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Kajani S, Laker RC, Ratkova E, Will S, Rhodes CJ. Hepatic glucagon action: beyond glucose mobilization. Physiol Rev 2024; 104:1021-1060. [PMID: 38300523 DOI: 10.1152/physrev.00028.2023] [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: 07/11/2023] [Revised: 01/10/2024] [Accepted: 01/11/2024] [Indexed: 02/02/2024] Open
Abstract
Glucagon's ability to promote hepatic glucose production has been known for over a century, with initial observations touting this hormone as a diabetogenic agent. However, glucagon receptor agonism [when balanced with an incretin, including glucagon-like peptide 1 (GLP-1) to dampen glucose excursions] is now being developed as a promising therapeutic target in the treatment of metabolic diseases, like metabolic dysfunction-associated steatotic disease/metabolic dysfunction-associated steatohepatitis (MASLD/MASH), and may also have benefit for obesity and chronic kidney disease. Conventionally regarded as the opposing tag-team partner of the anabolic mediator insulin, glucagon is gradually emerging as more than just a "catabolic hormone." Glucagon action on glucose homeostasis within the liver has been well characterized. However, growing evidence, in part thanks to new and sensitive "omics" technologies, has implicated glucagon as more than just a "glucose liberator." Elucidation of glucagon's capacity to increase fatty acid oxidation while attenuating endogenous lipid synthesis speaks to the dichotomous nature of the hormone. Furthermore, glucagon action is not limited to just glucose homeostasis and lipid metabolism, as traditionally reported. Glucagon plays key regulatory roles in hepatic amino acid and ketone body metabolism, as well as mitochondrial turnover and function, indicating broader glucagon signaling consequences for metabolic homeostasis mediated by the liver. Here we examine the broadening role of glucagon signaling within the hepatocyte and question the current dogma, to appreciate glucagon as more than just that "catabolic hormone."
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Affiliation(s)
- Sarina Kajani
- Early Cardiovascular, Renal and Metabolism, Biopharmaceuticals R&D, AstraZeneca, Gaithersburg, Maryland, United States
| | - Rhianna C Laker
- Early Cardiovascular, Renal and Metabolism, Biopharmaceuticals R&D, AstraZeneca, Gaithersburg, Maryland, United States
| | - Ekaterina Ratkova
- Early Cardiovascular, Renal and Metabolism, Biopharmaceuticals R&D, AstraZeneca, Mölndal, Sweden
| | - Sarah Will
- Early Cardiovascular, Renal and Metabolism, Biopharmaceuticals R&D, AstraZeneca, Gaithersburg, Maryland, United States
| | - Christopher J Rhodes
- Early Cardiovascular, Renal and Metabolism, Biopharmaceuticals R&D, AstraZeneca, Gaithersburg, Maryland, United States
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2
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Paknejad N, Sapuru V, Hite RK. Structural titration reveals Ca 2+-dependent conformational landscape of the IP 3 receptor. Nat Commun 2023; 14:6897. [PMID: 37898605 PMCID: PMC10613215 DOI: 10.1038/s41467-023-42707-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Accepted: 10/18/2023] [Indexed: 10/30/2023] Open
Abstract
Inositol 1,4,5-trisphosphate receptors (IP3Rs) are endoplasmic reticulum Ca2+ channels whose biphasic dependence on cytosolic Ca2+ gives rise to Ca2+ oscillations that regulate fertilization, cell division and cell death. Despite the critical roles of IP3R-mediated Ca2+ responses, the structural underpinnings of the biphasic Ca2+ dependence that underlies Ca2+ oscillations are incompletely understood. Here, we collect cryo-EM images of an IP3R with Ca2+ concentrations spanning five orders of magnitude. Unbiased image analysis reveals that Ca2+ binding does not explicitly induce conformational changes but rather biases a complex conformational landscape consisting of resting, preactivated, activated, and inhibited states. Using particle counts as a proxy for relative conformational free energy, we demonstrate that Ca2+ binding at a high-affinity site allows IP3Rs to activate by escaping a low-energy resting state through an ensemble of preactivated states. At high Ca2+ concentrations, IP3Rs preferentially enter an inhibited state stabilized by a second, low-affinity Ca2+ binding site. Together, these studies provide a mechanistic basis for the biphasic Ca2+-dependence of IP3R channel activity.
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Affiliation(s)
- Navid Paknejad
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, 10065, USA
- Physiology, Biophysics, and Systems Biology (PBSB) Program, Weill Cornell Graduate School of Biomedical Sciences, 1300 York Avenue, New York, NY, 10065, USA
| | - Vinay Sapuru
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, 10065, USA
- Physiology, Biophysics, and Systems Biology (PBSB) Program, Weill Cornell Graduate School of Biomedical Sciences, 1300 York Avenue, New York, NY, 10065, USA
| | - Richard K Hite
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, 10065, USA.
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3
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Rosa N, Speelman-Rooms F, Parys JB, Bultynck G. Modulation of Ca 2+ signaling by antiapoptotic Bcl-2 versus Bcl-xL: From molecular mechanisms to relevance for cancer cell survival. Biochim Biophys Acta Rev Cancer 2022; 1877:188791. [PMID: 36162541 DOI: 10.1016/j.bbcan.2022.188791] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 08/29/2022] [Accepted: 08/29/2022] [Indexed: 11/17/2022]
Abstract
Members of the Bcl-2-protein family are key controllers of apoptotic cell death. The family is divided into antiapoptotic (including Bcl-2 itself, Bcl-xL, Mcl-1, etc.) and proapoptotic members (Bax, Bak, Bim, Bim, Puma, Noxa, Bad, etc.). These proteins are well known for their canonical role in the mitochondria, where they control mitochondrial outer membrane permeabilization and subsequent apoptosis. However, several proteins are recognized as modulators of intracellular Ca2+ signals that originate from the endoplasmic reticulum (ER), the major intracellular Ca2+-storage organelle. More than 25 years ago, Bcl-2, the founding member of the family, was reported to control apoptosis through Ca2+ signaling. Further work elucidated that Bcl-2 directly targets and inhibits inositol 1,4,5-trisphosphate receptors (IP3Rs), thereby suppressing proapoptotic Ca2+ signaling. In addition to Bcl-2, Bcl-xL was also shown to impact cell survival by sensitizing IP3R function, thereby promoting prosurvival oscillatory Ca2+ release. However, new work challenges this model and demonstrates that Bcl-2 and Bcl-xL can both function as inhibitors of IP3Rs. This suggests that, depending on the cell context, Bcl-xL could support very distinct Ca2+ patterns. This not only raises several questions but also opens new possibilities for the treatment of Bcl-xL-dependent cancers. In this review, we will discuss the similarities and divergences between Bcl-2 and Bcl-xL regarding Ca2+ homeostasis and IP3R modulation from both a molecular and a functional point of view, with particular emphasis on cancer cell death resistance mechanisms.
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Affiliation(s)
- Nicolas Rosa
- KU Leuven, Laboratory of Molecular & Cellular Signaling, Department of Cellular & Molecular Medicine, Campus Gasthuisberg O/N-I bus 802, Herestraat 49, BE-3000 Leuven, Belgium
| | - Femke Speelman-Rooms
- KU Leuven, Laboratory of Molecular & Cellular Signaling, Department of Cellular & Molecular Medicine, Campus Gasthuisberg O/N-I bus 802, Herestraat 49, BE-3000 Leuven, Belgium
| | - Jan B Parys
- KU Leuven, Laboratory of Molecular & Cellular Signaling, Department of Cellular & Molecular Medicine, Campus Gasthuisberg O/N-I bus 802, Herestraat 49, BE-3000 Leuven, Belgium
| | - Geert Bultynck
- KU Leuven, Laboratory of Molecular & Cellular Signaling, Department of Cellular & Molecular Medicine, Campus Gasthuisberg O/N-I bus 802, Herestraat 49, BE-3000 Leuven, Belgium.
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4
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Arige V, Yule DI. Spatial and temporal crosstalk between the cAMP and Ca 2+ signaling systems. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2022; 1869:119293. [PMID: 35588944 DOI: 10.1016/j.bbamcr.2022.119293] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 05/09/2022] [Accepted: 05/11/2022] [Indexed: 12/31/2022]
Abstract
The ubiquitous secondary messengers, Ca2+ and cAMP, play a vital role in shaping a diverse array of physiological processes. More significantly, accumulating evidence over the past several decades underpin extensive crosstalk between these two canonical messengers in discrete sub-cellular nanodomains across various cell types. Within such specialized nanodomains, each messenger fine-tunes signaling to maintain homeostasis by manipulating the activities of cellular machinery accountable for the metabolism or activity of the complementary pathway. Interaction between these messengers is ensured by scaffolding proteins which tether components of the signaling machinery in close proximity. Disruption of dynamic communications between Ca2+ and cAMP at these loci consequently is linked to several pathological conditions. This review summarizes recent novel mechanisms underlying effective crosstalk between Ca2+ and cAMP in such nanodomains.
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Affiliation(s)
- Vikas Arige
- Department of Pharmacology and Physiology, University of Rochester, 601 Elmwood Avenue, Rochester, NY 14642, USA
| | - David I Yule
- Department of Pharmacology and Physiology, University of Rochester, 601 Elmwood Avenue, Rochester, NY 14642, USA..
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5
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Paschou M, Papazafiri P, Charalampous C, Zachariadis M, Dedos SG, Doxakis E. Neuronal microRNAs safeguard ER Ca 2+ homeostasis and attenuate the unfolded protein response upon stress. Cell Mol Life Sci 2022; 79:373. [PMID: 35727337 PMCID: PMC11073139 DOI: 10.1007/s00018-022-04398-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 04/23/2022] [Accepted: 05/21/2022] [Indexed: 11/30/2022]
Abstract
Ca2+ is a critical mediator of neurotransmitter release, synaptic plasticity, and gene expression, but also excitotoxicity. Ca2+ signaling and homeostasis are coordinated by an intricate network of channels, pumps, and calcium-binding proteins, which must be rapidly regulated at all expression levels. Τhe role of neuronal miRNAs in regulating ryanodine receptors (RyRs) and inositol 1,4,5-triphosphate receptors (IP3Rs) was investigated to understand the underlying mechanisms that modulate ER Ca2+ release. RyRs and IP3Rs are critical in mounting and propagating cytosolic Ca2+ signals by functionally linking the ER Ca2+ content, while excessive ER Ca2+ release via these receptors is central to the pathophysiology of a wide range of neurological diseases. Herein, two brain-restricted microRNAs, miR-124-3p and miR-153-3p, were found to bind to RyR1-3 and IP3R3 3'UTRs, and suppress their expression at both the mRNA and protein level. Ca2+ imaging studies revealed that overexpression of these miRNAs reduced ER Ca2+ release upon RyR/IP3R activation, but had no effect on [Ca2+]i under resting conditions. Interestingly, treatments that cause excessive ER Ca2+ release decreased expression of these miRNAs and increased expression of their target ER Ca2+ channels, indicating interdependence of miRNAs, RyRs, and IP3Rs in Ca2+ homeostasis. Furthermore, by maintaining the ER Ca2+ content, miR-124 and miR-153 reduced cytosolic Ca2+ overload and preserved protein-folding capacity by attenuating PERK signaling. Overall, this study shows that miR-124-3p and miR-153-3p fine-tune ER Ca2+ homeostasis and alleviate ER stress responses.
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Affiliation(s)
- Maria Paschou
- Center for Basic Research, Biomedical Research Foundation, Academy of Athens (BRFAA), Soranou Efesiou 4, 11527, Athens, Greece
- Department of Biology, National and Kapodistrian University of Athens (NKUA), Panepistimiopolis, 15784, Athens, Greece
| | - Panagiota Papazafiri
- Department of Biology, National and Kapodistrian University of Athens (NKUA), Panepistimiopolis, 15784, Athens, Greece
| | - Chrysanthi Charalampous
- Center for Basic Research, Biomedical Research Foundation, Academy of Athens (BRFAA), Soranou Efesiou 4, 11527, Athens, Greece
| | - Michael Zachariadis
- Department of Biology, National and Kapodistrian University of Athens (NKUA), Panepistimiopolis, 15784, Athens, Greece
- Material and Chemical Characterization Facility (MC2), Faculty of Science, University of Bath, Claverton Down, Bath, BA2 7AY, UK
| | - Skarlatos G Dedos
- Department of Biology, National and Kapodistrian University of Athens (NKUA), Panepistimiopolis, 15784, Athens, Greece.
| | - Epaminondas Doxakis
- Center for Basic Research, Biomedical Research Foundation, Academy of Athens (BRFAA), Soranou Efesiou 4, 11527, Athens, Greece.
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6
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Woll KA, Van Petegem F. Calcium Release Channels: Structure and Function of IP3 Receptors and Ryanodine Receptors. Physiol Rev 2021; 102:209-268. [PMID: 34280054 DOI: 10.1152/physrev.00033.2020] [Citation(s) in RCA: 87] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Ca2+-release channels are giant membrane proteins that control the release of Ca2+ from the endoplasmic and sarcoplasmic reticulum. The two members, ryanodine receptors (RyRs) and inositol-1,4,5-trisphosphate Receptors (IP3Rs), are evolutionarily related and are both activated by cytosolic Ca2+. They share a common architecture, but RyRs have evolved additional modules in the cytosolic region. Their massive size allows for the regulation by tens of proteins and small molecules, which can affect the opening and closing of the channels. In addition to Ca2+, other major triggers include IP3 for the IP3Rs, and depolarization of the plasma membrane for a particular RyR subtype. Their size has made them popular targets for study via electron microscopic methods, with current structures culminating near 3Å. The available structures have provided many new mechanistic insights int the binding of auxiliary proteins and small molecules, how these can regulate channel opening, and the mechanisms of disease-associated mutations. They also help scrutinize previously proposed binding sites, as some of these are now incompatible with the structures. Many questions remain around the structural effects of post-translational modifications, additional binding partners, and the higher-order complexes these channels can make in situ. This review summarizes our current knowledge about the structures of Ca2+-release channels and how this informs on their function.
