1
|
Wei W, Smrcka AV. Internalized β2-Adrenergic Receptors Oppose PLC-Dependent Hypertrophic Signaling. Circ Res 2024; 135:e24-e38. [PMID: 38813686 PMCID: PMC11223973 DOI: 10.1161/circresaha.123.323201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Accepted: 05/16/2024] [Indexed: 05/31/2024]
Abstract
BACKGROUND Chronically elevated neurohumoral drive, and particularly elevated adrenergic tone leading to β-adrenergic receptor (β-AR) overstimulation in cardiac myocytes, is a key mechanism involved in the progression of heart failure. β1-AR (β1-adrenergic receptor) and β2-ARs (β2-adrenergic receptor) are the 2 major subtypes of β-ARs present in the human heart; however, they elicit different or even opposite effects on cardiac function and hypertrophy. For example, chronic activation of β1-ARs drives detrimental cardiac remodeling while β2-AR signaling is protective. The underlying molecular mechanisms for cardiac protection through β2-ARs remain unclear. METHODS β2-AR signaling mechanisms were studied in isolated neonatal rat ventricular myocytes and adult mouse ventricular myocytes using live cell imaging and Western blotting methods. Isolated myocytes and mice were used to examine the roles of β2-AR signaling mechanisms in the regulation of cardiac hypertrophy. RESULTS Here, we show that β2-AR activation protects against hypertrophy through inhibition of phospholipaseCε signaling at the Golgi apparatus. The mechanism for β2-AR-mediated phospholipase C inhibition requires internalization of β2-AR, activation of Gi and Gβγ subunit signaling at endosome and ERK (extracellular regulated kinase) activation. This pathway inhibits both angiotensin II and Golgi-β1-AR-mediated stimulation of phosphoinositide hydrolysis at the Golgi apparatus ultimately resulting in decreased PKD (protein kinase D) and histone deacetylase 5 phosphorylation and protection against cardiac hypertrophy. CONCLUSIONS This reveals a mechanism for β2-AR antagonism of the phospholipase Cε pathway that may contribute to the known protective effects of β2-AR signaling on the development of heart failure.
Collapse
Affiliation(s)
- Wenhui Wei
- Department of Pharmacology, University of Michigan School of Medicine, Ann Arbor, United States
| | - Alan V. Smrcka
- Department of Pharmacology, University of Michigan School of Medicine, Ann Arbor, United States
| |
Collapse
|
2
|
Wei W, Smrcka AV. Internalized β2-Adrenergic Receptors Inhibit Subcellular Phospholipase C-Dependent Cardiac Hypertrophic Signaling. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.07.544153. [PMID: 37333278 PMCID: PMC10274790 DOI: 10.1101/2023.06.07.544153] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/20/2023]
Abstract
Chronically elevated neurohumoral drive, and particularly elevated adrenergic tone leading to β-adrenergic receptor (β-AR) overstimulation in cardiac myocytes, is a key mechanism involved in the progression of heart failure. β1-AR and β2-ARs are the two major subtypes of β-ARs present in the human heart, however, they elicit different or even opposite effects on cardiac function and hypertrophy. For example, chronic activation of β1ARs drives detrimental cardiac remodeling while β2AR signaling is protective. The underlying molecular mechanisms for cardiac protection through β2ARs remain unclear. Here we show that β2-AR protects against hypertrophy through inhibition of PLCε signaling at the Golgi apparatus. The mechanism for β2AR-mediated PLC inhibition requires internalization of β2AR, activation of Gi and Gβγ subunit signaling at endosomes and ERK activation. This pathway inhibits both angiotensin II and Golgi-β1-AR-mediated stimulation of phosphoinositide hydrolysis at the Golgi apparatus ultimately resulting in decreased PKD and HDAC5 phosphorylation and protection against cardiac hypertrophy. This reveals a mechanism for β2-AR antagonism of the PLCε pathway that may contribute to the known protective effects of β2-AR signaling on the development of heart failure.
Collapse
Affiliation(s)
- Wenhui Wei
- Department of Pharmacology, University of Michigan School of Medicine, Ann Arbor, United States
| | - Alan V. Smrcka
- Department of Pharmacology, University of Michigan School of Medicine, Ann Arbor, United States
| |
Collapse
|
3
|
Kanemaru K, Nakamura Y. Activation Mechanisms and Diverse Functions of Mammalian Phospholipase C. Biomolecules 2023; 13:915. [PMID: 37371495 DOI: 10.3390/biom13060915] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2023] [Revised: 05/28/2023] [Accepted: 05/29/2023] [Indexed: 06/29/2023] Open
Abstract
Phospholipase C (PLC) plays pivotal roles in regulating various cellular functions by metabolizing phosphatidylinositol 4,5-bisphosphate in the plasma membrane. This process generates two second messengers, inositol 1,4,5-trisphosphate and diacylglycerol, which respectively regulate the intracellular Ca2+ levels and protein kinase C activation. In mammals, six classes of typical PLC have been identified and classified based on their structure and activation mechanisms. They all share X and Y domains, which are responsible for enzymatic activity, as well as subtype-specific domains. Furthermore, in addition to typical PLC, atypical PLC with unique structures solely harboring an X domain has been recently discovered. Collectively, seven classes and 16 isozymes of mammalian PLC are known to date. Dysregulation of PLC activity has been implicated in several pathophysiological conditions, including cancer, cardiovascular diseases, and neurological disorders. Therefore, identification of new drug targets that can selectively modulate PLC activity is important. The present review focuses on the structures, activation mechanisms, and physiological functions of mammalian PLC.
Collapse
Affiliation(s)
- Kaori Kanemaru
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Chiba 278-8510, Japan
| | - Yoshikazu Nakamura
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Chiba 278-8510, Japan
| |
Collapse
|
4
|
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.
Collapse
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.
| |
Collapse
|
5
|
A Naturally Occurring Membrane-Anchored Gα s Variant, XLαs, Activates Phospholipase Cβ4. J Biol Chem 2022; 298:102134. [PMID: 35709985 PMCID: PMC9294334 DOI: 10.1016/j.jbc.2022.102134] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 05/31/2022] [Accepted: 06/01/2022] [Indexed: 12/02/2022] Open
Abstract
Extra-large stimulatory Gα (XLαs) is a large variant of G protein αs subunit (Gαs) that uses an alternative promoter and thus differs from Gαs at the first exon. XLαs activation by G protein–coupled receptors mediates cAMP generation, similarly to Gαs; however, Gαs and XLαs have been shown to have distinct cellular and physiological functions. For example, previous work suggests that XLαs can stimulate inositol phosphate production in renal proximal tubules and thereby regulate serum phosphate levels. In this study, we show that XLαs directly and specifically stimulates a specific isoform of phospholipase Cβ (PLCβ), PLCβ4, both in transfected cells and with purified protein components. We demonstrate that neither the ability of XLαs to activate cAMP generation nor the canonical G protein switch II regions are required for PLCβ stimulation. Furthermore, this activation is nucleotide independent but is inhibited by Gβγ, suggesting a mechanism of activation that relies on Gβγ subunit dissociation. Surprisingly, our results indicate that enhanced membrane targeting of XLαs relative to Gαs confers the ability to activate PLCβ4. We also show that PLCβ4 is required for isoproterenol-induced inositol phosphate accumulation in osteocyte-like Ocy454 cells. Taken together, we demonstrate a novel mechanism for activation of phosphoinositide turnover downstream of Gs-coupled receptors that may have a critical role in endocrine physiology.
Collapse
|
6
|
Tennakoon M, Senarath K, Kankanamge D, Ratnayake K, Wijayaratna D, Olupothage K, Ubeysinghe S, Martins-Cannavino K, Hébert TE, Karunarathne A. Subtype-dependent regulation of Gβγ signalling. Cell Signal 2021; 82:109947. [PMID: 33582184 PMCID: PMC8026654 DOI: 10.1016/j.cellsig.2021.109947] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 02/01/2021] [Accepted: 02/02/2021] [Indexed: 01/04/2023]
Abstract
G protein-coupled receptors (GPCRs) transmit information to the cell interior by transducing external signals to heterotrimeric G protein subunits, Gα and Gβγ subunits, localized on the inner leaflet of the plasma membrane. Though the initial focus was mainly on Gα-mediated events, Gβγ subunits were later identified as major contributors to GPCR-G protein signalling. A broad functional array of Gβγ signalling has recently been attributed to Gβ and Gγ subtype diversity, comprising 5 Gβ and 12 Gγ subtypes, respectively. In addition to displaying selectivity towards each other to form the Gβγ dimer, numerous studies have identified preferences of distinct Gβγ combinations for specific GPCRs, Gα subtypes and effector molecules. Importantly, Gβ and Gγ subtype-dependent regulation of downstream effectors, representing a diverse range of signalling pathways and physiological functions have been found. Here, we review the literature on the repercussions of Gβ and Gγ subtype diversity on direct and indirect regulation of GPCR/G protein signalling events and their physiological outcomes. Our discussion additionally provides perspective in understanding the intricacies underlying molecular regulation of subtype-specific roles of Gβγ signalling and associated diseases.
