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Kvistad CE, Kråkenes T, Gavasso S, Bø L. Neural regeneration in the human central nervous system-from understanding the underlying mechanisms to developing treatments. Where do we stand today? Front Neurol 2024; 15:1398089. [PMID: 38803647 PMCID: PMC11129638 DOI: 10.3389/fneur.2024.1398089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Accepted: 04/22/2024] [Indexed: 05/29/2024] Open
Abstract
Mature neurons in the human central nervous system (CNS) fail to regenerate after injuries. This is a common denominator across different aetiologies, including multiple sclerosis, spinal cord injury and ischemic stroke. The lack of regeneration leads to permanent functional deficits with a substantial impact on patient quality of life, representing a significant socioeconomic burden worldwide. Great efforts have been made to decipher the responsible mechanisms and we now know that potent intra- and extracellular barriers prevent axonal repair. This knowledge has resulted in numerous clinical trials, aiming to promote neuroregeneration through different approaches. Here, we summarize the current understanding of the causes to the poor regeneration within the human CNS. We also review the results of the treatment attempts that have been translated into clinical trials so far.
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Affiliation(s)
| | - Torbjørn Kråkenes
- Neuro-SysMed, Department of Neurology, Haukeland University Hospital, Bergen, Norway
| | - Sonia Gavasso
- Neuro-SysMed, Department of Neurology, Haukeland University Hospital, Bergen, Norway
- Department of Clinical Medicine, University of Bergen, Bergen, Norway
| | - Lars Bø
- Neuro-SysMed, Department of Neurology, Haukeland University Hospital, Bergen, Norway
- Department of Clinical Medicine, University of Bergen, Bergen, Norway
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2
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DeVault L, Mateusiak C, Palucki J, Brent M, Milbrandt J, DiAntonio A. The response of Dual-leucine zipper kinase (DLK) to nocodazole: Evidence for a homeostatic cytoskeletal repair mechanism. PLoS One 2024; 19:e0300539. [PMID: 38574058 PMCID: PMC10994325 DOI: 10.1371/journal.pone.0300539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Accepted: 02/28/2024] [Indexed: 04/06/2024] Open
Abstract
Genetic and pharmacological perturbation of the cytoskeleton enhances the regenerative potential of neurons. This response requires Dual-leucine Zipper Kinase (DLK), a neuronal stress sensor that is a central regulator of axon regeneration and degeneration. The damage and repair aspects of this response are reminiscent of other cellular homeostatic systems, suggesting that a cytoskeletal homeostatic response exists. In this study, we propose a framework for understanding DLK mediated neuronal cytoskeletal homeostasis. We demonstrate that low dose nocodazole treatment activates DLK signaling. Activation of DLK signaling results in a DLK-dependent transcriptional signature, which we identify through RNA-seq. This signature includes genes likely to attenuate DLK signaling while simultaneously inducing actin regulating genes. We identify alterations to the cytoskeleton including actin-based morphological changes to the axon. These results are consistent with the model that cytoskeletal disruption in the neuron induces a DLK-dependent homeostatic mechanism, which we term the Cytoskeletal Stress Response (CSR) pathway.
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Affiliation(s)
- Laura DeVault
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Chase Mateusiak
- Department of Genetics, Washington University School of Medicine, St. Louis, Missouri, United States of America
- Department of Computer Science & Engineering, Washington University, St. Louis, MO, United States of America
| | - John Palucki
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Michael Brent
- Department of Genetics, Washington University School of Medicine, St. Louis, Missouri, United States of America
- Department of Computer Science & Engineering, Washington University, St. Louis, MO, United States of America
| | - Jeffrey Milbrandt
- Department of Genetics, Washington University School of Medicine, St. Louis, Missouri, United States of America
- Needleman Center for Neurometabolism and Axonal Therapeutics, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Aaron DiAntonio
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri, United States of America
- Needleman Center for Neurometabolism and Axonal Therapeutics, Washington University School of Medicine, St. Louis, Missouri, United States of America
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3
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Köster KA, Dethlefs M, Duque Escobar J, Oetjen E. Regulation of the Activity of the Dual Leucine Zipper Kinase by Distinct Mechanisms. Cells 2024; 13:333. [PMID: 38391946 PMCID: PMC10886912 DOI: 10.3390/cells13040333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2023] [Revised: 02/05/2024] [Accepted: 02/07/2024] [Indexed: 02/24/2024] Open
Abstract
The dual leucine zipper kinase (DLK) alias mitogen-activated protein 3 kinase 12 (MAP3K12) has gained much attention in recent years. DLK belongs to the mixed lineage kinases, characterized by homology to serine/threonine and tyrosine kinase, but exerts serine/threonine kinase activity. DLK has been implicated in many diseases, including several neurodegenerative diseases, glaucoma, and diabetes mellitus. As a MAP3K, it is generally assumed that DLK becomes phosphorylated and activated by upstream signals and phosphorylates and activates itself, the downstream serine/threonine MAP2K, and, ultimately, MAPK. In addition, other mechanisms such as protein-protein interactions, proteasomal degradation, dephosphorylation by various phosphatases, palmitoylation, and subcellular localization have been shown to be involved in the regulation of DLK activity or its fine-tuning. In the present review, the diverse mechanisms regulating DLK activity will be summarized to provide better insights into DLK action and, possibly, new targets to modulate DLK function.
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Affiliation(s)
- Kyra-Alexandra Köster
- Department of Clinical Pharmacology and Toxicology, University Medical Centre Hamburg-Eppendorf, 20246 Hamburg, Germany; (K.-A.K.); (M.D.)
- DZHK Standort Hamburg, Kiel, Lübeck, Germany;
| | - Marten Dethlefs
- Department of Clinical Pharmacology and Toxicology, University Medical Centre Hamburg-Eppendorf, 20246 Hamburg, Germany; (K.-A.K.); (M.D.)
- DZHK Standort Hamburg, Kiel, Lübeck, Germany;
| | - Jorge Duque Escobar
- DZHK Standort Hamburg, Kiel, Lübeck, Germany;
- University Center of Cardiovascular Science, Department of Cardiology, University Heart & Vascular Center Hamburg, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Elke Oetjen
- Department of Clinical Pharmacology and Toxicology, University Medical Centre Hamburg-Eppendorf, 20246 Hamburg, Germany; (K.-A.K.); (M.D.)
- DZHK Standort Hamburg, Kiel, Lübeck, Germany;
- Institute of Pharmacy, University of Hamburg, 20146 Hamburg, Germany
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4
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Kim S, Quagraine Y, Singh M, Kim JH. Rab11 suppresses neuronal stress signaling by localizing Dual leucine zipper kinase to axon terminals for protein turnover. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.04.18.537392. [PMID: 37131782 PMCID: PMC10153120 DOI: 10.1101/2023.04.18.537392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Dual Leucine Zipper Kinase (DLK) mediates multiple neuronal stress responses, and its expression levels are constantly suppressed to prevent excessive stress signaling. We found that Wallenda (Wnd), the Drosophila ortholog of DLK, is highly enriched in the axon terminals of Drosophila sensory neurons in vivo and that this subcellular localization is necessary for Highwire-mediated Wnd protein turnover under normal conditions. Our structure-function analysis found that Wnd palmitoylation is essential for its axon terminal localization. Palmitoylation-defective Wnd accumulated in neuronal cell bodies, exhibited dramatically increased protein expression levels, and triggered excessive neuronal stress responses. Defective intracellular transport is implicated in neurodegenerative conditions. Comprehensive dominant-negative Rab protein screening identified Rab11 as an essential factor for Wnd localization in axon terminals. Consequently, Rab11 loss-of-function increased the protein levels of Wnd and induced neuronal stress responses. Inhibiting Wnd activity significantly ameliorated neuronal loss and c-Jun N-terminal kinase signaling triggered by Rab11 loss-of-function. Taken together, these suggest that DLK proteins are constantly transported to axon terminals by Rab11 for protein turnover. Our study demonstrates how subcellular protein localization is coupled to protein turnover for neuronal stress signaling. Highlights Wnd is highly enriched in axon terminals.Wnd protein turnover by Hiw is restricted in the axon terminals.Protein palmitoylation of Wnd and Rab11 activity is essential for Wnd axonal localization. Rab11 mutations and defective Wnd palmitoylation impair Wnd protein turnover leading to increased Wnd protein levels and neuronal loss. Inhibiting Wnd activity mitigates neuronal stress response caused by Rab11 loss-of-function.
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DeVault L, Mateusiak C, Palucki J, Brent M, Milbrandt J, DiAntonio A. The response of Dual-Leucine Zipper Kinase (DLK) to nocodazole: evidence for a homeostatic cytoskeletal repair mechanism. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.06.561227. [PMID: 37873434 PMCID: PMC10592635 DOI: 10.1101/2023.10.06.561227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
Genetic and pharmacological perturbation of the cytoskeleton enhances the regenerative potential of neurons. This response requires Dual-leucine Zipper Kinase (DLK), a neuronal stress sensor that is a central regulator of axon regeneration and degeneration. The damage and repair aspects of this response are reminiscent of other cellular homeostatic systems, suggesting that a cytoskeletal homeostatic response exists. In this study, we propose a framework for understanding DLK mediated neuronal cytoskeletal homeostasis. We demonstrate that a) low dose nocodazole treatment activates DLK signaling and b) DLK signaling mitigates the microtubule damage caused by the cytoskeletal perturbation. We also perform RNA-seq to discover a DLK-dependent transcriptional signature. This signature includes genes likely to attenuate DLK signaling while simultaneously inducing actin regulating genes and promoting actin-based morphological changes to the axon. These results are consistent with the model that cytoskeletal disruption in the neuron induces a DLK-dependent homeostatic mechanism, which we term the Cytoskeletal Stress Response (CSR) pathway.
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6
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Thornburg-Suresh EJC, Richardson JE, Summers DW. The Stathmin-2 membrane-targeting domain is required for axon protection and regulated degradation by DLK signaling. J Biol Chem 2023; 299:104861. [PMID: 37236359 PMCID: PMC10404615 DOI: 10.1016/j.jbc.2023.104861] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 05/16/2023] [Accepted: 05/19/2023] [Indexed: 05/28/2023] Open
Abstract
Axon integrity is essential for functional connectivity in the nervous system. The degeneration of stressed or damaged axons is a common and sometimes initiating event in neurodegenerative disorders. Stathmin-2 (Stmn2) is an axon maintenance factor that is depleted in amyotrophic lateral sclerosis, and replenishment of Stmn2 can restore neurite outgrowth in diseased neurons. However, mechanisms responsible for Stmn2-mediated axon maintenance in injured neurons are not known. We used primary sensory neurons to interrogate the role of Stmn2 in the degeneration of severed axons. We discover that membrane association of Stmn2 is critical for its axon-protective activity. Structure-function studies revealed that axonal enrichment of Stmn2 is driven by palmitoylation as well as tubulin interaction. Using live imaging, we discover that another Stmn, Stmn3, comigrates with Stmn2-containing vesicles. We also demonstrate that Stmn3 undergoes regulated degradation through dual leucine zipper kinase (DLK)-c-Jun N-terminal kinase signaling. The Stmn2 membrane-targeting domain is both necessary and sufficient for localization to a specific vesicle population and confers sensitivity to DLK-dependent degradation. Our findings reveal a broader role for DLK in tuning the local abundance of palmitoylated Stmns in axon segments. Moreover, palmitoylation is a critical component of Stmn-mediated axon protection, and defining the Stmn2-containing vesicle population will provide important clues toward mechanisms of axon maintenance.
