1
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Virdee S. An atypical ubiquitin ligase at the heart of neural development and programmed axon degeneration. Neural Regen Res 2022; 17:2347-2350. [PMID: 35535869 PMCID: PMC9120709 DOI: 10.4103/1673-5374.338992] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The degeneration of nerve fibres following injury was first described by Augustus Waller over 170 years ago. Initially assumed to be a passive process, it is now evident that axons respond to insult via regulated cellular signaling events resulting in their programmed degeneration. Pro-survival and pro-degenerative factors have been identified and their regulatory mechanisms are beginning to emerge. The ubiquitin system has been implicated in the pro-degenerative process and a key component is the ubiquitin E3 ligase MYCBP2 (also known as PHR1). Ubiquitin E3 ligases are tasked with the transfer of the small protein modifier ubiquitin to substrates and consist of hundreds of members. They can be classified as single subunit systems or as multi-subunit complexes. Their catalytic domains can also be assigned to three general architectures. Hints that MYCBP2 might not conform to these established formats came to light and it is now clear from biochemical and structural studies that MYCBP2 is indeed an outlier in terms of its modus operandi. Furthermore, the unconventional way in which MYCBP2 transfers ubiquitin to substrates has been linked to neurodevelopmental and pro-degenerative function. Herein, we will summarize these research developments relating to the unusual features of MYCBP2 and postulate therapeutic strategies that prevent Wallerian degeneration. These have exciting potential for providing relief from pathological neuropathies and neurodegenerative diseases.
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Affiliation(s)
- Satpal Virdee
- MRC Protein Phosphorylation and Ubiquitylation Unit, University of Dundee, Scotland, UK
- Correspondence to: Satpal Virdee, .
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2
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Mathien S, Tesnière C, Meloche S. Regulation of Mitogen-Activated Protein Kinase Signaling Pathways by the Ubiquitin-Proteasome System and Its Pharmacological Potential. Pharmacol Rev 2021; 73:263-296. [PMID: 34732541 DOI: 10.1124/pharmrev.120.000170] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Mitogen-activated protein kinase (MAPK) cascades are evolutionarily conserved signaling pathways that play essential roles in transducing extracellular environmental signals into diverse cellular responses to maintain homeostasis. These pathways are classically organized into an architecture of three sequentially acting protein kinases: a MAPK kinase kinase that phosphorylates and activates a MAPK kinase, which in turn phosphorylates and activates the effector MAPK. The activity of MAPKs is tightly regulated by phosphorylation of their activation loop, which can be modulated by positive and negative feedback mechanisms to control the amplitude and duration of the signal. The signaling outcomes of MAPK pathways are further regulated by interactions of MAPKs with scaffolding and regulatory proteins. Accumulating evidence indicates that, in addition to these mechanisms, MAPK signaling is commonly regulated by ubiquitin-proteasome system (UPS)-mediated control of the stability and abundance of MAPK pathway components. Notably, the biologic activity of some MAPKs appears to be regulated mainly at the level of protein turnover. Recent studies have started to explore the potential of targeted protein degradation as a powerful strategy to investigate the biologic functions of individual MAPK pathway components and as a new therapeutic approach to overcome resistance to current small-molecule kinase inhibitors. Here, we comprehensively review the mechanisms, physiologic importance, and pharmacological potential of UPS-mediated protein degradation in the control of MAPK signaling. SIGNIFICANCE STATEMENT: Accumulating evidence highlights the importance of targeted protein degradation by the ubiquitin-proteasome system in regulating and fine-tuning the signaling output of mitogen-activated protein kinase (MAPK) pathways. Manipulating protein levels of MAPK cascade components may provide a novel approach for the development of selective pharmacological tools and therapeutics.
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Affiliation(s)
- Simon Mathien
- Institute for Research in Immunology and Cancer, Montreal, Quebec, Canada (S.Ma., C.T., S.Me.); and Molecular Biology Program, Faculty of Medicine (C.T., S.Me.) and Department of Pharmacology and Physiology (S.Me.), Université de Montréal, Montreal, Quebec, Canada
| | - Chloé Tesnière
- Institute for Research in Immunology and Cancer, Montreal, Quebec, Canada (S.Ma., C.T., S.Me.); and Molecular Biology Program, Faculty of Medicine (C.T., S.Me.) and Department of Pharmacology and Physiology (S.Me.), Université de Montréal, Montreal, Quebec, Canada
| | - Sylvain Meloche
- Institute for Research in Immunology and Cancer, Montreal, Quebec, Canada (S.Ma., C.T., S.Me.); and Molecular Biology Program, Faculty of Medicine (C.T., S.Me.) and Department of Pharmacology and Physiology (S.Me.), Université de Montréal, Montreal, Quebec, Canada
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3
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Wang X, Liang H, Xu W, Ma X. Wallenda-Nmo Axis Regulates Growth via Hippo Signaling. Front Cell Dev Biol 2021; 9:658288. [PMID: 33937258 PMCID: PMC8085559 DOI: 10.3389/fcell.2021.658288] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Accepted: 03/04/2021] [Indexed: 12/26/2022] Open
Abstract
Both Hippo signaling pathways and cell polarity regulation are critical for cell proliferation and the maintenance of tissue homeostasis, despite the well-established connections between cell polarity disruption and Hippo inactivation, the molecular mechanism by which aberrant cell polarity induces Hippo-mediated overgrowth remains underexplored. Here we use Drosophila wing discs as a model and identify the Wnd-Nmo axis as an important molecular link that bridges loss-of-cell polarity-triggered Hippo inactivation and overgrowth. We show that Wallenda (Wnd), a MAPKKK (mitogen-activated protein kinase kinase kinase) family member, is a novel regulator of Hippo pathways in Drosophila and that overexpression of Wnd promotes growth via Nemo (Nmo)- mediated Hippo pathway inactivation. We further demonstrate that both Wnd and Nmo are required for loss-of-cell polarity-induced overgrowth and Hippo inactivation. In summary, our findings provide a novel insight on how cell polarity loss contributes to overgrowth and uncover the Wnd-Nmo axis as an essential additional branch that regulates Hippo pathways in Drosophila.
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Affiliation(s)
- Xianping Wang
- Key Laboratory of Growth Regulation and Translational Research of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China.,Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China.,Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, China
| | - Hui Liang
- Key Laboratory of Growth Regulation and Translational Research of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China.,Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China.,Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, China
| | - Wenyan Xu
- Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China.,Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, China.,Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
| | - Xianjue Ma
- Key Laboratory of Growth Regulation and Translational Research of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China.,Westlake Laboratory of Life Sciences and Biomedicine, Hangzhou, China.,Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, China
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4
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Pinto MJ, Tomé D, Almeida RD. The Ubiquitinated Axon: Local Control of Axon Development and Function by Ubiquitin. J Neurosci 2021; 41:2796-2813. [PMID: 33789876 PMCID: PMC8018891 DOI: 10.1523/jneurosci.2251-20.2021] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 01/15/2021] [Accepted: 01/22/2021] [Indexed: 02/01/2023] Open
Abstract
Ubiquitin tagging sets protein fate. With a wide range of possible patterns and reversibility, ubiquitination can assume many shapes to meet specific demands of a particular cell across time and space. In neurons, unique cells with functionally distinct axons and dendrites harboring dynamic synapses, the ubiquitin code is exploited at the height of its power. Indeed, wide expression of ubiquitination and proteasome machinery at synapses, a diverse brain ubiquitome, and the existence of ubiquitin-related neurodevelopmental diseases support a fundamental role of ubiquitin signaling in the developing and mature brain. While special attention has been given to dendritic ubiquitin-dependent control, how axonal biology is governed by this small but versatile molecule has been considerably less discussed. Herein, we set out to explore the ubiquitin-mediated spatiotemporal control of an axon's lifetime: from its differentiation and growth through presynaptic formation, function, and pruning.
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Affiliation(s)
- Maria J Pinto
- Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, 3004-504, Portugal
| | - Diogo Tomé
- Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, 3004-504, Portugal
- Institute of Biomedicine, Department of Medical Sciences, University of Aveiro, Aveiro, 3810-193, Portugal
| | - Ramiro D Almeida
- Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, 3004-504, Portugal
- Institute of Biomedicine, Department of Medical Sciences, University of Aveiro, Aveiro, 3810-193, Portugal
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5
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Ugbode C, Garnham N, Fort-Aznar L, Evans GJO, Chawla S, Sweeney ST. JNK signalling regulates antioxidant responses in neurons. Redox Biol 2020; 37:101712. [PMID: 32949970 PMCID: PMC7502373 DOI: 10.1016/j.redox.2020.101712] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 08/14/2020] [Accepted: 08/31/2020] [Indexed: 02/06/2023] Open
Abstract
Reactive oxygen species (ROS) are generated during physiological bouts of synaptic activity and as a consequence of pathological conditions in the central nervous system. How neurons respond to and distinguish between ROS in these different contexts is currently unknown. In Drosophila mutants with enhanced JNK activity, lower levels of ROS are observed and these animals are resistant to both changes in ROS and changes in synapse morphology induced by oxidative stress. In wild type flies, disrupting JNK-AP-1 signalling perturbs redox homeostasis suggesting JNK activity positively regulates neuronal antioxidant defense. We validated this hypothesis in mammalian neurons, finding that JNK activity regulates the expression of the antioxidant gene Srxn-1, in a c-Jun dependent manner. We describe a conserved ‘adaptive’ role for neuronal JNK in the maintenance of redox homeostasis that is relevant to several neurodegenerative diseases.
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Affiliation(s)
- Chris Ugbode
- Department of Biology, University of York, York, YO10 5DD, UK; York Biomedical Research Institute, University of York, York, YO10 5DD, UK
| | - Nathan Garnham
- Department of Biology, University of York, York, YO10 5DD, UK; York Biomedical Research Institute, University of York, York, YO10 5DD, UK
| | - Laura Fort-Aznar
- Department of Biology, University of York, York, YO10 5DD, UK; York Biomedical Research Institute, University of York, York, YO10 5DD, UK
| | - Gareth J O Evans
- Department of Biology, University of York, York, YO10 5DD, UK; York Biomedical Research Institute, University of York, York, YO10 5DD, UK
| | - Sangeeta Chawla
- Department of Biology, University of York, York, YO10 5DD, UK; York Biomedical Research Institute, University of York, York, YO10 5DD, UK.
| | - Sean T Sweeney
- Department of Biology, University of York, York, YO10 5DD, UK; York Biomedical Research Institute, University of York, York, YO10 5DD, UK.
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6
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Tracy Cai X, Li H, Safyan A, Gawlik J, Pyrowolakis G, Jasper H. AWD regulates timed activation of BMP signaling in intestinal stem cells to maintain tissue homeostasis. Nat Commun 2019; 10:2988. [PMID: 31278345 PMCID: PMC6611797 DOI: 10.1038/s41467-019-10926-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 06/06/2019] [Indexed: 12/28/2022] Open
Abstract
Precise control of stem cell (SC) proliferation ensures tissue homeostasis. In the Drosophila intestine, injury-induced regeneration involves initial activation of intestinal SC (ISC) proliferation and subsequent return to quiescence. These two phases of the regenerative response are controlled by differential availability of the BMP type I receptor Thickveins (Tkv), yet how its expression is dynamically regulated remains unclear. Here we show that during homeostasis, the E3 ubiquitin ligase Highwire and the ubiquitin-proteasome system maintain low Tkv protein expression. After ISC activation, Tkv is stabilized by proteasome inhibition and undergoes endocytosis due to the induction of the nucleoside diphosphate kinase Abnormal Wing Disc (AWD). Tkv internalization is required for the activation of the Smad protein Mad, and for the return to quiescence after a regenerative episode. Our data provide insight into the mechanisms ensuring tissue homeostasis by dynamic control of somatic stem cell activity. Regeneration after injury in the Drosophila intestine involves early activation of intestinal stem cells (ISCs) and subsequent return to quiescence. Here the authors show that return to quiescence by ISCs involves BMP Type I receptor Tkv protein stabilization along with AWD mediated internalization into endocytic vesicles.
