1
|
Cuentas-Condori A, Chen S, Krout M, Gallik KL, Tipps J, Gailey C, Flautt L, Kim H, Mulcahy B, Zhen M, Richmond JE, Miller DM. The epithelial Na + channel UNC-8 promotes an endocytic mechanism that recycles presynaptic components to new boutons in remodeling neurons. Cell Rep 2023; 42:113327. [PMID: 37906594 PMCID: PMC10921563 DOI: 10.1016/j.celrep.2023.113327] [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: 08/18/2022] [Revised: 06/01/2023] [Accepted: 10/06/2023] [Indexed: 11/02/2023] Open
Abstract
Circuit refinement involves the formation of new presynaptic boutons as others are dismantled. Nascent presynaptic sites can incorporate material from recently eliminated synapses, but the recycling mechanisms remain elusive. In early-stage C. elegans larvae, the presynaptic boutons of GABAergic DD neurons are removed and new outputs established at alternative sites. Here, we show that developmentally regulated expression of the epithelial Na+ channel (ENaC) UNC-8 in remodeling DD neurons promotes a Ca2+ and actin-dependent mechanism, involving activity-dependent bulk endocytosis (ADBE), that recycles presynaptic material for reassembly at nascent DD synapses. ADBE normally functions in highly active neurons to accelerate local recycling of synaptic vesicles. In contrast, we find that an ADBE-like mechanism results in the distal recycling of synaptic material from old to new synapses. Thus, our findings suggest that a native mechanism (ADBE) can be repurposed to dismantle presynaptic terminals for reassembly at new, distant locations.
Collapse
Affiliation(s)
- Andrea Cuentas-Condori
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - Siqi Chen
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - Mia Krout
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - Kristin L Gallik
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - John Tipps
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - Casey Gailey
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - Leah Flautt
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA
| | - Hongkyun Kim
- Department of Cell Biology and Anatomy, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL 60064, USA
| | - Ben Mulcahy
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON M5G 1X5, Canada
| | - Mei Zhen
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON M5G 1X5, Canada
| | - Janet E Richmond
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA
| | - David M Miller
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37240, USA; Neurosience Program, Vanderbilt University, Nashville, TN 37240, USA.
| |
Collapse
|
2
|
Imomnazarov K, Torrence SE, Lindgren CA. Reduced Plasma-Membrane Calcium ATPase Activity and Extracellular Acidification Trigger Presynaptic Homeostatic Potentiation at the Mouse Neuromuscular Junction. Neuroscience 2023; 532:103-112. [PMID: 37778690 DOI: 10.1016/j.neuroscience.2023.09.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 08/23/2023] [Accepted: 09/24/2023] [Indexed: 10/03/2023]
Abstract
At the vertebrate neuromuscular junction (NMJ), presynaptic homeostatic potentiation (PHP) refers to an increase in neurotransmitter release that restores the strength of synaptic transmission following a blockade of nicotinic acetylcholine receptors (nAChRs). Mechanisms informing the presynaptic terminal of the loss of postsynaptic receptivity remain poorly understood. Previous research at the mouse NMJ suggests that extracellular protons may function as a retrograde signal that triggers an upregulation of neurotransmitter output (measured by quantal content, QC) through the activation of acid-sensing ion channels (ASICs). We further investigated the pH-dependency of PHP in an ex-vivo mouse muscle preparation. We observed that increasing the buffering capacity of the perfusion saline with HEPES abolishes PHP and that acidifying the saline from pH 7.4 to pH 7.2-7.1 increases QC, demonstrating the necessity and sufficiency of extracellular acidification for PHP. We then sought to uncover how the blockade of nAChRs leads to the pH decrease. Plasma-membrane calcium ATPase (PMCA), a calcium-proton antiporter, is known to alkalize the synaptic cleft following neurotransmission in a calcium-dependent manner. We hypothesize that since nAChR blockade reduces postsynaptic calcium entry, it also reduces the alkalizing activity of the PMCA, thereby causing acidosis, ASIC activation, and QC upregulation. In line with this hypothesis, we found that pharmacological inhibition of the PMCA with carboxyeosin induces QC upregulation and that this effect requires functional ASICs. We also demonstrated that muscles pre-treated with carboxyeosin fail to generate PHP. These findings suggest that reduced PMCA activity causes presynaptic homeostatic potentiation by activating ASICs at the mouse NMJ.
