1
|
Landisman CE, Coulon P. A mixed electrical and chemical synapse in the thalamic reticular nucleus. J Neurophysiol 2024; 132:1955-1963. [PMID: 39475494 DOI: 10.1152/jn.00339.2024] [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: 07/31/2024] [Revised: 10/17/2024] [Accepted: 10/17/2024] [Indexed: 12/17/2024] Open
Abstract
The thalamic reticular nucleus (TRN) plays a major role in modulating the transfer of information from the thalamus to the cortex. GABAergic inhibition by the TRN is potentially synchronized by electrical synapses between TRN neurons, and TRN neurons are also sparsely connected to each other via chemical synapses. Paired recordings have shown that electrical coupling is abundant between TRN neurons, especially among those within close proximity, but combined electrical and chemical coupling has not yet been directly demonstrated in rats. Here, we report on a single pair of TRN neurons that were coupled both electrically and chemically. This is the only such example that we have found in hundreds of paired recordings of closely apposed neurons within the TRN.NEW & NOTEWORTHY Combined electrical and chemical coupling is demonstrated in a single couple of thalamic reticular nucleus (TRN) neurons. Single action potentials in one neuron resulted in a spikelet [electrical postsynaptic potential (ePSP)] followed by a longer lasting hyperpolarization [from an inhibitory postsynaptic potential (IPSP)] in the target neuron. The IPSPs were most prominent at depolarized potentials and all but disappeared when approaching the chloride equilibrium potential. This is the only such example that we have found in hundreds of paired recordings within the TRN.
Collapse
Affiliation(s)
- Carole E Landisman
- Center For Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington, United States
- Center for Brain Science, Harvard University, Cambridge, Massachusetts, United States
- Department of Neuroscience, Brown University, Providence, Rhode Island, United States
| | - Philippe Coulon
- Center For Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington, United States
- Faculty of Biology, Institute of Biology III, Group: Cellular Neurophysiology, University of Freiburg, Freiburg, Germany
- Faculty of Biology, Institute of Biology III, Optophysiology, University of Freiburg, Freiburg, Germany
- BrainLinks-BrainTools//Intelligent Machine Brain Interfacing Technology (IMBIT), University of Freiburg, Freiburg, Germany
| |
Collapse
|
2
|
Michel JC, Martin EA, Crow WE, Kissinger JS, Lukowicz-Bedford RM, Horrocks M, Branon TC, Ting AY, Miller AC. Electrical synapse molecular diversity revealed by proximity-based proteomic discovery. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.11.22.624763. [PMID: 39605535 PMCID: PMC11601576 DOI: 10.1101/2024.11.22.624763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/29/2024]
Abstract
Neuronal circuits are composed of synapses that are either chemical, where signals are transmitted via neurotransmitter release and reception, or electrical, where signals pass directly through interneuronal gap junction channels. While the molecular complexity that controls chemical synapse structure and function is well appreciated, the proteins of electrical synapses beyond the gap-junction-forming Connexins are not well defined. Yet, electrical synapses are expected to be molecularly complex beyond the gap junctions. Connexins are integral membrane proteins requiring vesicular transport and membrane insertion/retrieval to achieve function, homeostasis, and plasticity. Additionally, electron microscopy of neuronal gap junctions reveals neighboring electron dense regions termed the electrical synapse density (ESD). To reveal the molecular complexity of the electrical synapse proteome, we used proximity-dependent biotinylation (TurboID) linked to neural Connexins in zebrafish. Proteomic analysis of developing and mature nervous systems identifies hundreds of Connexin-associated proteins, with overlapping and distinct representation during development and adulthood. The identified protein classes span cell adhesion molecules, cytoplasmic scaffolds, vesicular trafficking, and proteins usually associated with the post synaptic density (PSD) of chemical synapses. Using circuits with stereotyped electrical and chemical synapses, we define molecular sub-synaptic compartments of ESD localizing proteins, we find molecular heterogeneity amongst electrical synapse populations, and we examine the synaptic intermingling of electrical and chemical synapse proteins. Taken together, these results reveal a new complexity of electrical synapse molecular diversity and highlight a novel overlap between chemical and electrical synapse proteomes. Moreover, human homologs of the electrical synapse proteins are associated with autism, epilepsy, and other neurological disorders, providing a novel framework towards understanding neuro-atypical states.
Collapse
|
3
|
Silwal P, Singhal P, Senecal JM, Senecal JE, Lynn BD, Nagy JI. Patterns of connexin36 and eGFP reporter expression among motoneurons in spinal sexually dimorphic motor nuclei in mouse. INTERNATIONAL JOURNAL OF PHYSIOLOGY, PATHOPHYSIOLOGY AND PHARMACOLOGY 2024; 16:55-76. [PMID: 39021417 PMCID: PMC11249853 DOI: 10.62347/ogwv9376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Accepted: 05/06/2024] [Indexed: 07/20/2024]
Abstract
BACKGROUND Sexually dimorphic spinal motoneurons (MNs) in the dorsomedial nucleus (DMN) and dorsolateral nucleus (DLN) as well as those in the cremaster nucleus are involved in reproductive behaviours, and the cremaster nucleus additionally contributes to testicular thermoregulation. It has been reported that MNs in DMN and DLN are extensively linked by gap junctions forming electrical synapses composed of connexin36 (Cx36) and there is evidence that subpopulation of MNs in the cremaster nucleus are also electrically coupled by these synapses. METHODOLOGY We used immunofluorescence methods to detect enhanced green fluorescent protein (eGFP) reporter for Cx36 expression in these motor nuclei. RESULTS We document in male mice that about half the MNs in each of DMN and DLN express eGFP, while the remaining half do not. Further, we found that the eGFP+ vs. eGFP- subsets of MNs in each of these motor nuclei innervate different target muscles; eGFP+ MNs in DMN and DLN project to sexually dimorphic bulbocavernosus and ischiocavernosus muscles, while the eGFP- subsets project to sexually non-dimorphic anal and external urethral sphincter muscles. Similarly, eGFP+ vs. eGFP- cremaster MNs were found to project to anatomically distinct portions of the cremaster muscle. By immunofluorescence, nearly all motoneurons in both DMN and DLN displayed punctate labelling for Cx36, including at eGFP+/eGFP+, eGFP+/eGFP- and eGFP-/eGFP- cell appositions. CONCLUSIONS Most if not all motoneurons in DMN and DLN are electrically coupled, including sexually dimorphic and non-dimorphic motoneurons with each other, despite absence of eGFP reporter in the non-dimorphic populations in these nuclei that have selective projections to sexually non-dimorphic target muscles.
Collapse
Affiliation(s)
- Prabhisha Silwal
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba Winnipeg, Manitoba R3E 0J9, Canada
| | - Pratyaksh Singhal
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba Winnipeg, Manitoba R3E 0J9, Canada
| | - Joanne Mm Senecal
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba Winnipeg, Manitoba R3E 0J9, Canada
| | - Julie Em Senecal
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba Winnipeg, Manitoba R3E 0J9, Canada
| | - Bruce D Lynn
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba Winnipeg, Manitoba R3E 0J9, Canada
| | - James I Nagy
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba Winnipeg, Manitoba R3E 0J9, Canada
| |
Collapse
|
4
|
Thomas D, Recabal-Beyer A, Senecal JMM, Serletis D, Lynn BD, Jackson MF, Nagy JI. Association of connexin36 with adherens junctions at mixed synapses and distinguishing electrophysiological features of those at mossy fiber terminals in rat ventral hippocampus. INTERNATIONAL JOURNAL OF PHYSIOLOGY, PATHOPHYSIOLOGY AND PHARMACOLOGY 2024; 16:28-54. [PMID: 39021415 PMCID: PMC11249852 DOI: 10.62347/rtmh4490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Accepted: 05/06/2024] [Indexed: 07/20/2024]
Abstract
BACKGROUND Granule cells in the hippocampus project axons to hippocampal CA3 pyramidal cells where they form large mossy fiber terminals. We have reported that these terminals contain the gap junction protein connexin36 (Cx36) specifically in the stratum lucidum of rat ventral hippocampus, thus creating morphologically mixed synapses that have the potential for dual chemical/electrical transmission. METHODOLOGY Here, we used various approaches to characterize molecular and electrophysiological relationships between the Cx36-containing gap junctions at mossy fiber terminals and their postsynaptic elements and to examine molecular relationships at mixed synapses in the brainstem. RESULTS In rat and human ventral hippocampus, many of these terminals, identified by their selective expression of vesicular zinc transporter-3 (ZnT3), displayed multiple, immunofluorescent Cx36-puncta representing gap junctions, which were absent at mossy fiber terminals in the dorsal hippocampus. In rat, these were found in close proximity to the protein constituents of adherens junctions (i.e., N-cadherin and nectin-1) that are structural hallmarks of mossy fiber terminals, linking these terminals to the dendritic shafts of CA3 pyramidal cells, thus indicating the loci of gap junctions at these contacts. Cx36-puncta were also associated with adherens junctions at mixed synapses in the brainstem, supporting emerging views of the structural organization of the adherens junction-neuronal gap junction complex. Electrophysiologically induced long-term potentiation (LTP) of field responses evoked by mossy fiber stimulation was greater in the ventral than dorsal hippocampus. CONCLUSIONS The electrical component of transmission at mossy fiber terminals may contribute to enhanced LTP responses in the ventral hippocampus.
