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Han TH, Vicidomini R, Ramos CI, Wang Q, Nguyen P, Jarnik M, Lee CH, Stawarski M, Hernandez RX, Macleod GT, Serpe M. Neto-α Controls Synapse Organization and Homeostasis at the Drosophila Neuromuscular Junction. Cell Rep 2021; 32:107866. [PMID: 32640231 PMCID: PMC7484471 DOI: 10.1016/j.celrep.2020.107866] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Revised: 02/27/2020] [Accepted: 06/16/2020] [Indexed: 02/06/2023] Open
Abstract
Glutamate receptor auxiliary proteins control receptor distribution and function, ultimately controlling synapse assembly, maturation, and plasticity. At the Drosophila neuromuscular junction (NMJ), a synapse with both pre- and postsynaptic kainate-type glutamate receptors (KARs), we show that the auxiliary protein Neto evolved functionally distinct isoforms to modulate synapse development and homeostasis. Using genetics, cell biology, and electrophysiology, we demonstrate that Neto-α functions on both sides of the NMJ. In muscle, Neto-α limits the size of the postsynaptic receptor field. In motor neurons (MNs), Neto-α controls neurotransmitter release in a KAR-dependent manner. In addition, Neto-α is both required and sufficient for the presynaptic increase in neurotransmitter release in response to reduced postsynaptic sensitivity. This KAR-independent function of Neto-α is involved in activity-induced cytomatrix remodeling. We propose that Drosophila ensures NMJ functionality by acquiring two Neto isoforms with differential expression patterns and activities.
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Affiliation(s)
- Tae Hee Han
- Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD, USA
| | - Rosario Vicidomini
- Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD, USA
| | - Cathy Isaura Ramos
- Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD, USA; Institute of Functional Genomics of Lyon, Lyon, France
| | - Qi Wang
- Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD, USA
| | - Peter Nguyen
- Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD, USA
| | - Michal Jarnik
- Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD, USA
| | - Chi-Hon Lee
- Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD, USA; Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
| | - Michal Stawarski
- Wilkes Honors College and Department of Biology, Florida Atlantic University, Jupiter, FL, USA; Biomedical Department, University of Basel, Basel, Switzerland
| | - Roberto X Hernandez
- Wilkes Honors College and Department of Biology, Florida Atlantic University, Jupiter, FL, USA
| | - Gregory T Macleod
- Wilkes Honors College and Department of Biology, Florida Atlantic University, Jupiter, FL, USA
| | - Mihaela Serpe
- Cell Biology and Neurobiology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD, USA.
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Endogenous Tagging Reveals Differential Regulation of Ca 2+ Channels at Single Active Zones during Presynaptic Homeostatic Potentiation and Depression. J Neurosci 2019; 39:2416-2429. [PMID: 30692227 PMCID: PMC6435823 DOI: 10.1523/jneurosci.3068-18.2019] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Revised: 01/14/2019] [Accepted: 01/21/2019] [Indexed: 12/19/2022] Open
Abstract
Neurons communicate through Ca2+-dependent neurotransmitter release at presynaptic active zones (AZs). Neurotransmitter release properties play a key role in defining information flow in circuits and are tuned during multiple forms of plasticity. Despite their central role in determining neurotransmitter release properties, little is known about how Ca2+ channel levels are modulated to calibrate synaptic function. We used CRISPR to tag the Drosophila CaV2 Ca2+ channel Cacophony (Cac) and, in males in which all Cac channels are tagged, investigated the regulation of endogenous Ca2+ channels during homeostatic plasticity. We found that heterogeneously distributed Cac is highly predictive of neurotransmitter release probability at individual AZs and differentially regulated during opposing forms of presynaptic homeostatic plasticity. Specifically, AZ Cac levels are increased during chronic and acute presynaptic homeostatic potentiation (PHP), and live imaging during acute expression of PHP reveals proportional Ca2+ channel accumulation across heterogeneous AZs. In contrast, endogenous Cac levels do not change during presynaptic homeostatic depression (PHD), implying that the reported reduction in Ca2+ influx during PHD is achieved through functional adaptions to pre-existing Ca2+ channels. Thus, distinct mechanisms bidirectionally modulate presynaptic Ca2+ levels to maintain stable synaptic strength in response to diverse challenges, with Ca2+ channel abundance providing a rapidly tunable substrate for potentiating neurotransmitter release over both acute and chronic timescales. SIGNIFICANCE STATEMENT Presynaptic Ca2+ dynamics play an important role in establishing neurotransmitter release properties. Presynaptic Ca2+ influx is modulated during multiple forms of homeostatic plasticity at Drosophila neuromuscular junctions to stabilize synaptic communication. However, it remains unclear how this dynamic regulation is achieved. We used CRISPR gene editing to endogenously tag the sole Drosophila Ca2+ channel responsible for synchronized neurotransmitter release, and found that channel abundance is regulated during homeostatic potentiation, but not homeostatic depression. Through live imaging experiments during the adaptation to acute homeostatic challenge, we visualize the accumulation of endogenous Ca2+ channels at individual active zones within 10 min. We propose that differential regulation of Ca2+ channels confers broad capacity for tuning neurotransmitter release properties to maintain neural communication.
