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Chakraborty P, Deb BK, Arige V, Musthafa T, Malik S, Yule DI, Taylor CW, Hasan G. Regulation of store-operated Ca 2+ entry by IP 3 receptors independent of their ability to release Ca 2. eLife 2023; 12:e80447. [PMID: 37466241 PMCID: PMC10406432 DOI: 10.7554/elife.80447] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 07/18/2023] [Indexed: 07/20/2023] Open
Abstract
Loss of endoplasmic reticular (ER) Ca2+ activates store-operated Ca2+ entry (SOCE) by causing the ER localized Ca2+ sensor STIM to unfurl domains that activate Orai channels in the plasma membrane at membrane contact sites (MCS). Here, we demonstrate a novel mechanism by which the inositol 1,4,5 trisphosphate receptor (IP3R), an ER-localized IP3-gated Ca2+ channel, regulates neuronal SOCE. In human neurons, SOCE evoked by pharmacological depletion of ER-Ca2+ is attenuated by loss of IP3Rs, and restored by expression of IP3Rs even when they cannot release Ca2+, but only if the IP3Rs can bind IP3. Imaging studies demonstrate that IP3Rs enhance association of STIM1 with Orai1 in neuronal cells with empty stores; this requires an IP3-binding site, but not a pore. Convergent regulation by IP3Rs, may tune neuronal SOCE to respond selectively to receptors that generate IP3.
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Affiliation(s)
- Pragnya Chakraborty
- National Centre for Biological Sciences, Tata Institute of Fundamental ResearchBangaloreIndia
- SASTRA UniversityThanjavurIndia
| | - Bipan Kumar Deb
- National Centre for Biological Sciences, Tata Institute of Fundamental ResearchBangaloreIndia
| | - Vikas Arige
- Department of Pharmacology and Physiology, University of RochesterRochesterUnited States
| | - Thasneem Musthafa
- National Centre for Biological Sciences, Tata Institute of Fundamental ResearchBangaloreIndia
| | - Sundeep Malik
- Department of Pharmacology and Physiology, University of RochesterRochesterUnited States
| | - David I Yule
- Department of Pharmacology and Physiology, University of RochesterRochesterUnited States
| | - Colin W Taylor
- Department of Pharmacology, University of CambridgeCambridgeUnited Kingdom
| | - Gaiti Hasan
- National Centre for Biological Sciences, Tata Institute of Fundamental ResearchBangaloreIndia
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2
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Yao Y, Borkar NA, Zheng M, Wang S, Pabelick CM, Vogel ER, Prakash YS. Interactions between calcium regulatory pathways and mechanosensitive channels in airways. Expert Rev Respir Med 2023; 17:903-917. [PMID: 37905552 PMCID: PMC10872943 DOI: 10.1080/17476348.2023.2276732] [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: 09/20/2023] [Accepted: 10/25/2023] [Indexed: 11/02/2023]
Abstract
INTRODUCTION Asthma is a chronic lung disease influenced by environmental and inflammatory triggers and involving complex signaling pathways across resident airway cells such as epithelium, airway smooth muscle, fibroblasts, and immune cells. While our understanding of asthma pathophysiology is continually progressing, there is a growing realization that cellular microdomains play critical roles in mediating signaling relevant to asthma in the context of contractility and remodeling. Mechanosensitive pathways are increasingly recognized as important to microdomain signaling, with Piezo and transient receptor protein (TRP) channels at the plasma membrane considered important for converting mechanical stimuli into cellular behavior. Given their ion channel properties, particularly Ca2+ conduction, a question becomes whether and how mechanosensitive channels contribute to Ca2+ microdomains in airway cells relevant to asthma. AREAS COVERED Mechanosensitive TRP and Piezo channels regulate key Ca2+ regulatory proteins such as store operated calcium entry (SOCE) involving STIM and Orai channels, and sarcoendoplasmic (SR) mechanisms such as IP3 receptor channels (IP3Rs), and SR Ca2+ ATPase (SERCA) that are important in asthma pathophysiology including airway hyperreactivity and remodeling. EXPERT OPINION Physical and/or functional interactions between Ca2+ regulatory proteins and mechanosensitive channels such as TRP and Piezo can toward understanding asthma pathophysiology and identifying novel therapeutic approaches.
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Affiliation(s)
- Yang Yao
- Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Xi’an Medical University, Xi’an, Shaanxi, China
- Department of Anesthesiology, Mayo Clinic, Rochester, MN, USA
| | - Niyati A Borkar
- Department of Anesthesiology, Mayo Clinic, Rochester, MN, USA
| | - Mengning Zheng
- Department of Anesthesiology, Mayo Clinic, Rochester, MN, USA
- Department of Respiratory and Critical Care Medicine, Guizhou Province People’s Hospital, Guiyang, Guizhou, China
| | - Shengyu Wang
- Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Xi’an Medical University, Xi’an, Shaanxi, China
| | - Christina M Pabelick
- Department of Anesthesiology, Mayo Clinic, Rochester, MN, USA
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
| | - Elizabeth R Vogel
- Department of Anesthesiology, Mayo Clinic, Rochester, MN, USA
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
| | - YS Prakash
- Department of Anesthesiology, Mayo Clinic, Rochester, MN, USA
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
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3
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Smith HA, Thillaiappan NB, Rossi AM. IP 3 receptors: An "elementary" journey from structure to signals. Cell Calcium 2023; 113:102761. [PMID: 37271052 DOI: 10.1016/j.ceca.2023.102761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 05/15/2023] [Accepted: 05/18/2023] [Indexed: 06/06/2023]
Abstract
Inositol 1,4,5-trisphosphate receptors (IP3Rs) are large tetrameric channels which sit mostly in the membrane of the endoplasmic reticulum (ER) and mediate Ca2+ release from intracellular stores in response to extracellular stimuli in almost all cells. Dual regulation of IP3Rs by IP3 and Ca2+ itself, upstream "licensing", and the arrangement of IP3Rs into small clusters in the ER membrane, allow IP3Rs to generate spatially and temporally diverse Ca2+ signals. The characteristic biphasic regulation of IP3Rs by cytosolic Ca2+ concentration underpins regenerative Ca2+ signals by Ca2+-induced Ca2+-release, while also preventing uncontrolled explosive Ca2+ release. In this way, cells can harness a simple ion such as Ca2+ as a near-universal intracellular messenger to regulate diverse cellular functions, including those with conflicting outcomes such as cell survival and cell death. High-resolution structures of the IP3R bound to IP3 and Ca2+ in different combinations have together started to unravel the workings of this giant channel. Here we discuss, in the context of recently published structures, how the tight regulation of IP3Rs and their cellular geography lead to generation of "elementary" local Ca2+ signals known as Ca2+ "puffs", which form the fundamental bottleneck through which all IP3-mediated cytosolic Ca2+ signals must first pass.
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Affiliation(s)
- Holly A Smith
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom
| | | | - Ana M Rossi
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, United Kingdom.
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4
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Abstract
Inositol 1,4,5-trisphosphate (IP3) plays a key role in calcium signaling. After stimulation, it diffuses from the plasma membrane where it is produced to the endoplasmic reticulum where its receptors are localized. Based on in vitro measurements, IP3 was long thought to be a global messenger characterized by a diffusion coefficient of ~ 280 μm2s-1. However, in vivo observations revealed that this value does not match with the timing of localized Ca2+ increases induced by the confined release of a non-metabolizable IP3 analog. A theoretical analysis of these data concluded that in intact cells diffusion of IP3 is strongly hindered, leading to a 30-fold reduction of the diffusion coefficient. Here, we performed a new computational analysis of the same observations using a stochastic model of Ca2+ puffs. Our simulations concluded that the value of the effective IP3 diffusion coefficient is close to 100 μm2s-1. Such moderate reduction with respect to in vitro estimations quantitatively agrees with a buffering effect by non-fully bound inactive IP3 receptors. The model also reveals that IP3 spreading is not much affected by the endoplasmic reticulum, which represents an obstacle to the free displacement of molecules, but can be significantly increased in cells displaying elongated, 1-dimensional like geometries.
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5
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Feliziani C, Fernandez M, Quasollo G, Holstein D, Bairo SM, Paton JC, Paton AW, de Batista J, Lechleiter JD, Bollo M. Ca 2+ signalling system initiated by endoplasmic reticulum stress stimulates PERK activation. Cell Calcium 2022; 106:102622. [PMID: 35908318 PMCID: PMC9982837 DOI: 10.1016/j.ceca.2022.102622] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 06/11/2022] [Accepted: 07/05/2022] [Indexed: 01/25/2023]
Abstract
The accumulation of unfolded proteins within the Endoplasmic Reticulum (ER) activates a signal transduction pathway termed the unfolded protein response (UPR), which attempts to restore ER homoeostasis. If this cannot be done, UPR signalling ultimately induces apoptosis. Ca2+ depletion in the ER is a potent inducer of ER stress. Despite the ubiquity of Ca2+ as an intracellular messenger, the precise mechanism(s) by which Ca2+ release affects the UPR remains unknown. Tethering a genetically encoded Ca2+ indicator (GCamP6) to the ER membrane revealed novel Ca2+ signalling events initiated by Ca2+ microdomains in human astrocytes under ER stress, induced by tunicamycin (Tm), an N-glycosylation inhibitor, as well as in a cell model deficient in all three inositol triphosphate receptor isoforms. Pharmacological and molecular studies indicate that these local events are mediated by translocons and that the Ca2+ microdomains impact (PKR)-like-ER kinase (PERK), an UPR sensor, activation. These findings reveal the existence of a Ca2+ signal mechanism by which stressor-mediated Ca2+ release regulates ER stress.
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Affiliation(s)
- Constanza Feliziani
- Instituto de Investigación Médica M y M
Ferreyra, INIMEC-CONICET, Universidad Nacional de Córdoba, 2434 Friuli,
Córdoba 5016, Argentina
| | - Macarena Fernandez
- Instituto de Investigación Médica M y M
Ferreyra, INIMEC-CONICET, Universidad Nacional de Córdoba, 2434 Friuli,
Córdoba 5016, Argentina
| | - Gonzalo Quasollo
- Instituto de Investigación Médica M y M
Ferreyra, INIMEC-CONICET, Universidad Nacional de Córdoba, 2434 Friuli,
Córdoba 5016, Argentina
| | - Deborah Holstein
- Department of Cell Systems and Anatomy, UT Health San
Antonio, 8403 Floyd Curl Dr., San Antonio, TX 78229-3904, USA
| | - Sebastián M Bairo
- Instituto de Investigación Médica M y M
Ferreyra, INIMEC-CONICET, Universidad Nacional de Córdoba, 2434 Friuli,
Córdoba 5016, Argentina
| | - James C Paton
- Research Centre for Infectious Diseases, School of
Molecular and Biomedical Science, University of Adelaide, South Australia 5005,
Australia
| | - Adrienne W Paton
- Research Centre for Infectious Diseases, School of
Molecular and Biomedical Science, University of Adelaide, South Australia 5005,
Australia
| | - Juan de Batista
- Instituto Universitario de Ciencias Biomédicas de
Córdoba (IUCBC), Hospital Privado Universitario de Córdoba, 420
Naciones Unidas, Córdoba 5016, Argentina
| | - James D Lechleiter
- Department of Cell Systems and Anatomy, UT Health San
Antonio, 8403 Floyd Curl Dr., San Antonio, TX 78229-3904, USA
| | - Mariana Bollo
- Instituto de Investigación Médica M y M Ferreyra, INIMEC-CONICET, Universidad Nacional de Córdoba, 2434 Friuli, Córdoba 5016, Argentina.
