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Pali E, D’Angelo E, Prestori F. Understanding Cerebellar Input Stage through Computational and Plasticity Rules. BIOLOGY 2024; 13:403. [PMID: 38927283 PMCID: PMC11200477 DOI: 10.3390/biology13060403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2024] [Revised: 05/21/2024] [Accepted: 05/27/2024] [Indexed: 06/28/2024]
Abstract
A central hypothesis concerning brain functioning is that plasticity regulates the signal transfer function by modifying the efficacy of synaptic transmission. In the cerebellum, the granular layer has been shown to control the gain of signals transmitted through the mossy fiber pathway. Until now, the impact of plasticity on incoming activity patterns has been analyzed by combining electrophysiological recordings in acute cerebellar slices and computational modeling, unraveling a broad spectrum of different forms of synaptic plasticity in the granular layer, often accompanied by forms of intrinsic excitability changes. Here, we attempt to provide a brief overview of the most prominent forms of plasticity at the excitatory synapses formed by mossy fibers onto primary neuronal components (granule cells, Golgi cells and unipolar brush cells) in the granular layer. Specifically, we highlight the current understanding of the mechanisms and their functional implications for synaptic and intrinsic plasticity, providing valuable insights into how inputs are processed and reconfigured at the cerebellar input stage.
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Affiliation(s)
- Eleonora Pali
- Department of Brain and Behavioral Sciences, University of Pavia, 27100 Pavia, Italy; (E.P.)
| | - Egidio D’Angelo
- Department of Brain and Behavioral Sciences, University of Pavia, 27100 Pavia, Italy; (E.P.)
- Digital Neuroscience Center, IRCCS Mondino Foundation, 27100 Pavia, Italy
| | - Francesca Prestori
- Department of Brain and Behavioral Sciences, University of Pavia, 27100 Pavia, Italy; (E.P.)
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2
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Mao F, Yang W. How Merkel cells transduce mechanical stimuli: A biophysical model of Merkel cells. PLoS Comput Biol 2023; 19:e1011720. [PMID: 38117763 PMCID: PMC10732429 DOI: 10.1371/journal.pcbi.1011720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2023] [Accepted: 11/27/2023] [Indexed: 12/22/2023] Open
Abstract
Merkel cells combine with Aβ afferents, producing slowly adapting type 1(SA1) responses to mechanical stimuli. However, how Merkel cells transduce mechanical stimuli into neural signals to Aβ afferents is still unclear. Here we develop a biophysical model of Merkel cells for mechanical transduction by incorporating main ingredients such as Ca2+ and K+ voltage-gated channels, Piezo2 channels, internal Ca2+ stores, neurotransmitters release, and cell deformation. We first validate our model with several experiments. Then we reveal that Ca2+ and K+ channels on the plasma membrane shape the depolarization of membrane potentials, further regulating the Ca2+ transients in the cells. We also show that Ca2+ channels on the plasma membrane mainly inspire the Ca2+ transients, while internal Ca2+ stores mainly maintain the Ca2+ transients. Moreover, we show that though Piezo2 channels are rapidly adapting mechanical-sensitive channels, they are sufficient to inspire sustained Ca2+ transients in Merkel cells, which further induce the release of neurotransmitters for tens of seconds. Thus our work provides a model that captures the membrane potentials and Ca2+ transients features of Merkel cells and partly explains how Merkel cells transduce the mechanical stimuli by Piezo2 channels.
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Affiliation(s)
- Fangtao Mao
- Research Center for Humanoid Sensing, Intelligent Perception Research Institute of Zhejiang Lab, Hangzhou, Zhejiang, China
| | - Wenzhen Yang
- Research Center for Humanoid Sensing, Intelligent Perception Research Institute of Zhejiang Lab, Hangzhou, Zhejiang, China
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3
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Paknejad N, Sapuru V, Hite RK. Structural titration reveals Ca 2+-dependent conformational landscape of the IP 3 receptor. Nat Commun 2023; 14:6897. [PMID: 37898605 PMCID: PMC10613215 DOI: 10.1038/s41467-023-42707-3] [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: 02/16/2023] [Accepted: 10/18/2023] [Indexed: 10/30/2023] Open
Abstract
Inositol 1,4,5-trisphosphate receptors (IP3Rs) are endoplasmic reticulum Ca2+ channels whose biphasic dependence on cytosolic Ca2+ gives rise to Ca2+ oscillations that regulate fertilization, cell division and cell death. Despite the critical roles of IP3R-mediated Ca2+ responses, the structural underpinnings of the biphasic Ca2+ dependence that underlies Ca2+ oscillations are incompletely understood. Here, we collect cryo-EM images of an IP3R with Ca2+ concentrations spanning five orders of magnitude. Unbiased image analysis reveals that Ca2+ binding does not explicitly induce conformational changes but rather biases a complex conformational landscape consisting of resting, preactivated, activated, and inhibited states. Using particle counts as a proxy for relative conformational free energy, we demonstrate that Ca2+ binding at a high-affinity site allows IP3Rs to activate by escaping a low-energy resting state through an ensemble of preactivated states. At high Ca2+ concentrations, IP3Rs preferentially enter an inhibited state stabilized by a second, low-affinity Ca2+ binding site. Together, these studies provide a mechanistic basis for the biphasic Ca2+-dependence of IP3R channel activity.
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Affiliation(s)
- Navid Paknejad
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, 10065, USA
- Physiology, Biophysics, and Systems Biology (PBSB) Program, Weill Cornell Graduate School of Biomedical Sciences, 1300 York Avenue, New York, NY, 10065, USA
| | - Vinay Sapuru
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, 10065, USA
- Physiology, Biophysics, and Systems Biology (PBSB) Program, Weill Cornell Graduate School of Biomedical Sciences, 1300 York Avenue, New York, NY, 10065, USA
| | - Richard K Hite
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, 10065, USA.
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Tambeaux A, Aguilar-Sánchez Y, Santiago DJ, Mascitti M, DiNovo KM, Mejía-Alvarez R, Fill M, Wayne Chen SR, Ramos-Franco J. Ligand sensitivity of type-1 inositol 1,4,5-trisphosphate receptor is enhanced by the D2594K mutation. Pflugers Arch 2023; 475:569-581. [PMID: 36881190 PMCID: PMC10105685 DOI: 10.1007/s00424-023-02796-x] [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: 11/28/2022] [Revised: 02/06/2023] [Accepted: 02/12/2023] [Indexed: 03/08/2023]
Abstract
Inositol 1,4,5-trisphosphate receptor (IP3R) and ryanodine receptor (RyR) are homologous cation channels that mediate release of Ca2+ from the endoplasmic/sarcoplasmic reticulum (ER/SR) and thereby are involved in many physiological processes. In previous studies, we determined that when the D2594 residue, located at or near the gate of the IP3R type 1, was replaced by lysine (D2594K), a gain of function was obtained. This mutant phenotype was characterized by increased IP3 sensitivity. We hypothesized the IP3R1-D2594 determines the ligand sensitivity of the channel by electrostatically affecting the stability of the closed and open states. To test this possibility, the relationship between the D2594 site and IP3R1 regulation by IP3, cytosolic, and luminal Ca2+ was determined at the cellular, subcellular, and single-channel levels using fluorescence Ca2+ imaging and single-channel reconstitution. We found that in cells, D2594K mutation enhances the IP3 ligand sensitivity. Single-channel IP3R1 studies revealed that the conductance of IP3R1-WT and -D2594K channels is similar. However, IP3R1-D2594K channels exhibit higher IP3 sensitivity, with substantially greater efficacy. In addition, like its wild type (WT) counterpart, IP3R1-D2594K showed a bell-shape cytosolic Ca2+-dependency, but D2594K had greater activity at each tested cytosolic free Ca2+ concentration. The IP3R1-D2594K also had altered luminal Ca2+ sensitivity. Unlike IP3R1-WT, D2594K channel activity did not decrease at low luminal Ca2+ levels. Taken together, our functional studies indicate that the substitution of a negatively charged residue by a positive one at the channels' pore cytosolic exit affects the channel's gating behavior thereby explaining the enhanced ligand-channel's sensitivity.
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Affiliation(s)
- Allison Tambeaux
- Department of Physiology and Biophysics, Rush University Medical Center, Chicago, IL, USA
| | - Yuriana Aguilar-Sánchez
- Department of Physiology and Biophysics, Rush University Medical Center, Chicago, IL, USA.,Molecular Physiology & Biophysics, Baylor College of Medicine, Houston, TX, USA
| | - Demetrio J Santiago
- Department of Physiology and Biophysics, Rush University Medical Center, Chicago, IL, USA.,Centro Nacional de Investigaciones Cardiovasculares, Madrid, Spain
| | | | - Karyn M DiNovo
- Department of Physiology, Midwestern University, Downers Grove, IL, USA
| | | | - Michael Fill
- Department of Physiology and Biophysics, Rush University Medical Center, Chicago, IL, USA
| | - S R Wayne Chen
- Department of Physiology and Biophysics, Rush University Medical Center, Chicago, IL, USA.,Department of Physiology and Pharmacology, Libin Cardiovascular Institute, University of Calgary, Calgary, AB, Canada
| | - Josefina Ramos-Franco
- Department of Physiology and Biophysics, Rush University Medical Center, Chicago, IL, USA.
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Atakpa-Adaji P, Ivanova A. IP 3R at ER-Mitochondrial Contact Sites: Beyond the IP 3R-GRP75-VDAC1 Ca 2+ Funnel. CONTACT (THOUSAND OAKS (VENTURA COUNTY, CALIF.)) 2023; 6:25152564231181020. [PMID: 37426575 PMCID: PMC10328019 DOI: 10.1177/25152564231181020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Accepted: 05/23/2023] [Indexed: 07/11/2023]
Abstract
Membrane contact sites (MCS) circumvent the topological constraints of functional coupling between different membrane-bound organelles by providing a means of communication and exchange of materials. One of the most characterised contact sites in the cell is that between the endoplasmic reticulum and the mitochondrial (ERMCS) whose function is to couple cellular Ca2+ homeostasis and mitochondrial function. Inositol 1,4,5-trisphosphate receptors (IP3Rs) on the ER, glucose-regulated protein 75 (GRP 75) and voltage-dependent anion channel 1 (VDAC1) on the outer mitochondrial membrane are the canonical component of the Ca2+ transfer unit at ERMCS. These are often reported to form a Ca2+ funnel that fuels the mitochondrial low-affinity Ca2+ uptake system. We assess the available evidence on the IP3R subtype selectivity at the ERMCS and consider if IP3Rs have other roles at the ERMCS beyond providing Ca2+. Growing evidence suggests that all three IP3R subtypes can localise and regulate Ca2+ signalling at ERMCS. Furthermore, IP3Rs may be structurally important for assembly of the ERMCS in addition to their role in providing Ca2+ at these sites. Evidence that various binding partners regulate the assembly and Ca2+ transfer at ERMCS populated by IP3R-GRP75-VDAC1, suggesting that cells have evolved mechanisms that stabilise these junctions forming a Ca2+ microdomain that is required to fuel mitochondrial Ca2+ uptake.
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Affiliation(s)
- Peace Atakpa-Adaji
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK
| | - Adelina Ivanova
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK
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Fan G, Baker MR, Terry LE, Arige V, Chen M, Seryshev AB, Baker ML, Ludtke SJ, Yule DI, Serysheva II. Conformational motions and ligand-binding underlying gating and regulation in IP 3R channel. Nat Commun 2022; 13:6942. [PMID: 36376291 PMCID: PMC9663519 DOI: 10.1038/s41467-022-34574-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 10/28/2022] [Indexed: 11/16/2022] Open
Abstract
Inositol-1,4,5-trisphosphate receptors (IP3Rs) are activated by IP3 and Ca2+ and their gating is regulated by various intracellular messengers that finely tune the channel activity. Here, using single particle cryo-EM analysis we determined 3D structures of the nanodisc-reconstituted IP3R1 channel in two ligand-bound states. These structures provide unprecedented details governing binding of IP3, Ca2+ and ATP, revealing conformational changes that couple ligand-binding to channel opening. Using a deep-learning approach and 3D variability analysis we extracted molecular motions of the key protein domains from cryo-EM density data. We find that IP3 binding relies upon intrinsic flexibility of the ARM2 domain in the tetrameric channel. Our results highlight a key role of dynamic side chains in regulating gating behavior of IP3R channels. This work represents a stepping-stone to developing mechanistic understanding of conformational pathways underlying ligand-binding, activation and regulation of the channel.
