1
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Khazma T, Golan-Vaishenker Y, Guez-Haddad J, Grossman A, Sain R, Weitman M, Plotnikov A, Zalk R, Yaron A, Hons M, Opatowsky Y. A duplex structure of SARM1 octamers stabilized by a new inhibitor. Cell Mol Life Sci 2022; 80:16. [PMID: 36564647 PMCID: PMC11072711 DOI: 10.1007/s00018-022-04641-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Revised: 11/16/2022] [Accepted: 11/19/2022] [Indexed: 12/25/2022]
Abstract
In recent years, there has been growing interest in SARM1 as a potential breakthrough drug target for treating various pathologies of axon degeneration. SARM1-mediated axon degeneration relies on its TIR domain NADase activity, but recent structural data suggest that the non-catalytic ARM domain could also serve as a pharmacological site as it has an allosteric inhibitory function. Here, we screened for synthetic small molecules that inhibit SARM1, and tested a selected set of these compounds in a DRG axon degeneration assay. Using cryo-EM, we found that one of the newly discovered inhibitors, a calmidazolium designated TK106, not only stabilizes the previously reported inhibited conformation of the octamer, but also a meta-stable structure: a duplex of octamers (16 protomers), which we have now determined to 4.0 Å resolution. In the duplex, each ARM domain protomer is engaged in lateral interactions with neighboring protomers, and is further stabilized by contralateral contacts with the opposing octamer ring. Mutagenesis of the duplex contact sites leads to a moderate increase in SARM1 activation in cultured cells. Based on our data we propose that the duplex assembly constitutes an additional auto-inhibition mechanism that tightly prevents pre-mature activation and axon degeneration.
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Affiliation(s)
- Tami Khazma
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | | | - Julia Guez-Haddad
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | - Atira Grossman
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | - Radhika Sain
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | - Michal Weitman
- Department of Chemistry, Bar-Ilan University, Ramat Gan, Israel
| | - Alexander Plotnikov
- The Nancy and Stephen Grand Israel National Center for Personalized Medicine, Weizmann Institute of Science, Rehovot, Israel
| | - Ran Zalk
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
- Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Avraham Yaron
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Michael Hons
- European Molecular Biology Laboratory, Grenoble, France.
| | - Yarden Opatowsky
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel.
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2
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Huang Y, Ma M, Mao X, Pehlivan D, Kanca O, Un-Candan F, Shu L, Akay G, Mitani T, Lu S, Candan S, Wang H, Xiao B, Lupski JR, Bellen HJ. Novel dominant and recessive variants in human ROBO1 cause distinct neurodevelopmental defects through different mechanisms. Hum Mol Genet 2022; 31:2751-2765. [PMID: 35348658 PMCID: PMC9402236 DOI: 10.1093/hmg/ddac070] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 03/17/2022] [Accepted: 03/20/2022] [Indexed: 07/27/2023] Open
Abstract
The Roundabout (Robo) receptors, located on growth cones of neurons, induce axon repulsion in response to the extracellular ligand Slit. The Robo family of proteins controls midline crossing of commissural neurons during development in flies. Mono- and bi-allelic variants in human ROBO1 (HGNC: 10249) have been associated with incomplete penetrance and variable expressivity for a breath of phenotypes, including neurodevelopmental defects such as strabismus, pituitary defects, intellectual impairment, as well as defects in heart and kidney. Here, we report two novel ROBO1 variants associated with very distinct phenotypes. A homozygous missense p.S1522L variant in three affected siblings with nystagmus; and a monoallelic de novo p.D422G variant in a proband who presented with early-onset epileptic encephalopathy. We modeled these variants in Drosophila and first generated a null allele by inserting a CRIMIC T2A-GAL4 in an intron. Flies that lack robo1 exhibit reduced viability but have very severe midline crossing defects in the central nervous system. The fly wild-type cDNA driven by T2A-Gal4 partially rescues both defects. Overexpression of the human reference ROBO1 with T2A-GAL4 is toxic and reduces viability, whereas the recessive p.S1522L variant is less toxic, suggesting that it is a partial loss-of-function allele. In contrast, the dominant variant in fly robo1 (p.D413G) affects protein localization, impairs axonal guidance activity and induces mild phototransduction defects, suggesting that it is a neomorphic allele. In summary, our studies expand the phenotypic spectrum associated with ROBO1 variant alleles.