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Vorontsova I, Lock JT, Parker I. KRAP is required for diffuse and punctate IP 3-mediated Ca 2+ liberation and determines the number of functional IP 3R channels within clusters. Cell Calcium 2022; 107:102638. [PMID: 36030740 DOI: 10.1016/j.ceca.2022.102638] [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: 05/13/2022] [Revised: 08/03/2022] [Accepted: 08/11/2022] [Indexed: 11/02/2022]
Abstract
KRas-induced actin-interacting protein (KRAP) has been identified as crucial for the appropriate localization and functioning of the inositol trisphosphate receptors (IP3Rs) that mediate Ca2+ release from the endoplasmic reticulum. Here, we used siRNA knockdown of KRAP expression in HeLa and HEK293 cells to examine the roles of KRAP in the generation of IP3-mediated local Ca2+ puffs and global, cell-wide Ca2+ signals. High resolution Ca2+ imaging revealed that the mean amplitude of puffs was strongly reduced by KRAP knockdown, whereas the Ca2+ flux during openings of individual IP3R channels was little affected. In both control and KRAP knockdown cells the numbers of functional channels in the clusters underlying puff sites were stochastically distributed following a Poisson relationship, but the mean number of functional channels per site was reduced by about two thirds by KRAP knockdown. We conclude that KRAP is required for activity of IP3R channels at puff sites and stochastically 'licenses' the function of individual channels on a one-to-one basis, rather than determining the functioning of the puff site as a whole. In addition to puff activity ('punctate' Ca2+ release), global, cell-wide Ca2+ signals evoked by higher levels of IP3 are further composed from a discrete 'diffuse' mode of Ca2+ release. By applying fluctuation analysis to isolate the punctate component during global Ca2+ signals, we find that KRAP knockdown suppresses to similar extents punctate and diffuse Ca2+ release in wild-type cells and in HEK293 cells exclusively expressing type 1 and type 3 IP3Rs. Thus, KRAP appears essential for the functioning of the IP3Rs involved in diffuse Ca2+ release as well as the clustered IP3Rs that generate local Ca2+ puffs.
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Affiliation(s)
- Irene Vorontsova
- Department of Neurobiology & Behavior, UC Irvine, Irvine, CA, United States
| | - Jeffrey T Lock
- Department of Neurobiology & Behavior, UC Irvine, Irvine, CA, United States
| | - Ian Parker
- Department of Neurobiology & Behavior, UC Irvine, Irvine, CA, United States; Department of Physiology & Biophysics, UC Irvine, Irvine, CA, United States.
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Kolar K, Dondorp D, Zwiggelaar JC, Høyer J, Chatzigeorgiou M. Mesmerize is a dynamically adaptable user-friendly analysis platform for 2D and 3D calcium imaging data. Nat Commun 2021; 12:6569. [PMID: 34772921 PMCID: PMC8589933 DOI: 10.1038/s41467-021-26550-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Accepted: 10/13/2021] [Indexed: 01/09/2023] Open
Abstract
Calcium imaging is an increasingly valuable technique for understanding neural circuits, neuroethology, and cellular mechanisms. The analysis of calcium imaging data presents challenges in image processing, data organization, analysis, and accessibility. Tools have been created to address these problems independently, however a comprehensive user-friendly package does not exist. Here we present Mesmerize, an efficient, expandable and user-friendly analysis platform, which uses a Findable, Accessible, Interoperable and Reproducible (FAIR) system to encapsulate the entire analysis process, from raw data to interactive visualizations for publication. Mesmerize provides a user-friendly graphical interface to state-of-the-art analysis methods for signal extraction & downstream analysis. We demonstrate the broad scientific scope of Mesmerize's applications by analyzing neuronal datasets from mouse and a volumetric zebrafish dataset. We also applied contemporary time-series analysis techniques to analyze a novel dataset comprising neuronal, epidermal, and migratory mesenchymal cells of the protochordate Ciona intestinalis.
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Affiliation(s)
- Kushal Kolar
- Sars International Centre for Marine Molecular Biology, University of Bergen, 5006, Bergen, Norway.
| | - Daniel Dondorp
- Sars International Centre for Marine Molecular Biology, University of Bergen, 5006, Bergen, Norway
| | | | - Jørgen Høyer
- Sars International Centre for Marine Molecular Biology, University of Bergen, 5006, Bergen, Norway
| | - Marios Chatzigeorgiou
- Sars International Centre for Marine Molecular Biology, University of Bergen, 5006, Bergen, Norway.
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8
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Lock JT, Smith IF, Parker I. Spatial-temporal patterning of Ca 2+ signals by the subcellular distribution of IP 3 and IP 3 receptors. Semin Cell Dev Biol 2019; 94:3-10. [PMID: 30703557 DOI: 10.1016/j.semcdb.2019.01.012] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 01/17/2019] [Accepted: 01/22/2019] [Indexed: 12/25/2022]
Abstract
The patterning of cytosolic Ca2+ signals in space and time underlies their ubiquitous ability to specifically regulate numerous cellular processes. Signals mediated by liberation of Ca2+ sequestered in the endoplasmic reticulum (ER) through inositol trisphosphate receptor (IP3R) channels constitute a hierarchy of events; ranging from openings of individual IP3 channels, through the concerted openings of several clustered IP3Rs to generate local Ca2+ puffs, to global Ca2+ waves and oscillations that engulf the entire cell. Here, we review recent progress in elucidating how this hierarchy is shaped by an interplay between the functional gating properties of IP3Rs and their spatial distribution within the cell. We focus in particular on the subset of IP3Rs that are organized in stationary clusters and are endowed with the ability to preferentially liberate Ca2+.
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Affiliation(s)
- Jeffrey T Lock
- Department of Neurobiology & Behavior, UC Irvine, Irvine, CA, USA.
| | - Ian F Smith
- Department of Neurobiology & Behavior, UC Irvine, Irvine, CA, USA
| | - Ian Parker
- Department of Neurobiology & Behavior, UC Irvine, Irvine, CA, USA; Department of Physiology & Biophysics, UC Irvine, Irvine, CA, USA
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9
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Ohnishi N, Fujiwara Y, Kamezaki T, Katsuki S. Variations of Intracellular Ca 2+ Mobilization Initiated by Nanosecond and Microsecond Electrical Pulses in HeLa Cells. IEEE Trans Biomed Eng 2018; 66:2259-2268. [PMID: 30561339 DOI: 10.1109/tbme.2018.2886602] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
GOAL Herein, the variations in transient Ca2+ mobilizations in HeLa cells exposed to a single, non-thermal pulsed electric field (PEF) are described. METHODS Three PEF waveforms categorized by pulse duration and intensity were used to deduce the kinetics involved in Ca2+ mobilization. A fast microscopic fluorescent imaging system and a fluorescent molecular probe were used to observe transient intracellular Ca2+ mobilization after pulse exposure. The sources and pathways in the transient Ca2+ mobilizations were investigated using an inhibitor of inositol-1,4,5-trisphosphate receptor (IP3R) on the endoplasmic reticulum (ER) along with a Ca2+-free buffer. RESULTS When exposed to the 10-μs-long PEF, the Ca2+ concentration increased mainly at the cathodic region near the membrane. However, Ca2+ concentration increased at both anodic and cathodic regions when Na+ concentration in the buffer was reduced. Ca2+ concentration increased only in the presence of extracellular Ca2+. CONCLUSION These results suggest that the 10-μs PEF takes a large amount of extracellular Na+ into the cell through the electropermeabilized plasma membrane, especially at the anodic side, resulting in the suppression of the Ca2+ influx. On the contrary, the 20-ns-long PEF increased Ca2+ concentration in the surrounding region of the nucleus only in the presence of extracellular Ca2+. The PEF exposure with inhibition of the IP3R indicates that increased Ca2+ ions are released from the ER via the activated IP3R. SIGNIFICANCE These mechanisms could induce specific cell responses, such as Ca2+ oscillations, Ca2+ waves, and Ca2+ puffs.
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10
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Keebler MV, Taylor CW. Endogenous signalling pathways and caged IP 3 evoke Ca 2+ puffs at the same abundant immobile intracellular sites. J Cell Sci 2017; 130:3728-3739. [PMID: 28893841 PMCID: PMC5702060 DOI: 10.1242/jcs.208520] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 09/04/2017] [Indexed: 12/18/2022] Open
Abstract
The building blocks of intracellular Ca2+ signals evoked by inositol 1,4,5-trisphosphate receptors (IP3Rs) are Ca2+ puffs, transient focal increases in Ca2+ concentration that reflect the opening of small clusters of IP3Rs. We use total internal reflection fluorescence microscopy and automated analyses to detect Ca2+ puffs evoked by photolysis of caged IP3 or activation of endogenous muscarinic receptors with carbachol in human embryonic kidney 293 cells. Ca2+ puffs evoked by carbachol initiated at an estimated 65±7 sites/cell, and the sites remained immobile for many minutes. Photolysis of caged IP3 evoked Ca2+ puffs at a similar number of sites (100±35). Increasing the carbachol concentration increased the frequency of Ca2+ puffs without unmasking additional Ca2+ release sites. By measuring responses to sequential stimulation with carbachol or photolysed caged IP3, we established that the two stimuli evoked Ca2+ puffs at the same sites. We conclude that IP3-evoked Ca2+ puffs initiate at numerous immobile sites and the sites become more likely to fire as the IP3 concentration increases; there is no evidence that endogenous signalling pathways selectively deliver IP3 to specific sites. Summary: Ca2+ puffs are the building blocks for IP3-evoked Ca2+ signals. Ca2+ puffs evoked by caged IP3 or via endogenous signalling pathways initiate at the same fixed intracellular sites.
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Affiliation(s)
- Michael V Keebler
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
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11
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Lock JT, Smith IF, Parker I. Comparison of Ca 2+ puffs evoked by extracellular agonists and photoreleased IP 3. Cell Calcium 2017; 63:43-47. [PMID: 28108028 PMCID: PMC5459673 DOI: 10.1016/j.ceca.2016.11.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2016] [Revised: 11/29/2016] [Accepted: 11/30/2016] [Indexed: 11/19/2022]
Abstract
The inositol trisphosphate (IP3) signaling pathway evokes local Ca2+ signals (Ca2+ puffs) that arise from the concerted openings of clustered IP3 receptor/channels in the ER membrane. Physiological activation is triggered by binding of agonists to G-protein-coupled receptors (GPCRs) on the cell surface, leading to cleavage of phosphatidyl inositol bisphosphate and release of IP3 into the cytosol. Photorelease of IP3 from a caged precursor provides a convenient and widely employed means to study the final stage of IP3-mediated Ca2+ liberation, bypassing upstream signaling events to enable more precise control of the timing and relative concentration of cytosolic IP3. Here, we address whether Ca2+ puffs evoked by photoreleased IP3 fully replicate those arising from physiological agonist stimulation. We imaged puffs in individual SH-SY5Y neuroblastoma cells that were sequentially stimulated by picospritzing extracellular agonist (carbachol, CCH or bradykinin, BK) followed by photorelease of a poorly-metabolized IP3 analog, i-IP3. The centroid localizations of fluorescence signals during puffs evoked in the same cells by agonists and photorelease substantially overlapped (within ∼1μm), suggesting that IP3 from both sources accesses the same, or closely co-localized clusters of IP3Rs. Moreover, the time course and spatial spread of puffs evoked by agonists and photorelease matched closely. Because photolysis generates IP3 uniformly throughout the cytoplasm, our results imply that IP3 generated in SH-SY5Y cells by activation of receptors to CCH and BK also exerts broadly distributed actions, rather than specifically activating a subpopulation of IP3Rs that are scaffolded in close proximity to cell surface receptors to form a signaling nanodomain.