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Affiliation(s)
- Emma J C Thornburg-Suresh
- Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, Iowa, USA; Department of Biology, University of Iowa, Iowa City, Iowa, USA
| | | | - Daniel W Summers
- Department of Biology, University of Iowa, Iowa City, Iowa, USA; Iowa Neuroscience Institute, University of Iowa, Iowa City, Iowa, USA.
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Liu X, Zhao Y, Zou W. Molecular mechanisms of neurite regeneration and repair: insights from C. elegans and Drosophila. CELL REGENERATION (LONDON, ENGLAND) 2023; 12:12. [PMID: 37005942 PMCID: PMC10067779 DOI: 10.1186/s13619-022-00155-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 12/01/2022] [Indexed: 04/04/2023]
Abstract
The difficulties of injured and degenerated neurons to regenerate neurites and regain functions are more significant than in other body tissues, making neurodegenerative and related diseases hard to cure. Uncovering the secrets of neural regeneration and how this process may be inhibited after injury will provide insights into novel management and potential treatments for these diseases. Caenorhabditis elegans and Drosophila melanogaster are two of the most widely used and well-established model organisms endowed with advantages in genetic manipulation and live imaging to explore this fundamental question about neural regeneration. Here, we review the classical models and techniques, and the involvement and cooperation of subcellular structures during neurite regeneration using these two organisms. Finally, we list several important open questions that we look forward to inspiring future research.
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Affiliation(s)
- Xiaofan Liu
- The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, China
- Institute of Translational Medicine, Zhejiang University, Hangzhou, China
| | - Yuqing Zhao
- The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, China
- Institute of Translational Medicine, Zhejiang University, Hangzhou, China
- Institute of Zhejiang University and University of Edinburgh, Jiaxing, China
| | - Wei Zou
- The Fourth Affiliated Hospital, Zhejiang University School of Medicine, Yiwu, China.
- Institute of Translational Medicine, Zhejiang University, Hangzhou, China.
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8
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Axonal Regeneration: Underlying Molecular Mechanisms and Potential Therapeutic Targets. Biomedicines 2022; 10:biomedicines10123186. [PMID: 36551942 PMCID: PMC9775075 DOI: 10.3390/biomedicines10123186] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 11/21/2022] [Accepted: 12/01/2022] [Indexed: 12/13/2022] Open
Abstract
Axons in the peripheral nervous system have the ability to repair themselves after damage, whereas axons in the central nervous system are unable to do so. A common and important characteristic of damage to the spinal cord, brain, and peripheral nerves is the disruption of axonal regrowth. Interestingly, intrinsic growth factors play a significant role in the axonal regeneration of injured nerves. Various factors such as proteomic profile, microtubule stability, ribosomal location, and signalling pathways mark a line between the central and peripheral axons' capacity for self-renewal. Unfortunately, glial scar development, myelin-associated inhibitor molecules, lack of neurotrophic factors, and inflammatory reactions are among the factors that restrict axonal regeneration. Molecular pathways such as cAMP, MAPK, JAK/STAT, ATF3/CREB, BMP/SMAD, AKT/mTORC1/p70S6K, PI3K/AKT, GSK-3β/CLASP, BDNF/Trk, Ras/ERK, integrin/FAK, RhoA/ROCK/LIMK, and POSTN/integrin are activated after nerve injury and are considered significant players in axonal regeneration. In addition to the aforementioned pathways, growth factors, microRNAs, and astrocytes are also commendable participants in regeneration. In this review, we discuss the detailed mechanism of each pathway along with key players that can be potentially valuable targets to help achieve quick axonal healing. We also identify the prospective targets that could help close knowledge gaps in the molecular pathways underlying regeneration and shed light on the creation of more powerful strategies to encourage axonal regeneration after nervous system injury.
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9
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Costa AC, Sousa MM. The Role of Spastin in Axon Biology. Front Cell Dev Biol 2022; 10:934522. [PMID: 35865632 PMCID: PMC9294387 DOI: 10.3389/fcell.2022.934522] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Accepted: 06/07/2022] [Indexed: 12/05/2022] Open
Abstract
Neurons are highly polarized cells with elaborate shapes that allow them to perform their function. In neurons, microtubule organization—length, density, and dynamics—are essential for the establishment of polarity, growth, and transport. A mounting body of evidence shows that modulation of the microtubule cytoskeleton by microtubule-associated proteins fine tunes key aspects of neuronal cell biology. In this respect, microtubule severing enzymes—spastin, katanin and fidgetin—a group of microtubule-associated proteins that bind to and generate internal breaks in the microtubule lattice, are emerging as key modulators of the microtubule cytoskeleton in different model systems. In this review, we provide an integrative view on the latest research demonstrating the key role of spastin in neurons, specifically in the context of axonal cell biology. We focus on the function of spastin in the regulation of microtubule organization, and axonal transport, that underlie its importance in the intricate control of axon growth, branching and regeneration.
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Affiliation(s)
- Ana Catarina Costa
- Nerve Regeneration Group, Instituto de Biologia Molecular e Celular (IBMC), Instituto de Investigação e Inovação Em Saúde (i3S), University of Porto, Porto, Portugal
- Graduate Program in Molecular and Cell Biology, Instituto de Ciências Biomédicas Abel Salazar (ICBAS), University of Porto, Porto, Portugal
- *Correspondence: Ana Catarina Costa, ; Monica Mendes Sousa,
| | - Monica Mendes Sousa
- Nerve Regeneration Group, Instituto de Biologia Molecular e Celular (IBMC), Instituto de Investigação e Inovação Em Saúde (i3S), University of Porto, Porto, Portugal
- *Correspondence: Ana Catarina Costa, ; Monica Mendes Sousa,
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10
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Brace EJ, Essuman K, Mao X, Palucki J, Sasaki Y, Milbrandt J, DiAntonio A. Distinct developmental and degenerative functions of SARM1 require NAD+ hydrolase activity. PLoS Genet 2022; 18:e1010246. [PMID: 35737728 PMCID: PMC9223315 DOI: 10.1371/journal.pgen.1010246] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 05/10/2022] [Indexed: 11/25/2022] Open
Abstract
SARM1 is the founding member of the TIR-domain family of NAD+ hydrolases and the central executioner of pathological axon degeneration. SARM1-dependent degeneration requires NAD+ hydrolysis. Prior to the discovery that SARM1 is an enzyme, SARM1 was studied as a TIR-domain adaptor protein with non-degenerative signaling roles in innate immunity and invertebrate neurodevelopment, including at the Drosophila neuromuscular junction (NMJ). Here we explore whether the NADase activity of SARM1 also contributes to developmental signaling. We developed transgenic Drosophila lines that express SARM1 variants with normal, deficient, and enhanced NADase activity and tested their function in NMJ development. We find that NMJ overgrowth scales with the amount of NADase activity, suggesting an instructive role for NAD+ hydrolysis in this developmental signaling pathway. While degenerative and developmental SARM1 signaling share a requirement for NAD+ hydrolysis, we demonstrate that these signals use distinct upstream and downstream mechanisms. These results identify SARM1-dependent NAD+ hydrolysis as a heretofore unappreciated component of developmental signaling. SARM1 now joins sirtuins and Parps as enzymes that regulate signal transduction pathways via mechanisms that involve NAD+ cleavage, greatly expanding the potential scope of SARM1 TIR NADase functions. SARM1 is the central executioner of axon loss, and inhibition of SARM1 is a therapeutic target for many devastating neurodegenerative disorders. SARM1 is the founding member of the TIR-domain family of NAD+ cleaving enzymes, destroying the essential metabolite NAD+ and inducing an energetic crisis in the axon. This was a surprising finding, as previously studied TIR-domain proteins were characterized as scaffolds that bind signaling proteins to coordinate signal transduction cascades. Indeed, before the discovery of the role of SARM1 in axon degeneration, SARM1 was studied as a regulator of intracellular signaling in immunity and neurodevelopment where it was assumed to act as a scaffold. Here we investigate whether the recently described SARM1 enzymatic activity also regulates such signal transduction pathways. Indeed, we show that a developmental signaling pathway scales with the amount of NADase activity, suggesting an instructive role for NAD+ cleavage. While degenerative and developmental SARM1 signaling share a requirement for NAD+ cleavage, they utilize distinct upstream and downstream mechanisms. With these findings, SARM1 now joins sirtuins and Parps as enzymes that regulate signal transduction pathways via mechanisms that involve NAD+ cleavage, greatly expanding the potential scope of SARM1 TIR NADase functions.
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Affiliation(s)
- E J Brace
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Kow Essuman
- Department of Genetics, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Xianrong Mao
- Department of Genetics, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - John Palucki
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Yo Sasaki
- Department of Genetics, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Jeff Milbrandt
- Department of Genetics, Washington University School of Medicine, St. Louis, Missouri, United States of America.,Needleman Center for Neurometabolism and Axonal Therapeutics, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Aaron DiAntonio
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri, United States of America.,Needleman Center for Neurometabolism and Axonal Therapeutics, Washington University School of Medicine, St. Louis, Missouri, United States of America
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11
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Hayne M, DiAntonio A. Protein phosphatase 2A restrains DLK signaling to promote proper Drosophila synaptic development and mammalian cortical neuron survival. Neurobiol Dis 2022; 163:105586. [PMID: 34923110 PMCID: PMC9359336 DOI: 10.1016/j.nbd.2021.105586] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 11/23/2021] [Accepted: 12/15/2021] [Indexed: 02/03/2023] Open
Abstract
Protein phosphatase 2A (PP2A) is a major cellular phosphatase with many protein substrates. As expected for a signaling molecule with many targets, inhibition of PP2A disrupts fundamental aspects of cellular physiology including cell division and survival. In post-mitotic neurons, the microtubule associated protein Tau is a particularly well-studied PP2A substrate as hyperphosphorylation of Tau is a hallmark of Alzheimer's disease. Although many cellular targets are likely altered by loss of PP2A, here we find that activation of a single pathway can explain important aspects of the PP2A loss-of-function phenotype in neurons. We demonstrate that PP2A inhibits activation of the neuronal stress kinase DLK and its Drosophila ortholog Wallenda. In the fly, PP2A inhibition activates a DLK/Wallenda-regulated transcriptional program that induces synaptic terminal overgrowth at the neuromuscular junction. In cultured mammalian neurons, PP2A inhibition activates a DLK-dependent apoptotic program that induces cell death. Since hyperphosphorylated Tau is toxic, we wished to test the hypothesis that dephosphorylation of Tau by PP2A is required for neuronal survival. Contrary to expectations, in the absence of Tau PP2A inhibition still activates DLK and induces neuronal cell death, demonstrating that hyperphosphorylated Tau is not required for cell death in this model. Moreover, hyperphosphorylation of Tau following PP2A inhibition does not require DLK. Hence, loss of PP2A function in cortical neurons triggers two independent neuropathologies: 1) Tau hyperphosphorylation and 2) DLK activation and subsequent neuronal cell death. These findings demonstrate that inhibition of the DLK pathway is an essential function of PP2A required for normal Drosophila synaptic terminal development and mammalian cortical neuron survival.