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Affiliation(s)
- Kellie A Woll
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
| | - Filip Van Petegem
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada
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Crul T, Maléth J. Endoplasmic Reticulum-Plasma Membrane Contact Sites as an Organizing Principle for Compartmentalized Calcium and cAMP Signaling. Int J Mol Sci 2021; 22:4703. [PMID: 33946838 PMCID: PMC8124356 DOI: 10.3390/ijms22094703] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 04/20/2021] [Accepted: 04/27/2021] [Indexed: 01/14/2023] Open
Abstract
In eukaryotic cells, ultimate specificity in activation and action-for example, by means of second messengers-of the myriad of signaling cascades is primordial. In fact, versatile and ubiquitous second messengers, such as calcium (Ca2+) and cyclic adenosine monophosphate (cAMP), regulate multiple-sometimes opposite-cellular functions in a specific spatiotemporal manner. Cells achieve this through segregation of the initiators and modulators to specific plasma membrane (PM) subdomains, such as lipid rafts and caveolae, as well as by dynamic close contacts between the endoplasmic reticulum (ER) membrane and other intracellular organelles, including the PM. Especially, these membrane contact sites (MCSs) are currently receiving a lot of attention as their large influence on cell signaling regulation and cell physiology is increasingly appreciated. Depletion of ER Ca2+ stores activates ER membrane STIM proteins, which activate PM-residing Orai and TRPC Ca2+ channels at ER-PM contact sites. Within the MCS, Ca2+ fluxes relay to cAMP signaling through highly interconnected networks. However, the precise mechanisms of MCS formation and the influence of their dynamic lipid environment on their functional maintenance are not completely understood. The current review aims to provide an overview of our current understanding and to identify open questions of the field.
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Affiliation(s)
- Tim Crul
- First Department of Medicine, University of Szeged, H6720 Szeged, Hungary
- HAS-USZ Momentum Epithelial Cell Signaling and Secretion Research Group, University of Szeged, H6720 Szeged, Hungary
- HCEMM-SZTE Molecular Gastroenterology Research Group, University of Szeged, H6720 Szeged, Hungary
| | - József Maléth
- First Department of Medicine, University of Szeged, H6720 Szeged, Hungary
- HAS-USZ Momentum Epithelial Cell Signaling and Secretion Research Group, University of Szeged, H6720 Szeged, Hungary
- HCEMM-SZTE Molecular Gastroenterology Research Group, University of Szeged, H6720 Szeged, Hungary
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8
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Zeigerer A, Sekar R, Kleinert M, Nason S, Habegger KM, Müller TD. Glucagon's Metabolic Action in Health and Disease. Compr Physiol 2021; 11:1759-1783. [PMID: 33792899 PMCID: PMC8513137 DOI: 10.1002/cphy.c200013] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Discovered almost simultaneously with insulin, glucagon is a pleiotropic hormone with metabolic action that goes far beyond its classical role to increase blood glucose. Albeit best known for its ability to directly act on the liver to increase de novo glucose production and to inhibit glycogen breakdown, glucagon lowers body weight by decreasing food intake and by increasing metabolic rate. Glucagon further promotes lipolysis and lipid oxidation and has positive chronotropic and inotropic effects in the heart. Interestingly, recent decades have witnessed a remarkable renaissance of glucagon's biology with the acknowledgment that glucagon has pharmacological value beyond its classical use as rescue medication to treat severe hypoglycemia. In this article, we summarize the multifaceted nature of glucagon with a special focus on its hepatic action and discuss the pharmacological potential of either agonizing or antagonizing the glucagon receptor for health and disease. © 2021 American Physiological Society. Compr Physiol 11:1759-1783, 2021.
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Affiliation(s)
- Anja Zeigerer
- Institute for Diabetes and Cancer, Helmholtz Center Munich, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Revathi Sekar
- Institute for Diabetes and Cancer, Helmholtz Center Munich, Neuherberg, Germany
- German Center for Diabetes Research (DZD), Neuherberg, Germany
| | - Maximilian Kleinert
- German Center for Diabetes Research (DZD), Neuherberg, Germany
- Institute for Diabetes and Obesity, Helmholtz Center Munich, Neuherberg, Germany
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Shelly Nason
- Comprehensive Diabetes Center, Department of Medicine - Endocrinology, Diabetes & Metabolism, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Kirk M. Habegger
- Comprehensive Diabetes Center, Department of Medicine - Endocrinology, Diabetes & Metabolism, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Timo D. Müller
- German Center for Diabetes Research (DZD), Neuherberg, Germany
- Institute for Diabetes and Obesity, Helmholtz Center Munich, Neuherberg, Germany
- Department of Pharmacology, Experimental Therapy and Toxicology, Institute of Experimental and Clinical Pharmacology and Pharmacogenomics, Eberhard Karls University Hospitals and Clinics, Tübingen, Germany
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9
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Hodeify R, Chakkour M, Rida R, Kreydiyyeh S. PGE2 upregulates the Na+/K+ ATPase in HepG2 cells via EP4 receptors and intracellular calcium. PLoS One 2021; 16:e0245400. [PMID: 33444342 PMCID: PMC7808645 DOI: 10.1371/journal.pone.0245400] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 12/29/2020] [Indexed: 11/18/2022] Open
Abstract
The Na+/K+ ATPase is a key regulator of the hepatocytes ionic homeostasis, which when altered may lead to many liver disorders. We demonstrated recently, a significant stimulation of the Na+/K+ ATPase in HepG2 cells treated with the S1P analogue FTY 720P, that was mediated through PGE2. The mechanism by which the prostaglandin exerts its effect was not investigated, and is the focus of this work. The type of receptors involved was determined using pharmacological inhibitors, while western blot analysis, fluorescence imaging of GFP-tagged Na+/K+ ATPase, and time-lapse imaging on live cells were used to detect changes in membrane abundance of the Na+/K+ ATPase. The activity of the ATPase was assayed by measuring the amount of inorganic phosphate liberated in the presence and absence of ouabain. The enhanced activity of the ATPase was not observed when EP4 receptors were blocked but still appeared in presence inhibitors of EP1, EP2 and EP3 receptors. The involvement of EP4 was confirmed by the stimulation observed with EP4 agonist. The stimulatory effect of PGE2 did not appear in presence of Rp-cAMP, an inhibitor of PKA, and was imitated by db-cAMP, a PKA activator. Chelating intracellular calcium with BAPTA-AM abrogated the effect of db-cAMP as well as that of PGE2, but PGE2 treatment in a calcium-free PBS medium did not, suggesting an involvement of intracellular calcium, that was confirmed by the results obtained with 2-APB treatment. Live cell imaging showed movement of GFP–Na+/K+ ATPase-positive vesicles to the membrane and increased abundance of the ATPase at the membrane after PGE2 treatment. It was concluded that PGE2 acts via EP4, PKA, and intracellular calcium.
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Affiliation(s)
- Rawad Hodeify
- Department of Biotechnology, School of Arts and Sciences, American University of Ras Al Khaimah, Ras Al Khaimah, United Arab Emirates
| | - Mohamed Chakkour
- Department of Biology, Faculty of Arts & Sciences, American University of Beirut, Beirut, Lebanon
| | - Reem Rida
- Department of Biology, Faculty of Arts & Sciences, American University of Beirut, Beirut, Lebanon
| | - Sawsan Kreydiyyeh
- Department of Biology, Faculty of Arts & Sciences, American University of Beirut, Beirut, Lebanon
- * E-mail:
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10
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Burton RAB, Terrar DA. Emerging Evidence for cAMP-calcium Cross Talk in Heart Atrial Nanodomains Where IP 3-Evoked Calcium Release Stimulates Adenylyl Cyclases. CONTACT (THOUSAND OAKS (VENTURA COUNTY, CALIF.)) 2021; 4:25152564211008341. [PMID: 37366374 PMCID: PMC10243587 DOI: 10.1177/25152564211008341] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 03/01/2021] [Accepted: 03/07/2021] [Indexed: 06/28/2023]
Abstract
Calcium handling is vital to normal physiological function in the heart. Human atrial arrhythmias, eg. atrial fibrillation, are a major morbidity and mortality burden, yet major gaps remain in our understanding of how calcium signaling pathways function and interact. Inositol trisphosphate (IP3) is a calcium-mobilizing second messenger and its agonist-induced effects have been observed in many tissue types. In the atria IP3 receptors (IR3Rs) residing on junctional sarcoplasmic reticulum augment cellular calcium transients and, when over-stimulated, lead to arrhythmogenesis. Recent studies have demonstrated that the predominant pathway for IP3 actions in atrial myocytes depends on stimulation of calcium-dependent forms of adenylyl cyclase (AC8 and AC1) by IP3-evoked calcium release from the sarcoplasmic reticulum. AC8 shows co-localisation with IP3Rs and AC1 appears to be nearby. These observations support crosstalk between calcium and cAMP pathways in nanodomains in atria. Similar mechanisms also appear to operate in the pacemaker region of the sinoatrial node. Here we discuss these significant advances in our understanding of atrial physiology and pathology, together with implications for the identification of potential novel targets and modulators for the treatment of atrial arrhythmias.
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Affiliation(s)
| | - Derek A. Terrar
- Department of Pharmacology, University of Oxford, Oxford, UK
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11
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Jiang SJ, Wang W. Research progress on the role of CaMKII in heart disease. Am J Transl Res 2020; 12:7625-7639. [PMID: 33437349 PMCID: PMC7791482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Accepted: 11/21/2020] [Indexed: 06/12/2023]
Abstract
In the heart, Ca2+ participates in electrical activity and myocardial contraction, which is closely related to the generation of action potential and excitation contraction coupling (ECC) and plays an important role in various signal cascades and regulates different physiological processes. In the Ca2+ related physiological activities, CaMKII is a key downstream regulator, involving autophosphorylation and post-translational modification, and plays an important role in the excitation contraction coupling and relaxation events of cardiomyocytes. This paper reviews the relationship between CaMKII and various substances in the pathological process of myocardial apoptosis and necrosis, myocardial hypertrophy and arrhythmia, and what roles it plays in the development of disease in complex networks. This paper also introduces the drugs targeting at CaMKII to treat heart disease.
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Affiliation(s)
- Shi-Jun Jiang
- School of Basic Medicine, Tongji Medical College, Huazhong University of Science and TechnologyWuhan 430030, Hubei, China
| | - Wei Wang
- Department of Cardiology, Affiliated Taihe Hospital of Hubei University of MedicineShiyan 442000, Hubei, China
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12
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Capel RA, Bose SJ, Collins TP, Rajasundaram S, Ayagama T, Zaccolo M, Burton RAB, Terrar DA. IP 3-mediated Ca 2+ release regulates atrial Ca 2+ transients and pacemaker function by stimulation of adenylyl cyclases. Am J Physiol Heart Circ Physiol 2020; 320:H95-H107. [PMID: 33064562 PMCID: PMC7864251 DOI: 10.1152/ajpheart.00380.2020] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Inositol trisphosphate (IP3) is a Ca2+-mobilizing second messenger shown to modulate atrial muscle contraction and is thought to contribute to atrial fibrillation. Cellular pathways underlying IP3 actions in cardiac tissue remain poorly understood, and the work presented here addresses the question whether IP3-mediated Ca2+ release from the sarcoplasmic reticulum is linked to adenylyl cyclase activity including Ca2+-stimulated adenylyl cyclases (AC1 and AC8) that are selectively expressed in atria and sinoatrial node (SAN). Immunocytochemistry in guinea pig atrial myocytes identified colocalization of type 2 IP3 receptors with AC8, while AC1 was located in close vicinity. Intracellular photorelease of IP3 by UV light significantly enhanced the amplitude of the Ca2+ transient (CaT) evoked by electrical stimulation of atrial myocytes (31 ± 6% increase 60 s after photorelease, n = 16). The increase in CaT amplitude was abolished by inhibitors of adenylyl cyclases (MDL-12,330) or protein kinase A (H89), showing that cAMP signaling is required for this effect of photoreleased IP3. In mouse, spontaneously beating right atrial preparations, phenylephrine, an α-adrenoceptor agonist with effects that depend on IP3-mediated Ca2+ release, increased the maximum beating rate by 14.7 ± 0.5%, n = 10. This effect was substantially reduced by 2.5 µmol/L 2-aminoethyl diphenylborinate and abolished by a low dose of MDL-12,330, observations which are again consistent with a functional interaction between IP3 and cAMP signaling involving Ca2+ stimulation of adenylyl cyclases in the SAN pacemaker. Understanding the interaction between IP3 receptor pathways and Ca2+-stimulated adenylyl cyclases provides important insights concerning acute mechanisms for initiation of atrial arrhythmias. NEW & NOTEWORTHY This study provides evidence supporting the proposal that IP3 signaling in cardiac atria and sinoatrial node involves stimulation of Ca2+-activated adenylyl cyclases (AC1 and AC8) by IP3-evoked Ca2+ release from junctional sarcoplasmic reticulum. AC8 and IP3 receptors are shown to be located close together, while AC1 is nearby. Greater understanding of these novel aspects of the IP3 signal transduction mechanism is important for future study in atrial physiology and pathophysiology, particularly atrial fibrillation.
