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Zacher AC, Felmy F. Anatomy of superior olivary complex and lateral lemniscus in Etruscan shrew. Sci Rep 2024; 14:14734. [PMID: 38926520 PMCID: PMC11208622 DOI: 10.1038/s41598-024-65451-0] [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: 04/15/2024] [Accepted: 06/20/2024] [Indexed: 06/28/2024] Open
Abstract
Based on the auditory periphery and the small head size, Etruscan shrews (Suncus etruscus) approximate ancestral mammalian conditions. The auditory brainstem in this insectivore has not been investigated. Using labelling techniques, we assessed the structures of their superior olivary complex (SOC) and the nuclei of the lateral lemniscus (NLL). There, we identified the position of the major nuclei, their input pattern, transmitter content, expression of calcium binding proteins (CaBPs) and two voltage-gated ion channels. The most prominent SOC structures were the medial nucleus of the trapezoid body (MNTB), the lateral nucleus of the trapezoid body (LNTB), the lateral superior olive (LSO) and the superior paraolivary nucleus (SPN). In the NLL, the ventral (VNLL), a specific ventrolateral VNLL (VNLLvl) cell population, the intermediate (INLL) and dorsal (DNLL) nucleus, as well as the inferior colliculus's central aspect were discerned. INLL and VNLL were clearly separated by the differential distribution of various marker proteins. Most labelled proteins showed expression patterns comparable to rodents. However, SPN neurons were glycinergic and not GABAergic and the overall CaBPs expression was low. Next to the characterisation of the Etruscan shrew's auditory brainstem, our work identifies conserved nuclei and indicates variable structures in a species that approximates ancestral conditions.
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Affiliation(s)
- Alina C Zacher
- Institute of Zoology, University of Veterinary Medicine Foundation, Buenteweg 17, 30559, Hannover, Germany
- Hannover Graduate School for Neurosciences, Infection Medicine and Veterinary Sciences (HGNI), Buenteweg 2, 30559, Hannover, Germany
| | - Felix Felmy
- Institute of Zoology, University of Veterinary Medicine Foundation, Buenteweg 17, 30559, Hannover, Germany.
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2
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López-Murcia FJ, Lin KH, Berns MMM, Ranjan M, Lipstein N, Neher E, Brose N, Reim K, Taschenberger H. Complexin has a dual synaptic function as checkpoint protein in vesicle priming and as a promoter of vesicle fusion. Proc Natl Acad Sci U S A 2024; 121:e2320505121. [PMID: 38568977 PMCID: PMC11009659 DOI: 10.1073/pnas.2320505121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2023] [Accepted: 03/04/2024] [Indexed: 04/05/2024] Open
Abstract
The presynaptic SNARE-complex regulator complexin (Cplx) enhances the fusogenicity of primed synaptic vesicles (SVs). Consequently, Cplx deletion impairs action potential-evoked transmitter release. Conversely, though, Cplx loss enhances spontaneous and delayed asynchronous release at certain synapse types. Using electrophysiology and kinetic modeling, we show that such seemingly contradictory transmitter release phenotypes seen upon Cplx deletion can be explained by an additional of Cplx in the control of SV priming, where its ablation facilitates the generation of a "faulty" SV fusion apparatus. Supporting this notion, a sequential two-step priming scheme, featuring reduced vesicle fusogenicity and increased transition rates into the faulty primed state, reproduces all aberrations of transmitter release modes and short-term synaptic plasticity seen upon Cplx loss. Accordingly, we propose a dual presynaptic function for the SNARE-complex interactor Cplx, one as a "checkpoint" protein that guarantees the proper assembly of the fusion machinery during vesicle priming, and one in boosting vesicle fusogenicity.
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Affiliation(s)
- Francisco José López-Murcia
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen37075, Germany
| | - Kun-Han Lin
- Laboratory of Membrane Biophysics, Max Planck Institute for Multidisciplinary Sciences, Göttingen37077, Germany
| | - Manon M. M. Berns
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen37075, Germany
| | - Mrinalini Ranjan
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen37075, Germany
- Göttingen Graduate School for Neurosciences, Biophysics, and Molecular Biosciences, Georg August University Göttingen, Göttingen37077, Germany
| | - Noa Lipstein
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen37075, Germany
| | - Erwin Neher
- Laboratory of Membrane Biophysics, Max Planck Institute for Multidisciplinary Sciences, Göttingen37077, Germany
- Cluster of Excellence ‘Multiscale Bioimaging’, Georg August University Göttingen, Göttingen37073, Germany
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen37075, Germany
- Cluster of Excellence ‘Multiscale Bioimaging’, Georg August University Göttingen, Göttingen37073, Germany
| | - Kerstin Reim
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen37075, Germany
| | - Holger Taschenberger
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen37075, Germany
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3
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Kumar P, Goettemoeller AM, Espinosa-Garcia C, Tobin BR, Tfaily A, Nelson RS, Natu A, Dammer EB, Santiago JV, Malepati S, Cheng L, Xiao H, Duong DD, Seyfried NT, Wood LB, Rowan MJM, Rangaraju S. Native-state proteomics of Parvalbumin interneurons identifies unique molecular signatures and vulnerabilities to early Alzheimer's pathology. Nat Commun 2024; 15:2823. [PMID: 38561349 PMCID: PMC10985119 DOI: 10.1038/s41467-024-47028-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Accepted: 03/18/2024] [Indexed: 04/04/2024] Open
Abstract
Dysfunction in fast-spiking parvalbumin interneurons (PV-INs) may represent an early pathophysiological perturbation in Alzheimer's Disease (AD). Defining early proteomic alterations in PV-INs can provide key biological and translationally-relevant insights. We used cell-type-specific in-vivo biotinylation of proteins (CIBOP) coupled with mass spectrometry to obtain native-state PV-IN proteomes. PV-IN proteomic signatures include high metabolic and translational activity, with over-representation of AD-risk and cognitive resilience-related proteins. In bulk proteomes, PV-IN proteins were associated with cognitive decline in humans, and with progressive neuropathology in humans and the 5xFAD mouse model of Aβ pathology. PV-IN CIBOP in early stages of Aβ pathology revealed signatures of increased mitochondria and metabolism, synaptic and cytoskeletal disruption and decreased mTOR signaling, not apparent in whole-brain proteomes. Furthermore, we demonstrated pre-synaptic defects in PV-to-excitatory neurotransmission, validating our proteomic findings. Overall, in this study we present native-state proteomes of PV-INs, revealing molecular insights into their unique roles in cognitive resiliency and AD pathogenesis.
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Affiliation(s)
- Prateek Kumar
- Department of Neurology, Emory University School of Medicine, Atlanta, GA, 30322, USA
- Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, USA
- 3 Department of Neurology, Yale University School of Medicine, New Haven, CT, 06510, USA
| | - Annie M Goettemoeller
- Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, USA
- Neuroscience Graduate Program, Laney Graduate School, Emory University, Atlanta, USA
| | - Claudia Espinosa-Garcia
- Department of Neurology, Emory University School of Medicine, Atlanta, GA, 30322, USA
- 3 Department of Neurology, Yale University School of Medicine, New Haven, CT, 06510, USA
| | - Brendan R Tobin
- Georgia W. Woodruff School of Mechanical Engineering, Parker H. Petit Institute for Bioengineering and Bioscience, and Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, 30322, USA
| | - Ali Tfaily
- 3 Department of Neurology, Yale University School of Medicine, New Haven, CT, 06510, USA
| | - Ruth S Nelson
- 3 Department of Neurology, Yale University School of Medicine, New Haven, CT, 06510, USA
| | - Aditya Natu
- Department of Neurology, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Eric B Dammer
- Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, USA
- Department of Biochemistry, Emory University, Atlanta, GA, 30322, USA
| | - Juliet V Santiago
- Department of Neurology, Emory University School of Medicine, Atlanta, GA, 30322, USA
- Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, USA
- Neuroscience Graduate Program, Laney Graduate School, Emory University, Atlanta, USA
| | - Sneha Malepati
- Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, USA
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Lihong Cheng
- Department of Neurology, Emory University School of Medicine, Atlanta, GA, 30322, USA
- Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, USA
| | - Hailian Xiao
- Department of Neurology, Emory University School of Medicine, Atlanta, GA, 30322, USA
- Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, USA
| | - Duc D Duong
- Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, USA
- Department of Biochemistry, Emory University, Atlanta, GA, 30322, USA
| | - Nicholas T Seyfried
- Department of Neurology, Emory University School of Medicine, Atlanta, GA, 30322, USA
- Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, USA
- Department of Biochemistry, Emory University, Atlanta, GA, 30322, USA
| | - Levi B Wood
- Georgia W. Woodruff School of Mechanical Engineering, Parker H. Petit Institute for Bioengineering and Bioscience, and Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, 30322, USA
- School of Chemical and Biological Engineering, GeoInsrgia titute of Technology, Atlanta, GA, 30322, USA
| | - Matthew J M Rowan
- Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, USA.
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, 30322, USA.
| | - Srikant Rangaraju
- Department of Neurology, Emory University School of Medicine, Atlanta, GA, 30322, USA.
- Center for Neurodegenerative Disease, Emory University School of Medicine, Atlanta, USA.
- 3 Department of Neurology, Yale University School of Medicine, New Haven, CT, 06510, USA.
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4
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Zhang XQ, Xu L, Zhu XY, Tang ZH, Dong YB, Yu ZP, Shang Q, Wang ZC, Shen HW. D-serine reconstitutes synaptic and intrinsic inhibitory control of pyramidal neurons in a neurodevelopmental mouse model for schizophrenia. Nat Commun 2023; 14:8255. [PMID: 38086803 PMCID: PMC10716516 DOI: 10.1038/s41467-023-43930-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 11/24/2023] [Indexed: 12/18/2023] Open
Abstract
The hypothesis of N-methyl-D-aspartate receptor (NMDAR) dysfunction for cognitive impairment in schizophrenia constitutes the theoretical basis for the translational application of NMDAR co-agonist D-serine or its analogs. However, the cellular mechanism underlying the therapeutic effect of D-serine remains unclear. In this study, we utilize a mouse neurodevelopmental model for schizophrenia that mimics prenatal pathogenesis and exhibits hypoexcitability of parvalbumin-positive (PV) neurons, as well as PV-preferential NMDAR dysfunction. We find that D-serine restores excitation/inhibition balance by reconstituting both synaptic and intrinsic inhibitory control of cingulate pyramidal neurons through facilitating PV excitability and activating small-conductance Ca2+-activated K+ (SK) channels in pyramidal neurons, respectively. Either amplifying inhibitory drive via directly strengthening PV neuron activity or inhibiting pyramidal excitability via activating SK channels is sufficient to improve cognitive function in this model. These findings unveil a dual mechanism for how D-serine improves cognitive function in this model.
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Affiliation(s)
- Xiao-Qin Zhang
- Department of Pharmacology, School of Medicine, Ningbo University, 818 Fenghua Rd, Ningbo, Zhejiang, 315211, China
| | - Le Xu
- Department of Pharmacology, School of Medicine, Ningbo University, 818 Fenghua Rd, Ningbo, Zhejiang, 315211, China
| | - Xin-Yi Zhu
- Department of Pharmacology, School of Medicine, Ningbo University, 818 Fenghua Rd, Ningbo, Zhejiang, 315211, China
| | - Zi-Hang Tang
- Department of Pharmacology, School of Medicine, Ningbo University, 818 Fenghua Rd, Ningbo, Zhejiang, 315211, China
| | - Yi-Bei Dong
- Department of Pharmacology, School of Medicine, Ningbo University, 818 Fenghua Rd, Ningbo, Zhejiang, 315211, China
| | - Zhi-Peng Yu
- Department of Pharmacology, School of Medicine, Ningbo University, 818 Fenghua Rd, Ningbo, Zhejiang, 315211, China
| | - Qing Shang
- Department of Neurology, The First Affiliated Hospital of Ningbo University, 59 Liuting Street, Haishu District, Ningbo, Zhejiang, 315211, China
| | - Zheng-Chun Wang
- Department of Pharmacology, School of Medicine, Ningbo University, 818 Fenghua Rd, Ningbo, Zhejiang, 315211, China
| | - Hao-Wei Shen
- Department of Pharmacology, School of Medicine, Ningbo University, 818 Fenghua Rd, Ningbo, Zhejiang, 315211, China.