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Affiliation(s)
- Margaret Hayne
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO 63110
| | - Aaron DiAntonio
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO 63110,Needleman Center for Neurometabolism and Axonal Therapeutics, Washington University School of Medicine, St. Louis, MO 63110
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12
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Bush KM, Barber KR, Martinez JA, Tang SJ, Wairkar YP. Drosophila model of anti-retroviral therapy induced peripheral neuropathy and nociceptive hypersensitivity. Biol Open 2021; 10:bio.054635. [PMID: 33504470 PMCID: PMC7860131 DOI: 10.1242/bio.054635] [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] [Indexed: 01/09/2023] Open
Abstract
The success of antiretroviral therapy (ART) has improved the survival of HIV-infected patients significantly. However, significant numbers of patients on ART whose HIV disease is well controlled show peripheral sensory neuropathy (PSN), suggesting that ART may cause PSN. Although the nucleoside reverse transcriptase inhibitors (NRTIs), one of the vital components of ART, are thought to contribute to PSN, the mechanisms underlying the PSN induced by NRTIs are unclear. In this study, we developed a Drosophila model of NRTI-induced PSN that recapitulates the salient features observed in patients undergoing ART: PSN and nociceptive hypersensitivity. Furthermore, our data demonstrate that pathways known to suppress PSN induced by chemotherapeutic drugs are ineffective in suppressing the PSN or nociception induced by NRTIs. Instead, we found that increased dynamics of a peripheral sensory neuron may possibly underlie NRTI-induced PSN and nociception. Our model provides a solid platform in which to investigate further mechanisms of ART-induced PSN and nociceptive hypersensitivity. This article has an associated First Person interview with the first author of the paper. Summary: Nucleoside reverse transcriptase inhibitors (NRTIs) that are important components of anti-retroviral therapies also cause peripheral sensory neuropathies (PSN). This article investigates ways in which NRTIs may cause PSN and outlines ways to better understand the mechanisms underlying it.
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Affiliation(s)
- Keegan M Bush
- Neuroscience Graduate Program, University of. Texas Medical Branch, Galveston, TX 77555, USA.,Mitchell Center for Neurodegenerative Diseases, Department of Neurology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Kara R Barber
- Neuroscience Graduate Program, University of. Texas Medical Branch, Galveston, TX 77555, USA.,Mitchell Center for Neurodegenerative Diseases, Department of Neurology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Jade A Martinez
- Mitchell Center for Neurodegenerative Diseases, Department of Neurology, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Shao-Jun Tang
- Neuroscience Graduate Program, University of. Texas Medical Branch, Galveston, TX 77555, USA .,Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Yogesh P Wairkar
- Neuroscience Graduate Program, University of. Texas Medical Branch, Galveston, TX 77555, USA .,Mitchell Center for Neurodegenerative Diseases, Department of Neurology, University of Texas Medical Branch, Galveston, TX 77555, USA.,Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX 77555, USA
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13
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Bicker G, Stern M. Structural and Functional Plasticity in the Regenerating Olfactory System of the Migratory Locust. Front Physiol 2020; 11:608661. [PMID: 33424632 PMCID: PMC7793960 DOI: 10.3389/fphys.2020.608661] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 11/12/2020] [Indexed: 12/19/2022] Open
Abstract
Regeneration after injury is accompanied by transient and lasting changes in the neuroarchitecture of the nervous system and, thus, a form of structural plasticity. In this review, we introduce the olfactory pathway of a particular insect as a convenient model to visualize neural regeneration at an anatomical level and study functional recovery at an electrophysiological level. The olfactory pathway of the locust (Locusta migratoria) is characterized by a multiglomerular innervation of the antennal lobe by olfactory receptor neurons. These olfactory afferents were axotomized by crushing the base of the antenna. The resulting degeneration and regeneration in the antennal lobe could be quantified by size measurements, dye labeling, and immunofluorescence staining of cell surface proteins implicated in axonal guidance during development. Within 3 days post lesion, the antennal lobe volume was reduced by 30% and from then onward regained size back to normal by 2 weeks post injury. The majority of regenerating olfactory receptor axons reinnervated the glomeruli of the antennal lobe. A few regenerating axons project erroneously into the mushroom body on a pathway that is normally chosen by second-order projection neurons. Based on intracellular responses of antennal lobe output neurons to odor stimulation, regenerated fibers establish functional synapses again. Following complete absence after nerve crush, responses to odor stimuli return to control level within 10–14 days. On average, regeneration of afferents, and re-established synaptic connections appear faster in younger fifth instar nymphs than in adults. The initial degeneration of olfactory receptor axons has a trans-synaptic effect on a second order brain center, leading to a transient size reduction of the mushroom body calyx. Odor-evoked oscillating field potentials, absent after nerve crush, were restored in the calyx, indicative of regenerative processes in the network architecture. We conclude that axonal regeneration in the locust olfactory system appears to be possible, precise, and fast, opening an avenue for future mechanistic studies. As a perspective of biomedical importance, the current evidence for nitric oxide/cGMP signaling as positive regulator of axon regeneration in connectives of the ventral nerve cord is considered in light of particular regeneration studies in vertebrate central nervous systems.
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Affiliation(s)
- Gerd Bicker
- Division of Cell Biology, Institute of Physiology and Cell Biology, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Michael Stern
- Division of Cell Biology, Institute of Physiology and Cell Biology, University of Veterinary Medicine Hannover, Hannover, Germany
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14
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Mangleburg CG, Wu T, Yalamanchili HK, Guo C, Hsieh YC, Duong DM, Dammer EB, De Jager PL, Seyfried NT, Liu Z, Shulman JM. Integrated analysis of the aging brain transcriptome and proteome in tauopathy. Mol Neurodegener 2020; 15:56. [PMID: 32993812 PMCID: PMC7526226 DOI: 10.1186/s13024-020-00405-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Accepted: 09/18/2020] [Indexed: 01/09/2023] Open
Abstract
Background Tau neurofibrillary tangle pathology characterizes Alzheimer’s disease and other neurodegenerative tauopathies. Brain gene expression profiles can reveal mechanisms; however, few studies have systematically examined both the transcriptome and proteome or differentiated Tau- versus age-dependent changes. Methods Paired, longitudinal RNA-sequencing and mass-spectrometry were performed in a Drosophila model of tauopathy, based on pan-neuronal expression of human wildtype Tau (TauWT) or a mutant form causing frontotemporal dementia (TauR406W). Tau-induced, differentially expressed transcripts and proteins were examined cross-sectionally or using linear regression and adjusting for age. Hierarchical clustering was performed to highlight network perturbations, and we examined overlaps with human brain gene expression profiles in tauopathy. Results TauWT induced 1514 and 213 differentially expressed transcripts and proteins, respectively. TauR406W had a substantially greater impact, causing changes in 5494 transcripts and 697 proteins. There was a ~ 70% overlap between age- and Tau-induced changes and our analyses reveal pervasive bi-directional interactions. Strikingly, 42% of Tau-induced transcripts were discordant in the proteome, showing opposite direction of change. Tau-responsive gene expression networks strongly implicate innate immune activation. Cross-species analyses pinpoint human brain gene perturbations specifically triggered by Tau pathology and/or aging, and further differentiate between disease amplifying and protective changes. Conclusions Our results comprise a powerful, cross-species functional genomics resource for tauopathy, revealing Tau-mediated disruption of gene expression, including dynamic, age-dependent interactions between the brain transcriptome and proteome.
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Affiliation(s)
- Carl Grant Mangleburg
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, 77030, USA.,Medical Scientist Training Program, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Timothy Wu
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, 77030, USA.,Medical Scientist Training Program, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Hari K Yalamanchili
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Caiwei Guo
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Yi-Chen Hsieh
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, 77030, USA
| | - Duc M Duong
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Eric B Dammer
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Philip L De Jager
- Center for Translational & Computational Neuroimmunology, Department of Neurology and Taub Institute for the study of Alzheimer's disease and the aging brain, Columbia University Medical Center, New York, NY, 10032, USA.,Cell Circuits Program, Broad Institute, Cambridge, MA, 02142, USA
| | - Nicholas T Seyfried
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA, 30322, USA.,Department of Neurology, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Zhandong Liu
- Department of Pediatrics, Baylor College of Medicine, Houston, TX, 77030, USA.,Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, 1250 Moursund St., Suite N.1150, Houston, TX, 77030, USA
| | - Joshua M Shulman
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, 77030, USA. .,Department of Neuroscience, Baylor College of Medicine, Houston, TX, 77030, USA. .,Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, 1250 Moursund St., Suite N.1150, Houston, TX, 77030, USA. .,Department of Neurology, Baylor College of Medicine, Houston, TX, 77030, USA.
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15
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Jin Y, Zheng B. Multitasking: Dual Leucine Zipper-Bearing Kinases in Neuronal Development and Stress Management. Annu Rev Cell Dev Biol 2020; 35:501-521. [PMID: 31590586 DOI: 10.1146/annurev-cellbio-100617-062644] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The dual leucine zipper-bearing kinase (DLK) and leucine zipper-bearing kinase (LZK) are evolutionarily conserved MAPKKKs of the mixed-lineage kinase family. Acting upstream of stress-responsive JNK and p38 MAP kinases, DLK and LZK have emerged as central players in neuronal responses to a variety of acute and traumatic injuries. Recent studies also implicate their function in astrocytes, microglia, and other nonneuronal cells, reflecting their expanding roles in the multicellular response to injury and in disease. Of particular note is the potential link of these kinases to neurodegenerative diseases and cancer. It is thus critical to understand the physiological contexts under which these kinases are activated, as well as the signal transduction mechanisms that mediate specific functional outcomes. In this review we first provide a historical overview of the biochemical and functional dissection of these kinases. We then discuss recent findings on regulating their activity to enhance cellular protection following injury and in disease, focusing on but not limited to the nervous system.