Collapse
Affiliation(s)
- Deepthi Thomas
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of ManitobaWinnipeg, Manitoba, Canada
| | - Antonia Recabal-Beyer
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of ManitobaWinnipeg, Manitoba, Canada
- Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de ConcepciónVíctor Lamas 1290, Casilla 160, Concepción, Chile
| | - Joanne MM Senecal
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of ManitobaWinnipeg, Manitoba, Canada
| | - Demitre Serletis
- Epilepsy Center, Neurological Institute, Cleveland ClinicCleveland, Ohio, USA
| | - Bruce D Lynn
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of ManitobaWinnipeg, Manitoba, Canada
| | - Michael F Jackson
- Department of Pharmacology and Therapeutics, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of ManitobaWinnipeg, Manitoba, Canada
- PrairieNeuro Research Centre, Kleysen Institute for Advanced Medicine, Health Science CentreWinnipeg, Manitoba, Canada
| | - James I Nagy
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of ManitobaWinnipeg, Manitoba, Canada
| |
Collapse
|
5
|
Hansel C. Contiguity in perception: origins in cellular associative computations. Trends Neurosci 2024; 47:170-180. [PMID: 38310022 PMCID: PMC10939850 DOI: 10.1016/j.tins.2024.01.001] [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: 08/16/2023] [Revised: 11/30/2023] [Accepted: 01/05/2024] [Indexed: 02/05/2024]
Abstract
Our brains are good at detecting and learning associative structures; according to some linguistic theories, this capacity even constitutes a prerequisite for the development of syntax and compositionality in language and verbalized thought. I will argue that the search for associative motifs in input patterns is an evolutionary old brain function that enables contiguity in sensory perception and orientation in time and space. It has its origins in an elementary material property of cells that is particularly evident at chemical synapses: input-assigned calcium influx that activates calcium sensor proteins involved in memory storage. This machinery for the detection and learning of associative motifs generates knowledge about input relationships and integrates this knowledge into existing networks through updates in connectivity patterns.
Collapse
Affiliation(s)
- Christian Hansel
- Department of Neurobiology, University of Chicago, Chicago, IL 60637, USA.
| |
Collapse
|
6
|
González-González MA, Conde SV, Latorre R, Thébault SC, Pratelli M, Spitzer NC, Verkhratsky A, Tremblay MÈ, Akcora CG, Hernández-Reynoso AG, Ecker M, Coates J, Vincent KL, Ma B. Bioelectronic Medicine: a multidisciplinary roadmap from biophysics to precision therapies. Front Integr Neurosci 2024; 18:1321872. [PMID: 38440417 PMCID: PMC10911101 DOI: 10.3389/fnint.2024.1321872] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Accepted: 01/10/2024] [Indexed: 03/06/2024] Open
Abstract
Bioelectronic Medicine stands as an emerging field that rapidly evolves and offers distinctive clinical benefits, alongside unique challenges. It consists of the modulation of the nervous system by precise delivery of electrical current for the treatment of clinical conditions, such as post-stroke movement recovery or drug-resistant disorders. The unquestionable clinical impact of Bioelectronic Medicine is underscored by the successful translation to humans in the last decades, and the long list of preclinical studies. Given the emergency of accelerating the progress in new neuromodulation treatments (i.e., drug-resistant hypertension, autoimmune and degenerative diseases), collaboration between multiple fields is imperative. This work intends to foster multidisciplinary work and bring together different fields to provide the fundamental basis underlying Bioelectronic Medicine. In this review we will go from the biophysics of the cell membrane, which we consider the inner core of neuromodulation, to patient care. We will discuss the recently discovered mechanism of neurotransmission switching and how it will impact neuromodulation design, and we will provide an update on neuronal and glial basis in health and disease. The advances in biomedical technology have facilitated the collection of large amounts of data, thereby introducing new challenges in data analysis. We will discuss the current approaches and challenges in high throughput data analysis, encompassing big data, networks, artificial intelligence, and internet of things. Emphasis will be placed on understanding the electrochemical properties of neural interfaces, along with the integration of biocompatible and reliable materials and compliance with biomedical regulations for translational applications. Preclinical validation is foundational to the translational process, and we will discuss the critical aspects of such animal studies. Finally, we will focus on the patient point-of-care and challenges in neuromodulation as the ultimate goal of bioelectronic medicine. This review is a call to scientists from different fields to work together with a common endeavor: accelerate the decoding and modulation of the nervous system in a new era of therapeutic possibilities.
Collapse
Affiliation(s)
- María Alejandra González-González
- Jan and Dan Duncan Neurological Research Institute, Texas Children’s Hospital, Houston, TX, United States
- Department of Pediatric Neurology, Baylor College of Medicine, Houston, TX, United States
| | - Silvia V. Conde
- iNOVA4Health, NOVA Medical School, Faculdade de Ciências Médicas, NOVA University, Lisbon, Portugal
| | - Ramon Latorre
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Stéphanie C. Thébault
- Laboratorio de Investigación Traslacional en salud visual (D-13), Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Querétaro, Mexico
| | - Marta Pratelli
- Neurobiology Department, Kavli Institute for Brain and Mind, UC San Diego, La Jolla, CA, United States
| | - Nicholas C. Spitzer
- Neurobiology Department, Kavli Institute for Brain and Mind, UC San Diego, La Jolla, CA, United States
| | - Alexei Verkhratsky
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom
- Achucarro Centre for Neuroscience, IKERBASQUE, Basque Foundation for Science, Bilbao, Spain
- Department of Forensic Analytical Toxicology, School of Forensic Medicine, China Medical University, Shenyang, China
- International Collaborative Center on Big Science Plan for Purinergic Signaling, Chengdu University of Traditional Chinese Medicine, Chengdu, China
- Department of Stem Cell Biology, State Research Institute Centre for Innovative Medicine, Vilnius, Lithuania
| | - Marie-Ève Tremblay
- Division of Medical Sciences, University of Victoria, Victoria, BC, Canada
- Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada
- Department of Molecular Medicine, Université Laval, Québec City, QC, Canada
- Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, BC, Canada
| | - Cuneyt G. Akcora
- Department of Computer Science, University of Central Florida, Orlando, FL, United States
| | | | - Melanie Ecker
- Department of Biomedical Engineering, University of North Texas, Denton, TX, United States
| | | | - Kathleen L. Vincent
- Department of Obstetrics and Gynecology, University of Texas Medical Branch, Galveston, TX, United States
| | - Brandy Ma
- Stanley H. Appel Department of Neurology, Houston Methodist Hospital, Houston, TX, United States
| |
Collapse
|
7
|
Ribelayga CP, O’Brien J. When microscopy and electrophysiology meet connectomics-Steve Massey's contribution to unraveling the structure and function of the rod/cone gap junction. FRONTIERS IN OPHTHALMOLOGY 2023; 3:1305131. [PMID: 38983007 PMCID: PMC11182179 DOI: 10.3389/fopht.2023.1305131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Accepted: 10/31/2023] [Indexed: 07/11/2024]
Abstract
Electrical synapses, formed of gap junctions, are ubiquitous components of the central nervous system (CNS) that shape neuronal circuit connectivity and dynamics. In the retina, electrical synapses can create a circuit, control the signal-to-noise ratio in individual neurons, and support the coordinated neuronal firing of ganglion cells, hence, regulating signal processing at the network, single-cell, and dendritic level. We, the authors, and Steve Massey have had a long interest in gap junctions in retinal circuits, in general, and in the network of photoreceptors, in particular. Our combined efforts, based on a wide array of techniques of molecular biology, microscopy, and electrophysiology, have provided fundamental insights into the molecular structure and properties of the rod/cone gap junction. Yet, a full understanding of how rod/cone coupling controls circuit dynamics necessitates knowing its operating range. It is well established that rod/cone coupling can be greatly reduced or eliminated by bright-light adaptation or pharmacological treatment; however, the upper end of its dynamic range has long remained elusive. This held true until Steve Massey's recent interest for connectomics led to the development of a new strategy to assess this issue. The effort proved effective in establishing, with precision, the connectivity rules between rods and cones and estimating the theoretical upper limit of rod/cone electrical coupling. Comparing electrophysiological measurements and morphological data indicates that under pharmacological manipulation, rod/cone coupling can reach the theoretical maximum of its operating range, implying that, under these conditions, all the gap junction channels present at the junctions are open. As such, channel open probability is likely the main determinant of rod/cone coupling that can change momentarily in a time-of-day- and light-dependent manner. In this article we briefly review our current knowledge of the molecular structure of the rod/cone gap junction and of the mechanisms behind its modulation, and we highlight the recent work led by Steve Massey. Steve's contribution has been critical toward asserting the modulation depth of rod/cone coupling as well as elevating the rod/cone gap junction as one of the most suitable models to examine the role of electrical synapses and their plasticity in neural processing.
