang
- Buck Institute for Research on Aging, Novato, CA, USA
| | - Rammohan Rao
- Buck Institute for Research on Aging, Novato, CA, USA
| | | | | | | | | | - Janine Beyer
- Laboratory for Translational Neuroscience Research, Department of Neurological Surgery, University of California, San Francisco, CA, USA
| | - Jesus Campagna
- Buck Institute for Research on Aging, Novato, CA, USA.,Drug Discovery Laboratory, Department of Neurology & Easton Center for AD Research, University of California, Los Angeles, CA, USA
| | - Krystof Bankiewicz
- Laboratory for Translational Neuroscience Research, Department of Neurological Surgery, University of California, San Francisco, CA, USA
| | - Patrick Mehlen
- Apoptosis, Cancer and Development Laboratory, University of Lyon Cancer Center, Centre Léon Bérard, Lyon, France
| | - Varghese John
- Buck Institute for Research on Aging, Novato, CA, USA.,Drug Discovery Laboratory, Department of Neurology & Easton Center for AD Research, University of California, Los Angeles, CA, USA
| | - Dale E Bredesen
- Buck Institute for Research on Aging, Novato, CA, USA.,Drug Discovery Laboratory, Department of Neurology & Easton Center for AD Research, University of California, Los Angeles, CA, USA
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30
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Wang S, Bolós M, Clark R, Cullen CL, Southam KA, Foa L, Dickson TC, Young KM. Amyloid β precursor protein regulates neuron survival and maturation in the adult mouse brain. Mol Cell Neurosci 2016; 77:21-33. [DOI: 10.1016/j.mcn.2016.09.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 08/12/2016] [Accepted: 09/19/2016] [Indexed: 01/08/2023] Open
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31
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Ramaker JM, Cargill RS, Swanson TL, Quirindongo H, Cassar M, Kretzschmar D, Copenhaver PF. Amyloid Precursor Proteins Are Dynamically Trafficked and Processed during Neuronal Development. Front Mol Neurosci 2016; 9:130. [PMID: 27932950 PMCID: PMC5122739 DOI: 10.3389/fnmol.2016.00130] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Accepted: 11/10/2016] [Indexed: 01/10/2023] Open
Abstract
Proteolytic processing of the Amyloid Precursor Protein (APP) produces beta-amyloid (Aβ) peptide fragments that accumulate in Alzheimer's Disease (AD), but APP may also regulate multiple aspects of neuronal development, albeit via mechanisms that are not well understood. APP is a member of a family of transmembrane glycoproteins expressed by all higher organisms, including two mammalian orthologs (APLP1 and APLP2) that have complicated investigations into the specific activities of APP. By comparison, insects express only a single APP-related protein (APP-Like, or APPL) that contains the same protein interaction domains identified in APP. However, unlike its mammalian orthologs, APPL is only expressed by neurons, greatly simplifying an analysis of its functions in vivo. Like APP, APPL is processed by secretases to generate a similar array of extracellular and intracellular cleavage fragments, as well as an Aβ-like fragment that can induce neurotoxic responses in the brain. Exploiting the complementary advantages of two insect models (Drosophila melanogaster and Manduca sexta), we have investigated the regulation of APPL trafficking and processing with respect to different aspects of neuronal development. By comparing the behavior of endogenously expressed APPL with fluorescently tagged versions of APPL and APP, we have shown that some full-length protein is consistently trafficked into the most motile regions of developing neurons both in vitro and in vivo. Concurrently, much of the holoprotein is rapidly processed into N- and C-terminal fragments that undergo bi-directional transport within distinct vesicle populations. Unexpectedly, we also discovered that APPL can be transiently sequestered into an amphisome-like compartment in developing neurons, while manipulations targeting APPL cleavage altered their motile behavior in cultured embryos. These data suggest that multiple mechanisms restrict the bioavailability of the holoprotein to regulate APPL-dependent responses within the nervous system. Lastly, targeted expression of our double-tagged constructs (combined with time-lapse imaging) revealed that APP family proteins are subject to complex patterns of trafficking and processing that vary dramatically between different neuronal subtypes. In combination, our results provide a new perspective on how the regulation of APP family proteins can be modulated to accommodate a variety of cell type-specific responses within the embryonic and adult nervous system.
