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Vincent PFY, Young ED, Edge ASB, Glowatzki E. Auditory hair cells and spiral ganglion neurons regenerate synapses with refined release properties in vitro. Proc Natl Acad Sci U S A 2024; 121:e2315599121. [PMID: 39058581 PMCID: PMC11294990 DOI: 10.1073/pnas.2315599121] [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: 09/10/2023] [Accepted: 06/12/2024] [Indexed: 07/28/2024] Open
Abstract
Ribbon synapses between inner hair cells (IHCs) and type I spiral ganglion neurons (SGNs) in the inner ear are damaged by noise trauma and with aging, causing "synaptopathy" and hearing loss. Cocultures of neonatal denervated organs of Corti and newly introduced SGNs have been developed to find strategies for improving IHC synapse regeneration, but evidence of the physiological normality of regenerated synapses is missing. This study utilizes IHC optogenetic stimulation and SGN recordings, showing that, when P3-5 denervated organs of Corti are cocultured with SGNs, newly formed IHC/SGN synapses are indeed functional, exhibiting glutamatergic excitatory postsynaptic currents. When using older organs of Corti at P10-11, synaptic activity probed by deconvolution showed more mature release properties, closer to the specialized mode of IHC synaptic transmission crucial for coding the sound signal. This functional assessment of newly formed IHC synapses developed here, provides a powerful tool for testing approaches to improve synapse regeneration.
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Affiliation(s)
- Philippe F. Y. Vincent
- The Center for Hearing and Balance, The Johns Hopkins School of Medicine, Baltimore, MD21205
- Department of Otolaryngology Head and Neck Surgery, The Johns Hopkins School of Medicine, Baltimore, MD21205
| | - Eric D. Young
- The Center for Hearing and Balance, The Johns Hopkins School of Medicine, Baltimore, MD21205
- Department of Otolaryngology Head and Neck Surgery, The Johns Hopkins School of Medicine, Baltimore, MD21205
- Department of Neuroscience, The Johns Hopkins School of Medicine, Baltimore, MD21205
- Department of Biomedical Engineering, The Johns Hopkins School of Medicine, Baltimore, MD21205
| | - Albert S. B. Edge
- Department of Otolaryngology, Harvard Medical School, Boston, MA02115
- Eaton-Peabody Laboratory, Massachusetts Eye and Ear, Boston, MA02114
- Program in Speech and Hearing Bioscience and Technology, Harvard Medical School, Boston, MA02115
- Harvard Stem Cell Institute, Cambridge, MA02139
| | - Elisabeth Glowatzki
- The Center for Hearing and Balance, The Johns Hopkins School of Medicine, Baltimore, MD21205
- Department of Otolaryngology Head and Neck Surgery, The Johns Hopkins School of Medicine, Baltimore, MD21205
- Department of Neuroscience, The Johns Hopkins School of Medicine, Baltimore, MD21205
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2
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Bhatia P, Mehmood S, Doyon-Reale N, Rosati R, Stemmer PM, Jamesdaniel S. Unraveling the molecular landscape of lead-induced cochlear synaptopathy: a quantitative proteomics analysis. Front Cell Neurosci 2024; 18:1408208. [PMID: 39104440 PMCID: PMC11298392 DOI: 10.3389/fncel.2024.1408208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2024] [Accepted: 07/03/2024] [Indexed: 08/07/2024] Open
Abstract
Introduction Exposure to heavy metal lead can cause serious health effects such as developmental neurotoxicity in infants, cognitive impairment in children, and cardiovascular and nephrotoxic effects in adults. Hearing loss is one of the toxic effects induced by exposure to lead. Previous studies demonstrated that exposure to lead causes oxidative stress in the cochlea and disrupts ribbon synapses in the inner hair cells. Methods This study investigated the underlying mechanism by evaluating the changes in the abundance of cochlear synaptosomal proteins that accompany lead-induced cochlear synaptopathy and hearing loss in mice. Young-adult CBA/J mice were given lead acetate in drinking water for 28 days. Results Lead exposure significantly increased the hearing thresholds, particularly at the higher frequencies in both male and female mice, but it did not affect the activity of outer hair cells or induce hair cell loss. However, lead exposure decreased wave-I amplitude, suggesting lead-induced cochlear synaptopathy. In agreement, colocalization of pre- and post-synaptic markers indicated that lead exposure decreased the number of paired synapses in the basal turn of the cochlea. Proteomics analysis indicated that lead exposure increased the abundance of 352 synaptic proteins and decreased the abundance of 394 synaptic proteins in the cochlea. Bioinformatics analysis indicated that proteins that change in abundance are highly enriched in the synaptic vesicle cycle pathway. Discussion Together, these results suggest that outer hair cells are not the primary target in lead-induced ototoxicity, that lead-induced cochlear synaptopathy is more pronounced in the basal turn of the cochlea, and that synaptic vesicle cycle signaling potentially plays a critical role in lead-induced cochlear synaptopathy.
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Affiliation(s)
- Pankaj Bhatia
- Institute of Environmental Health Sciences, Wayne State University, Detroit, MI, United States
| | - Shomaila Mehmood
- Institute of Environmental Health Sciences, Wayne State University, Detroit, MI, United States
| | - Nicole Doyon-Reale
- Institute of Environmental Health Sciences, Wayne State University, Detroit, MI, United States
| | - Rita Rosati
- Institute of Environmental Health Sciences, Wayne State University, Detroit, MI, United States
| | - Paul M. Stemmer
- Institute of Environmental Health Sciences, Wayne State University, Detroit, MI, United States
| | - Samson Jamesdaniel
- Institute of Environmental Health Sciences, Wayne State University, Detroit, MI, United States
- Department of Family Medicine and Public Health Sciences, Wayne State University, Detroit, MI, United States
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3
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Pan K, Jinnah HA, Hess EJ, Smith Y, Villalba RM. Ultrastructural analysis of nigrostriatal dopaminergic terminals in a knockin mouse model of DYT1 dystonia. Eur J Neurosci 2024; 59:1407-1427. [PMID: 38123503 DOI: 10.1111/ejn.16197] [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: 03/08/2023] [Revised: 11/02/2023] [Accepted: 11/05/2023] [Indexed: 12/23/2023]
Abstract
DYT1 dystonia is associated with decreased striatal dopamine release. In this study, we examined the possibility that ultrastructural changes of nigrostriatal dopamine terminals could contribute to this neurochemical imbalance using a serial block face/scanning electron microscope (SBF/SEM) and three-dimensional reconstruction to analyse striatal tyrosine hydroxylase-immunoreactive (TH-IR) terminals and their synapses in a DYT1(ΔE) knockin (DYT1-KI) mouse model of DYT1 dystonia. Furthermore, to study possible changes in vesicle packaging capacity of dopamine, we used transmission electron microscopy to assess the synaptic vesicle size in striatal dopamine terminals. Quantitative comparative analysis of 80 fully reconstructed TH-IR terminals in the WT and DYT1-KI mice indicate (1) no significant difference in the volume of TH-IR terminals; (2) no major change in the proportion of axo-spinous versus axo-dendritic synapses; (3) no significant change in the post-synaptic density (PSD) area of axo-dendritic synapses, while the PSDs of axo-spinous synapses were significantly smaller in DYT1-KI mice; (4) no significant change in the contact area between TH-IR terminals and dendritic shafts or spines, while the ratio of PSD area/contact area decreased significantly for both axo-dendritic and axo-spinous synapses in DYT1-KI mice; (5) no significant difference in the mitochondria volume; and (6) no significant difference in the synaptic vesicle area between the two groups. Altogether, these findings suggest that abnormal morphometric changes of nigrostriatal dopamine terminals and their post-synaptic targets are unlikely to be a major source of reduced striatal dopamine release in DYT1 dystonia.
