1
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Srikanth KD, Elahi H, Chander P, Washburn HR, Hassler S, Mwirigi JM, Kume M, Loucks J, Arjarapu R, Hodge R, Shiers SI, Sankaranarayanan I, Erdjument-Bromage H, Neubert TA, Campbell ZT, Paik R, Price TJ, Dalva MB. VLK drives extracellular phosphorylation of EphB2 to govern the EphB2-NMDAR interaction and injury-induced pain. bioRxiv 2024:2024.03.18.585314. [PMID: 38562765 PMCID: PMC10983893 DOI: 10.1101/2024.03.18.585314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Phosphorylation of hundreds of protein extracellular domains is mediated by two kinase families, yet the significance of these kinases is underexplored. Here, we find that the presynaptic release of the tyrosine directed-ectokinase, Vertebrate Lonesome Kinase (VLK/Pkdcc), is necessary and sufficient for the direct extracellular interaction between EphB2 and GluN1 at synapses, for phosphorylation of the ectodomain of EphB2, and for injury-induced pain. Pkdcc is an essential gene in the nervous system, and VLK is found in synaptic vesicles, and is released from neurons in a SNARE-dependent fashion. VLK is expressed by nociceptive sensory neurons where presynaptic sensory neuron-specific knockout renders mice impervious to post-surgical pain, without changing proprioception. VLK defines an extracellular mechanism that regulates protein-protein interaction and non-opioid-dependent pain in response to injury.
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Affiliation(s)
- Kolluru D. Srikanth
- Tulane Brain Institute, Department of Cell and Molecular Biology, Tulane University; New Orleans, LA 70118, USA
- Jefferson Synaptic Biology Center, Department of Neuroscience, Thomas Jefferson University, Philadelphia, PA 19107
| | - Hajira Elahi
- Department of Neuroscience, The University of Texas at Dallas; Richardson, TX 75080, USA
- Center for Advanced Pain Studies, University of Texas at Dallas; Richardson, TX 75080, USA
| | - Praveen Chander
- Tulane Brain Institute, Department of Cell and Molecular Biology, Tulane University; New Orleans, LA 70118, USA
- Jefferson Synaptic Biology Center, Department of Neuroscience, Thomas Jefferson University, Philadelphia, PA 19107
| | - Halley R. Washburn
- Jefferson Synaptic Biology Center, Department of Neuroscience, Thomas Jefferson University, Philadelphia, PA 19107
- Department of Molecular Biology, Princeton University; Princeton, NJ 08544, USA
| | - Shayne Hassler
- Department of Neuroscience, The University of Texas at Dallas; Richardson, TX 75080, USA
- College of Medicine, University of Houston; Houston, TX 77004, USA
| | - Juliet M. Mwirigi
- Department of Neuroscience, The University of Texas at Dallas; Richardson, TX 75080, USA
- Center for Advanced Pain Studies, University of Texas at Dallas; Richardson, TX 75080, USA
| | - Moeno Kume
- Department of Neuroscience, The University of Texas at Dallas; Richardson, TX 75080, USA
- Center for Advanced Pain Studies, University of Texas at Dallas; Richardson, TX 75080, USA
| | - Jessica Loucks
- Department of Neuroscience, The University of Texas at Dallas; Richardson, TX 75080, USA
| | - Rohita Arjarapu
- Department of Neuroscience, The University of Texas at Dallas; Richardson, TX 75080, USA
| | - Rachel Hodge
- Jefferson Synaptic Biology Center, Department of Neuroscience, Thomas Jefferson University, Philadelphia, PA 19107
| | - Stephanie I. Shiers
- Department of Neuroscience, The University of Texas at Dallas; Richardson, TX 75080, USA
- Center for Advanced Pain Studies, University of Texas at Dallas; Richardson, TX 75080, USA
| | - Ishwarya Sankaranarayanan
- Department of Neuroscience, The University of Texas at Dallas; Richardson, TX 75080, USA
- Center for Advanced Pain Studies, University of Texas at Dallas; Richardson, TX 75080, USA
| | - Hediye Erdjument-Bromage
- Department of Neuroscience and Physiology and Neuroscience Institute, NYU Grossman School of Medicine, New York, NY, 10016, USA
| | - Thomas A. Neubert
- Department of Neuroscience and Physiology and Neuroscience Institute, NYU Grossman School of Medicine, New York, NY, 10016, USA
| | - Zachary T. Campbell
- Department of Anesthesiology, University of Wisconsin-Madison; Madison, WI 53792, USA
| | - Raehum Paik
- Department of Anesthesiology, University of Wisconsin-Madison; Madison, WI 53792, USA
- Department of Genetics, University of Texas Health Science Center at San Antonio; San Antonio, TX 78229, USA
| | - Theodore J. Price
- Department of Neuroscience, The University of Texas at Dallas; Richardson, TX 75080, USA
- Center for Advanced Pain Studies, University of Texas at Dallas; Richardson, TX 75080, USA
| | - Matthew B. Dalva
- Tulane Brain Institute, Department of Cell and Molecular Biology, Tulane University; New Orleans, LA 70118, USA
- Jefferson Synaptic Biology Center, Department of Neuroscience, Thomas Jefferson University, Philadelphia, PA 19107
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2
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Urban MW, Charsar BA, Heinsinger NM, Markandaiah SS, Sprimont L, Zhou W, Brown EV, Henderson NT, Thomas SJ, Ghosh B, Cain RE, Trotti D, Pasinelli P, Wright MC, Dalva MB, Lepore AC. EphrinB2 knockdown in cervical spinal cord preserves diaphragm innervation in a mutant SOD1 mouse model of ALS. eLife 2024; 12:RP89298. [PMID: 38224498 PMCID: PMC10945582 DOI: 10.7554/elife.89298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2024] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by motor neuron loss. Importantly, non-neuronal cell types such as astrocytes also play significant roles in disease pathogenesis. However, mechanisms of astrocyte contribution to ALS remain incompletely understood. Astrocyte involvement suggests that transcellular signaling may play a role in disease. We examined contribution of transmembrane signaling molecule ephrinB2 to ALS pathogenesis, in particular its role in driving motor neuron damage by spinal cord astrocytes. In symptomatic SOD1G93A mice (a well-established ALS model), ephrinB2 expression was dramatically increased in ventral horn astrocytes. Reducing ephrinB2 in the cervical spinal cord ventral horn via viral-mediated shRNA delivery reduced motor neuron loss and preserved respiratory function by maintaining phrenic motor neuron innervation of diaphragm. EphrinB2 expression was also elevated in human ALS spinal cord. These findings implicate ephrinB2 upregulation as both a transcellular signaling mechanism in mutant SOD1-associated ALS and a promising therapeutic target.
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Affiliation(s)
- Mark W Urban
- Department of Neuroscience, Jefferson Synaptic Biology Center, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson UniversityPhiladelphiaUnited States
| | - Brittany A Charsar
- Department of Neuroscience, Jefferson Synaptic Biology Center, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson UniversityPhiladelphiaUnited States
| | - Nicolette M Heinsinger
- Department of Neuroscience, Jefferson Synaptic Biology Center, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson UniversityPhiladelphiaUnited States
| | - Shashirekha S Markandaiah
- Jefferson Weinberg ALS Center, Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Thomas Jefferson UniversityPhiladelphiaUnited States
| | - Lindsay Sprimont
- Department of Neuroscience, Jefferson Synaptic Biology Center, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson UniversityPhiladelphiaUnited States
| | - Wei Zhou
- Department of Neuroscience, Jefferson Synaptic Biology Center, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson UniversityPhiladelphiaUnited States
| | - Eric V Brown
- Department of Neuroscience, Jefferson Synaptic Biology Center, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson UniversityPhiladelphiaUnited States
| | - Nathan T Henderson
- Department of Neuroscience, Jefferson Synaptic Biology Center, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson UniversityPhiladelphiaUnited States
| | - Samantha J Thomas
- Department of Neuroscience, Jefferson Synaptic Biology Center, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson UniversityPhiladelphiaUnited States
| | - Biswarup Ghosh
- Department of Neuroscience, Jefferson Synaptic Biology Center, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson UniversityPhiladelphiaUnited States
| | - Rachel E Cain
- Department of Neuroscience, Jefferson Synaptic Biology Center, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson UniversityPhiladelphiaUnited States
| | - Davide Trotti
- Jefferson Weinberg ALS Center, Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Thomas Jefferson UniversityPhiladelphiaUnited States
| | - Piera Pasinelli
- Jefferson Weinberg ALS Center, Department of Neuroscience, Vickie and Jack Farber Institute for Neuroscience, Thomas Jefferson UniversityPhiladelphiaUnited States
| | - Megan C Wright
- Department of Biology, Arcadia UniversityGlensideUnited States
| | - Matthew B Dalva
- Department of Neuroscience, Jefferson Synaptic Biology Center, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson UniversityPhiladelphiaUnited States
- Department of Cell and Molecular Biology, Tulane Brain Institute, Tulane UniversityNew OrleansUnited States
| | - Angelo C Lepore
- Department of Neuroscience, Jefferson Synaptic Biology Center, Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson UniversityPhiladelphiaUnited States
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3
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Dalva MB. Brain cancer thrives by hijacking mechanisms to boost synapse strength. Nature 2023; 623:260-262. [PMID: 37932559 DOI: 10.1038/d41586-023-03306-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2023]
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4
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Urban MW, Charsar BA, Heinsinger NM, Markandaiah SS, Sprimont L, Zhou W, Brown EV, Henderson NT, Thomas SJ, Ghosh B, Cain RE, Trotti D, Pasinelli P, Wright MC, Dalva MB, Lepore AC. EphrinB2 knockdown in cervical spinal cord preserves diaphragm innervation in a mutant SOD1 mouse model of ALS. bioRxiv 2023:2023.05.10.538887. [PMID: 37215009 PMCID: PMC10197713 DOI: 10.1101/2023.05.10.538887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by motor neuron loss. Importantly, non-neuronal cell types such as astrocytes also play significant roles in disease pathogenesis. However, mechanisms of astrocyte contribution to ALS remain incompletely understood. Astrocyte involvement suggests that transcellular signaling may play a role in disease. We examined contribution of transmembrane signaling molecule ephrinB2 to ALS pathogenesis, in particular its role in driving motor neuron damage by spinal cord astrocytes. In symptomatic SOD1-G93A mice (a well-established ALS model), ephrinB2 expression was dramatically increased in ventral horn astrocytes. Reducing ephrinB2 in the cervical spinal cord ventral horn via viral-mediated shRNA delivery reduced motor neuron loss and preserved respiratory function by maintaining phrenic motor neuron innervation of diaphragm. EphrinB2 expression was also elevated in human ALS spinal cord. These findings implicate ephrinB2 upregulation as both a transcellular signaling mechanism in mutant SOD1-associated ALS and a promising therapeutic target.