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Affiliation(s)
- Jenna M Ramaker
- Department of Cell, Developmental and Cancer Biology, Oregon Health and Science UniversityPortland, OR, USA; Neuroscience Graduate Program, Oregon Health and Science UniversityPortland, OR, USA
| | - Robert S Cargill
- Oregon Institute of Occupational Health Sciences, Oregon Health and Science University Portland, OR, USA
| | - Tracy L Swanson
- Department of Cell, Developmental and Cancer Biology, Oregon Health and Science University Portland, OR, USA
| | - Hanil Quirindongo
- Oregon Institute of Occupational Health Sciences, Oregon Health and Science University Portland, OR, USA
| | - Marlène Cassar
- Oregon Institute of Occupational Health Sciences, Oregon Health and Science University Portland, OR, USA
| | - Doris Kretzschmar
- Oregon Institute of Occupational Health Sciences, Oregon Health and Science University Portland, OR, USA
| | - Philip F Copenhaver
- Department of Cell, Developmental and Cancer Biology, Oregon Health and Science University Portland, OR, USA
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32
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Rappaz B, Lai Wing Sun K, Correia JP, Wiseman PW, Kennedy TE. FLIM FRET Visualization of Cdc42 Activation by Netrin-1 in Embryonic Spinal Commissural Neuron Growth Cones. PLoS One 2016; 11:e0159405. [PMID: 27482713 PMCID: PMC4970703 DOI: 10.1371/journal.pone.0159405] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 07/02/2016] [Indexed: 12/29/2022] Open
Abstract
Netrin-1 is an essential extracellular chemoattractant that signals through its receptor DCC to guide commissural axon extension in the embryonic spinal cord. DCC directs the organization of F-actin in growth cones by activating an intracellular protein complex that includes the Rho GTPase Cdc42, a critical regulator of cell polarity and directional migration. To address the spatial distribution of signaling events downstream of netrin-1, we expressed the FRET biosensor Raichu-Cdc42 in cultured embryonic rat spinal commissural neurons. Using FLIM-FRET imaging we detected rapid activation of Cdc42 in neuronal growth cones following application of netrin-1. Investigating the signaling mechanisms that control Cdc42 activation by netrin-1, we demonstrate that netrin-1 rapidly enriches DCC at the leading edge of commissural neuron growth cones and that netrin-1 induced activation of Cdc42 in the growth cone is blocked by inhibiting src family kinase signaling. These findings reveal the activation of Cdc42 in embryonic spinal commissural axon growth cones and support the conclusion that src family kinase activation downstream of DCC is required for Cdc42 activation by netrin-1.
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Affiliation(s)
- Benjamin Rappaz
- Program in NeuroEngineering, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Neurology and Neurosurgery, Montréal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Physics, McGill University, Montreal, QC, H3A 2T8, Canada
| | - Karen Lai Wing Sun
- Program in NeuroEngineering, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Neurology and Neurosurgery, Montréal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada
| | - James P. Correia
- Program in NeuroEngineering, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Neurology and Neurosurgery, Montréal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada
| | - Paul W. Wiseman
- Program in NeuroEngineering, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Physics, McGill University, Montreal, QC, H3A 2T8, Canada
- Department of Chemistry, McGill University, Montreal, QC, H3A 0B8, Canada
| | - Timothy E. Kennedy
- Program in NeuroEngineering, McGill University, Montreal, QC, H3A 2B4, Canada
- Department of Neurology and Neurosurgery, Montréal Neurological Institute, McGill University, Montreal, QC, H3A 2B4, Canada
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33
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Batmanghelich NK, Dalca A, Quon G, Sabuncu M, Golland P. Probabilistic Modeling of Imaging, Genetics and Diagnosis. IEEE TRANSACTIONS ON MEDICAL IMAGING 2016; 35:1765-1779. [PMID: 26886973 PMCID: PMC5364030 DOI: 10.1109/tmi.2016.2527784] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We propose a unified Bayesian framework for detecting genetic variants associated with disease by exploiting image-based features as an intermediate phenotype. The use of imaging data for examining genetic associations promises new directions of analysis, but currently the most widely used methods make sub-optimal use of the richness that these data types can offer. Currently, image features are most commonly selected based on their relevance to the disease phenotype. Then, in a separate step, a set of genetic variants is identified to explain the selected features. In contrast, our method performs these tasks simultaneously in order to jointly exploit information in both data types. The analysis yields probabilistic measures of clinical relevance for both imaging and genetic markers. We derive an efficient approximate inference algorithm that handles the high dimensionality of image and genetic data. We evaluate the algorithm on synthetic data and demonstrate that it outperforms traditional models. We also illustrate our method on Alzheimer's Disease Neuroimaging Initiative data.
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Affiliation(s)
| | - Adrian Dalca
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
| | - Gerald Quon
- University of California, Davis, CA 95616 USA
| | - Mert Sabuncu
- Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129 USA
| | - Polina Golland
- Computer Science and Artificial Intelligence Laboratory, and also with the Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA 02139 USA
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Leggere JC, Saito Y, Darnell RB, Tessier-Lavigne M, Junge HJ, Chen Z. NOVA regulates Dcc alternative splicing during neuronal migration and axon guidance in the spinal cord. eLife 2016; 5. [PMID: 27223328 PMCID: PMC4930329 DOI: 10.7554/elife.14264] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Accepted: 05/23/2016] [Indexed: 02/03/2023] Open
Abstract
RNA-binding proteins (RBPs) control multiple aspects of post-transcriptional gene regulation and function during various biological processes in the nervous system. To further reveal the functional significance of RBPs during neural development, we carried out an in vivo RNAi screen in the dorsal spinal cord interneurons, including the commissural neurons. We found that the NOVA family of RBPs play a key role in neuronal migration, axon outgrowth, and axon guidance. Interestingly, Nova mutants display similar defects as the knockout of the Dcc transmembrane receptor. We show here that Nova deficiency disrupts the alternative splicing of Dcc, and that restoring Dcc splicing in Nova knockouts is able to rescue the defects. Together, our results demonstrate that the production of DCC splice variants controlled by NOVA has a crucial function during many stages of commissural neuron development.
