1
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Kaoullas MG, Thal DM, Christopoulos A, Valant C. Ligand bias at the muscarinic acetylcholine receptor family: Opportunities and challenges. Neuropharmacology 2024; 258:110092. [PMID: 39067666 DOI: 10.1016/j.neuropharm.2024.110092] [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: 03/18/2024] [Revised: 06/25/2024] [Accepted: 07/24/2024] [Indexed: 07/30/2024]
Abstract
Muscarinic acetylcholine receptors (mAChRs) are G protein-coupled receptors (GPCRs) that are activated by the endogenous neurotransmitter, acetylcholine (ACh). Disruption of mAChR signalling has been associated with a variety of neurological disorders and non-neurological diseases. Consequently, the development of agonists and antagonists of the mAChRs has been a major avenue in drug discovery. Unfortunately, mAChR ligands are often associated with on-target side effects for two reasons. The first reason is due to the high sequence conservation at the orthosteric ACh binding site among all five receptor subtypes (M1-M5), making on-target subtype selectivity a major challenge. The second reason is due to on-target side effects of mAChR drugs that are associated with the pleiotropic nature of mAChR signalling at the level of a single mAChR subtype. Indeed, there is growing evidence that within the myriad of signalling events produced by mAChR ligands, some will have therapeutic benefits, whilst others may promote cholinergic side effects. This paradigm of drug action, known as ligand bias or biased agonism, is an attractive feature for next-generation mAChR drugs, as it holds the promise of developing drugs devoid of on-target adverse effects. Although relatively simple to detect and even quantify in vitro, ligand bias, as observed in recombinant systems, does not always translate to in vivo systems, which remains a major hurdle in GPCR drug discovery, including the mAChR family. Here we report recent studies that have attempted to detect and quantify ligand bias at the mAChR family, and briefly discuss the challenges associated with biased agonist drug development.
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Affiliation(s)
- Michaela G Kaoullas
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, 399 Royal Parade, 3052, VIC, Parkville, Melbourne, Australia
| | - David M Thal
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, 399 Royal Parade, 3052, VIC, Parkville, Melbourne, Australia
| | - Arthur Christopoulos
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, 399 Royal Parade, 3052, VIC, Parkville, Melbourne, Australia.
| | - Celine Valant
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, 399 Royal Parade, 3052, VIC, Parkville, Melbourne, Australia.
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2
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Kim YJ, Tohyama S, Nagashima T, Nagase M, Hida Y, Hamada S, Watabe AM, Ohtsuka T. A light-controlled phospholipase C for imaging of lipid dynamics and controlling neural plasticity. Cell Chem Biol 2024; 31:1336-1348.e7. [PMID: 38582083 DOI: 10.1016/j.chembiol.2024.03.001] [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: 10/25/2023] [Revised: 02/05/2024] [Accepted: 03/12/2024] [Indexed: 04/08/2024]
Abstract
Phospholipase C (PLC) is a key enzyme that regulates physiological processes via lipid and calcium signaling. Despite advances in protein engineering, no tools are available for direct PLC control. Here, we developed a novel optogenetic tool, light-controlled PLCβ (opto-PLCβ). Opto-PLCβ uses a light-induced dimer module, which directs an engineered PLC to the plasma membrane in a light-dependent manner. Our design includes an autoinhibitory capacity, ensuring stringent control over PLC activity. Opto-PLCβ triggers reversible calcium responses and lipid dynamics in a restricted region, allowing precise spatiotemporal control of PLC signaling. Using our system, we discovered that phospholipase D-mediated phosphatidic acid contributes to diacylglycerol clearance on the plasma membrane. Moreover, we extended its applicability in vivo, demonstrating that opto-PLCβ can enhance amygdala synaptic plasticity and associative fear learning in mice. Thus, opto-PLCβ offers precise spatiotemporal control, enabling comprehensive investigation of PLC-mediated signaling pathways, lipid dynamics, and their physiological consequences in vivo.
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Affiliation(s)
- Yeon-Jeong Kim
- Department of Biochemistry, Graduate School of Medicine, Faculty of Medicine, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi 409-3898, Japan
| | - Suguru Tohyama
- Institute of Clinical Medicine and Research, Research Center for Medical Sciences, The Jikei University School of Medicine, Chiba, Japan
| | - Takashi Nagashima
- Institute of Clinical Medicine and Research, Research Center for Medical Sciences, The Jikei University School of Medicine, Chiba, Japan
| | - Masashi Nagase
- Institute of Clinical Medicine and Research, Research Center for Medical Sciences, The Jikei University School of Medicine, Chiba, Japan
| | - Yamato Hida
- Department of Biochemistry, Graduate School of Medicine, Faculty of Medicine, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi 409-3898, Japan
| | - Shun Hamada
- Department of Biochemistry, Graduate School of Medicine, Faculty of Medicine, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi 409-3898, Japan
| | - Ayako M Watabe
- Institute of Clinical Medicine and Research, Research Center for Medical Sciences, The Jikei University School of Medicine, Chiba, Japan.
| | - Toshihisa Ohtsuka
- Department of Biochemistry, Graduate School of Medicine, Faculty of Medicine, University of Yamanashi, 1110 Shimokato, Chuo, Yamanashi 409-3898, Japan.
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3
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Falzone ME, MacKinnon R. The mechanism of Gαq regulation of PLCβ3-catalyzed PIP2 hydrolysis. Proc Natl Acad Sci U S A 2023; 120:e2315011120. [PMID: 37991948 PMCID: PMC10691244 DOI: 10.1073/pnas.2315011120] [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: 08/30/2023] [Accepted: 10/13/2023] [Indexed: 11/24/2023] Open
Abstract
PLCβ (Phospholipase Cβ) enzymes cleave phosphatidylinositol 4,5-bisphosphate (PIP2) producing IP3 and DAG (diacylglycerol). PIP2 modulates the function of many ion channels, while IP3 and DAG regulate intracellular Ca2+ levels and protein phosphorylation by protein kinase C, respectively. PLCβ enzymes are under the control of G protein coupled receptor signaling through direct interactions with G proteins Gβγ and Gαq and have been shown to be coincidence detectors for dual stimulation of Gαq and Gαi-coupled receptors. PLCβs are aqueous-soluble cytoplasmic enzymes but partition onto the membrane surface to access their lipid substrate, complicating their functional and structural characterization. Using newly developed methods, we recently showed that Gβγ activates PLCβ3 by recruiting it to the membrane. Using these same methods, here we show that Gαq increases the catalytic rate constant, kcat, of PLCβ3. Since stimulation of PLCβ3 by Gαq depends on an autoinhibitory element (the X-Y linker), we propose that Gαq produces partial relief of the X-Y linker autoinhibition through an allosteric mechanism. We also determined membrane-bound structures of the PLCβ3·Gαq and PLCβ3·Gβγ(2)·Gαq complexes, which show that these G proteins can bind simultaneously and independently of each other to regulate PLCβ3 activity. The structures rationalize a finding in the enzyme assay, that costimulation by both G proteins follows a product rule of each independent stimulus. We conclude that baseline activity of PLCβ3 is strongly suppressed, but the effect of G proteins, especially acting together, provides a robust stimulus upon G protein stimulation.
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Affiliation(s)
- Maria E. Falzone
- Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University, New York, NY10065
- HHMI, The Rockefeller University, New York, NY10065
| | - Roderick MacKinnon
- Laboratory of Molecular Neurobiology and Biophysics, The Rockefeller University, New York, NY10065
- HHMI, The Rockefeller University, New York, NY10065
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4
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Daly C, Plouffe B. Gα q signalling from endosomes: A new conundrum. Br J Pharmacol 2023. [PMID: 37740273 DOI: 10.1111/bph.16248] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 08/08/2023] [Accepted: 09/13/2023] [Indexed: 09/24/2023] Open
Abstract
G-protein-coupled receptors (GPCRs) constitute the largest family of membrane receptors, and are involved in the transmission of a variety of extracellular stimuli such as hormones, neurotransmitters, light and odorants into intracellular responses. They regulate every aspect of physiology and, for this reason, about one third of all marketed drugs target these receptors. Classically, upon binding to their agonist, GPCRs are thought to activate G-proteins from the plasma membrane and to stop signalling by subsequent desensitisation and endocytosis. However, accumulating evidence indicates that, upon internalisation, some GPCRs can continue to activate G-proteins in endosomes. Importantly, this signalling from endomembranes mediates alternative cellular responses other than signalling at the plasma membrane. Endosomal G-protein signalling and its physiological relevance have been abundantly documented for Gαs - and Gαi -coupled receptors. Recently, some Gαq -coupled receptors have been reported to activate Gαq on endosomes and mediate important cellular processes. However, several questions relative to the series of cellular events required to translate endosomal Gαq activation into cellular responses remain unanswered and constitute a new conundrum. How are these responses in endosomes mediated in the quasi absence of the substrate for the canonical Gαq -activated effector? Is there another effector? Is there another substrate? If so, how does this alternative endosomal effector or substrate produce a downstream signal? This review aims to unravel and discuss these important questions, and proposes possible routes of investigation.
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Affiliation(s)
- Carole Daly
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Belfast, UK
| | - Bianca Plouffe
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Belfast, UK
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5
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Falzone ME, MacKinnon R. The mechanism of Gα q regulation of PLCβ3 -catalyzed PIP2 hydrolysis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.29.555394. [PMID: 37693483 PMCID: PMC10491199 DOI: 10.1101/2023.08.29.555394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
PLCβ enzymes cleave PIP2 producing IP3 and DAG. PIP2 modulates the function of many ion channels, while IP3 and DAG regulate intracellular Ca 2+ levels and protein phosphorylation by protein kinase C, respectively. PLCβ enzymes are under the control of GPCR signaling through direct interactions with G proteins Gβγ and Gα q and have been shown to be coincidence detectors for dual stimulation of Gα q and G α i coupled receptors. PLCβs are aqueous-soluble cytoplasmic enzymes, but partition onto the membrane surface to access their lipid substrate, complicating their functional and structural characterization. Using newly developed methods, we recently showed that Gβγ activates PLCβ3 by recruiting it to the membrane. Using these same methods, here we show that Gα q increases the catalytic rate constant, k cat , of PLCβ3 . Since stimulation of PLCβ3 by Gα q depends on an autoinhibitory element (the X-Y linker), we propose that Gα q produces partial relief of the X-Y linker autoinhibition through an allosteric mechanism. We also determined membrane-bound structures of the PLCβ3-Gα q , and PLCβ3-Gβγ(2)-Gα q complexes, which show that these G proteins can bind simultaneously and independently of each other to regulate PLCβ3 activity. The structures rationalize a finding in the enzyme assay, that co-stimulation by both G proteins follows a product rule of each independent stimulus. We conclude that baseline activity of PLCβ3 is strongly suppressed, but the effect of G proteins, especially acting together, provides a robust stimulus upon G protein stimulation. Significance Statement For certain cellular signaling processes, the background activity of signaling enzymes must be minimal and stimulus-dependent activation robust. Nowhere is this truer than in signaling by PLCβ3 , whose activity regulates intracellular Ca 2+ , phosphorylation by Protein Kinase C, and the activity of numerous ion channels and membrane receptors. In this study we show how PLCβ3 enzymes are regulated by two kinds of G proteins, Gβγ and Gα q . Enzyme activity studies and structures on membranes show how these G proteins act by separate, independent mechanisms, leading to a product rule of co-stimulation when they act together. The findings explain how cells achieve robust stimulation of PLCβ3 in the setting of very low background activity, properties essential to cell health and survival.