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Affiliation(s)
- Ke Pan
- Emory National Primate Research Center, Emory University, Atlanta, Georgia, USA
- Department of Physical Therapy & Human Movement Sciences, Northwestern University, Chicago, Illinois, USA
| | - Hyder A Jinnah
- Department of Neurology, Emory University, Atlanta, Georgia, USA
- Department of Human Genetics and Pediatrics, Emory University, Atlanta, Georgia, USA
| | - Ellen J Hess
- Department of Neurology, Emory University, Atlanta, Georgia, USA
- Department of Pharmacology and Chemical Biology, Emory University, Atlanta, Georgia, USA
| | - Yoland Smith
- Emory National Primate Research Center, Emory University, Atlanta, Georgia, USA
- Department of Neurology, Emory University, Atlanta, Georgia, USA
| | - Rosa M Villalba
- Emory National Primate Research Center, Emory University, Atlanta, Georgia, USA
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Abstract
Membrane fusion and budding mediate fundamental processes like intracellular trafficking, exocytosis, and endocytosis. Fusion is thought to open a nanometer-range pore that may subsequently close or dilate irreversibly, whereas budding transforms flat membranes into vesicles. Reviewing recent breakthroughs in real-time visualization of membrane transformations well exceeding this classical view, we synthesize a new model and describe its underlying mechanistic principles and functions. Fusion involves hemi-to-full fusion, pore expansion, constriction and/or closure while fusing vesicles may shrink, enlarge, or receive another vesicle fusion; endocytosis follows exocytosis primarily by closing Ω-shaped profiles pre-formed through the flat-to-Λ-to-Ω-shape transition or formed via fusion. Calcium/SNARE-dependent fusion machinery, cytoskeleton-dependent membrane tension, osmotic pressure, calcium/dynamin-dependent fission machinery, and actin/dynamin-dependent force machinery work together to generate fusion and budding modes differing in pore status, vesicle size, speed and quantity, controls release probability, synchronization and content release rates/amounts, and underlies exo-endocytosis coupling to maintain membrane homeostasis. These transformations, underlying mechanisms, and functions may be conserved for fusion and budding in general.
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Affiliation(s)
- Ling-Gang Wu
- National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA.
| | - Chung Yu Chan
- National Institute of Neurological Disorders and Stroke, Bethesda, MD, USA
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5
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Jaime Tobón LM, Moser T. Ca 2+ regulation of glutamate release from inner hair cells of hearing mice. Proc Natl Acad Sci U S A 2023; 120:e2311539120. [PMID: 38019860 DOI: 10.1073/pnas.2311539120] [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: 07/07/2023] [Accepted: 10/11/2023] [Indexed: 12/01/2023] Open
Abstract
In our hearing organ, sound is encoded at ribbon synapses formed by inner hair cells (IHCs) and spiral ganglion neurons (SGNs). How the underlying synaptic vesicle (SV) release is controlled by Ca2+ in IHCs of hearing animals remained to be investigated. Here, we performed patch-clamp SGN recordings of the initial rate of release evoked by brief IHC Ca2+-influx in an ex vivo cochlear preparation from hearing mice. We aimed to closely mimic physiological conditions by perforated-patch recordings from IHCs kept at the physiological resting potential and at body temperature. We found release to relate supralinearly to Ca2+-influx (power, m: 4.3) when manipulating the [Ca2+] available for SV release by Zn2+-flicker-blocking of the single Ca2+-channel current. In contrast, a near linear Ca2+ dependence (m: 1.2 to 1.5) was observed when varying the number of open Ca2+-channels during deactivating Ca2+-currents and by dihydropyridine channel-inhibition. Concurrent changes of number and current of open Ca2+-channels over the range of physiological depolarizations revealed m: 1.8. These findings indicate that SV release requires ~4 Ca2+-ions to bind to their Ca2+-sensor of fusion. We interpret the near linear Ca2+-dependence of release during manipulations that change the number of open Ca2+-channels to reflect control of SV release by the high [Ca2+] in the Ca2+-nanodomain of one or few nearby Ca2+-channels. We propose that a combination of Ca2+ nanodomain control and supralinear intrinsic Ca2+-dependence of fusion optimally links SV release to the timing and amplitude of the IHC receptor potential and separates it from other IHC Ca2+-signals unrelated to afferent synaptic transmission.
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Affiliation(s)
- Lina María Jaime Tobón
- Auditory Neuroscience and Synaptic Nanophysiology Group, Max Planck Institute for Multidisciplinary Sciences, Göttingen 37077, Germany
- Institute for Auditory Neuroscience, University Medical Center Göttingen, Göttingen 37075, Germany
- Collaborative Research Center 889, University of Göttingen, Göttingen 37075, Germany
- Multiscale Bioimaging of Excitable Cells, Cluster of Excellence, Göttingen 37075, Germany
| | - Tobias Moser
- Auditory Neuroscience and Synaptic Nanophysiology Group, Max Planck Institute for Multidisciplinary Sciences, Göttingen 37077, Germany
- Institute for Auditory Neuroscience, University Medical Center Göttingen, Göttingen 37075, Germany
- Collaborative Research Center 889, University of Göttingen, Göttingen 37075, Germany
- Multiscale Bioimaging of Excitable Cells, Cluster of Excellence, Göttingen 37075, Germany
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6
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Moser T, Karagulyan N, Neef J, Jaime Tobón LM. Diversity matters - extending sound intensity coding by inner hair cells via heterogeneous synapses. EMBO J 2023; 42:e114587. [PMID: 37800695 PMCID: PMC10690447 DOI: 10.15252/embj.2023114587] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 06/26/2023] [Accepted: 08/07/2023] [Indexed: 10/07/2023] Open
Abstract
Our sense of hearing enables the processing of stimuli that differ in sound pressure by more than six orders of magnitude. How to process a wide range of stimulus intensities with temporal precision is an enigmatic phenomenon of the auditory system. Downstream of dynamic range compression by active cochlear micromechanics, the inner hair cells (IHCs) cover the full intensity range of sound input. Yet, the firing rate in each of their postsynaptic spiral ganglion neurons (SGNs) encodes only a fraction of it. As a population, spiral ganglion neurons with their respective individual coding fractions cover the entire audible range. How such "dynamic range fractionation" arises is a topic of current research and the focus of this review. Here, we discuss mechanisms for generating the diverse functional properties of SGNs and formulate testable hypotheses. We postulate that an interplay of synaptic heterogeneity, molecularly distinct subtypes of SGNs, and efferent modulation serves the neural decomposition of sound information and thus contributes to a population code for sound intensity.
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Affiliation(s)
- Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLabUniversity Medical Center GöttingenGöttingenGermany
- Auditory Neuroscience and Synaptic Nanophysiology GroupMax Planck Institute for Multidisciplinary SciencesGöttingenGermany
- Cluster of Excellence “Multiscale Bioimaging of Excitable Cells”GöttingenGermany
| | - Nare Karagulyan
- Institute for Auditory Neuroscience and InnerEarLabUniversity Medical Center GöttingenGöttingenGermany
- Auditory Neuroscience and Synaptic Nanophysiology GroupMax Planck Institute for Multidisciplinary SciencesGöttingenGermany
- Hertha Sponer CollegeCluster of Excellence “Multiscale Bioimaging of Excitable Cells” Cluster of ExcellenceGöttingenGermany
| | - Jakob Neef
- Institute for Auditory Neuroscience and InnerEarLabUniversity Medical Center GöttingenGöttingenGermany
- Auditory Neuroscience and Synaptic Nanophysiology GroupMax Planck Institute for Multidisciplinary SciencesGöttingenGermany
| | - Lina María Jaime Tobón
- Institute for Auditory Neuroscience and InnerEarLabUniversity Medical Center GöttingenGöttingenGermany
- Auditory Neuroscience and Synaptic Nanophysiology GroupMax Planck Institute for Multidisciplinary SciencesGöttingenGermany
- Hertha Sponer CollegeCluster of Excellence “Multiscale Bioimaging of Excitable Cells” Cluster of ExcellenceGöttingenGermany
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James B, Piekarz P, Moya-Díaz J, Lagnado L. The Impact of Multivesicular Release on the Transmission of Sensory Information by Ribbon Synapses. J Neurosci 2022; 42:9401-9414. [PMID: 36344266 PMCID: PMC9794368 DOI: 10.1523/jneurosci.0717-22.2022] [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: 04/11/2022] [Revised: 10/01/2022] [Accepted: 10/06/2022] [Indexed: 11/09/2022] Open
Abstract
The statistics of vesicle release determine how synapses transfer information, but the classical Poisson model of independent release does not always hold at the first stages of vision and hearing. There, ribbon synapses also encode sensory signals as events comprising two or more vesicles released simultaneously. The implications of such coordinated multivesicular release (MVR) for spike generation are not known. Here we investigate how MVR alters the transmission of sensory information compared with Poisson synapses using a pure rate-code. We used leaky integrate-and-fire models incorporating the statistics of release measured experimentally from glutamatergic synapses of retinal bipolar cells in zebrafish (both sexes) and compared these with models assuming Poisson inputs constrained to operate at the same average rates. We find that MVR can increase the number of spikes generated per vesicle while reducing interspike intervals and latency to first spike. The combined effect was to increase the efficiency of information transfer (bits per vesicle) over a range of conditions mimicking target neurons of different size. MVR was most advantageous in neurons with short time constants and reliable synaptic inputs, when less convergence was required to trigger spikes. In the special case of a single input driving a neuron, as occurs in the auditory system of mammals, MVR increased information transfer whenever spike generation required more than one vesicle. This study demonstrates how presynaptic integration of vesicles by MVR can increase the efficiency with which sensory information is transmitted compared with a rate-code described by Poisson statistics.SIGNIFICANCE STATEMENT Neurons communicate by the stochastic release of vesicles at the synapse and the statistics of this process will determine how information is represented by spikes. The classical model is that vesicles are released independently by a Poisson process, but this does not hold at ribbon-type synapses specialized to transmit the first electrical signals in vision and hearing, where two or more vesicles can fuse in a single event by a process termed coordinated multivesicular release. This study shows that multivesicular release can increase the number of spikes generated per vesicle and the efficiency of information transfer (bits per vesicle) over a range of conditions found in the retina and peripheral auditory system.