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Affiliation(s)
- Janelle C Leggere
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, United States
| | - Yuhki Saito
- Laboratory of Molecular Neuro-Oncology, Howard Hughes Medical Institute, The Rockefeller University, New York, United States
| | - Robert B Darnell
- Laboratory of Molecular Neuro-Oncology, Howard Hughes Medical Institute, The Rockefeller University, New York, United States
| | - Marc Tessier-Lavigne
- Laboratory of Brain Development and Repair, The Rockefeller University, New York, United States
| | - Harald J Junge
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, United States
| | - Zhe Chen
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, United States
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Deyts C, Clutter M, Herrera S, Jovanovic N, Goddi A, Parent AT. Loss of presenilin function is associated with a selective gain of APP function. eLife 2016; 5. [PMID: 27196744 PMCID: PMC4915812 DOI: 10.7554/elife.15645] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 05/18/2016] [Indexed: 12/12/2022] Open
Abstract
Presenilin 1 (PS1) is an essential γ-secretase component, the enzyme responsible for amyloid precursor protein (APP) intramembraneous cleavage. Mutations in PS1 lead to dominant-inheritance of early-onset familial Alzheimer’s disease (FAD). Although expression of FAD-linked PS1 mutations enhances toxic Aβ production, the importance of other APP metabolites and γ-secretase substrates in the etiology of the disease has not been confirmed. We report that neurons expressing FAD-linked PS1 variants or functionally deficient PS1 exhibit enhanced axodendritic outgrowth due to increased levels of APP intracellular C-terminal fragment (APP-CTF). APP expression is required for exuberant neurite outgrowth and hippocampal axonal sprouting observed in knock-in mice expressing FAD-linked PS1 mutation. APP-CTF accumulation initiates CREB signaling cascade through an association of APP-CTF with Gαs protein. We demonstrate that pathological PS1 loss-of-function impinges on neurite formation through a selective APP gain-of-function that could impact on axodendritic connectivity and contribute to aberrant axonal sprouting observed in AD patients. DOI:http://dx.doi.org/10.7554/eLife.15645.001 One of the hallmarks of Alzheimer’s disease is the accumulation within the brain of sticky deposits called plaques. These plaques form from clumps of molecules called amyloid-beta peptide. An enzyme called gamma-secretase generates the amyloid-beta peptide, by cutting it from a membrane-associated protein called APP. This enzyme consists of multiple subunits, and a mutation in one of these – presenilin-1 – causes a particularly severe form of Alzheimer’s disease. For decades, research into Alzheimer’s disease has focused on the harmful effects of amyloid-beta peptides and plaques. However, Deyts et al. now argue that the protein that gives rise to amyloid-beta peptides has a more direct role in Alzheimer’s disease than previously thought. Specifically, APP may contribute to the harmful effects of the presenilin-1 mutations. By studying genetically modified mice carrying a human presenilin-1 mutation, Deyts et al. show that some of these animals’ nerve cells grow abnormally. Their cell bodies sprout too many branches, while their nerve fibers – which carry electrical signals away from the cell body – become too long. These abnormalities resemble changes seen in the brain in Alzheimer’s disease. Unexpectedly, however, deleting the gene for APP in the presenilin-1 mutant mice prevents the changes from occurring. This suggests that APP must be present for the presenilin-1 mutation to exert this unwanted effect. An increase in APP-driven signaling within cells seems to trigger the observed abnormalities in nerve cells. The presenilin-1 mutation modifies how gamma-secretase cuts APP at the cell membrane to produce amyloid-beta peptides. This frees up the APP to instead interact with signaling cascades inside the cell. Given that gamma-secretase is a key therapeutic target in Alzheimer’s disease, further work is needed to explore the implications of these protein interactions for potential treatments. DOI:http://dx.doi.org/10.7554/eLife.15645.002
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Affiliation(s)
- Carole Deyts
- Departments of Neurobiology, The University of Chicago, Chicago, United States
| | - Mary Clutter
- Departments of Neurobiology, The University of Chicago, Chicago, United States
| | - Stacy Herrera
- Departments of Neurobiology, The University of Chicago, Chicago, United States
| | - Natalia Jovanovic
- Departments of Neurobiology, The University of Chicago, Chicago, United States
| | - Anna Goddi
- Departments of Neurobiology, The University of Chicago, Chicago, United States
| | - Angèle T Parent
- Departments of Neurobiology, The University of Chicago, Chicago, United States
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36
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Yu Y, Li Y, Zhang Y. Yeast Two-Hybrid Screening for Proteins that Interact with the Extracellular Domain of Amyloid Precursor Protein. Neurosci Bull 2016; 32:171-6. [PMID: 26960425 DOI: 10.1007/s12264-016-0021-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Accepted: 12/11/2015] [Indexed: 12/25/2022] Open
Abstract
Alzheimer's disease (AD) is a neurodegenerative disorder in which amyloid β plaques are a pathological characteristic. Little is known about the physiological functions of amyloid β precursor protein (APP). Based on its structure as a type I transmembrane protein, it has been proposed that APP might be a receptor, but so far, no ligand has been reported. In the present study, 9 proteins binding to the extracellular domain of APP were identified using a yeast two-hybrid system. After confirming the interactions in the mammalian system, mutated PLP1, members of the FLRT protein family, and KCTD16 were shown to interact with APP. These proteins have been reported to be involved in Pelizaeus-Merzbacher disease (PMD) and axon guidance. Therefore, our results shed light on the mechanisms of physiological function of APP in AD, PMD, and axon guidance.
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Affiliation(s)
- You Yu
- State Key Laboratory of Membrane Biology, College of Life Sciences, PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China
| | - Yinan Li
- State Key Laboratory of Membrane Biology, College of Life Sciences, PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China
| | - Yan Zhang
- State Key Laboratory of Membrane Biology, College of Life Sciences, PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China.