Collapse
Affiliation(s)
- Christophe P. Ribelayga
- Department of Vision Sciences, University of Houston College of Optometry, Houston, TX, United States
| | | |
Collapse
|
8
|
Michel JC, Grivette MMB, Harshfield AT, Huynh L, Komons AP, Loomis B, McKinnis K, Miller BT, Nguyen EQ, Huang TW, Lauf S, Michel ES, Michel ME, Kissinger JS, Marsh AJ, Crow WE, Kaye LE, Lasseigne AM, Lukowicz-Bedford RM, Farnsworth DR, Martin EA, Miller AC. Electrical synapse structure requires distinct isoforms of a postsynaptic scaffold. PLoS Genet 2023; 19:e1011045. [PMID: 38011265 PMCID: PMC10703405 DOI: 10.1371/journal.pgen.1011045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Revised: 12/07/2023] [Accepted: 11/01/2023] [Indexed: 11/29/2023] Open
Abstract
Electrical synapses are neuronal gap junction (GJ) channels associated with a macromolecular complex called the electrical synapse density (ESD), which regulates development and dynamically modifies electrical transmission. However, the proteomic makeup and molecular mechanisms utilized by the ESD that direct electrical synapse formation are not well understood. Using the Mauthner cell of zebrafish as a model, we previously found that the intracellular scaffolding protein ZO1b is a member of the ESD, localizing postsynaptically, where it is required for GJ channel localization, electrical communication, neural network function, and behavior. Here, we show that the complexity of the ESD is further diversified by the genomic structure of the ZO1b gene locus. The ZO1b gene is alternatively initiated at three transcriptional start sites resulting in isoforms with unique N-termini that we call ZO1b-Alpha, -Beta, and -Gamma. We demonstrate that ZO1b-Beta and ZO1b-Gamma are broadly expressed throughout the nervous system and localize to electrical synapses. By contrast, ZO1b-Alpha is expressed mainly non-neuronally and is not found at synapses. We generate mutants in all individual isoforms, as well as double mutant combinations in cis on individual chromosomes, and find that ZO1b-Beta is necessary and sufficient for robust GJ channel localization. ZO1b-Gamma, despite its localization to the synapse, plays an auxiliary role in channel localization. This study expands the notion of molecular complexity at the ESD, revealing that an individual genomic locus can contribute distinct isoforms to the macromolecular complex at electrical synapses. Further, independent scaffold isoforms have differential contributions to developmental assembly of the interneuronal GJ channels. We propose that ESD molecular complexity arises both from the diversity of unique genes and from distinct isoforms encoded by single genes. Overall, ESD proteomic diversity is expected to have critical impacts on the development, structure, function, and plasticity of electrical transmission.
Collapse
Affiliation(s)
- Jennifer Carlisle Michel
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Margaret M. B. Grivette
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Amber T. Harshfield
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Lisa Huynh
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Ava P. Komons
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Bradley Loomis
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Kaitlan McKinnis
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Brennen T. Miller
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Ethan Q. Nguyen
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Tiffany W. Huang
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Sophia Lauf
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Elias S. Michel
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Mia E. Michel
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Jane S. Kissinger
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Audrey J. Marsh
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - William E. Crow
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Lila E. Kaye
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Abagael M. Lasseigne
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Rachel M. Lukowicz-Bedford
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Dylan R. Farnsworth
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - E. Anne Martin
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| | - Adam C. Miller
- Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, United States of America
| |
Collapse
|
9
|
Lee YH, Kothmann WW, Lin YP, Chuang AZ, Diamond JS, O'Brien J. Sources of Calcium at Connexin 36 Gap Junctions in the Retina. eNeuro 2023; 10:ENEURO.0493-22.2023. [PMID: 37527925 PMCID: PMC10450809 DOI: 10.1523/eneuro.0493-22.2023] [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: 12/01/2022] [Revised: 07/07/2023] [Accepted: 07/20/2023] [Indexed: 08/03/2023] Open
Abstract
Synaptic plasticity is a fundamental feature of the CNS that controls the magnitude of signal transmission between communicating cells. Many electrical synapses exhibit substantial plasticity that modulates the degree of coupling within groups of neurons, alters the fidelity of signal transmission, or even reconfigures functional circuits. In several known examples, such plasticity depends on calcium and is associated with neuronal activity. Calcium-driven signaling is known to promote potentiation of electrical synapses in fish Mauthner cells, mammalian retinal AII amacrine cells, and inferior olive neurons, and to promote depression in thalamic reticular neurons. To measure local calcium dynamics in situ, we developed a transgenic mouse expressing a GCaMP calcium biosensor fused to Connexin 36 (Cx36) at electrical synapses. We examined the sources of calcium for activity-dependent plasticity in retina slices using confocal or Super-Resolution Radial Fluctuations imaging. More than half of Cx36-GCaMP gap junctions responded to puffs of glutamate with transient increases in fluorescence. The responses were strongly dependent on NMDA receptors, in keeping with known activity-dependent signaling in some amacrine cells. We also found that some responses depended on the activity of voltage-gated calcium channels, representing a previously unrecognized source of calcium to control retinal electrical synaptic plasticity. The high prevalence of calcium signals at electrical synapses in response to glutamate application indicates that a large fraction of electrical synapses has the potential to be regulated by neuronal activity. This provides a means to tune circuit connectivity dynamically based on local activity.
Collapse
Affiliation(s)
- Yuan-Hao Lee
- Richard S. Ruiz, Department of Ophthalmology and Visual Science, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas 77030
| | - W Wade Kothmann
- Synaptic Physiology Section, National Institute of Neurological Diseases and Stroke, Bethesda, Maryland 20892
| | - Ya-Ping Lin
- Richard S. Ruiz, Department of Ophthalmology and Visual Science, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas 77030
| | - Alice Z Chuang
- Richard S. Ruiz, Department of Ophthalmology and Visual Science, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas 77030
| | - Jeffrey S Diamond
- Synaptic Physiology Section, National Institute of Neurological Diseases and Stroke, Bethesda, Maryland 20892
| | - John O'Brien
- Richard S. Ruiz, Department of Ophthalmology and Visual Science, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas 77030
- MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, Texas 77030
| |
Collapse
|
10
|
Lee SN, Cho HJ, Jeong H, Ryu B, Lee HJ, Kim M, Yoo J, Woo JS, Lee HH. Cryo-EM structures of human Cx36/GJD2 neuronal gap junction channel. Nat Commun 2023; 14:1347. [PMID: 36906653 PMCID: PMC10008584 DOI: 10.1038/s41467-023-37040-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 02/28/2023] [Indexed: 03/13/2023] Open
Abstract
Connexin 36 (Cx36) is responsible for signal transmission in electrical synapses by forming interneuronal gap junctions. Despite the critical role of Cx36 in normal brain function, the molecular architecture of the Cx36 gap junction channel (GJC) is unknown. Here, we determine cryo-electron microscopy structures of Cx36 GJC at 2.2-3.6 Å resolutions, revealing a dynamic equilibrium between its closed and open states. In the closed state, channel pores are obstructed by lipids, while N-terminal helices (NTHs) are excluded from the pore. In the open state with pore-lining NTHs, the pore is more acidic than those in Cx26 and Cx46/50 GJCs, explaining its strong cation selectivity. The conformational change during channel opening also includes the α-to-π-helix transition of the first transmembrane helix, which weakens the protomer-protomer interaction. Our structural analyses provide high resolution information on the conformational flexibility of Cx36 GJC and suggest a potential role of lipids in the channel gating.
Collapse
Affiliation(s)
- Seu-Na Lee
- Department of Life Sciences, Korea University, Seoul, 02841, Republic of Korea
| | - Hwa-Jin Cho
- Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul, 08826, Korea
| | - Hyeongseop Jeong
- Center for Research Equipment, Korea Basic Science Institute, Chungcheongbuk-do, 28119, Korea
| | - Bumhan Ryu
- Research Solution Center, Institute for Basic Science, Daejeon, 34126, Republic of Korea
| | - Hyuk-Joon Lee
- Department of Life Sciences, Korea University, Seoul, 02841, Republic of Korea
| | - Minsoo Kim
- Department of Physics, Sungkyunkwan University, Suwon, 16419, South Korea
| | - Jejoong Yoo
- Department of Physics, Sungkyunkwan University, Suwon, 16419, South Korea
| | - Jae-Sung Woo
- Department of Life Sciences, Korea University, Seoul, 02841, Republic of Korea.
| | - Hyung Ho Lee
- Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul, 08826, Korea.
| |
Collapse
|
11
|
Kanishka, Jha SK. Compensatory cognition in neurological diseases and aging: A review of animal and human studies. AGING BRAIN 2023; 3:100061. [PMID: 36911258 PMCID: PMC9997140 DOI: 10.1016/j.nbas.2022.100061] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Revised: 12/06/2022] [Accepted: 12/12/2022] [Indexed: 12/27/2022] Open
Abstract
Specialized individual circuits in the brain are recruited for specific functions. Interestingly, multiple neural circuitries continuously compete with each other to acquire the specialized function. However, the dominant among them compete and become the central neural network for that particular function. For example, the hippocampal principal neural circuitries are the dominant networks among many which are involved in learning processes. But, in the event of damage to the principal circuitry, many times, less dominant networks compensate for the primary network. This review highlights the psychopathologies of functional loss and the aspects of functional recuperation in the absence of the hippocampus.
