1
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Wu X, Seida M, Abe T, Higashitani A. Mitochonic acid 5 attenuates age-related neuromuscular dysfunction associated with mitochondrial Ca 2+ overload in Caenorhabditis elegans. NPJ AGING 2023; 9:20. [PMID: 37528117 PMCID: PMC10394014 DOI: 10.1038/s41514-023-00116-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Accepted: 06/28/2023] [Indexed: 08/03/2023]
Abstract
Mitochonic acid-5 ameliorates the pathophysiology of human mitochondrial-disease fibroblasts and Caenorhabditis elegans Duchenne muscular dystrophy and Parkinson's disease models. Here, we found that 10 μM MA-5 attenuates the age-related decline in motor performance, loss of muscle mitochondria, and degeneration of dopaminergic neurons associated with mitochondrial Ca2+ overload in C. elegans. These findings suggest that MA-5 may act as an anti-aging agent against a wide range of neuromuscular dysfunctions in metazoans.
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Affiliation(s)
- XinTong Wu
- Graduate School of Life Sciences, Tohoku University, Sendai, 980-8577, Japan
| | - Miku Seida
- Graduate School of Life Sciences, Tohoku University, Sendai, 980-8577, Japan
| | - Takaaki Abe
- Division of Medical Science, Tohoku University Graduate School of Biomedical Engineering, Sendai, 980-0872, Japan
- Department of Clinical Biology and Hormonal Regulation, Tohoku University Graduate School of Medicine, Sendai, 980-0872, Japan
| | - Atsushi Higashitani
- Graduate School of Life Sciences, Tohoku University, Sendai, 980-8577, Japan.
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2
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AlAbdi L, Desbois M, Rusnac DV, Sulaiman RA, Rosenfeld JA, Lalani S, Murdock DR, Burrage LC, Billie Au PY, Towner S, Wilson WG, Wong L, Brunet T, Strobl-Wildemann G, Burton JE, Hoganson G, McWalter K, Begtrup A, Zarate YA, Christensen EL, Opperman KJ, Giles AC, Helaby R, Kania A, Zheng N, Grill B, Alkuraya FS. Loss-of-function variants in MYCBP2 cause neurobehavioural phenotypes and corpus callosum defects. Brain 2023; 146:1373-1387. [PMID: 36200388 PMCID: PMC10319777 DOI: 10.1093/brain/awac364] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Revised: 08/11/2022] [Accepted: 08/22/2022] [Indexed: 11/14/2022] Open
Abstract
The corpus callosum is a bundle of axon fibres that connects the two hemispheres of the brain. Neurodevelopmental disorders that feature dysgenesis of the corpus callosum as a core phenotype offer a valuable window into pathology derived from abnormal axon development. Here, we describe a cohort of eight patients with a neurodevelopmental disorder characterized by a range of deficits including corpus callosum abnormalities, developmental delay, intellectual disability, epilepsy and autistic features. Each patient harboured a distinct de novo variant in MYCBP2, a gene encoding an atypical really interesting new gene (RING) ubiquitin ligase and signalling hub with evolutionarily conserved functions in axon development. We used CRISPR/Cas9 gene editing to introduce disease-associated variants into conserved residues in the Caenorhabditis elegans MYCBP2 orthologue, RPM-1, and evaluated functional outcomes in vivo. Consistent with variable phenotypes in patients with MYCBP2 variants, C. elegans carrying the corresponding human mutations in rpm-1 displayed axonal and behavioural abnormalities including altered habituation. Furthermore, abnormal axonal accumulation of the autophagy marker LGG-1/LC3 occurred in variants that affect RPM-1 ubiquitin ligase activity. Functional genetic outcomes from anatomical, cell biological and behavioural readouts indicate that MYCBP2 variants are likely to result in loss of function. Collectively, our results from multiple human patients and CRISPR gene editing with an in vivo animal model support a direct link between MYCBP2 and a human neurodevelopmental spectrum disorder that we term, MYCBP2-related developmental delay with corpus callosum defects (MDCD).