Collapse
Affiliation(s)
- Mithila Tennakoon
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
| | - Kanishka Senarath
- Genetics and Molecular Biology Unit, University of Sri Jayewardenepura, Nugegoda, Sri Lanka
| | - Dinesh Kankanamge
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
| | - Kasun Ratnayake
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA; Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Dhanushan Wijayaratna
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
| | - Koshala Olupothage
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
| | - Sithurandi Ubeysinghe
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA
| | | | - Terence E Hébert
- Department of Pharmacology and Therapeutics, McGill University, Montréal, QC H3G 1Y6, Canada.
| | - Ajith Karunarathne
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo, OH 43606, USA.
| |
Collapse
|
7
|
Inaba H, Miao Q, Nakata T. Optogenetic control of small GTPases reveals RhoA mediates intracellular calcium signaling. J Biol Chem 2021; 296:100290. [PMID: 33453281 PMCID: PMC7949103 DOI: 10.1016/j.jbc.2021.100290] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 01/06/2021] [Accepted: 01/11/2021] [Indexed: 01/05/2023] Open
Abstract
Rho/Ras family small GTPases are known to regulate numerous cellular processes, including cytoskeletal reorganization, cell proliferation, and cell differentiation. These processes are also controlled by Ca2+, and consequently, cross talk between these signals is considered likely. However, systematic quantitative evaluation has not yet been reported. To fill this gap, we constructed optogenetic tools to control the activity of small GTPases (RhoA, Rac1, Cdc42, Ras, Rap, and Ral) using an improved light-inducible dimer system (iLID). We characterized these optogenetic tools with genetically encoded red fluorescence intensity-based small GTPase biosensors and confirmed these optogenetic tools’ specificities. Using these optogenetic tools, we investigated calcium mobilization immediately after small GTPase activation. Unexpectedly, we found that a transient intracellular calcium elevation was specifically induced by RhoA activation in RPE1 and HeLa cells. RhoA activation also induced transient intracellular calcium elevation in MDCK and HEK293T cells, suggesting that generally RhoA induces calcium signaling. Interestingly, the molecular mechanisms linking RhoA activation to calcium increases were shown to be different among the different cell types: In RPE1 and HeLa cells, RhoA activated phospholipase C epsilon (PLCε) at the plasma membrane, which in turn induced Ca2+ release from the endoplasmic reticulum (ER). The RhoA–PLCε axis induced calcium-dependent nuclear factor of activated T cells nuclear translocation, suggesting that it does activate intracellular calcium signaling. Conversely, in MDCK and HEK293T cells, RhoA–ROCK–myosin II axis induced the calcium transients. These data suggest universal coordination of RhoA and calcium signaling in cellular processes, such as cellular contraction and gene expression.
Collapse
Affiliation(s)
- Hironori Inaba
- Department of Cell Biology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan; The Center for Brain Integration Research (CBIR), Tokyo Medical and Dental University (TMDU), Tokyo, Japan
| | - Qianqian Miao
- Department of Cell Biology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan; The Center for Brain Integration Research (CBIR), Tokyo Medical and Dental University (TMDU), Tokyo, Japan
| | - Takao Nakata
- Department of Cell Biology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), Tokyo, Japan; The Center for Brain Integration Research (CBIR), Tokyo Medical and Dental University (TMDU), Tokyo, Japan.
| |
Collapse
|
8
|
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.
Collapse
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.
| |
Collapse
|
9
|
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: 40] [Impact Index Per Article: 10.0] [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.
Collapse
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.
| |
Collapse
|
10
|
Nam O, Suzuki I, Shiraiwa Y, Jin E. Association of Phosphatidylinositol-Specific Phospholipase C with Calcium-Induced Biomineralization in the Coccolithophore Emiliania huxleyi. Microorganisms 2020; 8:E1389. [PMID: 32927844 PMCID: PMC7563939 DOI: 10.3390/microorganisms8091389] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 09/08/2020] [Accepted: 09/09/2020] [Indexed: 11/17/2022] Open
Abstract
Biomineralization by calcifying microalgae is a precisely controlled intracellular calcification process that produces delicate calcite scales (or coccoliths) in the coccolithophore Emiliania huxleyi (Haptophycea). Despite its importance in biogeochemical cycles and the marine environment globally, the underlying molecular mechanism of intracellular coccolith formation, which requires calcium, bicarbonate, and coccolith-polysaccharides, remains unclear. In E. huxleyi CCMP 371, we demonstrated that reducing the calcium concentration from 10 (ambient seawater) to 0.1 mM strongly restricted coccolith production, which was then recovered by adding 10 mM calcium, irrespective of inorganic phosphate conditions, indicating that coccolith production could be finely controlled by the calcium supply. Using this strain, we investigated the expression of differentially expressed genes (DEGs) to observe the cellular events induced by changes in calcium concentrations. Intriguingly, DEG analysis revealed that the phosphatidylinositol-specific phospholipase C (PI-PLC) gene was upregulated and coccolith production by cells was blocked by the PI-PLC inhibitor U73122 under conditions closely associated with calcium-induced calcification. These findings imply that PI-PLC plays an important role in the biomineralization process of the coccolithophore E. huxleyi.
Collapse
Affiliation(s)
- Onyou Nam
- Department of Life Science, Research Institute for Natural Sciences, Hanyang University, Seoul 04763, Korea;
| | - Iwane Suzuki
- Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan; (I.S.); (Y.S.)
| | - Yoshihiro Shiraiwa
- Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan; (I.S.); (Y.S.)
| | - EonSeon Jin
- Department of Life Science, Research Institute for Natural Sciences, Hanyang University, Seoul 04763, Korea;
| |
Collapse
|
11
|
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.
Collapse
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
| |
Collapse
|
12
|
Madukwe JC, Garland-Kuntz EE, Lyon AM, Smrcka AV. G protein βγ subunits directly interact with and activate phospholipase Cϵ. J Biol Chem 2018. [PMID: 29535186 DOI: 10.1074/jbc.ra118.002354] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phospholipase C (PLC) enzymes hydrolyze membrane phosphatidylinositol 4,5 bisphosphate (PIP2) and regulate Ca2+ and protein kinase signaling in virtually all mammalian cell types. Chronic activation of the PLCϵ isoform downstream of G protein-coupled receptors (GPCRs) contributes to the development of cardiac hypertrophy. We have previously shown that PLCϵ-catalyzed hydrolysis of Golgi-associated phosphatidylinositol 4-phosphate (PI4P) in cardiac myocytes depends on G protein βγ subunits released upon stimulation with endothelin-1. PLCϵ binds and is directly activated by Ras family small GTPases, but whether they directly interact with Gβγ has not been demonstrated. To identify PLCϵ domains that interact with Gβγ, here we designed various single substitutions and truncations of WT PLCϵ and tested them for activation by Gβγ in transfected COS-7 cells. Deletion of only a single domain in PLCϵ was not sufficient to completely block its activation by Gβγ, but blocked activation by Ras. Simultaneous deletion of the C-terminal RA2 domain and the N-terminal CDC25 and cysteine-rich domains completely abrogated PLCϵ activation by Gβγ, but activation by the GTPase Rho was retained. In vitro reconstitution experiments further revealed that purified Gβγ directly interacts with a purified fragment of PLCϵ (PLCϵ-PH-RA2) and increases PIP2 hydrolysis. Deletion of the RA2 domain decreased Gβγ binding and eliminated Gβγ stimulation of PIP2 hydrolysis. These results provide first evidence that Gβγ directly interacts with PLCϵ and yield insights into the mechanism by which βγ subunits activate PLCϵ.
