1
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Wu KC, Leong IL, Leung YM. Ca 2+-sensing receptor-TRP channel-mediated Ca 2+ signaling: Functional diversity and pharmacological complexity. Eur J Pharmacol 2024; 977:176717. [PMID: 38857682 DOI: 10.1016/j.ejphar.2024.176717] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Revised: 05/07/2024] [Accepted: 06/05/2024] [Indexed: 06/12/2024]
Abstract
The Ca2+-sensing receptor (CaSR) is a G-protein-coupled receptor activated by elevated concentrations of extracellular Ca2+, and was initially known for its regulation of parathyroid hormone (PTH) release. Ubiquitous expression of CaSR in different tissues and organs was later noted and CaSR participation in various physiological functions was demonstrated. Accumulating evidence has suggested that CaSR functionally interacts with transient receptor potential (TRP) channels, which are mostly non-selective cation channels involved in sensing temperature, pain and stress. This review describes the interactions of CaSR with TRP channels in diverse cell types to trigger a variety of biological responses. CaSR has been known to interact with different types of G proteins. Possible involvements of G proteins, other signaling and scaffolding protein intermediates in CaSR-TRP interaction are discussed. In addition, an attempt will be made to extend the current understanding of biased agonism of CaSR.
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Affiliation(s)
- King-Chuen Wu
- Department of Anesthesiology, Chang Gung Memorial Hospital, Chiayi, Taiwan; Chang Gung University of Science and Technology, Chiayi, Taiwan; Shu-Zen Junior College of Medicine and Management, Kaohsiung, Taiwan
| | - Iat-Lon Leong
- Division of Cardiology, University Hospital, Macau University of Science and Technology, Macau
| | - Yuk-Man Leung
- Department of Physiology, China Medical University, Taichung, Taiwan.
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2
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Zhai Y, Chan WWR, Li W, Lau KF. ARNO is recruited by the neuronal adaptor FE65 to potentiate ARF6-mediated neurite outgrowth. Open Biol 2022; 12:220071. [PMID: 36168805 PMCID: PMC9516341 DOI: 10.1098/rsob.220071] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
ADP-ribosylation factor 6 (ARF6) is a small GTPase that has a variety of neuronal functions including stimulating neurite outgrowth, a crucial process for the establishment and maintenance of neural connectivity. As impaired and atrophic neurites are often observed in various brain injuries and neurological diseases, understanding the intrinsic pathways that stimulate neurite outgrowth may provide insights into developing strategies to trigger the reconnection of injured neurons. The neuronal adaptor FE65 has been shown to interact with ARF6 and potentiate ARF6-mediated neurite outgrowth. However, the precise mechanism that FE65 activates ARF6 remains unclear, as FE65 does not possess a guanine nucleotide exchange factor (GEF) domain/function. Here, we show that FE65 interacts with the ARF6 GEF, namely the ARF nucleotide-binding site opener (ARNO). Moreover, a complex consisting of ARNO, ARF6 and FE65 is detected. Notably, FE65 potentiates the stimulatory effect of ARNO on ARF6-mediated neurite outgrowth, and the effect of FE65 is abrogated by an FE65 mutation that disrupts FE65–ARNO interaction. Additionally, the intramolecular interaction for mediating the autoinhibited conformation of ARNO is attenuated by FE65. Moreover, FE65 potentiates the effects of wild-type ARNO, but not the monomeric mutant, suggesting an association between FE65 and ARNO dimerization. Collectively, we demonstrate that FE65 binds to and activates ARNO and, consequently, potentiates ARF6-mediated neurite outgrowth.
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Affiliation(s)
- Yuqi Zhai
- School of Life Sciences, Faculty of Science, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, People's Republic of China
| | - Wai Wa Ray Chan
- School of Life Sciences, Faculty of Science, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, People's Republic of China
| | - Wen Li
- School of Life Sciences, Faculty of Science, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, People's Republic of China.,Research Laboratory for Biomedical Optics and Molecular Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, People's Republic of China
| | - Kwok-Fai Lau
- School of Life Sciences, Faculty of Science, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, People's Republic of China
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3
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Ito A, Fukaya M, Okamoto H, Sakagami H. Physiological and Pathological Roles of the Cytohesin Family in Neurons. Int J Mol Sci 2022; 23:5087. [PMID: 35563476 PMCID: PMC9104363 DOI: 10.3390/ijms23095087] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2022] [Revised: 05/01/2022] [Accepted: 05/02/2022] [Indexed: 02/05/2023] Open
Abstract
The cytohesin proteins, consisting of four closely related members (cytohesins-1, -2, -3, and -4), are a subfamily of the Sec7 domain-containing guanine nucleotide exchange factors for ADP ribosylation factors (Arfs), which are critical regulators of membrane trafficking and actin cytoskeleton remodeling. Recent advances in molecular biological techniques and the development of a specific pharmacological inhibitor for cytohesins, SecinH3, have revealed the functional involvement of the cytohesin-Arf pathway in diverse neuronal functions from the formation of axons and dendrites, axonal pathfinding, and synaptic vesicle recycling, to pathophysiological processes including chronic pain and neurotoxicity induced by proteins related to neurodegenerative disorders, such as amyotrophic lateral sclerosis and Alzheimer's disease. Here, we review the physiological and pathological roles of the cytohesin-Arf pathway in neurons and discuss the future directions of this research field.
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Affiliation(s)
- Akiko Ito
- Department of Anesthesiology, Kitasato University School of Medicine, Sagamihara 252-0374, Kanagawa, Japan; (A.I.); (H.O.)
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara 252-0374, Kanagawa, Japan;
| | - Masahiro Fukaya
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara 252-0374, Kanagawa, Japan;
| | - Hirotsugu Okamoto
- Department of Anesthesiology, Kitasato University School of Medicine, Sagamihara 252-0374, Kanagawa, Japan; (A.I.); (H.O.)
| | - Hiroyuki Sakagami
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara 252-0374, Kanagawa, Japan;
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4
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Erdogan BR, Michel MC. Does coupling to ADP ribosylation factor 6 explain differences between muscarinic and other receptors in interaction with β-adrenoceptor-mediated smooth muscle relaxation? Naunyn Schmiedebergs Arch Pharmacol 2022; 395:381-386. [PMID: 35175382 PMCID: PMC8873149 DOI: 10.1007/s00210-022-02221-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Accepted: 02/10/2022] [Indexed: 11/29/2022]
Abstract
Numerous studies in airways, ileum, and urinary bladder have demonstrated that relaxation by β-adrenoceptor agonists has lower potency and/or efficacy when contraction was elicited by muscarinic receptor agonists as compared to other G-protein-coupled receptors, KCl, or basal tone, but the molecular mechanisms behind this relative resistance remain unclear. A paper by Huang et al. in this issue demonstrates that NAV2729, an inhibitor of ADP ribosylation factor 6, inhibits contraction of isolated blood vessels elicited by muscarinic receptor agonists, but not by α1-adrenoceptor agonists or KCl. Against this background, we discuss the role of ADP ribosylation factor 6 in cellular responses to G-protein-coupled receptor stimulation. While ADP ribosylation factor 6 apparently is the only promising molecular explanation for the relative resistance of smooth muscle contraction elicited by muscarinic agonists, the existing data are insufficient for a robust conclusion.
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Affiliation(s)
- Betül R Erdogan
- Department of Pharmacology, Faculty of Pharmacy, Izmir Katip Celebi University, Izmir, Turkey
| | - Martin C Michel
- Department of Pharmacology, Johannes Gutenberg University, Langenbeckstr. 1, 55131, Mainz, Germany.
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5
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Doodnauth SA, Grinstein S, Maxson ME. Constitutive and stimulated macropinocytosis in macrophages: roles in immunity and in the pathogenesis of atherosclerosis. Philos Trans R Soc Lond B Biol Sci 2020; 374:20180147. [PMID: 30967001 DOI: 10.1098/rstb.2018.0147] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Macrophages respond to several stimuli by forming florid membrane ruffles that lead to fluid uptake by macropinocytosis. This type of induced macropinocytosis, executed by a variety of non-malignant and malignant cells, is initiated by transmembrane receptors and is involved in nutrient acquisition and mTOR signalling. However, macrophages also perform a unique type of constitutive ruffling and macropinocytosis that is dependent on the presence of extracellular calcium. Calcium-sensing receptors are responsible for this activity. This distinct form of macropinocytosis enables macrophages to continuously sample their microenvironment for antigenic molecules and for pathogen- and danger-associated molecular patterns, as part of their immune surveillance functions. Interestingly, even within the monocyte lineage, there are differences in macropinocytic ability that reflect the polarized functional roles of distinct macrophage subsets. This review discusses the shared and distinct features of both induced and constitutive macropinocytosis displayed by the macrophage lineage and their roles in physiology, immunity and pathophysiology. In particular, we analyse the role of macropinocytosis in the uptake of modified low-density lipoprotein (LDL) and its contribution to foam cell and atherosclerotic plaque formation. We propose a combined role of scavenger receptors and constitutive macropinocytosis in oxidized LDL uptake, a process we have termed 'receptor-assisted macropinocytosis'. This article is part of the Theo Murphy meeting issue 'Macropinocytosis'.