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37
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APP Receptor? To Be or Not To Be. Trends Pharmacol Sci 2016; 37:390-411. [PMID: 26837733 DOI: 10.1016/j.tips.2016.01.005] [Citation(s) in RCA: 81] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 01/07/2016] [Accepted: 01/11/2016] [Indexed: 11/22/2022]
Abstract
Amyloid precursor protein (APP) and its metabolites play a key role in Alzheimer's disease pathogenesis. The idea that APP may function as a receptor has gained momentum based on its structural similarities to type I transmembrane receptors and the identification of putative APP ligands. We review the recent experimental evidence in support of this notion and discuss how this concept is viewed in the field. Specifically, we focus on the structural and functional characteristics of APP as a cell surface receptor, and on its interaction with adaptors and signaling proteins. We also address the importance of APP function as a receptor in Alzheimer's disease etiology and discuss how this function might be potentially important for the development of novel therapeutic approaches.
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38
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DeGeer J, Kaplan A, Mattar P, Morabito M, Stochaj U, Kennedy TE, Debant A, Cayouette M, Fournier AE, Lamarche-Vane N. Hsc70 chaperone activity underlies Trio GEF function in axon growth and guidance induced by netrin-1. J Cell Biol 2015; 210:817-32. [PMID: 26323693 PMCID: PMC4555821 DOI: 10.1083/jcb.201505084] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
During development, netrin-1 is both an attractive and repulsive axon guidance cue and mediates its attractive function through the receptor Deleted in Colorectal Cancer (DCC). The activation of Rho guanosine triphosphatases within the extending growth cone facilitates the dynamic reorganization of the cytoskeleton required to drive axon extension. The Rac1 guanine nucleotide exchange factor (GEF) Trio is essential for netrin-1-induced axon outgrowth and guidance. Here, we identify the molecular chaperone heat shock cognate protein 70 (Hsc70) as a novel Trio regulator. Hsc70 dynamically associated with the N-terminal region and Rac1 GEF domain of Trio. Whereas Hsc70 expression supported Trio-dependent Rac1 activation, adenosine triphosphatase-deficient Hsc70 (D10N) abrogated Trio Rac1 GEF activity and netrin-1-induced Rac1 activation. Hsc70 was required for netrin-1-mediated axon growth and attraction in vitro, whereas Hsc70 activity supported callosal projections and radial neuronal migration in the embryonic neocortex. These findings demonstrate that Hsc70 chaperone activity is required for Rac1 activation by Trio and this function underlies netrin-1/DCC-dependent axon outgrowth and guidance.
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Affiliation(s)
- Jonathan DeGeer
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec H3A 0C7, Canada The Research Institute of McGill University Health Centre, Montreal, Quebec H4A 3J1, Canada
| | - Andrew Kaplan
- Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec H3A 2B4, Canada
| | - Pierre Mattar
- Cellular Neurobiology Research Unit, Institut de Recherches Cliniques de Montréal, Montreal, Quebec H2W 1R7, Canada
| | - Morgane Morabito
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec H3A 0C7, Canada The Research Institute of McGill University Health Centre, Montreal, Quebec H4A 3J1, Canada
| | - Ursula Stochaj
- Department of Physiology, McGill University, Montreal, Quebec H3G 1Y6, Canada
| | - Timothy E Kennedy
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec H3A 0C7, Canada Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec H3A 2B4, Canada
| | - Anne Debant
- Centre de Recherche de Biochimie Macromoléculaire, Centre National de la Recherche Scientifique, UMR5237, University of Montpellier, Montpellier 34293, France
| | - Michel Cayouette
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec H3A 0C7, Canada Cellular Neurobiology Research Unit, Institut de Recherches Cliniques de Montréal, Montreal, Quebec H2W 1R7, Canada Department of Medicine, Université de Montréal, Montreal, Quubec H3T 1J4, Canada
| | - Alyson E Fournier
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec H3A 0C7, Canada Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec H3A 2B4, Canada
| | - Nathalie Lamarche-Vane
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec H3A 0C7, Canada The Research Institute of McGill University Health Centre, Montreal, Quebec H4A 3J1, Canada
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39
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Shinwari J, Khan A, Awad S, Shinwari Z, Alaiya A, Alanazi M, Tahir A, Poizat C, Al Tassan N. Recessive mutations in COL25A1 are a cause of congenital cranial dysinnervation disorder. Am J Hum Genet 2015; 96:147-52. [PMID: 25500261 DOI: 10.1016/j.ajhg.2014.11.006] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 11/11/2014] [Indexed: 12/27/2022] Open
Abstract
Abnormal ocular motility is a common clinical feature in congenital cranial dysinnervation disorder (CCDD). To date, eight genes related to neuronal development have been associated with different CCDD phenotypes. By using linkage analysis, candidate gene screening, and exome sequencing, we identified three mutations in collagen, type XXV, alpha 1 (COL25A1) in individuals with autosomal-recessive inheritance of CCDD ophthalmic phenotypes. These mutations affected either stability or levels of the protein. We further detected altered levels of sAPP (neuronal protein involved in axon guidance and synaptogenesis) and TUBB3 (encoded by TUBB3, which is mutated in CFEOM3) as a result of null mutations in COL25A1. Our data suggest that lack of COL25A1 might interfere with molecular pathways involved in oculomotor neuron development, leading to CCDD phenotypes.
