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Wang ZJ, Sun L, Heinbockel T. Firing Patterns of Mitral Cells and Their Transformation in the Main Olfactory Bulb. Brain Sci 2024; 14:678. [PMID: 39061419 PMCID: PMC11275187 DOI: 10.3390/brainsci14070678] [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: 05/31/2024] [Revised: 06/27/2024] [Accepted: 06/28/2024] [Indexed: 07/28/2024] Open
Abstract
Mitral cells (MCs) in the main olfactory bulb relay odor information to higher-order olfactory centers by encoding the information in the form of action potentials. The firing patterns of these cells are influenced by both their intrinsic properties and their synaptic connections within the neural network. However, reports on MC firing patterns have been inconsistent, and the mechanisms underlying these patterns remain unclear. Using whole-cell patch-clamp recordings in mouse brain slices, we discovered that MCs exhibit two types of integrative behavior: regular/rhythmic firing and bursts of action potentials. These firing patterns could be transformed both spontaneously and chemically. MCs with regular firing maintained their pattern even in the presence of blockers of fast synaptic transmission, indicating this was an intrinsic property. However, regular firing could be transformed into bursting by applying GABAA receptor antagonists to block inhibitory synaptic transmission. Burst firing could be reverted to regular firing by blocking ionotropic glutamate receptors, rather than applying a GABAA receptor agonist, indicating that ionotropic glutamatergic transmission mediated this transformation. Further experiments on long-lasting currents (LLCs), which generated burst firing, also supported this mechanism. In addition, cytoplasmic Ca2+ in MCs was involved in the transformation of firing patterns mediated by glutamatergic transmission. Metabotropic glutamate receptors also played a role in LLCs in MCs. These pieces of evidence indicate that odor information can be encoded on a mitral cell (MC) platform, where it can be relayed to higher-order olfactory centers through intrinsic and dendrodendritic mechanisms in MCs.
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Affiliation(s)
- Ze-Jun Wang
- Department of Anatomy, Howard University College of Medicine, Washington, DC 20059, USA
- Department of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Liqin Sun
- Department of Anatomy, Howard University College of Medicine, Washington, DC 20059, USA
| | - Thomas Heinbockel
- Department of Anatomy, Howard University College of Medicine, Washington, DC 20059, USA
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Borrus DS, Stettler MK, Grover CJ, Kalajian EJ, Gu J, Conradi Smith GD, Del Negro CA. Inspiratory and sigh breathing rhythms depend on distinct cellular signalling mechanisms in the preBötzinger complex. J Physiol 2024; 602:809-834. [PMID: 38353596 PMCID: PMC10940220 DOI: 10.1113/jp285582] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Accepted: 12/21/2023] [Indexed: 02/21/2024] Open
Abstract
Breathing behaviour involves the generation of normal breaths (eupnoea) on a timescale of seconds and sigh breaths on the order of minutes. Both rhythms emerge in tandem from a single brainstem site, but whether and how a single cell population can generate two disparate rhythms remains unclear. We posit that recurrent synaptic excitation in concert with synaptic depression and cellular refractoriness gives rise to the eupnoea rhythm, whereas an intracellular calcium oscillation that is slower by orders of magnitude gives rise to the sigh rhythm. A mathematical model capturing these dynamics simultaneously generates eupnoea and sigh rhythms with disparate frequencies, which can be separately regulated by physiological parameters. We experimentally validated key model predictions regarding intracellular calcium signalling. All vertebrate brains feature a network oscillator that drives the breathing pump for regular respiration. However, in air-breathing mammals with compliant lungs susceptible to collapse, the breathing rhythmogenic network may have refashioned ubiquitous intracellular signalling systems to produce a second slower rhythm (for sighs) that prevents atelectasis without impeding eupnoea. KEY POINTS: A simplified activity-based model of the preBötC generates inspiratory and sigh rhythms from a single neuron population. Inspiration is attributable to a canonical excitatory network oscillator mechanism. Sigh emerges from intracellular calcium signalling. The model predicts that perturbations of calcium uptake and release across the endoplasmic reticulum counterintuitively accelerate and decelerate sigh rhythmicity, respectively, which was experimentally validated. Vertebrate evolution may have adapted existing intracellular signalling mechanisms to produce slow oscillations needed to optimize pulmonary function in mammals.
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Affiliation(s)
- Daniel S. Borrus
- Applied Science and Neuroscience, William & Mary, Williamsburg, VA 23185
| | - Marco K. Stettler
- Applied Science and Neuroscience, William & Mary, Williamsburg, VA 23185
| | - Cameron J. Grover
- Applied Science and Neuroscience, William & Mary, Williamsburg, VA 23185
| | - Eva J. Kalajian
- Applied Science and Neuroscience, William & Mary, Williamsburg, VA 23185
| | - Jeffrey Gu
- Applied Science and Neuroscience, William & Mary, Williamsburg, VA 23185
| | - Gregory D. Conradi Smith
- Applied Science and Neuroscience, William & Mary, Williamsburg, VA 23185
- Conradi Smith and Del Negro contributed equally
| | - Christopher A. Del Negro
- Applied Science and Neuroscience, William & Mary, Williamsburg, VA 23185
- Conradi Smith and Del Negro contributed equally
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Dagnino-Acosta A, Guerrero-Hernandez A. PKC Inhibits Sec61 Translocon-Mediated Sarcoplasmic Reticulum Ca2+ Leak in Smooth Muscle Cells. Front Physiol 2022; 13:925023. [PMID: 35837019 PMCID: PMC9275787 DOI: 10.3389/fphys.2022.925023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Accepted: 06/03/2022] [Indexed: 01/13/2023] Open
Abstract
PKC inhibitors stimulate Ca2+ release from internal stores in diverse cell types. Our data indicate that this action cannot be explained by an increased agonist-induced IP3 production or an overloaded SR Ca2+ pool in smooth muscle cells from guinea pig urinary bladder. The incubation of these cells with three different PKC inhibitors, such as Go6976, Go6983, and BIM 1, resulted in a higher SR Ca2+ leak revealed by inhibition of the SERCA pump with thapsigargin. This SR Ca2+ leakage was sensitive to protein translocation inhibitors such as emetine and anisomycin. Since this increased SR Ca2+ leak did not result in a depleted SR Ca2+ store, we have inferred there was a compensatory increase in SERCA pump activity, resulting in a higher steady-state. This new steady-state increased the frequency of Spontaneous Transient Outward Currents (STOCs), which reflect the activation of high conductance, Ca2+-sensitive potassium channels in response to RyR-mediated Ca2+ sparks. This increased STOC frequency triggered by PKC inhibition was restored to normal by inhibiting translocon-mediated Ca2+ leak with emetine. These results suggest a critical role of PKC-mediated translocon phosphorylation in regulating SR Ca2+ steady-state, which, in turn, alters SR Ca2+ releasing activity.