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Affiliation(s)
- Sasha A Doodnauth
- 1 Princess Margaret Cancer Center, University Health Network , Toronto, ON , Canada M5G 1L7.,2 Department of Medical Biophysics, University of Toronto , Toronto, ON , Canada M5G 1L7
| | - Sergio Grinstein
- 3 Program in Cell Biology, Hospital for Sick Children , 686 Bay Street, Toronto, ON , Canada M5G 0A4.,4 Department of Biochemistry, University of Toronto , 1 King's Circle, Toronto, ON , Canada M5S 1A8.,5 Keenan Research Centre of the Li Ka Shing Knowledge Institute , St. Michael's Hospital, 290 Victoria Street, Toronto, ON , Canada M5C 1N8
| | - Michelle E Maxson
- 3 Program in Cell Biology, Hospital for Sick Children , 686 Bay Street, Toronto, ON , Canada M5G 0A4
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Sensing Extracellular Calcium - An Insight into the Structure and Function of the Calcium-Sensing Receptor (CaSR). ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1131:1031-1063. [PMID: 31646544 DOI: 10.1007/978-3-030-12457-1_41] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The calcium-sensing receptor (CaSR) is a G protein-coupled receptor that plays a key role in calcium homeostasis, by sensing free calcium levels in blood and regulating parathyroid hormone secretion in response. The CaSR is highly expressed in parathyroid gland and kidney where its role is well characterised, but also in other tissues where its function remains to be determined. The CaSR can be activated by a variety of endogenous ligands, as well as by synthetic modulators such as Cinacalcet, used in the clinic to treat secondary hyperparathyroidism in patients with chronic kidney disease. The CaSR couples to multiple G proteins, in a tissue-specific manner, activating several signalling pathways and thus regulating diverse intracellular events. The multifaceted nature of this receptor makes it a valuable therapeutic target for calciotropic and non-calciotropic diseases. It is therefore essential to understand the complexity behind the pharmacology, trafficking, and signalling characteristics of this receptor. This review provides an overview of the latest knowledge about the CaSR and discusses future hot topics in this field.
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7
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Nakhoul NL, Tu CL, Brown KL, Islam MT, Hodges AG, Abdulnour-Nakhoul SM. Calcium-sensing receptor deletion in the mouse esophagus alters barrier function. Am J Physiol Gastrointest Liver Physiol 2020; 318:G144-G161. [PMID: 31709833 PMCID: PMC6985844 DOI: 10.1152/ajpgi.00021.2019] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Calcium-sensing receptor (CaSR) is the molecular sensor by which cells respond to small changes in extracellular Ca2+ concentrations. CaSR has been reported to play a role in glandular and fluid secretion in the gastrointestinal tract and to regulate differentiation and proliferation of skin keratinocytes. CaSR is present in the esophageal epithelium, but its role in this tissue has not been defined. We deleted CaSR in the mouse esophagus by generating keratin 5 CreER;CaSRFlox+/+compound mutants, in which loxP sites flank exon 7 of CaSR gene. Recombination was initiated with multiple tamoxifen injections, and we demonstrated exon 7 deletion by PCR analysis of genomic DNA. Quantitative real-time PCR and Western blot analyses showed a significant reduction in CaSR mRNA and protein expression in the knockout mice (EsoCaSR-/-) as compared with control mice. Microscopic examination of EsoCaSR-/- esophageal tissues showed morphological changes including elongation of the rete pegs, abnormal keratinization and stratification, and bacterial buildup on the luminal epithelial surface. Western analysis revealed a significant reduction in levels of adherens junction proteins E-cadherin and β catenin and tight junction protein claudin-1, 4, and 5. Levels of small GTPase proteins Rac/Cdc42, involved in actin remodeling, were also reduced. Ussing chamber experiments showed a significantly lower transepithelial resistance in knockout (KO) tissues. In addition, luminal-to-serosal-fluorescein dextran (4 kDa) flux was higher in KO tissues. Our data indicate that CaSR plays a role in regulating keratinization and cell-cell junctional complexes and is therefore important for the maintenance of the barrier function of the esophagus.NEW & NOTEWORTHY The esophageal stratified squamous epithelium maintains its integrity by continuous proliferation and differentiation of the basal cells. Here, we demonstrate that deletion of the calcium-sensing receptor, a G protein-coupled receptor, from the basal cells disrupts the structure and barrier properties of the epithelium.
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Affiliation(s)
- Nazih L. Nakhoul
- 1Department of Medicine, Tulane University School of Medicine, New Orleans, Louisiana,2Department of Physiology, Tulane University School of Medicine, New Orleans, Louisiana
| | - Chia-Ling Tu
- 3Endocrine Unit, Veterans Affairs Medical Center, University of California, San Francisco, California
| | - Karen L. Brown
- 1Department of Medicine, Tulane University School of Medicine, New Orleans, Louisiana,2Department of Physiology, Tulane University School of Medicine, New Orleans, Louisiana
| | - M. Toriqul Islam
- 1Department of Medicine, Tulane University School of Medicine, New Orleans, Louisiana,2Department of Physiology, Tulane University School of Medicine, New Orleans, Louisiana
| | - Anna G. Hodges
- 1Department of Medicine, Tulane University School of Medicine, New Orleans, Louisiana,2Department of Physiology, Tulane University School of Medicine, New Orleans, Louisiana
| | - Solange M. Abdulnour-Nakhoul
- 1Department of Medicine, Tulane University School of Medicine, New Orleans, Louisiana,2Department of Physiology, Tulane University School of Medicine, New Orleans, Louisiana,4Southeast Louisiana Veterans Health Care System, New Orleans, Louisiana
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8
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Antagonism of Ca 2+-sensing receptors by NPS 2143 is transiently masked by p38 activation in mouse brain bEND.3 endothelial cells. Naunyn Schmiedebergs Arch Pharmacol 2019; 392:823-832. [PMID: 30826858 DOI: 10.1007/s00210-019-01637-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Accepted: 02/22/2019] [Indexed: 10/27/2022]
Abstract
Ca2+-sensing receptors (CaSR) are G protein-coupled receptors which are activated by a rise in extracellular Ca2+. CaSR activation has been known to inhibit parathyroid hormone release and stimulate calcitonin release from parathyroid glands and thyroid parafollicular C cells, respectively. The roles of CaSR in other cell types including endothelial cells (EC) are much less understood. In this work, we demonstrated protein and functional expression of CaSR in mouse cerebral EC (bEND.3). Unexpectedly, CaSR response (high Ca2+-elicited cytosolic [Ca2+] elevation) was unaffected by edelfosine or U73122 but strongly suppressed by SK&F 96365, ruthenium red, and 2-aminoethoxydiphenyl borate (2-APB), suggesting involvement of TRPV and TRPC channels but not Gq-phospholipase C. Acute application of NPS2143, a negative allosteric modulator of CaSR, suppressed CaSR response. However, a 40-min NPS2143 pre-treatment surprisingly enhanced CaSR response. After 4-24 h of application, this enhancement faded away and suppression of CaSR response was observed again. Similar results were obtained when La3+ and Sr2+ were used as CaSR agonists. The transient NPS 2143 enhancement effect was abolished by SB203580, a p38 inhibitor. Consistently, NPS 2143 triggered a transient p38 activation. Taken together, results suggest that in bEND.3 cells, NPS 2143 caused acute suppression of CaSR response, but then elicited a transient enhancement of CaSR response in a p38-dependent manner. NPS 2143 effects on CaSR in bEND.3 cells therefore depended on drug exposure time. These findings warrant cautious use of this agent as a CaSR modulator and potential cardiovascular drug.
