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Sakazume H, Morita T, Yamaguchi H, Tanaka A. Intracellular Signaling Pathways Involved in the Regulation of Gene Expression by Pilocarpine. J Oral Biosci 2024:S1349-0079(24)00152-X. [PMID: 38992855 DOI: 10.1016/j.job.2024.07.004] [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: 12/05/2023] [Revised: 07/06/2024] [Accepted: 07/08/2024] [Indexed: 07/13/2024]
Abstract
OBJECTIVES Pilocarpine is commonly used clinically to treat dry mouth. The long-term administration of pilocarpine reportedly improves salivary secretion more effectively than short-term administration. Therefore, we hypothesized that pilocarpine alters gene expression in salivary glands via muscarinic receptor stimulation. This study aimed to investigate the effects of pilocarpine use on gene expression mediated by mitogen-activated protein kinase (MAPK) activity. METHODS The effects of pilocarpine on gene expression were investigated in rats and human salivary gland (HSY) cells using several inhibitors of intracellular signaling pathways. Gene expression in the rat submandibular gland and HSY cells was determined using reverse transcription-quantitative polymerase chain reaction analysis of total RNA. RESULTS In animal experiments, at 7 days after pilocarpine stimulation, Ctgf and Sgk1 expressions were increased in the submandibular gland. In cell culture experiments, pilocarpine increased Ctgf expression in HSY cells. The mitogen-activated protein kinase kinase inhibitor trametinib, the Src inhibitor PP2, and the muscarinic acetylcholine receptor antagonist atropine suppressed the effect of pilocarpine on gene expression. CONCLUSIONS Pilocarpine enhances Ctgf and Sgk1 expressions by activating Src-mediated MAPK activity. Although further studies are required to fully understand the roles of Ctgf and Sgk1, changes in gene expression may play an important role in improving salivary secretions.
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Affiliation(s)
- Hirohito Sakazume
- Course of Clinical Science, Field of Oral and Maxillofacial Surgery and Systemic Medicine, Oral and Maxillofacial Surgery, Graduate School of Life Dentistry at Niigata, The Nippon Dental University
| | - Takao Morita
- Department of Biochemistry, School of Life Dentistry at Niigata, The Nippon Dental University.
| | - Haruka Yamaguchi
- Department of Biochemistry, School of Life Dentistry at Niigata, The Nippon Dental University
| | - Akira Tanaka
- Course of Clinical Science, Field of Oral and Maxillofacial Surgery and Systemic Medicine, Oral and Maxillofacial Surgery, Graduate School of Life Dentistry at Niigata, The Nippon Dental University; Department of Oral and Maxillofacial Surgery, School of Life Dentistry at Niigata, The Nippon Dental University
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Shimatani M, Morita T, Yanuar R, Nezu A, Tanimura A. Local anesthetics inhibit muscarinic acetylcholine receptor-mediated calcium responses and the recruitment of β-arrestin in HSY human parotid cells. J Oral Biosci 2024; 66:465-472. [PMID: 38614428 DOI: 10.1016/j.job.2024.04.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 04/05/2024] [Accepted: 04/07/2024] [Indexed: 04/15/2024]
Abstract
OBJECTIVES Local anesthetics act on G protein-coupled receptors (GPCRs); thus, their potential as allosteric modulators of GPCRs has attracted attention. Intracellular signaling via GPCRs involves both G-protein- and β-arrestin-mediated pathways. To determine the effects of local anesthetics on muscarinic acetylcholine receptors (mAChR), a family of GPCRs, we analyzed the effects of local anesthetics on mAChR-mediated Ca2+ responses and formation of receptor-β-arrestin complexes in the HSY human parotid cell line. METHODS Ca2+ responses were monitored by fura-2 spectrofluorimetry. Ligand-induced interactions between mAChR and β-arrestin were examined using a β-arrestin GPCR assay kit. RESULTS Lidocaine reduced mAChR-mediated Ca2+ responses but did not change the intracellular Ca2+ concentration in non-stimulated cells. The membrane-impermeant lidocaine analog QX314 and procaine inhibited mAChR-mediated Ca2+ responses, with EC50 values of 48.0 and 20.4 μM, respectively, for 50 μM carbachol-stimulated Ca2+ responses. In the absence of extracellular Ca2+, the pretreatment of cells with QX314 reduced carbachol-induced Ca2+ release, indicating that QX314 reduced Ca2+ release from intracellular stores. Lidocaine and QX314 did not affect store-operated Ca2+ entry as they did not alter the thapsigargin-induced Ca2+ response. QX314 and procaine reduced the carbachol-mediated recruitment of β-arrestin, and administration of procaine suppressed pilocarpine-induced salivary secretion in mice. CONCLUSION Local anesthetics, including QX314, act on mAChR to reduce carbachol-induced Ca2+ release from intracellular stores and the recruitment of β-arrestin. These findings support the notion that local anesthetics and their derivatives are starting points for the development of functional allosteric modulators of mAChR.
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Affiliation(s)
- Mari Shimatani
- Division of Reconstructive Surgery for Oral and Maxillofacial Region, Department of Human Biology and Pathophysiology, School of Dentistry, Health Sciences University of Hokkaido, Hokkaido, Japan
| | - Takao Morita
- Department of Biochemistry, School of Life Dentistry at Niigata, The Nippon Dental University, Niigata, Japan
| | - Rezon Yanuar
- Division of Pharmacology, Department of Oral Biology, School of Dentistry, Health Sciences University of Hokkaido, Hokkaido, Japan
| | - Akihiro Nezu
- Division of Pharmacology, Department of Oral Biology, School of Dentistry, Health Sciences University of Hokkaido, Hokkaido, Japan
| | - Akihiko Tanimura
- Division of Pharmacology, Department of Oral Biology, School of Dentistry, Health Sciences University of Hokkaido, Hokkaido, Japan.
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Chen G, Kong D, Lin Y. Neo-Antigen-Reactive T Cells Immunotherapy for Colorectal Cancer: A More Personalized Cancer Therapy Approach. GLOBAL CHALLENGES (HOBOKEN, NJ) 2023; 7:2200186. [PMID: 37970536 PMCID: PMC10632666 DOI: 10.1002/gch2.202200186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 05/09/2023] [Indexed: 11/17/2023]
Abstract
Colorectal cancer (CRC) is the second most common malignancy in women and the third most frequent cancer in men. Evidence has revealed that the survival of patients with metastatic CRC is very low, between one and three years. Neoantigens are known proteins encoded by mutations in tumor cells. It is theorized that recognizing neoantigens by T cells leads to T cell activation and further antitumor responses. Neoantigen-reactive T cells (NRTs) are designed against the mentioned neoantigens expressed by tumor cells. NRTs selectively kill tumor cells without damage to non-cancerous cells. Identifying patient-specific and high immunogen neoantigens is important in NRT immunotherapy of patients with CRC. However, the main challenges are the side effects and preparation of NRTs, as well as the effectiveness of these cells in vivo. This review summarized the properties of neoantigens as well as the preparation and therapeutic outcomes of NRTs for the treatment of CRC.
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Affiliation(s)
- Guan‐Liang Chen
- Department of Gastroenterology SurgeryAffiliated Hospital of Shaoxing UniversityShaoxing312000China
| | - De‐Xia Kong
- Center for General Practice MedicineDepartment of GastroenterologyZhejiang Provincial People's Hospital (Affiliated People's Hospital), Hangzhou Medical CollegeNo. 158 Shangtang RoadHangzhouZhejiang310014China
| | - Yan Lin
- Center for General Practice MedicineDepartment of GastroenterologyZhejiang Provincial People's Hospital (Affiliated People's Hospital), Hangzhou Medical CollegeNo. 158 Shangtang RoadHangzhouZhejiang310014China
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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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Jahan A, Akter MT, Takemoto K, Oura T, Shitara A, Semba S, Nezu A, Suto S, Nagai T, Tanimura A. Insertion of circularly permuted cyan fluorescent protein into the ligand-binding domain of inositol 1,4,5-trisphosphate receptor for enhanced FRET upon binding of fluorescent ligand. Cell Calcium 2022; 108:102668. [PMID: 36335765 DOI: 10.1016/j.ceca.2022.102668] [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: 04/03/2022] [Revised: 10/22/2022] [Accepted: 10/25/2022] [Indexed: 01/25/2023]
Abstract
Binding of fluorescent ligand (FL) to the cyan fluorescent protein (CFP)-coupled ligand-binding domain of the inositol 1,4,5-trisphosphate (IP3) receptor (CFP-LBP) produces fluorescence (Förster) resonance energy transfer (FRET). A competitive fluorescent ligand assay (CFLA), using the FRET signal from competition between FLs and IP3, can measure IP3 concentration. The FRET signal should be enhanced by attaching a FRET donor to an appropriate position. Herein, we inserted five different circularly permuted CFPs in the loop between the second and third α-helices to generate membrane-targeted fluorescent ligand-binding proteins (LBPs). Two such proteins, LBP-cpC157 and LBP-cpC173, localized at the plasma membrane, displayed FRET upon binding the high-affinity ligand fluorescent adenophostin A (F-ADA), and exhibited a decreased fluorescence emission ratio (480 nm / 535 nm) by 1.6- to 1.8-fold that of CFP-LBP. In addition, binding of a fluorescent low-affinity ligand (F-LL) also reduced the fluorescence ratio in a concentration-dependent manner, with EC50 values for LBP-cpC157 and LBP-cpC173 of 34.7 nM and 27.6 nM, respectively. These values are comparable to that with CFP-LBP (29.2 nM), indicating that insertion of cpC157 and cpC173 did not disrupt LBP structure and function. The effect of 100 nM F-LL on the decrease in fluorescence ratio was reversed upon addition of IP3, indicating binding competition between F-LL and IP3. We also constructed cytoplasmic fluorescent proteins cyLBP-cpC157 and cyLBP-cpC173, and bound them to DYK beads for imaging analyses. Application of F-ADA decreased the fluorescence ratio of the beads from the periphery to the center over 3 - 5 min. Application of F-LL also decreased the fluorescence ratio of cyLBP-cpC157 and cyLBP-cpC173 by 20-25%, and subsequent addition of IP3 recovered the fluorescence ratio in a concentration-dependent manner. The EC50 value and Hill coefficient obtained by curve fitting against the IP3-dependent recovery of fluorescence ratio can be used to estimate the IP3 concentration.