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6
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Ubeysinghe S, Wijayaratna D, Kankanamge D, Karunarathne A. Molecular regulation of PLCβ signaling. Methods Enzymol 2023; 682:17-52. [PMID: 36948701 DOI: 10.1016/bs.mie.2023.01.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
Phospholipase C (PLC) enzymes convert the membrane phospholipid phosphatidylinositol-4,5-bisphosphate (PIP2) into inositol-1,4,5-triphosphate (IP3) and diacylglycerol (DAG). IP3 and DAG regulate numerous downstream pathways, eliciting diverse and profound cellular changes and physiological responses. In the six PLC subfamilies in higher eukaryotes, PLCβ is intensively studied due to its prominent role in regulating crucial cellular events underlying many processes including cardiovascular and neuronal signaling, and associated pathological conditions. In addition to GαqGTP, Gβγ generated upon G protein heterotrimer dissociation also regulates PLCβ activity. Here, we not only review how Gβγ directly activates PLCβ, and also extensively modulates Gαq-mediated PLCβ activity, but also provide a structure-function overview of PLC family members. Given that Gαq and PLCβ are oncogenes, and Gβγ shows unique cell-tissue-organ specific expression profiles, Gγ subtype-dependent signaling efficacies, and distinct subcellular activities, this review proposes that Gβγ is a major regulator of Gαq-dependent and independent PLCβ signaling.
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Affiliation(s)
| | | | - Dinesh Kankanamge
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, United States
| | - Ajith Karunarathne
- Department of Chemistry, St. Louis University, St. Louis, MO, United States.
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7
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Xiang G, Acosta-Ruiz A, Radoux-Mergault A, Kristt M, Kim J, Moon JD, Broichhagen J, Inoue A, Lee FS, Stoeber M, Dittman JS, Levitz J. Control of Gα q signaling dynamics and GPCR cross-talk by GRKs. SCIENCE ADVANCES 2022; 8:eabq3363. [PMID: 36427324 PMCID: PMC9699688 DOI: 10.1126/sciadv.abq3363] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Numerous processes contribute to the regulation of G protein-coupled receptors (GPCRs), but relatively little is known about rapid mechanisms that control signaling on the seconds time scale or regulate cross-talk between receptors. Here, we reveal that the ability of some GPCR kinases (GRKs) to bind Gαq both drives acute signaling desensitization and regulates functional interactions between GPCRs. GRK2/3-mediated acute desensitization occurs within seconds, is rapidly reversible, and can occur upon local, subcellular activation. This rapid desensitization is kinase independent, insensitive to pharmacological inhibition, and generalizable across receptor families and effectors. We also find that the ability of GRK2 to bind G proteins also enables it to regulate the extent and timing of Gαq-dependent signaling cross-talk between GPCRs. Last, we find that G protein/GRK2 interactions enable a novel form of GPCR trafficking cross-talk. Together, this work reveals potent forms of Gαq-dependent GPCR regulation with wide-ranging pharmacological and physiological implications.
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Affiliation(s)
- Guoqing Xiang
- Department of Biochemistry, Weill Cornell Medicine, New York, NY, USA
- Department of Psychiatry, Weill Cornell Medicine, New York, NY, USA
| | | | | | - Melanie Kristt
- Department of Biochemistry, Weill Cornell Medicine, New York, NY, USA
| | - Jihye Kim
- Department of Psychiatry, Weill Cornell Medicine, New York, NY, USA
| | - Jared D. Moon
- Department of Biochemistry, Weill Cornell Medicine, New York, NY, USA
| | | | - Asuka Inoue
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - Francis S. Lee
- Department of Psychiatry, Weill Cornell Medicine, New York, NY, USA
| | - Miriam Stoeber
- Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland
| | - Jeremy S. Dittman
- Department of Biochemistry, Weill Cornell Medicine, New York, NY, USA
| | - Joshua Levitz
- Department of Biochemistry, Weill Cornell Medicine, New York, NY, USA
- Department of Psychiatry, Weill Cornell Medicine, New York, NY, USA
- Corresponding author.
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8
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Le Huray KIP, Bunney TD, Pinotsis N, Kalli AC, Katan M. Characterization of the membrane interactions of phospholipase Cγ reveals key features of the active enzyme. SCIENCE ADVANCES 2022; 8:eabp9688. [PMID: 35749497 PMCID: PMC9232102 DOI: 10.1126/sciadv.abp9688] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 05/06/2022] [Indexed: 06/15/2023]
Abstract
PLCγ enzymes are autoinhibited in resting cells and form key components of intracellular signaling that are also linked to disease development. Insights into physiological and aberrant activation of PLCγ require understanding of an active, membrane-bound form, which can hydrolyze inositol-lipid substrates. Here, we demonstrate that PLCγ1 cannot bind membranes unless the autoinhibition is disrupted. Through extensive molecular dynamics simulations and experimental evidence, we characterize membrane binding by the catalytic core domains and reveal previously unknown sites of lipid interaction. The identified sites act in synergy, overlap with autoinhibitory interfaces, and are shown to be critical for the phospholipase activity in cells. This work provides direct evidence that PLCγ1 is inhibited through obstruction of its membrane-binding surfaces by the regulatory region and that activation must shift PLCγ1 to a conformation competent for membrane binding. Knowledge of the critical sites of membrane interaction extends the mechanistic framework for activation, dysregulation, and therapeutic intervention.
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Affiliation(s)
- Kyle I. P. Le Huray
- Astbury Centre for Structural Molecular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT UK
- Leeds Institute of Cardiovascular and Metabolic Medicine, School of Medicine, University of Leeds, Leeds LS2 9JT, UK
| | - Tom D. Bunney
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, Gower St., London WC1E 6BT, UK
| | - Nikos Pinotsis
- Institute of Structural and Molecular Biology, Birkbeck College, London, WC1E 6BT, UK
| | - Antreas C. Kalli
- Astbury Centre for Structural Molecular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
- Leeds Institute of Cardiovascular and Metabolic Medicine, School of Medicine, University of Leeds, Leeds LS2 9JT, UK
| | - Matilda Katan
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, Gower St., London WC1E 6BT, UK
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9
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Phan HTN, Kim NH, Wei W, Tall GG, Smrcka AV. Uveal melanoma-associated mutations in PLCβ4 are constitutively activating and promote melanocyte proliferation and tumorigenesis. Sci Signal 2021; 14:eabj4243. [PMID: 34905385 DOI: 10.1126/scisignal.abj4243] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Hoa T N Phan
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Nam Hoon Kim
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Wenhui Wei
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Gregory G Tall
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Alan V Smrcka
- Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
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10
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From spikes to intercellular waves: Tuning intercellular calcium signaling dynamics modulates organ size control. PLoS Comput Biol 2021; 17:e1009543. [PMID: 34723960 PMCID: PMC8601605 DOI: 10.1371/journal.pcbi.1009543] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 11/18/2021] [Accepted: 10/07/2021] [Indexed: 12/18/2022] Open
Abstract
Information flow within and between cells depends significantly on calcium (Ca2+) signaling dynamics. However, the biophysical mechanisms that govern emergent patterns of Ca2+ signaling dynamics at the organ level remain elusive. Recent experimental studies in developing Drosophila wing imaginal discs demonstrate the emergence of four distinct patterns of Ca2+ activity: Ca2+ spikes, intercellular Ca2+ transients, tissue-level Ca2+ waves, and a global “fluttering” state. Here, we used a combination of computational modeling and experimental approaches to identify two different populations of cells within tissues that are connected by gap junction proteins. We term these two subpopulations “initiator cells,” defined by elevated levels of Phospholipase C (PLC) activity, and “standby cells,” which exhibit baseline activity. We found that the type and strength of hormonal stimulation and extent of gap junctional communication jointly determine the predominate class of Ca2+ signaling activity. Further, single-cell Ca2+ spikes are stimulated by insulin, while intercellular Ca2+ waves depend on Gαq activity. Our computational model successfully reproduces how the dynamics of Ca2+ transients varies during organ growth. Phenotypic analysis of perturbations to Gαq and insulin signaling support an integrated model of cytoplasmic Ca2+ as a dynamic reporter of overall tissue growth. Further, we show that perturbations to Ca2+ signaling tune the final size of organs. This work provides a platform to further study how organ size regulation emerges from the crosstalk between biochemical growth signals and heterogeneous cell signaling states. Calcium (Ca2+) is a universal second messenger that regulates a myriad of cellular processes such as cell division, cell proliferation and apoptosis. Multiple patterns of Ca2+ signaling including single-cell spikes, multicellular Ca2+ transients, large-scale Ca2+ waves, and global “fluttering” have been observed in epithelial systems during organ development. Key molecular players and biophysical mechanisms involved in formation of these patterns during organ development are not well understood. In this work, we developed a generalized multicellular model of Ca2+ that captures all the key categories of Ca2+ activity as a function of key hormonal signals. Integration of model predictions and experiments reveals two subclasses of cell populations and demonstrates that Ca2+ signaling activity at the organ scale is defined by a general decrease in gap junction communication as an organ grows. Our experiments also reveal that a “goldilocks zone” of optimal Ca2+ activity is required to achieve optimal growth at the organ level.
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11
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Qifti A, Jackson L, Singla A, Garwain O, Scarlata S. Stimulation of phospholipase Cβ1 by Gα q promotes the assembly of stress granule proteins. Sci Signal 2021; 14:eaav1012. [PMID: 34665639 DOI: 10.1126/scisignal.aav1012] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
[Figure: see text].
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Affiliation(s)
- Androniqi Qifti
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, MA 01609, USA
| | - Lela Jackson
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, MA 01609, USA
| | - Ashima Singla
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, MA 01609, USA
| | - Osama Garwain
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, MA 01609, USA
| | - Suzanne Scarlata
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, MA 01609, USA
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12
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Wilkie TM, Hale MA, Reddy S. Gq-Gi-PLCβ in cells: More than the sum of its reconstituted parts. Cell Calcium 2021; 94:102340. [PMID: 33601151 DOI: 10.1016/j.ceca.2020.102340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Accepted: 12/24/2020] [Indexed: 11/16/2022]
Abstract
The recent paper by Pfeil et al., "Heterotrimeric G Protein Subunit Gαq Is a Master Switch for Gβγ-Mediated Calcium Mobilization by Gi-Coupled GPCRs", opens another path from biochemical in vitro reconstitution to understanding the complex regulation of calcium signaling inside the cell.