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Affiliation(s)
- Adan Dagnino-Acosta
- Centro Universitario de Investigaciones Biomédicas, CONACYT-Universidad de Colima, Colima, Mexico
| | - Agustín Guerrero-Hernandez
- Departamento de Bioquímica, Centro de Investigación y de Estudios Avanzados, Mexico City, Mexico
- *Correspondence: Agustín Guerrero-Hernandez,
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4
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Kawano H, Mitchell SB, Koh JY, Goodman KM, Harata NC. Calcium-induced calcium release in noradrenergic neurons of the locus coeruleus. Brain Res 2020; 1729:146627. [PMID: 31883849 DOI: 10.1016/j.brainres.2019.146627] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 12/19/2019] [Accepted: 12/24/2019] [Indexed: 12/11/2022]
Abstract
The locus coeruleus (LC) is a nucleus within the brainstem that consists of norepinephrine-releasing neurons. It is involved in broad processes including cognitive and emotional functions. Understanding the mechanisms that control the excitability of LC neurons is important because they innervate widespread brain regions. One of the key regulators is cytosolic calcium concentration ([Ca2+]c), the increases in which can be amplified by calcium-induced calcium release (CICR) from intracellular calcium stores. Although the electrical activities of LC neurons are regulated by changes in [Ca2+]c, the extent of CICR involvement in this regulation has remained unclear. Here we show that CICR hyperpolarizes acutely dissociated LC neurons of the rat and demonstrate the underlying pathway. When CICR was activated by extracellular application of 10 mM caffeine, LC neurons were hyperpolarized in the current-clamp mode of patch-clamp recording, and the majority of neurons showed an outward current in the voltage-clamp mode. This outward current was accompanied by increased membrane conductance, and its reversal potential was close to the K+ equilibrium potential, indicating that it is mediated by opening of K+ channels. The outward current was generated in the absence of extracellular calcium and was blocked when the calcium stores were inhibited by applying ryanodine. Pharmacological blockers indicated that it was mediated by Ca2+-activated K+ channels of the non-small conductance type. The application of caffeine increased [Ca2+]c, as visualized by fluorescence microscopy. These findings show CICR suppresses LC neuronal activity, and indicate its dynamic role in modulating the LC-mediated noradrenergic tone in the brain.
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Affiliation(s)
- Hiroyuki Kawano
- Department of Molecular Physiology and Biophysics, University of Iowa Carver College of Medicine, Iowa City, IA, USA
| | - Sara B Mitchell
- Department of Molecular Physiology and Biophysics, University of Iowa Carver College of Medicine, Iowa City, IA, USA
| | - Jin-Young Koh
- Department of Molecular Physiology and Biophysics, University of Iowa Carver College of Medicine, Iowa City, IA, USA; Molecular Otolaryngology and Renal Research Laboratories, Department of Otolaryngology-Head and Neck Surgery, University of Iowa Carver College of Medicine, Iowa City, IA, USA; Department of Biomedical Engineering, University of Iowa College of Engineering, Iowa City, IA, USA
| | - Kirsty M Goodman
- Department of Molecular Physiology and Biophysics, University of Iowa Carver College of Medicine, Iowa City, IA, USA; Department of Biology & Biochemistry, University of Bath, Bath, UK
| | - N Charles Harata
- Department of Molecular Physiology and Biophysics, University of Iowa Carver College of Medicine, Iowa City, IA, USA.
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Potter S, Sifers J, Yocom E, Blümich SLE, Potter R, Nadolski J, Harrison DA, Cooper RL. Effects of inhibiting mTOR with rapamycin on behavior, development, neuromuscular physiology and cardiac function in larval Drosophila. Biol Open 2019; 8:bio.046508. [PMID: 31704693 PMCID: PMC6899040 DOI: 10.1242/bio.046508] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Rapamycin and other mTOR inhibitors are being heralded as possible treatments for many human ailments. It is currently being utilized clinically as an immunomodulator after transplantation procedures and as a treatment for certain forms of cancer, but it has numerous potential clinical indications. Some studies have shown profound effects on life cycle and muscle physiology, but these issues have not been addressed in an organism undergoing developmental processes. This paper fills this void by examining the effect of mTOR inhibition by rapamycin on several different qualities of larval Drosophila. Various dosages of the compound were fed to second instar larvae. These larvae were monitored for pupae formation to elucidate possible life cycle effects, and a delay to pupation was quantified. Behavioral deficits were documented in rapamycin-treated larvae. Electrophysiological measurements were taken to discern changes in muscle physiology and synaptic signaling (i.e. resting membrane potential, amplitude of excitatory post-synaptic potentials, synaptic facilitation). Pupation delay and effects on behavior that are likely due to synaptic alterations within the central nervous system were discovered in rapamycin-fed larvae. These results allow for several conclusions as to how mTOR inhibition by rapamycin affects a developing organism. This could eventually allow for a more informed decision when using rapamycin and other mTOR inhibitors to treat human diseases, especially in children and adolescents, to account for known side effects. Summary: Inhibiting mTOR by rapamycin delays pupation, reduced body wall contractions and mouth-hook movements while synaptic transmission appeared normal in larval Drosophila.
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Affiliation(s)
- Samuel Potter
- Deptartment of Biology and Center for Muscle Biology, University of Kentucky, Lexington, KY, 40506, USA
| | - Jacob Sifers
- Deptartment of Biology and Center for Muscle Biology, University of Kentucky, Lexington, KY, 40506, USA.,Alice Lloyd College, 100 Purpose Road, Pippa Passes, KY, 41844, USA
| | - Emily Yocom
- Deptartment of Biology and Center for Muscle Biology, University of Kentucky, Lexington, KY, 40506, USA.,Kentucky Wesleyan College, Owensboro, KY, 42301, USA
| | - Sandra L E Blümich
- Deptartment of Biology and Center for Muscle Biology, University of Kentucky, Lexington, KY, 40506, USA.,Veterinärmedizinische Fakultät, Universität Leipzig, Leipzig, Germany
| | - Rachel Potter
- Deptartment of Biology and Center for Muscle Biology, University of Kentucky, Lexington, KY, 40506, USA
| | - Jeremy Nadolski
- Department of Mathematical and Computational Sciences, Benedictine University, Lisle, IL, 60532 , USA
| | - Douglas A Harrison
- Deptartment of Biology and Center for Muscle Biology, University of Kentucky, Lexington, KY, 40506, USA
| | - Robin L Cooper
- Deptartment of Biology and Center for Muscle Biology, University of Kentucky, Lexington, KY, 40506, USA
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6
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Zanatta AP, Gonçalves R, Zanatta L, de Oliveria GT, Ludwig Moraes AL, Zamoner A, Fernández-Dueñas V, Lanznaster D, Ciruela F, Tasca CI, Delalande C, Menegaz D, Mena Barreto Silva FR. New ionic targets of 3,3′,5′-triiodothyronine at the plasma membrane of rat Sertoli cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:748-759. [DOI: 10.1016/j.bbamem.2019.01.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Revised: 12/18/2018] [Accepted: 01/07/2019] [Indexed: 11/26/2022]
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7