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Ogunmowo TH, Jing H, Raychaudhuri S, Kusick GF, Imoto Y, Li S, Itoh K, Ma Y, Jafri H, Dalva MB, Chapman ER, Ha T, Watanabe S, Liu J. Membrane compression by synaptic vesicle exocytosis triggers ultrafast endocytosis. Nat Commun 2023; 14:2888. [PMID: 37210439 PMCID: PMC10199930 DOI: 10.1038/s41467-023-38595-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2022] [Accepted: 05/09/2023] [Indexed: 05/22/2023] Open
Abstract
Compensatory endocytosis keeps the membrane surface area of secretory cells constant following exocytosis. At chemical synapses, clathrin-independent ultrafast endocytosis maintains such homeostasis. This endocytic pathway is temporally and spatially coupled to exocytosis; it initiates within 50 ms at the region immediately next to the active zone where vesicles fuse. However, the coupling mechanism is unknown. Here, we demonstrate that filamentous actin is organized as a ring, surrounding the active zone at mouse hippocampal synapses. Assuming the membrane area conservation is due to this actin ring, our theoretical model suggests that flattening of fused vesicles exerts lateral compression in the plasma membrane, resulting in rapid formation of endocytic pits at the border between the active zone and the surrounding actin-enriched region. Consistent with model predictions, our data show that ultrafast endocytosis requires sufficient compression by exocytosis of multiple vesicles and does not initiate when actin organization is disrupted, either pharmacologically or by ablation of the actin-binding protein Epsin1. Our work suggests that membrane mechanics underlie the rapid coupling of exocytosis to endocytosis at synapses.
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Affiliation(s)
- Tyler H Ogunmowo
- Department of Cell Biology, School of Medicine, Johns Hopkins University, Baltimore, MD, US
- Center for Cell Dynamics, School of Medicine, Johns Hopkins University, Baltimore, MD, US
- Biochemistry, Cellular and Molecular Biology graduate program, Johns Hopkins University, Baltimore, MD, US
| | - Haoyuan Jing
- Department of Cell Biology, School of Medicine, Johns Hopkins University, Baltimore, MD, US
- Center for Cell Dynamics, School of Medicine, Johns Hopkins University, Baltimore, MD, US
| | - Sumana Raychaudhuri
- Department of Cell Biology, School of Medicine, Johns Hopkins University, Baltimore, MD, US
- Center for Cell Dynamics, School of Medicine, Johns Hopkins University, Baltimore, MD, US
| | - Grant F Kusick
- Department of Cell Biology, School of Medicine, Johns Hopkins University, Baltimore, MD, US
- Center for Cell Dynamics, School of Medicine, Johns Hopkins University, Baltimore, MD, US
- Biochemistry, Cellular and Molecular Biology graduate program, Johns Hopkins University, Baltimore, MD, US
| | - Yuuta Imoto
- Department of Cell Biology, School of Medicine, Johns Hopkins University, Baltimore, MD, US
- Center for Cell Dynamics, School of Medicine, Johns Hopkins University, Baltimore, MD, US
| | - Shuo Li
- Department of Cell Biology, School of Medicine, Johns Hopkins University, Baltimore, MD, US
- Center for Cell Dynamics, School of Medicine, Johns Hopkins University, Baltimore, MD, US
- Department of Ophthalmology, School of Medicine, Stanford University, Palo Alto, CA, US
| | - Kie Itoh
- Department of Cell Biology, School of Medicine, Johns Hopkins University, Baltimore, MD, US
- Center for Cell Dynamics, School of Medicine, Johns Hopkins University, Baltimore, MD, US
| | - Ye Ma
- Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD, US
| | - Haani Jafri
- Department of Neuroscience and Jefferson Synaptic Biology Center, Thomas Jefferson University, Philadelphia, PA, US
| | - Matthew B Dalva
- Department of Neuroscience and Jefferson Synaptic Biology Center, Thomas Jefferson University, Philadelphia, PA, US
- Department of Cell and Molecular Biology and the Tulane Brain Institute, Tulane University, New Orleans, LA, US
| | - Edwin R Chapman
- Department of Neuroscience, University of Wisconsin-Madison, Madison, WI, US
- Howard Hughes Medical Institute, Madison, WI, US
| | - Taekjip Ha
- Department of Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD, US
- Department of Biophysics and Biophysical Chemistry, School of Medicine, Johns Hopkins University, Baltimore, MD, US
- Department of Biophysics, Johns Hopkins University, Baltimore, MD, US
- Howard Hughes Medical Institute, Baltimore, MD, US
| | - Shigeki Watanabe
- Department of Cell Biology, School of Medicine, Johns Hopkins University, Baltimore, MD, US.
- Center for Cell Dynamics, School of Medicine, Johns Hopkins University, Baltimore, MD, US.
- Solomon H. Snyder Department of Neuroscience, School of Medicine, Johns Hopkins University, Baltimore, MD, US.
| | - Jian Liu
- Department of Cell Biology, School of Medicine, Johns Hopkins University, Baltimore, MD, US.
- Center for Cell Dynamics, School of Medicine, Johns Hopkins University, Baltimore, MD, US.
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6
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Washburn HR, Chander P, Srikanth KD, Dalva MB. Transsynaptic Signaling of Ephs in Synaptic Development, Plasticity, and Disease. Neuroscience 2023; 508:137-152. [PMID: 36460219 DOI: 10.1016/j.neuroscience.2022.11.030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 11/22/2022] [Accepted: 11/23/2022] [Indexed: 12/03/2022]
Abstract
Synapse formation between neurons is critical for proper circuit and brain function. Prior to activity-dependent refinement of connections between neurons, activity-independent cues regulate the contact and recognition of potential synaptic partners. Formation of a synapse results in molecular recognition events that initiate the process of synaptogenesis. Synaptogenesis requires contact between axon and dendrite, selection of correct and rejection of incorrect partners, and recruitment of appropriate pre- and postsynaptic proteins needed for the establishment of functional synaptic contact. Key regulators of these events are families of transsynaptic proteins, where one protein is found on the presynaptic neuron and the other is found on the postsynaptic neuron. Of these families, the EphBs and ephrin-Bs are required during each phase of synaptic development from target selection, recruitment of synaptic proteins, and formation of spines to regulation of synaptic plasticity at glutamatergic spine synapses in the mature brain. These roles also place EphBs and ephrin-Bs as important regulators of human neurological diseases. This review will focus on the role of EphBs and ephrin-Bs at synapses.