Collapse
Affiliation(s)
- Kanishka
- School of Life Sciences, Jawaharlal Nehru University, New Delhi 110067, India
| | - Sushil K Jha
- School of Life Sciences, Jawaharlal Nehru University, New Delhi 110067, India
| |
Collapse
|
12
|
Sandamirskaya Y, Kaboli M, Conradt J, Celikel T. Neuromorphic computing hardware and neural architectures for robotics. Sci Robot 2022; 7:eabl8419. [PMID: 35767646 DOI: 10.1126/scirobotics.abl8419] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Neuromorphic hardware enables fast and power-efficient neural network-based artificial intelligence that is well suited to solving robotic tasks. Neuromorphic algorithms can be further developed following neural computing principles and neural network architectures inspired by biological neural systems. In this Viewpoint, we provide an overview of recent insights from neuroscience that could enhance signal processing in artificial neural networks on chip and unlock innovative applications in robotics and autonomous intelligent systems. These insights uncover computing principles, primitives, and algorithms on different levels of abstraction and call for more research into the basis of neural computation and neuronally inspired computing hardware.
Collapse
Affiliation(s)
| | - Mohsen Kaboli
- BMW Group, Department of Research, New Technologies and Innovation, Munich, Germany.,Donders Institute for Brain, Cognition, and Behavior, Radboud University, Nijmegen, Netherlands
| | - Jorg Conradt
- Kungliga Tekniska Högskolan (KTH), School of Electrical Engineering and Computer Science, Stockholm, Sweden
| | | |
Collapse
|
13
|
Grodstein J, Levin M. A Computational Approach to Explaining Bioelectrically Induced Persistent, Stochastic Changes of Axial Polarity in Planarian Regeneration. Bioelectricity 2022; 4:18-30. [PMID: 39372228 PMCID: PMC11450330 DOI: 10.1089/bioe.2021.0036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Morphogenesis results when cells cooperate to construct a specific anatomical structure. The behavior of such cell swarms exhibits not only robustness but also plasticity with respect to what specific anatomies will be built. Important aspects of evolutionary biology, regenerative medicine, and cancer are impacted by the algorithms by which instructive information guides invariant or stochastic outcomes of such collective activity. Planarian flatworms are an important model system in this field, as flatworms reliably regenerate a primary body axis after diverse kinds of injury. Importantly, the number of heads to which they regenerate is not determined genetically: lines of worms can be produced, which, with no further manipulation, regenerate as two-headed (2H) worms, or as "Cryptic" worms. When cut into pieces, Cryptic worms produce one-headed (1H) and 2H regenerates stochastically. Neural and bioelectric mechanisms have been proposed to explain aspects of the regenerative dataset. However, these models have not been unified and do not explain all of the Cryptic worm data. In this study, we propose a model in which two separate systems (a bioelectric circuit and a neural polarity mechanism) compete to determine the anatomical structure of a regenerate. We show how our model accounts for existing data and provides a consistent synthesis of mechanisms that explain both the robustness of planarian regeneration and its remarkable re-writability toward novel stable and stochastic anatomical states.
Collapse
Affiliation(s)
- Joel Grodstein
- Department of Electrical and Computer Engineering, Tufts University, Medford, Massachusetts, USA
| | - Michael Levin
- Allen Discovery Center at Tufts University, Medford, Massachusetts, USA
- Wyss Institute for Biologically Inspired Engineering at Harvard University, Boston, Massachusetts, USA
| |
Collapse
|
14
|
Recabal-Beyer AJ, Senecal JMM, Senecal JEM, Lynn BD, Nagy JI. On the Organization of Connexin36 Expression in Electrically Coupled Cholinergic V0c Neurons (Partition Cells) in the Spinal Cord and Their C-terminal Innervation of Motoneurons. Neuroscience 2022; 485:91-115. [PMID: 35090881 DOI: 10.1016/j.neuroscience.2022.01.015] [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: 11/22/2021] [Revised: 01/07/2022] [Accepted: 01/19/2022] [Indexed: 12/13/2022]
Abstract
Large cholinergic neurons (V0c neurons; aka, partition cells) in the spinal cord project profusely to motoneurons on which they form C-terminal contacts distinguished by their specialized postsynaptic subsurface cisterns (SSCs). The V0c neurons are known to be rhythmically active during locomotion and release of acetylcholine (ACh) from their terminals is known to modulate the excitability of motoneurons in what appears to be a task-dependent manner. Here, we present evidence that a subpopulation of V0c neurons express the gap junction forming protein connexin36 (Cx36), indicating that they are coupled by electrical synapses. Based on immunofluorescence imaging and the use of Cx36BAC-enhanced green fluorescent protein (eGFP) mice in which C-terminals immunolabelled for their marker vesicular acetylcholine transporter (vAChT) are also labelled for eGFP, we found a heterogeneous distribution of eGFP+ C-terminals on motoneurons at cervical, thoracic and lumber spinal levels. The density of C-terminals on motoneurons varied as did the proportion of those that were eGFP+ vs. eGFP-. We present evidence that fast vs. slow motoneurons have a greater abundance of these terminals and fast motoneurons also have the highest density that were eGFP+. Thus, our results indicate that a subpopulation of V0c neurons projects preferentially to fast motoneurons, suggesting that the capacity for synchronous activity conferred by electrical synapses among networks of coupled V0c neurons enhances their dynamic capabilities for synchronous regulation of motoneuron excitability during high muscle force generation. The eGFP+ vs. eGFP- V0c neurons were more richly innervated by serotonergic terminals, suggesting their greater propensity for regulation by descending serotonergic systems.
Collapse
Affiliation(s)
- A J Recabal-Beyer
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg, Canada
| | - J M M Senecal
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg, Canada
| | - J E M Senecal
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg, Canada
| | - B D Lynn
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg, Canada
| | - J I Nagy
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg, Canada.
| |
Collapse
|
15
|
Héja L, Simon Á, Szabó Z, Kardos J. Connexons Coupling to Gap Junction Channel: Potential Role for Extracellular Protein Stabilization Centers. Biomolecules 2021; 12:biom12010049. [PMID: 35053197 PMCID: PMC8773650 DOI: 10.3390/biom12010049] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2021] [Revised: 12/21/2021] [Accepted: 12/27/2021] [Indexed: 12/13/2022] Open
Abstract
Connexin (Cx) proteins establish intercellular gap junction channels (Cx GJCs) through coupling of two apposed hexameric Cx hemichannels (Cx HCs, connexons). Pre- and post-GJ interfaces consist of extracellular EL1 and EL2 loops, each with three conserved cysteines. Previously, we reported that known peptide inhibitors, mimicking a variety of Cx43 sequences, appear non-selective when binding to homomeric Cx43 vs. Cx36 GJC homology model subtypes. In pursuit of finding potentially Cx subtype-specific inhibitors of connexon-connexon coupling, we aimed at to understand better how the GJ interface is formed. Here we report on the discovery of Cx GJC subtype-specific protein stabilization centers (SCs) featuring GJ interface architecture. First, the Cx43 GJC homology model, embedded in two opposed membrane bilayers, has been devised. Next, we endorsed the fluctuation dynamics of SCs of the interface domain of Cx43 GJC by applying standard molecular dynamics under open and closed cystine disulfide bond (CS-SC) preconditions. The simulations confirmed the major role of the unique trans-GJ SC pattern comprising conserved (55N, 56T) and non-conserved (57Q) residues of the apposed EL1 loops in the stabilization of the GJC complex. Importantly, clusters of SC patterns residing close to the GJ interface domain appear to orient the interface formation via the numerous SCs between EL1 and EL2. These include central 54CS-S198C or 61CS-S192C contacts with residues 53R, 54C, 55N, 197D, 199F or 64V, 191P, respectively. In addition, we revealed that GJC interface formation is favoured when the psi dihedral angle of the nearby 193P residue is stable around 180° and the interface SCs disappear when this angle moves to the 0° to −45° range. The potential of the association of non-conserved residues with SC motifs in connexon-connexon coupling makes the development of Cx subtype-specific inhibitors viable.