Collapse
Affiliation(s)
- Jerry C Madukwe
- From the Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, New York 14267.,Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan 48109
| | | | - Angeline M Lyon
- Department of Chemistry Purdue University, West Lafayette, Indiana 47907, and
| | - Alan V Smrcka
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan 48109
| |
Collapse
|
13
|
Smrcka AV. Regulation of phosphatidylinositol-specific phospholipase C at the nuclear envelope in cardiac myocytes. J Cardiovasc Pharmacol 2016; 65:203-10. [PMID: 25658460 DOI: 10.1097/fjc.0000000000000195] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Phosphatidylinositol 4,5-bisphosphate hydrolysis at the plasma membrane by phospholipase C is one of the major hormone regulated intracellular signaling systems. The system generates the diffusible second messenger IP3 and the membrane bound messenger diacylglycerol. Spatial regulation of this system has been thought to be through specific subcellular distributions of the IP3 receptor or PKC. As is becoming increasingly apparent, receptor-stimulated signaling systems are also found at intracellular membranes. As discussed in this issue, G protein-coupled receptors have been identified at the nuclear envelope implying intracellular localization of the signaling systems that respond to G protein-coupled receptors. Here, we discuss the evidence for the existence of PLC signals that regulate nuclear processes, as well as the evidence for nuclear and nuclear envelope localization of PLC signaling components, and their implications for cardiac physiology and disease.
Collapse
Affiliation(s)
- Alan V Smrcka
- Department of Pharmacology and Physiology, University of Rochester School of Medicine and Dentistry, Rochester, NY
| |
Collapse
|
14
|
Lu S, Jang H, Muratcioglu S, Gursoy A, Keskin O, Nussinov R, Zhang J. Ras Conformational Ensembles, Allostery, and Signaling. Chem Rev 2016; 116:6607-65. [PMID: 26815308 DOI: 10.1021/acs.chemrev.5b00542] [Citation(s) in RCA: 262] [Impact Index Per Article: 32.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Ras proteins are classical members of small GTPases that function as molecular switches by alternating between inactive GDP-bound and active GTP-bound states. Ras activation is regulated by guanine nucleotide exchange factors that catalyze the exchange of GDP by GTP, and inactivation is terminated by GTPase-activating proteins that accelerate the intrinsic GTP hydrolysis rate by orders of magnitude. In this review, we focus on data that have accumulated over the past few years pertaining to the conformational ensembles and the allosteric regulation of Ras proteins and their interpretation from our conformational landscape standpoint. The Ras ensemble embodies all states, including the ligand-bound conformations, the activated (or inactivated) allosteric modulated states, post-translationally modified states, mutational states, transition states, and nonfunctional states serving as a reservoir for emerging functions. The ensemble is shifted by distinct mutational events, cofactors, post-translational modifications, and different membrane compositions. A better understanding of Ras biology can contribute to therapeutic strategies.
Collapse
Affiliation(s)
- Shaoyong Lu
- Department of Pathophysiology, Shanghai Universities E-Institute for Chemical Biology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University, School of Medicine , Shanghai, 200025, China.,Cancer and Inflammation Program, Leidos Biomedical Research, Inc., Frederick National Laboratory, National Cancer Institute , Frederick, Maryland 21702, United States
| | - Hyunbum Jang
- Cancer and Inflammation Program, Leidos Biomedical Research, Inc., Frederick National Laboratory, National Cancer Institute , Frederick, Maryland 21702, United States
| | | | | | | | - Ruth Nussinov
- Cancer and Inflammation Program, Leidos Biomedical Research, Inc., Frederick National Laboratory, National Cancer Institute , Frederick, Maryland 21702, United States.,Department of Human Genetics and Molecular Medicine, Sackler School of Medicine, Sackler Institute of Molecular Medicine, Tel Aviv University , Tel Aviv 69978, Israel
| | - Jian Zhang
- Department of Pathophysiology, Shanghai Universities E-Institute for Chemical Biology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University, School of Medicine , Shanghai, 200025, China
| |
Collapse
|
15
|
Malik S, deRubio RG, Trembley M, Irannejad R, Wedegaertner PB, Smrcka AV. G protein βγ subunits regulate cardiomyocyte hypertrophy through a perinuclear Golgi phosphatidylinositol 4-phosphate hydrolysis pathway. Mol Biol Cell 2015; 26:1188-98. [PMID: 25609085 PMCID: PMC4357516 DOI: 10.1091/mbc.e14-10-1476] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Gβγ regulation of the perinuclear Golgi PI4P pathway and a separate pathway at the PM is required for ET-1–stimulated hypertrophy, and the efficacy of Gβγ inhibition in preventing heart failure may be due, in part, to its blocking both of these pathways. We recently identified a novel GPCR-dependent pathway for regulation of cardiac hypertrophy that depends on Golgi phosphatidylinositol 4-phosphate (PI4P) hydrolysis by a specific isoform of phospholipase C (PLC), PLCε, at the nuclear envelope. How stimuli are transmitted from cell surface GPCRs to activation of perinuclear PLCε is not clear. Here we tested the role of G protein βγ subunits. Gβγ inhibition blocked ET-1–stimulated Golgi PI4P depletion in neonatal and adult ventricular myocytes. Blocking Gβγ at the Golgi inhibited ET-1–dependent PI4P depletion and nuclear PKD activation. Translocation of Gβγ to the Golgi stimulated perinuclear Golgi PI4P depletion and nuclear PKD activation. Finally, blocking Gβγ at the Golgi or PM blocked ET-1–dependent cardiomyocyte hypertrophy. These data indicate that Gβγ regulation of the perinuclear Golgi PI4P pathway and a separate pathway at the PM is required for ET-1–stimulated hypertrophy, and the efficacy of Gβγ inhibition in preventing heart failure maybe due in part to its blocking both these pathways.
Collapse
Affiliation(s)
- S Malik
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642
| | - R G deRubio
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642
| | - M Trembley
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642
| | - R Irannejad
- Department of Psychiatry, University of California, San Francisco, San Francisco, CA 94158
| | - P B Wedegaertner
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA 19107
| | - A V Smrcka
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642
| |
Collapse
|
16
|
Dusaban SS, Brown JH. PLCε mediated sustained signaling pathways. Adv Biol Regul 2014; 57:17-23. [PMID: 25453218 DOI: 10.1016/j.jbior.2014.09.014] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Revised: 09/22/2014] [Accepted: 09/25/2014] [Indexed: 01/09/2023]
Abstract
Phospholipase C-ε (PLCε) integrates signaling from G-protein coupled receptors (GPCRs) to downstream kinases to regulate a broad range of biological and pathophysiological responses. Relative to other PLCs, PLCε is unique in that it not only serves a catalytic function in phosphoinositide hydrolysis but also functions as an exchange factor small the low molecular weight G-protein Rap1. PLCε is selectively stimulated by agonists for GPCRs that couple to RhoA, which bind directly to the enzyme to regulate its activity. Rap1 also regulates PLCε activity by binding to its RA2 domain and this generates a feedback mechanism allowing sustained signaling. As a result of its regulation by inflammatory ligands for GPCRs and its ability to promote chronic signals, PLCε has been implicated in diseases ranging from cancer to ischemia/reperfusion injury. This review will discuss the regulation of PLCε, molecular mechanisms that contribute to sustained signaling, and the role of the enzyme in various disease contexts.
Collapse
Affiliation(s)
- Stephanie S Dusaban
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA; Biomedical Sciences Graduate Program, University of California, San Diego, La Jolla, CA 92093, USA
| | - Joan Heller Brown
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA.
| |
Collapse
|
17
|
Khan SM, Sleno R, Gora S, Zylbergold P, Laverdure JP, Labbé JC, Miller GJ, Hébert TE. The expanding roles of Gβγ subunits in G protein-coupled receptor signaling and drug action. Pharmacol Rev 2013; 65:545-77. [PMID: 23406670 DOI: 10.1124/pr.111.005603] [Citation(s) in RCA: 172] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Gβγ subunits from heterotrimeric G proteins perform a vast array of functions in cells with respect to signaling, often independently as well as in concert with Gα subunits. However, the eponymous term "Gβγ" does not do justice to the fact that 5 Gβ and 12 Gγ isoforms have evolved in mammals to serve much broader roles beyond their canonical roles in cellular signaling. We explore the phylogenetic diversity of Gβγ subunits with a view toward understanding these expanded roles in different cellular organelles. We suggest that the particular content of distinct Gβγ subunits regulates cellular activity, and that the granularity of individual Gβ and Gγ action is only beginning to be understood. Given the therapeutic potential of targeting Gβγ action, this larger view serves as a prelude to more specific development of drugs aimed at individual isoforms.