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Affiliation(s)
- Halley R Washburn
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA; Department of Neuroscience, Jefferson Synaptic Biology Center, Sidney Kimmel Medical College at Thomas Jefferson University, 233 South 10th Street, Bluemle Life Sciences Building, Room 324, Philadelphia, PA 19107, USA
| | - Praveen Chander
- Department of Neuroscience, Jefferson Synaptic Biology Center, Sidney Kimmel Medical College at Thomas Jefferson University, 233 South 10th Street, Bluemle Life Sciences Building, Room 324, Philadelphia, PA 19107, USA
| | - Kolluru D Srikanth
- Department of Neuroscience, Jefferson Synaptic Biology Center, Sidney Kimmel Medical College at Thomas Jefferson University, 233 South 10th Street, Bluemle Life Sciences Building, Room 324, Philadelphia, PA 19107, USA
| | - Matthew B Dalva
- Department of Neuroscience, Jefferson Synaptic Biology Center, Sidney Kimmel Medical College at Thomas Jefferson University, 233 South 10th Street, Bluemle Life Sciences Building, Room 324, Philadelphia, PA 19107, USA.
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Hruska M, Cain RE, Dalva MB. Nanoscale rules governing the organization of glutamate receptors in spine synapses are subunit specific. Nat Commun 2022; 13:920. [PMID: 35177616 PMCID: PMC8854560 DOI: 10.1038/s41467-022-28504-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 01/20/2022] [Indexed: 12/21/2022] Open
Abstract
Heterotetrameric glutamate receptors are essential for the development, function, and plasticity of spine synapses but how they are organized to achieve this is not known. Here we show that the nanoscale organization of glutamate receptors containing specific subunits define distinct subsynaptic features. Glutamate receptors containing GluA2 or GluN1 subunits establish nanomodular elements precisely positioned relative to Synaptotagmin-1 positive presynaptic release sites that scale with spine size. Glutamate receptors containing GluA1 or GluN2B specify features that exhibit flexibility: GluA1-subunit containing AMPARs are found in larger spines, while GluN2B-subunit containing NMDARs are enriched in the smallest spines with neither following a strict modular organization. Given that the precise positioning of distinct classes of glutamate receptors is linked to diverse events including cell death and synaptic plasticity, this unexpectedly robust synaptic nanoarchitecture provides a resilient system, where nanopositioned glutamate receptor heterotetramers define specific subsynaptic regions of individual spine synapses. Glutamate receptors comprise two obligate subunits and two subunits that confer distinct properties and functions to the specific tetramers, which also localize to distinct synaptic spines. Here, the authors use STimulated Emission Depletion nanoscopy (STED) to provide detailed insights into the spatial organization of glutamate receptor types.
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Affiliation(s)
- Martin Hruska
- Department of Neuroscience, Rockefeller Neuroscience Institute, West Virginia University, 108 Biomedical Road, Morgantown, WV, 26506, USA
| | - Rachel E Cain
- Department of Neuroscience and Jefferson Synaptic Biology Center, Sidney Kimmel Medical College at Thomas Jefferson University, 233 South 10th Street, Bluemle Life Sciences Building, Room 324, Philadelphia, PA, 19107, USA
| | - Matthew B Dalva
- Department of Neuroscience and Jefferson Synaptic Biology Center, Sidney Kimmel Medical College at Thomas Jefferson University, 233 South 10th Street, Bluemle Life Sciences Building, Room 324, Philadelphia, PA, 19107, USA.
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Hanamura K, Washburn HR, Sheffler-Collins SI, Xia NL, Henderson N, Tillu DV, Hassler S, Spellman DS, Zhang G, Neubert TA, Price TJ, Dalva MB. Correction: Extracellular phosphorylation of a receptor tyrosine kinase controls synaptic localization of NMDA receptors and regulates pathological pain. PLoS Biol 2021; 19:e3001452. [PMID: 34752444 PMCID: PMC8577777 DOI: 10.1371/journal.pbio.3001452] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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9
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Xu Y, Robev D, Saha N, Wang B, Dalva MB, Xu K, Himanen JP, Nikolov DB. The Ephb2 Receptor Uses Homotypic, Head-to-Tail Interactions within Its Ectodomain as an Autoinhibitory Control Mechanism. Int J Mol Sci 2021; 22:10473. [PMID: 34638814 PMCID: PMC8508685 DOI: 10.3390/ijms221910473] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 09/17/2021] [Accepted: 09/23/2021] [Indexed: 11/16/2022] Open
Abstract
The Eph receptor tyrosine kinases and their ephrin ligands direct axon pathfinding and neuronal cell migration, as well as mediate many other cell-cell communication events. Their dysfunctional signaling has been shown to lead to various diseases, including cancer. The Ephs and ephrins both localize to the plasma membrane and, upon cell-cell contact, form extensive signaling assemblies at the contact sites. The Ephs and the ephrins are divided into A and B subclasses based on their sequence conservation and affinities for each other. The molecular details of Eph-ephrin recognition have been previously revealed and it has been documented that ephrin binding induces higher-order Eph assemblies, which are essential for full biological activity, via multiple, distinct Eph-Eph interfaces. One Eph-Eph interface type is characterized by a homotypic, head-to-tail interaction between the ligand-binding and the fibronectin domains of two adjacent Eph molecules. While the previous Eph ectodomain structural studies were focused on A class receptors, we now report the crystal structure of the full ectodomain of EphB2, revealing distinct and unique head-to-tail receptor-receptor interactions. The EphB2 structure and structure-based mutagenesis document that EphB2 uses the head-to-tail interactions as a novel autoinhibitory control mechanism for regulating downstream signaling and that these interactions can be modulated by posttranslational modifications.
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Affiliation(s)
- Yan Xu
- Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210, USA; (Y.X.); (K.X.)
- Structural Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA; (D.R.); (N.S.)
| | - Dorothea Robev
- Structural Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA; (D.R.); (N.S.)
| | - Nayanendu Saha
- Structural Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA; (D.R.); (N.S.)
| | - Bingcheng Wang
- Rammelkamp Center for Research, MetroHealth Medical Center, 2500 MetroHealth Drive, Cleveland, OH 44109, USA;
| | - Matthew B. Dalva
- Department of Neuroscience and Jefferson Center for Synaptic Biology, Thomas Jefferson University, 233 South 10th Street, Bluemle Life Sciences Building, Room 324, Philadelphia, PA 19107, USA;
| | - Kai Xu
- Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210, USA; (Y.X.); (K.X.)
- Structural Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA; (D.R.); (N.S.)
| | - Juha P. Himanen
- Structural Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA; (D.R.); (N.S.)
| | - Dimitar B. Nikolov
- Structural Biology Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA; (D.R.); (N.S.)
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Henderson NT, Le Marchand SJ, Hruska M, Hippenmeyer S, Luo L, Dalva MB. Ephrin-B3 controls excitatory synapse density through cell-cell competition for EphBs. eLife 2019; 8:e41563. [PMID: 30789343 PMCID: PMC6384025 DOI: 10.7554/elife.41563] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Accepted: 01/31/2019] [Indexed: 11/13/2022] Open
Abstract
Cortical networks are characterized by sparse connectivity, with synapses found at only a subset of axo-dendritic contacts. Yet within these networks, neurons can exhibit high connection probabilities, suggesting that cell-intrinsic factors, not proximity, determine connectivity. Here, we identify ephrin-B3 (eB3) as a factor that determines synapse density by mediating a cell-cell competition that requires ephrin-B-EphB signaling. In a microisland culture system designed to isolate cell-cell competition, we find that eB3 determines winning and losing neurons in a contest for synapses. In a Mosaic Analysis with Double Markers (MADM) genetic mouse model system in vivo the relative levels of eB3 control spine density in layer 5 and 6 neurons. MADM cortical neurons in vitro reveal that eB3 controls synapse density independently of action potential-driven activity. Our findings illustrate a new class of competitive mechanism mediated by trans-synaptic organizing proteins which control the number of synapses neurons receive relative to neighboring neurons.
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Affiliation(s)
- Nathan T Henderson
- Department of Neuroscience, The Vickie and Jack Farber Institute for Neuroscience, Thomas Jefferson University, Philadelphia, United States
- Department of Neuroscience, University of Pennsylvania, Philadelphia, United States
| | | | - Martin Hruska
- Department of Neuroscience, The Vickie and Jack Farber Institute for Neuroscience, Thomas Jefferson University, Philadelphia, United States
| | - Simon Hippenmeyer
- Institute of Science and Technology Austria, Klosterneuburg, Austria
| | - Liqun Luo
- Department of Biology, Howard Hughes Medical Institute, Stanford University, Stanford, United States
| | - Matthew B Dalva
- Department of Neuroscience, The Vickie and Jack Farber Institute for Neuroscience, Thomas Jefferson University, Philadelphia, United States
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11
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Henderson NT, Dalva MB. EphBs and ephrin-Bs: Trans-synaptic organizers of synapse development and function. Mol Cell Neurosci 2018; 91:108-121. [PMID: 30031105 DOI: 10.1016/j.mcn.2018.07.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Revised: 07/17/2018] [Accepted: 07/18/2018] [Indexed: 12/31/2022] Open
Abstract
Synapses are specialized cell-cell junctions that underlie the function of neural circuits by mediating communication between neurons. Both the formation and function of synapses require tight coordination of signaling between pre- and post-synaptic neurons. Trans-synaptic organizing molecules are important mediators of such signaling. Here we discuss how the EphB and ephrin-B families of trans-synaptic organizing proteins direct synapse formation during early development and regulate synaptic function and plasticity at mature synapses. Finally, we highlight recent evidence linking the synaptic organizing role of EphBs and ephrin-Bs to diseases of maladaptive synaptic function and plasticity.