Collapse
|
16
|
Vila A, Shihabeddin E, Zhang Z, Santhanam A, Ribelayga CP, O’Brien J. Synaptic Scaffolds, Ion Channels and Polyamines in Mouse Photoreceptor Synapses: Anatomy of a Signaling Complex. Front Cell Neurosci 2021; 15:667046. [PMID: 34393723 PMCID: PMC8356055 DOI: 10.3389/fncel.2021.667046] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 07/05/2021] [Indexed: 12/29/2022] Open
Abstract
Synaptic signaling complexes are held together by scaffold proteins, each of which is selectively capable of interacting with a number of other proteins. In previous studies of rabbit retina, we found Synapse-Associated Protein-102 (SAP102) and Channel Associated Protein of Synapse-110 (Chapsyn110) selectively localized in the tips of horizontal cell processes at contacts with rod and cone photoreceptors, along with several interacting ion channels. We have examined the equivalent suites of proteins in mouse retina and found similarities and differences. In the mouse retina we identified Chapsyn110 as the scaffold selectively localized in the tips of horizontal cells contacting photoreceptors, with Sap102 more diffusely present. As in rabbit, the inward rectifier potassium channel Kir2.1 was present with Chapsyn110 on the tips of horizontal cell dendrites within photoreceptor invaginations, where it could provide a hyperpolarization-activated current that could contribute to ephaptic signaling in the photoreceptor synapses. Pannexin 1 and Pannexin 2, thought to play a role in ephaptic and/or pH mediated signaling, were present in the outer plexiform layer, but likely not in the horizontal cells. Polyamines regulate many ion channels and control the degree of rectification of Kir2.1 by imposing a voltage-dependent block. During the day polyamine immunolabeling was unexpectedly high in photoreceptor terminals compared to other areas of the retina. This content was significantly lower at night, when polyamine content was predominantly in Müller glia, indicating daily rhythms of polyamine content. Both rod and cone terminals displayed the same rhythm. While polyamine content was not prominent in horizontal cells, if polyamines are released, they may regulate the activity of Kir2.1 channels located in the tips of HCs. The rhythmic change in polyamine content of photoreceptor terminals suggests that a daily rhythm tunes the behavior of suites of ion channels within the photoreceptor synapses.
Collapse
Affiliation(s)
- Alejandro Vila
- Richard S. Ruiz M.D. Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Houston, TX, United States
- MD Anderson Cancer Center, UTHealth Graduate School of Biomedical Sciences, Houston, TX, United States
| | - Eyad Shihabeddin
- Richard S. Ruiz M.D. Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Houston, TX, United States
- MD Anderson Cancer Center, UTHealth Graduate School of Biomedical Sciences, Houston, TX, United States
| | - Zhijing Zhang
- Richard S. Ruiz M.D. Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Houston, TX, United States
| | - Abirami Santhanam
- Richard S. Ruiz M.D. Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Houston, TX, United States
| | - Christophe P. Ribelayga
- Richard S. Ruiz M.D. Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Houston, TX, United States
- MD Anderson Cancer Center, UTHealth Graduate School of Biomedical Sciences, Houston, TX, United States
| | - John O’Brien
- Richard S. Ruiz M.D. Department of Ophthalmology and Visual Science, University of Texas Health Science Center at Houston, Houston, TX, United States
- MD Anderson Cancer Center, UTHealth Graduate School of Biomedical Sciences, Houston, TX, United States
| |
Collapse
|
17
|
A Model for Evolutionary Structural Plasticity and Synchronization of a Network of Neurons. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2021; 2021:9956319. [PMID: 34221108 PMCID: PMC8225422 DOI: 10.1155/2021/9956319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 05/12/2021] [Accepted: 06/01/2021] [Indexed: 11/18/2022]
Abstract
A model of time-dependent structural plasticity for the synchronization of neuron networks is presented. It is known that synchronized oscillations reproduce structured communities, and this synchronization is transient since it can be enhanced or suppressed, and the proposed model reproduces this characteristic. The evolutionary behavior of the couplings is comparable to those of a network of biological neurons. In the structural network, the physical connections of axons and dendrites between neurons are modeled, and the evolution in the connections depends on the neurons' potential. Moreover, it is shown that the coupling force's function behaves as an adaptive controller that leads the neurons in the network to synchronization. The change in the node's degree shows that the network exhibits time-dependent structural plasticity, achieved through the evolutionary or adaptive change of the coupling force between the nodes. The coupling force function is based on the computed magnitude of the membrane potential deviations with its neighbors and a threshold that determines the neuron's connections. These rule the functional network structure along the time.
Collapse
|
18
|
Zoidl GR, Spray DC. The Roles of Calmodulin and CaMKII in Cx36 Plasticity. Int J Mol Sci 2021; 22:4473. [PMID: 33922931 PMCID: PMC8123330 DOI: 10.3390/ijms22094473] [Citation(s) in RCA: 7] [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: 03/29/2021] [Revised: 04/17/2021] [Accepted: 04/20/2021] [Indexed: 01/07/2023] Open
Abstract
Anatomical and electrophysiological evidence that gap junctions and electrical coupling occur between neurons was initially confined to invertebrates and nonmammals and was thought to be a primitive form of synaptic transmission. More recent studies revealed that electrical communication is common in the mammalian central nervous system (CNS), often coexisting with chemical synaptic transmission. The subsequent progress indicated that electrical synapses formed by the gap junction protein connexin-36 (Cx36) and its paralogs in nonmammals constitute vital elements in mammalian and fish synaptic circuitry. They govern the collective activity of ensembles of coupled neurons, and Cx36 gap junctions endow them with enormous adaptive plasticity, like that seen at chemical synapses. Moreover, they orchestrate the synchronized neuronal network activity and rhythmic oscillations that underlie the fundamental integrative processes, such as memory and learning. Here, we review the available mechanistic evidence and models that argue for the essential roles of calcium, calmodulin, and the Ca2+/calmodulin-dependent protein kinase II in integrating calcium signals to modulate the strength of electrical synapses through interactions with the gap junction protein Cx36.
Collapse
Affiliation(s)
- Georg R. Zoidl
- Department of Biology & Center for Vision Research (CVR), York University, Toronto, ON M3J 1P3, Canada
| | - David C. Spray
- Dominick P. Purpura Department of Neuroscience & Department of Medicine (Cardiology), Albert Einstein College of Medicine, New York, NY 10461, USA;
| |
Collapse
|
19
|
Fournel R, Hartveit E, Veruki ML. Differential Contribution of Gap Junctions to the Membrane Properties of ON- and OFF-Bipolar Cells of the Rat Retina. Cell Mol Neurobiol 2021; 41:229-245. [PMID: 32323153 PMCID: PMC7870642 DOI: 10.1007/s10571-020-00845-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 04/08/2020] [Indexed: 01/31/2023]
Abstract
Gap junctions are ubiquitous within the retina, but in general, it remains to be determined whether gap junction coupling between specific cell types is sufficiently strong to mediate functionally relevant coupling via electrical synapses. From ultrastructural, tracer coupling and immunolabeling studies, there is clear evidence for gap junctions between cone bipolar cells, but it is not known if these gap junctions function as electrical synapses. Here, using whole-cell voltage-clamp recording in rat (male and female) retinal slices, we investigated whether the gap junctions of bipolar cells make a measurable contribution to the membrane properties of these cells. We measured the input resistance (RN) of bipolar cells before and after applying meclofenamic acid (MFA) to block gap junctions. In the presence of MFA, RN of ON-cone bipolar cells displayed a clear increase, paralleled by block of the electrical coupling between these cells and AII amacrine cells in recordings of coupled cell pairs. For OFF-cone and rod bipolar cells, RN did not increase in the presence of MFA. The results for rod bipolar cells are consistent with the lack of gap junctions in these cells. However, for OFF-cone bipolar cells, our results suggest that the morphologically identified gap junctions between these cells do not support a junctional conductance that is sufficient to mediate effective electrical coupling. Instead, these junctions might play a role in chemical and/or metabolic coupling between subcellular compartments.
Collapse
Affiliation(s)
- Rémi Fournel
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5009, Bergen, Norway
| | - Espen Hartveit
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5009, Bergen, Norway.
| | - Margaret Lin Veruki
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5009, Bergen, Norway.
| |
Collapse
|
20
|
Wu L, Wang Z, Wang B, Chen Q, Bao L, Yu Z, Yang Y, Ling Y, Qin Y, Tang K, Cai Y, Huang R. Emulation of biphasic plasticity in retinal electrical synapses for light-adaptive pattern pre-processing. NANOSCALE 2021; 13:3483-3492. [PMID: 33475123 DOI: 10.1039/d0nr08012h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Electrical synapses provide rapid, bidirectional communication in nervous systems, accomplishing tasks distinct from and complementary to chemical synapses. Here, we demonstrate an artificial electrical synapse based on second-order conductance transition (SOCT) in an Ag-based memristor for the first time. High-resolution transmission electron microscopy indicates that SOCT is mediated by the virtual silver electrode. Besides the conventional chemical synaptic behaviors, the biphasic plasticity of electrical synapses is well emulated by integrating the device with a photosensitive element to form an optical pre-processing unit (OPU), which contributes to the retinal neural circuitry and is adaptive to ambient illumination. By synergizing the OPU and spiking neural network (SNN), adaptive pattern recognition tasks are accomplished under different light and noise settings. This work not only contributes to the further completion of synaptic behaviour for hardware-level neuromorphic computing, but also potentially enables image pre-processing with light adaptation and noise suppression for adaptive visual recognition.