Collapse
Affiliation(s)
- Shahriar M Khan
- Department of Pharmacology and Therapeutics, McGill University, 3655 Promenade Sir-William-Osler, Room 1303, Montréal, Québec H3G 1Y6, Canada
| | | | | | | | | | | | | | | |
Collapse
|
18
|
Wang LD, Bi X, Song X, Pohl NM, Cheng Y, Zhou Y, Shears S, Ansong E, Xing M, Wang S, Xu XC, Huang P, Xu L, Wang L, Fan Z, Zhao X, Dong H, Meltzer SJ, Ding I, Yang W. A sequence variant in the phospholipase C epsilon C2 domain is associated with esophageal carcinoma and esophagitis. Mol Carcinog 2013; 52 Suppl 1:E80-6. [PMID: 23390063 DOI: 10.1002/mc.22016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2012] [Revised: 01/13/2013] [Accepted: 01/18/2013] [Indexed: 12/14/2022]
Abstract
A single-nucleotide polymorphism (rs2274223: A5780G:His1927Arg) in the phospholipase C epsilon gene (PLCϵ) was recently identified as a susceptibility locus for esophageal cancer in Chinese subjects. To determine the underlying mechanisms of PLCϵ and this SNP in esophageal carcinogenesis, we analyzed PLCϵ genotypes, expression, and their correlation in esophageal cancer cell lines, non-transformed esophageal cells, 58 esophageal squamous cell carcinomas and 10,614 non-cancer subjects from China. We found that the G allele (AG or GG) was associated with increased PLCϵ mRNA and protein expression in esophageal cancer tissues and in esophageal cancer cell lines. G allele was also associated with higher enzyme activity, which might be associated with increased protein expression. Quantitative analysis of the C2 domain sequences revealed that A:G allelic imbalance was strongly linked to esophageal malignancy. Moreover, the analysis of 10,614 non-cancer subjects demonstrated that the G allele was strongly associated with moderate to severe esophagitis in the subjects from the high-incidence areas of China (OR 6.03, 95% CI 1.59-22.9 in high-incidence area vs. OR 0.74, 95% CI 0.33-1.64 in low-incidence area; P = 0.008). In conclusion, the PLCϵ gene, particularly the 5780G allele, might play a pivotal role in esophageal carcinogenesis via upregulating PLCϵ mRNA, protein, and enzyme activity, and augmenting inflammatory process in esophageal epithelium. Thus, 5780G allele may constitute a promising biomarker for esophageal squamous cell carcinoma risk stratification, early detection, and progression prediction.
Collapse
Affiliation(s)
- Li-Dong Wang
- Department of Pathology, Xinxiang Medical University, Xinxiang, China; Henan Key Laboratory for Esophageal Cancer Research, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, China
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
19
|
Abstract
Phospholipase C (PLC) converts phosphatidylinositol 4,5-bisphosphate (PIP(2)) to inositol 1,4,5-trisphosphate (IP(3)) and diacylglycerol (DAG). DAG and IP(3) each control diverse cellular processes and are also substrates for synthesis of other important signaling molecules. PLC is thus central to many important interlocking regulatory networks. Mammals express six families of PLCs, each with both unique and overlapping controls over expression and subcellular distribution. Each PLC also responds acutely to its own spectrum of activators that includes heterotrimeric G protein subunits, protein tyrosine kinases, small G proteins, Ca(2+), and phospholipids. Mammalian PLCs are autoinhibited by a region in the catalytic TIM barrel domain that is the target of much of their acute regulation. In combination, the PLCs act as a signaling nexus that integrates numerous signaling inputs, critically governs PIP(2) levels, and regulates production of important second messengers to determine cell behavior over the millisecond to hour timescale.
Collapse
Affiliation(s)
- Ganesh Kadamur
- Department of Pharmacology, Molecular Biophysics Graduate Program and Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | | |
Collapse
|
20
|
Smrcka AV, Brown JH, Holz GG. Role of phospholipase Cε in physiological phosphoinositide signaling networks. Cell Signal 2012; 24:1333-43. [PMID: 22286105 PMCID: PMC3325758 DOI: 10.1016/j.cellsig.2012.01.009] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2012] [Accepted: 01/13/2012] [Indexed: 02/05/2023]
Abstract
Receptor-initiated phospholipase C activation and generation of IP(3) and DAG are important common triggers for a diversity of signal transduction processes in many cell types. Contributing to this diversity is the existence and differential cellular and subcellular distribution of distinct phospholipase C isoforms with distinct regulatory properties. The recently identified PLCε enzyme is an isoform that is uniquely regulated by multiple upstream signals including ras-family GTP binding proteins as well as heterotrimeric G-proteins. In this review we will consider the well documented biochemical regulation of this isoform in the context of cell and whole animal physiology and in the context of other G protein-regulated PLC isoforms. These studies together reveal a surprisingly wide range of unexpected functions for PLCε in cellular signaling, physiology and disease.
Collapse
Affiliation(s)
- Alan V Smrcka
- Department of Pharmacology and Physiology, University of Rochester School of Medicine, 601 Elmwood Ave, Rochester, NY 14642, USA.
| | | | | |
Collapse
|
21
|
Bosch DE, Willard FS, Ramanujam R, Kimple AJ, Willard MD, Naqvi NI, Siderovski DP. A P-loop mutation in Gα subunits prevents transition to the active state: implications for G-protein signaling in fungal pathogenesis. PLoS Pathog 2012; 8:e1002553. [PMID: 22383884 PMCID: PMC3285607 DOI: 10.1371/journal.ppat.1002553] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Accepted: 01/12/2012] [Indexed: 11/26/2022] Open
Abstract
Heterotrimeric G-proteins are molecular switches integral to a panoply of different physiological responses that many organisms make to environmental cues. The switch from inactive to active Gαβγ heterotrimer relies on nucleotide cycling by the Gα subunit: exchange of GTP for GDP activates Gα, whereas its intrinsic enzymatic activity catalyzes GTP hydrolysis to GDP and inorganic phosphate, thereby reverting Gα to its inactive state. In several genetic studies of filamentous fungi, such as the rice blast fungus Magnaporthe oryzae, a G42R mutation in the phosphate-binding loop of Gα subunits is assumed to be GTPase-deficient and thus constitutively active. Here, we demonstrate that Gα(G42R) mutants are not GTPase deficient, but rather incapable of achieving the activated conformation. Two crystal structure models suggest that Arg-42 prevents a typical switch region conformational change upon Gαi1(G42R) binding to GDP·AlF4− or GTP, but rotameric flexibility at this locus allows for unperturbed GTP hydrolysis. Gα(G42R) mutants do not engage the active state-selective peptide KB-1753 nor RGS domains with high affinity, but instead favor interaction with Gβγ and GoLoco motifs in any nucleotide state. The corresponding Gαq(G48R) mutant is not constitutively active in cells and responds poorly to aluminum tetrafluoride activation. Comparative analyses of M. oryzae strains harboring either G42R or GTPase-deficient Q/L mutations in the Gα subunits MagA or MagB illustrate functional differences in environmental cue processing and intracellular signaling outcomes between these two Gα mutants, thus demonstrating the in vivo functional divergence of G42R and activating G-protein mutants. Heterotrimeric G-proteins function as molecular switches to convey cellular signals. When a G-protein coupled receptor encounters its ligand at the cellular membrane, it catalyzes guanine nucleotide exchange on the Gα subunit, resulting in a shift from an inactive to an active conformation. G-protein signaling pathways are conserved from mammals to plants and fungi, including the rice blast fungus Magnaporthe oryzae. A mutation in the Gα subunit (G42R), previously thought to eliminate its GTPase activity, leading to constitutive activation, has been utilized to investigate roles of heterotrimeric G-protein signaling pathways in multiple species of filamentous fungi. Here, we demonstrate through structural, biochemical, and cellular approaches that G42R mutants are neither GTPase deficient nor constitutively active, but rather are unable to transition to the activated conformation. A direct comparison of M. oryzae fungal strains harboring either G42R or truly constitutively activating mutations in two Gα subunits, MagA and MagB, revealed markedly different phenotypes. Our results suggest that activation of MagB is critical for pathogenic development of M. oryzae in response to hydrophobic surfaces, such as plant leaves. Furthermore, the lack of constitutive activity by Gα(G42R) mutants prompts a re-evaluation of its use in previous genetic experiments in multiple fungal species.