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Affiliation(s)
- Guizhen Fan
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, McGovern Medical School at The University of Texas Health Science Center at Houston, 6431, Fannin Street, Houston, TX, USA
| | - Mariah R Baker
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, McGovern Medical School at The University of Texas Health Science Center at Houston, 6431, Fannin Street, Houston, TX, USA
| | - Lara E Terry
- Department of Pharmacology and Physiology, School of Medicine and Dentistry, University of Rochester, Rochester, NY, USA
| | - Vikas Arige
- Department of Pharmacology and Physiology, School of Medicine and Dentistry, University of Rochester, Rochester, NY, USA
| | - Muyuan Chen
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX, USA
- SLAC National Accelerator Laboratory, Menlo Park, CA, USA
| | - Alexander B Seryshev
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, McGovern Medical School at The University of Texas Health Science Center at Houston, 6431, Fannin Street, Houston, TX, USA
| | - Matthew L Baker
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, McGovern Medical School at The University of Texas Health Science Center at Houston, 6431, Fannin Street, Houston, TX, USA
| | - Steven J Ludtke
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX, USA
| | - David I Yule
- Department of Pharmacology and Physiology, School of Medicine and Dentistry, University of Rochester, Rochester, NY, USA.
| | - Irina I Serysheva
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, McGovern Medical School at The University of Texas Health Science Center at Houston, 6431, Fannin Street, Houston, TX, USA.
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Arige V, Terry LE, Wagner LE, Malik S, Baker MR, Fan G, Joseph SK, Serysheva II, Yule DI. Functional determination of calcium-binding sites required for the activation of inositol 1,4,5-trisphosphate receptors. Proc Natl Acad Sci U S A 2022; 119:e2209267119. [PMID: 36122240 PMCID: PMC9522344 DOI: 10.1073/pnas.2209267119] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Accepted: 08/23/2022] [Indexed: 01/25/2023] Open
Abstract
Inositol 1,4,5-trisphosphate receptors (IP3Rs) initiate a diverse array of physiological responses by carefully orchestrating intracellular calcium (Ca2+) signals in response to various external cues. Notably, IP3R channel activity is determined by several obligatory factors, including IP3, Ca2+, and ATP. The critical basic amino acid residues in the N-terminal IP3-binding core (IBC) region that facilitate IP3 binding are well characterized. In contrast, the residues conferring regulation by Ca2+ have yet to be ascertained. Using comparative structural analysis of Ca2+-binding sites identified in two main families of intracellular Ca2+-release channels, ryanodine receptors (RyRs) and IP3Rs, we identified putative acidic residues coordinating Ca2+ in the cytosolic calcium sensor region in IP3Rs. We determined the consequences of substituting putative Ca2+ binding, acidic residues in IP3R family members. We show that the agonist-induced Ca2+ release, single-channel open probability (P0), and Ca2+ sensitivities are markedly altered when the negative charge on the conserved acidic side chain residues is neutralized. Remarkably, neutralizing the negatively charged side chain on two of the residues individually in the putative Ca2+-binding pocket shifted the Ca2+ required to activate IP3R to higher concentrations, indicating that these residues likely are a component of the Ca2+ activation site in IP3R. Taken together, our findings indicate that Ca2+ binding to a well-conserved activation site is a common underlying mechanism resulting in increased channel activity shared by IP3Rs and RyRs.
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Affiliation(s)
- Vikas Arige
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642
| | - Lara E. Terry
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642
| | - Larry E. Wagner
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642
| | - Sundeep Malik
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642
| | - Mariah R. Baker
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030
| | - Guizhen Fan
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030
| | - Suresh K. Joseph
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107
| | - Irina I. Serysheva
- Department of Biochemistry and Molecular Biology, Structural Biology Imaging Center, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030
| | - David I. Yule
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642
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Sokolov RA, Mukhina IV. Spontaneous Ca 2+ events are linked to the development of neuronal firing during maturation in mice primary hippocampal culture cells. Arch Biochem Biophys 2022; 727:109330. [PMID: 35750097 DOI: 10.1016/j.abb.2022.109330] [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: 01/31/2022] [Revised: 04/21/2022] [Accepted: 06/19/2022] [Indexed: 11/30/2022]
Abstract
Calcium is one of the most vital intracellular secondary messengers that tightly regulates a variety of cell physiology processes, especially in the brain. Using a fluorescent Ca2+-sensitive Oregon Green probe, we revealed three different amplitude distributions of spontaneous Ca2+ events (SCEs) in neurons between 15 and 26 days in vitro (DIV) culture maturation. We detected a series of amplitude events: micro amplitude SCE (microSCE) 25% increase from the baseline, intermediate amplitude SCE (interSCE) as 25-75%, and macro amplitude SCE (macroSCE) - over 75%. The SCEs were fully dependent on extracellular Ca2+ and neuronal network activity and vanished in the Ca2+-free solution, 10 mM Mg2+-block, or in the presence of voltage-gated Na+-channel blocker, tetrodotoxin. Combined patch-clamp and Ca2+-imaging techniques revealed that microSCE match single action potential (AP), interSCE - burst of 3-12 APs, and macroSCE - 'superburst' of 10+ APs. MicroSCEs were blocked by a common α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainic acid (KA) receptor antagonist, CNQX. The γ-aminobutyric acid (GABA) A-type receptor (GABAAR) picrotoxin blockade and L-type voltage-dependent Ca2+-channel inhibitor diltiazem significantly reduced microSCE frequency. InterSCEs were inhibited by CNQX, but picrotoxin treatment significantly increased its amplitude. The N-methyl-d-aspartate (NMDA) receptor antagonist, D-APV, voltage-gated K+-channel blocker, tetraethylammonium, noticeably suppressed interSCE amplitude. We also demonstrate that macroSCEs were AMPA/KA receptor-independent.
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Affiliation(s)
- Rostislav A Sokolov
- Institute of Biology and Biomedicine, Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod, Russia; In Vivo Research Center, Sirius University of Science and Technology, Olympic Avenue, 1, Sochi, Russia.
| | - Irina V Mukhina
- Institute of Biology and Biomedicine, Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod, Russia; Institute of Fundamental Medicine, Privolzhsky Research Medical University, Nizhny Novgorod, Russia.
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9
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Phillips RS, Rubin JE. Putting the theory into 'burstlet theory' with a biophysical model of burstlets and bursts in the respiratory preBötzinger complex. eLife 2022; 11:75713. [PMID: 35380537 PMCID: PMC9023056 DOI: 10.7554/elife.75713] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2021] [Accepted: 04/04/2022] [Indexed: 11/17/2022] Open
Abstract
Inspiratory breathing rhythms arise from synchronized neuronal activity in a bilaterally distributed brainstem structure known as the preBötzinger complex (preBötC). In in vitro slice preparations containing the preBötC, extracellular potassium must be elevated above physiological levels (to 7–9 mM) to observe regular rhythmic respiratory motor output in the hypoglossal nerve to which the preBötC projects. Reexamination of how extracellular K+ affects preBötC neuronal activity has revealed that low-amplitude oscillations persist at physiological levels. These oscillatory events are subthreshold from the standpoint of transmission to motor output and are dubbed burstlets. Burstlets arise from synchronized neural activity in a rhythmogenic neuronal subpopulation within the preBötC that in some instances may fail to recruit the larger network events, or bursts, required to generate motor output. The fraction of subthreshold preBötC oscillatory events (burstlet fraction) decreases sigmoidally with increasing extracellular potassium. These observations underlie the burstlet theory of respiratory rhythm generation. Experimental and computational studies have suggested that recruitment of the non-rhythmogenic component of the preBötC population requires intracellular Ca2+ dynamics and activation of a calcium-activated nonselective cationic current. In this computational study, we show how intracellular calcium dynamics driven by synaptically triggered Ca2+ influx as well as Ca2+ release/uptake by the endoplasmic reticulum in conjunction with a calcium-activated nonselective cationic current can reproduce and offer an explanation for many of the key properties associated with the burstlet theory of respiratory rhythm generation. Altogether, our modeling work provides a mechanistic basis that can unify a wide range of experimental findings on rhythm generation and motor output recruitment in the preBötC.
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Rosa N, Sneyers F, Parys JB, Bultynck G. Type 3 IP 3 receptors: The chameleon in cancer. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2020; 351:101-148. [PMID: 32247578 DOI: 10.1016/bs.ircmb.2020.02.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs), intracellular calcium (Ca2+) release channels, fulfill key functions in cell death and survival processes, whose dysregulation contributes to oncogenesis. This is essentially due to the presence of IP3Rs in microdomains of the endoplasmic reticulum (ER) in close proximity to the mitochondria. As such, IP3Rs enable efficient Ca2+ transfers from the ER to the mitochondria, thus regulating metabolism and cell fate. This review focuses on one of the three IP3R isoforms, the type 3 IP3R (IP3R3), which is linked to proapoptotic ER-mitochondrial Ca2+ transfers. Alterations in IP3R3 expression have been highlighted in numerous cancer types, leading to dysregulations of Ca2+ signaling and cellular functions. However, the outcome of IP3R3-mediated Ca2+ transfers for mitochondrial function is complex with opposing effects on oncogenesis. IP3R3 can either suppress cancer by promoting cell death and cellular senescence or support cancer by driving metabolism, anabolic processes, cell cycle progression, proliferation and invasion. The aim of this review is to provide an overview of IP3R3 dysregulations in cancer and describe how such dysregulations alter critical cellular processes such as proliferation or cell death and survival. Here, we pose that the IP3R3 isoform is not only linked to proapoptotic ER-mitochondrial Ca2+ transfers but might also be involved in prosurvival signaling.
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Affiliation(s)
- Nicolas Rosa
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Kanker Instituut (LKI), Leuven, Belgium
| | - Flore Sneyers
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Kanker Instituut (LKI), Leuven, Belgium
| | - Jan B Parys
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Kanker Instituut (LKI), Leuven, Belgium
| | - Geert Bultynck
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Kanker Instituut (LKI), Leuven, Belgium.
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11
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Conceptual Evolution of Cell Signaling. Int J Mol Sci 2019; 20:ijms20133292. [PMID: 31277491 PMCID: PMC6651758 DOI: 10.3390/ijms20133292] [Citation(s) in RCA: 68] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 06/26/2019] [Accepted: 06/28/2019] [Indexed: 12/27/2022] Open
Abstract
During the last 100 years, cell signaling has evolved into a common mechanism for most physiological processes across systems. Although the majority of cell signaling principles were initially derived from hormonal studies, its exponential growth has been supported by interdisciplinary inputs, e.g., from physics, chemistry, mathematics, statistics, and computational fields. As a result, cell signaling has grown out of scope for any general review. Here, we review how the messages are transferred from the first messenger (the ligand) to the receptor, and then decoded with the help of cascades of second messengers (kinases, phosphatases, GTPases, ions, and small molecules such as cAMP, cGMP, diacylglycerol, etc.). The message is thus relayed from the membrane to the nucleus where gene expression ns, subsequent translations, and protein targeting to the cell membrane and other organelles are triggered. Although there are limited numbers of intracellular messengers, the specificity of the response profiles to the ligands is generated by the involvement of a combination of selected intracellular signaling intermediates. Other crucial parameters in cell signaling are its directionality and distribution of signaling strengths in different pathways that may crosstalk to adjust the amplitude and quality of the final effector output. Finally, we have reflected upon its possible developments during the coming years.