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9
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Gorvin CM, Rogers A, Hastoy B, Tarasov AI, Frost M, Sposini S, Inoue A, Whyte MP, Rorsman P, Hanyaloglu AC, Breitwieser GE, Thakker RV. AP2σ Mutations Impair Calcium-Sensing Receptor Trafficking and Signaling, and Show an Endosomal Pathway to Spatially Direct G-Protein Selectivity. Cell Rep 2018; 22:1054-1066. [PMID: 29420171 PMCID: PMC5792449 DOI: 10.1016/j.celrep.2017.12.089] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Revised: 11/30/2017] [Accepted: 12/22/2017] [Indexed: 12/29/2022] Open
Abstract
Spatial control of G-protein-coupled receptor (GPCR) signaling, which is used by cells to translate complex information into distinct downstream responses, is achieved by using plasma membrane (PM) and endocytic-derived signaling pathways. The roles of the endomembrane in regulating such pleiotropic signaling via multiple G-protein pathways remain unknown. Here, we investigated the effects of disease-causing mutations of the adaptor protein-2 σ subunit (AP2σ) on signaling by the class C GPCR calcium-sensing receptor (CaSR). These AP2σ mutations increase CaSR PM expression yet paradoxically reduce CaSR signaling. Hypercalcemia-associated AP2σ mutations reduced CaSR signaling via Gαq/11 and Gαi/o pathways. The mutations also delayed CaSR internalization due to prolonged residency time of CaSR in clathrin structures that impaired or abolished endosomal signaling, which was predominantly mediated by Gαq/11. Thus, compartmental bias for CaSR-mediated Gαq/11 endomembrane signaling provides a mechanistic basis for multidimensional GPCR signaling. Disease-causing AP2σ mutants impair Gαq/11 and Gαi/o signaling by CaSR, a class C GPCR AP2σ mutants impair trafficking of the CaSR The CaSR can signal by a sustained endosomal pathway CaSR differentially uses Gαq/11 and Gαi/o for cell-surface and endosomal signaling
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Affiliation(s)
- Caroline M Gorvin
- Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, Oxford, UK; Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, UK; Centre for Endocrinology, Diabetes and Metabolism (CEDAM), Birmingham Health Partners, Birmingham, UK
| | - Angela Rogers
- Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Benoit Hastoy
- Diabetes Research Laboratory, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Andrei I Tarasov
- Diabetes Research Laboratory, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Morten Frost
- Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Silvia Sposini
- Institute of Reproductive and Developmental Biology, Faculty of Medicine, Imperial College London, London, UK
| | - Asuka Inoue
- Laboratory of Molecular and Cellular Biochemistry, Tohoku University, Sendai, Japan; Japan Science and Technology (JST) Agency, Precursory Research for Embryonic Science and Technology (PRESTO), Kawaguchi, Japan
| | - Michael P Whyte
- Center for Metabolic Bone Disease and Molecular Research, Shriners Hospitals for Children, St. Louis, MO, USA
| | - Patrik Rorsman
- Diabetes Research Laboratory, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Aylin C Hanyaloglu
- Institute of Reproductive and Developmental Biology, Faculty of Medicine, Imperial College London, London, UK
| | - Gerda E Breitwieser
- Geisinger Clinic, Weis Center for Research, Department of Functional and Molecular Genomics, Danville, PA, USA
| | - Rajesh V Thakker
- Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, Oxford, UK.
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10
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Cleghorn WM, Bulus N, Kook S, Gurevich VV, Zent R, Gurevich EV. Non-visual arrestins regulate the focal adhesion formation via small GTPases RhoA and Rac1 independently of GPCRs. Cell Signal 2018; 42:259-269. [PMID: 29133163 PMCID: PMC5732042 DOI: 10.1016/j.cellsig.2017.11.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 11/09/2017] [Accepted: 11/10/2017] [Indexed: 02/07/2023]
Abstract
Arrestins recruit a variety of signaling proteins to active phosphorylated G protein-coupled receptors in the plasma membrane and to the cytoskeleton. Loss of arrestins leads to decreased cell migration, altered cell shape, and an increase in focal adhesions. Small GTPases of the Rho family are molecular switches that regulate actin cytoskeleton and affect a variety of dynamic cellular functions including cell migration and cell morphology. Here we show that non-visual arrestins differentially regulate RhoA and Rac1 activity to promote cell spreading via actin reorganization, and focal adhesion formation via two distinct mechanisms. Arrestins regulate these small GTPases independently of G-protein-coupled receptor activation.
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Affiliation(s)
- Whitney M Cleghorn
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, United States
| | - Nada Bulus
- Department of Medicine, Vanderbilt University, Nashville, TN 37232, United States
| | - Seunghyi Kook
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, United States
| | - Vsevolod V Gurevich
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, United States
| | - Roy Zent
- Department of Medicine, Vanderbilt University, Nashville, TN 37232, United States; Department of Veterans Affairs Hospital, Nashville, TN, 37232, United States
| | - Eugenia V Gurevich
- Department of Pharmacology, Vanderbilt University, Nashville, TN 37232, United States.
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11
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Transduction of group I mGluR-mediated synaptic plasticity by β-arrestin2 signalling. Nat Commun 2016; 7:13571. [PMID: 27886171 PMCID: PMC5133636 DOI: 10.1038/ncomms13571] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 10/17/2016] [Indexed: 12/19/2022] Open
Abstract
Conventional signalling by the group I metabotropic glutamate receptors, mGluR1 and mGluR5, occurs through G-protein coupling, but evidence suggests they might also utilize other, non-canonical effector pathways. Here we test whether group I mGluRs require β-arrestin signalling during specific forms of plasticity at hippocampal excitatory synapses. We find that genetic ablation of β-arrestin2, but not β-arrestin1, results in deficits in plasticity mediated by mGlu1 receptors in CA3 pyramidal neurons and by mGlu5 receptors in CA1 pyramidal neurons. Pharmacological studies additionally support roles for Src kinases and MAPK/ERK downstream of β-arrestin2 in CA3 neurons. mGluR1 modulation of intrinsic conductances is otherwise preserved in β-arrestin2−/− mice with the exception of a rebound depolarization, and non-mGluR-mediated long-term potentiation is unaltered. These results reveal a signalling pathway engaged by group I mGluRs to effect changes in synaptic and cell intrinsic physiology dependent upon β-arrestin rather than G proteins. Pharmacological manipulation of mGluRs with effector-biased ligands could lead to novel therapies to treat neurological disease. mGluRs are known to undergo non-canonical signalling regulation, although the underlying mechanisms are unclear. Here, the authors identify a role for β-arrestin2, but not β-arrestin1, in group I mGluR-mediated plasticity at hippocampal synapses.
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12
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Abstract
Members of the ADP-ribosylation factor (Arf) family of small GTP-binding (G) proteins regulate several aspects of membrane trafficking, such as vesicle budding, tethering and cytoskeleton organization. Arf family members, including Arf-like (Arl) proteins have been implicated in several essential cellular functions, like cell spreading and migration. These functions are used by cancer cells to disseminate and invade the tissues surrounding the primary tumor, leading to the formation of metastases. Indeed, Arf and Arl proteins, as well as their guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs) have been found to be abnormally expressed in different cancer cell types and human cancers. Here, we review the current evidence supporting the involvement of Arf family proteins and their GEFs and GAPs in cancer progression, focusing on 3 different mechanisms: cell-cell adhesion, integrin internalization and recycling, and actin cytoskeleton remodeling.
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Affiliation(s)
- Cristina Casalou
- a CEDOC, NOVA Medical School - Faculdade de Ciências Médicas, Universidade NOVA de Lisboa , Lisbon , Portugal
| | - Alexandra Faustino
- a CEDOC, NOVA Medical School - Faculdade de Ciências Médicas, Universidade NOVA de Lisboa , Lisbon , Portugal.,b ProRegeM PhD Program, NOVA Medical School - Faculdade de Ciências Médicas, Universidade NOVA de Lisboa , Lisbon , Portugal
| | - Duarte C Barral
- a CEDOC, NOVA Medical School - Faculdade de Ciências Médicas, Universidade NOVA de Lisboa , Lisbon , Portugal
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13
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Schlam D, Canton J. Every day I'm rufflin': Calcium sensing and actin dynamics in the growth factor-independent membrane ruffling of professional phagocytes. Small GTPases 2016; 8:65-70. [PMID: 27267709 DOI: 10.1080/21541248.2016.1197873] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Professional phagocytes continuously extend dynamic, actin-driven membrane protrusions. These protrusions, often referred to as membrane ruffles, serve a critical role in the essential phagocyte processes of macropinocytosis and phagocytosis. Small GTPases, such as RAC1/2, spatially and temporally regulate membrane ruffle formation. We have recently shown that extracellular calcium regulates the elaboration of membrane ruffles primarily through the synthesis of phosphatidic acid (PtdOH) at the plasma membrane. RAC1/2 guanine nucleotide exchange factors harbouring polybasic stretches are recruited by PtdOH to sites of ruffle formation. Here we discuss our findings and offer perspectives on how the regulation of dynamic actin structures at the plasma membrane by small GTPases is a critical component of phagocyte function.