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Affiliation(s)
- Rebecca A Capel
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Samuel J Bose
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Thomas P Collins
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Skanda Rajasundaram
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Thamali Ayagama
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Manuela Zaccolo
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Rebecca-Ann Beatrice Burton
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
| | - Derek A Terrar
- Department of Pharmacology, British Heart Foundation Centre of Research Excellence, University of Oxford, Oxford, United Kingdom
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Sleiman Y, Souidi M, Kumar R, Yang E, Jaffré F, Zhou T, Bernardin A, Reiken S, Cazorla O, Kajava AV, Moreau A, Pasquié JL, Marks AR, Lerman BB, Chen S, Cheung JW, Evans T, Lacampagne A, Meli AC. Modeling polymorphic ventricular tachycardia at rest using patient-specific induced pluripotent stem cell-derived cardiomyocytes. EBioMedicine 2020; 60:103024. [PMID: 32980690 PMCID: PMC7519379 DOI: 10.1016/j.ebiom.2020.103024] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 08/27/2020] [Accepted: 09/09/2020] [Indexed: 12/21/2022] Open
Abstract
Background While mutations in the cardiac type 2 ryanodine receptor (RyR2) have been linked to exercise-induced or catecholaminergic polymorphic ventricular tachycardia (CPVT), its association with polymorphic ventricular tachycardia (PMVT) occurring at rest is unclear. We aimed at constructing a patient-specific human-induced pluripotent stem cell (hiPSC) model of PMVT occurring at rest linked to a single point mutation in RyR2. Methods Blood samples were obtained from a patient with PMVT at rest due to a heterozygous RyR2-H29D mutation. Patient-specific hiPSCs were generated from the blood samples, and the hiPSC-derived cardiomyocytes (CMs) were generated via directed differentiation. Using CRIPSR/Cas9 technology, isogenic controls were generated by correcting the RyR2-H29D mutation. Using patch-clamp, fluorescent confocal microscopy and video-image-based analysis, the molecular and functional properties of RyR2-H29D hiPSC—CMs and control hiPSC—CMs were compared. Findings RyR2-H29D hiPSC—CMs exhibit intracellular sarcoplasmic reticulum (SR) Ca2+ leak through RyR2 under physiological pacing. RyR2-H29D enhances the contribution of inositol 1,4,5-trisphosphate receptors to excitation-contraction coupling (ECC) that exacerbates abnormal Ca2+ release in RyR2-H29D hiPSC—CMs. RyR2-H29D hiPSC—CMs exhibit shorter action potentials, delayed afterdepolarizations, arrhythmias and aberrant contractile properties compared to isogenic controls. The RyR2-H29D mutation causes post-translational remodeling that is fully reversed with isogenic controls. Interpretation To conclude, in a model based on a RyR2 point mutation that is associated with short-coupled PMVT at rest, RyR2-H29D hiPSC—CMs exhibited aberrant intracellular Ca2+ homeostasis, shortened action potentials, arrhythmias and abnormal contractile properties. Funding French Muscular Dystrophy Association (AFM; project 16,073, MNM2 2012 and 20,225), “Fondation de la Recherche Médicale” (FRM; SPF20130526710), “Institut National pour la Santé et la Recherche Médicale” (INSERM), National Institutes of Health (ARM; R01 HL145473) and New York State Department of Health (NYSTEM C029156).
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Affiliation(s)
- Yvonne Sleiman
- PhyMedExp, Inserm, CNRS, University of Montpellier, Montpellier, France
| | - Monia Souidi
- PhyMedExp, Inserm, CNRS, University of Montpellier, Montpellier, France
| | - Ritu Kumar
- Department of Surgery, Weill Cornell Medical College, New York, NY, United States
| | - Ellen Yang
- Department of Surgery, Weill Cornell Medical College, New York, NY, United States
| | - Fabrice Jaffré
- Department of Surgery, Weill Cornell Medical College, New York, NY, United States
| | - Ting Zhou
- Department of Surgery, Weill Cornell Medical College, New York, NY, United States
| | - Albin Bernardin
- PhyMedExp, Inserm, CNRS, University of Montpellier, Montpellier, France
| | - Steve Reiken
- Department of Physiology and Cellular Biophysics, Clyde and Helen Wu Center for Molecular Cardiology, Columbia University College of Physicians and Surgeons, New York, NY, United States
| | - Olivier Cazorla
- PhyMedExp, Inserm, CNRS, University of Montpellier, Montpellier, France
| | | | - Adrien Moreau
- PhyMedExp, Inserm, CNRS, University of Montpellier, Montpellier, France
| | - Jean-Luc Pasquié
- PhyMedExp, Inserm, CNRS, University of Montpellier, Montpellier, France; Department of Cardiology, CHU of Montpellier, Montpellier, France
| | - Andrew R Marks
- Department of Physiology and Cellular Biophysics, Clyde and Helen Wu Center for Molecular Cardiology, Columbia University College of Physicians and Surgeons, New York, NY, United States
| | - Bruce B Lerman
- Division of Cardiology, Weill Cornell Medical College, New York, NY, United States
| | - Shuibing Chen
- Department of Surgery, Weill Cornell Medical College, New York, NY, United States
| | - Jim W Cheung
- Division of Cardiology, Weill Cornell Medical College, New York, NY, United States
| | - Todd Evans
- Department of Surgery, Weill Cornell Medical College, New York, NY, United States
| | - Alain Lacampagne
- PhyMedExp, Inserm, CNRS, University of Montpellier, Montpellier, France
| | - Albano C Meli
- PhyMedExp, Inserm, CNRS, University of Montpellier, Montpellier, France.
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Ahuja M, Chung WY, Lin WY, McNally BA, Muallem S. Ca 2+ Signaling in Exocrine Cells. Cold Spring Harb Perspect Biol 2020; 12:cshperspect.a035279. [PMID: 31636079 DOI: 10.1101/cshperspect.a035279] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Calcium (Ca2+) and cyclic AMP (cAMP) signaling cross talk and synergize to stimulate the cardinal functions of exocrine cells, regulated exocytosis, and fluid and electrolyte secretion. This physiological process requires the organization of the two signaling pathways into complexes at defined cellular domains and close placement. Such domains are formed by membrane contact sites (MCS). This review discusses the basic properties of Ca2+ signaling in exocrine cells, the role of MCS in the organization of cell signaling and in cross talk and synergism between the Ca2+ and cAMP signaling pathways and, finally, the mechanism by which the Ca2+ and cAMP pathways synergize to stimulate epithelial fluid and electrolyte secretion.
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Affiliation(s)
- Malini Ahuja
- Epithelial Signaling and Transport Section, National Institute of Dental and Craniofacial Research, National Institute of Health, Bethesda, Maryland 20892
| | - Woo Young Chung
- Epithelial Signaling and Transport Section, National Institute of Dental and Craniofacial Research, National Institute of Health, Bethesda, Maryland 20892
| | - Wei-Yin Lin
- Epithelial Signaling and Transport Section, National Institute of Dental and Craniofacial Research, National Institute of Health, Bethesda, Maryland 20892
| | - Beth A McNally
- Epithelial Signaling and Transport Section, National Institute of Dental and Craniofacial Research, National Institute of Health, Bethesda, Maryland 20892
| | - Shmuel Muallem
- Epithelial Signaling and Transport Section, National Institute of Dental and Craniofacial Research, National Institute of Health, Bethesda, Maryland 20892
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15
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Brill AL, Ehrlich BE. Polycystin 2: A calcium channel, channel partner, and regulator of calcium homeostasis in ADPKD. Cell Signal 2019; 66:109490. [PMID: 31805375 DOI: 10.1016/j.cellsig.2019.109490] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 11/30/2019] [Accepted: 12/01/2019] [Indexed: 01/26/2023]
Abstract
Polycystin 2 (PC2) is one of two main protein types responsible for the underlying etiology of autosomal dominant polycystic kidney disease (ADPKD), the most prevalent monogenic renal disease in the world. This debilitating and currently incurable condition is caused by loss-of-function mutations in PKD2 and PKD1, the genes encoding for PC2 and Polycystin 1 (PC1), respectively. Two-hit mutation events in these genes lead to renal cyst formation and eventual kidney failure, the main hallmarks of ADPKD. Though much is known concerning the physiological consequences and dysfunctional signaling mechanisms resulting from ADPKD development, to best understand the requirement of PC2 in maintaining organ homeostasis, it is important to recognize how PC2 acts under normal conditions. As such, an array of work has been performed characterizing the endogenous function of PC2, revealing it to be a member of the transient receptor potential (TRP) channel family of proteins. As a TRP protein, PC2 is a nonselective, cation-permeant, calcium-sensitive channel expressed in all tissue types, where it localizes primarily on the endoplasmic reticulum (ER), primary cilia, and plasma membrane. In addition to its channel function, PC2 interacts with and acts as a regulator of a number of other channels, ultimately further affecting intracellular signaling and leading to dysfunction in its absence. In this review, we describe the biophysical and physiological properties of PC2 as a cation channel and modulator of intracellular calcium channels, along with how these properties are altered in ADPKD.
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Affiliation(s)
- Allison L Brill
- Department of Cellular and Molecular Physiology, Yale University, New Haven, CT, USA
| | - Barbara E Ehrlich
- Department of Cellular and Molecular Physiology, Yale University, New Haven, CT, USA; Department of Pharmacology, Yale University, New Haven, CT, USA.
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16
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Type 3 inositol 1,4,5-trisphosphate receptor: A calcium channel for all seasons. Cell Calcium 2019; 85:102132. [PMID: 31790953 DOI: 10.1016/j.ceca.2019.102132] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Revised: 11/21/2019] [Accepted: 11/22/2019] [Indexed: 12/18/2022]
Abstract
Inositol 1,4,5 trisphosphate receptors (ITPRs) are a family of endoplasmic reticulum Ca2+ channels essential for the control of intracellular Ca2+ levels in virtually every mammalian cell type. The three isoforms (ITPR1, ITPR2 and ITPR3) are highly homologous in amino acid sequence, but they differ considerably in terms of biophysical properties, subcellular localization, and tissue distribution. Such differences underscore the variety of cellular responses triggered by each isoform and suggest that the expression/activity of specific isoforms might be linked to particular pathophysiological states. Indeed, recent findings demonstrate that changes in expression of ITPR isoforms are associated with a number of human diseases ranging from fatty liver disease to cancer. ITPR3 is emerging as the isoform that is particularly important in the pathogenesis of various human diseases. Here we review the physiological and pathophysiological roles of ITPR3 in various tissues and the mechanisms by which the expression of this isoform is modulated in health and disease.
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17
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Gaspers LD, Pierobon N, Thomas AP. Intercellular calcium waves integrate hormonal control of glucose output in the intact liver. J Physiol 2019; 597:2867-2885. [PMID: 30968953 PMCID: PMC6647271 DOI: 10.1113/jp277650] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Accepted: 04/08/2019] [Indexed: 11/21/2022] Open
Abstract
Key points Sympathetic outflow and circulating glucogenic hormones both regulate liver function by increasing cytosolic calcium, although how these calcium signals are integrated at the tissue level is currently unknown. We show that stimulation of hepatic nerve fibres or perfusing the liver with physiological concentrations of vasopressin only will evoke localized cytosolic calcium oscillations and modest increases in hepatic glucose production. The combination of these stimuli acted synergistically to convert localized and asynchronous calcium responses into co‐ordinated intercellular calcium waves that spread throughout the liver lobule and elicited a synergistic increase in hepatic glucose production. The results obtained in the present study demonstrate that subthreshold levels of one hormone can create an excitable medium across the liver lobule, which allows global propagation of calcium signals in response to local sympathetic innervation and integration of metabolic regulation by multiple hormones. This enables the liver lobules to respond as functional units to produce full‐strength metabolic output at physiological levels of hormone.
Abstract Glucogenic hormones, including catecholamines and vasopressin, induce frequency‐modulated cytosolic Ca2+ oscillations in hepatocytes, and these propagate as intercellular Ca2+ waves via gap junctions in the intact liver. We investigated the role of co‐ordinated Ca2+ waves as a mechanism for integrating multiple endocrine and neuroendocrine inputs to control hepatic glucose production in perfused rat liver. Sympathetic nerve stimulation elicited localized Ca2+ increases that were restricted to hepatocytes in the periportal zone. During perfusion with subthreshold vasopressin, sympathetic stimulation converted asynchronous Ca2+ signals in a limited number of hepatocytes into co‐ordinated intercellular Ca2+ waves that propagated across entire lobules. A similar synergism was observed between physiological concentrations of glucagon and vasopressin, where glucagon also facilitated the recruitment of hepatocytes into a Ca2+ wave. Hepatic glucose production was significantly higher with intralobular Ca2+ waves. We propose that inositol 1,4,5‐trisphosphate (IP3)‐dependent Ca2+ signalling gives rise to an excitable medium across the functional syncytium of the hepatic lobule, co‐ordinating and amplifying the metabolic responses to multiple hormonal inputs. Sympathetic outflow and circulating glucogenic hormones both regulate liver function by increasing cytosolic calcium, although how these calcium signals are integrated at the tissue level is currently unknown. We show that stimulation of hepatic nerve fibres or perfusing the liver with physiological concentrations of vasopressin only will evoke localized cytosolic calcium oscillations and modest increases in hepatic glucose production. The combination of these stimuli acted synergistically to convert localized and asynchronous calcium responses into co‐ordinated intercellular calcium waves that spread throughout the liver lobule and elicited a synergistic increase in hepatic glucose production. The results obtained in the present study demonstrate that subthreshold levels of one hormone can create an excitable medium across the liver lobule, which allows global propagation of calcium signals in response to local sympathetic innervation and integration of metabolic regulation by multiple hormones. This enables the liver lobules to respond as functional units to produce full‐strength metabolic output at physiological levels of hormone.