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Affiliation(s)
- Thomas M Wilkie
- Department of Pharmacology, UT Southwestern Medical Center, 6001 Forest Park Drive, Dallas, TX 75390, USA; Cancer Discovery Team, Wilkie Laboratory, Department of Pharmacology, UT Southwestern Medical Center, 6001 Forest Park Drive, Dallas, TX 75390, USA.
| | - Michael A Hale
- Department of Pharmacology, UT Southwestern Medical Center, 6001 Forest Park Drive, Dallas, TX 75390, USA; Cancer Discovery Team, Wilkie Laboratory, Department of Pharmacology, UT Southwestern Medical Center, 6001 Forest Park Drive, Dallas, TX 75390, USA
| | - Sarthak Reddy
- Cancer Discovery Team, Wilkie Laboratory, Department of Pharmacology, UT Southwestern Medical Center, 6001 Forest Park Drive, Dallas, TX 75390, USA
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13
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Muralidharan K, Van Camp MM, Lyon AM. Structure and regulation of phospholipase Cβ and ε at the membrane. Chem Phys Lipids 2021; 235:105050. [PMID: 33422547 DOI: 10.1016/j.chemphyslip.2021.105050] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 10/28/2020] [Accepted: 01/04/2021] [Indexed: 12/28/2022]
Abstract
Phospholipase C (PLC) β and ε enzymes hydrolyze phosphatidylinositol (PI) lipids in response to direct interactions with heterotrimeric G protein subunits and small GTPases, which are activated downstream of G protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs). PI hydrolysis generates second messengers that increase the intracellular Ca2+ concentration and activate protein kinase C (PKC), thereby regulating numerous physiological processes. PLCβ and PLCε share a highly conserved core required for lipase activity, but use different strategies and structural elements to autoinhibit basal activity, bind membranes, and engage G protein activators. In this review, we discuss recent structural insights into these enzymes and the implications for how they engage membranes alone or in complex with their G protein regulators.
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Affiliation(s)
- Kaushik Muralidharan
- Department of Biological Sciences, 560 Oval Drive, Purdue University, West Lafayette, IN, 47907, United States.
| | - Michelle M Van Camp
- Department of Chemistry, 560 Oval Drive, Purdue University, West Lafayette, IN, 47907, United States.
| | - Angeline M Lyon
- Department of Biological Sciences, 560 Oval Drive, Purdue University, West Lafayette, IN, 47907, United States; Department of Chemistry, 560 Oval Drive, Purdue University, West Lafayette, IN, 47907, United States.
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14
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Abstract
Pfeil et al., (2020) examine the mechanism of Gi-stimulated Ca2+ release in cells and find an unexpected role for Gαq in Gβγ-dependent activation of phospholipase Cβ (PLCβ).
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Affiliation(s)
- Isaac J Fisher
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA; Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA
| | - Angeline M Lyon
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA; Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
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15
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Pfeil EM, Brands J, Merten N, Vögtle T, Vescovo M, Rick U, Albrecht IM, Heycke N, Kawakami K, Ono Y, Ngako Kadji FM, Hiratsuka S, Aoki J, Häberlein F, Matthey M, Garg J, Hennen S, Jobin ML, Seier K, Calebiro D, Pfeifer A, Heinemann A, Wenzel D, König GM, Nieswandt B, Fleischmann BK, Inoue A, Simon K, Kostenis E. Heterotrimeric G Protein Subunit Gαq Is a Master Switch for Gβγ-Mediated Calcium Mobilization by Gi-Coupled GPCRs. Mol Cell 2020; 80:940-954.e6. [PMID: 33202251 DOI: 10.1016/j.molcel.2020.10.027] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 09/21/2020] [Accepted: 10/16/2020] [Indexed: 12/18/2022]
Abstract
Mechanisms that control mobilization of cytosolic calcium [Ca2+]i are key for regulation of numerous eukaryotic cell functions. One such paradigmatic mechanism involves activation of phospholipase Cβ (PLCβ) enzymes by G protein βγ subunits from activated Gαi-Gβγ heterotrimers. Here, we report identification of a master switch to enable this control for PLCβ enzymes in living cells. We find that the Gαi-Gβγ-PLCβ-Ca2+ signaling module is entirely dependent on the presence of active Gαq. If Gαq is pharmacologically inhibited or genetically ablated, Gβγ can bind to PLCβ but does not elicit Ca2+ signals. Removal of an auto-inhibitory linker that occludes the active site of the enzyme is required and sufficient to empower "stand-alone control" of PLCβ by Gβγ. This dependence of Gi-Gβγ-Ca2+ on Gαq places an entire signaling branch of G-protein-coupled receptors (GPCRs) under hierarchical control of Gq and changes our understanding of how Gi-GPCRs trigger [Ca2+]i via PLCβ enzymes.
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Affiliation(s)
- Eva Marie Pfeil
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany; Research Training Group 1873, University of Bonn, Bonn, Germany
| | - Julian Brands
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany; Research Training Group 1873, University of Bonn, Bonn, Germany
| | - Nicole Merten
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Timo Vögtle
- Institute of Experimental Biomedicine I, University Hospital Würzburg and Rudolf Virchow Center, University of Würzburg, 97080 Würzburg, Germany
| | - Maddalena Vescovo
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Ulrike Rick
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Ina-Maria Albrecht
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Nina Heycke
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Kouki Kawakami
- Graduate School of Pharmaceutical Science, Tohoku University, Sendai 980-8578, Japan
| | - Yuki Ono
- Graduate School of Pharmaceutical Science, Tohoku University, Sendai 980-8578, Japan
| | | | - Suzune Hiratsuka
- Graduate School of Pharmaceutical Science, Tohoku University, Sendai 980-8578, Japan
| | - Junken Aoki
- Graduate School of Pharmaceutical Science, Tohoku University, Sendai 980-8578, Japan
| | - Felix Häberlein
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany; Research Training Group 1873, University of Bonn, Bonn, Germany
| | - Michaela Matthey
- Department of Systems Physiology, Medical Faculty, Ruhr University Bochum, 44801 Bochum, Germany; Institute of Physiology I, Life and Brain Center, Medical Faculty, University of Bonn, Venusberg-Campus 1, 53127 Bonn, Germany
| | - Jaspal Garg
- Institute of Pharmacology and Toxicology, University Hospital Bonn, University of Bonn, 53127 Bonn, Germany
| | - Stephanie Hennen
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Marie-Lise Jobin
- Institute of Pharmacology and Toxicology and Bio-Imaging Center, University of Würzburg, 97078 Würzburg, Germany
| | - Kerstin Seier
- Institute of Pharmacology and Toxicology and Bio-Imaging Center, University of Würzburg, 97078 Würzburg, Germany
| | - Davide Calebiro
- Institute of Pharmacology and Toxicology and Bio-Imaging Center, University of Würzburg, 97078 Würzburg, Germany; Institute of Metabolism and Systems Research and Centre of Membrane Proteins and Receptors, University of Birmingham, B15 2TT Birmingham, UK
| | - Alexander Pfeifer
- Institute of Physiology I, Life and Brain Center, Medical Faculty, University of Bonn, Venusberg-Campus 1, 53127 Bonn, Germany
| | - Akos Heinemann
- Division of Pharmacology, Otto-Loewi Research Center for Vascular Biology, Immunology and Inflammation, Medical University of Graz, 8010 Graz, Austria
| | - Daniela Wenzel
- Department of Systems Physiology, Medical Faculty, Ruhr University Bochum, 44801 Bochum, Germany; Institute of Physiology I, Life and Brain Center, Medical Faculty, University of Bonn, Venusberg-Campus 1, 53127 Bonn, Germany
| | - Gabriele M König
- Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany
| | - Bernhard Nieswandt
- Institute of Experimental Biomedicine I, University Hospital Würzburg and Rudolf Virchow Center, University of Würzburg, 97080 Würzburg, Germany
| | - Bernd K Fleischmann
- Institute of Physiology I, Life and Brain Center, Medical Faculty, University of Bonn, Venusberg-Campus 1, 53127 Bonn, Germany
| | - Asuka Inoue
- Graduate School of Pharmaceutical Science, Tohoku University, Sendai 980-8578, Japan
| | - Katharina Simon
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany.
| | - Evi Kostenis
- Molecular, Cellular and Pharmacobiology Section, Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, 53115 Bonn, Germany.
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16
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Katan M, Cockcroft S. Phospholipase C families: Common themes and versatility in physiology and pathology. Prog Lipid Res 2020; 80:101065. [PMID: 32966869 DOI: 10.1016/j.plipres.2020.101065] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 08/14/2020] [Accepted: 09/17/2020] [Indexed: 12/20/2022]
Abstract
Phosphoinositide-specific phospholipase Cs (PLCs) are expressed in all mammalian cells and play critical roles in signal transduction. To obtain a comprehensive understanding of these enzymes in physiology and pathology, a detailed structural, biochemical, cell biological and genetic information is required. In this review, we cover all these aspects to summarize current knowledge of the entire superfamily. The families of PLCs have expanded from 13 enzymes to 16 with the identification of the atypical PLCs in the human genome. Recent structural insights highlight the common themes that cover not only the substrate catalysis but also the mechanisms of activation. This involves the release of autoinhibitory interactions that, in the absence of stimulation, maintain classical PLC enzymes in their inactive forms. Studies of individual PLCs provide a rich repertoire of PLC function in different physiologies. Furthermore, the genetic studies discovered numerous mutated and rare variants of PLC enzymes and their link to human disease development, greatly expanding our understanding of their roles in diverse pathologies. Notably, substantial evidence now supports involvement of different PLC isoforms in the development of specific cancer types, immune disorders and neurodegeneration. These advances will stimulate the generation of new drugs that target PLC enzymes, and will therefore open new possibilities for treatment of a number of diseases where current therapies remain ineffective.
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Affiliation(s)
- Matilda Katan
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, Gower Street, London WC1E 6BT, UK
| | - Shamshad Cockcroft
- Department of Neuroscience, Physiology and Pharmacology, Division of Biosciences, University College London, 21 University Street, London WC1E 6JJ, UK.
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17
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Rugema NY, Garland-Kuntz EE, Sieng M, Muralidharan K, Van Camp MM, O'Neill H, Mbongo W, Selvia AF, Marti AT, Everly A, McKenzie E, Lyon AM. Structure of phospholipase Cε reveals an integrated RA1 domain and previously unidentified regulatory elements. Commun Biol 2020; 3:445. [PMID: 32796910 PMCID: PMC7427993 DOI: 10.1038/s42003-020-01178-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 07/27/2020] [Indexed: 12/15/2022] Open
Abstract
Phospholipase Cε (PLCε) generates lipid-derived second messengers at the plasma and perinuclear membranes in the cardiovascular system. It is activated in response to a wide variety of signals, such as those conveyed by Rap1A and Ras, through a mechanism that involves its C-terminal Ras association (RA) domains (RA1 and RA2). However, the complexity and size of PLCε has hindered its structural and functional analysis. Herein, we report the 2.7 Å crystal structure of the minimal fragment of PLCε that retains basal activity. This structure includes the RA1 domain, which forms extensive interactions with other core domains. A conserved amphipathic helix in the autoregulatory X-Y linker of PLCε is also revealed, which we show modulates activity in vitro and in cells. The studies provide the structural framework for the core of this critical cardiovascular enzyme that will allow for a better understanding of its regulation and roles in disease.
