1
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Torres RM, Turner JA, D’Antonio M, Pelanda R, Kremer KN. Regulation of CD8 T-cell signaling, metabolism, and cytotoxic activity by extracellular lysophosphatidic acid. Immunol Rev 2023; 317:203-222. [PMID: 37096808 PMCID: PMC10523933 DOI: 10.1111/imr.13208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2023] [Revised: 04/07/2023] [Accepted: 04/08/2023] [Indexed: 04/26/2023]
Abstract
Lysophosphatidic acid (LPA) is an endogenous bioactive lipid that is produced extracellularly and signals to cells via cognate LPA receptors, which are G-protein coupled receptors (GPCRs). Mature lymphocytes in mice and humans express three LPA receptors, LPA2 , LPA5, and LPA6 , and work from our group has determined that LPA5 signaling by T lymphocytes inhibits specific antigen-receptor signaling pathways that ultimately impair lymphocyte activation, proliferation, and function. In this review, we discuss previous and ongoing work characterizing the ability of an LPA-LPA5 axis to serve as a peripheral immunological tolerance mechanism that restrains adaptive immunity but is subverted during settings of chronic inflammation. Specifically, LPA-LPA5 signaling is found to regulate effector cytotoxic CD8 T cells by (at least) two mechanisms: (i) regulating the actin-microtubule cytoskeleton in a manner that impairs immunological synapse formation between an effector CD8 T cell and antigen-specific target cell, thus directly impairing cytotoxic activity, and (ii) shifting T-cell metabolism to depend on fatty-acid oxidation for mitochondrial respiration and reducing metabolic efficiency. The in vivo outcome of LPA5 inhibitory activity impairs CD8 T-cell killing and tumor immunity in mouse models providing impetus to consider LPA5 antagonism for the treatment of malignancies and chronic infections.
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Affiliation(s)
- Raul M. Torres
- Department of Immunology & Microbiology, University of Colorado School of Medicine, Aurora Colorado, 80045
| | - Jacqueline A. Turner
- Department of Immunology & Microbiology, University of Colorado School of Medicine, Aurora Colorado, 80045
| | - Marc D’Antonio
- Department of Immunology & Microbiology, University of Colorado School of Medicine, Aurora Colorado, 80045
| | - Roberta Pelanda
- Department of Immunology & Microbiology, University of Colorado School of Medicine, Aurora Colorado, 80045
| | - Kimberly N. Kremer
- Department of Immunology & Microbiology, University of Colorado School of Medicine, Aurora Colorado, 80045
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2
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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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3
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Alves E, Nakaya H, Guimarães E, Garcia CR. Combining IP 3 affinity chromatography and bioinformatics reveals a novel protein-IP 3 binding site on Plasmodium falciparum MDR1 transporter. CURRENT RESEARCH IN MICROBIAL SCIENCES 2022; 4:100179. [PMID: 36582189 PMCID: PMC9792294 DOI: 10.1016/j.crmicr.2022.100179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Intracellular Ca2+ mobilization induced by second messenger IP3 controls many cellular events in most of the eukaryotic groups. Despite the increasing evidence of IP3-induced Ca2+ in apicomplexan parasites like Plasmodium, responsible for malaria infection, no protein with potential function as an IP3-receptor has been identified. The use of bioinformatic analyses based on previously known sequences of IP3-receptor failed to identify potential IP3-receptor candidates in any Apicomplexa. In this work, we combine the biochemical approach of an IP3 affinity chromatography column with bioinformatic meta-analyses to identify potential vital membrane proteins that present binding with IP3 in Plasmodium falciparum. Our analyses reveal that PF3D7_0523000, a gene that codes a transport protein associated with multidrug resistance as a potential target for IP3. This work provides a new insight for probing potential candidates for IP3-receptor in Apicomplexa.
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Affiliation(s)
- Eduardo Alves
- Life Science Department, Imperial College London, London, United Kingdom
| | - Helder Nakaya
- Department of Clinical and Toxicological Analyses of Pharmaceutical Sciences, University of São Paulo, São Paulo, Brazil,Computational Systems Biology Laboratory, INOVA, University of Sao Paulo, Sao Paulo, Brazil
| | - Euzébio Guimarães
- Federal University of Rio Grande do Norte, Pharmacy Department, Health Science Center, Natal, Brazil
| | - Célia R.S. Garcia
- Department of Clinical and Toxicological Analyses of Pharmaceutical Sciences, University of São Paulo, São Paulo, Brazil,Corresponding author.
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4
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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: 20] [Impact Index Per Article: 10.0] [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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5
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Cryo-EM reveals ligand induced allostery underlying InsP 3R channel gating. Cell Res 2018; 28:1158-1170. [PMID: 30470765 PMCID: PMC6274648 DOI: 10.1038/s41422-018-0108-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 09/02/2018] [Accepted: 10/22/2018] [Indexed: 01/06/2023] Open
Abstract
Inositol-1,4,5-trisphosphate receptors (InsP3Rs) are cation channels that mobilize Ca2+ from intracellular stores in response to a wide range of cellular stimuli. The paradigm of InsP3R activation is the coupled interplay between binding of InsP3 and Ca2+ that switches the ion conduction pathway between closed and open states to enable the passage of Ca2+ through the channel. However, the molecular mechanism of how the receptor senses and decodes ligand-binding signals into gating motion remains unknown. Here, we present the electron cryo-microscopy structure of InsP3R1 from rat cerebellum determined to 4.1 Å resolution in the presence of activating concentrations of Ca2+ and adenophostin A (AdA), a structural mimetic of InsP3 and the most potent known agonist of the channel. Comparison with the 3.9 Å-resolution structure of InsP3R1 in the Apo-state, also reported herein, reveals the binding arrangement of AdA in the tetrameric channel assembly and striking ligand-induced conformational rearrangements within cytoplasmic domains coupled to the dilation of a hydrophobic constriction at the gate. Together, our results provide critical insights into the mechanistic principles by which ligand-binding allosterically gates InsP3R channel.
