1
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DePew AT, Bruckner JJ, O'Connor-Giles KM, Mosca TJ. Neuronal LRP4 directs the development, maturation and cytoskeletal organization of Drosophila peripheral synapses. Development 2024; 151:dev202517. [PMID: 38738619 PMCID: PMC11190576 DOI: 10.1242/dev.202517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Accepted: 05/02/2024] [Indexed: 05/14/2024]
Abstract
Synaptic development requires multiple signaling pathways to ensure successful connections. Transmembrane receptors are optimally positioned to connect the synapse and the rest of the neuron, often acting as synaptic organizers to synchronize downstream events. One such organizer, the LDL receptor-related protein LRP4, is a cell surface receptor that has been most well-studied postsynaptically at mammalian neuromuscular junctions. Recent work, however, identified emerging roles, but how LRP4 acts as a presynaptic organizer and the downstream mechanisms of LRP4 are not well understood. Here, we show that LRP4 functions presynaptically at Drosophila neuromuscular synapses, acting in motoneurons to instruct pre- and postsynaptic development. Loss of presynaptic LRP4 results in multiple defects, impairing active zone organization, synapse growth, physiological function, microtubule organization, synaptic ultrastructure and synapse maturation. We further demonstrate that LRP4 promotes most aspects of presynaptic development via a downstream SR-protein kinase, SRPK79D. These data demonstrate a function for presynaptic LRP4 as a peripheral synaptic organizer, highlight a downstream mechanism conserved with its CNS function in Drosophila, and underscore previously unappreciated but important developmental roles for LRP4 in cytoskeletal organization, synapse maturation and active zone organization.
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Affiliation(s)
- Alison T. DePew
- Department of Neuroscience, Vickie and Jack Farber Institute of Neuroscience, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Joseph J. Bruckner
- Cell and Molecular Biology Training Program, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Kate M. O'Connor-Giles
- Department of Neuroscience, Brown University, Providence, RI 02912, USA
- Carney Institute for Brain Science, Brown University, Providence, RI 02912, USA
| | - Timothy J. Mosca
- Department of Neuroscience, Vickie and Jack Farber Institute of Neuroscience, Thomas Jefferson University, Philadelphia, PA 19107, USA
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2
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Medeiros AT, Gratz S, Delgado A, Ritt J, O’Connor-Giles KM. Ca 2+ channel and active zone protein abundance intersects with input-specific synapse organization to shape functional synaptic diversity. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.04.02.535290. [PMID: 37034654 PMCID: PMC10081318 DOI: 10.1101/2023.04.02.535290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/11/2023]
Abstract
Synaptic heterogeneity is a hallmark of nervous systems that enables complex and adaptable communication in neural circuits. To understand circuit function, it is thus critical to determine the factors that contribute to the functional diversity of synapses. We investigated the contributions of voltage-gated calcium channel (VGCC) abundance, spatial organization, and subunit composition to synapse diversity among and between synapses formed by two closely related Drosophila glutamatergic motor neurons with distinct neurotransmitter release probabilities (Pr). Surprisingly, VGCC levels are highly predictive of heterogeneous Pr among individual synapses of either low- or high-Pr inputs, but not between inputs. We find that the same number of VGCCs are more densely organized at high-Pr synapses, consistent with tighter VGCC-synaptic vesicle coupling. We generated endogenously tagged lines to investigate VGCC subunits in vivo and found that the α2δ-3 subunit Straightjacket along with the CAST/ELKS active zone (AZ) protein Bruchpilot, both key regulators of VGCCs, are less abundant at high-Pr inputs, yet positively correlate with Pr among synapses formed by either input. Consistently, both Straightjacket and Bruchpilot levels are dynamically increased across AZs of both inputs when neurotransmitter release is potentiated to maintain stable communication following glutamate receptor inhibition. Together, these findings suggest a model in which VGCC and AZ protein abundance intersects with input-specific spatial and molecular organization to shape the functional diversity of synapses.
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Affiliation(s)
- A. T. Medeiros
- Neuroscience Graduate Training Program, Brown University, Providence, RI
| | - S.J. Gratz
- Department of Neuroscience, Brown University, Providence, RI
| | - A. Delgado
- Department of Neuroscience, Brown University, Providence, RI
| | - J.T. Ritt
- Department of Neuroscience, Brown University, Providence, RI
- Carney Institute for Brain Science, Brown University, Providence, RI
| | - Kate M. O’Connor-Giles
- Neuroscience Graduate Training Program, Brown University, Providence, RI
- Department of Neuroscience, Brown University, Providence, RI
- Carney Institute for Brain Science, Brown University, Providence, RI
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3
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Thakur RS, O’Connor-Giles KM. PDZD8 promotes autophagy at ER-Lysosome contact sites to regulate synaptogenesis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.30.564828. [PMID: 37961523 PMCID: PMC10634952 DOI: 10.1101/2023.10.30.564828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Building synaptic connections, which are often far from the soma, requires coordinating a host of cellular activities from transcription to protein turnover, placing a high demand on intracellular communication. Membrane contact sites (MCSs) formed between cellular organelles have emerged as key signaling hubs for coordinating an array of cellular activities. We have found that the endoplasmic reticulum (ER) MCS tethering protein PDZD8 is required for activity-dependent synaptogenesis. PDZD8 is sufficient to drive ectopic synaptic bouton formation through an autophagy-dependent mechanism and required for basal synapse formation when autophagy biogenesis is limited. PDZD8 functions at ER-late endosome/lysosome (LEL) MCSs to promote lysosome maturation and accelerate autophagic flux. Mutational analysis of PDZD8's SMP domain further suggests a role for lipid transfer at ER-LEL MCSs. We propose that PDZD8-dependent lipid transfer from ER to LELs promotes lysosome maturation to increase autophagic flux during periods of high demand, including activity-dependent synapse formation.
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Affiliation(s)
- Rajan S. Thakur
- Department of Neuroscience, Brown University, Providence, RI
| | - Kate M. O’Connor-Giles
- Department of Neuroscience, Brown University, Providence, RI
- Carney Institute for Brain Science, Providence, RI
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4
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Madhwani KR, Sayied S, Ogata CH, Hogan CA, Lentini JM, Mallik M, Dumouchel JL, Storkebaum E, Fu D, O’Connor-Giles KM. tRNA modification enzyme-dependent redox homeostasis regulates synapse formation and memory. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.14.566895. [PMID: 38014328 PMCID: PMC10680711 DOI: 10.1101/2023.11.14.566895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Post-transcriptional modification of RNA regulates gene expression at multiple levels. ALKBH8 is a tRNA modifying enzyme that methylates wobble uridines in specific tRNAs to modulate translation. Through methylation of tRNA-selenocysteine, ALKBH8 promotes selenoprotein synthesis and regulates redox homeostasis. Pathogenic variants in ALKBH8 have been linked to intellectual disability disorders in the human population, but the role of ALKBH8 in the nervous system is unknown. Through in vivo studies in Drosophila, we show that ALKBH8 controls oxidative stress in the brain to restrain synaptic growth and support learning and memory. ALKBH8 null animals lack wobble uridine methylation and exhibit a global reduction in protein synthesis, including a specific decrease in selenoprotein levels. Loss of ALKBH8 or independent disruption of selenoprotein synthesis results in ectopic synapse formation. Genetic expression of antioxidant enzymes fully suppresses synaptic overgrowth in ALKBH8 null animals, confirming oxidative stress as the underlying cause of dysregulation. ALKBH8 animals also exhibit associative learning and memory impairments that are reversed by pharmacological antioxidant treatment. Together, these findings demonstrate the critical role of tRNA modification in redox homeostasis in the nervous system and reveal antioxidants as a potential therapy for ALKBH8-associated intellectual disability.
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Affiliation(s)
| | - Shanzeh Sayied
- Department of Neuroscience, Brown University, Providence, RI, USA
| | | | - Caley A. Hogan
- Laboratory of Genetics, University of Wisconsin-Madison, Madison, WI, USA
| | - Jenna M. Lentini
- Department of Biology, Center for RNA Biology, University of Rochester, Rochester, NY, USA
| | - Moushami Mallik
- Molecular Neurobiology Laboratory, Donders Institute for Brain, Cognition, and Behaviour, Radboud University, Nijmegen, NL
| | | | - Erik Storkebaum
- Molecular Neurobiology Laboratory, Donders Institute for Brain, Cognition, and Behaviour, Radboud University, Nijmegen, NL
| | - Dragony Fu
- Department of Biology, Center for RNA Biology, University of Rochester, Rochester, NY, USA
| | - Kate M. O’Connor-Giles
- Department of Neuroscience, Brown University, Providence, RI, USA
- Carney Institute for Brain Sciences, Brown University, Providence, RI, USA
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5
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DePew AT, Bruckner JJ, O’Connor-Giles KM, Mosca TJ. Neuronal LRP4 directs the development, maturation, and cytoskeletal organization of peripheral synapses. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.03.564481. [PMID: 37961323 PMCID: PMC10635100 DOI: 10.1101/2023.11.03.564481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Synapse development requires multiple signaling pathways to accomplish the myriad of steps needed to ensure a successful connection. Transmembrane receptors on the cell surface are optimally positioned to facilitate communication between the synapse and the rest of the neuron and often function as synaptic organizers to synchronize downstream signaling events. One such organizer, the LDL receptor-related protein LRP4, is a cell surface receptor most well-studied postsynaptically at mammalian neuromuscular junctions. Recent work, however, has identified emerging roles for LRP4 as a presynaptic molecule, but how LRP4 acts as a presynaptic organizer, what roles LRP4 plays in organizing presynaptic biology, and the downstream mechanisms of LRP4 are not well understood. Here we show that LRP4 functions presynaptically at Drosophila neuromuscular synapses, acting in motor neurons to instruct multiple aspects of pre- and postsynaptic development. Loss of presynaptic LRP4 results in a range of developmental defects, impairing active zone organization, synapse growth, physiological function, microtubule organization, synaptic ultrastructure, and synapse maturation. We further demonstrate that LRP4 promotes most aspects of presynaptic development via a downstream SR-protein kinase, SRPK79D. SRPK79D overexpression suppresses synaptic defects associated with loss of lrp4. These data demonstrate a function for LRP4 as a peripheral synaptic organizer acting presynaptically, highlight a downstream mechanism conserved with its CNS function, and indicate previously unappreciated roles for LRP4 in cytoskeletal organization, synapse maturation, and active zone organization, underscoring its developmental importance.