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Affiliation(s)
- Yan Huang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children’s Hospital, Baylor College of Medicine, Houston, TX 77030, USA
| | - Mengqi Ma
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children’s Hospital, Baylor College of Medicine, Houston, TX 77030, USA
| | - Xiao Mao
- National Health Commission Key Laboratory for Birth Defect Research and Prevention, Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan 410008, China
- Department of Medical Genetics, Maternal and Child Health Hospital of Hunan Province, Changsha, Hunan 410008, China
| | - Davut Pehlivan
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Division of Neurology and Developmental Neuroscience, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA
- Texas Children’s Hospital, Houston, TX 77030, USA
| | - Oguz Kanca
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children’s Hospital, Baylor College of Medicine, Houston, TX 77030, USA
| | - Feride Un-Candan
- Department of Neuroloy, Balikesir Ataturk Public Hospital, Balikesir 10100, Turkey
| | - Li Shu
- National Health Commission Key Laboratory for Birth Defect Research and Prevention, Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan 410008, China
- Department of Medical Genetics, Maternal and Child Health Hospital of Hunan Province, Changsha, Hunan 410008, China
| | - Gulsen Akay
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Tadahiro Mitani
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Shenzhao Lu
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children’s Hospital, Baylor College of Medicine, Houston, TX 77030, USA
| | - Sukru Candan
- Department of Medical Genetics, Balikesir Ataturk Public Hospital, Balikesir 10100, Turkey
| | - Hua Wang
- National Health Commission Key Laboratory for Birth Defect Research and Prevention, Hunan Provincial Maternal and Child Health Care Hospital, Changsha, Hunan 410008, China
- Department of Medical Genetics, Maternal and Child Health Hospital of Hunan Province, Changsha, Hunan 410008, China
| | - Bo Xiao
- Neurology Department, Xiangya Hospital, Central South University, Changsha, Hunan 410008, China
| | - James R Lupski
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Texas Children’s Hospital, Houston, TX 77030, USA
| | - Hugo J Bellen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children’s Hospital, Baylor College of Medicine, Houston, TX 77030, USA
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3
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Miyaguchi M, Nakanishi Y, Maturana AD, Mizutani K, Niimi T. Conformational Change of the Hairpin-like-structured Robo2 Ectodomain Allows NELL1/2 Binding. J Mol Biol 2022; 434:167777. [DOI: 10.1016/j.jmb.2022.167777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Revised: 07/29/2022] [Accepted: 08/02/2022] [Indexed: 10/16/2022]
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Zang Y, Chaudhari K, Bashaw GJ. New insights into the molecular mechanisms of axon guidance receptor regulation and signaling. Curr Top Dev Biol 2021; 142:147-196. [PMID: 33706917 DOI: 10.1016/bs.ctdb.2020.11.008] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
As the nervous system develops, newly differentiated neurons need to extend their axons toward their synaptic targets to form functional neural circuits. During this highly dynamic process of axon pathfinding, guidance receptors expressed at the tips of motile axons interact with soluble guidance cues or membrane tethered molecules present in the environment to be either attracted toward or repelled away from the source of these cues. As competing cues are often present at the same location and during the same developmental period, guidance receptors need to be both spatially and temporally regulated in order for the navigating axons to make appropriate guidance decisions. This regulation is exerted by a diverse array of molecular mechanisms that have come into focus over the past several decades and these mechanisms ensure that the correct complement of surface receptors is present on the growth cone, a fan-shaped expansion at the tip of the axon. This dynamic, highly motile structure is defined by a lamellipodial network lining the periphery of the growth cone interspersed with finger-like filopodial projections that serve to explore the surrounding environment. Once axon guidance receptors are deployed at the right place and time at the growth cone surface, they respond to their respective ligands by initiating a complex set of signaling events that serve to rearrange the growth cone membrane and the actin and microtubule cytoskeleton to affect axon growth and guidance. In this review, we highlight recent advances that shed light on the rich complexity of mechanisms that regulate axon guidance receptor distribution, activation and downstream signaling.
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Affiliation(s)
- Yixin Zang
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Karina Chaudhari
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Greg J Bashaw
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States.