Collapse
Affiliation(s)
| | - Sarah E Torrence
- Department of Biology, Grinnell College, Grinnell, IA 50112, United States
| | - Clark A Lindgren
- Department of Biology, Grinnell College, Grinnell, IA 50112, United States.
| |
Collapse
|
3
|
Gong J, Chen J, Gu P, Shang Y, Ruppell KT, Yang Y, Wang F, Wen Q, Xiang Y. Shear stress activates nociceptors to drive Drosophila mechanical nociception. Neuron 2022; 110:3727-3742.e8. [PMID: 36087585 DOI: 10.1016/j.neuron.2022.08.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 06/07/2022] [Accepted: 08/11/2022] [Indexed: 12/15/2022]
Abstract
Mechanical nociception is essential for animal survival. However, the forces involved in nociceptor activation and the underlying mechanotransduction mechanisms remain elusive. Here, we address these problems by investigating nocifensive behavior in Drosophila larvae. We show that strong poking stimulates nociceptors with a mixture of forces including shear stress and stretch. Unexpectedly, nociceptors are selectively activated by shear stress, but not stretch. Both the shear stress responses of nociceptors and nocifensive behavior require transient receptor potential A1 (TrpA1), which is specifically expressed in nociceptors. We further demonstrate that expression of mammalian or Drosophila TrpA1 in heterologous cells confers responses to shear stress but not stretch. Finally, shear stress activates TrpA1 in a membrane-delimited manner, through modulation of membrane fluidity. Together, our study reveals TrpA1 as an evolutionarily conserved mechanosensitive channel specifically activated by shear stress and suggests a critical role of shear stress in activating nociceptors to drive mechanical nociception.
Collapse
Affiliation(s)
- Jiaxin Gong
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Jiazhang Chen
- Department of Physics, Worcester Polytechnic Institute, Worcester, MA 01605, USA
| | - Pengyu Gu
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Ye Shang
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA; Program in Neuroscience, Morningside Graduate School of Biomedical Sciences, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Kendra Takle Ruppell
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA; Program in Neuroscience, Morningside Graduate School of Biomedical Sciences, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Ying Yang
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Fei Wang
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA; Program in Neuroscience, Morningside Graduate School of Biomedical Sciences, University of Massachusetts Medical School, Worcester, MA 01605, USA
| | - Qi Wen
- Department of Physics, Worcester Polytechnic Institute, Worcester, MA 01605, USA.
| | - Yang Xiang
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, MA 01605, USA; Program in Neuroscience, Morningside Graduate School of Biomedical Sciences, University of Massachusetts Medical School, Worcester, MA 01605, USA.