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Affiliation(s)
- Alison T. DePew
- Dept. of Neuroscience, Vickie and Jack Farber Institute of Neuroscience, Thomas Jefferson University, Philadelphia, PA 19107 USA
| | - Joseph J. Bruckner
- Cell and Molecular Biology Training Program, University of Wisconsin-Madison, Madison, WI 53706 USA
| | - Kate M. O’Connor-Giles
- Department of Neuroscience, Brown University, Providence, RI 02912 USA
- Carney Institute for Brain Science, Brown University, Providence, RI 02912, USA
| | - Timothy J. Mosca
- Dept. of Neuroscience, Vickie and Jack Farber Institute of Neuroscience, Thomas Jefferson University, Philadelphia, PA 19107 USA
- Lead Contact
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Hogan CA, Gratz SJ, Dumouchel JL, Thakur RS, Delgado A, Lentini JM, Madhwani KR, Fu D, O'Connor‐Giles KM. Expanded tRNA methyltransferase family member TRMT9B regulates synaptic growth and function. EMBO Rep 2023; 24:e56808. [PMID: 37642556 PMCID: PMC10561368 DOI: 10.15252/embr.202356808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 08/03/2023] [Accepted: 08/14/2023] [Indexed: 08/31/2023] Open
Abstract
Nervous system function rests on the formation of functional synapses between neurons. We have identified TRMT9B as a new regulator of synapse formation and function in Drosophila. TRMT9B has been studied for its role as a tumor suppressor and is one of two metazoan homologs of yeast tRNA methyltransferase 9 (Trm9), which methylates tRNA wobble uridines. Whereas Trm9 homolog ALKBH8 is ubiquitously expressed, TRMT9B is enriched in the nervous system. However, in the absence of animal models, TRMT9B's role in the nervous system has remained unstudied. Here, we generate null alleles of TRMT9B and find it acts postsynaptically to regulate synaptogenesis and promote neurotransmission. Through liquid chromatography-mass spectrometry, we find that ALKBH8 catalyzes canonical tRNA wobble uridine methylation, raising the question of whether TRMT9B is a methyltransferase. Structural modeling studies suggest TRMT9B retains methyltransferase function and, in vivo, disruption of key methyltransferase residues blocks TRMT9B's ability to rescue synaptic overgrowth, but not neurotransmitter release. These findings reveal distinct roles for TRMT9B in the nervous system and highlight the significance of tRNA methyltransferase family diversification in metazoans.
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Affiliation(s)
- Caley A Hogan
- Genetics Training ProgramUniversity of Wisconsin‐MadisonMadisonWIUSA
| | - Scott J Gratz
- Department of NeuroscienceBrown UniversityProvidenceRIUSA
| | | | - Rajan S Thakur
- Department of NeuroscienceBrown UniversityProvidenceRIUSA
| | - Ambar Delgado
- Department of NeuroscienceBrown UniversityProvidenceRIUSA
| | - Jenna M Lentini
- Department of Biology, Center for RNA BiologyUniversity of RochesterRochesterNYUSA
| | | | - Dragony Fu
- Department of Biology, Center for RNA BiologyUniversity of RochesterRochesterNYUSA
| | - Kate M O'Connor‐Giles
- Department of NeuroscienceBrown UniversityProvidenceRIUSA
- Carney Institute for Brain ScienceProvidenceRIUSA
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7
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Krout M, Oh KH, Xiong A, Frankel EB, Kurshan PT, Kim H, Richmond JE. C. elegans Clarinet/CLA-1 recruits RIMB-1/RIM-binding protein and UNC-13 to orchestrate presynaptic neurotransmitter release. Proc Natl Acad Sci U S A 2023; 120:e2220856120. [PMID: 37186867 PMCID: PMC10214197 DOI: 10.1073/pnas.2220856120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Accepted: 04/05/2023] [Indexed: 05/17/2023] Open
Abstract
Synaptic transmission requires the coordinated activity of multiple synaptic proteins that are localized at the active zone (AZ). We previously identified a Caenorhabditis elegans protein named Clarinet (CLA-1) based on homology to the AZ proteins Piccolo, Rab3-interactingmolecule (RIM)/UNC-10 and Fife. At the neuromuscular junction (NMJ), cla-1 null mutants exhibit release defects that are greatly exacerbated in cla-1;unc-10 double mutants. To gain insights into the coordinated roles of CLA-1 and UNC-10, we examined the relative contributions of each to the function and organization of the AZ. Using a combination of electrophysiology, electron microscopy, and quantitative fluorescence imaging we explored the functional relationship of CLA-1 to other key AZ proteins including: RIM1, Cav2.1 channels, RIM1-binding protein, and Munc13 (C. elegans UNC-10, UNC-2, RIMB-1 and UNC-13, respectively). Our analyses show that CLA-1 acts in concert with UNC-10 to regulate UNC-2 calcium channel levels at the synapse via recruitment of RIMB-1. In addition, CLA-1 exerts a RIMB-1-independent role in the localization of the priming factor UNC-13. Thus C. elegans CLA-1/UNC-10 exhibit combinatorial effects that have overlapping design principles with other model organisms: RIM/RBP and RIM/ELKS in mouse and Fife/RIM and BRP/RBP in Drosophila. These data support a semiconserved arrangement of AZ scaffolding proteins that are necessary for the localization and activation of the fusion machinery within nanodomains for precise coupling to Ca2+ channels.
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Affiliation(s)
- Mia Krout
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL60607
| | - Kelly H. Oh
- Department of Cell Biology and Anatomy, Center for Cancer Cell Biology, Immunology, and Infection, Chicago Medical School, School of Graduate and Postdoctoral Studies, Rosalind Franklin University of Medicine and Science, North Chicago, IL60064
| | - Ame Xiong
- Department of Cell Biology and Anatomy, Center for Cancer Cell Biology, Immunology, and Infection, Chicago Medical School, School of Graduate and Postdoctoral Studies, Rosalind Franklin University of Medicine and Science, North Chicago, IL60064
| | - Elisa B. Frankel
- Department of Genetics, Albert Einstein College of Medicine, New York, NY10461
| | - Peri T. Kurshan
- Department of Genetics, Albert Einstein College of Medicine, New York, NY10461
| | - Hongkyun Kim
- Department of Genetics, Albert Einstein College of Medicine, New York, NY10461
| | - Janet E. Richmond
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL60607
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Kudryashova I. Presynaptic Plasticity Is Associated with Actin Polymerization. BIOCHEMISTRY (MOSCOW) 2023; 88:392-403. [PMID: 37076285 DOI: 10.1134/s0006297923030082] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
Abstract
Modulation of presynaptic short-term plasticity induced by actin polymerization was studied in rat hippocampal slices using the paired-pulse paradigm. Schaffer collaterals were stimulated with paired pulses with a 70-ms interstimulus interval every 30 s before and during perfusion with jasplakinolide, an activator of actin polymerization. Jasplakinolide application resulted in the increase in the amplitudes of CA3-CA1 responses (potentiation) accompanied by a decrease in the paired-pulse facilitation, suggesting induction of presynaptic modifications. Jasplakinolide-induced potentiation depended on the initial paired-pulse rate. These data indicate that the jasplakinolide-mediated changes in actin polymerization increased the probability of neurotransmitter release. Less typical for CA3-CA1 synapses responses, such as a very low paired-pulse ratio (close to 1 or even lower) or even paired-pulse depression, were affected differently. Thus, jasplakinolide caused potentiation of the second, but not the first response to the paired stimulus, which increased the paired-pulse ratio from 0.8 to 1.0 on average, suggesting a negative impact of jasplakinolide on the mechanisms promoting paired-pulse depression. In general, actin polymerization facilitated potentiation, although the patterns of potentiation differed depending on the initial synapse characteristics. We conclude that in addition to the increase in the neurotransmitter release probability, jasplakinolide induced other actin polymerization-dependent mechanisms, including those involved in the paired-pulse depression.
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Affiliation(s)
- Irina Kudryashova
- Laboratory of Functional Biochemistry of the Nervous System, Institute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow, 119991, Russia.
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Cunningham KL, Littleton JT. Mechanisms controlling the trafficking, localization, and abundance of presynaptic Ca 2+ channels. Front Mol Neurosci 2023; 15:1116729. [PMID: 36710932 PMCID: PMC9880069 DOI: 10.3389/fnmol.2022.1116729] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Accepted: 12/26/2022] [Indexed: 01/14/2023] Open
Abstract
Voltage-gated Ca2+ channels (VGCCs) mediate Ca2+ influx to trigger neurotransmitter release at specialized presynaptic sites termed active zones (AZs). The abundance of VGCCs at AZs regulates neurotransmitter release probability (Pr ), a key presynaptic determinant of synaptic strength. Given this functional significance, defining the processes that cooperate to establish AZ VGCC abundance is critical for understanding how these mechanisms set synaptic strength and how they might be regulated to control presynaptic plasticity. VGCC abundance at AZs involves multiple steps, including channel biosynthesis (transcription, translation, and trafficking through the endomembrane system), forward axonal trafficking and delivery to synaptic terminals, incorporation and retention at presynaptic sites, and protein recycling. Here we discuss mechanisms that control VGCC abundance at synapses, highlighting findings from invertebrate and vertebrate models.
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Affiliation(s)
- Karen L. Cunningham
- The Picower Institute for Learning and Memory, Department of Biology, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA, United States
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10
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Jin Y, Zhai RG. Presynaptic Cytomatrix Proteins. ADVANCES IN NEUROBIOLOGY 2023; 33:23-42. [PMID: 37615862 DOI: 10.1007/978-3-031-34229-5_2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
The Cytomatrix Assembled at the active Zone (CAZ) of a presynaptic terminal displays electron-dense appearance and defines the center of the synaptic vesicle release. The protein constituents of CAZ are multiple-domain scaffolds that interact extensively with each other and also with an ensemble of synaptic vesicle proteins to ensure docking, fusion, and recycling. Reflecting the central roles of the active zone in synaptic transmission, CAZ proteins are highly conserved throughout evolution. As the nervous system increases complexity and diversity in types of neurons and synapses, CAZ proteins expand in the number of gene and protein isoforms and interacting partners. This chapter summarizes the discovery of the core CAZ proteins and current knowledge of their functions.
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Affiliation(s)
- Yishi Jin
- Department of Neurobiology, School of Biological Sciences, University of California San Diego, La Jolla, CA, USA.
| | - R Grace Zhai
- Department of Molecular and Cellular Pharmacology, Leonard M. Miller School of Medicine, University of Miami, Miami, FL, USA.
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Lang K, Milosavljevic J, Heinkele H, Chen M, Gerstner L, Spitz D, Kayser S, Helmstädter M, Walz G, Köttgen M, Spracklen A, Poulton J, Hermle T. Selective endocytosis controls slit diaphragm maintenance and dynamics in Drosophila nephrocytes. eLife 2022; 11:79037. [PMID: 35876643 PMCID: PMC9355562 DOI: 10.7554/elife.79037] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 07/24/2022] [Indexed: 11/28/2022] Open
Abstract
The kidneys generate about 180 l of primary urine per day by filtration of plasma. An essential part of the filtration barrier is the slit diaphragm, a multiprotein complex containing nephrin as major component. Filter dysfunction typically manifests with proteinuria and mutations in endocytosis regulating genes were discovered as causes of proteinuria. However, it is unclear how endocytosis regulates the slit diaphragm and how the filtration barrier is maintained without either protein leakage or filter clogging. Here, we study nephrin dynamics in podocyte-like nephrocytes of Drosophila and show that selective endocytosis either by dynamin- or flotillin-mediated pathways regulates a stable yet highly dynamic architecture. Short-term manipulation of endocytic functions indicates that dynamin-mediated endocytosis of ectopic nephrin restricts slit diaphragm formation spatially while flotillin-mediated turnover of nephrin within the slit diaphragm is needed to maintain filter permeability by shedding of molecules bound to nephrin in endosomes. Since slit diaphragms cannot be studied in vitro and are poorly accessible in mouse models, this is the first analysis of their dynamics within the slit diaphragm multiprotein complex. Identification of the mechanisms of slit diaphragm maintenance will help to develop novel therapies for proteinuric renal diseases that are frequently limited to symptomatic treatment.