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Affiliation(s)
- Lawrence D Gaspers
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School Rutgers, The State University of New Jersey, Newark, NJ, USA
| | - Nicola Pierobon
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School Rutgers, The State University of New Jersey, Newark, NJ, USA
| | - Andrew P Thomas
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School Rutgers, The State University of New Jersey, Newark, NJ, USA
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18
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Filadi R, Basso E, Lefkimmiatis K, Pozzan T. Beyond Intracellular Signaling: The Ins and Outs of Second Messengers Microdomains. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 981:279-322. [PMID: 29594866 DOI: 10.1007/978-3-319-55858-5_12] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
A typical characteristic of eukaryotic cells compared to prokaryotes is represented by the spatial heterogeneity of the different structural and functional components: for example, most of the genetic material is surrounded by a highly specific membrane structure (the nuclear membrane), continuous with, yet largely different from, the endoplasmic reticulum (ER); oxidative phosphorylation is carried out by organelles enclosed by a double membrane, the mitochondria; in addition, distinct domains, enriched in specific proteins, are present in the plasma membrane (PM) of most cells. Less obvious, but now generally accepted, is the notion that even the concentration of small molecules such as second messengers (Ca2+ and cAMP in particular) can be highly heterogeneous within cells. In the case of most organelles, the differences in the luminal levels of second messengers depend either on the existence on their membrane of proteins that allow the accumulation/release of the second messenger (e.g., in the case of Ca2+, pumps, exchangers or channels), or on the synthesis and degradation of the specific molecule within the lumen (the autonomous intramitochondrial cAMP system). It needs stressing that the existence of a surrounding membrane does not necessarily imply the existence of a gradient between the cytosol and the organelle lumen. For example, the nuclear membrane is highly permeable to both Ca2+ and cAMP (nuclear pores are permeable to solutes up to 50 kDa) and differences in [Ca2+] or [cAMP] between cytoplasm and nucleoplasm are not seen in steady state and only very transiently during cell activation. A similar situation has been observed, as far as Ca2+ is concerned, in peroxisomes.
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Affiliation(s)
- Riccardo Filadi
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Emy Basso
- Institute of Neuroscience, Padova Section, National Research Council, Padova, Italy
| | - Konstantinos Lefkimmiatis
- Institute of Neuroscience, Padova Section, National Research Council, Padova, Italy
- Venetian Institute of Molecular Medicine, Padova, Italy
| | - Tullio Pozzan
- Department of Biomedical Sciences, University of Padova, Padova, Italy.
- Institute of Neuroscience, Padova Section, National Research Council, Padova, Italy.
- Venetian Institute of Molecular Medicine, Padova, Italy.
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19
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Wang L, Wagner LE, Alzayady KJ, Yule DI. Region-specific proteolysis differentially modulates type 2 and type 3 inositol 1,4,5-trisphosphate receptor activity in models of acute pancreatitis. J Biol Chem 2018; 293:13112-13124. [PMID: 29970616 DOI: 10.1074/jbc.ra118.003421] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 06/04/2018] [Indexed: 12/22/2022] Open
Abstract
Fine-tuning of the activity of inositol 1,4,5-trisphosphate receptors (IP3R) by a diverse array of regulatory inputs results in intracellular Ca2+ signals with distinct characteristics. These events allow the activation of specific downstream effectors. We reported previously that region-specific proteolysis represents a novel regulatory event for type 1 IP3R (R1). Specifically, caspase-fragmented R1 display a marked increase in single-channel open probability. More importantly, the distinct characteristics of the Ca2+ signals elicited via fragmented R1 can activate alternate downstream effectors. In this report, we expand these studies to investigate whether all IP3R subtypes are regulated by proteolysis. We now show that type 2 and type 3 IP3R (R2 and R3, respectively) are proteolytically cleaved in rodent models of acute pancreatitis. Surprisingly, fragmented IP3R retained tetrameric architecture, remained embedded in endoplasmic reticulum membranes and were not functionally disabled. Proteolysis was associated with a marked attenuation of the frequency of Ca2+ signals in pancreatic lobules. Consistent with these data, expression of DNAs encoding complementary R2 and R3 peptides mimicking fragmented receptors at particular sites, resulted in a significant decrease in the frequency of agonist-stimulated Ca2+ oscillations. Further, proteolysis of R2 resulted in a marked decrease in single-channel open probability. Taken together, proteolytic fragmentation modulates R2 and R3 activity in a region-specific manner, and this event may contribute to the altered Ca2+ signals in pancreatic acinar cells during acute pancreatitis.
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Affiliation(s)
- Liwei Wang
- From the Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
| | - Larry E Wagner
- From the Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
| | - Kamil J Alzayady
- From the Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
| | - David I Yule
- From the Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
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20
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Wang L, Wagner LE, Alzayady KJ, Yule DI. Region-specific proteolysis differentially regulates type 1 inositol 1,4,5-trisphosphate receptor activity. J Biol Chem 2017; 292:11714-11726. [PMID: 28526746 DOI: 10.1074/jbc.m117.789917] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Revised: 05/11/2017] [Indexed: 12/31/2022] Open
Abstract
The inositol 1,4,5 trisphosphate receptor (IP3R) is an intracellular Ca2+ release channel expressed predominately on the membranes of the endoplasmic reticulum. IP3R1 can be cleaved by caspase or calpain into at least two receptor fragments. However, the functional consequences of receptor fragmentation are poorly understood. Our previous work has demonstrated that IP3R1 channels, formed following either enzymatic fragmentation or expression of the corresponding complementary polypeptide chains, retain tetrameric architecture and are still activated by IP3 binding despite the loss of peptide continuity. In this study, we demonstrate that region-specific receptor fragmentation modifies channel regulation. Specifically, the agonist-evoked temporal Ca2+ release profile and protein kinase A modulation of Ca2+ release are markedly altered. Moreover, we also demonstrate that activation of fragmented IP3R1 can result in a distinct functional outcome. Our work suggests that proteolysis of IP3R1 may represent a novel form of modulation of IP3R1 channel function and increases the repertoire of Ca2+ signals achievable through this channel.
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Affiliation(s)
- Liwei Wang
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
| | - Larry E Wagner
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
| | - Kamil J Alzayady
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
| | - David I Yule
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642.
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21
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Galaz-Montoya M, Wright SJ, Rodriguez GJ, Lichtarge O, Wensel TG. β 2-Adrenergic receptor activation mobilizes intracellular calcium via a non-canonical cAMP-independent signaling pathway. J Biol Chem 2017; 292:9967-9974. [PMID: 28442571 DOI: 10.1074/jbc.m117.787119] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Revised: 04/24/2017] [Indexed: 11/06/2022] Open
Abstract
Beta adrenergic receptors (βARs) are G-protein-coupled receptors essential for physiological responses to the hormones/neurotransmitters epinephrine and norepinephrine which are found in the nervous system and throughout the body. They are the targets of numerous widely used drugs, especially in the case of the most extensively studied βAR, β2AR, whose ligands are used for asthma and cardiovascular disease. βARs signal through Gαs G-proteins and via activation of adenylyl cyclase and cAMP-dependent protein kinase, but some alternative downstream pathways have also been proposed that could be important for understanding normal physiological functioning of βAR signaling and its disruption in disease. Using fluorescence-based Ca2+ flux assays combined with pharmacology and gene knock-out methods, we discovered a previously unrecognized endogenous pathway in HEK-293 cells whereby β2AR activation leads to robust Ca2+ mobilization from intracellular stores via activation of phospholipase C and opening of inositol trisphosphate (InsP3) receptors. This pathway did not involve cAMP, Gαs, or Gαi or the participation of the other members of the canonical β2AR signaling cascade and, therefore, constitutes a novel signaling mechanism for this receptor. This newly uncovered mechanism for Ca2+ mobilization by β2AR has broad implications for adrenergic signaling, cross-talk with other signaling pathways, and the effects of βAR-directed drugs.
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Affiliation(s)
- Monica Galaz-Montoya
- From the Verna and Marrs McLean Department of Biochemistry and Molecular Biology and
| | - Sara J Wright
- From the Verna and Marrs McLean Department of Biochemistry and Molecular Biology and
| | - Gustavo J Rodriguez
- From the Verna and Marrs McLean Department of Biochemistry and Molecular Biology and
| | - Olivier Lichtarge
- From the Verna and Marrs McLean Department of Biochemistry and Molecular Biology and.,the Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030
| | - Theodore G Wensel
- From the Verna and Marrs McLean Department of Biochemistry and Molecular Biology and
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Bartlett PJ, Antony AN, Agarwal A, Hilly M, Prince VL, Combettes L, Hoek JB, Gaspers LD. Chronic alcohol feeding potentiates hormone-induced calcium signalling in hepatocytes. J Physiol 2017; 595:3143-3164. [PMID: 28220501 DOI: 10.1113/jp273891] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Accepted: 01/26/2017] [Indexed: 12/14/2022] Open
Abstract
KEY POINTS Chronic alcohol consumption causes a spectrum of liver diseases, but the pathogenic mechanisms driving the onset and progression of disease are not clearly defined. We show that chronic alcohol feeding sensitizes rat hepatocytes to Ca2+ -mobilizing hormones resulting in a leftward shift in the concentration-response relationship and the transition from oscillatory to more sustained and prolonged Ca2+ increases. Our data demonstrate that alcohol-dependent adaptation in the Ca2+ signalling pathway occurs at the level of hormone-induced inositol 1,4,5 trisphosphate (IP3 ) production and does not involve changes in the sensitivity of the IP3 receptor or size of internal Ca2+ stores. We suggest that prolonged and aberrant hormone-evoked Ca2+ increases may stimulate the production of mitochondrial reactive oxygen species and contribute to alcohol-induced hepatocyte injury. ABSTRACT: 'Adaptive' responses of the liver to chronic alcohol consumption may underlie the development of cell and tissue injury. Alcohol administration can perturb multiple signalling pathways including phosphoinositide-dependent cytosolic calcium ([Ca2+ ]i ) increases, which can adversely affect mitochondrial Ca2+ levels, reactive oxygen species production and energy metabolism. Our data indicate that chronic alcohol feeding induces a leftward shift in the dose-response for Ca2+ -mobilizing hormones resulting in more sustained and prolonged [Ca2+ ]i increases in both cultured hepatocytes and hepatocytes within the intact perfused liver. Ca2+ increases were initiated at lower hormone concentrations, and intercellular calcium wave propagation rates were faster in alcoholics compared to controls. Acute alcohol treatment (25 mm) completely inhibited hormone-induced calcium increases in control livers, but not after chronic alcohol-feeding, suggesting desensitization to the inhibitory actions of ethanol. Hormone-induced inositol 1,4,5 trisphosphate (IP3 ) accumulation and phospholipase C (PLC) activity were significantly potentiated in hepatocytes from alcohol-fed rats compared to controls. Removal of extracellular calcium, or chelation of intracellular calcium did not normalize the differences in hormone-stimulated PLC activity, indicating calcium-dependent PLCs are not upregulated by alcohol. We propose that the liver 'adapts' to chronic alcohol exposure by increasing hormone-dependent IP3 formation, leading to aberrant calcium increases, which may contribute to hepatocyte injury.
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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
| | - Anil Noronha Antony
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA, 19107, USA
| | - Amit Agarwal
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School Rutgers, The State University of New Jersey, Newark, NJ, 07103, USA
| | - Mauricette Hilly
- INSERM UMR-S 757, Université de Paris-Sud, bât 443, 91405, Orsay, France
| | - Victoria L Prince
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School Rutgers, The State University of New Jersey, Newark, NJ, 07103, USA
| | - Laurent Combettes
- INSERM UMR-S 757, Université de Paris-Sud, bât 443, 91405, Orsay, France
| | - Jan B Hoek
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA, 19107, USA
| | - Lawrence D Gaspers
- 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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Kruglov E, Ananthanarayanan M, Sousa P, Weerachayaphorn J, Guerra MT, Nathanson MH. Type 2 inositol trisphosphate receptor gene expression in hepatocytes is regulated by cyclic AMP. Biochem Biophys Res Commun 2017; 486:659-664. [PMID: 28327356 DOI: 10.1016/j.bbrc.2017.03.086] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Accepted: 03/17/2017] [Indexed: 01/19/2023]
Abstract
The type 2 inositol 1,4,5-trisphosphate receptor (IP3R2) is the principal intracellular Ca2+ release channel in hepatocytes, and so is important for bile secretion and other functions. IP3R2 activity is regulated in part by post-translational modifications but little is known about transcriptional regulation of its expression. We found that both IP3R2 mRNA and protein levels in liver were increased during fasting. Treatment of hepatocytes with forskolin or 8-CPT-cAMP also increased IP3R2, and this was reduced by actinomycin D. Analysis of the IP3R2 promoter revealed five CREs, and CREB potently increased promoter activity. Mutation of CRE4 or CRE5 decreased induction by CREB, and ChIP assay showed recruitment of CREB to these sites. Adenylyl cyclase (AC) 6 and 9 were the principal AC isoforms detected in rat hepatocytes, and silencing either one decreased organic anion secretion, which depends on IP3R2. Secretion furthermore was increased by overnight but not acute treatment with forskolin or 8-CPT-cAMP. These findings provide evidence that IP3R2 expression is transcriptionally regulated by cAMP via CREB binding to CRE elements in its promoter. The findings furthermore suggest that this mechanism is relevant for hormonal regulation of bile secretion.