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Takeda Y. [Theoretical Investigations into the Quantitative Mechanisms Underlying the Regulation of [cAMP]i, Membrane Excitability and [Ca(2+)]i during GLP-1 Stimulation in Pancreatic β Cells]. YAKUGAKU ZASSHI 2017; 136:467-71. [PMID: 26935088 DOI: 10.1248/yakushi.15-00246-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Upon elevation of plasma glucose concentration, pancreatic β-cells generate bursts of action potentials to induce cyclic changes in [Ca(2+)]i regulating insulin release. Glucose-dependent insulin secretion is synergistically enhanced by glucagon-like peptide-1 (GLP-1), which increases [cAMP]i and activates protein kinase A (PKA) and exchange protein activated by cAMP (Epac). The insulinotropic effect of GLP-1 is mediated, at least in part, by modulating multiple ion channels/transporters at the plasma membrane and ER through PKA- and EPAC-dependent mechanisms, which increase membrane excitability and intracellular Ca(2+) release. However, because of complex interactions between multiple cellular factors involved in the GLP-1 effects, quantitative aspects of the molecular/ionic mechanisms have not yet been determined. We thus performed simulation studies and mathematical analysis to investigate how GLP-1 signals control [cAMP]i and subsequently modify the bursting activities and Ca(2+) dynamics. First, a GLP-1 receptor signal transduction model was developed and introduced to our β-cells model. Secondly, modulatory effects of PKA/Epac on ion channels/transporters were incorporated based on experimental studies. Increases in the frequency and duration of the bursting activity observed during GLP-1 stimulation were well reconstructed by our model, and lead potential analysis quantitatively determined the functional role of each ion channel/transporter in modifying the burst pattern. Finally, an IP3R model was developed to reproduce GLP-1-induced Ca(2+) transients/oscillations. Instantaneous equilibrium analysis and bifurcation analysis also elucidated the quantitative mechanisms involved in generating IP3R-mediated Ca(2+) mobilization. The results of this theoretical analysis of the effects of GLP-1 on membrane excitability/Ca(2+) dynamics are discussed in this review.
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Affiliation(s)
- Yukari Takeda
- Department of Bioinformatics, College of Life Sciences, Ritsumeikan University
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Takeda Y, Shimayoshi T, Holz GG, Noma A. Modeling analysis of inositol 1,4,5-trisphosphate receptor-mediated Ca2+ mobilization under the control of glucagon-like peptide-1 in mouse pancreatic β-cells. Am J Physiol Cell Physiol 2016; 310:C337-47. [PMID: 26741144 PMCID: PMC4888524 DOI: 10.1152/ajpcell.00234.2015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 11/19/2015] [Indexed: 01/22/2023]
Abstract
Glucagon-like peptide-1 (GLP-1) is an intestinally derived blood glucose-lowering hormone that potentiates glucose-stimulated insulin secretion from pancreatic β-cells. The secretagogue action of GLP-1 is explained, at least in part, by its ability to stimulate cAMP production so that cAMP may facilitate the release of Ca(2+) from inositol trisphosphate receptor (IP3R)-regulated Ca(2+) stores. However, a quantitative model has yet to be provided that explains the molecular mechanisms and dynamic processes linking GLP-1-stimulated cAMP production to Ca(2+) mobilization. Here, we performed simulation studies to investigate how GLP-1 alters the abilities of Ca(2+) and IP3 to act as coagonists at IP3R Ca(2+) release channels. A new dynamic model was constructed based on the Kaftan model, which demonstrates dual steady-state allosteric regulation of the IP3R by Ca(2+) and IP3. Data obtained from β-cells were then analyzed to understand how GLP-1 facilitates IP3R-mediated Ca(2+) mobilization when UV flash photolysis is used to uncage Ca(2+) and IP3 intracellularly. When the dynamic model for IP3R activation was incorporated into a minimal cell model, the Ca(2+) transients and oscillations induced by GLP-1 were successfully reconstructed. Simulation studies indicated that transient and oscillatory responses to GLP-1 were produced by sequential positive and negative feedback regulation due to fast activation and slow inhibition of the IP3R by Ca(2+). The slow rate of Ca(2+)-dependent inhibition was revealed to provide a remarkable contribution to the time course of the decay of cytosolic Ca(2+) transients. It also served to drive and pace Ca(2+) oscillations that are significant when evaluating how GLP-1 stimulates insulin secretion.
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Affiliation(s)
- Yukari Takeda
- Department of Bioinformatics, College of Life Sciences, Ritsumeikan University, Kusatsu City, Japan;
| | - Takao Shimayoshi
- Department of Systems Science, Kyoto University, Kyoto, Japan; and
| | - George G Holz
- Departments of Medicine and Pharmacology, SUNY Upstate Medical University, Syracuse, New York
| | - Akinori Noma
- Department of Bioinformatics, College of Life Sciences, Ritsumeikan University, Kusatsu City, Japan
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Pecze L, Blum W, Schwaller B. Routes of Ca2+ Shuttling during Ca2+ Oscillations: FOCUS ON THE ROLE OF MITOCHONDRIAL Ca2+ HANDLING AND CYTOSOLIC Ca2+ BUFFERS. J Biol Chem 2015; 290:28214-28230. [PMID: 26396196 PMCID: PMC4653679 DOI: 10.1074/jbc.m115.663179] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Indexed: 01/29/2023] Open
Abstract
In some cell types, Ca2+ oscillations are strictly dependent on Ca2+ influx across the plasma membrane, whereas in others, oscillations also persist in the absence of Ca2+ influx. We observed that, in primary mesothelial cells, the plasmalemmal Ca2+ influx played a pivotal role. However, when the Ca2+ transport across the plasma membrane by the “lanthanum insulation method” was blocked prior to the induction of the serum-induced Ca2+ oscillations, mitochondrial Ca2+ transport was found to be able to substitute for the plasmalemmal Ca2+ exchange function, thus rendering the oscillations independent of extracellular Ca2+. However, in a physiological situation, the Ca2+-buffering capacity of mitochondria was found not to be essential for Ca2+ oscillations. Moreover, brief spontaneous Ca2+ changes were observed in the mitochondrial Ca2+ concentration without apparent changes in the cytosolic Ca2+ concentration, indicating the presence of a mitochondrial autonomous Ca2+ signaling mechanism. In the presence of calretinin, a Ca2+-buffering protein, the amplitude of cytosolic spikes during oscillations was decreased, and the amount of Ca2+ ions taken up by mitochondria was reduced. Thus, the increased calretinin expression observed in mesothelioma cells and in certain colon cancer might be correlated to the increased resistance of these tumor cells to proapoptotic/pronecrotic signals. We identified and characterized (experimentally and by modeling) three Ca2+ shuttling pathways in primary mesothelial cells during Ca2+ oscillations: Ca2+ shuttled between (i) the endoplasmic reticulum (ER) and mitochondria, (ii) the ER and the extracellular space, and (iii) the ER and cytoplasmic Ca2+ buffers.
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Affiliation(s)
- László Pecze
- Anatomy, Department of Medicine, University of Fribourg, Route Albert-Gockel 1, CH-1700 Fribourg, Switzerland.
| | - Walter Blum
- Anatomy, Department of Medicine, University of Fribourg, Route Albert-Gockel 1, CH-1700 Fribourg, Switzerland
| | - Beat Schwaller
- Anatomy, Department of Medicine, University of Fribourg, Route Albert-Gockel 1, CH-1700 Fribourg, Switzerland
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15
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Liang J, Kulasiri D, Samarasinghe S. Ca2+ dysregulation in the endoplasmic reticulum related to Alzheimer's disease: A review on experimental progress and computational modeling. Biosystems 2015; 134:1-15. [PMID: 25998697 DOI: 10.1016/j.biosystems.2015.05.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Revised: 05/12/2015] [Accepted: 05/12/2015] [Indexed: 12/12/2022]
Abstract
Alzheimer's disease (AD) is a devastating, incurable neurodegenerative disease affecting millions of people worldwide. Dysregulation of intracellular Ca(2+) signaling has been observed as an early event prior to the presence of clinical symptoms of AD and is believed to be a crucial factor contributing to its pathogenesis. The progressive and sustaining increase in the resting level of cytosolic Ca(2+) will affect downstream activities and neural functions. This review focuses on the issues relating to the increasing Ca(2+) release from the endoplasmic reticulum (ER) observed in AD neurons. Numerous research papers have suggested that the dysregulation of ER Ca(2+) homeostasis is associated with mutations in the presenilin genes and amyloid-β oligomers. These disturbances could happen at many different points in the signaling process, directly affecting ER Ca(2+) channels or interfering with related pathways, which makes it harder to reveal the underlying mechanisms. This review paper also shows that computational modeling is a powerful tool in Ca(2+) signaling studies and discusses the progress in modeling related to Ca(2+) dysregulation in AD research.
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Affiliation(s)
- Jingyi Liang
- Centre for Advanced Computational Solutions (C-fACS), Lincoln University, Christchurch, New Zealand; Department of Molecular Biosciences, Lincoln University, Christchurch, New Zealand
| | - Don Kulasiri
- Centre for Advanced Computational Solutions (C-fACS), Lincoln University, Christchurch, New Zealand; Department of Molecular Biosciences, Lincoln University, Christchurch, New Zealand.
| | - Sandhya Samarasinghe
- Centre for Advanced Computational Solutions (C-fACS), Lincoln University, Christchurch, New Zealand; Department of Informatics and Enabling Technologies, Lincoln University, Christchurch, New Zealand
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16
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Shah SZA, Zhao D, Khan SH, Yang L. Regulatory Mechanisms of Endoplasmic Reticulum Resident IP3 Receptors. J Mol Neurosci 2015; 56:938-948. [PMID: 25859934 DOI: 10.1007/s12031-015-0551-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 03/23/2015] [Indexed: 11/25/2022]
Abstract
Dysregulated calcium signaling and accumulation of aberrant proteins causing endoplasmic reticulum stress are the early sign of intra-axonal pathological events in many neurodegenerative diseases, and apoptotic signaling is initiated when the stress goes beyond the maximum threshold level of endoplasmic reticulum. The fate of the cell to undergo apoptosis is controlled by Ca2(+) signaling and dynamics at the level of the endoplasmic reticulum. Endoplasmic reticulum resident inositol 1,4,5-trisphosphate receptors (IP3R) play a pivotal role in cell death signaling by mediating Ca2(+) flux from the endoplasmic reticulum into the cytosol and mitochondria. Hence, many prosurvival and prodeath signaling pathways and proteins affect Ca2(+) signaling by directly targeting IP3R channels, which can happen in an IP3R-isoform-dependent manner. Here, in this review, we summarize the regulatory mechanisms of inositol triphosphate receptors in calcium regulation and initiation of apoptosis during unfolded protein response.
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Affiliation(s)
- Syed Zahid Ali Shah
- State Key Laboratories for Agrobiotechnology, Key Lab of Animal Epidemiology and Zoonosis, Ministry of Agriculture, National Animal Transmissible Spongiform Encephalopathy Laboratory, College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China
| | - Deming Zhao
- State Key Laboratories for Agrobiotechnology, Key Lab of Animal Epidemiology and Zoonosis, Ministry of Agriculture, National Animal Transmissible Spongiform Encephalopathy Laboratory, College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China
| | - Sher Hayat Khan
- State Key Laboratories for Agrobiotechnology, Key Lab of Animal Epidemiology and Zoonosis, Ministry of Agriculture, National Animal Transmissible Spongiform Encephalopathy Laboratory, College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China
| | - Lifeng Yang
- State Key Laboratories for Agrobiotechnology, Key Lab of Animal Epidemiology and Zoonosis, Ministry of Agriculture, National Animal Transmissible Spongiform Encephalopathy Laboratory, College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China.
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17
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Pecze L, Schwaller B. Characterization and modeling of Ca2+ oscillations in mouse primary mesothelial cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:632-45. [DOI: 10.1016/j.bbamcr.2014.12.025] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Revised: 12/16/2014] [Accepted: 12/19/2014] [Indexed: 10/24/2022]
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18
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Mak DOD, Foskett JK. Inositol 1,4,5-trisphosphate receptors in the endoplasmic reticulum: A single-channel point of view. Cell Calcium 2014; 58:67-78. [PMID: 25555684 DOI: 10.1016/j.ceca.2014.12.008] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Revised: 12/09/2014] [Accepted: 12/10/2014] [Indexed: 10/24/2022]
Abstract
As an intracellular Ca(2+) release channel at the endoplasmic reticulum membrane, the ubiquitous inositol 1,4,5-trisphosphate (InsP3) receptor (InsP3R) plays a crucial role in the generation, propagation and regulation of intracellular Ca(2+) signals that regulate numerous physiological and pathophysiological processes. This review provides a concise account of the fundamental single-channel properties of the InsP3R channel: its conductance properties and its regulation by InsP3 and Ca(2+), its physiological ligands, studied using nuclear patch clamp electrophysiology.