Collapse
Affiliation(s)
- Dustin E. Bosch
- Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Francis S. Willard
- Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- * E-mail: (FSW); (DPS)
| | - Ravikrishna Ramanujam
- Fungal Patho-Biology Group, Temasek Life Sciences Laboratory, Singapore
- School of Biological Sciences, Nanyang Technological University, Singapore
| | - Adam J. Kimple
- Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Melinda D. Willard
- Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Naweed I. Naqvi
- Fungal Patho-Biology Group, Temasek Life Sciences Laboratory, Singapore
- School of Biological Sciences, Nanyang Technological University, Singapore
- Department of Biological Sciences, National University of Singapore, Singapore
| | - David P. Siderovski
- Department of Pharmacology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- UNC Neuroscience Center and Lineberger Comprehensive Cancer Center, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- * E-mail: (FSW); (DPS)
| |
Collapse
|
22
|
Abstract
The physiological effects of many extracellular neurotransmitters, hormones, growth factors, and other stimuli are mediated by receptor-promoted activation of phospholipase C (PLC) and consequential activation of inositol lipid signaling pathways. These signaling responses include the classically described conversion of phosphatidylinositol(4,5)P(2) to the Ca(2+)-mobilizing second messenger inositol(1,4,5)P(3) and the protein kinase C-activating second messenger diacylglycerol as well as alterations in membrane association or activity of many proteins that harbor phosphoinositide binding domains. The 13 mammalian PLCs elaborate a minimal catalytic core typified by PLC-d to confer multiple modes of regulation of lipase activity. PLC-b isozymes are activated by Gaq- and Gbg-subunits of heterotrimeric G proteins, and activation of PLC-g isozymes occurs through phosphorylation promoted by receptor and non-receptor tyrosine kinases. PLC-e and certain members of the PLC-b and PLC-g subclasses of isozymes are activated by direct binding of small G proteins of the Ras, Rho, and Rac subfamilies of GTPases. Recent high resolution three dimensional structures together with biochemical studies have illustrated that the X/Y linker region of the catalytic core mediates autoinhibition of most if not all PLC isozymes. Activation occurs as a consequence of removal of this autoinhibition.
Collapse
|
23
|
Zhang L, Malik S, Kelley GG, Kapiloff MS, Smrcka AV. Phospholipase C epsilon scaffolds to muscle-specific A kinase anchoring protein (mAKAPbeta) and integrates multiple hypertrophic stimuli in cardiac myocytes. J Biol Chem 2011; 286:23012-21. [PMID: 21550986 DOI: 10.1074/jbc.m111.231993] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To define a role for phospholipase Cε (PLCε) signaling in cardiac myocyte hypertrophic growth, PLCε protein was depleted from neonatal rat ventricular myocytes (NRVMs) using siRNA. NRVMs with PLCε depletion were stimulated with endothelin (ET-1), norepinephrine, insulin-like growth factor-1 (IGF-1), or isoproterenol and assessed for development of hypertrophy. PLCε depletion dramatically reduced hypertrophic growth and gene expression induced by all agonists tested. PLCε catalytic activity was required for hypertrophy development, yet PLCε depletion did not reduce global agonist-stimulated inositol phosphate production, suggesting a requirement for localized PLC activity. PLCε was found to be scaffolded to a muscle-specific A kinase anchoring protein (mAKAPβ) in heart and NRVMs, and mAKAPβ localizes to the nuclear envelope in NRVMs. PLCε-mAKAP interaction domains were defined and overexpressed to disrupt endogenous mAKAPβ-PLCε complexes in NRVMs, resulting in significantly reduced ET-1-dependent NRVM hypertrophy. We propose that PLCε integrates multiple upstream signaling pathways to generate local signals at the nucleus that regulate hypertrophy.
Collapse
Affiliation(s)
- Lianghui Zhang
- Department of Pharmacology and Physiology, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA
| | | | | | | | | |
Collapse
|
24
|
Epac2-dependent rap1 activation and the control of islet insulin secretion by glucagon-like peptide-1. VITAMINS AND HORMONES 2011; 84:279-302. [PMID: 21094904 DOI: 10.1016/b978-0-12-381517-0.00010-2] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Glucagon-like peptide-1 (GLP-1) binds its Class II G protein-coupled receptor to stimulate cyclic adenosine monophosphate (cAMP) production and to potentiate the glucose metabolism-dependent secretion of insulin from pancreatic β cells located within the islets of Langerhans. Prior clinical studies demonstrate that this cAMP-mediated action of GLP-1 to potentiate glucose-stimulated insulin secretion (GSIS) is of major therapeutic importance when evaluating the abilities of GLP-1 receptor (GLP-1R) agonists to lower levels of blood glucose in type 2 diabetic subjects. Surprisingly, recent in vitro studies of human or rodent islets of Langerhans provide evidence for the existence of a noncanonical mechanism of β cell cAMP signal transduction, one that may explain how GLP-1R agonists potentiate GSIS. What these studies demonstrate is that a cAMP-regulated guanine nucleotide exchange factor designated as Epac2 couples β cell cAMP production to the protein kinase A-independent stimulation of insulin exocytosis. Provided here is an overview of the Epac2 signal transduction system in β cells, with special emphasis on Rap1, a Ras-related GTPase that is an established target of Epac2.
Collapse
|
25
|
Sun J, Liu X, Pan Y. The physical interaction between LdPLCs and Arabidopsis G beta in a yeast two-hybrid system. ACTA ACUST UNITED AC 2011. [DOI: 10.1007/s11703-011-1063-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
26
|
Valenti G, Mira A, Mastrofrancesco L, Lasorsa DR, Ranieri M, Svelto M. Differential Modulation of Intracellular Ca 2+ Responses Associated with Calcium-Sensing Receptor Activation in Renal Collecting Duct Cells. Cell Physiol Biochem 2010; 26:901-12. [DOI: 10.1159/000323999] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/02/2010] [Indexed: 12/26/2022] Open
|
27
|
Sossin WS, Abrams TW. Evolutionary conservation of the signaling proteins upstream of cyclic AMP-dependent kinase and protein kinase C in gastropod mollusks. BRAIN, BEHAVIOR AND EVOLUTION 2009; 74:191-205. [PMID: 20029183 DOI: 10.1159/000258666] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The protein kinase C (PKC) and the cAMP-dependent kinase (protein kinase A; PKA) pathways are known to play important roles in behavioral plasticity and learning in the nervous systems of a wide variety of species across phyla. We briefly review the members of the PKC and PKA family and focus on the evolution of the immediate upstream activators of PKC and PKA i.e., phospholipase C (PLC) and adenylyl cyclase (AC), and their conservation in gastropod mollusks, taking advantage of the recent assembly of the Aplysiacalifornica and Lottia gigantea genomes. The diversity of PLC and AC family members present in mollusks suggests a multitude of possible mechanisms to activate PKA and PKC; we briefly discuss the relevance of these pathways to the known physiological activation of these kinases in Aplysia neurons during plasticity and learning. These multiple mechanisms of activation provide the gastropod nervous system with tremendous flexibility for implementing neuromodulatory responses to both neuronal activity and extracellular signals.
Collapse
Affiliation(s)
- Wayne S Sossin
- Department of Neurology and Neurosurgery, McGill University, Montreal Neurological Institute, Montreal, Que., Canada.
| | | |
Collapse
|
28
|
Harden TK, Hicks SN, Sondek J. Phospholipase C isozymes as effectors of Ras superfamily GTPases. J Lipid Res 2008; 50 Suppl:S243-8. [PMID: 19033212 DOI: 10.1194/jlr.r800045-jlr200] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The physiological effects of many extracellular stimuli are initiated through receptor-promoted activation of phospholipase C and inositol lipid signaling pathways. The historical view that phospholipase C-promoted signaling primarily occurs through activation of heterotrimeric G proteins or tyrosine kinases has expanded in recent years with the realization that at least three different mammalian phospholipase C isozymes are directly activated by members of the Ras superfamily of GTPases. Thus, Ras, Rap, Rac, and Rho GTPases all specifically regulate certain phospholipase C isozymes, and insight into the physiological significance of these signaling responses is beginning to accrue. High resolution three-dimensional structures of phospholipase C isozymes also are beginning to shed light on their mechanism of activation.