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6
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Egorova PA, Bezprozvanny IB. Inositol 1,4,5-trisphosphate receptors and neurodegenerative disorders. FEBS J 2018; 285:3547-3565. [PMID: 29253316 DOI: 10.1111/febs.14366] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Revised: 11/27/2017] [Accepted: 12/12/2017] [Indexed: 12/15/2022]
Abstract
The inositol 1,4,5-trisphosphate receptor (IP3 R) is an intracellular ion channel that mediates the release of calcium ions from the endoplasmic reticulum. It plays a role in basic biological functions, such as cell division, differentiation, fertilization and cell death, and is involved in developmental processes including learning, memory and behavior. Deregulation of neuronal calcium signaling results in disturbance of cell homeostasis, synaptic loss and dysfunction, eventually leading to cell death. Three IP3 R subtypes have been identified in mammalian cells and the predominant isoform in neurons is IP3 R type 1. Dysfunction of IP3 R type 1 may play a role in the pathogenesis of certain neurodegenerative diseases as enhanced activity of the IP3 R was observed in models of Huntington's disease, spinocerebellar ataxias and Alzheimer's disease. These results suggest that IP3 R-mediated signaling is a potential target for treatment of these disorders. In this review we discuss the structure, functions and regulation of the IP3 R in healthy neurons and in conditions of neurodegeneration.
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Affiliation(s)
- Polina A Egorova
- Laboratory of Molecular Neurodegeneration, Peter the Great St. Petersburg Polytechnic University, St Petersburg, Russia
| | - Ilya B Bezprozvanny
- Laboratory of Molecular Neurodegeneration, Peter the Great St. Petersburg Polytechnic University, St Petersburg, Russia.,Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX, USA
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7
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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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8
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Abstract
Mechanosensory hair cells are vulnerable to environmental insult, resulting in hearing and balance disorders. We demonstrate that directional compartmental flow of intracellular Ca(2+) underlies death in zebrafish lateral line hair cells after exposure to aminoglycoside antibiotics, a well characterized hair cell toxin. Ca(2+) is mobilized from the ER and transferred to mitochondria via IP3 channels with little cytoplasmic leakage. Pharmacological agents that shunt ER-derived Ca(2+) directly to cytoplasm mitigate toxicity, indicating that high cytoplasmic Ca(2+) levels alone are not cytotoxic. Inhibition of the mitochondrial transition pore sensitizes hair cells to the toxic effects of aminoglycosides, contrasting with current models of excitotoxicity. Hair cells display efficient ER-mitochondrial Ca(2+) flow, suggesting that tight coupling of these organelles drives mitochondrial activity under physiological conditions at the cost of increased susceptibility to toxins.
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9
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Mak DOD, Vais H, Cheung KH, Foskett JK. Patch-clamp electrophysiology of intracellular Ca2+ channels. Cold Spring Harb Protoc 2013; 2013:787-97. [PMID: 24003191 DOI: 10.1101/pdb.top066217] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The modulation of cytoplasmic free Ca(2+) concentration ([Ca(2+)]i) is a universal intracellular signaling pathway that regulates numerous cellular physiological processes. Ubiquitous intracellular Ca(2+)-release channels localized to the endoplasmic/sarcoplasmic reticulum-inositol 1,4,5-trisphosphate receptor (InsP3R) and ryanodine receptor (RyR) channels-play a central role in [Ca(2+)]i signaling in all animal cells. Despite their intracellular localization, electrophysiological studies of the single-channel permeation and gating properties of these Ca(2+)-release channels using the powerful patch-clamp approach have been possible by application of this technique to isolated nuclei because the channels are present in membranes of the nuclear envelope. Here we provide a concise description of how nuclear patch-clamp experiments have been used to study single-channel properties of different InsP3R channels in the outer nuclear membrane. We compare this with other methods for studying intracellular Ca(2+) release. We also briefly describe application of the technique to InsP3R channels in the inner nuclear membrane and to channels in the outer nuclear membrane of HEK293 cells expressing recombinant RyR.
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Affiliation(s)
- Don-On Daniel Mak
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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10
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Saleem H, Tovey SC, Riley AM, Potter BVL, Taylor CW. Stimulation of inositol 1,4,5-trisphosphate (IP3) receptor subtypes by adenophostin A and its analogues. PLoS One 2013; 8:e58027. [PMID: 23469136 PMCID: PMC3585173 DOI: 10.1371/journal.pone.0058027] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Accepted: 01/30/2013] [Indexed: 11/25/2022] Open
Abstract
Inositol 1,4,5-trisphosphate receptors (IP3R) are intracellular Ca(2+) channels. Most animal cells express mixtures of the three IP3R subtypes encoded by vertebrate genomes. Adenophostin A (AdA) is the most potent naturally occurring agonist of IP3R and it shares with IP3 the essential features of all IP3R agonists, namely structures equivalent to the 4,5-bisphosphate and 6-hydroxyl of IP3. The two essential phosphate groups contribute to closure of the clam-like IP3-binding core (IBC), and thereby IP3R activation, by binding to each of its sides (the α- and β-domains). Regulation of the three subtypes of IP3R by AdA and its analogues has not been examined in cells expressing defined homogenous populations of IP3R. We measured Ca(2+) release evoked by synthetic adenophostin A (AdA) and its analogues in permeabilized DT40 cells devoid of native IP3R and stably expressing single subtypes of mammalian IP3R. The determinants of high-affinity binding of AdA and its analogues were indistinguishable for each IP3R subtype. The results are consistent with a cation-π interaction between the adenine of AdA and a conserved arginine within the IBC α-domain contributing to closure of the IBC. The two complementary contacts between AdA and the α-domain (cation-π interaction and 3″-phosphate) allow activation of IP3R by an analogue of AdA (3″-dephospho-AdA) that lacks a phosphate group equivalent to the essential 5-phosphate of IP3. These data provide the first structure-activity analyses of key AdA analogues using homogenous populations of all mammalian IP3R subtypes. They demonstrate that differences in the Ca(2+) signals evoked by AdA analogues are unlikely to be due to selective regulation of IP3R subtypes.