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Affiliation(s)
- Xiaoyu Tracy Cai
- Buck Institute for Research on Aging, 8001 Redwood Boulevard, Novato, CA, 94945-1400, USA
| | - Hongjie Li
- Department of Biology and Howard Hughes Medical Institute, Stanford University, Stanford, CA, 94305, USA
| | - Abu Safyan
- International Max Planck Research School for Molecular and Cellular Biology (IMPRS-MCB), Max Planck Institute of Immunobiology and Epigenetics, 79108, Freiburg, Germany.,Institute for Biology I, Faculty of Biology, Albert-Ludwigs-University of Freiburg, 79104, Freiburg, Germany.,Center for Biological Systems Analysis (ZBSA), Albert-Ludwigs-University of Freiburg, 79104, Freiburg, Germany
| | - Jennifer Gawlik
- Institute for Biology I, Faculty of Biology, Albert-Ludwigs-University of Freiburg, 79104, Freiburg, Germany.,Center for Biological Systems Analysis (ZBSA), Albert-Ludwigs-University of Freiburg, 79104, Freiburg, Germany.,Spemann Graduate School of Biology and Medicine (SGBM), Albert-Ludwigs-University of Freiburg, 79104, Freiburg, Germany
| | - George Pyrowolakis
- Institute for Biology I, Faculty of Biology, Albert-Ludwigs-University of Freiburg, 79104, Freiburg, Germany.,Center for Biological Systems Analysis (ZBSA), Albert-Ludwigs-University of Freiburg, 79104, Freiburg, Germany.,Signalling Research Centre BIOSS and CIBSS, Albert-Ludwigs-University Freiburg, 79104, Freiburg, Germany
| | - Heinrich Jasper
- Buck Institute for Research on Aging, 8001 Redwood Boulevard, Novato, CA, 94945-1400, USA. .,Immunology Discovery, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA. .,Leibniz Institute on Aging - Fritz Lipmann Institute, 07745, Jena, Germany.
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7
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Hendi A, Kurashina M, Mizumoto K. Intrinsic and extrinsic mechanisms of synapse formation and specificity in C. elegans. Cell Mol Life Sci 2019; 76:2719-2738. [PMID: 31037336 PMCID: PMC11105629 DOI: 10.1007/s00018-019-03109-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 04/11/2019] [Accepted: 04/15/2019] [Indexed: 12/18/2022]
Abstract
Precise neuronal wiring is critical for the function of the nervous system and is ultimately determined at the level of individual synapses. Neurons integrate various intrinsic and extrinsic cues to form synapses onto their correct targets in a stereotyped manner. In the past decades, the nervous system of nematode (Caenorhabditis elegans) has provided the genetic platform to reveal the genetic and molecular mechanisms of synapse formation and specificity. In this review, we will summarize the recent discoveries in synapse formation and specificity in C. elegans.
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Affiliation(s)
- Ardalan Hendi
- Department of Zoology, The University of British Columbia, 2406-2350 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada
| | - Mizuki Kurashina
- Department of Zoology, The University of British Columbia, 2406-2350 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada
| | - Kota Mizumoto
- Department of Zoology, The University of British Columbia, 2406-2350 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada.
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8
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Emerging role of F-box proteins in the regulation of epithelial-mesenchymal transition and stem cells in human cancers. Stem Cell Res Ther 2019; 10:124. [PMID: 30999935 PMCID: PMC6472071 DOI: 10.1186/s13287-019-1222-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Emerging evidence shows that epithelial-mesenchymal transition (EMT) plays a crucial role in tumor invasion, metastasis, cancer stem cells, and drug resistance. Data obtained thus far have revealed that F-box proteins are critically involved in the regulation of the EMT process and stem cell differentiation in human cancers. In this review, we will briefly describe the role of EMT and stem cells in cell metastasis and drug resistance. We will also highlight how numerous F-box proteins govern the EMT process and stem cell survival by controlling their downstream targets. Additionally, we will discuss whether F-box proteins involved in drug resistance are associated with EMT and cancer stem cells. Targeting these F-box proteins might be a potential therapeutic strategy to reverse EMT and inhibit cancer stem cells and thus overcome drug resistance in human cancers.
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9
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Rivera O, McHan L, Konadu B, Patel S, Sint Jago S, Talbert ME. A high-fat diet impacts memory and gene expression of the head in mated female Drosophila melanogaster. J Comp Physiol B 2019; 189:179-198. [PMID: 30810797 PMCID: PMC6711602 DOI: 10.1007/s00360-019-01209-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 02/12/2019] [Accepted: 02/17/2019] [Indexed: 12/25/2022]
Abstract
Obesity predisposes humans to a range of life-threatening comorbidities, including type 2 diabetes and cardiovascular disease. Obesity also aggravates neural pathologies, such as Alzheimer's disease, but this class of comorbidity is less understood. When Drosophila melanogaster (flies) are exposed to high-fat diet (HFD) by supplementing a standard medium with coconut oil, they adopt an obese phenotype of decreased lifespan, increased triglyceride storage, and hindered climbing ability. The latter development has been previously regarded as a potential indicator of neurological decline in fly models of neurodegenerative disease. Our objective was to establish the obesity phenotype in Drosophila and identify a potential correlation, if any, between obesity and neurological decline through behavioral assays and gene expression microarray. We found that mated female w1118 flies exposed to HFD maintained an obese phenotype throughout adult life starting at 7 days, evidenced by increased triglyceride stores, diminished life span, and impeded climbing ability. While climbing ability worsened cumulatively between 7 and 14 days of exposure to HFD, there was no corresponding alteration in triglyceride content. Microarray analysis of the mated female w1118 fly head revealed HFD-induced changes in expression of genes with functions in memory, metabolism, olfaction, mitosis, cell signaling, and motor function. Meanwhile, an Aversive Phototaxis Suppression assay in mated female flies indicated reduced ability to recall an entrained memory 6 h after training. Overall, our results support the suitability of mated female flies for examining connections between diet-induced obesity and nervous or neurobehavioral pathology, and provide many directions for further investigation.
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Affiliation(s)
- Osvaldo Rivera
- Program in Biology, School of Sciences, University of Louisiana at Monroe, 700 University Avenue, Monroe, LA, 71209, USA
| | - Lara McHan
- Program in Biology, School of Sciences, University of Louisiana at Monroe, 700 University Avenue, Monroe, LA, 71209, USA
| | - Bridget Konadu
- Program in Biology, School of Sciences, University of Louisiana at Monroe, 700 University Avenue, Monroe, LA, 71209, USA
| | - Sumitkumar Patel
- Program in Biology, School of Sciences, University of Louisiana at Monroe, 700 University Avenue, Monroe, LA, 71209, USA
| | - Silvienne Sint Jago
- Program in Biology, School of Sciences, University of Louisiana at Monroe, 700 University Avenue, Monroe, LA, 71209, USA
| | - Matthew E Talbert
- Program in Biology, School of Sciences, University of Louisiana at Monroe, 700 University Avenue, Monroe, LA, 71209, USA.
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10
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BMP signaling downstream of the Highwire E3 ligase sensitizes nociceptors. PLoS Genet 2018; 14:e1007464. [PMID: 30001326 PMCID: PMC6042685 DOI: 10.1371/journal.pgen.1007464] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 06/01/2018] [Indexed: 01/18/2023] Open
Abstract
A comprehensive understanding of the molecular machinery important for nociception is essential to improving the treatment of pain. Here, we show that the BMP signaling pathway regulates nociception downstream of the E3 ubiquitin ligase highwire (hiw). hiw loss of function in nociceptors caused antagonistic and pleiotropic phenotypes with simultaneous insensitivity to noxious heat but sensitized responses to optogenetic activation of nociceptors. Thus, hiw functions to both positively and negatively regulate nociceptors. We find that a sensory reception-independent sensitization pathway was associated with BMP signaling. BMP signaling in nociceptors was up-regulated in hiw mutants, and nociceptor-specific expression of hiw rescued all nociception phenotypes including the increased BMP signaling. Blocking the transcriptional output of the BMP pathway with dominant negative Mad suppressed nociceptive hypersensitivity that was induced by interfering with hiw. The up-regulated BMP signaling phenotype in hiw genetic mutants could not be suppressed by mutation in wallenda suggesting that hiw regulates BMP in nociceptors via a wallenda independent pathway. In a newly established Ca2+ imaging preparation, we observed that up-regulated BMP signaling caused a significantly enhanced Ca2+ signal in the axon terminals of nociceptors that were stimulated by noxious heat. This response likely accounts for the nociceptive hypersensitivity induced by elevated BMP signaling in nociceptors. Finally, we showed that 24-hour activation of BMP signaling in nociceptors was sufficient to sensitize nociceptive responses to optogenetically-triggered nociceptor activation without altering nociceptor morphology. Overall, this study demonstrates the previously unrevealed roles of the Hiw-BMP pathway in the regulation of nociception and provides the first direct evidence that up-regulated BMP signaling physiologically sensitizes responses of nociceptors and nociception behaviors. Although pain is a universally experienced sensation that has a significant impact on human lives and society, the molecular mechanisms of pain remain poorly understood. Elucidating these mechanisms is particularly important to gaining insight into the clinical development of currently incurable chronic pain diseases. Taking an advantage of the powerful genetic model organism Drosophila melanogaster (fruit flies), we unveil the Highwire-BMP signaling pathway as a novel molecular pathway that regulates the sensitivity of nociceptive sensory neurons. Highwire and the molecular components of the BMP signaling pathway are known to be widely conserved among animal phyla, from nematode worms to humans. Since abnormal sensitivity of nociceptive sensory neurons can play a critical role in the development of chronic pain conditions, a deeper understanding of the regulation of nociceptor sensitivity has the potential to advance effective therapeutic strategies to treat difficult pain conditions.
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11
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Desbois M, Crawley O, Evans PR, Baker ST, Masuho I, Yasuda R, Grill B. PAM forms an atypical SCF ubiquitin ligase complex that ubiquitinates and degrades NMNAT2. J Biol Chem 2018; 293:13897-13909. [PMID: 29997255 DOI: 10.1074/jbc.ra118.002176] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 06/13/2018] [Indexed: 12/20/2022] Open
Abstract
PHR (PAM/Highwire/RPM-1) proteins are conserved RING E3 ubiquitin ligases that function in developmental processes, such as axon termination and synapse formation, as well as axon degeneration. At present, our understanding of how PHR proteins form ubiquitin ligase complexes remains incomplete. Although genetic studies indicate NMNAT2 is an important mediator of PHR protein function in axon degeneration, it remains unknown how PHR proteins inhibit NMNAT2. Here, we decipher the biochemical basis for how the human PHR protein PAM, also called MYCBP2, forms a noncanonical Skp/Cullin/F-box (SCF) complex that contains the F-box protein FBXO45 and SKP1 but lacks CUL1. We show FBXO45 does not simply function in substrate recognition but is important for assembly of the PAM/FBXO45/SKP1 complex. Interestingly, we demonstrate a novel role for SKP1 as an auxiliary component of the target recognition module that enhances binding of FBXO45 to NMNAT2. Finally, we provide biochemical evidence that PAM polyubiquitinates NMNAT2 and regulates NMNAT2 protein stability and degradation by the proteasome.