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Affiliation(s)
- Emma Kruglov
- Digestive Diseases Section, Yale School of Medicine, 333 Cedar Street, New Haven, CT 06520-8019, USA
| | | | - Pedro Sousa
- Digestive Diseases Section, Yale School of Medicine, 333 Cedar Street, New Haven, CT 06520-8019, USA
| | - Jittima Weerachayaphorn
- Digestive Diseases Section, Yale School of Medicine, 333 Cedar Street, New Haven, CT 06520-8019, USA
| | - Mateus T Guerra
- Digestive Diseases Section, Yale School of Medicine, 333 Cedar Street, New Haven, CT 06520-8019, USA
| | - Michael H Nathanson
- Digestive Diseases Section, Yale School of Medicine, 333 Cedar Street, New Haven, CT 06520-8019, USA.
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ISOBE K, YOKOYAMA T, MORIGUCHI-MORI K, KUMAGAI M, SATOH YI, KUJI A, SAINO T. Role of pituitary adenylyl cyclase-activating polypeptide in intracellular calcium dynamics of neurons and satellite cells in rat superior cervical ganglia . Biomed Res 2017; 38:99-109. [DOI: 10.2220/biomedres.38.99] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Kanako ISOBE
- Department of Anatomy (Cell Biology), Iwate Medical University
- Division of Special Care Dentistry, Department of Developmental Oral Health Science, School of Dentistry, Iwate Medical University
| | - Takuya YOKOYAMA
- Department of Anatomy (Cell Biology), Iwate Medical University
| | - Kasumi MORIGUCHI-MORI
- Division of Special Care Dentistry, Department of Developmental Oral Health Science, School of Dentistry, Iwate Medical University
| | - Miho KUMAGAI
- Division of Special Care Dentistry, Department of Developmental Oral Health Science, School of Dentistry, Iwate Medical University
| | - Yoh-ichi SATOH
- Department of Anatomy (Cell Biology), Iwate Medical University
- Department of Medical Education, Iwate Medical University
| | - Akiyoshi KUJI
- Division of Special Care Dentistry, Department of Developmental Oral Health Science, School of Dentistry, Iwate Medical University
| | - Tomoyuki SAINO
- Department of Anatomy (Cell Biology), Iwate Medical University
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25
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Taylor CW. Regulation of IP 3 receptors by cyclic AMP. Cell Calcium 2016; 63:48-52. [PMID: 27836216 PMCID: PMC5471599 DOI: 10.1016/j.ceca.2016.10.005] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 10/27/2016] [Accepted: 10/27/2016] [Indexed: 01/01/2023]
Abstract
Ca2+ and cAMP are ubiquitous intracellular messengers and interactions between them are commonplace. Here the effects of cAMP on inositol 1,4,5-trisphosphate receptors (IP3Rs) are briefly reviewed. All three subtypes of IP3R are phosphorylated by cAMP-dependent protein kinase (PKA). This potentiates IP3-evoked Ca2+ release through IP3R1 and IP3R2, but probably has little effect on IP3R3. In addition, cAMP can directly sensitize all three IP3R subtypes to IP3. The high concentrations of cAMP required for this PKA-independent modulation of IP3Rs is delivered to them within signalling junctions that include type 6 adenylyl cyclase and IP3R2.
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Affiliation(s)
- Colin W Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK.
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26
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Vardjan N, Horvat A, Anderson JE, Yu D, Croom D, Zeng X, Lužnik Z, Kreft M, Teng YD, Kirov SA, Zorec R. Adrenergic activation attenuates astrocyte swelling induced by hypotonicity and neurotrauma. Glia 2016; 64:1034-49. [PMID: 27018061 DOI: 10.1002/glia.22981] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 02/18/2016] [Accepted: 02/18/2016] [Indexed: 12/29/2022]
Abstract
Edema in the central nervous system can rapidly result in life-threatening complications. Vasogenic edema is clinically manageable, but there is no established medical treatment for cytotoxic edema, which affects astrocytes and is a primary trigger of acute post-traumatic neuronal death. To test the hypothesis that adrenergic receptor agonists, including the stress stimulus epinephrine protects neural parenchyma from damage, we characterized its effects on hypotonicity-induced cellular edema in cortical astrocytes by in vivo and in vitro imaging. After epinephrine administration, hypotonicity-induced swelling of astrocytes was markedly reduced and cytosolic 3'-5'-cyclic adenosine monophosphate (cAMP) was increased, as shown by a fluorescence resonance energy transfer nanosensor. Although, the kinetics of epinephrine-induced cAMP signaling was slowed in primary cortical astrocytes exposed to hypotonicity, the swelling reduction by epinephrine was associated with an attenuated hypotonicity-induced cytosolic Ca(2+) excitability, which may be the key to prevent astrocyte swelling. Furthermore, in a rat model of spinal cord injury, epinephrine applied locally markedly reduced neural edema around the contusion epicenter. These findings reveal new targets for the treatment of cellular edema in the central nervous system.
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Affiliation(s)
- Nina Vardjan
- Celica, BIOMEDICAL, Tehnološki park 24, Ljubljana, 1000, Slovenia.,Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, Ljubljana, 1000, Slovenia
| | - Anemari Horvat
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, Ljubljana, 1000, Slovenia
| | - Jamie E Anderson
- Departments of Neurosurgery and Physical Medicine & Rehabilitation, Harvard Medical School, Boston, Massachusetts
| | - Dou Yu
- Departments of Neurosurgery and Physical Medicine & Rehabilitation, Harvard Medical School, Boston, Massachusetts
| | - Deborah Croom
- Brain and Behaviour Discovery Institute, Medical College of Georgia, Augusta, Georgia.,Department of Neurosurgery, Medical College of Georgia, Augusta, Georgia
| | - Xiang Zeng
- Departments of Neurosurgery and Physical Medicine & Rehabilitation, Harvard Medical School, Boston, Massachusetts
| | - Zala Lužnik
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, Ljubljana, 1000, Slovenia
| | - Marko Kreft
- Celica, BIOMEDICAL, Tehnološki park 24, Ljubljana, 1000, Slovenia.,Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, Ljubljana, 1000, Slovenia.,Department of Biology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, Ljubljana, 1000, Slovenia
| | - Yang D Teng
- Departments of Neurosurgery and Physical Medicine & Rehabilitation, Harvard Medical School, Boston, Massachusetts.,Division of SCI Research, VA Boston Healthcare System, Boston, Massachusetts
| | - Sergei A Kirov
- Brain and Behaviour Discovery Institute, Medical College of Georgia, Augusta, Georgia.,Department of Neurosurgery, Medical College of Georgia, Augusta, Georgia
| | - Robert Zorec
- Celica, BIOMEDICAL, Tehnološki park 24, Ljubljana, 1000, Slovenia.,Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 4, Ljubljana, 1000, Slovenia
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27
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Chandrasekhar R, Alzayady KJ, Wagner LE, Yule DI. Unique Regulatory Properties of Heterotetrameric Inositol 1,4,5-Trisphosphate Receptors Revealed by Studying Concatenated Receptor Constructs. J Biol Chem 2016; 291:4846-60. [PMID: 26755721 DOI: 10.1074/jbc.m115.705301] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Indexed: 02/02/2023] Open
Abstract
The ability of inositol 1,4,5-trisphosphate receptors (IP3R) to precisely initiate and generate a diverse variety of intracellular Ca(2+) signals is in part mediated by the differential regulation of the three subtypes (R1, R2, and R3) by key functional modulators (IP3, Ca(2+), and ATP). However, the contribution of IP3R heterotetramerization to Ca(2+) signal diversity has largely been unexplored. In this report, we provide the first definitive biochemical evidence of endogenous heterotetramer formation. Additionally, we examine the contribution of individual subtypes within defined concatenated heterotetramers to the shaping of Ca(2+) signals. Under conditions where key regulators of IP3R function are optimal for Ca(2+) release, we demonstrate that individual monomers within heteromeric IP3Rs contributed equally toward generating a distinct 'blended' sensitivity to IP3 that is likely dictated by the unique IP3 binding affinity of the heteromers. However, under suboptimal conditions where [ATP] were varied, we found that one subtype dictated the ATP regulatory properties of heteromers. We show that R2 monomers within a heterotetramer were both necessary and sufficient to dictate the ATP regulatory properties. Finally, the ATP-binding site B in R2 critical for ATP regulation was mutated and rendered non-functional to address questions relating to the stoichiometry of IP3R regulation. Two intact R2 monomers were sufficient to maintain ATP regulation in R2 homotetramers. In summary, we demonstrate that heterotetrameric IP3R do not necessarily behave as the sum of the constituent subunits, and these properties likely extend the versatility of IP3-induced Ca(2+) signaling in cells expressing multiple IP3R isoforms.
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Affiliation(s)
- Rahul Chandrasekhar
- From the Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
| | - Kamil J Alzayady
- From the Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
| | - Larry E Wagner
- From the Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
| | - David I Yule
- From the Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642
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28
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Cao X, Choi S, Maléth JJ, Park S, Ahuja M, Muallem S. The ER/PM microdomain, PI(4,5)P₂ and the regulation of STIM1-Orai1 channel function. Cell Calcium 2015; 58:342-8. [PMID: 25843208 PMCID: PMC4564333 DOI: 10.1016/j.ceca.2015.03.003] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2015] [Revised: 03/06/2015] [Accepted: 03/09/2015] [Indexed: 12/18/2022]
Abstract
All forms of cell signaling occur in discreet cellular microdomains in which the ER is the main participant and include microdomains formed by the ER with lysosomes, endosomes, the nucleus, mitochondria and the plasma membrane. In the microdomains the two opposing organelles transfer and exchange constituents including lipids and ions. As is the case for other forms of signaling pathways, many components of the receptor-evoked Ca(2+) signal are clustered at the ER/PM microdomain, including the Orai1-STIM1 complex. This review discusses recent advances in understanding the molecular components that tether the ER and plasma membrane to form the ER/PM microdomains in which PI(4,5)P2 is enriched, and how dynamic targeting of the Orai1-STIM1 complex to PI(4,5)P2-poor and PI(4,5)P2-rich microdomains controls the activity of Orai1 and its regulation by Ca(2+) that is mediated by SARAF.
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Affiliation(s)
- Xu Cao
- Epithelial Signaling and Transport Section, Molecular Physiology and Therapeutics Branch, NIDCR, NIH, Bethesda, MD 20892, United States
| | - Seok Choi
- Department of Physiology, College of Medicine, Chosun University, 501-375, Republic of Korea
| | - Jozsef J Maléth
- First Department of Medicine, University of Szeged, Szeged H-6725, Hungary
| | - Seonghee Park
- Department of Physiology, School of Medicine, Ewha Womans University, 911-1 Mok-6-dong, Yang Chun-gu, Seoul 158-710, Republic of Korea
| | - Malini Ahuja
- Epithelial Signaling and Transport Section, Molecular Physiology and Therapeutics Branch, NIDCR, NIH, Bethesda, MD 20892, United States
| | - Shmuel Muallem
- Epithelial Signaling and Transport Section, Molecular Physiology and Therapeutics Branch, NIDCR, NIH, Bethesda, MD 20892, United States.
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29
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Vainio I, Abu Khamidakh A, Paci M, Skottman H, Juuti-Uusitalo K, Hyttinen J, Nymark S. Computational Model of Ca2+ Wave Propagation in Human Retinal Pigment Epithelial ARPE-19 Cells. PLoS One 2015; 10:e0128434. [PMID: 26070134 PMCID: PMC4466493 DOI: 10.1371/journal.pone.0128434] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 04/27/2015] [Indexed: 12/21/2022] Open
Abstract
Objective Computational models of calcium (Ca2+) signaling have been constructed for several cell types. There are, however, no such models for retinal pigment epithelium (RPE). Our aim was to construct a Ca2+ signaling model for RPE based on our experimental data of mechanically induced Ca2+ wave in the in vitro model of RPE, the ARPE-19 monolayer. Methods We combined six essential Ca2+ signaling components into a model: stretch-sensitive Ca2+ channels (SSCCs), P2Y2 receptors, IP3 receptors, ryanodine receptors, Ca2+ pumps, and gap junctions. The cells in our epithelial model are connected to each other to enable transport of signaling molecules. Parameterization was done by tuning the above model components so that the simulated Ca2+ waves reproduced our control experimental data and data where gap junctions were blocked. Results Our model was able to explain Ca2+ signaling in ARPE-19 cells, and the basic mechanism was found to be as follows: 1) Cells near the stimulus site are likely to conduct Ca2+ through plasma membrane SSCCs and gap junctions conduct the Ca2+ and IP3 between cells further away. 2) Most likely the stimulated cell secretes ligand to the extracellular space where the ligand diffusion mediates the Ca2+ signal so that the ligand concentration decreases with distance. 3) The phosphorylation of the IP3 receptor defines the cell’s sensitivity to the extracellular ligand attenuating the Ca2+ signal in the distance. Conclusions The developed model was able to simulate an array of experimental data including drug effects. Furthermore, our simulations predict that suramin may interfere ligand binding on P2Y2 receptors or accelerate P2Y2 receptor phosphorylation, which may partially be the reason for Ca2+ wave attenuation by suramin. Being the first RPE Ca2+ signaling model created based on experimental data on ARPE-19 cell line, the model offers a platform for further modeling of native RPE functions.