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Affiliation(s)
- Huma Saleem
- Department of Pharmacology, Cambridge, United Kingdom
| | | | - Andrew M. Riley
- Wolfson Laboratory of Medicinal Chemistry, Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom
| | - Barry V. L. Potter
- Wolfson Laboratory of Medicinal Chemistry, Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom
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11
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Vais H, Foskett JK, Ullah G, Pearson JE, Mak DOD. Permeant calcium ion feed-through regulation of single inositol 1,4,5-trisphosphate receptor channel gating. ACTA ACUST UNITED AC 2012; 140:697-716. [PMID: 23148262 PMCID: PMC3514735 DOI: 10.1085/jgp.201210804] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The ubiquitous inositol 1,4,5-trisphosphate (InsP(3)) receptor (InsP(3)R) Ca(2+) release channel plays a central role in the generation and modulation of intracellular Ca(2+) signals, and is intricately regulated by multiple mechanisms including cytoplasmic ligand (InsP(3), free Ca(2+), free ATP(4-)) binding, posttranslational modifications, and interactions with cytoplasmic and endoplasmic reticulum (ER) luminal proteins. However, regulation of InsP(3)R channel activity by free Ca(2+) in the ER lumen ([Ca(2+)](ER)) remains poorly understood because of limitations of Ca(2+) flux measurements and imaging techniques. Here, we used nuclear patch-clamp experiments in excised luminal-side-out configuration with perfusion solution exchange to study the effects of [Ca(2+)](ER) on homotetrameric rat type 3 InsP(3)R channel activity. In optimal [Ca(2+)](i) and subsaturating [InsP(3)], jumps of [Ca(2+)](ER) from 70 nM to 300 µM reduced channel activity significantly. This inhibition was abrogated by saturating InsP(3) but restored when [Ca(2+)](ER) was raised to 1.1 mM. In suboptimal [Ca(2+)](i), jumps of [Ca(2+)](ER) (70 nM to 300 µM) enhanced channel activity. Thus, [Ca(2+)](ER) effects on channel activity exhibited a biphasic dependence on [Ca(2+)](i). In addition, the effect of high [Ca(2+)](ER) was attenuated when a voltage was applied to oppose Ca(2+) flux through the channel. These observations can be accounted for by Ca(2+) flux driven through the open InsP(3)R channel by [Ca(2+)](ER), raising local [Ca(2+)](i) around the channel to regulate its activity through its cytoplasmic regulatory Ca(2+)-binding sites. Importantly, [Ca(2+)](ER) regulation of InsP(3)R channel activity depended on cytoplasmic Ca(2+)-buffering conditions: it was more pronounced when [Ca(2+)](i) was weakly buffered but completely abolished in strong Ca(2+)-buffering conditions. With strong cytoplasmic buffering and Ca(2+) flux sufficiently reduced by applied voltage, both activation and inhibition of InsP(3)R channel gating by physiological levels of [Ca(2+)](ER) were completely abolished. Collectively, these results rule out Ca(2+) regulation of channel activity by direct binding to the luminal aspect of the channel.
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Affiliation(s)
- Horia Vais
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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12
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Araki M, Nagayama T. IP3-mediated octopamine-induced synaptic enhancement of crayfish LG neurons. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2012; 198:607-15. [DOI: 10.1007/s00359-012-0733-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2011] [Revised: 04/28/2012] [Accepted: 04/28/2012] [Indexed: 01/06/2023]
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13
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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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14
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Resende RR, da Costa JL, Kihara AH, Adhikari A, Lorençon E. Intracellular Ca2+ Regulation During Neuronal Differentiation of Murine Embryonal Carcinoma and Mesenchymal Stem Cells. Stem Cells Dev 2010; 19:379-94. [DOI: 10.1089/scd.2008.0289] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Affiliation(s)
- Rodrigo R. Resende
- Department of Physics, Institute of Exacts Sciences, Federal University of Minas Gerais, Belo Horizonte, Brazil
- Instituto de Ensino e Pesquisa Santa Casa de BH (ISCM-BH), Belo Horizante, Brazil
| | - José L. da Costa
- Instrumental Analysis Laboratory, Criminalistic Institute of São Paulo, São Paulo, Brazil; Institute of Chemistry, University of São Paulo, São Paulo, Brazil
| | - Alexandre H. Kihara
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
- Centro de Matemática, Computação e Cognição, Universidade Federal do ABC, Santo André, Brasil
| | - Avishek Adhikari
- Department of Biological Sciences, Columbia University, New York
| | - Eudes Lorençon
- Department of Physics, Institute of Exacts Sciences, Federal University of Minas Gerais, Belo Horizonte, Brazil
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15
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Rossi AM, Riley AM, Potter BV, Taylor CW. Adenophostins. CURRENT TOPICS IN MEMBRANES 2010; 66:209-33. [DOI: 10.1016/s1063-5823(10)66010-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/04/2023]
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16
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Resende RR, Adhikari A, da Costa JL, Lorençon E, Ladeira MS, Guatimosim S, Kihara AH, Ladeira LO. Influence of spontaneous calcium events on cell-cycle progression in embryonal carcinoma and adult stem cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2009; 1803:246-60. [PMID: 19958796 DOI: 10.1016/j.bbamcr.2009.11.008] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2009] [Revised: 10/28/2009] [Accepted: 11/18/2009] [Indexed: 01/11/2023]
Abstract
Spontaneous Ca(2+) events have been observed in diverse stem cell lines, including carcinoma and mesenchymal stem cells. Interestingly, during cell cycle progression, cells exhibit Ca(2+) transients during the G(1) to S transition, suggesting that these oscillations may play a role in cell cycle progression. We aimed to study the influence of promoting and blocking calcium oscillations in cell proliferation and cell cycle progression, both in neural progenitor and undifferentiated cells. We also identified which calcium stores are required for maintaining these oscillations. Both in neural progenitor and undifferentiated cells calcium oscillations were restricted to the G1/S transition, suggesting a role for these events in progression of the cell cycle. Maintenance of the oscillations required calcium influx only through inositol 1,4,5-triphosphate receptors (IP(3)Rs) and L-type channels in undifferentiated cells, while neural progenitor cells also utilized ryanodine-sensitive stores. Interestingly, promoting calcium oscillations through IP(3)R agonists increased both proliferation and levels of cell cycle regulators such as cyclins A and E. Conversely, blocking calcium events with IP(3)R antagonists had the opposite effect in both undifferentiated and neural progenitor cells. This suggests that calcium events created by IP(3)Rs may be involved in cell cycle progression and proliferation, possibly due to regulation of cyclin levels, both in undifferentiated cells and in neural progenitor cells.
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Affiliation(s)
- R R Resende
- Department of Physics, Institute of Exact Sciences, Federal University of Minas Gerais, Belo Horizonte, MG 31270-901, Brazil.
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17
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Abstract
Calcium signals mediate diverse cellular functions in immunological cells. Early studies with mast cells, then a preeminent model for studying Ca2+-dependent exocytosis, revealed several basic features of calcium signaling in non-electrically excitable cells. Subsequent studies in these and other cells further defined the basic processes such as inositol 1,4,5-trisphosphate-mediated release of Ca2+ from Ca2+ stores in the endoplasmic reticulum (ER); coupling of ER store depletion to influx of external Ca2+ through a calcium-release activated calcium (CRAC) channel now attributed to the interaction of the ER Ca2+ sensor, stromal interacting molecule-1 (STIM1), with a unique Ca2+-channel protein, Orai1/CRACM1, and subsequent uptake of excess Ca2+ into ER and mitochondria through ATP-dependent Ca2+ pumps. In addition, transient receptor potential channels and ion exchangers also contribute to the generation of calcium signals that may be global or have dynamic (e.g., waves and oscillations) and spatial resolution for specific functional readouts. This review discusses past and recent developments in this field of research, the pharmacologic agents that have assisted in these endeavors, and the mast cell as an exemplar for sorting out how calcium signals may regulate multiple outputs in a single cell.