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Affiliation(s)
- Don-On Daniel Mak
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States.
| | - J Kevin Foskett
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States; Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States
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19
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Ibarra C, Vicencio JM, Varas-Godoy M, Jaimovich E, Rothermel BA, Uhlén P, Hill JA, Lavandero S. An integrated mechanism of cardiomyocyte nuclear Ca(2+) signaling. J Mol Cell Cardiol 2014; 75:40-8. [PMID: 24997440 PMCID: PMC4626248 DOI: 10.1016/j.yjmcc.2014.06.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Revised: 06/11/2014] [Accepted: 06/26/2014] [Indexed: 01/05/2023]
Abstract
In cardiomyocytes, Ca(2+) plays a central role in governing both contraction and signaling events that regulate gene expression. Current evidence indicates that discrimination between these two critical functions is achieved by segregating Ca(2+) within subcellular microdomains: transcription is regulated by Ca(2+) release within nuclear microdomains, and excitation-contraction coupling is regulated by cytosolic Ca(2+). Accordingly, a variety of agonists that control cardiomyocyte gene expression, such as endothelin-1, angiotensin-II or insulin-like growth factor-1, share the feature of triggering nuclear Ca(2+) signals. However, signaling pathways coupling surface receptor activation to nuclear Ca(2+) release, and the phenotypic responses to such signals, differ between agonists. According to earlier hypotheses, the selective control of nuclear Ca(2+) signals by activation of plasma membrane receptors relies on the strategic localization of inositol trisphosphate receptors at the nuclear envelope. There, they mediate Ca(2+) release from perinuclear Ca(2+) stores upon binding of inositol trisphosphate generated in the cytosol, which diffuses into the nucleus. More recently, identification of such receptors at nuclear membranes or perinuclear sarcolemmal invaginations has uncovered novel mechanisms whereby agonists control nuclear Ca(2+) release. In this review, we discuss mechanisms for the selective control of nuclear Ca(2+) signals with special focus on emerging models of agonist receptor activation.
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Affiliation(s)
- Cristián Ibarra
- Cardiovascular and Metabolic Diseases, Innovative Medicines and Early Development, AstraZeneca R&D, Mölndal, Sweden.
| | - Jose Miguel Vicencio
- Hatter Cardiovascular Institute, University College London, London, United Kingdom
| | - Manuel Varas-Godoy
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
| | - Enrique Jaimovich
- Centro de Estudios Moleculares de la Célula, Facultad de Ciencias Químicas y Farmacéuticas & Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Beverly A Rothermel
- Department of Internal Medicine, Cardiology Division, University of Texas Southwestern Medical Center, Dallas, TX, USA; Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Per Uhlén
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
| | - Joseph A Hill
- Department of Internal Medicine, Cardiology Division, University of Texas Southwestern Medical Center, Dallas, TX, USA; Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Sergio Lavandero
- Centro de Estudios Moleculares de la Célula, Facultad de Ciencias Químicas y Farmacéuticas & Facultad de Medicina, Universidad de Chile, Santiago, Chile; Department of Internal Medicine, Cardiology Division, University of Texas Southwestern Medical Center, Dallas, TX, USA; Advanced Center for Chronic Diseases, Facultad de Ciencias Químicas y Farmacéuticas & Facultad de Medicina, Universidad de Chile, Santiago, Chile.
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20
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Modeling of stochastic behavior of pacemaker potential in interstitial cells of Cajal. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2014; 116:56-69. [PMID: 25238716 DOI: 10.1016/j.pbiomolbio.2014.09.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 08/28/2014] [Accepted: 09/06/2014] [Indexed: 01/20/2023]
Abstract
It is widely accepted that interstitial cells of Cajal (ICCs) generate pacemaker potentials to propagate slow waves along the whole gastrointestinal tract. Previously, we constructed a biophysically based model of ICCs in mouse small intestine to explain the pacemaker mechanism. Our previous model, however, could not explain non-uniformity of pacemaker potentials and random occurrence of unitary potentials, thus we updated our model. The inositol 1,4,5-trisphosphate (IP3)-mediated Ca(2+) mobilization is a key event to drive the cycle of pacemaker activity and was updated to reproduce its stochastic behavior. The stochasticity was embodied by simulating random opening and closing of individual IP3-mediated Ca(2+) channel. The updated model reproduces the stochastic features of pacemaker potentials in ICCs. Reproduced pacemaker potentials are not uniform in duration and interval. The resting and peak potentials are -75.5 ± 1.1 mV and -0.8 ± 0.5 mV, respectively (n = 55). Frequency of pacemaker potential is 14.3 ± 0.4 min(-1) (n = 10). Width at half-maximal amplitude of pacemaker potential is 902 ± 6 ms (n = 55). There are random events of unitary potential-like depolarization. Finally, we compared our updated model with a recently published model to speculate which ion channel is the best candidate to drive pacemaker depolarization. In conclusion, our updated mathematical model could now reproduce stochastic features of pacemaker activity in ICCs.
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21
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Jia C, Jiang D, Qian M. An allosteric model of the inositol trisphosphate receptor with nonequilibrium binding. Phys Biol 2014; 11:056001. [PMID: 25118617 DOI: 10.1088/1478-3975/11/5/056001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The inositol trisphosphate receptor (IPR) is a crucial ion channel that regulates the Ca(2+) influx from the endoplasmic reticulum (ER) to the cytoplasm. A thorough study of the IPR channel contributes to a better understanding of calcium oscillations and waves. It has long been observed that the IPR channel is a typical biological system which performs adaptation. However, recent advances on the physical essence of adaptation show that adaptation systems with a negative feedback mechanism, such as the IPR channel, must break detailed balance and always operate out of equilibrium with energy dissipation. Almost all previous IPR models are equilibrium models assuming detailed balance and thus violate the dissipative nature of adaptation. In this article, we constructed a nonequilibrium allosteric model of single IPR channels based on the patch-clamp experimental data obtained from the IPR in the outer membranes of isolated nuclei of the Xenopus oocyte. It turns out that our model reproduces the patch-clamp experimental data reasonably well and produces both the correct steady-state and dynamic properties of the channel. Particularly, our model successfully describes the complicated bimodal [Ca(2+)] dependence of the mean open duration at high [IP3], a steady-state behavior which fails to be correctly described in previous IPR models. Finally, we used the patch-clamp experimental data to validate that the IPR channel indeed breaks detailed balance and thus is a nonequilibrium system which consumes energy.
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Affiliation(s)
- Chen Jia
- LMAM, School of Mathematical Sciences, Peking University, Beijing 100871, People's Republic of China. Beijing International Center for Mathematical Research, Beijing 100871, People's Republic of China
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22
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Ivanova H, Vervliet T, Missiaen L, Parys JB, De Smedt H, Bultynck G. Inositol 1,4,5-trisphosphate receptor-isoform diversity in cell death and survival. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:2164-83. [PMID: 24642269 DOI: 10.1016/j.bbamcr.2014.03.007] [Citation(s) in RCA: 139] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Revised: 03/06/2014] [Accepted: 03/09/2014] [Indexed: 01/22/2023]
Abstract
Cell-death and -survival decisions are critically controlled by intracellular Ca(2+) homeostasis and dynamics at the level of the endoplasmic reticulum (ER). Inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs) play a pivotal role in these processes by mediating Ca(2+) flux from the ER into the cytosol and mitochondria. Hence, it is clear that many pro-survival and pro-death signaling pathways and proteins affect Ca(2+) signaling by directly targeting IP3R channels, which can happen in an IP3R-isoform-dependent manner. In this review, we will focus on how the different IP3R isoforms (IP3R1, IP3R2 and IP3R3) control cell death and survival. First, we will present an overview of the isoform-specific regulation of IP3Rs by cellular factors like IP3, Ca(2+), Ca(2+)-binding proteins, adenosine triphosphate (ATP), thiol modification, phosphorylation and interacting proteins, and of IP3R-isoform specific expression patterns. Second, we will discuss the role of the ER as a Ca(2+) store in cell death and survival and how IP3Rs and pro-survival/pro-death proteins can modulate the basal ER Ca(2+) leak. Third, we will review the regulation of the Ca(2+)-flux properties of the IP3R isoforms by the ER-resident and by the cytoplasmic proteins involved in cell death and survival as well as by redox regulation. Hence, we aim to highlight the specific roles of the various IP3R isoforms in cell-death and -survival signaling. This article is part of a Special Issue entitled: Calcium signaling in health and disease. Guest Editors: Geert Bultynck, Jacques Haiech, Claus W. Heizmann, Joachim Krebs, and Marc Moreau.
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Affiliation(s)
- Hristina Ivanova
- KU Leuven Lab. of Molecular and Cellular Signaling, Dept. of Cellular and Molecular Medicine, Campus Gasthuisberg O&N I Box 802, Herestraat 49, BE-3000 Leuven, Belgium
| | - Tim Vervliet
- KU Leuven Lab. of Molecular and Cellular Signaling, Dept. of Cellular and Molecular Medicine, Campus Gasthuisberg O&N I Box 802, Herestraat 49, BE-3000 Leuven, Belgium
| | - Ludwig Missiaen
- KU Leuven Lab. of Molecular and Cellular Signaling, Dept. of Cellular and Molecular Medicine, Campus Gasthuisberg O&N I Box 802, Herestraat 49, BE-3000 Leuven, Belgium
| | - Jan B Parys
- KU Leuven Lab. of Molecular and Cellular Signaling, Dept. of Cellular and Molecular Medicine, Campus Gasthuisberg O&N I Box 802, Herestraat 49, BE-3000 Leuven, Belgium
| | - Humbert De Smedt
- KU Leuven Lab. of Molecular and Cellular Signaling, Dept. of Cellular and Molecular Medicine, Campus Gasthuisberg O&N I Box 802, Herestraat 49, BE-3000 Leuven, Belgium.
| | - Geert Bultynck
- KU Leuven Lab. of Molecular and Cellular Signaling, Dept. of Cellular and Molecular Medicine, Campus Gasthuisberg O&N I Box 802, Herestraat 49, BE-3000 Leuven, Belgium.
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Falkenburger BH, Dickson EJ, Hille B. Quantitative properties and receptor reserve of the DAG and PKC branch of G(q)-coupled receptor signaling. ACTA ACUST UNITED AC 2014; 141:537-55. [PMID: 23630338 PMCID: PMC3639584 DOI: 10.1085/jgp.201210887] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Gq protein–coupled receptors (GqPCRs) of the plasma membrane activate the phospholipase C (PLC) signaling cascade. PLC cleaves the membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP2) into the second messengers diacylgycerol (DAG) and inositol 1,4,5-trisphosphate (IP3), leading to calcium release, protein kinase C (PKC) activation, and in some cases, PIP2 depletion. We determine the kinetics of each of these downstream endpoints and also ask which is responsible for the inhibition of KCNQ2/3 (KV7.2/7.3) potassium channels in single living tsA-201 cells. We measure DAG production and PKC activity by Förster resonance energy transfer–based sensors, and PIP2 by KCNQ2/3 channels. Fully activating endogenous purinergic receptors by uridine 5′triphosphate (UTP) leads to calcium release, DAG production, and PKC activation, but no net PIP2 depletion. Fully activating high-density transfected muscarinic receptors (M1Rs) by oxotremorine-M (Oxo-M) leads to similar calcium, DAG, and PKC signals, but PIP2 is depleted. KCNQ2/3 channels are inhibited by the Oxo-M treatment (85%) and not by UTP (<1%), indicating that depletion of PIP2 is required to inhibit KCNQ2/3 in response to receptor activation. Overexpression of A kinase–anchoring protein (AKAP)79 or calmodulin (CaM) does not increase KCNQ2/3 inhibition by UTP. From these results and measurements of IP3 and calcium presented in our companion paper (Dickson et al. 2013. J. Gen. Physiol.http://dx.doi.org/10.1085/jgp.201210886), we extend our kinetic model for signaling from M1Rs to DAG/PKC and IP3/calcium signaling. We conclude that calcium/CaM and PKC-mediated phosphorylation do not underlie dynamic KCNQ2/3 channel inhibition during GqPCR activation in tsA-201 cells. Finally, our experimental data provide indirect evidence for cleavage of PI(4)P by PLC in living cells, and our modeling revisits/explains the concept of receptor reserve with measurements from all steps of GqPCR signaling.