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Zhang S, Wang X, Wang X, Shen X, Sun J, Hu X, Chen P. Sr2+has low efficiency in regulating spontaneous release at the Calyx of Held synapses. Synapse 2017; 71. [DOI: 10.1002/syn.21983] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Revised: 04/24/2017] [Accepted: 04/25/2017] [Indexed: 11/12/2022]
Affiliation(s)
- Shuli Zhang
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province; Kunming Institute of Zoology, Chinese Academy of Sciences; Kunming Yunnan 650223 China
- State Key Laboratory of Brain and Cognitive Sciences; CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences; Beijing 100101 China
- Kunming College of Life Science; University of Chinese Academy of Sciences; Kunming 650204 China
- University of Chinese Academy of Sciences; Beijing 100049 China
| | - Xuefeng Wang
- State Key Laboratory of Brain and Cognitive Sciences; CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences; Beijing 100101 China
- University of Chinese Academy of Sciences; Beijing 100049 China
| | - Xiaohui Wang
- Department of General Surgery; Xuan Wu Hospital, Capital Medical University; Beijing 100053 China
| | - Xuefeng Shen
- State Key Laboratory of Brain and Cognitive Sciences; CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences; Beijing 100101 China
| | - Jianyuan Sun
- State Key Laboratory of Brain and Cognitive Sciences; CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences; Beijing 100101 China
- Center of Parkinson?s Disease; Beijing Institute for Brain Disorders; Beijing 100053 China
| | - Xintian Hu
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences & Yunnan Province; Kunming Institute of Zoology, Chinese Academy of Sciences; Kunming Yunnan 650223 China
- Kunming College of Life Science; University of Chinese Academy of Sciences; Kunming 650204 China
| | - Peihua Chen
- State Key Laboratory of Brain and Cognitive Sciences; CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences; Beijing 100101 China
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Ordaz JD, Wu W, Xu XM. Optogenetics and its application in neural degeneration and regeneration. Neural Regen Res 2017; 12:1197-1209. [PMID: 28966628 PMCID: PMC5607808 DOI: 10.4103/1673-5374.213532] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/11/2017] [Indexed: 12/30/2022] Open
Abstract
Neural degeneration and regeneration are important topics in neurological diseases. There are limited options for therapeutic interventions in neurological diseases that provide simultaneous spatial and temporal control of neurons. This drawback increases side effects due to non-specific targeting. Optogenetics is a technology that allows precise spatial and temporal control of cells. Therefore, this technique has high potential as a therapeutic strategy for neurological diseases. Even though the application of optogenetics in understanding brain functional organization and complex behaviour states have been elaborated, reviews of its therapeutic potential especially in neurodegeneration and regeneration are still limited. This short review presents representative work in optogenetics in disease models such as spinal cord injury, multiple sclerosis, epilepsy, Alzheimer's disease and Parkinson's disease. It is aimed to provide a broader perspective on optogenetic therapeutic potential in neurodegeneration and neural regeneration.
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Affiliation(s)
- Josue D. Ordaz
- Spinal Cord and Brain Injury Research Group, Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, USA
- Department of Neurological Surgery, Indiana University School of Medicine, Indianapolis, IN, USA
- Goodman Campbell Brain and Spine, Indianapolis, Indiana, USA
| | - Wei Wu
- Spinal Cord and Brain Injury Research Group, Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, USA
- Department of Neurological Surgery, Indiana University School of Medicine, Indianapolis, IN, USA
- Goodman Campbell Brain and Spine, Indianapolis, Indiana, USA
| | - Xiao-Ming Xu
- Spinal Cord and Brain Injury Research Group, Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, USA
- Department of Neurological Surgery, Indiana University School of Medicine, Indianapolis, IN, USA
- Goodman Campbell Brain and Spine, Indianapolis, Indiana, USA
- Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN, USA
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Spontaneous Vesicle Release Is Not Tightly Coupled to Voltage-Gated Calcium Channel-Mediated Ca2+ Influx and Is Triggered by a Ca2+ Sensor Other Than Synaptotagmin-2 at the Juvenile Mice Calyx of Held Synapses. J Neurosci 2015; 35:9632-7. [PMID: 26134646 DOI: 10.1523/jneurosci.0457-15.2015] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
It is well known that voltage-gated calcium channels (VGCCs)-mediated Ca(2+) influx triggers evoked synaptic vesicle release. However, the mechanisms of Ca(2+) regulation of spontaneous miniature vesicle release (mini) remain poorly understood. Here we show that blocking VGCCs at the juvenile mice (C57BL/6) calyx of Held synapse failed to cause an immediate change in minis. Instead, it resulted in a significant reduction (∼40%) of mini frequency several minutes after the blockage. By recording VGCC activity and single vesicle fusion events directly at the presynaptic terminal, we found that minis did not couple to VGCC-mediated Ca(2+) entry, arguing for a lack of direct correlation between mini and transient Ca(2+) influx. Moreover, mini frequencies displayed a lower apparent Ca(2+) cooperativity than those of evoked release. In agreement with this observation, abrogation of the Ca(2+) sensor synaptotagmin-2 had no effect on apparent Ca(2+) cooperativity of minis. Together, our study provides the first direct evidence that spontaneous minis are not mediated by transient Ca(2+) signals through VGCCs and are triggered by a Ca(2+)-sensing mechanism that is different from the evoked release at these microdomain VGCC-vesicle coupled synapses.
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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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11
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Modelling mechanism of calcium oscillations in pancreatic acinar cells. J Bioenerg Biomembr 2014; 46:403-20. [DOI: 10.1007/s10863-014-9561-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Accepted: 06/24/2014] [Indexed: 01/18/2023]
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12
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Seghatoleslam M, Ghadiri MK, Ghaffarian N, Speckmann EJ, Gorji A. Cortical spreading depression modulates the caudate nucleus activity. Neuroscience 2014; 267:83-90. [DOI: 10.1016/j.neuroscience.2014.02.029] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Revised: 02/13/2014] [Accepted: 02/16/2014] [Indexed: 12/24/2022]
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Raol J, Cox SJ. Inverse problems in neuronal calcium signaling. J Math Biol 2014; 67:3-23. [PMID: 22290315 DOI: 10.1007/s00285-012-0507-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Revised: 01/14/2012] [Indexed: 10/14/2022]
Abstract
Calcium is the most important of the brain's second messengers. Thanks to engineered fluorescent indicators and caged compounds we have an excellent qualitative picture of its regulation and impact.With the advent of new scanning technology that permits one to observe the calcium signal throughout a highly branched neuron the potential exists for functional, single cell, quantitative calcium imaging. To help realize that potential we analyze a sequence of four inverse problems that infer the parameters of the cytosolic calcium buffers and plasma membrane calcium pumps and channels from the light shed by fluorescent indicators following specific stimulus protocols. Our analyses lead in each case to practical algorithms that we illustrate and test on synthetic data.