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Affiliation(s)
- Yishi Jin
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, California 92093, USA; .,Department of Neurosciences, School of Medicine, University of California, San Diego, La Jolla, California 92093, USA;
| | - Binhai Zheng
- Department of Neurosciences, School of Medicine, University of California, San Diego, La Jolla, California 92093, USA; .,VA San Diego Healthcare System, San Diego, California 92161, USA
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16
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Models of Axon Degeneration in Drosophila Larvae. Methods Mol Biol 2020. [PMID: 32524490 DOI: 10.1007/978-1-0716-0585-1_23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
The fruit fly Drosophila melanogaster has been a powerful model to study axonal biology including axon degeneration and regeneration (Brace et al., J Neurosci 34:8398-8410, 2014; Valakh et al. J Neurosci 33:17863-17,873, 2013; Xiong and Collins J Neurosci 32:610-615, 2012; Xiong et al. 191:211-223, 2010). Both adult and larval injury models have been developed in the fruit fly. This chapter focuses on in vivo and ex vivo methods developed for studying axon degeneration in Drosophila larvae. Additional models have been developed in the adult fly including injury models of olfactory receptor neurons in the brain and a model of axonal degeneration of sensory axons in the wing (Fang and Bonini, Annu Rev. Cell Dev Biol 28:575-597, 2012; Hoopfer et al. Neuron 50:883-895, 2006; Neukomm et al. Proc Natl Acad Sci U S A 111:9965-9970, 2014).
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17
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Abstract
Permanent disabilities following CNS injuries result from the failure of injured axons to regenerate and rebuild functional connections with their original targets. By contrast, injury to peripheral nerves is followed by robust regeneration, which can lead to recovery of sensory and motor functions. This regenerative response requires the induction of widespread transcriptional and epigenetic changes in injured neurons. Considerable progress has been made in recent years in understanding how peripheral axon injury elicits these widespread changes through the coordinated actions of transcription factors, epigenetic modifiers and, to a lesser extent, microRNAs. Although many questions remain about the interplay between these mechanisms, these new findings provide important insights into the pivotal role of coordinated gene expression and chromatin remodelling in the neuronal response to injury.
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Affiliation(s)
- Marcus Mahar
- Department of Neuroscience, Hope Center for Neurological Disorders and Center of Regenerative Medicine, Washington University School of Medicine, St Louis, MO, USA
| | - Valeria Cavalli
- Department of Neuroscience, Hope Center for Neurological Disorders and Center of Regenerative Medicine, Washington University School of Medicine, St Louis, MO, USA.
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18
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Feng C, Thyagarajan P, Shorey M, Seebold DY, Weiner AT, Albertson RM, Rao KS, Sagasti A, Goetschius DJ, Rolls MM. Patronin-mediated minus end growth is required for dendritic microtubule polarity. J Cell Biol 2019; 218:2309-2328. [PMID: 31076454 PMCID: PMC6605808 DOI: 10.1083/jcb.201810155] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Revised: 03/13/2019] [Accepted: 04/23/2019] [Indexed: 02/06/2023] Open
Abstract
Feng et al. describe persistent neuronal microtubule minus end growth that depends on the CAMSAP protein Patronin and is needed for dendritic minus-end-out polarity. Microtubule minus ends are thought to be stable in cells. Surprisingly, in Drosophila and zebrafish neurons, we observed persistent minus end growth, with runs lasting over 10 min. In Drosophila, extended minus end growth depended on Patronin, and Patronin reduction disrupted dendritic minus-end-out polarity. In fly dendrites, microtubule nucleation sites localize at dendrite branch points. Therefore, we hypothesized minus end growth might be particularly important beyond branch points. Distal dendrites have mixed polarity, and reduction of Patronin lowered the number of minus-end-out microtubules. More strikingly, extra Patronin made terminal dendrites almost completely minus-end-out, indicating low Patronin normally limits minus-end-out microtubules. To determine whether minus end growth populated new dendrites with microtubules, we analyzed dendrite development and regeneration. Minus ends extended into growing dendrites in the presence of Patronin. In sum, our data suggest that Patronin facilitates sustained microtubule minus end growth, which is critical for populating dendrites with minus-end-out microtubules.
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Affiliation(s)
- Chengye Feng
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA
| | - Pankajam Thyagarajan
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA
| | - Matthew Shorey
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA
| | - Dylan Y Seebold
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA
| | - Alexis T Weiner
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA
| | - Richard M Albertson
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA
| | - Kavitha S Rao
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA
| | - Alvaro Sagasti
- Molecular, Cell, and Developmental Biology, University of California, Los Angeles, Los Angeles, CA
| | - Daniel J Goetschius
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA
| | - Melissa M Rolls
- Biochemistry and Molecular Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA
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19
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Farley MM, Watkins TA. Intrinsic Neuronal Stress Response Pathways in Injury and Disease. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2019; 13:93-116. [PMID: 29414247 DOI: 10.1146/annurev-pathol-012414-040354] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
From injury to disease to aging, neurons, like all cells, may face various insults that can impact their function and survival. Although the consequences are substantially dictated by the type, context, and severity of insult, distressed neurons are far from passive. Activation of cellular stress responses aids in the preservation or restoration of nervous system function. However, stress responses themselves can further advance neuropathology and contribute significantly to neuronal dysfunction and neurodegeneration. Here we explore the recent advances in defining the cellular stress responses within neurodegenerative diseases and neuronal injury, and we emphasize axonal injury as a well-characterized model of neuronal insult. We highlight key findings and unanswered questions about neuronal stress response pathways, from the initial detection of cellular insults through the underlying mechanisms of the responses to their ultimate impact on the fates of distressed neurons.
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Affiliation(s)
- Madeline M Farley
- Department of Neurosurgery, Baylor College of Medicine, Houston, Texas 77030;
| | - Trent A Watkins
- Department of Neurosurgery, Baylor College of Medicine, Houston, Texas 77030;
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20
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Abstract
How the nervous system is wired has been a central question of neuroscience since the inception of the field, and many of the foundational discoveries and conceptual advances have been made through the study of invertebrate experimental organisms, including Caenorhabditis elegans and Drosophila melanogaster. Although many guidance molecules and receptors have been identified, recent experiments have shed light on the many modes of action for these pathways. Here, we summarize the recent progress in determining how the physical and temporal constraints of the surrounding environment provide instructive regulations in nervous system wiring. We use Netrin and its receptors as an example to analyze the complexity of how they guide neurite outgrowth. In neurite repair, conserved injury detection and response-signaling pathways regulate gene expression and cytoskeletal dynamics. We also describe recent developments in the research on molecular mechanisms of neurite regeneration in worms and flies.
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Affiliation(s)
- Claire E Richardson
- Department of Biology, Stanford University, Stanford, California 94305, USA;
| | - Kang Shen
- Department of Biology, Stanford University, Stanford, California 94305, USA; .,Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA
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21
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HSP90 is a chaperone for DLK and is required for axon injury signaling. Proc Natl Acad Sci U S A 2018; 115:E9899-E9908. [PMID: 30275300 DOI: 10.1073/pnas.1805351115] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Peripheral nerve injury induces a robust proregenerative program that drives axon regeneration. While many regeneration-associated genes are known, the mechanisms by which injury activates them are less well-understood. To identify such mechanisms, we performed a loss-of-function pharmacological screen in cultured adult mouse sensory neurons for proteins required to activate this program. Well-characterized inhibitors were present as injury signaling was induced but were removed before axon outgrowth to identify molecules that block induction of the program. Of 480 compounds, 35 prevented injury-induced neurite regrowth. The top hits were inhibitors to heat shock protein 90 (HSP90), a chaperone with no known role in axon injury. HSP90 inhibition blocks injury-induced activation of the proregenerative transcription factor cJun and several regeneration-associated genes. These phenotypes mimic loss of the proregenerative kinase, dual leucine zipper kinase (DLK), a critical neuronal stress sensor that drives axon degeneration, axon regeneration, and cell death. HSP90 is an atypical chaperone that promotes the stability of signaling molecules. HSP90 and DLK show two hallmarks of HSP90-client relationships: (i) HSP90 binds DLK, and (ii) HSP90 inhibition leads to rapid degradation of existing DLK protein. Moreover, HSP90 is required for DLK stability in vivo, where HSP90 inhibitor reduces DLK protein in the sciatic nerve. This phenomenon is evolutionarily conserved in Drosophila Genetic knockdown of Drosophila HSP90, Hsp83, decreases levels of Drosophila DLK, Wallenda, and blocks Wallenda-dependent synaptic terminal overgrowth and injury signaling. Our findings support the hypothesis that HSP90 chaperones DLK and is required for DLK functions, including proregenerative axon injury signaling.
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22
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Palmitoylation enables MAPK-dependent proteostasis of axon survival factors. Proc Natl Acad Sci U S A 2018; 115:E8746-E8754. [PMID: 30150401 DOI: 10.1073/pnas.1806933115] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Axon degeneration is a prominent event in many neurodegenerative disorders. Axon injury stimulates an intrinsic self-destruction program that culminates in activation of the prodegeneration factor SARM1 and local dismantling of damaged axon segments. In healthy axons, SARM1 activity is restrained by constant delivery of the axon survival factor NMNAT2. Elevating NMNAT2 is neuroprotective, while loss of NMNAT2 evokes SARM1-dependent axon degeneration. As a gatekeeper of axon survival, NMNAT2 abundance is an important regulatory node in neuronal health, highlighting the need to understand the mechanisms behind NMNAT2 protein homeostasis. We demonstrate that pharmacological inhibition of the MAP3Ks dual leucine zipper kinase (DLK) and leucine zipper kinase (LZK) elevates NMNAT2 abundance and strongly protects axons from injury-induced degeneration. We discover that MAPK signaling selectively promotes degradation of palmitoylated NMNAT2, as well as palmitoylated SCG10. Conversely, nonpalmitoylated NMNAT2 is degraded by the Phr1/Skp1a/Fbxo45 ligase complex. Combined inactivation of both pathways leads to synergistic accumulation of NMNAT2 in axons and dramatically enhanced protection against pathological axon degeneration. Hence, the subcellular localization of distinct pools of NMNAT2 enables differential regulation of NMNAT2 abundance to control axon survival.
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23
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Asghari Adib E, Smithson LJ, Collins CA. An axonal stress response pathway: degenerative and regenerative signaling by DLK. Curr Opin Neurobiol 2018; 53:110-119. [PMID: 30053694 DOI: 10.1016/j.conb.2018.07.002] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Accepted: 07/02/2018] [Indexed: 02/08/2023]
Abstract
Signaling through the dual leucine zipper-bearing kinase (DLK) is required for injured neurons to initiate new axonal growth; however, activation of this kinase also leads to neuronal degeneration and death in multiple models of injury and neurodegenerative diseases. This has spurred current consideration of DLK as a candidate therapeutic target, and raises a vital question: in what context is DLK a friend or foe to neurons? Here, we review our current understanding of DLK's function and mechanisms in regulating both regenerative and degenerative responses to axonal damage and stress in the nervous system.
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Affiliation(s)
- Elham Asghari Adib
- Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109-1048, USA
| | - Laura J Smithson
- Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109-1048, USA
| | - Catherine A Collins
- Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109-1048, USA.