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Affiliation(s)
- Azmeree Jahan
- Division of Pharmacology, Department of Oral Biology, School of Dentistry, Health Sciences University of Hokkaido, Hokkaido, Japan
| | - Mst Tahmina Akter
- Division of Pharmacology, Department of Oral Biology, School of Dentistry, Health Sciences University of Hokkaido, Hokkaido, Japan
| | - Kiwamu Takemoto
- Department of Biochemistry, Mie University, Graduate School of Medicine, Mie, Japan
| | - Tai Oura
- Laboratory of Organic Chemistry for Drug Development, Faculty of Pharmaceutical Sciences, Hokkaido University, Hokkaido, Japan
| | - Akiko Shitara
- Department of Pharmacology, Asahi University School of Dentistry, Aichi, Japan
| | - Shingo Semba
- Division of Pharmacology, Department of Oral Biology, School of Dentistry, Health Sciences University of Hokkaido, Hokkaido, Japan
| | - Akihiro Nezu
- Division of Pharmacology, Department of Oral Biology, School of Dentistry, Health Sciences University of Hokkaido, Hokkaido, Japan
| | - Satoshi Suto
- Laboratory of Organic Chemistry for Drug Development, Faculty of Pharmaceutical Sciences, Hokkaido University, Hokkaido, Japan
| | - Takeharu Nagai
- Department of Biomolecular Science and Engineering, SANKEN (The Institute of Scientific and Industrial Research) Osaka University, Osaka, Japan
| | - Akihiko Tanimura
- Division of Pharmacology, Department of Oral Biology, School of Dentistry, Health Sciences University of Hokkaido, Hokkaido, Japan.
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Zhu Y, Qian Y, Li Z, Li Y, Li B. Neoantigen-reactive T cell: An emerging role in adoptive cellular immunotherapy. MedComm (Beijing) 2021; 2:207-220. [PMID: 34766142 PMCID: PMC8491202 DOI: 10.1002/mco2.41] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 10/16/2020] [Accepted: 10/22/2020] [Indexed: 01/06/2023] Open
Abstract
Adoptive cellular immunotherapy harnessing the intrinsic immune system for precise treatment has exhibited preliminary success against malignant tumors. As one of the emerging roles in adoptive cellular immunotherapy, neoantigen-reactive T cell (NRT) focuses on the antigens expressed only by tumor cells. It exclusively obliterates tumor and spares normal tissues, achieving more satisfying effects. However, the development of NRT immunotherapy remains in a relatively primitive stage. Current challenges include identification of NRTs and maintenance of adoptive cell efficacy in vivo. The possible side effects and other limitations of this treatment also hinder its application. Here, we present an overview of NRT immunotherapy and discuss the progress and challenges as well as the prospects in this promising field.
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Affiliation(s)
- Yicheng Zhu
- Department of Immunology and Microbiology, Shanghai Institute of Immunology Shanghai Jiao Tong University School of Medicine Shanghai China
| | - Youkun Qian
- Department of Immunology and Microbiology, Shanghai Institute of Immunology Shanghai Jiao Tong University School of Medicine Shanghai China
| | - Zhile Li
- Department of Immunology and Microbiology, Shanghai Institute of Immunology Shanghai Jiao Tong University School of Medicine Shanghai China
| | - Yangyang Li
- Department of Immunology and Microbiology, Shanghai Institute of Immunology Shanghai Jiao Tong University School of Medicine Shanghai China
| | - Bin Li
- Department of Immunology and Microbiology, Shanghai Institute of Immunology Shanghai Jiao Tong University School of Medicine Shanghai China
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7
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Abstract
Ion channel are embedded in the lipid bilayers of biological membranes. Membrane phospholipids constitute a barrier to ion movement, and they have been considered for a long time as a passive environment for channel proteins. Membrane phospholipids, however, do not only serve as a passive amphipathic environment, but they also modulate channel activity by direct specific lipid-protein interactions. Phosphoinositides are quantitatively minor components of biological membranes, and they play roles in many cellular functions, including membrane traffic, cellular signaling and cytoskeletal organization. Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] is mainly found in the inner leaflet of the plasma membrane. Its role as a potential ion channel regulator was first appreciated over two decades ago and by now this lipid is a well-established cofactor or regulator of many different ion channels. The past two decades witnessed the steady development of techniques to study ion channel regulation by phosphoinositides with progress culminating in recent cryoEM structures that allowed visualization of how PI(4,5)P2 opens some ion channels. This chapter will provide an overview of the methods to study regulation by phosphoinositides, focusing on plasma membrane ion channels and PI(4,5)P2.
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8
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Bartlett PJ, Cloete I, Sneyd J, Thomas AP. IP 3-Dependent Ca 2+ Oscillations Switch into a Dual Oscillator Mechanism in the Presence of PLC-Linked Hormones. iScience 2020; 23:101062. [PMID: 32353764 PMCID: PMC7191650 DOI: 10.1016/j.isci.2020.101062] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 12/11/2019] [Accepted: 04/09/2020] [Indexed: 11/28/2022] Open
Abstract
Ca2+ oscillations that depend on inositol-1,4,5-trisphosphate (IP3) have been ascribed to biphasic Ca2+ regulation of the IP3 receptor (IP3R) or feedback mechanisms controlling IP3 levels in different cell types. IP3 uncaging in hepatocytes elicits Ca2+ transients that are often localized at the subcellular level and increase in magnitude with stimulus strength. However, this does not reproduce the broad baseline-separated global Ca2+ oscillations elicited by vasopressin. Addition of hormone to cells activated by IP3 uncaging initiates a qualitative transition from high-frequency spatially disorganized Ca2+ transients, to low-frequency, oscillatory Ca2+ waves that propagate throughout the cell. A mathematical model with dual coupled oscillators that integrates Ca2+-induced Ca2+ release at the IP3R and mutual feedback mechanisms of cross-coupling between Ca2+ and IP3 reproduces this behavior. Thus, multiple Ca2+ oscillation modes can coexist in the same cell, and hormonal stimulation can switch from the simpler to the more complex to yield robust signaling.
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Affiliation(s)
- Paula J Bartlett
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School Rutgers, The State University of New Jersey, Newark, NJ 07103, USA
| | - Ielyaas Cloete
- Department of Mathematics, The University of Auckland, Auckland, New Zealand
| | - James Sneyd
- Department of Mathematics, The University of Auckland, Auckland, New Zealand
| | - Andrew P Thomas
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School Rutgers, The State University of New Jersey, Newark, NJ 07103, USA.
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9
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Greenwald EC, Mehta S, Zhang J. Genetically Encoded Fluorescent Biosensors Illuminate the Spatiotemporal Regulation of Signaling Networks. Chem Rev 2018; 118:11707-11794. [PMID: 30550275 DOI: 10.1021/acs.chemrev.8b00333] [Citation(s) in RCA: 295] [Impact Index Per Article: 49.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Cellular signaling networks are the foundation which determines the fate and function of cells as they respond to various cues and stimuli. The discovery of fluorescent proteins over 25 years ago enabled the development of a diverse array of genetically encodable fluorescent biosensors that are capable of measuring the spatiotemporal dynamics of signal transduction pathways in live cells. In an effort to encapsulate the breadth over which fluorescent biosensors have expanded, we endeavored to assemble a comprehensive list of published engineered biosensors, and we discuss many of the molecular designs utilized in their development. Then, we review how the high temporal and spatial resolution afforded by fluorescent biosensors has aided our understanding of the spatiotemporal regulation of signaling networks at the cellular and subcellular level. Finally, we highlight some emerging areas of research in both biosensor design and applications that are on the forefront of biosensor development.
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Affiliation(s)
- Eric C Greenwald
- University of California , San Diego, 9500 Gilman Drive, BRFII , La Jolla , CA 92093-0702 , United States
| | - Sohum Mehta
- University of California , San Diego, 9500 Gilman Drive, BRFII , La Jolla , CA 92093-0702 , United States
| | - Jin Zhang
- University of California , San Diego, 9500 Gilman Drive, BRFII , La Jolla , CA 92093-0702 , United States
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10
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Tanimura A, Nezu A, Morita T, Murata K. [Advances in methods for analyzing IP 3 signaling and understanding of coupled Ca 2+ and IP 3 oscillations]. Nihon Yakurigaku Zasshi 2018; 152:21-27. [PMID: 29998948 DOI: 10.1254/fpj.152.21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Inositol 1,4,5-trisphosphate (IP3) is an important intracellular messenger produced by phospholipase C via the activation of G-protein-coupled receptor- or receptor-tyrosine-kinase-mediated pathways, and is involved in numerous responses to hormones, neurotransmitters, and growth factors through the releases of Ca2+ from intracellular stores via IP3 receptors. IP3-mediated Ca2+ signals often exhibit complex spatial and temporal organizations, such as Ca2+ oscillations. Recently, new methods have become available to measure IP3 concentration ([IP3]) using AlphaScreen technology, fluorescence polarization, and competitive ligand binding assay (CFLA). These methods are useful for the high throughput screening in drug discovery. Calcium ions generate versatile intracellular signals such as Ca2+ oscillations and waves. Fluorescent sensors molecules to monitor changes in [IP3] in single living cells are crucial to study the mechanism for the spatially and temporally regulated Ca2+ signals. In particular, FRET-based IP3 sensors are useful for the quantitative monitoring intracellular [IP3], and allowed to uncovered the oscillatory IP3 dynamics in association with Ca2+ oscillations. A mathematical model of coupled Ca2+ and IP3 oscillations predicts that Ca2+ oscillations are the result of modulation of the IP3 receptor by intracellular Ca2+, and that the period is modulated by the accompanying IP3 oscillations. These model predictions have also been confirmed experimentally. At present, however, usefulness of FRET-based IP3 sensors are limited by their relatively small change in fluorescence. Development of novel IP3 sensors with improve dynamic range would be important for understanding the regulatory mechanism of Ca2+ signaling and for in vivo IP3 imaging.
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Affiliation(s)
- Akihiko Tanimura
- Department of Pharmacology, School of Dentistry, Health Sciences University of Hokkaido
| | - Akihiro Nezu
- Department of Pharmacology, School of Dentistry, Health Sciences University of Hokkaido
| | - Takao Morita
- Department of Biochemistry, The Nippon Dental University, School of Life Dentistry at Niigata
| | - Kaori Murata
- Department of Pharmacology, School of Dentistry, Health Sciences University of Hokkaido
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11
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Arroyo-Olarte RD, Thurow L, Kozjak-Pavlovic V, Gupta N. Illuminating pathogen-host intimacy through optogenetics. PLoS Pathog 2018; 14:e1007046. [PMID: 30001435 PMCID: PMC6042787 DOI: 10.1371/journal.ppat.1007046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The birth and subsequent evolution of optogenetics has resulted in an unprecedented advancement in our understanding of the brain. Its outstanding success does usher wider applications; however, the tool remains still largely relegated to neuroscience. Here, we introduce selected aspects of optogenetics with potential applications in infection biology that will not only answer long-standing questions about intracellular pathogens (parasites, bacteria, viruses) but also broaden the dimension of current research in entwined models. In this essay, we illustrate how a judicious integration of optogenetics with routine methods can illuminate the host–pathogen interactions in a way that has not been feasible otherwise.