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Affiliation(s)
- Ngango Y Rugema
- Department of Chemistry, Purdue University, West Lafayette, 47907, IN, USA
| | | | - Monita Sieng
- Department of Chemistry, Purdue University, West Lafayette, 47907, IN, USA
| | - Kaushik Muralidharan
- Department of Biological Sciences, Purdue University, West Lafayette, 47907, IN, USA
| | | | - Hannah O'Neill
- Department of Chemistry, Purdue University, West Lafayette, 47907, IN, USA
| | - William Mbongo
- Department of Chemistry, Purdue University, West Lafayette, 47907, IN, USA
| | - Arielle F Selvia
- Department of Chemistry, Purdue University, West Lafayette, 47907, IN, USA
| | - Andrea T Marti
- Department of Biological Sciences, Purdue University, West Lafayette, 47907, IN, USA
| | - Amanda Everly
- Department of Chemistry, Purdue University, West Lafayette, 47907, IN, USA
| | - Emmanda McKenzie
- Department of Chemistry, Purdue University, West Lafayette, 47907, IN, USA
| | - Angeline M Lyon
- Department of Chemistry, Purdue University, West Lafayette, 47907, IN, USA.
- Department of Biological Sciences, Purdue University, West Lafayette, 47907, IN, USA.
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18
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Activation of Phospholipase C β by Gβγ and Gα q Involves C-Terminal Rearrangement to Release Autoinhibition. Structure 2020; 28:810-819.e5. [PMID: 32402248 DOI: 10.1016/j.str.2020.04.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 01/13/2020] [Accepted: 04/15/2020] [Indexed: 01/15/2023]
Abstract
Phospholipase C (PLC) enzymes hydrolyze phosphoinositide lipids to inositol phosphates and diacylglycerol. Direct activation of PLCβ by Gαq and/or Gβγ subunits mediates signaling by Gq and some Gi coupled G-protein-coupled receptors (GPCRs), respectively. PLCβ isoforms contain a unique C-terminal extension, consisting of proximal and distal C-terminal domains (CTDs) separated by a flexible linker. The structure of PLCβ3 bound to Gαq is known, however, for both Gαq and Gβγ; the mechanism for PLCβ activation on membranes is unknown. We examined PLCβ2 dynamics on membranes using hydrogen-deuterium exchange mass spectrometry (HDX-MS). Gβγ caused a robust increase in dynamics of the distal C-terminal domain (CTD). Gαq showed decreased deuterium incorporation at the Gαq binding site on PLCβ. In vitro Gβγ-dependent activation of PLC is inhibited by the distal CTD. The results suggest that disruption of autoinhibitory interactions with the CTD leads to increased PLCβ hydrolase activity.
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19
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Crystal structure of human PLD1 provides insight into activation by PI(4,5)P 2 and RhoA. Nat Chem Biol 2020; 16:400-407. [PMID: 32198492 PMCID: PMC7117805 DOI: 10.1038/s41589-020-0499-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2019] [Accepted: 02/10/2020] [Indexed: 11/08/2022]
Abstract
The signal transduction enzyme phospholipase D1 (PLD1) hydrolyzes phosphatidylcholine to generate the lipid second-messenger phosphatidic acid, which plays roles in disease processes such as thrombosis and cancer. PLD1 is directly and synergistically regulated by protein kinase C, Arf and Rho GTPases, and the membrane lipid phosphatidylinositol-4,5-bisphosphate (PIP2). Here, we present a 1.8 Å-resolution crystal structure of the human PLD1 catalytic domain, which is characterized by a globular fold with a funnel-shaped hydrophobic cavity leading to the active site. Adjacent is a PIP2-binding polybasic pocket at the membrane interface that is essential for activity. The C terminus folds into and contributes part of the catalytic pocket, which harbors a phosphohistidine that mimics an intermediate stage of the catalytic cycle. Mapping of PLD1 mutations that disrupt RhoA activation identifies the RhoA-PLD1 binding interface. This structure sheds light on PLD1 regulation by lipid and protein effectors, enabling rationale inhibitor design for this well-studied therapeutic target.
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20
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Hajicek N, Keith NC, Siraliev-Perez E, Temple BRS, Huang W, Zhang Q, Harden TK, Sondek J. Structural basis for the activation of PLC-γ isozymes by phosphorylation and cancer-associated mutations. eLife 2019; 8:e51700. [PMID: 31889510 PMCID: PMC7004563 DOI: 10.7554/elife.51700] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Accepted: 12/30/2019] [Indexed: 12/14/2022] Open
Abstract
Direct activation of the human phospholipase C-γ isozymes (PLC-γ1, -γ2) by tyrosine phosphorylation is fundamental to the control of diverse biological processes, including chemotaxis, platelet aggregation, and adaptive immunity. In turn, aberrant activation of PLC-γ1 and PLC-γ2 is implicated in inflammation, autoimmunity, and cancer. Although structures of isolated domains from PLC-γ isozymes are available, these structures are insufficient to define how release of basal autoinhibition is coupled to phosphorylation-dependent enzyme activation. Here, we describe the first high-resolution structure of a full-length PLC-γ isozyme and use it to underpin a detailed model of their membrane-dependent regulation. Notably, an interlinked set of regulatory domains integrates basal autoinhibition, tyrosine kinase engagement, and additional scaffolding functions with the phosphorylation-dependent, allosteric control of phospholipase activation. The model also explains why mutant forms of the PLC-γ isozymes found in several cancers have a wide spectrum of activities, and highlights how these activities are tuned during disease.
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Affiliation(s)
- Nicole Hajicek
- Department of PharmacologyThe University of North Carolina at Chapel HillChapel HillUnited States
| | - Nicholas C Keith
- Department of PharmacologyThe University of North Carolina at Chapel HillChapel HillUnited States
| | - Edhriz Siraliev-Perez
- Department of Biochemistry and BiophysicsThe University of North Carolina at Chapel HillChapel HillUnited States
| | - Brenda RS Temple
- Department of Biochemistry and BiophysicsThe University of North Carolina at Chapel HillChapel HillUnited States
- R L Juliano Structural Bioinformatics Core FacilityThe University of North Carolina at Chapel HillChapel HillUnited States
| | - Weigang Huang
- Division of Chemical Biology and Medicinal ChemistryThe University of North Carolina at Chapel HillChapel HillUnited States
| | - Qisheng Zhang
- Department of PharmacologyThe University of North Carolina at Chapel HillChapel HillUnited States
- Division of Chemical Biology and Medicinal ChemistryThe University of North Carolina at Chapel HillChapel HillUnited States
- Lineberger Comprehensive Cancer CenterThe University of North Carolina at Chapel HillChapel HillUnited States
| | - T Kendall Harden
- Department of PharmacologyThe University of North Carolina at Chapel HillChapel HillUnited States
| | - John Sondek
- Department of PharmacologyThe University of North Carolina at Chapel HillChapel HillUnited States
- Department of Biochemistry and BiophysicsThe University of North Carolina at Chapel HillChapel HillUnited States
- Lineberger Comprehensive Cancer CenterThe University of North Carolina at Chapel HillChapel HillUnited States
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21
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22
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Scarlata S. The role of phospholipase Cβ on the plasma membrane and in the cytosol: How modular domains enable novel functions. Adv Biol Regul 2019; 73:100636. [PMID: 31409535 DOI: 10.1016/j.jbior.2019.100636] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 07/14/2019] [Accepted: 07/25/2019] [Indexed: 01/14/2023]
Abstract
Phospholipase Cβ (PLCβ) is a signaling enzyme activated by G proteins to generate calcium signals. The catalytic core of PLCβ is surrounded by modular domains that mediate the interaction of the enzyme with known protein partners on the plasma membrane. The C-terminal region PLCβ contains a novel coiled-coil domain that is required for Gαq binding and activation. Recent work has shown that this domain also binds a number of cytosolic proteins that regulate protein translation, and that these proteins compete with Gαq for PLCβ binding. The ability of PLCβ to shuttle between the cytosol to impact protein translation and the plasma membrane to mediate calcium signals puts PLCβ in a central role in cell function.
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Affiliation(s)
- Suzanne Scarlata
- Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, 100 Institute Rd., Worcester, MA, 01609, United States.
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23
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Hudson BN, Jessup RE, Prahalad KK, Lyon AM. Gα q and the Phospholipase Cβ3 X-Y Linker Regulate Adsorption and Activity on Compressed Lipid Monolayers. Biochemistry 2019; 58:3454-3467. [PMID: 31322863 DOI: 10.1021/acs.biochem.9b00441] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Phospholipase Cβ (PLCβ) enzymes are peripheral membrane proteins required for normal cardiovascular function. PLCβ hydrolyzes phosphatidylinositol 4,5-bisphosphate, producing second messengers that increase intracellular Ca2+ level and activate protein kinase C. Under basal conditions, PLCβ is autoinhibited by its C-terminal domains and by the X-Y linker, which contains a stretch of conserved acidic residues required for interfacial activation. Following stimulation of G protein-coupled receptors, the heterotrimeric G protein subunit Gαq allosterically activates PLCβ and helps orient the activated complex at the membrane for efficient lipid hydrolysis. However, the molecular basis for how the PLCβ X-Y linker, its C-terminal domains, Gαq, and the membrane coordinately regulate activity is not well understood. Using compressed lipid monolayers and atomic force microscopy, we found that a highly conserved acidic region of the X-Y linker is sufficient to regulate adsorption. Regulation of adsorption and activity by the X-Y linker also occurs independently of the C-terminal domains. We next investigated whether Gαq-dependent activation of PLCβ altered interactions with the model membrane. Gαq increased PLCβ adsorption in a manner that was independent of the PLCβ regulatory elements and targeted adsorption to specific regions of the monolayer in the absence of the C-terminal domains. Thus, the mechanism of Gαq-dependent activation likely includes a spatial component.
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24
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Intramolecular electrostatic interactions contribute to phospholipase Cβ3 autoinhibition. Cell Signal 2019; 62:109349. [PMID: 31254604 DOI: 10.1016/j.cellsig.2019.109349] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Revised: 06/22/2019] [Accepted: 06/23/2019] [Indexed: 01/21/2023]
Abstract
Phospholipase Cβ (PLCβ) enzymes regulate second messenger production following the activation of G protein-coupled receptors (GPCRs). Under basal conditions, these enzymes are maintained in an autoinhibited state by multiple elements, including an insertion within the catalytic domain known as the X-Y linker. Although the PLCβ X-Y linker is variable in sequence and length, its C-terminus is conserved and features an acidic stretch, followed by a short helix. This helix interacts with residues near the active site, acting as a lid to sterically prevent substrate binding. However, deletions that remove the acidic stretch of the X-Y linker increase basal activity to the same extent as deletion of the entire X-Y linker. Thus, the acidic stretch may be the linchpin in autoinhibition mediated by the X-Y linker. We used site-directed mutagenesis and biochemical assays to investigate the importance of this acidic charge in mediating PLCβ3 autoinhibition. Loss of the acidic charge in the X-Y linker increases basal activity and decreases stability, consistent with loss of autoinhibition. However, introduction of compensatory electrostatic mutations on the surface of the PLCβ3 catalytic domain restore activity to basal levels. Thus, intramolecular electrostatics modulate autoinhibition by the X-Y linker.