Collapse
Affiliation(s)
- T Kendall Harden
- Department of Pharmacology, Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA.
| | | | | |
Collapse
|
29
|
Walliser C, Retlich M, Harris R, Everett KL, Josephs MB, Vatter P, Esposito D, Driscoll PC, Katan M, Gierschik P, Bunney TD. rac regulates its effector phospholipase Cgamma2 through interaction with a split pleckstrin homology domain. J Biol Chem 2008; 283:30351-62. [PMID: 18728011 PMCID: PMC2573054 DOI: 10.1074/jbc.m803316200] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2008] [Revised: 07/31/2008] [Indexed: 11/16/2022] Open
Abstract
Several isoforms of phospholipase C (PLC) are regulated through interactions with Ras superfamily GTPases, including Rac proteins. Interestingly, of two closely related PLCgamma isoforms, only PLCgamma(2) has previously been shown to be activated by Rac. Here, we explore the molecular basis of this interaction as well as the structural properties of PLCgamma(2) required for activation. Based on reconstitution experiments with isolated PLCgamma variants and Rac2, we show that an unusual pleckstrin homology (PH) domain, designated as the split PH domain (spPH), is both necessary and sufficient to effect activation of PLCgamma(2) by Rac2. We also demonstrate that Rac2 directly binds to PLCgamma(2) as well as to the isolated spPH of this isoform. Furthermore, through the use of NMR spectroscopy and mutational analysis, we determine the structure of spPH, define the structural features of spPH required for Rac interaction, and identify critical amino acid residues at the interaction interface. We further discuss parallels and differences between PLCgamma(1) and PLCgamma(2) and the implications of our findings for their respective signaling roles.
Collapse
Affiliation(s)
- Claudia Walliser
- Institute of Pharmacology and Toxicology, University of Ulm Medical Center, 89070 Ulm, Germany
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
30
|
Oestreich EA, Malik S, Goonasekera SA, Blaxall BC, Kelley GG, Dirksen RT, Smrcka AV. Epac and phospholipase Cepsilon regulate Ca2+ release in the heart by activation of protein kinase Cepsilon and calcium-calmodulin kinase II. J Biol Chem 2008; 284:1514-22. [PMID: 18957419 DOI: 10.1074/jbc.m806994200] [Citation(s) in RCA: 154] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Recently, we identified a novel signaling pathway involving Epac, Rap, and phospholipase C (PLC)epsilon that plays a critical role in maximal beta-adrenergic receptor (betaAR) stimulation of Ca2+-induced Ca2+ release (CICR) in cardiac myocytes. Here we demonstrate that PLCepsilon phosphatidylinositol 4,5-bisphosphate hydrolytic activity and PLCepsilon-stimulated Rap1 GEF activity are both required for PLCepsilon-mediated enhancement of sarcoplasmic reticulum Ca2+ release and that PLCepsilon significantly enhances Rap activation in response to betaAR stimulation in the heart. Downstream of PLCepsilon hydrolytic activity, pharmacological inhibition of PKC significantly inhibited both betaAR- and Epac-stimulated increases in CICR in PLCepsilon+/+ myocytes but had no effect in PLCepsilon-/- myocytes. betaAR and Epac activation caused membrane translocation of PKCepsilon in PLCepsilon+/+ but not PLCepsilon-/- myocytes and small interfering RNA-mediated PKCepsilon knockdown significantly inhibited both betaAR and Epac-mediated CICR enhancement. Further downstream, the Ca2+/calmodulin-dependent protein kinase II (CamKII) inhibitor, KN93, inhibited betaAR- and Epac-mediated CICR in PLCepsilon+/+ but not PLCepsilon-/- myocytes. Epac activation increased CamKII Thr286 phosphorylation and enhanced phosphorylation at CamKII phosphorylation sites on the ryanodine receptor (RyR2) (Ser2815) and phospholamban (Thr17) in a PKC-dependent manner. Perforated patch clamp experiments revealed that basal and betaAR-stimulated peak L-type current density are similar in PLCepsilon+/+ and PLCepsilon-/- myocytes suggesting that control of sarcoplasmic reticulum Ca2+ release, rather than Ca2+ influx through L-type Ca2+ channels, is the target of regulation of a novel signal transduction pathway involving sequential activation of Epac, PLCepsilon, PKCepsilon, and CamKII downstream of betaAR activation.
Collapse
Affiliation(s)
- Emily A Oestreich
- Department of Pharmacology, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA
| | | | | | | | | | | | | |
Collapse
|
31
|
Shemarova IV, Nesterov VP. Evolution of mechanisms of Ca2+-signaling. Role of Ca2+ in regulation of fundamental cell functions. J EVOL BIOCHEM PHYS+ 2008. [DOI: 10.1134/s0022093008040017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|
32
|
Seifert JP, Zhou Y, Hicks SN, Sondek J, Harden TK. Dual activation of phospholipase C-epsilon by Rho and Ras GTPases. J Biol Chem 2008; 283:29690-8. [PMID: 18765661 DOI: 10.1074/jbc.m805038200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Phospholipase C-epsilon (PLC-epsilon) is a highly elaborated PLC required for a diverse set of signaling pathways. Here we use a combination of cellular assays and studies with purified proteins to show that activated RhoA and Ras isoforms directly engage distinct regions of PLC-epsilon to stimulate its phospholipase activity. Purified PLC-epsilon was activated in a guanine nucleotide- and concentration-dependent fashion by purified lipidated K-Ras reconstituted in PtdIns(4,5)P(2)-containing phospholipid vesicles. Whereas mutation of two critical lysine residues within the second Ras-association domain of PLC-epsilon prevented K-Ras-dependent activation of the purified enzyme, guanine nucleotide-dependent activation by RhoA was retained. Deletion of a loop unique to PLC-epsilon eliminated its activation by RhoA but not H-Ras. In contrast, removal of the autoinhibitory X/Y-linker region of the catalytic core of PLC-epsilon markedly activates the enzyme (Hicks, S. N., Jezyk, M. R., Gershburg, S., Seifert, J. P., Harden, T. K., and Sondek, J. (2008) Mol. Cell, 31, 383-394), but PLC-epsilon lacking this regulatory region retained activation by both Rho and Ras GTPases. Additive activation of PLC-epsilon by RhoA and K- or H-Ras was observed in intact cell studies, and this additivity was recapitulated in experiments in which activation of purified PLC-epsilon was quantified with PtdIns(4,5)P(2)-containing phospholipid vesicles reconstituted with purified, isoprenylated GTPases. A maximally effective concentration of activated RhoA also increased the sensitivity of purified PLC-epsilon to activation by K-Ras. These results indicate that PLC-epsilon can be directly and concomitantly activated by both RhoA and individual Ras GTPases resulting in diverse upstream control of signaling cascades downstream of PLC-epsilon.
Collapse
Affiliation(s)
- Jason P Seifert
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA
| | | | | | | | | |
Collapse
|
33
|
Healy KD, Hodgson L, Kim TY, Shutes A, Maddileti S, Juliano RL, Hahn KM, Harden TK, Bang YJ, Der CJ. DLC-1 suppresses non-small cell lung cancer growth and invasion by RhoGAP-dependent and independent mechanisms. Mol Carcinog 2008; 47:326-37. [PMID: 17932950 DOI: 10.1002/mc.20389] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Expression of the tumor suppressor deleted in liver cancer-1 (DLC-1) is lost in non-small cell lung (NSCLC) and other human carcinomas, and ectopic DLC-1 expression dramatically reduces proliferation and tumorigenicity. DLC-1 is a multi-domain protein that includes a Rho GTPase activating protein (RhoGAP) domain which has been hypothesized to be the basis of its tumor suppressive actions. To address the importance of the RhoGAP function of DLC-1 in tumor suppression, we performed biochemical and biological studies evaluating DLC-1 in NSCLC. Full-length DLC-1 exhibited strong GAP activity for RhoA as well as RhoB and RhoC, but only very limited activity for Cdc42 in vitro. In contrast, the isolated RhoGAP domain showed 5- to 20-fold enhanced activity for RhoA, RhoB, RhoC, and Cdc42. DLC-1 protein expression was absent in six of nine NSCLC cell lines. Restoration of DLC-1 expression in DLC-1-deficient NSCLC cell lines reduced RhoA activity, and experiments with a RhoA biosensor demonstrated that DLC-1 dramatically reduces RhoA activity at the leading edge of cellular protrusions. Furthermore, DLC-1 expression in NSCLC cell lines impaired both anchorage-dependent and -independent growth, as well as invasion in vitro. Surprisingly, we found that the anti-tumor activity of DLC-1 was due to both RhoGAP-dependent and -independent activities. Unlike the rat homologue p122RhoGAP, DLC-1 was not capable of activating the phospholipid hydrolysis activity of phospholipase C-delta1. Combined, these studies provide information on the mechanism of DLC-1 function and regulation, and further support the role of DLC-1 tumor suppression in NSCLC.