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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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Eisner D, Neher E, Taschenberger H, Smith G. Physiology of intracellular calcium buffering. Physiol Rev 2023; 103:2767-2845. [PMID: 37326298 DOI: 10.1152/physrev.00042.2022] [Citation(s) in RCA: 18] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 05/08/2023] [Accepted: 06/11/2023] [Indexed: 06/17/2023] Open
Abstract
Calcium signaling underlies much of physiology. Almost all the Ca2+ in the cytoplasm is bound to buffers, with typically only ∼1% being freely ionized at resting levels in most cells. Physiological Ca2+ buffers include small molecules and proteins, and experimentally Ca2+ indicators will also buffer calcium. The chemistry of interactions between Ca2+ and buffers determines the extent and speed of Ca2+ binding. The physiological effects of Ca2+ buffers are determined by the kinetics with which they bind Ca2+ and their mobility within the cell. The degree of buffering depends on factors such as the affinity for Ca2+, the Ca2+ concentration, and whether Ca2+ ions bind cooperatively. Buffering affects both the amplitude and time course of cytoplasmic Ca2+ signals as well as changes of Ca2+ concentration in organelles. It can also facilitate Ca2+ diffusion inside the cell. Ca2+ buffering affects synaptic transmission, muscle contraction, Ca2+ transport across epithelia, and the killing of bacteria. Saturation of buffers leads to synaptic facilitation and tetanic contraction in skeletal muscle and may play a role in inotropy in the heart. This review focuses on the link between buffer chemistry and function and how Ca2+ buffering affects normal physiology and the consequences of changes in disease. As well as summarizing what is known, we point out the many areas where further work is required.
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Affiliation(s)
- David Eisner
- Division of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom
| | - Erwin Neher
- Membrane Biophysics Laboratory, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
- Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Göttingen, Germany
| | - Holger Taschenberger
- Department of Molecular Neurobiology, Max Planck Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Godfrey Smith
- School of Cardiovascular and Metabolic Health, College of Medical, Veterinary, and Life Sciences, University of Glasgow, Glasgow, United Kingdom
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7
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Ino Y, Ohira T, Kumagai K, Nakai Y, Akiyama T, Moriyama K, Takeda Y, Saito T, Ryo A, Inaba Y, Hirano H, Kimura Y. Identification of mouse soleus muscle proteins altered in response to changes in gravity loading. Sci Rep 2023; 13:15768. [PMID: 37737267 PMCID: PMC10517164 DOI: 10.1038/s41598-023-42875-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Accepted: 09/15/2023] [Indexed: 09/23/2023] Open
Abstract
Gravity-dependent physical processes strongly affect the ability of elderly people to maintain musculoskeletal health by reducing muscle atrophy and increasing bone mineral density, thereby increasing quality of life. A need therefore exists to identify molecules in the musculoskeletal system that are responsive to gravitational loading and to establish an objective indicator for the maintenance of healthy musculoskeletal systems. Here, we performed an integrated assessment of the results of soleus muscle proteomic analyses in three model mouse experiments under different gravity environments (hypergravity, hindlimb unloading, and spaceflight). Myl6b, Gpd1, Fbp2, Pvalb, and Actn3 were shown to be gravity-responsive muscle proteins, and alterations in the levels of these proteins indicated changes in muscle fiber type to slow-twitch type due to gravity loading. In addition, immunoblotting and enzyme-linked immunosorbent assays revealed that Pvalb levels in the sera of hindlimb-unloaded mice and osteoporosis patients were higher than in control subjects, suggesting that Pvalb levels might be useful to objectively evaluate soleus muscle atrophy and bone loss.
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Affiliation(s)
- Yoko Ino
- Advanced Medical Research Center, Yokohama City University, Fukuura 3-9, Kanazawa-Ku, Yokohama, 236-0004, Japan
| | - Takashi Ohira
- Advanced Medical Research Center, Yokohama City University, Fukuura 3-9, Kanazawa-Ku, Yokohama, 236-0004, Japan.
- Department of Physiology and Regenerative Medicine, Kindai University Faculty of Medicine, Ohno-Higashi 377-2, Osaka-Sayama, Osaka, Japan.
| | - Ken Kumagai
- Department of Orthopaedic Surgery, Yokohama City University School of Medicine, Yokohama, Japan
| | - Yusuke Nakai
- Advanced Medical Research Center, Yokohama City University, Fukuura 3-9, Kanazawa-Ku, Yokohama, 236-0004, Japan
| | - Tomoko Akiyama
- Advanced Medical Research Center, Yokohama City University, Fukuura 3-9, Kanazawa-Ku, Yokohama, 236-0004, Japan
| | - Kayano Moriyama
- Advanced Medical Research Center, Yokohama City University, Fukuura 3-9, Kanazawa-Ku, Yokohama, 236-0004, Japan
| | - Yuriko Takeda
- Department of Biostatistics, Yokohama City University School of Medicine, Yokohama, Japan
| | | | - Akihide Ryo
- Advanced Medical Research Center, Yokohama City University, Fukuura 3-9, Kanazawa-Ku, Yokohama, 236-0004, Japan
| | - Yutaka Inaba
- Department of Orthopaedic Surgery, Yokohama City University School of Medicine, Yokohama, Japan
| | - Hisashi Hirano
- Advanced Medical Research Center, Yokohama City University, Fukuura 3-9, Kanazawa-Ku, Yokohama, 236-0004, Japan
| | - Yayoi Kimura
- Advanced Medical Research Center, Yokohama City University, Fukuura 3-9, Kanazawa-Ku, Yokohama, 236-0004, Japan.
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8
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Kumar P, Goettemoeller AM, Espinosa-Garcia C, Tobin BR, Tfaily A, Nelson RS, Natu A, Dammer EB, Santiago JV, Malepati S, Cheng L, Xiao H, Duong D, Seyfried NT, Wood LB, Rowan MJ, Rangaraju S. Native-state proteomics of Parvalbumin interneurons identifies novel molecular signatures and metabolic vulnerabilities to early Alzheimer's disease pathology. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.17.541038. [PMID: 37292756 PMCID: PMC10245729 DOI: 10.1101/2023.05.17.541038] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
One of the earliest pathophysiological perturbations in Alzheimer's Disease (AD) may arise from dysfunction of fast-spiking parvalbumin (PV) interneurons (PV-INs). Defining early protein-level (proteomic) alterations in PV-INs can provide key biological and translationally relevant insights. Here, we use cell-type-specific in vivo biotinylation of proteins (CIBOP) coupled with mass spectrometry to obtain native-state proteomes of PV interneurons. PV-INs exhibited proteomic signatures of high metabolic, mitochondrial, and translational activity, with over-representation of causally linked AD genetic risk factors. Analyses of bulk brain proteomes indicated strong correlations between PV-IN proteins with cognitive decline in humans, and with progressive neuropathology in humans and mouse models of Aβ pathology. Furthermore, PV-IN-specific proteomes revealed unique signatures of increased mitochondrial and metabolic proteins, but decreased synaptic and mTOR signaling proteins in response to early Aβ pathology. PV-specific changes were not apparent in whole-brain proteomes. These findings showcase the first native state PV-IN proteomes in mammalian brain, revealing a molecular basis for their unique vulnerabilities in AD.
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9
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Gandhi T, Liu CC, Adeyelu TT, Canepa CR, Lee CC. Behavioral regulation by perineuronal nets in the prefrontal cortex of the CNTNAP2 mouse model of autism spectrum disorder. Front Behav Neurosci 2023; 17:1114789. [PMID: 36998537 PMCID: PMC10043266 DOI: 10.3389/fnbeh.2023.1114789] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Accepted: 02/23/2023] [Indexed: 03/17/2023] Open
Abstract
Autism spectrum disorders (ASDs) arise from altered development of the central nervous system, and manifest behaviorally as social interaction deficits and restricted and repetitive behaviors. Alterations to parvalbumin (PV) expressing interneurons have been implicated in the neuropathological and behavioral deficits in autism. In addition, perineuronal nets (PNNs), specialized extracellular matrix structures that enwrap the PV-expressing neurons, also may be altered, which compromises neuronal function and susceptibility to oxidative stress. In particular, the prefrontal cortex (PFC), which regulates several core autistic traits, relies on the normal organization of PNNs and PV-expressing cells, as well as other neural circuit elements. Consequently, we investigated whether PNNs and PV-expressing cells were altered in the PFC of the CNTNAP2 knockout mouse model of ASD and whether these contributed to core autistic-like behaviors in this model system. We observed an overexpression of PNNs, PV-expressing cells, and PNNs enwrapping PV-expressing cells in adult CNTNAP2 mice. Transient digestion of PNNs from the prefrontal cortex (PFC) by injection of chondroitinase ABC in CNTNAP2 mutant mice rescued some of the social interaction deficits, but not the restricted and repetitive behaviors. These findings suggest that the neurobiological regulation of PNNs and PVs in the PFC contribute to social interaction behaviors in neurological disorders including autism.
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Affiliation(s)
- Tanya Gandhi
- Department of Comparative Biomedical Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, LA, United States
| | - Chin-Chi Liu
- Department of Veterinary Clinical Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, LA, United States
| | - Tolulope T. Adeyelu
- Department of Comparative Biomedical Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, LA, United States
| | - Cade R. Canepa
- Department of Comparative Biomedical Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, LA, United States
| | - Charles C. Lee
- Department of Comparative Biomedical Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, LA, United States
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10
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Černotová D, Hrůzová K, Levčík D, Svoboda J, Stuchlík A. Linking Social Cognition, Parvalbumin Interneurons, and Oxytocin in Alzheimer's Disease: An Update. J Alzheimers Dis 2023; 96:861-875. [PMID: 37980658 PMCID: PMC10741376 DOI: 10.3233/jad-230333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/11/2023] [Indexed: 11/21/2023]
Abstract
Finding a cure for Alzheimer's disease (AD) has been notoriously challenging for many decades. Therefore, the current focus is mainly on prevention, timely intervention, and slowing the progression in the earliest stages. A better understanding of underlying mechanisms at the beginning of the disease could aid in early diagnosis and intervention, including alleviating symptoms or slowing down the disease progression. Changes in social cognition and progressive parvalbumin (PV) interneuron dysfunction are among the earliest observable effects of AD. Various AD rodent models mimic these early alterations, but only a narrow field of study has considered their mutual relationship. In this review, we discuss current knowledge about PV interneuron dysfunction in AD and emphasize their importance in social cognition and memory. Next, we propose oxytocin (OT) as a potent modulator of PV interneurons and as a promising treatment for managing some of the early symptoms. We further discuss the supporting evidence on its beneficial effects on AD-related pathology. Clinical trials have employed the use of OT in various neuropsychiatric diseases with promising results, but little is known about its prospective impacts on AD. On the other hand, the modulatory effects of OT in specific structures and local circuits need to be clarified in future studies. This review highlights the connection between PV interneurons and social cognition impairment in the early stages of AD and considers OT as a promising therapeutic agent for addressing these early deficits.
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Affiliation(s)
- Daniela Černotová
- Laboratory of Neurophysiology of Memory, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
- Third Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Karolína Hrůzová
- Laboratory of Neurophysiology of Memory, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
- Third Faculty of Medicine, Charles University, Prague, Czech Republic
| | - David Levčík
- Laboratory of Neurophysiology of Memory, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Jan Svoboda
- Laboratory of Neurophysiology of Memory, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
| | - Aleš Stuchlík
- Laboratory of Neurophysiology of Memory, Institute of Physiology of the Czech Academy of Sciences, Prague, Czech Republic
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11
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Weingarten DJ, Shrestha A, Juda-Nelson K, Kissiwaa SA, Spruston E, Jackman SL. Fast resupply of synaptic vesicles requires synaptotagmin-3. Nature 2022; 611:320-325. [PMID: 36261524 DOI: 10.1038/s41586-022-05337-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 09/12/2022] [Indexed: 01/09/2023]
Abstract
Sustained neuronal activity demands a rapid resupply of synaptic vesicles to maintain reliable synaptic transmission. Such vesicle replenishment is accelerated by submicromolar presynaptic Ca2+ signals by an as-yet unidentified high-affinity Ca2+ sensor1,2. Here we identify synaptotagmin-3 (SYT3)3,4 as that presynaptic high-affinity Ca2+ sensor, which drives vesicle replenishment and short-term synaptic plasticity. Synapses in Syt3 knockout mice exhibited enhanced short-term depression, and recovery from depression was slower and insensitive to presynaptic residual Ca2+. During sustained neuronal firing, SYT3 accelerated vesicle replenishment and increased the size of the readily releasable pool. SYT3 also mediated short-term facilitation under conditions of low release probability and promoted synaptic enhancement together with another high-affinity synaptotagmin, SYT7 (ref. 5). Biophysical modelling predicted that SYT3 mediates both replenishment and facilitation by promoting the transition of loosely docked vesicles to tightly docked, primed states. Our results reveal a crucial role for presynaptic SYT3 in the maintenance of reliable high-frequency synaptic transmission. Moreover, multiple forms of short-term plasticity may converge on a mechanism of reversible, Ca2+-dependent vesicle docking.
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Affiliation(s)
| | - Amita Shrestha
- Vollum Institute, Oregon Health and Science University, Portland, OR, USA
| | - Kessa Juda-Nelson
- Vollum Institute, Oregon Health and Science University, Portland, OR, USA
| | - Sarah A Kissiwaa
- Vollum Institute, Oregon Health and Science University, Portland, OR, USA
| | - Evan Spruston
- Vollum Institute, Oregon Health and Science University, Portland, OR, USA
| | - Skyler L Jackman
- Vollum Institute, Oregon Health and Science University, Portland, OR, USA.