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25
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Garland-Kuntz EE, Vago FS, Sieng M, Van Camp M, Chakravarthy S, Blaine A, Corpstein C, Jiang W, Lyon AM. Direct observation of conformational dynamics of the PH domain in phospholipases Cϵ and β may contribute to subfamily-specific roles in regulation. J Biol Chem 2018; 293:17477-17490. [PMID: 30242131 PMCID: PMC6231117 DOI: 10.1074/jbc.ra118.003656] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Revised: 09/17/2018] [Indexed: 12/19/2022] Open
Abstract
Phospholipase C (PLC) enzymes produce second messengers that increase the intracellular Ca2+ concentration and activate protein kinase C (PKC). These enzymes also share a highly conserved arrangement of core domains. However, the contributions of the individual domains to regulation are poorly understood, particularly in isoforms lacking high-resolution information, such as PLCϵ. Here, we used small-angle X-ray scattering (SAXS), EM, and functional assays to gain insights into the molecular architecture of PLCϵ, revealing that its PH domain is conformationally dynamic and essential for activity. We further demonstrate that the PH domain of PLCβ exhibits similar dynamics in solution that are substantially different from its conformation observed in multiple previously reported crystal structures. We propose that this conformational heterogeneity contributes to subfamily-specific differences in activity and regulation by extracellular signals.
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Affiliation(s)
| | - Frank S Vago
- Biological Sciences, Purdue University, West Lafayette, Indiana 47907 and
| | | | | | - Srinivas Chakravarthy
- the Biophysics Collaborative Access Team, Illinois Institute of Technology, Sector 18ID, Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439
| | | | | | - Wen Jiang
- Biological Sciences, Purdue University, West Lafayette, Indiana 47907 and
| | - Angeline M Lyon
- From the Departments of Chemistry and
- Biological Sciences, Purdue University, West Lafayette, Indiana 47907 and
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26
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Ben-Salem S, Robbins SM, Sobreira NLM, Lyon A, Al-Shamsi AM, Islam BK, Akawi NA, John A, Thachillath P, Hamed SA, Valle D, Ali BR, Al-Gazali L. Defect in phosphoinositide signalling through a homozygous variant in PLCB3 causes a new form of spondylometaphyseal dysplasia with corneal dystrophy. J Med Genet 2018; 55:122-130. [PMID: 29122926 PMCID: PMC8215682 DOI: 10.1136/jmedgenet-2017-104827] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Revised: 09/19/2017] [Accepted: 10/06/2017] [Indexed: 02/05/2023]
Abstract
BACKGROUND Bone dysplasias are a large group of disorders affecting the growth and structure of the skeletal system. METHODS In the present study, we report the clinical and molecular delineation of a new form of syndromic autosomal recessive spondylometaphyseal dysplasia (SMD) in two Emirati first cousins. They displayed postnatal growth deficiency causing profound limb shortening with proximal and distal segments involvement, narrow chest, radiological abnormalities involving the spine, pelvis and metaphyses, corneal clouding and intellectual disability. Whole genome homozygosity mapping localised the genetic cause to 11q12.1-q13.1, a region spanning 19.32 Mb with ~490 genes. Using whole exome sequencing, we identified four novel homozygous variants within the shared block of homozygosity. Pathogenic variants in genes involved in phospholipid metabolism, such as PLCB4 and PCYT1A, are known to cause bone dysplasia with or without eye anomalies, which led us to select PLCB3 as a strong candidate. This gene encodes phospholipase C β 3, an enzyme that converts phosphatidylinositol 4,5 bisphosphate (PIP2) to inositol 1,4,5 triphosphate (IP3) and diacylglycerol. RESULTS The identified variant (c.2632G>T) substitutes a serine for a highly conserved alanine within the Ha2' element of the proximal C-terminal domain. This disrupts binding of the Ha2' element to the catalytic core and destabilises PLCB3. Here we show that this hypomorphic variant leads to elevated levels of PIP2 in patient fibroblasts, causing disorganisation of the F-actin cytoskeleton. CONCLUSIONS Our results connect a homozygous loss of function variant in PLCB3 with a new SMD associated with corneal dystrophy and developmental delay (SMDCD).
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Affiliation(s)
- Salma Ben-Salem
- Department of Pathology, College of Medicine and Heath Sciences, University Al-Ain, Al Ain, AbuDhabi, United Arab Emirates
| | - Sarah M Robbins
- Human genetics and Molecular Biology, Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Nara LM Sobreira
- Human genetics and Molecular Biology, Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Angeline Lyon
- Chemistry and Biological Sciences, West Lafayette, USA
| | - Aisha M Al-Shamsi
- Department of Paediatrics, Tawam Hospital, Al-Ain, United Arab Emirates
| | - Barira K Islam
- Department of Paediatrics, College of Medicine and Heath Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Nadia A Akawi
- Division of Cardiovascular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, Oxfordshire, UK
| | - Anne John
- Department of Pathology, College of Medicine and Heath Sciences, University Al-Ain, Al Ain, AbuDhabi, United Arab Emirates
| | - Pramathan Thachillath
- Department of Paediatrics, College of Medicine and Heath Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Sania Al Hamed
- Department of Paediatrics, College of Medicine and Heath Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - David Valle
- Human genetics and Molecular Biology, Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Bassam R Ali
- Department of Pathology, College of Medicine and Heath Sciences, University Al-Ain, Al Ain, AbuDhabi, United Arab Emirates
| | - Lihadh Al-Gazali
- Department of Paediatrics, College of Medicine and Heath Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
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27
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Hudson BN, Hyun SH, Thompson DH, Lyon AM. Phospholipase Cβ3 Membrane Adsorption and Activation Are Regulated by Its C-Terminal Domains and Phosphatidylinositol 4,5-Bisphosphate. Biochemistry 2017; 56:5604-5614. [PMID: 28945350 DOI: 10.1021/acs.biochem.7b00547] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Phospholipase Cβ (PLCβ) enzymes hydrolyze phosphatidylinositol 4,5-bisphosphate to produce second messengers that regulate intracellular Ca2+, cell proliferation, and survival. Their activity is dependent upon interfacial activation that occurs upon localization to cell membranes. However, the molecular basis for how these enzymes productively interact with the membrane is poorly understood. Herein, atomic force microscopy demonstrates that the ∼300-residue C-terminal domain promotes adsorption to monolayers and is required for spatial organization of the protein on the monolayer surface. PLCβ variants lacking this C-terminal domain display differences in their distribution on the surface. In addition, a previously identified autoinhibitory helix that binds to the PLCβ catalytic core negatively impacts membrane binding, providing an additional level of regulation for membrane adsorption. Lastly, defects in phosphatidylinositol 4,5-bisphosphate hydrolysis also alter monolayer adsorption, reflecting a role for the active site in this process. Together, these findings support a model in which multiple elements of PLCβ modulate adsorption, distribution, and catalysis at the cell membrane.
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Affiliation(s)
- Brianna N Hudson
- Department of Chemistry and ‡Department of Biological Sciences, Purdue University , West Lafayette, Indiana 47907, United States
| | - Seok-Hee Hyun
- Department of Chemistry and ‡Department of Biological Sciences, Purdue University , West Lafayette, Indiana 47907, United States
| | - David H Thompson
- Department of Chemistry and ‡Department of Biological Sciences, Purdue University , West Lafayette, Indiana 47907, United States
| | - Angeline M Lyon
- Department of Chemistry and ‡Department of Biological Sciences, Purdue University , West Lafayette, Indiana 47907, United States
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Navaratnarajah P, Gershenson A, Ross EM. The binding of activated Gα q to phospholipase C-β exhibits anomalous affinity. J Biol Chem 2017; 292:16787-16801. [PMID: 28842497 DOI: 10.1074/jbc.m117.809673] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 08/22/2017] [Indexed: 01/01/2023] Open
Abstract
Upon activation by the Gq family of Gα subunits, Gβγ subunits, and some Rho family GTPases, phospholipase C-β (PLC-β) isoforms hydrolyze phosphatidylinositol 4,5-bisphosphate to the second messengers inositol 1,4,5-trisphosphate and diacylglycerol. PLC-β isoforms also function as GTPase-activating proteins, potentiating Gq deactivation. To elucidate the mechanism of this mutual regulation, we measured the thermodynamics and kinetics of PLC-β3 binding to Gαq FRET and fluorescence correlation spectroscopy, two physically distinct methods, both yielded Kd values of about 200 nm for PLC-β3-Gαq binding. This Kd is 50-100 times greater than the EC50 for Gαq-mediated PLC-β3 activation and for the Gαq GTPase-activating protein activity of PLC-β. The measured Kd was not altered either by the presence of phospholipid vesicles, phosphatidylinositol 4,5-bisphosphate and Ca2+, or by the identity of the fluorescent labels. FRET-based kinetic measurements were also consistent with a Kd of 200 nm We determined that PLC-β3 hysteresis, whereby PLC-β3 remains active for some time following either Gαq-PLC-β3 dissociation or PLC-β3-potentiated Gαq deactivation, is not sufficient to explain the observed discrepancy between EC50 and Kd These results indicate that the mechanism by which Gαq and PLC-β3 mutually regulate each other is far more complex than a simple, two-state allosteric model and instead is probably kinetically determined.
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Affiliation(s)
- Punya Navaratnarajah
- From the Department of Pharmacology and Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041 and
| | - Anne Gershenson
- the Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003-9292
| | - Elliott M Ross
- From the Department of Pharmacology and Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041 and
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Charpentier TH, Waldo GL, Lowery-Gionta EG, Krajewski K, Strahl BD, Kash TL, Harden TK, Sondek J. Potent and Selective Peptide-based Inhibition of the G Protein Gαq. J Biol Chem 2016; 291:25608-25616. [PMID: 27742837 DOI: 10.1074/jbc.m116.740407] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 10/13/2016] [Indexed: 11/06/2022] Open
Abstract
In contrast to G protein-coupled receptors, for which chemical and peptidic inhibitors have been extensively explored, few compounds are available that directly modulate heterotrimeric G proteins. Active Gαq binds its two major classes of effectors, the phospholipase C (PLC)-β isozymes and Rho guanine nucleotide exchange factors (RhoGEFs) related to Trio, in a strikingly similar fashion: a continuous helix-turn-helix of the effectors engages Gαq within its canonical binding site consisting of a groove formed between switch II and helix α3. This information was exploited to synthesize peptides that bound active Gαq in vitro with affinities similar to full-length effectors and directly competed with effectors for engagement of Gαq A representative peptide was specific for active Gαq because it did not bind inactive Gαq or other classes of active Gα subunits and did not inhibit the activation of PLC-β3 by Gβ1γ2 In contrast, the peptide robustly prevented activation of PLC-β3 or p63RhoGEF by Gαq; it also prevented G protein-coupled receptor-promoted neuronal depolarization downstream of Gαq in the mouse prefrontal cortex. Moreover, a genetically encoded form of this peptide flanked by fluorescent proteins inhibited Gαq-dependent activation of PLC-β3 at least as effectively as a dominant-negative form of full-length PLC-β3. These attributes suggest that related, cell-penetrating peptides should effectively inhibit active Gαq in cells and that these and genetically encoded sequences may find application as molecular probes, drug leads, and biosensors to monitor the spatiotemporal activation of Gαq in cells.