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Affiliation(s)
- Björn H Falkenburger
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA
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24
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Baker KD, Edwards TM, Rickard NS. The role of intracellular calcium stores in synaptic plasticity and memory consolidation. Neurosci Biobehav Rev 2013; 37:1211-39. [PMID: 23639769 DOI: 10.1016/j.neubiorev.2013.04.011] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Revised: 04/18/2013] [Accepted: 04/22/2013] [Indexed: 12/20/2022]
Abstract
Memory processing requires tightly controlled signalling cascades, many of which are dependent upon intracellular calcium (Ca(2+)). Despite this, most work investigating calcium signalling in memory formation has focused on plasma membrane channels and extracellular sources of Ca(2+). The intracellular Ca(2+) release channels, ryanodine receptors (RyRs) and inositol (1,4,5)-trisphosphate receptors (IP3Rs) have a significant capacity to regulate intracellular Ca(2+) signalling. Evidence at both cellular and behavioural levels implicates both RyRs and IP3Rs in synaptic plasticity and memory formation. Pharmacobehavioural experiments using young chicks trained on a single-trial discrimination avoidance task have been particularly useful by demonstrating that RyRs and IP3Rs have distinct roles in memory formation. RyR-dependent Ca(2+) release appears to aid the consolidation of labile memory into a persistent long-term memory trace. In contrast, IP3Rs are required during long-term memory. This review discusses various functions for RyRs and IP3Rs in memory processing, including neuro- and glio-transmitter release, dendritic spine remodelling, facilitating vasodilation, and the regulation of gene transcription and dendritic excitability. Altered Ca(2+) release from intracellular stores also has significant implications for neurodegenerative conditions.
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Affiliation(s)
- Kathryn D Baker
- School of Psychology and Psychiatry, Monash University, Clayton 3800, Victoria, Australia.
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25
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Comparison of models for IP3 receptor kinetics using stochastic simulations. PLoS One 2013; 8:e59618. [PMID: 23630568 PMCID: PMC3629942 DOI: 10.1371/journal.pone.0059618] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Accepted: 02/15/2013] [Indexed: 12/07/2022] Open
Abstract
Inositol 1,4,5-trisphosphate receptor (IP3R) is a ubiquitous intracellular calcium (Ca2+) channel which has a major role in controlling Ca2+ levels in neurons. A variety of computational models have been developed to describe the kinetic function of IP3R under different conditions. In the field of computational neuroscience, it is of great interest to apply the existing models of IP3R when modeling local Ca2+ transients in dendrites or overall Ca2+ dynamics in large neuronal models. The goal of this study was to evaluate existing IP3R models, based on electrophysiological data. This was done in order to be able to suggest suitable models for neuronal modeling. Altogether four models (Othmer and Tang, 1993; Dawson etal., 2003; Fraiman and Dawson, 2004; Doi etal., 2005) were selected for a more detailed comparison. The selection was based on the computational efficiency of the models and the type of experimental data that was used in developing the model. The kinetics of all four models were simulated by stochastic means, using the simulation software STEPS, which implements the Gillespie stochastic simulation algorithm. The results show major differences in the statistical properties of model functionality. Of the four compared models, the one by Fraiman and Dawson (2004) proved most satisfactory in producing the specific features of experimental findings reported in literature. To our knowledge, the present study is the first detailed evaluation of IP3R models using stochastic simulation methods, thus providing an important setting for constructing a new, realistic model of IP3R channel kinetics for compartmental modeling of neuronal functions. We conclude that the kinetics of IP3R with different concentrations of Ca2+ and IP3 should be more carefully addressed when new models for IP3R are developed.
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TRPV4 channels stimulate Ca2+-induced Ca2+ release in astrocytic endfeet and amplify neurovascular coupling responses. Proc Natl Acad Sci U S A 2013; 110:6157-62. [PMID: 23530219 DOI: 10.1073/pnas.1216514110] [Citation(s) in RCA: 151] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
In the CNS, astrocytes are sensory and regulatory hubs that play important roles in cerebral homeostatic processes, including matching local cerebral blood flow to neuronal metabolism (neurovascular coupling). These cells possess a highly branched network of processes that project from the soma to neuronal synapses as well as to arterioles and capillaries, where they terminate in "endfeet" that encase the blood vessels. Ca(2+) signaling within the endfoot mediates neurovascular coupling; thus, these functional microdomains control vascular tone and local perfusion in the brain. Transient receptor potential vanilloid 4 (TRPV4) channels--nonselective cation channels with considerable Ca(2+) conductance--have been identified in astrocytes, but their function is largely unknown. We sought to characterize the influence of TRPV4 channels on Ca(2+) dynamics in the astrocytic endfoot microdomain and assess their role in neurovascular coupling. We identified local TRPV4-mediated Ca(2+) oscillations in endfeet and further found that TRPV4 Ca(2+) signals are amplified and propagated by Ca(2+)-induced Ca(2+) release from inositol trisphosphate receptors (IP3Rs). Moreover, TRPV4-mediated Ca(2+) influx contributes to the endfoot Ca(2+) response to neuronal activation, enhancing the accompanying vasodilation. Our results identify a dynamic synergy between TRPV4 channels and IP3Rs in astrocyte endfeet and demonstrate that TRPV4 channels are engaged in and contribute to neurovascular coupling.
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De Pittà M, Volman V, Berry H, Parpura V, Volterra A, Ben-Jacob E. Computational quest for understanding the role of astrocyte signaling in synaptic transmission and plasticity. Front Comput Neurosci 2012; 6:98. [PMID: 23267326 PMCID: PMC3528083 DOI: 10.3389/fncom.2012.00098] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Accepted: 12/06/2012] [Indexed: 01/08/2023] Open
Abstract
The complexity of the signaling network that underlies astrocyte-synapse interactions may seem discouraging when tackled from a theoretical perspective. Computational modeling is challenged by the fact that many details remain hitherto unknown and conventional approaches to describe synaptic function are unsuitable to explain experimental observations when astrocytic signaling is taken into account. Supported by experimental evidence is the possibility that astrocytes perform genuine information processing by means of their calcium signaling and are players in the physiological setting of the basal tone of synaptic transmission. Here we consider the plausibility of this scenario from a theoretical perspective, focusing on the modulation of synaptic release probability by the astrocyte and its implications on synaptic plasticity. The analysis of the signaling pathways underlying such modulation refines our notion of tripartite synapse and has profound implications on our understanding of brain function.
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Affiliation(s)
- Maurizio De Pittà
- School of Physics and Astronomy, Tel Aviv University Ramat Aviv, Israel
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Awasthi M, Batra J, Kateriya S. Disulphide bridges of phospholipase C of Chlamydomonas reinhardtii modulates lipid interaction and dimer stability. PLoS One 2012; 7:e39258. [PMID: 22737232 PMCID: PMC3380823 DOI: 10.1371/journal.pone.0039258] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Accepted: 05/22/2012] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Phospholipase C (PLC) is an enzyme that plays pivotal role in a number of signaling cascades. These are active in the plasma membrane and triggers cellular responses by catalyzing the hydrolysis of membrane phospholipids and thereby generating the secondary messengers. Phosphatidylinositol-PLC (PI-PLC) specifically interacts with phosphoinositide and/or phosphoinositol and catalyzes specific cleavage of sn-3- phosphodiester bond. Several isoforms of PLC are known to form and function as dimer but very little is known about the molecular basis of the dimerization and its importance in the lipid interaction. PRINCIPAL FINDINGS We herein report that, the disruption of disulphide bond of a novel PI-specific PLC of C. reinhardtii (CrPLC) can modulate its interaction affinity with a set of phospholipids and also the stability of its dimer. CrPLC was found to form a mixture of higher oligomeric states with monomer and dimer as major species. Dimer adduct of CrPLC disappeared in the presence of DTT, which suggested the involvement of disulphide bond(s) in CrPLC oligomerization. Dimer-monomer equilibrium studies with the isolated fractions of CrPLC monomer and dimer supported the involvement of covalent forces in the dimerization of CrPLC. A disulphide bridge was found to be responsible for the dimerization and Cys7 seems to be involved in the formation of the disulphide bond. This crucial disulphide bond also modulated the lipid affinity of CrPLC. Oligomers of CrPLC were also captured in in vivo condition. CrPLC was mainly found to be localized in the plasma membrane of the cell. The cell surface localization of CrPLC may have significant implication in the downstream regulatory function of CrPLC. SIGNIFICANCE This study helps in establishing the role of CrPLC (or similar proteins) in the quaternary structure of the molecule its affinities during lipid interactions.
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Affiliation(s)
- Mayanka Awasthi
- Department of Biochemistry, University of Delhi, South Campus, New Delhi, India
| | - Jyoti Batra
- Department of Biochemistry, University of Delhi, South Campus, New Delhi, India
| | - Suneel Kateriya
- Department of Biochemistry, University of Delhi, South Campus, New Delhi, India
- * E-mail:
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Wagner LE, Yule DI. Differential regulation of the InsP₃ receptor type-1 and -2 single channel properties by InsP₃, Ca²⁺ and ATP. J Physiol 2012; 590:3245-59. [PMID: 22547632 DOI: 10.1113/jphysiol.2012.228320] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
An elevation of intracellular Ca2+ levels as a result of InsP3 receptor (InsP3R) activity represents a ubiquitous signalling pathway controlling a wide variety of cellular events. InsP3R activity is tightly controlled by the levels of the primary ligands, InsP3, Ca2+ and ATP. Importantly, InsP3Rs are regulated by Ca2+ i in a biphasic manner. Ca2+ release through all InsP3R family members is also modulated dramatically by ATP, albeit with sub-type-specific properties. To ascertain if a common mechanism can account for ATP and Ca2+ regulation of these InsP3R family members, we examined the effects of [ATP] on the Ca2+ dependency of rat InsP3R-1 (rInsP3R-1) and mouse InsP3R-2 (mInsP3R-2) activity expressed in DT40-3KO cells. We used the on-nucleus patch clamp recording technique with various [ATP], [InsP3] and [Ca2+] in the patch pipette and measured single InsP3R channel activity in stably transfected DT40 cells. Under identical conditions, at saturating [InsP3] and [ATP], the activity of rInsP3R-1 and mInsP3R-2 was essentially identical in terms of single channel conductance, maximal achievable open probability (Po) and the [Ca2+] required for activation and inhibition of activity. However, in contrast to rInsP3R-1 at saturating [InsP3], the activity of mInsP3R-2 was unaffected by [ATP]. At lower [InsP3], ATP had dramatic effects on mInsP3R-2 Po, but unlike the rInsP3R-1, this did not occur by altering the relative Ca2+ dependency, but by simply increasing the maximally achievable Po at a particular [InsP3] and [Ca2+]. [InsP3] did not alter the biphasic regulation of activity by Ca2+ in either rInsP3R-1 or mInsP3R-2. Analysis of the single channel kinetics indicated that Ca2+ and ATP modulate the Po predominately by facilitating extended bursting activity of the channel but the underlying biophysical mechanism appears to be distinct for each receptor. Subtype-specific regulation of InsP3R channel activity probably contributes to the fidelity of Ca2+ signalling in cells expressing these receptor subtypes.
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Affiliation(s)
- Larry E Wagner
- Department of Pharmacology, School of Medicine and Dentistry, University of Rochester Medical Center, Rochester, NY, USA
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Dupont G, Combettes L. Modelling the effect of specific inositol 1,4,5-trisphosphate receptor isoforms on cellular Ca2+ signals. Biol Cell 2012; 98:171-82. [PMID: 16033332 DOI: 10.1042/bc20050032] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND INFORMATION Oscillations of cytosolic Ca2+ are well-known to rely on the regulatory properties of the InsP3R (inositol 1,4,5-trisphosphate receptor). Three isoforms of this channel have been identified. They differ in their regulatory properties by Ca2+ and InsP3. Experiments in different cell types clearly indicate that the relative amounts of each isoform affect the time course of Ca2+ changes after agonist stimulation. In the present study, we investigate whether different steady-state curves for the open probability of the InsP3Rs as a function of Ca2+ imply different dynamical behaviours when these receptors are present in a cellular environment. We therefore describe by a specific phenomenological model the three main types of curves that have been reported: (i) the classical bell-shaped curve, (ii) the bell-shaped curve that is shifted towards higher Ca2+ concentrations when InsP3 is increased, and (iii) a monotonous increasing function of cytosolic Ca2+. RESULTS We show that, although these types of curves can be ascribed to slight differences in the channel regulation by Ca2+ and InsP3, they can indicate important variations as to the receptor role in cellular Ca2+ control. Thus the receptor associated with the classical bell-shaped curve appears to be the most robust Ca2+ oscillator. If the steady-state curve is supposed to be a monotonous increasing function of cytosolic Ca2+, the modelled receptor cannot sustain Ca2+ oscillations in the absence of Ca2+ exchanges with the extracellular medium. When the bell-shaped curve is shifted towards higher Ca2+ concentrations with increasing InsP3 levels, the model predicts that the receptor is less robust to changes in density; this receptor, however, provides a finer control of the steady-state level of Ca2+ when varying the InsP3 concentration. CONCLUSIONS Our model allows us to propose an explanation for the experimental observations about the effect of selectively expressing or down-regulating InsP3R isoforms, as well as to make theoretical predictions.