| |
Collapse
|
4
|
Kaulich E, Grundy LJ, Schafer WR, Walker DS. The diverse functions of the DEG/ENaC family: linking genetic and physiological insights. J Physiol 2022; 601:1521-1542. [PMID: 36314992 PMCID: PMC10148893 DOI: 10.1113/jp283335] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Accepted: 10/25/2022] [Indexed: 11/06/2022] Open
Abstract
The DEG/ENaC family of ion channels was defined based on the sequence similarity between degenerins (DEG) from the nematode Caenorhabditis elegans and subunits of the mammalian epithelial sodium channel (ENaC), and also includes a diverse array of non-voltage-gated cation channels from across animal phyla, including the mammalian acid-sensing ion channels (ASICs) and Drosophila pickpockets. ENaCs and ASICs have wide ranging medical importance; for example, ENaCs play an important role in respiratory and renal function, and ASICs in ischaemia and inflammatory pain, as well as being implicated in memory and learning. Electrophysiological approaches, both in vitro and in vivo, have played an essential role in establishing the physiological properties of this diverse family, identifying an array of modulators and implicating them in an extensive range of cellular functions, including mechanosensation, acid sensation and synaptic modulation. Likewise, genetic studies in both invertebrates and vertebrates have played an important role in linking our understanding of channel properties to function at the cellular and whole animal/behavioural level. Drawing together genetic and physiological evidence is essential to furthering our understanding of the precise cellular roles of DEG/ENaC channels, with the diversity among family members allowing comparative physiological studies to dissect the molecular basis of these diverse functions.
Collapse
Affiliation(s)
- Eva Kaulich
- Neurobiology Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge, UK
| | - Laura J Grundy
- Neurobiology Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge, UK
| | - William R Schafer
- Neurobiology Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge, UK.,Department of Biology, KU Leuven, Leuven, Belgium
| | - Denise S Walker
- Neurobiology Division, MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge, UK
| |
Collapse
|
5
|
Zhu Y, Warrenfelt CIC, Flannery JC, Lindgren CA. Extracellular Protons Mediate Presynaptic Homeostatic Potentiation at the Mouse Neuromuscular Junction. Neuroscience 2021; 467:188-200. [PMID: 34215419 DOI: 10.1016/j.neuroscience.2021.01.036] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 01/22/2021] [Accepted: 01/28/2021] [Indexed: 01/27/2023]
Abstract
At the vertebrate neuromuscular junction (NMJ), presynaptic homeostatic potentiation (PHP) refers to the upregulation of neurotransmitter release via an increase in quantal content (QC) when the postsynaptic nicotinic acetylcholine receptors (nAChRs) are partially blocked. The mechanism of PHP has not been completely worked out. In particular, the identity of the presumed retrograde signal is still a mystery. We investigated the role of acid-sensing ion channels (ASICs) and extracellular protons in mediating PHP at the mouse NMJ. We found that blocking AISCs using benzamil, psalmotoxin-1 (PcTx1), or mambalgin-3 (Mamb3) prevented PHP. Likewise, extracellular acidification from pH 7.4 to 7.2 triggered a significant, reversable increase in QC and this increase could be prevented by PcTx1. Interestingly, an acidic saline (pH 7.2) also precluded the subsequent induction of PHP. Using immunofluorescence we observed ASIC2a and ASIC1 subunits at the NMJ. Our results indicate that protons and ASIC channels are involved in activating PHP at the mouse NMJ. We speculate that the partial blockade of nAChRs leads to a modest decrease in the pH of the synaptic cleft (∼0.2 pH units) and this activates ASIC channels on the presynaptic nerve terminal.
Collapse
Affiliation(s)
- Yiyang Zhu
- Department of Biology, Grinnell College, Grinnell, IA 50112, USA
| | | | - Jill C Flannery
- Department of Biology, Grinnell College, Grinnell, IA 50112, USA
| | - Clark A Lindgren
- Department of Biology, Grinnell College, Grinnell, IA 50112, USA.
| |
Collapse
|
6
|
Müller M, Heckmann M. Linking Protons to Homeostatic Plasticity. Neuroscience 2021; 467:185-187. [PMID: 34029647 DOI: 10.1016/j.neuroscience.2021.05.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 05/13/2021] [Indexed: 10/21/2022]
Abstract
Editorial on Extracellular protons mediate presynaptic homeostatic potentiation at the mouse neuromuscular junction.