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Affiliation(s)
- Thomas H Charpentier
- From the Departments of Pharmacology and.,Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599
| | | | | | - Krzysztof Krajewski
- Biochemistry and Biophysics.,High-Throughput Peptide Synthesis and Array Facility, and
| | - Brian D Strahl
- Biochemistry and Biophysics.,High-Throughput Peptide Synthesis and Array Facility, and
| | | | | | - John Sondek
- From the Departments of Pharmacology and .,Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599.,Biochemistry and Biophysics
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Sprang SR. Invited review: Activation of G proteins by GTP and the mechanism of Gα-catalyzed GTP hydrolysis. Biopolymers 2016; 105:449-62. [PMID: 26996924 PMCID: PMC5319639 DOI: 10.1002/bip.22836] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 03/11/2016] [Accepted: 03/17/2016] [Indexed: 02/02/2023]
Abstract
This review addresses the regulatory consequences of the binding of GTP to the alpha subunits (Gα) of heterotrimeric G proteins, the reaction mechanism of GTP hydrolysis catalyzed by Gα and the means by which GTPase activating proteins (GAPs) stimulate the GTPase activity of Gα. The high energy of GTP binding is used to restrain and stabilize the conformation of the Gα switch segments, particularly switch II, to afford stable complementary to the surfaces of Gα effectors, while excluding interaction with Gβγ, the regulatory binding partner of GDP-bound Gα. Upon GTP hydrolysis, the energy of these conformational restraints is dissipated and the two switch segments, particularly switch II, become flexible and are able to adopt a conformation suitable for tight binding to Gβγ. Catalytic site pre-organization presents a significant activation energy barrier to Gα GTPase activity. The glutamine residue near the N-terminus of switch II (Glncat ) must adopt a conformation in which it orients and stabilizes the γ phosphate and the water nucleophile for an in-line attack. The transition state is probably loose with dissociative character; phosphoryl transfer may be concerted. The catalytic arginine in switch I (Argcat ), together with amide hydrogen bonds from the phosphate binding loop, stabilize charge at the β-γ bridge oxygen of the leaving group. GAPs that harbor "regulator of protein signaling" (RGS) domains, or structurally unrelated domains within G protein effectors that function as GAPs, accelerate catalysis by stabilizing the pre-transition state for Gα-catalyzed GTP hydrolysis, primarily by restraining Argcat and Glncat to their catalytic conformations. © 2016 Wiley Periodicals, Inc. Biopolymers 105: 449-462, 2016.
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Affiliation(s)
- Stephen R. Sprang
- Center for Biomolecular Structure and Dynamics, Division of Biological Sciences, University of Montana, 32 Campus Drive, Missoula, MT 59812, Telephone: (406) 243-6028, Fax: (406) 243-6024,
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31
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Cool-temperature-mediated activation of phospholipase C-γ2 in the human hereditary disease PLAID. Cell Signal 2016; 28:1237-1251. [PMID: 27196803 DOI: 10.1016/j.cellsig.2016.05.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2016] [Revised: 05/10/2016] [Accepted: 05/12/2016] [Indexed: 12/24/2022]
Abstract
Deletions in the gene encoding signal-transducing inositol phospholipid-specific phospholipase C-γ2 (PLCγ2) are associated with the novel human hereditary disease PLAID (PLCγ2-associated antibody deficiency and immune dysregulation). PLAID is characterized by a rather puzzling concurrence of augmented and diminished functions of the immune system, such as cold urticaria triggered by only minimal decreases in temperature, autoimmunity, and immunodeficiency. Understanding of the functional effects of the genomic alterations at the level of the affected enzyme, PLCγ2, is currently lacking. PLCγ2 is critically involved in coupling various cell surface receptors to regulation of important functions of immune cells such as mast cells, B cells, monocytes/macrophages, and neutrophils. PLCγ2 is unique by carrying three Src (SH) and one split pleckstrin homology domain (spPH) between the two catalytic subdomains (spPHn-SH2n-SH2c-SH3-spPHc). Prevailing evidence suggests that activation of PLCγ2 is primarily due to loss of SH-region-mediated autoinhibition and/or enhanced plasma membrane translocation. Here, we show that the two PLAID PLCγ2 mutants lacking portions of the SH region are strongly (>100-fold), rapidly, and reversibly activated by cooling by only a few degrees. We found that the mechanism(s) underlying PLCγ2 PLAID mutant activation by cool temperatures is distinct from a mere loss of SH-region-mediated autoinhibition and dependent on both the integrity and the pliability of the spPH domain. The results suggest a new mechanism of PLCγ activation with unique thermodynamic features and assign a novel regulatory role to its spPH domain. Involvement of this mechanism in other human disease states associated with cooling such as exertional asthma and certain acute coronary events appears an intriguing possibility.
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Abstract
Gαq signals with phospholipase C-β (PLC-β) to modify behavior in response to an agonist-bound GPCR. While the fundamental steps which prime Gαq to interact with PLC-β have been identified, questions remain concerning signal strength with PLC-β and other effectors. Gαq is generally viewed to function as a simple ON and OFF switch for its effector, dependent on the binding of GTP or GDP. However, Gαq does not have a single effector, Gαq has many different effectors. Furthermore, select effectors also regulate Gαq activity. PLC-β is a lipase and a GTPase activating protein (GAP) selective for Gαq. The contribution of G protein regulating activity to signal amplitude remains unclear. The unique PLC-β coiled-coil domain is essential for maximum Gαq response, both lipase and GAP. Nonetheless, coiled-coil domain associations necessary to maximum response have not been revealed by the structural approach. This review discusses progress towards understanding the basis for signal strength with PLC-β and other effectors. Shared and effector-specific interactions have been identified. Finally, the evidence for allosteric regulation of lipase stimulation by protein kinase C, the membrane, phosphatidic acid, phosphatidylinositol-4, 5-bisphosphate and GPCR is explored. Endogenous allosteric regulators can suppress or enhance maximum lipase stimulation dependent on the PLC-β coiled-coil domain. A better understanding of allosteric modulation may therefore identify a wealth of new targets to regulate signal strength and behavior.
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Affiliation(s)
- Irene Litosch
- Department of Molecular and Cellular Pharmacology, Miller School of Medicine University of Miami, Miami, FL 33101-6189, USA.
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33
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Kadamur G, Ross EM. Intrinsic Pleckstrin Homology (PH) Domain Motion in Phospholipase C-β Exposes a Gβγ Protein Binding Site. J Biol Chem 2016; 291:11394-406. [PMID: 27002154 DOI: 10.1074/jbc.m116.723940] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Indexed: 11/06/2022] Open
Abstract
Mammalian phospholipase C-β (PLC-β) isoforms are stimulated by heterotrimeric G protein subunits and members of the Rho GTPase family of small G proteins. Although recent structural studies showed how Gαq and Rac1 bind PLC-β, there is a lack of consensus regarding the Gβγ binding site in PLC-β. Using FRET between cerulean fluorescent protein-labeled Gβγ and the Alexa Fluor 594-labeled PLC-β pleckstrin homology (PH) domain, we demonstrate that the PH domain is the minimal Gβγ binding region in PLC-β3. We show that the isolated PH domain can compete with full-length PLC-β3 for binding Gβγ but not Gαq, Using sequence conservation, structural analyses, and mutagenesis, we identify a hydrophobic face of the PLC-β PH domain as the Gβγ binding interface. This PH domain surface is not solvent-exposed in crystal structures of PLC-β, necessitating conformational rearrangement to allow Gβγ binding. Blocking PH domain motion in PLC-β by cross-linking it to the EF hand domain inhibits stimulation by Gβγ without altering basal activity or Gαq response. The fraction of PLC-β cross-linked is proportional to the fractional loss of Gβγ response. Cross-linked PLC-β does not bind Gβγ in a FRET-based Gβγ-PLC-β binding assay. We propose that unliganded PLC-β exists in equilibrium between a closed conformation observed in crystal structures and an open conformation where the PH domain moves away from the EF hands. Therefore, intrinsic movement of the PH domain in PLC-β modulates Gβγ access to its binding site.
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Affiliation(s)
- Ganesh Kadamur
- From the Department of Pharmacology, Molecular Biophysics Graduate Program, and Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Elliott M Ross
- From the Department of Pharmacology, Molecular Biophysics Graduate Program, and Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
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34
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Litosch I. Regulating G protein activity by lipase-independent functions of phospholipase C. Life Sci 2015; 137:116-24. [DOI: 10.1016/j.lfs.2015.07.025] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Revised: 06/18/2015] [Accepted: 07/22/2015] [Indexed: 11/27/2022]
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35
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Lyon AM, Begley JA, Manett TD, Tesmer JJG. Molecular mechanisms of phospholipase C β3 autoinhibition. Structure 2015; 22:1844-1854. [PMID: 25435326 DOI: 10.1016/j.str.2014.10.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2014] [Revised: 09/29/2014] [Accepted: 10/04/2014] [Indexed: 01/01/2023]
Abstract
Phospholipase C β (PLCβ) enzymes are dramatically activated by heterotrimeric G proteins. Central to this response is the robust autoinhibition of PLCβ by the X-Y linker region within its catalytic core and by the Hα2' helix in the C-terminal extension of the enzyme. The molecular mechanism of each and their mutual dependence are poorly understood. Herein, it is shown that distinct regions within the X-Y linker have specific roles in regulating activity. Most important,an acidic stretch within the linker stabilizes a lid that occludes the active site, consistent with crystal structures of variants lacking this region. Inhibition by the Hα2' helix is independent of the X-Y linker and likely regulates activity by limiting membrane interaction of the catalytic core. Full activation of PLCβ thus requires multiple independent molecular events induced by membrane association of the catalytic core and by the binding of regulatory proteins.
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Affiliation(s)
- Angeline M Lyon
- Life Sciences Institute, University of Michigan, 210 Washtenaw Avenue, Ann Arbor, MI 48109-2216, USA; Department of Pharmacology, University of Michigan, 1150 W. Medical Center Drive, 1301 MSRB III, Ann Arbor, MI 48109, USA; Department of Biological Chemistry, University of Michigan, 1150 W. Medical Center Drive, RM 5301 MSRB III, Ann Arbor, MI 48109-0600, USA
| | - Jessica A Begley
- Life Sciences Institute, University of Michigan, 210 Washtenaw Avenue, Ann Arbor, MI 48109-2216, USA; Department of Pharmacology, University of Michigan, 1150 W. Medical Center Drive, 1301 MSRB III, Ann Arbor, MI 48109, USA; Department of Biological Chemistry, University of Michigan, 1150 W. Medical Center Drive, RM 5301 MSRB III, Ann Arbor, MI 48109-0600, USA
| | - Taylor D Manett
- Life Sciences Institute, University of Michigan, 210 Washtenaw Avenue, Ann Arbor, MI 48109-2216, USA; Department of Pharmacology, University of Michigan, 1150 W. Medical Center Drive, 1301 MSRB III, Ann Arbor, MI 48109, USA; Department of Biological Chemistry, University of Michigan, 1150 W. Medical Center Drive, RM 5301 MSRB III, Ann Arbor, MI 48109-0600, USA
| | - John J G Tesmer
- Life Sciences Institute, University of Michigan, 210 Washtenaw Avenue, Ann Arbor, MI 48109-2216, USA; Department of Pharmacology, University of Michigan, 1150 W. Medical Center Drive, 1301 MSRB III, Ann Arbor, MI 48109, USA; Department of Biological Chemistry, University of Michigan, 1150 W. Medical Center Drive, RM 5301 MSRB III, Ann Arbor, MI 48109-0600, USA.