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Affiliation(s)
- Daniel Schlam
- a Division of Cell Biology , Hospital for Sick Children , Toronto , ON , Canada
| | - Johnathan Canton
- a Division of Cell Biology , Hospital for Sick Children , Toronto , ON , Canada
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14
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Calcium-sensing receptors signal constitutive macropinocytosis and facilitate the uptake of NOD2 ligands in macrophages. Nat Commun 2016; 7:11284. [PMID: 27050483 PMCID: PMC4823870 DOI: 10.1038/ncomms11284] [Citation(s) in RCA: 104] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2015] [Accepted: 03/09/2016] [Indexed: 01/10/2023] Open
Abstract
Macropinocytosis can be induced in several cell types by stimulation with growth factors. In selected cell types, notably macrophages and dendritic cells, macropinocytosis occurs constitutively, supporting the uptake of antigens for subsequent presentation. Despite their different mode of initiation and contrasting physiological roles, it is tacitly assumed that both types of macropinocytosis are mechanistically identical. We report that constitutive macropinocytosis is stringently calcium dependent, while stimulus-induced macropinocytosis is not. Extracellular calcium is sensed by G-protein-coupled calcium-sensing receptors (CaSR) that signal macropinocytosis through Gα-, phosphatidylinositol 3-kinase and phospholipase C. These pathways promote the recruitment of exchange factors that stimulate Rac and/or Cdc42, driving actin-dependent formation of ruffles and macropinosomes. In addition, the heterologous expression of CaSR in HEK293 cells confers on them the ability to perform constitutive macropinocytosis. Finally, we show that CaSR-induced constitutive macropinocytosis facilitates the sentinel function of macrophages, promoting the efficient delivery of ligands to cytosolic pattern-recognition receptors. Macropinocytosis can be induced in several cell types by growth factors to promote nutrient acquisition. Here the authors find that constitutive macropinocytosis, unique to dendritic cells and macrophages, requires the activity of calcium-sensing receptors.
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15
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Abdulnour-Nakhoul S, Brown KL, Rabon EC, Al-Tawil Y, Islam MT, Schmieg JJ, Nakhoul NL. Cytoskeletal changes induced by allosteric modulators of calcium-sensing receptor in esophageal epithelial cells. Physiol Rep 2015; 3:3/11/e12616. [PMID: 26603452 PMCID: PMC4673644 DOI: 10.14814/phy2.12616] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The calcium-sensing receptor (CaSR), a G-protein-coupled receptor, plays a role in glandular and fluid secretion in the gastrointestinal tract, and regulates differentiation and proliferation of epithelial cells. We examined the expression of CaSR in normal and pathological conditions of human esophagus and investigated the effect of a CaSR agonist, cinacalcet (CCT), and antagonist, calhex (CHX), on cell growth and cell-cell junctional proteins in primary cultures of porcine stratified squamous esophageal epithelium. We used immunohistochemistry and Western analysis to monitor expression of CaSR and cell-cell adhesion molecules, and MTT assay to monitor cell proliferation in cultured esophageal cells. CCT treatment significantly reduced proliferation, changed the cell shape from polygonal to spindle-like, and caused redistribution of E-cadherin and β-catenin from the cell membrane to the cytoplasm. Furthermore, it reduced expression of β-catenin by 35% (P < 0.02) and increased expression of a proteolysis cleavage fragment of E-cadherin, Ecad/CFT2, by 2.3 folds (P < 0.01). On the other hand, CHX treatment enhanced cell proliferation by 27% (P < 0.01), increased the expression of p120-catenin by 24% (P < 0.04), and of Rho, a GTPase involved in cytoskeleton remodeling, by 18% (P < 0.03). In conclusion, CaSR is expressed in normal esophagus as well as in Barrett's, esophageal adenocarcinoma, squamous cell carcinoma, and eosinophilic esophagitis. Long-term activation of CaSR with CCT disrupted the cadherin-catenin complex, induced cytoskeletal remodeling, actin fiber formation, and redistribution of CaSR to the nuclear area. These changes indicate a significant and complex role of CaSR in epithelial remodeling and barrier function of esophageal cells.
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Affiliation(s)
- Solange Abdulnour-Nakhoul
- Medicine/Gastroenterology, Tulane Medical School, New Orleans, Louisiana South Louisiana Veterans Health Care System (SLVHCS), New Orleans, Louisiana
| | - Karen L Brown
- South Louisiana Veterans Health Care System (SLVHCS), New Orleans, Louisiana Medicine/Nephrology, Tulane Medical School, New Orleans, Louisiana
| | - Edd C Rabon
- South Louisiana Veterans Health Care System (SLVHCS), New Orleans, Louisiana
| | - Youhanna Al-Tawil
- Pediatric Gastroenterology and Nutrition-GI for Kids, East Tennessee Children's Hospital, Knoxville, Tennessee
| | - Mohammed T Islam
- South Louisiana Veterans Health Care System (SLVHCS), New Orleans, Louisiana Medicine/Nephrology, Tulane Medical School, New Orleans, Louisiana
| | - John J Schmieg
- Pathology, Tulane Medical School, New Orleans, Louisiana
| | - Nazih L Nakhoul
- South Louisiana Veterans Health Care System (SLVHCS), New Orleans, Louisiana Medicine/Nephrology, Tulane Medical School, New Orleans, Louisiana
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16
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Abstract
Integrins are adhesion and survival molecules involved in axon growth during CNS development, as well as axon regeneration after injury in the peripheral nervous system (PNS). Adult CNS axons do not regenerate after injury, partly due to a low intrinsic growth capacity. We have previously studied the role of integrins in axon growth in PNS axons; in the present study, we investigate whether integrin mechanisms involved in PNS regeneration may be altered or lacking from mature CNS axons by studying maturing CNS neurons in vitro. In rat cortical neurons, we find that integrins are present in axons during initial growth but later become restricted to the somato-dendritic domain. We investigated how this occurs and whether it can be altered to enhance axonal growth potential. We find a developmental change in integrin trafficking; transport becomes predominantly retrograde throughout axons, but not dendrites, as neurons mature. The directionality of transport is controlled through the activation state of ARF6, with developmental upregulation of the ARF6 GEF ARNO enhancing retrograde transport. Lowering ARF6 activity in mature neurons restores anterograde integrin flow, allows transport into axons, and increases axon growth. In addition, we found that the axon initial segment is partly responsible for exclusion of integrins and removal of this structure allows integrins into axons. Changing posttranslational modifications of tubulin with taxol also allows integrins into the proximal axon. The experiments suggest that the developmental loss of regenerative ability in CNS axons is due to exclusion of growth-related molecules due to changes in trafficking.
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17
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Huang S, Ren Y, Wang P, Li Y, Wang X, Zhuang H, Fang R, Wang Y, Liu N, Hehir M, Zhou JX. Transcription Factor CREB is Involved in CaSR-mediated Cytoskeleton Gene Expression. Anat Rec (Hoboken) 2014; 298:501-12. [PMID: 25382680 DOI: 10.1002/ar.23089] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2014] [Accepted: 09/13/2014] [Indexed: 12/21/2022]
Affiliation(s)
- Shuaishuai Huang
- Department of Medical School; Ningbo University; Ningbo 315211 China
- Department of the Center for Translational Medicine; The Affiliated Hospital, Ningbo University School of Medicine; Ningbo 315020 China
| | - Yu Ren
- Department of Urologic Surgery; Ningbo Urology and Nephrology Hospital, Ningbo University; Ningbo 315000 China
| | - Ping Wang
- Department of Medical School; Ningbo University; Ningbo 315211 China
- Department of the Center for Translational Medicine; The Affiliated Hospital, Ningbo University School of Medicine; Ningbo 315020 China
| | - Yanyuan Li
- Department of Pathology; First Affiliated Hospital, Zhejiang University School of Medicine; Hangzhou P.R.310003 China
| | - Xue Wang
- Department of Medical School; Ningbo University; Ningbo 315211 China
- Department of the Center for Translational Medicine; The Affiliated Hospital, Ningbo University School of Medicine; Ningbo 315020 China
| | - Haihui Zhuang
- Department of Medical School; Ningbo University; Ningbo 315211 China
- Department of the Center for Translational Medicine; The Affiliated Hospital, Ningbo University School of Medicine; Ningbo 315020 China
| | - Rong Fang
- Department of Medical School; Ningbo University; Ningbo 315211 China
- Department of the Center for Translational Medicine; The Affiliated Hospital, Ningbo University School of Medicine; Ningbo 315020 China
| | - Yuduo Wang
- Department of Medical School; Ningbo University; Ningbo 315211 China
| | - Ningsheng Liu
- Department of Medical School; Ningbo University; Ningbo 315211 China
| | - Michael Hehir
- Department of Medical School; Ningbo University; Ningbo 315211 China
- Department of the Center for Translational Medicine; The Affiliated Hospital, Ningbo University School of Medicine; Ningbo 315020 China
| | - Jeff X. Zhou
- Department of Medical School; Ningbo University; Ningbo 315211 China
- Department of the Center for Translational Medicine; The Affiliated Hospital, Ningbo University School of Medicine; Ningbo 315020 China
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18
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McGovern KW, DeFea KA. Molecular mechanisms underlying beta-arrestin-dependent chemotaxis and actin-cytoskeletal reorganization. Handb Exp Pharmacol 2014; 219:341-359. [PMID: 24292838 DOI: 10.1007/978-3-642-41199-1_17] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
β-Arrestins play a crucial role in cell migration downstream of multiple G-protein-coupled receptors (GPCRs) through multiple mechanisms. There is considerable evidence that β-arrestin-dependent scaffolding of actin assembly proteins facilitates the formation of a leading edge in response to a chemotactic signal. Conversely, there is substantial support for the hypothesis that β-arrestins facilitate receptor turnover through their ability to desensitize and internalize GPCRs. This chapter discusses both theories for β-arrestin-dependent chemotaxis in the context of recent studies, specifically addressing known actin assembly proteins regulated by β-arrestins, chemokine receptors, and signaling by chemotactic receptors.