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Affiliation(s)
- Ben James
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton, BN1 9QG, United Kingdom
| | - Pawel Piekarz
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton, BN1 9QG, United Kingdom
| | - José Moya-Díaz
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton, BN1 9QG, United Kingdom
| | - Leon Lagnado
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Brighton, BN1 9QG, United Kingdom
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8
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Davison A, Gierke K, Brandstätter JH, Babai N. Synaptic vesicle release during ribbon synapse formation of cone photoreceptors. Front Cell Neurosci 2022; 16:1022419. [PMID: 36406751 PMCID: PMC9672513 DOI: 10.3389/fncel.2022.1022419] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Accepted: 10/20/2022] [Indexed: 08/14/2023] Open
Abstract
Mammalian cone photoreceptors enable through their sophisticated synapse the high-fidelity transfer of visual information to second-order neurons in the retina. The synapse contains a proteinaceous organelle, called the synaptic ribbon, which tethers synaptic vesicles (SVs) at the active zone (AZ) close to voltage-gated Ca2+ channels. However, the exact contribution of the synaptic ribbon to neurotransmission is not fully understood, yet. In mice, precursors to synaptic ribbons appear within photoreceptor terminals shortly after birth as free-floating spherical structures, which progressively elongate and then attach to the AZ during the following days. Here, we took advantage of the process of synaptic ribbon maturation to study their contribution to SV release. We performed whole-cell patch-clamp recordings from cone photoreceptors at three postnatal (P) development stages (P8-9, P12-13, >P30) and measured evoked SV release, SV replenishment rate, recovery from synaptic depression, domain organization of voltage-sensitive Ca2+ channels, and Ca2+-sensitivity of exocytosis. Additionally, we performed electron microscopy to determine the density of SVs at ribbon-free and ribbon-occupied AZs. Our results suggest that ribbon attachment does not organize the voltage-sensitive Ca2+ channels into nanodomains or control SV release probability. However, ribbon attachment increases SV density at the AZ, increases the pool size of readily releasable SVs available for evoked SV release, facilitates SV replenishment without changing the SV pool refilling time, and increases the Ca2+- sensitivity of glutamate release.
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Affiliation(s)
| | | | | | - Norbert Babai
- Division of Animal Physiology/Neurobiology, Department of Biology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
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9
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Fritzsch B, Elliott KL, Yamoah EN. Neurosensory development of the four brainstem-projecting sensory systems and their integration in the telencephalon. Front Neural Circuits 2022; 16:913480. [PMID: 36213204 PMCID: PMC9539932 DOI: 10.3389/fncir.2022.913480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 08/23/2022] [Indexed: 11/18/2022] Open
Abstract
Somatosensory, taste, vestibular, and auditory information is first processed in the brainstem. From the brainstem, the respective information is relayed to specific regions within the cortex, where these inputs are further processed and integrated with other sensory systems to provide a comprehensive sensory experience. We provide the organization, genetics, and various neuronal connections of four sensory systems: trigeminal, taste, vestibular, and auditory systems. The development of trigeminal fibers is comparable to many sensory systems, for they project mostly contralaterally from the brainstem or spinal cord to the telencephalon. Taste bud information is primarily projected ipsilaterally through the thalamus to reach the insula. The vestibular fibers develop bilateral connections that eventually reach multiple areas of the cortex to provide a complex map. The auditory fibers project in a tonotopic contour to the auditory cortex. The spatial and tonotopic organization of trigeminal and auditory neuron projections are distinct from the taste and vestibular systems. The individual sensory projections within the cortex provide multi-sensory integration in the telencephalon that depends on context-dependent tertiary connections to integrate other cortical sensory systems across the four modalities.
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Affiliation(s)
- Bernd Fritzsch
- Department of Biology, The University of Iowa, Iowa City, IA, United States
- Department of Otolaryngology, The University of Iowa, Iowa City, IA, United States
- *Correspondence: Bernd Fritzsch,
| | - Karen L. Elliott
- Department of Biology, The University of Iowa, Iowa City, IA, United States
| | - Ebenezer N. Yamoah
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada, Reno, Reno, NV, United States
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10
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Mesnard CS, Barta CL, Sladek AL, Zenisek D, Thoreson WB. Eliminating Synaptic Ribbons from Rods and Cones Halves the Releasable Vesicle Pool and Slows Down Replenishment. Int J Mol Sci 2022; 23:6429. [PMID: 35742873 PMCID: PMC9223732 DOI: 10.3390/ijms23126429] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Revised: 06/03/2022] [Accepted: 06/05/2022] [Indexed: 01/25/2023] Open
Abstract
Glutamate release from rod and cone photoreceptor cells involves presynaptic ribbons composed largely of the protein RIBEYE. To examine roles of ribbons in rods and cones, we studied mice in which GCamP3 replaced the B-domain of RIBEYE. We discovered that ribbons were absent from rods and cones of both knock-in mice possessing GCamP3 and conditional RIBEYE knockout mice. The mice lacking ribbons showed reduced temporal resolution and contrast sensitivity assessed with optomotor reflexes. ERG recordings showed 50% reduction in scotopic and photopic b-waves. The readily releasable pool (RRP) of vesicles in rods and cones measured using glutamate transporter anion currents (IA(glu)) was also halved. We also studied the release from cones by stimulating them optogenetically with ChannelRhodopsin2 (ChR2) while recording postsynaptic currents in horizontal cells. Recovery of the release from paired pulse depression was twofold slower in the rods and cones lacking ribbons. The release from rods at -40 mV in darkness involves regularly spaced multivesicular fusion events. While the regular pattern of release remained in the rods lacking ribbons, the number of vesicles comprising each multivesicular event was halved. Our results support conclusions that synaptic ribbons in rods and cones expand the RRP, speed up vesicle replenishment, and augment some forms of multivesicular release. Slower replenishment and a smaller RRP in photoreceptors lacking ribbons may contribute to diminished temporal frequency responses and weaker contrast sensitivity.
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Affiliation(s)
- Chris S. Mesnard
- Department of Ophthalmology and Visual Sciences, Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE 68198, USA; (C.S.M.); (C.L.B.); (A.L.S.)
- Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Cody L. Barta
- Department of Ophthalmology and Visual Sciences, Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE 68198, USA; (C.S.M.); (C.L.B.); (A.L.S.)
| | - Asia L. Sladek
- Department of Ophthalmology and Visual Sciences, Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE 68198, USA; (C.S.M.); (C.L.B.); (A.L.S.)
| | - David Zenisek
- Department of Cellular and Molecular Physiology, Yale University, New Haven, CT 06510, USA;
| | - Wallace B. Thoreson
- Department of Ophthalmology and Visual Sciences, Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE 68198, USA; (C.S.M.); (C.L.B.); (A.L.S.)
- Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198, USA
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11
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Chakrabarti R, Jaime Tobón LM, Slitin L, Redondo Canales M, Hoch G, Slashcheva M, Fritsch E, Bodensiek K, Özçete ÖD, Gültas M, Michanski S, Opazo F, Neef J, Pangrsic T, Moser T, Wichmann C. Optogenetics and electron tomography for structure-function analysis of cochlear ribbon synapses. eLife 2022; 11:79494. [PMID: 36562477 PMCID: PMC9908081 DOI: 10.7554/elife.79494] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Accepted: 11/28/2022] [Indexed: 12/24/2022] Open
Abstract
Ribbon synapses of cochlear inner hair cells (IHCs) are specialized to indefatigably transmit sound information at high rates. To understand the underlying mechanisms, structure-function analysis of the active zone (AZ) of these synapses is essential. Previous electron microscopy studies of synaptic vesicle (SV) dynamics at the IHC AZ used potassium stimulation, which limited the temporal resolution to minutes. Here, we established optogenetic IHC stimulation followed by quick freezing within milliseconds and electron tomography to study the ultrastructure of functional synapse states with good temporal resolution in mice. We characterized optogenetic IHC stimulation by patch-clamp recordings from IHCs and postsynaptic boutons revealing robust IHC depolarization and neurotransmitter release. Ultrastructurally, the number of docked SVs increased upon short (17-25 ms) and long (48-76 ms) light stimulation paradigms. We did not observe enlarged SVs or other morphological correlates of homotypic fusion events. Our results indicate a rapid recruitment of SVs to the docked state upon stimulation and suggest that univesicular release prevails as the quantal mechanism of exocytosis at IHC ribbon synapses.