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Affiliation(s)
- Jeffrey T Lock
- Department of Neurobiology and Behavior, University of California, Irvine, CA, 92697, United States.
| | - Ian F Smith
- Department of Neurobiology and Behavior, University of California, Irvine, CA, 92697, United States.
| | - Ian Parker
- Department of Neurobiology and Behavior, University of California, Irvine, CA, 92697, United States; Department of Physiology and Biophysics, University of California, Irvine, CA, 92697, United States.
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12
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Dickinson GD, Ellefsen KL, Dawson SP, Pearson JE, Parker I. Hindered cytoplasmic diffusion of inositol trisphosphate restricts its cellular range of action. Sci Signal 2016; 9:ra108. [PMID: 27919026 DOI: 10.1126/scisignal.aag1625] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The range of action of intracellular messengers is determined by their rates of diffusion and degradation. Previous measurements in oocyte cytoplasmic extracts indicated that the Ca2+-liberating second messenger inositol trisphosphate (IP3) diffuses with a coefficient (~280 μm2 s-1) similar to that in water, corresponding to a range of action of ~25 μm. Consequently, IP3 is generally considered a "global" cellular messenger. We reexamined this issue by measuring local IP3-evoked Ca2+ puffs to monitor IP3 diffusing from spot photorelease in neuroblastoma cells. Fitting these data by numerical simulations yielded a diffusion coefficient (≤10 μm2 s-1) about 30-fold slower than that previously reported. We propose that diffusion of IP3 in mammalian cells is hindered by binding to immobile, functionally inactive receptors that were diluted in oocyte extracts. The predicted range of action of IP3 (<5 μm) is thus smaller than the size of typical mammalian cells, indicating that IP3 should better be considered as a local rather than a global cellular messenger.
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Affiliation(s)
- George D Dickinson
- Department of Neurobiology and Behavior, University of California, Irvine, CA 92697, USA.
| | - Kyle L Ellefsen
- Department of Neurobiology and Behavior, University of California, Irvine, CA 92697, USA
| | | | - John E Pearson
- Theoretical Biology and Biophysics, T-10 MS K710, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - Ian Parker
- Department of Neurobiology and Behavior, University of California, Irvine, CA 92697, USA.,Department of Physiology and Biophysics, University of California, Irvine, CA 92697, USA
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13
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Determining the Roles of Inositol Trisphosphate Receptors in Neurodegeneration: Interdisciplinary Perspectives on a Complex Topic. Mol Neurobiol 2016; 54:6870-6884. [PMID: 27771899 DOI: 10.1007/s12035-016-0205-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Accepted: 10/11/2016] [Indexed: 02/06/2023]
Abstract
It is well known that calcium (Ca2+) is involved in the triggering of neuronal death. Ca2+ cytosolic levels are regulated by Ca2+ release from internal stores located in organelles, such as the endoplasmic reticulum. Indeed, Ca2+ transit from distinct cell compartments follows complex dynamics that are mediated by specific receptors, notably inositol trisphosphate receptors (IP3Rs). Ca2+ release by IP3Rs plays essential roles in several neurological disorders; however, details of these processes are poorly understood. Moreover, recent studies have shown that subcellular location, molecular identity, and density of IP3Rs profoundly affect Ca2+ transit in neurons. Therefore, regulation of IP3R gene products in specific cellular vicinities seems to be crucial in a wide range of cellular processes from neuroprotection to neurodegeneration. In this regard, microRNAs seem to govern not only IP3Rs translation levels but also subcellular accumulation. Combining new data from molecular cell biology with mathematical modelling, we were able to summarize the state of the art on this topic. In addition to presenting how Ca2+ dynamics mediated by IP3R activation follow a stochastic regimen, we integrated a theoretical approach in an easy-to-apply, cell biology-coherent fashion. Following the presented premises and in contrast to previously tested hypotheses, Ca2+ released by IP3Rs may play different roles in specific neurological diseases, including Alzheimer's disease and Parkinson's disease.
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14
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Ghosh D, Syed AU, Prada MP, Nystoriak MA, Santana LF, Nieves-Cintrón M, Navedo MF. Calcium Channels in Vascular Smooth Muscle. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2016; 78:49-87. [PMID: 28212803 DOI: 10.1016/bs.apha.2016.08.002] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Calcium (Ca2+) plays a central role in excitation, contraction, transcription, and proliferation of vascular smooth muscle cells (VSMs). Precise regulation of intracellular Ca2+ concentration ([Ca2+]i) is crucial for proper physiological VSM function. Studies over the last several decades have revealed that VSMs express a variety of Ca2+-permeable channels that orchestrate a dynamic, yet finely tuned regulation of [Ca2+]i. In this review, we discuss the major Ca2+-permeable channels expressed in VSM and their contribution to vascular physiology and pathology.
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Affiliation(s)
- D Ghosh
- University of California, Davis, CA, United States
| | - A U Syed
- University of California, Davis, CA, United States
| | - M P Prada
- University of California, Davis, CA, United States
| | - M A Nystoriak
- Diabetes and Obesity Center, University of Louisville, Louisville, KY, United States
| | - L F Santana
- University of California, Davis, CA, United States
| | | | - M F Navedo
- University of California, Davis, CA, United States.
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Suzuki J, Kanemaru K, Iino M. Genetically Encoded Fluorescent Indicators for Organellar Calcium Imaging. Biophys J 2016; 111:1119-1131. [PMID: 27477268 DOI: 10.1016/j.bpj.2016.04.054] [Citation(s) in RCA: 91] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Revised: 03/30/2016] [Accepted: 04/01/2016] [Indexed: 12/14/2022] Open
Abstract
Optical Ca(2+) indicators are powerful tools for investigating intracellular Ca(2+) signals in living cells. Although a variety of Ca(2+) indicators have been developed, deciphering the physiological functions and spatiotemporal dynamics of Ca(2+) in intracellular organelles remains challenging. Genetically encoded Ca(2+) indicators (GECIs) using fluorescent proteins are promising tools for organellar Ca(2+) imaging, and much effort has been devoted to their development. In this review, we first discuss the key points of organellar Ca(2+) imaging and summarize the requirements for optimal organellar Ca(2+) indicators. Then, we highlight some of the recent advances in the engineering of fluorescent GECIs targeted to specific organelles. Finally, we discuss the limitations of currently available GECIs and the requirements for advancing the research on intraorganellar Ca(2+) signaling.
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Affiliation(s)
- Junji Suzuki
- Department of Pharmacology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; Department of Physiology, University of California San Francisco, San Francisco, California
| | - Kazunori Kanemaru
- Department of Pharmacology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
| | - Masamitsu Iino
- Department of Pharmacology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; Department of Cellular and Molecular Pharmacology, Nihon University School of Medicine, Tokyo, Japan.
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16
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Wright FA, Wojcikiewicz RJH. Chapter 4 - Inositol 1,4,5-Trisphosphate Receptor Ubiquitination. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2016; 141:141-59. [PMID: 27378757 DOI: 10.1016/bs.pmbts.2016.02.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Inositol 1,4,5-trisphosphate receptors (IP3Rs) are large (∼300kDa) proteins that associate into tetrameric ion channels in the endoplasmic reticulum (ER) membrane. Activation and opening of the channel upon binding of IP3 and Ca(2+) allows the flow of Ca(2+) ions from stores within the ER lumen to the cytosol, thereby promoting a number of Ca(2+)-dependent cellular events, such as secretion, neurotransmitter release, and cell division. Intriguingly, it appears that the same conformational change that IP3Rs undergo during activation makes them a target for degradation by the ubiquitin-proteasome pathway and that this mode of processing allows the cell to tune its internal Ca(2+) response to extracellular signals. Here, we review recent studies showing that activated IP3Rs interact with an array of proteins that mediate their degradation, that IP3Rs are modified by a complex array of ubiquitin conjugates, that this ubiquitination and degradation functions to regulate IP3-mediated Ca(2+) responses in the cell, and that mutations to different proteins involved in IP3R degradation result in a set of similar diseases.
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Affiliation(s)
- F A Wright
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY, United States
| | - R J H Wojcikiewicz
- Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY, United States.
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17
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Croft W, Reusch K, Tilunaite A, Russell NA, Thul R, Bellamy TC. Probabilistic encoding of stimulus strength in astrocyte global calcium signals. Glia 2015; 64:537-52. [PMID: 26651126 DOI: 10.1002/glia.22947] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Accepted: 11/16/2015] [Indexed: 12/21/2022]
Abstract
Astrocyte calcium signals can range in size from subcellular microdomains to waves that spread through the whole cell (and into connected cells). The differential roles of such local or global calcium signaling are under intense investigation, but the mechanisms by which local signals evolve into global signals in astrocytes are not well understood, nor are the computational rules by which physiological stimuli are transduced into a global signal. To investigate these questions, we transiently applied receptor agonists linked to calcium signaling to primary cultures of cerebellar astrocytes. Astrocytes repetitively tested with the same stimulus responded with global signals intermittently, indicating that each stimulus had a defined probability for triggering a response. The response probability varied between agonists, increased with agonist concentration, and could be positively and negatively modulated by crosstalk with other signaling pathways. To better understand the processes determining the evolution of a global signal, we recorded subcellular calcium "puffs" throughout the whole cell during stimulation. The key requirement for puffs to trigger a global calcium wave following receptor activation appeared to be the synchronous release of calcium from three or more sites, rather than an increasing calcium load accumulating in the cytosol due to increased puff size, amplitude, or frequency. These results suggest that the concentration of transient stimuli will be encoded into a probability of generating a global calcium response, determined by the likelihood of synchronous release from multiple subcellular sites.