Collapse
Affiliation(s)
- Lindong Wu
- Institute of Microelectronics, Peking University, Beijing 100871, P. R. China.
| | - Zongwei Wang
- Institute of Microelectronics, Peking University, Beijing 100871, P. R. China. and Advanced Institute of Information Technology (AIIT), Peking University, Hangzhou, Zhejiang 311215, P. R. China
| | - Bowen Wang
- Institute of Microelectronics, Peking University, Beijing 100871, P. R. China.
| | - Qingyu Chen
- Institute of Microelectronics, Peking University, Beijing 100871, P. R. China.
| | - Lin Bao
- Institute of Microelectronics, Peking University, Beijing 100871, P. R. China.
| | - Zhizhen Yu
- Institute of Microelectronics, Peking University, Beijing 100871, P. R. China.
| | - Yunfan Yang
- Institute of Microelectronics, Peking University, Beijing 100871, P. R. China.
| | - Yaotian Ling
- Institute of Microelectronics, Peking University, Beijing 100871, P. R. China.
| | - Yabo Qin
- Institute of Microelectronics, Peking University, Beijing 100871, P. R. China.
| | - Kechao Tang
- Institute of Microelectronics, Peking University, Beijing 100871, P. R. China.
| | - Yimao Cai
- Institute of Microelectronics, Peking University, Beijing 100871, P. R. China. and Frontiers Science Center for Nano-Optoelectronics, Peking University, Beijing 100871, P. R. China
| | - Ru Huang
- Institute of Microelectronics, Peking University, Beijing 100871, P. R. China. and Frontiers Science Center for Nano-Optoelectronics, Peking University, Beijing 100871, P. R. China
| |
Collapse
|
21
|
Cervera J, Ramirez P, Levin M, Mafe S. Community effects allow bioelectrical reprogramming of cell membrane potentials in multicellular aggregates: Model simulations. Phys Rev E 2020; 102:052412. [PMID: 33327213 DOI: 10.1103/physreve.102.052412] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Accepted: 11/04/2020] [Indexed: 12/11/2022]
Abstract
Bioelectrical patterns are established by spatiotemporal correlations of cell membrane potentials at the multicellular level, being crucial to development, regeneration, and tumorigenesis. We have conducted multicellular simulations on bioelectrical community effects and intercellular coupling in multicellular aggregates. The simulations aim at establishing under which conditions a local heterogeneity consisting of a small patch of cells can be stabilized against a large aggregate of surrounding identical cells which are in a different bioelectrical state. In this way, instructive bioelectrical information can be persistently encoded in spatiotemporal patterns of separated domains with different cell polarization states. The multicellular community effects obtained are regulated both at the single-cell and intercellular levels, and emerge from a delicate balance between the degrees of intercellular coupling in: (i) the small patch, (ii) the surrounding bulk, and (iii) the interface that separates these two regions. The model is experimentally motivated and consists of two generic voltage-gated ion channels that attempt to establish the depolarized and polarized cell states together with coupling conductances whose individual and intercellular different states permit a dynamic multicellular connectivity. The simulations suggest that community effects may allow the reprogramming of single-cell bioelectrical states, in agreement with recent experimental data. A better understanding of the resulting electrical regionalization can assist the electroceutical correction of abnormally depolarized regions initiated in the bulk of normal tissues as well as suggest new biophysical mechanisms for the establishment of target patterns in multicellular engineering.
Collapse
Affiliation(s)
- Javier Cervera
- Departamento Termodinàmica, Universitat de València, E-46100 Burjassot, Spain
| | - Patricio Ramirez
- Departamento Física Aplicada, Universidad Politécnica de Valencia, E-46022 Valencia, Spain
| | - Michael Levin
- Department of Biology and Allen Discovery Center at Tufts University, Medford, Massachusetts 02155-4243, USA
| | - Salvador Mafe
- Departamento Termodinàmica, Universitat de València, E-46100 Burjassot, Spain
| |
Collapse
|
22
|
Li Y, Cohen ED, Qian H. Rod and Cone Coupling Modulates Photopic ERG Responses in the Mouse Retina. Front Cell Neurosci 2020; 14:566712. [PMID: 33100974 PMCID: PMC7546330 DOI: 10.3389/fncel.2020.566712] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 08/31/2020] [Indexed: 11/13/2022] Open
Abstract
Light adaptation changes both the sensitivity and maximum amplitude (Rmax) of the mouse photopic electroretinogram (ERG) b-wave. Using the ERG, we examined how modulation of gap junctional coupling between rod and cones alters the light-adapted ERG. To measure changes, a b-wave light adaptation enhancement factor (LAEF), was defined as the ratio of Rmax after 15 min light adaptation to Rmax recorded at the onset of an adapting light. For wild-type mice (WT), the LAEF averaged 2.64 ± 0.29, however, it was significantly reduced (1.06 ± 0.04) for connexin 36 knock out (Cx36KO) mice, which lack electrical coupling between photoreceptors. Wild type mice intraocularly injected with meclofenamic acid (MFA), a gap junction blocker, also showed a significantly reduced LAEF. Degeneration of rod photoreceptors significantly alters the effects of light adaptation on the photopic ERG response. Rd10 mice at P21, with large portions of their rod photoreceptors present in the retina, exhibited a similar b-wave enhancement as wildtype controls, with a LAEF of 2.55 ± 0.19. However, by P31 with most of their rod photoreceptors degenerated, rd10 mice had a much reduced b-wave enhancement during light-adaptation (LAEF of 1.54 ± 0.12). Flicker ERG responses showed a higher temporal amplitude in mesopic conditions for WT than those of Cx36KO mice, suggesting rod-cone coupling help high-frequency signals to pass from rods to cone pathways in the retina. In conclusion, our study provides a novel method to noninvasively measure the dynamics and modulation by the light adaptation for rod-cone gap junctional coupling in intact eyes.
Collapse
Affiliation(s)
- Yichao Li
- Visual Function Core, National Eye Institute (NEI), National Institutes of Health, Bethesda, MD, United States
| | - Ethan D Cohen
- Division of Biomedical Physics, Office of Science and Engineering Labs, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, MD, United States
| | - Haohua Qian
- Visual Function Core, National Eye Institute (NEI), National Institutes of Health, Bethesda, MD, United States
| |
Collapse
|
23
|
Aseervatham J, Li X, Mitchell CK, Lin YP, Heidelberger R, O’Brien J. Calmodulin Binding to Connexin 35: Specializations to Function as an Electrical Synapse. Int J Mol Sci 2020; 21:E6346. [PMID: 32882943 PMCID: PMC7504508 DOI: 10.3390/ijms21176346] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 08/27/2020] [Accepted: 08/30/2020] [Indexed: 12/25/2022] Open
Abstract
Calmodulin binding is a nearly universal property of gap junction proteins, imparting a calcium-dependent uncoupling behavior that can serve in an emergency to decouple a stressed cell from its neighbors. However, gap junctions that function as electrical synapses within networks of neurons routinely encounter large fluctuations in local cytoplasmic calcium concentration; frequent uncoupling would be impractical and counterproductive. We have studied the properties and functional consequences of calmodulin binding to the electrical synapse protein Connexin 35 (Cx35 or gjd2b), homologous to mammalian Connexin 36 (Cx36 or gjd2). We find that specializations in Cx35 calmodulin binding sites make it relatively impervious to moderately high levels of cytoplasmic calcium. Calmodulin binding to a site in the C-terminus causes uncoupling when calcium reaches low micromolar concentrations, a behavior prevented by mutations that eliminate calmodulin binding. However, milder stimuli promote calcium/calmodulin-dependent protein kinase II activity that potentiates coupling without interference from calmodulin binding. A second calmodulin binding site in the end of the Cx35 cytoplasmic loop, homologous to a calmodulin binding site present in many connexins, binds calmodulin with very low affinity and stoichiometry. Together, the calmodulin binding sites cause Cx35 to uncouple only at extreme levels of intracellular calcium.
Collapse
Affiliation(s)
- Jaya Aseervatham
- Ruiz Department of Ophthalmology & Visual Science, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA; (J.A.); (X.L.); (C.K.M.); (Y.-P.L.)
| | - Xiaofan Li
- Ruiz Department of Ophthalmology & Visual Science, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA; (J.A.); (X.L.); (C.K.M.); (Y.-P.L.)
| | - Cheryl K. Mitchell
- Ruiz Department of Ophthalmology & Visual Science, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA; (J.A.); (X.L.); (C.K.M.); (Y.-P.L.)
| | - Ya-Ping Lin
- Ruiz Department of Ophthalmology & Visual Science, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA; (J.A.); (X.L.); (C.K.M.); (Y.-P.L.)
| | - Ruth Heidelberger
- Department of Neurobiology & Anatomy, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA;
- The MD Anderson Cancer Center/UTHealth Graduate School of Biomedical Sciences, Houston, TX 77030, USA
| | - John O’Brien
- Ruiz Department of Ophthalmology & Visual Science, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA; (J.A.); (X.L.); (C.K.M.); (Y.-P.L.)