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Affiliation(s)
- Nathan T Henderson
- The Jefferson Synaptic Biology Center, Department of Neuroscience, The Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson University, Jefferson Hospital for Neuroscience, Suite 463, 900 Walnut St., Philadelphia, PA 19107, United States
| | - Matthew B Dalva
- The Jefferson Synaptic Biology Center, Department of Neuroscience, The Vickie and Jack Farber Institute for Neuroscience, Sidney Kimmel Medical College at Thomas Jefferson University, Jefferson Hospital for Neuroscience, Suite 463, 900 Walnut St., Philadelphia, PA 19107, United States.
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12
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Mao YT, Zhu JX, Hanamura K, Iurilli G, Datta SR, Dalva MB. Filopodia Conduct Target Selection in Cortical Neurons Using Differences in Signal Kinetics of a Single Kinase. Neuron 2018; 98:767-782.e8. [PMID: 29731254 DOI: 10.1016/j.neuron.2018.04.011] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Revised: 10/26/2017] [Accepted: 04/09/2018] [Indexed: 02/07/2023]
Abstract
Dendritic filopodia select synaptic partner axons by interviewing the cell surface of potential targets, but how filopodia decipher the complex pattern of adhesive and repulsive molecular cues to find appropriate contacts is unknown. Here, we demonstrate in cortical neurons that a single cue is sufficient for dendritic filopodia to reject or select specific axonal contacts for elaboration as synaptic sites. Super-resolution and live-cell imaging reveals that EphB2 is located in the tips of filopodia and at nascent synaptic sites. Surprisingly, a genetically encoded indicator of EphB kinase activity, unbiased classification, and a photoactivatable EphB2 reveal that simple differences in the kinetics of EphB kinase signaling at the tips of filopodia mediate the choice between retraction and synaptogenesis. This may enable individual filopodia to choose targets based on differences in the activation rate of a single tyrosine kinase, greatly simplifying the process of partner selection and suggesting a general principle.
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Affiliation(s)
- Yu-Ting Mao
- Department of Neuroscience and Jefferson Synaptic Biology Center, The Vickie and Jack Farber Institute, Jefferson Hospital for Neuroscience, Thomas Jefferson University, Suite 461, 900 Walnut Street, Philadelphia, PA 19107, USA
| | - Julia X Zhu
- Department of Neuroscience and Jefferson Synaptic Biology Center, The Vickie and Jack Farber Institute, Jefferson Hospital for Neuroscience, Thomas Jefferson University, Suite 461, 900 Walnut Street, Philadelphia, PA 19107, USA
| | - Kenji Hanamura
- Department of Neuroscience and Jefferson Synaptic Biology Center, The Vickie and Jack Farber Institute, Jefferson Hospital for Neuroscience, Thomas Jefferson University, Suite 461, 900 Walnut Street, Philadelphia, PA 19107, USA; Department of Neurobiology and Behavior, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi City, Gunma 371-8511, Japan
| | - Giuliano Iurilli
- Department of Neurobiology, Harvard Medical School, Room 336 Warren Alpert Building, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Sandeep Robert Datta
- Department of Neurobiology, Harvard Medical School, Room 336 Warren Alpert Building, 220 Longwood Avenue, Boston, MA 02115, USA
| | - Matthew B Dalva
- Department of Neuroscience and Jefferson Synaptic Biology Center, The Vickie and Jack Farber Institute, Jefferson Hospital for Neuroscience, Thomas Jefferson University, Suite 461, 900 Walnut Street, Philadelphia, PA 19107, USA.
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13
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Hanamura K, Washburn HR, Sheffler-Collins SI, Xia NL, Henderson N, Tillu DV, Hassler S, Spellman DS, Zhang G, Neubert TA, Price TJ, Dalva MB. Extracellular phosphorylation of a receptor tyrosine kinase controls synaptic localization of NMDA receptors and regulates pathological pain. PLoS Biol 2017; 15:e2002457. [PMID: 28719605 PMCID: PMC5515392 DOI: 10.1371/journal.pbio.2002457] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Accepted: 06/12/2017] [Indexed: 11/18/2022] Open
Abstract
Extracellular phosphorylation of proteins was suggested in the late 1800s when it was demonstrated that casein contains phosphate. More recently, extracellular kinases that phosphorylate extracellular serine, threonine, and tyrosine residues of numerous proteins have been identified. However, the functional significance of extracellular phosphorylation of specific residues in the nervous system is poorly understood. Here we show that synaptic accumulation of GluN2B-containing N-methyl-D-aspartate receptors (NMDARs) and pathological pain are controlled by ephrin-B-induced extracellular phosphorylation of a single tyrosine (p*Y504) in a highly conserved region of the fibronectin type III (FN3) domain of the receptor tyrosine kinase EphB2. Ligand-dependent Y504 phosphorylation modulates the EphB-NMDAR interaction in cortical and spinal cord neurons. Furthermore, Y504 phosphorylation enhances NMDAR localization and injury-induced pain behavior. By mediating inducible extracellular interactions that are capable of modulating animal behavior, extracellular tyrosine phosphorylation of EphBs may represent a previously unknown class of mechanism mediating protein interaction and function. The activity of proteins can be finely and reversibly tuned by post-translational modifications. The attachment of phosphate groups to tyrosine residues is one of such modifications. While the existence of extracellular phosphoproteins has been known, the functional significance of extracellular phosphorylation is poorly understood. Here we describe a single extracellular tyrosine whose inducible phosphorylation may represent an archetype for a new class of mechanism mediating protein—protein interaction and regulating protein function. We show that the interaction between EphB2—which occurs upon receptor activation by its ligand ephrin-B—and the N-methyl-D-aspartate receptor (NMDAR) depends on extracellular phosphorylation of EphB2. This interaction regulates the localization of the NMDA receptor to synaptic sites in neurons. In vivo, EphB2 is phosphorylated in response to injury, and the subsequent up-regulation of the interaction between EphB2 and NMDA receptors enhances injury-induced pain behavior and mechanical hypersensitivity in mice. Importantly, our study defines a specific extracellular phosphorylation event as a mechanism driving protein interaction and suggests that extracellular phosphorylation of proteins is an underappreciated mechanism contributing to the development and function of the nervous system and synapse.