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40
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Chouraki V, De Bruijn RFAG, Chapuis J, Bis JC, Reitz C, Schraen S, Ibrahim-Verbaas CA, Grenier-Boley B, Delay C, Rogers R, Demiautte F, Mounier A, Fitzpatrick AL, Berr C, Dartigues JF, Uitterlinden AG, Hofman A, Breteler M, Becker JT, Lathrop M, Schupf N, Alpérovitch A, Mayeux R, van Duijn CM, Buée L, Amouyel P, Lopez OL, Ikram MA, Tzourio C, Lambert JC. A genome-wide association meta-analysis of plasma Aβ peptides concentrations in the elderly. Mol Psychiatry 2014; 19:1326-35. [PMID: 24535457 PMCID: PMC4418478 DOI: 10.1038/mp.2013.185] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Revised: 10/08/2013] [Accepted: 10/31/2013] [Indexed: 11/09/2022]
Abstract
Amyloid beta (Aβ) peptides are the major components of senile plaques, one of the main pathological hallmarks of Alzheimer disease (AD). However, Aβ peptides' functions are not fully understood and seem to be highly pleiotropic. We hypothesized that plasma Aβ peptides concentrations could be a suitable endophenotype for a genome-wide association study (GWAS) designed to (i) identify novel genetic factors involved in amyloid precursor protein metabolism and (ii) highlight relevant Aβ-related physiological and pathophysiological processes. Hence, we performed a genome-wide association meta-analysis of four studies totaling 3 528 healthy individuals of European descent and for whom plasma Aβ1-40 and Aβ1-42 peptides levels had been quantified. Although we did not observe any genome-wide significant locus, we identified 18 suggestive loci (P<1 × 10(-)(5)). Enrichment-pathway analyses revealed canonical pathways mainly involved in neuronal functions, for example, axonal guidance signaling. We also assessed the biological impact of the gene most strongly associated with plasma Aβ1-42 levels (cortexin 3, CTXN3) on APP metabolism in vitro and found that the gene protein was able to modulate Aβ1-42 secretion. In conclusion, our study results suggest that plasma Aβ peptides levels are valid endophenotypes in GWASs and can be used to characterize the metabolism and functions of APP and its metabolites.
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Affiliation(s)
- V Chouraki
- INSERM U744, Lille, France,Institut pasteur de Lille, Lille, France,Université Lille-Nord de France, Lille, France
| | - RFAG De Bruijn
- Department of Epidemiology, Erasmus MC University Medical Center,
Rotterdam, The Netherlands,Department of Neurology, Erasmus MC University Medical Center,
Rotterdam, The Netherlands,Netherlands Consortium for Healthy Aging, Leiden, The
Netherlands
| | - J Chapuis
- INSERM U744, Lille, France,Institut pasteur de Lille, Lille, France,Université Lille-Nord de France, Lille, France
| | - JC Bis
- Cardiovascular Health Resarch Unit and Department of Medicine,
University of Washington, Seattle, WA, USA
| | - C Reitz
- The Taub Institute for Research on Alzheimer’s Disease and
the Aging Brain, Columbia University, New York, NY, USA,The Gertrude H. Sergievsky Center, Columbia University, New York,
NY, USA,The Department of Neurology, College of Physicians and Surgeons,
Columbia University, New York, NY, USA
| | - S Schraen
- Université Lille-Nord de France, Lille, France,Inserm U837, Jean-Pierre Aubert Research Centre, Lille,
France,Centre Hospitalier Régional Universitaire de Lille, Lille,
France
| | - CA Ibrahim-Verbaas
- Department of Epidemiology, Erasmus MC University Medical Center,
Rotterdam, The Netherlands,Department of Neurology, Erasmus MC University Medical Center,
Rotterdam, The Netherlands
| | - B Grenier-Boley
- INSERM U744, Lille, France,Institut pasteur de Lille, Lille, France,Université Lille-Nord de France, Lille, France
| | - C Delay
- INSERM U744, Lille, France,Institut pasteur de Lille, Lille, France,Université Lille-Nord de France, Lille, France
| | - R Rogers
- The Taub Institute for Research on Alzheimer’s Disease and
the Aging Brain, Columbia University, New York, NY, USA
| | - F Demiautte
- INSERM U744, Lille, France,Institut pasteur de Lille, Lille, France,Université Lille-Nord de France, Lille, France
| | - A Mounier
- INSERM U744, Lille, France,Institut pasteur de Lille, Lille, France,Université Lille-Nord de France, Lille, France
| | - AL Fitzpatrick
- Cardiovascular Health Resarch Unit and Department of Medicine,
University of Washington, Seattle, WA, USA
| | | | - C Berr
- INSERM U888, Hôpital La Colombière, Montpellier,
France
| | - J-F Dartigues
- INSERM U593, Victor Segalen University, Bordeaux, France
| | - AG Uitterlinden
- Netherlands Consortium for Healthy Aging, Leiden, The
Netherlands,Department of Internal medicine, Leiden, Erasmus MC University
Medical Center, Rotterdam, The Netherlands
| | - A Hofman
- Department of Epidemiology, Erasmus MC University Medical Center,
Rotterdam, The Netherlands,Netherlands Consortium for Healthy Aging, Leiden, The
Netherlands
| | - M Breteler
- Department of Epidemiology, Erasmus MC University Medical Center,
Rotterdam, The Netherlands,DZNE, German Center for Neurodegenerative Diseases, Bonn,
Germany
| | - JT Becker
- Alzheimer’s Disease Research Center, Departments of
Neurology, Psychiatry and Psychology, University of Pittsburgh School of Medicine,
Pittsburgh, PA, USA
| | - M Lathrop
- Fondation Jean Dausset—Centre d’Etude du
Polymorphisme Humain, Paris, France,Centre National de Genotypage, Institut Genomique, Commissariat
à l’énergie Atomique, Evry, France
| | - N Schupf
- The Gertrude H. Sergievsky Center, Columbia University, New York,
NY, USA
| | | | - R Mayeux
- The Taub Institute for Research on Alzheimer’s Disease and
the Aging Brain, Columbia University, New York, NY, USA,The Department of Psychiatry, College of Physicians and Surgeons,
Columbia University, New York, NY, USA
| | - CM van Duijn
- Department of Epidemiology, Erasmus MC University Medical Center,