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Affiliation(s)
- Ruben Dario Arroyo-Olarte
- Department of Molecular Parasitology, Faculty of Life Sciences, Humboldt University, Berlin, Germany
| | - Laura Thurow
- Department of Molecular Parasitology, Faculty of Life Sciences, Humboldt University, Berlin, Germany
| | - Vera Kozjak-Pavlovic
- Department of Microbiology, Biocenter, Julius Maximilian University, Würzburg, Germany
| | - Nishith Gupta
- Department of Molecular Parasitology, Faculty of Life Sciences, Humboldt University, Berlin, Germany
- * E-mail:
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12
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Taheri M, Handy G, Borisyuk A, White JA. Diversity of Evoked Astrocyte Ca 2+ Dynamics Quantified through Experimental Measurements and Mathematical Modeling. Front Syst Neurosci 2017; 11:79. [PMID: 29109680 PMCID: PMC5660282 DOI: 10.3389/fnsys.2017.00079] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 10/04/2017] [Indexed: 01/06/2023] Open
Abstract
Astrocytes are a major cell type in the mammalian brain. They are not electrically excitable, but generate prominent Ca2+ signals related to a wide variety of critical functions. The mechanisms driving these Ca2+ events remain incompletely understood. In this study, we integrate Ca2+ imaging, quantitative data analysis, and mechanistic computational modeling to study the spatial and temporal heterogeneity of cortical astrocyte Ca2+ transients evoked by focal application of ATP in mouse brain slices. Based on experimental results, we tune a single-compartment mathematical model of IP3-dependent Ca2+ responses in astrocytes and use that model to study response heterogeneity. Using information from the experimental data and the underlying bifurcation structure of our mathematical model, we categorize all astrocyte Ca2+ responses into four general types based on their temporal characteristics: Single-Peak, Multi-Peak, Plateau, and Long-Lasting responses. We find that the distribution of experimentally-recorded response types depends on the location within an astrocyte, with somatic responses dominated by Single-Peak (SP) responses and large and small processes generating more Multi-Peak responses. On the other hand, response kinetics differ more between cells and trials than with location within a given astrocyte. We use the computational model to elucidate possible sources of Ca2+ response variability: (1) temporal dynamics of IP3, and (2) relative flux rates through Ca2+ channels and pumps. Our model also predicts the effects of blocking Ca2+ channels/pumps; for example, blocking store-operated Ca2+ (SOC) channels in the model eliminates Plateau and Long-Lasting responses (consistent with previous experimental observations). Finally, we propose that observed differences in response type distributions between astrocyte somas and processes can be attributed to systematic differences in IP3 rise durations and Ca2+ flux rates.
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Affiliation(s)
- Marsa Taheri
- Department of Bioengineering, University of Utah, Salt Lake City, UT, United States
| | - Gregory Handy
- Department of Mathematics, University of Utah, Salt Lake City, UT, United States
| | - Alla Borisyuk
- Department of Mathematics, University of Utah, Salt Lake City, UT, United States
| | - John A White
- Department of Biomedical Engineering, Boston University, Boston, MA, United States
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13
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Lodygin D, Flügel A. Intravital real-time analysis of T-cell activation in health and disease. Cell Calcium 2017; 64:118-129. [DOI: 10.1016/j.ceca.2016.12.007] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 12/23/2016] [Indexed: 01/27/2023]
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14
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Mathematical investigation of IP 3-dependent calcium dynamics in astrocytes. J Comput Neurosci 2017; 42:257-273. [PMID: 28353176 DOI: 10.1007/s10827-017-0640-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 02/14/2017] [Accepted: 03/09/2017] [Indexed: 10/19/2022]
Abstract
We study evoked calcium dynamics in astrocytes, a major cell type in the mammalian brain. Experimental evidence has shown that such dynamics are highly variable between different trials, cells, and cell subcompartments. Here we present a qualitative analysis of a recent mathematical model of astrocyte calcium responses. We show how the major response types are generated in the model as a result of the underlying bifurcation structure. By varying key channel parameters, mimicking blockers used by experimentalists, we manipulate this underlying bifurcation structure and predict how the distributions of responses can change. We find that store-operated calcium channels, plasma membrane bound channels with little activity during calcium transients, have a surprisingly strong effect, underscoring the importance of considering these channels in both experiments and mathematical settings. Variation in the maximum flow in different calcium channels is also shown to determine the range of stable oscillations, as well as set the range of frequencies of the oscillations. Further, by conducting a randomized search through the parameter space and recording the resulting calcium responses, we create a database that can be used by experimentalists to help estimate the underlying channel distribution of their cells.
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15
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Han JM, Tanimura A, Kirk V, Sneyd J. A mathematical model of calcium dynamics in HSY cells. PLoS Comput Biol 2017; 13:e1005275. [PMID: 28199326 PMCID: PMC5310762 DOI: 10.1371/journal.pcbi.1005275] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Accepted: 11/30/2016] [Indexed: 12/03/2022] Open
Abstract
Saliva is an essential part of activities such as speaking, masticating and swallowing. Enzymes in salivary fluid protect teeth and gums from infectious diseases, and also initiate the digestion process. Intracellular calcium (Ca2+) plays a critical role in saliva secretion and regulation. Experimental measurements of Ca2+ and inositol trisphosphate (IP3) concentrations in HSY cells, a human salivary duct cell line, show that when the cells are stimulated with adenosine triphosphate (ATP) or carbachol (CCh), they exhibit coupled oscillations with Ca2+ spike peaks preceding IP3 spike peaks. Based on these data, we construct a mathematical model of coupled Ca2+ and IP3 oscillations in HSY cells and perform model simulations of three different experimental settings to forecast Ca2+ responses. The model predicts that when Ca2+ influx from the extracellular space is removed, oscillations gradually slow down until they stop. The model simulation of applying a pulse of IP3 predicts that photolysis of caged IP3 causes a transient increase in the frequency of the Ca2+ oscillations. Lastly, when Ca2+-dependent activation of PLC is inhibited, we see an increase in the oscillation frequency and a decrease in the amplitude. These model predictions are confirmed by experimental data. We conclude that, although concentrations of Ca2+ and IP3 oscillate, Ca2+ oscillations in HSY cells are the result of modulation of the IP3 receptor by intracellular Ca2+, and that the period is modulated by the accompanying IP3 oscillations.
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Affiliation(s)
- Jung Min Han
- Department of Mathematics, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - Akihiko Tanimura
- Department of Pharmacology, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido 061-0293, Japan
| | - Vivien Kirk
- Department of Mathematics, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - James Sneyd
- Department of Mathematics, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
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16
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Abstract
Oscillations in the concentration of free cytosolic Ca2+ are an important and ubiquitous control mechanism in many cell types. It is thus correspondingly important to understand the mechanisms that underlie the control of these oscillations and how their period is determined. We show that Class I Ca2+ oscillations (i.e., oscillations that can occur at a constant concentration of inositol trisphosphate) have a common dynamical structure, irrespective of the oscillation period. This commonality allows the construction of a simple canonical model that incorporates this underlying dynamical behavior. Predictions from the model are tested, and confirmed, in three different cell types, with oscillation periods ranging over an order of magnitude. The model also predicts that Ca2+ oscillation period can be controlled by modulation of the rate of activation by Ca2+ of the inositol trisphosphate receptor. Preliminary experimental evidence consistent with this hypothesis is presented. Our canonical model has a structure similar to, but not identical to, the classic FitzHugh-Nagumo model. The characterization of variables by speed of evolution, as either fast or slow variables, changes over the course of a typical oscillation, leading to a model without globally defined fast and slow variables.
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17
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Dougoud M, Vinckenbosch L, Mazza C, Schwaller B, Pecze L. The Effect of Gap Junctional Coupling on the Spatiotemporal Patterns of Ca2+ Signals and the Harmonization of Ca2+-Related Cellular Responses. PLoS Comput Biol 2016; 12:e1005295. [PMID: 28027293 PMCID: PMC5226819 DOI: 10.1371/journal.pcbi.1005295] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 01/11/2017] [Accepted: 12/08/2016] [Indexed: 12/18/2022] Open
Abstract
Calcium ions (Ca2+) are important mediators of a great variety of cellular activities e.g. in response to an agonist activation of a receptor. The magnitude of a cellular response is often encoded by frequency modulation of Ca2+ oscillations and correlated with the stimulation intensity. The stimulation intensity highly depends on the sensitivity of a cell to a certain agonist. In some cases, it is essential that neighboring cells produce a similar and synchronized response to an agonist despite their different sensitivity. In order to decipher the presumed function of Ca2+ waves spreading among connecting cells, a mathematical model was developed. This model allows to numerically modifying the connectivity probability between neighboring cells, the permeability of gap junctions and the individual sensitivity of cells to an agonist. Here, we show numerically that strong gap junctional coupling between neighbors ensures an equilibrated response to agonist stimulation via formation of Ca2+ phase waves, i.e. a less sensitive neighbor will produce the same or similar Ca2+ signal as its highly sensitive neighbor. The most sensitive cells within an ensemble are the wave initiator cells. The Ca2+ wave in the cytoplasm is driven by a sensitization wave front in the endoplasmic reticulum. The wave velocity is proportional to the cellular sensitivity and to the strength of the coupling. The waves can form different patterns including circular rings and spirals. The observed pattern depends on the strength of noise, gap junctional permeability and the connectivity probability between neighboring cells. Our simulations reveal that one highly sensitive region gradually takes the lead within the entire noisy system by generating directed circular phase waves originating from this region. The calcium ion (Ca2+), a universal signaling molecule, is widely recognized to play a fundamental role in the regulation of various biological processes. Agonist–evoked Ca2+ signals often manifest as rhythmic changes in the cytosolic free Ca2+ concentration (ccyt) called Ca2+ oscillations. Stimuli intensity was found to be proportional to the oscillation frequency and the evoked down-steam cellular response. Stochastic receptor expression in individual cells in a cell population inevitably leads to individually different oscillation frequencies and individually different Ca2+-related cellular responses. However, in many organs, the neighboring cells have to overcome their individually different sensitivity and produce a synchronized response. Gap junctions are integral membrane structures that enable the direct cytoplasmic exchange of Ca2+ ions and InsP3 molecules between neighboring cells. By simulations, we were able to demonstrate how the strength of intercellular gap junctional coupling in relation to stimulus intensity can modify the spatiotemporal patterns of Ca2+ signals and harmonize the Ca2+-related cellular responses via synchronization of oscillation frequency. We demonstrate that the most sensitive cells are the wave initiator cells and that a highly sensitive region plays an important role in the determination of the Ca2+ phase wave direction. This sensitive region will then also progressively determine the global behavior of the entire system.