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Affiliation(s)
- Iina Vainio
- Department of Electronics and Communications Engineering, Tampere University of Technology, Tampere, Finland
- Institute of Biosciences and Medical Technology, Tampere University of Technology, Tampere, Finland
- * E-mail:
| | - Amna Abu Khamidakh
- Department of Electronics and Communications Engineering, Tampere University of Technology, Tampere, Finland
- Institute of Biosciences and Medical Technology, Tampere University of Technology, Tampere, Finland
| | - Michelangelo Paci
- Department of Electronics and Communications Engineering, Tampere University of Technology, Tampere, Finland
- Institute of Biosciences and Medical Technology, Tampere University of Technology, Tampere, Finland
| | - Heli Skottman
- Institute of Biosciences and Medical Technology, University of Tampere, Tampere, Finland
| | - Kati Juuti-Uusitalo
- Institute of Biosciences and Medical Technology, University of Tampere, Tampere, Finland
| | - Jari Hyttinen
- Department of Electronics and Communications Engineering, Tampere University of Technology, Tampere, Finland
- Institute of Biosciences and Medical Technology, Tampere University of Technology, Tampere, Finland
| | - Soile Nymark
- Department of Electronics and Communications Engineering, Tampere University of Technology, Tampere, Finland
- Institute of Biosciences and Medical Technology, Tampere University of Technology, Tampere, Finland
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30
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Chandrasekhar R, Alzayady KJ, Yule DI. Using concatenated subunits to investigate the functional consequences of heterotetrameric inositol 1,4,5-trisphosphate receptors. Biochem Soc Trans 2015; 43:364-70. [PMID: 26009177 PMCID: PMC4677331 DOI: 10.1042/bst20140287] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Inositol 1,4,5-trisphosphate receptors (IP3Rs) are a family of ubiquitous, ER localized, tetrameric Ca2+ release channels. There are three subtypes of the IP3Rs (R1, R2, R3), encoded by three distinct genes, that share ∼60-70% sequence identity. The diversity of Ca2+ signals generated by IP3Rs is thought to be largely the result of differential tissue expression, intracellular localization and subtype-specific regulation of the three subtypes by various cellular factors, most significantly InsP3, Ca2+ and ATP. However, largely unexplored is the notion of additional signal diversity arising from the assembly of both homo and heterotetrameric InsP3Rs. In the present article, we review the biochemical and functional evidence supporting the existence of homo and heterotetrameric populations of InsP3Rs. In addition, we consider a strategy that utilizes genetically concatenated InsP3Rs to study the functional characteristics of heterotetramers with unequivocally defined composition. This approach reveals that the overall properties of IP3R are not necessarily simply a blend of the constituent monomers but that specific subtypes appear to dominate the overall characteristics of the tetramer. It is envisioned that the ability to generate tetramers with defined wild type and mutant subunits will be useful in probing fundamental questions relating to IP3R structure and function.
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MESH Headings
- Adenosine Triphosphate/chemistry
- Adenosine Triphosphate/metabolism
- Calcium Signaling/genetics
- Humans
- Inositol 1,4,5-Trisphosphate/chemistry
- Inositol 1,4,5-Trisphosphate/metabolism
- Inositol 1,4,5-Trisphosphate Receptors/chemistry
- Inositol 1,4,5-Trisphosphate Receptors/genetics
- Inositol 1,4,5-Trisphosphate Receptors/metabolism
- Protein Multimerization
- Protein Structure, Tertiary
- Structure-Activity Relationship
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31
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Cooper DMF. Store-operated Ca²⁺-entry and adenylyl cyclase. Cell Calcium 2015; 58:368-75. [PMID: 25978874 DOI: 10.1016/j.ceca.2015.04.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2015] [Revised: 04/13/2015] [Accepted: 04/15/2015] [Indexed: 02/06/2023]
Abstract
One of the longest-standing effects of SOCE is in its selective regulation of Ca(2+)-sensitive adenylyl cyclase (AC) activity in non-excitable cells. Remarkably it was this source of Ca(2+) (SOCE) rather than the apparent magnitude of the Ca(2+)-rise that conferred AC responsiveness. The molecular basis for this dependence is now resolved in the case of adenylyl cyclase 8 (AC8). Sensors for Ca(2+) and cAMP targeted to ACs have been particularly useful in dissecting the influences upon and composition of what turn out to be signalling microdomains centred on ACs. A number of physiological processes depend on the regulation by SOCE of ACs, but the issue is under-studied. Here I will expand on these topics and point to some immediate unresolved questions.
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Affiliation(s)
- Dermot M F Cooper
- Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, United Kingdom.
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32
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Shah SZA, Zhao D, Khan SH, Yang L. Regulatory Mechanisms of Endoplasmic Reticulum Resident IP3 Receptors. J Mol Neurosci 2015; 56:938-948. [PMID: 25859934 DOI: 10.1007/s12031-015-0551-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 03/23/2015] [Indexed: 11/25/2022]
Abstract
Dysregulated calcium signaling and accumulation of aberrant proteins causing endoplasmic reticulum stress are the early sign of intra-axonal pathological events in many neurodegenerative diseases, and apoptotic signaling is initiated when the stress goes beyond the maximum threshold level of endoplasmic reticulum. The fate of the cell to undergo apoptosis is controlled by Ca2(+) signaling and dynamics at the level of the endoplasmic reticulum. Endoplasmic reticulum resident inositol 1,4,5-trisphosphate receptors (IP3R) play a pivotal role in cell death signaling by mediating Ca2(+) flux from the endoplasmic reticulum into the cytosol and mitochondria. Hence, many prosurvival and prodeath signaling pathways and proteins affect Ca2(+) signaling by directly targeting IP3R channels, which can happen in an IP3R-isoform-dependent manner. Here, in this review, we summarize the regulatory mechanisms of inositol triphosphate receptors in calcium regulation and initiation of apoptosis during unfolded protein response.
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Affiliation(s)
- Syed Zahid Ali Shah
- State Key Laboratories for Agrobiotechnology, Key Lab of Animal Epidemiology and Zoonosis, Ministry of Agriculture, National Animal Transmissible Spongiform Encephalopathy Laboratory, College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China
| | - Deming Zhao
- State Key Laboratories for Agrobiotechnology, Key Lab of Animal Epidemiology and Zoonosis, Ministry of Agriculture, National Animal Transmissible Spongiform Encephalopathy Laboratory, College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China
| | - Sher Hayat Khan
- State Key Laboratories for Agrobiotechnology, Key Lab of Animal Epidemiology and Zoonosis, Ministry of Agriculture, National Animal Transmissible Spongiform Encephalopathy Laboratory, College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China
| | - Lifeng Yang
- State Key Laboratories for Agrobiotechnology, Key Lab of Animal Epidemiology and Zoonosis, Ministry of Agriculture, National Animal Transmissible Spongiform Encephalopathy Laboratory, College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China.
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Mak DOD, Foskett JK. Inositol 1,4,5-trisphosphate receptors in the endoplasmic reticulum: A single-channel point of view. Cell Calcium 2014; 58:67-78. [PMID: 25555684 DOI: 10.1016/j.ceca.2014.12.008] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Revised: 12/09/2014] [Accepted: 12/10/2014] [Indexed: 10/24/2022]
Abstract
As an intracellular Ca(2+) release channel at the endoplasmic reticulum membrane, the ubiquitous inositol 1,4,5-trisphosphate (InsP3) receptor (InsP3R) plays a crucial role in the generation, propagation and regulation of intracellular Ca(2+) signals that regulate numerous physiological and pathophysiological processes. This review provides a concise account of the fundamental single-channel properties of the InsP3R channel: its conductance properties and its regulation by InsP3 and Ca(2+), its physiological ligands, studied using nuclear patch clamp electrophysiology.
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Affiliation(s)
- Don-On Daniel Mak
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States.
| | - J Kevin Foskett
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States; Department of Cell and Developmental Biology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States
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Vervloessem T, Yule DI, Bultynck G, Parys JB. The type 2 inositol 1,4,5-trisphosphate receptor, emerging functions for an intriguing Ca²⁺-release channel. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1853:1992-2005. [PMID: 25499268 DOI: 10.1016/j.bbamcr.2014.12.006] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2014] [Revised: 12/02/2014] [Accepted: 12/03/2014] [Indexed: 12/19/2022]
Abstract
The inositol 1,4,5-trisphosphate (IP3) receptor (IP3R) type 2 (IP3R2) is an intracellular Ca²⁺-release channel located on the endoplasmic reticulum (ER). IP3R2 is characterized by a high sensitivity to both IP3 and ATP and is biphasically regulated by Ca²⁺. Furthermore, IP3R2 is modulated by various protein kinases. In addition to its regulation by protein kinase A, IP3R2 forms a complex with adenylate cyclase 6 and is directly regulated by cAMP. Finally, in the ER, IP3R2 is less mobile than the other IP3R isoforms, while its functional properties appear dominant in heterotetramers. These properties make the IP3R2 a Ca²⁺ channel with exquisite properties for setting up intracellular Ca²⁺ signals with unique characteristics. IP3R2 plays a crucial role in the function of secretory cell types (e.g. pancreatic acinar cells, hepatocytes, salivary gland, eccrine sweat gland). In cardiac myocytes, the role of IP3R2 appears more complex, because, together with IP3R1, it is needed for normal cardiogenesis, while its aberrant activity is implicated in cardiac hypertrophy and arrhythmias. Most importantly, its high sensitivity to IP3 makes IP3R2 a target for anti-apoptotic proteins (e.g. Bcl-2) in B-cell cancers. Disrupting IP3R/Bcl-2 interaction therefore leads in those cells to increased Ca²⁺ release and apoptosis. Intriguingly, IP3R2 is not only implicated in apoptosis but also in the induction of senescence, another tumour-suppressive mechanism. These results were the first to unravel the physiological and pathophysiological role of IP3R2 and we anticipate that further progress will soon be made in understanding the function of IP3R2 in various tissues and organs.
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Affiliation(s)
- Tamara Vervloessem
- KU Leuven, Laboratory of Molecular and Cellular Signalling, Department of Cellular and Molecular Medicine, Leuven, Belgium
| | - David I Yule
- University of Rochester, Department of Pharmacology and Physiology, Rochester, NY, USA
| | - Geert Bultynck
- KU Leuven, Laboratory of Molecular and Cellular Signalling, Department of Cellular and Molecular Medicine, Leuven, Belgium
| | - Jan B Parys
- KU Leuven, Laboratory of Molecular and Cellular Signalling, Department of Cellular and Molecular Medicine, Leuven, Belgium.
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35
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Ivanova H, Vervliet T, Missiaen L, Parys JB, De Smedt H, Bultynck G. Inositol 1,4,5-trisphosphate receptor-isoform diversity in cell death and survival. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:2164-83. [PMID: 24642269 DOI: 10.1016/j.bbamcr.2014.03.007] [Citation(s) in RCA: 142] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Revised: 03/06/2014] [Accepted: 03/09/2014] [Indexed: 01/22/2023]
Abstract
Cell-death and -survival decisions are critically controlled by intracellular Ca(2+) homeostasis and dynamics at the level of the endoplasmic reticulum (ER). Inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs) play a pivotal role in these processes by mediating Ca(2+) flux from the ER into the cytosol and mitochondria. Hence, it is clear that many pro-survival and pro-death signaling pathways and proteins affect Ca(2+) signaling by directly targeting IP3R channels, which can happen in an IP3R-isoform-dependent manner. In this review, we will focus on how the different IP3R isoforms (IP3R1, IP3R2 and IP3R3) control cell death and survival. First, we will present an overview of the isoform-specific regulation of IP3Rs by cellular factors like IP3, Ca(2+), Ca(2+)-binding proteins, adenosine triphosphate (ATP), thiol modification, phosphorylation and interacting proteins, and of IP3R-isoform specific expression patterns. Second, we will discuss the role of the ER as a Ca(2+) store in cell death and survival and how IP3Rs and pro-survival/pro-death proteins can modulate the basal ER Ca(2+) leak. Third, we will review the regulation of the Ca(2+)-flux properties of the IP3R isoforms by the ER-resident and by the cytoplasmic proteins involved in cell death and survival as well as by redox regulation. Hence, we aim to highlight the specific roles of the various IP3R isoforms in cell-death and -survival signaling. This article is part of a Special Issue entitled: Calcium signaling in health and disease. Guest Editors: Geert Bultynck, Jacques Haiech, Claus W. Heizmann, Joachim Krebs, and Marc Moreau.