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Bavishi K, Hatzakis NS. Shedding light on protein folding, structural and functional dynamics by single molecule studies. Molecules 2014; 19:19407-34. [PMID: 25429564 PMCID: PMC6272019 DOI: 10.3390/molecules191219407] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Revised: 11/07/2014] [Accepted: 11/12/2014] [Indexed: 11/16/2022] Open
Abstract
The advent of advanced single molecule measurements unveiled a great wealth of dynamic information revolutionizing our understanding of protein dynamics and behavior in ways unattainable by conventional bulk assays. Equipped with the ability to record distribution of behaviors rather than the mean property of a population, single molecule measurements offer observation and quantification of the abundance, lifetime and function of multiple protein states. They also permit the direct observation of the transient and rarely populated intermediates in the energy landscape that are typically averaged out in non-synchronized ensemble measurements. Single molecule studies have thus provided novel insights about how the dynamic sampling of the free energy landscape dictates all aspects of protein behavior; from its folding to function. Here we will survey some of the state of the art contributions in deciphering mechanisms that underlie protein folding, structural and functional dynamics by single molecule fluorescence microscopy techniques. We will discuss a few selected examples highlighting the power of the emerging techniques and finally discuss the future improvements and directions.
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Affiliation(s)
- Krutika Bavishi
- Plant Biochemistry Laboratory, Department of Plant and Environmental Sciences, Center for Synthetic Biology "bioSYNergy", Villum Research Center "Plant Plasticity", University of Copenhagen, Thorvaldsenvej 40, DK-1871 Frederiksberg C, Denmark.
| | - Nikos S Hatzakis
- Bio-Nanotechnology Laboratory, Department of Chemistry, Nano-Science Center, Lundbeck Foundation Center Biomembranes in Nanomedicine, University of Copenhagen, 2100 Copenhagen, Denmark.
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37
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Charpentier TH, Waldo GL, Barrett MO, Huang W, Zhang Q, Harden TK, Sondek J. Membrane-induced allosteric control of phospholipase C-β isozymes. J Biol Chem 2014; 289:29545-57. [PMID: 25193662 PMCID: PMC4207972 DOI: 10.1074/jbc.m114.586784] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Revised: 08/13/2014] [Indexed: 11/06/2022] Open
Abstract
All peripheral membrane proteins must negotiate unique constraints intrinsic to the biological interface of lipid bilayers and the cytosol. Phospholipase C-β (PLC-β) isozymes hydrolyze the membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP2) to propagate diverse intracellular responses that underlie the physiological action of many hormones, neurotransmitters, and growth factors. PLC-β isozymes are autoinhibited, and several proteins, including Gαq, Gβγ, and Rac1, directly engage distinct regions of these phospholipases to release autoinhibition. To understand this process, we used a novel, soluble analog of PIP2 that increases in fluorescence upon cleavage to monitor phospholipase activity in real time in the absence of membranes or detergents. High concentrations of Gαq or Gβ1γ2 did not activate purified PLC-β3 under these conditions despite their robust capacity to activate PLC-β3 at membranes. In addition, mutants of PLC-β3 with crippled autoinhibition dramatically accelerated the hydrolysis of PIP2 in membranes without an equivalent acceleration in the hydrolysis of the soluble analog. Our results illustrate that membranes are integral for the activation of PLC-β isozymes by diverse modulators, and we propose a model describing membrane-mediated allosterism within PLC-β isozymes.
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Affiliation(s)
| | | | | | - Weigang Huang
- the Division of Chemical Biology and Medicinal Chemistry, University of North Carolina School of Pharmacy, Chapel Hill, North Carolina 27599
| | - Qisheng Zhang
- the Division of Chemical Biology and Medicinal Chemistry, University of North Carolina School of Pharmacy, Chapel Hill, North Carolina 27599
| | | | - John Sondek
- From the Departments of Pharmacology and Biochemistry and Biophysics and the Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599 and
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38
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Litosch I. Regulation of phospholipase C-β(1) GTPase-activating protein (GAP) function and relationship to G(q) efficacy. IUBMB Life 2014; 65:936-40. [PMID: 24170560 DOI: 10.1002/iub.1218] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Revised: 09/30/2013] [Accepted: 09/30/2013] [Indexed: 11/08/2022]
Abstract
How cells regulate Gq efficacy (initiation and termination of Gq signaling) to effect response remains a central question in pharmacology and drug discovery. Phospholipase C-β1 (PLC-β1) is an effector and a GTPase activating protein (GAP) specific to Gαq. The physiological function of PLC-β1 GAP remains unclear and controversial. GAPs are generally thought to function in deactivation of Gq signaling. However, PLC-β1 GAP has also been shown to increase signaling efficiency through kinetic coupling with the ligand-activated GPCR. GPCRs function as guanine nucleotide exchange factors (GEF) on the G protein activation cycle. This article sets forth a new hypothesis that could unify these conflicting paradigms as it pertains to physiological signaling and native levels of protein. It is proposed that the physiological function of PLC-β1 GAP is context-dependent and regulated by phosphatidic acid (PA). PA stimulates PLC-β1 GAP activity. In the absence of ligand, PLC-β1 GAP does indeed deactivate Gq signaling, limiting leaky activation to set the threshold for stimulation to sharpen signal kinetics. However in the presence of activating ligand, the increase in levels of PA would stimulate PLC-β1 GAP to kinetically couple with GPCR GEF to increase signaling efficiency. We found that PA-increased Gq efficiency is dependent on signaling via the unique PLC-β1 PA binding domain.
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Sánchez-Fernández G, Cabezudo S, García-Hoz C, Benincá C, Aragay AM, Mayor F, Ribas C. Gαq signalling: the new and the old. Cell Signal 2014; 26:833-48. [PMID: 24440667 DOI: 10.1016/j.cellsig.2014.01.010] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 01/09/2014] [Indexed: 01/25/2023]
Abstract
In the last few years the interactome of Gαq has expanded considerably, contributing to improve our understanding of the cellular and physiological events controlled by this G alpha subunit. The availability of high-resolution crystal structures has led the identification of an effector-binding region within the surface of Gαq that is able to recognise a variety of effector proteins. Consequently, it has been possible to ascribe different Gαq functions to specific cellular players and to identify important processes that are triggered independently of the canonical activation of phospholipase Cβ (PLCβ), the first identified Gαq effector. Novel effectors include p63RhoGEF, that provides a link between G protein-coupled receptors and RhoA activation, phosphatidylinositol 3-kinase (PI3K), implicated in the regulation of the Akt pathway, or the cold-activated TRPM8 channel, which is directly inhibited upon Gαq binding. Recently, the activation of ERK5 MAPK by Gq-coupled receptors has also been described as a novel PLCβ-independent signalling axis that relies upon the interaction between this G protein and two novel effectors (PKCζ and MEK5). Additionally, the association of Gαq with different regulatory proteins can modulate its effector coupling ability and, therefore, its signalling potential. Regulators include accessory proteins that facilitate effector activation or, alternatively, inhibitory proteins that downregulate effector binding or promote signal termination. Moreover, Gαq is known to interact with several components of the cytoskeleton as well as with important organisers of membrane microdomains, which suggests that efficient signalling complexes might be confined to specific subcellular environments. Overall, the complex interaction network of Gαq underlies an ever-expanding functional diversity that puts forward this G alpha subunit as a major player in the control of physiological functions and in the development of different pathological situations.
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Affiliation(s)
- Guzmán Sánchez-Fernández
- Departamento de Biología Molecular and Centro de Biologia Molecular "Severo Ochoa", CSIC-UAM, Universidad Autónoma de Madrid, Spain; Instituto de Investigación Sanitaria La Princesa, Madrid, Spain
| | - Sofía Cabezudo
- Departamento de Biología Molecular and Centro de Biologia Molecular "Severo Ochoa", CSIC-UAM, Universidad Autónoma de Madrid, Spain; Instituto de Investigación Sanitaria La Princesa, Madrid, Spain
| | - Carlota García-Hoz
- Departamento de Biología Molecular and Centro de Biologia Molecular "Severo Ochoa", CSIC-UAM, Universidad Autónoma de Madrid, Spain; Instituto de Investigación Sanitaria La Princesa, Madrid, Spain
| | | | - Anna M Aragay
- Department of Cell Biology, Molecular Biology Institute of Barcelona, Spain
| | - Federico Mayor
- Departamento de Biología Molecular and Centro de Biologia Molecular "Severo Ochoa", CSIC-UAM, Universidad Autónoma de Madrid, Spain; Instituto de Investigación Sanitaria La Princesa, Madrid, Spain
| | - Catalina Ribas
- Departamento de Biología Molecular and Centro de Biologia Molecular "Severo Ochoa", CSIC-UAM, Universidad Autónoma de Madrid, Spain; Instituto de Investigación Sanitaria La Princesa, Madrid, Spain.
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40
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Sahu S, Philip F, Scarlata S. Hydrolysis rates of different small interfering RNAs (siRNAs) by the RNA silencing promoter complex, C3PO, determines their regulation by phospholipase Cβ. J Biol Chem 2013; 289:5134-44. [PMID: 24338081 DOI: 10.1074/jbc.m113.531467] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
C3PO plays a key role in promoting RNA-induced gene silencing. C3PO consists of two subunits of the endonuclease translin-associated factor X (TRAX) and six subunits of the nucleotide-binding protein translin. We have found that TRAX binds strongly to phospholipase Cβ (PLCβ), which transmits G protein signals from many hormones and sensory inputs. The association between PLCβ and TRAX is thought to underlie the ability of PLCβ to reverse gene silencing by small interfering RNAs. However, this reversal only occurs for some genes (e.g. GAPDH and LDH) but not others (e.g. Hsp90 and cyclophilin A). To understand this specificity, we carried out studies using fluorescence-based methods. In cells, we find that PLCβ, TRAX, and their complexes are identically distributed through the cytosol suggesting that selectivity is not due to large scale sequestration of either the free or complexed proteins. Using purified proteins, we find that PLCβ binds ∼5-fold more weakly to translin than to TRAX but ∼2-fold more strongly to C3PO. PLCβ does not alter TRAX-translin assembly to C3PO, and brightness studies suggest one PLCβ binds to one C3PO octamer without a change in the number of TRAX/translin molecules suggesting that PLCβ binds to an external site. Functionally, we find that C3PO hydrolyzes siRNA(GAPDH) at a faster rate than siRNA(Hsp90). However, when PLCβ is bound to C3PO, the hydrolysis rate of siRNA(GAPDH) becomes comparable with siRNA(Hsp90). Our results show that the selectivity of PLCβ toward certain genes lies in the rate at which the RNA is hydrolyzed by C3PO.
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Affiliation(s)
- Shriya Sahu
- From the Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York 11794-8661
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Lyon AM, Taylor VG, Tesmer JJG. Strike a pose: Gαq complexes at the membrane. Trends Pharmacol Sci 2013; 35:23-30. [PMID: 24287282 DOI: 10.1016/j.tips.2013.10.008] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 10/16/2013] [Accepted: 10/21/2013] [Indexed: 12/20/2022]
Abstract
The heterotrimeric G protein Gαq is a central player in signal transduction, relaying signals from activated G-protein-coupled receptors (GPCRs) to effectors and other proteins to elicit changes in intracellular Ca(2+), the actin cytoskeleton, and gene transcription. Gαq functions at the intracellular surface of the plasma membrane, as do its best-characterized targets, phospholipase C-β, p63RhoGEF, and GPCR kinase 2 (GRK2). Recent insights into the structure and function of these signaling complexes reveal several recurring themes, including complex multivalent interactions between Gαq, its protein target, and the membrane, that are likely essential for allosteric control and maximum efficiency in signal transduction. Thus, the plasma membrane is not only a source of substrates but also a key player in the scaffolding of Gαq-dependent signaling pathways.