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Affiliation(s)
- Kathryn W McGovern
- Biochemistry and Molecular Biology Graduate Program, University of California, Riverside, CA, USA
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19
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Gilliland CT, Salanga CL, Kawamura T, Trejo J, Handel TM. The chemokine receptor CCR1 is constitutively active, which leads to G protein-independent, β-arrestin-mediated internalization. J Biol Chem 2013; 288:32194-32210. [PMID: 24056371 DOI: 10.1074/jbc.m113.503797] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activation of G protein-coupled receptors by their associated ligands has been extensively studied, and increasing structural information about the molecular mechanisms underlying ligand-dependent receptor activation is beginning to emerge with the recent expansion in GPCR crystal structures. However, some GPCRs are also able to adopt active conformations in the absence of agonist binding that result in the initiation of signal transduction and receptor down-modulation. In this report, we show that the CC-type chemokine receptor 1 (CCR1) exhibits significant constitutive activity leading to a variety of cellular responses. CCR1 expression is sufficient to induce inhibition of cAMP formation, increased F-actin content, and basal migration of human and murine leukocytes. The constitutive activity leads to basal phosphorylation of the receptor, recruitment of β-arrestin-2, and subsequent receptor internalization. CCR1 concurrently engages Gαi and β-arrestin-2 in a multiprotein complex, which may be accommodated by homo-oligomerization or receptor clustering. The data suggest the presence of two functional states for CCR1; whereas receptor coupled to Gαi functions as a canonical GPCR, albeit with high constitutive activity, the CCR1·β-arrestin-2 complex is required for G protein-independent constitutive receptor internalization. The pertussis toxin-insensitive uptake of chemokine by the receptor suggests that the CCR1·β-arrestin-2 complex may be related to a potential scavenging function of the receptor, which may be important for maintenance of chemokine gradients and receptor responsiveness in complex fields of chemokines during inflammation.
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Affiliation(s)
| | | | | | - JoAnn Trejo
- the Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California 92093
| | - Tracy M Handel
- From the Skaggs School of Pharmacy and Pharmaceutical Sciences.
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20
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Arrestins in actin reorganization and cell migration. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2013; 118:205-22. [PMID: 23764055 DOI: 10.1016/b978-0-12-394440-5.00008-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Arrestins have emerged as important regulators of actin reorganization and cell migration. Both in their classical roles as mediators of receptor desensitization and internalization, and in their newer role as signaling scaffolds, β-arrestins help orchestrate the cellular response to chemotactic signals. However, there is still a considerable amount to be learned about the precise molecular mechanisms underlying these processes. This review discusses how, by regulating receptor internalization and by scaffolding of signaling molecules in discrete cellular locations, arrestins facilitate gradient sensing and cytoskeletal reorganization, ultimately resulting in cell migration. In addition, putative new targets of β-arrestin regulation that may play important roles in cell migration are discussed, as continued research on these targets may provide important details to fill in the current gaps in our understanding of these processes.
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21
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β-Arrestins: modulators of small GTPase activation and function. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2013; 118:149-74. [PMID: 23764053 DOI: 10.1016/b978-0-12-394440-5.00006-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Most cellular events responsible for accurate G protein-coupled receptor trafficking involve small GTP-binding proteins. For example, trafficking of receptors via the endocytic and exocytic pathways requires activation of ADP-ribosylation factors and Rab proteins, while receptor-mediated complex responses such as migration are well characterized to be dependent upon Rho family members. Because β-arrestin proteins are recruited to activated receptors and now considered as key signaling molecules, whether they act to control small GTPase activity remains a subject of great interest. Over the years, considerable evidence has suggested that β-arrestins and GTPases might be effectors of the same signaling pathways. One example is the roles of both β-arrestin and Ras, the prototypical GTPase, in coordinating activation of mitogen-activated protein kinase. Recently developed tools effective in suppressing the expression of β-arrestins will help define whether they are essential for small G protein activation. Furthermore, novel approaches to identify protein complexes will greatly advance our understanding of the possible cross talk between β-arrestin and small GTPases.
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22
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Thomsen ARB, Worm J, Jacobsen SE, Stahlhut M, Latta M, Bräuner-Osborne H. Strontium is a biased agonist of the calcium-sensing receptor in rat medullary thyroid carcinoma 6-23 cells. J Pharmacol Exp Ther 2012; 343:638-49. [PMID: 22942242 PMCID: PMC11047797 DOI: 10.1124/jpet.112.197210] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Accepted: 08/30/2012] [Indexed: 09/23/2023] Open
Abstract
The calcium-sensing receptor (CaSR)-specific allosteric modulator cinacalcet has revolutionized the treatment of secondary hyperparathyroidism in patients with chronic kidney disease. However, its application is limited to patients with end-stage renal disease because of hypocalcemic side effects presumably caused by CaSR-mediated calcitonin secretion from thyroid parafollicular C-cells. These hypocalcemic side effects might be dampened by compounds that bias the signaling of CaSR, causing similar therapeutic effects as cinacalcet without stimulating calcitonin secretion. Because biased signaling of CaSR is poorly understood, the objective of the present study was to investigate biased signaling of CaSR by using rat medullary thyroid carcinoma 6-23 cells as a model of thyroid parafollicular C-cells. By doing concentration-response experiments we focused on the ability of two well known CaSR agonists, calcium and strontium, to activate six different signaling entities: G(q/11) signaling, G(i/o) signaling, G(s) signaling, extracellular signal-regulated kinases 1 and 2 (ERK1/2) signaling, intracellular calcium ([Ca(2+)](i)) mobilization, and calcitonin secretion. The experiments showed that strontium biases CaSR signaling toward ERK1/2 signaling and possibly another pathway independent of G(q/11) signaling and [Ca(2+)](i) mobilization. It is noteworthy that the potency of strontium-stimulated calcitonin secretion was elevated compared with calcium. Combining these results with experiments investigating signaling pathway components involved in calcitonin secretion, we found that the enhanced potency of strontium-mediated calcitonin secretion was caused by a different signaling pattern than that produced by calcium. Together, our results suggest that calcitonin secretion can be affected by CaSR-stimulated signaling bias, which may be used to develop novel drugs for the treatment of secondary hyperparathyroidism.
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Affiliation(s)
- Alex Rojas Bie Thomsen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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23
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Halls ML. Constitutive formation of an RXFP1-signalosome: a novel paradigm in GPCR function and regulation. Br J Pharmacol 2012; 165:1644-1658. [PMID: 21557732 DOI: 10.1111/j.1476-5381.2011.01470.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The classical second messenger cAMP is important in diverse physiological processes, where its spatial and temporal compartmentalization allows precise control over multiple cellular events. Within this context, G-protein-coupled receptors (GPCRs) govern specialized pools of cAMP, which are functionally specific for the unique cellular effects attributed to a particular system. The relaxin receptor, RXFP1, is a GPCR that exerts pleiotropic physiological effects including a potent anti-fibrotic response, increased cancer metastases, and has efficacy as a vasodilator in heart failure. On a cellular level, relaxin stimulation of RXFP1 results in the activation of multiple G-protein pathways affecting cAMP accumulation. Specificity and diversity in the cAMP signal generated by RXFP1 is controlled by differential G-protein coupling dependent upon the background of cellular expression, and cAMP compartmentalization. Further complexity in cAMP signalling results from the constitutive assembly of an RXFP1-signalosome, which specifically responds to low concentrations of relaxin, and activates a distinct cAMP pathway. The RXFP1-signalosome is a higher-order protein complex that facilitates receptor sensitivity to attomolar concentration of peptide, exhibits constitutive activity and dual coupling to G-proteins and β-arrestins and reveals a concentration-biased agonism mediated by relaxin. The specific and directed formation of GPCR-centered signalosomes allows an even greater spatial and temporal control of cAMP, thus rationalizing the considerable physiological scope of this ubiquitous second messenger.