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Affiliation(s)
- Michaël Dougoud
- Department of Mathematics, University of Fribourg, Fribourg, Switzerland
| | - Laura Vinckenbosch
- Department of Mathematics, University of Fribourg, Fribourg, Switzerland
- University of Applied Sciences and Arts Western Switzerland // HES-SO, HEIG-VD, Yverdon-les-Bains, Switzerland
| | - Christian Mazza
- Department of Mathematics, University of Fribourg, Fribourg, Switzerland
| | - Beat Schwaller
- Anatomy, Department of Medicine, University of Fribourg, Fribourg, Switzerland
| | - László Pecze
- Anatomy, Department of Medicine, University of Fribourg, Fribourg, Switzerland
- * E-mail:
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18
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Jung SR, Seo JB, Deng Y, Asbury CL, Hille B, Koh DS. Contributions of protein kinases and β-arrestin to termination of protease-activated receptor 2 signaling. ACTA ACUST UNITED AC 2016; 147:255-71. [PMID: 26927499 PMCID: PMC4772372 DOI: 10.1085/jgp.201511477] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Systematic imaging studies and modeling reveal new details of the regulation of the Gq-coupled GPCR, protease-activated receptor 2, by phosphorylation and β-arrestin. Activated Gq protein–coupled receptors (GqPCRs) can be desensitized by phosphorylation and β-arrestin binding. The kinetics and individual contributions of these two mechanisms to receptor desensitization have not been fully distinguished. Here, we describe the shut off of protease-activated receptor 2 (PAR2). PAR2 activates Gq and phospholipase C (PLC) to hydrolyze phosphatidylinositol 4,5-bisphosphate (PIP2) into diacylglycerol and inositol trisphosphate (IP3). We used fluorescent protein–tagged optical probes to monitor several consequences of PAR2 signaling, including PIP2 depletion and β-arrestin translocation in real time. During continuous activation of PAR2, PIP2 was depleted transiently and then restored within a few minutes, indicating fast receptor activation followed by desensitization. Knockdown of β-arrestin 1 and 2 using siRNA diminished the desensitization, slowing PIP2 restoration significantly and even adding a delayed secondary phase of further PIP2 depletion. These effects of β-arrestin knockdown on PIP2 recovery were prevented when serine/threonine phosphatases that dephosphorylate GPCRs were inhibited. Thus, PAR2 may continuously regain its activity via dephosphorylation when there is insufficient β-arrestin to trap phosphorylated receptors. Similarly, blockers of protein kinase C (PKC) and G protein–coupled receptor kinase potentiated the PIP2 depletion. In contrast, an activator of PKC inhibited receptor activation, presumably by augmenting phosphorylation of PAR2. Our interpretations were strengthened by modeling. Simulations supported the conclusions that phosphorylation of PAR2 by protein kinases initiates receptor desensitization and that recruited β-arrestin traps the phosphorylated state of the receptor, protecting it from phosphatases. Speculative thinking suggested a sequestration of phosphatidylinositol 4-phosphate 5 kinase (PIP5K) to the plasma membrane by β-arrestin to explain why knockdown of β-arrestin led to secondary depletion of PIP2. Indeed, artificial recruitment of PIP5K removed the secondary loss of PIP2 completely. Altogether, our experimental and theoretical approaches demonstrate roles and dynamics of the protein kinases, β-arrestin, and PIP5K in the desensitization of PAR2.
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Affiliation(s)
- Seung-Ryoung Jung
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195
| | - Jong Bae Seo
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195
| | - Yi Deng
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195
| | - Charles L Asbury
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195
| | - Bertil Hille
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195
| | - Duk-Su Koh
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195 Department of Physics, Pohang University of Science and Technology, Pohang, Kyungbuk, 790-784, Republic of Korea
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19
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Miyamoto A, Mikoshiba K. Probes for manipulating and monitoring IP 3. Cell Calcium 2016; 64:57-64. [PMID: 27887748 DOI: 10.1016/j.ceca.2016.11.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 11/14/2016] [Indexed: 12/31/2022]
Abstract
Inositol 1,4,5-trisphosphate (IP3) is an important second messenger produced via G-protein-coupled receptor- or receptor tyrosine kinase-mediated pathways. IP3 levels induce Ca2+ release from the endoplasmic reticulum (ER) via IP3 receptor (IP3R) located in the ER membrane. The resultant spatiotemporal pattern of Ca2+ signals regulates diverse cellular functions, including fertilization, gene expression, synaptic plasticity, and cell death. Therefore, monitoring and manipulating IP3 levels is important to elucidate not only the functions of IP3-mediated pathways but also the encoding mechanism of IP3R as a converter of intracellular signals from IP3 to Ca2+.
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Affiliation(s)
- Akitoshi Miyamoto
- Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Katsuhiko Mikoshiba
- Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
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20
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Rückl M, Rüdiger S. Calcium waves in a grid of clustered channels with synchronous IP 3 binding and unbinding. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2016; 39:108. [PMID: 27848113 DOI: 10.1140/epje/i2016-16108-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 10/26/2016] [Indexed: 06/06/2023]
Abstract
Calcium signals in cells occur at multiple spatial scales and variable temporal duration. However, a physical explanation for transitions between long-lasting global oscillations and localized short-term elevations (puffs) of cytoplasmic Ca2+ is still lacking. Here we introduce a phenomenological, coarse-grained model for the calcium variable, which is represented by ordinary differential equations. Due to its small number of parameters, and its simplicity, this model allows us to numerically study the interplay of multi-scale calcium concentrations with stochastic ion channel gating dynamics even in larger systems. We apply this model to a single cluster of inositol trisphosphate (IP 3) receptor channels and find further evidence for the results presented in earlier work: a single cluster may be capable of producing different calcium release types, where long-lasting events are accompanied by unbinding of IP 3 from the receptor (Rückl et al., PLoS Comput. Biol. 11, e1003965 (2015)). Finally, we show the practicability of the model in a grid of 64 clusters which is computationally intractable with previous high-resolution models. Here long-lasting events can lead to synchronized oscillations and waves, while short events stay localized. The frequency of calcium releases as well as their coherence can thereby be regulated by the amplitude of IP 3 stimulation. Finally the model allows for a new explanation of oscillating [IP 3], which is not based on metabolic production and degradation of IP 3.
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Affiliation(s)
- M Rückl
- Institut für Physik, Humboldt-Universität zu Berlin, Berlin, Germany.
| | - S Rüdiger
- Institut für Physik, Humboldt-Universität zu Berlin, Berlin, Germany
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21
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Oura T, Murata K, Morita T, Nezu A, Arisawa M, Shuto S, Tanimura A. Highly Sensitive Measurement of Inositol 1,4,5-Trisphosphate by Using a New Fluorescent Ligand and Ligand Binding Domain Combination. Chembiochem 2016; 17:1509-12. [DOI: 10.1002/cbic.201600096] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Indexed: 01/03/2023]
Affiliation(s)
- Tai Oura
- Faculty of Pharmaceutical Sciences; Hokkaido University; Kita-12 Kita-12Nishi-6 Kita-ku Sapporo 060-0812 Japan
| | - Kaori Murata
- Department of Pediatric Dentistry; School of Dentistry; Health Sciences University of Hokkaido; Kita-121757 Kanazawa Ishikari-Tobetsu Hokkaido 061-0293 Japan
| | - Takao Morita
- Department of Pharmacology; School of Dentistry; Health Sciences University of Hokkaido; Kita-121757 Kanazawa Kita-12Ishikari-Tobetsu Hokkaido 061-0293 Japan
| | - Akihiro Nezu
- Department of Pharmacology; School of Dentistry; Health Sciences University of Hokkaido; Kita-121757 Kanazawa Kita-12Ishikari-Tobetsu Hokkaido 061-0293 Japan
| | - Mitsuhiro Arisawa
- Faculty of Pharmaceutical Sciences; Hokkaido University; Kita-12 Kita-12Nishi-6 Kita-ku Sapporo 060-0812 Japan
| | - Satoshi Shuto
- Faculty of Pharmaceutical Sciences; Hokkaido University; Kita-12 Kita-12Nishi-6 Kita-ku Sapporo 060-0812 Japan
| | - Akihiko Tanimura
- Department of Pharmacology; School of Dentistry; Health Sciences University of Hokkaido; Kita-121757 Kanazawa Kita-12Ishikari-Tobetsu Hokkaido 061-0293 Japan
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22
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Abstract
UNLABELLED In neurons, loss of plasma membrane phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] leads to a decrease in exocytosis and changes in electrical excitability. Restoration of PI(4,5)P2 levels after phospholipase C activation is therefore essential for a return to basal neuronal activity. However, the dynamics of phosphoinositide metabolism have not been analyzed in neurons. We measured dynamic changes of PI(4,5)P2, phosphatidylinositol 4-phosphate, diacylglycerol, inositol 1,4,5-trisphosphate, and Ca(2+) upon muscarinic stimulation in sympathetic neurons from adult male Sprague-Dawley rats with electrophysiological and optical approaches. We used this kinetic information to develop a quantitative description of neuronal phosphoinositide metabolism. The measurements and analysis show and explain faster synthesis of PI(4,5)P2 in sympathetic neurons than in electrically nonexcitable tsA201 cells. They can be used to understand dynamic effects of receptor-mediated phospholipase C activation on excitability and other PI(4,5)P2-dependent processes in neurons. SIGNIFICANCE STATEMENT Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] is a minor phospholipid in the cytoplasmic leaflet of the plasma membrane. Depletion of PI(4,5)P2 via phospholipase C-mediated hydrolysis leads to a decrease in exocytosis and alters electrical excitability in neurons. Restoration of PI(4,5)P2 is essential for a return to basal neuronal activity. However, the dynamics of phosphoinositide metabolism have not been analyzed in neurons. We studied the dynamics of phosphoinositide metabolism in sympathetic neurons upon muscarinic stimulation and used the kinetic information to develop a quantitative description of neuronal phosphoinositide metabolism. The measurements and analysis show a several-fold faster synthesis of PI(4,5)P2 in sympathetic neurons than in an electrically nonexcitable cell line, and provide a framework for future studies of PI(4,5)P2-dependent processes in neurons.
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Sneyd J, Means S, Zhu D, Rugis J, Won JH, Yule DI. Modeling calcium waves in an anatomically accurate three-dimensional parotid acinar cell. J Theor Biol 2016; 419:383-393. [PMID: 27155044 DOI: 10.1016/j.jtbi.2016.04.030] [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: 02/26/2016] [Revised: 04/20/2016] [Accepted: 04/25/2016] [Indexed: 11/24/2022]
Abstract
We construct a model of calcium waves in a three-dimensional anatomically accurate parotid acinar cell, constructed from experimental data. Gradients of inositol trisphosphate receptor (IPR) density are imposed, with the IPR density being greater closer to the lumen, which has a branched structure, and inositol trisphosphate (IP3) is produced only at the basal membrane. We show (1) that IP3 equilibrates so quickly across the cell that it can be assumed to be spatially homogeneous; (2) spatial separation of the sites of IP3 action and IP3 production does not preclude the formation of stable oscillatory Ca2+ waves. However, these waves are not waves in the mathematical sense of a traveling wave with fixed profile. They result instead from a time delay between the Ca2+ rise in the apical and basal regions; (3) the ryanodine receptors serve to reinforce the Ca2+ wave, but are not necessary for the wave to exist; (4) a spatially independent model is not sufficient to study saliva secretion, although a one-dimensional model might be sufficient. Our results here form the first stages of the construction of a multiscale and multicellular model of saliva secretion in an entire acinus.