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Affiliation(s)
- Hong-Tao Ma
- Laboratory of Molecular Immunology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
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18
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Distribution of inositol-1,4,5-trisphosphate receptor isotypes and ryanodine receptor isotypes during maturation of the rat hippocampus. Neuroscience 2007; 150:625-38. [PMID: 17981403 DOI: 10.1016/j.neuroscience.2007.09.058] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2007] [Revised: 09/22/2007] [Accepted: 09/28/2007] [Indexed: 11/23/2022]
Abstract
Activation of inositol-1,4,5-trisphosphate receptors (InsP(3)Rs) and ryanodine receptors (RyRs) can lead to the release of Ca(2+) from intracellular stores and propagating Ca(2+) waves. Previous studies of these proteins in neurons have focused on their distribution in adult tissue, whereas, recent functional studies have examined neural tissue extracted from prenatal and young postnatal animals. In this study we examined the distribution of InsP(3)R isotypes 1-3 and RyR isotypes 1-3 in rat hippocampus during postnatal maturation, with a focus on InsP(3)R1 because it is most prominent in the hippocampus. InsP(3)R1 was observed in pyramidal cells and granule cells, InsP(3)R2 immunoreactivity was observed in perivascular astrocytes and endothelial cells, and InsP(3)R3 immunoreactivity was detected in axon terminals located in stratum pyramidale of CA1 and microvessels in stratum radiatum. RyR1 immunolabeling was enriched in CA1, RyR2 was most intense in CA3 and the dentate gyrus, and RyR3 immunolabeling was detected in all subfields of the hippocampus, but was most intense in stratum lacunosum-moleculare. During maturation from 2 to 10 weeks of age there was a shift in InsP(3)R1 immunoreactivity from a high density in the proximal apical dendrites to a uniform distribution along the dendrites. Independent of age, InsP(3)R1 immunoreactivity was observed to form clusters within the primary apical dendrite and at dendritic bifurcations of pyramidal neurons. As CA1 pyramidal neurons matured, InsP(3)R1 was often co-localized with the Ca(2+) binding protein calbindin D-28k. In contrast, InsP(3)R1 immunolabel was never co-localized with calbindin D-28k immunopositive interneurons located outside of stratum pyramidale or with parvalbumin, typically found in hippocampal basket cells, suggesting that InsP(3)R1s do not play a role in internal Ca(2+) release in these interneurons. These findings should help to interpret past functional studies and inform future studies examining the characteristics and consequences of InsP(3)R-mediated internal Ca(2+) release and Ca(2+) waves in hippocampal neurons.
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19
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Caride AJ, Filoteo AG, Penniston JT, Strehler EE. The plasma membrane Ca2+ pump isoform 4a differs from isoform 4b in the mechanism of calmodulin binding and activation kinetics: implications for Ca2+ signaling. J Biol Chem 2007; 282:25640-8. [PMID: 17595168 PMCID: PMC2680277 DOI: 10.1074/jbc.m701129200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The inhibition by the regulatory domain and the interaction with calmodulin (CaM) vary among plasma membrane calcium pump (PMCA) isoforms. To explore these differences, the kinetics of CaM effects on PMCA4a were investigated and compared with those of PMCA4b. The maximal apparent rate constant for CaM activation of PMCA4a was almost twice that for PMCA4b, whereas the rates of activation for both isoforms showed similar dependence on Ca2+. The inactivation of PMCA4a by CaM removal was also faster than for PMCA4b, and Ca2+ showed a much smaller effect (2- versus 30-fold modification). The rate constants of the individual steps that determine the overall rates were obtained from stopped-flow experiments in which binding of TA-CaM was observed by changes in its fluorescence. TA-CaM binds to two conformations of PMCA4a, an "open" conformation with high activity, and a "closed" one with lower activity. Compared with PMCA4b (Penheiter, A. R., Bajzer, Z., Filoteo, A. G., Thorogate, R., Török, K., and Caride, A. J. (2003) Biochemistry 41, 12115-12124), the model for PMCA4a predicts less inhibition in the closed form and a much faster equilibrium between the open and closed forms. Based on the available kinetic parameters, we determined the constants to fit the shape of a Ca2+ signal in PMCA4b-overexpressing Chinese hamster ovary cells. Using the constants for PMCA4a, and allowing small variations in parameters of other systems contributing to a Ca2+ signal, we then simulated the effect of PMCA4a on the shape of a Ca2+ signal in Chinese hamster ovary cells. The results reproduce the published data (Brini, M., Coletto, L., Pierobon, N., Kraev, N., Guerini, D., and Carafoli, E. (2003) J. Biol. Chem. 278, 24500-24508), and thereby demonstrate the importance of altered regulatory kinetics for the different functional properties of PMCA isoforms.
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Affiliation(s)
- Ariel J. Caride
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, MN 55905
| | - Adelaida G. Filoteo
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, MN 55905
| | | | - Emanuel E. Strehler
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, MN 55905
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20
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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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21
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Abstract
The liberation of calcium ions sequestered in the endoplasmic reticulum through inositol 1,4,5-trisphosphate receptors/channels (IP(3)Rs) results in a spatiotemporal hierarchy of calcium signaling events that range from single-channel openings to local Ca(2+) puffs believed to arise from several to tens of clustered IP(3)Rs to global calcium waves. Using high-resolution confocal linescan imaging and a sensitive Ca(2+) indicator dye (fluo-4-dextran), we show that puffs are often preceded by small, transient Ca(2+) elevations that we christen "trigger events". The magnitude of triggers is consistent with their arising from the opening of a single IP(3) receptor/channel, and we propose that they initiate puffs by recruiting neighboring IP(3)Rs within the cluster by a regenerative process of Ca(2+)-induced Ca(2+) release. Puff amplitudes (fluorescence ratio change) are on average approximately 6 times greater than that of the triggers, suggesting that at least six IP(3)Rs may simultaneously be open during a puff. Trigger events have average durations of approximately 12 ms, as compared to 19 ms for the mean rise time of puffs, and their spatial extent is approximately 3 times smaller than puffs (respective widths at half peak amplitude 0.6 and 1.6 micro m). All these parameters were relatively independent of IP(3) concentration, although the proportion of puffs showing resolved triggers was greatest (approximately 80%) at low [IP(3)]. Because Ca(2+) puffs constitute the building blocks from which cellular IP(3)-mediated Ca(2+) signals are constructed, the events that initiate them are likely to be of fundamental importance for cell signaling. Moreover, the trigger events provide a useful yardstick by which to derive information regarding the number and spatial arrangement of IP(3)Rs within clusters.