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12
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A sequential two-step priming scheme reproduces diversity in synaptic strength and short-term plasticity. Proc Natl Acad Sci U S A 2022; 119:e2207987119. [PMID: 35969787 PMCID: PMC9407230 DOI: 10.1073/pnas.2207987119] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
Central nervous system synapses are diverse in strength and plasticity. Short-term plasticity has traditionally been evaluated with models postulating a single pool of functionally homogeneous fusion-competent synaptic vesicles. Many observations are not easily explainable by such simple models. We established and experimentally validated a scheme of synaptic vesicle priming consisting of two sequential and reversible steps of release–machinery assembly. This sequential two-step priming scheme faithfully reproduced plasticity at a glutamatergic model synapse. The proposed priming and fusion scheme was consistent with the measured mean responses and with the experimentally observed heterogeneity between synapses. Vesicle fusion probability was found to be relatively uniform among synapses, while the priming equilibrium at rest of mature versus immature vesicle priming states differed greatly. Glutamatergic synapses display variable strength and diverse short-term plasticity (STP), even for a given type of connection. Using nonnegative tensor factorization and conventional state modeling, we demonstrate that a kinetic scheme consisting of two sequential and reversible steps of release–machinery assembly and a final step of synaptic vesicle (SV) fusion reproduces STP and its diversity among synapses. Analyzing transmission at the calyx of Held synapses reveals that differences in synaptic strength and STP are not primarily caused by variable fusion probability (pfusion) but are determined by the fraction of docked synaptic vesicles equipped with a mature release machinery. Our simulations show that traditional quantal analysis methods do not necessarily report pfusion of SVs with a mature release machinery but reflect both pfusion and the distribution between mature and immature priming states at rest. Thus, the approach holds promise for a better mechanistic dissection of the roles of presynaptic proteins in the sequence of SV docking, two-step priming, and fusion. It suggests a mechanism for activity-induced redistribution of synaptic efficacy.
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13
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Zavalin K, Hassan A, Fu C, Delpire E, Lagrange AH. Loss of KCC2 in GABAergic Neurons Causes Seizures and an Imbalance of Cortical Interneurons. Front Mol Neurosci 2022; 15:826427. [PMID: 35370549 PMCID: PMC8966887 DOI: 10.3389/fnmol.2022.826427] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 02/21/2022] [Indexed: 11/24/2022] Open
Abstract
K-Cl transporter KCC2 is an important regulator of neuronal development and neuronal function at maturity. Through its canonical transporter role, KCC2 maintains inhibitory responses mediated by γ-aminobutyric acid (GABA) type A receptors. During development, late onset of KCC2 transporter activity defines the period when depolarizing GABAergic signals promote a wealth of developmental processes. In addition to its transporter function, KCC2 directly interacts with a number of proteins to regulate dendritic spine formation, cell survival, synaptic plasticity, neuronal excitability, and other processes. Either overexpression or loss of KCC2 can lead to abnormal circuit formation, seizures, or even perinatal death. GABA has been reported to be especially important for driving migration and development of cortical interneurons (IN), and we hypothesized that properly timed onset of KCC2 expression is vital to this process. To test this hypothesis, we created a mouse with conditional knockout of KCC2 in Dlx5-lineage neurons (Dlx5 KCC2 cKO), which targets INs and other post-mitotic GABAergic neurons in the forebrain starting during embryonic development. While KCC2 was first expressed in the INs of layer 5 cortex, perinatal IN migrations and laminar localization appeared to be unaffected by the loss of KCC2. Nonetheless, the mice had early seizures, failure to thrive, and premature death in the second and third weeks of life. At this age, we found an underlying change in IN distribution, including an excess number of somatostatin neurons in layer 5 and a decrease in parvalbumin-expressing neurons in layer 2/3 and layer 6. Our research suggests that while KCC2 expression may not be entirely necessary for early IN migration, loss of KCC2 causes an imbalance in cortical interneuron subtypes, seizures, and early death. More work will be needed to define the specific cellular basis for these findings, including whether they are due to abnormal circuit formation versus the sequela of defective IN inhibition.
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Affiliation(s)
- Kirill Zavalin
- Department of Neurology, School of Medicine, Vanderbilt University, Nashville, TN, United States
| | - Anjana Hassan
- Department of Neurology, School of Medicine, Vanderbilt University, Nashville, TN, United States
| | - Cary Fu
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, United States
| | - Eric Delpire
- Department of Anesthesiology, School of Medicine, Vanderbilt University, Nashville, TN, United States
| | - Andre H. Lagrange
- Department of Neurology, School of Medicine, Vanderbilt University, Nashville, TN, United States,Department of Neurology, Tennessee Valley Healthcare – Veterans Affairs (TVH VA), Medical Center, Nashville, TN, United States,*Correspondence: Andre H. Lagrange,
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14
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Mellado S, Moreno-Ruiz B, Expósito S, Fernández M, Martín ED. Prolactin Reduces Hippocampal Parvalbumin and GABAA Receptor Expression in Female Mice. Neuroendocrinology 2022; 112:796-806. [PMID: 34666336 PMCID: PMC9533442 DOI: 10.1159/000520279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Accepted: 10/18/2021] [Indexed: 11/19/2022]
Abstract
INTRODUCTION Parvalbumin (PV)-positive cells are strategic elements of neuronal networks capable of influencing memory and learning processes. However, it is not known whether pituitary hormones may be related to PV expression in the hippocampus - a part of the limbic system with important functions in learning and memory. OBJECTIVE Since previous studies indicate that prolactin (PRL) plays a significant role in hippocampal-dependent learning and synaptic plasticity, we hypothesized that a rise in PRL levels can modify PV expression in the hippocampus. METHODS We employed biochemical, immunohistochemistry, and densitometry techniques - as well as a behavioural assay - in a hyperprolactinemia model using subcutaneous osmotic pumps in female mice. RESULTS PRL treatment via osmotic pump induced an increase in PRL receptor (PRLR) expression in most regions of the hippocampus analysed by Western blotting and immunohistochemistry methods. Fluorescent densitometry analysis revealed that PV expression decreases in the same layers in the hippocampus following PRL treatment, while double labelling immunostaining indicated close localization of PV and PRLR in PV-positive interneurons. In addition, we found that PRL induced a reduction in the β2/3 subunit of GABAA receptor (GABAAR) expression that was linearly correlated with the reduction in PV expression. This reduction in the β2/3 subunit of GABAAR expression was maintained in trained animals in which PRL treatment improved the learning of a spatial memory task. CONCLUSIONS These data show, for the first time, that an increase in PRL level is associated with changes in key constituent elements of inhibitory circuits in the hippocampus and may be of relevance for the alterations in cognitive function reported in hyperprolactinemia.
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Affiliation(s)
- Susana Mellado
- Laboratory of Neurophysiology and Synaptic Plasticity, Instituto Cajal, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Beatriz Moreno-Ruiz
- Laboratory of Neurophysiology and Synaptic Plasticity, Instituto Cajal, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Sara Expósito
- Laboratory of Neurophysiology and Synaptic Plasticity, Instituto Cajal, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - Miriam Fernández
- Research Institute for Neurological Disabilities (IDINE), Medical School, University of Castilla-La Mancha, Albacete, Spain
| | - Eduardo D. Martín
- Laboratory of Neurophysiology and Synaptic Plasticity, Instituto Cajal, Consejo Superior de Investigaciones Científicas, Madrid, Spain
- *Eduardo D. Martín,
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15
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Abstract
Rapid and precise neuronal communication is enabled through a highly synchronous release of signaling molecules neurotransmitters within just milliseconds of the action potential. Yet neurotransmitter release lacks a theoretical framework that is both phenomenologically accurate and mechanistically realistic. Here, we present an analytic theory of the action-potential-triggered neurotransmitter release at the chemical synapse. The theory is demonstrated to be in detailed quantitative agreement with existing data on a wide variety of synapses from electrophysiological recordings in vivo and fluorescence experiments in vitro. Despite up to ten orders of magnitude of variation in the release rates among the synapses, the theory reveals that synaptic transmission obeys a simple, universal scaling law, which we confirm through a collapse of the data from strikingly diverse synapses onto a single master curve. This universality is complemented by the capacity of the theory to readily extract, through a fit to the data, the kinetic and energetic parameters that uniquely identify each synapse. The theory provides a means to detect cooperativity among the SNARE complexes that mediate vesicle fusion and reveals such cooperativity in several existing data sets. The theory is further applied to establish connections between molecular constituents of synapses and synaptic function. The theory allows competing hypotheses of short-term plasticity to be tested and identifies the regimes where particular mechanisms of synaptic facilitation dominate or, conversely, fail to account for the existing data for the paired-pulse ratio. The derived trade-off relation between the transmission rate and fidelity shows how transmission failure can be controlled by changing the microscopic properties of the vesicle pool and SNARE complexes. The established condition for the maximal synaptic efficacy reveals that no fine tuning is needed for certain synapses to maintain near-optimal transmission. We discuss the limitations of the theory and propose possible routes to extend it. These results provide a quantitative basis for the notion that the molecular-level properties of synapses are crucial determinants of the computational and information-processing functions in synaptic transmission.
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Affiliation(s)
- Bin Wang
- Department of Physics, University of California, San DiegoLa JollaUnited States
| | - Olga K Dudko
- Department of Physics, University of California, San DiegoLa JollaUnited States
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16
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Lipstein N, Chang S, Lin KH, López-Murcia FJ, Neher E, Taschenberger H, Brose N. Munc13-1 is a Ca 2+-phospholipid-dependent vesicle priming hub that shapes synaptic short-term plasticity and enables sustained neurotransmission. Neuron 2021; 109:3980-4000.e7. [PMID: 34706220 PMCID: PMC8691950 DOI: 10.1016/j.neuron.2021.09.054] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 08/10/2021] [Accepted: 09/23/2021] [Indexed: 11/28/2022]
Abstract
During ongoing presynaptic action potential (AP) firing, transmitter release is limited by the availability of release-ready synaptic vesicles (SVs). The rate of SV recruitment (SVR) to release sites is strongly upregulated at high AP frequencies to balance SV consumption. We show that Munc13-1-an essential SV priming protein-regulates SVR via a Ca2+-phospholipid-dependent mechanism. Using knockin mouse lines with point mutations in the Ca2+-phospholipid-binding C2B domain of Munc13-1, we demonstrate that abolishing Ca2+-phospholipid binding increases synaptic depression, slows recovery of synaptic strength after SV pool depletion, and reduces temporal fidelity of synaptic transmission, while increased Ca2+-phospholipid binding has the opposite effects. Thus, Ca2+-phospholipid binding to the Munc13-1-C2B domain accelerates SVR, reduces short-term synaptic depression, and increases the endurance and temporal fidelity of neurotransmission, demonstrating that Munc13-1 is a core vesicle priming hub that adjusts SV re-supply to demand.
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Affiliation(s)
- Noa Lipstein
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Shuwen Chang
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany
| | - Kun-Han Lin
- Emeritus Laboratory of Membrane Biophysics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | | | - Erwin Neher
- Emeritus Laboratory of Membrane Biophysics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany; Cluster of Excellence "Multiscale Bioimaging," Georg August University, Göttingen, Germany
| | - Holger Taschenberger
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany.
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany; Cluster of Excellence "Multiscale Bioimaging," Georg August University, Göttingen, Germany.
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17
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Correlation of Electrophysiological and Gene Transcriptional Dysfunctions in Single Cortical Parvalbumin Neurons After Noise Trauma. Neuroscience 2021; 482:87-99. [PMID: 34902495 DOI: 10.1016/j.neuroscience.2021.12.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 12/03/2021] [Accepted: 12/06/2021] [Indexed: 11/21/2022]
Abstract
Parvalbumin-expressing (PV+) interneurons in the sensory cortex form powerful inhibitory synapses on the perisomatic compartments and axon initial segments of excitatory principal neurons (PNs), and perform diverse computational functions. Impaired PV+ interneuron functions have been reported in neural developmental and degenerative disorders. Expression of the unique marker parvalbumin (PV) is often used as a proxy of PV+ interneuron functions. However, it is not entirely clear how PV expression is correlated with PV+ interneuron properties such as spike firing and synaptic transmission. To address this question, we characterized electrophysiological properties of PV+ interneurons in the primary auditory cortex (AI) using whole-cell patch clamp recording, and analyzed the expression of several genes in samples collected from single neurons using the patch pipettes. We found that, after noise induced hearing loss (NIHL), the spike frequency adaptation increased, and the expression of PV, glutamate decarboxylase 67 (GAD67) and Shaw-like potassium channel (KV3.1) decreased in PV+ neurons. In samples prepared from the auditory cortical tissue, the mRNA levels of the target genes were all pairwise correlated. At the single neuron level, however, the expression of PV was significantly correlated with the expression of GAD67, but not KV3.1, maximal spike frequency, or spike frequency adaptation. The expression of KV3.1 was correlated with spike frequency adaptation, but not with the expression of GAD67. These results suggest separate transcriptional regulations of PV/GAD67 vs. KV3.1, both of which are modulated by NIHL.