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Affiliation(s)
- Lama AlAbdi
- Department of Zoology, College of Science, King Saud University, Riyadh 11362, Saudi Arabia
- Department of Translational Genomics, Center for Genomic Medicine, King Faisal Specialist Hospital and Research Center, Riyadh 11564, Saudi Arabia
| | - Muriel Desbois
- Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, WA 98101, USA
| | - Domniţa-Valeria Rusnac
- Department of Pharmacology, University of Washington School of Medicine, Seattle, WA 98195, USA
- Howard Hughes Medical Institute, Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - Raashda A Sulaiman
- Department of Medical Genetics, King Faisal Specialist Hospital and Research Center, Riyadh 11564, Saudi Arabia
| | - Jill A Rosenfeld
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Seema Lalani
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - David R Murdock
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Lindsay C Burrage
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | | | - Ping Yee Billie Au
- Department of Medical Genetics, Alberta Children’s Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Shelley Towner
- Pediatric Genetics, University of Virginia, Charlottesville, VA 22903, USA
| | - William G Wilson
- Pediatric Genetics, University of Virginia, Charlottesville, VA 22903, USA
| | - Lawrence Wong
- Department of Genetics, Northern California Kaiser Permanente, Oakland, CA 94611, USA
| | - Theresa Brunet
- Institute of Human Genetics, Klinikum rechts der Isar, School of Medicine, Technical University of Munich, 81675 Munich, Germany
- Institute of Neurogenomics (ING), Helmholtz Zentrum München, German Research Center for Environmental Health, 85764 Neuherberg, Germany
| | | | - Jennifer E Burton
- Department of Genetics, University of Illinois College of Medicine at Peoria, Peoria, IL 61605, USA
| | - George Hoganson
- Department of Genetics, University of Illinois College of Medicine at Peoria, Peoria, IL 61605, USA
| | - Kirsty McWalter
- Genedx, Inc., 207 Perry Parkway, Gaithersburg, MD 20877, USA
| | - Amber Begtrup
- Genedx, Inc., 207 Perry Parkway, Gaithersburg, MD 20877, USA
| | - Yuri A Zarate
- Section of Genetics and Metabolism, Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, AR 72202, USA
| | - Elyse L Christensen
- Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, WA 98101, USA
| | - Karla J Opperman
- Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, WA 98101, USA
| | - Andrew C Giles
- Division of Medical Sciences, University of Northern British Columbia, Prince George, BC V2N 4Z9, Canada
| | - Rana Helaby
- Department of Translational Genomics, Center for Genomic Medicine, King Faisal Specialist Hospital and Research Center, Riyadh 11564, Saudi Arabia
| | - Artur Kania
- Institut de recherches cliniques de Montréal (IRCM), Montréal, QC H2W 1R7, Canada
- Integrated Program in Neuroscience, McGill University, Montréal, QC H3A 2B4, Canada
- Division of Experimental Medicine, McGill University, Montréal, QC H3A 2B2, Canada
- Department of Anatomy and Cell Biology, McGill University, Montréal, QC H3A 0C7, Canada
| | - Ning Zheng
- Department of Pharmacology, University of Washington School of Medicine, Seattle, WA 98195, USA
- Howard Hughes Medical Institute, Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - Brock Grill
- Center for Integrative Brain Research, Seattle Children’s Research Institute, Seattle, WA 98101, USA
- Department of Pharmacology, University of Washington School of Medicine, Seattle, WA 98195, USA
- Department of Pediatrics, University of Washington School of Medicine, Seattle, WA 98101, USA
| | - Fowzan S Alkuraya
- Department of Translational Genomics, Center for Genomic Medicine, King Faisal Specialist Hospital and Research Center, Riyadh 11564, Saudi Arabia
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3
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Yoshiyama KO, Okamoto NL, Hidema J, Higashitani A. 222 nm far-UVC efficiently introduces nerve damage in Caenorhabditis elegans. PLoS One 2023; 18:e0281162. [PMID: 36719882 PMCID: PMC9888708 DOI: 10.1371/journal.pone.0281162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 01/16/2023] [Indexed: 02/01/2023] Open
Abstract
Far-ultraviolet radiation C light (far-UVC; 222 nm wavelength) has received attention as a safer light for killing pathogenic bacteria and viruses, as no or little DNA damage is observed after irradiation in mammalian skin models. Far-UVC does not penetrate deeply into tissues; therefore, it cannot reach the underlying critical basal cells. However, it was unclear whether far-UVC (222-UVC) irradiation could cause more biological damage at shallower depths than the 254 nm UVC irradiation (254-UVC), which penetrates more deeply. This study investigated the biological effects of 222- and 254-UVC on the small and transparent model organism Caenorhabditis elegans. At the same energy level of irradiation, 222-UVC introduced slightly less cyclobutane pyrimidine dimer damage to naked DNA in solution than 254-UVC. The survival of eggs laid during 0-4 h after irradiation showed a marked decrease with 254-UVC but not 222-UVC. In addition, defect of chromosomal condensation was observed in a full-grown oocyte by 254-UVC irradiation. In contrast, 222-UVC had a significant effect on the loss of motility of C. elegans. The sensory nervous system, which includes dopamine CEP and PVD neurons on the body surface, was severely damaged by 222-UVC, but not by the same dose of 254-UVC. Interestingly, increasing 254-UVC irradiation by about 10-fold causes similar damage to CEP neurons. These results suggest that 222-UVC is less penetrating, so energy transfer occurs more effectively in tissues near the surface, causing more severe damage than 254-UVC.