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Affiliation(s)
- Heather J Rose
- Department of Neurobiology and Behavior, University of California, Irvine, CA 92697, USA.
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22
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Fraiman D, Pando B, Dargan S, Parker I, Dawson SP. Analysis of puff dynamics in oocytes: interdependence of puff amplitude and interpuff interval. Biophys J 2006; 90:3897-907. [PMID: 16533853 PMCID: PMC1459518 DOI: 10.1529/biophysj.105.075911] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Puffs are localized Ca(2+) signals that arise in oocytes in response to inositol 1,4,5-trisphosphate (IP(3)). They are analogous to the sparks of myocytes and are believed to be the result of the liberation of Ca(2+) from the endoplasmic reticulum through the coordinated opening of IP(3) receptor/channels clustered at a functional release site. In this article, we analyze sequences of puffs that occur at the same site to help elucidate the mechanisms underlying puff dynamics. In particular, we show a dependence of the interpuff time on the amplitude of the preceding puff, and of the amplitude of the following puff on the preceding interval. These relationships can be accounted for by an inhibitory role of the Ca(2+) that is liberated during puffs. We construct a stochastic model for a cluster of IP(3) receptor/channels that quantitatively replicates the observed behavior, and we determine that the characteristic time for a channel to escape from the inhibitory state is of the order of seconds.
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Affiliation(s)
- Daniel Fraiman
- Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Buenos Aires, Argentina.
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23
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Abstract
A large amount of data and observations on inositol 1,4,5-trisphosphate (IP(3)) binding to the IP(3) receptor/Ca(2+) channel, the steady-state activity of the channel, and its inactivation by IP(3) can be explained by assuming one activation and one inhibition module, both allosterically operated by Ca(2+), IP(3), and ATP, and one adaptation element, driven by IP(3), Ca(2+), and the interconversion between two possible conformations of the receptor. The adaptation module becomes completely insensitive to a second IP(3) pulse within 80 s. Observed kinetic responses are well reproduced if, in addition, two module open states are rendered inactive by the current charge carrier Mn(2+). The inactivation time constants are 59 s in the activation, and 0.75 s in the adaptation module. The in vivo open probability of the channel is predicted to be almost in coincidence with the behavior in lipid bilayers for IP(3) levels of 0.2 and 2 microM and one-order-higher at 0.02 microM IP(3), whereas at 180 microM IP(3) the maximal in vivo activity may be 2.5-orders higher than in bilayers and restricted to a narrower Ca(2+) domain (approximately 10 microM-wide versus approximately 100 microM-wide). IP(3) is likely to inhibit channel activity at < or =120 nM Ca(2+) in vivo.
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Affiliation(s)
- Irina Baran
- Biophysics Department, Faculty of Medicine, University of Medicine and Pharmacy Carol Davila, Bucharest, Romania.
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24
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Machaca K. Increased sensitivity and clustering of elementary Ca2+ release events during oocyte maturation. Dev Biol 2004; 275:170-82. [PMID: 15464580 DOI: 10.1016/j.ydbio.2004.08.004] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2004] [Revised: 07/10/2004] [Accepted: 08/02/2004] [Indexed: 10/26/2022]
Abstract
The universal signal for egg activation at fertilization is a rise in cytoplasmic Ca(2+) with defined spatial and temporal kinetics. Mammalian and amphibian eggs acquire the ability to produce such Ca(2+) signals during a maturation period that precedes fertilization and encompasses resumption of meiosis and progression to metaphase II. In Xenopus, immature oocytes produce fast, saltatory Ca(2+) waves that can be oscillatory in nature in response to IP(3). In contrast, mature eggs produce a single continuous, sweeping Ca(2+) wave in response to IP(3) or sperm fusion. The mechanisms mediating the differentiation of Ca(2+) signaling during oocyte maturation are not well understood. Here, I characterized elementary Ca(2+) release events (Ca(2+) puffs) in oocytes and eggs and show that the sensitivity of IP(3)-dependent Ca(2+) release is greatly enhanced during oocyte maturation. Furthermore, Ca(2+) puffs in eggs have a larger spatial fingerprint, yet are short lived compared to oocyte puffs. Most interestingly, Ca(2+) puffs cluster during oocyte maturation resulting in a continuum of Ca(2+) release sites over space in eggs. These changes in the spatial distribution of elementary Ca(2+) release events during oocyte maturation explain the continuous nature and slower speed of the fertilization Ca(2+) wave.
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Affiliation(s)
- Khaled Machaca
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
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25
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Fraiman D, Dawson SP. A model of IP3 receptor with a luminal calcium binding site: stochastic simulations and analysis. Cell Calcium 2004; 35:403-13. [PMID: 15003850 DOI: 10.1016/j.ceca.2003.10.004] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2003] [Revised: 08/20/2003] [Accepted: 10/16/2003] [Indexed: 11/26/2022]
Abstract
We have constructed a stochastic model of the inositol 1,4,5-trisphosphate receptor-Ca2+ channel that is based on quantitative measurements of the channel's properties. It displays the observed dependence of the open probability of the channel with cytosolic [Ca2+] and [IP3] and gives values for the dwell times that agree with the observations. The model includes an explicit dependence of channel gating with luminal calcium. This not only explains several observations reported in the literature, but also provides a possible explanation of why the open probabilities and shapes of the bell-shaped curves reported in [Nature 351 (1991) 751] and in [Proc. Natl. Acad. Sci. U.S.A. 269 (1998) 7238] are so different.
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Affiliation(s)
- Daniel Fraiman
- Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón I (1428), Buenos Aires, Argentina.