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Affiliation(s)
- Jay Raol
- Department of Computational and Applied Mathematics, Rice University, Houston, TX, USA
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14
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Restoration of stressor-induced calcium dysregulation and autophagy inhibition by polyphenol-rich açaí (Euterpe spp.) fruit pulp extracts in rodent brain cells in vitro. Nutrition 2013; 30:853-62. [PMID: 24985004 DOI: 10.1016/j.nut.2013.11.011] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Revised: 11/15/2013] [Accepted: 11/26/2013] [Indexed: 12/31/2022]
Abstract
OBJECTIVES Oxidative damage to lipids, proteins, and nucleic acids in the brain often causes progressive neuronal degeneration and death that are the focal traits of chronic and acute pathologies, including those involving cognitive decline. The aim of this study was to investigate the specific effects of both Euterpe oleracea and Euterpe precatoria açaí fruit pulp on restoring stressor-induced calcium dysregulation, stunted growth of basal dendrites, and autophagy inhibition using embryonic hippocampal and HT22 hippocampal neurons. METHODS Water-soluble whole fruit pulp extracts from two açaí species were applied to rat primary neurons and HT22 hippocampal neurons with varied time and concentrations. Recovery of neurons from dopamine-induced Ca(2+) dysregulation was measured by live cell imaging using fluorescent microscopy. The effect of açaí fruit pulp extracts on neurons following chemically-induced autophagy inhibition was measured using both immunofluorescence and immunohistochemical techniques. RESULTS It has been postulated that at least part of the loss of cognitive function in aging may depend on a dysregulation in calcium ion (Ca(2+)) homeostasis and a loss of autophagy function in the brain, which affects numerous signaling pathways and alters protein homeostasis. In the present study, polyphenol-rich fruit pulp extracts from two species of açaí, Euterpe precatoria and Euterpe oleracea, when applied to rat hippocampal primary neuronal cells (E18), caused a significant (P < 0.05) recovery of depolarized brain cells from dopamine-induced Ca(2+) influx. Autophagy, a protein homeostasis mechanism in brain, when blocked by known inhibitors such as bafilomycin A1 or wortmannin, caused a significant reduction in the growth of primary basal dendrites in rodent primary hippocampal neurons and significant accumulation of polyubiquitinated proteins in mouse HT22 hippocampal neurons in culture. However, pretreatment with açaí extracts up to 1 mg/mL significantly increased the length of basal dendrites and attenuated the inhibitor-induced autophagy dysfunction. Açaí extracts activated the phosphorylation of mammalian target of rapamycin, increased the turnover of autophagosomes and MAP1 B LC3-II, and decreased accumulation of LC3-ubiquitin binding P62/SQSTM1. CONCLUSION Although the polyphenol profile of Euterpe precatoria showed substantially higher concentrations of major flavonoids han Euterpe oleracea, the relative effects were essentially similar for both species. The study adds to growing evidence that supports the putative health effects of açaí fruit species on brain cells.
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Abstract
The calcium sensing receptor (CaSR) is expressed by subpopulations of neuronal and glial cells throughout the brain and is activated by extracellular calcium [Formula: see text] . During development, the CaSR regulates neuronal cell growth and migration as well as oligodendroglial maturation and function. Emerging evidence suggests that in nerve terminals, CaSR is implicated in synaptic plasticity and neurotransmission. In this review, we analyze the roles attributed to CaSR in regulating diverse brain functions, including central regulation of body fluid composition and blood pressure. We also discuss the potential relevance of Ca(2+)-sensing in brain by other family C G protein-coupled receptors. Finally, evidence that the CaSR contributes to the pathogenesis of various brain disorders raises the possibility that pharmacological modulators of the CaSR may have therapeutic benefit.
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Affiliation(s)
- Martial Ruat
- CNRS-UPR-3294, Laboratory of Neurobiology and Development, Institute of Neurobiology, Alfred Fessard IFR2118, Signal Transduction and Developmental Neuropharmacology Team, 1 Avenue de la Terrasse, F-91198, Gif-sur-Yvette, France.
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The role of calcium in intracellular pathways of rutin in rat pancreatic islets: potential insulin secretagogue effect. Eur J Pharmacol 2013; 702:264-8. [PMID: 23399767 DOI: 10.1016/j.ejphar.2013.01.055] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Revised: 01/21/2013] [Accepted: 01/31/2013] [Indexed: 01/31/2023]
Abstract
Rutin is a flavonol glycoside with multiple biological activities and it has been demonstrated that rutin modulates glucose homeostasis. In pancreatic β-cell, an increase in intracellular calcium concentration triggers exocytosis and thus insulin secretion. The aim of the study reported herein was to investigate the effect of rutin associated intracellular pathways on Ca(2+) uptake in isolated rat pancreatic islets. We focused on the acute effects of rutin on in vivo insulin secretion and the in vitro cellular signaling of pancreatic islets related to this effect. The results show that rutin significantly increased glucose-induced insulin secretion in an in vivo treatment. Moreover, it was demonstrated that rutin stimulated Ca(2+) uptake after 10 min of incubation compared with the respective control group. The involvement of L-type voltage-dependent Ca(2+) channels (L-VDCCs) was evidenced using nifedipine, while the use of glibenclamide and diazoxide demonstrated that the ATP-sensitive potassium (KATP) channels are not involved in the rutin action in pancreatic islets. In conclusion, rutin diminish glycemia, potentiate insulin secretion in vivo and significantly stimulates Ca(2+) uptake in rat pancreatic islets. A novel cellular mechanism of action of rutin in Ca(2+) uptake on pancreatic β-cells was elucidated. Rutin modulates Ca(2+) uptake in pancreatic islets by opening L-VDCCs, alter intracellular Ca(2+), PLC and PKC signaling pathways, characterizing KATP channel-independent pathways. These findings highlight rutin, a dietary adjuvant, as a potential insulin secretagogue contributing to glucose homeostasis.
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Abstract
Intracellular calcium dynamics is critical for many functions of cerebellar granule cells (GrCs) including membrane excitability, synaptic plasticity, apoptosis, and regulation of gene transcription. Recent measurements of calcium responses in GrCs to depolarization and synaptic stimulation reveal spatial compartmentalization and heterogeneity within dendrites of these cells. However, the main determinants of local calcium dynamics in GrCs are still poorly understood. One reason is that there have been few published studies of calcium dynamics in intact GrCs in their native environment. In the absence of complete information, biophysically realistic models are useful for testing whether specific Ca(2+) handling mechanisms may account for existing experimental observations. Simulation results can be used to identify critical measurements that would discriminate between different models. In this review, we briefly describe experimental studies and phenomenological models of Ca(2+) signaling in GrC, and then discuss a particular biophysical model, with a special emphasis on an approach for obtaining information regarding the distribution of Ca(2+) handling systems under conditions of incomplete experimental data. Use of this approach suggests that Ca(2+) channels and fixed endogenous Ca(2+) buffers are highly heterogeneously distributed in GrCs. Research avenues for investigating calcium dynamics in GrCs by a combination of experimental and modeling studies are proposed.
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Affiliation(s)
- Elena È Saftenku
- Department of General Physiology of Nervous System, A. A. Bogomoletz Institute of Physiology, 4 Bogomoletz St., Kyiv 01024, Ukraine.