Rotterdam, The Netherlands,Netherlands Consortium for Healthy Aging, Leiden, The
Netherlands
| | - L Buée
- Université Lille-Nord de France, Lille, France,Inserm U837, Jean-Pierre Aubert Research Centre, Lille,
France,Centre Hospitalier Régional Universitaire de Lille, Lille,
France
| | - P Amouyel
- INSERM U744, Lille, France,Institut pasteur de Lille, Lille, France,Université Lille-Nord de France, Lille, France,Centre Hospitalier Régional Universitaire de Lille, Lille,
France
| | - OL Lopez
- Alzheimer’s Disease Research Center, Departments of
Neurology, Psychiatry and Psychology, University of Pittsburgh School of Medicine,
Pittsburgh, PA, USA
| | - MA Ikram
- Department of Epidemiology, Erasmus MC University Medical Center,
Rotterdam, The Netherlands,Department of Neurology, Erasmus MC University Medical Center,
Rotterdam, The Netherlands,Netherlands Consortium for Healthy Aging, Leiden, The
Netherlands,Department of Radiology, Erasmus MC University Medical Center,
Rotterdam, The Netherlands
| | - C Tzourio
- INSERM U593, Victor Segalen University, Bordeaux, France,INSERM U708, Paris, France
| | - J-C Lambert
- INSERM U744, Lille, France,Institut pasteur de Lille, Lille, France,Université Lille-Nord de France, Lille, France
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41
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Engel PA. Does metabolic failure at the synapse cause Alzheimer's disease? Med Hypotheses 2014; 83:802-8. [PMID: 25456790 DOI: 10.1016/j.mehy.2014.10.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 10/15/2014] [Indexed: 01/01/2023]
Abstract
Alzheimer's disease (AD) a neurodegenerative disorder of widely distributed cortical networks evolves over years while A beta (Aβ) oligomer neurotoxicity occurs within seconds to minutes. This disparity combined with disappointing outcomes of anti-amyloid clinical trials challenges the centrality of Aβ as principal mediator of neurodegeneration. Reconsideration of late life AD as the end-product of intermittent regional failure of the neuronal support system to meet the needs of vulnerable brain areas offers an alternative point of view. This model introduces four ideas: (1) That Aβ is a synaptic signaling peptide that becomes toxic in circumstances of metabolic stress. (2) That intense synaptic energy and maintenance requirements of cortical hubs may exceed resources during peak demand initiating a neurotoxic cascade in these selectively vulnerable regions. (3) That axonal transport to and from neuron soma cannot account fully for high mitochondrial densities and other requirements of distant terminal axons. (4) That neurons as specialists in information management, delegate generic support functions to astrocytes and other cell types. Astrocytes use intercellular transport by exosomes and tunneling nanotubes (TNTs) to deliver mitochondria, substrates and protein reprocessing services to axonal sites distant from neuronal soma. This viewpoint implicates the brain's support system and its disruption by various age and disease-related insults as significant mediators of neurodegenerative disease. A better understanding of this system should broaden concepts of neurodegeneration and facilitate development of effective treatments.
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Affiliation(s)
- Peter A Engel
- Geriatric Research, Education and Clinical Center, VA Boston Healthcare System, Harvard Medical School, United States.
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42
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Abstract
Interest in the amyloid precursor protein (APP) has increased in recent years due to its involvement in Alzheimer's disease. Since its molecular cloning, significant genetic and biochemical work has focused on the role of APP in the pathogenesis of this disease. Thus far, however, these studies have failed to deliver successful therapies. This suggests that understanding the basic biology of APP and its physiological role during development might be a crucial missing link for a better comprehension of Alzheimer's disease. Here, we present an overview of some of the key studies performed in various model organisms that have revealed roles for APP at different stages of neuronal development.
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Affiliation(s)
- Maya Nicolas
- VIB Center for the Biology of Disease, VIB, 3000 Leuven, Belgium Center for Human Genetics, University of Leuven School of Medicine, 3000 Leuven, Belgium Doctoral Program in Molecular and Developmental Genetics, University of Leuven Group Biomedicine, 3000 Leuven, Belgium
| | - Bassem A Hassan
- VIB Center for the Biology of Disease, VIB, 3000 Leuven, Belgium Center for Human Genetics, University of Leuven School of Medicine, 3000 Leuven, Belgium Doctoral Program in Molecular and Developmental Genetics, University of Leuven Group Biomedicine, 3000 Leuven, Belgium
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43
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Soldano A, Hassan BA. Beyond pathology: APP, brain development and Alzheimer's disease. Curr Opin Neurobiol 2014; 27:61-7. [PMID: 24632309 DOI: 10.1016/j.conb.2014.02.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 01/15/2014] [Accepted: 02/06/2014] [Indexed: 12/20/2022]
Abstract
Alzheimer's disease (AD) is the most common form of dementia among the elderly. Research in the AD field has been mostly focused on the biology of the Aβ peptide but increasing evidence is shifting attention toward the physiological role of APP as key to understanding AD pathology. It is becoming apparent that APP plays a central role in the mechanisms that guarantee the accuracy and the robustness of brain wiring. In the present review we explore APP functions with focus on some of the underlying molecular mechanisms.