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Affiliation(s)
- Wayne Croft
- School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Katharina Reusch
- School of Life Sciences, University of Nottingham, Nottingham, United Kingdom.,Department of Electrical and Electronic Engineering, University of Nottingham, Nottingham, United Kingdom
| | - Agne Tilunaite
- School of Mathematical Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Noah A Russell
- Department of Electrical and Electronic Engineering, University of Nottingham, Nottingham, United Kingdom
| | - Rüdiger Thul
- School of Mathematical Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Tomas C Bellamy
- School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
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18
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Litosch I. Regulating G protein activity by lipase-independent functions of phospholipase C. Life Sci 2015; 137:116-24. [DOI: 10.1016/j.lfs.2015.07.025] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Revised: 06/18/2015] [Accepted: 07/22/2015] [Indexed: 11/27/2022]
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Single-molecule tracking of inositol trisphosphate receptors reveals different motilities and distributions. Biophys J 2015; 107:834-45. [PMID: 25140418 DOI: 10.1016/j.bpj.2014.05.051] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 04/24/2014] [Accepted: 05/01/2014] [Indexed: 11/20/2022] Open
Abstract
Puffs are local Ca(2+) signals that arise by Ca(2+) liberation from the endoplasmic reticulum through the concerted opening of tightly clustered inositol trisphosphate receptors/channels (IP3Rs). The locations of puff sites observed by Ca(2+) imaging remain static over several minutes, whereas fluorescence recovery after photobleaching (FRAP) experiments employing overexpression of fluorescently tagged IP3Rs have shown that the majority of IP3Rs are freely motile. To address this discrepancy, we applied single-molecule imaging to locate and track type 1 IP3Rs tagged with a photoswitchable fluorescent protein and expressed in COS-7 cells. We found that ∼ 70% of the IP3R1 molecules were freely motile, undergoing random walk motility with an apparent diffusion coefficient of ∼ 0.095 μm s(-1), whereas the remaining molecules were essentially immotile. A fraction of the immotile IP3Rs were organized in clusters, with dimensions (a few hundred nanometers across) comparable to those previously estimated for the IP3R clusters underlying functional puff sites. No short-term (seconds) changes in overall motility or in clustering of immotile IP3Rs were apparent following activation of IP3/Ca(2+) signaling. We conclude that stable clusters of small numbers of immotile IP3Rs may underlie local Ca(2+) release sites, whereas the more numerous motile IP3Rs appear to be functionally silent.
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Thul R, Rietdorf K, Bootman MD, Coombes S. Unifying principles of calcium wave propagation - Insights from a three-dimensional model for atrial myocytes. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:2131-43. [PMID: 25746480 DOI: 10.1016/j.bbamcr.2015.02.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Revised: 02/17/2015] [Accepted: 02/23/2015] [Indexed: 11/30/2022]
Abstract
Atrial myocytes in a number of species lack transverse tubules. As a consequence the intracellular calcium signals occurring during each heartbeat exhibit complex spatio-temporal dynamics. These calcium patterns arise from saltatory calcium waves that propagate via successive rounds of diffusion and calcium-induced calcium release. The many parameters that impinge on calcium-induced calcium release and calcium signal propagation make it difficult to know a priori whether calcium waves will successfully travel, or be extinguished. In this study, we describe in detail a mathematical model of calcium signalling that allows the effect of such parameters to be independently assessed. A key aspect of the model is to follow the triggering and evolution of calcium signals within a realistic three-dimensional cellular volume of an atrial myocyte, but with low computational costs. This is achieved by solving the linear transport equation for calcium analytically between calcium release events and by expressing the onset of calcium liberation as a threshold process. The model makes non-intuitive predictions about calcium signal propagation. For example, our modelling illustrates that the boundary of a cell produces a wave-guiding effect that enables calcium ions to propagate further and for longer, and can subtly alter the pattern of calcium wave movement. The high spatial resolution of the modelling framework allows the study of any arrangement of calcium release sites. We demonstrate that even small variations in randomly positioned release sites cause highly heterogeneous cellular responses. This article is part of a Special Issue entitled: 13th European Symposium on Calcium.
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Affiliation(s)
- R Thul
- School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD, UK
| | - K Rietdorf
- Department of Life, Health and Chemical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
| | - M D Bootman
- Department of Life, Health and Chemical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK
| | - S Coombes
- School of Mathematical Sciences, University of Nottingham, Nottingham NG7 2RD, UK
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Hohendanner F, Walther S, Maxwell JT, Kettlewell S, Awad S, Smith GL, Lonchyna VA, Blatter LA. Inositol-1,4,5-trisphosphate induced Ca2+ release and excitation-contraction coupling in atrial myocytes from normal and failing hearts. J Physiol 2014; 593:1459-77. [PMID: 25416623 DOI: 10.1113/jphysiol.2014.283226] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Accepted: 11/10/2014] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Impaired calcium (Ca(2+)) signalling is the main contributor to depressed ventricular contractile function and occurrence of arrhythmia in heart failure (HF). Here we report that in atrial cells of a rabbit HF model, Ca(2+) signalling is enhanced and we identified the underlying cellular mechanisms. Enhanced Ca(2+) transients (CaTs) are due to upregulation of inositol-1,4,5-trisphosphate receptor induced Ca(2+) release (IICR) and decreased mitochondrial Ca(2+) sequestration. Enhanced IICR, however, together with an increased activity of the sodium-calcium exchange mechanism, also facilitates spontaneous Ca(2+) release in form of arrhythmogenic Ca(2+) waves and spontaneous action potentials, thus enhancing the arrhythmogenic potential of atrial cells. Our data show that enhanced Ca(2+) signalling in HF provides atrial cells with a mechanism to improve ventricular filling and to maintain cardiac output, but also increases the susceptibility to develop atrial arrhythmias facilitated by spontaneous Ca(2+) release. ABSTRACT We studied excitation-contraction coupling (ECC) and inositol-1,4,5-triphosphate (IP3)-dependent Ca(2+) release in normal and heart failure (HF) rabbit atrial cells. Left ventricular HF was induced by combined volume and pressure overload. In HF atrial myocytes diastolic [Ca(2+)]i was increased, action potential (AP)-induced Ca(2+) transients (CaTs) were larger in amplitude, primarily due to enhanced Ca(2+) release from central non-junctional sarcoplasmic reticulum (SR) and centripetal propagation of activation was accelerated, whereas HF ventricular CaTs were depressed. The larger CaTs were due to enhanced IP3 receptor-induced Ca(2+) release (IICR) and reduced mitochondrial Ca(2+) buffering, consistent with a reduced mitochondrial density and Ca(2+) uptake capacity in HF. Elementary IP3 receptor-mediated Ca(2+) release events (Ca(2+) puffs) were more frequent in HF atrial myoctes and were detected more often in central regions of the non-junctional SR compared to normal cells. HF cells had an overall higher frequency of spontaneous Ca(2+) waves and a larger fraction of waves (termed arrhythmogenic Ca(2+) waves) triggered APs and global CaTs. The higher propensity of arrhythmogenic Ca(2+) waves resulted from the combined action of enhanced IICR and increased activity of sarcolemmal Na(+)-Ca(2+) exchange depolarizing the cell membrane. In conclusion, the data support the hypothesis that in atrial myocytes from hearts with left ventricular failure, enhanced CaTs during ECC exert positive inotropic effects on atrial contractility which facilitates ventricular filling and contributes to maintaining cardiac output. However, HF atrial cells were also more susceptible to developing arrhythmogenic Ca(2+) waves which might form the substrate for atrial rhythm disorders frequently encountered in HF.
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Affiliation(s)
- Felix Hohendanner
- Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL, 60612, USA
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22
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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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Park HK, Lee JE, Lim J, Kang BH. Mitochondrial Hsp90s suppress calcium-mediated stress signals propagating from mitochondria to the ER in cancer cells. Mol Cancer 2014; 13:148. [PMID: 24924916 PMCID: PMC4070406 DOI: 10.1186/1476-4598-13-148] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 06/05/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Resistance to cell death in the presence of stressful stimuli is one of the hallmarks of cancer cells acquired during multistep tumorigenesis, and knowledge of the molecular mechanism of stress adaptation can be exploited to develop cancer-selective therapeutics. Mitochondria and the endoplasmic reticulum (ER) are physically interconnected organelles that can sense and exchange various stress signals. Although there have been many studies on stress propagation from the ER to mitochondria, reverse stress signals originating from mitochondria have not been well reported. METHODS After inactivation of the proteins by pharmacologic and genetic methods, the signal pathways were analyzed by fluorescence microscopy, flow cytometry, MTT assay, and western blotting. A mouse xenograft model was used to examine synergistic anticancer activity and the action mechanism of drugs in vivo. RESULTS We show in this study that mitochondrial heat shock protein 90 (Hsp90) suppresses mitochondria-initiated calcium-mediated stress signals propagating into the ER in cancer cells. Mitochondrial Hsp90 inhibition triggers the calcium signal by opening the mitochondrial permeability transition pore and, in turn, the ER ryanodine receptor, via calcium-induced calcium release. Subsequent depletion of ER calcium activates unfolded protein responses in the ER lumen, thereby increasing the expression of a pro-apoptotic transcription factor, CEBP homologous protein (CHOP). Combined treatment with the ER stressor thapsigargin and the mitochondrial Hsp90 inhibitor gamitrinib augmented interorganelle stress signaling by elevating CHOP expression, and showed synergistic cytotoxic activity exclusively in cancer cells in vitro and in vivo. CONCLUSIONS Collectively, mitochondrial Hsp90s confer cell death resistance to cancer cells by suppressing the mitochondria-initiated calcium-mediated interorganelle stress response.
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Affiliation(s)
| | | | | | - Byoung Heon Kang
- Department of Biological Sciences, School of Life Sciences, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST St,, Ulsan 689-798, South Korea.
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Amberg GC, Navedo MF. Calcium dynamics in vascular smooth muscle. Microcirculation 2013; 20:281-9. [PMID: 23384444 DOI: 10.1111/micc.12046] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Accepted: 01/31/2013] [Indexed: 12/31/2022]
Abstract
Smooth muscle cells are ultimately responsible for determining vascular luminal diameter and blood flow. Dynamic changes in intracellular calcium are a critical mechanism regulating vascular smooth muscle contractility. Processes influencing intracellular calcium are therefore important regulators of vascular function with physiological and pathophysiological consequences. In this review we discuss the major dynamic calcium signals identified and characterized in vascular smooth muscle cells. These signals vary with respect to their mechanisms of generation, temporal properties, and spatial distributions. The calcium signals discussed include calcium waves, junctional calcium transients, calcium sparks, calcium puffs, and L-type calcium channel sparklets. For each calcium signal we address underlying mechanisms, general properties, physiological importance, and regulation.
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Affiliation(s)
- Gregory C Amberg
- Vascular Physiology Research Group, Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA.