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Affiliation(s)
- Konrad Lang
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | | | - Helena Heinkele
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Mengmeng Chen
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Lea Gerstner
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Dominik Spitz
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Severine Kayser
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | | | - Gerd Walz
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Michael Köttgen
- Department of Medicine, University of Freiburg, Freiburg, Germany
| | - Andrew Spracklen
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - John Poulton
- Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - Tobias Hermle
- Department of Medicine, University of Freiburg, Freiburg, Germany
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12
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The evolution of synaptic and cognitive capacity: Insights from the nervous system transcriptome of Aplysia. Proc Natl Acad Sci U S A 2022; 119:e2122301119. [PMID: 35867761 PMCID: PMC9282427 DOI: 10.1073/pnas.2122301119] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The gastropod mollusk Aplysia is an important model for cellular and molecular neurobiological studies, particularly for investigations of molecular mechanisms of learning and memory. We developed an optimized assembly pipeline to generate an improved Aplysia nervous system transcriptome. This improved transcriptome enabled us to explore the evolution of cognitive capacity at the molecular level. Were there evolutionary expansions of neuronal genes between this relatively simple gastropod Aplysia (20,000 neurons) and Octopus (500 million neurons), the invertebrate with the most elaborate neuronal circuitry and greatest behavioral complexity? Are the tremendous advances in cognitive power in vertebrates explained by expansion of the synaptic proteome that resulted from multiple rounds of whole genome duplication in this clade? Overall, the complement of genes linked to neuronal function is similar between Octopus and Aplysia. As expected, a number of synaptic scaffold proteins have more isoforms in humans than in Aplysia or Octopus. However, several scaffold families present in mollusks and other protostomes are absent in vertebrates, including the Fifes, Lev10s, SOLs, and a NETO family. Thus, whereas vertebrates have more scaffold isoforms from select families, invertebrates have additional scaffold protein families not found in vertebrates. This analysis provides insights into the evolution of the synaptic proteome. Both synaptic proteins and synaptic plasticity evolved gradually, yet the last deuterostome-protostome common ancestor already possessed an elaborate suite of genes associated with synaptic function, and critical for synaptic plasticity.
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13
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Palu RAS, Owings KG, Garces JG, Nicol A. A natural genetic variation screen identifies insulin signaling, neuronal communication, and innate immunity as modifiers of hyperglycemia in the absence of Sirt1. G3 (BETHESDA, MD.) 2022; 12:jkac090. [PMID: 35435227 PMCID: PMC9157059 DOI: 10.1093/g3journal/jkac090] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Accepted: 04/07/2022] [Indexed: 11/13/2022]
Abstract
Variation in the onset, progression, and severity of symptoms associated with metabolic disorders such as diabetes impairs the diagnosis and treatment of at-risk patients. Diabetes symptoms, and patient variation in these symptoms, are attributed to a combination of genetic and environmental factors, but identifying the genes and pathways that modify diabetes in humans has proven difficult. A greater understanding of genetic modifiers and the ways in which they interact with metabolic pathways could improve the ability to predict a patient's risk for severe symptoms, as well as enhance the development of individualized therapeutic approaches. In this study, we use the Drosophila Genetic Reference Panel to identify genetic variation influencing hyperglycemia associated with loss of Sirt1 function. Through analysis of individual candidate functions, physical interaction networks, and gene set enrichment analysis, we identify not only modifiers involved in canonical glucose metabolism and insulin signaling, but also genes important for neuronal signaling and the innate immune response. Furthermore, reducing the expression of several of these candidates suppressed hyperglycemia, making them potential candidate therapeutic targets. These analyses showcase the diverse processes contributing to glucose homeostasis and open up several avenues of future investigation.
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Affiliation(s)
- Rebecca A S Palu
- Department of Biological Sciences, Purdue University-Fort Wayne, Fort Wayne, IN 46818, USA
| | - Katie G Owings
- Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, UT 84112, USA
| | - John G Garces
- Department of Biological Sciences, Purdue University-Fort Wayne, Fort Wayne, IN 46818, USA
| | - Audrey Nicol
- Department of Biological Sciences, Purdue University-Fort Wayne, Fort Wayne, IN 46818, USA
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14
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Newman ZL, Bakshinskaya D, Schultz R, Kenny SJ, Moon S, Aghi K, Stanley C, Marnani N, Li R, Bleier J, Xu K, Isacoff EY. Determinants of synapse diversity revealed by super-resolution quantal transmission and active zone imaging. Nat Commun 2022; 13:229. [PMID: 35017509 PMCID: PMC8752601 DOI: 10.1038/s41467-021-27815-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Accepted: 12/06/2021] [Indexed: 01/23/2023] Open
Abstract
Neural circuit function depends on the pattern of synaptic connections between neurons and the strength of those connections. Synaptic strength is determined by both postsynaptic sensitivity to neurotransmitter and the presynaptic probability of action potential evoked transmitter release (Pr). Whereas morphology and neurotransmitter receptor number indicate postsynaptic sensitivity, presynaptic indicators and the mechanism that sets Pr remain to be defined. To address this, we developed QuaSOR, a super-resolution method for determining Pr from quantal synaptic transmission imaging at hundreds of glutamatergic synapses at a time. We mapped the Pr onto super-resolution 3D molecular reconstructions of the presynaptic active zones (AZs) of the same synapses at the Drosophila larval neuromuscular junction (NMJ). We find that Pr varies greatly between synapses made by a single axon, quantify the contribution of key AZ proteins to Pr diversity and find that one of these, Complexin, suppresses spontaneous and evoked transmission differentially, thereby generating a spatial and quantitative mismatch between release modes. Transmission is thus regulated by the balance and nanoscale distribution of release-enhancing and suppressing presynaptic proteins to generate high signal-to-noise evoked transmission.
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Affiliation(s)
- Zachary L Newman
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Dariya Bakshinskaya
- Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Ryan Schultz
- Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Samuel J Kenny
- Department of Chemistry, University of California, Berkeley, CA, 94720, USA
| | - Seonah Moon
- Department of Chemistry, University of California, Berkeley, CA, 94720, USA
| | - Krisha Aghi
- Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Cherise Stanley
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Nadia Marnani
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Rachel Li
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Julia Bleier
- Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA, 94720, USA
| | - Ke Xu
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, 94720, USA
- Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA, 94720, USA
- Department of Chemistry, University of California, Berkeley, CA, 94720, USA
- Molecular Biophysics and Integrated BioImaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Ehud Y Isacoff
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, 94720, USA.
- Helen Wills Neuroscience Institute, University of California Berkeley, Berkeley, CA, 94720, USA.
- Molecular Biophysics and Integrated BioImaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
- Weill Neurohub, University of California Berkeley, Berkeley, CA, 94720, USA.
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15
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Rivard EL, Ludwig AG, Patel PH, Grandchamp A, Arnold SE, Berger A, Scott EM, Kelly BJ, Mascha GC, Bornberg-Bauer E, Findlay GD. A putative de novo evolved gene required for spermatid chromatin condensation in Drosophila melanogaster. PLoS Genet 2021; 17:e1009787. [PMID: 34478447 PMCID: PMC8445463 DOI: 10.1371/journal.pgen.1009787] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 09/16/2021] [Accepted: 08/19/2021] [Indexed: 02/07/2023] Open
Abstract
Comparative genomics has enabled the identification of genes that potentially evolved de novo from non-coding sequences. Many such genes are expressed in male reproductive tissues, but their functions remain poorly understood. To address this, we conducted a functional genetic screen of over 40 putative de novo genes with testis-enriched expression in Drosophila melanogaster and identified one gene, atlas, required for male fertility. Detailed genetic and cytological analyses showed that atlas is required for proper chromatin condensation during the final stages of spermatogenesis. Atlas protein is expressed in spermatid nuclei and facilitates the transition from histone- to protamine-based chromatin packaging. Complementary evolutionary analyses revealed the complex evolutionary history of atlas. The protein-coding portion of the gene likely arose at the base of the Drosophila genus on the X chromosome but was unlikely to be essential, as it was then lost in several independent lineages. Within the last ~15 million years, however, the gene moved to an autosome, where it fused with a conserved non-coding RNA and evolved a non-redundant role in male fertility. Altogether, this study provides insight into the integration of novel genes into biological processes, the links between genomic innovation and functional evolution, and the genetic control of a fundamental developmental process, gametogenesis.
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Affiliation(s)
- Emily L. Rivard
- College of the Holy Cross, Worcester, Massachusetts, United States of America
| | - Andrew G. Ludwig
- College of the Holy Cross, Worcester, Massachusetts, United States of America
| | - Prajal H. Patel
- College of the Holy Cross, Worcester, Massachusetts, United States of America
| | | | - Sarah E. Arnold
- College of the Holy Cross, Worcester, Massachusetts, United States of America
| | | | - Emilie M. Scott
- College of the Holy Cross, Worcester, Massachusetts, United States of America
| | - Brendan J. Kelly
- College of the Holy Cross, Worcester, Massachusetts, United States of America
| | - Grace C. Mascha
- College of the Holy Cross, Worcester, Massachusetts, United States of America
| | - Erich Bornberg-Bauer
- University of Münster, Münster, Germany
- Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Geoffrey D. Findlay
- College of the Holy Cross, Worcester, Massachusetts, United States of America
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16
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Goel P, Dickman D. Synaptic homeostats: latent plasticity revealed at the Drosophila neuromuscular junction. Cell Mol Life Sci 2021; 78:3159-3179. [PMID: 33449150 PMCID: PMC8044042 DOI: 10.1007/s00018-020-03732-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 11/19/2020] [Accepted: 12/04/2020] [Indexed: 12/11/2022]
Abstract
Homeostatic signaling systems are fundamental forms of biological regulation that maintain stable functionality in a changing environment. In the nervous system, synapses are crucial substrates for homeostatic modulation, serving to establish, maintain, and modify the balance of excitation and inhibition. Synapses must be sufficiently flexible to enable the plasticity required for learning and memory but also endowed with the stability to last a lifetime. In response to the processes of development, growth, remodeling, aging, and disease that challenge synapses, latent forms of adaptive plasticity become activated to maintain synaptic stability. In recent years, new insights into the homeostatic control of synaptic function have been achieved using the powerful Drosophila neuromuscular junction (NMJ). This review will focus on work over the past 10 years that has illuminated the cellular and molecular mechanisms of five homeostats that operate at the fly NMJ. These homeostats adapt to loss of postsynaptic neurotransmitter receptor functionality, glutamate imbalance, axonal injury, as well as aberrant synaptic growth and target innervation. These diverse homeostats work independently yet can be simultaneously expressed to balance neurotransmission. Growing evidence from this model glutamatergic synapse suggests these ancient homeostatic signaling systems emerged early in evolution and are fundamental forms of plasticity that also function to stabilize mammalian cholinergic NMJs and glutamatergic central synapses.