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18
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Ermakov EA, Dmitrieva EM, Parshukova DA, Kazantseva DV, Vasilieva AR, Smirnova LP. Oxidative Stress-Related Mechanisms in Schizophrenia Pathogenesis and New Treatment Perspectives. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2021; 2021:8881770. [PMID: 33552387 PMCID: PMC7847339 DOI: 10.1155/2021/8881770] [Citation(s) in RCA: 99] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Revised: 12/15/2020] [Accepted: 01/02/2021] [Indexed: 02/07/2023]
Abstract
Schizophrenia is recognized to be a highly heterogeneous disease at various levels, from genetics to clinical manifestations and treatment sensitivity. This heterogeneity is also reflected in the variety of oxidative stress-related mechanisms contributing to the phenotypic realization and manifestation of schizophrenia. At the molecular level, these mechanisms are supposed to include genetic causes that increase the susceptibility of individuals to oxidative stress and lead to gene expression dysregulation caused by abnormal regulation of redox-sensitive transcriptional factors, noncoding RNAs, and epigenetic mechanisms favored by environmental insults. These changes form the basis of the prooxidant state and lead to altered redox signaling related to glutathione deficiency and impaired expression and function of redox-sensitive transcriptional factors (Nrf2, NF-κB, FoxO, etc.). At the cellular level, these changes lead to mitochondrial dysfunction and metabolic abnormalities that contribute to aberrant neuronal development, abnormal myelination, neurotransmitter anomalies, and dysfunction of parvalbumin-positive interneurons. Immune dysfunction also contributes to redox imbalance. At the whole-organism level, all these mechanisms ultimately contribute to the manifestation and development of schizophrenia. In this review, we consider oxidative stress-related mechanisms and new treatment perspectives associated with the correction of redox imbalance in schizophrenia. We suggest that not only antioxidants but also redox-regulated transcription factor-targeting drugs (including Nrf2 and FoxO activators or NF-κB inhibitors) have great promise in schizophrenia. But it is necessary to develop the stratification criteria of schizophrenia patients based on oxidative stress-related markers for the administration of redox-correcting treatment.
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Affiliation(s)
- Evgeny A. Ermakov
- Laboratory of Repair Enzymes, Institute of Chemical Biology and Fundamental Medicine, Siberian Division of Russian Academy of Sciences, Novosibirsk 630090, Russia
| | - Elena M. Dmitrieva
- Laboratory of Molecular Genetics and Biochemistry, Mental Health Research Institute, Tomsk National Research Medical Center of the Russian Academy of Sciences, Tomsk 634014, Russia
| | - Daria A. Parshukova
- Laboratory of Molecular Genetics and Biochemistry, Mental Health Research Institute, Tomsk National Research Medical Center of the Russian Academy of Sciences, Tomsk 634014, Russia
| | | | | | - Liudmila P. Smirnova
- Laboratory of Molecular Genetics and Biochemistry, Mental Health Research Institute, Tomsk National Research Medical Center of the Russian Academy of Sciences, Tomsk 634014, Russia
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19
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Neher E, Taschenberger H. Non-negative Matrix Factorization as a Tool to Distinguish Between Synaptic Vesicles in Different Functional States. Neuroscience 2021; 458:182-202. [PMID: 33454165 DOI: 10.1016/j.neuroscience.2020.10.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Revised: 10/06/2020] [Accepted: 10/07/2020] [Indexed: 10/22/2022]
Abstract
Synaptic vesicles (SVs) undergo multiple steps of functional maturation (priming) before being fusion competent. We present an analysis technique, which decomposes the time course of quantal release during repetitive stimulation as a sum of contributions of SVs, which existed in distinct functional states prior to stimulation. Such states may represent different degrees of maturation in priming or relate to different molecular composition of the release apparatus. We apply the method to rat calyx of Held synapses. These synapses display a high degree of variability, both with respect to synaptic strength and short-term plasticity during high-frequency stimulus trains. The method successfully describes time courses of quantal release at individual synapses as linear combinations of three components, representing contributions from functionally distinct SV subpools, with variability among synapses largely covered by differences in subpool sizes. Assuming that SVs transit in sequence through at least two priming steps before being released by an action potential (AP) we interpret the components as representing SVs which had been 'fully primed', 'incompletely primed' or undocked prior to stimulation. Given these assumptions, the analysis reports an initial release probability of 0.43 for SVs that were fully primed prior to stimulation. Release probability of that component was found to increase during high-frequency stimulation, leading to rapid depletion of that subpool. SVs that were incompletely primed at rest rapidly obtain fusion-competence during repetitive stimulation and contribute the majority of release after 3-5 stimuli.
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Affiliation(s)
- Erwin Neher
- Emeritus Laboratory of Membrane Biophysics, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany; Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), University of Göttingen, Germany.
| | - Holger Taschenberger
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
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20
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Mochida S. Neurotransmitter Release Site Replenishment and Presynaptic Plasticity. Int J Mol Sci 2020; 22:ijms22010327. [PMID: 33396919 PMCID: PMC7794938 DOI: 10.3390/ijms22010327] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 12/23/2020] [Accepted: 12/27/2020] [Indexed: 12/19/2022] Open
Abstract
An action potential (AP) triggers neurotransmitter release from synaptic vesicles (SVs) docking to a specialized release site of presynaptic plasma membrane, the active zone (AZ). The AP simultaneously controls the release site replenishment with SV for sustainable synaptic transmission in response to incoming neuronal signals. Although many studies have suggested that the replenishment time is relatively slow, recent studies exploring high speed resolution have revealed SV dynamics with milliseconds timescale after an AP. Accurate regulation is conferred by proteins sensing Ca2+ entering through voltage-gated Ca2+ channels opened by an AP. This review summarizes how millisecond Ca2+ dynamics activate multiple protein cascades for control of the release site replenishment with release-ready SVs that underlie presynaptic short-term plasticity.
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Affiliation(s)
- Sumiko Mochida
- Department of Physiology, Tokyo Medical University, Tokyo 160-8402, Japan
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21
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Filice F, Janickova L, Henzi T, Bilella A, Schwaller B. The Parvalbumin Hypothesis of Autism Spectrum Disorder. Front Cell Neurosci 2020; 14:577525. [PMID: 33390904 PMCID: PMC7775315 DOI: 10.3389/fncel.2020.577525] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 11/10/2020] [Indexed: 12/11/2022] Open
Abstract
The prevalence of autism spectrum disorder (ASD)-a type of neurodevelopmental disorder-is increasing and is around 2% in North America, Asia, and Europe. Besides the known genetic link, environmental, epigenetic, and metabolic factors have been implicated in ASD etiology. Although highly heterogeneous at the behavioral level, ASD comprises a set of core symptoms including impaired communication and social interaction skills as well as stereotyped and repetitive behaviors. This has led to the suggestion that a large part of the ASD phenotype is caused by changes in a few and common set of signaling pathways, the identification of which is a fundamental aim of autism research. Using advanced bioinformatics tools and the abundantly available genetic data, it is possible to classify the large number of ASD-associated genes according to cellular function and pathways. Cellular processes known to be impaired in ASD include gene regulation, synaptic transmission affecting the excitation/inhibition balance, neuronal Ca2+ signaling, development of short-/long-range connectivity (circuits and networks), and mitochondrial function. Such alterations often occur during early postnatal neurodevelopment. Among the neurons most affected in ASD as well as in schizophrenia are those expressing the Ca2+-binding protein parvalbumin (PV). These mainly inhibitory interneurons present in many different brain regions in humans and rodents are characterized by rapid, non-adaptive firing and have a high energy requirement. PV expression is often reduced at both messenger RNA (mRNA) and protein levels in human ASD brain samples and mouse ASD (and schizophrenia) models. Although the human PVALB gene is not a high-ranking susceptibility/risk gene for either disorder and is currently only listed in the SFARI Gene Archive, we propose and present supporting evidence for the Parvalbumin Hypothesis, which posits that decreased PV level is causally related to the etiology of ASD (and possibly schizophrenia).
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Affiliation(s)
| | | | | | | | - Beat Schwaller
- Section of Medicine, Anatomy, University of Fribourg, Fribourg, Switzerland
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22
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Janickova L, Schwaller B. Parvalbumin-Deficiency Accelerates the Age-Dependent ROS Production in Pvalb Neurons in vivo: Link to Neurodevelopmental Disorders. Front Cell Neurosci 2020; 14:571216. [PMID: 33132847 PMCID: PMC7549402 DOI: 10.3389/fncel.2020.571216] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 08/12/2020] [Indexed: 12/26/2022] Open
Abstract
In neurodevelopmental disorders (NDDs) including autism spectrum disorder (ASD) and schizophrenia, impairment/malfunctioning of a subpopulation of interneurons expressing the calcium-binding protein parvalbumin (PV) -here termed Pvalb neurons- has gradually emerged as a possible cause. These neurons may represent a hub or point-of-convergence in the etiology of NDD. Increased oxidative stress associated with mitochondria impairment in Pvalb neurons is discussed as an essential step in schizophrenia etiology. Since PV downregulation is a common finding in ASD and schizophrenia individuals and PV-deficient (PV-/-) mice show a strong ASD-like behavior phenotype, we investigated the putative link between PV expression, alterations in mitochondria and oxidative stress. In a longitudinal study with 1, 3, and 6-months old PV-/- and wild type mice, oxidative stress was investigated in 9 Pvalb neuron subpopulations in the hippocampus, striatum, somatosensory cortex, medial prefrontal cortex, thalamic reticular nucleus (TRN) and cerebellum. In Pvalb neuron somata in the striatum and TRN, we additionally determined mitochondria volume and distribution at these three time points. In all Pvalb neuron subpopulations, we observed an age-dependent increase in oxidative stress and the increase strongly correlated with PV expression levels, but not with mitochondria density in these Pvalb neurons. Moreover, oxidative stress was elevated in Pvalb neurons of PV-/- mice and the magnitude of the effect was again correlated with PV expression levels in the corresponding wild type Pvalb neuron subpopulations. The PV-dependent effect was insignificant at 1 month and relative differences between WT and PV-/- Pvalb neurons were largest at 3 months. Besides the increase in mitochondria volume in PV's absence in TRN and striatal PV-/- Pvalb neurons fully present already at 1 month, we observed a redistribution of mitochondria from the perinuclear region toward the plasma membrane at all time points. We suggest that in absence of PV, slow Ca2+ buffering normally exerted by PV is compensated by a (mal)adaptive, mostly sub-plasmalemmal increase in mitochondria resulting in increased oxidative stress observed in 3- and 6-months old mice. Since PV-/- mice display core ASD-like symptoms already at 1 month, oxidative stress in Pvalb neurons is not a likely cause for their ASD-related behavior observed at this age.
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Affiliation(s)
| | - Beat Schwaller
- Department of Neurosciences amd Movement Science, Section of Medicine, University of Fribourg, Fribourg, Switzerland
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23
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López-Murcia FJ, Reim K, Jahn O, Taschenberger H, Brose N. Acute Complexin Knockout Abates Spontaneous and Evoked Transmitter Release. Cell Rep 2020; 26:2521-2530.e5. [PMID: 30840877 DOI: 10.1016/j.celrep.2019.02.030] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 09/05/2018] [Accepted: 02/07/2019] [Indexed: 12/21/2022] Open
Abstract
SNARE-mediated synaptic vesicle (SV) fusion is controlled by multiple regulatory proteins that determine neurotransmitter release efficiency. Complexins are essential SNARE regulators whose mode of action is unclear, as available evidence indicates positive SV fusion facilitation and negative "fusion clamp"-like activities, with the latter occurring only in certain contexts. Because these contradictory findings likely originate in part from different experimental perturbation strategies, we attempted to resolve them by examining a conditional complexin-knockout mouse line as the most stringent genetic perturbation model available. We found that acute complexin loss after synaptogenesis in autaptic and mass-cultured hippocampal neurons reduces SV fusion probability and thus abates the rates of spontaneous, synchronous, asynchronous, and delayed transmitter release but does not affect SV priming or cause "unclamping" of spontaneous SV fusion. Thus, complexins act as facilitators of SV fusion but are dispensable for "fusion clamping" in mammalian forebrain neurons.
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Affiliation(s)
- Francisco José López-Murcia
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Kerstin Reim
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany
| | - Olaf Jahn
- Proteomics Group, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany; DFG-Research Center for Nanoscale Microscopy and Molecular Physiology of the Brain, 37073 Göttingen, Germany
| | - Holger Taschenberger
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany; DFG-Research Center for Nanoscale Microscopy and Molecular Physiology of the Brain, 37073 Göttingen, Germany.
| | - Nils Brose
- Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075 Göttingen, Germany; DFG-Research Center for Nanoscale Microscopy and Molecular Physiology of the Brain, 37073 Göttingen, Germany.