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Affiliation(s)
- Rituparna Chakrabarti
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany,Center for Biostructural Imaging of Neurodegeneration, University Medical Center GöttingenGöttingenGermany,Collaborative Research Center 889 "Cellular Mechanisms of Sensory Processing"GöttingenGermany
| | - Lina María Jaime Tobón
- Collaborative Research Center 889 "Cellular Mechanisms of Sensory Processing"GöttingenGermany,Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany,Auditory Neuroscience & Synaptic Nanophysiology Group, Max Planck Institute for Multidisciplinary SciencesGöttingenGermany
| | - Loujin Slitin
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany,Center for Biostructural Imaging of Neurodegeneration, University Medical Center GöttingenGöttingenGermany,Collaborative Research Center 889 "Cellular Mechanisms of Sensory Processing"GöttingenGermany
| | - Magdalena Redondo Canales
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany,Center for Biostructural Imaging of Neurodegeneration, University Medical Center GöttingenGöttingenGermany,Collaborative Research Center 889 "Cellular Mechanisms of Sensory Processing"GöttingenGermany
| | - Gerhard Hoch
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany,Auditory Neuroscience & Synaptic Nanophysiology Group, Max Planck Institute for Multidisciplinary SciencesGöttingenGermany
| | - Marina Slashcheva
- Göttingen Graduate School for Neuroscience and Molecular Biosciences, University of GöttingenGöttingenGermany
| | - Elisabeth Fritsch
- Göttingen Graduate School for Neuroscience and Molecular Biosciences, University of GöttingenGöttingenGermany
| | - Kai Bodensiek
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany
| | - Özge Demet Özçete
- Collaborative Research Center 889 "Cellular Mechanisms of Sensory Processing"GöttingenGermany,Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany,Auditory Neuroscience & Synaptic Nanophysiology Group, Max Planck Institute for Multidisciplinary SciencesGöttingenGermany
| | - Mehmet Gültas
- Faculty of Agriculture, South Westphalia University of Applied SciencesSoestGermany
| | - Susann Michanski
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany,Center for Biostructural Imaging of Neurodegeneration, University Medical Center GöttingenGöttingenGermany,Collaborative Research Center 889 "Cellular Mechanisms of Sensory Processing"GöttingenGermany
| | - Felipe Opazo
- Center for Biostructural Imaging of Neurodegeneration, University Medical Center GöttingenGöttingenGermany,NanoTag Biotechnologies GmbHGöttingenGermany,Institute of Neuro- and Sensory Physiology, University Medical Center GöttingenGöttingenGermany
| | - Jakob Neef
- Collaborative Research Center 889 "Cellular Mechanisms of Sensory Processing"GöttingenGermany,Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany,Auditory Neuroscience & Synaptic Nanophysiology Group, Max Planck Institute for Multidisciplinary SciencesGöttingenGermany
| | - Tina Pangrsic
- Collaborative Research Center 889 "Cellular Mechanisms of Sensory Processing"GöttingenGermany,Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany,Auditory Neuroscience & Synaptic Nanophysiology Group, Max Planck Institute for Multidisciplinary SciencesGöttingenGermany,Multiscale Bioimaging: from Molecular Machines to Networks of Excitable CellsGöttingenGermany,Synaptic Physiology of Mammalian Vestibular Hair Cells Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany
| | - Tobias Moser
- Collaborative Research Center 889 "Cellular Mechanisms of Sensory Processing"GöttingenGermany,Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany,Auditory Neuroscience & Synaptic Nanophysiology Group, Max Planck Institute for Multidisciplinary SciencesGöttingenGermany,Multiscale Bioimaging: from Molecular Machines to Networks of Excitable CellsGöttingenGermany
| | - Carolin Wichmann
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center GöttingenGöttingenGermany,Center for Biostructural Imaging of Neurodegeneration, University Medical Center GöttingenGöttingenGermany,Collaborative Research Center 889 "Cellular Mechanisms of Sensory Processing"GöttingenGermany,Multiscale Bioimaging: from Molecular Machines to Networks of Excitable CellsGöttingenGermany
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12
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Kearns A, Jayasi J, Liu X, Wang J, Shi Y, Chung JM, La JH, Tang SJ, Bae C. Neuron Type-Dependent Synaptic Activity in the Spinal Dorsal Horn of Opioid-Induced Hyperalgesia Mouse Model. Front Synaptic Neurosci 2021; 13:748929. [PMID: 34867259 PMCID: PMC8637419 DOI: 10.3389/fnsyn.2021.748929] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Accepted: 10/26/2021] [Indexed: 11/26/2022] Open
Abstract
Opioids are widely used for pain relief; however, chronic opioid use causes a paradoxical state of enhanced pain sensitivity, termed “Opioid-induced hyperalgesia (OIH).” Despite the clinical importance of OIH, the detailed mechanism by which it enhances pain sensitivity remains unclear. In this study, we tested whether repeated morphine induces a neuronal circuit polarization in the mouse spinal dorsal horn (SDH). Transgenic mice expressing GFP to neurokinin 1 receptor-expressing neurons (sNK1Rn) and GABAergic interneurons (sGABAn) that received morphine [20 mg/kg, once daily for four consecutive days (i.p.)] developed mechanical hypersensitivity. Repeated morphine altered synaptic strengths in the SDH as a specific cell-type but not in a gender-dependent manner. In sNK1Rn and non-tonic firing neurons, repeated morphine treatment significantly increased frequency of spontaneous excitatory postsynaptic current (sEPSC) and evoked EPSC (eEPSC). In addition, repeated morphine treatment significantly decreased evoked inhibitory postsynaptic current (eIPSC) in sNK1Rn. Conversely, in sGABAn and tonic firing neurons, repeated morphine treatment significantly decreased sEPSC frequency and eEPSC, but had no change of eIPSC in sGABAn. Interestingly, repeated morphine treatment significantly decreased neuronal rheobase of sNK1Rn but had no effect on sGABAn. These findings suggest that spinal neuronal circuit polarization maybe the mechanism of OIH and identify a potential therapeutic mechanism to prevent or treat opioid-induced pain.
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Affiliation(s)
- Austin Kearns
- School of Electrical, Computer, and Biomedical Engineering, Southern Illinois University, Carbondale, IL, United States
| | - Jazmine Jayasi
- School of Electrical, Computer, and Biomedical Engineering, Southern Illinois University, Carbondale, IL, United States
| | - Xin Liu
- Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, United States
| | - Jigong Wang
- Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, United States
| | - Yuqiang Shi
- Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, United States
| | - Jin Mo Chung
- Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, United States
| | - Jun-Ho La
- Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, United States
| | - Shao-Jun Tang
- Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, United States
| | - Chilman Bae
- School of Electrical, Computer, and Biomedical Engineering, Southern Illinois University, Carbondale, IL, United States.,Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, United States
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13
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Rituper B, Guček A, Lisjak M, Gorska U, Šakanović A, Bobnar ST, Lasič E, Božić M, Abbineni PS, Jorgačevski J, Kreft M, Verkhratsky A, Platt FM, Anderluh G, Stenovec M, Božič B, Coorssen JR, Zorec R. Vesicle cholesterol controls exocytotic fusion pore. Cell Calcium 2021; 101:102503. [PMID: 34844123 DOI: 10.1016/j.ceca.2021.102503] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 11/15/2021] [Accepted: 11/16/2021] [Indexed: 12/24/2022]
Abstract
In some lysosomal storage diseases (LSD) cholesterol accumulates in vesicles. Whether increased vesicle cholesterol affects vesicle fusion with the plasmalemma, where the fusion pore, a channel between the vesicle lumen and the extracellular space, is formed, is unknown. Super-resolution microscopy revealed that after stimulation of exocytosis, pituitary lactotroph vesicles discharge cholesterol which transfers to the plasmalemma. Cholesterol depletion in lactotrophs and astrocytes, both exhibiting Ca2+-dependent exocytosis regulated by distinct Ca2+sources, evokes vesicle secretion. Although this treatment enhanced cytosolic levels of Ca2+ in lactotrophs but decreased it in astrocytes, this indicates that cholesterol may well directly define the fusion pore. In an attempt to explain this mechanism, a new model of cholesterol-dependent fusion pore regulation is proposed. High-resolution membrane capacitance measurements, used to monitor fusion pore conductance, a parameter related to fusion pore diameter, confirm that at resting conditions reducing cholesterol increases, while enrichment with cholesterol decreases the conductance of the fusion pore. In resting fibroblasts, lacking the Npc1 protein, a cellular model of LSD in which cholesterol accumulates in vesicles, the fusion pore conductance is smaller than in controls, showing that vesicle cholesterol controls fusion pore and is relevant for pathophysiology of LSD.