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Affiliation(s)
- Muriel Desbois
- From the Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, Florida 33458 and
| | - Oliver Crawley
- From the Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, Florida 33458 and
| | - Paul R Evans
- the Max Planck Florida Institute for Neuroscience, Jupiter, Florida 33458
| | - Scott T Baker
- From the Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, Florida 33458 and
| | - Ikuo Masuho
- From the Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, Florida 33458 and
| | - Ryohei Yasuda
- the Max Planck Florida Institute for Neuroscience, Jupiter, Florida 33458
| | - Brock Grill
- From the Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, Florida 33458 and
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12
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Shimanoe C, Hachiya T, Hara M, Nishida Y, Tanaka K, Sutoh Y, Shimizu A, Hishida A, Kawai S, Okada R, Tamura T, Matsuo K, Ito H, Ozaki E, Matsui D, Ibusuki R, Shimoshikiryo I, Takashima N, Kadota A, Arisawa K, Uemura H, Suzuki S, Watanabe M, Kuriki K, Endoh K, Mikami H, Nakamura Y, Momozawa Y, Kubo M, Nakatochi M, Naito M, Wakai K. A genome-wide association study of coping behaviors suggests FBXO45
is associated with emotional expression. GENES BRAIN AND BEHAVIOR 2018; 18:e12481. [DOI: 10.1111/gbb.12481] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Revised: 03/15/2018] [Accepted: 04/11/2018] [Indexed: 12/20/2022]
Affiliation(s)
- C. Shimanoe
- Department of Preventive Medicine, Faculty of Medicine; Saga University; Saga Japan
| | - T. Hachiya
- Division of Biomedical Information Analysis, Iwate Tohoku Medical Megabank Organization; Disaster Reconstruction Center, Iwate Medical University; Iwate Japan
| | - M. Hara
- Department of Preventive Medicine, Faculty of Medicine; Saga University; Saga Japan
| | - Y. Nishida
- Department of Preventive Medicine, Faculty of Medicine; Saga University; Saga Japan
| | - K. Tanaka
- Department of Preventive Medicine, Faculty of Medicine; Saga University; Saga Japan
| | - Y. Sutoh
- Division of Biomedical Information Analysis, Iwate Tohoku Medical Megabank Organization; Disaster Reconstruction Center, Iwate Medical University; Iwate Japan
| | - A. Shimizu
- Division of Biomedical Information Analysis, Iwate Tohoku Medical Megabank Organization; Disaster Reconstruction Center, Iwate Medical University; Iwate Japan
| | - A. Hishida
- Department of Preventive Medicine; Nagoya University Graduate School of Medicine; Nagoya Japan
| | - S. Kawai
- Department of Preventive Medicine; Nagoya University Graduate School of Medicine; Nagoya Japan
| | - R. Okada
- Department of Preventive Medicine; Nagoya University Graduate School of Medicine; Nagoya Japan
| | - T. Tamura
- Department of Preventive Medicine; Nagoya University Graduate School of Medicine; Nagoya Japan
| | - K. Matsuo
- Division of Molecular and Clinical Epidemiology; Aichi Cancer Center Research Institute; Nagoya Japan
| | - H. Ito
- Division of Molecular and Clinical Epidemiology; Aichi Cancer Center Research Institute; Nagoya Japan
| | - E. Ozaki
- Department of Epidemiology for Community Health and Medicine; Kyoto Prefectural University of Medicine; Kyoto Japan
| | - D. Matsui
- Department of Epidemiology for Community Health and Medicine; Kyoto Prefectural University of Medicine; Kyoto Japan
| | - R. Ibusuki
- Department of International Island and Community Medicine; Kagoshima University Graduate School of Medical and Dental Sciences; Kagoshima Japan
| | - I. Shimoshikiryo
- Department of International Island and Community Medicine; Kagoshima University Graduate School of Medical and Dental Sciences; Kagoshima Japan
| | - N. Takashima
- Department of Public Health; Shiga University of Medical Science; Otsu Japan
| | - A. Kadota
- Department of Public Health; Shiga University of Medical Science; Otsu Japan
- Center for Epidemiologic Research in Asia; Shiga University of Medical Science; Otsu Japan
| | - K. Arisawa
- Department of Preventive Medicine; Institute of Biomedical Sciences, Tokushima University Graduate School; Tokushima Japan
| | - H. Uemura
- Department of Preventive Medicine; Institute of Biomedical Sciences, Tokushima University Graduate School; Tokushima Japan
| | - S. Suzuki
- Department of Public Health; Nagoya City University Graduate School of Medical Sciences; Nagoya Japan
| | - M. Watanabe
- Department of Public Health; Nagoya City University Graduate School of Medical Sciences; Nagoya Japan
| | - K. Kuriki
- Laboratory of Public Health, Division of Nutritional Sciences, School of Food and Nutritional Sciences; University of Shizuoka; Shizuoka Japan
| | - K. Endoh
- Laboratory of Public Health, Division of Nutritional Sciences, School of Food and Nutritional Sciences; University of Shizuoka; Shizuoka Japan
| | - H. Mikami
- Division of Cancer Prevention and Epidemiology; Chiba Cancer Center; Chiba Japan
| | - Y. Nakamura
- Division of Cancer Prevention and Epidemiology; Chiba Cancer Center; Chiba Japan
| | - Y. Momozawa
- Laboratory for Genotyping Development; RIKEN Center for Integrative Medical Sciences; Yokohama Japan
| | - M. Kubo
- RIKEN Center for Integrative Medical Sciences; Yokohama Japan
| | - M. Nakatochi
- Statistical Analysis Section; Center for Advanced Medicine and Clinical Research, Nagoya University Hospital; Nagoya Japan
| | - M. Naito
- Department of Maxillofacial Functional Development; Graduate School of Biomedical and Health Sciences, Hiroshima University; Hiroshima Japan
| | - K. Wakai
- Department of Preventive Medicine; Nagoya University Graduate School of Medicine; Nagoya Japan
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13
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Koch M, Nicolas M, Zschaetzsch M, de Geest N, Claeys A, Yan J, Morgan MJ, Erfurth ML, Holt M, Schmucker D, Hassan BA. A Fat-Facets-Dscam1-JNK Pathway Enhances Axonal Growth in Development and after Injury. Front Cell Neurosci 2018; 11:416. [PMID: 29472843 PMCID: PMC5809495 DOI: 10.3389/fncel.2017.00416] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 12/12/2017] [Indexed: 11/13/2022] Open
Abstract
Injury to the adult central nervous systems (CNS) can result in severe long-term disability because damaged CNS connections fail to regenerate after trauma. Identification of regulators that enhance the intrinsic growth capacity of severed axons is a first step to restore function. Here, we conducted a gain-of-function genetic screen in Drosophila to identify strong inducers of axonal growth after injury. We focus on a novel axis the Down Syndrome Cell Adhesion Molecule (Dscam1), the de-ubiquitinating enzyme Fat Facets (Faf)/Usp9x and the Jun N-Terminal Kinase (JNK) pathway transcription factor Kayak (Kay)/Fos. Genetic and biochemical analyses link these genes in a common signaling pathway whereby Faf stabilizes Dscam1 protein levels, by acting on the 3'-UTR of its mRNA, and Dscam1 acts upstream of the growth-promoting JNK signal. The mammalian homolog of Faf, Usp9x/FAM, shares both the regenerative and Dscam1 stabilizing activities, suggesting a conserved mechanism.
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Affiliation(s)
- Marta Koch
- Laboratory of Neurogenetics, Center for Brain and Disease Research, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium.,Center for Human Genetics, University of Leuven School of Medicine, KU Leuven, Leuven, Belgium
| | - Maya Nicolas
- Laboratory of Neurogenetics, Center for Brain and Disease Research, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium.,Center for Human Genetics, University of Leuven School of Medicine, KU Leuven, Leuven, Belgium
| | - Marlen Zschaetzsch
- Laboratory of Neurogenetics, Center for Brain and Disease Research, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium.,Center for Human Genetics, University of Leuven School of Medicine, KU Leuven, Leuven, Belgium
| | - Natalie de Geest
- Laboratory of Neurogenetics, Center for Brain and Disease Research, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium.,Center for Human Genetics, University of Leuven School of Medicine, KU Leuven, Leuven, Belgium
| | - Annelies Claeys
- Laboratory of Neurogenetics, Center for Brain and Disease Research, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium.,Center for Human Genetics, University of Leuven School of Medicine, KU Leuven, Leuven, Belgium
| | - Jiekun Yan
- Laboratory of Neurogenetics, Center for Brain and Disease Research, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium.,Center for Human Genetics, University of Leuven School of Medicine, KU Leuven, Leuven, Belgium
| | - Matthew J Morgan
- Laboratory of Neurogenetics, Center for Brain and Disease Research, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium.,Center for Human Genetics, University of Leuven School of Medicine, KU Leuven, Leuven, Belgium
| | - Maria-Luise Erfurth
- Center for Human Genetics, University of Leuven School of Medicine, KU Leuven, Leuven, Belgium.,Neuronal Wiring Lab, Center for Brain and Disease Research, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium
| | - Matthew Holt
- Center for Human Genetics, University of Leuven School of Medicine, KU Leuven, Leuven, Belgium.,Laboratory of Glia Biology, Center for Brain and Disease Research, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium
| | - Dietmar Schmucker
- Center for Human Genetics, University of Leuven School of Medicine, KU Leuven, Leuven, Belgium.,Neuronal Wiring Lab, Center for Brain and Disease Research, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium
| | - Bassem A Hassan
- Laboratory of Neurogenetics, Center for Brain and Disease Research, Vlaams Instituut voor Biotechnologie (VIB), Leuven, Belgium.,Center for Human Genetics, University of Leuven School of Medicine, KU Leuven, Leuven, Belgium.,Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Institut du Cerveau et de la Moelle Epinière, Hôpital Pitié-Salpêtrière, UPMC, Sorbonne Universités, Paris, France
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14
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Li J, Zhang YV, Asghari Adib E, Stanchev DT, Xiong X, Klinedinst S, Soppina P, Jahn TR, Hume RI, Rasse TM, Collins CA. Restraint of presynaptic protein levels by Wnd/DLK signaling mediates synaptic defects associated with the kinesin-3 motor Unc-104. eLife 2017; 6. [PMID: 28925357 PMCID: PMC5605197 DOI: 10.7554/elife.24271] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Accepted: 08/11/2017] [Indexed: 12/19/2022] Open
Abstract
The kinesin-3 family member Unc-104/KIF1A is required for axonal transport of many presynaptic components to synapses, and mutation of this gene results in synaptic dysfunction in mice, flies and worms. Our studies at the Drosophila neuromuscular junction indicate that many synaptic defects in unc-104-null mutants are mediated independently of Unc-104's transport function, via the Wallenda (Wnd)/DLK MAP kinase axonal damage signaling pathway. Wnd signaling becomes activated when Unc-104's function is disrupted, and leads to impairment of synaptic structure and function by restraining the expression level of active zone (AZ) and synaptic vesicle (SV) components. This action concomitantly suppresses the buildup of synaptic proteins in neuronal cell bodies, hence may play an adaptive role to stresses that impair axonal transport. Wnd signaling also becomes activated when pre-synaptic proteins are over-expressed, suggesting the existence of a feedback circuit to match synaptic protein levels to the transport capacity of the axon.
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Affiliation(s)
- Jiaxing Li
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Yao V Zhang
- Junior Research Group Synaptic Plasticity, Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.,Graduate School of Cellular and Molecular Neuroscience, University of Tübingen, Tübingen, Germany
| | - Elham Asghari Adib
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Doychin T Stanchev
- Junior Research Group Synaptic Plasticity, Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.,Graduate School of Cellular and Molecular Neuroscience, University of Tübingen, Tübingen, Germany
| | - Xin Xiong
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Susan Klinedinst
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Pushpanjali Soppina
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Thomas Robert Jahn
- CHS Research Group Proteostasis in Neurodegenerative Disease, DKFZ Deutsches Krebsforschungszentrum, Heidelberg, Germany
| | - Richard I Hume
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Tobias M Rasse
- Junior Research Group Synaptic Plasticity, Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany.,CHS Research Group Proteostasis in Neurodegenerative Disease, DKFZ Deutsches Krebsforschungszentrum, Heidelberg, Germany
| | - Catherine A Collins
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
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15
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Baker ST, Grill B. Defining Minimal Binding Regions in Regulator of Presynaptic Morphology 1 (RPM-1) Using Caenorhabditis elegans Neurons Reveals Differential Signaling Complexes. J Biol Chem 2016; 292:2519-2530. [PMID: 27979965 DOI: 10.1074/jbc.m116.748004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Revised: 12/14/2016] [Indexed: 12/22/2022] Open
Abstract
The intracellular signaling protein regulator of presynaptic morphology 1 (RPM-1) is a conserved regulator of synapse formation and axon termination in Caenorhabditis elegans RPM-1 functions in a ubiquitin ligase complex with the F-box protein FSN-1 and functions through the microtubule binding protein RAE-1. Using a structure-function approach and positive selection for transgenic C. elegans, we explored the biochemical relationship between RPM-1, FSN-1, and RAE-1. This led to the identification of two new domains in RPM-1 that are sufficient for binding to FSN-1, called FSN-1 binding domain 2 (FBD2) and FBD3. Furthermore, we map the RAE-1 binding domain to a much smaller region of RPM-1. Point mutations in RPM-1 that reduce binding to RAE-1 did not affect FSN-1 binding, indicating that RPM-1 utilizes different biochemical mechanisms to bind these molecules. Analysis of RPM-1 protein complexes in the neurons of C. elegans elucidated two further discoveries: FSN-1 binds to RAE-1, and this interaction is not mediated by RPM-1, and RPM-1 binding to FSN-1 and RAE-1 reduces FSN-1·RAE-1 complex formation. These results indicate that RPM-1 uses different mechanisms to recruit FSN-1 and RAE-1 into independent signaling complexes in neurons.