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Salm EJ, Thayer SA. Homer proteins accelerate Ca2+ clearance mediated by the plasma membrane Ca2+ pump in hippocampal neurons. Biochem Biophys Res Commun 2012; 424:76-81. [PMID: 22732411 DOI: 10.1016/j.bbrc.2012.06.069] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Accepted: 06/15/2012] [Indexed: 10/28/2022]
Abstract
The plasma membrane Ca(2+) ATPase (PMCA) is responsible for maintaining basal intracellular Ca(2+) concentration ([Ca(2+)](i)) and returning small increases in [Ca(2+)](i) back to resting levels. The carboxyl terminus of some PMCA splice variants bind Homer proteins; how binding affects PMCA function is unknown. Here, we examined the effects of altered expression of Homer proteins on PMCA-mediated Ca(2+) clearance from rat hippocampal neurons in culture. The kinetics of PMCA-mediated recovery from the [Ca(2+)](i) increase evoked by a brief train of action potentials was determined in the soma of single neurons using indo-1-based photometry. Exogenous expression of Homer 1a, Homer 1c or Homer 2a did not affect PMCA function. However, shRNA mediated knockdown of Homer 1 slowed PMCA mediated Ca(2+) clearance by 28% relative to cells expressing non-silencing shRNA. The slowed recovery rate in cells expressing Homer 1 shRNA was reversed by expression of a short Homer 2 truncation mutant. These results indicate that constitutively expressed Homer proteins tonically stimulate PMCA function in hippocampal neurons. We propose a model in which binding of short or long Homer proteins to the carboxyl terminus of the PMCA stimulates Ca(2+) clearance rate. PMCA-mediated Ca(2+) clearance may be stimulated following incorporation of the pump into Homer organized signaling domains and following induction of the Homer 1a immediate early gene.
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Affiliation(s)
- Elizabeth J Salm
- Department of Pharmacology, University of Minnesota Medical School, Minneapolis, MN 55455, USA
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19
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Assembly of a new growth cone after axotomy: the precursor to axon regeneration. Nat Rev Neurosci 2012; 13:183-93. [PMID: 22334213 DOI: 10.1038/nrn3176] [Citation(s) in RCA: 327] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The assembly of a new growth cone is a prerequisite for axon regeneration after injury. Creation of a new growth cone involves multiple processes, including calcium signalling, restructuring of the cytoskeleton, transport of materials, local translation of messenger RNAs and the insertion of new membrane and cell surface molecules. In axons that have an intrinsic ability to regenerate, these processes are executed in a timely fashion. However, in axons that lack regenerative capacity, such as those of the mammalian CNS, several of the steps that are required for regeneration fail, and these axons do not begin the growth process. Identification of the points of failure can suggest targets for promoting regeneration.
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Combined computational and experimental approaches to understanding the Ca(2+) regulatory network in neurons. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:569-601. [PMID: 22453961 DOI: 10.1007/978-94-007-2888-2_26] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Ca(2+) is a ubiquitous signaling ion that regulates a variety of neuronal functions by binding to and altering the state of effector proteins. Spatial relationships and temporal dynamics of Ca(2+) elevations determine many cellular responses of neurons to chemical and electrical stimulation. There is a wealth of information regarding the properties and distribution of Ca(2+) channels, pumps, exchangers, and buffers that participate in Ca(2+) regulation. At the same time, new imaging techniques permit characterization of evoked Ca(2+) signals with increasing spatial and temporal resolution. However, understanding the mechanistic link between functional properties of Ca(2+) handling proteins and the stimulus-evoked Ca(2+) signals they orchestrate requires consideration of the way Ca(2+) handling mechanisms operate together as a system in native cells. A wide array of biophysical modeling approaches is available for studying this problem and can be used in a variety of ways. Models can be useful to explain the behavior of complex systems, to evaluate the role of individual Ca(2+) handling mechanisms, to extract valuable parameters, and to generate predictions that can be validated experimentally. In this review, we discuss recent advances in understanding the underlying mechanisms of Ca(2+) signaling in neurons via mathematical modeling. We emphasize the value of developing realistic models based on experimentally validated descriptions of Ca(2+) transport and buffering that can be tested and refined through new experiments to develop increasingly accurate biophysical descriptions of Ca(2+) signaling in neurons.
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21
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Ghadiri MK, Kozian M, Ghaffarian N, Stummer W, Kazemi H, Speckmann EJ, Gorji A. Sequential changes in neuronal activity in single neocortical neurons after spreading depression. Cephalalgia 2011; 32:116-24. [PMID: 22174359 DOI: 10.1177/0333102411431308] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
BACKGROUND Cortical spreading depression (CSD) has an important role in migraine with aura. Prolonged neuronal depression is followed by a late excitatory synaptic plasticity after CSD. METHOD Intra- and extracellular recordings were performed to investigate the effect of CSD on intracellular properties of mouse neocortical tissues in the late excitatory period. RESULTS During CSD, changes in the membrane potentials usually began with a relatively short hyperpolarization followed by an abrupt depolarization. These changes occurred roughly at the same time point after CSD as the beginning of the negative extracellular deflection. Forty-five minutes after CSD, neurons showed significantly smaller amplitude of afterhyperpolarization and a reduced input resistance. Depolarization and hyperpolarization of the cells by constant intracellular current injections in this period significantly changed the frequency of the action potentials. CONCLUSION These data indicate higher excitability of the neocortical neurons after CSD, which can be assumed to contribute to hyperexcitability of neocortical tissues in patients suffering from migraine.
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Affiliation(s)
- Maryam Khaleghi Ghadiri
- Klinik und Poliklinik für Neurochirurgie, Westfälische Wilhelms-Universität Münster, Germany
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22
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1α,25(OH)2-Vitamin D3 stimulates rapid plasma membrane calcium influx via MAPK activation in immature rat Sertoli cells. Biochimie 2011; 94:146-54. [PMID: 22015633 DOI: 10.1016/j.biochi.2011.10.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2011] [Accepted: 10/05/2011] [Indexed: 11/20/2022]
Abstract
It was characterized that the rapid response to 1α,25(OH)(2)-vitamin D(3) (1,25D(3)) on (45)Ca(2+) influx in rat Sertoli cells was mediated by voltage-dependent Ca(2+) channels (VDCCs), PKC, ERK1/2 and p38 MAPK pathways. In primary culture of 10 day-old rat Sertoli cells as well as in the whole testis, the time-course of (45)Ca(2+) influx did not change significantly in basal conditions. However, 1,25D(3) showed stimulatory effect on (45)Ca(2+) influx from 10(-15) to 10(-8) M after 60 s of incubation. The maximum effect was around 140% at 10(-12) M on purified Sertoli cells showing a steady state on (45)Ca(2+) influx between 10(-11) and 10(-9) M. Under this experimental condition, 1,25D(3) stimulated (45)Ca(2+) influx from 73% to 106% and no effect was observed at 10(-16), 10(-8) and 10(-7) M in whole testis. VDCC activities are mandatory for a full and complete stimulatory effect of 1,25D(3) in these approaches. K(+) and Cl(-) channels also are strongly involved in this rapid response coordinated by 1,25D(3). The participation of some selected kinases, points to PKC and ERK1/2 upstream activity to p38 MAPK activation suggesting an intracellular cross-talk between rapid (45)Ca(2+) influx and nuclear events. In addition, the comparative effect of microtubule disassembles and ClC-3 channel blocker on (45)Ca(2+) influx provides evidence of secretory activity of Sertoli cells triggered by 1,25D(3). Our results suggest that 1,25D(3) activates p38 MAPK and reorganizes microtubules, involving Ca(2+), PKC and ERK1/2 as upstream regulators and that extracellular Ca(2+) have a central role to rapidly start hormone-induced gene transcription and/or the secretory activity of Sertoli cell.