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25
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Dragoni S, Laforenza U, Bonetti E, Lodola F, Bottino C, Guerra G, Borghesi A, Stronati M, Rosti V, Tanzi F, Moccia F. Canonical transient receptor potential 3 channel triggers vascular endothelial growth factor-induced intracellular Ca2+ oscillations in endothelial progenitor cells isolated from umbilical cord blood. Stem Cells Dev 2013; 22:2561-80. [PMID: 23682725 DOI: 10.1089/scd.2013.0032] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Endothelial colony-forming cells (ECFCs) are the only endothelial progenitor cells (EPCs) that are capable of acquiring a mature endothelial phenotype. ECFCs are mainly mobilized from bone marrow to promote vascularization and represent a promising tool for cell-based therapy of severe ischemic diseases. Vascular endothelial growth factor (VEGF) stimulates the proliferation of peripheral blood-derived ECFCs (PB-ECFCs) through oscillations in intracellular Ca(2+) concentration ([Ca(2+)]i). VEGF-induced Ca(2+) spikes are driven by the interplay between inositol-1,4,5-trisphosphate (InsP3)-dependent Ca(2+) release and store-operated Ca(2+) entry (SOCE). The therapeutic potential of umbilical cord blood-derived ECFCs (UCB-ECFCs) has also been shown in recent studies. However, VEGF-induced proliferation of UCB-ECFCs is faster compared with their peripheral counterpart. Unlike PB-ECFCs, UCB-ECFCs express canonical transient receptor potential channel 3 (TRPC3) that mediates diacylglycerol-dependent Ca(2+) entry. The present study aimed at investigating whether the higher proliferative potential of UCB-ECFCs was associated to any difference in the molecular underpinnings of their Ca(2+) response to VEGF. We found that VEGF induces oscillations in [Ca(2+)]i that are patterned by the interaction between InsP3-dependent Ca(2+) release and SOCE. Unlike PB-ECFCs, VEGF-evoked Ca(2+) oscillations do not arise in the absence of extracellular Ca(2+) entry and after pharmacological (with Pyr3 and flufenamic acid) and genetic (by employing selective small interference RNA) suppression of TRPC3. VEGF-induced UCB-ECFC proliferation is abrogated on inhibition of the intracellular Ca(2+) spikes. Therefore, the Ca(2+) response to VEGF in UCB-ECFCs is shaped by a different Ca(2+) machinery as compared with PB-ECFCs, and TRPC3 stands out as a promising target in EPC-based treatment of ischemic pathologies.
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Affiliation(s)
- Silvia Dragoni
- 1 Department of Biology and Biotechnology "Lazzaro Spallanzani,", University of Pavia , Pavia, Italy
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Tovey SC, Taylor CW. Cyclic AMP directs inositol (1,4,5)-trisphosphate-evoked Ca2+ signalling to different intracellular Ca2+ stores. J Cell Sci 2013; 126:2305-13. [PMID: 23525004 DOI: 10.1242/jcs.126144] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Cholesterol depletion reversibly abolishes carbachol-evoked Ca(2+) release from inositol (1,4,5)-trisphosphate (IP3)-sensitive stores, without affecting the distribution of IP3 receptors (IP3R) or endoplasmic reticulum, IP3 formation or responses to photolysis of caged IP3. Receptors that stimulate cAMP formation do not alone evoke Ca(2+) signals, but they potentiate those evoked by carbachol. We show that these potentiated signals are entirely unaffected by cholesterol depletion and that, within individual cells, different IP3-sensitive Ca(2+) stores are released by carbachol alone and by carbachol combined with receptors that stimulate cAMP formation. We suggest that muscarinic acetylcholine receptors in lipid rafts deliver IP3 at high concentration to associated IP3R, stimulating them to release Ca(2+). Muscarinic receptors outside rafts are less closely associated with IP3R and provide insufficient local IP3 to activate IP3R directly. These IP3R, probably type 2 IP3R within a discrete Ca(2+) store, are activated only when their sensitivity is increased by cAMP. Sensitization of IP3R by cAMP extends the effective range of signalling by phospholipase C, allowing muscarinic receptors that are otherwise ineffective to recruit additional IP3-sensitive Ca(2+) stores.
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Affiliation(s)
- Stephen C Tovey
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
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27
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Horn T, Ullrich ND, Egger M. 'Eventless' InsP3-dependent SR-Ca2+ release affecting atrial Ca2+ sparks. J Physiol 2013; 591:2103-11. [PMID: 23381902 DOI: 10.1113/jphysiol.2012.247288] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Augmented inositol 1,4,5-trisphosphate receptor (InsP3R) function has been linked to a variety of cardiac pathologies, including cardiac arrhythmia. The contribution of inositol 1,4,5-trisphosphate-induced Ca(2+) release (IP3ICR) in excitation-contraction coupling (ECC) under physiological conditions, as well as under cellular remodelling, remains controversial. Here we test the hypothesis that local IP3ICR directly affects ryanodine receptor (RyR) function and subsequent Ca(2+)-induced Ca(2+) release in atrial myocytes. IP3ICR was evoked by UV-flash photolysis of caged InsP3 under whole-cell configuration of the voltage-clamp technique in atrial myocytes isolated from C57/BL6 mice. Photolytic release of InsP3 was accompanied by a significant increase in the Ca(2+) release event frequency (4.14 ± 0.72 vs. 6.20 ± 0.76 events (100 μm)(-1) s(-1)). These individual photolytically triggered Ca(2+) release events were identified as Ca(2+) sparks, which originated from RyR openings. This was verified by Ca(2+) spark analysis and pharmacological separation between RyR and InsP3R-dependent sarcoplasmic reticulum (SR)-Ca(2+) release (2-aminoethoxydiphenyl borate, xestospongin C, tetracaine). Significant SR-Ca(2+) flux but eventless SR-Ca(2+) release through InsP3R were characterized using SR-Ca(2+) leak/SR-Ca(2+) load measurements. These results strongly support the idea that IP3ICR can effectively modulate RyR openings and Ca(2+) spark probability. We conclude that eventless and highly efficient InsP3-dependent SR-Ca(2+) flux is the main mechanism of functional cross-talk between InsP3Rs and RyRs, which may be an important factor in the modulation of ECC sensitivity.
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Affiliation(s)
- Tamara Horn
- Department of Physiology, University of Bern, Bühlplatz 5, CH-3012 Bern, Switzerland
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Abstract
AbstractThe Gq-linked G protein coupled receptors (GPCRs) and their signaling pathways are important clinical targets for the dementia of Alzheimer’s disease and cognitive decline with aging. Gq stimulates phospholipase C-β1 (PLC-β1) activity, increasing levels of inositol-1, 4, 5-trisphosphate (IP3) and diacylglycerol, to initiate mobilization of intracellular Ca2+ and activation of protein kinase C, respectively. While high concentrations of ligand typically evoke large sustained increases in cytosolic Ca2+ levels, it has long been appreciated that the dynamics of the Ca2+ increase are more complex and consistent with multiple levels of regulation. Physiologically relevant concentrations of Gq-ligands evoke rhythmic fluctuations or an oscillation in the level of cytosolic Ca2+. Downstream targets are tuned to respond to the frequency of the Ca2+ oscillations which in turn, reflect the oscillations in IP3 levels. Oscillatory behavior depends on the assembly of self-organizing interactions. The components that contribute to and regulate the Ca2+ oscillator have been unclear, precluding transfer of this fundamental knowledge from bench to bedside. Many GPCRs that signal with Gq also co-signal with G12. G protein co-signaling could therefore regulate the Ca2+ oscillator. This letter explores the potential relationship between Ca2+ oscillations, G protein co-signaling and cellular response in the context of our recent observations. We found that Gq efficacy is synergistic with phosphatidic acid, (PA), a signaling mediator generated downstream of activated G12 and RhoA. Regulation by PA depends on interaction with the unique PLC-β1 PA binding region. G protein co-signaling is therefore a mechanism for GPCRs to collectively assemble self-organizing interactions that regulate the Ca2+ oscillator.
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Spatial and temporal characteristics of Ca2+ signaling in endothelial cells of intact rat tail artery. Artery Res 2013. [DOI: 10.1016/j.artres.2013.03.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
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Drawnel FM, Wachten D, Molkentin JD, Maillet M, Aronsen JM, Swift F, Sjaastad I, Liu N, Catalucci D, Mikoshiba K, Hisatsune C, Okkenhaug H, Andrews SR, Bootman MD, Roderick HL. Mutual antagonism between IP(3)RII and miRNA-133a regulates calcium signals and cardiac hypertrophy. J Cell Biol 2012; 199:783-98. [PMID: 23166348 PMCID: PMC3514786 DOI: 10.1083/jcb.201111095] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Accepted: 10/25/2012] [Indexed: 11/22/2022] Open
Abstract
Inositol 1,4,5'-triphosphate receptor II (IP(3)RII) calcium channel expression is increased in both hypertrophic failing human myocardium and experimentally induced models of the disease. The ectopic calcium released from these receptors induces pro-hypertrophic gene expression and may promote arrhythmias. Here, we show that IP(3)RII expression was constitutively restrained by the muscle-specific miRNA, miR-133a. During the hypertrophic response to pressure overload or neurohormonal stimuli, miR-133a down-regulation permitted IP(3)RII levels to increase, instigating pro-hypertrophic calcium signaling and concomitant pathological remodeling. Using a combination of in vivo and in vitro approaches, we demonstrated that IP(3)-induced calcium release (IICR) initiated the hypertrophy-associated decrease in miR-133a. In this manner, hypertrophic stimuli that engage IICR set a feed-forward mechanism in motion whereby IICR decreased miR-133a expression, further augmenting IP(3)RII levels and therefore pro-hypertrophic calcium release. Consequently, IICR can be considered as both an initiating event and a driving force for pathological remodeling.
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Affiliation(s)
- Faye M. Drawnel
- Babraham Institute, Babraham, Cambridge CB22 3AT, England, UK
| | - Dagmar Wachten
- Babraham Institute, Babraham, Cambridge CB22 3AT, England, UK
- Department of Molecular Sensory Systems, Center of Advanced European Studies and Research, 53175 Bonn, Germany
| | - Jeffery D. Molkentin
- Department of Pediatrics, University of Cincinnati, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH 45229
| | - Marjorie Maillet
- Department of Pediatrics, University of Cincinnati, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH 45229
| | - Jan Magnus Aronsen
- Institute for Experimental Medical Research, Faculty of Medicine, Oslo University Hospital, 0407 Oslo, Norway
- Bjørknes College, 0456 Oslo, Norway
| | - Fredrik Swift
- Institute for Experimental Medical Research, Faculty of Medicine, Oslo University Hospital, 0407 Oslo, Norway
| | - Ivar Sjaastad
- Institute for Experimental Medical Research, Faculty of Medicine, Oslo University Hospital, 0407 Oslo, Norway
| | - Ning Liu
- Department of Molecular Biology, UT Southwestern Medical Center, Dallas, TX 75390
| | - Daniele Catalucci
- Humanitas Clinical and Research Center, 20089 Rozzano, Milan, Italy
- Institute of Genetic and Biomedical Research, Milan Section, National Research Council, 20138 Milan, Italy
| | - Katsuhiko Mikoshiba
- Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute, Wako, Saitama 531-0198, Japan
| | - Chihiro Hisatsune
- Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute, Wako, Saitama 531-0198, Japan
| | | | | | | | - H. Llewelyn Roderick
- Babraham Institute, Babraham, Cambridge CB22 3AT, England, UK
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, England, UK
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Nakamura H, Bannai H, Inoue T, Michikawa T, Sano M, Mikoshiba K. Cooperative and stochastic calcium releases from multiple calcium puff sites generate calcium microdomains in intact Hela cells. J Biol Chem 2012; 287:24563-72. [PMID: 22637479 DOI: 10.1074/jbc.m111.311399] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ca(2+) microdomains or locally restricted Ca(2+) increases in the cell have recently been reported to regulate many essential physiological events. Ca(2+) increases through the inositol 1,4,5-trisphosphate (IP(3)) receptor (IP(3)R)/Ca(2+) release channels contribute to the formation of a class of such Ca(2+) microdomains, which were often observed and referred to as Ca(2+) puffs in their isolated states. In this report, we visualized IP(3)-evoked Ca(2+) microdomains in histamine-stimulated intact HeLa cells using a total internal reflection fluorescence microscope, and quantitatively characterized the spatial profile by fitting recorded images to a two-dimensional Gaussian distribution. Ca(2+) concentration profiles were marginally spatially anisotropic, with the size increasing linearly even after the amplitude began to decline. We found the event centroid drifted with an apparent diffusion coefficient of 4.20 ± 0.50 μm(2)/s, which is significantly larger than those estimated for IP(3)Rs. The sites of maximal Ca(2+) increase, rather than initiation or termination sites, were detected repeatedly at the same location. These results indicate that Ca(2+) microdomains in intact HeLa cell are generated from spatially distributed multiple IP(3)R clusters or Ca(2+) puff sites, rather than a single IP(3)R cluster reported in cells loaded with Ca(2+) buffers.