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Affiliation(s)
- Boštjan Rituper
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, University of Ljubljana, Faculty of Medicine, Ljubljana, Slovenia
| | - Alenka Guček
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, University of Ljubljana, Faculty of Medicine, Ljubljana, Slovenia
| | - Marjeta Lisjak
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, University of Ljubljana, Faculty of Medicine, Ljubljana, Slovenia
| | - Urszula Gorska
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, University of Ljubljana, Faculty of Medicine, Ljubljana, Slovenia
| | - Aleksandra Šakanović
- Laboratory for Molecular Biology and Nanobiotechnology, National Institute of Chemistry, Ljubljana, Slovenia
| | - Saša Trkov Bobnar
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, University of Ljubljana, Faculty of Medicine, Ljubljana, Slovenia; Celica Biomedical, 1000, Ljubljana, Slovenia
| | - Eva Lasič
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, University of Ljubljana, Faculty of Medicine, Ljubljana, Slovenia
| | - Mićo Božić
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, University of Ljubljana, Faculty of Medicine, Ljubljana, Slovenia
| | - Prabhodh S Abbineni
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109-5632, United States of America
| | - Jernej Jorgačevski
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, University of Ljubljana, Faculty of Medicine, Ljubljana, Slovenia; Celica Biomedical, 1000, Ljubljana, Slovenia
| | - Marko Kreft
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, University of Ljubljana, Faculty of Medicine, Ljubljana, Slovenia; Celica Biomedical, 1000, Ljubljana, Slovenia
| | - Alexei Verkhratsky
- Celica Biomedical, 1000, Ljubljana, Slovenia; Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, M13 9PT, United Kingdom; Achucarro Center for Neuroscience, IKERBASQUE, 48011 Bilbao, Spain
| | - Frances M Platt
- Department of Pharmacology, University of Oxford, Oxford, OX1 3QT, United Kingdom
| | - Gregor Anderluh
- Laboratory for Molecular Biology and Nanobiotechnology, National Institute of Chemistry, Ljubljana, Slovenia
| | - Matjaž Stenovec
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, University of Ljubljana, Faculty of Medicine, Ljubljana, Slovenia; Celica Biomedical, 1000, Ljubljana, Slovenia
| | - Bojan Božič
- Institute of Biophysics, Faculty of Medicine, University of Ljubljana, Slovenia
| | - Jens R Coorssen
- Department of Health Sciences, Faculty of Applied Health Sciences and Department of Biological Sciences, Faculty of Mathematics & Science, Brock University, St Catherine's, Ontario, Canada
| | - Robert Zorec
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, University of Ljubljana, Faculty of Medicine, Ljubljana, Slovenia; Celica Biomedical, 1000, Ljubljana, Slovenia.
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14
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Boero LE, Payne S, Gómez-Casati ME, Rutherford MA, Goutman JD. Noise Exposure Potentiates Exocytosis From Cochlear Inner Hair Cells. Front Synaptic Neurosci 2021; 13:740368. [PMID: 34658832 PMCID: PMC8511412 DOI: 10.3389/fnsyn.2021.740368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Accepted: 09/10/2021] [Indexed: 11/19/2022] Open
Abstract
Noise-induced hearing loss has gained relevance as one of the most common forms of hearing impairment. The anatomical correlates of hearing loss, principally cell damage and/or death, are relatively well-understood histologically. However, much less is known about the physiological aspects of damaged, surviving cells. Here we addressed the functional consequences of noise exposure on the capacity of inner hair cells (IHCs) to release synaptic vesicles at synapses with spiral ganglion neurons (SGNs). Mice of either sex at postnatal day (P) 15–16 were exposed to 1–12 kHz noise at 120 dB sound pressure level (SPL), for 1 h. Exocytosis was measured by tracking changes in membrane capacitance (ΔCm) from IHCs of the apical cochlea. Upon IHC depolarization to different membrane potentials, ΔCm showed the typical bell-shaped curve that mirrors the voltage dependence of Ca2+ influx, in both exposed and unexposed cells. Surprisingly, from IHCs at 1-day after exposure (d.a.e.), we found potentiation of exocytosis at the peak of the bell-shaped curve. The increase in exocytosis was not accompanied by changes in whole-cell Ca2+ influx, suggesting a modification in coupling between Ca2+ channels and synaptic vesicles. Consistent with this notion, noise exposure also changed the Ca2+-dependence of exocytosis from linear to supralinear. Noise exposure did not cause loss of IHCs, but did result in a small reduction in the number of IHC-SGN synapses at 1-d.a.e. which recovered by 14-d.a.e. In contrast, a strong reduction in auditory brainstem response wave-I amplitude (representing synchronous firing of SGNs) and distortion product otoacoustic emissions (reflecting outer hair cell function) indicated a profound hearing loss at 1- and 14-d.a.e. To determine the role of glutamate release in the noise-induced potentiation of exocytosis, we evaluated vesicular glutamate transporter-3 (Vglut3) knock-out (KO) mice. Unlike WT, IHCs from Vglut3KO mice showed a noise-induced reduction in ΔCm and Ca2+ influx with no change in the Ca2+-dependence of exocytosis. Together, these results indicate that traumatic noise exposure triggers changes of IHC synaptic function including a Vglut3-dependent potentiation of exocytosis.
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Affiliation(s)
- Luis E Boero
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Buenos Aires, Argentina.,Instituto de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Shelby Payne
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO, United States
| | | | - Mark A Rutherford
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO, United States
| | - Juan D Goutman
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Buenos Aires, Argentina
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15
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Grabner CP, Moser T. The mammalian rod synaptic ribbon is essential for Ca v channel facilitation and ultrafast synaptic vesicle fusion. eLife 2021; 10:63844. [PMID: 34617508 PMCID: PMC8594941 DOI: 10.7554/elife.63844] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 10/06/2021] [Indexed: 12/19/2022] Open
Abstract
Rod photoreceptors (PRs) use ribbon synapses to transmit visual information. To signal ‘no light detected’ they release glutamate continually to activate post-synaptic receptors. When light is detected glutamate release pauses. How a rod’s individual ribbon enables this process was studied here by recording evoked changes in whole-cell membrane capacitance from wild-type and ribbonless (Ribeye-ko) mice. Wild-type rods filled with high (10 mM) or low (0.5 mM) concentrations of the Ca2+-buffer EGTA created a readily releasable pool (RRP) of 87 synaptic vesicles (SVs) that emptied as a single kinetic phase with a τ<0.4 ms. The lower concentration of EGTA accelerated Cav channel opening and facilitated release kinetics. In contrast, ribbonless rods created a much smaller RRP of 22 SVs, and they lacked Cav channel facilitation; however, Ca2+ channel-release coupling remained tight. These release deficits caused a sharp attenuation of rod-driven scotopic light responses. We conclude that the synaptic ribbon facilitates Ca2+-influx and establishes a large RRP of SVs.