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Faas GC, Mody I. Measuring the kinetics of calcium binding proteins with flash photolysis. Biochim Biophys Acta Gen Subj 2011; 1820:1195-204. [PMID: 22001612 DOI: 10.1016/j.bbagen.2011.09.012] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Accepted: 09/22/2011] [Indexed: 11/19/2022]
Abstract
BACKGROUND Calcium-binding proteins (CBPs) are instrumental in the control of Ca2+ signaling. They are the fastest players within the Ca2+ toolkit responding within microseconds to [Ca2+] changes. The CBPs compete for Ca2+ which plays a direct role in modulating Ca2+ transients and the resulting biochemical message. The kinetic properties of the CBPs have to be known to have a good understanding of Ca2+ signaling. SCOPE OF REVIEW Most techniques used to measure binding kinetics are too slow to accurately determine the fast kinetics of most CBP. Furthermore, many CBPs bind Ca2+ in a cooperative way, which should be incorporated in the kinetic modeling. Here we will review a new ultra-fast in vitro technique for measuring Ca2+ binding properties of CBPs following flash photolysis of caged Ca2+. Compartmental modeling is used to resolve the kinetics of fast cooperative Ca2+ binding to CBPs. MAJOR CONCLUSIONS Currently this technique has only been used to quantify the kinetics of three CBPs (calbindin, calretinin and calmodulin), but has already provided remarkable insights into the specific role that these kinetics in Ca2+ signaling. GENERAL SIGNIFICANCE The potential to gain novel insights into Ca2+ signaling by quantifying kinetics of other CBPs using this technique is very promising. This article is part of a Special Issue entitled Biochemical, biophysical and genetic approaches to intracellular calcium signaling.
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Affiliation(s)
- Guido C Faas
- Department of Neurology, UCLA David Geffen School of Medicine, NRB 1, Room 575E, 635 Charles Young Drive South, Los Angeles, CA 90095-7335, USA.
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24
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Spontaneous glutamate release is independent of calcium influx and tonically activated by the calcium-sensing receptor. J Neurosci 2011; 31:4593-606. [PMID: 21430159 DOI: 10.1523/jneurosci.6398-10.2011] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Spontaneous release of glutamate is important for maintaining synaptic strength and controlling spike timing in the brain. Mechanisms regulating spontaneous exocytosis remain poorly understood. Extracellular calcium concentration ([Ca(2+)](o)) regulates Ca(2+) entry through voltage-activated calcium channels (VACCs) and consequently is a pivotal determinant of action potential-evoked vesicle fusion. Extracellular Ca(2+) also enhances spontaneous release, but via unknown mechanisms. Here we report that external Ca(2+) triggers spontaneous glutamate release more weakly than evoked release in mouse neocortical neurons. Blockade of VACCs has no effect on the spontaneous release rate or its dependence on [Ca(2+)](o). Intracellular [Ca(2+)] slowly increases in a minority of neurons following increases in [Ca(2+)](o). Furthermore, the enhancement of spontaneous release by extracellular calcium is insensitive to chelation of intracellular calcium by BAPTA. Activation of the calcium-sensing receptor (CaSR), a G-protein-coupled receptor present in nerve terminals, by several specific agonists increased spontaneous glutamate release. The frequency of spontaneous synaptic transmission was decreased in CaSR mutant neurons. The concentration-effect relationship for extracellular calcium regulation of spontaneous release was well described by a combination of CaSR-dependent and CaSR-independent mechanisms. Overall these results indicate that extracellular Ca(2+) does not trigger spontaneous glutamate release by simply increasing calcium influx but stimulates CaSR and thereby promotes resting spontaneous glutamate release.
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Giacomello M, Girardi S, Scorzeto M, Peruffo A, Maschietto M, Cozzi B, Vassanelli S. Stimulation of Ca²+ signals in neurons by electrically coupled electrolyte-oxide-semiconductor capacitors. J Neurosci Methods 2011; 198:1-7. [PMID: 21345350 DOI: 10.1016/j.jneumeth.2011.02.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Revised: 02/10/2011] [Accepted: 02/11/2011] [Indexed: 01/12/2023]
Abstract
Electrolyte-oxide-semiconductor capacitors (EOSCs) are a class of microtransducers for extracellular electrical stimulation that have been successfully employed to activate voltage-dependent sodium channels at the neuronal soma to generate action potentials in vitro. In the present work, we report on their use to control Ca²+ signalling in cultured mammalian cells, including neurons. Evidence is provided that EOSC stimulation with voltage waveforms in the microsecond or nanosecond range activates two distinct Ca²+ pathways, either by triggering Ca²+ entry through the plasma membrane or its release from intracellular stores. Ca²+ signals were activated in non-neuronal and neuronal cell lines, CHO-K1 and SH-SY5Y. On this basis, stimulation was tailored to rat and bovine neurons to mimic physiological somatic Ca²+ transients evoked by glutamate. Being minimally invasive and easy to use, the new method represents a versatile complement to standard electrophysiology and imaging techniques for the investigation of Ca²+ signalling in dissociated primary neurons and cell lines.
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Affiliation(s)
- M Giacomello
- Department of Experimental Veterinary Science, University of Padova, viale dell'Università 16, 35020 Legnaro-Agripolis (PD), Italy
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Kenyon KA, Bushong EA, Mauer AS, Strehler EE, Weinberg RJ, Burette AC. Cellular and subcellular localization of the neuron-specific plasma membrane calcium ATPase PMCA1a in the rat brain. J Comp Neurol 2010; 518:3169-83. [PMID: 20575074 PMCID: PMC2894304 DOI: 10.1002/cne.22409] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Regulation of intracellular calcium is crucial both for proper neuronal function and survival. By coupling ATP hydrolysis with Ca(2+) extrusion from the cell, the plasma membrane calcium-dependent ATPases (PMCAs) play an essential role in controlling intracellular calcium levels in neurons. In contrast to PMCA2 and PMCA3, which are expressed in significant levels only in the brain and a few other tissues, PMCA1 is ubiquitously distributed, and is thus widely believed to play a "housekeeping" function in mammalian cells. Whereas the PMCA1b splice variant is predominant in most tissues, an alternative variant, PMCA1a, is the major form of PMCA1 in the adult brain. Here, we use immunohistochemistry to analyze the cellular and subcellular distribution of PMCA1a in the brain. We show that PMCA1a is not ubiquitously expressed, but rather is confined to neurons, where it concentrates in the plasma membrane of somata, dendrites, and spines. Thus, rather than serving a general housekeeping function, our data suggest that PMCA1a is a calcium pump specialized for neurons, where it may contribute to the modulation of somatic and dendritic Ca(2+) transients.