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Affiliation(s)
- Scott T Baker
- From the Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, Florida 33458
| | - Brock Grill
- From the Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, Florida 33458
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16
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Zwarts L, Goossens T, Clements J, Kang YY, Callaerts P. Axon Branch-Specific Semaphorin-1a Signaling in Drosophila Mushroom Body Development. Front Cell Neurosci 2016; 10:210. [PMID: 27656129 PMCID: PMC5011136 DOI: 10.3389/fncel.2016.00210] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 08/23/2016] [Indexed: 11/25/2022] Open
Abstract
Correct wiring of the mushroom body (MB) neuropil in the Drosophila brain involves appropriate positioning of different axonal lobes, as well as the sister branches that develop from individual axons. This positioning requires the integration of various guidance cues provided by different cell types, which help the axons find their final positions within the neuropil. Semaphorins are well-known for their conserved roles in neuronal development and axon guidance. We investigated the role of Sema-1a in MB development more closely. We show that Sema-1a is expressed in the MBs as well as surrounding structures, including the glial transient interhemispheric fibrous ring, throughout development. By loss- and gain-of-function experiments, we show that the MB axons display lobe and sister branch-specific Sema-1a signaling, which controls different aspects of axon outgrowth and guidance. Furthermore, we demonstrate that these effects are modulated by the integration of MB intrinsic and extrinsic Sema-1a signaling pathways involving PlexA and PlexB. Finally, we also show a role for neuronal- glial interaction in Sema-1a dependent β-lobe outgrowth.
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Affiliation(s)
- Liesbeth Zwarts
- Laboratory of Behavioral and Developmental Genetics, Department of Human Genetics, KU Leuven, LeuvenBelgium; Center for the Biology of Disease, Vlaams Instituut voor Biotechnologie, LeuvenBelgium
| | - Tim Goossens
- Laboratory of Behavioral and Developmental Genetics, Department of Human Genetics, KU Leuven, LeuvenBelgium; Center for the Biology of Disease, Vlaams Instituut voor Biotechnologie, LeuvenBelgium
| | - Jason Clements
- Laboratory of Behavioral and Developmental Genetics, Department of Human Genetics, KU Leuven, LeuvenBelgium; Center for the Biology of Disease, Vlaams Instituut voor Biotechnologie, LeuvenBelgium
| | - Yuan Y Kang
- Department of Biology and Biochemistry, University of Houston, Houston, TX USA
| | - Patrick Callaerts
- Laboratory of Behavioral and Developmental Genetics, Department of Human Genetics, KU Leuven, LeuvenBelgium; Center for the Biology of Disease, Vlaams Instituut voor Biotechnologie, LeuvenBelgium
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17
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Feoktistov AI, Herman TG. Wallenda/DLK protein levels are temporally downregulated by Tramtrack69 to allow R7 growth cones to become stationary boutons. Development 2016; 143:2983-93. [PMID: 27402706 DOI: 10.1242/dev.134403] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 06/23/2016] [Indexed: 11/20/2022]
Abstract
Dual leucine zipper kinase (DLK) promotes growth cone motility and must be restrained to ensure normal development. PHR (Pam/Highwire/RPM-1) ubiquitin ligases therefore target DLK for degradation unless axon injury occurs. Overall DLK levels decrease during development, but how DLK levels are regulated within a developing growth cone has not been examined. We analyzed the expression of the fly DLK Wallenda (Wnd) in R7 photoreceptor growth cones as they halt at their targets and become presynaptic boutons. We found that Wnd protein levels are repressed by the PHR protein Highwire (Hiw) during R7 growth cone halting, as has been observed in other systems. However, as R7 growth cones become boutons, Wnd levels are further repressed by a temporally expressed transcription factor, Tramtrack69 (Ttk69). Previously unobserved negative feedback from JNK also contributes to Wnd repression at both time points. We conclude that neurons deploy additional mechanisms to downregulate DLK as they form stable, synaptic connections. We use live imaging to probe the effects of Wnd and Ttk69 on R7 bouton development and conclude that Ttk69 coordinates multiple regulators of this process.
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Affiliation(s)
- Alexander I Feoktistov
- Institute of Molecular Biology, Department of Biology, University of Oregon, Eugene, OR 97403, USA
| | - Tory G Herman
- Institute of Molecular Biology, Department of Biology, University of Oregon, Eugene, OR 97403, USA
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18
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Grill B, Murphey RK, Borgen MA. The PHR proteins: intracellular signaling hubs in neuronal development and axon degeneration. Neural Dev 2016; 11:8. [PMID: 27008623 PMCID: PMC4806438 DOI: 10.1186/s13064-016-0063-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 03/15/2016] [Indexed: 11/10/2022] Open
Abstract
During development, a coordinated and integrated series of events must be accomplished in order to generate functional neural circuits. Axons must navigate toward target cells, build synaptic connections, and terminate outgrowth. The PHR proteins (consisting of mammalian Phr1/MYCBP2, Drosophila Highwire and C. elegans RPM-1) function in each of these events in development. Here, we review PHR function across species, as well as the myriad of signaling pathways PHR proteins regulate. These findings collectively suggest that the PHR proteins are intracellular signaling hubs, a concept we explore in depth. Consistent with prominent developmental functions, genetic links have begun to emerge between PHR signaling networks and neurodevelopmental disorders, such as autism, schizophrenia and intellectual disability. Finally, we discuss the recent and important finding that PHR proteins regulate axon degeneration, which has further heightened interest in this fascinating group of molecules.
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Affiliation(s)
- Brock Grill
- Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, FL, 33458, USA.
| | - Rodney K Murphey
- Department of Biological Sciences, Florida Atlantic University, Jupiter, FL, 33458, USA
| | - Melissa A Borgen
- Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, FL, 33458, USA
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19
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Harris KP, Littleton JT. Transmission, Development, and Plasticity of Synapses. Genetics 2015; 201:345-75. [PMID: 26447126 PMCID: PMC4596655 DOI: 10.1534/genetics.115.176529] [Citation(s) in RCA: 119] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 05/28/2015] [Indexed: 01/03/2023] Open
Abstract
Chemical synapses are sites of contact and information transfer between a neuron and its partner cell. Each synapse is a specialized junction, where the presynaptic cell assembles machinery for the release of neurotransmitter, and the postsynaptic cell assembles components to receive and integrate this signal. Synapses also exhibit plasticity, during which synaptic function and/or structure are modified in response to activity. With a robust panel of genetic, imaging, and electrophysiology approaches, and strong evolutionary conservation of molecular components, Drosophila has emerged as an essential model system for investigating the mechanisms underlying synaptic assembly, function, and plasticity. We will discuss techniques for studying synapses in Drosophila, with a focus on the larval neuromuscular junction (NMJ), a well-established model glutamatergic synapse. Vesicle fusion, which underlies synaptic release of neurotransmitters, has been well characterized at this synapse. In addition, studies of synaptic assembly and organization of active zones and postsynaptic densities have revealed pathways that coordinate those events across the synaptic cleft. We will also review modes of synaptic growth and plasticity at the fly NMJ, and discuss how pre- and postsynaptic cells communicate to regulate plasticity in response to activity.
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Affiliation(s)
- Kathryn P Harris
- Department of Biology and Department of Brain and Cognitive Sciences, The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - J Troy Littleton
- Department of Biology and Department of Brain and Cognitive Sciences, The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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20
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Dörr A, Pierre S, Zhang DD, Henke M, Holland S, Scholich K. MYCBP2 Is a Guanosine Exchange Factor for Ran Protein and Determines Its Localization in Neurons of Dorsal Root Ganglia. J Biol Chem 2015; 290:25620-35. [PMID: 26304119 DOI: 10.1074/jbc.m115.646901] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Indexed: 11/06/2022] Open
Abstract
The small GTPase Ran coordinates retrograde axonal transport in neurons, spindle assembly during mitosis, and the nucleo-cytoplasmic transport of mRNA. Its localization is tightly regulated by the GTPase-activating protein RanGAP1 and the nuclear guanosine exchange factor (GEF) RCC1. We show that loss of the neuronal E3 ubiquitin ligase MYCBP2 caused the up-regulation of Ran and RanGAP1 in dorsal root ganglia (DRG) under basal conditions and during inflammatory hyperalgesia. SUMOylated RanGAP1 physically interacted with MYCBP2 and inhibited its E3 ubiquitin ligase activity. Stimulation of neurons induced a RanGAP1-dependent translocation of MYCBP2 to the nucleus. In the nucleus of DRG neurons MYCBP2 co-localized with Ran and facilitated through its RCC1-like domain the GDP/GTP exchange of Ran. In accordance with the necessity of a GEF to promote GTP-binding and nuclear export of Ran, the nuclear localization of Ran was strongly increased in MYCBP2-deficient DRGs. The finding that other GEFs for Ran besides RCC1 exist gives new insights in the complexity of the regulation of the Ran signaling pathway.
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Affiliation(s)
- Angela Dörr
- From the Institut für Klinische Pharmakologie, Pharmazentrum Frankfurt, Klinikum der Goethe-Universität Frankfurt, Frankfurt 60590, Germany
| | - Sandra Pierre
- From the Institut für Klinische Pharmakologie, Pharmazentrum Frankfurt, Klinikum der Goethe-Universität Frankfurt, Frankfurt 60590, Germany
| | - Dong D Zhang
- From the Institut für Klinische Pharmakologie, Pharmazentrum Frankfurt, Klinikum der Goethe-Universität Frankfurt, Frankfurt 60590, Germany
| | - Marina Henke
- From the Institut für Klinische Pharmakologie, Pharmazentrum Frankfurt, Klinikum der Goethe-Universität Frankfurt, Frankfurt 60590, Germany
| | - Sabrina Holland
- From the Institut für Klinische Pharmakologie, Pharmazentrum Frankfurt, Klinikum der Goethe-Universität Frankfurt, Frankfurt 60590, Germany
| | - Klaus Scholich
- From the Institut für Klinische Pharmakologie, Pharmazentrum Frankfurt, Klinikum der Goethe-Universität Frankfurt, Frankfurt 60590, Germany
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21
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Sharma J, Baker ST, Turgeon SM, Gurney AM, Opperman KJ, Grill B. Identification of a peptide inhibitor of the RPM-1 · FSN-1 ubiquitin ligase complex. J Biol Chem 2014; 289:34654-66. [PMID: 25326385 DOI: 10.1074/jbc.m114.614065] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The Pam/Highwire/RPM-1 (PHR) proteins include: Caenorhabditis elegans RPM-1 (Regulator of Presynaptic Morphology 1), Drosophila Highwire, and murine Phr1. These important regulators of neuronal development function in synapse formation, axon guidance, and axon termination. In mature neurons the PHR proteins also regulate axon degeneration and regeneration. PHR proteins function, in part, through an ubiquitin ligase complex that includes the F-box protein FSN-1 in C. elegans and Fbxo45 in mammals. At present, the structure-function relationships that govern formation of this complex are poorly understood. We cloned 9 individual domains that compose the entire RPM-1 protein sequence and found a single domain centrally located in RPM-1 that is sufficient for binding to FSN-1. Deletion analysis further refined FSN-1 binding to a conserved 97-amino acid region of RPM-1. Mutagenesis identified several conserved motifs and individual amino acids that mediate this interaction. Transgenic overexpression of this recombinant peptide, which we refer to as the RPM-1·FSN-1 complex inhibitory peptide (RIP), yields similar phenotypes and enhancer effects to loss of function in fsn-1. Defects caused by transgenic RIP were suppressed by loss of function in the dlk-1 MAP3K and were alleviated by point mutations that reduce binding to FSN-1. These findings suggest that RIP specifically inhibits the interaction between RPM-1 and FSN-1 in vivo, thereby blocking formation of a functional ubiquitin ligase complex. Our results are consistent with the FSN-1 binding domain of RPM-1 recruiting FSN-1 and a target protein, such as DLK-1, whereas the RING-H2 domain of RPM-1 ubiquitinates the target.