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5
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Brown HE, Evans TA. Minimal structural elements required for midline repulsive signaling and regulation of Drosophila Robo1. PLoS One 2020; 15:e0241150. [PMID: 33091076 PMCID: PMC7580999 DOI: 10.1371/journal.pone.0241150] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Accepted: 10/08/2020] [Indexed: 02/07/2023] Open
Abstract
The Roundabout (Robo) family of axon guidance receptors has a conserved ectodomain arrangement of five immunoglobulin-like (Ig) domains plus three fibronectin type III (Fn) repeats. Based on the strong evolutionary conservation of this domain structure among Robo receptors, as well as in vitro structural and domain-domain interaction studies of Robo family members, this ectodomain arrangement is predicted to be important for Robo receptor signaling in response to Slit ligands. Here, we define the minimal ectodomain structure required for Slit binding and midline repulsive signaling in vivo by Drosophila Robo1. We find that the majority of the Robo1 ectodomain is dispensable for both Slit binding and repulsive signaling. We show that a significant level of midline repulsive signaling activity is retained when all Robo1 ectodomain elements apart from Ig1 are deleted, and that the combination of Ig1 plus one additional ectodomain element (Ig2, Ig5, or Fn3) is sufficient to restore midline repulsion to wild type levels. Further, we find that deleting four out of five Robo1 Ig domains (ΔIg2-5) does not affect negative regulation of Robo1 by Commissureless (Comm) or Robo2, while variants lacking all three fibronectin repeats (ΔFn1-3 and ΔIg2-Fn3) are insensitive to regulation by both Comm and Robo2, signifying a novel regulatory role for Robo1's Fn repeats. Our results provide an in vivo perspective on the importance of the conserved 5+3 ectodomain structure of Robo receptors, and suggest that specific biochemical properties and/or ectodomain structural conformations observed in vitro for domains other than Ig1 may have limited significance for in vivo signaling in the context of midline repulsion.
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Affiliation(s)
- Haley E. Brown
- Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas, United States of America
| | - Timothy A. Evans
- Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas, United States of America
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Sherchan P, Travis ZD, Tang J, Zhang JH. The potential of Slit2 as a therapeutic target for central nervous system disorders. Expert Opin Ther Targets 2020; 24:805-818. [PMID: 32378435 PMCID: PMC7529836 DOI: 10.1080/14728222.2020.1766445] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 05/05/2020] [Indexed: 10/24/2022]
Abstract
Introduction: Slit2 is an extracellular matrix protein that regulates migration of developing axons during central nervous system (CNS) development. Roundabout (Robo) receptors expressed by various cell types in the CNS, mediate intracellular signal transduction pathways for Slit2. Recent studies indicate that Slit2 plays important protective roles in a myriad of processes such as cell migration, immune response, vascular permeability, and angiogenesis in CNS pathologies. Areas covered: This review provides an overview of the diverse functions of Slit2 in CNS disorders and discusses the potential of Slit2 as a therapeutic target. We reviewed preclinical studies reporting the role of Slit2 in various CNS disease models, transgenic animal research, and rodent models that utilized Slit2 as a therapy. Expert opinion: Slit2 exerts a wide array of beneficial effects ranging from anti-migration, blood-brain barrier (BBB) protection, inhibition of peripheral immune cell infiltration, and anti-apoptosis in various disease models. However, a dual role of Slit2 in endothelial permeability has been observed in transgenic animals. Further research on Slit2 will be crucial including key issues such as effects of transgenic overexpression versus exogenous Slit2, function of Slit2 dependent on cellular expression of Robo receptors and the underlying pathology for potential clinical translation.