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Affiliation(s)
- Pragya Goel
- Department of Neurobiology, University of Southern California, Los Angeles, CA, 90089, USA
| | - Dion Dickman
- Department of Neurobiology, University of Southern California, Los Angeles, CA, 90089, USA.
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17
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Petzoldt AG, Götz TWB, Driller JH, Lützkendorf J, Reddy-Alla S, Matkovic-Rachid T, Liu S, Knoche E, Mertel S, Ugorets V, Lehmann M, Ramesh N, Beuschel CB, Kuropka B, Freund C, Stelzl U, Loll B, Liu F, Wahl MC, Sigrist SJ. RIM-binding protein couples synaptic vesicle recruitment to release sites. J Cell Biol 2021; 219:151735. [PMID: 32369542 PMCID: PMC7337501 DOI: 10.1083/jcb.201902059] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Revised: 02/03/2020] [Accepted: 04/07/2020] [Indexed: 11/24/2022] Open
Abstract
At presynaptic active zones, arrays of large conserved scaffold proteins mediate fast and temporally precise release of synaptic vesicles (SVs). SV release sites could be identified by clusters of Munc13, which allow SVs to dock in defined nanoscale relation to Ca2+ channels. We here show in Drosophila that RIM-binding protein (RIM-BP) connects release sites physically and functionally to the ELKS family Bruchpilot (BRP)-based scaffold engaged in SV recruitment. The RIM-BP N-terminal domain, while dispensable for SV release site organization, was crucial for proper nanoscale patterning of the BRP scaffold and needed for SV recruitment of SVs under strong stimulation. Structural analysis further showed that the RIM-BP fibronectin domains form a “hinge” in the protein center, while the C-terminal SH3 domain tandem binds RIM, Munc13, and Ca2+ channels release machinery collectively. RIM-BPs’ conserved domain architecture seemingly provides a relay to guide SVs from membrane far scaffolds into membrane close release sites.
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Affiliation(s)
- Astrid G Petzoldt
- Freie Universität Berlin, Institute for Biology and Genetics, Berlin, Germany
| | - Torsten W B Götz
- Freie Universität Berlin, Institute for Biology and Genetics, Berlin, Germany
| | - Jan Heiner Driller
- Freie Universität Berlin, Institute of Chemistry and Biochemistry/Structural Biochemistry Berlin, Berlin, Germany
| | - Janine Lützkendorf
- Freie Universität Berlin, Institute for Biology and Genetics, Berlin, Germany
| | - Suneel Reddy-Alla
- Freie Universität Berlin, Institute for Biology and Genetics, Berlin, Germany
| | | | - Sunbin Liu
- Freie Universität Berlin, Institute of Chemistry and Biochemistry/Structural Biochemistry Berlin, Berlin, Germany
| | - Elena Knoche
- Freie Universität Berlin, Institute for Biology and Genetics, Berlin, Germany
| | - Sara Mertel
- Freie Universität Berlin, Institute for Biology and Genetics, Berlin, Germany
| | - Vladimir Ugorets
- Freie Universität Berlin, Institute for Biology and Genetics, Berlin, Germany
| | - Martin Lehmann
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie im Forschungsverbund Berlin e.V., Campus Berlin-Buch, Berlin, Germany
| | - Niraja Ramesh
- Freie Universität Berlin, Institute for Biology and Genetics, Berlin, Germany
| | | | - Benno Kuropka
- Universität Berlin, Institute for Chemistry and Biochemistry, Berlin, Germany
| | - Christian Freund
- Universität Berlin, Institute for Chemistry and Biochemistry, Berlin, Germany
| | - Ulrich Stelzl
- Institut für Pharmazeutische Wissenschaften, Graz, Austria
| | - Bernhard Loll
- Freie Universität Berlin, Institute of Chemistry and Biochemistry/Structural Biochemistry Berlin, Berlin, Germany
| | - Fan Liu
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie im Forschungsverbund Berlin e.V., Campus Berlin-Buch, Berlin, Germany
| | - Markus C Wahl
- Freie Universität Berlin, Institute of Chemistry and Biochemistry/Structural Biochemistry Berlin, Berlin, Germany.,Helmholtz-Zentrum Berlin für Materialien und Energie, Macromolecular Crystallography, Berlin, Germany
| | - Stephan J Sigrist
- Freie Universität Berlin, Institute for Biology and Genetics, Berlin, Germany.,NeuroCure, Charité, Berlin, Germany
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18
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Gao T, Zhang Z, Yang Y, Zhang H, Li N, Liu B. Impact of RIM-BPs in neuronal vesicles release. Brain Res Bull 2021; 170:129-136. [PMID: 33581313 DOI: 10.1016/j.brainresbull.2021.02.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 02/04/2021] [Accepted: 02/05/2021] [Indexed: 12/13/2022]
Abstract
Accurate signal transmission between neurons is accomplished by vesicle release with high spatiotemporal resolution in the central nervous system. The vesicle release occurs mainly in the active zone (AZ), a unique area on the presynaptic membrane. Many structural proteins expressed in the AZ connect with other proteins nearby. They can also regulate the precise release of vesicles through protein-protein interactions. RIM-binding proteins (RIM-BPs) are one of the essential proteins in the AZ. This review summarizes the structures and functions of three subtypes of RIM-BPs, including the interaction between RIM-BPs and other proteins such as Bassoon and voltage-gated calcium channel, their significance in stabilizing the AZ structure in the presynaptic region and collecting ion channels, and ultimately regulating the fusion and release of neuronal vesicles.
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Affiliation(s)
- Tianyu Gao
- School of Biomedical Engineering, Liaoning Key Lab of Integrated Circuit and Biomedical Electronic System, Dalian University of Technology, Dalian, 116024, China
| | - Zhengyao Zhang
- School of Life and Pharmaceutical Sciences, Panjin Campus of Dalian University of Technology, Panjin, 124221, China
| | - Yunong Yang
- School of Biomedical Engineering, Liaoning Key Lab of Integrated Circuit and Biomedical Electronic System, Dalian University of Technology, Dalian, 116024, China
| | - Hangyu Zhang
- School of Biomedical Engineering, Liaoning Key Lab of Integrated Circuit and Biomedical Electronic System, Dalian University of Technology, Dalian, 116024, China
| | - Na Li
- School of Biomedical Engineering, Liaoning Key Lab of Integrated Circuit and Biomedical Electronic System, Dalian University of Technology, Dalian, 116024, China.
| | - Bo Liu
- School of Biomedical Engineering, Liaoning Key Lab of Integrated Circuit and Biomedical Electronic System, Dalian University of Technology, Dalian, 116024, China.
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19
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Nosov G, Kahms M, Klingauf J. The Decade of Super-Resolution Microscopy of the Presynapse. Front Synaptic Neurosci 2020; 12:32. [PMID: 32848695 PMCID: PMC7433402 DOI: 10.3389/fnsyn.2020.00032] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 07/21/2020] [Indexed: 01/05/2023] Open
Abstract
The presynaptic compartment of the chemical synapse is a small, yet extremely complex structure. Considering its size, most methods of optical microscopy are not able to resolve its nanoarchitecture and dynamics. Thus, its ultrastructure could only be studied by electron microscopy. In the last decade, new methods of optical superresolution microscopy have emerged allowing the study of cellular structures and processes at the nanometer scale. While this is a welcome addition to the experimental arsenal, it has necessitated careful analysis and interpretation to ensure the data obtained remains artifact-free. In this article we review the application of nanoscopic techniques to the study of the synapse and the progress made over the last decade with a particular focus on the presynapse. We find to our surprise that progress has been limited, calling for imaging techniques and probes that allow dense labeling, multiplexing, longer imaging times, higher temporal resolution, while at least maintaining the spatial resolution achieved thus far.
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Affiliation(s)
- Georgii Nosov
- Institute of Medical Physics and Biophysics, University of Münster, Münster, Germany.,CIM-IMPRS Graduate Program in Münster, Münster, Germany
| | - Martin Kahms
- Institute of Medical Physics and Biophysics, University of Münster, Münster, Germany
| | - Jurgen Klingauf
- Institute of Medical Physics and Biophysics, University of Münster, Münster, Germany
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20
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Assembly of the presynaptic active zone. Curr Opin Neurobiol 2020; 63:95-103. [PMID: 32403081 DOI: 10.1016/j.conb.2020.03.008] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 02/29/2020] [Accepted: 03/18/2020] [Indexed: 12/11/2022]
Abstract
In a presynaptic nerve terminal, the active zone is composed of sophisticated protein machinery that enables secretion on a submillisecond time scale and precisely targets it toward postsynaptic receptors. The past two decades have provided deep insight into the roles of active zone proteins in exocytosis, but we are only beginning to understand how a neuron assembles active zone protein complexes into effective molecular machines. In this review, we outline the fundamental processes that are necessary for active zone assembly and discuss recent advances in understanding assembly mechanisms that arise from genetic, morphological and biochemical studies. We further outline the challenges ahead for understanding this important problem.
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21
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Kobbersmed JR, Grasskamp AT, Jusyte M, Böhme MA, Ditlevsen S, Sørensen JB, Walter AM. Rapid regulation of vesicle priming explains synaptic facilitation despite heterogeneous vesicle:Ca 2+ channel distances. eLife 2020; 9:51032. [PMID: 32077852 PMCID: PMC7145420 DOI: 10.7554/elife.51032] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Accepted: 02/14/2020] [Indexed: 12/27/2022] Open
Abstract
Chemical synaptic transmission relies on the Ca2+-induced fusion of transmitter-laden vesicles whose coupling distance to Ca2+ channels determines synaptic release probability and short-term plasticity, the facilitation or depression of repetitive responses. Here, using electron- and super-resolution microscopy at the Drosophila neuromuscular junction we quantitatively map vesicle:Ca2+ channel coupling distances. These are very heterogeneous, resulting in a broad spectrum of vesicular release probabilities within synapses. Stochastic simulations of transmitter release from vesicles placed according to this distribution revealed strong constraints on short-term plasticity; particularly facilitation was difficult to achieve. We show that postulated facilitation mechanisms operating via activity-dependent changes of vesicular release probability (e.g. by a facilitation fusion sensor) generate too little facilitation and too much variance. In contrast, Ca2+-dependent mechanisms rapidly increasing the number of releasable vesicles reliably reproduce short-term plasticity and variance of synaptic responses. We propose activity-dependent inhibition of vesicle un-priming or release site activation as novel facilitation mechanisms. Cells in the nervous system of all animals communicate by releasing and sensing chemicals at contact points named synapses. The ‘talking’ (or pre-synaptic) cell stores the chemicals close to the synapse, in small spheres called vesicles. When the cell is activated, calcium ions flow in and interact with the release-ready vesicles, which then spill the chemicals into the synapse. In turn, the ‘listening’ (or post-synaptic) cell can detect the chemicals and react accordingly. When the pre-synaptic cell is activated many times in a short period, it can release a greater quantity of chemicals, allowing a bigger reaction in the post-synaptic cell. This phenomenon is known as facilitation, but it is still unclear how exactly it can take place. This is especially the case when many of the vesicles are not ready to respond, for example when they are too far from where calcium flows into the cell. Computer simulations have been created to model facilitation but they have assumed that all vesicles are placed at the same distance to the calcium entry point: Kobbersmed et al. now provide evidence that this assumption is incorrect. Two high-resolution imaging techniques were used to measure the actual distances between the vesicles and the calcium source in the pre-synaptic cells of fruit flies: this showed that these distances are quite variable – some vesicles sit much closer to the source than others. This information was then used to create a new computer model to simulate facilitation. The results from this computing work led Kobbersmed et al. to suggest that facilitation may take place because a calcium-based mechanism in the cell increases the number of vesicles ready to release their chemicals. This new model may help researchers to better understand how the cells in the nervous system work. Ultimately, this can guide experiments to investigate what happens when information processing at synapses breaks down, for example in diseases such as epilepsy.