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Affiliation(s)
- Chad Paul Grabner
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute of Biophysical Chemistry, Göttingen, Germany.,Collaborative Research Center 1286 'Quantitative Synaptology', University of Göttingen, Göttingen, Germany
| | - Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute of Biophysical Chemistry, Göttingen, Germany.,Collaborative Research Center 1286 'Quantitative Synaptology', University of Göttingen, Göttingen, Germany.,Multiscale Bioimaging Cluster of Excellence (MBExC), University of Göttingen, Göttingen, Germany
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16
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Selective ablation of inner hair cells and subsequent in-situ hair cell regeneration in the neonatal mouse cochlea. Hear Res 2021; 407:108275. [PMID: 34089989 DOI: 10.1016/j.heares.2021.108275] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 04/24/2021] [Accepted: 05/10/2021] [Indexed: 11/24/2022]
Abstract
Loss of hair cells (HCs) accounts for most sensorineural hearing loss, and regeneration of cochlear HCs is considered as the ultimate strategy for restoring hearing. Several lines of evidence have shown that Lgr5+ progenitor cells can spontaneously regenerate new HCs after HC loss at the neonatal stage, and most of which are immature. IHCs are resistant to ototoxic drugs and noise and cannot be ablated efficiently in order to precisely investigate IHC regeneration in existing hearing injury models, and thus we generated a new transgenic mouse model by inserting diphtheria toxin receptor (DTR) under the control of the Vglut3 promoter. In this model, IHCs were selectively ablated in a dose-dependent manner after the injection of diphtheria toxin (DT) at the neonatal stage, while OHCs remained intact with normal hair bundle structures until adulthood. With this IHC-specific injury model, we observed HC regeneration from Lgr5+ progenitors after IHC ablation at the neonatal stage. Some of the newly generated HCs replaced the lost IHCs in-situ and re-build the structure of the organ of Corti through the asymmetrical mitosis of progenitor cells. While, the majority of the regenerated HCs did not survive until adulthood, and the loss of spiral ganglion neurons was observed after the IHC ablation, which led to profound hearing loss after DT injection in Vglut3DTR+ mice at the neonatal stage. The model presented here shows promise for investigating the mechanisms behind IHC loss and subsequent regeneration.
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17
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Young ED, Wu 武靜靜 JS, Niwa M, Glowatzki E. Resolution of subcomponents of synaptic release from postsynaptic currents in rat hair-cell/auditory-nerve fiber synapses. J Neurophysiol 2021; 125:2444-2460. [PMID: 33949889 DOI: 10.1152/jn.00450.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The synapse between inner hair cells and auditory nerve fiber dendrites shows large excitatory postsynaptic currents (EPSCs), which are either monophasic or multiphasic. Multiquantal or uniquantal (flickering) release of neurotransmitter has been proposed to underlie the unusual multiphasic waveforms. Here the nature of multiphasic waveforms is analyzed using EPSCs recorded in vitro in rat afferent dendrites. Spontaneous EPSCs were deconvolved into a sum of presumed release events having monophasic EPSC waveforms. Results include, first, the charge of EPSCs is about the same for multiphasic versus monophasic EPSCs. Second, EPSC amplitudes decline with the number of release events per EPSC. Third, there is no evidence of a mini-EPSC. Most results can be accounted for by versions of either uniquantal or multiquantal release. However, serial neurotransmitter release in multiphasic EPSCs shows properties that are not fully explained by either model, especially that the amplitudes of individual release events are established at the beginning of a multiphasic EPSC, constraining possible models of vesicle release.NEW & NOTEWORTHY How do monophasic and multiphasic waveshapes arise in auditory-nerve dendrites; mainly are they uniquantal, arising from release of a single vesicle, or multiquantal, requiring several vesicles? The charge injected by excitatory postsynaptic currents (EPSCs) is the same for monophasic or multiphasic EPSCs, supporting uniquantal release. Serial adaptation of responses to sequential EPSCs favors a multiquantal model. Finally, neurotransmitter partitioning into similar sized release boluses occurs at the first bolus in the EPSC, not easily explained with either model.
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Affiliation(s)
- Eric D Young
- Center for Hearing and Balance, Johns Hopkins School of Medicine, Baltimore, Maryland.,Department of Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, Maryland.,Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins School of Medicine, Baltimore, Maryland.,Department of Neuroscience, Johns Hopkins School of Medicine, Baltimore, Maryland
| | - Jingjing Sherry Wu 武靜靜
- Center for Hearing and Balance, Johns Hopkins School of Medicine, Baltimore, Maryland.,Department of Neuroscience, Johns Hopkins School of Medicine, Baltimore, Maryland
| | - Mamiko Niwa
- Center for Hearing and Balance, Johns Hopkins School of Medicine, Baltimore, Maryland.,Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins School of Medicine, Baltimore, Maryland
| | - Elisabeth Glowatzki
- Center for Hearing and Balance, Johns Hopkins School of Medicine, Baltimore, Maryland.,Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins School of Medicine, Baltimore, Maryland.,Department of Neuroscience, Johns Hopkins School of Medicine, Baltimore, Maryland
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18
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Özçete ÖD, Moser T. A sensory cell diversifies its output by varying Ca 2+ influx-release coupling among active zones. EMBO J 2020; 40:e106010. [PMID: 33346936 PMCID: PMC7917556 DOI: 10.15252/embj.2020106010] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 10/30/2020] [Accepted: 11/03/2020] [Indexed: 02/06/2023] Open
Abstract
The cochlea encodes sound pressures varying over six orders of magnitude by collective operation of functionally diverse spiral ganglion neurons (SGNs). The mechanisms enabling this functional diversity remain elusive. Here, we asked whether the sound intensity information, contained in the receptor potential of the presynaptic inner hair cell (IHC), is fractionated via heterogeneous synapses. We studied the transfer function of individual IHC synapses by combining patch‐clamp recordings with dual‐color Rhod‐FF and iGluSnFR imaging of presynaptic Ca2+ signals and glutamate release. Synapses differed in the voltage dependence of release: Those residing at the IHC' pillar side activated at more hyperpolarized potentials and typically showed tight control of release by few Ca2+ channels. We conclude that heterogeneity of voltage dependence and release site coupling of Ca2+ channels among the synapses varies synaptic transfer within individual IHCs and, thereby, likely contributes to the functional diversity of SGNs. The mechanism reported here might serve sensory cells and neurons more generally to diversify signaling even in close‐by synapses.
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Affiliation(s)
- Özge D Özçete
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Collaborative Research Center 889, University of Göttingen, Göttingen, Germany.,Auditory Neuroscience Group, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Göttingen Graduate Center for Neurosciences, Biophysics and Molecular Biosciences, University of Göttingen, Göttingen, Germany
| | - Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Collaborative Research Center 889, University of Göttingen, Göttingen, Germany.,Auditory Neuroscience Group, Max Planck Institute of Experimental Medicine, Göttingen, Germany.,Göttingen Graduate Center for Neurosciences, Biophysics and Molecular Biosciences, University of Göttingen, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute of Biophysical Chemistry, Göttingen, Germany.,Multiscale Bioimaging Cluster of Excellence (MBExC), University of Göttingen, Göttingen, Germany
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19
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Chowdhury HH, Zorec R. Exocytotic fusion pore under stress. Cell Stress 2020; 4:218-226. [PMID: 32908961 PMCID: PMC7453636 DOI: 10.15698/cst2020.09.230] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 07/19/2020] [Accepted: 07/29/2020] [Indexed: 11/13/2022] Open
Abstract
Exocytosis is a universal process of eukaryotic cells, consisting of fusion between the vesicle and the plasma membranes, leading to the formation of a fusion pore, a channel through which vesicle cargo exits into the extracellular space. In 1986, Rand and Parsegian proposed several stages to explain the nature of membrane fusion. Following stimulation, it starts with focused stress destabilization of membranes in contact, followed by the coalescence of two membrane surfaces. In the next fraction of a millisecond, restabilization of fused membranes is considered to occur to maintain the cell's integrity. This view predicted that once a fusion pore is formed, it must widen abruptly, irreversibly and fully, whereby the vesicle membrane completely integrates with and collapses into the plasma membrane (full fusion exocytosis). However, recent experimental evidence has revealed that once the fusion pore opens, it may also reversibly close (transient or kiss-and-run exocytosis). Here, we present a historical perspective on understanding the mechanisms that initiate the membrane merger and fusion pore formation. Next, post-fusion mechanisms that regulate fusion pore stability are considered, reflecting the state in which the forces of widening and constriction of fusion pores are balanced. Although the mechanisms generating these forces are unclear, they may involve lipids and proteins, including SNAREs, which play a role not only in the pre-fusion but also post-fusion stages of exocytosis. How molecules stabilize the fusion pore in the open state is key for a better understanding of fusion pore physiology in health and disease.
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Affiliation(s)
- Helena Haque Chowdhury
- Laboratory of Cell Engineering, Celica Biomedical, 1000 Ljubljana, Slovenia
- Laboratory of Neuroendocrinology – Molecular Cell Physiology, Institute of Pathophysiology, University of Ljubljana, Medical Faculty, 1000 Ljubljana, Slovenia
| | - Robert Zorec
- Laboratory of Cell Engineering, Celica Biomedical, 1000 Ljubljana, Slovenia
- Laboratory of Neuroendocrinology – Molecular Cell Physiology, Institute of Pathophysiology, University of Ljubljana, Medical Faculty, 1000 Ljubljana, Slovenia
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20
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Moser T, Grabner CP, Schmitz F. Sensory Processing at Ribbon Synapses in the Retina and the Cochlea. Physiol Rev 2020; 100:103-144. [DOI: 10.1152/physrev.00026.2018] [Citation(s) in RCA: 80] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
In recent years, sensory neuroscientists have made major efforts to dissect the structure and function of ribbon synapses which process sensory information in the eye and ear. This review aims to summarize our current understanding of two key aspects of ribbon synapses: 1) their mechanisms of exocytosis and endocytosis and 2) their molecular anatomy and physiology. Our comparison of ribbon synapses in the cochlea and the retina reveals convergent signaling mechanisms, as well as divergent strategies in different sensory systems.