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Affiliation(s)
- Prativa Sherchan
- Center for Neuroscience Research, Department of Physiology and Pharmacology, Basic Sciences, Loma Linda University School of Medicine, Loma Linda, CA 92354, USA
| | - Zachary D. Travis
- Department of Earth and Biological Sciences, School of Medicine, Loma Linda University, Loma Linda, CA, 92354, USA and Center for Neuroscience Research, Loma Linda University School of Medicine, Loma Linda, CA, 92354, USA
- Department of Physiology and Pharmacology, Basic Sciences, Loma Linda University School of Medicine, Loma Linda, CA 92354, USA
| | - Jiping Tang
- Department of Physiology and Pharmacology, Basic Sciences, Loma Linda University School of Medicine, Loma Linda, CA 92354, USA
| | - John H. Zhang
- Center for Neuroscience Research, Department of Physiology and Pharmacology, Basic Sciences, Loma Linda University School of Medicine, Loma Linda, CA 92354, USA
- Departments of Anesthesiology, Neurosurgery and Neurology, Loma Linda University School of Medicine, Loma Linda, CA 92354, USA
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7
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Rozbesky D, Jones EY. Cell guidance ligands, receptors and complexes - orchestrating signalling in time and space. Curr Opin Struct Biol 2020; 61:79-85. [PMID: 31862615 PMCID: PMC7171467 DOI: 10.1016/j.sbi.2019.11.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Accepted: 11/15/2019] [Indexed: 01/28/2023]
Abstract
Members of four cell guidance molecule families (the netrins, slits, ephrins and semaphorins) interact with their cognate cell surface receptors to guide cells during development and maintain tissue homeostasis. Integrated structure and cell-based analyses are providing insight into the mechanisms by which these signalling systems can deliver myriad outcomes that require exquisite accuracy in timing and location. Here we review recent advances in our understanding of the roles of oligomeric states, auto-inhibition, signalling assembly size and composition in cell guidance cue function.
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Affiliation(s)
- Daniel Rozbesky
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, United Kingdom
| | - Edith Yvonne Jones
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN, United Kingdom.
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8
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Pak JS, DeLoughery ZJ, Wang J, Acharya N, Park Y, Jaworski A, Özkan E. NELL2-Robo3 complex structure reveals mechanisms of receptor activation for axon guidance. Nat Commun 2020; 11:1489. [PMID: 32198364 PMCID: PMC7083938 DOI: 10.1038/s41467-020-15211-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2019] [Accepted: 02/24/2020] [Indexed: 11/24/2022] Open
Abstract
Axon pathfinding is critical for nervous system development, and it is orchestrated by molecular cues that activate receptors on the axonal growth cone. Robo family receptors bind Slit guidance cues to mediate axon repulsion. In mammals, the divergent family member Robo3 does not bind Slits, but instead signals axon repulsion from its own ligand, NELL2. Conversely, canonical Robos do not mediate NELL2 signaling. Here, we present the structures of NELL-Robo3 complexes, identifying a mode of ligand engagement for Robos that is orthogonal to Slit binding. We elucidate the structural basis for differential binding between NELL and Robo family members and show that NELL2 repulsive activity is a function of its Robo3 affinity and is enhanced by ligand trimerization. Our results reveal a mechanism of oligomerization-induced Robo activation for axon guidance and shed light on Robo family member ligand binding specificity, conformational variability, divergent modes of signaling, and evolution.
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Affiliation(s)
- Joseph S Pak
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, 60637, USA
- Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, University of Chicago, Chicago, IL, 60637, USA
| | - Zachary J DeLoughery
- Department of Neuroscience, Division of Biology and Medicine, Brown University, Providence, RI, 02912, USA
- Robert J. and Nancy D. Carney Institute for Brain Science, Providence, RI, 02912, USA
| | - Jing Wang
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, 60637, USA
- Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, University of Chicago, Chicago, IL, 60637, USA
| | - Nischal Acharya
- Department of Neuroscience, Division of Biology and Medicine, Brown University, Providence, RI, 02912, USA
- Robert J. and Nancy D. Carney Institute for Brain Science, Providence, RI, 02912, USA
| | - Yeonwoo Park
- Department of Human Genetics, University of Chicago, Chicago, IL, 60637, USA
| | - Alexander Jaworski
- Department of Neuroscience, Division of Biology and Medicine, Brown University, Providence, RI, 02912, USA.
- Robert J. and Nancy D. Carney Institute for Brain Science, Providence, RI, 02912, USA.
| | - Engin Özkan
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, 60637, USA.
- Grossman Institute for Neuroscience, Quantitative Biology and Human Behavior, University of Chicago, Chicago, IL, 60637, USA.