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Affiliation(s)
| | | | - Jun Hidema
- Graduate School of Life Sciences, Tohoku University, Sendai, Japan
- Division for the Establishment of Frontier Sciences of the Organization for Advanced Studies, Tohoku University, Sendai, Japan
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4
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Crawley O, Grill B. Autophagy in axonal and presynaptic development. Curr Opin Neurobiol 2021; 69:139-148. [PMID: 33940492 DOI: 10.1016/j.conb.2021.03.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Revised: 03/17/2021] [Accepted: 03/21/2021] [Indexed: 10/21/2022]
Abstract
The study of autophagy in the nervous system has predominantly centered on degeneration. Evidence is now cementing crucial roles for autophagy in neuronal development and growth, especially in axonal and presynaptic compartments. A picture is emerging that autophagy typically promotes the growth of axons and reduces presynaptic stability. Nonetheless, these are not rigid principles, and it remains unclear why autophagy does not always display these relationships during axonal and presynaptic development. Recent progress has identified mechanisms underlying spatiotemporal control of autophagy in neurons and begun to unravel how autophagy is integrated with other cellular processes, such as proteasomal degradation and axon guidance. Ultimately, understanding how autophagy is regulated and its role in the developing nervous system is key to comprehending how the nervous system assembles its stereotyped yet plastic configuration. It is also likely to inform how we think about neurodevelopmental disorders and neurodegenerative diseases.
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Affiliation(s)
- Oliver Crawley
- Unidad de Neurobiología Celular y de Sistemas, Instituto de Neurociencias (CSIC-UMH), San Juan de Alicante, 03550, Spain.
| | - Brock Grill
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA, 98199, USA; Department of Pediatrics, University of Washington School of Medicine, Seattle, WA, USA; Department of Pharmacology, University of Washington School of Medicine, Seattle, WA, USA.
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5
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Nelson JC, Witze E, Ma Z, Ciocco F, Frerotte A, Randlett O, Foskett JK, Granato M. Acute Regulation of Habituation Learning via Posttranslational Palmitoylation. Curr Biol 2020; 30:2729-2738.e4. [PMID: 32502414 PMCID: PMC8446937 DOI: 10.1016/j.cub.2020.05.016] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Revised: 01/06/2020] [Accepted: 05/05/2020] [Indexed: 12/16/2022]
Abstract
Habituation is an adaptive learning process that enables animals to adjust innate behaviors to changes in their environment. Despite its well-documented implications for a wide diversity of behaviors, the molecular and cellular basis of habituation learning is not well understood. Using whole-genome sequencing of zebrafish mutants isolated in an unbiased genetic screen, we identified the palmitoyltransferase Huntingtin interacting protein 14 (Hip14) as a critical regulator of habituation learning. We demonstrate that Hip14 regulates depression of sensory inputs onto an identified hindbrain neuron and provide evidence that Hip14 palmitoylates the Shaker-like K+ voltage-gated channel subunit (Kv1.1), thereby regulating Kv1.1 subcellular localization. Furthermore, we show that, like for Hip14, loss of Kv1.1 leads to habituation deficits and that Hip14 is dispensable in development and instead acts acutely to promote habituation. Combined, these results uncover a previously unappreciated role for acute posttranslational palmitoylation at defined circuit components to regulate learning.