Collapse
Affiliation(s)
- Kevin D Healy
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, NC 27599-7295, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
34
|
Zhou Y, Sondek J, Harden TK. Activation of human phospholipase C-eta2 by Gbetagamma. Biochemistry 2008; 47:4410-7. [PMID: 18361507 DOI: 10.1021/bi800044n] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Phospholipase C-eta2 (PLC-eta2) was recently identified as a novel broadly expressed phosphoinositide-hydrolyzing isozyme [Zhou, Y., et al. (2005) Biochem. J. 391, 667-676; Nakahara, M., et al. (2005) J. Biol. Chem. 280, 29128-29134]. In this study, we investigated the direct regulation of PLC-eta2 by Gbetagamma subunits of heterotrimeric G proteins. Coexpression of PLC-eta2 with Gbeta 1gamma 2, as well as with certain other Gbetagamma dimers, in COS-7 cells resulted in increases in inositol phosphate accumulation. Gbeta 1gamma 2-dependent increases in phosphoinositide hydrolysis also were observed with a truncation mutant of PLC-eta2 that lacks the long alternatively spliced carboxy-terminal domain of the isozyme. To begin to define the enzymatic properties of PLC-eta2 and its potential direct activation by Gbetagamma, a construct of PLC-eta2 encompassing the canonical domains conserved in all PLCs (PH domain through C2 domain) was purified to homogeneity after expression from a baculovirus in insect cells. Enzyme activity of purified PLC-eta2 was quantified after reconstitution with PtdIns(4,5)P 2-containing phospholipid vesicles, and values for K m (14.4 microM) and V max [12.6 micromol min (-1) (mg of protein) (-1)] were similar to activities previously observed with purified PLC-beta or PLC-epsilon isozymes. Moreover, purified Gbeta 1gamma 2 stimulated the activity of purified PLC-eta2 in a concentration-dependent manner similar to that observed with purified PLC-beta2. Activation was dependent on the presence of free Gbeta 1gamma 2 since its sequestration in the presence of Galpha i1 or GRK2-ct reversed Gbeta 1gamma 2-promoted activation. The PH domain of PLC-eta2 is not required for Gbeta 1gamma 2-mediated regulation since a purified fragment encompassing the EF-hand through C2 domains but lacking the PH domain nonetheless was activated by Gbeta 1gamma 2. Taken together, these studies illustrate that PLC-eta2 is a direct downstream effector of Gbetagamma and, therefore, of receptor-activated heterotrimeric G proteins.
Collapse
Affiliation(s)
- Yixing Zhou
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA
| | | | | |
Collapse
|
35
|
Citro S, Malik S, Oestreich EA, Radeff-Huang J, Kelley GG, Smrcka AV, Brown JH. Phospholipase Cepsilon is a nexus for Rho and Rap-mediated G protein-coupled receptor-induced astrocyte proliferation. Proc Natl Acad Sci U S A 2007; 104:15543-8. [PMID: 17878312 PMCID: PMC2000505 DOI: 10.1073/pnas.0702943104] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Phospholipase Cepsilon (PLCepsilon) has been suggested to transduce signals from small GTPases, but its biological function has not yet been clarified. Using astrocytes from PLCepsilon-deficient mice, we demonstrate that endogenous G protein-coupled receptors (GPCRs) for lysophosphatidic acid, sphingosine 1-phosphate, and thrombin regulate phosphoinositide hydrolysis primarily through PLCepsilon. Stimulation by lysophospholipids occurs through G(i), whereas thrombin activates PLC through Rho. Further studies reveal that PLCepsilon is required for thrombin- but not LPA-induced sustained ERK activation and DNA synthesis, providing a novel mechanism for GPCR and Rho signaling to cell proliferation. The requirement for PLCepsilon in this pathway can be explained by its role as a guanine nucleotide exchange factor for Rap1. Thus, PLCepsilon serves to transduce mitogenic signals through a mechanism distinct from its role in generation of PLC-derived second messengers.
Collapse
Affiliation(s)
- Simona Citro
- *Department of Pharmacology, University of California at San Diego, La Jolla, CA 92093
| | - Sundeep Malik
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642
| | - Emily A. Oestreich
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642
| | - Julie Radeff-Huang
- *Department of Pharmacology, University of California at San Diego, La Jolla, CA 92093
| | - Grant G. Kelley
- Departments of Medicine and Pharmacology, State University of New York Upstate Medical University, Syracuse, NY 13210; and
| | - Alan V. Smrcka
- Department of Pharmacology and Physiology, University of Rochester, Rochester, NY 14642
| | - Joan Heller Brown
- *Department of Pharmacology, University of California at San Diego, La Jolla, CA 92093
- To whom correspondence should be addressed. E-mail:
| |
Collapse
|
36
|
Díaz Añel AM. Phospholipase C beta3 is a key component in the Gbetagamma/PKCeta/PKD-mediated regulation of trans-Golgi network to plasma membrane transport. Biochem J 2007; 406:157-65. [PMID: 17492941 PMCID: PMC1948997 DOI: 10.1042/bj20070359] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2007] [Accepted: 05/10/2007] [Indexed: 11/17/2022]
Abstract
The requirement of DAG (diacylglycerol) to recruit PKD (protein kinase D) to the TGN (trans-Golgi network) for the targeting of transport carriers to the cell surface, has led us to a search for new components involved in this regulatory pathway. Previous findings reveal that the heterotrimeric Gbetagamma (GTP-binding protein betagamma subunits) act as PKD activators, leading to fission of transport vesicles at the TGN. We have recently shown that PKCeta (protein kinase Ceta) functions as an intermediate member in the vesicle generating pathway. DAG is capable of activating this kinase at the TGN, and at the same time is able to recruit PKD to this organelle in order to interact with PKCeta, allowing phosphorylation of PKD's activation loop. The most qualified candidates for the production of DAG at the TGN are PI-PLCs (phosphatidylinositol-specific phospholipases C), since some members of this family can be directly activated by Gbetagamma, utilizing PtdIns(4,5)P2 as a substrate, to produce the second messengers DAG and InsP3. In the present study we show that betagamma-dependent Golgi fragmentation, PKD1 activation and TGN to plasma membrane transport were affected by a specific PI-PLC inhibitor, U73122 [1-(6-{[17-3-methoxyestra-1,3,5(10)-trien-17-yl]amino}hexyl)-1H-pyrrole-2,5-dione]. In addition, a recently described PI-PLC activator, m-3M3FBS [2,4,6-trimethyl-N-(m-3-trifluoromethylphenyl)benzenesulfonamide], induced vesiculation of the Golgi apparatus as well as PKD1 phosphorylation at its activation loop. Finally, using siRNA (small interfering RNA) to block several PI-PLCs, we were able to identify PLCbeta3 as the sole member of this family involved in the regulation of the formation of transport carriers at the TGN. In conclusion, we demonstrate that fission of transport carriers at the TGN is dependent on PI-PLCs, specifically PLCbeta3, which is necessary to activate PKCeta and PKD in that Golgi compartment, via DAG production.