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Affiliation(s)
- Alessia Soldano
- VIB Center for the Biology of Disease, VIB, 3000 Leuven, Belgium; Center for Human Genetics, University of Leuven School of Medicine, 3000 Leuven, Belgium
| | - Bassem A Hassan
- VIB Center for the Biology of Disease, VIB, 3000 Leuven, Belgium; Center for Human Genetics, University of Leuven School of Medicine, 3000 Leuven, Belgium.
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44
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Jurisch-Yaksi N, Sannerud R, Annaert W. A fast growing spectrum of biological functions of γ-secretase in development and disease. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:2815-27. [PMID: 24099003 DOI: 10.1016/j.bbamem.2013.04.016] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 04/03/2013] [Accepted: 04/11/2013] [Indexed: 12/17/2022]
Abstract
γ-secretase, which assembles as a tetrameric complex, is an aspartyl protease that proteolytically cleaves substrate proteins within their membrane-spanning domain; a process also known as regulated intramembrane proteolysis (RIP). RIP regulates signaling pathways by abrogating or releasing signaling molecules. Since the discovery, already >15 years ago, of its catalytic component, presenilin, and even much earlier with the identification of amyloid precursor protein as its first substrate, γ-secretase has been commonly associated with Alzheimer's disease. However, starting with Notch and thereafter a continuously increasing number of novel substrates, γ-secretase is becoming linked to an equally broader range of biological processes. This review presents an updated overview of the current knowledge on the diverse molecular mechanisms and signaling pathways controlled by γ-secretase, with a focus on organ development, homeostasis and dysfunction. This article is part of a Special Issue entitled: Intramembrane Proteases.
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Affiliation(s)
- Nathalie Jurisch-Yaksi
- Laboratory for Membrane Trafficking, VIB-Center for the Biology of Disease & Department for Human Genetics (KU Leuven), Leuven, Belgium
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45
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Huang HC, Tang D, Xu K, Jiang ZF. Curcumin attenuates amyloid-β-induced tau hyperphosphorylation in human neuroblastoma SH-SY5Y cells involving PTEN/Akt/GSK-3β signaling pathway. J Recept Signal Transduct Res 2013; 34:26-37. [DOI: 10.3109/10799893.2013.848891] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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46
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Cheung HNM, Dunbar C, Mórotz GM, Cheng WH, Chan HYE, Miller CCJ, Lau KF. FE65 interacts with ADP-ribosylation factor 6 to promote neurite outgrowth. FASEB J 2013; 28:337-49. [PMID: 24056087 DOI: 10.1096/fj.13-232694] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
FE65 is an adaptor protein that binds to the amyloid precursor protein (APP). As such, FE65 has been implicated in the pathogenesis of Alzheimer's disease. In addition, evidence suggests that FE65 is involved in brain development. It is generally believed that FE65 participates in these processes by recruiting various interacting partners to form functional complexes. Here, we show that via its first phosphotyrosine binding (PTB) domain, FE65 binds to the small GTPase ADP-ribosylation factor 6 (ARF6). FE65 preferentially binds to ARF6-GDP, and they colocalize in neuronal growth cones. Interestingly, FE65 stimulates the activation of both ARF6 and its downstream GTPase Rac1, a regulator of actin dynamics, and functions in growth cones to stimulate neurite outgrowth. We show that transfection of FE65 and/or ARF6 promotes whereas small interfering RNA knockdown of FE65 or ARF6 inhibits neurite outgrowth in cultured neurons as compared to the mock-transfected control cells. Moreover, knockdown of ARF6 attenuates FE65 stimulation of neurite outgrowth and defective neurite outgrowth seen in FE65-deficient neurons is partially corrected by ARF6 overexpression. Notably, the stimulatory effect of FE65 and ARF6 on neurite outgrowth is abrogated either by dominant-negative Rac1 or knockdown of Rac1. Thus, we identify FE65 as a novel regulator of neurite outgrowth via controlling ARF6-Rac1 signaling.
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Affiliation(s)
- Hei Nga Maggie Cheung
- 1School of Life Sciences, Chinese University of Hong Kong, Shatin, NT, Hong Kong SAR, China.
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47
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Morgenstern NA, Giacomini D, Lombardi G, Castaño EM, Schinder AF. Delayed dendritic development in newly generated dentate granule cells by cell-autonomous expression of the amyloid precursor protein. Mol Cell Neurosci 2013; 56:298-306. [PMID: 23851186 DOI: 10.1016/j.mcn.2013.07.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Revised: 05/15/2013] [Accepted: 07/03/2013] [Indexed: 11/30/2022] Open
Abstract
Neuronal connectivity and synaptic remodeling are fundamental substrates for higher brain functions. Understanding their dynamics in the mammalian allocortex emerges as a critical step to tackle the cellular basis of cognitive decline that occurs during normal aging and in neurodegenerative disorders. In this work we have designed a novel approach to assess alterations in the dynamics of functional and structural connectivity elicited by chronic cell-autonomous overexpression of the human amyloid precursor protein (hAPP). We have taken advantage of the fact that the hippocampus continuously generates new dentate granule cells (GCs) to probe morphofunctional development of GCs expressing different variants of hAPP in a healthy background. hAPP was expressed together with a fluorescent reporter in neural progenitor cells of the dentate gyrus of juvenile mice by retroviral delivery. Neuronal progeny was analyzed several days post infection (dpi). Amyloidogenic cleavage products of hAPP such as the β-C terminal fragment (β-CTF) induced a substantial reduction in glutamatergic connectivity at 21 dpi, at which time new GCs undergo active growth and synaptogenesis. Interestingly, this effect was transient, since the strength of glutamatergic inputs was normal by 35 dpi. This delay in glutamatergic synaptogenesis was paralleled by a decrease in dendritic length with no changes in spine density, consistent with a protracted dendritic development without alterations in synapse formation. Finally, similar defects in newborn GC development were observed by overexpression of α-CTF, a non-amyloidogenic cleavage product of hAPP. These results indicate that hAPP can elicit protracted dendritic development independently of the amyloidogenic processing pathway.