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Affiliation(s)
- Michelle L Halls
- Department of Pharmacology, University of Cambridge, Cambridge, UK
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24
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Davey AE, Leach K, Valant C, Conigrave AD, Sexton PM, Christopoulos A. Positive and negative allosteric modulators promote biased signaling at the calcium-sensing receptor. Endocrinology 2012; 153:1232-41. [PMID: 22210744 DOI: 10.1210/en.2011-1426] [Citation(s) in RCA: 123] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The calcium-sensing receptor (CaSR) is a G protein-coupled receptor whose function can be allosterically modulated in a positive or negative manner by calcimimetics or calcilytics, respectively. Indeed, the second-generation calcimimetic, cinacalcet, has proven clinically useful in the treatment of chronic kidney disease patients with secondary hyperparathyroidism but is not widely used in earlier stages of renal disease due to the potential to predispose such patients to hypocalcaemia and hyperphosphatemia. The development of a biased CaSR ligand that is more selective for specific signaling pathway(s) leading only to beneficial effects may overcome this limitation. The detection of such stimulus-bias at a G protein-coupled receptor requires investigation across multiple signaling pathways and the development of methods to quantify the effects of allosteric ligands on orthosteric ligand affinity and cooperativity at each pathway. In the current study, we determined the effects of the calcimimetics, NPS-R568 or cinacalcet, and the calcilytic, NPS-2143, on Ca(o)(2+)-mediated intracellular Ca(2+) mobilization, ERK1/2 phosphorylation, and plasma membrane ruffling in a stably transfected human embryonic kidney 293-TREx c-myc-CaSR cell line and applied a novel analytical model to quantify these modulator effects. We present quantitative evidence for the generation of stimulus bias by both positive and negative allosteric modulators of the CaSR, manifested as greater allosteric modulation of intracellular Ca(2+) mobilization relative to ERK1/2 phosphorylation, and a higher affinity of the modulators for the state of the CaSR mediating plasma membrane ruffling relative to the other two pathways. Our findings provide the first evidence that an allosteric modulator used in clinical practice exhibits stimulus bias.
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Affiliation(s)
- Anna E Davey
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences and Department of Pharmacology, Monash University, Parkville, Victoria 3052, Australia
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25
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Thomsen ARB, Hvidtfeldt M, Bräuner-Osborne H. Biased agonism of the calcium-sensing receptor. Cell Calcium 2012; 51:107-16. [PMID: 22192592 DOI: 10.1016/j.ceca.2011.11.009] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Revised: 11/05/2011] [Accepted: 11/24/2011] [Indexed: 02/01/2023]
Abstract
After the discovery of molecules modulating G protein-coupled receptors (GPCRs) that are able to selectively affect one signaling pathway over others for a specific GPCR, thereby "biasing" the signaling, it has become obvious that the original model of GPCRs existing in either an "on" or "off" conformation is too simple. The current explanation for this biased agonism is that GPCRs can adopt multiple active conformations stabilized by different molecules, and that each conformation affects intracellular signaling in a different way. In the present study we sought to investigate biased agonism of the calcium-sensing receptor (CaSR), by looking at 12 well-known orthosteric CaSR agonists in 3 different CaSR signaling pathways: G(q/11) protein, G(i/o) protein, and extracellular signal-regulated kinases 1 and 2 (ERK1/2). Here we show that apart from G(q/11) and G(i/o) signaling, ERK1/2 is activated through recruitment of β-arrestins. Next, by measuring activity of all three signaling pathways we found that barium, spermine, neomycin, and tobramycin act as biased agonist in terms of efficacy and/or potency. Finally, polyamines and aminoglycosides in general were biased in their potencies toward ERK1/2 signaling. In conclusion, the results of this study indicate that several active conformations of CaSR, stabilized by different molecules, exist, which affect intracellular signaling distinctly.
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Affiliation(s)
- Alex Rojas Bie Thomsen
- Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, Fruebjergvej 3, Copenhagen, Denmark
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26
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Signaling through the extracellular calcium-sensing receptor (CaSR). ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:103-42. [PMID: 22453940 DOI: 10.1007/978-94-007-2888-2_5] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The extracellular calcium ([Formula: see text])-sensing receptor (CaSR) was the first GPCR identified whose principal physiological ligand is an ion, namely extracellular Ca(2+). It maintains the near constancy of [Formula: see text] that complex organisms require to ensure normal cellular function. A wealth of information has accumulated over the past two decades about the CaSR's structure and function, its role in diseases and CaSR-based therapeutics. This review briefly describes the CaSR and key features of its structure and function, then discusses the extracellular signals modulating its activity, provides an overview of the intracellular signaling pathways that it controls, and, finally, briefly describes CaSR signaling both in tissues participating in [Formula: see text] homeostasis as well as those that do not. Factors controlling CaSR signaling include various factors affecting the expression of the CaSR gene as well as modulation of its trafficking to and from the cell surface. The dimeric cell surface CaSR, in turn, links to various heterotrimeric and small molecular weight G proteins to regulate intracellular second messengers, lipid kinases, various protein kinases, and transcription factors that are part of the machinery enabling the receptor to modulate the functions of the wide variety of cells in which it is expressed. CaSR signaling is impacted by its interactions with several binding partners in addition to signaling elements per se (i.e., G proteins), including filamin-A and caveolin-1. These latter two proteins act as scaffolds that bind signaling components and other key cellular elements (e.g., the cytoskeleton). Thus CaSR signaling likely does not take place randomly throughout the cell, but is compartmentalized and organized so as to facilitate the interaction of the receptor with its various signaling pathways.
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27
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Tharmalingam S, Daulat AM, Antflick JE, Ahmed SM, Nemeth EF, Angers S, Conigrave AD, Hampson DR. Calcium-sensing receptor modulates cell adhesion and migration via integrins. J Biol Chem 2011; 286:40922-33. [PMID: 21969374 DOI: 10.1074/jbc.m111.265454] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The calcium-sensing receptor (CaSR) is a family C G protein-coupled receptor that is activated by elevated levels of extracellular divalent cations. The CaSR couples to members of the G(q) family of G proteins, and in the endocrine system this receptor is instrumental in regulating the release of parathyroid hormone from the parathyroid gland and calcitonin from thyroid cells. Here, we demonstrate that in medullary thyroid carcinoma cells, the CaSR promotes cellular adhesion and migration via coupling to members of the integrin family of extracellular matrix-binding proteins. Immunopurification and mass spectrometry, co-immunoprecipitation, and co-localization studies showed that the CaSR and β1-containing integrins are components of a macromolecular protein complex. In fibronectin-based cell adhesion and migration assays, the CaSR-positive allosteric modulator NPS R-568 induced a concentration-dependent increase in cell adhesion and migration; both of these effects were blocked by a specific CaSR-negative allosteric modulator. These effects were mediated by integrins because they were blocked by a peptide inhibitor of integrin binding to fibronectin and β1 knockdown experiments. An analysis of intracellular signaling pathways revealed a key role for CaSR-induced phospholipase C activation and the release of intracellular calcium. These results demonstrate for the first time that an ion-sensing G protein-coupled receptor functionally couples to the integrins and, in conjunction with intracellular calcium release, promotes cellular adhesion and migration in tumor cells. The significance of this interaction is further highlighted by studies implicating the CaSR in cancer metastasis, axonal growth, and stem cell attachment, functions that rely on integrin-mediated cell adhesion.
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Affiliation(s)
- Sujeenthar Tharmalingam
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario M5S 3M2, Canada
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28
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Tilley DG. Functional relevance of biased signaling at the angiotensin II type 1 receptor. Endocr Metab Immune Disord Drug Targets 2011; 11:99-111. [PMID: 21476968 DOI: 10.2174/187153011795564133] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2010] [Accepted: 02/07/2011] [Indexed: 01/04/2023]
Abstract
Angiotensin II type 1 receptor antagonists (AT1R blockers, or ARBs) are used commonly in the treatment of cardiovascular disorders such as heart failure and hypertension. Their clinical success arises from their ability to prevent deleterious Gα(q) protein activation downstream of AT1R, which leads to a decrease in morbidity and mortality. Recent studies have identified AT1R ligands that concurrently inhibit Gα(q) protein-dependent signaling and activate Gα(q) protein-independent/β-arrestin-dependent signaling downstream of AT1R, events that may actually improve cardiovascular performance more than conventional ARBs. The ability of such ligands to induce intracellular signaling events in an AT1R-β-arrestin-dependent manner while preventing AT1R-Gα(q) protein activity defines them as biased AT1R ligands. This mini-review will highlight recent studies that have defined biased signaling at the AT1R and discuss the possible clinical relevance of β-arrestin-biased AT1R ligands in the cardiovascular system.
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Affiliation(s)
- Douglas G Tilley
- Department of Pharmaceutical Sciences, Jefferson School of Pharmacy, Thomas Jefferson University, Philadelphia, PA 1917, USA.
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29
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Min J, Defea K. β-arrestin-dependent actin reorganization: bringing the right players together at the leading edge. Mol Pharmacol 2011; 80:760-8. [PMID: 21836019 DOI: 10.1124/mol.111.072470] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
First identified as mediators of G-protein-coupled receptor desensitization and internalization and later as signaling platforms, β-arrestins play a requisite role in chemotaxis and reorganization of the actin cytoskeleton, downstream of multiple receptors. However, the precise molecular mechanisms underlying their involvement have remained elusive. Initial interest in β-arrestins as facilitators of cell migration and actin reorganization stemmed from the known interplay between receptor endocytosis and actin filament formation, because disruption of the actin cytoskeleton inhibits these β-arrestin-dependent events. With growing interest in the mechanisms by which cells can sense a gradient of agonist during cell migration, investigators began to hypothesize that β-arrestins may contribute to directed migration by controlling chemotactic receptor turnover at the plasma membrane. Finally, increasing evidence emerged that β-arrestins are more than just clathrin adaptor proteins involved in turning off receptor signals; they are actually capable of generating their own signals by scaffolding signaling molecules and controlling the activity of multiple cellular enzymes. This new role of β-arrestins as signaling scaffolds has led to the hypothesis that they can facilitate cell migration by sequestering actin assembly activities and upstream regulators of actin assembly at the leading edge. This Minireview discusses recent advances in our understanding of how β-arrestin scaffolds contribute to cell migration, focusing on recently identified β-arrestin interacting proteins and phosphorylation targets that have known roles in actin reorganization.