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Affiliation(s)
- Jessica C Nelson
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, 421 Curie Boulevard, Philadelphia, PA 19104, USA
| | - Eric Witze
- Department of Cancer Biology, Perelman School of Medicine, University of Pennsylvania, 421 Curie Boulevard, Philadelphia, PA 19104, USA
| | - Zhongming Ma
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, 415 Curie Boulevard, Philadelphia, PA 19104, USA
| | - Francesca Ciocco
- Department of Biology, Haverford College, 370 Lancaster Avenue, Haverford, PA 19041, USA
| | - Abigaile Frerotte
- Department of Biology, Haverford College, 370 Lancaster Avenue, Haverford, PA 19041, USA
| | - Owen Randlett
- Institut NeuroMyoGène, Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR 5310, INSERM U1217, Lyon 69008, France
| | - J Kevin Foskett
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, 415 Curie Boulevard, Philadelphia, PA 19104, USA
| | - Michael Granato
- Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, 421 Curie Boulevard, Philadelphia, PA 19104, USA.
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6
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Autophagy is inhibited by ubiquitin ligase activity in the nervous system. Nat Commun 2019; 10:5017. [PMID: 31676756 PMCID: PMC6825199 DOI: 10.1038/s41467-019-12804-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Accepted: 10/01/2019] [Indexed: 12/17/2022] Open
Abstract
Autophagy is an intracellular catabolic process prominent in starvation, aging and disease. Neuronal autophagy is particularly important, as it affects the development and function of the nervous system, and is heavily implicated in neurodegenerative disease. Nonetheless, how autophagy is regulated in neurons remains poorly understood. Using an unbiased proteomics approach, we demonstrate that the primary initiator of autophagy, the UNC-51/ULK kinase, is negatively regulated by the ubiquitin ligase RPM-1. RPM-1 ubiquitin ligase activity restricts UNC-51 and autophagosome formation within specific axonal compartments, and exerts effects broadly across the nervous system. By restraining UNC-51 activity, RPM-1 inhibits autophagosome formation to affect axon termination, synapse maintenance and behavioral habituation. These results demonstrate how UNC-51 and autophagy are regulated subcellularly in axons, and unveils a mechanism for restricting initiation of autophagy across the nervous system. Our findings have important implications beyond nervous system development, given growing links between altered autophagy regulation and neurodegenerative diseases.
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7
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Borgen MA, Giles AC, Wang D, Grill B. Synapse maintenance is impacted by ATAT-2 tubulin acetyltransferase activity and the RPM-1 signaling hub. eLife 2019; 8:44040. [PMID: 30652969 PMCID: PMC6355192 DOI: 10.7554/elife.44040] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 01/15/2019] [Indexed: 12/16/2022] Open
Abstract
Synapse formation is comprised of target cell recognition, synapse assembly, and synapse maintenance. Maintaining established synaptic connections is essential for generating functional circuitry and synapse instability is a hallmark of neurodegenerative disease. While many molecules impact synapse formation generally, we know little about molecules that affect synapse maintenance in vivo. Using genetics and developmental time course analysis in C.elegans, we show that the α-tubulin acetyltransferase ATAT-2 and the signaling hub RPM-1 are required presynaptically to maintain stable synapses. Importantly, the enzymatic acetyltransferase activity of ATAT-2 is required for synapse maintenance. Our analysis revealed that RPM-1 is a hub in a genetic network composed of ATAT-2, PTRN-1 and DLK-1. In this network, ATAT-2 functions independent of the DLK-1 MAPK and likely acts downstream of RPM-1. Thus, our study reveals an important role for tubulin acetyltransferase activity in presynaptic maintenance, which occurs via the RPM-1/ATAT-2 pathway.