Collapse
Affiliation(s)
- Martin Müller
- Department of Molecular Life Sciences, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
| | - Manfred Heckmann
- Institute for Physiology, Department of Neurophysiology, Julius-Maximilians-University Würzburg, D-97070 Würzburg, Germany.
| |
Collapse
|
7
|
Spierer AN, Mossman JA, Smith SP, Crawford L, Ramachandran S, Rand DM. Natural variation in the regulation of neurodevelopmental genes modifies flight performance in Drosophila. PLoS Genet 2021; 17:e1008887. [PMID: 33735180 PMCID: PMC7971549 DOI: 10.1371/journal.pgen.1008887] [Citation(s) in RCA: 6] [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: 05/20/2020] [Accepted: 01/26/2021] [Indexed: 12/28/2022] Open
Abstract
The winged insects of the order Diptera are colloquially named for their most recognizable phenotype: flight. These insects rely on flight for a number of important life history traits, such as dispersal, foraging, and courtship. Despite the importance of flight, relatively little is known about the genetic architecture of flight performance. Accordingly, we sought to uncover the genetic modifiers of flight using a measure of flies’ reaction and response to an abrupt drop in a vertical flight column. We conducted a genome wide association study (GWAS) using 197 of the Drosophila Genetic Reference Panel (DGRP) lines, and identified a combination of additive and marginal variants, epistatic interactions, whole genes, and enrichment across interaction networks. Egfr, a highly pleiotropic developmental gene, was among the most significant additive variants identified. We functionally validated 13 of the additive candidate genes’ (Adgf-A/Adgf-A2/CG32181, bru1, CadN, flapper (CG11073), CG15236, flippy (CG9766), CREG, Dscam4, form3, fry, Lasp/CG9692, Pde6, Snoo), and introduce a novel approach to whole gene significance screens: PEGASUS_flies. Additionally, we identified ppk23, an Acid Sensing Ion Channel (ASIC) homolog, as an important hub for epistatic interactions. We propose a model that suggests genetic modifiers of wing and muscle morphology, nervous system development and function, BMP signaling, sexually dimorphic neural wiring, and gene regulation are all important for the observed differences flight performance in a natural population. Additionally, these results represent a snapshot of the genetic modifiers affecting drop-response flight performance in Drosophila, with implications for other insects. Insect flight is a widely recognizable phenotype of many winged insects, hence the name: flies. While fruit flies, or Drosophila melanogaster, are a genetically tractable model, flight performance is a highly integrative phenotype, and therefore challenging to identify comprehensively which genetic modifiers contribute to its genetic architecture. Accordingly, we screened 197 Drosophila Genetic Reference Panel lines for their ability to react and respond to an abrupt drop. Using several computational approaches, we identified additive, marginal, and epistatic variants, as well as whole genes and altered sub-networks of gene-gene and protein-protein interaction networks that contribute to variation in flight performance. More generally, we demonstrate the benefits of employing multiple methodologies to elucidate the genetic architecture of complex traits. Many variants and genes mapped to regions of the genome that affect neurodevelopment, wing and muscle development, and regulation of gene expression. We also introduce PEGASUS_flies, a Drosophila-adapted version of the PEGASUS platform first used in human studies, to infer gene-level significance of association based on the gene’s distribution of individual variant P-values. Our results contribute to the debate over the relative importance of individual, additive factors and epistatic, or higher order, interactions, in the mapping of genotype to phenotype.