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Affiliation(s)
- Janus Rl Kobbersmed
- Department of Mathematical Sciences, University of Copenhagen, København, Denmark.,Department of Neuroscience, University of Copenhagen, København, Denmark
| | - Andreas T Grasskamp
- Molecular and Theoretical Neuroscience, Leibniz-Forschungsinstitut für Molekulare Pharmakologie, FMP im CharitéCrossOver, Berlin, Germany
| | - Meida Jusyte
- Molecular and Theoretical Neuroscience, Leibniz-Forschungsinstitut für Molekulare Pharmakologie, FMP im CharitéCrossOver, Berlin, Germany.,Einstein Center for Neuroscience, Berlin, Germany
| | - Mathias A Böhme
- Molecular and Theoretical Neuroscience, Leibniz-Forschungsinstitut für Molekulare Pharmakologie, FMP im CharitéCrossOver, Berlin, Germany
| | - Susanne Ditlevsen
- Department of Mathematical Sciences, University of Copenhagen, København, Denmark
| | | | - Alexander M Walter
- Molecular and Theoretical Neuroscience, Leibniz-Forschungsinstitut für Molekulare Pharmakologie, FMP im CharitéCrossOver, Berlin, Germany.,Einstein Center for Neuroscience, Berlin, Germany
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22
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Hoover KM, Gratz SJ, Qi N, Herrmann KA, Liu Y, Perry-Richardson JJ, Vanderzalm PJ, O'Connor-Giles KM, Broihier HT. The calcium channel subunit α 2δ-3 organizes synapses via an activity-dependent and autocrine BMP signaling pathway. Nat Commun 2019; 10:5575. [PMID: 31811118 PMCID: PMC6898181 DOI: 10.1038/s41467-019-13165-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Accepted: 10/23/2019] [Indexed: 12/17/2022] Open
Abstract
Synapses are highly specialized for neurotransmitter signaling, yet activity-dependent growth factor release also plays critical roles at synapses. While efficient neurotransmitter signaling relies on precise apposition of release sites and neurotransmitter receptors, molecular mechanisms enabling high-fidelity growth factor signaling within the synaptic microenvironment remain obscure. Here we show that the auxiliary calcium channel subunit α2δ-3 promotes the function of an activity-dependent autocrine Bone Morphogenetic Protein (BMP) signaling pathway at the Drosophila neuromuscular junction (NMJ). α2δ proteins have conserved synaptogenic activity, although how they execute this function has remained elusive. We find that α2δ-3 provides an extracellular scaffold for an autocrine BMP signal, suggesting a mechanistic framework for understanding α2δ's conserved role in synapse organization. We further establish a transcriptional requirement for activity-dependent, autocrine BMP signaling in determining synapse density, structure, and function. We propose that activity-dependent, autocrine signals provide neurons with continuous feedback on their activity state for modulating both synapse structure and function.
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Affiliation(s)
- Kendall M Hoover
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA
| | - Scott J Gratz
- Department of Neuroscience, Brown University, Providence, RI, 02912, USA
| | - Nova Qi
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA
| | - Kelsey A Herrmann
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA
| | - Yizhou Liu
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA
| | - Jahci J Perry-Richardson
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA
| | - Pamela J Vanderzalm
- Department of Biology, John Carroll University, University Heights, OH, 44118, USA
| | | | - Heather T Broihier
- Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH, 44106, USA.
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23
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Frank CA, James TD, Müller M. Homeostatic control of Drosophila neuromuscular junction function. Synapse 2019; 74:e22133. [PMID: 31556149 PMCID: PMC6817395 DOI: 10.1002/syn.22133] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Revised: 09/05/2019] [Accepted: 09/19/2019] [Indexed: 02/06/2023]
Abstract
The ability to adapt to changing internal and external conditions is a key feature of biological systems. Homeostasis refers to a regulatory process that stabilizes dynamic systems to counteract perturbations. In the nervous system, homeostatic mechanisms control neuronal excitability, neurotransmitter release, neurotransmitter receptors, and neural circuit function. The neuromuscular junction (NMJ) of Drosophila melanogaster has provided a wealth of molecular information about how synapses implement homeostatic forms of synaptic plasticity, with a focus on the transsynaptic, homeostatic modulation of neurotransmitter release. This review examines some of the recent findings from the Drosophila NMJ and highlights questions the field will ponder in coming years.
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Affiliation(s)
- C Andrew Frank
- Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA.,Interdisciplinary Programs in Neuroscience, Genetics, and Molecular Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Thomas D James
- Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA.,Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, Iowa, USA
| | - Martin Müller
- Institute of Molecular Life Sciences, University of Zurich, Zurich, Switzerland.,Neuroscience Center Zurich, Zurich, Switzerland
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24
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RIMB-1/RIM-Binding Protein and UNC-10/RIM Redundantly Regulate Presynaptic Localization of the Voltage-Gated Calcium Channel in Caenorhabditis elegans. J Neurosci 2019; 39:8617-8631. [PMID: 31530643 DOI: 10.1523/jneurosci.0506-19.2019] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 09/03/2019] [Accepted: 09/10/2019] [Indexed: 11/21/2022] Open
Abstract
Presynaptic active zones (AZs) contain many molecules essential for neurotransmitter release and are assembled in a highly organized manner. A network of adaptor proteins known as cytomatrix at the AZ (CAZ) is important for shaping the structural characteristics of AZ. Rab3-interacting molecule (RIM)-binding protein (RBP) family are binding partners of the CAZ protein RIM and also bind the voltage-gated calcium channels (VGCCs) in mice and flies. Here, we investigated the physiological roles of RIMB-1, the homolog of RBPs in the nematode Caenorhabditis elegans RIMB-1 is expressed broadly in neurons and predominantly localized at presynaptic sites. Loss-of-function animals of rimb-1 displayed slight defects in motility and response to pharmacological inhibition of synaptic transmission, suggesting a modest involvement of rimb-1 in synapse function. We analyzed genetic interactions of rimb-1 by testing candidate genes and by an unbiased forward genetic screen for rimb-1 enhancer. Both analyses identified the RIM homolog UNC-10 that acts together with RIMB-1 to regulate presynaptic localization of the P/Q-type VGCC UNC-2/Cav2. We also find that the precise localization of RIMB-1 to presynaptic sites requires presynaptic UNC-2/Cav2. RIMB-1 has multiple FN3 and SH3 domains. Our transgenic rescue analysis with RIMB-1 deletion constructs revealed a functional requirement of a C-terminal SH3 in regulating UNC-2/Cav2 localization. Together, these findings suggest a redundant role of RIMB-1/RBP and UNC-10/RIM to regulate the abundance of UNC-2/Cav2 at the presynaptic AZ in C. elegans, depending on the bidirectional interplay between CAZ adaptor and channel proteins.SIGNIFICANCE STATEMENT Presynaptic active zones (AZs) are highly organized structures for synaptic transmission with characteristic networks of adaptor proteins called cytomatrix at the AZ (CAZ). In this study, we characterized a CAZ protein RIMB-1, named for RIM-binding protein (RBP), in the nematode Caenorhabditis elegans Through systematic analyses of genetic interactions and an unbiased genetic enhancer screen of rimb-1, we revealed a redundant role of two CAZ proteins RIMB-1/RBP and UNC-10/RIM in regulating presynaptic localization of UNC-2/Cav2, a voltage-gated calcium channel (VGCC) critical for proper neurotransmitter release. Additionally, the precise localization of RIMB-1/RBP requires presynaptic UNC-2/Cav2. These findings provide new mechanistic insight about how the interplay among multiple CAZ adaptor proteins and VGCC contributes to the organization of presynaptic AZ.
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25
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Hill AS, Jain P, Folan NE, Ben-Shahar Y. The Drosophila ERG channel seizure plays a role in the neuronal homeostatic stress response. PLoS Genet 2019; 15:e1008288. [PMID: 31393878 PMCID: PMC6687100 DOI: 10.1371/journal.pgen.1008288] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 07/04/2019] [Indexed: 11/24/2022] Open
Abstract
Neuronal physiology is particularly sensitive to acute stressors that affect excitability, many of which can trigger seizures and epilepsies. Although intrinsic neuronal homeostasis plays an important role in maintaining overall nervous system robustness and its resistance to stressors, the specific genetic and molecular mechanisms that underlie these processes are not well understood. Here we used a reverse genetic approach in Drosophila to test the hypothesis that specific voltage-gated ion channels contribute to neuronal homeostasis, robustness, and stress resistance. We found that the activity of the voltage-gated potassium channel seizure (sei), an ortholog of the mammalian ERG channel family, is essential for protecting flies from acute heat-induced seizures. Although sei is broadly expressed in the nervous system, our data indicate that its impact on the organismal robustness to acute environmental stress is primarily mediated via its action in excitatory neurons, the octopaminergic system, as well as neuropile ensheathing and perineurial glia. Furthermore, our studies suggest that human mutations in the human ERG channel (hERG), which have been primarily implicated in the cardiac Long QT Syndrome (LQTS), may also contribute to the high incidence of seizures in LQTS patients via a cardiovascular-independent neurogenic pathway.
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Affiliation(s)
- Alexis S. Hill
- Department of Biology, College of the Holy Cross, Worcester, Massachusetts, United States of America
| | - Poorva Jain
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Nicole E. Folan
- Department of Biology, College of the Holy Cross, Worcester, Massachusetts, United States of America
| | - Yehuda Ben-Shahar
- Department of Biology, Washington University in St. Louis, St. Louis, Missouri, United States of America
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26
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Skouloudaki K, Christodoulou I, Khalili D, Tsarouhas V, Samakovlis C, Tomancak P, Knust E, Papadopoulos DK. Yorkie controls tube length and apical barrier integrity during airway development. J Cell Biol 2019; 218:2762-2781. [PMID: 31315941 PMCID: PMC6683733 DOI: 10.1083/jcb.201809121] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Revised: 05/02/2019] [Accepted: 06/04/2019] [Indexed: 12/18/2022] Open
Abstract
Skouloudaki et al. identify an alternative role of the transcriptional coactivator Yorkie (Yki) in controlling water impermeability and tube size of developing Drosophila airways. Tracheal impermeability is triggered by Yki-mediated transcriptional regulation of δ-aminolevulinate synthase (Alas), whereas tube elongation is controlled by binding of Yki to the actin-severing factor Twinstar. Epithelial organ size and shape depend on cell shape changes, cell–matrix communication, and apical membrane growth. The Drosophila melanogaster embryonic tracheal network is an excellent model to study these processes. Here, we show that the transcriptional coactivator of the Hippo pathway, Yorkie (YAP/TAZ in vertebrates), plays distinct roles in the developing Drosophila airways. Yorkie exerts a cytoplasmic function by binding Drosophila Twinstar, the orthologue of the vertebrate actin-severing protein Cofilin, to regulate F-actin levels and apical cell membrane size, which are required for proper tracheal tube elongation. Second, Yorkie controls water tightness of tracheal tubes by transcriptional regulation of the δ-aminolevulinate synthase gene (Alas). We conclude that Yorkie has a dual role in tracheal development to ensure proper tracheal growth and functionality.