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Affiliation(s)
- Melissa A Borgen
- Department of Neuroscience, The Scripps Research Institute, Jupiter, United States
| | - Andrew C Giles
- Department of Neuroscience, The Scripps Research Institute, Jupiter, United States
| | - Dandan Wang
- Department of Neuroscience, The Scripps Research Institute, Jupiter, United States
| | - Brock Grill
- Department of Neuroscience, The Scripps Research Institute, Jupiter, United States
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8
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Opperman KJ, Mulcahy B, Giles AC, Risley MG, Birnbaum RL, Tulgren ED, Dawson-Scully K, Zhen M, Grill B. The HECT Family Ubiquitin Ligase EEL-1 Regulates Neuronal Function and Development. Cell Rep 2018; 19:822-835. [PMID: 28445732 DOI: 10.1016/j.celrep.2017.04.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Revised: 03/01/2017] [Accepted: 03/31/2017] [Indexed: 12/21/2022] Open
Abstract
Genetic changes in the HECT ubiquitin ligase HUWE1 are associated with intellectual disability, but it remains unknown whether HUWE1 functions in post-mitotic neurons to affect circuit function. Using genetics, pharmacology, and electrophysiology, we show that EEL-1, the HUWE1 ortholog in C. elegans, preferentially regulates GABAergic presynaptic transmission. Decreasing or increasing EEL-1 function alters GABAergic transmission and the excitatory/inhibitory (E/I) balance in the worm motor circuit, which leads to impaired locomotion and increased sensitivity to electroshock. Furthermore, multiple mutations associated with intellectual disability impair EEL-1 function. Although synaptic transmission defects did not result from abnormal synapse formation, sensitizing genetic backgrounds revealed that EEL-1 functions in the same pathway as the RING family ubiquitin ligase RPM-1 to regulate synapse formation and axon termination. These findings from a simple model circuit provide insight into the molecular mechanisms required to obtain E/I balance and could have implications for the link between HUWE1 and intellectual disability.
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Affiliation(s)
- Karla J Opperman
- Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, FL 33458, USA
| | - Ben Mulcahy
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON M5G 1X5, Canada
| | - Andrew C Giles
- Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, FL 33458, USA
| | - Monica G Risley
- Department of Biological Sciences, Florida Atlantic University, Boca Raton, FL 33431, USA
| | - Rayna L Birnbaum
- Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, FL 33458, USA; Harriet L. Wilkes Honors College, Florida Atlantic University, Jupiter, FL 33458, USA
| | - Erik D Tulgren
- Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Ken Dawson-Scully
- Department of Biological Sciences, Florida Atlantic University, Boca Raton, FL 33431, USA
| | - Mei Zhen
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON M5G 1X5, Canada; Department of Molecular Genetics and Physiology, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Brock Grill
- Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, FL 33458, USA.
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9
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Crawley O, Giles AC, Desbois M, Kashyap S, Birnbaum R, Grill B. A MIG-15/JNK-1 MAP kinase cascade opposes RPM-1 signaling in synapse formation and learning. PLoS Genet 2017; 13:e1007095. [PMID: 29228003 PMCID: PMC5754208 DOI: 10.1371/journal.pgen.1007095] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 01/04/2018] [Accepted: 11/01/2017] [Indexed: 12/18/2022] Open
Abstract
The Pam/Highwire/RPM-1 (PHR) proteins are conserved intracellular signaling hubs that regulate synapse formation and axon termination. The C. elegans PHR protein, called RPM-1, acts as a ubiquitin ligase to inhibit the DLK-1 and MLK-1 MAP kinase pathways. We have identified several kinases that are likely to form a new MAP kinase pathway that suppresses synapse formation defects, but not axon termination defects, in the mechanosensory neurons of rpm-1 mutants. This pathway includes: MIG-15 (MAP4K), NSY-1 (MAP3K), JKK-1 (MAP2K) and JNK-1 (MAPK). Transgenic overexpression of kinases in the MIG-15/JNK-1 pathway is sufficient to impair synapse formation in wild-type animals. The MIG-15/JNK-1 pathway functions cell autonomously in the mechanosensory neurons, and these kinases localize to presynaptic terminals providing further evidence of a role in synapse development. Loss of MIG-15/JNK-1 signaling also suppresses defects in habituation to repeated mechanical stimuli in rpm-1 mutants, a behavioral deficit that is likely to arise from impaired glutamatergic synapse formation. Interestingly, habituation results are consistent with the MIG-15/JNK-1 pathway functioning as a parallel opposing pathway to RPM-1. These findings indicate the MIG-15/JNK-1 pathway can restrict both glutamatergic synapse formation and short-term learning.