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26
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Mak DOD, McBride SMJ, Petrenko NB, Foskett JK. Novel regulation of calcium inhibition of the inositol 1,4,5-trisphosphate receptor calcium-release channel. ACTA ACUST UNITED AC 2004; 122:569-81. [PMID: 14581583 PMCID: PMC2229581 DOI: 10.1085/jgp.200308808] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [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), a Ca2+-release channel localized to the endoplasmic reticulum, plays a critical role in generating complex cytoplasmic Ca2+ signals in many cell types. Three InsP3R isoforms are expressed in different subcellular locations, at variable relative levels with heteromultimer formation in different cell types. A proposed reason for this diversity of InsP3R expression is that the isoforms are differentially inhibited by high cytoplasmic free Ca2+ concentrations ([Ca2+]i), possibly due to their different interactions with calmodulin. Here, we have investigated the possible roles of calmodulin and bath [Ca2+] in mediating high [Ca2+]i inhibition of InsP3R gating by studying single endogenous type 1 InsP3R channels through patch clamp electrophysiology of the outer membrane of isolated Xenopus oocyte nuclei. Neither high concentrations of a calmodulin antagonist nor overexpression of a dominant-negative Ca2+-insensitive mutant calmodulin affected inhibition of gating by high [Ca2+]i. However, a novel, calmodulin-independent regulation of [Ca2+]i inhibition of gating was revealed: whereas channels recorded from nuclei kept in the regular bathing solution with [Ca2+] approximately 400 nM were inhibited by 290 muM [Ca2+]i, exposure of the isolated nuclei to a bath solution with ultra-low [Ca2+] (<5 nM, for approximately 300 s) before the patch-clamp experiments reversibly relieved Ca2+ inhibition, with channel activities observed in [Ca2+]i up to 1.5 mM. Although InsP3 activates gating by relieving high [Ca2+]i inhibition, it was nevertheless still required to activate channels that lacked high [Ca2+]i inhibition. Our observations suggest that high [Ca2+]i inhibition of InsP3R channel gating is not regulated by calmodulin, whereas it can be disrupted by environmental conditions experienced by the channel, raising the possibility that presence or absence of high [Ca2+]i inhibition may not be an immutable property of different InsP3R isoforms. Furthermore, these observations support an allosteric model in which Ca2+ inhibition of the InsP3R is mediated by two Ca2+ binding sites, only one of which is sensitive to InsP3.
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Affiliation(s)
- Don-On Daniel Mak
- Department of Physiology, B39 Anatomy-Chemistry Bldg/6085, University of Pennsylvania, Philadelphia, PA 19104-6085, USA.
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27
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Mak DOD, McBride SMJ, Foskett JK. Spontaneous channel activity of the inositol 1,4,5-trisphosphate (InsP3) receptor (InsP3R). Application of allosteric modeling to calcium and InsP3 regulation of InsP3R single-channel gating. J Gen Physiol 2003; 122:583-603. [PMID: 14581584 PMCID: PMC2229577 DOI: 10.1085/jgp.200308809] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2003] [Accepted: 09/16/2003] [Indexed: 12/05/2022] Open
Abstract
The InsP3R Ca2+ release channel has a biphasic dependence on cytoplasmic free Ca2+ concentration ([Ca2+]i). InsP3 activates gating primarily by reducing the sensitivity of the channel to inhibition by high [Ca2+]i. To determine if relieving Ca2+ inhibition is sufficient for channel activation, we examined single-channel activities in low [Ca2+]i in the absence of InsP3, by patch clamping isolated Xenopus oocyte nuclei. For both endogenous Xenopus type 1 and recombinant rat type 3 InsP3R channels, spontaneous InsP3-independent channel activities with low open probability Po ( approximately 0.03) were observed in [Ca2+]i < 5 nM with the same frequency as in the presence of InsP3, whereas no activities were observed in 25 nM Ca2+. These results establish the half-maximal inhibitory [Ca2+]i of the channel to be 1.2-4.0 nM in the absence of InsP3, and demonstrate that the channel can be active when all of its ligand-binding sites (including InsP3) are unoccupied. In the simplest allosteric model that fits all observations in nuclear patch-clamp studies of [Ca2+]i and InsP3 regulation of steady-state channel gating behavior of types 1 and 3 InsP3R isoforms, including spontaneous InsP3-independent channel activities, the tetrameric channel can adopt six different conformations, the equilibria among which are controlled by two inhibitory and one activating Ca2+-binding and one InsP3-binding sites in a manner outlined in the Monod-Wyman-Changeux model. InsP3 binding activates gating by affecting the Ca2+ affinities of the high-affinity inhibitory sites in different conformations, transforming it into an activating site. Ca2+ inhibition of InsP3-liganded channels is mediated by an InsP3-independent low-affinity inhibitory site. The model also suggests that besides the ligand-regulated gating mechanism, the channel has a ligand-independent gating mechanism responsible for maximum channel Po being less than unity. The validity of this model was established by its successful quantitative prediction of channel behavior after it had been exposed to ultra-low bath [Ca2+].
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Affiliation(s)
- Don-On Daniel Mak
- Department of Physiology, B39 Anatomy-Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6085, USA.
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28
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Cadiou H, Molle G. Adenophostin A and imipramine are two activators of the olfactory inositol 1,4,5-trisphosphate-gated channel in fish olfatory cilia. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2003; 32:106-12. [PMID: 12734698 DOI: 10.1007/s00249-002-0271-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2002] [Accepted: 11/19/2002] [Indexed: 10/25/2022]
Abstract
Binding of an odorant to its receptor activates the cAMP-dependent pathway, and also leads to inositol 1,4,5-trisphosphate (InsP(3)) production. This induces opening of a plasma membrane channel in olfactory receptor cells (ORCs). We investigated single-channel properties of this channel in the presence of a phospholipase C (PLC) activator (imipramine) and of a potent activator of the InsP(3)/Ca(2+) release channel (adenophostin A) by reconstituting carp olfactory cilia into planar lipid bilayers. In the presence of 53 mM barium as a charge carrier, the addition of 50 microM imipramine induced a current of 1.53+/-0.05 pA at 0 mV. There were two different mean open times (6.0+/-0.6 ms and 49.6+/-6.4 ms). The I/ V curve displayed a slope conductance of 50+/-2 pS. Channel activity was transient and was blocked by neomycin (50 microM). These observations suggest that imipramine may activate the olfactory InsP(3)-gated channel through PLC. Using the same ionic conditions, the application of 0.5 microM adenophostin A triggered a current of 1.47+/-0.04 pA at 0 mV. The I/ V curve displayed a slope conductance of 60+/-2 pS. This channel showed only a single mean open time (15.0+/-0.3 ms) and was strongly inhibited by ruthenium red (30 microM) and heparin (10 microg/mL). These results indicate that adenophostin A and imipramine may act on the ciliary InsP(3)-gated channel and are potentially valuable pharmacological tools for studying olfactory transduction mechanisms.