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Affiliation(s)
- Jaiprakash Sharma
- From the Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, Florida, 33458 and
| | - Scott T Baker
- From the Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, Florida, 33458 and Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota 55455
| | - Shane M Turgeon
- From the Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, Florida, 33458 and
| | - Allison M Gurney
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota 55455
| | - Karla J Opperman
- From the Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, Florida, 33458 and
| | - Brock Grill
- From the Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, Florida, 33458 and
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22
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Chung FZ, Sahasrabuddhe AA, Ma K, Chen X, Basrur V, Lim MS, Elenitoba-Johnson KSJ. Fbxo45 inhibits calcium-sensitive proteolysis of N-cadherin and promotes neuronal differentiation. J Biol Chem 2014; 289:28448-59. [PMID: 25143387 DOI: 10.1074/jbc.m114.561241] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Fbxo45 is an atypical E3 ubiquitin ligase, which specifically targets proteins for ubiquitin-mediated degradation. Fbxo45 ablation results in defective neuronal differentiation and abnormal formation of neural connections; however, the mechanisms underlying these defects are poorly understood. Using an unbiased mass spectrometry-based proteomic screen, we show here that N-cadherin is a novel interactor of Fbxo45. N-cadherin specifically interacts with Fbxo45 through two consensus motifs overlapping the site of calcium-binding and dimerization of the cadherin molecule. N-cadherin interaction with Fbxo45 is significantly abrogated by calcium treatment. Surprisingly, Fbxo45 depletion by RNAi-mediated silencing results in enhanced proteolysis of N-cadherin. Conversely, ectopic expression of Fbxo45 results in decreased proteolysis of N-cadherin. Fbxo45 depletion results in dramatic reduction in N-cadherin expression, impaired neuronal differentiation, and diminished formation of neuronal processes. Our studies reveal an unanticipated role for an F-box protein that inhibits proteolysis in the regulation of a critical biological process.
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Affiliation(s)
| | | | - Kaiyu Ma
- From the Department of Pathology
| | | | | | - Megan S Lim
- From the Department of Pathology, the Center for Computational Medicine and Bioinformatics, and
| | - Kojo S J Elenitoba-Johnson
- From the Department of Pathology, the Center for Computational Medicine and Bioinformatics, and the Protein Folding Diseases Initiative, University of Michigan Medical School, Ann Arbor, Michigan 48109
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23
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Wang C, Koide T, Kimura H, Kunimoto S, Yoshimi A, Nakamura Y, Kushima I, Banno M, Kawano N, Takasaki Y, Xing J, Noda Y, Mouri A, Aleksic B, Ikeda M, Okada T, Iidaka T, Inada T, Iwata N, Ozaki N. Novel rare variants in F-box protein 45 (FBXO45) in schizophrenia. Schizophr Res 2014; 157:149-56. [PMID: 24878430 DOI: 10.1016/j.schres.2014.04.032] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 03/31/2014] [Accepted: 04/23/2014] [Indexed: 10/25/2022]
Abstract
The ubiquitin ligase F-box protein 45 (FBXO45) is critical for synaptogenesis, neuronal migration, and synaptic transmission. FBXO45 is included in the 3q29 microdeletion region that confers a significant risk for schizophrenia, as shown by rare structural variant studies. Thus, FBXO45 is considered a prominent candidate for mediating schizophrenia pathogenesis. Here, we investigated rare, deleterious single nucleotide variants (SNVs) as well as small insertions and deletions (INDELs) in FBXO45 that may contribute to schizophrenia susceptibility. Using Sanger sequencing, we performed mutation screening in FBXO45 exon regions in 337 schizophrenia patients. Novel missense or nonsense variants were followed up with a genetic association study in an independent sample set of 601 schizophrenia patients and 916 controls, a case report for assessing the clinical consequence of the mutations, a pedigree study for measuring mutation inheritance in the proband's family, bioinformatics analyses for evaluating mutation effect on protein structure and function, and mRNA expression analysis for examining mutation transcriptional influence on FBXO45 expression. One heterozygous, novel, and rare missense mutation (R108C) was identified in a single schizophrenia patient and in his healthy mother. At age 20, this patient was diagnosed with paranoid schizophrenia and carried some clinical features of 3q29 deletion phenotypes, including premorbid IQ decline. With follow-up genotyping, this mutation was not found in either the schizophrenia group (0/601) or the healthy control group (0/916). Bioinformatics analyses predicted that R108C probably pathologically impacted the structure and function of the FBXO45 protein. The relative expression of FBXO45 in SCZ case with R108C mutation was relatively low when compared to 50 schizophrenia patients and 52 healthy controls. The R108C mutation in FBXO45 is a rare variant with a modest effect on schizophrenia risk that may disrupt the structure and function of the FBXO45 protein. Our findings also suggest that FBXO45 may be a new attractive candidate gene for schizophrenia.
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Affiliation(s)
- Chenyao Wang
- Department of Psychiatry, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Takayoshi Koide
- Department of Psychiatry, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Hiroki Kimura
- Department of Psychiatry, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Shohko Kunimoto
- Department of Psychiatry, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Akira Yoshimi
- Department of Psychiatry, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Yukako Nakamura
- Department of Psychiatry, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Itaru Kushima
- Department of Psychiatry, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Masahiro Banno
- Department of Psychiatry, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Naoko Kawano
- Department of Psychiatry, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Yuto Takasaki
- Department of Psychiatry, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Jingrui Xing
- Department of Psychiatry, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Yukihiro Noda
- Division of Clinical Sciences and Neuropsychopharmacology, Graduate School of Pharmacy, Meijo University, Nagoya, Japan
| | - Akihiro Mouri
- Division of Clinical Sciences and Neuropsychopharmacology, Graduate School of Pharmacy, Meijo University, Nagoya, Japan
| | - Branko Aleksic
- Department of Psychiatry, Nagoya University Graduate School of Medicine, Nagoya, Japan.
| | - Masashi Ikeda
- Department of Psychiatry, School of Medicine, Fujita Health University, Toyoake, Aichi, Japan
| | - Takashi Okada
- Department of Psychiatry, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Tetsuya Iidaka
- Department of Psychiatry, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Toshiya Inada
- Institute of Neuropsychiatry, Seiwa Hospital, Tokyo, Japan
| | - Nakao Iwata
- Department of Psychiatry, School of Medicine, Fujita Health University, Toyoake, Aichi, Japan
| | - Norio Ozaki
- Department of Psychiatry, Nagoya University Graduate School of Medicine, Nagoya, Japan
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Fbxo45-mediated degradation of the tumor-suppressor Par-4 regulates cancer cell survival. Cell Death Differ 2014; 21:1535-45. [PMID: 24992930 DOI: 10.1038/cdd.2014.92] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Revised: 05/09/2014] [Accepted: 05/23/2014] [Indexed: 11/09/2022] Open
Abstract
Prostate apoptosis response protein 4 (Par-4) also known as PRKC apoptosis WT1 regulator is a tumor suppressor that selectively induces apoptosis in cancer cells. However, its post-translational regulation by ubiquitin-mediated proteolysis and the cellular machinery that is responsible for its proteasomal degradation are unknown. Using immunopurification and an unbiased mass spectrometry-based approach, we show that Par-4 interacts with the SPRY-domain containing E3 ubiquitin ligase Fbxo45 through a short consensus sequence motif. Fbxo45 interacts with Par-4 in the cytoplasm and mediates its ubiquitylation and proteasomal degradation. Fbxo45 silencing results in stabilization of Par-4 with increased apoptosis. Importantly, a Par-4 mutant that is unable to bind Fbxo45 is stabilized and further enhances staurosporine-induced apoptosis. Co-expression of Fbxo45 with Par-4 protects cancer cells against Par-4-induced apoptosis. Our studies reveal that Fbxo45 is the substrate-receptor subunit of a functional E3 ligase for Par-4 that has a critical role in cancer cell survival.
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25
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Brace EJ, Wu C, Valakh V, DiAntonio A. SkpA restrains synaptic terminal growth during development and promotes axonal degeneration following injury. J Neurosci 2014; 34:8398-410. [PMID: 24948796 PMCID: PMC4061385 DOI: 10.1523/jneurosci.4715-13.2014] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Revised: 04/22/2014] [Accepted: 05/13/2014] [Indexed: 02/04/2023] Open
Abstract
The Wallenda (Wnd)/dual leucine zipper kinase (DLK)-Jnk pathway is an evolutionarily conserved MAPK signaling pathway that functions during neuronal development and following axonal injury. Improper pathway activation causes defects in axonal guidance and synaptic growth, whereas loss-of-function mutations in pathway components impairs axonal regeneration and degeneration after injury. Regulation of this pathway is in part through the E3 ubiquitin ligase Highwire (Hiw), which targets Wnd/DLK for degradation to limit MAPK signaling. To explore mechanisms controlling Wnd/DLK signaling, we performed a large-scale genetic screen in Drosophila to identify negative regulators of the pathway. Here we describe the identification and characterization of SkpA, a core component of SCF E3 ubiquitin ligases. Mutants in SkpA display synaptic overgrowth and an increase in Jnk signaling, similar to hiw mutants. The combination of hypomorphic alleles of SkpA and hiw leads to enhanced synaptic growth. Mutants in the Wnd-Jnk pathway suppress the overgrowth of SkpA mutants demonstrating that the synaptic overgrowth is due to increased Jnk signaling. These findings support the model that SkpA and the E3 ligase Hiw function as part of an SCF-like complex that attenuates Wnd/DLK signaling. In addition, SkpA, like Hiw, is required for synaptic and axonal responses to injury. Synapses in SkpA mutants are more stable following genetic or traumatic axonal injury, and axon loss is delayed in SkpA mutants after nerve crush. As in highwire mutants, this axonal protection requires Nmnat. Hence, SkpA is a novel negative regulator of the Wnd-Jnk pathway that functions with Hiw to regulate both synaptic development and axonal maintenance.
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Affiliation(s)
- E J Brace
- Department of Developmental Biology, Washington University School of Medicine, St Louis, Missouri 63110, and
| | - Chunlai Wu
- Neuroscience Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112
| | - Vera Valakh
- Department of Developmental Biology, Washington University School of Medicine, St Louis, Missouri 63110, and
| | - Aaron DiAntonio
- Department of Developmental Biology, Washington University School of Medicine, St Louis, Missouri 63110, and
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26
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RPM-1 uses both ubiquitin ligase and phosphatase-based mechanisms to regulate DLK-1 during neuronal development. PLoS Genet 2014; 10:e1004297. [PMID: 24810406 PMCID: PMC4014440 DOI: 10.1371/journal.pgen.1004297] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Accepted: 02/21/2014] [Indexed: 01/06/2023] Open
Abstract
The Pam/Highwire/RPM-1 (PHR) proteins are key regulators of neuronal development that function in axon extension and guidance, termination of axon outgrowth, and synapse formation. Outside of development, the PHR proteins also regulate axon regeneration and Wallerian degeneration. The PHR proteins function in part by acting as ubiquitin ligases that degrade the Dual Leucine zipper-bearing Kinase (DLK). Here, we show that the Caenorhabditis elegans PHR protein, Regulator of Presynaptic Morphology 1 (RPM-1), also utilizes a phosphatase-based mechanism to regulate DLK-1. Using mass spectrometry, we identified Protein Phosphatase Magnesium/Manganese dependent 2 (PPM-2) as a novel RPM-1 binding protein. Genetic, transgenic, and biochemical studies indicated that PPM-2 functions coordinately with the ubiquitin ligase activity of RPM-1 and the F-box protein FSN-1 to negatively regulate DLK-1. PPM-2 acts on S874 of DLK-1, a residue implicated in regulation of DLK-1 binding to a short, inhibitory isoform of DLK-1 (DLK-1S). Our study demonstrates that PHR proteins function through both phosphatase and ubiquitin ligase mechanisms to inhibit DLK. Thus, PHR proteins are potentially more accurate and sensitive regulators of DLK than originally thought. Our results also highlight an important and expanding role for the PP2C phosphatase family in neuronal development. The molecular mechanisms that govern formation of functional synaptic connections are central to brain development and function. We have used the nematode C. elegans to explore the mechanism of how the intracellular signaling protein RPM-1 regulates neuronal development. Using a combination of proteomic, genetic, transgenic, and biochemical approaches we have shown that RPM-1 functions through a PP2C phosphatase, PPM-2, to regulate the activity of a MAP3 kinase, DLK-1. Our results indicate that a combination of PPM-2 phosphatase activity and RPM-1 ubiquitin ligase activity inhibit DLK-1.