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Affiliation(s)
- Katharine A Kenyon
- Department of Cell and Developmental Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA
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27
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Hickey CM, Geiger JE, Groten CJ, Magoski NS. Mitochondrial Ca2+ Activates a Cation Current in Aplysia Bag Cell Neurons. J Neurophysiol 2010; 103:1543-56. [DOI: 10.1152/jn.01121.2009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Ion channels may be gated by Ca2+ entering from the extracellular space or released from intracellular stores—typically the endoplasmic reticulum. The present study examines how Ca2+ impacts ion channels in the bag cell neurons of Aplysia californica. These neuroendocrine cells trigger ovulation through an afterdischarge involving Ca2+ influx from Ca2+ channels and Ca2+ release from both the mitochondria and endoplasmic reticulum. Liberating mitochondrial Ca2+ with the protonophore, carbonyl cyanide-4-trifluoromethoxyphenyl-hydrazone (FCCP), depolarized bag cell neurons, whereas depleting endoplasmic reticulum Ca2+ with the Ca2+-ATPase inhibitor, cyclopiazonic acid, did not. In a concentration-dependent manner, FCCP elicited an inward current associated with an increase in conductance and a linear current/voltage relationship that reversed near −40 mV. The reversal potential was unaffected by changing intracellular Cl−, but left-shifted when extracellular Ca2+ was removed and right-shifted when intracellular K+ was decreased. Strong buffering of intracellular Ca2+ decreased the current, although the response was not altered by blocking Ca2+-dependent proteases. Furthermore, fura imaging demonstrated that FCCP elevated intracellular Ca2+ with a time course similar to the current itself. Inhibiting either the V-type H+-ATPase or the ATP synthetase failed to produce a current, ruling out acidic Ca2+ stores or disruption of ATP production as mechanisms for the FCCP response. Similarly, any involvement of reactive oxygen species potentially produced by mitochondrial depolarization was mitigated by the fact that dialysis with xanthine/xanthine oxidase did not evoke an inward current. However, both the FCCP-induced current and Ca2+ elevation were diminished by disabling the mitochondrial permeability transition pore with the alkylating agent, N-ethylmaleimide. The data suggest that mitochondrial Ca2+ gates a voltage-independent, nonselective cation current with the potential to drive the afterdischarge and contribute to reproduction. Employing Ca2+ from mitochondria, rather than the more common endoplasmic reticulum, represents a diversification of the mechanisms that influence neuronal activity.
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Affiliation(s)
| | - Julia E. Geiger
- Department of Physiology, Queen's University, Kingston, Ontario, Canada
| | - Chris J. Groten
- Department of Physiology, Queen's University, Kingston, Ontario, Canada
| | - Neil S. Magoski
- Department of Physiology, Queen's University, Kingston, Ontario, Canada
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Desai-Shah M, Cooper RL. Different mechanisms of Ca2+ regulation that influence synaptic transmission: comparison between crayfish and Drosophila neuromuscular junctions. Synapse 2010; 63:1100-21. [PMID: 19650116 DOI: 10.1002/syn.20695] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A brief historical background on synaptic transmission in relation to Ca(2+) dynamics and short-term facilitation is described. This study focuses on the mechanisms responsible for the regulation of intracellular calcium concentration ([Ca(2+)](i)) in high output terminals of larval Drosophila compared to a low-output terminal of the crayfish neuromuscular junction (NMJ). Three processes; plasmalemmal Na(+)/Ca(2+) exchanger [NCX], Ca(2+)-ATPase (PMCA), and sarcoplasmic/endoplasmic Ca(2+)-ATPase (SERCA) are important in regulating the [Ca(2+)](i) are examined. When the NCX is compromised by reduced [Na(+)](o), no consistent effect occurred; but a NCX blocker KB-R7943 decreased the excitatory postsynaptic potential (EPSP) amplitudes. Compromising the PMCA with pH 8.8 resulted in an increase in EPSP amplitude but treatment with a PMCA specific inhibitor carboxyeosin produced opposite results. Thapsigargin exposure to block the SERCA generally decreases EPSP amplitude. Compromising the activity of the above Ca(2+) regulating proteins had no substantial effects on short-term depression. The Kum(170TS) strain (with dysfunctional SERCA), showed a decrease in EPSP amplitudes including the first EPSP within the train. Synaptic transmission is altered by reducing the function of the above three [Ca(2+)](i) regulators; but they are not consistent among different species as expected. Results in crayfish NMJ were more consistent with expected results as compared to the Drosophila NMJ. It is predicated that different mechanisms are used for regulating the [Ca(2+)](i) in high and low output synaptic terminals.
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Affiliation(s)
- Mohati Desai-Shah
- Department of Biology, University of Kentucky, Lexington, Kentucky 40506-0225, USA
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Chiel HJ, McManus JM, Shaw KM. From biology to mathematical models and back: teaching modeling to biology students, and biology to math and engineering students. CBE LIFE SCIENCES EDUCATION 2010; 9:248-65. [PMID: 20810957 PMCID: PMC2931672 DOI: 10.1187/cbe.10-03-0022] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
We describe the development of a course to teach modeling and mathematical analysis skills to students of biology and to teach biology to students with strong backgrounds in mathematics, physics, or engineering. The two groups of students have different ways of learning material and often have strong negative feelings toward the area of knowledge that they find difficult. To give students a sense of mastery in each area, several complementary approaches are used in the course: 1) a "live" textbook that allows students to explore models and mathematical processes interactively; 2) benchmark problems providing key skills on which students make continuous progress; 3) assignment of students to teams of two throughout the semester; 4) regular one-on-one interactions with instructors throughout the semester; and 5) a term project in which students reconstruct, analyze, extend, and then write in detail about a recently published biological model. Based on student evaluations and comments, an attitude survey, and the quality of the students' term papers, the course has significantly increased the ability and willingness of biology students to use mathematical concepts and modeling tools to understand biological systems, and it has significantly enhanced engineering students' appreciation of biology.
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Affiliation(s)
- Hillel J Chiel
- Departments of Biology, Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106-7080, USA.