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9
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Niimi T. Roles of Slit Ligands and Their Roundabout (Robo) Family of Receptors in Bone Remodeling. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 21:143-154. [PMID: 32986130 DOI: 10.1007/5584_2020_586] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Slit guidance ligands (Slits) and their roundabout (Robo) family of receptors are well-known axon guidance molecules that were originally identified in Drosophila mutants with commissural axon pathfinding defects. However, Slit-Robo signaling has been shown to be involved in not only neurogenesis, but also the development of other organs such as the kidney and heart. Recently, it was also revealed that Slit-Robo signaling plays an important role in bone metabolism. For example, osteoclast-derived Slit3 plays an osteoprotective role by synchronously stimulating bone formation by osteoblasts and suppressing bone resorption by osteoclasts through Robo receptors expressed on osteoblastic and osteoclastic cell lineages, making it a potential therapeutic target for metabolic bone disorders. Furthermore, osteoblast-derived Slit3 promotes bone formation indirectly as a proangiogenic factor. This review summarizes the recent progress on defining the roles of the Slit-Robo signaling in bone metabolism, and discusses the possible roles of the interaction between Robo and neural epidermal growth factor-like (NEL)-like (NELL) proteins that are novel ligands for Robo receptors.
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Affiliation(s)
- Tomoaki Niimi
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan.
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11
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Tong M, Jun T, Nie Y, Hao J, Fan D. The Role of the Slit/Robo Signaling Pathway. J Cancer 2019; 10:2694-2705. [PMID: 31258778 PMCID: PMC6584916 DOI: 10.7150/jca.31877] [Citation(s) in RCA: 77] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Accepted: 04/28/2019] [Indexed: 12/25/2022] Open
Abstract
The Slit family is a family of secreted proteins that play important roles in various physiologic and pathologic activities via interacting with Robo receptors. Slit/Robo signaling was first identified in the nervous system, where it functions in neuronal axon guidance; nevertheless, an increasing number of studies have shown that Slit/Robo signaling even regulates other activities, such as angiogenesis, inflammatory cell chemotaxis, tumor cell migration and metastasis. Although the precise role of the ligand-receptor in organisms has been obscure and the conclusions drawn are sometimes paradoxical, tremendous advances in understanding the Slit/Robo signaling pathway have been made. As such, our review summarizes the characteristics of the Slit/Robo signaling pathway and its role in various cell types.
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Affiliation(s)
- Mingfu Tong
- Department of Gastroenterology, Beijing Chao-Yang Hospital, Capital Medical University, Beijing 100020, China.,State Key Laboratory of Cancer Biology and Xijing Hospital of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China
| | - Tie Jun
- State Key Laboratory of Cancer Biology and Xijing Hospital of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China
| | - Yongzhan Nie
- State Key Laboratory of Cancer Biology and Xijing Hospital of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China
| | - Jianyu Hao
- Department of Gastroenterology, Beijing Chao-Yang Hospital, Capital Medical University, Beijing 100020, China
| | - Daiming Fan
- State Key Laboratory of Cancer Biology and Xijing Hospital of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China
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12
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Barak R, Yom-Tov G, Guez-Haddad J, Gasri-Plotnitsky L, Maimon R, Cohen-Berkman M, McCarthy AA, Perlson E, Henis-Korenblit S, Isupov MN, Opatowsky Y. Structural Principles in Robo Activation and Auto-inhibition. Cell 2019; 177:272-285.e16. [PMID: 30853216 DOI: 10.1016/j.cell.2019.02.004] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2018] [Revised: 12/06/2018] [Accepted: 02/06/2019] [Indexed: 01/28/2023]
Abstract
Proper brain function requires high-precision neuronal expansion and wiring, processes controlled by the transmembrane Roundabout (Robo) receptor family and their Slit ligands. Despite their great importance, the molecular mechanism by which Robos' switch from "off" to "on" states remains unclear. Here, we report a 3.6 Å crystal structure of the intact human Robo2 ectodomain (domains D1-8). We demonstrate that Robo cis dimerization via D4 is conserved through hRobo1, 2, and 3 and the C. elegans homolog SAX-3 and is essential for SAX-3 function in vivo. The structure reveals two levels of auto-inhibition that prevent premature activation: (1) cis blocking of the D4 dimerization interface and (2) trans interactions between opposing Robo receptors that fasten the D4-blocked conformation. Complementary experiments in mouse primary neurons and C. elegans support the auto-inhibition model. These results suggest that Slit stimulation primarily drives the release of Robo auto-inhibition required for dimerization and activation.
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Affiliation(s)
- Reut Barak
- The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Israel
| | - Galit Yom-Tov
- The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Israel
| | - Julia Guez-Haddad
- The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Israel
| | | | - Roy Maimon
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Israel
| | - Moran Cohen-Berkman
- The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Israel
| | | | - Eran Perlson
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Israel
| | | | | | - Yarden Opatowsky
- The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Israel.