Collapse
Affiliation(s)
- Adam N Spierer
- Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island, United States of America
| | - Jim A Mossman
- Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island, United States of America
- Center for Computational Molecular Biology, Brown University, Providence, Rhode Island, United States of America
| | - Samuel Pattillo Smith
- Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island, United States of America
- Center for Computational Molecular Biology, Brown University, Providence, Rhode Island, United States of America
| | - Lorin Crawford
- Center for Computational Molecular Biology, Brown University, Providence, Rhode Island, United States of America
- Microsoft Research New England, Cambridge, Massachusetts, United States of America
| | - Sohini Ramachandran
- Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island, United States of America
- Center for Computational Molecular Biology, Brown University, Providence, Rhode Island, United States of America
| | - David M Rand
- Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island, United States of America
- Center for Computational Molecular Biology, Brown University, Providence, Rhode Island, United States of America
| |
Collapse
|
8
|
DEG/ENaC Ion Channels in the Function of the Nervous System: From Worm to Man. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1349:165-192. [DOI: 10.1007/978-981-16-4254-8_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
|
9
|
Muhanna D, Arnipalli SR, Kumar SB, Ziouzenkova O. Osmotic Adaptation by Na +-Dependent Transporters and ACE2: Correlation with Hemostatic Crisis in COVID-19. Biomedicines 2020; 8:E460. [PMID: 33142989 PMCID: PMC7693583 DOI: 10.3390/biomedicines8110460] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 10/27/2020] [Accepted: 10/28/2020] [Indexed: 01/08/2023] Open
Abstract
COVID-19 symptoms, including hypokalemia, hypoalbuminemia, ageusia, neurological dysfunctions, D-dimer production, and multi-organ microthrombosis reach beyond effects attributed to impaired angiotensin-converting enzyme 2 (ACE2) signaling and elevated concentrations of angiotensin II (Ang II). Although both SARS-CoV (Severe Acute Respiratory Syndrome Coronavirus) and SARS-CoV-2 utilize ACE2 for host entry, distinct COVID-19 pathogenesis coincides with the acquisition of a new sequence, which is homologous to the furin cleavage site of the human epithelial Na+ channel (ENaC). This review provides a comprehensive summary of the role of ACE2 in the assembly of Na+-dependent transporters of glucose, imino and neutral amino acids, as well as the functions of ENaC. Data support an osmotic adaptation mechanism in which osmotic and hemostatic instability induced by Ang II-activated ENaC is counterbalanced by an influx of organic osmolytes and Na+ through the ACE2 complex. We propose a paradigm for the two-site attack of SARS-CoV-2 leading to ENaC hyperactivation and inactivation of the ACE2 complex, which collapses cell osmolality and leads to rupture and/or necrotic death of swollen pulmonary, endothelial, and cardiac cells, thrombosis in infected and non-infected tissues, and aberrant sensory and neurological perception in COVID-19 patients. This dual mechanism employed by SARS-CoV-2 calls for combinatorial treatment strategies to address and prevent severe complications of COVID-19.
Collapse
Affiliation(s)
| | | | | | - Ouliana Ziouzenkova
- Department of Human Sciences, The Ohio State University, Columbus, OH 43210, USA; (D.M.); (S.R.A.); (S.B.K.)
| |
Collapse
|
10
|
Cuentas-Condori A, Miller Rd DM. Synaptic remodeling, lessons from C. elegans. J Neurogenet 2020; 34:307-322. [PMID: 32808848 PMCID: PMC7855814 DOI: 10.1080/01677063.2020.1802725] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Accepted: 07/07/2020] [Indexed: 02/08/2023]
Abstract
Sydney Brenner's choice of Caenorhabditis elegans as a model organism for understanding the nervous system has accelerated discoveries of gene function in neural circuit development and behavior. In this review, we discuss a striking example of synaptic remodeling in the C. elegans motor circuit in which DD class motor neurons effectively reverse polarity as presynaptic and postsynaptic domains at opposite ends of the DD neurite switch locations. Originally revealed by EM reconstruction conducted over 40 years ago, DD remodeling has since been investigated by live cell imaging methods that exploit the power of C. elegans genetics to reveal key effectors of synaptic plasticity. Although synapses are also extensively rewired in developing mammalian circuits, the underlying remodeling mechanisms are largely unknown. Here, we highlight the possibility that studies in C. elegans can reveal pathways that orchestrate synaptic remodeling in more complex organisms. Specifically, we describe (1) transcription factors that regulate DD remodeling, (2) the cellular and molecular cascades that drive synaptic remodeling and (3) examples of circuit modifications in vertebrate neurons that share some similarities with synaptic remodeling in C. elegans DD neurons.