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24
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Chen L. Microtubules and axon regeneration in C. elegans. Mol Cell Neurosci 2018; 91:160-166. [PMID: 29551667 DOI: 10.1016/j.mcn.2018.03.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 03/14/2018] [Accepted: 03/15/2018] [Indexed: 11/28/2022] Open
Abstract
Axon regeneration is a fundamental and conserved process that allows the nervous system to repair circuits after trauma. Due to its conserved genome, transparent body, and relatively simple neuroanatomy, C. elegans has become a powerful model organism for studying the cellular and molecular mechanisms underlying axon regeneration. Various studies from different model organisms have found microtubule dynamics to be pivotal to axon regrowth. In this review, we will discuss the latest findings on how microtubule dynamics are regulated during axon regeneration in C. elegans. Understanding the mechanisms of axon regeneration will aid in the development of more effective therapeutic strategies for treatments of diseases involving disconnection of axons, such as spinal cord injury and stroke.
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Affiliation(s)
- Lizhen Chen
- Barshop Institute for Longevity and Aging Studies, Department of Cell Systems and Anatomy, Department of Molecular Medicine, University of Texas Health Science Center San Antonio, San Antonio, TX, USA.
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25
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Unsain N, Bordenave MD, Martinez GF, Jalil S, von Bilderling C, Barabas FM, Masullo LA, Johnstone AD, Barker PA, Bisbal M, Stefani FD, Cáceres AO. Remodeling of the Actin/Spectrin Membrane-associated Periodic Skeleton, Growth Cone Collapse and F-Actin Decrease during Axonal Degeneration. Sci Rep 2018; 8:3007. [PMID: 29445221 PMCID: PMC5812996 DOI: 10.1038/s41598-018-21232-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Accepted: 01/26/2018] [Indexed: 11/09/2022] Open
Abstract
Axonal degeneration occurs in the developing nervous system for the appropriate establishment of mature circuits, and is also a hallmark of diverse neurodegenerative diseases. Despite recent interest in the field, little is known about the changes (and possible role) of the cytoskeleton during axonal degeneration. We studied the actin cytoskeleton in an in vitro model of developmental pruning induced by trophic factor withdrawal (TFW). We found that F-actin decrease and growth cone collapse (GCC) occur early after TFW; however, treatments that prevent axonal fragmentation failed to prevent GCC, suggesting independent pathways. Using super-resolution (STED) microscopy we found that the axonal actin/spectrin membrane-associated periodic skeleton (MPS) abundance and organization drop shortly after deprivation, remaining low until fragmentation. Fragmented axons lack MPS (while maintaining microtubules) and acute pharmacological treatments that stabilize actin filaments prevent MPS loss and protect from axonal fragmentation, suggesting that MPS destruction is required for axon fragmentation to proceed.
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Affiliation(s)
- Nicolas Unsain
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), UNC, Friuli, 2434 - 5016, Córdoba, Argentina. .,Universidad Nacional de Córdoba, Córdoba, Argentina.
| | - Martin D Bordenave
- Centro de Investigaciones en Bionanociencias (CIBION)-CONICET, Buenos Aires, Argentina
| | - Gaby F Martinez
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), UNC, Friuli, 2434 - 5016, Córdoba, Argentina.,Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Sami Jalil
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), UNC, Friuli, 2434 - 5016, Córdoba, Argentina.,Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Catalina von Bilderling
- Centro de Investigaciones en Bionanociencias (CIBION)-CONICET, Buenos Aires, Argentina.,Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Federico M Barabas
- Centro de Investigaciones en Bionanociencias (CIBION)-CONICET, Buenos Aires, Argentina.,Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Luciano A Masullo
- Centro de Investigaciones en Bionanociencias (CIBION)-CONICET, Buenos Aires, Argentina.,Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Aaron D Johnstone
- Montreal Neurological Institute, McGill University, Montreal, Canada
| | - Philip A Barker
- Department of Biology, University of British Columbia, Kelowna, BC, Canada
| | - Mariano Bisbal
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), UNC, Friuli, 2434 - 5016, Córdoba, Argentina.,Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Fernando D Stefani
- Centro de Investigaciones en Bionanociencias (CIBION)-CONICET, Buenos Aires, Argentina.,Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Alfredo O Cáceres
- Instituto de Investigación Médica Mercedes y Martín Ferreyra, INIMEC-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), UNC, Friuli, 2434 - 5016, Córdoba, Argentina. .,Universidad Nacional de Córdoba, Córdoba, Argentina. .,Instituto Universitario Ciencias Biomédicas de Córdoba (IUCBC), Córdoba, Argentina.
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26
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Larhammar M, Huntwork-Rodriguez S, Rudhard Y, Sengupta-Ghosh A, Lewcock JW. The Ste20 Family Kinases MAP4K4, MINK1, and TNIK Converge to Regulate Stress-Induced JNK Signaling in Neurons. J Neurosci 2017; 37:11074-11084. [PMID: 28993483 PMCID: PMC6596808 DOI: 10.1523/jneurosci.0905-17.2017] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Revised: 09/13/2017] [Accepted: 10/02/2017] [Indexed: 11/21/2022] Open
Abstract
The c-Jun-N-terminal kinase (JNK) signaling pathway regulates nervous system development, axon regeneration, and neuronal degeneration after acute injury or in chronic neurodegenerative disease. Dual leucine zipper kinase (DLK) is required for stress-induced JNK signaling in neurons, yet the factors that initiate DLK/JNK pathway activity remain poorly defined. In the present study, we identify the Ste20 kinases MAP4K4, misshapen-like kinase 1 (MINK1 or MAP4K6) and TNIK Traf2- and Nck-interacting kinase (TNIK or MAP4K7), as upstream regulators of DLK/JNK signaling in neurons. Using a trophic factor withdrawal-based model of neurodegeneration in both male and female embryonic mouse dorsal root ganglion neurons, we show that MAP4K4, MINK1, and TNIK act redundantly to regulate DLK activation and downstream JNK-dependent phosphorylation of c-Jun in response to stress. Targeting MAP4K4, MINK1, and TNIK, but not any of these kinases individually, is sufficient to protect neurons potently from degeneration. Pharmacological inhibition of MAP4Ks blocks stabilization and phosphorylation of DLK within axons and subsequent retrograde translocation of the JNK signaling complex to the nucleus. These results position MAP4Ks as important regulators of the DLK/JNK signaling pathway.SIGNIFICANCE STATEMENT Neuronal degeneration occurs in disparate circumstances: during development to refine neuronal connections, after injury to clear damaged neurons, or pathologically during disease. The dual leucine zipper kinase (DLK)/c-Jun-N-terminal kinase (JNK) pathway represents a conserved regulator of neuronal injury signaling that drives both neurodegeneration and axon regeneration, yet little is known about the factors that initiate DLK activity. Here, we uncover a novel role for a subfamily of MAP4 kinases consisting of MAP4K4, Traf2- and Nck-interacting kinase (TNIK or MAP4K7), and misshapen-like kinase 1 (MINK1 or MAP4K6) in regulating DLK/JNK signaling in neurons. Inhibition of these MAP4Ks blocks stress-induced retrograde JNK signaling and protects from neurodegeneration, suggesting that these kinases may represent attractive therapeutic targets.
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Affiliation(s)
- Martin Larhammar
- Department of Neuroscience, Genentech, Inc., San Francisco, California 94080
- Denali Therapeutics Inc., South San Francisco, California 94080
| | - Sarah Huntwork-Rodriguez
- Department of Neuroscience, Genentech, Inc., San Francisco, California 94080
- Denali Therapeutics Inc., South San Francisco, California 94080
| | - York Rudhard
- In Vitro Pharmacology, Evotec AG, Manfred Eigen Campus, 22419 Hamburg, Germany, and
| | | | - Joseph W Lewcock
- Department of Neuroscience, Genentech, Inc., San Francisco, California 94080,
- Denali Therapeutics Inc., South San Francisco, California 94080
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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:e24271. [PMID: 28925357 PMCID: PMC5605197 DOI: 10.7554/elife.24271] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [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 BiologyUniversity of MichiganAnn ArborUnited States
| | - Yao V Zhang
- Junior Research Group Synaptic PlasticityHertie-Institute for Clinical Brain Research, University of TübingenTübingenGermany
- Graduate School of Cellular and Molecular NeuroscienceUniversity of TübingenTübingenGermany
| | - Elham Asghari Adib
- Department of Molecular, Cellular, and Developmental BiologyUniversity of MichiganAnn ArborUnited States
| | - Doychin T Stanchev
- Junior Research Group Synaptic PlasticityHertie-Institute for Clinical Brain Research, University of TübingenTübingenGermany
- Graduate School of Cellular and Molecular NeuroscienceUniversity of TübingenTübingenGermany
| | - Xin Xiong
- Department of Molecular, Cellular, and Developmental BiologyUniversity of MichiganAnn ArborUnited States
| | - Susan Klinedinst
- Department of Molecular, Cellular, and Developmental BiologyUniversity of MichiganAnn ArborUnited States
| | - Pushpanjali Soppina
- Department of Molecular, Cellular, and Developmental BiologyUniversity of MichiganAnn ArborUnited States
| | - Thomas Robert Jahn
- CHS Research Group Proteostasis in Neurodegenerative DiseaseDKFZ Deutsches KrebsforschungszentrumHeidelbergGermany
| | - Richard I Hume
- Department of Molecular, Cellular, and Developmental BiologyUniversity of MichiganAnn ArborUnited States
| | - Tobias M Rasse
- Junior Research Group Synaptic PlasticityHertie-Institute for Clinical Brain Research, University of TübingenTübingenGermany
- CHS Research Group Proteostasis in Neurodegenerative DiseaseDKFZ Deutsches KrebsforschungszentrumHeidelbergGermany
| | - Catherine A Collins
- Department of Molecular, Cellular, and Developmental BiologyUniversity of MichiganAnn ArborUnited States
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28
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Voelzmann A, Liew YT, Qu Y, Hahn I, Melero C, Sánchez-Soriano N, Prokop A. Drosophila Short stop as a paradigm for the role and regulation of spectraplakins. Semin Cell Dev Biol 2017; 69:40-57. [DOI: 10.1016/j.semcdb.2017.05.019] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 05/22/2017] [Accepted: 05/29/2017] [Indexed: 02/07/2023]
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29
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Zhang J, Yue J, Wu X. Spectraplakin family proteins - cytoskeletal crosslinkers with versatile roles. J Cell Sci 2017; 130:2447-2457. [PMID: 28679697 PMCID: PMC5558266 DOI: 10.1242/jcs.196154] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The different cytoskeletal networks in a cell are responsible for many fundamental cellular processes. Current studies have shown that spectraplakins, cytoskeletal crosslinkers that combine features of both the spectrin and plakin families of crosslinkers, have a critical role in integrating these different cytoskeletal networks. Spectraplakin genes give rise to a variety of isoforms that have distinct functions. Importantly, all spectraplakin isoforms are uniquely able to associate with all three elements of the cytoskeleton, namely, F-actin, microtubules and intermediate filaments. In this Review, we will highlight recent studies that have unraveled their function in a wide range of different processes, from regulating cell adhesion in skin keratinocytes to neuronal cell migration. Taken together, this work has revealed a diverse and indispensable role for orchestrating the function of different cytoskeletal elements in vivo.