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13
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Approaching the Roundabout: cis and trans Robo1 Contacts Revealed. Structure 2019; 26:183-184. [PMID: 29413320 DOI: 10.1016/j.str.2018.01.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
In this issue of Structure,Aleksandrova et al. (2018) present low- and high-resolution structures of Robo1, a key player in axonal guidance. The structures shed light on the arrangement of Robo1 at the plasma membrane and provide evidence for back-to-back trans Robo1 contacts.
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14
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Yamamoto N, Kashiwagi M, Ishihara M, Kojima T, Maturana AD, Kuroda S, Niimi T. Robo2 contains a cryptic binding site for neural EGFL-like (NELL) protein 1/2. J Biol Chem 2019; 294:4693-4703. [PMID: 30700556 DOI: 10.1074/jbc.ra118.005819] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 01/14/2019] [Indexed: 12/15/2022] Open
Abstract
The signaling pathways that are mediated by Slit ligands and their Roundabout (Robo) family of receptors play multifunctional roles in the development of the nervous system and other organs. A recent study identified neural epidermal growth factor-like (NEL)-like 2 (NELL2) as a novel ligand for Robo3. In this study, we carried out a comprehensive analysis of the interaction between NELL1 and the Robo family of receptors and demonstrated that Robo2 contains a cryptic binding site for both NELL1 and NELL2. NELL1/2 binds to the first fibronectin type III (FNIII) domain of Robo2 but not to intact Robo2. Mutation analysis revealed that several amino acids within the first FNIII domain are critical for NELL1 binding to Robo2 but not to Robo1. The Robo2 deletion mutants without the fourth immunoglobulin domain and single amino acid substitution mutants that can influence the architecture of the ectodomain facilitated binding to NELL1/2. Acidic conditions increased the binding affinity of Robo2 for NELL1. These results suggest that Robo2 functions as a receptor for NELL1/2, particularly under circumstances where Robo2 undergoes proteolytic digestion. If this is not the case, conformational changes of the ectodomain of Robo2 may unmask the binding site for NELL1/2.
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Affiliation(s)
- Naoka Yamamoto
- From the Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan and
| | - Manabu Kashiwagi
- From the Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan and
| | - Manami Ishihara
- From the Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan and
| | - Takaaki Kojima
- From the Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan and
| | - Andrés D Maturana
- From the Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan and
| | - Shun'ichi Kuroda
- the Institute of Scientific and Industrial Research, Osaka University, Osaka 567-0047, Japan
| | - Tomoaki Niimi
- From the Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan and
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15
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Abstract
The creation of complex neuronal networks relies on ligand-receptor interactions that mediate attraction or repulsion towards specific targets. Roundabouts comprise a family of single-pass transmembrane receptors facilitating this process upon interaction with the soluble extracellular ligand Slit protein family emanating from the midline. Due to the complexity and flexible nature of Robo receptors , their overall structure has remained elusive until now. Recent structural studies of the Robo 1 and Robo 2 ectodomains have provided the basis for a better understanding of their signalling mechanism. These structures reveal how Robo receptors adopt an auto-inhibited conformation on the cell surface that can be further stabilised by cis and/or trans oligmerisation arrays. Upon Slit -N binding Robo receptors must undergo a conformational change for Ig4 mediated dimerisation and signaling, probably via endocytosis. Furthermore, it's become clear that Robo receptors do not only act alone, but as large and more complex cell surface receptor assemblies to manifest directional and growth effects in a concerted fashion. These context dependent assemblies provide a mechanism to fine tune attractive and repulsive signals in a combinatorial manner required during neuronal development. While a mechanistic understanding of Slit mediated Robo signaling has advanced significantly further structural studies on larger assemblies are required for the design of new experiments to elucidate their role in cell surface receptor complexes. These will be necessary to understand the role of Slit -Robo signaling in neurogenesis, angiogenesis, organ development and cancer progression. In this chapter, we provide a review of the current knowledge in the field with a particular focus on the Roundabout receptor family.
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Affiliation(s)
- Francesco Bisiak
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue Des Martyrs, 38042, Grenoble, France.
| | - Andrew A McCarthy
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue Des Martyrs, 38042, Grenoble, France.
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