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Schwaller B. Cytosolic Ca 2+ Buffers Are Inherently Ca 2+ Signal Modulators. Cold Spring Harb Perspect Biol 2020; 12:cshperspect.a035543. [PMID: 31308146 DOI: 10.1101/cshperspect.a035543] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
For precisely regulating intracellular Ca2+ signals in a time- and space-dependent manner, cells make use of various components of the "Ca2+ signaling toolkit," including Ca2+ entry and Ca2+ extrusion systems. A class of cytosolic Ca2+-binding proteins termed Ca2+ buffers serves as modulators of such, mostly short-lived Ca2+ signals. Prototypical Ca2+ buffers include parvalbumins (α and β isoforms), calbindin-D9k, calbindin-D28k, and calretinin. Although initially considered to function as pure Ca2+ buffers, that is, as intracellular Ca2+ signal modulators controlling the shape (amplitude, decay, spread) of Ca2+ signals, evidence has accumulated that calbindin-D28k and calretinin have additional Ca2+ sensor functions. These other functions are brought about by direct interactions with target proteins, thereby modulating their targets' function/activity. Dysregulation of Ca2+ buffer expression is associated with several neurologic/neurodevelopmental disorders including autism spectrum disorder (ASD) and schizophrenia. In some cases, the presence of these proteins is presumed to confer a neuroprotective effect, as evidenced in animal models of Parkinson's or Alzheimer's disease.
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Affiliation(s)
- Beat Schwaller
- Department of Anatomy, Section of Medicine, University of Fribourg, CH-1700 Fribourg, Switzerland
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Quantitation and Simulation of Single Action Potential-Evoked Ca 2+ Signals in CA1 Pyramidal Neuron Presynaptic Terminals. eNeuro 2019; 6:ENEURO.0343-19.2019. [PMID: 31551250 PMCID: PMC6800293 DOI: 10.1523/eneuro.0343-19.2019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Accepted: 09/10/2019] [Indexed: 01/07/2023] Open
Abstract
Presynaptic Ca2+ evokes exocytosis, endocytosis, and synaptic plasticity. However, Ca2+ flux and interactions at presynaptic molecular targets are difficult to quantify because fluorescence imaging has limited resolution. In rats of either sex, we measured single varicosity presynaptic Ca2+ using Ca2+ dyes as buffers, and constructed models of Ca2+ dispersal. Action potentials evoked Ca2+ transients with little variation when measured with low-affinity dye (peak amplitude 789 ± 39 nM, within 2 ms of stimulation; decay times, 119 ± 10 ms). Endogenous Ca2+ buffering capacity, action potential-evoked free [Ca2+]i, and total Ca2+ amounts entering terminals were determined using Ca2+ dyes as buffers. These data constrained Monte Carlo (MCell) simulations of Ca2+ entry, buffering, and removal. Simulations of experimentally-determined Ca2+ fluxes, buffered by simulated calbindin28K well fit data, and were consistent with clustered Ca2+ entry followed within 4 ms by diffusion throughout the varicosity. Repetitive stimulation caused free varicosity Ca2+ to sum. However, simulated in nanometer domains, its removal by pumps and buffering was negligible, while local diffusion dominated. Thus, Ca2+ within tens of nanometers of entry, did not accumulate. A model of synaptotagmin1 (syt1)-Ca2+ binding indicates that even with 10 µM free varicosity evoked Ca2+, syt1 must be within tens of nanometers of channels to ensure occupation of all its Ca2+-binding sites. Repetitive stimulation, evoking short-term synaptic enhancement, does not modify probabilities of Ca2+ fully occupying syt1’s C2 domains, suggesting that enhancement is not mediated by Ca2+-syt1 interactions. We conclude that at spatiotemporal scales of fusion machines, Ca2+ necessary for their activation is diffusion dominated.
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Nanou E, Catterall WA. Calcium Channels, Synaptic Plasticity, and Neuropsychiatric Disease. Neuron 2019; 98:466-481. [PMID: 29723500 DOI: 10.1016/j.neuron.2018.03.017] [Citation(s) in RCA: 279] [Impact Index Per Article: 55.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Revised: 03/06/2018] [Accepted: 03/09/2018] [Indexed: 12/14/2022]
Abstract
Voltage-gated calcium channels couple depolarization of the cell-surface membrane to entry of calcium, which triggers secretion, contraction, neurotransmission, gene expression, and other physiological responses. They are encoded by ten genes, which generate three voltage-gated calcium channel subfamilies: CaV1; CaV2; and CaV3. At synapses, CaV2 channels form large signaling complexes in the presynaptic nerve terminal, which are responsible for the calcium entry that triggers neurotransmitter release and short-term presynaptic plasticity. CaV1 channels form signaling complexes in postsynaptic dendrites and dendritic spines, where their calcium entry induces long-term potentiation. These calcium channels are the targets of mutations and polymorphisms that alter their function and/or regulation and cause neuropsychiatric diseases, including migraine headache, cerebellar ataxia, autism, schizophrenia, bipolar disorder, and depression. This article reviews the molecular properties of calcium channels, considers their multiple roles in synaptic plasticity, and discusses their potential involvement in this wide range of neuropsychiatric diseases.
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Affiliation(s)
- Evanthia Nanou
- Department of Pharmacology, University of Washington, Seattle, WA 98195-7280, USA
| | - William A Catterall
- Department of Pharmacology, University of Washington, Seattle, WA 98195-7280, USA.
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27
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Presynaptic Calcium Channels. Int J Mol Sci 2019; 20:ijms20092217. [PMID: 31064106 PMCID: PMC6539076 DOI: 10.3390/ijms20092217] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 04/22/2019] [Accepted: 04/26/2019] [Indexed: 12/27/2022] Open
Abstract
Presynaptic Ca2+ entry occurs through voltage-gated Ca2+ (CaV) channels which are activated by membrane depolarization. Depolarization accompanies neuronal firing and elevation of Ca2+ triggers neurotransmitter release from synaptic vesicles. For synchronization of efficient neurotransmitter release, synaptic vesicles are targeted by presynaptic Ca2+ channels forming a large signaling complex in the active zone. The presynaptic CaV2 channel gene family (comprising CaV2.1, CaV2.2, and CaV2.3 isoforms) encode the pore-forming α1 subunit. The cytoplasmic regions are responsible for channel modulation by interacting with regulatory proteins. This article overviews modulation of the activity of CaV2.1 and CaV2.2 channels in the control of synaptic strength and presynaptic plasticity.
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Fairless R, Williams SK, Diem R. Calcium-Binding Proteins as Determinants of Central Nervous System Neuronal Vulnerability to Disease. Int J Mol Sci 2019; 20:ijms20092146. [PMID: 31052285 PMCID: PMC6539299 DOI: 10.3390/ijms20092146] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2019] [Revised: 04/26/2019] [Accepted: 04/27/2019] [Indexed: 12/14/2022] Open
Abstract
Neuronal subpopulations display differential vulnerabilities to disease, but the factors that determine their susceptibility are poorly understood. Toxic increases in intracellular calcium are a key factor in several neurodegenerative processes, with calcium-binding proteins providing an important first line of defense through their ability to buffer incoming calcium, allowing the neuron to quickly achieve homeostasis. Since neurons expressing different calcium-binding proteins have been reported to be differentially susceptible to degeneration, it can be hypothesized that rather than just serving as markers of different neuronal subpopulations, they might actually be a key determinant of survival. In this review, we will summarize some of the evidence that expression of the EF-hand calcium-binding proteins, calbindin, calretinin and parvalbumin, may influence the susceptibility of distinct neuronal subpopulations to disease processes.
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Affiliation(s)
- Richard Fairless
- Department of Neurology, University Clinic Heidelberg, 69120 Heidelberg, Germany.
- Clinical Cooperation Unit (CCU) Neurooncology, German Cancer Consortium (DKTK), German Cancer Research Center (DFKZ), 69120 Heidelberg, Germany.
| | - Sarah K Williams
- Department of Neurology, University Clinic Heidelberg, 69120 Heidelberg, Germany.
- Clinical Cooperation Unit (CCU) Neurooncology, German Cancer Consortium (DKTK), German Cancer Research Center (DFKZ), 69120 Heidelberg, Germany.
| | - Ricarda Diem
- Department of Neurology, University Clinic Heidelberg, 69120 Heidelberg, Germany.
- Clinical Cooperation Unit (CCU) Neurooncology, German Cancer Consortium (DKTK), German Cancer Research Center (DFKZ), 69120 Heidelberg, Germany.
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29
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He T, Nitabach MN, Lnenicka GA. Parvalbumin expression affects synaptic development and physiology at the Drosophila larval NMJ. J Neurogenet 2018; 32:209-220. [PMID: 30175644 DOI: 10.1080/01677063.2018.1498496] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Presynaptic Ca2+ appears to play multiple roles in synaptic development and physiology. We examined the effect of buffering presynaptic Ca2+ by expressing parvalbumin (PV) in Drosophila neurons, which do not normally express PV. The studies were performed on the identified Ib terminal that innervates muscle fiber 5. The volume-averaged, residual Ca2+ resulting from single action potentials (APs) and AP trains was measured using the fluorescent Ca2+ indicator, OGB-1. PV reduced the amplitude and decay time constant (τ) for single-AP Ca2+ transients. For AP trains, there was a reduction in the rate of rise and decay of [Ca2+]i but the plateau [Ca2+]i was not affected. Electrophysiological recordings from muscle fiber 5 showed a reduction in paired-pulse facilitation, particularly the F1 component; this was likely due to the reduction in residual Ca2+. These synapses also showed reduced synaptic enhancement during AP trains, presumably due to less buildup of synaptic facilitation. The transmitter release for single APs was increased for the PV-expressing terminals and this may have been a homeostatic response to the decrease in facilitation. Confocal microscopy was used to examine the structure of the motor terminals and PV expression resulted in smaller motor terminals with fewer synaptic boutons and active zones. This result supports earlier proposals that increased AP activity promotes motor terminal growth through increases in presynaptic [Ca2+]i.
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Affiliation(s)
- Tao He
- a Division of Pulmonary and Critical Care Medicine , David Geffen School of Medicine at UCLA , Los Angeles , CA , USA
| | - Michael N Nitabach
- b Department of Cellular and Molecular Physiology , Yale School of Medicine , New Haven , CT , USA
| | - Gregory A Lnenicka
- c Department of Biological Sciences , University at Albany , Albany , NY , USA
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Tran V, Stricker C. Diffusion of Ca 2+ from Small Boutons en Passant into the Axon Shapes AP-Evoked Ca 2+ Transients. Biophys J 2018; 115:1344-1356. [PMID: 30103908 DOI: 10.1016/j.bpj.2018.07.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Revised: 07/01/2018] [Accepted: 07/16/2018] [Indexed: 01/16/2023] Open
Abstract
Not only the amplitude but also the time course of a presynaptic Ca2+ transient determine multiple aspects of synaptic transmission. In small bouton-type synapses, the mechanisms underlying the Ca2+ decay kinetics have not been fully investigated. Here, factors that shape an action-potential-evoked Ca2+ transient were quantitatively studied in synaptic boutons of neocortical layer 5 pyramidal neurons. Ca2+ transients were measured with different concentrations of fluorescent Ca2+ indicators and analyzed based on a single-compartment model. We found a small endogenous Ca2+-binding ratio (7 ± 2) and a high activity of Ca2+ transporters (0.64 ± 0.03 ms-1), both of which enable rapid clearance of Ca2+ from the boutons. However, contrary to predictions of the single-compartment model, the decay time course of the measured Ca2+ transients was biexponential and became prolonged during repetitive stimulation. Measurements of [Ca2+]i along the adjoining axon, together with an experimentally constrained model, showed that the initial fast decay of the Ca2+ transients predominantly arose from the diffusion of Ca2+ from the boutons into the axon. Therefore, for small boutons en passant, factors like terminal volume, axon diameter, and the concentration of mobile Ca2+-binding molecules are critical determinants of Ca2+ dynamics and thus Ca2+-dependent processes, including short-term synaptic plasticity.
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Affiliation(s)
- Van Tran
- Eccles Institute of Neuroscience, JCSMR.
| | - Christian Stricker
- Eccles Institute of Neuroscience, JCSMR; ANU Medical School, ANU, Acton, Australian Capital Territory, Australia
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31
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Singh M, Lujan B, Renden R. Presynaptic GCaMP expression decreases vesicle release probability at the calyx of Held. Synapse 2018; 72:e22040. [PMID: 29935099 PMCID: PMC6186185 DOI: 10.1002/syn.22040] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Revised: 06/04/2018] [Accepted: 06/05/2018] [Indexed: 12/15/2022]
Abstract
Synaptic vesicle (SV) exocytosis is intimately dependent on free local Ca2+ near active zones. Genetically encoded calcium indicators (GECIs) have become an indispensable tool to monitor calcium dynamics during physiological responses, and they are widely used as a proxy to monitor activity in neuronal ensembles and at synaptic terminals. However, GECIs’ ability to bind Ca2+ at physiologically relevant concentration makes them strong candidates to affect calcium homeostasis and alter synaptic transmission by exogenously increasing Ca2+ buffering. In the present study, we show that genetically expressed GCaMP6m modulates SV release probability at the mouse calyx of Held synapse. GCaMP6m expression for approximately three weeks decreased initial SV release for both low‐frequency stimulation and high‐frequency stimulation trains, and slowed presynaptic short‐term depression. However, GCaMP6m does not affect quantal events during spontaneous activity at this synapse. This study emphasizes the careful use of GECIs as monitors of neuronal activity and inspects the role of these transgenic indicators which may alter calcium‐dependent physiological responses.