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Affiliation(s)
- Hideki Nakamura
- Laboratory for Developmental Neurobiology, RIKEN, Brain Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
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Abstract
Ca2+ transfer from endoplasmic reticulum (ER) to mitochondria can trigger apoptotic pathways by inducing release of mitochondrial pro-apoptotic factors. Three different types of inositol 1,4,5-trisphosphate receptor (IP3R) serve to discharge Ca2+ from ER, but possess some peculiarities, especially in apoptosis induction. The anti-apoptotic protein Akt can phosphorylate all IP3R isoforms and protect cells from apoptosis, reducing ER Ca2+ release. However, it has not been elucidated which IP3R subtypes mediate these effects. Here, we show that Akt activation in COS7 cells, which lack of IP3R I, strongly suppresses IP3-mediated Ca2+ release and apoptosis. Conversely, in SH-SY 5Y cells, which are type III-deficient, Akt is unable to modulate ER Ca2+ flux, losing its anti-apoptotic activity. In SH-SY 5Y-expressing subtype III, Akt recovers its protective function on cell death, by reduction of Ca2+ release. Moreover, regulating Ca2+ flux to mitochondria, Akt maintains the mitochondrial integrity and delays the trigger of apoptosis, in a type III-dependent mechanism. These results demonstrate a specific activity of Akt on IP3R III, leading to diminished Ca2+ transfer to mitochondria and protection from apoptosis, suggesting an additional level of cell death regulation mediated by Akt.
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Hoegg MB, Robbins SM, McGhee JD. Characterization of the C. elegans erlin homologue. BMC Cell Biol 2012; 13:2. [PMID: 22269071 PMCID: PMC3292932 DOI: 10.1186/1471-2121-13-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2011] [Accepted: 01/23/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Erlins are highly conserved proteins associated with lipid rafts within the endoplasmic reticulum (ER). Biochemical studies in mammalian cell lines have shown that erlins are required for ER associated protein degradation (ERAD) of activated inositol-1,4,5-trisphosphate receptors (IP3Rs), implying that erlin proteins might negatively regulate IP3R signalling. In humans, loss of erlin function appears to cause progressive intellectual disability, motor dysfunction and joint contractures. However, it is unknown if defects in IP3R ERAD are the underlying cause of this disease phenotype, whether ERAD of activated IP3Rs is the only function of erlin proteins, and what role ERAD plays in regulating IP3R-dependent processes in the context of an intact animal or embryo. In this study, we characterize the erlin homologue of the nematode Caenorhabditis elegans and examine erlin function in vivo. We specifically set out to test whether C. elegans erlin modulates IP3R-dependent processes, such as egg laying, embryonic development and defecation rates. We also explore the possibility that erlin might play a more general role in the ERAD pathway of C. elegans. RESULTS We first show that the C. elegans erlin homologue, ERL-1, is highly similar to mammalian erlins with respect to amino acid sequence, domain structure, biochemical properties and subcellular location. ERL-1 is present throughout the C. elegans embryo; in adult worms, ERL-1 appears restricted to the germline. The expression pattern of ERL-1 thus only partially overlaps with that of ITR-1, eliminating the possibility of ERL-1 being a ubiquitous and necessary regulator of ITR-1. We show that loss of ERL-1 does not affect overall phenotype, or alter brood size, embryonic development or defecation cycle length in either wild type or sensitized itr-1 mutant animals. Moreover we show that ERL-1 deficient worms respond normally to ER stress conditions, suggesting that ERL-1 is not an essential component of the general ERAD pathway. CONCLUSIONS Although loss of erlin function apparently causes a strong phenotype in humans, no such effect is seen in C. elegans. C. elegans erlin does not appear to be a ubiquitous major modulator of IP3 receptor activity nor does erlin appear to play a major role in ERAD.
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Affiliation(s)
- Maja B Hoegg
- Department of Biochemistry & Molecular Biology, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada
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Skupin A, Thurley K. Calcium signaling: from single channels to pathways. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:531-51. [PMID: 22453959 DOI: 10.1007/978-94-007-2888-2_24] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Ca(2+) is not only one of the most versatile and ubiquitous second messengers but also a well-established representative example of cell signaling. The identification of most key elements involved in Ca(2+) signaling enables a mechanistic and quantitative understanding of this particular pathway. Cellular behavior relies in general on the orchestration of molecular behavior leading to reliable cellular responses that allow for regulation and adaptation. Ca(2+) signaling uses a hierarchical organization to transform single molecule behavior into cell wide signals. We have recently shown experimentally that this organization carries single channel signatures onto the whole cell level and renders Ca(2+) oscillations stochastic. Here, we briefly review the co-evolution of experimental and theoretical studies in Ca(2+) -signaling and show how dynamic bottom-up modeling can be used to address -biological questions and illuminate biological principles of cell signaling.
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Affiliation(s)
- Alexander Skupin
- Luxembourg Centre of Systems Biomedicine, University Luxembourg, Luxembourg.
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35
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Abstract
The Ca(2) (+) signals evoked by inositol 1,4,5-trisphosphate (IP(3)) are built from elementary Ca(2) (+) release events involving progressive recruitment of IP(3) receptors (IP(3)R), intracellular Ca(2) (+) channels that are expressed in almost all animal cells. The smallest events ('blips') result from opening of single IP(3)R. Larger events ('puffs') reflect the near-synchronous opening of a small cluster of IP(3)R. These puffs become more frequent as the stimulus intensity increases and they eventually trigger regenerative Ca(2) (+) waves that propagate across the cell. This hierarchical recruitment of IP(3)R is important in allowing Ca(2) (+) signals to be delivered locally to specific target proteins or more globally to the entire cell. Co-regulation of IP(3)R by Ca(2) (+) and IP(3), the ability of a single IP(3)R rapidly to mediate a large efflux of Ca(2) (+) from the endoplasmic reticulum, and the assembly of IP(3)R into clusters are key features that allow IP(3)R to propagate Ca(2) (+) signals regeneratively. We review these properties of IP(3)R and the structural basis of IP(3)R behavior.
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Affiliation(s)
- Colin W Taylor
- Department of Pharmacology, Tennis Court Road, CB2 1PD, Cambridge, UK,
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36
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Fundamental properties of Ca2+ signals. Biochim Biophys Acta Gen Subj 2011; 1820:1185-94. [PMID: 22040723 DOI: 10.1016/j.bbagen.2011.10.007] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Revised: 10/16/2011] [Accepted: 10/17/2011] [Indexed: 11/21/2022]
Abstract
BACKGROUND Ca2+ is a ubiquitous and versatile second messenger that transmits information through changes of the cytosolic Ca2+ concentration. Recent investigations changed basic ideas on the dynamic character of Ca2+ signals and challenge traditional ideas on information transmission. SCOPE OF REVIEW We present recent findings on key characteristics of the cytosolic Ca2+ dynamics and theoretical concepts that explain the wide range of experimentally observed Ca2+ signals. Further, we relate properties of the dynamical regulation of the cytosolic Ca2+ concentration to ideas about information transmission by stochastic signals. MAJOR CONCLUSIONS We demonstrate the importance of the hierarchal arrangement of Ca2+ release sites on the emergence of cellular Ca2+ spikes. Stochastic Ca2+ signals are functionally robust and adaptive to changing environmental conditions. Fluctuations of interspike intervals (ISIs) and the moment relation derived from ISI distributions contain information on the channel cluster open probability and on pathway properties. GENERAL SIGNIFICANCE Robust and reliable signal transduction pathways that entail Ca2+ dynamics are essential for eukaryotic organisms. Moreover, we expect that the design of a stochastic mechanism which provides robustness and adaptivity will be found also in other biological systems. Ca2+ dynamics demonstrate that the fluctuations of cellular signals contain information on molecular behavior. This article is part of a Special Issue entitled Biochemical, biophysical and genetic approaches to intracellular calcium signaling.
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Rossi AM, Tovey SC, Rahman T, Prole DL, Taylor CW. Analysis of IP3 receptors in and out of cells. Biochim Biophys Acta Gen Subj 2011; 1820:1214-27. [PMID: 22033379 DOI: 10.1016/j.bbagen.2011.10.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Revised: 10/07/2011] [Accepted: 10/08/2011] [Indexed: 10/16/2022]
Abstract
BACKGROUND Inositol 1,4,5-trisphosphate receptors (IP3R) are expressed in almost all animal cells. Three mammalian genes encode closely related IP3R subunits, which assemble into homo- or hetero-tetramers to form intracellular Ca2+ channels. SCOPE OF THE REVIEW In this brief review, we first consider a variety of complementary methods that allow the links between IP3 binding and channel gating to be defined. How does IP3 binding to the IP3-binding core in each IP3R subunit cause opening of a cation-selective pore formed by residues towards the C-terminal? We then describe methods that allow IP3, Ca2+ signals and IP3R mobility to be examined in intact cells. A final section briefly considers genetic analyses of IP3R signalling. MAJOR CONCLUSIONS All IP3R are regulated by both IP3 and Ca2+. This allows them to initiate and regeneratively propagate intracellular Ca2+ signals. The elementary Ca2+ release events evoked by IP3 in intact cells are mediated by very small numbers of active IP3R and the Ca2+-mediated interactions between them. The spatial organization of these Ca2+ signals and their stochastic dependence on so few IP3Rs highlight the need for methods that allow the spatial organization of IP3R signalling to be addressed with single-molecule resolution. GENERAL SIGNIFICANCE A variety of complementary methods provide insight into the structural basis of IP3R activation and the contributions of IP3-evoked Ca2+ signals to cellular physiology. This article is part of a Special Issue entitled Biochemical, biophysical and genetic approaches to intracellular calcium signaling.