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Affiliation(s)
- James Sneyd
- Department of Mathematics, University of Auckland, New Zealand.
| | - Shawn Means
- Department of Mathematics, University of Auckland, New Zealand
| | - Di Zhu
- Department of Mathematics, University of Auckland, New Zealand
| | - John Rugis
- Department of Mathematics, University of Auckland, New Zealand
| | - Jong Hak Won
- Department of Pharmacology and Physiology, University of Rochester Medical Centre, Rochester, USA
| | - David I Yule
- Department of Pharmacology and Physiology, University of Rochester Medical Centre, Rochester, USA
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24
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Oral biosciences: The annual review 2015. J Oral Biosci 2016. [DOI: 10.1016/j.job.2015.12.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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25
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Pecze L, Blum W, Schwaller B. Routes of Ca2+ Shuttling during Ca2+ Oscillations: FOCUS ON THE ROLE OF MITOCHONDRIAL Ca2+ HANDLING AND CYTOSOLIC Ca2+ BUFFERS. J Biol Chem 2015; 290:28214-28230. [PMID: 26396196 PMCID: PMC4653679 DOI: 10.1074/jbc.m115.663179] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Indexed: 01/29/2023] Open
Abstract
In some cell types, Ca2+ oscillations are strictly dependent on Ca2+ influx across the plasma membrane, whereas in others, oscillations also persist in the absence of Ca2+ influx. We observed that, in primary mesothelial cells, the plasmalemmal Ca2+ influx played a pivotal role. However, when the Ca2+ transport across the plasma membrane by the “lanthanum insulation method” was blocked prior to the induction of the serum-induced Ca2+ oscillations, mitochondrial Ca2+ transport was found to be able to substitute for the plasmalemmal Ca2+ exchange function, thus rendering the oscillations independent of extracellular Ca2+. However, in a physiological situation, the Ca2+-buffering capacity of mitochondria was found not to be essential for Ca2+ oscillations. Moreover, brief spontaneous Ca2+ changes were observed in the mitochondrial Ca2+ concentration without apparent changes in the cytosolic Ca2+ concentration, indicating the presence of a mitochondrial autonomous Ca2+ signaling mechanism. In the presence of calretinin, a Ca2+-buffering protein, the amplitude of cytosolic spikes during oscillations was decreased, and the amount of Ca2+ ions taken up by mitochondria was reduced. Thus, the increased calretinin expression observed in mesothelioma cells and in certain colon cancer might be correlated to the increased resistance of these tumor cells to proapoptotic/pronecrotic signals. We identified and characterized (experimentally and by modeling) three Ca2+ shuttling pathways in primary mesothelial cells during Ca2+ oscillations: Ca2+ shuttled between (i) the endoplasmic reticulum (ER) and mitochondria, (ii) the ER and the extracellular space, and (iii) the ER and cytoplasmic Ca2+ buffers.
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Affiliation(s)
- László Pecze
- Anatomy, Department of Medicine, University of Fribourg, Route Albert-Gockel 1, CH-1700 Fribourg, Switzerland.
| | - Walter Blum
- Anatomy, Department of Medicine, University of Fribourg, Route Albert-Gockel 1, CH-1700 Fribourg, Switzerland
| | - Beat Schwaller
- Anatomy, Department of Medicine, University of Fribourg, Route Albert-Gockel 1, CH-1700 Fribourg, Switzerland
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26
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Geyer M, Huang F, Sun Y, Vogel SM, Malik AB, Taylor CW, Komarova YA. Microtubule-Associated Protein EB3 Regulates IP3 Receptor Clustering and Ca(2+) Signaling in Endothelial Cells. Cell Rep 2015; 12:79-89. [PMID: 26119739 PMCID: PMC4487770 DOI: 10.1016/j.celrep.2015.06.001] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Revised: 03/27/2015] [Accepted: 05/31/2015] [Indexed: 01/12/2023] Open
Abstract
The mechanisms by which the microtubule cytoskeleton regulates the permeability of endothelial barrier are not well understood. Here, we demonstrate that microtubule-associated end-binding protein 3 (EB3), a core component of the microtubule plus-end protein complex, binds to inositol 1,4,5-trisphosphate receptors (IP3Rs) through an S/TxIP EB-binding motif. In endothelial cells, α-thrombin, a pro-inflammatory mediator that stimulates phospholipase Cβ, increases the cytosolic Ca(2+) concentration and elicits clustering of IP3R3s. These responses, and the resulting Ca(2+)-dependent phosphorylation of myosin light chain, are prevented by depletion of either EB3 or mutation of the TxIP motif of IP3R3 responsible for mediating its binding to EB3. We also show that selective EB3 gene deletion in endothelial cells of mice abrogates α-thrombin-induced increase in endothelial permeability. We conclude that the EB3-mediated interaction of IP3Rs with microtubules controls the assembly of IP3Rs into effective Ca(2+) signaling clusters, which thereby regulate microtubule-dependent endothelial permeability.
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Affiliation(s)
- Melissa Geyer
- Department of Pharmacology and The Center for Lung and Vascular Biology, University of Illinois College of Medicine, Chicago, IL 60612, USA
| | - Fei Huang
- Department of Pharmacology and The Center for Lung and Vascular Biology, University of Illinois College of Medicine, Chicago, IL 60612, USA
| | - Ying Sun
- Department of Pharmacology and The Center for Lung and Vascular Biology, University of Illinois College of Medicine, Chicago, IL 60612, USA
| | - Stephen M Vogel
- Department of Pharmacology and The Center for Lung and Vascular Biology, University of Illinois College of Medicine, Chicago, IL 60612, USA
| | - Asrar B Malik
- Department of Pharmacology and The Center for Lung and Vascular Biology, University of Illinois College of Medicine, Chicago, IL 60612, USA
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, UK
| | - Yulia A Komarova
- Department of Pharmacology and The Center for Lung and Vascular Biology, University of Illinois College of Medicine, Chicago, IL 60612, USA.
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27
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Gulyás G, Tóth JT, Tóth DJ, Kurucz I, Hunyady L, Balla T, Várnai P. Measurement of inositol 1,4,5-trisphosphate in living cells using an improved set of resonance energy transfer-based biosensors. PLoS One 2015; 10:e0125601. [PMID: 25932648 PMCID: PMC4416922 DOI: 10.1371/journal.pone.0125601] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 03/24/2015] [Indexed: 01/22/2023] Open
Abstract
Improved versions of inositol-1,4,5-trisphosphate (InsP3) sensors were created to follow intracellular InsP3 changes in single living cells and in cell populations. Similar to previous InsP3 sensors the new sensors are based on the ligand binding domain of the human type-I InsP3 receptor (InsP3R-LBD), but contain a mutation of either R265K or R269K to lower their InsP3 binding affinity. Tagging the InsP3R-LBD with N-terminal Cerulean and C-terminal Venus allowed measurement of InsP3 in single-cell FRET experiments. Replacing Cerulean with a Luciferase enzyme allowed experiments in multi-cell format by measuring the change in the BRET signal upon stimulation. These sensors faithfully followed the agonist-induced increase in InsP3 concentration in HEK 293T cells expressing the Gq-coupled AT1 angiotensin receptor detecting a response to agonist concentration as low as 10 pmol/L. Compared to the wild type InsP3 sensor, the mutant sensors showed an improved off-rate, enabling a more rapid and complete return of the signal to the resting value of InsP3 after termination of M3 muscarinic receptor stimulation by atropine. For parallel measurements of intracellular InsP3 and Ca2+ levels in BRET experiments, the Cameleon D3 Ca2+ sensor was modified by replacing its CFP with luciferase. In these experiments depletion of plasma membrane PtdIns(4,5)P2 resulted in the fall of InsP3 level, followed by the decrease of the Ca2+-signal evoked by the stimulation of the AT1 receptor. In contrast, when type-III PI 4-kinases were inhibited with a high concentration of wortmannin or a more specific inhibitor, A1, the decrease of the Ca2+-signal preceded the fall of InsP3 level indicating an InsP3-, independent, direct regulation of capacitative Ca2+ influx by plasma membrane inositol lipids. Taken together, our results indicate that the improved InsP3 sensor can be used to monitor both the increase and decrease of InsP3 levels in live cells suitable for high-throughput BRET applications.