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Affiliation(s)
- Geneviève Dupont
- Université Libre de Bruxelles, Faculté des Sciences CP231, Boulevard du Triomphe, B-1050 Brussels, Belgium.
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HAERI HH, HASHEMIANZADEH SM, MONAJJEMI M. TEMPERATURE EFFECTS ON THE STOCHASTIC GATING OF THE IP3R CALCIUM RELEASE CHANNEL: A NUMERICAL SIMULATION STUDY. J BIOL SYST 2011. [DOI: 10.1142/s0218339009003058] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
Abstract
The importance of the kinetic study of endoplasmatic calcium ion channels in different intracellular processes is known today. Although there are few experimental reports on the temperature dependency of IP3R channel functions, we did not find any detailed theoretical study on this subject. For this purpose, we used a modified Gillespie algorithm to investigate the effect of temperature on the conditions affecting the open state of a single subunit of the De Young-Keizer (DYK) model. Population of the states was considered as the subject of fluctuation. Key features of the channel, such as bell-shaped dependency of open probability to the Calcium concentrations were modeled at different temperatures, too. The range of temperature variation was selected by regarding the experimental data on IP3R channel. By increasing the temperature, we had the very slow time domains (t: 10-1 s ) and the much slower time domains (t: 100 s ) in addition to other time domains, which could be seen as new time categories in InsP3R studies, and so the results were reported in these time domains, as well. We found out that increase in temperature declined the open probability in some concentrations of Ca 2+ and/or IP3. Also, by introducing the intensity graphs, broadening of the range of fluctuations and lowering of the order of frequency of fluctuations for the population of each state were observed due to the temperature increments. The temperature effects on the activation and inactivation states of the channel were studied in the framework of the reaction paths. We did not find similar paths at different time domains; several paths observed which were totally different all together. These time-dependent reaction paths are also depending on the Ca 2+ and/or the IP3 concentrations. So, one can predict the most probable reaction paths at different concentrations and temperatures and also determine which kind of the path it is; a path for closing the channel or a path to open it. Finally, the temperature effects on the calcium inhibited states were studied. We found out that calcium ion inhibitions were shifted to lower calcium concentration by increasing the temperature. The results suggests that inhibiting role of calcium is not only [ Ca 2+] and/or [IP3] dependent, but also temperature dependent.
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Affiliation(s)
- H. H. HAERI
- Department of Physical Chemistry, Tehran-Sharq Branch, Islamic Azad University, P.O. Box 33955/163, Tehran, Iran
| | - S. M. HASHEMIANZADEH
- College of Chemistry, Iran University of Science and Technology (IUST), P.O. Box 16765-163, Tehran, Iran
| | - M. MONAJJEMI
- Department of Physical Chemistry, Science and Research Campus, Islamic Azad University, P.O. Box 33955/163, Tehran, Iran
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Mechanistic basis of bell-shaped dependence of inositol 1,4,5-trisphosphate receptor gating on cytosolic calcium. Proc Natl Acad Sci U S A 2011; 108:15486-91. [PMID: 21876165 DOI: 10.1073/pnas.1101677108] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The inositol 1,4,5-trisphosphate (IP(3)) receptor (IP(3)R) is an intracellular Ca(2+) release channel, and its opening is controlled by IP(3) and Ca(2+). A single IP(3) binding site and multiple Ca(2+) binding sites exist on single subunits, but the precise nature of the interplay between these two ligands in regulating biphasic dependence of channel activity on cytosolic Ca(2+) is unknown. In this study, we visualized conformational changes in IP(3)R evoked by various concentrations of ligands by using the FRET between two fluorescent proteins fused to the N terminus of individual subunits. IP(3) and Ca(2+) have opposite effects on the FRET signal change, but the combined effect of these ligands is not a simple summative response. The bell-shaped Ca(2+) dependence of FRET efficiency was observed after the subtraction of the component corresponding to the FRET change evoked by Ca(2+) alone from the FRET changes evoked by both ligands together. A mutant IP(3)R containing a single amino acid substitution at K508, which is critical for IP(3) binding, did not exhibit this bell-shaped Ca(2+) dependence of the subtracted FRET efficiency. Mutation at E2100, which is known as a Ca(2+) sensor, resulted in ∼10-fold reduction in the Ca(2+) dependence of the subtracted signal. These results suggest that the subtracted FRET signal reflects IP(3)R activity. We propose a five-state model, which implements a dual-ligand competition response without complex allosteric regulation of Ca(2+) binding affinity, as the mechanism underlying the IP(3)-dependent regulation of the bell-shaped relationship between the IP(3)R activity and cytosolic Ca(2+).
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The role of agonist-independent conformational transformation (AICT) in IP₃ cluster behavior. Cell Calcium 2011; 49:145-52. [PMID: 21334066 DOI: 10.1016/j.ceca.2010.11.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Revised: 11/04/2010] [Accepted: 11/08/2010] [Indexed: 11/23/2022]
Abstract
Inositol 1,4,5-trisphosphate (IP(3)) receptor is a central unit in intracellular Ca(2+) signaling. Regulation of the IP₃ receptor by calcium is well characterized. High open probability values are reported for a single IP₃ receptor in nuclear patch clamp experiments. These experimental observations are in contrast with the lower open probability values of the lipid bilayer experiments. Most theoretical models do not account for high open probabilities of the receptor. But more recently, new models of the IP₃ receptor have been put forward which are constrained by single-channel nuclear patch clamp recordings, which generate the larger open probability with the aid of an additional agonist-independent conformational transformation (AICT)-'active' state. The main aim of this work is to constrain the AICT models with a wealth of experimental data characterizing calcium release from IP₃ receptor clusters. Our results suggest that consistency of cluster release between theory and experiments constrains the kinetics of the agonist-independent conformational transition rates (AICT) to values which lead to small open probabilities for the IP₃ receptor inconsistent with nuclear patch clamp experimental data.
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Vais H, Foskett JK, Daniel Mak DO. Unitary Ca(2+) current through recombinant type 3 InsP(3) receptor channels under physiological ionic conditions. J Gen Physiol 2010; 136:687-700. [PMID: 21078871 PMCID: PMC2995152 DOI: 10.1085/jgp.201010513] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2010] [Accepted: 10/21/2010] [Indexed: 11/20/2022] Open
Abstract
The ubiquitous inositol 1,4,5-trisphosphate (InsP(3)) receptor (InsP(3)R) channel, localized primarily in the endoplasmic reticulum (ER) membrane, releases Ca(2+) into the cytoplasm upon binding InsP(3), generating and modulating intracellular Ca(2+) signals that regulate numerous physiological processes. Together with the number of channels activated and the open probability of the active channels, the size of the unitary Ca(2+) current (i(Ca)) passing through an open InsP(3)R channel determines the amount of Ca(2+) released from the ER store, and thus the amplitude and the spatial and temporal nature of Ca(2+) signals generated in response to extracellular stimuli. Despite its significance, i(Ca) for InsP(3)R channels in physiological ionic conditions has not been directly measured. Here, we report the first measurement of i(Ca) through an InsP(3)R channel in its native membrane environment under physiological ionic conditions. Nuclear patch clamp electrophysiology with rapid perfusion solution exchanges was used to study the conductance properties of recombinant homotetrameric rat type 3 InsP(3)R channels. Within physiological ranges of free Ca(2+) concentrations in the ER lumen ([Ca(2+)](ER)), free cytoplasmic [Ca(2+)] ([Ca(2+)](i)), and symmetric free [Mg(2+)] ([Mg(2+)](f)), the i(Ca)-[Ca(2+)](ER) relation was linear, with no detectable dependence on [Mg(2+)](f). i(Ca) was 0.15 +/- 0.01 pA for a filled ER store with 500 microM [Ca(2+)](ER). The i(Ca)-[Ca(2+)](ER) relation suggests that Ca(2+) released by an InsP(3)R channel raises [Ca(2+)](i) near the open channel to approximately 13-70 microM, depending on [Ca(2+)](ER). These measurements have implications for the activities of nearby InsP(3)-liganded InsP(3)R channels, and they confirm that Ca(2+) released by an open InsP(3)R channel is sufficient to activate neighboring channels at appropriate distances away, promoting Ca(2+)-induced Ca(2+) release.
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Affiliation(s)
- Horia Vais
- Department of Physiology and Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104
| | - J. Kevin Foskett
- Department of Physiology and Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104
| | - Don-On Daniel Mak
- Department of Physiology and Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104
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35
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Yamazaki H, Chan J, Ikura M, Michikawa T, Mikoshiba K. Tyr-167/Trp-168 in type 1/3 inositol 1,4,5-trisphosphate receptor mediates functional coupling between ligand binding and channel opening. J Biol Chem 2010; 285:36081-91. [PMID: 20813840 PMCID: PMC2975230 DOI: 10.1074/jbc.m110.140129] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2010] [Revised: 08/01/2010] [Indexed: 02/02/2023] Open
Abstract
The N-terminal ∼220-amino acid region of the inositol 1,4,5-trisphosphate (IP(3)) receptor (IP(3)R)/Ca(2+) release channel has been referred to as the suppressor/coupling domain because it is required for both IP(3) binding suppression and IP(3)-induced channel gating. Measurements of IP(3)-induced Ca(2+) fluxes of mutagenized mouse type 1 IP(3)R (IP(3)R1) showed that the residues responsible for IP(3) binding suppression in this domain were not essential for channel opening. On the other hand, a single amino acid substitution of Tyr-167 to alanine completely impaired IP(3)-induced Ca(2+) release without reducing the IP(3) binding activity. The corresponding residue in type 3 IP(3)R (IP(3)R3), Trp-168, was also critical for channel opening. Limited trypsin digestion experiments showed that the trypsin sensitivities of the C-terminal gatekeeper domain differed markedly between the wild-type channel and the Tyr-167 mutant under the optimal conditions for channel opening. These results strongly suggest that the Tyr/Trp residue (Tyr-167 in IP(3)R1 and Trp-168 in IP(3)R3) is critical for the functional coupling between IP(3) binding and channel gating by maintaining the structural integrity of the C-terminal gatekeeper domain at least under activation gating.