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Affiliation(s)
- Jamie Zhang
- Ben May Department for Cancer Research, University of Chicago, Chicago, IL 60637, USA
| | - Jiping Yue
- Ben May Department for Cancer Research, University of Chicago, Chicago, IL 60637, USA
| | - Xiaoyang Wu
- Ben May Department for Cancer Research, University of Chicago, Chicago, IL 60637, USA
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30
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Welsbie DS, Mitchell KL, Jaskula-Ranga V, Sluch VM, Yang Z, Kim J, Buehler E, Patel A, Martin SE, Zhang PW, Ge Y, Duan Y, Fuller J, Kim BJ, Hamed E, Chamling X, Lei L, Fraser IDC, Ronai ZA, Berlinicke CA, Zack DJ. Enhanced Functional Genomic Screening Identifies Novel Mediators of Dual Leucine Zipper Kinase-Dependent Injury Signaling in Neurons. Neuron 2017. [PMID: 28641113 DOI: 10.1016/j.neuron.2017.06.008] [Citation(s) in RCA: 100] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Dual leucine zipper kinase (DLK) has been implicated in cell death signaling secondary to axonal damage in retinal ganglion cells (RGCs) and other neurons. To better understand the pathway through which DLK acts, we developed enhanced functional genomic screens in primary RGCs, including use of arrayed, whole-genome, small interfering RNA libraries. Explaining why DLK inhibition is only partially protective, we identify leucine zipper kinase (LZK) as cooperating with DLK to activate downstream signaling and cell death in RGCs, including in a mouse model of optic nerve injury, and show that the same pathway is active in human stem cell-derived RGCs. Moreover, we identify four transcription factors, JUN, activating transcription factor 2 (ATF2), myocyte-specific enhancer factor 2A (MEF2A), and SRY-Box 11 (SOX11), as being the major downstream mediators through which DLK/LZK activation leads to RGC cell death. Increased understanding of the DLK pathway has implications for understanding and treating neurodegenerative diseases.
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Affiliation(s)
- Derek S Welsbie
- Department of Ophthalmology, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA; Shiley Eye Institute, University of California, San Diego, La Jolla, CA 92093, USA.
| | - Katherine L Mitchell
- Department of Ophthalmology, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Vinod Jaskula-Ranga
- Department of Ophthalmology, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Valentin M Sluch
- Department of Ophthalmology, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Zhiyong Yang
- Department of Ophthalmology, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA; Shiley Eye Institute, University of California, San Diego, La Jolla, CA 92093, USA
| | - Jessica Kim
- Department of Ophthalmology, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Eugen Buehler
- National Center for Advancing Translational Sciences, NIH, Bethesda, MD 20892, USA
| | - Amit Patel
- Department of Ophthalmology, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA; Shiley Eye Institute, University of California, San Diego, La Jolla, CA 92093, USA
| | - Scott E Martin
- National Center for Advancing Translational Sciences, NIH, Bethesda, MD 20892, USA
| | - Ping-Wu Zhang
- Department of Ophthalmology, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Yan Ge
- Department of Ophthalmology, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Yukan Duan
- Department of Ophthalmology, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - John Fuller
- Department of Ophthalmology, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Byung-Jin Kim
- Department of Ophthalmology, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Eman Hamed
- Department of Ophthalmology, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Xitiz Chamling
- Department of Ophthalmology, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Lei Lei
- Department of Biology, University of New England, Biddeford, ME 04005, USA
| | - Iain D C Fraser
- Signaling Systems Unit, Laboratory of Systems Biology, National Institute for Allergy and Infectious Diseases, NIH, Bethesda, MD 20892, USA
| | - Ze'ev A Ronai
- Signal Transduction Program, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037, USA
| | - Cynthia A Berlinicke
- Department of Ophthalmology, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
| | - Donald J Zack
- Department of Ophthalmology, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA; Solomon H. Snyder Department of Neuroscience, Department of Molecular Biology and Genetics, Institute of Genetic Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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31
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Hao Y, Collins C. Intrinsic mechanisms for axon regeneration: insights from injured axons in Drosophila. Curr Opin Genet Dev 2017; 44:84-91. [PMID: 28232273 PMCID: PMC5447494 DOI: 10.1016/j.gde.2017.01.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Revised: 01/17/2017] [Accepted: 01/26/2017] [Indexed: 12/18/2022]
Abstract
Axonal damage and loss are common and negative consequences of neuronal injuries, and also occur in some neurodegenerative diseases. For neurons to have a chance to repair their connections, they need to survive the damage, initiate new axonal growth, and ultimately establish new synaptic connections. This review discusses how recent work in Drosophila models have informed our understanding of the cellular pathways used by neurons to respond to axonal injuries. Similarly to mammalian neurons, Drosophila neurons appear to be more limited in their capacity regrow (regenerate) damaged axons in the central nervous system, but can undergo axonal regeneration to varying extents in the peripheral nervous system. Conserved cellular pathways are activated by axonal injury via mechanisms that are specific to axons but not dendrites, and new unanticipated inhibitors of axon regeneration can be identified via genetic screening. These findings, made predominantly via genetic and live imaging methods in Drosophila, emphasize the utility of this model organism for the identification and study of basic cellular mechanisms used for neuronal repair.
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Affiliation(s)
- Yan Hao
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109-1048, USA
| | - Catherine Collins
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109-1048, USA.
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32
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Börchers S, Babaei R, Klimpel C, Duque Escobar J, Schröder S, Blume R, Malik MNH, Oetjen E. TNFα-induced DLK activation contributes to apoptosis in the beta-cell line HIT. Naunyn Schmiedebergs Arch Pharmacol 2017; 390:813-825. [DOI: 10.1007/s00210-017-1385-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Accepted: 05/17/2017] [Indexed: 12/20/2022]
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33
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Hisamoto N, Matsumoto K. Signal transduction cascades in axon regeneration: insights from C. elegans. Curr Opin Genet Dev 2017; 44:54-60. [PMID: 28213159 DOI: 10.1016/j.gde.2017.01.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 01/13/2017] [Accepted: 01/26/2017] [Indexed: 02/07/2023]
Abstract
Axon regeneration after nerve injury is a conserved biological process in many animals, including humans. The nematode Caenorhabditis elegans (C. elegans) has recently emerged as a genetically tractable model for studying regenerative responses in neurons. Extensive studies over several years using this organism have revealed a number of intrinsic and extrinsic signal transduction cascades that regulate axon regeneration, and these are found to be conserved from worms to humans. Further studies have demonstrated that these cascades consist of several signaling networks that ultimately merge into the c-Jun N-terminal kinase (JNK) cascade. In this review, we describe some recent insights into the signaling cascades controlling axon regeneration in C. elegans and describe their conserved roles in other organisms including mammals.
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Affiliation(s)
- Naoki Hisamoto
- Department of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan.
| | - Kunihiro Matsumoto
- Department of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan.
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34
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Brace EJ, DiAntonio A. Models of axon regeneration in Drosophila. Exp Neurol 2017; 287:310-317. [PMID: 26996133 PMCID: PMC5026866 DOI: 10.1016/j.expneurol.2016.03.014] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Revised: 03/11/2016] [Accepted: 03/14/2016] [Indexed: 12/14/2022]
Abstract
Maintaining neuronal connectivity in the face of injury and disease is a major challenge for the nervous system. The great length of axons makes them particularly vulnerable to insult with dire consequences for neuronal function. In the peripheral nervous system there is a program of axonal regeneration that can reestablish connectivity. In the mammalian central nervous system, however, injured axons have little or no capacity to regenerate. The molecular mechanisms that promote axon regeneration have begun to be identified and many of the implicated pathways are evolutionarily conserved. Here we discuss Drosophila models of axonal regrowth, describe insights derived from these studies, and highlight future directions in the use of the fly for dissecting the mechanisms of axonal regeneration.
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Affiliation(s)
- E J Brace
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, USA, 63110
| | - Aaron DiAntonio
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, USA, 63110.
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35
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Qu Y, Hahn I, Webb SED, Pearce SP, Prokop A. Periodic actin structures in neuronal axons are required to maintain microtubules. Mol Biol Cell 2016; 28:296-308. [PMID: 27881663 PMCID: PMC5231898 DOI: 10.1091/mbc.e16-10-0727] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Revised: 11/09/2016] [Accepted: 11/15/2016] [Indexed: 12/31/2022] Open
Abstract
Drosophila genetics is combined with high-resolution microscopy and a number of functional readouts to demonstrate key factors required for the presence of regularly spaced rings of cortical actin in axons. The data suggest important roles for the actin rings in microtubule regulation, most likely by sustaining their polymerization. Axons are cable-like neuronal processes wiring the nervous system. They contain parallel bundles of microtubules as structural backbones, surrounded by regularly spaced actin rings termed the periodic membrane skeleton (PMS). Despite being an evolutionarily conserved, ubiquitous, highly ordered feature of axons, the function of PMS is unknown. Here we studied PMS abundance, organization, and function, combining versatile Drosophila genetics with superresolution microscopy and various functional readouts. Analyses with 11 actin regulators and three actin-targeting drugs suggest that PMS contains short actin filaments that are depolymerization resistant and sensitive to spectrin, adducin, and nucleator deficiency, consistent with microscopy-derived models proposing PMS as specialized cortical actin. Upon actin removal, we observed gaps in microtubule bundles, reduced microtubule polymerization, and reduced axon numbers, suggesting a role of PMS in microtubule organization. These effects become strongly enhanced when carried out in neurons lacking the microtubule-stabilizing protein Short stop (Shot). Combining the aforementioned actin manipulations with Shot deficiency revealed a close correlation between PMS abundance and microtubule regulation, consistent with a model in which PMS-dependent microtubule polymerization contributes to their maintenance in axons. We discuss potential implications of this novel PMS function along axon shafts for axon maintenance and regeneration.
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Affiliation(s)
- Yue Qu
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Ines Hahn
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Stephen E D Webb
- Rutherford Appleton Laboratory, Science and Technology Facilities Council, Didcot OX11 0QX, United Kingdom
| | - Simon P Pearce
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom.,School of Mathematics, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Andreas Prokop
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, United Kingdom
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36
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McLaughlin CN, Nechipurenko IV, Liu N, Broihier HT. A Toll receptor-FoxO pathway represses Pavarotti/MKLP1 to promote microtubule dynamics in motoneurons. J Cell Biol 2016; 214:459-74. [PMID: 27502486 PMCID: PMC4987293 DOI: 10.1083/jcb.201601014] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 07/07/2016] [Indexed: 02/06/2023] Open
Abstract
McLaughlin et al. uncover a motoneuronal Toll-6–directed pathway that functions via dSARM and FoxO to attenuate microtubule stability through repression of Pavarotti/MKLP1 transcription. Genetic and pharmacological strategies reveal a novel requirement for dynamic synaptic microtubules in structural plasticity, which are established by Toll-6–FoxO signaling. FoxO proteins are evolutionarily conserved regulators of neuronal structure and function, yet the neuron-specific pathways within which they act are poorly understood. To elucidate neuronal FoxO function in Drosophila melanogaster, we first screened for FoxO’s upstream regulators and downstream effectors. On the upstream side, we present genetic and molecular pathway analyses indicating that the Toll-6 receptor, the Toll/interleukin-1 receptor domain adaptor dSARM, and FoxO function in a linear pathway. On the downstream side, we find that Toll-6–FoxO signaling represses the mitotic kinesin Pavarotti/MKLP1 (Pav-KLP), which itself attenuates microtubule (MT) dynamics. We next probed in vivo functions for this novel pathway and found that it is essential for axon transport and structural plasticity in motoneurons. We demonstrate that elevated expression of Pav-KLP underlies transport and plasticity phenotypes in pathway mutants, indicating that Toll-6–FoxO signaling promotes MT dynamics by limiting Pav-KLP expression. In addition to uncovering a novel molecular pathway, our work reveals an unexpected function for dynamic MTs in enabling rapid activity-dependent structural plasticity.