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Samigullin DV, Khaziev EF, Zhilyakov NV, Bukharaeva EA, Nikolsky EE. Loading a Calcium Dye into Frog Nerve Endings Through the Nerve Stump: Calcium Transient Registration in the Frog Neuromuscular Junction. J Vis Exp 2017. [PMID: 28715368 PMCID: PMC5609652 DOI: 10.3791/55122] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
One of the most feasible methods of measuring presynaptic calcium levels in presynaptic nerve terminals is optical recording. It is based on using calcium-sensitive fluorescent dyes that change their emission intensity or wavelength depending on the concentration of free calcium in the cell. There are several methods used to stain cells with calcium dyes. Most common are the processes of loading the dyes through a micropipette or pre-incubating with the acetoxymethyl ester forms of the dyes. However, these methods are not quite applicable to neuromuscular junctions (NMJs) due to methodological issues that arise. In this article, we present a method for loading a calcium-sensitive dye through the frog nerve stump of the frog nerve into the nerve endings. Since entry of external calcium into nerve terminals and the subsequent binding to the calcium dye occur within the millisecond time-scale, it is necessary to use a fast imaging system to record these interactions. Here, we describe a protocol for recording the calcium transient with a fast CCD camera.
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Affiliation(s)
- Dmitry V Samigullin
- Laboratory of Biophysics of Synaptic Processes, Kazan Scientific Centre, Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences; Open Laboratory of Neuropharmacology, Kazan Federal University; Department of Radiophotonics and Microwave Technologies, A.N. Tupolev Kazan National Research Technical University;
| | - Eduard F Khaziev
- Laboratory of Biophysics of Synaptic Processes, Kazan Scientific Centre, Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences; Open Laboratory of Neuropharmacology, Kazan Federal University; Department of Radiophotonics and Microwave Technologies, A.N. Tupolev Kazan National Research Technical University
| | - Nikita V Zhilyakov
- Laboratory of Biophysics of Synaptic Processes, Kazan Scientific Centre, Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences; Open Laboratory of Neuropharmacology, Kazan Federal University
| | - Ellya A Bukharaeva
- Laboratory of Biophysics of Synaptic Processes, Kazan Scientific Centre, Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences; Open Laboratory of Neuropharmacology, Kazan Federal University
| | - Eugeny E Nikolsky
- Laboratory of Biophysics of Synaptic Processes, Kazan Scientific Centre, Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences; Open Laboratory of Neuropharmacology, Kazan Federal University; Department of Medical and Biological Physics, Kazan State Medical University
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Macleod GT. Direct injection of indicators for calcium imaging at the Drosophila larval neuromuscular junction. Cold Spring Harb Protoc 2012; 2012:797-801. [PMID: 22753595 DOI: 10.1101/pdb.prot070102] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Calcium imaging is a technique in which Ca(2+)-binding molecules are loaded into live cells and as they bind Ca(2+) they "indicate" the concentration of free calcium through a change in either the intensity or the wavelength of light emitted (fluorescence or bioluminescence). There are several possible methods for loading synthetic Ca(2+) indicators into subcellular compartments, including topical application of membrane-permeant Ca(2+) indicators, forward-filling of dextran conjugates, and direct injection. Calcium imaging is a highly informative technique in neurobiology because Ca(2+) is involved in many neuronal signaling pathways and serves as the trigger for neurotransmitter release. This article describes the direct injection of Ca(2+) indicators at the Drosophila larval neuromuscular junction (NMJ). This technique allows rapid loading of most Ca(2+) indicators, but there are drawbacks in that it is a difficult technique to master and requires additional electrophysiological equipment. Also, Ca(2+) indicators that are easily injected are usually susceptible to compartmentalization.