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MESH Headings
- Amino Acid Sequence
- Amino Acid Substitution
- Animals
- Binding Sites/genetics
- Blotting, Western
- Calcium/metabolism
- Cell Line, Tumor
- Inositol 1,4,5-Trisphosphate/chemistry
- Inositol 1,4,5-Trisphosphate/metabolism
- Inositol 1,4,5-Trisphosphate/pharmacology
- Inositol 1,4,5-Trisphosphate Receptors/chemistry
- Inositol 1,4,5-Trisphosphate Receptors/genetics
- Inositol 1,4,5-Trisphosphate Receptors/metabolism
- Ion Channel Gating/drug effects
- Ion Channel Gating/genetics
- Ion Channel Gating/physiology
- Ligands
- Mice
- Models, Molecular
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Mutation
- Protein Binding
- Protein Isoforms/chemistry
- Protein Isoforms/genetics
- Protein Isoforms/metabolism
- Protein Structure, Tertiary
- Sequence Homology, Amino Acid
- Trypsin/metabolism
- Tryptophan/chemistry
- Tryptophan/genetics
- Tryptophan/metabolism
- Tyrosine/chemistry
- Tyrosine/genetics
- Tyrosine/metabolism
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Affiliation(s)
- Haruka Yamazaki
- From the Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute, Saitama 351-0198, Japan
- the Calcium Oscillation Project, Solution Oriented Research for Science and Technology, Japan Science and Technology Agency, Saitama 332-0012, Japan, and
| | - Jenny Chan
- the Division of Signaling Biology, Ontario Cancer Institute and Department of Medical Biophysics, University of Toronto, Ontario M5G IL7, Canada
| | - Mitsuhiko Ikura
- the Division of Signaling Biology, Ontario Cancer Institute and Department of Medical Biophysics, University of Toronto, Ontario M5G IL7, Canada
| | - Takayuki Michikawa
- From the Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute, Saitama 351-0198, Japan
- the Calcium Oscillation Project, Solution Oriented Research for Science and Technology, Japan Science and Technology Agency, Saitama 332-0012, Japan, and
| | - Katsuhiko Mikoshiba
- From the Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute, Saitama 351-0198, Japan
- the Calcium Oscillation Project, Solution Oriented Research for Science and Technology, Japan Science and Technology Agency, Saitama 332-0012, Japan, and
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Mechanisms of propagation of intercellular calcium waves in arterial smooth muscle cells. Biophys J 2010; 99:333-43. [PMID: 20643050 DOI: 10.1016/j.bpj.2010.04.031] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2010] [Revised: 03/29/2010] [Accepted: 04/12/2010] [Indexed: 11/24/2022] Open
Abstract
In rat mesenteric arteries, smooth muscle cells exhibit intercellular calcium waves in response to local phenylephrine stimulation. These waves have a velocity of approximately 20 cells/s and a range of approximately 80 cells. We analyze these waves in a theoretical model of a population of coupled smooth muscle cells, based on the hypothesis that the wave results from cell membrane depolarization propagation. We study the underlying mechanisms and highlight the importance of voltage-operated channels, calcium-induced calcium release, and chloride channels. Our model is in agreement with experimental observations, and we demonstrate that calcium waves presenting a velocity of approximately 20 cells/s can be mediated by electrical coupling. The wave velocity is limited by the time needed for calcium influx through voltage-operated calcium channels and the subsequent calcium-induced calcium release, and not by the speed of the depolarization spreading. The waves are partially regenerated, but have a spatial limit in propagation. Moreover, the model predicts that a refractory period of calcium signaling may significantly affect the wave appearance.
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37
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Taylor CW, Tovey SC. IP(3) receptors: toward understanding their activation. Cold Spring Harb Perspect Biol 2010; 2:a004010. [PMID: 20980441 DOI: 10.1101/cshperspect.a004010] [Citation(s) in RCA: 167] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Inositol 1,4,5-trisphosphate receptors (IP(3)R) and their relatives, ryanodine receptors, are the channels that most often mediate Ca(2+) release from intracellular stores. Their regulation by Ca(2+) allows them also to propagate cytosolic Ca(2+) signals regeneratively. This brief review addresses the structural basis of IP(3)R activation by IP(3) and Ca(2+). IP(3) initiates IP(3)R activation by promoting Ca(2+) binding to a stimulatory Ca(2+)-binding site, the identity of which is unresolved. We suggest that interactions of critical phosphate groups in IP(3) with opposite sides of the clam-like IP(3)-binding core cause it to close and propagate a conformational change toward the pore via the adjacent N-terminal suppressor domain. The pore, assembled from the last pair of transmembrane domains and the intervening pore loop from each of the four IP(3)R subunits, forms a structure in which a luminal selectivity filter and a gate at the cytosolic end of the pore control cation fluxes through the IP(3)R.
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Affiliation(s)
- Colin W Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, United Kingdom.
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38
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Foskett JK, Daniel Mak DO. Regulation of IP(3)R Channel Gating by Ca(2+) and Ca(2+) Binding Proteins. CURRENT TOPICS IN MEMBRANES 2010; 66:235-72. [PMID: 22353483 PMCID: PMC6707373 DOI: 10.1016/s1063-5823(10)66011-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- J Kevin Foskett
- Department of Physiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA; Department of Cell and Developmental Biology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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39
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Dupont G, Croisier H. Spatiotemporal organization of Ca dynamics: a modeling-based approach. HFSP JOURNAL 2010; 4:43-51. [PMID: 20885772 DOI: 10.2976/1.3385660] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2010] [Accepted: 02/19/2010] [Indexed: 12/26/2022]
Abstract
Calcium is a ubiquitous second messenger that mediates vital physiological responses such as fertilization, secretion, gene expression, or apoptosis. Given this variety of processes mediated by Ca(2+), these signals are highly organized both in time and space to ensure reliability and specificity. This review deals with the spatiotemporal organization of the Ca(2+) signaling pathway in electrically nonexcitable cells in which InsP(3) receptors are by far the most important Ca(2+) channels. We focus on the aspects of this highly regulated dynamical system for which an interplay between experiments and modeling is particularly fruitful. In particular, the importance of the relative densities of the different InsP(3) receptor subtypes will be discussed on the basis of a modeling approach linking the steady-state behaviors of these channels in electrophysiological experiments with their behavior in a cellular environment. Also, the interplay between InsP(3) metabolism and Ca(2+) oscillations will be considered. Finally, we discuss the relationships between stochastic openings of the Ca(2+) releasing channels at the microscopic level and the coordinated, regular behavior observed at the whole cell level on the basis of a combined experimental and modeling approach.
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Affiliation(s)
- Geneviève Dupont
- Unité de Chronobiologie Théorique, Faculté des Sciences, Université Libre de Bruxelles, CP231, Boulevard du Triomphe, B-1050 Brussels, Belgium
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Swaminathan D, Ullah G, Jung P. A simple sequential-binding model for calcium puffs. CHAOS (WOODBURY, N.Y.) 2009; 19:037109. [PMID: 19792034 PMCID: PMC2826368 DOI: 10.1063/1.3152227] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2009] [Accepted: 05/19/2009] [Indexed: 05/28/2023]
Abstract
Calcium puffs describe the transient release of Ca(2+) ions into the cytosol, through small clusters of 1,4,5-inositol triphosphate (IP(3)) receptors, present on internal stores such as the endoplasmic reticulum. Statistical properties of puffs, such as puff amplitudes and durations, have been well characterized experimentally. We model calcium puffs using a simple, sequential-binding model for the IP(3) receptor in conjunction with a computationally inexpensive point-source approximation. We follow two different protocols, a sequential protocol and a renewal protocol. In the sequential protocol, puffs are generated successively by the same cluster; in the renewal protocol, the system is reset after each puff. In both cases for a single set of parameters our results are in excellent agreement with experimental results for puff amplitudes and durations but indicate puff-to-puff correlations for the sequential protocol, consistent with recent experimental findings [H. J. Rose, S. Dargan, J. W. Shuai, and I. Parker, Biophys. J. 91, 4024 (2006)]. The model is then used to test the consistency of the hypothesized steep Ca(2+) gradients around single channels with the experimentally observed features of puff durations and amplitudes. A three-dimensional implementation of our point-source model suggests that a peak Ca(2+) concentration of the order of 10 muM at the cluster site (not channel) is consistent with the statistical features of observed calcium puffs.
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Affiliation(s)
- D Swaminathan
- Department of Physics, Ohio University, Athens, Ohio 45701, USA
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41
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Shuai JW, Yang DP, Pearson JE, Rüdiger S. An investigation of models of the IP3R channel in Xenopus oocyte. CHAOS (WOODBURY, N.Y.) 2009; 19:037105. [PMID: 19792030 PMCID: PMC2771705 DOI: 10.1063/1.3156402] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2009] [Accepted: 05/29/2009] [Indexed: 05/28/2023]
Abstract
We consider different models of inositol 1,4,5-trisphosphate (IP(3)) receptor (IP(3)R) channels in order to fit nuclear membrane patch clamp data of the stationary open probability, mean open time, and mean close time of channels in the Xenopus oocyte. Our results indicate that rather than to treat the tetrameric IP(3)R as four independent and identical subunits, one should assume sequential binding-unbinding processes of Ca(2+) ions and IP(3) messengers. Our simulations also favor the assumption that a channel opens through a conformational transition from a close state to an active state.
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Affiliation(s)
- J W Shuai
- Department of Physics, Xiamen University, Xiamen, China.
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Bai Y, Edelmann M, Sanderson MJ. The contribution of inositol 1,4,5-trisphosphate and ryanodine receptors to agonist-induced Ca(2+) signaling of airway smooth muscle cells. Am J Physiol Lung Cell Mol Physiol 2009; 297:L347-61. [PMID: 19465516 DOI: 10.1152/ajplung.90559.2008] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The relative contribution of inositol 1,4,5-trisphosphate (IP(3)) receptors (IP(3)Rs) and ryanodine receptors (RyRs) to agonist-induced Ca(2+) signaling in mouse airway smooth muscle cells (SMCs) was investigated in lung slices with phase-contrast or laser scanning microscopy. At room temperature (RT), methacholine (MCh) or 5-hydroxytryptamine (5-HT) induced Ca(2+) oscillations and an associated contraction in small airway SMCs. The subsequent exposure to an IP(3)R antagonist, 2-aminoethoxydiphenyl borate (2-APB), inhibited the Ca(2+) oscillations and induced airway relaxation in a concentration-dependent manner. 2-APB also inhibited Ca(2+) waves generated by the photolytic release of IP(3). However, the RyR antagonist ryanodine had no significant effect, at any concentration, on airway contraction or agonist- or IP(3)-induced Ca(2+) oscillations or Ca(2+) wave propagation. By contrast, a second RyR antagonist, tetracaine, relaxed agonist-contracted airways and inhibited agonist-induced Ca(2+) oscillations in a concentration-dependent manner. However, tetracaine did not affect IP(3)-induced Ca(2+) release or wave propagation nor the Ca(2+) content of SMC Ca(2+) stores as evaluated by Ca(2+)-release induced by caffeine. Conversely, both ryanodine and tetracaine completely blocked agonist-independent slow Ca(2+) oscillations induced by KCl. The inhibitory effects of 2-APB and absence of an effect of ryanodine on MCh-induced airway contraction or Ca(2+) oscillations of SMCs were also observed at 37 degrees C. In Ca(2+)-permeable SMCs, tetracaine inhibited agonist-induced contraction without affecting intracellular Ca(2+) levels indicating that relaxation also resulted from a reduction in Ca(2+) sensitivity. These results indicate that agonist-induced Ca(2+) oscillations in mouse small airway SMCs are primary mediated via IP(3)Rs and that tetracaine induces relaxation by both decreasing Ca(2+) sensitivity and inhibiting agonist-induced Ca(2+) oscillations via an IP(3)-dependent mechanism.
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Affiliation(s)
- Yan Bai
- Dept. of Physiology, Univ. of Massachusetts Medical School, Worcester, 01655, USA
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2-Aminoethoxydiphenyl-borate (2-APB) increases excitability in pyramidal neurons. Cell Calcium 2008; 45:310-7. [PMID: 19100621 DOI: 10.1016/j.ceca.2008.11.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2008] [Revised: 09/09/2008] [Accepted: 11/04/2008] [Indexed: 12/29/2022]
Abstract
Calcium ions (Ca(2+)) released from inositol trisphosphate (IP(3))-sensitive intracellular stores may participate in both the transient and extended regulation of neuronal excitability in neocortical and hippocampal pyramidal neurons. IP(3) receptor (IP(3)R) antagonists represent an important tool for dissociating these consequences of IP(3) generation and IP(3)R-dependent internal Ca(2+) release from the effects of other, concurrently stimulated second messenger signaling cascades and Ca(2+) sources. In this study, we have described the actions of the IP(3)R and store-operated Ca(2+) channel antagonist, 2-aminoethoxydiphenyl-borate (2-APB), on internal Ca(2+) release and plasma membrane excitability in neocortical and hippocampal pyramidal neurons. Specifically, we found that a dose of 2-APB (100 microM) sufficient for attenuating or blocking IP(3)-mediated internal Ca(2+) release also raised pyramidal neuron excitability. The 2-APB-dependent increase in excitability reversed upon washout and was characterized by an increase in input resistance, a decrease in the delay to action potential onset, an increase in the width of action potentials, a decrease in the magnitude of afterhyperpolarizations (AHPs), and an increase in the magnitude of post-spike afterdepolarizations (ADPs). From these observations, we conclude that 2-APB potently and reversibly increases neuronal excitability, likely via the inhibition of voltage- and Ca(2+)-dependent potassium (K(+)) conductances.