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Affiliation(s)
- Gergő Gulyás
- Department of Physiology, Faculty of Medicine, Semmelweis University, Budapest 1094, Hungary
| | - József T. Tóth
- Department of Physiology, Faculty of Medicine, Semmelweis University, Budapest 1094, Hungary
| | - Dániel J. Tóth
- Department of Physiology, Faculty of Medicine, Semmelweis University, Budapest 1094, Hungary
| | - István Kurucz
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, United States of America
| | - László Hunyady
- Department of Physiology, Faculty of Medicine, Semmelweis University, Budapest 1094, Hungary
| | - Tamas Balla
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, United States of America
| | - Péter Várnai
- Department of Physiology, Faculty of Medicine, Semmelweis University, Budapest 1094, Hungary
- * E-mail:
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28
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Tanimura A. Development and application of fluorescent protein-based indicators for live cell imaging. J Oral Biosci 2015. [DOI: 10.1016/j.job.2015.02.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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Willems PHGM, Pahle J, Stalpers XL, Mugahid D, Nikolaew A, Koopman WJH, Kummer U. PKC-mediated inhibitory feedback of the cholecystokinin 1 receptor controls the shape of oscillatory Ca2+signals. FEBS J 2015; 282:2187-201. [DOI: 10.1111/febs.13267] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Revised: 01/31/2015] [Accepted: 03/11/2015] [Indexed: 01/10/2023]
Affiliation(s)
- Peter H. G. M. Willems
- Department of Biochemistry; Radboud Institute for Molecular Life Sciences and Centre for Systems Biology and Bioenergetics; Radboud University Medical Center; Nijmegen The Netherlands
| | - Jürgen Pahle
- BIOMS; BioQuant; Heidelberg University; Germany
- School of Computer Science; Manchester Institute of Biotechnology; University of Manchester; UK
| | - Xenia L. Stalpers
- Department of Biochemistry; Radboud Institute for Molecular Life Sciences and Centre for Systems Biology and Bioenergetics; Radboud University Medical Center; Nijmegen The Netherlands
| | - Douaa Mugahid
- Department of Modelling of Biological Processes; COS Heidelberg/BioQuant; Heidelberg University; Germany
| | - Alexander Nikolaew
- Department of Modelling of Biological Processes; COS Heidelberg/BioQuant; Heidelberg University; Germany
| | - Werner J. H. Koopman
- Department of Biochemistry; Radboud Institute for Molecular Life Sciences and Centre for Systems Biology and Bioenergetics; Radboud University Medical Center; Nijmegen The Netherlands
| | - Ursula Kummer
- Department of Modelling of Biological Processes; COS Heidelberg/BioQuant; Heidelberg University; Germany
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Pecze L, Schwaller B. Characterization and modeling of Ca2+ oscillations in mouse primary mesothelial cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:632-45. [DOI: 10.1016/j.bbamcr.2014.12.025] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Revised: 12/16/2014] [Accepted: 12/19/2014] [Indexed: 10/24/2022]
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Kim TJ, Joo C, Seong J, Vafabakhsh R, Botvinick EL, Berns MW, Palmer AE, Wang N, Ha T, Jakobsson E, Sun J, Wang Y. Distinct mechanisms regulating mechanical force-induced Ca²⁺ signals at the plasma membrane and the ER in human MSCs. eLife 2015; 4:e04876. [PMID: 25667984 PMCID: PMC4337650 DOI: 10.7554/elife.04876] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Accepted: 01/21/2015] [Indexed: 12/21/2022] Open
Abstract
It is unclear that how subcellular organelles respond to external mechanical stimuli. Here, we investigated the molecular mechanisms by which mechanical force regulates Ca2+ signaling at endoplasmic reticulum (ER) in human mesenchymal stem cells. Without extracellular Ca2+, ER Ca2+ release is the source of intracellular Ca2+ oscillations induced by laser-tweezer-traction at the plasma membrane, providing a model to study how mechanical stimuli can be transmitted deep inside the cell body. This ER Ca2+ release upon mechanical stimulation is mediated not only by the mechanical support of cytoskeleton and actomyosin contractility, but also by mechanosensitive Ca2+ permeable channels on the plasma membrane, specifically TRPM7. However, Ca2+ influx at the plasma membrane via mechanosensitive Ca2+ permeable channels is only mediated by the passive cytoskeletal structure but not active actomyosin contractility. Thus, active actomyosin contractility is essential for the response of ER to the external mechanical stimuli, distinct from the mechanical regulation at the plasma membrane. DOI:http://dx.doi.org/10.7554/eLife.04876.001 Cells receive many signals from their environment, for example, when they are compressed or pulled about by neighboring cells. Information about these ‘mechanical stimuli’ can be transmitted within the cell to trigger changes in gene expression and cell behavior. When a cell receives a mechanical stimulus, it can activate the release of calcium ions from storage compartments within the cell, including from a compartment called the endoplasmic reticulum. Calcium ions can also enter the cell from outside via channels located in the membrane that surrounds the cell (the plasma membrane). Kim et al. investigated how mechanical forces are transmitted in a type of human cell called mesenchymal stem cells using optical tweezers to apply a gentle force to the outside of a cell. These tweezers use a laser to attract tiny objects, in this case a bead attached to proteins in the cell's outer membrane. The cell's response to this mechanical stimulation was measured using a sensor protein that fluoresces a different color when it binds to calcium ions. With this set-up, Kim et al. found that mesenchymal stem cells are able to transmit mechanical forces to different depths within the cell. The forces can travel deep to trigger the release of calcium ions from the endoplasmic reticulum. This process involves a network of protein fibers that criss-cross to support the structure of a cell—called the cytoskeleton—and also requires proteins that are associated with the cytoskeleton to contract. However, calcium ion entry through the plasma membrane due to a mechanical force does not require these contractile proteins—only the cytoskeleton is involved. These results demonstrate that the transmission of mechanical signals to different depths within mesenchymal stem cells involves different components. Future work should shed light on how these mechanical signals control gene expression and the development of mesenchymal stem cells. DOI:http://dx.doi.org/10.7554/eLife.04876.002
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Affiliation(s)
- Tae-Jin Kim
- Neuroscience Program, University of Illinois, Urbana-Champaign, Urbana, United States
| | - Chirlmin Joo
- Department of Physics, University of Illinois, Urbana-Champaign, Urbana, United States
| | - Jihye Seong
- Neuroscience Program, University of Illinois, Urbana-Champaign, Urbana, United States
| | - Reza Vafabakhsh
- Department of Physics, University of Illinois, Urbana-Champaign, Urbana, United States
| | - Elliot L Botvinick
- Department of Biomedical Engineering, Beckman Laser Institute, University of California, Irvine, Irvine, United States
| | - Michael W Berns
- Department of Biomedical Engineering, Beckman Laser Institute, University of California, Irvine, Irvine, United States
| | - Amy E Palmer
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Boulder, United States
| | - Ning Wang
- Department of Mechanical Science and Engineering, University of Illinois, Urbana-Champaign, Urbana, United States
| | - Taekjip Ha
- Department of Physics, University of Illinois, Urbana-Champaign, Urbana, United States
| | - Eric Jakobsson
- Beckman Institute for Advanced Science and Technology, University of Illinois, Urbana-Champaign, Urbana, United States
| | - Jie Sun
- Beckman Institute for Advanced Science and Technology, University of Illinois, Urbana-Champaign, Urbana, United States
| | - Yingxiao Wang
- Neuroscience Program, University of Illinois, Urbana-Champaign, Urbana, United States
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Rückl M, Parker I, Marchant JS, Nagaiah C, Johenning FW, Rüdiger S. Modulation of elementary calcium release mediates a transition from puffs to waves in an IP3R cluster model. PLoS Comput Biol 2015; 11:e1003965. [PMID: 25569772 PMCID: PMC4288706 DOI: 10.1371/journal.pcbi.1003965] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 10/06/2014] [Indexed: 11/18/2022] Open
Abstract
The oscillating concentration of intracellular calcium is one of the most important examples for collective dynamics in cell biology. Localized releases of calcium through clusters of inositol 1,4,5-trisphosphate receptor channels constitute elementary signals called calcium puffs. Coupling by diffusing calcium leads to global releases and waves, but the exact mechanism of inter-cluster coupling and triggering of waves is unknown. To elucidate the relation of puffs and waves, we here model a cluster of IP3R channels using a gating scheme with variable non-equilibrium IP3 binding. Hybrid stochastic and deterministic simulations show that puffs are not stereotyped events of constant duration but are sensitive to stimulation strength and residual calcium. For increasing IP3 concentration, the release events become modulated at a timescale of minutes, with repetitive wave-like releases interspersed with several puffs. This modulation is consistent with experimental observations we present, including refractoriness and increase of puff frequency during the inter-wave interval. Our results suggest that waves are established by a random but time-modulated appearance of sustained release events, which have a high potential to trigger and synchronize activity throughout the cell.
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Affiliation(s)
- Martin Rückl
- Institut für Physik, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Ian Parker
- Departments of Neurobiology and Behavior, Physiology and Biophysics, University of California, Irvine, Irvine, California, United States of America
| | - Jonathan S. Marchant
- Department of Pharmacology, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Chamakuri Nagaiah
- Johann Radon Institute for Computational and Applied Mathematics, Austrian Academy of Sciences, Linz, Austria
| | | | - Sten Rüdiger
- Institut für Physik, Humboldt-Universität zu Berlin, Berlin, Germany
- * E-mail:
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Gaspers LD, Bartlett PJ, Politi A, Burnett P, Metzger W, Johnston J, Joseph SK, Höfer T, Thomas AP. Hormone-induced calcium oscillations depend on cross-coupling with inositol 1,4,5-trisphosphate oscillations. Cell Rep 2014; 9:1209-18. [PMID: 25456123 PMCID: PMC6469397 DOI: 10.1016/j.celrep.2014.10.033] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 08/08/2014] [Accepted: 10/10/2014] [Indexed: 11/29/2022] Open
Abstract
Receptor-mediated oscillations in cytosolic Ca2+ concentration ([Ca2+]i) could originate either directly from an autonomous Ca2+ feedback oscillator at the inositol 1,4,5-trisphosphate (IP3) receptor or as a secondary consequence of IP3 oscillations driven by Ca2+ feedback on IP3 metabolism. It is challenging to discriminate these alternatives, because IP3 fluctuations could drive Ca2+ oscillations or could just be a secondary response to the [Ca2+]i spikes. To investigate this problem, we constructed a recombinant IP3 buffer using type-I IP3 receptor ligand-binding domain fused to GFP (GFP-LBD), which buffers IP3 in the physiological range. This IP3 buffer slows hormone-induced [IP3] dynamics without changing steady-state [IP3]. GFP-LBD perturbed [Ca2+]i oscillations in a dose-dependent manner: it decreased both the rate of [Ca2+]i rise and the speed of Ca2+ wave propagation and, at high levels, abolished [Ca2+]i oscillations completely. These data, together with computational modeling, demonstrate that IP3 dynamics play a fundamental role in generating [Ca2+]i oscillations and waves. Gaspers et al. use a genetically encoded IP3 buffer to suppress IP3 dynamics during hormonal stimulation. Using this approach, they find that positive feedback of Ca2+ on IP3 formation is an essential component, generating long-period, baseline-separated Ca2+ oscillations and intracellular Ca2+ waves.
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Affiliation(s)
- Lawrence D Gaspers
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers, The State University of New Jersey, 185 South Orange Avenue, Newark, NJ 07103, USA
| | - Paula J Bartlett
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers, The State University of New Jersey, 185 South Orange Avenue, Newark, NJ 07103, USA
| | - Antonio Politi
- German Cancer Research Center, Division of Theoretical Systems Biology, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany
| | - Paul Burnett
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers, The State University of New Jersey, 185 South Orange Avenue, Newark, NJ 07103, USA
| | - Walson Metzger
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers, The State University of New Jersey, 185 South Orange Avenue, Newark, NJ 07103, USA
| | - Jane Johnston
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers, The State University of New Jersey, 185 South Orange Avenue, Newark, NJ 07103, USA
| | - Suresh K Joseph
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, 1020 Locust Street, Philadelphia, PA 19107, USA
| | - Thomas Höfer
- German Cancer Research Center, Division of Theoretical Systems Biology, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany
| | - Andrew P Thomas
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers, The State University of New Jersey, 185 South Orange Avenue, Newark, NJ 07103, USA.