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Affiliation(s)
| | - Ioannis Christodoulou
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, UK
| | - Dilan Khalili
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Vasilios Tsarouhas
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Christos Samakovlis
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden.,Excellence Cluster Cardio-Pulmonary System, University of Giessen, Giessen, Germany
| | - Pavel Tomancak
- Max-Planck Institute for Molecular Cell Biology and Genetics, Dresden, Germany
| | - Elisabeth Knust
- Max-Planck Institute for Molecular Cell Biology and Genetics, Dresden, Germany
| | - Dimitrios K Papadopoulos
- Max-Planck Institute for Molecular Cell Biology and Genetics, Dresden, Germany .,Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh, UK
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27
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Kikuma K, Li X, Perry S, Li Q, Goel P, Chen C, Kim D, Stavropoulos N, Dickman D. Cul3 and insomniac are required for rapid ubiquitination of postsynaptic targets and retrograde homeostatic signaling. Nat Commun 2019; 10:2998. [PMID: 31278365 PMCID: PMC6611771 DOI: 10.1038/s41467-019-10992-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Accepted: 06/14/2019] [Indexed: 01/05/2023] Open
Abstract
At the Drosophila neuromuscular junction, inhibition of postsynaptic glutamate receptors activates retrograde signaling that precisely increases presynaptic neurotransmitter release to restore baseline synaptic strength. However, the nature of the underlying postsynaptic induction process remains enigmatic. Here, we design a forward genetic screen to discover factors in the postsynaptic compartment necessary to generate retrograde homeostatic signaling. This approach identified insomniac (inc), a putative adaptor for the Cullin-3 (Cul3) ubiquitin ligase complex, which together with Cul3 is essential for normal sleep regulation. Interestingly, we find that Inc and Cul3 rapidly accumulate at postsynaptic compartments following acute receptor inhibition and are required for a local increase in mono-ubiquitination. Finally, we show that Peflin, a Ca2+-regulated Cul3 co-adaptor, is necessary for homeostatic communication, suggesting a relationship between Ca2+ signaling and control of Cul3/Inc activity in the postsynaptic compartment. Our study suggests that Cul3/Inc-dependent mono-ubiquitination, compartmentalized at postsynaptic densities, gates retrograde signaling and provides an intriguing molecular link between the control of sleep and homeostatic plasticity at synapses. The authors use a forward genetic screen to discover postsynaptic factors required for homeostatic synaptic plasticity at the Drosophila neuromuscular junction. They identify insomniac and the ubiquitin ligase Cul3, genes involved in sleep regulation, to be necessary for retrograde homeostatic signalling at this synapse.
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Affiliation(s)
- Koto Kikuma
- Department of Neurobiology, University of Southern California, Los Angeles, CA, 90089, USA
| | - Xiling Li
- Department of Neurobiology, University of Southern California, Los Angeles, CA, 90089, USA
| | - Sarah Perry
- Department of Neurobiology, University of Southern California, Los Angeles, CA, 90089, USA
| | - Qiuling Li
- Neuroscience Institute, Department of Neuroscience and Physiology, NYU School of Medicine, New York, NY, 10016, USA
| | - Pragya Goel
- Department of Neurobiology, University of Southern California, Los Angeles, CA, 90089, USA
| | - Catherine Chen
- Department of Neurobiology, University of Southern California, Los Angeles, CA, 90089, USA
| | - Daniel Kim
- Department of Neurobiology, University of Southern California, Los Angeles, CA, 90089, USA
| | - Nicholas Stavropoulos
- Neuroscience Institute, Department of Neuroscience and Physiology, NYU School of Medicine, New York, NY, 10016, USA
| | - Dion Dickman
- Department of Neurobiology, University of Southern California, Los Angeles, CA, 90089, USA.
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28
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Yang R, Li E, Kwon YJ, Mani M, Beitel GJ. QuBiT: a quantitative tool for analyzing epithelial tubes reveals unexpected patterns of organization in the Drosophila trachea. Development 2019; 146:dev.172759. [PMID: 30967427 DOI: 10.1242/dev.172759] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Accepted: 04/03/2019] [Indexed: 01/26/2023]
Abstract
Biological tubes are essential for animal survival, and their functions are dependent on tube shape. Analyzing the contributions of cell shape and organization to the morphogenesis of small tubes has been hampered by the limitations of existing programs in quantifying cell geometry on highly curved tubular surfaces and calculating tube-specific parameters. We therefore developed QuBiT (Quantitative Tool for Biological Tubes) and used it to analyze morphogenesis of the embryonic Drosophila trachea (airway). In the main tube, we find previously unknown anterior-to-posterior (A-P) gradients of cell apical orientation and aspect ratio, and periodicity in the organization of apical cell surfaces. Inferred cell intercalation during development dampens an A-P gradient of the number of cells per cross-section of the tube, but does not change the patterns of cell connectivity. Computationally 'unrolling' the apical surface of wild-type trachea and the hindgut reveals previously unrecognized spatial patterns of the apical marker Uninflatable and a non-redundant role for the Na+/K+ ATPase in apical marker organization. These unexpected findings demonstrate the importance of a computational tool for analyzing small diameter biological tubes.
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Affiliation(s)
- Ran Yang
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
| | - Eric Li
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
| | - Yong-Jae Kwon
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
| | - Madhav Mani
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA.,Department of Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, IL 60208, USA.,NSF-Simons Center for Quantitative Biology, Northwestern University, Evanston, IL 60208, USA
| | - Greg J Beitel
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
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29
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Böhme MA, McCarthy AW, Grasskamp AT, Beuschel CB, Goel P, Jusyte M, Laber D, Huang S, Rey U, Petzoldt AG, Lehmann M, Göttfert F, Haghighi P, Hell SW, Owald D, Dickman D, Sigrist SJ, Walter AM. Rapid active zone remodeling consolidates presynaptic potentiation. Nat Commun 2019; 10:1085. [PMID: 30842428 PMCID: PMC6403334 DOI: 10.1038/s41467-019-08977-6] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 02/07/2019] [Indexed: 01/22/2023] Open
Abstract
Neuronal communication across synapses relies on neurotransmitter release from presynaptic active zones (AZs) followed by postsynaptic transmitter detection. Synaptic plasticity homeostatically maintains functionality during perturbations and enables memory formation. Postsynaptic plasticity targets neurotransmitter receptors, but presynaptic mechanisms regulating the neurotransmitter release apparatus remain largely enigmatic. By studying Drosophila neuromuscular junctions (NMJs) we show that AZs consist of nano-modular release sites and identify a molecular sequence that adds modules within minutes of inducing homeostatic plasticity. This requires cognate transport machinery and specific AZ-scaffolding proteins. Structural remodeling is not required for immediate potentiation of neurotransmitter release, but necessary to sustain potentiation over longer timescales. Finally, mutations in Unc13 disrupting homeostatic plasticity at the NMJ also impair short-term memory when central neurons are targeted, suggesting that both plasticity mechanisms utilize Unc13. Together, while immediate synaptic potentiation capitalizes on available material, it triggers the coincident incorporation of modular release sites to consolidate synaptic potentiation.
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Affiliation(s)
- Mathias A Böhme
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125, Berlin, Germany.,NeuroCure Cluster of Excellence, Charité Universitätsmedizin, 10117, Berlin, Germany.,Institute for Biology/Genetics, Freie Universität Berlin, 14195, Berlin, Germany
| | - Anthony W McCarthy
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125, Berlin, Germany
| | - Andreas T Grasskamp
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125, Berlin, Germany.,NeuroCure Cluster of Excellence, Charité Universitätsmedizin, 10117, Berlin, Germany
| | - Christine B Beuschel
- NeuroCure Cluster of Excellence, Charité Universitätsmedizin, 10117, Berlin, Germany.,Institute for Biology/Genetics, Freie Universität Berlin, 14195, Berlin, Germany
| | - Pragya Goel
- Department of Neurobiology, University of Southern California, Los Angeles, CA, 90089, USA
| | - Meida Jusyte
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125, Berlin, Germany
| | - Desiree Laber
- Institut für Neurophysiologie, Charité Universitätsmedizin, 10117, Berlin, Germany
| | - Sheng Huang
- Institute for Biology/Genetics, Freie Universität Berlin, 14195, Berlin, Germany
| | - Ulises Rey
- Institute for Biology/Genetics, Freie Universität Berlin, 14195, Berlin, Germany.,Department of Theory and Bio-systems, Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14424, Potsdam, Germany
| | - Astrid G Petzoldt
- Institute for Biology/Genetics, Freie Universität Berlin, 14195, Berlin, Germany
| | - Martin Lehmann
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125, Berlin, Germany
| | - Fabian Göttfert
- Department of Nanobiophotonics, Max Planck Institute for Biophysical Chemistry, 37077, Göttingen, Germany
| | | | - Stefan W Hell
- Department of Nanobiophotonics, Max Planck Institute for Biophysical Chemistry, 37077, Göttingen, Germany
| | - David Owald
- Institut für Neurophysiologie, Charité Universitätsmedizin, 10117, Berlin, Germany
| | - Dion Dickman
- Department of Neurobiology, University of Southern California, Los Angeles, CA, 90089, USA
| | - Stephan J Sigrist
- NeuroCure Cluster of Excellence, Charité Universitätsmedizin, 10117, Berlin, Germany. .,Institute for Biology/Genetics, Freie Universität Berlin, 14195, Berlin, Germany.
| | - Alexander M Walter
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125, Berlin, Germany.