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Antigny F, Norez C, Cantereau A, Becq F, Vandebrouck C. Abnormal spatial diffusion of Ca2+ in F508del-CFTR airway epithelial cells. Respir Res 2008; 9:70. [PMID: 18973672 PMCID: PMC2584091 DOI: 10.1186/1465-9921-9-70] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2008] [Accepted: 10/30/2008] [Indexed: 11/25/2022] Open
Abstract
Background In airway epithelial cells, calcium mobilization can be elicited by selective autocrine and/or paracrine activation of apical or basolateral membrane heterotrimeric G protein-coupled receptors linked to phospholipase C (PLC) stimulation, which generates inositol 1,4,5-trisphosphate (IP3) and 1,2-diacylglycerol (DAG) and induces Ca2+ release from endoplasmic reticulum (ER) stores. Methods In the present study, we monitored the cytosolic Ca2+ transients using the UV light photolysis technique to uncage caged Ca2+ or caged IP3 into the cytosol of loaded airway epithelial cells of cystic fibrosis (CF) and non-CF origin. We compared in these cells the types of Ca2+ receptors present in the ER, and measured their Ca2+ dependent activity before and after correction of F508del-CFTR abnormal trafficking either by low temperature or by the pharmacological corrector miglustat (N-butyldeoxynojirimycin). Results We showed reduction of the inositol 1,4,5-trisphosphate receptors (IP3R) dependent-Ca2+ response following both correcting treatments compared to uncorrected cells in such a way that Ca2+ responses (CF+treatment vs wild-type cells) were normalized. This normalization of the Ca2+ rate does not affect the activity of Ca2+-dependent chloride channel in miglustat-treated CF cells. Using two inhibitors of IP3R1, we observed a decrease of the implication of IP3R1 in the Ca2+ response in CF corrected cells. We observed a similar Ca2+ mobilization between CF-KM4 cells and CFTR-cDNA transfected CF cells (CF-KM4-reverted). When we restored the F508del-CFTR trafficking in CFTR-reverted cells, the specific IP3R activity was also reduced to a similar level as in non CF cells. At the structural level, the ER morphology of CF cells was highly condensed around the nucleus while in non CF cells or corrected CF cells the ER was extended at the totality of cell. Conclusion These results suggest reversal of the IP3R dysfunction in F508del-CFTR epithelial cells by correction of the abnormal trafficking of F508del-CFTR in cystic fibrosis cells. Moreover, using CFTR cDNA-transfected CF cells, we demonstrated that abnormal increase of IP3R Ca2+ release in CF human epithelial cells could be the consequence of F508del-CFTR retention in ER compartment.
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Affiliation(s)
- Fabrice Antigny
- Institut de Physiologie et Biologie Cellulaires, Université de Poitiers, CNRS, 86022 Poitiers, France.
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Baran I, Ganea C, Baran V. A two-gate model for the ryanodine receptor with allosteric modulation by caffeine and quercetin. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2008; 37:793-806. [DOI: 10.1007/s00249-008-0271-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2007] [Revised: 12/22/2007] [Accepted: 01/17/2008] [Indexed: 12/01/2022]
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Ionescu L, White C, Cheung KH, Shuai J, Parker I, Pearson JE, Foskett JK, Mak DOD. Mode switching is the major mechanism of ligand regulation of InsP3 receptor calcium release channels. ACTA ACUST UNITED AC 2007; 130:631-45. [PMID: 17998395 PMCID: PMC2151663 DOI: 10.1085/jgp.200709859] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The inositol 1,4,5-trisphosphate (InsP3) receptor (InsP3R) plays a critical role in generation of complex Ca2+ signals in many cell types. In patch clamp recordings of isolated nuclei from insect Sf9 cells, InsP3R channels were consistently detected with regulation by cytoplasmic InsP3 and free Ca2+ concentrations ([Ca2+]i) very similar to that observed for vertebrate InsP3R. Long channel activity durations of the Sf9-InsP3R have now enabled identification of a novel aspect of InsP3R gating: modal gating. Using a novel algorithm to analyze channel modal gating kinetics, InsP3R gating can be separated into three distinct modes: a low activity mode, a fast kinetic mode, and a burst mode with channel open probability (Po) within each mode of 0.007 ± 0.002, 0.24 ± 0.03, and 0.85 ± 0.02, respectively. Channels reside in each mode for long periods (tens of opening and closing events), and transitions between modes can be discerned with high resolution (within two channel opening and closing events). Remarkably, regulation of channel gating by [Ca2+]i and [InsP3] does not substantially alter channel Po within a mode. Instead, [Ca2+]i and [InsP3] affect overall channel Po primarily by changing the relative probability of the channel being in each mode, especially the high and low Po modes. This novel observation therefore reveals modal switching as the major mechanism of physiological regulation of InsP3R channel activity, with implications for the kinetics of Ca2+ release events in cells.
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Affiliation(s)
- Lucian Ionescu
- Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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47
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Shuai J, Pearson JE, Foskett JK, Mak DOD, Parker I. A kinetic model of single and clustered IP3 receptors in the absence of Ca2+ feedback. Biophys J 2007; 93:1151-62. [PMID: 17526578 PMCID: PMC1929031 DOI: 10.1529/biophysj.107.108795] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ca2+ liberation through inositol 1,4,5-trisphosphate receptor (IP3R) channels generates complex patterns of spatiotemporal cellular Ca2+ signals owing to the biphasic modulation of channel gating by Ca2+ itself. These processes have been extensively studied in Xenopus oocytes, where imaging studies have revealed local Ca2+ signals ("puffs") arising from clusters of IP3R, and patch-clamp studies on isolated oocyte nuclei have yielded extensive data on IP3R gating kinetics. To bridge these two levels of experimental data, we developed an IP3R model and applied stochastic simulation and transition matrix theory to predict the behavior of individual and clustered IP3R channels. The channel model consists of four identical, independent subunits, each of which has an IP3-binding site together with one activating and one inactivating Ca2+-binding site. The channel opens when at least three subunits undergo a conformational change to an "active" state after binding IP3 and Ca2+. The model successfully reproduces patch-clamp data; including the dependence of open probability, mean open duration, and mean closed duration on [IP3] and [Ca2+]. Notably, the biexponential distribution of open-time duration and the dependence of mean open time on [Ca2+] are explained by populations of openings involving either three or four active subunits. As a first step toward applying the single IP3R model to describe cellular responses, we then simulated measurements of puff latency after step increases of [IP3]. Assuming that stochastic opening of a single IP3R at basal cytosolic [Ca2+] and any given [IP3] has a high probability of rapidly triggering neighboring channels by calcium-induced calcium release to evoke a puff, optimal correspondence with experimental data of puff latencies after photorelease of IP3 was obtained when the cluster contained a total of 40-70 IP3Rs.
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Affiliation(s)
- Jianwei Shuai
- Department of Neurobiology and Behavior, University of California, Irvine, California 92697-4550, USA.
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Rüdiger S, Shuai JW, Huisinga W, Nagaiah C, Warnecke G, Parker I, Falcke M. Hybrid stochastic and deterministic simulations of calcium blips. Biophys J 2007; 93:1847-57. [PMID: 17496042 PMCID: PMC1959544 DOI: 10.1529/biophysj.106.099879] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Intracellular calcium release is a prime example for the role of stochastic effects in cellular systems. Recent models consist of deterministic reaction-diffusion equations coupled to stochastic transitions of calcium channels. The resulting dynamics is of multiple time and spatial scales, which complicates far-reaching computer simulations. In this article, we introduce a novel hybrid scheme that is especially tailored to accurately trace events with essential stochastic variations, while deterministic concentration variables are efficiently and accurately traced at the same time. We use finite elements to efficiently resolve the extreme spatial gradients of concentration variables close to a channel. We describe the algorithmic approach and we demonstrate its efficiency compared to conventional methods. Our single-channel model matches experimental data and results in intriguing dynamics if calcium is used as charge carrier. Random openings of the channel accumulate in bursts of calcium blips that may be central for the understanding of cellular calcium dynamics.
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Affiliation(s)
- S Rüdiger
- Institut für Physik, Humboldt-Universität zu Berlin, Berlin, Germany.
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49
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Santo-Domingo J, Vay L, Hernández-SanMiguel E, Lobatón CD, Moreno A, Montero M, Alvarez J. The plasma membrane Na+/Ca2+ exchange inhibitor KB-R7943 is also a potent inhibitor of the mitochondrial Ca2+ uniporter. Br J Pharmacol 2007; 151:647-54. [PMID: 17471180 PMCID: PMC2014000 DOI: 10.1038/sj.bjp.0707260] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE The thiourea derivative KB-R7943, originally developed as inhibitor of the plasma membrane Na(+)/Ca(2+) exchanger, has been shown to protect against myocardial ischemia-reperfusion injury. We have studied here its effects on mitochondrial Ca(2+) fluxes. EXPERIMENTAL APPROACH [Ca(2+)] in cytosol, mitochondria and endoplasmic reticulum (ER), and mitochondrial membrane potential were monitored using both luminescent (targeted aequorins) and fluorescent (fura-2, tetramethylrhodamine ethyl ester) probes in HeLa cells. KEY RESULTS KB-R7943 was also a potent inhibitor of the mitochondrial Ca(2+) uniporter (MCU). In permeabilized HeLa cells, KB-R7943 inhibited mitochondrial Ca(2+) uptake with a Ki of 5.5+/-1.3 microM (mean+/-S.D.). In intact cells, 10 microM KB-R7943 reduced by 80% the mitochondrial [Ca(2+)] peak induced by histamine. KB-R7943 did not modify the mitochondrial membrane potential and had no effect on the mitochondrial Na(+)/Ca(2+) exchanger. KB-R7943 inhibited histamine-induced ER-Ca(2+) release in intact cells, but not in cells loaded with a Ca(2+)-chelator to damp cytosolic [Ca(2+)] changes. Therefore, inhibition of ER-Ca(2+)-release by KB-R7943 was probably due to the increased feedback Ca(2+)-inhibition of inositol 1,4,5-trisphosphate receptors after MCU block. This mechanism also explains why KB-R7943 reversibly blocked histamine-induced cytosolic [Ca(2+)] oscillations in the same range of concentrations required to inhibit MCU. CONCLUSIONS AND IMPLICATIONS Inhibition of MCU by KB-R7943 may contribute to its cardioprotective activity by preventing mitochondrial Ca(2+)-overload during ischemia-reperfusion. In addition, the effects of KB-R7943 on Ca(2+) homeostasis provide new evidence for the role of mitochondria modulating Ca(2+)-release and regenerative Ca(2+)-oscillations. Search for permeable and selective MCU inhibitors may yield useful pharmacological tools in the future.
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Affiliation(s)
- J Santo-Domingo
- Departamento de Bioquímica y Biología Molecular y Fisiología, Facultad de Medicina, Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC) Valladolid, Spain
| | - L Vay
- Departamento de Bioquímica y Biología Molecular y Fisiología, Facultad de Medicina, Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC) Valladolid, Spain
| | - E Hernández-SanMiguel
- Departamento de Bioquímica y Biología Molecular y Fisiología, Facultad de Medicina, Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC) Valladolid, Spain
| | - C D Lobatón
- Departamento de Bioquímica y Biología Molecular y Fisiología, Facultad de Medicina, Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC) Valladolid, Spain
| | - A Moreno
- Departamento de Bioquímica y Biología Molecular y Fisiología, Facultad de Medicina, Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC) Valladolid, Spain
| | - M Montero
- Departamento de Bioquímica y Biología Molecular y Fisiología, Facultad de Medicina, Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC) Valladolid, Spain
| | - J Alvarez
- Departamento de Bioquímica y Biología Molecular y Fisiología, Facultad de Medicina, Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC) Valladolid, Spain
- Author for correspondence:
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Abstract
The inositol 1,4,5-trisphosphate (InsP3) receptors (InsP3Rs) are a family of Ca2+ release channels localized predominately in the endoplasmic reticulum of all cell types. They function to release Ca2+ into the cytoplasm in response to InsP3 produced by diverse stimuli, generating complex local and global Ca2+ signals that regulate numerous cell physiological processes ranging from gene transcription to secretion to learning and memory. The InsP3R is a calcium-selective cation channel whose gating is regulated not only by InsP3, but by other ligands as well, in particular cytoplasmic Ca2+. Over the last decade, detailed quantitative studies of InsP3R channel function and its regulation by ligands and interacting proteins have provided new insights into a remarkable richness of channel regulation and of the structural aspects that underlie signal transduction and permeation. Here, we focus on these developments and review and synthesize the literature regarding the structure and single-channel properties of the InsP3R.
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Affiliation(s)
- J Kevin Foskett
- Department of Physiology, University of Pennsylvania, Philadelphia 19104-6085, USA.
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