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Affiliation(s)
- Hristina Ivanova
- KU Leuven Lab. of Molecular and Cellular Signaling, Dept. of Cellular and Molecular Medicine, Campus Gasthuisberg O&N I Box 802, Herestraat 49, BE-3000 Leuven, Belgium
| | - Tim Vervliet
- KU Leuven Lab. of Molecular and Cellular Signaling, Dept. of Cellular and Molecular Medicine, Campus Gasthuisberg O&N I Box 802, Herestraat 49, BE-3000 Leuven, Belgium
| | - Ludwig Missiaen
- KU Leuven Lab. of Molecular and Cellular Signaling, Dept. of Cellular and Molecular Medicine, Campus Gasthuisberg O&N I Box 802, Herestraat 49, BE-3000 Leuven, Belgium
| | - Jan B Parys
- KU Leuven Lab. of Molecular and Cellular Signaling, Dept. of Cellular and Molecular Medicine, Campus Gasthuisberg O&N I Box 802, Herestraat 49, BE-3000 Leuven, Belgium
| | - Humbert De Smedt
- KU Leuven Lab. of Molecular and Cellular Signaling, Dept. of Cellular and Molecular Medicine, Campus Gasthuisberg O&N I Box 802, Herestraat 49, BE-3000 Leuven, Belgium.
| | - Geert Bultynck
- KU Leuven Lab. of Molecular and Cellular Signaling, Dept. of Cellular and Molecular Medicine, Campus Gasthuisberg O&N I Box 802, Herestraat 49, BE-3000 Leuven, Belgium.
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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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37
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cAMP and Ca²⁺ signaling in secretory epithelia: crosstalk and synergism. Cell Calcium 2014; 55:385-93. [PMID: 24613710 DOI: 10.1016/j.ceca.2014.01.006] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Revised: 01/29/2014] [Accepted: 01/30/2014] [Indexed: 12/15/2022]
Abstract
The Ca(2+) and cAMP/PKA pathways are the primary signaling systems in secretory epithelia that control virtually all secretory gland functions. Interaction and crosstalk in Ca(2+) and cAMP signaling occur at multiple levels to control and tune the activity of each other. Physiologically, Ca(2+) and cAMP signaling operate at 5-10% of maximal strength, but synergize to generate the maximal response. Although synergistic action of the Ca(2+) and cAMP signaling is the common mode of signaling and has been known for many years, we know very little of the molecular mechanism and mediators of the synergism. In this review, we discuss crosstalk between the Ca(2+) and cAMP signaling and the function of IRBIT (IP3 receptors binding protein release with IP3) as a third messenger that mediates the synergistic action of the Ca(2+) and cAMP signaling.
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Hong JH, Park S, Shcheynikov N, Muallem S. Mechanism and synergism in epithelial fluid and electrolyte secretion. Pflugers Arch 2013; 466:1487-99. [PMID: 24240699 DOI: 10.1007/s00424-013-1390-1] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Revised: 10/16/2013] [Accepted: 10/17/2013] [Indexed: 01/04/2023]
Abstract
A central function of epithelia is the control of the volume and electrolyte composition of bodily fluids through vectorial transport of electrolytes and the obligatory H2O. In exocrine glands, fluid and electrolyte secretion is carried out by both acinar and duct cells, with the portion of fluid secreted by each cell type varying among glands. All acinar cells secrete isotonic, plasma-like fluid, while the duct determines the final electrolyte composition of the fluid by absorbing most of the Cl(-) and secreting HCO3 (-). The key transporters mediating acinar fluid and electrolyte secretion are the basolateral Na(+)/K(+) /2Cl(-) cotransporter, the luminal Ca(2+)-activated Cl(-) channel ANO1 and basolateral and luminal Ca(2+)-activated K(+) channels. Ductal fluid and HCO3 (-) secretion are mediated by the basolateral membrane Na(+)-HCO3 (-) cotransporter NBCe1-B and the luminal membrane Cl(-)/HCO3 (-) exchanger slc26a6 and the Cl(-) channel CFTR. The function of the transporters is regulated by multiple inputs, which in the duct include major regulation by the WNK/SPAK pathway that inhibit secretion and the IRBIT/PP1 pathway that antagonize the effects of the WNK/SPAK pathway to both stimulate and coordinate the secretion. The function of these regulatory pathways in secretory glands acinar cells is yet to be examined. An important concept in biology is synergism among signaling pathways to generate the final physiological response that ensures regulation with high fidelity and guards against cell toxicity. While synergism is observed in all epithelial functions, the molecular mechanism mediating the synergism is not known. Recent work reveals a central role for IRBIT as a third messenger that integrates and synergizes the function of the Ca(2+) and cAMP signaling pathways in activation of epithelial fluid and electrolyte secretion. These concepts are discussed in this review using secretion by the pancreatic and salivary gland ducts as model systems.
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Affiliation(s)
- Jeong Hee Hong
- Epithelial Signaling and Transport Section, Molecular Physiology and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institute of Health, Bethesda, MD, 20892, USA
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39
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Mak DOD, Vais H, Cheung KH, Foskett JK. Patch-clamp electrophysiology of intracellular Ca2+ channels. Cold Spring Harb Protoc 2013; 2013:787-97. [PMID: 24003191 DOI: 10.1101/pdb.top066217] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The modulation of cytoplasmic free Ca(2+) concentration ([Ca(2+)]i) is a universal intracellular signaling pathway that regulates numerous cellular physiological processes. Ubiquitous intracellular Ca(2+)-release channels localized to the endoplasmic/sarcoplasmic reticulum-inositol 1,4,5-trisphosphate receptor (InsP3R) and ryanodine receptor (RyR) channels-play a central role in [Ca(2+)]i signaling in all animal cells. Despite their intracellular localization, electrophysiological studies of the single-channel permeation and gating properties of these Ca(2+)-release channels using the powerful patch-clamp approach have been possible by application of this technique to isolated nuclei because the channels are present in membranes of the nuclear envelope. Here we provide a concise description of how nuclear patch-clamp experiments have been used to study single-channel properties of different InsP3R channels in the outer nuclear membrane. We compare this with other methods for studying intracellular Ca(2+) release. We also briefly describe application of the technique to InsP3R channels in the inner nuclear membrane and to channels in the outer nuclear membrane of HEK293 cells expressing recombinant RyR.
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Affiliation(s)
- Don-On Daniel Mak
- Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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40
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Tovey SC, Taylor CW. Cyclic AMP directs inositol (1,4,5)-trisphosphate-evoked Ca2+ signalling to different intracellular Ca2+ stores. J Cell Sci 2013; 126:2305-13. [PMID: 23525004 DOI: 10.1242/jcs.126144] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Cholesterol depletion reversibly abolishes carbachol-evoked Ca(2+) release from inositol (1,4,5)-trisphosphate (IP3)-sensitive stores, without affecting the distribution of IP3 receptors (IP3R) or endoplasmic reticulum, IP3 formation or responses to photolysis of caged IP3. Receptors that stimulate cAMP formation do not alone evoke Ca(2+) signals, but they potentiate those evoked by carbachol. We show that these potentiated signals are entirely unaffected by cholesterol depletion and that, within individual cells, different IP3-sensitive Ca(2+) stores are released by carbachol alone and by carbachol combined with receptors that stimulate cAMP formation. We suggest that muscarinic acetylcholine receptors in lipid rafts deliver IP3 at high concentration to associated IP3R, stimulating them to release Ca(2+). Muscarinic receptors outside rafts are less closely associated with IP3R and provide insufficient local IP3 to activate IP3R directly. These IP3R, probably type 2 IP3R within a discrete Ca(2+) store, are activated only when their sensitivity is increased by cAMP. Sensitization of IP3R by cAMP extends the effective range of signalling by phospholipase C, allowing muscarinic receptors that are otherwise ineffective to recruit additional IP3-sensitive Ca(2+) stores.
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Affiliation(s)
- Stephen C Tovey
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
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41
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Alzayady KJ, Chandrasekhar R, Yule DI. Fragmented inositol 1,4,5-trisphosphate receptors retain tetrameric architecture and form functional Ca2+ release channels. J Biol Chem 2013; 288:11122-34. [PMID: 23479737 DOI: 10.1074/jbc.m113.453241] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Inositol 1,4,5-trisphosphate receptor isoforms are a family of ubiquitously expressed ligand-gated channels encoded by three individual genes. The proteins are localized to membranes of intracellular Ca(2+) stores and play pivotal roles in Ca(2+) homeostasis. Previous studies have demonstrated that IP3R1 is cleaved by the intracellular proteases calpain and caspase both in vivo and in vitro. However, the resultant cleavage products are poorly defined, and the functional consequences of these proteolytic events are not fully understood. We demonstrate that IP3R1 is cleaved during staurosporine-induced apoptosis, yielding N-terminal fragments encompassing the ligand-binding domain and the majority of the central modulatory domain together with a C-terminal fragment containing the channel domain and cytosolic tail. Notably, these fragments remain associated with the membrane after initiation of apoptotic cleavage. Furthermore, when recombinant IP3R1 fragments, corresponding to those predicted to be generated by caspase or calpain cleavage, are stably coexpressed in cells, they physically associate and form functional channels. These data provide novel insights regarding the regulation of IP3R1 during proteolysis and provide direct evidence that polypeptide continuity is not required for IP3R activation and Ca(2+) release.
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Affiliation(s)
- Kamil J Alzayady
- Department of Pharmacology and Physiology, University of Rochester, Rochester, New York 14642, USA
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42
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Fechner L, Baumann O, Walz B. Activation of the cyclic AMP pathway promotes serotonin-induced Ca2+ oscillations in salivary glands of the blowfly Calliphora vicina. Cell Calcium 2012; 53:94-101. [PMID: 23131569 DOI: 10.1016/j.ceca.2012.10.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Revised: 10/12/2012] [Accepted: 10/12/2012] [Indexed: 11/28/2022]
Abstract
Ca(2+) and cAMP signalling pathways interact in a complex manner at multiple sites. This crosstalk fine-tunes the spatiotemporal patterns of Ca(2+) and cAMP signals. In salivary glands of the blowfly Calliphora vicina fluid secretion is stimulated by serotonin (5-hydroxytryptamine, 5-HT) via activation of two different 5-HT receptors coupled to the InsP(3)/Ca(2+) (Cv5-HT(2α)) or the cAMP pathway (Cv5-HT(7)), respectively. We have shown recently in permeabilized gland cells that cAMP sensitizes InsP(3)-induced Ca(2+) release to InsP(3). Here we study the effects of the cAMP signalling pathway on 5-HT-induced oscillations in transepithelial potential (TEP) and in intracellular [Ca(2+)]. We show: (1) Blocking the activation of the cAMP pathway by cinanserin suppresses the generation of TEP and Ca(2+) oscillations, (2) application of 8-CPT-cAMP in the presence of cinanserin restores 5-HT-induced TEP and Ca(2+) oscillations, (3) 8-CPT-cAMP sensitizes the InsP(3)/Ca(2+) signalling pathway to 5-HT and the Cv5-HT(2α) receptor agonist 5-MeOT, (4) 8-CPT-cAMP induces Ca(2+) oscillations in cells loaded with subthreshold concentrations of InsP(3), (5) inhibition of protein kinase A by H-89 abolishes 5-HT-induced TEP and Ca(2+) spiking and mimics the effect of cinanserin. These results suggest that activation of the cyclic AMP pathway promotes the generation of 5-HT-induced Ca(2+) oscillations in blowfly salivary glands.
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Affiliation(s)
- Lennart Fechner
- Institute of Biochemistry and Biology, Department of Animal Physiology, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany
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43
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Béliveau È, Lapointe F, Guillemette G. The activation state of the inositol 1,4,5-trisphosphate receptor regulates the velocity of intracellular Ca2+ waves in bovine aortic endothelial cells. J Cell Biochem 2012; 112:3722-31. [PMID: 21815194 DOI: 10.1002/jcb.23301] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Ca(2+) is a highly versatile second messenger that plays a key role in the regulation of many cell processes. This versatility resides in the fact that different signals can be encoded spatio-temporally by varying the frequency and amplitude of the Ca(2+) response. A typical example of an organized Ca(2+) signal is a Ca(2+) wave initiated in a given area of a cell that propagates throughout the entire cell or within a specific subcellular region. In non-excitable cells, the inositol 1,4,5-trisphosphate receptor (IP(3) R) is responsible for the release of Ca(2+) from the endoplasmic reticulum. IP(3) R activity can be directly modulated in many ways, including by interacting molecules, proteins, and kinases such as PKA, PKC, and mTOR. In the present study, we used a videomicroscopic approach to measure the velocity of Ca(2+) waves in bovine aortic endothelial cells under various conditions that affect IP(3) R function. The velocity of the Ca(2+) waves increased with the intensity of the stimulus while extracellular Ca(2+) had no significant impact on wave velocity. Forskolin increased the velocity of IP(3) R-dependent Ca(2+) waves whereas PMA and rapamycin decreased the velocity. We used scatter plots and Pearson's correlation test to visualize and quantify the relationship between the Ca(2+) peak amplitude and the velocity of Ca(2+) waves. The velocity of IP(3) R-dependent Ca(2+) waves poorly correlated with the amplitude of the Ca(2+) response elicited by agonists in all the conditions evaluated, indicating that the velocity depended on the activation state of IP(3) R, which can be modulated in many ways.