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30
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Delvendahl I, Müller M. Homeostatic plasticity—a presynaptic perspective. Curr Opin Neurobiol 2019; 54:155-162. [DOI: 10.1016/j.conb.2018.10.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2018] [Accepted: 10/04/2018] [Indexed: 01/05/2023]
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31
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Endogenous Tagging Reveals Differential Regulation of Ca 2+ Channels at Single Active Zones during Presynaptic Homeostatic Potentiation and Depression. J Neurosci 2019; 39:2416-2429. [PMID: 30692227 PMCID: PMC6435823 DOI: 10.1523/jneurosci.3068-18.2019] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 01/14/2019] [Accepted: 01/21/2019] [Indexed: 12/19/2022] Open
Abstract
Neurons communicate through Ca2+-dependent neurotransmitter release at presynaptic active zones (AZs). Neurotransmitter release properties play a key role in defining information flow in circuits and are tuned during multiple forms of plasticity. Despite their central role in determining neurotransmitter release properties, little is known about how Ca2+ channel levels are modulated to calibrate synaptic function. We used CRISPR to tag the Drosophila CaV2 Ca2+ channel Cacophony (Cac) and, in males in which all Cac channels are tagged, investigated the regulation of endogenous Ca2+ channels during homeostatic plasticity. We found that heterogeneously distributed Cac is highly predictive of neurotransmitter release probability at individual AZs and differentially regulated during opposing forms of presynaptic homeostatic plasticity. Specifically, AZ Cac levels are increased during chronic and acute presynaptic homeostatic potentiation (PHP), and live imaging during acute expression of PHP reveals proportional Ca2+ channel accumulation across heterogeneous AZs. In contrast, endogenous Cac levels do not change during presynaptic homeostatic depression (PHD), implying that the reported reduction in Ca2+ influx during PHD is achieved through functional adaptions to pre-existing Ca2+ channels. Thus, distinct mechanisms bidirectionally modulate presynaptic Ca2+ levels to maintain stable synaptic strength in response to diverse challenges, with Ca2+ channel abundance providing a rapidly tunable substrate for potentiating neurotransmitter release over both acute and chronic timescales. SIGNIFICANCE STATEMENT Presynaptic Ca2+ dynamics play an important role in establishing neurotransmitter release properties. Presynaptic Ca2+ influx is modulated during multiple forms of homeostatic plasticity at Drosophila neuromuscular junctions to stabilize synaptic communication. However, it remains unclear how this dynamic regulation is achieved. We used CRISPR gene editing to endogenously tag the sole Drosophila Ca2+ channel responsible for synchronized neurotransmitter release, and found that channel abundance is regulated during homeostatic potentiation, but not homeostatic depression. Through live imaging experiments during the adaptation to acute homeostatic challenge, we visualize the accumulation of endogenous Ca2+ channels at individual active zones within 10 min. We propose that differential regulation of Ca2+ channels confers broad capacity for tuning neurotransmitter release properties to maintain neural communication.
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32
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Mansilla A, Jordán-Álvarez S, Santana E, Jarabo P, Casas-Tintó S, Ferrús A. Molecular mechanisms that change synapse number. J Neurogenet 2018; 32:155-170. [DOI: 10.1080/01677063.2018.1506781] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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33
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Harris KP, Littleton JT, Stewart BA. Postsynaptic Syntaxin 4 negatively regulates the efficiency of neurotransmitter release. J Neurogenet 2018; 32:221-229. [PMID: 30175640 PMCID: PMC6317344 DOI: 10.1080/01677063.2018.1501372] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 07/13/2018] [Indexed: 12/12/2022]
Abstract
Signaling from the postsynaptic compartment regulates multiple aspects of synaptic development and function. Syntaxin 4 (Syx4) is a plasma membrane t-SNARE that promotes the growth and plasticity of Drosophila neuromuscular junctions (NMJs) by regulating the localization of key synaptic proteins in the postsynaptic compartment. Here, we describe electrophysiological analyses and report that loss of Syx4 leads to enhanced neurotransmitter release, despite a decrease in the number of active zones. We describe a requirement for postsynaptic Syx4 in regulating several presynaptic parameters, including Ca2+ cooperativity and the abundance of the presynaptic calcium channel Cacophony (Cac) at active zones. These findings indicate Syx4 negatively regulates presynaptic neurotransmitter release through a retrograde signaling mechanism from the postsynaptic compartment.
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Affiliation(s)
- Kathryn P Harris
- a Department of Biology , University of Toronto Mississauga , Mississauga , ON, Canada
- b Department of Cell and Systems Biology , University of Toronto , Toronto , ON, Canada
| | - J Troy Littleton
- c The Picower Institute for Learning and Memory , Massachusetts Institute of Technology , Cambridge , MA , USA
- d Department of Biology , Massachusetts Institute of Technology , Cambridge , MA , USA
- e Department of Brain and Cognitive Sciences , Massachusetts Institute of Technology , Cambridge , MA , USA
| | - Bryan A Stewart
- a Department of Biology , University of Toronto Mississauga , Mississauga , ON, Canada
- b Department of Cell and Systems Biology , University of Toronto , Toronto , ON, Canada
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34
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Akbergenova Y, Cunningham KL, Zhang YV, Weiss S, Littleton JT. Characterization of developmental and molecular factors underlying release heterogeneity at Drosophila synapses. eLife 2018; 7:38268. [PMID: 29989549 PMCID: PMC6075867 DOI: 10.7554/elife.38268] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 06/30/2018] [Indexed: 12/14/2022] Open
Abstract
Neurons communicate through neurotransmitter release at specialized synaptic regions known as active zones (AZs). Using biosensors to visualize single synaptic vesicle fusion events at Drosophila neuromuscular junctions, we analyzed the developmental and molecular determinants of release probability (Pr) for a defined connection with ~300 AZs. Pr was heterogeneous but represented a stable feature of each AZ. Pr remained stable during high frequency stimulation and retained heterogeneity in mutants lacking the Ca2+ sensor Synaptotagmin 1. Pr correlated with both presynaptic Ca2+ channel abundance and Ca2+ influx at individual release sites. Pr heterogeneity also correlated with glutamate receptor abundance, with high Pr connections developing receptor subtype segregation. Intravital imaging throughout development revealed that AZs acquire high Pr during a multi-day maturation period, with Pr heterogeneity largely reflecting AZ age. The rate of synapse maturation was activity-dependent, as both increases and decreases in neuronal activity modulated glutamate receptor field size and segregation. To send a message to its neighbor, a neuron releases chemicals called neurotransmitters into the gap – or synapse – between them. The neurotransmitter molecules bind to proteins on the receiver neuron called receptors. But what causes the sender neuron to release neurotransmitter in the first place? The process starts when an electrical impulse called an action potential arrives at the sender cell. Its arrival causes channels in the membrane of the sender neuron to open, so that calcium ions flood into the cell. The calcium ions interact with packages of neurotransmitter molecules, known as synaptic vesicles. This causes some of the vesicles to empty their contents into the synapse. But this process is not particularly reliable. Only a small fraction of action potentials cause vesicles to fuse with the synaptic membrane. How likely this is to occur varies greatly between neurons, and even between synapses formed by the same neuron. Synapses that are likely to release neurotransmitter are said to be strong. They are good at passing messages from the sender neuron to the receiver. Synapses with a low probability of release are said to be weak. But what exactly differs between strong and weak synapses? Akbergenova et al. studied synapses between motor neurons and muscle cells in the fruit fly Drosophila. Each motor neuron forms several hundred synapses. Some of these synapses are 50 times more likely to release neurotransmitter than others. Using calcium imaging and genetics, Akbergenova et al. showed that sender cells at strong synapses have more calcium channels than sender cells at weak synapses. The subtypes and arrangement of receptor proteins also differ between the receiver neurons of strong versus weak synapses. Finally, studies in larvae revealed that newly formed synapses all start out weak and then gradually become stronger. How fast this strengthening occurs depends on how active the neuron at the synapse is. This study has shown, in unprecedented detail, key molecular factors that make some fruit fly synapses more likely to release neurotransmitter than others. Many proteins at synapses of mammals resemble those at fruit fly synapses. This means that similar factors may also explain differences in synaptic strength in the mammalian brain. Changes in the strength of synapses underlie the ability to learn. Furthermore, many neurological and psychiatric disorders result from disruption of synapses. Understanding the molecular basis of synapses will thus provide clues to the origins of certain brain diseases.
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Affiliation(s)
- Yulia Akbergenova
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, United States.,Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
| | - Karen L Cunningham
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, United States
| | - Yao V Zhang
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, United States.,Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
| | - Shirley Weiss
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, United States.,Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
| | - J Troy Littleton
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, United States.,Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
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35
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Li X, Goel P, Chen C, Angajala V, Chen X, Dickman DK. Synapse-specific and compartmentalized expression of presynaptic homeostatic potentiation. eLife 2018; 7:34338. [PMID: 29620520 PMCID: PMC5927770 DOI: 10.7554/elife.34338] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 04/04/2018] [Indexed: 01/23/2023] Open
Abstract
Postsynaptic compartments can be specifically modulated during various forms of synaptic plasticity, but it is unclear whether this precision is shared at presynaptic terminals. Presynaptic homeostatic plasticity (PHP) stabilizes neurotransmission at the Drosophila neuromuscular junction, where a retrograde enhancement of presynaptic neurotransmitter release compensates for diminished postsynaptic receptor functionality. To test the specificity of PHP induction and expression, we have developed a genetic manipulation to reduce postsynaptic receptor expression at one of the two muscles innervated by a single motor neuron. We find that PHP can be induced and expressed at a subset of synapses, over both acute and chronic time scales, without influencing transmission at adjacent release sites. Further, homeostatic modulations to CaMKII, vesicle pools, and functional release sites are compartmentalized and do not spread to neighboring pre- or post-synaptic structures. Thus, both PHP induction and expression mechanisms are locally transmitted and restricted to specific synaptic compartments. Everything we think and do is the result of communication between neurons. This communication takes place at junctions called synapses. When two nerve cells or neurons communicate at a synapse, the output terminal of the first cell releases a chemical called a neurotransmitter. This binds to receiver proteins, or receptors, on the second cell. When this communication is interrupted, synapses can adapt to maintain a stable dialogue between them. This can occur in two ways. Either the first neuron starts to release more neurotransmitter from its output terminal, or the second neuron produces extra receptors with which to detect the neurotransmitter. But how specific are these changes? The brain contains far more synapses than neurons because each neuron can form synapses with many other cells. Can a neuron adjust how much of the neurotransmitter it releases at some of its synapses while leaving the others unchanged? Li et al. have now addressed this question by studying a special type of synapse that forms between neurons and muscles, known as a neuromuscular junction. At one particular neuromuscular junction in fruit flies, a single neuron splits into two output terminals, each of which forms a synapse with a different muscle. Li et al. show that when the number of neurotransmitter receptors in one of the muscles is artificially reduced, the associated output terminal compensates by increasing its neurotransmitter release. By contrast, the other output terminal remains unaffected. This suggests that a neuron can induce remarkably specific changes in a subset of its synapses. This discovery paves the way towards identifying the smallest possible unit of change that can occur in the neurons’ ability to communicate. This unit may in turn be the smallest change that can support learning. Such knowledge will help us understand how the nervous system processes and stabilizes information transfer, both in health and after injury or disease.