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Affiliation(s)
- Colleen N McLaughlin
- Department of Neurosciences, Case Western Reserve University, Cleveland, OH 44106
| | - Inna V Nechipurenko
- Department of Neurosciences, Case Western Reserve University, Cleveland, OH 44106
| | - Nan Liu
- Department of Neurosciences, Case Western Reserve University, Cleveland, OH 44106
| | - Heather T Broihier
- Department of Neurosciences, Case Western Reserve University, Cleveland, OH 44106
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37
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Voelzmann A, Okenve-Ramos P, Qu Y, Chojnowska-Monga M, del Caño-Espinel M, Prokop A, Sanchez-Soriano N. Tau and spectraplakins promote synapse formation and maintenance through Jun kinase and neuronal trafficking. eLife 2016; 5:e14694. [PMID: 27501441 PMCID: PMC4977155 DOI: 10.7554/elife.14694] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Accepted: 07/12/2016] [Indexed: 11/13/2022] Open
Abstract
The mechanisms regulating synapse numbers during development and ageing are essential for normal brain function and closely linked to brain disorders including dementias. Using Drosophila, we demonstrate roles of the microtubule-associated protein Tau in regulating synapse numbers, thus unravelling an important cellular requirement of normal Tau. In this context, we find that Tau displays a strong functional overlap with microtubule-binding spectraplakins, establishing new links between two different neurodegenerative factors. Tau and the spectraplakin Short Stop act upstream of a three-step regulatory cascade ensuring adequate delivery of synaptic proteins. This cascade involves microtubule stability as the initial trigger, JNK signalling as the central mediator, and kinesin-3 mediated axonal transport as the key effector. This cascade acts during development (synapse formation) and ageing (synapse maintenance) alike. Therefore, our findings suggest novel explanations for intellectual disability in Tau deficient individuals, as well as early synapse loss in dementias including Alzheimer's disease.
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Affiliation(s)
- Andre Voelzmann
- Faculty of Life Sciences, The University of Manchester, Manchester, United Kingdom
| | - Pilar Okenve-Ramos
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Yue Qu
- Faculty of Life Sciences, The University of Manchester, Manchester, United Kingdom
| | - Monika Chojnowska-Monga
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Manuela del Caño-Espinel
- Instituto de Biología y Genética Molecular-Departamento de Bioquímica y Biología Molecular y Fisiología, Universidad de Valladolid-CSIC, Valladolid, Spain
| | - Andreas Prokop
- Faculty of Life Sciences, The University of Manchester, Manchester, United Kingdom
| | - Natalia Sanchez-Soriano
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
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38
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He Z, Jin Y. Intrinsic Control of Axon Regeneration. Neuron 2016; 90:437-51. [DOI: 10.1016/j.neuron.2016.04.022] [Citation(s) in RCA: 337] [Impact Index Per Article: 42.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Revised: 03/10/2016] [Accepted: 04/13/2016] [Indexed: 01/12/2023]
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39
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Abstract
The capacity of an axon to regenerate is regulated by its external environment and by cell-intrinsic factors. Studies in a variety of organisms suggest that alterations in axonal microtubule (MT) dynamics have potent effects on axon regeneration. We review recent findings on the regulation of MT dynamics during axon regeneration, focusing on the nematode Caenorhabditis elegans. In C. elegans the dual leucine zipper kinase (DLK) promotes axon regeneration, whereas the exchange factor for Arf6 (EFA-6) inhibits axon regeneration. Both DLK and EFA-6 respond to injury and control axon regeneration in part via MT dynamics. How the DLK and EFA-6 pathways are related is a topic of active investigation, as is the mechanism by which EFA-6 responds to axonal injury. We evaluate potential candidates, such as the MT affinity-regulating kinase PAR-1/MARK, in regulation of EFA-6 and axonal MT dynamics in regeneration.
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Affiliation(s)
- Ngang Heok Tang
- Section of Neurobiology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Andrew D Chisholm
- Section of Neurobiology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA, 92093, USA
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40
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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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Gerdts J, Summers DW, Milbrandt J, DiAntonio A. Axon Self-Destruction: New Links among SARM1, MAPKs, and NAD+ Metabolism. Neuron 2016; 89:449-60. [PMID: 26844829 PMCID: PMC4742785 DOI: 10.1016/j.neuron.2015.12.023] [Citation(s) in RCA: 245] [Impact Index Per Article: 30.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Wallerian axon degeneration is a form of programmed subcellular death that promotes axon breakdown in disease and injury. Active degeneration requires SARM1 and MAP kinases, including DLK, while the NAD+ synthetic enzyme NMNAT2 prevents degeneration. New studies reveal that these pathways cooperate in a locally mediated axon destruction program, with NAD+ metabolism playing a central role. Here, we review the biology of Wallerian-type axon degeneration and discuss the most recent findings, with special emphasis on critical signaling events and their potential as therapeutic targets for axonopathy.
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Affiliation(s)
- Josiah Gerdts
- Department of Genetics, Washington University School of Medicine in St. Louis, 660 Euclid Avenue, St. Louis, MO 63110, USA
| | - Daniel W Summers
- Department of Genetics, Washington University School of Medicine in St. Louis, 660 Euclid Avenue, St. Louis, MO 63110, USA; Department of Developmental Biology, Washington University School of Medicine in St. Louis, 660 Euclid Avenue, St. Louis, MO 63110, USA
| | - Jeffrey Milbrandt
- Department of Genetics, Washington University School of Medicine in St. Louis, 660 Euclid Avenue, St. Louis, MO 63110, USA; Hope Center for Neurological Disorders, Washington University School of Medicine in St. Louis, 660 Euclid Avenue, St. Louis, MO 63110, USA
| | - Aaron DiAntonio
- Department of Developmental Biology, Washington University School of Medicine in St. Louis, 660 Euclid Avenue, St. Louis, MO 63110, USA; Hope Center for Neurological Disorders, Washington University School of Medicine in St. Louis, 660 Euclid Avenue, St. Louis, MO 63110, USA.
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Li C, Hisamoto N, Matsumoto K. Axon Regeneration Is Regulated by Ets-C/EBP Transcription Complexes Generated by Activation of the cAMP/Ca2+ Signaling Pathways. PLoS Genet 2015; 11:e1005603. [PMID: 26484536 PMCID: PMC4618690 DOI: 10.1371/journal.pgen.1005603] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2015] [Accepted: 09/23/2015] [Indexed: 11/19/2022] Open
Abstract
The ability of specific neurons to regenerate their axons after injury is governed by cell-intrinsic regeneration pathways. In Caenorhabditis elegans, the JNK and p38 MAPK pathways are important for axon regeneration. Axonal injury induces expression of the svh-2 gene encoding a receptor tyrosine kinase, stimulation of which by the SVH-1 growth factor leads to activation of the JNK pathway. Here, we identify ETS-4 and CEBP-1, related to mammalian Ets and C/EBP, respectively, as transcriptional activators of svh-2 expression following axon injury. ETS-4 and CEBP-1 function downstream of the cAMP and Ca2+-p38 MAPK pathways, respectively. We show that PKA-dependent phosphorylation of ETS-4 promotes its complex formation with CEBP-1. Furthermore, activation of both cAMP and Ca2+ signaling is required for activation of svh-2 expression. Thus, the cAMP/Ca2+ signaling pathways cooperatively activate the JNK pathway, which then promotes axon regeneration.
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Affiliation(s)
- Chun Li
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, Japan
| | - Naoki Hisamoto
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, Japan
- * E-mail: (NH); (KM)
| | - Kunihiro Matsumoto
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, Japan
- * E-mail: (NH); (KM)
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Dubey J, Ratnakaran N, Koushika SP. Neurodegeneration and microtubule dynamics: death by a thousand cuts. Front Cell Neurosci 2015; 9:343. [PMID: 26441521 PMCID: PMC4563776 DOI: 10.3389/fncel.2015.00343] [Citation(s) in RCA: 113] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2015] [Accepted: 08/18/2015] [Indexed: 12/11/2022] Open
Abstract
Microtubules form important cytoskeletal structures that play a role in establishing and maintaining neuronal polarity, regulating neuronal morphology, transporting cargo, and scaffolding signaling molecules to form signaling hubs. Within a neuronal cell, microtubules are found to have variable lengths and can be both stable and dynamic. Microtubule associated proteins, post-translational modifications of tubulin subunits, microtubule severing enzymes, and signaling molecules are all known to influence both stable and dynamic pools of microtubules. Microtubule dynamics, the process of interconversion between stable and dynamic pools, and the proportions of these two pools have the potential to influence a wide variety of cellular processes. Reduced microtubule stability has been observed in several neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), Amyotrophic Lateral Sclerosis (ALS), and tauopathies like Progressive Supranuclear Palsy. Hyperstable microtubules, as seen in Hereditary Spastic Paraplegia (HSP), also lead to neurodegeneration. Therefore, the ratio of stable and dynamic microtubules is likely to be important for neuronal function and perturbation in microtubule dynamics might contribute to disease progression.
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Affiliation(s)
- Jyoti Dubey
- Department of Biological Sciences, Tata Institute of Fundamental Research Mumbai, India ; InStem Bangalore, India
| | - Neena Ratnakaran
- Department of Biological Sciences, Tata Institute of Fundamental Research Mumbai, India
| | - Sandhya P Koushika
- Department of Biological Sciences, Tata Institute of Fundamental Research Mumbai, India
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Abstract
The cytoskeleton is a dynamic network of filamentous protein polymers required for virtually all cellular processes. It consists of three major classes, filamentous actin (F-actin), intermediate filaments, and microtubules, all displaying characteristic structural properties, functions, cellular distributions, and sets of interacting regulatory proteins. One unique class of proteins, the spectraplakins, bind, regulate, and integrate the functions of all three classes of cytoskeleton proteins. Spectraplakins are giant, evolutionary conserved multidomain proteins (spanning up to 9000 aa) that are true members of the plakin, spectrin, and Gas2-like protein families. They have OMIM-listed disease links to epidermolysis bullosa and hereditary sensory and autonomic neuropathy. Their role in disease is likely underrepresented since studies in model animal systems have revealed critical roles in polarity, morphogenesis, differentiation and maintenance, migration, signaling, and intracellular trafficking in a variety of tissues. This enormous diversity of spectraplakin function is consistent with the numerous isoforms produced from single genomic loci that combine different sets of functional domains in distinct cellular contexts. To study the broad range of functions and complexity of these proteins, Drosophila is a powerful model. Thus, the fly spectraplakin Short stop (Shot) acts as an actin-microtubule linker and plays important roles in many developmental processes, which provide experimentally amenable and relevant contexts in which to study spectraplakin functions. For these studies, a versatile range of relevant experimental resources that facilitate genetics and transgenic approaches, highly refined genomics tools, and an impressive set of spectraplakin-specific genetic and molecular tools are readily available. Here, we use the example of Shot to illustrate how the various tools and strategies available for Drosophila can be employed to decipher and dissect cellular roles and molecular mechanisms of spectraplakins.