Collapse
|
11
|
Presynaptic Homeostasis Opposes Disease Progression in Mouse Models of ALS-Like Degeneration: Evidence for Homeostatic Neuroprotection. Neuron 2020; 107:95-111.e6. [PMID: 32380032 DOI: 10.1016/j.neuron.2020.04.009] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 03/06/2020] [Accepted: 04/06/2020] [Indexed: 12/11/2022]
Abstract
Progressive synapse loss is an inevitable and insidious part of age-related neurodegenerative disease. Typically, synapse loss precedes symptoms of cognitive and motor decline. This suggests the existence of compensatory mechanisms that can temporarily counteract the effects of ongoing neurodegeneration. Here, we demonstrate that presynaptic homeostatic plasticity (PHP) is induced at degenerating neuromuscular junctions, mediated by an evolutionarily conserved activity of presynaptic ENaC channels in both Drosophila and mouse. To assess the consequence of eliminating PHP in a mouse model of ALS-like degeneration, we generated a motoneuron-specific deletion of Scnn1a, encoding the ENaC channel alpha subunit. We show that Scnn1a is essential for PHP without adversely affecting baseline neural function or lifespan. However, Scnn1a knockout in a degeneration-causing mutant background accelerated motoneuron loss and disease progression to twice the rate observed in littermate controls with intact PHP. We propose a model of neuroprotective homeostatic plasticity, extending organismal lifespan and health span.
Collapse
|
12
|
Northcutt AJ, Schulz DJ. Molecular mechanisms of homeostatic plasticity in central pattern generator networks. Dev Neurobiol 2019; 80:58-69. [PMID: 31778295 DOI: 10.1002/dneu.22727] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Revised: 10/09/2019] [Accepted: 11/22/2019] [Indexed: 01/27/2023]
Abstract
Central pattern generator (CPG) networks rely on a balance of intrinsic and network properties to produce reliable, repeatable activity patterns. This balance is maintained by homeostatic plasticity where alterations in neuronal properties dynamically maintain appropriate neural output in the face of changing environmental conditions and perturbations. However, it remains unclear just how these neurons and networks can both monitor their ongoing activity and use this information to elicit homeostatic physiological responses to ensure robustness of output over time. Evidence exists that CPG networks use a mixed strategy of activity-dependent, activity-independent, modulator-dependent, and synaptically regulated homeostatic plasticity to achieve this critical stability. In this review, we focus on some of the current understanding of the molecular pathways and mechanisms responsible for this homeostatic plasticity in the context of central pattern generator function, with a special emphasis on some of the smaller invertebrate networks that have allowed for extensive cellular-level analyses that have brought recent insights to these questions.
Collapse
Affiliation(s)
- Adam J Northcutt
- Division of Biological Sciences, University of Missouri-Columbia, Columbia, Missouri
| | - David J Schulz
- Division of Biological Sciences, University of Missouri-Columbia, Columbia, Missouri
| |
Collapse
|
13
|
Genç Ö, Davis GW. Target-wide Induction and Synapse Type-Specific Robustness of Presynaptic Homeostasis. Curr Biol 2019; 29:3863-3873.e2. [PMID: 31708391 PMCID: PMC7518040 DOI: 10.1016/j.cub.2019.09.036] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 09/08/2019] [Accepted: 09/13/2019] [Indexed: 11/23/2022]
Abstract
Presynaptic homeostatic plasticity (PHP) is an evolutionarily conserved form of adaptive neuromodulation and is observed at both central and peripheral synapses. In this work, we make several fundamental advances by interrogating the synapse specificity of PHP. We define how PHP remains robust to acute versus long-term neurotransmitter receptor perturbation. We describe a general PHP property that includes global induction and synapse-specific expression mechanisms. Finally, we detail a novel synapse-specific PHP expression mechanism that enables the conversion from short- to long-term PHP expression. If our data can be extended to other systems, including the mammalian central nervous system, they suggest that PHP can be broadly induced and expressed to sustain the function of complex neural circuitry.