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27
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Loss of the spectraplakin short stop activates the DLK injury response pathway in Drosophila. J Neurosci 2013; 33:17863-73. [PMID: 24198375 DOI: 10.1523/jneurosci.2196-13.2013] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The MAPKKK dual leucine zipper-containing kinase (DLK, Wallenda in Drosophila) is an evolutionarily conserved component of the axonal injury response pathway. After nerve injury, DLK promotes degeneration of distal axons and regeneration of proximal axons. This dual role in coordinating degeneration and regeneration suggests that DLK may be a sensor of axon injury, and so understanding how DLK is activated is important. Two mechanisms are known to activate DLK. First, increasing the levels of DLK via overexpression or loss of the PHR ubiquitin ligases that target DLK activate DLK signaling. Second, in Caenorhabditis elegans, a calcium-dependent mechanism, can activate DLK. Here we describe a new mechanism that activates DLK in Drosophila: loss of the spectraplakin short stop (shot). In a genetic screen for mutants with defective neuromuscular junction development, we identify a hypomorphic allele of shot that displays synaptic terminal overgrowth and a precocious regenerative response to nerve injury. We demonstrate that both phenotypes are the result of overactivation of the DLK signaling pathway. We further show that, unlike mutations in the PHR ligase Highwire, loss of function of shot activates DLK without a concomitant increase in the levels of DLK. As a spectraplakin, Shot binds to both actin and microtubules and promotes cytoskeletal stability. The DLK pathway is also activated by downregulation of the TCP1 chaperonin complex, whose normal function is to promote cytoskeletal stability. These findings support the model that DLK is activated by cytoskeletal instability, which is a shared feature of both spectraplakin mutants and injured axons.
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28
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Tian X, Zhu M, Li L, Wu C. Identifying protein-protein interaction in Drosophila adult heads by Tandem Affinity Purification (TAP). J Vis Exp 2013:50968. [PMID: 24335807 DOI: 10.3791/50968] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Genetic screens conducted using Drosophila melanogaster (fruit fly) have made numerous milestone discoveries in the advance of biological sciences. However, the use of biochemical screens aimed at extending the knowledge gained from genetic analysis was explored only recently. Here we describe a method to purify the protein complex that associates with any protein of interest from adult fly heads. This method takes advantage of the Drosophila GAL4/UAS system to express a bait protein fused with a Tandem Affinity Purification (TAP) tag in fly neurons in vivo, and then implements two rounds of purification using a TAP procedure similar to the one originally established in yeast(1) to purify the interacting protein complex. At the end of this procedure, a mixture of multiple protein complexes is obtained whose molecular identities can be determined by mass spectrometry. Validation of the candidate proteins will benefit from the resource and ease of performing loss-of-function studies in flies. Similar approaches can be applied to other fly tissues. We believe that the combination of genetic manipulations and this proteomic approach in the fly model system holds tremendous potential for tackling fundamental problems in the field of neurobiology and beyond.
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Affiliation(s)
- Xiaolin Tian
- Neuroscience Center of Excellence, Louisiana State University Health Sciences Center
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29
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Babetto E, Beirowski B, Russler EV, Milbrandt J, DiAntonio A. The Phr1 ubiquitin ligase promotes injury-induced axon self-destruction. Cell Rep 2013; 3:1422-9. [PMID: 23665224 PMCID: PMC3671584 DOI: 10.1016/j.celrep.2013.04.013] [Citation(s) in RCA: 121] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2013] [Revised: 03/28/2013] [Accepted: 04/12/2013] [Indexed: 11/16/2022] Open
Abstract
Axon degeneration is an evolutionarily conserved process that drives the loss of damaged axons and is an early event in many neurological disorders, so it is important to identify the molecular constituents of this poorly understood mechanism. Here, we demonstrate that the Phr1 E3 ubiquitin ligase is a central component of this axon degeneration program. Loss of Phr1 results in prolonged survival of severed axons in both the peripheral and central nervous systems, as well as preservation of motor and sensory nerve terminals. Phr1 depletion increases the axonal level of the axon survival molecule nicotinamide mononucleotide adenyltransferase 2 (NMNAT2), and NMNAT2 is necessary for Phr1-dependent axon stability. The profound long-term protection of peripheral and central mammalian axons following Phr1 deletion suggests that pharmacological inhibition of Phr1 function may be an attractive therapeutic candidate for amelioration of axon loss in neurological disease.
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Affiliation(s)
- Elisabetta Babetto
- Department of Developmental Biology, Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO 63110, USA
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30
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Hung WL, Hwang C, Gao S, Liao EH, Chitturi J, Wang Y, Li H, Stigloher C, Bessereau JL, Zhen M. Attenuation of insulin signalling contributes to FSN-1-mediated regulation of synapse development. EMBO J 2013; 32:1745-60. [PMID: 23665919 DOI: 10.1038/emboj.2013.91] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2012] [Accepted: 03/27/2013] [Indexed: 01/07/2023] Open
Abstract
A neuronal F-box protein FSN-1 regulates Caenorhabditis elegans neuromuscular junction development by negatively regulating DLK-mediated MAPK signalling. In the present study, we show that attenuation of insulin/IGF signalling also contributes to FSN-1-dependent synaptic development and function. The aberrant synapse morphology and synaptic transmission in fsn-1 mutants are partially and specifically rescued by reducing insulin/IGF-signalling activity in postsynaptic muscles, as well as by reducing the activity of EGL-3, a prohormone convertase that processes agonistic insulin/IGF ligands INS-4 and INS-6, in neurons. FSN-1 interacts with, and potentiates the ubiquitination of EGL-3 in vitro, and reduces the EGL-3 level in vivo. We propose that FSN-1 may negatively regulate insulin/IGF signalling, in part, through EGL-3-dependent insulin-like ligand processing.
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Affiliation(s)
- Wesley L Hung
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
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31
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Tian X, Wu C. The role of ubiquitin-mediated pathways in regulating synaptic development, axonal degeneration and regeneration: insights from fly and worm. J Physiol 2013; 591:3133-43. [PMID: 23613532 DOI: 10.1113/jphysiol.2012.247940] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The covalent attachment of the 76 amino acid peptide ubiquitin to target proteins is a rapid and reversible modification that regulates protein stability, activity and localization. As such, it is a potent mechanism for sculpting the synapse. Recent studies from two genetic model organisms, Caenorhabditis elegans and Drosophila, have provided mounting evidence that ubiquitin-mediated pathways play important roles in controlling the presynaptic size, synaptic elimination and stabilization, synaptic transmission, postsynaptic receptor abundance, axonal degeneration and regeneration. While the data supporting the requirement of ubiquitination/deubiquitination for normal synaptic development and repair are compelling, detailed analyses of signalling events up- and downstream of these ubiquitin modifications are often challenging. This article summarizes the related research conducted in worms and flies and provides insight into the fundamental questions facing this field.
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Affiliation(s)
- Xiaolin Tian
- Neuroscience Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA
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32
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The F-box protein MEC-15 (FBXW9) promotes synaptic transmission in GABAergic motor neurons in C. elegans. PLoS One 2013; 8:e59132. [PMID: 23527112 PMCID: PMC3601060 DOI: 10.1371/journal.pone.0059132] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Accepted: 02/11/2013] [Indexed: 11/19/2022] Open
Abstract
Ubiquitination controls the activity of many proteins and has been implicated in almost every aspect of neuronal cell biology. Characterizing the precise function of ubiquitin ligases, the enzymes that catalyze ubiquitination of target proteins, is key to understanding distinct functions of ubiquitination. F-box proteins are the variable subunits of the large family of SCF ubiquitin ligases and are responsible for binding and recognizing specific ubiquitination targets. Here, we investigated the function of the F-box protein MEC-15 (FBXW9), one of a small number of F-box proteins evolutionarily conserved from C. elegans to mammals. mec-15 is widely expressed in the nervous system including GABAergic and cholinergic motor neurons. Electrophysiological and behavioral analyses indicate that GABAergic synaptic transmission is reduced in mec-15 mutants while cholinergic transmission appears normal. In the absence of MEC-15, the abundance of the synaptic vesicle protein SNB-1 (synaptobrevin) is reduced at synapses and increased in cell bodies of GABAergic motor neurons, suggesting that MEC-15 affects the trafficking of SNB-1 between cell bodies and synapses and may promote GABA release by regulating the abundance of SNB-1 at synapses.
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33
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Breaking it down: the ubiquitin proteasome system in neuronal morphogenesis. Neural Plast 2013; 2013:196848. [PMID: 23476809 PMCID: PMC3586504 DOI: 10.1155/2013/196848] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Accepted: 12/31/2012] [Indexed: 01/20/2023] Open
Abstract
The ubiquitin-proteasome system (UPS) is most widely known for its role in intracellular protein degradation; however, in the decades since its discovery, ubiquitination has been associated with the regulation of a wide variety of cellular processes. The addition of ubiquitin tags, either as single moieties or as polyubiquitin chains, has been shown not only to mediate degradation by the proteasome and the lysosome, but also to modulate protein function, localization, and endocytosis. The UPS plays a particularly important role in neurons, where local synthesis and degradation work to balance synaptic protein levels at synapses distant from the cell body. In recent years, the UPS has come under increasing scrutiny in neurons, as elements of the UPS have been found to regulate such diverse neuronal functions as synaptic strength, homeostatic plasticity, axon guidance, and neurite outgrowth. Here we focus on recent advances detailing the roles of the UPS in regulating the morphogenesis of axons, dendrites, and dendritic spines, with an emphasis on E3 ubiquitin ligases and their identified regulatory targets.
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34
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Xiong X, Hao Y, Sun K, Li J, Li X, Mishra B, Soppina P, Wu C, Hume RI, Collins CA. The Highwire ubiquitin ligase promotes axonal degeneration by tuning levels of Nmnat protein. PLoS Biol 2012; 10:e1001440. [PMID: 23226106 PMCID: PMC3514318 DOI: 10.1371/journal.pbio.1001440] [Citation(s) in RCA: 141] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 10/24/2012] [Indexed: 11/18/2022] Open
Abstract
Highwire, a conserved axonal E3 ubiquitin ligase, regulates the initiation of axonal degeneration after injury in Drosophila by regulating the levels of the NAD+ biosynthetic enzyme, Nmnat, and the Wnd kinase. Axonal degeneration is a hallmark of many neuropathies, neurodegenerative diseases, and injuries. Here, using a Drosophila injury model, we have identified a highly conserved E3 ubiquitin ligase, Highwire (Hiw), as an important regulator of axonal and synaptic degeneration. Mutations in hiw strongly inhibit Wallerian degeneration in multiple neuron types and developmental stages. This new phenotype is mediated by a new downstream target of Hiw: the NAD+ biosynthetic enzyme nicotinamide mononucleotide adenyltransferase (Nmnat), which acts in parallel to a previously known target of Hiw, the Wallenda dileucine zipper kinase (Wnd/DLK) MAPKKK. Hiw promotes a rapid disappearance of Nmnat protein in the distal stump after injury. An increased level of Nmnat protein in hiw mutants is both required and sufficient to inhibit degeneration. Ectopically expressed mouse Nmnat2 is also subject to regulation by Hiw in distal axons and synapses. These findings implicate an important role for endogenous Nmnat and its regulation, via a conserved mechanism, in the initiation of axonal degeneration. Through independent regulation of Wnd/DLK, whose function is required for proximal axons to regenerate, Hiw plays a central role in coordinating both regenerative and degenerative responses to axonal injury. Axons degenerate after injury and during neurodegenerative diseases, but we are still searching for the cellular mechanism responsible for this degeneration. Here, using a nerve crush injury assay in the fruit fly Drosophila, we have identified a role for a conserved molecule named Highwire (Hiw) in the initiation of axonal degeneration. Hiw is an E3 ubiquitin ligase thought to regulate the levels of specific downstream proteins by targeting their destruction. We show that Hiw promotes axonal degeneration by regulating two independent downstream targets: the Wallenda (Wnd) kinase, and the NAD+ biosynthetic enzyme nicotinamide mononucleotide adenyltransferase (Nmnat). Interestingly, Nmnat has previously been implicated in a protective role in neurons. Our findings indicate that Nmnat protein is down-regulated in axons by Hiw and that this regulation plays a critical role in the degeneration of axons and synapses. The other target, the Wnd kinase, was previously known for its role in promoting new axonal growth after injury. We propose that Hiw coordinates multiple responses to regenerate damaged neuronal circuits after injury: degeneration of the distal axon via Nmnat, and new growth of the proximal axon via Wnd.