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Bearce EA, Erdogan B, Lowery LA. TIPsy tour guides: how microtubule plus-end tracking proteins (+TIPs) facilitate axon guidance. Front Cell Neurosci 2015; 9:241. [PMID: 26175669 PMCID: PMC4485311 DOI: 10.3389/fncel.2015.00241] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 06/15/2015] [Indexed: 01/01/2023] Open
Abstract
The growth cone is a dynamic cytoskeletal vehicle, which drives the end of a developing axon. It serves to interpret and navigate through the complex landscape and guidance cues of the early nervous system. The growth cone’s distinctive cytoskeletal organization offers a fascinating platform to study how extracellular cues can be translated into mechanical outgrowth and turning behaviors. While many studies of cell motility highlight the importance of actin networks in signaling, adhesion, and propulsion, both seminal and emerging works in the field have highlighted a unique and necessary role for microtubules (MTs) in growth cone navigation. Here, we focus on the role of singular pioneer MTs, which extend into the growth cone periphery and are regulated by a diverse family of microtubule plus-end tracking proteins (+TIPs). These +TIPs accumulate at the dynamic ends of MTs, where they are well-positioned to encounter and respond to key signaling events downstream of guidance receptors, catalyzing immediate changes in microtubule stability and actin cross-talk, that facilitate both axonal outgrowth and turning events.
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Affiliation(s)
| | - Burcu Erdogan
- Department of Biology, Boston College Chestnut Hill, MA, USA
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Kurup N, Yan D, Goncharov A, Jin Y. Dynamic microtubules drive circuit rewiring in the absence of neurite remodeling. Curr Biol 2015; 25:1594-605. [PMID: 26051896 DOI: 10.1016/j.cub.2015.04.061] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Revised: 04/06/2015] [Accepted: 04/29/2015] [Indexed: 11/18/2022]
Abstract
A striking neuronal connectivity change in C. elegans involves the coordinated elimination of existing synapses and formation of synapses at new locations, without altering neuronal morphology. Here, we investigate the tripartite interaction between dynamic microtubules (MTs), kinesin-1, and vesicular cargo during this synapse remodeling. We find that a reduction in the dynamic MT population in motor neuron axons, resulting from genetic interaction between loss of function in the conserved MAPKKK dlk-1 and an α-tubulin mutation, specifically blocks synapse remodeling. Using live imaging and pharmacological modulation of the MT cytoskeleton, we show that dynamic MTs are increased at the onset of remodeling and are critical for new synapse formation. DLK-1 acts during synapse remodeling, and its function involves MT catastrophe factors including kinesin-13/KLP-7 and spastin/SPAS-1. Through a forward genetic screen, we identify gain-of-function mutations in kinesin-1 that can compensate for reduced dynamic MTs to promote synaptic vesicle transport during remodeling. Our data provide in vivo evidence supporting the requirement of dynamic MTs for kinesin-1-dependent axonal transport and shed light on the role of the MT cytoskeleton in facilitating neural circuit plasticity.
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Affiliation(s)
- Naina Kurup
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Dong Yan
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Alexandr Goncharov
- Howard Hughes Medical Institute, University of California, San Diego, La Jolla, CA 92093, USA
| | - Yishi Jin
- Neurobiology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA; Howard Hughes Medical Institute, University of California, San Diego, La Jolla, CA 92093, USA; Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093, USA.
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Valakh V, Frey E, Babetto E, Walker LJ, DiAntonio A. Cytoskeletal disruption activates the DLK/JNK pathway, which promotes axonal regeneration and mimics a preconditioning injury. Neurobiol Dis 2015; 77:13-25. [PMID: 25726747 DOI: 10.1016/j.nbd.2015.02.014] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 01/12/2015] [Accepted: 02/15/2015] [Indexed: 10/23/2022] Open
Abstract
Nerve injury can lead to axonal regeneration, axonal degeneration, and/or neuronal cell death. Remarkably, the MAP3K dual leucine zipper kinase, DLK, promotes each of these responses, suggesting that DLK is a sensor of axon injury. In Drosophila, mutations in proteins that stabilize the actin and microtubule cytoskeletons activate the DLK pathway, suggesting that DLK may be activated by cytoskeletal disruption. Here we test this model in mammalian sensory neurons. We find that pharmacological agents designed to disrupt either the actin or microtubule cytoskeleton activate the DLK pathway, and that activation is independent of calcium influx or induction of the axon degeneration program. Moreover, activation of the DLK pathway by targeting the cytoskeleton induces a pro-regenerative state, enhancing axon regeneration in response to a subsequent injury in a process akin to preconditioning. This highlights the potential utility of activating the DLK pathway as a method to improve axon regeneration. Moreover, DLK is required for these responses to cytoskeletal perturbations, suggesting that DLK functions as a key neuronal sensor of cytoskeletal damage.
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Affiliation(s)
- Vera Valakh
- Department of Developmental Biology, Hope Center for Neurological Disorders, Washington University School of Medicine, St Louis, MO 63110, USA
| | - Erin Frey
- Department of Developmental Biology, Hope Center for Neurological Disorders, Washington University School of Medicine, St Louis, MO 63110, USA
| | - Elisabetta Babetto
- Department of Developmental Biology, Hope Center for Neurological Disorders, Washington University School of Medicine, St Louis, MO 63110, USA
| | - Lauren J Walker
- Department of Developmental Biology, Hope Center for Neurological Disorders, Washington University School of Medicine, St Louis, MO 63110, USA
| | - Aaron DiAntonio
- Department of Developmental Biology, Hope Center for Neurological Disorders, Washington University School of Medicine, St Louis, MO 63110, USA.
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PASTUHOV SI, HISAMOTO N, MATSUMOTO K. MAP kinase cascades regulating axon regeneration in C. elegans. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2015; 91:63-75. [PMID: 25792136 PMCID: PMC4410086 DOI: 10.2183/pjab.91.63] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/24/2014] [Accepted: 01/13/2015] [Indexed: 06/04/2023]
Abstract
Mitogen-activated protein kinase (MAPK) signaling cascades are activated by diverse stimuli such as growth factors, cytokines, neurotransmitters and various types of cellular stress. Our evolving understanding of these signal cascades has been facilitated by genetic analyses and physiological characterization in model organisms such as the nematode Caenorhabditis elegans. Genetic and biochemical studies in C. elegans have shed light on the physiological roles of MAPK cascades in the control of cell fate decision, neuronal function and immunity. Recently it was demonstrated that MAPK signaling is also important for axon regeneration in C. elegans, and the use of C. elegans as a model system has significantly advanced our understanding of the largely conserved molecular mechanisms underlying axon regeneration. This review summarizes our current understanding of the role and regulation of MAPK signaling in C. elegans axon regeneration.
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Affiliation(s)
- Strahil Iv. PASTUHOV
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, Japan
| | - Naoki HISAMOTO
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, Japan
| | - Kunihiro MATSUMOTO
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, Japan
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49
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Luo S, Schaefer AM, Dour S, Nonet ML. The conserved LIM domain-containing focal adhesion protein ZYX-1 regulates synapse maintenance in Caenorhabditis elegans. Development 2014; 141:3922-33. [PMID: 25252943 DOI: 10.1242/dev.108217] [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: 01/21/2023]
Abstract
We describe the identification of zyxin as a regulator of synapse maintenance in mechanosensory neurons in C. elegans. zyx-1 mutants lacked PLM mechanosensory synapses as adult animals. However, most PLM synapses initially formed during development but were subsequently lost as the animals developed. Vertebrate zyxin regulates cytoskeletal responses to mechanical stress in culture. Our work provides in vivo evidence in support of such a role for zyxin. In particular, zyx-1 mutant synaptogenesis phenotypes were suppressed by disrupting locomotion of the mutant animals, suggesting that zyx-1 protects mechanosensory synapses from locomotion-induced forces. In cultured cells, zyxin is recruited to focal adhesions and stress fibers via C-terminal LIM domains and modulates cytoskeletal organization via the N-terminal domain. The synapse-stabilizing activity was mediated by a short isoform of ZYX-1 containing only the LIM domains. Consistent with this notion, PLM synaptogenesis was independent of α-actinin and ENA-VASP, both of which bind to the N-terminal domain of zyxin. Our results demonstrate that the LIM domain moiety of zyxin functions autonomously to mediate responses to mechanical stress and provide in vivo evidence for a role of zyxin in neuronal development.
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Affiliation(s)
- Shuo Luo
- Department of Anatomy and Neurobiology, Washington University Medical School, 660 S Euclid Ave, St Louis, MO 63110, USA
| | - Anneliese M Schaefer
- Department of Anatomy and Neurobiology, Washington University Medical School, 660 S Euclid Ave, St Louis, MO 63110, USA Department of Neurology, Washington University Medical School, 660 S Euclid Ave, St Louis, MO 63110, USA
| | - Scott Dour
- Department of Anatomy and Neurobiology, Washington University Medical School, 660 S Euclid Ave, St Louis, MO 63110, USA
| | - Michael L Nonet
- Department of Anatomy and Neurobiology, Washington University Medical School, 660 S Euclid Ave, St Louis, MO 63110, USA
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50
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Pease SE, Segal RA. Preserve and protect: maintaining axons within functional circuits. Trends Neurosci 2014; 37:572-82. [PMID: 25167775 DOI: 10.1016/j.tins.2014.07.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 07/21/2014] [Accepted: 07/27/2014] [Indexed: 12/14/2022]
Abstract
During development, neural circuits are initially generated by exuberant innervation and are rapidly refined by selective preservation and elimination of axons. The establishment and maintenance of functional circuits therefore requires coordination of axon survival and degeneration pathways. Both developing and mature circuits rely on interdependent mitochondrial and cytoskeletal components to maintain axonal health and homeostasis; injury or diseases that impinge on these components frequently cause pathologic axon loss. Here, we review recent findings that identify mechanisms of axonal preservation in the contexts of development, injury, and disease.
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Affiliation(s)
- Sarah E Pease
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA; Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA; Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
| | - Rosalind A Segal
- Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA; Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA; Department of Pediatric Oncology, Dana-Farber Cancer Institute, Boston, MA 02215, USA.
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