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Affiliation(s)
- Kenji Hanamura
- Department of Neuroscience and Farber Institute for Neurosciences, Thomas Jefferson University, Jefferson Hospital for Neuroscience, Philadelphia, Pennsylvania, United States of America
- Department of Neurobiology and Behavior, Gunma University Graduate School of Medicine, Maebashi City, Gunma, Japan
| | - Halley R. Washburn
- Department of Neuroscience and Farber Institute for Neurosciences, Thomas Jefferson University, Jefferson Hospital for Neuroscience, Philadelphia, Pennsylvania, United States of America
| | - Sean I. Sheffler-Collins
- Department of Neuroscience and Farber Institute for Neurosciences, Thomas Jefferson University, Jefferson Hospital for Neuroscience, Philadelphia, Pennsylvania, United States of America
- Neuroscience Graduate Group, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Nan L. Xia
- Department of Neuroscience and Farber Institute for Neurosciences, Thomas Jefferson University, Jefferson Hospital for Neuroscience, Philadelphia, Pennsylvania, United States of America
| | - Nathan Henderson
- Department of Neuroscience and Farber Institute for Neurosciences, Thomas Jefferson University, Jefferson Hospital for Neuroscience, Philadelphia, Pennsylvania, United States of America
| | - Dipti V. Tillu
- Department of Pharmacology, University of Arizona College of Medicine, Tucson, Arizona, United States of America
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas, United States of America
| | - Shayne Hassler
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas, United States of America
| | - Daniel S. Spellman
- Department of Cell Biology and Kimmel Center for Biology and Medicine at the Skirball Institute, New York University School of Medicine, New York, New York, United States of America
| | - Guoan Zhang
- Department of Cell Biology and Kimmel Center for Biology and Medicine at the Skirball Institute, New York University School of Medicine, New York, New York, United States of America
| | - Thomas A. Neubert
- Department of Cell Biology and Kimmel Center for Biology and Medicine at the Skirball Institute, New York University School of Medicine, New York, New York, United States of America
| | - Theodore J. Price
- Department of Pharmacology, University of Arizona College of Medicine, Tucson, Arizona, United States of America
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas, United States of America
| | - Matthew B. Dalva
- Department of Neuroscience and Farber Institute for Neurosciences, Thomas Jefferson University, Jefferson Hospital for Neuroscience, Philadelphia, Pennsylvania, United States of America
- * E-mail:
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14
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Poliak S, Morales D, Croteau LP, Krawchuk D, Palmesino E, Morton S, Cloutier JF, Charron F, Dalva MB, Ackerman SL, Kao TJ, Kania A. Synergistic integration of Netrin and ephrin axon guidance signals by spinal motor neurons. eLife 2015; 4. [PMID: 26633881 PMCID: PMC4764565 DOI: 10.7554/elife.10841] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 12/02/2015] [Indexed: 01/09/2023] Open
Abstract
During neural circuit assembly, axonal growth cones are exposed to multiple guidance signals at trajectory choice points. While axonal responses to individual guidance cues have been extensively studied, less is known about responses to combination of signals and underlying molecular mechanisms. Here, we studied the convergence of signals directing trajectory selection of spinal motor axons entering the limb. We first demonstrate that Netrin-1 attracts and repels distinct motor axon populations, according to their expression of Netrin receptors. Quantitative in vitro assays demonstrate that motor axons synergistically integrate both attractive or repulsive Netrin-1 signals together with repulsive ephrin signals. Our investigations of the mechanism of ephrin-B2 and Netrin-1 integration demonstrate that the Netrin receptor Unc5c and the ephrin receptor EphB2 can form a complex in a ligand-dependent manner and that Netrin–ephrin synergistic growth cones responses involve the potentiation of Src family kinase signaling, a common effector of both pathways. DOI:http://dx.doi.org/10.7554/eLife.10841.001 The ability of animals to walk and perform skilled movements depends on particular groups of muscles contracting in a coordinated manner. Muscles are activated by nerve cells called motor neurons found in the spinal cord. The connections between the motor neurons and muscles are established in the developing embryo. Each motor neuron produces a long projection called an axon whose growth is guided towards the target muscle by signal proteins. The motor neurons are exposed to many such signal proteins at the same time and it is not clear how they integrate all this information so that their axons target the correct muscles. Poliak, Morales et al. used a variety of genetic and biochemical approaches to study the formation of motor neuron and muscle connections in the limbs of mice and chicks. The experiments show that a signal protein called Netrin-1 is produced in the limbs of developing embryos and attracts the axons of some types of motor neurons and repels others. This is due to the motor neurons producing different types of receptor proteins to detect Netrin-1. Further experiments show that individual axons can combine information from attractive or repulsive Netrin-1 signals together with repulsive signals from another family of proteins called ephrins in a 'synergistic' manner. That is, the combined effect of both cues is stronger than their individual effects added together. This synergy involves ligand-dependent interactions between the Netrin-1 and ephrin receptor proteins, and the activation of a common enzyme. Poliak, Morales et al.’s findings reveal a new role for Netrin-1 in guiding the development of motor neurons in the limb. Future work will focus on further understanding the mechanism of synergy between Netrin-1 and ephrins. Netrin-1 and ephrins are also involved in the formation of blood vessels and many other developmental processes, so understanding how they work together would have a wide-reaching impact on research into human health and disease. DOI:http://dx.doi.org/10.7554/eLife.10841.002
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Affiliation(s)
- Sebastian Poliak
- Department of Neuroscience, Columbia University, New York, United States.,Department of Biochemistry and Molecular Biophysics, Columbia University, New York, United States
| | - Daniel Morales
- Institut de recherches cliniques de Montréal, Montréal, Canada.,Integrated Program in Neuroscience, McGill University, Montréal, Canada
| | | | - Dayana Krawchuk
- Institut de recherches cliniques de Montréal, Montréal, Canada.,The Jackson Laboratory, Bar Harbor, United States
| | - Elena Palmesino
- Institut de recherches cliniques de Montréal, Montréal, Canada
| | - Susan Morton
- Department of Neuroscience, Columbia University, New York, United States.,Department of Biochemistry and Molecular Biophysics, Columbia University, New York, United States.,Howard Hughes Medical Institute, Columbia University, New York, United States
| | - Jean-François Cloutier
- Integrated Program in Neuroscience, McGill University, Montréal, Canada.,Montréal Neurological Institute, Montréal, Canada
| | - Frederic Charron
- Institut de recherches cliniques de Montréal, Montréal, Canada.,Faculté de Médecine, Université de Montréal, Montréal, Canada.,Department of Biology, McGill University, Montréal, Canada.,Department of Anatomy and Cell Biology, McGill University, Montréal, Canada.,Division of Experimental Medicine, McGill University, Montréal, Canada
| | - Matthew B Dalva
- Department of Neuroscience, The Farber Institute for Neurosciences, Jefferson Hospital for Neuroscience, Thomas Jefferson University, Philadelphia, United States
| | - Susan L Ackerman
- The Jackson Laboratory, Bar Harbor, United States.,Howard Hughes Medical Institute, The Jackson Laboratory, Bar Harbor, United States
| | - Tzu-Jen Kao
- Institut de recherches cliniques de Montréal, Montréal, Canada.,Graduate Institute of Neural Regenerative Medicine, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan.,Center for Neurotrauma and Neuroregeneration, Taipei Medical University, Taipei, Taiwan
| | - Artur Kania
- Institut de recherches cliniques de Montréal, Montréal, Canada.,Faculté de Médecine, Université de Montréal, Montréal, Canada.,Integrated Program in Neuroscience, McGill University, Montréal, Canada.,Department of Biology, McGill University, Montréal, Canada.,Department of Anatomy and Cell Biology, McGill University, Montréal, Canada.,Division of Experimental Medicine, McGill University, Montréal, Canada
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15
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Hruska M, Henderson NT, Xia NL, Le Marchand SJ, Dalva MB. Anchoring and synaptic stability of PSD-95 is driven by ephrin-B3. Nat Neurosci 2015; 18:1594-605. [PMID: 26479588 PMCID: PMC5396457 DOI: 10.1038/nn.4140] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 09/17/2015] [Indexed: 02/07/2023]
Abstract
Organization of signaling complexes at excitatory synapses by Membrane Associated Guanylate Kinase (MAGUK) proteins regulates synapse development, plasticity, senescence, and disease. Post-translational modification of MAGUK family proteins can drive their membrane localization, yet it is unclear how these intracellular proteins are targeted to sites of synaptic contact. Here we show using super-resolution imaging, biochemical approaches, and in vivo models that the trans-synaptic organizing protein, ephrin-B3, controls the synaptic localization and stability of PSD-95 and links these events to changes in neuronal activity via negative regulation of a novel MAPK-dependent phosphorylation site on ephrin-B3 (S332). Unphosphorylated ephrin-B3 is enriched at synapses, interacts directly with and stabilizes PSD-95 at synapses. Activity induced phosphorylation of S332 disperses ephrin-B3 from synapses, prevents the interaction with, and enhances the turnover of PSD-95. Thus, ephrin-B3 specifies the synaptic localization of PSD-95 and likely links the synaptic stability of PSD-95 to changes in neuronal activity.
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Affiliation(s)
- Martin Hruska
- Department of Neuroscience and the Farber Institute for Neuroscience, Thomas Jefferson University, Jefferson Hospital for Neuroscience, Philadelphia, Pennsylvania, USA
| | - Nathan T Henderson
- Department of Neuroscience and the Farber Institute for Neuroscience, Thomas Jefferson University, Jefferson Hospital for Neuroscience, Philadelphia, Pennsylvania, USA
| | - Nan L Xia
- Department of Neuroscience and the Farber Institute for Neuroscience, Thomas Jefferson University, Jefferson Hospital for Neuroscience, Philadelphia, Pennsylvania, USA
| | - Sylvain J Le Marchand
- Department of Neuroscience and the Farber Institute for Neuroscience, Thomas Jefferson University, Jefferson Hospital for Neuroscience, Philadelphia, Pennsylvania, USA
| | - Matthew B Dalva
- Department of Neuroscience and the Farber Institute for Neuroscience, Thomas Jefferson University, Jefferson Hospital for Neuroscience, Philadelphia, Pennsylvania, USA
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16
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Jepson JEC, Shahidullah M, Liu D, le Marchand SJ, Liu S, Wu MN, Levitan IB, Dalva MB, Koh K. Regulation of synaptic development and function by the Drosophila PDZ protein Dyschronic. Development 2014; 141:4548-57. [PMID: 25359729 DOI: 10.1242/dev.109538] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Synaptic scaffold proteins control the localization of ion channels and receptors, and facilitate molecular associations between signaling components that modulate synaptic transmission and plasticity. Here, we define novel roles for a recently described scaffold protein, Dsychronic (DYSC), at the Drosophila larval neuromuscular junction. DYSC is the Drosophila homolog of whirlin/DFNB31, a PDZ domain protein linked to Usher syndrome, the most common form of human deaf-blindness. We show that DYSC is expressed presynaptically and is often localized adjacent to the active zone, the site of neurotransmitter release. Loss of DYSC results in marked alterations in synaptic morphology and cytoskeletal organization. Moreover, active zones are frequently enlarged and misshapen in dysc mutants. Electrophysiological analyses further demonstrate that dysc mutants exhibit substantial increases in both evoked and spontaneous synaptic transmission. We have previously shown that DYSC binds to and regulates the expression of the Slowpoke (SLO) BK potassium channel. Consistent with this, slo mutant larvae exhibit similar alterations in synapse morphology, active zone size and neurotransmission, and simultaneous loss of dysc and slo does not enhance these phenotypes, suggesting that dysc and slo act in a common genetic pathway to modulate synaptic development and output. Our data expand our understanding of the neuronal functions of DYSC and uncover non-canonical roles for the SLO potassium channel at Drosophila synapses.