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Affiliation(s)
- Angeline M Lyon
- Life Sciences Institute and the Departments of Pharmacology and Biological Chemistry, University of Michigan, Ann Arbor, MI, USA
| | - Veronica G Taylor
- Life Sciences Institute and the Departments of Pharmacology and Biological Chemistry, University of Michigan, Ann Arbor, MI, USA
| | - John J G Tesmer
- Life Sciences Institute and the Departments of Pharmacology and Biological Chemistry, University of Michigan, Ann Arbor, MI, USA.
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42
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Abstract
Rapid progress has recently been made regarding how phospholipase C (PLC)-β functions downstream of G protein-coupled receptors and how PLC-β functions in the nucleus. PLC-β has also been shown to interplay with tyrosine kinase-based signaling pathways, specifically to inhibit Stat5 activation by recruiting the protein-tyrosine phosphatase SHP-1. In this regard, a new multimolecular signaling platform, named SPS complex, has been identified. The SPS complex has important regulatory roles in tumorigenesis and immune cell activation. Furthermore, a growing body of work suggests that PLC-β also participates in the differentiation and activation of immune cells that control both the innate and adaptive immune systems.
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Affiliation(s)
- Wenbin Xiao
- Department of Pathology, University Hospital Case Medical Center, Case Western Reserve University, Cleveland, OH 44106, USA.
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43
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Philip F, Sahu S, Caso G, Scarlata S. Role of phospholipase C-β in RNA interference. Adv Biol Regul 2013; 53:319-330. [PMID: 23916604 PMCID: PMC3805765 DOI: 10.1016/j.jbior.2013.07.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Revised: 07/03/2013] [Accepted: 07/04/2013] [Indexed: 06/02/2023]
Abstract
Phospholipase C-β (PLCβ) enzymes are activated by G proteins in response to agents such as hormones and neurotransmitters, and have been implicated in leukemias and neurological disorders. PLCβ activity causes an increase in intracellular calcium which ultimately leads to profound changes in the cell. PLCβ localizes to three cellular compartments: the plasma membrane, the cytosol and the nucleus. Under most cell conditions, the majority of PLCβ localizes to the plasma membrane where it interacts with G proteins. In trying to determine the factors that localize PLCβ to the cytosol and nucleus, we have recently identified the binding partner, TRAX. TRAX is a nuclease and part of the machinery involved in RNA interference. This review discusses the interaction between PLCβ and TRAX, and its repercussions in G protein signaling and RNA silencing.
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Affiliation(s)
- Finly Philip
- Department of Physiology & Biophysics, Stony Brook University, Stony Brook, NY 11794-8661, USA
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44
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Kawakami T, Xiao W. Phospholipase C-β in immune cells. Adv Biol Regul 2013; 53:249-57. [PMID: 23981313 DOI: 10.1016/j.jbior.2013.08.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2013] [Revised: 07/29/2013] [Accepted: 08/02/2013] [Indexed: 12/22/2022]
Abstract
Great progress has recently been made in structural and functional research of phospholipase C (PLC)-β. We now understand how PLC-β isoforms (β1-β4) are activated by GTP-bound Gαq downstream of G protein-coupled receptors. Numerous studies indicate that PLC-βs participate in the differentiation and activation of immune cells that control both the innate and adaptive immune systems. The PLC-β3 isoform also interplays with tyrosine kinase-based signaling pathways, to inhibit Stat5 activation by recruiting the protein-tyrosine phosphatase SHP-1, with which PLC-β3 and Stat5 form a multi-molecular signaling platform, named SPS complex. The SPS complex has important regulatory roles in tumorigenesis and immune cell activation.
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Affiliation(s)
- Toshiaki Kawakami
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, La Jolla, CA 92037, USA; Laboratory of Allergic Disease, RIKEN Center for Integrative Medical Sciences (IMS-RCAI), Yokohama 230-0045, Japan.
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45
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Abstract
Phospholipase C (PLC) enzymes convert phosphatidylinositol-4,5-bisphosphate into the second messengers diacylglycerol and inositol-1,4,5-triphosphate. The production of these molecules promotes the release of intracellular calcium and activation of protein kinase C, which results in profound cellular changes. The PLCβ subfamily is of particular interest given its prominent role in cardiovascular and neuronal signaling and its regulation by G protein-coupled receptors, as PLCβ is the canonical downstream target of the heterotrimeric G protein Gαq. However, this is not the only mechanism regulating PLCβ activity. Extensive structural and biochemical evidence has revealed regulatory roles for autoinhibitory elements within PLCβ, Gβγ, small molecular weight G proteins, and the lipid membrane itself. Such complex regulation highlights the central role that this enzyme plays in cell signaling. A better understanding of the molecular mechanisms underlying the control of its activity will greatly facilitate the search for selective small molecule modulators of PLCβ.
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Affiliation(s)
- Angeline M Lyon
- Life Sciences Institute and the Departments of Pharmacology and Biological Chemistry, University of Michigan, Ann Arbor, Michigan
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46
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Abstract
Phosphoinositides (PIs) make up only a small fraction of cellular phospholipids, yet they control almost all aspects of a cell's life and death. These lipids gained tremendous research interest as plasma membrane signaling molecules when discovered in the 1970s and 1980s. Research in the last 15 years has added a wide range of biological processes regulated by PIs, turning these lipids into one of the most universal signaling entities in eukaryotic cells. PIs control organelle biology by regulating vesicular trafficking, but they also modulate lipid distribution and metabolism via their close relationship with lipid transfer proteins. PIs regulate ion channels, pumps, and transporters and control both endocytic and exocytic processes. The nuclear phosphoinositides have grown from being an epiphenomenon to a research area of its own. As expected from such pleiotropic regulators, derangements of phosphoinositide metabolism are responsible for a number of human diseases ranging from rare genetic disorders to the most common ones such as cancer, obesity, and diabetes. Moreover, it is increasingly evident that a number of infectious agents hijack the PI regulatory systems of host cells for their intracellular movements, replication, and assembly. As a result, PI converting enzymes began to be noticed by pharmaceutical companies as potential therapeutic targets. This review is an attempt to give an overview of this enormous research field focusing on major developments in diverse areas of basic science linked to cellular physiology and disease.
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Affiliation(s)
- Tamas Balla
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
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47
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Abstract
In this issue of Structure, Bunney and colleagues use a combination of NMR, SAXS, crystallography, ITC, and biochemical methods to elucidate, in molecular detail, the sequence of events causing receptor-mediated activation of phospholipase C-γ(1) by protein tyrosine phosphorylation.
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Affiliation(s)
- Peter Gierschik
- Institute of Pharmacology and Toxicology, University of Ulm Medical Center, 89081 Ulm, Germany.
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48
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Nance MR, Kreutz B, Tesmer VM, Sterne-Marr R, Kozasa T, Tesmer JJG. Structural and functional analysis of the regulator of G protein signaling 2-gαq complex. Structure 2013; 21:438-48. [PMID: 23434405 DOI: 10.1016/j.str.2012.12.016] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Revised: 11/20/2012] [Accepted: 12/13/2012] [Indexed: 10/27/2022]
Abstract
The heterotrimeric G protein Gαq is a key regulator of blood pressure, and excess Gαq signaling leads to hypertension. A specific inhibitor of Gαq is the GTPase activating protein (GAP) known as regulator of G protein signaling 2 (RGS2). The molecular basis for how Gαq/11 subunits serve as substrates for RGS proteins and how RGS2 mandates its selectivity for Gαq is poorly understood. In crystal structures of the RGS2-Gαq complex, RGS2 docks to Gαq in a different orientation from that observed in RGS-Gαi/o complexes. Despite its unique pose, RGS2 maintains canonical interactions with the switch regions of Gαq in part because its α6 helix adopts a distinct conformation. We show that RGS2 forms extensive interactions with the α-helical domain of Gαq that contribute to binding affinity and GAP potency. RGS subfamilies that do not serve as GAPs for Gαq are unlikely to form analogous stabilizing interactions.
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Affiliation(s)
- Mark R Nance
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109-2216, USA
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Full-length Gα(q)-phospholipase C-β3 structure reveals interfaces of the C-terminal coiled-coil domain. Nat Struct Mol Biol 2013; 20:355-62. [PMID: 23377541 PMCID: PMC3594540 DOI: 10.1038/nsmb.2497] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2012] [Accepted: 12/18/2012] [Indexed: 01/18/2023]
Abstract
Phospholipase C-β (PLCβ) is directly activated by Gαq, but the molecular basis for how its distal C-terminal domain (CTD) contributes to maximal activity is poorly understood. Herein we present both the crystal structure and cryo-EM 3D reconstructions of human full-length PLCβ3 in complex with murine Gαq. The distal CTD forms an extended, monomeric helical bundle consisting of three anti-parallel segments with structural similarity to membrane-binding bin–amphiphysin–Rvs (BAR) domains. Sequence conservation of the distal CTD identifies putative membrane and protein interaction sites, the latter of which bind the N-terminal helix of Gαq in both the crystal structure and cryo-EM reconstructions. Functional analysis suggests the distal CTD plays roles in membrane targeting and in optimizing the orientation of the catalytic core at the membrane for maximal rates of lipid hydrolysis.
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Abstract
AbstractThe Gq-linked G protein coupled receptors (GPCRs) and their signaling pathways are important clinical targets for the dementia of Alzheimer’s disease and cognitive decline with aging. Gq stimulates phospholipase C-β1 (PLC-β1) activity, increasing levels of inositol-1, 4, 5-trisphosphate (IP3) and diacylglycerol, to initiate mobilization of intracellular Ca2+ and activation of protein kinase C, respectively. While high concentrations of ligand typically evoke large sustained increases in cytosolic Ca2+ levels, it has long been appreciated that the dynamics of the Ca2+ increase are more complex and consistent with multiple levels of regulation. Physiologically relevant concentrations of Gq-ligands evoke rhythmic fluctuations or an oscillation in the level of cytosolic Ca2+. Downstream targets are tuned to respond to the frequency of the Ca2+ oscillations which in turn, reflect the oscillations in IP3 levels. Oscillatory behavior depends on the assembly of self-organizing interactions. The components that contribute to and regulate the Ca2+ oscillator have been unclear, precluding transfer of this fundamental knowledge from bench to bedside. Many GPCRs that signal with Gq also co-signal with G12. G protein co-signaling could therefore regulate the Ca2+ oscillator. This letter explores the potential relationship between Ca2+ oscillations, G protein co-signaling and cellular response in the context of our recent observations. We found that Gq efficacy is synergistic with phosphatidic acid, (PA), a signaling mediator generated downstream of activated G12 and RhoA. Regulation by PA depends on interaction with the unique PLC-β1 PA binding region. G protein co-signaling is therefore a mechanism for GPCRs to collectively assemble self-organizing interactions that regulate the Ca2+ oscillator.
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