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Affiliation(s)
- Èric Béliveau
- Faculty of Medicine and Health Sciences, Department of Pharmacology, Université de Sherbrooke, Sherbrooke, Quebec, J1H 5N4, Canada
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44
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Park HS, Betzenhauser MJ, Zhang Y, Yule DI. Regulation of Ca²⁺ release through inositol 1,4,5-trisphosphate receptors by adenine nucleotides in parotid acinar cells. Am J Physiol Gastrointest Liver Physiol 2012; 302:G97-G104. [PMID: 21960523 PMCID: PMC3345966 DOI: 10.1152/ajpgi.00328.2011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Secretagogue-stimulated intracellular Ca(2+) signals are fundamentally important for initiating the secretion of the fluid and ion component of saliva from parotid acinar cells. The Ca(2+) signals have characteristic spatial and temporal characteristics, which are defined by the specific properties of Ca(2+) release mediated by inositol 1,4,5-trisphosphate receptors (InsP(3)R). In this study we have investigated the role of adenine nucleotides in modulating Ca(2+) release in mouse parotid acinar cells. In permeabilized cells, the Ca(2+) release rate induced by submaximal [InsP(3)] was increased by 5 mM ATP. Enhanced Ca(2+) release was not observed at saturating [InsP(3)]. The EC(50) for the augmented Ca(2+) release was ∼8 μM ATP. The effect was mimicked by nonhydrolysable ATP analogs. ADP and AMP also potentiated Ca(2+) release but were less potent than ATP. In acini isolated from InsP(3)R-2-null transgenic animals, the rate of Ca(2+) release was decreased under all conditions but now enhanced by ATP at all [InsP(3)]. In addition the EC(50) for ATP potentiation increased to ∼500 μM. These characteristics are consistent with the properties of the InsP(3)R-2 dominating the overall features of InsP(3)R-induced Ca(2+) release despite the expression of all isoforms. Finally, Ca(2+) signals were measured in intact parotid lobules by multiphoton microscopy. Consistent with the release data, carbachol-stimulated Ca(2+) signals were reduced in lobules exposed to experimental hypoxia compared with control lobules only at submaximal concentrations. Adenine nucleotide modulation of InsP(3)R in parotid acinar cells likely contributes to the properties of Ca(2+) signals in physiological and pathological conditions.
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Affiliation(s)
- Hyung Seo Park
- University of Rochester Medical Center, Department of Pharmacology and Physiology, University of Rochester, Rochester, New York
| | - Matthew J. Betzenhauser
- University of Rochester Medical Center, Department of Pharmacology and Physiology, University of Rochester, Rochester, New York
| | - Yu Zhang
- University of Rochester Medical Center, Department of Pharmacology and Physiology, University of Rochester, Rochester, New York
| | - David I. Yule
- University of Rochester Medical Center, Department of Pharmacology and Physiology, University of Rochester, Rochester, New York
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45
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Pantazaka E, Taylor CW. Differential distribution, clustering, and lateral diffusion of subtypes of the inositol 1,4,5-trisphosphate receptor. J Biol Chem 2011; 286:23378-87. [PMID: 21550988 PMCID: PMC3123102 DOI: 10.1074/jbc.m111.236372] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Revised: 04/27/2011] [Indexed: 01/19/2023] Open
Abstract
Regulation of inositol 1,4,5-trisphosphate (IP(3)) receptors (IP(3)R) by IP(3) and Ca(2+) allows them to initiate and regeneratively propagate intracellular Ca(2+) signals. The distribution and mobility of IP(3)R determines the spatial organization of these Ca(2+) signals. Until now, there has been no systematic comparison of the distribution and mobility of the three mammalian IP(3)R subtypes in a uniform background. We used confocal microscopy and fluorescence recovery after photobleaching to define these properties for each IP(3)R subtype expressed heterologously in COS-7 cells. IP(3)R1 and IP(3)R3 were uniformly distributed within the membranes of the endoplasmic reticulum (ER), but the distribution of IP(3)R2 was punctate. The mobile fractions (M(f) = 84 ± 2 and 80 ± 2%) and diffusion coefficients (D = 0.018 ± 0.001 and 0.016 ± 0.002 μm(2)/s) of IP(3)R1 and IP(3)R3 were similar. Other ER membrane proteins (ryanodine receptor type 1 and sarco/endoplasmic reticulum Ca(2+)-ATPase type 1) and a luminal protein (enhanced GFP with a KDEL retrieval sequence) had similar mobile fractions, suggesting that IP(3)R1 and IP(3)R3 move freely within an ER that is largely, although not entirely, continuous. IP(3)R2 was less mobile, but IP(3)R2 mobility differed between perinuclear (M(f) = 47 ± 4% and D = 0.004 ± 0.001 μm(2)/s) and near-plasma membrane (M(f) = 64 ± 6% and D = 0.013 ± 0.004 μm(2)/s) regions, whereas IP(3)R3 behaved similarly in both regions. We conclude that IP(3)R1 and IP(3)R3 diffuse freely within a largely continuous ER, but IP(3)R2 is more heterogeneously distributed and less mobile, and its mobility differs between regions of the cell.
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Affiliation(s)
- Evangelia Pantazaka
- From the Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, United Kingdom
| | - Colin W. Taylor
- From the Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, United Kingdom
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Erlbruch A, Hung CW, Seidler J, Borrmann K, Gesellchen F, König N, Kübler D, Herberg FW, Lehmann WD, Bossemeyer D. Uncoupling of bait-protein expression from the prey protein environment adds versatility for cell and tissue interaction proteomics and reveals a complex of CARP-1 and the PKA Cbeta1 subunit. Proteomics 2010; 10:2890-900. [PMID: 20564261 DOI: 10.1002/pmic.200900593] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
An expression-uncoupled tandem affinity purification assay is introduced which differs from the standard TAP assay by uncoupling the expression of the TAP-bait protein from the target cells. Here, the TAP-tagged bait protein is expressed in Escherichia coli and purified. The two concatenated purification steps of the classical TAP are performed after addition of the purified bait to brain tissue homogenates, cell and nuclear extracts. Without prior genetic manipulation of the target, upscaling, free choice of cell compartments and avoidance of expression triggered heat shock responses could be achieved in one go. By the strategy of separating bait expression from the prey protein environment numerous established, mostly tissue-specific binding partners of the protein kinase A catalytic subunit Cbeta1 were identified, including interactions in binary, ternary and quaternary complexes. In addition, the previously unknown small molecule inhibitor-dependent interaction of Cbeta1 with the cell cycle and apoptosis regulatory protein-1 was verified. The uncoupled tandem affinity purification procedure presented here expands the application range of the in vivo TAP assay and may serve as a simple strategy for identifying cell- and tissue-specific protein complexes.
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Affiliation(s)
- Andrea Erlbruch
- Structural Biochemistry, German Cancer Research Center, Heidelberg, Germany.
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47
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Sliter DA, Aguiar M, Gygi SP, Wojcikiewicz RJH. Activated inositol 1,4,5-trisphosphate receptors are modified by homogeneous Lys-48- and Lys-63-linked ubiquitin chains, but only Lys-48-linked chains are required for degradation. J Biol Chem 2010; 286:1074-82. [PMID: 21071436 DOI: 10.1074/jbc.m110.188383] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Inositol 1,4,5-trisphosphate (IP(3)) receptors (IP(3)Rs) are large, ubiquitously expressed, endoplasmic reticulum membrane proteins that form tetrameric IP(3) and Ca(2+)-gated Ca(2+) channels. Endogenous IP(3)Rs provide very appealing tools for studying the ubiquitin-proteasome pathway in intact mammalian cells because, upon activation, they are rapidly ubiquitinated and degraded. Using mass spectrometry, we previously examined the ubiquitination of IP(3)R1 in αT3-1 pituitary gonadotrophs and found that IP(3)R1 ubiquitination is highly complex, with receptors being modified at multiple sites by monoubiquitin and polyubiquitin chains formed through both Lys-48 and Lys-63 linkages (Sliter, D. A., Kubota, K., Kirkpatrick, D. S., Alzayady, K. J., Gygi, S. P., and Wojcikiewicz, R. J. H. (2008) J. Biol. Chem. 283, 35319-35328). Here, we have extended these studies to determine whether IP(3)R2 and IP(3)R3 are similarly modified and if ubiquitination is cell type-dependent. Using mass spectrometry and linkage-specific ubiquitin antibodies, we found that all IP(3)R types are subject to ubiquitination at approximately the same locations and that, independent of cell type, IP(3)Rs are modified by monoubiquitin and Lys-48- and Lys-63-linked ubiquitin chains, although in differing proportions. Remarkably, the attached Lys-48- and Lys-63-linked ubiquitin chains are homogeneous and are segregated to separate IP(3)R subunits, and Lys-48-linked ubiquitin chains, but not Lys-63-linked chains, are required for IP(3)R degradation. Together, these data provide unique insight into the complexities of ubiquitination of an endogenous ubiquitin-proteasome pathway substrate in unperturbed mammalian cells. Importantly, although Lys-48-linked ubiquitin chains appear to trigger proteasomal degradation, the presence of Lys-63-linked ubiquitin chains suggests that ubiquitination of IP(3)Rs may have physiological consequences beyond signaling for degradation.
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Affiliation(s)
- Danielle A Sliter
- Department of Pharmacology, State University of New York Upstate Medical University, Syracuse, New York 13210, USA
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48
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Masuda W, Betzenhauser MJ, Yule DI. InsP3R-associated cGMP kinase substrate determines inositol 1,4,5-trisphosphate receptor susceptibility to phosphoregulation by cyclic nucleotide-dependent kinases. J Biol Chem 2010; 285:37927-38. [PMID: 20876535 DOI: 10.1074/jbc.m110.168989] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ca(2+) release through inositol 1,4,5-trisphosphate receptors (InsP(3)R) can be modulated by numerous factors, including input from other signal transduction cascades. These events shape the spatio-temporal characteristics of the Ca(2+) signal and provide fidelity essential for the appropriate activation of effectors. In this study, we investigate the regulation of Ca(2+) release via InsP(3)R following activation of cyclic nucleotide-dependent kinases in the presence and absence of expression of a binding partner InsP(3)R-associated cGMP kinase substrate (IRAG). cGMP-dependent kinase (PKG) phosphorylation of only the S2+ InsP(3)R-1 subtype resulted in enhanced Ca(2+) release in the absence of IRAG expression. In contrast, IRAG bound to each InsP(3)R subtype, and phosphorylation of IRAG by PKG attenuated Ca(2+) release through all InsP(3)R subtypes. Surprisingly, simply the expression of IRAG attenuated phosphorylation and inhibited the enhanced Ca(2+) release through InsP(3)R-1 following cAMP-dependent protein kinase (PKA) activation. In contrast, IRAG expression did not influence the PKA-enhanced activity of the InsP(3)R-2. Phosphorylation of IRAG resulted in reduced Ca(2+) release through all InsP(3)R subtypes during concurrent activation of PKA and PKG, indicating that IRAG modulation is dominant under these conditions. These studies yield mechanistic insight into how cells with various complements of proteins integrate and prioritize signals from ubiquitous signaling pathways.
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Affiliation(s)
- Wataru Masuda
- Department of Pharmacology and Physiology, University of Rochester Medical School, Rochester, New York 14642, USA
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49
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Betzenhauser MJ, Yule DI. Regulation of inositol 1,4,5-trisphosphate receptors by phosphorylation and adenine nucleotides. CURRENT TOPICS IN MEMBRANES 2010; 66:273-98. [PMID: 22353484 DOI: 10.1016/s1063-5823(10)66012-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Affiliation(s)
- Matthew J Betzenhauser
- Department of Physiology and Cellular Biophysics, Columbia University Medical School, New York City, New York, USA
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50
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Nakayama H, Bodi I, Maillet M, DeSantiago J, Domeier TL, Mikoshiba K, Lorenz JN, Blatter LA, Bers DM, Molkentin JD. The IP3 receptor regulates cardiac hypertrophy in response to select stimuli. Circ Res 2010; 107:659-66. [PMID: 20616315 DOI: 10.1161/circresaha.110.220038] [Citation(s) in RCA: 140] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
RATIONALE Inositol 1,4,5-trisphosphate (IP(3)) is a second messenger that regulates intracellular Ca(2+) release through IP(3) receptors located in the sarco(endo)plasmic reticulum of cardiac myocytes. Many prohypertrophic G protein-coupled receptor (GPCR) signaling events lead to IP(3) liberation, although its importance in transducing the hypertrophic response has not been established in vivo. OBJECTIVE Here, we generated conditional, heart-specific transgenic mice with both gain- and loss-of-function for IP(3) receptor signaling to examine its hypertrophic growth effects following pathological and physiological stimulation. METHODS AND RESULTS Overexpression of the mouse type-2 IP(3) receptor (IP(3)R2) in the heart generated mild baseline cardiac hypertrophy at 3 months of age. Isolated myocytes from overexpressing lines showed increased Ca(2+) transients and arrhythmias in response to endothelin-1 stimulation. Although low levels of IP(3)R2 overexpression failed to augment/synergize cardiac hypertrophy following 2 weeks of pressure-overload stimulation, such levels did enhance hypertrophy following 2 weeks of isoproterenol infusion, in response to Galphaq overexpression, and/or in response to exercise stimulation. To inhibit IP(3) signaling in vivo, we generated transgenic mice expressing an IP(3) chelating protein (IP(3)-sponge). IP(3)-sponge transgenic mice abrogated cardiac hypertrophy in response to isoproterenol and angiotensin II infusion but not pressure-overload stimulation. Mechanistically, IP(3)R2-enhanced cardiac hypertrophy following isoproterenol infusion was significantly reduced in the calcineurin-Abeta-null background. CONCLUSION These results indicate that IP(3)-mediated Ca(2+) release plays a central role in regulating cardiac hypertrophy downstream of GPCR signaling, in part, through a calcineurin-dependent mechanism.
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Affiliation(s)
- Hiroyuki Nakayama
- Howard Hughes Medical Institute, Cincinnati Children's Hospital Medical Center, 240 Albert Sabin Way, Cincinnati, OH 45229-3039, USA
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