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Affiliation(s)
- Hervé Cadiou
- UMR 6522 CNRS, IFRMP 23, Université de Rouen, 76821 Mont-Saint-Aignan, France
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29
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Abstract
Inositol 1,4,5-trisphosphate (IP(3)) receptors are tetrameric intracellular Ca(2+) channels, the opening of which is regulated by both IP(3) and Ca(2+). We suggest that all IP(3) receptors are biphasically regulated by cytosolic Ca(2+), which binds to two distinct sites. IP(3) promotes channel opening by controlling whether Ca(2+) binds to the stimulatory or inhibitory sites. The stimulatory site is probably an integral part of the receptor lying just upstream of the pore region. Inhibition of IP(3) receptors by Ca(2+) probably requires an accessory protein, which has not yet been unequivocally identified, but calmodulin is a prime candidate. We speculate that one lobe of calmodulin tethers it to the IP(3) receptor, while the other lobe can bind Ca(2+) and then interact with a second site on the receptor to cause inhibition.
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Affiliation(s)
- C W Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, CB2 1PD, Cambridge, UK.
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30
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Morris SA, Nerou EP, Riley AM, Potter BVL, Taylor CW. Determinants of adenophostin A binding to inositol trisphosphate receptors. Biochem J 2002; 367:113-20. [PMID: 12088506 PMCID: PMC1222864 DOI: 10.1042/bj20020675] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2002] [Revised: 06/25/2002] [Accepted: 06/27/2002] [Indexed: 11/17/2022]
Abstract
Inositol 1,4,5-trisphosphate (IP(3)) receptors from cerebellum and recombinant type 1 IP(3) receptors expressed in Sf9 cells had indistinguishable affinities for IP(3) ( K (d)=6.40+/-0.48 nM) and adenophostin A ( K (d)=0.89+/-0.05 nM). In cytosol-like medium, each of the three mammalian IP(3) receptor subtypes when expressed in Sf9 cells bound adenophostin A with greater affinity than IP(3). It has been suggested that adenophostin A binds with high affinity only in the presence of ATP, but we found that adenophostin A similarly displaced [(3)H]IP(3) from type 1 IP(3) receptors whatever the ATP concentration. N-terminal fragments of the type 1 receptor were expressed with and without the S1 splice site; its removal had no effect on [(3)H]IP(3) binding to the 1-604 protein, but abolished binding to the 224-604 protein. The 1-604 fragment and full-length receptor bound adenophostin A with the same affinity, but the fragment had 3-fold greater affinity for IP(3), suggesting that C-terminal residues selectively inhibit IP(3) binding. The 224-604S1(+) fragment bound IP(3) and adenophostin A with increased affinity, but as with the 1-604 fragment it bound adenophostin A with only 2-fold greater affinity than IP(3). High-affinity binding of adenophostin A may be partially determined by its 2'-phosphate interacting more effectively than the 1-phosphate of IP(3) with residues within the IP(3)-binding core. This may account for the 2-fold greater affinity of adenophostin A relative to IP(3) for the minimal IP(3)-binding domain. In addition we suggest that C-terminal residues, which impede access of IP(3), may selectively interact with adenophostin A to allow it unhindered access to the IP(3)-binding domain.
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Affiliation(s)
- Stephen A Morris
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, U.K
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31
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Moore-Nichols D, Arnott A, Dunn RC. Regulation of nuclear pore complex conformation by IP(3) receptor activation. Biophys J 2002; 83:1421-8. [PMID: 12202368 PMCID: PMC1302241 DOI: 10.1016/s0006-3495(02)73913-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
In recent years, both the molecular architecture and functional dynamics of nuclear pore complexes (NPCs) have been revealed with increasing detail. These large, supramolecular assemblages of proteins form channels that span the nuclear envelope of cells, acting as crucial regulators of nuclear import and export. From the cytoplasmic face of the nuclear envelope, nuclear pore complexes exhibit an eightfold symmetric ring structure encompassing a central lumen. The lumen often appears occupied by an additional structure alternatively referred to as the central granule, nuclear transport complex, or nuclear plug. Previous studies have suggested that the central granule may play a role in mediating calcium-dependent regulation of diffusion across the nuclear envelope for intermediate sized molecules (10-40 kDa). Using atomic force microscopy to measure the surface topography of chemically fixed Xenopus laevis oocyte nuclear envelopes, we present measurements of the relative position of the central granule within the NPC lumen under a variety of conditions known to modify nuclear Ca(2+) stores. These measurements reveal a large, approximately 9-nm displacement of the central granule toward the cytoplasmic face of the nuclear envelope under calcium depleting conditions. Additionally, activation of nuclear inositol triphosphate (IP(3)) receptors by the specific agonist, adenophostin A, results in a concentration-dependent displacement of central granule position with an EC(50) of ~1.2 nM. The displacement of the central granule within the NPC is observed on both the cytoplasmic and nucleoplasmic faces of the nuclear envelope. The displacement is blocked upon treatment with xestospongin C, a specific inhibitor of IP(3) receptor activation. These results extend previous models of NPC conformational dynamics linking central granule position to depletion of IP(3) sensitive nuclear envelope calcium stores.
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32
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Shuai JW, Jung P. Stochastic properties of Ca(2+) release of inositol 1,4,5-trisphosphate receptor clusters. Biophys J 2002; 83:87-97. [PMID: 12080102 PMCID: PMC1302129 DOI: 10.1016/s0006-3495(02)75151-5] [Citation(s) in RCA: 150] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Intracellular Ca(2+) release is controlled by inositol 1,4,5-trisphosphate (IP(3)) receptors or ryanodine receptors. These receptors are typically distributed in clusters with several or tens of channels. The random opening and closing of these channels introduces stochasticity into the elementary calcium release mechanism. Stochastic release events have been experimentally observed in a variety of cell types and have been termed sparks and puffs. We put forward a stochastic version of the Li-Rinzel model (the deactivation binding process is described by a Markovian scheme) and a computationally more efficient Langevin approach to model the stochastic Ca(2+) oscillation of single clusters. Statistical properties such as Ca(2+) puff amplitudes, lifetimes, and interpuff intervals are studied with both models and compared with experimental observations. For clusters with tens of channels, a simply decaying amplitude distribution is typically observed at low IP(3) concentration, while a single peak distribution appears at high IP(3) concentration.
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Affiliation(s)
- Jian-Wei Shuai
- Department of Physics and Astronomy and Institute for Quantitative Biology, Ohio University, Athens, Ohio 45701, USA.