Collapse
Affiliation(s)
- Özgür Genç
- Department of Biochemistry and Biophysics, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Graeme W Davis
- Department of Biochemistry and Biophysics, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, CA 94158, USA.
| |
Collapse
|
14
|
Abstract
Degenerin/Epithelial Sodium Channels (DEG/ENaCs) are a large family of animal-specific non-voltage gated ion channels, with enriched expression in neuronal and epithelial tissues. While neuronal DEG/ENaCs were originally characterized as sensory receptor channels, recent studies indicate that several DEG/ENaC family members are also expressed throughout the central nervous system. Human genome-wide association studies have linked DEG/ENaC-coding genes with several neurologic and psychiatric disorders, including epilepsy and panic disorder. In addition, studies in rodent models further indicate that DEG/ENaC activity in the brain contributes to many behaviors, including those related to anxiety and long-term memory. Although the exact neurophysiological functions of DEG/ENaCs remain mostly unknown, several key studies now suggest that multiple family members might exert their neuronal function via the direct modulation of synaptic processes. Here, we review and discuss recent findings on the synaptic functions of DEG/ENaCs in both vertebrate and invertebrate species, and propose models for their possible roles in synaptic physiology.
Collapse
Affiliation(s)
- Alexis S Hill
- a Department of Biology , Washington University in St. Louis , St. Louis , USA
| | - Yehuda Ben-Shahar
- a Department of Biology , Washington University in St. Louis , St. Louis , USA
| |
Collapse
|
15
|
James TD, Zwiefelhofer DJ, Frank CA. Maintenance of homeostatic plasticity at the Drosophila neuromuscular synapse requires continuous IP 3-directed signaling. eLife 2019; 8:39643. [PMID: 31180325 PMCID: PMC6557630 DOI: 10.7554/elife.39643] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 05/27/2019] [Indexed: 12/18/2022] Open
Abstract
Synapses and circuits rely on neuroplasticity to adjust output and meet physiological needs. Forms of homeostatic synaptic plasticity impart stability at synapses by countering destabilizing perturbations. The Drosophila melanogaster larval neuromuscular junction (NMJ) is a model synapse with robust expression of homeostatic plasticity. At the NMJ, a homeostatic system detects impaired postsynaptic sensitivity to neurotransmitter and activates a retrograde signal that restores synaptic function by adjusting neurotransmitter release. This process has been separated into temporally distinct phases, induction and maintenance. One prevailing hypothesis is that a shared mechanism governs both phases. Here, we show the two phases are separable. Combining genetics, pharmacology, and electrophysiology, we find that a signaling system consisting of PLCβ, inositol triphosphate (IP3), IP3 receptors, and Ryanodine receptors is required only for the maintenance of homeostatic plasticity. We also find that the NMJ is capable of inducing homeostatic signaling even when its sustained maintenance process is absent. Editorial note: This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).