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Affiliation(s)
- Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany; Synaptic Nanophysiology Group, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany; and Institute for Anatomy and Cell Biology, Department of Neuroanatomy, Medical School, Saarland University, Homburg, Germany
| | - Chad P. Grabner
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany; Synaptic Nanophysiology Group, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany; and Institute for Anatomy and Cell Biology, Department of Neuroanatomy, Medical School, Saarland University, Homburg, Germany
| | - Frank Schmitz
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany; Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany; Synaptic Nanophysiology Group, Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany; and Institute for Anatomy and Cell Biology, Department of Neuroanatomy, Medical School, Saarland University, Homburg, Germany
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21
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Dürst CD, Wiegert JS, Helassa N, Kerruth S, Coates C, Schulze C, Geeves MA, Török K, Oertner TG. High-speed imaging of glutamate release with genetically encoded sensors. Nat Protoc 2019; 14:1401-1424. [PMID: 30988508 PMCID: PMC6751072 DOI: 10.1038/s41596-019-0143-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Accepted: 01/22/2019] [Indexed: 11/08/2022]
Abstract
The strength of an excitatory synapse depends on its ability to release glutamate and on the density of postsynaptic receptors. Genetically encoded glutamate indicators (GEGIs) allow eavesdropping on synaptic transmission at the level of cleft glutamate to investigate properties of the release machinery in detail. Based on the sensor iGluSnFR, we recently developed accelerated versions of GEGIs that allow investigation of synaptic release during 100-Hz trains. Here, we describe the detailed procedures for design and characterization of fast iGluSnFR variants in vitro, transfection of pyramidal cells in organotypic hippocampal cultures, and imaging of evoked glutamate transients with two-photon laser-scanning microscopy. As the released glutamate spreads from a point source-the fusing vesicle-it is possible to localize the vesicle fusion site with a precision exceeding the optical resolution of the microscope. By using a spiral scan path, the temporal resolution can be increased to 1 kHz to capture the peak amplitude of fast iGluSnFR transients. The typical time frame for these experiments is 30 min per synapse.
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Affiliation(s)
- Céline D Dürst
- Institute for Synaptic Physiology, Center for Molecular Neurobiology Hamburg, Hamburg, Germany
| | - J Simon Wiegert
- Institute for Synaptic Physiology, Center for Molecular Neurobiology Hamburg, Hamburg, Germany
- Research Group Synaptic Wiring and Information Processing, Center for Molecular Neurobiology Hamburg, Hamburg, Germany
| | - Nordine Helassa
- Molecular and Clinical Sciences Research Institute, St George's, University of London, London, UK
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, UK
| | - Silke Kerruth
- Molecular and Clinical Sciences Research Institute, St George's, University of London, London, UK
- Department of Biophysical Chemistry, J. Heyrovský Institute of Physical Chemistry, Prague, Czech Republic
| | - Catherine Coates
- Molecular and Clinical Sciences Research Institute, St George's, University of London, London, UK
| | - Christian Schulze
- Institute for Synaptic Physiology, Center for Molecular Neurobiology Hamburg, Hamburg, Germany
| | | | - Katalin Török
- Molecular and Clinical Sciences Research Institute, St George's, University of London, London, UK
| | - Thomas G Oertner
- Institute for Synaptic Physiology, Center for Molecular Neurobiology Hamburg, Hamburg, Germany.
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22
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Fetoni AR, Paciello F, Rolesi R, Paludetti G, Troiani D. Targeting dysregulation of redox homeostasis in noise-induced hearing loss: Oxidative stress and ROS signaling. Free Radic Biol Med 2019; 135:46-59. [PMID: 30802489 DOI: 10.1016/j.freeradbiomed.2019.02.022] [Citation(s) in RCA: 111] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 02/04/2019] [Accepted: 02/18/2019] [Indexed: 12/20/2022]
Abstract
Hearing loss caused by exposure to recreational and occupational noise remains a worldwide disabling condition and dysregulation of redox homeostasis is the hallmark of cochlear damage induced by noise exposure. In this review we discuss the dual function of ROS to both promote cell damage (oxidative stress) and cell adaptive responses (ROS signaling) in the cochlea undergoing a stressful condition such as noise exposure. We focus on animal models of noise-induced hearing loss (NIHL) and on the function of exogenous antioxidants to maintaining a physiological role of ROS signaling by distinguishing the effect of exogenous "direct" antioxidants (i.e. CoQ10, NAC), that react with ROS to decrease oxidative stress, from the exogenous "indirect" antioxidants (i.e. nutraceutics and phenolic compounds) that can activate cellular redox enzymes through the Keap1-Nrf2-ARE pathway. The anti-inflammatory properties of Nrf2 signaling are discussed in relation to the ROS/inflammation interplay in noise exposure. Unveiling the mechanisms of ROS regulating redox-associated signaling pathways is essential in providing relevant targets for innovative and effective therapeutic strategies against NIHL.
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Affiliation(s)
- Anna Rita Fetoni
- Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy; Institute of Otolaryngology, Università Cattolica del Sacro Cuore, Rome, Italy; CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy
| | - Fabiola Paciello
- Institute of Otolaryngology, Università Cattolica del Sacro Cuore, Rome, Italy; CNR Institute of Cell Biology and Neurobiology, Monterotondo, Italy
| | - Rolando Rolesi
- Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy; Institute of Otolaryngology, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Gaetano Paludetti
- Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy; Institute of Otolaryngology, Università Cattolica del Sacro Cuore, Rome, Italy
| | - Diana Troiani
- Institute of Human Physiology, Università Cattolica del Sacro Cuore, Rome, Italy.
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23
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Phase Locking of Auditory-Nerve Fibers Reveals Stereotyped Distortions and an Exponential Transfer Function with a Level-Dependent Slope. J Neurosci 2019; 39:4077-4099. [PMID: 30867259 DOI: 10.1523/jneurosci.1801-18.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 02/28/2019] [Accepted: 03/07/2019] [Indexed: 12/16/2022] Open
Abstract
Phase locking of auditory-nerve-fiber (ANF) responses to the fine structure of acoustic stimuli is a hallmark of the auditory system's temporal precision and is important for many aspects of hearing. Period histograms from phase-locked ANF responses to low-frequency tones exhibit spike-rate and temporal asymmetries, but otherwise retain an approximately sinusoidal shape as stimulus level increases, even beyond the level at which the mean spike rate saturates. This is intriguing because apical cochlear mechanical vibrations show little compression, and mechanoelectrical transduction in the receptor cells is thought to obey a static sigmoidal nonlinearity, which might be expected to produce peak clipping at moderate and high stimulus levels. Here we analyze phase-locked responses of ANFs from cats of both sexes. We show that the lack of peak clipping is due neither to ANF refractoriness nor to spike-rate adaptation on time scales longer than the stimulus period. We demonstrate that the relationship between instantaneous pressure and instantaneous rate is well described by an exponential function whose slope decreases with increasing stimulus level. Relatively stereotyped harmonic distortions in the input to the exponential can account for the temporal asymmetry of the period histograms, including peak splitting. We show that the model accounts for published membrane-potential waveforms when assuming a power-of-three, but not a power-of-one, relationship to exocytosis. Finally, we demonstrate the relationship between the exponential transfer functions and the sigmoidal pseudotransducer functions obtained in the literature by plotting the maxima and minima of the voltage responses against the maxima and minima of the stimuli.SIGNIFICANCE STATEMENT Phase locking of auditory-nerve-fiber responses to the temporal fine structure of acoustic stimuli is important for many aspects of hearing, but the mechanisms underlying phase locking are not fully understood. Intriguingly, period histograms retain an approximately sinusoidal shape across sound levels, even when the mean rate has saturated. We find that neither refractoriness nor spike-rate adaptation is responsible for this behavior. Instead, the peripheral auditory system operates as though it contains an exponential transfer function whose slope changes with stimulus level. The underlying mechanism is distinct from the comparatively weak cochlear mechanical compression in the cochlear apex, and likely resides in the receptor cells.