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Riley AM, Jenkins DJ, Marwood RD, Potter BVL. Synthesis of glucopyranoside-based ligands for D-myo-inositol 1,4,5-trisphosphate receptors. Carbohydr Res 2002; 337:1067-82. [PMID: 12062522 DOI: 10.1016/s0008-6215(02)00103-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Adenophostins A and B are naturally occurring glyconucleotides that interact potently with receptors for D-myo-inositol 1,4,5-trisphosphate, an important second messenger molecule in most cell types. Here we describe the design and synthesis of glucopyranoside-based analogues of adenophostin A lacking the adenine component. The key synthetic strategy involves glycosylation of selectively protected alcohols, derived from methyl beta-D-ribofuranoside or 1,4-anhydroerythritol, using glycosyl donors synthesised from 2,6-di-O-benzyl-D-glucopyranose derivatives. Further elaboration and deprotection of the coupled products gave two trisphosphate analogues; methyl 3-O-alpha-D-glucopyranosyl-beta-D-ribofuranoside 2,3',4'-trisphosphate ("ribophostin") and (3'S,4'R)-3'-hydroxytetrahydrofuran-4'-yl alpha-D-glucopyranoside 3,4,3'-trisphosphosphate ("furanophostin"). The route to furanophostin was further modified to give (3'S,4'R)-3'-hydroxytetrahydrofuran-4'-yl alpha-D-glucopyranoside 3'-phosphate 3,4-bisphosphorothioate, the first phosphorothioate-containing adenophostin analogue.
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Affiliation(s)
- Andrew M Riley
- Wolfson Laboratory of Medicinal Chemistry, Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, UK
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Yang J, McBride S, Mak DOD, Vardi N, Palczewski K, Haeseleer F, Foskett JK. Identification of a family of calcium sensors as protein ligands of inositol trisphosphate receptor Ca(2+) release channels. Proc Natl Acad Sci U S A 2002; 99:7711-6. [PMID: 12032348 PMCID: PMC124329 DOI: 10.1073/pnas.102006299] [Citation(s) in RCA: 162] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The inositol trisphosphate (InsP(3)) receptor (InsP(3)R) is a ubiquitously expressed intracellular Ca(2+) channel that mediates complex cytoplasmic Ca(2+) signals, regulating diverse cellular processes, including synaptic plasticity. Activation of the InsP(3)R channel is normally thought to require binding of InsP(3) derived from receptor-mediated activation of phosphatidylinositol lipid hydrolysis. Here we identify a family of neuronal Ca(2+)-binding proteins as high-affinity protein agonists of the InsP(3)R, which bind to the channel and activate gating in the absence of InsP(3). CaBP/caldendrin, a subfamily of the EF-hand-containing neuronal calcium sensor family of calmodulin-related proteins, bind specifically to the InsP(3)-binding region of all three InsP(3)R channel isoforms with high affinity (K(a) approximately 25 nM) in a Ca(2+)-dependent manner (K(a) approximately 1 microM). Binding activates single-channel gating as efficaciously as InsP(3), dependent on functional EF-hands in CaBP. In contrast, calmodulin neither bound with high affinity nor activated channel gating. CaBP1 and the type 1 InsP(3)R associate in rat whole brain and cerebellum lysates, and colocalize extensively in subcellular regions in cerebellar Purkinje neurons. Thus, InsP(3)R-mediated Ca(2+) signaling in cells is possible even in the absence of InsP(3) generation, a process that may be particularly important in responding to and shaping changes in intracellular Ca(2+) concentration by InsP(3)-independent pathways and for localizing InsP(3)-mediated Ca(2+) signals to individual synapses.
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Affiliation(s)
- Jun Yang
- Department of Physiology, University of Pennsylvania, Philadelphia, PA 19104-6085, USA
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Parekh AB, Riley AM, Potter BVL. Adenophostin A and ribophostin, but not inositol 1,4,5-trisphosphate or manno-adenophostin, activate the Ca2+ release-activated Ca2+ current, I(CRAC), in weak intracellular Ca2+ buffer. Biochem J 2002; 361:133-41. [PMID: 11742538 PMCID: PMC1222288 DOI: 10.1042/0264-6021:3610133] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Under physiological conditions of weak intracellular Ca(2+) buffering (0.1 mM EGTA), the second messenger Ins(1,4,5)P(3) often fails to activate any detectable store-operated Ca(2+) current. However, it has been reported that the fungal metabolite adenophostin A [which has a severalfold higher affinity than Ins(1,4,5)P(3) for Ins(1,4,5)P(3) receptors] consistently activates the current under similar conditions. Here, whole-cell patch clamp experiments have been performed to examine how adenophostin A can activate the store-operated Ca(2+) current (I(CRAC)) in RBL-1 (rat basophilic leukaemia) cells. In a strong intracellular Ca(2+) buffer, saturating concentrations of adenophostin A activated I(CRAC) maximally and the current amplitude and kinetics were indistinguishable from those obtained with high concentrations of Ins(1,4,5)P(3). In a weak Ca(2+) buffer, adenophostin A consistently activated I(CRAC), but the current was submaximal. High concentrations of Ins(1,4,5)P(3) or the non-metabolizable analogue Ins(2,4,5)P(3) were largely ineffective under these conditions. The size of I(CRAC) to adenophostin A in weak Ca(2+) buffer could be significantly increased by either inhibiting sarcoplasmic/endoplasmic-reticulum Ca(2+)-ATPase ('SERCA') pumps with thapsi-gargin or enhancing mitochondrial Ca(2+) uptake, although blocking the mitochondrial Ca(2+) uniporter with Ruthenium Red did not suppress the activation of the current. Changing the levels of free ATP in the recording pipette did not enhance the size of I(CRAC) evoked by adenophostin A. We also examined two structurally distinct analogues of adenophostin A (manno-adenophostin and ribophostin), for which the affinities for the Ins(1,4,5)P(3) receptor are similar to that of Ins(1,4,5)P(3) in equilibrium binding experiments. Although these analogues were able to activate I(CRAC) to its maximal extent in strong buffer, ribophostin, but not manno-adenophostin, consistently activated the current in weak buffer. We conclude that adenophostin A and ribophostin are able to activate I(CRAC) in weak buffer through a mechanism that is quite distinct from that employed by Ins(1,4,5)P(3) and manno-adenophostin and is not related to equilibrium affinities.
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Affiliation(s)
- Anant B Parekh
- Laboratory of Molecular and Cellular Signalling, Department of Physiology, University of Oxford, Parks Road, Oxford OX1 3PT, U.K.
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