Collapse
Affiliation(s)
- Thomas D James
- Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine, Iowa City, United States.,Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, United States
| | - Danielle J Zwiefelhofer
- Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine, Iowa City, United States
| | - C Andrew Frank
- Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine, Iowa City, United States.,Interdisciplinary Programs in Neuroscience, Genetics and Molecular Medicine, University of Iowa, Iowa City, United States
| |
Collapse
|
16
|
Kulik Y, Jones R, Moughamian AJ, Whippen J, Davis GW. Dual separable feedback systems govern firing rate homeostasis. eLife 2019; 8:45717. [PMID: 30973325 PMCID: PMC6491091 DOI: 10.7554/elife.45717] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 04/10/2019] [Indexed: 12/02/2022] Open
Abstract
Firing rate homeostasis (FRH) stabilizes neural activity. A pervasive and intuitive theory argues that a single variable, calcium, is detected and stabilized through regulatory feedback. A prediction is that ion channel gene mutations with equivalent effects on neuronal excitability should invoke the same homeostatic response. In agreement, we demonstrate robust FRH following either elimination of Kv4/Shal protein or elimination of the Kv4/Shal conductance. However, the underlying homeostatic signaling mechanisms are distinct. Eliminating Shal protein invokes Krüppel-dependent rebalancing of ion channel gene expression including enhanced slo, Shab, and Shaker. By contrast, expression of these genes remains unchanged in animals harboring a CRISPR-engineered, Shal pore-blocking mutation where compensation is achieved by enhanced IKDR. These different homeostatic processes have distinct effects on homeostatic synaptic plasticity and animal behavior. We propose that FRH includes mechanisms of proteostatic feedback that act in parallel with activity-driven feedback, with implications for the pathophysiology of human channelopathies.
Collapse
Affiliation(s)
- Yelena Kulik
- Department of Biochemistry and Biophysics, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, United States
| | - Ryan Jones
- Department of Biochemistry and Biophysics, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, United States
| | - Armen J Moughamian
- Department of Neurology, University of California, San Francisco, San Francisco, United States
| | - Jenna Whippen
- Department of Biochemistry and Biophysics, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, United States
| | - Graeme W Davis
- Department of Biochemistry and Biophysics, Kavli Institute for Fundamental Neuroscience, University of California, San Francisco, San Francisco, United States
| |
Collapse
|
17
|
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]
|
18
|
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.
Collapse
|
19
|
Ribchester RR, Slater CR. Rapid retrograde regulation of transmitter release at the NMJ. CURRENT OPINION IN PHYSIOLOGY 2018. [DOI: 10.1016/j.cophys.2018.06.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
|
20
|
The Maintenance of Synaptic Homeostasis at the Drosophila Neuromuscular Junction Is Reversible and Sensitive to High Temperature. eNeuro 2017; 4:eN-NWR-0220-17. [PMID: 29255795 PMCID: PMC5732017 DOI: 10.1523/eneuro.0220-17.2017] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2017] [Revised: 11/20/2017] [Accepted: 11/23/2017] [Indexed: 11/25/2022] Open
Abstract
Homeostasis is a vital mode of biological self-regulation. The hallmarks of homeostasis for any biological system are a baseline set point of physiological activity, detection of unacceptable deviations from the set point, and effective corrective measures to counteract deviations. Homeostatic synaptic plasticity (HSP) is a form of neuroplasticity in which neurons and circuits resist environmental perturbations and stabilize levels of activity. One assumption is that if a perturbation triggers homeostatic corrective changes in neuronal properties, those corrective measures should be reversed upon removal of the perturbation. We test the reversibility and limits of HSP at the well-studied Drosophila melanogaster neuromuscular junction (NMJ). At the Drosophila NMJ, impairment of glutamate receptors causes a decrease in quantal size, which is offset by a corrective, homeostatic increase in the number of vesicles released per evoked presynaptic stimulus, or quantal content. This process has been termed presynaptic homeostatic potentiation (PHP). Taking advantage of the GAL4/GAL80TS/UAS expression system, we triggered PHP by expressing a dominant-negative glutamate receptor subunit at the NMJ. We then reversed PHP by halting expression of the dominant-negative receptor. Our data show that PHP is fully reversible over a time course of 48–72 h after the dominant-negative glutamate receptor stops being genetically expressed. As an extension of these experiments, we find that when glutamate receptors are impaired, neither PHP nor NMJ growth is reliably sustained at high culturing temperatures (30–32°C). These data suggest that a limitation of homeostatic signaling at high temperatures could stem from the synapse facing a combination of challenges simultaneously.
Collapse
|