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Affiliation(s)
- Xin Xiong
- Department of Molecular Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Yan Hao
- Department of Molecular Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Kan Sun
- Department of Molecular Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Jiaxing Li
- Department of Molecular Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Xia Li
- Neuroscience Center for Excellence, Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States of America
| | - Bibhudatta Mishra
- Department of Molecular Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Pushpanjali Soppina
- Department of Molecular Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Chunlai Wu
- Neuroscience Center for Excellence, Louisiana State University Health Sciences Center, New Orleans, Louisiana, United States of America
| | - Richard I. Hume
- Department of Molecular Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Catherine A. Collins
- Department of Molecular Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan, United States of America
- * E-mail:
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35
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Ma XJ, Xue L. [Regulation of the JNK signaling pathway by dual leucine zipper kinase DLK.]. YI CHUAN = HEREDITAS 2012; 32:785-90. [PMID: 20709675 DOI: 10.3724/sp.j.1005.2010.00785] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The C-Jun NH2-terminal kinase (JNK) belongs to the evolutionarily conserved sub-group of mitogen-activated protein (MAP) kinases family. Many studies have shown that JNK pathway plays physiological roles in cell proliferation, differentiation, migration and apoptosis, and its deregulation has been associated with developmental defects and various human diseases. Dual leucine zipper kinase (DLK) is a member of the mixed-lineage kinases that performs important cellu-lar functions as a MAP triple kinase (MAPKKK) in regulating the JNK signaling pathway. In this paper, we described the DLK protein structures, physiological roles, and their functional interactions with JNK signaling, as well as the molecular mechanisms underlying their involvement in various human diseases.
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Affiliation(s)
- Xian-Jue Ma
- School of Life Science and Technology, Tongji University, Shanghai, China.
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36
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Lee AR, Lamb RR, Chang JH, Erdmann-Gilmore P, Lichti CF, Rohrs HW, Malone JP, Wairkar YP, DiAntonio A, Townsend RR, Culican SM. Identification of potential mediators of retinotopic mapping: a comparative proteomic analysis of optic nerve from WT and Phr1 retinal knockout mice. J Proteome Res 2012; 11:5515-26. [PMID: 22985349 DOI: 10.1021/pr300767a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Retinal ganglion cells (RGCs) transmit visual information topographically from the eye to the brain, creating a map of visual space in retino-recipient nuclei (retinotopy). This process is affected by retinal activity and by activity-independent molecular cues. Phr1, which encodes a presumed E3 ubiquitin ligase (PHR1), is required presynaptically for proper placement of RGC axons in the lateral geniculate nucleus and the superior colliculus, suggesting that increased levels of PHR1 target proteins may be instructive for retinotopic mapping of retinofugal projections. To identify potential target proteins, we conducted a proteomic analysis of optic nerve to identify differentially abundant proteins in the presence or absence of Phr1 in RGCs. 1D gel electrophoresis identified a specific band in controls that was absent in mutants. Targeted proteomic analysis of this band demonstrated the presence of PHR1. Additionally, we conducted an unbiased proteomic analysis that identified 30 proteins as being significantly different between the two genotypes. One of these, heterogeneous nuclear ribonucleoprotein M (hnRNP-M), regulates antero-posterior patterning in invertebrates and can function as a cell surface adhesion receptor in vertebrates. Thus, we have demonstrated that network analysis of quantitative proteomic data is a useful approach for hypothesis generation and for identifying biologically relevant targets in genetically altered biological models.
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Affiliation(s)
- Andrew R Lee
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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37
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A Systematic Phenotypic Screen of F-box Genes Through a Tissue-specific RNAi-based Approach in Drosophila. J Genet Genomics 2012; 39:397-413. [DOI: 10.1016/j.jgg.2012.05.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Revised: 05/25/2012] [Accepted: 05/30/2012] [Indexed: 02/03/2023]
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Han S, Kim S, Bahl S, Li L, Burande CF, Smith N, James M, Beauchamp RL, Bhide P, DiAntonio A, Ramesh V. The E3 ubiquitin ligase protein associated with Myc (Pam) regulates mammalian/mechanistic target of rapamycin complex 1 (mTORC1) signaling in vivo through N- and C-terminal domains. J Biol Chem 2012; 287:30063-72. [PMID: 22798074 DOI: 10.1074/jbc.m112.353987] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Pam and its homologs (the PHR protein family) are large E3 ubiquitin ligases that function to regulate synapse formation and growth in mammals, zebrafish, Drosophila, and Caenorhabditis elegans. Phr1-deficient mouse models (Phr1(Δ8,9) and Phr1(Magellan), with deletions in the N-terminal putative guanine exchange factor region and the C-terminal ubiquitin ligase region, respectively) exhibit axon guidance/outgrowth defects and striking defects of major axon tracts in the CNS. Our earlier studies identified Pam to be associated with tuberous sclerosis complex (TSC) proteins, ubiquitinating TSC2 and regulating mammalian/mechanistic target of rapamycin (mTOR) signaling. Here, we examine the potential involvement of the TSC/mTOR complex 1(mTORC1) signaling pathway in Phr1-deficient mouse models. We observed attenuation of mTORC1 signaling in the brains of both Phr1(Δ8,9) and Phr1(Magellan) mouse models. Our results establish that Pam regulates TSC/mTOR signaling in vitro and in vivo through two distinct domains. To further address whether Pam regulates mTORC1 through two functionally independent domains, we undertook heterozygous mutant crossing between Phr1(Δ8,9) and Phr1(Magellan) mice to generate a compound heterozygous model to determine whether these two domains can complement each other. mTORC1 signaling was not attenuated in the brains of double mutants (Phr1(Δ8,9/Mag)), confirming that Pam displays dual regulation of the mTORC1 pathway through two functional domains. Our results also suggest that although dysregulation of mTORC1 signaling may be responsible for the corpus callosum defects, other neurodevelopmental defects observed with Phr1 deficiency are independent of mTORC1 signaling. The ubiquitin ligase complex containing Pam-Fbxo45 likely targets additional synaptic and axonal proteins, which may explain the overlapping neurodevelopmental defects observed in Phr1 and Fbxo45 deficiency.
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Affiliation(s)
- Sangyeul Han
- Center for Human Genetic Research, Massachusetts General Hospital, Boston, MA 02114, USA
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Abstract
Axons often form synaptic contacts with multiple targets by extending branches along different paths. PHR (Pam/Highwire/RPM-1) family ubiquitin ligases are important regulators of axon development, with roles in axon outgrowth, target selection, and synapse formation. Here we report the function of Highwire, the Drosophila member of the PHR family, in promoting the segregation of sister axons during mushroom body (MB) formation. Loss of highwire results in abnormal development of the axonal lobes in the MB, leading to thinned and shortened lobes. The highwire defect is attributable to guidance errors after axon branching, in which sister axons that should target different lobes instead extend together into the same lobe. The highwire mutant MB displays elevation in the level of the MAPKKK Wallenda/DLK (dual leucine zipper kinase), a previously identified substrate of Highwire, and genetic suppression studies show that Wallenda/DLK is required for the highwire MB phenotype. The highwire lobe defect is limited to α/β lobe axons, but transgenic expression of highwire in the pioneering α'/β' neurons rescues the phenotype. Mosaic analysis further shows that α/β axons of highwire mutant clones develop normally, demonstrating a non-cell-autonomous role of Highwire for axon guidance. Genetic interaction studies suggest that Highwire and Plexin A signals may interact to regulate normal morphogenesis of α/β axons.
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PPM-1, a PP2Cα/β phosphatase, regulates axon termination and synapse formation in Caenorhabditis elegans. Genetics 2011; 189:1297-307. [PMID: 21968191 PMCID: PMC3241410 DOI: 10.1534/genetics.111.134791] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The PHR (Pam/Highwire/RPM-1) proteins are evolutionarily conserved ubiquitin ligases that regulate axon guidance and synapse formation in Caenorhabditis elegans, Drosophila, zebrafish, and mice. In C. elegans, RPM-1 (Regulator of Presynaptic Morphology-1) functions in synapse formation, axon guidance, axon termination, and postsynaptic GLR-1 trafficking. Acting as an E3 ubiquitin ligase, RPM-1 negatively regulates a MAP kinase pathway that includes: dlk-1, mkk-4, and the p38 MAPK, pmk-3. Here we provide evidence that ppm-1, a serine/threonine phosphatase homologous to human PP2Cα(PPM1A) and PP2Cβ(PPM1B) acts as a second negative regulatory mechanism to control the dlk-1 pathway. We show that ppm-1 functions through its phosphatase activity in a parallel genetic pathway with glo-4 and fsn-1 to regulate both synapse formation in the GABAergic motorneurons and axon termination in the mechanosensory neurons. Our transgenic analysis shows that ppm-1 acts downstream of rpm-1 to negatively regulate the DLK-1 pathway, with PPM-1 most likely acting at the level of pmk-3. Our study provides insight into the negative regulatory mechanisms that control the dlk-1 pathway in neurons and demonstrates a new role for the PP2C/PPM phosphatases as regulators of neuronal development.
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Tian X, Li J, Valakh V, DiAntonio A, Wu C. Drosophila Rae1 controls the abundance of the ubiquitin ligase Highwire in post-mitotic neurons. Nat Neurosci 2011; 14:1267-75. [PMID: 21874015 DOI: 10.1038/nn.2922] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Accepted: 07/25/2011] [Indexed: 01/12/2023]
Abstract
The evolutionarily conserved Highwire (Hiw)/Drosophila Fsn E3 ubiquitin ligase complex is required for normal synaptic morphology during development and axonal regeneration after injury. However, little is known about the molecular mechanisms that regulate the Hiw E3 ligase complex. Using tandem affinity purification techniques, we identified Drosophila Rae1 as a previously unknown component of the Hiw/Fsn complex. Loss of Rae1 function in neurons results in morphological defects at the neuromuscular junction that are similar to those seen in hiw mutants. We found that Rae1 physically and genetically interacts with Hiw and restrains synaptic terminal growth by regulating the MAP kinase kinase kinase Wallenda. Moreover, we found that the Rae1 is both necessary and sufficient to promote Hiw protein abundance, and it does so by binding to Hiw and protecting Hiw from autophagy-mediated degradation. These results describe a previously unknown mechanism that selectively controls Hiw protein abundance during synaptic development.