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Affiliation(s)
- Mahendra Singh
- Department of Physiology and Cell Biology, University of Nevada, Reno, Nevada, 89557
| | - Brendan Lujan
- Department of Physiology and Cell Biology, University of Nevada, Reno, Nevada, 89557.,Currently at Vollum Institute, Oregon Health and Science University, Portland, Oregon
| | - Robert Renden
- Department of Physiology and Cell Biology, University of Nevada, Reno, Nevada, 89557
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Makowiecki K, Garrett A, Harvey AR, Rodger J. Low-intensity repetitive transcranial magnetic stimulation requires concurrent visual system activity to modulate visual evoked potentials in adult mice. Sci Rep 2018; 8:5792. [PMID: 29643395 PMCID: PMC5895738 DOI: 10.1038/s41598-018-23979-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Accepted: 03/19/2018] [Indexed: 12/16/2022] Open
Abstract
Repetitive transcranial stimulation (rTMS) is an increasingly popular method to non-invasively modulate cortical excitability in research and clinical settings. During rTMS, low-intensity magnetic fields reach areas perifocal to the target brain region, however, effects of these low-intensity (LI-) fields and how they interact with ongoing neural activity remains poorly defined. We evaluated whether coordinated neural activity during electromagnetic stimulation alters LI-rTMS effects on cortical excitability by comparing visually evoked potentials (VEP) and densities of parvalbumin-expressing (PV+) GABAergic interneurons in adult mouse visual cortex after LI-rTMS under different conditions: LI-rTMS applied during visually evoked (strong, coordinated) activity or in darkness (weak, spontaneous activity).We also compared response to LI-rTMS in wildtype and ephrin-A2A5−/− mice, which have visuotopic anomalies thought to disrupt coherence of visually-evoked cortical activity. Demonstrating that LI-rTMS effects in V1 require concurrent sensory-evoked activity, LI-rTMS delivered during visually-evoked activity increased PV+ immunoreactivity in both genotypes; however, VEP peak amplitudes changed only in wildtypes, consistent with intracortical disinhibition. We show, for the first time, that neural activity and the degree of coordination in cortical population activity interact with LI-rTMS to alter excitability in a context-dependent manner.
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Affiliation(s)
- Kalina Makowiecki
- Experimental and Regenerative Neuroscience, The University of Western Australia, Crawley, Australia. .,School of Biological Sciences, The University of Western Australia, Crawley, Australia. .,Department of Systems Neuroscience, JFB, University of Goettingen, Göttingen, Germany.
| | - Andrew Garrett
- Experimental and Regenerative Neuroscience, The University of Western Australia, Crawley, Australia.,School of Biological Sciences, The University of Western Australia, Crawley, Australia
| | - Alan R Harvey
- Experimental and Regenerative Neuroscience, The University of Western Australia, Crawley, Australia.,School of Human Sciences, The University of Western Australia, Crawley, Australia.,Perron Institute for Neurological and Translational Science, Nedlands, Australia
| | - Jennifer Rodger
- Experimental and Regenerative Neuroscience, The University of Western Australia, Crawley, Australia.,School of Biological Sciences, The University of Western Australia, Crawley, Australia.,School of Human Sciences, The University of Western Australia, Crawley, Australia.,Perron Institute for Neurological and Translational Science, Nedlands, Australia
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33
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Variations in Ca 2+ Influx Can Alter Chelator-Based Estimates of Ca 2+ Channel-Synaptic Vesicle Coupling Distance. J Neurosci 2018; 38:3971-3987. [PMID: 29563180 DOI: 10.1523/jneurosci.2061-17.2018] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Revised: 02/23/2018] [Accepted: 02/28/2018] [Indexed: 12/20/2022] Open
Abstract
The timing and probability of synaptic vesicle fusion from presynaptic terminals is governed by the distance between voltage-gated Ca2+ channels (VGCCs) and Ca2+ sensors for exocytosis. This VGCC-sensor coupling distance can be determined from the fractional block of vesicular release by exogenous Ca2+ chelators, which depends on biophysical factors that have not been thoroughly explored. Using numerical simulations of Ca2+ reaction and diffusion, as well as vesicular release, we examined the contributions of conductance, density, and open duration of VGCCs, and the influence of endogenous Ca2+ buffers on the inhibition of exocytosis by EGTA. We found that estimates of coupling distance are critically influenced by the duration and amplitude of Ca2+ influx at active zones, but relatively insensitive to variations of mobile endogenous buffer. High concentrations of EGTA strongly inhibit vesicular release in close proximity (20-30 nm) to VGCCs if the flux duration is brief, but have little influence for longer flux durations that saturate the Ca2+ sensor. Therefore, the diversity in presynaptic action potential duration is sufficient to alter EGTA inhibition, resulting in errors potentially as large as 300% if Ca2+ entry durations are not considered when estimating VGCC-sensor coupling distances.SIGNIFICANT STATEMENT The coupling distance between voltage-gated Ca2+ channels and Ca2+ sensors for exocytosis critically determines the timing and probability of neurotransmitter release. Perfusion of presynaptic terminals with the exogenous Ca2+ chelator EGTA has been widely used for both qualitative and quantitative estimates of this distance. However, other presynaptic terminal parameters such as the amplitude and duration of Ca2+ entry can also influence EGTA inhibition of exocytosis, thus confounding conclusions based on EGTA alone. Here, we performed reaction-diffusion simulations of Ca2+-driven synaptic vesicle fusion, which delineate the critical parameters influencing an accurate prediction of coupling distance. Our study provides guidelines for characterizing and understanding how variability in coupling distance across chemical synapses could be estimated accurately.
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34
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Shepard R, Heslin K, Coutellier L. The transcription factor Npas4 contributes to adolescent development of prefrontal inhibitory circuits, and to cognitive and emotional functions: Implications for neuropsychiatric disorders. Neurobiol Dis 2017; 99:36-46. [DOI: 10.1016/j.nbd.2016.12.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2016] [Revised: 12/13/2016] [Accepted: 12/15/2016] [Indexed: 10/20/2022] Open
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35
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Lin KH, Taschenberger H, Neher E. Dynamics of volume-averaged intracellular Ca 2+ in a rat CNS nerve terminal during single and repetitive voltage-clamp depolarizations. J Physiol 2017; 595:3219-3236. [PMID: 27957749 DOI: 10.1113/jp272773] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Accepted: 11/28/2016] [Indexed: 12/28/2022] Open
Abstract
KEY POINTS The intracellular concentration of free calcium ions ([Ca2+ ]i ) in a nerve terminal controls both transmitter release and synaptic plasticity. The rapid triggering of transmitter release depends on the local micro- or nanodomain of highly elevated [Ca2+ ]i in the vicinity of open voltage-gated Ca2+ channels, whereas short-term synaptic plasticity is often controlled by global changes in residual [Ca2+ ]i , averaged over the whole nerve terminal volume. Here we describe dynamic changes of such global [Ca2+ ]i in the calyx of Held - a giant mammalian glutamatergic nerve terminal, which is particularly suited for biophysical studies. We provide quantitative data on Ca2+ inflow, Ca2+ buffering and Ca2+ clearance. These data allow us to predict changes in [Ca2+ ]i in the nerve terminal in response to a wide range of stimulus protocols at high temporal resolution and provide a basis for the modelling of short-term plasticity of glutamatergic synapses. ABSTRACT Many aspects of short-term synaptic plasticity (STP) are controlled by relatively slow changes in the presynaptic intracellular concentration of free calcium ions ([Ca2+ ]i ) that occur in the time range of a few milliseconds to several seconds. In nerve terminals, [Ca2+ ]i equilibrates diffusionally during such slow changes, such that the globally measured, residual [Ca2+ ]i that persists after the collapse of local domains is often the appropriate parameter governing STP. Here, we study activity-dependent dynamic changes in global [Ca2+ ]i at the rat calyx of Held nerve terminal in acute brainstem slices using patch-clamp and microfluorimetry. We use low concentrations of a low-affinity Ca2+ indicator dye (100 μm Fura-6F) in order not to overwhelm endogenous Ca2+ buffers. We first study voltage-clamped terminals, dialysed with pipette solutions containing minimal amounts of Ca2+ buffers, to determine Ca2+ binding properties of endogenous fixed buffers as well as the mechanisms of Ca2+ clearance. Subsequently, we use pipette solutions including 500 μm EGTA to determine the Ca2+ binding kinetics of this chelator. We provide a formalism and parameters that allow us to predict [Ca2+ ]i changes in calyx nerve terminals in response to a wide range of stimulus protocols. Unexpectedly, the Ca2+ affinity of EGTA under the conditions of our measurements was substantially lower (KD = 543 ± 51 nm) than measured in vitro, mainly as a consequence of a higher than previously assumed dissociation rate constant (2.38 ± 0.20 s-1 ), which we need to postulate in order to model the measured presynaptic [Ca2+ ]i transients.
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Affiliation(s)
- Kun-Han Lin
- Emeritus Group Membrane Biophysics, Max Planck Institute for Biophysical Chemistry, 37077, Göttingen, Germany
| | - Holger Taschenberger
- Emeritus Group Membrane Biophysics, Max Planck Institute for Biophysical Chemistry, 37077, Göttingen, Germany.,Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, 37075, Göttingen, Germany.,DFG-Research Centre for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), 37073, Göttingen, Germany
| | - Erwin Neher
- Emeritus Group Membrane Biophysics, Max Planck Institute for Biophysical Chemistry, 37077, Göttingen, Germany.,DFG-Research Centre for Nanoscale Microscopy and Molecular Physiology of the Brain (CNMPB), 37073, Göttingen, Germany
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36
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Delvendahl I, Hallermann S. The Cerebellar Mossy Fiber Synapse as a Model for High-Frequency Transmission in the Mammalian CNS. Trends Neurosci 2016; 39:722-737. [DOI: 10.1016/j.tins.2016.09.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 09/17/2016] [Accepted: 09/20/2016] [Indexed: 10/20/2022]
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37
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Zinchenko VP, Turovskaya MV, Teplov IY, Berezhnov AV, Turovsky EA. The role of parvalbumin-containing interneurons in the regulation of spontaneous synchronous activity of brain neurons in culture. Biophysics (Nagoya-shi) 2016. [DOI: 10.1134/s0006350916010280] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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38
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Baydyuk M, Xu J, Wu LG. The calyx of Held in the auditory system: Structure, function, and development. Hear Res 2016; 338:22-31. [PMID: 27018297 DOI: 10.1016/j.heares.2016.03.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Revised: 03/10/2016] [Accepted: 03/17/2016] [Indexed: 12/19/2022]
Abstract
The calyx of Held synapse plays an important role in the auditory system, relaying information about sound localization via fast and precise synaptic transmission, which is achieved by its specialized structure and giant size. During development, the calyx of Held undergoes anatomical, morphological, and physiological changes necessary for performing its functions. The large dimensions of the calyx of Held nerve terminal are well suited for direct electrophysiological recording of many presynaptic events that are difficult, if not impossible to record at small conventional synapses. This unique accessibility has been used to investigate presynaptic ion channels, transmitter release, and short-term plasticity, providing invaluable information about basic presynaptic mechanisms of transmission at a central synapse. Here, we review anatomical and physiological specializations of the calyx of Held, summarize recent studies that provide new mechanisms important for calyx development and reliable synaptic transmission, and examine fundamental presynaptic mechanisms learned from studies using calyx as a model nerve terminal. This article is part of a Special Issue entitled <Annual Reviews 2016>.