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38
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Ma HT, Beaven MA. Regulators of Ca(2+) signaling in mast cells: potential targets for treatment of mast cell-related diseases? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 716:62-90. [PMID: 21713652 DOI: 10.1007/978-1-4419-9533-9_5] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
A calcium signal is essential for degranulation, generation of eicosanoids and optimal production of cytokines in mast cells in response to antigen and other stimulants. The signal is initiated by phospholipase C-mediated production of inositol1,4,5-trisphosphate resulting in release of stored Ca(2+) from the endoplasmic reticulum (ER) and Golgi. Depletion of these stores activates influx of extracellular Ca(2+), usually referred to as store-operated calcium entry (SOCE), through the interaction of the Ca(2+)-sensor, stromal interacting molecule-1 (STIM1 ), in ER with Orai1(CRACM1) and transient receptor potential canonical (TRPC) channel proteins in the plasma membrane (PM). This interaction is enabled by microtubular-directed reorganization of ER to form ER/PM contact points or "punctae" in which STIM1 and channel proteins colocalize. The ensuing influx of Ca(2+) replenishes Ca(2+) stores and sustains elevated levels of cytosolic Ca(2+) ions-the obligatory signal for mast-cell activation. In addition, the signal can acquire spatial and dynamic characteristics (e.g., calcium puffs, waves, oscillations) that encode signals for specific functional outputs. This is achieved by coordinated regulation of Ca(2+) fluxes through ATP-dependent Ca(2+)-pumps and ion exchangers in mitochondria, ER and PM. As discussed in this chapter, studies in mast cells revealed much about the mechanisms described above but little about allergic and autoimmune diseases although studies in other types of cells have exposed genetic defects that lead to aberrant calcium signaling in immune diseases. Pharmacologic agents that inhibit or activate the regulatory components of calcium signaling in mast cells are also discussed along with the prospects for development of novel SOCE inhibitors that may prove beneficial in the treatment inflammatory mast-cell related diseases.
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Affiliation(s)
- Hong-Tao Ma
- Laboratory of Molecular Immunology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
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Modulation of Ca²+ activity in cardiomyocytes through caveolae-Gαq interactions. Biophys J 2011; 100:1599-607. [PMID: 21463572 DOI: 10.1016/j.bpj.2011.02.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Revised: 01/14/2011] [Accepted: 02/07/2011] [Indexed: 11/22/2022] Open
Abstract
Cardiomyocytes have a complex Ca(2+) behavior and changes in this behavior may underlie certain disease states. Intracellular Ca(2+) activity can be regulated by the phospholipase Cβ-Gα(q) pathway localized on the plasma membrane. The plasma membranes of cardiomycoytes are rich in caveolae domains organized by caveolin proteins. Caveolae may indirectly affect cell signals by entrapping and localizing specific proteins. Recently, we found that caveolin may specifically interact with activated Gα(q), which could affect Ca(2+) signals. Here, using fluorescence imaging and correlation techniques we show that Gα(q)-Gβγ subunits localize to caveolae in adult ventricular canine cardiomyoctyes. Carbachol stimulation releases Gβγ subunits from caveolae with a concurrent stabilization of activated Gα(q) by caveolin-3 (Cav3). These cells show oscillating Ca(2+) waves that are not seen in neonatal cells that do not contain Cav3. Microinjection of a peptide that disrupts Cav3-Gα(q) association, but not a control peptide, extinguishes the waves. Furthermore, these waves are unchanged with rynaodine treatment, but not seen with treatment of a phospholipase C inhibitor, implying that Cav3-Gα(q) is responsible for this Ca(2+) activity. Taken together, these studies show that caveolae play a direct and active role in regulating basal Ca(2+) activity in cardiomyocytes.
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Inositol 1,4,5-trisphosphate receptor subtype-specific regulation of calcium oscillations. Neurochem Res 2011; 36:1175-85. [PMID: 21479917 PMCID: PMC3111726 DOI: 10.1007/s11064-011-0457-7] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/18/2011] [Indexed: 11/18/2022]
Abstract
Oscillatory fluctuations in the cytosolic concentration of free calcium ions (Ca2+) are considered a ubiquitous mechanism for controlling multiple cellular processes. Inositol 1,4,5-trisphosphate (IP3) receptors (IP3R) are intracellular Ca2+ release channels that mediate Ca2+ release from endoplasmic reticulum (ER) Ca2+ stores. The three IP3R subtypes described so far exhibit differential structural, biophysical, and biochemical properties. Subtype specific regulation of IP3R by the endogenous modulators IP3, Ca2+, protein kinases and associated proteins have been thoroughly examined. In this article we will review the contribution of each IP3R subtype in shaping cytosolic Ca2+ oscillations.
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Sammels E, Devogelaere B, Mekahli D, Bultynck G, Missiaen L, Parys JB, De Smedt H. Unraveling the role of polycystin-2/inositol 1,4,5-trisphosphate receptor interaction in Ca signaling. Commun Integr Biol 2010; 3:530-2. [PMID: 21331231 DOI: 10.4161/cib.3.6.12751] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Accepted: 06/18/2010] [Indexed: 01/04/2023] Open
Abstract
Autosomal dominant polycystic kidney disease (ADPKD) arises as a consequence of mutations of the genes PKD1 and PKD2, encoding respectively the integral membrane proteins polycystin-1 and polycystin-2 (TRPP2), resulting in a disturbance in intracellular Ca(2+) signaling. Previously we investigated the interaction between TRPP2 and the inositol 1,4,5-trisphosphate (IP(3)) receptor (IP(3)R), an intracellular Ca(2+) channel in the endoplasmic reticulum (ER). We identified the molecular determinants of this interaction and observed an enhanced IP(3)-induced Ca(2+) release (IICR). Since we found that TRPP2 strongly bound to a cluster of positively charged amino acids in the N-terminal ligand-binding domain (LBD) of the IP(3)R, we now investigated whether TRPP2 would interfere with the binding of IP(3) to the IP(3)R. In in vitro experiments we observed that TRPP2 partially inhibited the binding of IP(3) to the LBD of the IP(3)R with an IC(50) of ∼350 nM. The suppressor domain, i.e., the N-terminal 225 amino acids of the LBD of the IP(3)R, mediated this inhibitory effect of TRPP2 on IP(3) binding. The observation that the interaction between the IP(3)R and TRPP2 decreased IP(3) binding is in apparent contrast to the increased IICR. The data can be explained however by a subsequent activation of Ca(2+)-induced Ca(2+) release (CICR) via TRPP2. Implications of this mechanism for cellular Ca(2+) signaling are discussed in this addendum.
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Affiliation(s)
- Eva Sammels
- Laboratory of Molecular and Cellular Signaling; Department of Molecular Cell Biology; K.U. Leuven, Leuven Belgium
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42
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Parker I, Smith IF. Recording single-channel activity of inositol trisphosphate receptors in intact cells with a microscope, not a patch clamp. J Gen Physiol 2010; 136:119-27. [PMID: 20660654 PMCID: PMC2912063 DOI: 10.1085/jgp.200910390] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Optical single-channel recording is a novel tool for the study of individual Ca2+-permeable channels within intact cells under minimally perturbed physiological conditions. As applied to the functioning and spatial organization of IP3Rs, this approach complements our existing knowledge, which derives largely from reduced systems - such as reconstitution into lipid bilayers and patch clamping of IP3Rs on the membrane of excised nuclei - where the spatial arrangement and interactions among IP3Rs via CICR are disrupted. The ability to image the activity of single IP3R channels with millisecond resolution together with localization of their positions with a precision of a few tens of nanometers both raises several intriguing questions and holds promise of answers. In particular, what mechanism underlies the anchoring of puffs and blips to static locations; why do these Ca2+ release events appear to involve only a very small fraction of the IP3Rs within a cell; and how can we reconcile the relative immotility of functional IP3Rs with numerous studies reporting free diffusion of IP3R protein in the ER membrane?
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Affiliation(s)
- Ian Parker
- Department of Neurobiology and Behavior, and Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA 92697
| | - Ian F. Smith
- Department of Neurobiology and Behavior, and Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA 92697
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Calì C, Bezzi P. CXCR4-mediated glutamate exocytosis from astrocytes. J Neuroimmunol 2010; 224:13-21. [PMID: 20580441 DOI: 10.1016/j.jneuroim.2010.05.004] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Accepted: 05/04/2010] [Indexed: 12/28/2022]
Abstract
The role of astrocytes as structural and metabolic support for neurons is known since the beginning of the last century. Because of their strategic localization between neurons and capillaries they can monitor and control the level of synaptic activity by providing energetic metabolites to neurons and remove excess of neurotransmitters. During the last two decades number of papers further established that the astrocytic plasma-membrane G-protein coupled receptors (GPCR) can sense external inputs (such as the spillover of neurotransmitters) and transduce them as intracellular calcium elevations and release of chemical transmitters such as glutamate. The chemokine CXCR4 receptor is a GPCR widely expressed on glial cells (especially astrocytes and microglia). Activation of the astrocytic CXCR4 by its natural ligand CXCL12 (or SDF1 alpha) results in a long chain of intracellular and extracellular events (including the release of the pro-inflammatory cytokine TNFalpha and prostanglandins) leading to glutamate release. The emerging role of CXCR4-CXCL12 signalling axis in brain physiology came from the recent observation that glutamate in astrocytes is released via a regulated exocytosis process and occurs with a relatively fast time-scale, in the order of few hundred milliseconds. Taking into account that astrocytes are electrically non-excitable and thus exocytosis rely only on a signalling pathway that involves the release Ca(2+) from the internal stores, these results suggested a close relationship between sites of Ca(2+) release and those of fusion events. Indeed, a recent observation describes structural sub-membrane microdomains where fast ER-dependent calcium elevations occur in spatial and temporal correlation with fusion events.
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Affiliation(s)
- Corrado Calì
- Department of Cell Biology and Morphology, University of Lausanne, FBM, Lausanne, Switzerland
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44
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Smith IF, Wiltgen SM, Shuai J, Parker I. Ca(2+) puffs originate from preestablished stable clusters of inositol trisphosphate receptors. Sci Signal 2009; 2:ra77. [PMID: 19934435 PMCID: PMC2897231 DOI: 10.1126/scisignal.2000466] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Intracellular calcium ion (Ca(2+)) signaling crucially depends on the clustered organization of inositol trisphosphate receptors (IP(3)Rs) in the endoplasmic reticulum (ER) membrane. These ligand-gated ion channels liberate Ca(2+) to generate local signals known as Ca(2+) puffs. We tested the hypothesis that IP(3) itself elicits rapid clustering of IP(3)Rs by using flash photolysis of caged IP(3) in conjunction with high-resolution Ca(2+) imaging to monitor the activity and localization of individual IP(3)Rs within intact mammalian cells. Our results indicate that Ca(2+) puffs arising with latencies as short as 100 to 200 ms after photorelease of IP(3) already involve at least four IP(3)R channels, and that this number does not subsequently grow. Moreover, single active IP(3)Rs show limited mobility, and stochastic simulations suggest that aggregation of IP(3)Rs at puff sites by a diffusional trapping mechanism would require many seconds. We thus conclude that puff sites represent preestablished, stable clusters of IP(3)Rs and that functional IP(3)Rs are not readily diffusible within the ER membrane.
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Affiliation(s)
- Ian F Smith
- Department of Neurobiology and Behavior, University of California, Irvine, CA 92697-4550, USA.