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24
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Gustafsson B, Ma R, Hanse E. The Small and Dynamic Pre-primed Pool at the Release Site; A Useful Concept to Understand Release Probability and Short-Term Synaptic Plasticity? Front Synaptic Neurosci 2019; 11:7. [PMID: 30899219 PMCID: PMC6416800 DOI: 10.3389/fnsyn.2019.00007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Accepted: 02/20/2019] [Indexed: 11/23/2022] Open
Abstract
Advanced imaging techniques have revealed that synapses contain nanomodules in which pre- and post-synaptic molecules are brought together to form an integrated subsynaptic component for vesicle release and transmitter reception. Based on data from an electrophysiological study of ours in which release from synapses containing a single nanomodule was induced by brief 50 Hz trains using minimal stimulation, and on data from such imaging studies, we present a possible modus operandi of such a nanomodule. We will describe the techniques and tools used to obtain and analyze the electrophysiological data from single CA3–CA1 hippocampal synapses from the neonatal rat brain. This analysis leads to the proposal that a nanomodule, despite containing a number of release locations, operates as a single release site, releasing at most a single vesicle at a time. In this nanomodule there appears to be two separate sets of release locations, one set that is responsible for release in response to the first few action potentials and another set that produces the release thereafter. The data also suggest that vesicles at the first set of release locations are primed by synaptic inactivity lasting seconds, this synaptic inactivity also resulting in a large heterogeneity in the values for vesicle release probability among the synapses. The number of vesicles being primed at this set of release locations prior to the arrival of an action potential is small (0–3) and varies from train to train. Following the first action potential, this heterogeneity in vesicle release probability largely vanishes in a release-independent manner, shaping a variation in paired-pulse plasticity among the synapses. After the first few action potentials release is produced from the second set of release locations, and is given by vesicles that have been recruited after the onset of synaptic activity. This release depends on the number of such release locations and the recruitment to such a location. The initial heterogeneity in vesicle release probability, its disappearance after a single action potential, and variation in the recruitment to the second set of release locations are instrumental in producing the heterogeneity in short-term synaptic plasticity among these synapses, and can be seen as means to create differential dynamics within a synapse population.
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Affiliation(s)
- Bengt Gustafsson
- Department of Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Rong Ma
- Department of Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Eric Hanse
- Department of Physiology, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
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25
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Takago H, Oshima-Takago T, Moser T. Disruption of Otoferlin Alters the Mode of Exocytosis at the Mouse Inner Hair Cell Ribbon Synapse. Front Mol Neurosci 2019; 11:492. [PMID: 30687007 PMCID: PMC6338019 DOI: 10.3389/fnmol.2018.00492] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2018] [Accepted: 12/19/2018] [Indexed: 11/24/2022] Open
Abstract
Sound encoding relies on Ca2+-mediated exocytosis at the ribbon synapse between cochlear inner hair cells (IHCs) and type I spiral ganglion neurons (SGNs). Otoferlin, a multi-C2 domain protein, is proposed to regulate Ca2+-triggered exocytosis at this synapse, but the precise mechanisms of otoferlin function remain to be elucidated. Here, performing whole-cell voltage-clamp recordings of excitatory postsynaptic currents (EPSCs) from SGNs in otoferlin mutant mice, we investigated the impact of Otof disruption at individual synapses with single release event resolution. Otof deletion decreased the spontaneous release rate and abolished the stimulus-secretion coupling. This was evident from failure of potassium-induced IHC depolarization to stimulate release and supports the proposed role of otoferlin in Ca2+ sensing for fusion. A missense mutation in the Otof gene (pachanga), in which otoferlin level at the IHC plasma membrane was lowered without changing its Ca2+ binding, also reduced the spontaneous release rate but spared the stimulus-secretion coupling. The slowed stimulated release rate supports the hypothesis that a sufficient abundance of otoferlin at the plasma membrane is crucial for the vesicle supply. Large-sized monophasic EPSCs remained present upon Otof deletion despite the drastic reduction of the rate of exocytosis. However, EPSC amplitude, on average, was modestly decreased. Moreover, a reduced contribution of multiphasic EPSC was observed in both Otof mutants. We argue that the presence of large monophasic EPSCs despite the exocytic defect upon Otof deletion supports the uniquantal hypothesis of transmitter release at the IHC ribbon synapse. Based upon the reduced contribution of multiphasic EPSC, we propose a role of otoferlin in regulating the mode of exocytosis in IHCs.
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Affiliation(s)
- Hideki Takago
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Department of Rehabilitation for Sensory Functions, Research Institute, National Rehabilitation Center for Persons with Disabilities, Saitama, Japan.,Collaborative Research Center 889 Cellular Mechanisms of Sensory Processing, Göttingen, Germany
| | - Tomoko Oshima-Takago
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Department of Rehabilitation for Sensory Functions, Research Institute, National Rehabilitation Center for Persons with Disabilities, Saitama, Japan.,Collaborative Research Center 889 Cellular Mechanisms of Sensory Processing, Göttingen, Germany.,Göttingen Graduate School for Neurosciences and Molecular Biosciences, University of Göttingen, Göttingen, Germany
| | - Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Collaborative Research Center 889 Cellular Mechanisms of Sensory Processing, Göttingen, Germany.,Göttingen Graduate School for Neurosciences and Molecular Biosciences, University of Göttingen, Göttingen, Germany.,Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
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26
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Kroll J, Özçete ÖD, Jung S, Maritzen T, Milosevic I, Wichmann C, Moser T. AP180 promotes release site clearance and clathrin-dependent vesicle reformation in mouse cochlear inner hair cells. J Cell Sci 2019; 133:jcs.236737. [DOI: 10.1242/jcs.236737] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Accepted: 12/09/2019] [Indexed: 12/18/2022] Open
Abstract
High-throughput neurotransmission at ribbon synapses of cochlear inner hair cells (IHCs) requires tight coupling of neurotransmitter release and balanced recycling of synaptic vesicles (SVs) as well as rapid restoration of release sites. Here, we examined the role of the adaptor protein AP180 for IHC synaptic transmission in AP180-KO mice using high-pressure freezing and electron tomography, confocal microscopy, patch-clamp membrane-capacitance measurements and systems physiology. AP180 was found predominantly at the synaptic pole of IHCs. AP180-deficient IHCs had severely reduced SV numbers, slowed endocytic membrane retrieval, and accumulated endocytic intermediates near ribbon synapses, indicating that AP180 is required for clathrin-dependent endocytosis and SV reformation in IHCs. Moreover, AP180 deletion led to a high prevalence of SVs in a multi-tethered or docked state after stimulation, a reduced rate of SV replenishment, and a hearing impairment. We conclude that, in addition to its role in clathrin recruitment, AP180 contributes to release site clearance in IHCs.
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Affiliation(s)
- Jana Kroll
- Synaptic Vesicle Dynamics Group, European Neuroscience Institute Göttingen – A Joint Initiative of the University Medical Center Göttingen and the Max-Planck-Society, Göttingen, Germany
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience, InnerEarLab and Center for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany
- Collaborative Research Center 889, University of Göttingen, Göttingen, Germany
- Göttingen Graduate School for Neuroscience and Molecular Biosciences, University of Göttingen, Göttingen, Germany
| | - Özge Demet Özçete
- Collaborative Research Center 889, University of Göttingen, Göttingen, Germany
- Göttingen Graduate School for Neuroscience and Molecular Biosciences, University of Göttingen, Göttingen, Germany
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany
- Auditory Neuroscience Group, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Sangyong Jung
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany
- Neuro Modulation and Neuro Circuitry Group, Singapore Bioimaging Consortium (SBIC), Biomedical Sciences Institutes, 138667 Singapore
| | - Tanja Maritzen
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
| | - Ira Milosevic
- Synaptic Vesicle Dynamics Group, European Neuroscience Institute Göttingen – A Joint Initiative of the University Medical Center Göttingen and the Max-Planck-Society, Göttingen, Germany
- Collaborative Research Center 889, University of Göttingen, Göttingen, Germany
| | - Carolin Wichmann
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience, InnerEarLab and Center for Biostructural Imaging of Neurodegeneration, University Medical Center Göttingen, Göttingen, Germany
- Collaborative Research Center 889, University of Göttingen, Göttingen, Germany
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany
| | - Tobias Moser
- Collaborative Research Center 889, University of Göttingen, Göttingen, Germany
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany
- Auditory Neuroscience Group, Max Planck Institute of Experimental Medicine, Göttingen, Germany
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), Berlin, Germany
- Synaptic Nanophysiology Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
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