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Affiliation(s)
- Nicolás A Morgenstern
- Laboratory of Neuronal Plasticity Leloir Institute (IIBBA-CONICET) Buenos Aires (1405), Argentina
| | - Damiana Giacomini
- Laboratory of Neuronal Plasticity Leloir Institute (IIBBA-CONICET) Buenos Aires (1405), Argentina
| | - Gabriela Lombardi
- Laboratory of Neuronal Plasticity Leloir Institute (IIBBA-CONICET) Buenos Aires (1405), Argentina
| | - Eduardo M Castaño
- Laboratory of Amyloidosis and Neurodegeneration Leloir Institute (IIBBA-CONICET) Buenos Aires (1405), Argentina
| | - Alejandro F Schinder
- Laboratory of Neuronal Plasticity Leloir Institute (IIBBA-CONICET) Buenos Aires (1405), Argentina
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48
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Abstract
Commissural circuits are brain and spinal cord connections which interconnect the two sides of the central nervous system (CNS). They play essential roles in brain and spinal cord processing, ensuring left-right coordination and synchronization of information and commands. During the formation of neuronal circuits, all commissural neurons of the central nervous system must accomplish a common task, which is to project their axon onto the other side of the nervous system, across the midline that delineates the two halves of the CNS. How this task is accomplished has been the topic of extensive studies over the last past 20 years and remains one of the best models to investigate axon guidance mechanisms. In the first part of this review, I will introduce the commissural circuits, their general role in the physiology of the nervous system, and their recognized or suspected pathogenic properties in human diseases. In the second part of the review, I will concentrate on two commissural circuits, the spinal commissures and the corpus callosum, to detail the cellular and molecular mechanisms governing their formation, mostly during their navigation at the midline.
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49
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Rice HC, Young-Pearse TL, Selkoe DJ. Systematic evaluation of candidate ligands regulating ectodomain shedding of amyloid precursor protein. Biochemistry 2013; 52:3264-77. [PMID: 23597280 DOI: 10.1021/bi400165f] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Despite intense interest in the proteolysis of the β-Amyloid Precursor Protein (APP) in Alzheimer's disease, how the normal processing of this type I receptor-like glycoprotein is physiologically regulated remains ill-defined. In recent years, several candidate protein ligands for APP, including F-spondin, Reelin, β1 Integrin, Contactins, Lingo-1, and Pancortin, have been reported. However, a cognate ligand for APP that regulates its processing by α- or β-secretase has yet to be widely confirmed in multiple laboratories. Here, we developed new assays in an effort to confirm a role for one or more of these candidate ligands in regulating APP ectodomain shedding in a biologically relevant context. A comprehensive quantification of APPsα and APPsβ, the immediate products of secretase processing, in both non-neuronal cell lines and primary neuronal cultures expressing endogenous APP yielded no evidence that any of these published candidate ligands stimulate ectodomain shedding. Rather, Reelin, Lingo-1, and Pancortin-1 emerged as the most consistent ligands for significantly inhibiting ectodomain shedding. These findings led us to conduct further detailed analyses of the interactions of Reelin and Lingo-1 with APP.
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Affiliation(s)
- Heather C Rice
- Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School , Boston, Massachusetts 02115, United States
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Tyrosine phosphorylation of the Rho guanine nucleotide exchange factor Trio regulates netrin-1/DCC-mediated cortical axon outgrowth. Mol Cell Biol 2012; 33:739-51. [PMID: 23230270 DOI: 10.1128/mcb.01264-12] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The chemotropic guidance cue netrin-1 mediates attraction of migrating axons during central nervous system development through the receptor Deleted in Colorectal Cancer (DCC). Downstream of netrin-1, activated Rho GTPases Rac1 and Cdc42 induce cytoskeletal rearrangements within the growth cone. The Rho guanine nucleotide exchange factor (GEF) Trio is essential for Rac1 activation downstream of netrin-1/DCC, but the molecular mechanisms governing Trio activity remain elusive. Here, we demonstrate that Trio is phosphorylated by Src family kinases in the embryonic rat cortex in response to netrin-1. In vitro, Trio was predominantly phosphorylated at Tyr(2622) by the Src kinase Fyn. Though the phospho-null mutant Trio(Y2622F) retained GEF activity toward Rac1, its expression impaired netrin-1-induced Rac1 activation and DCC-mediated neurite outgrowth in N1E-115 neuroblastoma cells. Trio(Y2622F) impaired netrin-1-induced axonal extension in cultured cortical neurons and was unable to colocalize with DCC in growth cones, in contrast to wild-type Trio. Furthermore, depletion of Trio in cortical neurons reduced the level of cell surface DCC in growth cones, which could be restored by expression of wild-type Trio but not Trio(Y2622F). Together, these findings demonstrate that Trio(Y2622) phosphorylation is essential for the regulation of the DCC/Trio signaling complex in cortical neurons during netrin-1-mediated axon outgrowth.
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