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Macleod GT. Topical application of indicators for calcium imaging at the Drosophila larval neuromuscular junction. Cold Spring Harb Protoc 2012; 2012:786-90. [PMID: 22753610 DOI: 10.1101/pdb.prot070086] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Calcium imaging is a technique in which Ca(2+)-binding molecules are loaded into live cells and as they bind Ca(2+) they "indicate" the concentration of free calcium through a change in either the intensity or the wavelength of light emitted (fluorescence or bioluminescence). There are several possible methods for loading synthetic Ca(2+) indicators into subcellular compartments, including topical application of membrane-permeant Ca(2+) indicators, forward-filling of dextran conjugates, and direct injection. Calcium imaging is a highly informative technique in neurobiology because Ca(2+) is involved in many neuronal signaling pathways and serves as the trigger for neurotransmitter release. This article describes the topical application of Ca(2+) indicators at the Drosophila larval neuromuscular junction (NMJ). This loading technique is simple to execute and yields data quickly. The drawback is that the data can be difficult to interpret, primarily because it is difficult to ascertain which cellular and subcellular compartment(s) are loaded (e.g., muscle, nerve, or glia; cytosol, mitochondrion, or endoplasmic reticulum).
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Macleod GT. Imaging and analysis of nonratiometric calcium indicators at the Drosophila larval neuromuscular junction. Cold Spring Harb Protoc 2012; 2012:802-9. [PMID: 22753596 DOI: 10.1101/pdb.prot070110] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Ca(2+) indicators can be loaded into a Drosophila larval neuromuscular junction (NMJ) preparation using several methods, including topical application of membrane-permeant Ca(2+) indicators, forward-filling of dextran conjugates, and direct injection. This article describes how such an NMJ preparation loaded with Ca(2+) indicator is set up for imaging of the muscle fiber during stimulation of its innervating nerve cell. A simple protocol is provided for collecting and analyzing a set of imaging data, together with the sequence of calculations involved in image analysis. The change in the intensity of the Ca(2+) indicator must be quantified to obtain an estimate of the change in the concentration of free Ca(2+) (Δ[Ca(2+)]). The change in intensity is conventionally represented as the expression "ΔF/F." Simply put, this is the change in fluorescence intensity relative to the resting fluorescence intensity. If the K(D) of the Ca(2+) indicator is in excess of the maximum value of [Ca(2+)] during the response, then ΔF/F is considered to be linearly related to Δ[Ca(2+)]. In practice, ΔF/F is calculated for each image using a simple algorithm ([F(stim) - F(rest)]/F(rest)), where F(stim) is the intensity of the Ca(2+) indicator in each image, and F(rest) is the intensity before nerve stimulation. Finally, various options for building a Ca(2+)-imaging rig are considered.
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Macleod GT. Calcium imaging at the Drosophila larval neuromuscular junction. Cold Spring Harb Protoc 2012; 2012:758-66. [PMID: 22753609 DOI: 10.1101/pdb.top070078] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Calcium imaging uses optical imaging techniques to measure the concentration of free calcium [Ca(2+)] in live cells. It is a highly informative technique in neurobiology because Ca(2+) is involved in many neuronal signaling pathways and serves as the trigger for neurotransmitter release. The technique relies on loading Ca(2+) indicators into cells, measuring the quantity and/or wavelength of the photons emitted by the Ca(2+) indicator, and interpreting these data in terms of [Ca(2+)]. There are several possible methods for loading synthetic Ca(2+) indicators into subcellular compartments, for example, topical application of membrane-permeant Ca(2+) indicators, forward-filling of dextran conjugates, and direct injection. These techniques are applicable to calcium imaging at the Drosophila larval neuromuscular junction (NMJ), and are also readily adaptable to Drosophila embryo and adult preparations.
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