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Affiliation(s)
- Maryna Baydyuk
- National Institute of Neurological Disorders and Stroke, 35 Convent Dr., Bldg 35, Bethesda, MD 20892, USA.
| | - Jianhua Xu
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA; Department of Neurology, Medical College of Georgia, Augusta University, Augusta, GA 30912, USA
| | - Ling-Gang Wu
- National Institute of Neurological Disorders and Stroke, 35 Convent Dr., Bldg 35, Bethesda, MD 20892, USA
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39
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Mileva GR, Kozak IJ, Lewis JE. Short-term synaptic plasticity across topographic maps in the electrosensory system. Neuroscience 2016; 318:1-11. [PMID: 26791523 DOI: 10.1016/j.neuroscience.2016.01.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Revised: 12/16/2015] [Accepted: 01/06/2016] [Indexed: 10/22/2022]
Abstract
The early pathways underlying the active electric sense of the weakly electric fish Apteronotus leptorhynchus involve three parallel processing streams. An array of tuberous electroreceptors distributed over the skin provides inputs to the electrosensory lateral line lobe (ELL), forming the basis for three topographic maps: LS (lateral segment), CLS (centrolateral segment), and CMS (centromedial segment). In addition, each map receives topographically preserved inputs from a direct feedback pathway. How this feedback contributes to the distinct spatiotemporal filtering properties of ELL pyramidal neurons across maps is not clear. We used an in vitro approach to characterize short-term plasticity (STP) in the direct feedback synapses onto pyramidal neurons in each map. Our findings indicated that the dynamics of STP varied across maps in a manner that was consistent with the temporal filtering properties of pyramidal neurons in vivo. Using a modeling approach, we found that the STP of direct feedback synapses in CMS was best described by a simple facilitation-depression model. On the other hand, STP in LS was best described by synaptic facilitation with a use-dependent recovery rate. These results suggest that differential regulation of overlapping STP processes in feedback pathways can contribute to the functional specialization of topographic sensory maps.
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Affiliation(s)
- G R Mileva
- Department of Biology and Centre for Neural Dynamics, University of Ottawa, Ottawa, Canada.
| | - I J Kozak
- Department of Biology and Centre for Neural Dynamics, University of Ottawa, Ottawa, Canada
| | - J E Lewis
- Department of Biology and Centre for Neural Dynamics, University of Ottawa, Ottawa, Canada
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Abstract
UNLABELLED The role of interneurons in cortical microcircuits is strongly influenced by their passive and active electrical properties. Although different types of interneurons exhibit unique electrophysiological properties recorded at the soma, it is not yet clear whether these differences are also manifested in other neuronal compartments. To address this question, we have used voltage-sensitive dye to image the propagation of action potentials into the fine collaterals of axons and dendrites in two of the largest cortical interneuron subtypes in the mouse: fast-spiking interneurons, which are typically basket or chandelier neurons; and somatostatin containing interneurons, which are typically regular spiking Martinotti cells. We found that fast-spiking and somatostatin-expressing interneurons differed in their electrophysiological characteristics along their entire dendrosomatoaxonal extent. The action potentials generated in the somata and axons, including axon collaterals, of somatostatin-expressing interneurons are significantly broader than those generated in the same compartments of fast-spiking inhibitory interneurons. In addition, action potentials back-propagated into the dendrites of somatostatin-expressing interneurons much more readily than fast-spiking interneurons. Pharmacological investigations suggested that axonal action potential repolarization in both cell types depends critically upon Kv1 channels, whereas the axonal and somatic action potentials of somatostatin-expressing interneurons also depend on BK Ca(2+)-activated K(+) channels. These results indicate that the two broad classes of interneurons studied here have expressly different subcellular physiological properties, allowing them to perform unique computational roles in cortical circuit operations. SIGNIFICANCE STATEMENT Neurons in the cerebral cortex are of two major types: excitatory and inhibitory. The proper balance of excitation and inhibition in the brain is critical for its operation. Neurons contain three main compartments: dendritic, somatic, and axonal. How the neurons receive information, process it, and pass on new information depends upon how these three compartments operate. While it has long been assumed that axons are simply for conducting information from the cell body to the synapses, here we demonstrate that the axons of different types of interneurons, the inhibitory cells, possess differing electrophysiological properties. This result implies that differing types of interneurons perform different tasks in the cortex, not only through their anatomical connections, but also through how their axons operate.
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Filice F, Vörckel KJ, Sungur AÖ, Wöhr M, Schwaller B. Reduction in parvalbumin expression not loss of the parvalbumin-expressing GABA interneuron subpopulation in genetic parvalbumin and shank mouse models of autism. Mol Brain 2016; 9:10. [PMID: 26819149 PMCID: PMC4729132 DOI: 10.1186/s13041-016-0192-8] [Citation(s) in RCA: 161] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Accepted: 01/20/2016] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND A reduction of the number of parvalbumin (PV)-immunoreactive (PV(+)) GABAergic interneurons or a decrease in PV immunoreactivity was reported in several mouse models of autism spectrum disorders (ASD). This includes Shank mutant mice, with SHANK being one of the most important gene families mutated in human ASD. Similar findings were obtained in heterozygous (PV+/-) mice for the Pvalb gene, which display a robust ASD-like phenotype. Here, we addressed the question whether the observed reduction in PV immunoreactivity was the result of a decrease in PV expression levels and/or loss of the PV-expressing GABA interneuron subpopulation hereafter called "Pvalb neurons". The two alternatives have important implications as they likely result in opposing effects on the excitation/inhibition balance, with decreased PV expression resulting in enhanced inhibition, but loss of the Pvalb neuron subpopulation in reduced inhibition. METHODS Stereology was used to determine the number of Pvalb neurons in ASD-associated brain regions including the medial prefrontal cortex, somatosensory cortex and striatum of PV-/-, PV+/-, Shank1-/- and Shank3B-/- mice. As a second marker for the identification of Pvalb neurons, we used Vicia Villosa Agglutinin (VVA), a lectin recognizing the specific extracellular matrix enwrapping Pvalb neurons. PV protein and Pvalb mRNA levels were determined quantitatively by Western blot analyses and qRT-PCR, respectively. RESULTS Our analyses of total cell numbers in different brain regions indicated that the observed "reduction of PV(+) neurons" was in all cases, i.e., in PV+/-, Shank1-/- and Shank3B-/- mice, due to a reduction in Pvalb mRNA and PV protein, without any indication of neuronal cell decrease/loss of Pvalb neurons evidenced by the unaltered numbers of VVA(+) neurons. CONCLUSIONS Our findings suggest that the PV system might represent a convergent downstream endpoint for some forms of ASD, with the excitation/inhibition balance shifted towards enhanced inhibition due to the down-regulation of PV being a promising target for future pharmacological interventions. Testing whether approaches aimed at restoring normal PV protein expression levels and/or Pvalb neuron function might reverse ASD-relevant phenotypes in mice appears therefore warranted and may pave the way for novel therapeutic treatment strategies.
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Affiliation(s)
- Federica Filice
- Anatomy, Department of Medicine, University of Fribourg, Route Albert-Gockel 1, CH-1700, Fribourg, Switzerland.
| | - Karl Jakob Vörckel
- Behavioral Neuroscience, Faculty of Psychology, Philipps-University of Marburg, Gutenbergstraβe 18, D-35032, Marburg, Germany.
| | - Ayse Özge Sungur
- Behavioral Neuroscience, Faculty of Psychology, Philipps-University of Marburg, Gutenbergstraβe 18, D-35032, Marburg, Germany.
| | - Markus Wöhr
- Behavioral Neuroscience, Faculty of Psychology, Philipps-University of Marburg, Gutenbergstraβe 18, D-35032, Marburg, Germany.
| | - Beat Schwaller
- Anatomy, Department of Medicine, University of Fribourg, Route Albert-Gockel 1, CH-1700, Fribourg, Switzerland.
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Shaping Neuronal Network Activity by Presynaptic Mechanisms. PLoS Comput Biol 2015; 11:e1004438. [PMID: 26372048 PMCID: PMC4570815 DOI: 10.1371/journal.pcbi.1004438] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 06/23/2015] [Indexed: 02/06/2023] Open
Abstract
Neuronal microcircuits generate oscillatory activity, which has been linked to basic functions such as sleep, learning and sensorimotor gating. Although synaptic release processes are well known for their ability to shape the interaction between neurons in microcircuits, most computational models do not simulate the synaptic transmission process directly and hence cannot explain how changes in synaptic parameters alter neuronal network activity. In this paper, we present a novel neuronal network model that incorporates presynaptic release mechanisms, such as vesicle pool dynamics and calcium-dependent release probability, to model the spontaneous activity of neuronal networks. The model, which is based on modified leaky integrate-and-fire neurons, generates spontaneous network activity patterns, which are similar to experimental data and robust under changes in the model's primary gain parameters such as excitatory postsynaptic potential and connectivity ratio. Furthermore, it reliably recreates experimental findings and provides mechanistic explanations for data obtained from microelectrode array recordings, such as network burst termination and the effects of pharmacological and genetic manipulations. The model demonstrates how elevated asynchronous release, but not spontaneous release, synchronizes neuronal network activity and reveals that asynchronous release enhances utilization of the recycling vesicle pool to induce the network effect. The model further predicts a positive correlation between vesicle priming at the single-neuron level and burst frequency at the network level; this prediction is supported by experimental findings. Thus, the model is utilized to reveal how synaptic release processes at the neuronal level govern activity patterns and synchronization at the network level. The activity of neuronal networks underlies basic neural functions such as sleep, learning and sensorimotor gating. Computational models of neuronal networks have been developed to capture the complexity of the network activity and predict how neuronal networks generate spontaneous activity. However, most computational models do not simulate the intricate synaptic release process that governs the interaction between neurons and has been shown to significantly impact neuronal network activity and animal behavior, learning and memory. Our paper demonstrates the importance of simulating the elaborate synaptic release process to understand how neuronal networks generate spontaneous activity and respond to manipulations of the release process. The model provides mechanistic explanations and predictions for experimental pharmacological and genetic manipulations. Thus, the model presents a novel computational platform to understand how mechanistic changes in the synaptic release process modulate network oscillatory activity that might impact basic neural functions.
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Complexin stabilizes newly primed synaptic vesicles and prevents their premature fusion at the mouse calyx of held synapse. J Neurosci 2015; 35:8272-90. [PMID: 26019341 DOI: 10.1523/jneurosci.4841-14.2015] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Complexins (Cplxs) are small synaptic proteins that cooperate with SNARE-complexes in the control of synaptic vesicle (SV) fusion. Studies involving genetic mutation, knock-down, or knock-out indicated two key functions of Cplx that are not mutually exclusive but cannot easily be reconciled, one in facilitating SV fusion, and one in "clamping" SVs to prevent premature fusion. Most studies on the role of Cplxs in mammalian synapse function have relied on cultured neurons, heterologous expression systems, or membrane fusion assays in vitro, whereas little is known about the function of Cplxs in native synapses. We therefore studied consequences of genetic ablation of Cplx1 in the mouse calyx of Held synapse, and discovered a developmentally exacerbating phenotype of reduced spontaneous and evoked transmission but excessive asynchronous release after stimulation, compatible with combined facilitating and clamping functions of Cplx1. Because action potential waveforms, Ca(2+) influx, readily releasable SV pool size, and quantal size were unaltered, the reduced synaptic strength in the absence of Cplx1 is most likely a consequence of a decreased release probability, which is caused, in part, by less tight coupling between Ca(2+) channels and docked SV. We found further that the excessive asynchronous release in Cplx1-deficient calyces triggered aberrant action potentials in their target neurons, and slowed-down the recovery of EPSCs after depleting stimuli. The augmented asynchronous release had a delayed onset and lasted hundreds of milliseconds, indicating that it predominantly represents fusion of newly recruited SVs, which remain unstable and prone to premature fusion in the absence of Cplx1.
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Wichmann C. Molecularly and structurally distinct synapses mediate reliable encoding and processing of auditory information. Hear Res 2015; 330:178-90. [PMID: 26188105 DOI: 10.1016/j.heares.2015.07.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Revised: 06/21/2015] [Accepted: 07/10/2015] [Indexed: 01/20/2023]
Abstract
Hearing impairment is the most common human sensory deficit. Considering the sophisticated anatomy and physiology of the auditory system, disease-related failures frequently occur. To meet the demands of the neuronal circuits responsible for processing auditory information, the synapses of the lower auditory pathway are anatomically and functionally specialized to process acoustic information indefatigably with utmost temporal precision. Despite sharing some functional properties, the afferent synapses of the cochlea and of auditory brainstem differ greatly in their morphology and employ distinct molecular mechanisms for regulating synaptic vesicle release. Calyceal synapses of the endbulb of Held and the calyx of Held profit from a large number of release sites that project onto one principal cell. Cochlear inner hair cell ribbon synapses exhibit a unique one-to-one relation of the presynaptic active zone to the postsynaptic cell and use hair-cell-specific proteins such as otoferlin for vesicle release. The understanding of the molecular physiology of the hair cell ribbon synapse has been advanced by human genetics studies of sensorineural hearing impairment, revealing human auditory synaptopathy as a new nosological entity.
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Affiliation(s)
- Carolin Wichmann
- Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience & InnerEarLab, University Medical Center, Göttingen, Germany.