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Cohen R, Torres A, Ma HT, Holowka D, Baird B. Ca2+ waves initiate antigen-stimulated Ca2+ responses in mast cells. THE JOURNAL OF IMMUNOLOGY 2009; 183:6478-88. [PMID: 19864608 DOI: 10.4049/jimmunol.0901615] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Ca(2+) mobilization is central to many cellular processes, including stimulated exocytosis and cytokine production in mast cells. Using single cell stimulation by IgE-specific Ag and high-speed imaging of conventional or genetically encoded Ca(2+) sensors in rat basophilic leukemia and bone marrow-derived rat mast cells, we observe Ca(2+) waves that originate most frequently from the tips of extended cell protrusions, as well as Ca(2+) oscillations throughout the cell that usually follow the initiating Ca(2+) wave. In contrast, Ag conjugated to the tip of a micropipette stimulates local, repetitive Ca(2+) puffs at the region of cell contact. Initiating Ca(2+) waves are observed in most rat basophilic leukemia cells stimulated with soluble Ag and are sensitive to inhibitors of Ca(2+) release from endoplasmic reticulum stores and to extracellular Ca(2+), but they do not depend on store-operated Ca(2+) entry. Knockdown of transient receptor potential channel (TRPC)1 and TRPC3 channel proteins by short hairpin RNA reduces the sensitivity of these cells to Ag and shifts the wave initiation site from protrusions to the cell body. Our results reveal spatially encoded Ca(2+) signaling in response to immunoreceptor activation that utilizes TRPC channels to specify the initiation site of the Ca(2+) response.
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Affiliation(s)
- Roy Cohen
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14850, USA
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Skupin A, Falcke M. From puffs to global Ca2+ signals: how molecular properties shape global signals. CHAOS (WOODBURY, N.Y.) 2009; 19:037111. [PMID: 19792036 DOI: 10.1063/1.3184537] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The universality of Ca(2+) as second messenger in living cells is achieved by a rich spectrum of spatiotemporal cellular concentration dynamics. Ca(2+) release from internal storage compartments plays a key role in shaping cytosolic Ca(2+) signals. Deciphering this signaling mechanism is essential for a deeper understanding of its physiological function and general concepts of cell signaling. Here, we review recent experimental findings demonstrating the stochasticity of Ca(2+) oscillations and its relevance for modeling Ca(2+) dynamics. The stochasticity arises by the hierarchical signal structure that carries molecular fluctuations of single channels onto the level of the cell leading to a stochastic medium as theoretically predicted. The result contradicts the current opinion of Ca(2+) being a cellular oscillator. We demonstrate that cells use array enhanced coherence resonance to form rather regular spiking signals and that the "oscillations" carry information despite the involved stochasticity. The knowledge on the underlying mechanism also allows for determination of intrinsic properties from global observations. In the second part of the paper, we briefly survey different modeling approaches with regard to the experimental results. We focus on the dependence of the standard deviation on the mean period of the oscillations. It shows that limit cycle oscillations cannot describe the experimental data and that generic models have to include the spatial aspects of Ca(2+) signaling.
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Affiliation(s)
- Alexander Skupin
- Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, Germany
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Wojcikiewicz RJH, Pearce MMP, Sliter DA, Wang Y. When worlds collide: IP(3) receptors and the ERAD pathway. Cell Calcium 2009; 46:147-53. [PMID: 19709743 DOI: 10.1016/j.ceca.2009.05.002] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Revised: 05/01/2009] [Accepted: 05/05/2009] [Indexed: 12/13/2022]
Abstract
While cell signaling devotees tend to think of the endoplasmic reticulum (ER) as a Ca(2+) store, those who study protein synthesis tend to see it more as site for protein maturation, or even degradation when proteins do not fold properly. These two worldviews collide when inositol 1,4,5-trisphosphate (IP(3)) receptors are activated, since in addition to acting as release channels for stored ER Ca(2+), IP(3) receptors are rapidly destroyed via the ER-associated degradation (ERAD) pathway, a ubiquitination- and proteasome-dependent mechanism that clears the ER of aberrant proteins. Here we review recent studies showing that activated IP(3) receptors are ubiquitinated in an unexpectedly complex manner, and that a novel complex composed of the ER membrane proteins SPFH1 and SPFH2 (erlin 1 and 2) binds to IP(3) receptors immediately after they are activated and mediates their ERAD. Remarkably, it seems that the conformational changes that underpin channel opening make IP(3) receptors resemble aberrant proteins, which triggers their binding to the SPFH1/2 complex, their ubiquitination and extraction from the ER membrane and finally, their degradation by the proteasome. This degradation of activated IP(3) receptors by the ERAD pathway serves to reduce the sensitivity of ER Ca(2+) stores to IP(3) and may protect cells against deleterious effects of over-activation of Ca(2+) signaling pathways.
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Increased InsP3Rs in the junctional sarcoplasmic reticulum augment Ca2+ transients and arrhythmias associated with cardiac hypertrophy. Proc Natl Acad Sci U S A 2009; 106:11406-11. [PMID: 19549843 DOI: 10.1073/pnas.0905485106] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cardiac hypertrophy is a growth response of the heart to increased hemodynamic demand or damage. Accompanying this heart enlargement is a remodeling of Ca(2+) signaling. Due to its fundamental role in controlling cardiomyocyte contraction during every heartbeat, modifications in Ca(2+) fluxes significantly impact on cardiac output and facilitate the development of arrhythmias. Using cardiomyocytes from spontaneously hypertensive rats (SHRs), we demonstrate that an increase in Ca(2+) release through inositol 1,4,5-trisphosphate receptors (InsP(3)Rs) contributes to the larger excitation contraction coupling (ECC)-mediated Ca(2+) transients characteristic of hypertrophic myocytes and underlies the more potent enhancement of ECC-mediated Ca(2+) transients and contraction elicited by InsP(3) or endothelin-1 (ET-1). Responsible for this is an increase in InsP(3)R expression in the junctional sarcoplasmic reticulum. Due to their close proximity to ryanodine receptors (RyRs) in this region, enhanced Ca(2+) release through InsP(3)Rs served to sensitize RyRs, thereby increasing diastolic Ca(2+) levels, the incidence of extra-systolic Ca(2+) transients, and the induction of ECC-mediated Ca(2+) elevations. Unlike the increase in InsP(3)R expression and Ca(2+) transient amplitude in the cytosol, InsP(3)R expression and ECC-mediated Ca(2+) transients in the nucleus were not altered during hypertrophy. Elevated InsP(3)R2 expression was also detected in hearts from human patients with heart failure after ischemic dilated cardiomyopathy, as well as in aortic-banded hypertrophic mouse hearts. Our data establish that increased InsP(3)R expression is a general mechanism that underlies remodeling of Ca(2+) signaling during heart disease, and in particular, in triggering ventricular arrhythmia during hypertrophy.
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Cooper Z, Greenwood M, Mazzag B. A computational analysis of localized Ca2+-dynamics generated by heterogeneous release sites. Bull Math Biol 2009; 71:1543-79. [PMID: 19440797 DOI: 10.1007/s11538-009-9413-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2007] [Accepted: 02/10/2009] [Indexed: 11/30/2022]
Abstract
We investigate the role of heterogeneous expression of IP3R and RyR in generating diverse elementary Ca2+ signals. It has been shown empirically (Wojcikiewicz and Luo in Mol. Pharmacol. 53(4):656-662, 1998; Newton et al. in J. Biol. Chem. 269(46):28613-28619, 1994; Smedt et al. in Biochem. J. 322(Pt. 2):575-583, 1997) that tissues express various proportions of IP3 and RyR isoforms and this expression is dynamically regulated (Parrington et al. in Dev. Biol. 203(2):451-461, 1998; Fissore et al. in Biol. Reprod. 60(1):49-57, 1999; Tovey et al. in J. Cell Sci. 114(Pt. 22):3979-3989, 2001). Although many previous theoretical studies have investigated the dynamics of localized calcium release sites (Swillens et al. in Proc. Natl. Acad. Sci. U.S.A. 96(24):13750-13755, 1999; Shuai and Jung in Proc. Natl. Acad. Sci. U.S.A. 100(2):506-510, 2003a; Shuai and Jung in Phys. Rev. E, Stat. Nonlinear Soft Matter Phys. 67(3 Pt. 1):031905, 2003b; Thul and Falcke in Biophys. J. 86(5):2660-2673, 2004; DeRemigio and Smith in Cell Calcium 38(2):73-86, 2005; Nguyen et al. in Bull. Math. Biol. 67(3):393-432, 2005), so far all such studies focused on release sites consisting of identical channel types. We have extended an existing mathematical model (Nguyen et al. in Bull. Math. Biol. 67(3):393-432, 2005) to release sites with two (or more) receptor types, each with its distinct channel kinetics. Mathematically, the release site is represented by a transition probability matrix for a collection of nonidentical stochastically gating channels coupled through a shared Ca2+ domain. We demonstrate that under certain conditions a previously defined mean-field approximation of the coupling strength does not accurately reproduce the release site dynamics. We develop a novel approximation and establish that its performance in these instances is superior. We use this mathematical framework to study the effect of heterogeneity in the Ca2+-regulation of two colocalized channel types on the release site dynamics. We consider release sites consisting of channels with both Ca2+-activation and inactivation ("four-state channels") and channels with Ca2+-activation only ("two-state channels") and show that for the appropriate parameter values, synchronous channel openings within a release site with any proportion of two-state to four-state channels are possible, however, the larger the proportion of two-state channels, the more sensitive the dynamics are to the exact spatial positioning of the channels and the distance between channels. Specifically, the clustering of even a small number of two-state channels interferes with puff/spark termination and increases puff durations or leads to a tonic response.
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Affiliation(s)
- Zachary Cooper
- Department of Mathematics, Humboldt State University, Arcata, CA 95521, USA
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Calì C, Marchaland J, Spagnuolo P, Gremion J, Bezzi P. Regulated exocytosis from astrocytes physiological and pathological related aspects. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2009; 85:261-93. [PMID: 19607976 DOI: 10.1016/s0074-7742(09)85020-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Astrocytes have traditionally been considered ancillary, satellite cells of the nervous system. However, it is a very recent acquisition that glial cells generate signaling loops which are integral to the brain circuitry and participate, interactively with neuronal networks, in the processing of information. Such a conceptual breakthrough makes this field of investigation one of the hottest in neuroscience, as it calls for a revision of past theories of brain function as well as for new strategies of experimental exploration of brain function. Glial cells are electrically not excitable, and it was only the use of optical recording techniques together with calcium sensitive dyes, that allowed the chemical excitability of glial cells to become apparent. Studies using these new techniques have shown for the first time that glial cells are activated by surrounding synaptic activity and translate neuronal signals into their own calcium code. Intracellular calcium concentration([Ca2+]i) elevations in glial cells have then shown to underlie spatial transfer of information in the glial network, accompanied by release of chemical transmitters (gliotransmitters) such as glutamate and back-signaling to neurons. As a consequence, optical imaging techniques applied to cell cultures or intact tissue have become a state-of-the-art technology for studying glial cell signaling. The molecular mechanisms leading to release of "gliotransmitters," especially glutamate, from glia are under debate. Accumulating evidence clearly indicates that astrocytes secrete numerous transmitters by Ca(2+)-dependent exocytosis. This review will discuss the mechanisms underlying the release of chemical transmitters from astrocytes with a particular emphasis to the regulated exocytosis processes.
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Affiliation(s)
- Corrado Calì
- Department of Cellular Biology and Morphology (DBCM), Faculty of Medicine, University of Lausanne, rue du Bugnon 9, 1005 Lausanne, Switzerland
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