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34
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SIRT1 Regulates Lamellipodium Extension and Migration of Melanoma Cells. J Invest Dermatol 2014; 134:1693-1700. [DOI: 10.1038/jid.2014.50] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Revised: 12/14/2013] [Accepted: 12/17/2013] [Indexed: 01/08/2023]
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Falkenburger BH, Dickson EJ, Hille B. Quantitative properties and receptor reserve of the DAG and PKC branch of G(q)-coupled receptor signaling. ACTA ACUST UNITED AC 2014; 141:537-55. [PMID: 23630338 PMCID: PMC3639584 DOI: 10.1085/jgp.201210887] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Gq protein–coupled receptors (GqPCRs) of the plasma membrane activate the phospholipase C (PLC) signaling cascade. PLC cleaves the membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP2) into the second messengers diacylgycerol (DAG) and inositol 1,4,5-trisphosphate (IP3), leading to calcium release, protein kinase C (PKC) activation, and in some cases, PIP2 depletion. We determine the kinetics of each of these downstream endpoints and also ask which is responsible for the inhibition of KCNQ2/3 (KV7.2/7.3) potassium channels in single living tsA-201 cells. We measure DAG production and PKC activity by Förster resonance energy transfer–based sensors, and PIP2 by KCNQ2/3 channels. Fully activating endogenous purinergic receptors by uridine 5′triphosphate (UTP) leads to calcium release, DAG production, and PKC activation, but no net PIP2 depletion. Fully activating high-density transfected muscarinic receptors (M1Rs) by oxotremorine-M (Oxo-M) leads to similar calcium, DAG, and PKC signals, but PIP2 is depleted. KCNQ2/3 channels are inhibited by the Oxo-M treatment (85%) and not by UTP (<1%), indicating that depletion of PIP2 is required to inhibit KCNQ2/3 in response to receptor activation. Overexpression of A kinase–anchoring protein (AKAP)79 or calmodulin (CaM) does not increase KCNQ2/3 inhibition by UTP. From these results and measurements of IP3 and calcium presented in our companion paper (Dickson et al. 2013. J. Gen. Physiol.http://dx.doi.org/10.1085/jgp.201210886), we extend our kinetic model for signaling from M1Rs to DAG/PKC and IP3/calcium signaling. We conclude that calcium/CaM and PKC-mediated phosphorylation do not underlie dynamic KCNQ2/3 channel inhibition during GqPCR activation in tsA-201 cells. Finally, our experimental data provide indirect evidence for cleavage of PI(4)P by PLC in living cells, and our modeling revisits/explains the concept of receptor reserve with measurements from all steps of GqPCR signaling.
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Affiliation(s)
- Björn H Falkenburger
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA
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36
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Dickson EJ, Falkenburger BH, Hille B. Quantitative properties and receptor reserve of the IP(3) and calcium branch of G(q)-coupled receptor signaling. ACTA ACUST UNITED AC 2014; 141:521-35. [PMID: 23630337 PMCID: PMC3639578 DOI: 10.1085/jgp.201210886] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Gq-coupled plasma membrane receptors activate phospholipase C (PLC), which hydrolyzes membrane phosphatidylinositol 4,5-bisphosphate (PIP2) into the second messengers inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). This leads to calcium release, protein kinase C (PKC) activation, and sometimes PIP2 depletion. To understand mechanisms governing these diverging signals and to determine which of these signals is responsible for the inhibition of KCNQ2/3 (KV7.2/7.3) potassium channels, we monitored levels of PIP2, IP3, and calcium in single living cells. DAG and PKC are monitored in our companion paper (Falkenburger et al. 2013. J. Gen. Physiol.http://dx.doi.org/10.1085/jgp.201210887). The results extend our previous kinetic model of Gq-coupled receptor signaling to IP3 and calcium. We find that activation of low-abundance endogenous P2Y2 receptors by a saturating concentration of uridine 5′-triphosphate (UTP; 100 µM) leads to calcium release but not to PIP2 depletion. Activation of overexpressed M1 muscarinic receptors by 10 µM Oxo-M leads to a similar calcium release but also depletes PIP2. KCNQ2/3 channels are inhibited by Oxo-M (by 85%), but not by UTP (<1%). These differences can be attributed purely to differences in receptor abundance. Full amplitude calcium responses can be elicited even after PIP2 was partially depleted by overexpressed inducible phosphatidylinositol 5-phosphatases, suggesting that very low amounts of IP3 suffice to elicit a full calcium release. Hence, weak PLC activation can elicit robust calcium signals without net PIP2 depletion or KCNQ2/3 channel inhibition.
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Affiliation(s)
- Eamonn J Dickson
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA
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37
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Bartlett PJ, Gaspers LD, Pierobon N, Thomas AP. Calcium-dependent regulation of glucose homeostasis in the liver. Cell Calcium 2014; 55:306-16. [PMID: 24630174 DOI: 10.1016/j.ceca.2014.02.007] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2014] [Revised: 02/07/2014] [Accepted: 02/08/2014] [Indexed: 02/09/2023]
Abstract
A major role of the liver is to integrate multiple signals to maintain normal blood glucose levels. The balance between glucose storage and mobilization is primarily regulated by the counteracting effects of insulin and glucagon. However, numerous signals converge in the liver to ensure energy demand matches the physiological status of the organism. Many circulating hormones regulate glycogenolysis, gluconeogenesis and mitochondrial metabolism by calcium-dependent signaling mechanisms that manifest as cytosolic Ca(2+) oscillations. Stimulus-strength is encoded in the Ca(2+) oscillation frequency, and also by the range of intercellular Ca(2+) wave propagation in the intact liver. In this article, we describe how Ca(2+) oscillations and waves can regulate glucose output and oxidative metabolism in the intact liver; how multiple stimuli are decoded though Ca(2+) signaling at the organ level, and the implications of Ca(2+) signal dysregulation in diseases such as metabolic syndrome and non-alcoholic fatty liver disease.
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Affiliation(s)
- Paula J Bartlett
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ, USA.
| | - Lawrence D Gaspers
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ, USA
| | - Nicola Pierobon
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ, USA
| | - Andrew P Thomas
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ, USA
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38
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Hille B, Dickson E, Kruse M, Falkenburger B. Dynamic metabolic control of an ion channel. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 123:219-47. [PMID: 24560147 DOI: 10.1016/b978-0-12-397897-4.00008-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
G-protein-coupled receptors mediate responses to external stimuli in various cell types. We are interested in the modulation of KCNQ2/3 potassium channels by the Gq-coupled M1 muscarinic (acetylcholine) receptor (M1R). Here, we describe development of a mathematical model that incorporates all known steps along the M1R signaling cascade and accurately reproduces the macroscopic behavior we observe when KCNQ2/3 currents are inhibited following M1R activation. Gq protein-coupled receptors of the plasma membrane activate phospholipase C (PLC) which cleaves the minor plasma membrane lipid phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) into the second messengers diacylgycerol and inositol 1,4,5-trisphosphate, leading to calcium release, protein kinase C (PKC) activation, and PI(4,5)P2 depletion. Combining optical and electrical techniques with knowledge of relative abundance of each signaling component has allowed us to develop a kinetic model and determine that (i) M1R activation and M1R/Gβ interaction are fast; (ii) Gαq/Gβ separation and Gαq/PLC interaction have intermediate time constants; (iii) the amount of activated PLC limits the rate of KCNQ2/3 suppression; (iv) weak PLC activation can elicit robust calcium signals without net PI(4,5)P2 depletion or KCNQ2/3 channel inhibition; and (v) depletion of PI(4,5)P2, and not calcium/CaM or PKC-mediated phosphorylation, closes KCNQ2/3 potassium channels, thereby increasing neuronal excitability.
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Affiliation(s)
- Bertil Hille
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA
| | - Eamonn Dickson
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA
| | - Martin Kruse
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, USA
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39
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A fluorescence-based method for evaluating inositol 1,4,5-trisphosphate receptor ligands: Determination of subtype selectivity and partial agonist effects. J Biotechnol 2013; 167:248-54. [DOI: 10.1016/j.jbiotec.2013.06.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Revised: 05/19/2013] [Accepted: 06/23/2013] [Indexed: 11/22/2022]
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40
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Zhang C, Wei ZH, Ye BC. Quantitative monitoring of 2-oxoglutarate in Escherichia coli cells by a fluorescence resonance energy transfer-based biosensor. Appl Microbiol Biotechnol 2013; 97:8307-16. [PMID: 23893310 DOI: 10.1007/s00253-013-5121-5] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Revised: 06/07/2013] [Accepted: 07/10/2013] [Indexed: 11/25/2022]
Abstract
2-Oxoglutarate (2OG) is a metabolite from the highly conserved Krebs cycle and not only plays a critical role in metabolism but also acts as a signaling molecule in a variety of organisms. Environmental inorganic nitrogen is reduced to ammonium by microorganisms, whose metabolic pathways involve the conversion of 2OG to glutamate and glutamine. Tracking of 2OG in real time would be useful for studies on cell metabolism and signal transduction. Here, we developed a genetically encoded 2OG biosensor based on fluorescent resonance energy transfer by inserting the functional 2OG-binding domain GAF of the NifA protein between the fluorescence resonance energy transfer (FRET) pair YFP/CFP. The dynamic range of the sensors is 100 μM to 10 mM, which appeared identical to the physiological range observed in E. coli. We optimized the peptide lengths of the binding domain to obtain a sensor with a maximal ratio change of 0.95 upon 2OG binding and demonstrated the feasibility of this sensor for the visualization of metabolites both in vitro and in vivo.
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Affiliation(s)
- Chang Zhang
- Laboratory of Biosystems and Microanalysis, State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China
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41
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Tanimura A, Nezu A, Morita T. [Light microscopy techniques for live cell and animal imaging using fluorescent proteins]. Nihon Yakurigaku Zasshi 2013; 141:262-7. [PMID: 23665557 DOI: 10.1254/fpj.141.262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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42
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Mak DOD. A mechanism for different receptors coupled to the same G protein to generate different responses mediated by different second messengers. J Gen Physiol 2013; 141:513-6. [PMID: 23630335 PMCID: PMC3639579 DOI: 10.1085/jgp.201311006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Don-On Daniel Mak
- Physiology Department, University of Pennsylvania, Philadelphia, PA 19104, USA.
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43
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Ida Y, Kidera A. The conserved Arg241-Glu439 salt bridge determines flexibility of the inositol 1,4,5-trisphosphate receptor binding core in the ligand-free state. Proteins 2013; 81:1699-708. [PMID: 23606071 DOI: 10.1002/prot.24304] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2013] [Revised: 03/15/2013] [Accepted: 03/26/2013] [Indexed: 12/13/2022]
Abstract
Inositol 1,4,5-trisphosphate receptor (InsP3 R) is an intracellular Ca(2+) -release channel activated by binding of inositol 1,4,5-trisphosphate (InsP3 ) to the InsP3 binding core (IBC). Structural change in the IBC upon InsP3 binding is the key process in channel pore opening. In this study, we performed molecular dynamics (MD) simulations of the InsP3 -free form of the IBC, starting with removal of InsP3 from the InsP3 -bound crystal structure, and obtained the structural ensemble of the InsP3 -free form of the IBC. The simulation revealed that the two domains of the IBC largely fluctuate around the average structure with the hinge angle opened 17° more than in the InsP3 -bound form, and the twist angle rotated by 45°, forming interdomain contacts that are different from those in the bound form. The InsP3 binding loop was disordered. The InsP3 -free form thus obtained was reproduced four times in simulations started from a fully extended configuration of the two domains. Simulations beginning with the fully extended form indicated that formation of a salt bridge between Arg241 and Glu439 is crucial for stabilizing the closed form of the two domains. Mutation of Arg241 to Gln prevented formation of the compact structure by the two domains, but the fully flexible domain arrangement was maintained. Thus, the Arg241-Glu439 salt bridge determines the flexibility of the InsP3 -free form of the IBC.