- The MD Anderson Cancer Center/UTHealth Graduate School of Biomedical Sciences, Houston, TX 77030, USA
| |
Collapse
|
24
|
Network Architecture of Gap Junctional Coupling among Parallel Processing Channels in the Mammalian Retina. J Neurosci 2020; 40:4483-4511. [PMID: 32332119 DOI: 10.1523/jneurosci.1810-19.2020] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2019] [Revised: 03/27/2020] [Accepted: 04/12/2020] [Indexed: 01/04/2023] Open
Abstract
Gap junctions are ubiquitous throughout the nervous system, mediating critical signal transmission and integration, as well as emergent network properties. In mammalian retina, gap junctions within the Aii amacrine cell-ON cone bipolar cell (CBC) network are essential for night vision, modulation of day vision, and contribute to visual impairment in retinal degenerations, yet neither the extended network topology nor its conservation is well established. Here, we map the network contribution of gap junctions using a high-resolution connectomics dataset of an adult female rabbit retina. Gap junctions are prominent synaptic components of ON CBC classes, constituting 5%-25% of all axonal synaptic contacts. Many of these mediate canonical transfer of rod signals from Aii cells to ON CBCs for night vision, and we find that the uneven distribution of Aii signals to ON CBCs is conserved in rabbit, including one class entirely lacking direct Aii coupling. However, the majority of gap junctions formed by ON CBCs unexpectedly occur between ON CBCs, rather than with Aii cells. Such coupling is extensive, creating an interconnected network with numerous lateral paths both within, and particularly across, these parallel processing streams. Coupling patterns are precise with ON CBCs accepting and rejecting unique combinations of partnerships according to robust rulesets. Coupling specificity extends to both size and spatial topologies, thereby rivaling the synaptic specificity of chemical synapses. These ON CBC coupling motifs dramatically extend the coupled Aii-ON CBC network, with implications for signal flow in both scotopic and photopic retinal networks during visual processing and disease.SIGNIFICANCE STATEMENT Electrical synapses mediated by gap junctions are fundamental components of neural networks. In retina, coupling within the Aii-ON CBC network shapes visual processing in both the scotopic and photopic networks. In retinal degenerations, these same gap junctions mediate oscillatory activity that contributes to visual impairment. Here, we use high-resolution connectomics strategies to identify gap junctions and cellular partnerships. We describe novel, pervasive motifs both within and across classes of ON CBCs that dramatically extend the Aii-ON CBC network. These motifs are highly specific with implications for both signal processing within the retina and therapeutic interventions for blinding conditions. These findings highlight the underappreciated contribution of coupling motifs in retinal circuitry and the necessity of their detection in connectomics studies.
Collapse
|
25
|
Moore KB, Mitchell CK, Lin YP, Lee YH, Shihabeddin E, O'Brien J. Localized Calcium Signaling and the Control of Coupling at Cx36 Gap Junctions. eNeuro 2020; 7:ENEURO.0445-19.2020. [PMID: 32179580 PMCID: PMC7168262 DOI: 10.1523/eneuro.0445-19.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 01/29/2020] [Accepted: 02/21/2020] [Indexed: 01/10/2023] Open
Abstract
A variety of electrical synapses are capable of activity-dependent plasticity, including both activity-dependent potentiation and activity-dependent depression. In several types of neurons, activity-dependent electrical synapse plasticity depends on changes in the local Ca2+ environment. To enable study of local Ca2+ signaling that regulates plasticity, we developed a GCaMP Ca2+ biosensor fused to the electrical synapse protein Connexin 36 (Cx36). Cx36-GCaMP transfected into mammalian cell cultures formed gap junctions at cell-cell boundaries and supported Neurobiotin tracer coupling that was regulated by protein kinase A signaling in the same way as Cx36. Cx36-GCaMP gap junctions robustly reported local Ca2+ increases in response to addition of a Ca2+ ionophore with increases in fluorescence that recovered during washout. Recovery was strongly dependent on Na+-Ca2+ exchange activity. In cells transfected with NMDA receptor subunits, Cx36-GCaMP revealed transient and concentration-dependent increases in local Ca2+ on brief application of glutamate. In HeLa cells, glutamate application increased Cx36-GCaMP tracer coupling through a mechanism that depended in part on Ca2+, calmodulin-dependent protein kinase II (CaMKII) activity. This potentiation of coupling did not require exogenous expression of glutamate receptors, but could be accomplished by endogenously expressed glutamate receptors with pharmacological characteristics reminiscent of NMDA and kainate receptors. Analysis of RNA Sequencing data from HeLa cells confirmed expression of NMDA receptor subunits NR1, NR2C, and NR3B. In summary, Cx36-GCaMP is an effective tool to measure changes in the Ca2+ microenvironment around Cx36 gap junctions. Furthermore, HeLa cells can serve as a model system to study glutamate receptor-driven potentiation of electrical synapses.
Collapse
Affiliation(s)
- Keith B Moore
- Richard S. Ruiz, M.D. Department of Ophthalmology and Visual Science, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030
| | - Cheryl K Mitchell
- Richard S. Ruiz, M.D. Department of Ophthalmology and Visual Science, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030
| | - Ya-Ping Lin
- Richard S. Ruiz, M.D. Department of Ophthalmology and Visual Science, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030
| | - Yuan-Hao Lee
- Richard S. Ruiz, M.D. Department of Ophthalmology and Visual Science, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030
| | - Eyad Shihabeddin
- Richard S. Ruiz, M.D. Department of Ophthalmology and Visual Science, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030
- The MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, TX 77030
| | - John O'Brien
- Richard S. Ruiz, M.D. Department of Ophthalmology and Visual Science, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030
- The MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, TX 77030
| |
Collapse
|
26
|
Zhang L, Wu Q, Zhang Y. Early visual motion experience shapes the gap junction connections among direction selective ganglion cells. PLoS Biol 2020; 18:e3000692. [PMID: 32210427 PMCID: PMC7135332 DOI: 10.1371/journal.pbio.3000692] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 04/06/2020] [Accepted: 03/12/2020] [Indexed: 11/30/2022] Open
Abstract
Gap junction connections between neurons play critical roles in the development of the nervous system. However, studies on the sensory experience–driven plasticity during the critical period rarely examine the involvement of gap junction connections. ON-OFF direction selective ganglion cells (ooDSGCs) in the mouse retina that prefer upward motion are connected by gap junctions throughout development. Here, we show that after exposing the mice to a visual environment dominated by upward motion from eye-opening to puberty, ooDSGCs that respond preferentially to upward motion show enhanced spike synchronization, while downward motion training has the opposite effect. The effect is long-term, persisting at least three months after the training. Correlated activity during training is tightly linked to this effect: Cells trained by stimuli that promote higher levels of activity correlation show stronger gap junction connection after the training, while stimuli that produce very low activity correlation leave the cells with much weaker gap junction connections afterwards. Direct investigation of the gap junction connections among upward motion–preferring ooDSGCs show that both the percentage of electrically coupled ooDSGCs and the strength of the coupling are affected by visual motion training. Our results demonstrate that in the retina, one of the peripheral sensory systems, gap junction connections can be shaped by experience during development. Gap junction connections between upward motion–preferring direction selective ganglion cells can be shaped by early visual experience; upward motion training leads to enhanced connectivity, while downward motion greatly suppresses the connection, suggesting a form of activity-dependent plasticity.
Collapse
Affiliation(s)
- Li Zhang
- Institute of Neuroscience, Chinese Academy of Sciences, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Qiwen Wu
- Institute of Neuroscience, Chinese Academy of Sciences, Shanghai, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Yifeng Zhang
- Institute of Neuroscience, Chinese Academy of Sciences, Shanghai, China
- * E-mail:
| |
Collapse
|
27
|
Christie AE, Hull JJ, Dickinson PS. In silico analyses suggest the cardiac ganglion of the lobster, Homarus americanus, contains a diverse array of putative innexin/innexin-like proteins, including both known and novel members of this protein family. INVERTEBRATE NEUROSCIENCE 2020; 20:5. [PMID: 32115669 DOI: 10.1007/s10158-020-0238-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2019] [Accepted: 01/31/2020] [Indexed: 01/16/2023]
Abstract
Gap junctions are physical channels that connect adjacent cells, permitting the flow of small molecules/ions between the cytoplasms of the coupled units. Innexin/innexin-like proteins are responsible for the formation of invertebrate gap junctions. Within the nervous system, gap junctions often function as electrical synapses, providing a means for coordinating activity among electrically coupled neurons. While some gap junctions allow the bidirectional flow of small molecules/ions between coupled cells, others permit flow in one direction only or preferentially. The complement of innexins present in a gap junction determines its specific properties. Thus, understanding innexin diversity is key for understanding the full potential of electrical coupling in a species/system. The decapod crustacean cardiac ganglion (CG), which controls cardiac muscle contractions, is a simple pattern-generating neural network with extensive electrical coupling among its circuit elements. In the lobster, Homarus americanus, prior work suggested that the adult neuronal innexin complement consists of six innexins (Homam-Inx1-4 and Homam-Inx6-7). Here, using a H. americanus CG-specific transcriptome, we explored innexin complement in this portion of the lobster nervous system. With the exception of Homam-Inx4, all of the previously described innexins appear to be expressed in the H. americanus CG. In addition, transcripts encoding seven novel putative innexins (Homam-Inx8-14) were identified, four (Homam-Inx8-11) having multiple splice variants, e.g., six for Homam-Inx8. Collectively, these data indicate that the innexin complement of the lobster nervous system in general, and the CG specifically, is likely significantly greater than previously reported, suggesting the possibility of expanded gap junction diversity and function in H. americanus.