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Affiliation(s)
- Xiling Li
- Department of Neurobiology, University of Southern California, Los Angeles, United States.,Neuroscience Graduate Program, University of Southern California, California, United States
| | - Pragya Goel
- Department of Neurobiology, University of Southern California, Los Angeles, United States.,Graduate Program in Molecular and Computational Biology, University of Southern California, California, United States
| | - Catherine Chen
- Department of Neurobiology, University of Southern California, Los Angeles, United States
| | | | - Xun Chen
- Neuroscience Graduate Program, University of Southern California, California, United States
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36
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Ehmann N, Owald D, Kittel RJ. Drosophila active zones: From molecules to behaviour. Neurosci Res 2018; 127:14-24. [DOI: 10.1016/j.neures.2017.11.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2017] [Revised: 11/30/2017] [Accepted: 11/30/2017] [Indexed: 11/15/2022]
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37
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A conserved maternal-specific repressive domain in Zelda revealed by Cas9-mediated mutagenesis in Drosophila melanogaster. PLoS Genet 2017; 13:e1007120. [PMID: 29261646 PMCID: PMC5752043 DOI: 10.1371/journal.pgen.1007120] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Revised: 01/03/2018] [Accepted: 11/20/2017] [Indexed: 12/13/2022] Open
Abstract
In nearly all metazoans, the earliest stages of development are controlled by maternally deposited mRNAs and proteins. The zygotic genome becomes transcriptionally active hours after fertilization. Transcriptional activation during this maternal-to-zygotic transition (MZT) is tightly coordinated with the degradation of maternally provided mRNAs. In Drosophila melanogaster, the transcription factor Zelda plays an essential role in widespread activation of the zygotic genome. While Zelda expression is required both maternally and zygotically, the mechanisms by which it functions to remodel the embryonic genome and prepare the embryo for development remain unclear. Using Cas9-mediated genome editing to generate targeted mutations in the endogenous zelda locus, we determined the functional relevance of protein domains conserved amongst Zelda orthologs. We showed that neither a conserved N-terminal zinc finger nor an acidic patch were required for activity. Similarly, a previously identified splice isoform of zelda is dispensable for viability. By contrast, we identified a highly conserved zinc-finger domain that is essential for the maternal, but not zygotic functions of Zelda. Animals homozygous for mutations in this domain survived to adulthood, but embryos inheriting these loss-of-function alleles from their mothers died late in embryogenesis. These mutations did not interfere with the capacity of Zelda to activate transcription in cell culture. Unexpectedly, these mutations generated a hyperactive form of the protein and enhanced Zelda-dependent gene expression. These data have defined a protein domain critical for controlling Zelda activity during the MZT, but dispensable for its roles later in development, for the first time separating the maternal and zygotic requirements for Zelda. This demonstrates that highly regulated levels of Zelda activity are required for establishing the developmental program during the MZT. We propose that tightly regulated gene expression is essential to navigate the MZT and that failure to precisely execute this developmental program leads to embryonic lethality. Following fertilization, the one-celled zygote must be rapidly reprogrammed to enable the development of a new, unique organism. During these initial stages of development there is little or no transcription of the zygotic genome, and maternally deposited products control this process. Among the essential maternal products are mRNAs that encode transcription factors required for preparing the zygotic genome for transcriptional activation. This ensures that there is a precisely coordinated hand-off from maternal to zygotic control. In Drosophila melanogaster, the transcription factor Zelda is essential for activating the zygotic genome and coupling this activation to the degradation of the maternally deposited products. Nonetheless, the mechanism by which Zelda functions remains unclear. Here we used Cas9-mediated genome engineering to determine the functional requirements for highly conserved domains within Zelda. We identified a domain required specifically for Zelda’s role in reprogramming the early embryonic genome, but not essential for its functions later in development. Surprisingly, this domain restricts the ability of Zelda to activate transcription. These data demonstrate that Zelda activity is tightly regulated, and we propose that precise regulation of both the timing and levels of genome activation is required for the embryo to successfully transition from maternal to zygotic control.
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Xuan Z, Manning L, Nelson J, Richmond JE, Colón-Ramos DA, Shen K, Kurshan PT. Clarinet (CLA-1), a novel active zone protein required for synaptic vesicle clustering and release. eLife 2017; 6:29276. [PMID: 29160205 PMCID: PMC5728718 DOI: 10.7554/elife.29276] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2017] [Accepted: 11/20/2017] [Indexed: 01/03/2023] Open
Abstract
Active zone proteins cluster synaptic vesicles at presynaptic terminals and coordinate their release. In forward genetic screens, we isolated a novel Caenorhabditis elegans active zone gene, clarinet (cla-1). cla-1 mutants exhibit defects in synaptic vesicle clustering, active zone structure and synapse number. As a result, they have reduced spontaneous vesicle release and increased synaptic depression. cla-1 mutants show defects in vesicle distribution near the presynaptic dense projection, with fewer undocked vesicles contacting the dense projection and more docked vesicles at the plasma membrane. cla-1 encodes three isoforms containing common C-terminal PDZ and C2 domains with homology to vertebrate active zone proteins Piccolo and RIM. The C-termini of all isoforms localize to the active zone. Specific loss of the ~9000 amino acid long isoform results in vesicle clustering defects and increased synaptic depression. Our data indicate that specific isoforms of clarinet serve distinct functions, regulating synapse development, vesicle clustering and release.
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Affiliation(s)
- Zhao Xuan
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, United States.,Department of Cell Biology, Yale University School of Medicine, New Haven, United States.,Department of Neuroscience, Yale University School of Medicine, New Haven, United States
| | - Laura Manning
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois
| | - Jessica Nelson
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, United States.,Department of Cell Biology, Yale University School of Medicine, New Haven, United States.,Department of Neuroscience, Yale University School of Medicine, New Haven, United States
| | - Janet E Richmond
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, Illinois
| | - Daniel A Colón-Ramos
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, United States.,Department of Cell Biology, Yale University School of Medicine, New Haven, United States.,Department of Neuroscience, Yale University School of Medicine, New Haven, United States.,Instituto de Neurobiología, Recinto de Ciencias Médicas, Universidad de Puerto Rico, San Juan, Puerto Rico
| | - Kang Shen
- Department of Biology, Stanford University, Stanford, United States.,Howard Hughes Medical Institute
| | - Peri T Kurshan
- Department of Biology, Stanford University, Stanford, United States
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Torres VI, Inestrosa NC. Vertebrate Presynaptic Active Zone Assembly: a Role Accomplished by Diverse Molecular and Cellular Mechanisms. Mol Neurobiol 2017; 55:4513-4528. [PMID: 28685386 DOI: 10.1007/s12035-017-0661-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 06/14/2017] [Indexed: 01/22/2023]
Abstract
Among all the biological systems in vertebrates, the central nervous system (CNS) is the most complex, and its function depends on specialized contacts among neurons called synapses. The assembly and organization of synapses must be exquisitely regulated for a normal brain function and network activity. There has been a tremendous effort in recent decades to understand the molecular and cellular mechanisms participating in the formation of new synapses and their organization, maintenance, and regulation. At the vertebrate presynapses, proteins such as Piccolo, Bassoon, RIM, RIM-BPs, CAST/ELKS, liprin-α, and Munc13 are constant residents and participate in multiple and dynamic interactions with other regulatory proteins, which define network activity and normal brain function. Here, we review the function of these active zone (AZ) proteins and diverse factors involved in AZ assembly and maintenance, with an emphasis on axonal trafficking of precursor vesicles, protein homo- and hetero-oligomeric interactions as a mechanism of AZ trapping and stabilization, and the role of F-actin in presynaptic assembly and its modulation by Wnt signaling.
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Affiliation(s)
- Viviana I Torres
- Centro de Envejecimiento y Regeneración (CARE), Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Nibaldo C Inestrosa
- Centro de Envejecimiento y Regeneración (CARE), Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile. .,Center for Healthy Brain Ageing, School of Psychiatry, Faculty of Medicine, University of New South Wales, Sydney, Australia. .,Centro de Excelencia en Biomedicina de Magallanes (CEBIMA), Universidad de Magallanes, Punta Arenas, Chile.
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Van Vactor D, Sigrist SJ. Presynaptic morphogenesis, active zone organization and structural plasticity in Drosophila. Curr Opin Neurobiol 2017; 43:119-129. [PMID: 28388491 DOI: 10.1016/j.conb.2017.03.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Revised: 03/06/2017] [Accepted: 03/08/2017] [Indexed: 12/31/2022]
Abstract
Effective adaptation of neural circuit function to a changing environment requires many forms of plasticity. Among these, structural plasticity is one of the most durable, and is also an intrinsic part of the developmental logic for the formation and refinement of synaptic connectivity. Structural plasticity of presynaptic sites can involve the addition, remodeling, or removal of pre- and post-synaptic elements. However, this requires coordination of morphogenesis and assembly of the subcellular machinery for neurotransmitter release within the presynaptic neuron, as well as coordination of these events with the postsynaptic cell. While much progress has been made in revealing the cell biological mechanisms of postsynaptic structural plasticity, our understanding of presynaptic mechanisms is less complete.
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Affiliation(s)
- David Van Vactor
- Department of Cell Biology and Program in Neuroscience, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA; Okinawa Institute of Science and Technology, Graduate University, Tancha 1919-1, Onna-son, Okinawa, Japan.
| | - Stephan J Sigrist
- Institut für Biologie/Genetik and NeuroCure, Freie Universität Berlin, Takustrasse 6, D-14195 Berlin, Germany.
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Zhan H, Bruckner J, Zhang Z, O’Connor-Giles K. Three-dimensional imaging of Drosophila motor synapses reveals ultrastructural organizational patterns. J Neurogenet 2016; 30:237-246. [PMID: 27981875 PMCID: PMC5281062 DOI: 10.1080/01677063.2016.1253693] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Revised: 10/22/2016] [Accepted: 10/24/2016] [Indexed: 01/18/2023]
Abstract
We combined cryo-preservation of intact Drosophila larvae and electron tomography with comprehensive segmentation of key features to reconstruct the complete ultrastructure of a model glutamatergic synapse in a near-to-native state. Presynaptically, we detail a complex network of filaments that connects and organizes synaptic vesicles. We link the complexity of this synaptic vesicle network to proximity to the active zone cytomatrix, consistent with the model that these protein structures function together to regulate synaptic vesicle pools. We identify a net-shaped network of electron-dense filaments spanning the synaptic cleft that suggests conserved organization of trans-synaptic adhesion complexes at excitatory synapses. Postsynaptically, we characterize a regular pattern of macromolecules that yields structural insights into the scaffolding of neurotransmitter receptors. Together, these analyses reveal an unexpected level of conservation in the nanoscale organization of diverse glutamatergic synapses and provide a structural foundation for understanding the molecular machines that regulate synaptic communication at a powerful model synapse.
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Affiliation(s)
- Hong Zhan
- Laboratory of Cell and Molecular Biology, University of Wisconsin-Madison, Madison, WI 53706
| | - Joseph Bruckner
- Cell and Molecular Biology Training Program, University of Wisconsin-Madison, Madison, WI 53706
| | - Ziheng Zhang
- Laboratory of Cell and Molecular Biology, University of Wisconsin-Madison, Madison, WI 53706
| | - Kate O’Connor-Giles
- Laboratory of Cell and Molecular Biology, University of Wisconsin-Madison, Madison, WI 53706
- Cell and Molecular Biology Training Program, University of Wisconsin-Madison, Madison, WI 53706
- Laboratory of Genetics, University of Wisconsin-Madison, Madison, WI 53706
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