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Affiliation(s)
- Yoichi Ida
- Department of Supramolecular Biology, Graduate School of Nanobioscience, Yokohama City University, Yokohama, 230-0045, Japan
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44
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Mathiesen JM, Vedel L, Bräuner-Osborne H. cAMP biosensors applied in molecular pharmacological studies of G protein-coupled receptors. Methods Enzymol 2013; 522:191-207. [PMID: 23374187 DOI: 10.1016/b978-0-12-407865-9.00011-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Cyclic adenosine monophosphate (cAMP) is a common second messenger that mediates numerous biological responses. Intracellular cAMP levels are increased by activation of G(s)-coupled G protein-coupled receptors (GPCRs) and decreased by activation of G(i)-coupled GPCRs via the adenylyl cyclase. Many end-point assays for quantifying GPCR-mediated changes in intracellular cAMP levels exist. More recently, fluorescence resonance energy transfer (FRET)-based cAMP biosensors that can quantify intracellular cAMP levels in real time have been developed. These FRET-based cAMP biosensors have been used primarily in single cell FRET microscopy to monitor and visualize changes in cAMP upon GPCR activation. Here, a similar cAMP biosensor with a more efficient mCerulean/mCitrine FRET pair is described for use in the 384-well plate format. After cloning and expression in HEK293 cells, the biosensor is characterized in the 384-well plate format and used for measuring the signaling of the G(s)-coupled β(2)-adrenergic receptor. The procedures described may be applied for other FRET-based biosensors in terms of characterization and conversion to the 384-well plate format.
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Affiliation(s)
- Jesper Mosolff Mathiesen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
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Komarova YA, Huang F, Geyer M, Daneshjou N, Garcia A, Idalino L, Kreutz B, Mehta D, Malik AB. VE-cadherin signaling induces EB3 phosphorylation to suppress microtubule growth and assemble adherens junctions. Mol Cell 2012; 48:914-25. [PMID: 23159740 DOI: 10.1016/j.molcel.2012.10.011] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Revised: 07/23/2012] [Accepted: 10/09/2012] [Indexed: 11/28/2022]
Abstract
Vascular endothelial (VE)-cadherin homophilic adhesion controls endothelial barrier permeability through assembly of adherens junctions (AJs). We observed that loss of VE-cadherin-mediated adhesion induced the activation of Src and phospholipase C (PLC)γ2, which mediated Ca(2+) release from endoplasmic reticulum (ER) stores, resulting in activation of calcineurin (CaN), a Ca(2+)-dependent phosphatase. Downregulation of CaN activity induced phosphorylation of serine 162 in end binding (EB) protein 3. This phospho-switch was required to destabilize the EB3 dimer, suppress microtubule (MT) growth, and assemble AJs. The phospho-defective S162A EB3 mutant, in contrast, induced MT growth in confluent endothelial monolayers and disassembled AJs. Thus, VE-cadherin outside-in signaling regulates cytosolic Ca(2+) homeostasis and EB3 phosphorylation, which are required for assembly of AJs. These results identify a pivotal function of VE-cadherin homophilic interaction in modulating endothelial barrier through the tuning of MT dynamics.
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Affiliation(s)
- Yulia A Komarova
- Department of Pharmacology, University of Illinois College of Medicine, Chicago, IL 60612, USA.
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Abstract
Phospholipase C (PLC) converts phosphatidylinositol 4,5-bisphosphate (PIP(2)) to inositol 1,4,5-trisphosphate (IP(3)) and diacylglycerol (DAG). DAG and IP(3) each control diverse cellular processes and are also substrates for synthesis of other important signaling molecules. PLC is thus central to many important interlocking regulatory networks. Mammals express six families of PLCs, each with both unique and overlapping controls over expression and subcellular distribution. Each PLC also responds acutely to its own spectrum of activators that includes heterotrimeric G protein subunits, protein tyrosine kinases, small G proteins, Ca(2+), and phospholipids. Mammalian PLCs are autoinhibited by a region in the catalytic TIM barrel domain that is the target of much of their acute regulation. In combination, the PLCs act as a signaling nexus that integrates numerous signaling inputs, critically governs PIP(2) levels, and regulates production of important second messengers to determine cell behavior over the millisecond to hour timescale.
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Affiliation(s)
- Ganesh Kadamur
- Department of Pharmacology, Molecular Biophysics Graduate Program and Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
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47
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Ataei F, Torkzadeh-Mahani M, Hosseinkhani S. A novel luminescent biosensor for rapid monitoring of IP3 by split-luciferase complementary assay. Biosens Bioelectron 2012; 41:642-8. [PMID: 23122229 DOI: 10.1016/j.bios.2012.09.037] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Revised: 09/17/2012] [Accepted: 09/21/2012] [Indexed: 10/27/2022]
Abstract
Inositol 1,4,5-trisphosphate (IP(3)) is a crucial second messenger that regulates complicated signaling processes in various physiological events. Alteration in its content has been observed in many diseases. Hence, development of a high-throughput screening system to monitor temporal changes of IP(3) is essential for screening of new potential therapeutic compounds. Toward a simple, sensitive and rapid method for measuring IP(3), we describe the development and application of a novel biosensor based on luciferase fragment assisted complementation strategy, which converts the ligand-induced conformational changes to light. Designed sensor comprising the IP(3)-binding core domain of IP(3)-receptor fused between complementary non-functional fragments of firefly luciferase allows direct detection of IP(3) in presence of luciferin substrate both in cell lysate and in living cells. According to the result presented in this manuscript, the screening time was very fast and maximum response was obtained up to 11-fold higher than untreated cells. Moreover, the designed biosensor was able to monitor release of IP(3) upon induction by different inducers like Bradykinin and ATP. The current biosensor not only provides a specific IP(3) detector in vitro but also facilitates monitoring of the response of IP(3) in living organisms.
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Affiliation(s)
- Farangis Ataei
- Department of Biochemistry, Faculty of Biological Sciences, Tarbiat Modares University, Tehran, Iran
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48
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Sprenger JU, Perera RK, Götz KR, Nikolaev VO. FRET microscopy for real-time monitoring of signaling events in live cells using unimolecular biosensors. J Vis Exp 2012:e4081. [PMID: 22929080 DOI: 10.3791/4081] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Förster resonance energy transfer (FRET) microscopy continues to gain increasing interest as a technique for real-time monitoring of biochemical and signaling events in live cells and tissues. Compared to classical biochemical methods, this novel technology is characterized by high temporal and spatial resolution. FRET experiments use various genetically-encoded biosensors which can be expressed and imaged over time in situ or in vivo. Typical biosensors can either report protein-protein interactions by measuring FRET between a fluorophore-tagged pair of proteins or conformational changes in a single protein which harbors donor and acceptor fluorophores interconnected with a binding moiety for a molecule of interest. Bimolecular biosensors for protein-protein interactions include, for example, constructs designed to monitor G-protein activation in cells, while the unimolecular sensors measuring conformational changes are widely used to image second messengers such as calcium, cAMP, inositol phosphates and cGMP. Here we describe how to build a customized epifluorescence FRET imaging system from single commercially available components and how to control the whole setup using the Micro-Manager freeware. This simple but powerful instrument is designed for routine or more sophisticated FRET measurements in live cells. Acquired images are processed using self-written plug-ins to visualize changes in FRET ratio in real-time during any experiments before being stored in a graphics format compatible with the build-in ImageJ freeware used for subsequent data analysis. This low-cost system is characterized by high flexibility and can be successfully used to monitor various biochemical events and signaling molecules by a plethora of available FRET biosensors in live cells and tissues. As an example, we demonstrate how to use this imaging system to perform real-time monitoring of cAMP in live 293A cells upon stimulation with a β-adrenergic receptor agonist and blocker.
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Affiliation(s)
- Julia U Sprenger
- Emmy Noether Group of the DFG, Department of Cardiology and Pneumology, European Heart Research Insitute Göttingen, Georg August University Medical Center, Göttingen, Germany
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Termination of Ca²+ release for clustered IP₃R channels. PLoS Comput Biol 2012; 8:e1002485. [PMID: 22693433 PMCID: PMC3364945 DOI: 10.1371/journal.pcbi.1002485] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2011] [Accepted: 03/07/2012] [Indexed: 01/17/2023] Open
Abstract
In many cell types, release of calcium ions is controlled by inositol 1,4,5-trisphosphate () receptor channels. Elevations in concentration after intracellular release through receptors (R) can either propagate in the form of waves spreading through the entire cell or produce spatially localized puffs. The appearance of waves and puffs is thought to implicate random initial openings of one or a few channels and subsequent activation of neighboring channels because of an “autocatalytic” feedback. It is much less clear, however, what determines the further time course of release, particularly since the lifetime is very different for waves (several seconds) and puffs (around 100 ms). Here we study the lifetime of signals and their dependence on residual microdomains. Our general idea is that microdomains are dynamical and mediate the effect of other physiological processes. Specifically, we focus on the mechanism by which binding proteins (buffers) alter the lifetime of signals. We use stochastic simulations of channel gating coupled to a coarse-grained description for the concentration. To describe the concentration in a phenomenological way, we here introduce a differential equation, which reflects the buffer characteristics by a few effective parameters. This non-stationary model for microdomains gives deep insight into the dynamical differences between puffs and waves. It provides a novel explanation for the different lifetimes of puffs and waves and suggests that puffs are terminated by inhibition while unbinding is responsible for termination of waves. Thus our analysis hints at an additional role of and shows how cells can make use of the full complexity in R gating behavior to achieve different signals. Calcium signals are important for a host of cellular processes such as neurotransmitter release, cell contraction and gene expression. While the principles of activation and spreading of calcium signals have been largely understood, it is much less clear how their spatio-temporal appearance is shaped. This issue is of high relevance since the spatio-temporal signature is thought to carry the information content. In our paper we study the dynamical mechanisms that determine the time course of calcium release from receptor channels. We use a stochastic channel description combined with a recently developed model for the distribution of released calcium in a microdomain. The simulations uncover a complex control mechanism, which allows for the tuning of release from short frequent puffs to extended and less frequent wave-like release. Unexpectedly, the model predicts that for wave-like release the dissociation of from the receptors leads to termination of the calcium signal. This effect relies on a well-known gating property of R channels, which earlier has been regarded as superfluous in studies for groups of channels. Our results also provide a missing link to understand cellular response to calcium-binding proteins and present a novel mechanism for information processing by R channels.
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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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