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Behringer EJ, Leite LD, Buchholz NE, Keeney MG, Pearce WJ, Vanterpool CK, Wilson SM, Buchholz JN. Maturation and long-term hypoxia alters Ca2+-induced Ca2+ release in sheep cerebrovascular sympathetic neurons. J Appl Physiol (1985) 2009; 107:1223-34. [PMID: 19644029 PMCID: PMC2763832 DOI: 10.1152/japplphysiol.00363.2009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2009] [Accepted: 07/24/2009] [Indexed: 11/22/2022] Open
Abstract
The contribution of sympathetic nerves arising from the superior cervical ganglia (SCG) toward the growth and function of cerebral blood vessels is pertinent throughout maturation as well as in response to cardiovascular stress imposed by high-altitude long-term hypoxia (LTH). The function of SCG sympathetic neurons is dependent on intracellular Ca2+ concentration ([Ca2+]i) signaling, which is strongly influenced by a process known as Ca(2+)-induced Ca2+ release (CICR) from the smooth endoplasmic reticulum (SER). In this study, we used the sheep SCG neuronal model to test the hypotheses that maturation decreases CICR and high-altitude LTH depresses CICR in fetal SCG neurons but not in those of the adult. We found that the contribution of CICR to electric field stimulation (EFS)-evoked [Ca2+]i transients was greatest in SCG cells from normoxic fetuses and was abolished by LTH. The decline in CICR was associated with a reduction in sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) function in fetal SCG cells during LTH, reducing SER Ca2+ levels below the threshold needed for the coupling of Ca2+ influx and CICR. With respect to the maturation from the fetus to adult, the decrease in CICR may reflect both a reduction in the levels of ryanodine receptor isoforms 2 and 3 and SERCA function. In response to LTH and in contrast to the fetus, CICR function in adult SCG cells is maintained and may reflect alterations in other mechanisms that modulate the CICR process. As CICR is instrumental in the function of sympathetic neurons within the cerebrovasculature, the loss of this signaling mechanism in the fetus may have consequences for the adaptation to LTH in terms of fetal susceptibility to vascular insults.
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Affiliation(s)
- Erik J Behringer
- Department of Physiology and Pharmacology, Loma Linda Univ. School of Medicine, Loma Linda, CA 92350, USA
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31
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Ca2+ entry through a non-selective cation channel in Aplysia bag cell neurons. Neuroscience 2009; 162:1023-38. [DOI: 10.1016/j.neuroscience.2009.05.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2009] [Revised: 05/03/2009] [Accepted: 05/05/2009] [Indexed: 11/20/2022]
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Nagarkatti N, Deshpande LS, DeLorenzo RJ. Development of the calcium plateau following status epilepticus: role of calcium in epileptogenesis. Expert Rev Neurother 2009; 9:813-24. [PMID: 19496685 DOI: 10.1586/ern.09.21] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Status epilepticus is a clinical emergency defined as continuous seizure activity or rapid, recurrent seizures without regaining consciousness and can lead to the development of acquired epilepsy, characterized by spontaneous, recurrent seizures. Understanding epileptogenesis--the transformation of healthy brain tissue into hyperexcitable neuronal networks--is an important challenge and the elucidation of molecular mechanisms can lend insight into new therapeutic targets to halt this progression. It has been demonstrated that intracellular calcium increases during status epilepticus and that these elevations are maintained past the duration of the injury (Ca(2+) plateau). As an important second messenger, Ca(2+) elevations can lead to changes in gene expression, neurotransmitter release and plasticity. Thus, characterization of the post-injury Ca(2+) plateau may be important in eventually understanding the pathophysiology of epileptogenesis and preventing the progression to chronic epilepsy after brain injury.
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Affiliation(s)
- Nisha Nagarkatti
- Department of , Virginia Commonwealth University, Richmond, VA 23298, USA.
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33
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Sehring IM, Klotz C, Beisson J, Plattner H. Rapid downregulation of the Ca2+-signal after exocytosis stimulation in Paramecium cells: essential role of a centrin-rich filamentous cortical network, the infraciliary lattice. Cell Calcium 2008; 45:89-97. [PMID: 18653233 DOI: 10.1016/j.ceca.2008.06.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2008] [Revised: 04/15/2008] [Accepted: 06/17/2008] [Indexed: 01/18/2023]
Abstract
We analysed in Paramecium tetraurelia cells the role of the infraciliary lattice, a cytoskeletal network containing numerous centrin isoforms tightly bound to large binding proteins, in the re-establishment of Ca2+ homeostasis following exocytosis stimulation. The wild type strain d4-2 has been compared with the mutant cell line Delta-PtCenBP1 which is devoid of the infraciliary lattice ("Delta-PtCenBP1" cells). Exocytosis is known to involve the mobilization of cortical Ca2+-stores and a superimposed Ca2+-influx and was analysed using Fura Red ratio imaging. No difference in the initial signal generation was found between wild type and Delta-PtCenBP1 cells. In contrast, decay time was greatly increased in Delta-PtCenBP1 cells particularly when stimulated, e.g., in presence of 1mM extracellular Ca2+, [Ca2+]o. Apparent halftimes of f/f0 decrease were 8.5 s in wild type and approximately 125 s in Delta-PtCenBP1 cells, requiring approximately 30 s and approximately 180 s, respectively, to re-establish intracellular [Ca2+] homeostasis. Lowering [Ca2+]o to 0.1 and 0.01 mM caused an acceleration of intracellular [Ca2+] decay to t(1/2)=33 s and 28 s, respectively, in Delta-PtCenBP1 cells as compared to 8.1 and 5.6, respectively, for wild type cells. We conclude that, in Paramecium cells, the infraciliary lattice is the most efficient endogenous Ca2+ buffering system allowing the rapid downregulation of Ca2+ signals after exocytosis stimulation.
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Affiliation(s)
- Ivonne M Sehring
- Department of Biology, University of Konstanz, P.O. Box 5560, 78457 Konstanz, Germany
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Geiger JE, Magoski NS. Ca2+-induced Ca2+ release in Aplysia bag cell neurons requires interaction between mitochondrial and endoplasmic reticulum stores. J Neurophysiol 2008; 100:24-37. [PMID: 18463180 DOI: 10.1152/jn.90356.2008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Intracellular Ca2+ is influenced by both Ca2+ influx and release. We examined intracellular Ca2+ following action potential firing in the bag cell neurons of Aplysia californica. Following brief synaptic input, these neuroendocrine cells undergo an afterdischarge, resulting in elevated Ca2+ and the secretion of neuropeptides to initiate reproduction. Cultured bag cell neurons were injected with the Ca2+ indicator, fura-PE3, and subjected to simultaneous imaging and electrophysiology. Delivery of a 5-Hz, 1-min train of action potentials (mimicking the fast phase of the afterdischarge) produced a Ca2+ rise that markedly outlasted the initial influx, consistent with Ca2+-induced Ca2+ release (CICR). This response was attenuated by about half with ryanodine or depletion of the endoplasmic reticulum (ER) by cyclopiazonic acid. However, depletion of the mitochondria, with carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone, essentially eliminated CICR. Dual depletion of the ER and mitochondria did not reduce CICR further than depletion of the mitochondria alone. Moreover, tetraphenylphosphonium, a blocker of mitochondrial Ca2+ release, largely prevented CICR. The Ca2+ elevation during and subsequent to a stimulus mimicking the full afterdischarge was prominent and enhanced by protein kinase C activation. Traditionally, the ER is seen as the primary Ca2+ source for CICR. However, bag cell neuron CICR represents a departure from this view in that it relies on store interaction, where Ca2+ released from the mitochondria may in turn liberate Ca2+ from the ER. This unique form of CICR may be used by both bag cell neurons, and other neurons, to initiate secretion, activate channels, or induce gene expression.
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Affiliation(s)
- Julia E Geiger
- Department of Physiology, Queen's University, Kingston, Ontario, Canada
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