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Affiliation(s)
- James E C Jepson
- Department of Neuroscience, The Farber Institute for Neurosciences, Thomas Jefferson University, Philadelphia, PA 19107, USA UCL Institute of Neurology, London WC1N 3BG, UK
| | - Mohammed Shahidullah
- Department of Neuroscience, The Farber Institute for Neurosciences, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Die Liu
- Department of Neuroscience, The Farber Institute for Neurosciences, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Sylvain J le Marchand
- Department of Neuroscience, The Farber Institute for Neurosciences, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Sha Liu
- Department of Neurology, John Hopkins University, Baltimore, MD 21287, USA
| | - Mark N Wu
- Department of Neurology, John Hopkins University, Baltimore, MD 21287, USA
| | - Irwin B Levitan
- Department of Neuroscience, The Farber Institute for Neurosciences, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Matthew B Dalva
- Department of Neuroscience, The Farber Institute for Neurosciences, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Kyunghee Koh
- Department of Neuroscience, The Farber Institute for Neurosciences, Thomas Jefferson University, Philadelphia, PA 19107, USA
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17
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Dai J, Buhusi M, Demyanenko GP, Brennaman LH, Hruska M, Dalva MB, Maness PF. Neuron glia-related cell adhesion molecule (NrCAM) promotes topographic retinocollicular mapping. PLoS One 2013; 8:e73000. [PMID: 24023801 PMCID: PMC3759449 DOI: 10.1371/journal.pone.0073000] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Accepted: 07/16/2013] [Indexed: 11/18/2022] Open
Abstract
NrCAM (Neuron-glial related cell adhesion molecule), a member of the L1 family of cell adhesion molecules, reversibly binds ankyrin and regulates axon growth, but it has not been studied for a role in retinotopic mapping. During development of retino-collicular topography, NrCAM was expressed uniformly in retinal ganglion cells (RGCs) along both mediolateral and anteroposterior retinal axes, and was localized on RGC axons within the optic tract and superior colliculus (SC). Anterograde tracing of RGC axons in NrCAM null mutant mice at P10, when the map resembles its mature form, revealed laterally displaced ectopic termination zones (eTZs) of axons from the temporal retina, indicating defective mediolateral topography, which is governed by ephrinB/EphBs. Axon tracing at P2 revealed that interstitial branch orientation of ventral-temporal RGC axons in NrCAM null mice was compromised in the medial direction, likely accounting for displacement of eTZs. A similar retinocollicular targeting defect in EphB mutant mice suggested that NrCAM and EphB interact to regulate mediolateral retino-collicular targeting. We found that EphB2 tyrosine kinase but not an EphB2 kinase dead mutant, phosphorylated NrCAM at a conserved tyrosine residue in the FIGQY ankyrin binding motif, perturbing ankyrin recruitment in NrCAM transfected HEK293 cells. Furthermore, the phosphorylation of NrCAM at FIGQY in SC was decreased in EphB1/3 and EphB1/2/3 null mice compared to WT, while phospho-FIGQY of NrCAM in SC was increased in EphB2 constitutively active (F620D/F620D) mice. These results demonstrate that NrCAM contributes to mediolateral retinocollicular axon targeting by regulating RGC branch orientation through a likely mechanism in which ephrinB/EphB phosphorylates NrCAM to modulate linkage to the actin cytoskeleton.
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Affiliation(s)
- Jinxia Dai
- Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina, United States of America
| | - Mona Buhusi
- Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina, United States of America
| | - Galina P. Demyanenko
- Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina, United States of America
| | - Leann H. Brennaman
- Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina, United States of America
| | - Martin Hruska
- Thomas Jefferson University, Department of Neuroscience, Jefferson Hospital for Neuroscience, Philadelphia, Pennsylvania, United States of America
| | - Matthew B. Dalva
- Thomas Jefferson University, Department of Neuroscience, Jefferson Hospital for Neuroscience, Philadelphia, Pennsylvania, United States of America
| | - Patricia F. Maness
- Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina, United States of America
- * E-mail:
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18
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Sheffler-Collins SI, Dalva MB. EphBs: an integral link between synaptic function and synaptopathies. Trends Neurosci 2012; 35:293-304. [PMID: 22516618 DOI: 10.1016/j.tins.2012.03.003] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2012] [Revised: 03/08/2012] [Accepted: 03/08/2012] [Indexed: 11/19/2022]
Abstract
The assembly and function of neuronal circuits rely on selective cell-cell interactions to control axon targeting, generate pre- and postsynaptic specialization and recruit neurotransmitter receptors. In neurons, EphB receptor tyrosine kinases mediate excitatory synaptogenesis early during development, and then later coordinate synaptic function by controlling synaptic glutamate receptor localization and function. EphBs direct synapse formation and function to regulate cellular morphology through downstream signaling mechanisms and by interacting with glutamate receptors. In humans, defective EphB-dependent regulation of NMDA receptor (NMDAR) localization and function is associated with neurological disorders, including neuropathic pain, anxiety disorders and Alzheimer's disease (AD). Here, we propose that EphBs act as a central organizer of excitatory synapse formation and function, and as a key regulator of diseases linked to NMDAR dysfunction.
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Affiliation(s)
- Sean I Sheffler-Collins
- Department of Neuroscience and Farber Institute for Neurosciences, Thomas Jefferson University, 900 Walnut Street, Suite 462, Philadelphia, PA 19107, USA
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19
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Abstract
Synapses enable the transmission of information within neural circuits and allow the brain to change in response to experience. During the last decade numerous proteins that can induce synapse formation have been identified. Many of these synaptic inducers rely on trans-synaptic cell-cell interactions to generate functional contacts. Moreover, evidence now suggests that the same proteins that function early in development to regulate synapse formation may help to maintain and/or regulate the function and plasticity of mature synapses. One set of receptors and ligands that appear to impact both the development and the mature function of synapses are Eph receptors (erythropoietin-producing human hepatocellular carcinoma cell line) and their surface associated ligands, ephrins (Eph family receptor interacting proteins). Ephs can initiate new synaptic contacts, recruit and stabilize glutamate receptors at nascent synapses and regulate dendritic spine morphology. Recent evidence demonstrates that ephrin ligands also play major roles at synapses. Activation of ephrins by Eph receptors can induce synapse formation and spine morphogenesis, whereas in the mature nervous system ephrin signaling modulates synaptic function and long-term changes in synaptic strength. In this review we will summarize the recent progress in understanding the role of ephrins in presynaptic and postsynaptic differentiation, and synapse development, function and plasticity.
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Affiliation(s)
- Martin Hruska
- Department of Neuroscience and the Farber Institute, Thomas Jefferson University, Philadelphia, PA 19107, USA.
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20
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Abstract
The flow of information between neurons in many neural circuits is controlled by a highly specialized site of cell-cell contact known as a synapse. A number of molecules have been identified that are involved in central nervous system synapse development, but knowledge is limited regarding whether these cues direct organization of specific synapse types or on particular regions of individual neurons. Glutamate is the primary excitatory neurotransmitter in the brain, and the majority of glutamatergic synapses occur on mushroom-shaped protrusions called dendritic spines. Changes in the morphology of these structures are associated with long-lasting modulation of synaptic strength thought to underlie learning and memory, and can be abnormal in neuropsychiatric disease. Here, we use rat cortical slice cultures to examine how a previously-described synaptogenic molecule, the EphB2 receptor tyrosine kinase, regulates dendritic protrusion morphology in specific regions of the dendritic arbor in cortical pyramidal neurons. We find that alterations in EphB2 signaling can bidirectionally control protrusion length, and knockdown of EphB2 expression levels reduces the number of dendritic spines and filopodia. Expression of wild-type or dominant negative EphB2 reveals that EphB2 preferentially regulates dendritic protrusion structure in basal dendrites. Our findings suggest that EphB2 may act to specify synapse formation in a particular subcellular region of cortical pyramidal neurons.
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Affiliation(s)
- Matthew S. Kayser
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Anderson C. Lee
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Martin Hruska
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
| | - Matthew B. Dalva
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America
- * E-mail:
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21
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Abstract
Alterations in synapse number and morphology are associated with devastating psychiatric and neurologic disorders. In this issue of Cell, Margolis et al. (2010) show that the RhoA-guanine exchange factor (GEF) Ephexin5 limits the numbers of excitatory synapses that neurons receive, thus identifying a new mechanism controlling synaptogenesis.
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Affiliation(s)
- Matthew B Dalva
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, 19104, USA.