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Affiliation(s)
- Jungah Min
- Division of Biomedical Sciences and Graduate Program in Cell, Molecular and Developmental Biology, University of California, Riverside, CA, USA
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30
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Aubry L, Guetta D, Klein G. The arrestin fold: variations on a theme. Curr Genomics 2011; 10:133-42. [PMID: 19794886 PMCID: PMC2699828 DOI: 10.2174/138920209787847014] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2008] [Revised: 12/30/2008] [Accepted: 01/05/2009] [Indexed: 12/26/2022] Open
Abstract
Endocytosis of ligand-activated plasma membrane receptors has been shown to contribute to the regulation of their downstream signaling. β-arrestins interact with the phosphorylated tail of activated receptors and act as scaffolds for the recruitment of adaptor proteins and clathrin, that constitute the machinery used for receptor endocytosis. Visual- and β-arrestins have a two-lobe, immunoglobulin-like, β-strand sandwich structure. The recent resolution of the crystal structure of VPS26, one of the retromer subunits, unexpectedly evidences an arrestin fold in this protein, which is otherwise unrelated to arrestins. From a functional point of view, VPS26 is involved in the retrograde transport of the mannose 6-P receptor from the endosomes to the trans-Golgi network. In addition to the group of genuine arrestins and Vps26, mammalian cells harbor a vast repertoire of proteins that are related to arrestins on the basis of their PFAM Nter and Cter arrestin- domains, which are named Arrestin Domain- Containing proteins (ADCs). The biological role of ADC proteins is still poorly understood. The three subfamilies have been merged into an arrestin-related protein clan. This paper provides an overall analysis of arrestin clan proteins. The structures and functions of members of the subfamilies are reviewed in mammals and model organisms such as Drosophila, Caenorhabditis, Saccharomyces and Dictyostelium.
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Affiliation(s)
- Laurence Aubry
- CNRS, UMR 5092, 17 rue des Martyrs, Grenoble, 38054, France
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Kantamneni S, Wilkinson KA, Jaafari N, Ashikaga E, Rocca D, Rubin P, Jacobs SC, Nishimune A, Henley JM. Activity-dependent SUMOylation of the brain-specific scaffolding protein GISP. Biochem Biophys Res Commun 2011; 409:657-62. [PMID: 21616059 PMCID: PMC3308138 DOI: 10.1016/j.bbrc.2011.05.060] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Accepted: 05/11/2011] [Indexed: 11/21/2022]
Abstract
G-protein coupled receptor interacting scaffold protein (GISP) is a multi-domain, brain-specific protein derived from the A-kinase anchoring protein (AKAP)-9 gene. Using yeast two-hybrid screens to identify GISP interacting proteins we isolated the SUMO conjugating enzyme Ubc9. GISP interacts with Ubc9 in vitro, in heterologous cells and in neurons. SUMOylation is a post-translational modification in which the small protein SUMO is covalently conjugated to target proteins, modulating their function. Consistent with its interaction with Ubc9, we show that GISP is SUMOylated by both SUMO-1 and SUMO-2 in both in vitro SUMOylation assays and in mammalian cells. Intriguingly, SUMOylation of GISP in neurons occurs in an activity-dependent manner in response to chemical LTP. These data suggest that GISP is a novel neuronal SUMO substrate whose SUMOylation status is modulated by neuronal activity.
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Affiliation(s)
- Sriharsha Kantamneni
- MRC Centre for Synaptic Plasticity, School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Kevin A. Wilkinson
- MRC Centre for Synaptic Plasticity, School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Nadia Jaafari
- MRC Centre for Synaptic Plasticity, School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Emi Ashikaga
- MRC Centre for Synaptic Plasticity, School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Daniel Rocca
- MRC Centre for Synaptic Plasticity, School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Philip Rubin
- MRC Centre for Synaptic Plasticity, School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Susan C. Jacobs
- MRC Centre for Synaptic Plasticity, School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
| | - Atsushi Nishimune
- Division of Pharmacology, Department of Biochemistry and Bioinformative Sciences, School of Medicine, University of Fukui, 23-3 Shimoaizuki, Matsuoka, Eiheiji-cho, Yoshida-gun, Fukui 910-1193, Japan
| | - Jeremy M. Henley
- MRC Centre for Synaptic Plasticity, School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK
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Jiang J, Liu G, Miao X, Hua S, Zhong D. Overexpression of engulfment and cell motility 1 promotes cell invasion and migration of hepatocellular carcinoma. Exp Ther Med 2011; 2:505-511. [PMID: 22977532 DOI: 10.3892/etm.2011.229] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Accepted: 03/15/2011] [Indexed: 11/05/2022] Open
Abstract
Engulfment and cell motility 1 (Elmo1) has been linked to the invasive phenotype of glioma cells. The use of Elmo1 inhibitors is currently being evaluated in hepato-cellular carcinoma (HCC), but the molecular mechanisms of their therapeutic effect have yet to be determined. Elmo1 expression in HCC tissue samples from 131 cases and in 5 HCC cell lines was determined by immunohistochemistry, quantitative RT-PCR and Western blotting. To functionally characterize Elmo1 in HCC, Elmo1 expression in the HCCLM3 cell line was blocked by siRNA. Cell migration was measured by wound healing and transwell migration assays in vitro. Elmo1 overexpression was significantly correlated with cell invasion and the poor prognosis of HCC. Elmo1-siRNA-treated HCCLM3 cells demonstrated a reduction in cell migration. The present study demonstrated for the first time that the suppression of Elmo1 expression inhibits cell invasion in HCC.
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Affiliation(s)
- Jiarui Jiang
- Department of Hepatobiliary Surgery, The Second Xiangya Hospital, Central South University, Changsha, Hunan 410011, P.R. China
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El Azreq MA, Garceau V, Bourgoin SG. Cytohesin-1 regulates fMLF-mediated activation and functions of the β2 integrin Mac-1 in human neutrophils. J Leukoc Biol 2011; 89:823-36. [PMID: 21233413 DOI: 10.1189/jlb.0410222] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The nucleotide exchange factor cytohesin-1 was previously reported to interact with the cytoplasmic domains of the integrin β-chain common to all β(2) integrins such as LFA-1 and Mac-1. We show here that cytohesin-1, which contributes to fMLF-induced functional responses in PMNs through activation of Arf6, restrains the activation of the β(2) integrin Mac-1 (αMβ(2)) in PMNs or dcAMP-differentiated PLB-985 cells. We found that the cytohesin-1 inhibitor SecinH3 or siRNA increased cell adhesion to immobilized fibrinogen and fMLF-mediated conformational changes of Mac-1, monitored using mAb CBRM1/5, specific for the activation epitope of the αM subunit. In contrast, PLB-985 cells overexpressing cytohesin-1 showed little adhesion to fibrinogen. The use of SecinH3 and siRNA also revealed that interference with cytohesin-1 signaling also enhanced phagocytosis of zymosan particles and chemotaxis toward fMLF in transwell migration assays. These increments of phagocytosis and chemotaxis in cells treated with SecinH3 and cytohesin-1 siRNA were reversed by a blocking mAb to the integrin-αM subunit. We provide evidence for increased polymerized cortical actin in cells treated with SecinH3 and that altered signaling through cytohesin-1 increased cell surface expression of FPRL-1 and impairs the late calcium mobilization response elicited by fMLF. The data provide evidence that stimulation with fMLF initiates a signaling cascade that restrains Mac-1 activation in PMNs. Such crosstalk between FPRL-1 and Mac-1 involves cytohesin-1. We suggest that cytohesin-1 may coordinate activation of the β(2) integrins to regulate PMN adhesion, phagocytosis, and chemotaxis.