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Affiliation(s)
- Xiaolin Tian
- Neuroscience Center of Excellence, Louisiana State University Health Sciences Center, New Orleans, Louisiana, USA
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Holland S, Coste O, Zhang DD, Pierre SC, Geisslinger G, Scholich K. The ubiquitin ligase MYCBP2 regulates transient receptor potential vanilloid receptor 1 (TRPV1) internalization through inhibition of p38 MAPK signaling. J Biol Chem 2010; 286:3671-80. [PMID: 21098484 DOI: 10.1074/jbc.m110.154765] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The E3 ubiquitin ligase MYCBP2 negatively regulates neuronal growth, synaptogenesis, and synaptic strength. More recently it was shown that MYCBP2 is also involved in receptor and ion channel internalization. We found that mice with a MYCBP2-deficiency in peripheral sensory neurons show prolonged thermal hyperalgesia. Loss of MYCBP2 constitutively activated p38 MAPK and increased expression of several proteins involved in receptor trafficking. Surprisingly, loss of MYCBP2 inhibited internalization of transient receptor potential vanilloid receptor 1 (TRPV1) and prevented desensitization of capsaicin-induced calcium increases. Lack of desensitization, TRPV internalization and prolonged hyperalgesia were reversed by inhibition of p38 MAPK. The effects were TRPV-specific, since neither mustard oil-induced desensitization nor behavioral responses to mechanical stimuli were affected. In summary, we show here for the first time that p38 MAPK activation can inhibit activity-induced ion channel internalization and that MYCBP2 regulates internalization of TRPV1 in peripheral sensory neurons as well as duration of thermal hyperalgesia through p38 MAPK.
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Affiliation(s)
- Sabrina Holland
- Institute of Clinical Pharmacology, Pharmazentrum Frankfurt/ZAFES, Klinikum der Goethe-Universität Frankfurt, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany
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Xiong X, Wang X, Ewanek R, Bhat P, Diantonio A, Collins CA. Protein turnover of the Wallenda/DLK kinase regulates a retrograde response to axonal injury. ACTA ACUST UNITED AC 2010; 191:211-23. [PMID: 20921142 PMCID: PMC2953441 DOI: 10.1083/jcb.201006039] [Citation(s) in RCA: 213] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Regenerative responses to axonal injury involve changes in gene expression; however, little is known about how such changes can be induced from a distant site of injury. In this study, we describe a nerve crush assay in Drosophila melanogaster to study injury signaling and regeneration mechanisms. We find that Wallenda (Wnd), a conserved mitogen-activated protein kinase (MAPK) kinase kinase homologous to dual leucine zipper kinase, functions as an upstream mediator of a cell-autonomous injury signaling cascade that involves the c-Jun NH(2)-terminal kinase MAPK and Fos transcription factor. Wnd is physically transported in axons, and axonal transport is required for the injury signaling mechanism. Wnd is regulated by a conserved E3 ubiquitin ligase, named Highwire (Hiw) in Drosophila. Injury induces a rapid increase in Wnd protein concomitantly with a decrease in Hiw protein. In hiw mutants, injury signaling is constitutively active, and neurons initiate a faster regenerative response. Our data suggest that the regulation of Wnd protein turnover by Hiw can function as a damage surveillance mechanism for responding to axonal injury.
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Affiliation(s)
- Xin Xiong
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
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Long AA, Mahapatra CT, Woodruff EA, Rohrbough J, Leung HT, Shino S, An L, Doerge RW, Metzstein MM, Pak WL, Broadie K. The nonsense-mediated decay pathway maintains synapse architecture and synaptic vesicle cycle efficacy. J Cell Sci 2010; 123:3303-15. [PMID: 20826458 DOI: 10.1242/jcs.069468] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
A systematic Drosophila forward genetic screen for photoreceptor synaptic transmission mutants identified no-on-and-no-off transient C (nonC) based on loss of retinal synaptic responses to light stimulation. The cloned gene encodes phosphatidylinositol-3-kinase-like kinase (PIKK) Smg1, a regulatory kinase of the nonsense-mediated decay (NMD) pathway. The Smg proteins act in an mRNA quality control surveillance mechanism to selectively degrade transcripts containing premature stop codons, thereby preventing the translation of truncated proteins with dominant-negative or deleterious gain-of-function activities. At the neuromuscular junction (NMJ) synapse, an extended allelic series of Smg1 mutants show impaired structural architecture, with decreased terminal arbor size, branching and synaptic bouton number. Functionally, loss of Smg1 results in a ~50% reduction in basal neurotransmission strength, as well as progressive transmission fatigue and greatly impaired synaptic vesicle recycling during high-frequency stimulation. Mutation of other NMD pathways genes (Upf2 and Smg6) similarly impairs neurotransmission and synaptic vesicle cycling. These findings suggest that the NMD pathway acts to regulate proper mRNA translation to safeguard synapse morphology and maintain the efficacy of synaptic function.
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Affiliation(s)
- A Ashleigh Long
- Department of Biological Sciences, Vanderbilt Brain Institute, Kennedy Center for Research on Human Development, Vanderbilt University, Nashville, TN 37235-1634, USA
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Trujillo G, Nakata K, Yan D, Maruyama IN, Jin Y. A ubiquitin E2 variant protein acts in axon termination and synaptogenesis in Caenorhabditis elegans. Genetics 2010; 186:135-45. [PMID: 20592265 PMCID: PMC2940282 DOI: 10.1534/genetics.110.117341] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2010] [Accepted: 06/19/2010] [Indexed: 11/18/2022] Open
Abstract
In the developing nervous system, cohorts of events regulate the precise patterning of axons and formation of synapses between presynaptic neurons and their targets. The conserved PHR proteins play important roles in many aspects of axon and synapse development from C. elegans to mammals. The PHR proteins act as E3 ubiquitin ligases for the dual-leucine-zipper-bearing MAP kinase kinase kinase (DLK MAPKKK) to regulate the signal transduction cascade. In C. elegans, loss-of-function of the PHR protein RPM-1 (Regulator of Presynaptic Morphology-1) results in fewer synapses, disorganized presynaptic architecture, and axon overextension. Inactivation of the DLK-1 pathway suppresses these defects. By characterizing additional genetic suppressors of rpm-1, we present here a new member of the DLK-1 pathway, UEV-3, an E2 ubiquitin-conjugating enzyme variant. We show that uev-3 acts cell autonomously in neurons, despite its ubiquitous expression. Our genetic epistasis analysis supports a conclusion that uev-3 acts downstream of the MAPKK mkk-4 and upstream of the MAPKAPK mak-2. UEV-3 can interact with the p38 MAPK PMK-3. We postulate that UEV-3 may provide additional specificity in the DLK-1 pathway by contributing to activation of PMK-3 or limiting the substrates accessible to PMK-3.
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Affiliation(s)
- Gloriana Trujillo
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, CA 92093 Information Processing Biology Unit, Okinawa Institute of Science and Technology, Onna-Son, Okinawa 904-0412, Japan and Howard Hughes Medical Institute, La Jolla, CA 92093
| | - Katsunori Nakata
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, CA 92093 Information Processing Biology Unit, Okinawa Institute of Science and Technology, Onna-Son, Okinawa 904-0412, Japan and Howard Hughes Medical Institute, La Jolla, CA 92093
| | - Dong Yan
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, CA 92093 Information Processing Biology Unit, Okinawa Institute of Science and Technology, Onna-Son, Okinawa 904-0412, Japan and Howard Hughes Medical Institute, La Jolla, CA 92093
| | - Ichi N. Maruyama
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, CA 92093 Information Processing Biology Unit, Okinawa Institute of Science and Technology, Onna-Son, Okinawa 904-0412, Japan and Howard Hughes Medical Institute, La Jolla, CA 92093
| | - Yishi Jin
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, CA 92093 Information Processing Biology Unit, Okinawa Institute of Science and Technology, Onna-Son, Okinawa 904-0412, Japan and Howard Hughes Medical Institute, La Jolla, CA 92093
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Sampathkumar P, Ozyurt SA, Miller SA, Bain KT, Rutter ME, Gheyi T, Abrams B, Wang Y, Atwell S, Luz JG, Thompson DA, Wasserman SR, Emtage JS, Park EC, Rongo C, Jin Y, Klemke RL, Sauder JM, Burley SK. Structures of PHR domains from Mus musculus Phr1 (Mycbp2) explain the loss-of-function mutation (Gly1092-->Glu) of the C. elegans ortholog RPM-1. J Mol Biol 2010; 397:883-92. [PMID: 20156452 DOI: 10.1016/j.jmb.2010.02.017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2009] [Revised: 02/09/2010] [Accepted: 02/10/2010] [Indexed: 01/16/2023]
Abstract
PHR [PAM (protein associated with Myc)-HIW (Highwire)-RPM-1 (regulator of presynaptic morphology 1)] proteins are conserved, large multi-domain E3 ubiquitin ligases with modular architecture. PHR proteins presynaptically control synaptic growth and axon guidance and postsynaptically regulate endocytosis of glutamate receptors. Dysfunction of neuronal ubiquitin-mediated proteasomal degradation is implicated in various neurodegenerative diseases. PHR proteins are characterized by the presence of two PHR domains near the N-terminus, which are essential for proper localization and function. Structures of both the first and second PHR domains of Mus musculus (mouse) Phr1 (MYC binding protein 2, Mycbp2) have been determined, revealing a novel beta sandwich fold composed of 11 antiparallel beta-strands. Conserved loops decorate the apical side of the first PHR domain (MmPHR1), yielding a distinct conserved surface feature. The surface of the second PHR domain (MmPHR2), in contrast, lacks significant conservation. Importantly, the structure of MmPHR1 provides insights into a loss-of-function mutation, Gly1092-->Glu, observed in the Caenorhabditis elegans ortholog RPM-1.
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Affiliation(s)
- Parthasarathy Sampathkumar
- Eli Lilly and Company, Lilly Biotechnology Center, 10300 Campus Point Drive, Suite 200, San Diego, CA 92121, USA.
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Regulation of Drosophila vasa in vivo through paralogous cullin-RING E3 ligase specificity receptors. Mol Cell Biol 2010; 30:1769-82. [PMID: 20123973 DOI: 10.1128/mcb.01100-09] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Drosophila species, molecular asymmetries guiding embryonic development are established maternally. Vasa, a DEAD-box RNA helicase, accumulates in the posterior pole plasm, where it is required for embryonic germ cell specification. Maintenance of Vasa at the posterior pole requires the deubiquitinating enzyme Fat facets, which protects Vasa from degradation. Here, we found that Gustavus (Gus) and Fsn, two ubiquitin Cullin-RING E3 ligase specificity receptors, bind to the same motif on Vasa through their paralogous B30.2/SPRY domains. Both Gus and Fsn accumulate in the pole plasm in a Vasa-dependent manner. Posterior Vasa accumulation is precocious in Fsn mutant oocytes; Fsn overexpression reduces ovarian Vasa levels, and embryos from Fsn-overexpressing females form fewer primordial germ cells (PGCs); thus, Fsn destabilizes Vasa. In contrast, endogenous Gus may promote Vasa activity in the pole plasm, as gus females produce embryos with fewer PGCs, and posterior accumulation of Vas is delayed in gus mutant oocytes that also lack one copy of cullin-5. We propose that Fsn- and Gus-containing E3 ligase complexes contribute to establishing a fine-tuned steady state of Vasa ubiquitination that influences the kinetics of posterior Vasa deployment.
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Po MD, Hwang C, Zhen M. PHRs: bridging axon guidance, outgrowth and synapse development. Curr Opin Neurobiol 2010; 20:100-7. [PMID: 20079626 DOI: 10.1016/j.conb.2009.12.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2009] [Revised: 12/19/2009] [Accepted: 12/22/2009] [Indexed: 10/20/2022]
Abstract
Axon guidance, outgrowth, and synapse formation are interrelated developmental events during the maturation of the nervous system. Establishing proper synaptic connectivity requires precise axon navigation and a coordinated switch between axon outgrowth and synaptogenesis. The PHR (human Pam, mouse Phr1, zebrafish Esrom, DrosophilaHighwire, and C. elegansRPM-1) protein family regulates both axon and synapse development through their biochemical and functional interactions with multiple signaling pathways. Recent studies have begun to elucidate a common underlying mechanism for PHR functions: Consisting of motifs that affect intracellular signaling, selective protein degradation, and cytoskeleton organization, PHR proteins probably mediate the transition between axon outgrowth and synaptogenesis through integrating intracellular signaling and microtubule remodeling.
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Affiliation(s)
- Michelle D Po
- Department of Molecular Genetics, University of Toronto, Canada; Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Canada
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