Collapse
Affiliation(s)
- Andrew E Christie
- Békésy Laboratory of Neurobiology, Pacific Biosciences Research Center, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, 1993 East-West Road, Honolulu, HI, 96822, USA.
| | - J Joe Hull
- Pest Management and Biocontrol Research Unit, US Arid Land Agricultural Research Center, USDA Agricultural Research Services, Maricopa, AZ, 85138, USA
| | - Patsy S Dickinson
- Department of Biology, Bowdoin College, 6500 College Station, Brunswick, ME, 04011, USA
| |
Collapse
|
28
|
Abudara V, Retamal MA, Del Rio R, Orellana JA. Synaptic Functions of Hemichannels and Pannexons: A Double-Edged Sword. Front Mol Neurosci 2018; 11:435. [PMID: 30564096 PMCID: PMC6288452 DOI: 10.3389/fnmol.2018.00435] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 11/08/2018] [Indexed: 01/18/2023] Open
Abstract
The classical view of synapses as the functional contact between presynaptic and postsynaptic neurons has been challenged in recent years by the emerging regulatory role of glial cells. Astrocytes, traditionally considered merely supportive elements are now recognized as active modulators of synaptic transmission and plasticity at the now so-called "tripartite synapse." In addition, an increasing body of evidence indicates that beyond immune functions microglia also participate in various processes aimed to shape synaptic plasticity. Release of neuroactive compounds of glial origin, -process known as gliotransmission-, constitute a widespread mechanism through which glial cells can either potentiate or reduce the synaptic strength. The prevailing vision states that gliotransmission depends on an intracellular Ca2+/exocytotic-mediated release; notwithstanding, growing evidence is pointing at hemichannels (connexons) and pannexin channels (pannexons) as alternative non-vesicular routes for gliotransmitters efflux. In concurrence with this novel concept, both hemichannels and pannexons are known to mediate the transfer of ions and signaling molecules -such as ATP and glutamate- between the cytoplasm and the extracellular milieu. Importantly, recent reports show that glial hemichannels and pannexons are capable to perceive synaptic activity and to respond to it through changes in their functional state. In this article, we will review the current information supporting the "double edge sword" role of hemichannels and pannexons in the function of central and peripheral synapses. At one end, available data support the idea that these channels are chief components of a feedback control mechanism through which gliotransmitters adjust the synaptic gain in either resting or stimulated conditions. At the other end, we will discuss how the excitotoxic release of gliotransmitters and [Ca2+]i overload linked to the opening of hemichannels/pannexons might impact cell function and survival in the nervous system.
Collapse
Affiliation(s)
- Verónica Abudara
- Departamento de Fisiología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay
| | - Mauricio A Retamal
- Centro de Fisiología Celular e Integrativa, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile.,Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, TX, United States.,Programa de Comunicación Celular en Cáncer, Instituto de Ciencias e Innovación en Medicina, Santiago, Chile
| | - Rodrigo Del Rio
- Laboratory of Cardiorespiratory Control, Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Envejecimiento y Regeneración, Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Excelencia en Biomedicina de Magallanes, Universidad de Magallanes, Punta Arenas, Chile
| | - Juan A Orellana
- Departamento de Neurología, Escuela de Medicina and Centro Interdisciplinario de Neurociencias, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.,Centro de Investigación y Estudio del Consumo de Alcohol en Adolescentes, Santiago, Chile
| |
Collapse
|
29
|
Faber DS, Pereda AE. Two Forms of Electrical Transmission Between Neurons. Front Mol Neurosci 2018; 11:427. [PMID: 30534051 PMCID: PMC6276723 DOI: 10.3389/fnmol.2018.00427] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Accepted: 11/05/2018] [Indexed: 12/30/2022] Open
Abstract
Electrical signaling is a cardinal feature of the nervous system and endows it with the capability of quickly reacting to changes in the environment. Although synaptic communication between nerve cells is perceived to be mainly chemically mediated, electrical synaptic interactions also occur. Two different strategies are responsible for electrical communication between neurons. One is the consequence of low resistance intercellular pathways, called "gap junctions", for the spread of electrical currents between the interior of two cells. The second occurs in the absence of cell-to-cell contacts and is a consequence of the extracellular electrical fields generated by the electrical activity of neurons. Here, we place present notions about electrical transmission in a historical perspective and contrast the contributions of the two different forms of electrical communication to brain function.
Collapse
Affiliation(s)
- Donald S. Faber
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, NY, United States
- Marine Biological Laboratory, Woods Hole, MA, United States
| | - Alberto E. Pereda
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, New York, NY, United States
- Marine Biological Laboratory, Woods Hole, MA, United States
| |
Collapse
|
30
|
Marc RE, Sigulinsky CL, Pfeiffer RL, Emrich D, Anderson JR, Jones BW. Heterocellular Coupling Between Amacrine Cells and Ganglion Cells. Front Neural Circuits 2018; 12:90. [PMID: 30487737 PMCID: PMC6247779 DOI: 10.3389/fncir.2018.00090] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 09/28/2018] [Indexed: 01/08/2023] Open
Abstract
All superclasses of retinal neurons, including bipolar cells (BCs), amacrine cells (ACs) and ganglion cells (GCs), display gap junctional coupling. However, coupling varies extensively by class. Heterocellular AC coupling is common in many mammalian GC classes. Yet, the topology and functions of coupling networks remains largely undefined. GCs are the least frequent superclass in the inner plexiform layer and the gap junctions mediating GC-to-AC coupling (GC::AC) are sparsely arrayed amidst large cohorts of homocellular AC::AC, BC::BC, GC::GC and heterocellular AC::BC gap junctions. Here, we report quantitative coupling for identified GCs in retinal connectome 1 (RC1), a high resolution (2 nm) transmission electron microscopy-based volume of rabbit retina. These reveal that most GC gap junctions in RC1 are suboptical. GC classes lack direct cross-class homocellular coupling with other GCs, despite opportunities via direct membrane contact, while OFF alpha GCs and transient ON directionally selective (DS) GCs are strongly coupled to distinct AC cohorts. Integrated small molecule immunocytochemistry identifies these as GABAergic ACs (γ+ ACs). Multi-hop synaptic queries of RC1 connectome further profile these coupled γ+ ACs. Notably, OFF alpha GCs couple to OFF γ+ ACs and transient ON DS GCs couple to ON γ+ ACs, including a large interstitial amacrine cell, revealing matched ON/OFF photic drive polarities within coupled networks. Furthermore, BC input to these γ+ ACs is tightly matched to the GCs with which they couple. Evaluation of the coupled versus inhibitory targets of the γ+ ACs reveals that in both ON and OFF coupled GC networks these ACs are presynaptic to GC classes that are different than the classes with which they couple. These heterocellular coupling patterns provide a potential mechanism for an excited GC to indirectly inhibit nearby GCs of different classes. Similarly, coupled γ+ ACs engaged in feedback networks can leverage the additional gain of BC synapses in shaping the signaling of downstream targets based on their own selective coupling with GCs. A consequence of coupling is intercellular fluxes of small molecules. GC::AC coupling involves primarily γ+ cells, likely resulting in GABA diffusion into GCs. Surveying GABA signatures in the GC layer across diverse species suggests the majority of vertebrate retinas engage in GC::γ+ AC coupling.
Collapse
Affiliation(s)
| | | | | | | | | | - Bryan William Jones
- Moran Eye Center, Department of Ophthalmology and Visual Sciences, The University of Utah, Salt Lake City, UT, United States
| |
Collapse
|
31
|
O'Brien J, Bloomfield SA. Plasticity of Retinal Gap Junctions: Roles in Synaptic Physiology and Disease. Annu Rev Vis Sci 2018; 4:79-100. [DOI: 10.1146/annurev-vision-091517-034133] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Electrical synaptic transmission via gap junctions underlies direct and rapid neuronal communication in the central nervous system. The diversity of functional roles played by electrical synapses is perhaps best exemplified in the vertebrate retina, in which gap junctions are expressed by each of the five major neuronal types. These junctions are highly plastic; they are dynamically regulated by ambient illumination and circadian rhythms acting through light-activated neuromodulators. The networks formed by electrically coupled neurons provide plastic, reconfigurable circuits positioned to play key and diverse roles in the transmission and processing of visual information at every retinal level. Recent work indicates gap junctions also play a role in the progressive cell death and aberrant activity seen in various pathological conditions of the retina. Gap junctions thus form potential targets for novel neuroprotective therapies in the treatment of neurodegenerative retinal diseases such as glaucoma and ischemic retinopathies.
Collapse
Affiliation(s)
- John O'Brien
- Department of Ophthalmology and Visual Science, University of Texas Health Science Center, Houston, Texas 77030, USA
| | - Stewart A. Bloomfield
- Department of Biological and Vision Sciences, State University of New York College of Optometry, New York, NY 10036, USA
| |
Collapse
|