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22
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Antion MD, Christie LA, Bond AM, Dalva MB, Contractor A. Ephrin-B3 regulates glutamate receptor signaling at hippocampal synapses. Mol Cell Neurosci 2010; 45:378-88. [PMID: 20678574 DOI: 10.1016/j.mcn.2010.07.011] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2009] [Revised: 07/16/2010] [Accepted: 07/20/2010] [Indexed: 11/26/2022] Open
Abstract
B-ephrin-EphB receptor signaling modulates NMDA receptors by inducing tyrosine phosphorylation of NR2 subunits. Ephrins and EphB RTKs are localized to postsynaptic compartments in the CA1, and therefore potentially interact in a non-canonical cis- configuration. However, it is not known whether cis- configured receptor-ligand signaling is utilized by this class of RTKs, and whether this might influence excitatory synapses. We found that ablation of ephrin-B3 results in an enhancement of the NMDA receptor component of synaptic transmission relative to the AMPA receptor component in CA1 synapses. Synaptic AMPA receptor expression is reduced in ephrin-B3 knockout mice, and there is a marked enhancement of tyrosine phosphorylation of the NR2B receptor subunit. In a reduced system co-expression of ephrin-B3 attenuated EphB2-mediated NR2B tyrosine phosphorylation. Moreover, phosphorylation of EphB2 was elevated in the hippocampus of ephrin-B3 knockout mice, suggesting that regulation of EphB2 activity is lost in these mice. Direct activation of EphB RTKs resulted in phosphorylation of NR2B and a potential signaling partner, the non-receptor tyrosine kinase Pyk2. Our data suggests that ephrin-B3 limits EphB RTK-mediated phosphorylation of the NR2B subunit through an inhibitory cis- interaction which is required for the correct function of glutamatergic CA1 synapses.
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Affiliation(s)
- Marcia D Antion
- Department of Physiology, Northwestern University Feinberg School of Medicine, 303 E Chicago Ave, Chicago, Il 60611, USA
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23
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Abstract
Background In the visual cortex, as in many other regions of the developing brain, excitatory synaptic connections undergo substantial remodeling during development. While evidence suggests that local inhibitory synapses may behave similarly, the extent and mechanisms that mediate remodeling of inhibitory connections are not well understood. Results Using scanning laser photostimulation in slices of developing ferret visual cortex, we assessed the overall patterns of developing inhibitory and excitatory synaptic connections converging onto individual neurons. Inhibitory synaptic inputs onto pyramidal neurons in cortical layers 2 and 3 were already present as early as postnatal day 20, well before eye opening, and originated from regions close to the recorded neurons. During the ensuing 2 weeks, the numbers of synaptic inputs increased, with the numbers of inhibitory (and excitatory) synaptic inputs peaking near the time of eye opening. The pattern of inhibitory inputs refined rapidly prior to the refinement of excitatory inputs. By uncaging the neurotransmtter GABA in brain slices from animals of different ages, we find that this rapid refinement correlated with a loss of excitatory activity by GABA. Conclusion Inhibitory synapses, like excitatory synapses, undergo significant postnatal remodeling. The time course of the remodeling of inhibitory connections correlates with the emergence of orientation tuning in the visual cortex, implicating these rearrangements in the genesis of adult cortical response properties.
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Affiliation(s)
- Matthew B Dalva
- Department of Neuroscience, BRB II/III rm 1114, University of Pennsylvania Medical School, 421 Curie Blvd, Philadelphia, PA 19104, USA.
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24
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Abstract
Many neuronal proteins undergo lipid modification that regulates their function and subcellular localization. One such modification is palmitoylation, which is mediated by a large class of protein palmitoyl acyltransferases (PATs). Now, a paper in this issue (Noritake et al. 2009. J. Cell Biol. doi:10.1083/jcb.200903101) demonstrates that the localization of the PAT DHHC2 is regulated by neuronal activity and thereby selectively controls the palmitoylation and subsequent accumulation of specific proteins in the synapse.
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Affiliation(s)
- Matthew B Dalva
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
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25
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Abstract
In two manuscripts published in Neuron (Beg et al. and Wegmeyer et al.) and one published in Cell (Iwasato et al.), investigators have found that a particular GAP, alpha-chimaerin, is required in vivo for ephrinB3/EphA4-dependent motor circuit formation.
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Affiliation(s)
- Matthew B Dalva
- Department of Neuroscience, University of Pennsylvania Medical Center, Philadelphia, PA 19104, USA.
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26
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Abstract
Many cell adhesion molecules are localized at synaptic sites in neuronal axons and dendrites. These molecules bridge pre- and postsynaptic specializations but do far more than simply provide a mechanical link between cells. In this review, we will discuss the roles these proteins have during development and at mature synapses. Synaptic adhesion proteins participate in the formation, maturation, function and plasticity of synaptic connections. Together with conventional synaptic transmission mechanisms, these molecules are an important element in the trans-cellular communication mediated by synapses.
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Affiliation(s)
- Matthew B Dalva
- University of Pennsylvania Medical Center, Department of Neuroscience, BRB II/III, Room 1114, 421 Curie Blvd., Philadelphia, Pennsylvania 19104, USA.
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27
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Abstract
The majority of mature excitatory synapses in the CNS are found on dendritic spines and contain AMPA- and NMDA-type glutamate receptors apposed to presynaptic specializations. EphB receptor tyrosine kinase signaling has been implicated in both NMDA-type glutamate receptor clustering and dendritic spine formation, but it remains unclear whether EphB plays a broader role in presynaptic and postsynaptic development. Here, we find that EphB2 is involved in organizing excitatory synapses through the independent activities of particular EphB2 protein domains. We demonstrate that EphB2 controls AMPA-type glutamate receptor localization through PDZ (postsynaptic density-95/Discs large/zona occludens-1) binding domain interactions and triggers presynaptic differentiation via its ephrin binding domain. Knockdown of EphB2 in dissociated neurons results in decreased functional synaptic inputs, spines, and presynaptic specializations. Mice lacking EphB1-EphB3 have reduced numbers of synapses, and defects are rescued with postnatal reexpression of EphB2 in single neurons in brain slice. These results demonstrate that EphB2 acts to control the organization of specific classes of mature glutamatergic synapses.
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Affiliation(s)
- Matthew S. Kayser
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104
| | - Andrew C. McClelland
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104
| | - Ethan G. Hughes
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104
| | - Matthew B. Dalva
- Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104
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28
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Abstract
Protein-protein interactions and calcium entry through the N-methyl-d-aspartate (NMDA)-type glutamate receptor regulate synaptic development and plasticity in the central nervous system. The EphB receptor tyrosine kinases are localized at excitatory synapses where they cluster and associate with NMDA receptors. We identified a mechanism whereby EphBs modulate NMDA receptor function. EphrinB2 activation of EphB in primary cortical neurons potentiates NMDA receptor-dependent influx of calcium. Treatment of cells with ephrinB2 led to NMDA receptor tyrosine phosphorylation through activation of the Src family of tyrosine kinases. These ephrinB2-dependent events result in enhanced NMDA receptor-dependent gene expression. Our findings indicate that ephrinB2 stimulation of EphB modulates the functional consequences of NMDA receptor activation and suggest a mechanism whereby activity-independent and activity-dependent signals converge to regulate the development and remodeling of synaptic connections.
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Affiliation(s)
- Mari A Takasu
- Division of Neuroscience, Children's Hospital, and the Department of Neurobiology, Harvard Medical School, 300 Longwood Avenue, Boston, MA 02115, USA
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29
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West AE, Chen WG, Dalva MB, Dolmetsch RE, Kornhauser JM, Shaywitz AJ, Takasu MA, Tao X, Greenberg ME. Calcium regulation of neuronal gene expression. Proc Natl Acad Sci U S A 2001; 98:11024-31. [PMID: 11572963 PMCID: PMC58677 DOI: 10.1073/pnas.191352298] [Citation(s) in RCA: 781] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Plasticity is a remarkable feature of the brain, allowing neuronal structure and function to accommodate to patterns of electrical activity. One component of these long-term changes is the activity-driven induction of new gene expression, which is required for both the long-lasting long-term potentiation of synaptic transmission associated with learning and memory, and the activity dependent survival events that help to shape and wire the brain during development. We have characterized molecular mechanisms by which neuronal membrane depolarization and subsequent calcium influx into the cytoplasm lead to the induction of new gene transcription. We have identified three points within this cascade of events where the specificity of genes induced by different types of stimuli can be regulated. By using the induction of the gene that encodes brain-derived neurotrophic factor (BDNF) as a model, we have found that the ability of a calcium influx to induce transcription of this gene is regulated by the route of calcium entry into the cell, by the pattern of phosphorylation induced on the transcription factor cAMP-response element (CRE) binding protein (CREB), and by the complement of active transcription factors recruited to the BDNF promoter. These results refine and expand the working model of activity-induced gene induction in the brain, and help to explain how different types of neuronal stimuli can activate distinct transcriptional responses.