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Affiliation(s)
- Oliver Crawley
- Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, Florida, United States of America
| | - Andrew C. Giles
- Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, Florida, United States of America
| | - Muriel Desbois
- Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, Florida, United States of America
| | - Sudhanva Kashyap
- Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, Florida, United States of America
| | - Rayna Birnbaum
- Harriet L. Wilkes Honors College, Florida Atlantic University, Jupiter, FL, United States of America
| | - Brock Grill
- Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, Florida, United States of America
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10
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Borgen MA, Wang D, Grill B. RPM-1 regulates axon termination by affecting growth cone collapse and microtubule stability. Development 2017; 144:4658-4672. [PMID: 29084805 DOI: 10.1242/dev.154187] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Accepted: 10/21/2017] [Indexed: 12/14/2022]
Abstract
Axon termination is essential for efficient and accurate nervous system construction. At present, relatively little is known about how growth cone collapse occurs prior to axon termination in vivo Using the mechanosensory neurons of C. elegans, we found collapse prior to axon termination is protracted, with the growth cone transitioning from a dynamic to a static state. Growth cone collapse prior to termination is facilitated by the signaling hub RPM-1. Given the prominence of the cytoskeleton in growth cone collapse, we assessed the relationship between RPM-1 and regulators of actin dynamics and microtubule stability. Our results reveal several important findings about how axon termination is orchestrated: (1) RPM-1 functions in parallel to RHO-1 and CRMP/UNC-33, but is suppressed by the Rac isoform MIG-2; (2) RPM-1 opposes the function of microtubule stabilizers, including tubulin acetyltransferases; and (3) genetic epistasis suggests the microtubule-stabilizing protein Tau/PTL-1 potentially inhibits RPM-1. These findings provide insight into how growth cone collapse is regulated during axon termination in vivo, and suggest that RPM-1 signaling destabilizes microtubules to facilitate growth cone collapse and axon termination.
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Affiliation(s)
- Melissa A Borgen
- Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, FL 33458, USA
| | - Dandan Wang
- Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, FL 33458, USA
| | - Brock Grill
- Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, FL 33458, USA
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11
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Baker ST, Grill B. Defining Minimal Binding Regions in Regulator of Presynaptic Morphology 1 (RPM-1) Using Caenorhabditis elegans Neurons Reveals Differential Signaling Complexes. J Biol Chem 2016; 292:2519-2530. [PMID: 27979965 DOI: 10.1074/jbc.m116.748004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Revised: 12/14/2016] [Indexed: 12/22/2022] Open
Abstract
The intracellular signaling protein regulator of presynaptic morphology 1 (RPM-1) is a conserved regulator of synapse formation and axon termination in Caenorhabditis elegans RPM-1 functions in a ubiquitin ligase complex with the F-box protein FSN-1 and functions through the microtubule binding protein RAE-1. Using a structure-function approach and positive selection for transgenic C. elegans, we explored the biochemical relationship between RPM-1, FSN-1, and RAE-1. This led to the identification of two new domains in RPM-1 that are sufficient for binding to FSN-1, called FSN-1 binding domain 2 (FBD2) and FBD3. Furthermore, we map the RAE-1 binding domain to a much smaller region of RPM-1. Point mutations in RPM-1 that reduce binding to RAE-1 did not affect FSN-1 binding, indicating that RPM-1 utilizes different biochemical mechanisms to bind these molecules. Analysis of RPM-1 protein complexes in the neurons of C. elegans elucidated two further discoveries: FSN-1 binds to RAE-1, and this interaction is not mediated by RPM-1, and RPM-1 binding to FSN-1 and RAE-1 reduces FSN-1·RAE-1 complex formation. These results indicate that RPM-1 uses different mechanisms to recruit FSN-1 and RAE-1 into independent signaling complexes in neurons.
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Affiliation(s)
- Scott T Baker
- From the Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, Florida 33458
| | - Brock Grill
- From the Department of Neuroscience, The Scripps Research Institute, Scripps Florida, Jupiter, Florida 33458
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12
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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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