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Affiliation(s)
- Mohammed-Amine El Azreq
- Centre de Recherche en Rhumatologie et Immunologie, Centre de Recherche du CHUQ-CHUL, Faculté de Médecine, Université Laval, Québec, Canada
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El Azreq MA, Garceau V, Harbour D, Pivot-Pajot C, Bourgoin SG. Cytohesin-1 regulates the Arf6-phospholipase D signaling axis in human neutrophils: impact on superoxide anion production and secretion. THE JOURNAL OF IMMUNOLOGY 2009; 184:637-49. [PMID: 20018626 DOI: 10.4049/jimmunol.0901654] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Polymorphonuclear neutrophil (PMN) stimulation with fMLP stimulates small G proteins such as ADP-ribosylation factors (Arfs) Arf1 and Arf6, leading to phospholipase D (PLD) activation and functions such as degranulation and the oxidative burst. However, the molecular links between fMLF receptors and PLD remain unclear. PMNs express cytohesin-1, an Arf-guanine exchange factor that activates Arfs, and its expression is strongly induced during the acquisition of the neutrophilic phenotype by neutrophil-like cells. The role of cytohesin-1 in the activation of the fMLF-Arf-PLD signaling axis, and the accomplishment of superoxide anion production, and degranulation was investigated in PMNs using the selective inhibitor of cytohesin, Sec 7 inhibitor H3 (secinH3). Cytohesin-1 inhibition with secinH3 leads to Arf6 but not Arf1 inhibition, demonstrating the specificity for Arf6, and fMLF-mediated activation of PLD and of the oxidative burst as well. We observed a decrease in fMLF-mediated protein secretion and expression of cell surface markers corresponding to primary (CD63/myeloperoxidase), secondary (CD66/lactoferrin), and tertiary (matrix metalloproteinase-9) granules in PMNs incubated with secinH3. Similarly, silencing cytohesin-1 or Arf6 in PLB-985 cells negatively affected fMLF-induced activation of PLD, superoxide production, and expression of granule markers on the cell surface. In contrast, stable overexpression of cytohesin-1 in PLB-985 cells enhanced fMLF-induced activation of Arf6, PLD, and NADPH oxidase. The results of this study provide evidence for an involvement of cytohesin-1 in the regulation of the functional responses of human PMNs and link these events, in part at least, to the activation of Arf6.
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Affiliation(s)
- Mohammed-Amine El Azreq
- Centre de Recherche en Rhumatologie et Immunologie, Centre de Recherche du Centre Hospitalier de l'Université Québec-Centre Hospitalier de l'Université Laval, Québec, Canada
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Hannan FM, Nesbit MA, Turner JJO, Stacey JM, Cianferotti L, Christie PT, Conigrave AD, Whyte MP, Thakker RV. Comparison of human chromosome 19q13 and syntenic region on mouse chromosome 7 reveals absence, in man, of 11.6 Mb containing four mouse calcium-sensing receptor-related sequences: relevance to familial benign hypocalciuric hypercalcaemia type 3. Eur J Hum Genet 2009; 18:442-7. [PMID: 19809483 DOI: 10.1038/ejhg.2009.161] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Familial benign hypocalciuric hypercalcaemia (FBHH) is a genetically heterogeneous disorder that consists of three designated types, FBHH1, FBHH2 and FBHH3, whose chromosomal locations are 3q21.1, 19p and 19q13, respectively. FBHH1 is caused by mutations of a calcium-sensing receptor (CaSR), but the abnormalities underlying FBHH2 and FBHH3 are unknown. FBHH3, also referred to as the Oklahoma variant (FBHH(Ok)), has been mapped to a 12cM interval, flanked by D19S908 and D19S866. To refine the location of FBHH3, we pursued linkage studies using 24 polymorphic loci. Our results establish a linkage between FBHH3 and 17 of these loci, and indicate that FBHH3 is located in a 4.1 Mb region flanked centromerically by D19S112 and telomerically by rs245111, which in the syntenic region on mouse chromosome 7 contains four Casr-related sequences (Gprc2a-rss). However, human homologues of these Gprc2a-rss were not found and a comparative analysis of the 22.0 Mb human and 39.3 Mb mouse syntenic regions showed evolutionary conservation of two segments that were inverted with loss from the human genome of 11.6 Mb that contained the four Gprc2a-rss. Thus, FBHH3 cannot be attributed to Gprc2a-rss abnormalities. DNA sequence analysis of 12 other genes from the interval that were expressed in the parathyroids and/or kidneys did not detect any abnormalities, thereby indicating that these genes are unlikely to be the cause of FBHH3. The results of this study have refined the map location of FBHH3, which will facilitate the identification of another CaSR or a mediator of calcium homeostasis.
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Affiliation(s)
- Fadil M Hannan
- Academic Endocrine Unit, Nuffield Department of Clinical Medicine, Churchill Hospital, University of Oxford, Oxford, UK
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G protein-coupled receptors stimulation and the control of cell migration. Cell Signal 2009; 21:1045-53. [DOI: 10.1016/j.cellsig.2009.02.008] [Citation(s) in RCA: 128] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2008] [Revised: 02/03/2009] [Accepted: 02/17/2009] [Indexed: 01/14/2023]
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Cytohesin-1 controls the activation of RhoA and modulates integrin-dependent adhesion and migration of dendritic cells. Blood 2009; 113:5801-10. [PMID: 19346499 DOI: 10.1182/blood-2008-08-176123] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Adhesion and motility of mammalian leukocytes are essential requirements for innate and adaptive immune defense mechanisms. We show here that the guanine nucleotide exchange factor cytohesin-1, which had previously been demonstrated to be an important component of beta-2 integrin activation in lymphocytes, regulates the activation of the small GTPase RhoA in primary dendritic cells (DCs). Cytohesin-1 and RhoA are both required for the induction of chemokine-dependent conformational changes of the integrin beta-2 subunit of DCs during adhesion under physiological flow conditions. Furthermore, use of RNAi in murine bone marrow DCs (BM-DCs) revealed that interference with cytohesin-1 signaling impairs migration of wild-type dendritic cells in complex 3D environments and in vivo. This phenotype was not observed in the complete absence of integrins. We thus demonstrate an essential role of cytohesin-1/RhoA during ameboid migration in the presence of integrins and further suggest that DCs without integrins switch to a different migration mode.
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Bouschet T, Martin S, Henley JM. Regulation of calcium-sensing-receptor trafficking and cell-surface expression by GPCRs and RAMPs. Trends Pharmacol Sci 2008; 29:633-9. [PMID: 18930324 DOI: 10.1016/j.tips.2008.09.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2008] [Revised: 09/15/2008] [Accepted: 09/16/2008] [Indexed: 12/14/2022]
Abstract
The calcium-sensing (CaS) receptor is a G-protein-coupled receptor (GPCR) that is of fundamental importance for extracellular calcium signalling and calcium homeostasis. The CaS receptor detects changes in free, ionized extracellular calcium concentration and initiates pathways that constantly re-adjust levels of circulating calcium. In addition, the CaS receptor is involved in processes such as stem-cell homing and regulation of neuronal-process outgrowth. To perform these functions, the CaS receptor must be appropriately targeted to the plasma membrane so that its large N-terminal calcium-sensing domain is positioned in the extracellular environment to detect dynamic changes in ionic calcium concentration. Here, we provide an overview of the molecular determinants controlling CaS receptor forward traffic and highlight the roles of CaS receptor interactors such as receptor-activity-modifying proteins and subunits of other class C GPCRs in this process.
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Affiliation(s)
- Tristan Bouschet
- Department of Anatomy, Medical Research Council Centre for Synaptic Plasticity, School of Medical Sciences, University of Bristol, University Walk, Bristol, UK
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Breitwieser GE. Extracellular calcium as an integrator of tissue function. Int J Biochem Cell Biol 2008; 40:1467-80. [PMID: 18328773 PMCID: PMC2441573 DOI: 10.1016/j.biocel.2008.01.019] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2007] [Revised: 01/16/2008] [Accepted: 01/18/2008] [Indexed: 12/23/2022]
Abstract
The past several decades of research into calcium signaling have focused on intracellular calcium (Ca(i)(2+)), revealing both exquisite spatial and dynamic control of this potent second messenger. Our understanding of Ca(i)(2+) signaling has benefited from the evolution of cell culture methods, development of high affinity fluorescent calcium indicators (both membrane-permeant small molecules and genetically encoded proteins), and high-resolution fluorescence microscopy. As our understanding of single cell calcium dynamics has increased, translational efforts have attempted to push calcium signaling studies back into tissues, organs and whole animals. Emerging results from these more complicated, diffusion-limited systems have begun to define a role for extracellular calcium (Ca(o)(2+)) as an agonist, spurred by the cloning and characterization of a G protein-coupled receptor activated by Ca(o)(2+) (the calcium sensing receptor, CaR). Here, we review the current state-of-the art for measurement of Ca(o)(2+) fluctuations, and the evidence that fluctuations in Ca(o)(2+) can act as primary signals regulating cell function. Current results suggest that Ca(o)(2+) in bone and epidermis may act as a chemotactic homing signal, targeting cells to the appropriate tissue locations prior to initiation of the differentiation program. Ca(i)(2+) signaling-mediated Ca(o)(2+) fluctuations in interstitial spaces may integrate cell signaling responses in multicellular networks through activation of CaR. Appreciation of the importance of Ca(o)(2+) fluctuations in coordinating cell function will likely spur identification of additional, niche-specific Ca(2+) sensors, and provide unique insights into the regulation of multicellular signaling networks.
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Affiliation(s)
- Gerda E Breitwieser
- Weis Center for Research, Geisinger Clinic, 100 N. Academy Avenue, Danville, PA 17822, United States.
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