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Affiliation(s)
- A E West
- Division of Neuroscience, Children's Hospital, 300 Longwood Avenue, Boston, MA 02115, USA
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30
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Abstract
EphB receptor tyrosine kinases are enriched at synapses, suggesting that these receptors play a role in synapse formation or function. We find that EphrinB binding to EphB induces a direct interaction of EphB with NMDA-type glutamate receptors. This interaction occurs at the cell surface and is mediated by the extracellular regions of the two receptors, but does not require the kinase activity of EphB. The kinase activity of EphB may be important for subsequent steps in synapse formation, as perturbation of EphB tyrosine kinase activity affects the number of synaptic specializations that form in cultured neurons. These findings indicate that EphrinB activation of EphB promotes an association of EphB with NMDA receptors that may be critical for synapse development or function.
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Affiliation(s)
- M B Dalva
- Division of Neuroscience, Children's Hospital, and the Department of Neurobiology Harvard Medical School 02115, Boston, MA, USA
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31
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Spiro JE, Dalva MB, Mooney R. Long-range inhibition within the zebra finch song nucleus RA can coordinate the firing of multiple projection neurons. J Neurophysiol 1999; 81:3007-20. [PMID: 10368416 DOI: 10.1152/jn.1999.81.6.3007] [Citation(s) in RCA: 132] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The zebra finch forebrain song control nucleus RA (robust nucleus of the archistriatum) generates a phasic and temporally precise neural signal that drives vocal and respiratory motoneurons during singing. RA's output during singing predicts individual notes, even though afferent drive to RA from the song nucleus HVc is more tonic, and predicts song syllables, independent of the particular notes that comprise the syllable. Therefore RA's intrinsic circuitry transforms neural activity from HVc into a highly precise premotor output. To understand how RA's intrinsic circuitry effects this transformation, we characterized RA interneurons and projection neurons using intracellular recordings in brain slices. RA interneurons fired fast action potentials with steep current-frequency relationships and had small somata with thin aspinous processes that extended throughout large portions of the nucleus; the similarity of their fine processes to those labeled with a glutamic acid decarboxylase (GAD) antibody strongly suggests that these interneurons are GABAergic. Electrical stimulation revealed that RA interneurons receive excitatory inputs from RA's afferents, the lateral magnocellular nucleus of the anterior neostriatum (LMAN) and HVc, and from local axon collaterals of RA projection neurons. To map the functional connections that RA interneurons make onto RA projection neurons, we focally uncaged glutamate, revealing long-range inhibitory connections in RA. Thus these interneurons provide fast feed-forward and feedback inhibition to RA projection neurons and could help create the phasic pattern of bursts and pauses that characterizes RA output during singing. Furthermore, selectively activating the inhibitory network phase locks the firing of otherwise unconnected pairs of projection neurons, suggesting that local inhibition could coordinate RA output during singing.
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Affiliation(s)
- J E Spiro
- Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710, USA
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32
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Abstract
Learning, making memories, and forgetting are thought to require changes in the strengths of connections between neurons. Such changes in synaptic strength occur in two phases: an early phase that is likely mediated by covalent modifications to existing proteins, and a delayed phase that depends on new gene expression and protein synthesis. However, the biochemical mechanisms by which neuronal activity leads to changes in synaptic strength are poorly understood. Recently, it has been shown that animals that lack Ras guanine nucleotide releasing factor (Ras-GRF), a Ca(2+)-dependent activator of the small GTP-binding protein, Ras, do not learn fear responses normally, although other types of learning appear normal. These animals show defects in the delayed phase of memory formation within the neuronal circuit that mediates fear conditioning. This paper suggests that Ras-GRF couples synaptic activity to the molecular mechanisms that consolidate changes in synaptic strength within specific neuronal circuits.
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Affiliation(s)
- S Finkbeiner
- Department of Neurology, Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
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33
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Abstract
Combined optical imaging of ferret primary visual cortex in vivo and scanning laser photostimulation in brain slices were used to determine the spatial relationships between synaptic inputs onto individual neurons and the pattern of orientation columns. In the upper cortical layers, both excitatory and inhibitory inputs originated primarily from regions with orientation tuning similar to that of the recorded neurons; the shapes of the input tuning curves were indistinguishable. The orientation distributions of both types of inputs centered around the orientation of the recorded neurons, and no evidence for preferential cross-orientation inputs, either excitatory or inhibitory, was observed. These patterns of synaptic connectivity are most consistent with feedforward models for generation of orientation selectivity and are inconsistent with the patterns required by models based on cross-orientation inhibition.
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Affiliation(s)
- M B Dalva
- Howard Hughes Medical Institute, and Department of Neurobiology, Duke University Medical Center, Durham, North Carolina 27710, USA
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34
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Abstract
A new technique for understanding the organization of complex circuits in the vertebrate brain, scanning laser photostimulation, is described. This approach is based on the photolysis of a caged form of the excitatory neurotransmitter glutamate. Computer-controlled photostimulation and whole cell recording in brain slices allow the construction of detailed maps of the position, strength, sign and number of inputs converging on a single postsynaptic neuron. Scanning laser photostimulation offers many advantages over current techniques: spatial resolution is superb, fibers of passage are not activated, and thousands of presynaptic locations can be stimulated. This review describes the technique of photostimulation, outlines the instrumentation, necessary to implement it, and discusses the interpretation of photostimulation-derived data. Several examples of applications, ranging from mapping circuits in the mammalian visual cortex to determining receptor distributions on single neurons are considered. Although still in its early stages, scanning laser photostimulation offers neuroscientists a powerful tool for determining the organization and function of local brain circuits.
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Affiliation(s)
- L C Katz
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710
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35
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Affiliation(s)
- Matthew B. Dalva
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Lawrence C. Katz
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
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36
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Affiliation(s)
- Matthew B. Dalva
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Lawrence C. Katz
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
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37
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Abstract
Assessing patterns of synaptic connections in the developing mammalian neocortex has relied primarily on anatomical studies. In a physiological approach described here, the patterns of synaptic connections in slices of developing ferret visual cortex were determined with scanning laser photostimulation. Functional synaptic inputs to pyramidal cells in cortical layers 2 and 3 originating from sites close to the neuronal cell body appeared at least 2 weeks before eye opening, prior to the formation of long-range horizontal connections. Extensive long-range horizontal connections appeared in the next 10 days of development. The number of local connections peaked at the time of eye opening; the number of these connections subsequently declined to the level found in the adult while the specificity of long-distance connections increased. Thus, the relative influence of local connections on the activity of layer 2 and layer 3 neurons declines as the cortex matures while the influence of longer range connections increases substantially.
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Affiliation(s)
- M B Dalva
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710
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38
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Dalva MB, Ghosh A, Shatz CJ. Independent control of dendritic and axonal form in the developing lateral geniculate nucleus. J Neurosci 1994; 14:3588-602. [PMID: 8207474 PMCID: PMC6576932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
To identify mechanisms that regulate neuronal form in the mammalian CNS, we have examined dendritic development in the lateral geniculate nucleus (LGN) during the period of segregation of retinal ganglion cell axons. The tracer Dil was used to label retrogradely LGN neurons that send their axons to primary visual cortex at different ages between embryonic day 36 (E36) and E60 in the cat. LGN neurons grow extensively during this period, in concert with the progressive restriction of ganglion cell axons from the two eyes to their appropriate eye-specific layers. At E36 neurons have simple bipolar morphology; by E60 all have acquired complex multipolar dendritic trees. During this period, soma size increases by 190% and total dendritic length increases 240%. Dendritic complexity, as measured by dendritic branch points, also increases. As dendrites grow, the number of spines increases, but their density remains constant at 0.015/micron throughout this period. Since it is known that blockade of action potential activity significantly alters the branching pattern and extent of retinal ganglion cell axonal arbors within the LGN, we also investigated whether the dendritic development of the postsynaptic LGN neurons is similarly susceptible. Following 2 weeks of the intracranial minipump infusion of TTX between E42 and E56, the morphology of LGN neurons was examined. Surprisingly in view of the striking effect of the treatment on the morphology of retinal ganglion cell axons, dendritic growth and development were essentially normal. However, the density of dendritic spines increased almost threefold, suggesting that this specific feature of dendritic morphology is highly regulated by action potential activity. These observations indicate that normally during this period of development, the previously described changes that occur in the morphology of the presynaptic inputs to LGN neurons are accompanied by a progressive growth of post-synaptic dendrites. Because the intracranial TTX infusions have almost certainly blocked all sodium action potentials, our results suggest that the basic dendritic framework of LGN neurons can be achieved even in the absence of this form of neural activity. Moreover, since the same treatment causes a profound change in the morphology of the presynaptic axons, at least some aspects of axonal and dendritic form must be controlled independently during this prenatal period of development.
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Affiliation(s)
- M B Dalva
- Department of Neurobiology, Stanford University School of Medicine, California 94305
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