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Abstract
Calcium influx during action potentials triggers neurotransmitter release at presynaptic active zones. Calcium buffers limit the spread of calcium and restrict neurotransmitter release to the vicinity of calcium channels. To sustain synchronous release during repetitive activity, rapid removal of calcium from the active zone is essential, but the underlying mechanisms are unclear. Therefore, we focused on cerebellar mossy fiber synapses, which are among the fastest synapses in the mammalian brain and found very weak presynaptic calcium buffering. One might assume that strong calcium buffering has the potential to efficiently remove calcium from active zones. In contrast, our results show that weak calcium buffering speeds active zone calcium clearance. Thus, the strength of presynaptic buffering limits the rate of synaptic transmission. Fast synchronous neurotransmitter release at the presynaptic active zone is triggered by local Ca2+ signals, which are confined in their spatiotemporal extent by endogenous Ca2+ buffers. However, it remains elusive how rapid and reliable Ca2+ signaling can be sustained during repetitive release. Here, we established quantitative two-photon Ca2+ imaging in cerebellar mossy fiber boutons, which fire at exceptionally high rates. We show that endogenous fixed buffers have a surprisingly low Ca2+-binding ratio (∼15) and low affinity, whereas mobile buffers have high affinity. Experimentally constrained modeling revealed that the low endogenous buffering promotes fast clearance of Ca2+ from the active zone during repetitive firing. Measuring Ca2+ signals at different distances from active zones with ultra-high-resolution confirmed our model predictions. Our results lead to the concept that reduced Ca2+ buffering enables fast active zone Ca2+ signaling, suggesting that the strength of endogenous Ca2+ buffering limits the rate of synchronous synaptic transmission.
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Keller D, Babai N, Kochubey O, Han Y, Markram H, Schürmann F, Schneggenburger R. An Exclusion Zone for Ca2+ Channels around Docked Vesicles Explains Release Control by Multiple Channels at a CNS Synapse. PLoS Comput Biol 2015; 11:e1004253. [PMID: 25951120 PMCID: PMC4423980 DOI: 10.1371/journal.pcbi.1004253] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Accepted: 03/23/2015] [Indexed: 01/08/2023] Open
Abstract
The spatial arrangement of Ca2+ channels and vesicles remains unknown for most CNS synapses, despite of the crucial importance of this geometrical parameter for the Ca2+ control of transmitter release. At a large model synapse, the calyx of Held, transmitter release is controlled by several Ca2+ channels in a "domain overlap" mode, at least in young animals. To study the geometrical constraints of Ca2+ channel placement in domain overlap control of release, we used stochastic MCell modelling, at active zones for which the position of docked vesicles was derived from electron microscopy (EM). We found that random placement of Ca2+ channels was unable to produce high slope values between release and presynaptic Ca2+ entry, a hallmark of domain overlap, and yielded excessively large release probabilities. The simple assumption that Ca2+ channels can be located anywhere at active zones, except below a critical distance of ~ 30 nm away from docked vesicles ("exclusion zone"), rescued high slope values and low release probabilities. Alternatively, high slope values can also be obtained by placing all Ca2+ channels into a single supercluster, which however results in significantly higher heterogeneity of release probabilities. We also show experimentally that high slope values, and the sensitivity to the slow Ca2+ chelator EGTA-AM, are maintained with developmental maturation of the calyx synapse. Taken together, domain overlap control of release represents a highly organized active zone architecture in which Ca2+ channels must obey a certain distance to docked vesicles. Furthermore, domain overlap can be employed by near-mature, fast-releasing synapses. Ca2+ channels provide the rise in intracellular Ca2+ concentration necessary to initiate the membrane fusion of transmitter—filled vesicles at synapses. Because Ca2+ diffuses away from Ca2+ channels, the distance between Ca2+ channels and vesicles on the range of tens of nanometers is a crucial determinant of the vesicle fusion probability. However, there is still little experimental evidence on how Ca2+ channels and vesicles co-localize in the nanospace of a single synapse. We show by computational modelling that the channels should be located at some distance to vesicles (~ 30 nm), to allow for release control by several channels, a release mechanism found at many synapses. In realistic synapses with a high density of docked vesicles, this translates into a likely localization of Ca2+ channels at membrane sites not occupied by docked vesicles. Thus, we present a computational model of how Ca2+ channels can be localized in an active zone with several docked vesicles, to enable control of release by several Ca2+ channels.
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Affiliation(s)
- Daniel Keller
- Blue Brain Project, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Norbert Babai
- Laboratory of Synaptic Mechanisms, Brain Mind Institute, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Olexiy Kochubey
- Laboratory of Synaptic Mechanisms, Brain Mind Institute, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Yunyun Han
- Laboratory of Synaptic Mechanisms, Brain Mind Institute, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Henry Markram
- Blue Brain Project, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Felix Schürmann
- Blue Brain Project, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Ralf Schneggenburger
- Laboratory of Synaptic Mechanisms, Brain Mind Institute, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
- * E-mail:
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Synaptic plasticity in the auditory system: a review. Cell Tissue Res 2015; 361:177-213. [PMID: 25896885 DOI: 10.1007/s00441-015-2176-x] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 03/18/2015] [Indexed: 01/19/2023]
Abstract
Synaptic transmission via chemical synapses is dynamic, i.e., the strength of postsynaptic responses may change considerably in response to repeated synaptic activation. Synaptic strength is increased during facilitation, augmentation and potentiation, whereas a decrease in synaptic strength is characteristic for depression and attenuation. This review attempts to discuss the literature on short-term and long-term synaptic plasticity in the auditory brainstem of mammals and birds. One hallmark of the auditory system, particularly the inner ear and lower brainstem stations, is information transfer through neurons that fire action potentials at very high frequency, thereby activating synapses >500 times per second. Some auditory synapses display morphological specializations of the presynaptic terminals, e.g., calyceal extensions, whereas other auditory synapses do not. The review focuses on short-term depression and short-term facilitation, i.e., plastic changes with durations in the millisecond range. Other types of short-term synaptic plasticity, e.g., posttetanic potentiation and depolarization-induced suppression of excitation, will be discussed much more briefly. The same holds true for subtypes of long-term plasticity, like prolonged depolarizations and spike-time-dependent plasticity. We also address forms of plasticity in the auditory brainstem that do not comprise synaptic plasticity in a strict sense, namely short-term suppression, paired tone facilitation, short-term adaptation, synaptic adaptation and neural adaptation. Finally, we perform a meta-analysis of 61 studies in which short-term depression (STD) in the auditory system is opposed to short-term depression at non-auditory synapses in order to compare high-frequency neurons with those that fire action potentials at a lower rate. This meta-analysis reveals considerably less STD in most auditory synapses than in non-auditory ones, enabling reliable, failure-free synaptic transmission even at frequencies >100 Hz. Surprisingly, the calyx of Held, arguably the best-investigated synapse in the central nervous system, depresses most robustly. It will be exciting to reveal the molecular mechanisms that set high-fidelity synapses apart from other synapses that function much less reliably.
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A single-compartment model of calcium dynamics in nerve terminals and dendrites. Cold Spring Harb Protoc 2015; 2015:155-67. [PMID: 25646507 DOI: 10.1101/pdb.top085910] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
This introduction describes a single-compartment model of calcium dynamics that has been applied to fluorescence measurements of intracellular free calcium concentration ([Ca(2+)]i) changes in neurons. The model describes intracellular calcium handling under simplified conditions, for which analytical expressions for the amplitude and the time constants of [Ca(2+)]i changes can be explicitly derived. In particular, it reveals the dependence of the measured [Ca(2+)]i changes on the calcium indicator concentration. Applied to experimental data from small cells or subcellular compartments, the model equations have been extremely useful for obtaining quantitative information about essential parameters of Ca(2+) influx, buffering, and clearance. We illustrate also several changes that occur when the basic assumptions do not hold (e.g., when calcium diffusion, dye saturation, or kinetic effects become significant). Finally, we discuss how the changes in calcium dynamics, which are explained by the model, have been exploited for measuring properties of calcium-driven reactions, such as those regulating short-term synaptic enhancement, vesicle recycling, and adaptation.
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Samigullin D, Fatikhov N, Khaziev E, Skorinkin A, Nikolsky E, Bukharaeva E. Estimation of presynaptic calcium currents and endogenous calcium buffers at the frog neuromuscular junction with two different calcium fluorescent dyes. Front Synaptic Neurosci 2015; 6:29. [PMID: 25709579 PMCID: PMC4285738 DOI: 10.3389/fnsyn.2014.00029] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 12/12/2014] [Indexed: 12/02/2022] Open
Abstract
At the frog neuromuscular junction, under physiological conditions, the direct measurement of calcium currents and of the concentration of intracellular calcium buffers—which determine the kinetics of calcium concentration and neurotransmitter release from the nerve terminal—has hitherto been technically impossible. With the aim of quantifying both Ca2+ currents and the intracellular calcium buffers, we measured fluorescence signals from nerve terminals loaded with the low-affinity calcium dye Magnesium Green or the high-affinity dye Oregon Green BAPTA-1, simultaneously with microelectrode recordings of nerve-action potentials and end-plate currents. The action-potential-induced fluorescence signals in the nerve terminals developed much more slowly than the postsynaptic response. To clarify the reasons for this observation and to define a spatiotemporal profile of intracellular calcium and of the concentration of mobile and fixed calcium buffers, mathematical modeling was employed. The best approximations of the experimental calcium transients for both calcium dyes were obtained when the calcium current had an amplitude of 1.6 ± 0.08 pA and a half-decay time of 1.2 ± 0.06 ms, and when the concentrations of mobile and fixed calcium buffers were 250 ± 13 μM and 8 ± 0.4 mM, respectively. High concentrations of endogenous buffers define the time course of calcium transients after an action potential in the axoplasm, and may modify synaptic plasticity.
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Affiliation(s)
- Dmitry Samigullin
- Laboratory of the Biophysics of Synaptic Processes, Kazan Scientific Centre, Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences Kazan, Russia ; Open Laboratory of Neuropharmacology, Kazan Federal University Kazan, Russia ; Department of Radiophotonics and Microwave Technologies, Kazan National Research Technical University named after A. N. Tupolev Kazan, Russia
| | - Nijaz Fatikhov
- Laboratory of the Biophysics of Synaptic Processes, Kazan Scientific Centre, Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences Kazan, Russia
| | - Eduard Khaziev
- Laboratory of the Biophysics of Synaptic Processes, Kazan Scientific Centre, Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences Kazan, Russia ; Open Laboratory of Neuropharmacology, Kazan Federal University Kazan, Russia
| | - Andrey Skorinkin
- Laboratory of the Biophysics of Synaptic Processes, Kazan Scientific Centre, Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences Kazan, Russia ; Department of Neurobiology and Radioelectronics, Kazan Federal University Kazan, Russia
| | - Eugeny Nikolsky
- Laboratory of the Biophysics of Synaptic Processes, Kazan Scientific Centre, Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences Kazan, Russia ; Open Laboratory of Neuropharmacology, Kazan Federal University Kazan, Russia ; Department of Medical and Biological Physics, Kazan State Medical University Kazan, Russia
| | - Ellya Bukharaeva
- Laboratory of the Biophysics of Synaptic Processes, Kazan Scientific Centre, Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences Kazan, Russia ; Open Laboratory of Neuropharmacology, Kazan Federal University Kazan, Russia
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Szabolcsi V, Celio MR. De novo expression of parvalbumin in ependymal cells in response to brain injury promotes ependymal remodeling and wound repair. Glia 2014; 63:567-94. [PMID: 25421913 DOI: 10.1002/glia.22768] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 11/06/2014] [Indexed: 12/21/2022]
Abstract
The calcium-binding protein parvalbumin (PV) hallmarks subpopulations of interneurons in the murine brain. We serendipitously observed the de novo expression of PV in ependymal cells of the lateral ventricle wall following in vivo lesioning and brain slicing for the preparation of organotypic hippocampal slice cultures (OHSCs). In OHSCs, de novo PV-expression begins shortly after the onset of culturing, and the number of ependymal cells implicated in this process increases with time. PV-immunopositive ependymal cells aggregate and form compact cell clusters, which are characterized by lumen-formation and beating cilia. Scratches inflicted on such clusters with a sharp knife are rapidly closed. Exposure of OHSCs to NF-КB-inhibitors and to antioxidants reduces PV-expression in ependymal cells, thereby implicating injury-induced inflammation in this process. Indeed, in vivo stab injury enhances PV-expression in ependymal cells adjacent to the lesion, whereas neuraminidase denudation is without effect. PV-knock-out mice manifest an impaired wound-healing response to in vivo injury, and a reduced scratch-wound reparation capacity in OHSCs. Whole-transcriptome analysis of ependymal-cell clusters in OHSCs revealed down-regulation of genes involved in cytoskeletal rearrangement, cell motility and cell adhesion in PV-knock out mice as compared with wild-type mice. Our data indicate that the injury-triggered up-regulation of PV-expression is mediated by inflammatory cytokines, and promotes the motility and adhesion of ependymal cells, thereby contributing to leakage closure by the re-establishment of a continuous ependymal layer.
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Affiliation(s)
- Viktória Szabolcsi
- Anatomy and Program in Neuroscience, Department of Medicine, University of Fribourg, Rte Albert Gockel 1, CH-1700, Fribourg, Switzerland
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