Collapse
Key Words
- diacylglycerol (dag)
- golgi
- gtp-binding protein βγ subunits (gβγ)
- phospholipase c (plc)
- protein kinase d (pkd)
- trafficking
- bfa, brefeldin a
- dag, diacylglycerol
- dgk, sn-1,2-diacylglycerol kinase
- er, endoplasmic reticulum
- gβγ, gtp-binding protein βγ subunits
- gfp, green fluorescent protein
- gpcr, g-protein-coupled receptor
- gst, glutathione s-transferase
- ha, haemagglutinin
- hek-293 cells, human embryonic kidney cells
- hek-293t cells, hek-293 cells expressing the large t-antigen of sv40 (simian virus 40)
- iq, ilimaquinone
- m-3m3fbs, 2,4,6-trimethyl-n-(m-3-trifluoromethylphenyl)benzenesulfonamide
- ndga, nordihydroguaiaretic acid
- nrk cell, normal rat kidney cell
- pa, phosphatidic acid
- ph domain, pleckstrin homology domain
- plc, phospholipase c
- pi-plc, phosphatidylinositol-specific plc
- pkc, protein kinase c
- sirna, small interfering rna
- tgn, trans-golgi network
- u73122, 1-(6-{[17-3-methoxyestra-1,3,5(10)-trien-17-yl]amino}hexyl)-1h-pyrrole-2,5-dione
- vsv, vesicular stomatitis virus
- vsv-g, vsv glycoprotein
- wt, wild-type
Collapse
Affiliation(s)
- Alberto M Díaz Añel
- Center for Molecular Genetics, University of California at San Diego, San Diego, CA, USA.
| |
Collapse
|
37
|
Abstract
In the trans-Golgi network (TGN), proteins are sorted for transport to the endosomes, plasma membrane, preceding Golgi cisternae, and endoplasmic reticulum. The formation of clathrin-coated vesicles for transport to the endosomes and of COP-I-coated vesicles for retrograde trafficking is fairly well characterized at the molecular level. We describe our current understanding of the TGN-to-cell-surface carriers, with a specific focus on the components involved in membrane fission. Inhibiting the fission machinery promotes growth of transport carriers into large tubules that remain attached to the TGN. Overactivating this machinery, on the other hand, vesiculates the TGN. To understand how membrane fission is regulated by cargo to form transport carriers yet prevents complete vesiculation of the TGN remains a daunting challenge. We discuss these issues with regard to TGN-to-cell-surface transport carriers.
Collapse
Affiliation(s)
- Frédéric Bard
- Cell and Developmental Biology Department, University of California San Diego, La Jolla, California 92093, USA.
| | | |
Collapse
|
38
|
Oude Weernink PA, Han L, Jakobs KH, Schmidt M. Dynamic phospholipid signaling by G protein-coupled receptors. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1768:888-900. [PMID: 17054901 DOI: 10.1016/j.bbamem.2006.09.012] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2006] [Revised: 09/18/2006] [Accepted: 09/18/2006] [Indexed: 11/19/2022]
Abstract
G protein-coupled receptors (GPCRs) control a variety of fundamental cellular processes by regulating phospholipid signaling pathways. Essential for signaling by a large number of receptors is the hydrolysis of the membrane phosphoinositide PIP(2) by phospholipase C (PLC) into the second messengers IP(3) and DAG. Many receptors also stimulate phospholipase D (PLD), leading to the generation of the versatile lipid, phosphatidic acid. Particular PLC and PLD isoforms take differential positions in receptor signaling and are additionally regulated by small GTPases of the Ras, Rho and ARF families. It is now recognized that the PLC substrate, PIP(2), has signaling capacity by itself and can, by direct interaction, affect the activity and subcellular localization of PLD and several other proteins. As expected, the synthesis of PIP(2) by phosphoinositide 5-kinases is tightly regulated as well. In this review, we present an overview of how these signaling pathways are governed by GPCRs, explain the molecular basis for the spatially and temporally organized, highly dynamic quality of phospholipid signaling, and point to the functional connection of the pathways.
Collapse
Affiliation(s)
- Paschal A Oude Weernink
- Institut für Pharmakologie, Universitätsklinikum Essen, Hufelandstrasse 55, 45122 Essen, Germany.
| | | | | | | |
Collapse
|
39
|
Lad Y, McHugh B, Hodkinson PS, Mackinnon AC, Haslett C, Ginsberg MH, Sethi T. Phospholipase C epsilon suppresses integrin activation. J Biol Chem 2006; 281:29501-12. [PMID: 16895916 DOI: 10.1074/jbc.m513471200] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phospholipase Cepsilon (PLCepsilon) is a newly described effector of the small GTP-binding protein H-Ras. Utilizing H-Ras effector mutants, we show that mutants H-Ras(G12V/E37G) and H-Ras(G12V/D38N) suppressed integrin activation in an ERK-independent manner. H-Ras(G12V/D38N) specifically activated the PLCepsilon effector pathway and suppressed integrin activation. Inhibition of PLCepsilon activation with a kinase-dead PLCepsilon mutant prevented H-Ras(G12V/D38N) from suppressing integrin activation, and low level expression of H-Ras(G12V/D38N) could synergize with wild-type PLCepsilon to suppress integrins. In addition, knockdown of endogenous PLCepsilon with small interfering RNA blocked H-Ras(G12V/D38N)-mediated integrin suppression. Suppressing integrin function with the H-Ras(G12V/D38N) mutant reduced cell adhesion to von Willebrand factor and fibronectin; this reduction in cell adhesion was blocked by coexpression of the kinase-dead PLCepsilon mutant. These results show that H-Ras suppresses integrin affinity via independent Raf and PLCepsilon signaling pathways and demonstrate a new physiological function for PLCepsilon in the regulation of integrin activation.
Collapse
Affiliation(s)
- Yatish Lad
- Medical Research Council Centre for Inflammation Research, Queen's Medical Research Institute, University of Edinburgh, 47 Little France Crescent, Edinburgh EH16 4SA, Scotland, United Kingdom
| | | | | | | | | | | | | |
Collapse
|
40
|
Abstract
The physiological effects of many extracellular stimuli are mediated by receptor-promoted activation of phospholipase C (PLC) and consequential activation of inositol lipid-signaling pathways. These signaling responses include the classically described conversion of PtdIns(4,5)P(2) to the Ca(2+)-mobilizing second messenger Ins(1,4,5)P(3) and the protein kinase C-activating second messenger diacylglycerol as well as alterations in membrane association or activity of many proteins that harbor phosphoinositide binding domains. Here we discuss how the family of PLCs elaborates a minimal catalytic core typified by PLC-delta to confer multiple modes of regulation on their phospholipase activities. Although PLC-dependent signaling is prominently regulated by direct interactions with heterotrimeric G proteins or tyrosine kinases, the existence of at least 13 divergent PLC isozymes promises a diverse repertoire of regulatory mechanisms for this class of important signaling proteins. We focus here on the recently realized and extensive regulation of inositol lipid signaling by Ras superfamily GTPases directly acting on PLC isozymes and conclude by considering the biological and pharmacological ramifications of this regulation.
Collapse
Affiliation(s)
- T Kendall Harden
- Departments of Pharmacology, Biochemistry and Biophysics, and Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA.
| | | |
Collapse
|
41
|
Bourguignon LYW, Gilad E, Brightman A, Diedrich F, Singleton P. Hyaluronan-CD44 interaction with leukemia-associated RhoGEF and epidermal growth factor receptor promotes Rho/Ras co-activation, phospholipase C epsilon-Ca2+ signaling, and cytoskeleton modification in head and neck squamous cell carcinoma cells. J Biol Chem 2006; 281:14026-40. [PMID: 16565089 DOI: 10.1074/jbc.m507734200] [Citation(s) in RCA: 172] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
In this study we have examined the interaction of CD44 (a major hyaluronan (HA) receptor) with a RhoA-specific guanine nucleotide exchange factor (leukemia-associated RhoGEF (LARG)) in human head and neck squamous carcinoma cells (HNSCC-HSC-3 cell line). Immunoprecipitation and immunoblot analyses indicate that CD44 and the LARG protein are expressed in HSC-3 cells and that these two proteins are physically associated as a complex. HA-CD44 binding induces LARG-specific RhoA signaling and phospholipase C epsilon (PLC epsilon) activity. In particular, the activation of RhoA-PLC epsilon by HA stimulates inositol 1,4,5-triphosphate production, intracellular Ca2+ mobilization, and the up-regulation of Ca2+/calmodulin-dependent kinase II (CaMKII), leading to phosphorylation of the cytoskeletal protein, filamin. The phosphorylation of filamin reduces its interaction with filamentous actin, promoting tumor cell migration. The CD44-LARG complex also interacts with the EGF receptor (EGFR). Most importantly, the binding of HA to the CD44-LARG-EGFR complex activates the EGFR receptor kinase, which in turn promotes Ras-mediated stimulation of a downstream kinase cascade including the Raf-1 and ERK pathways leading to HNSCC cell growth. Using a recombinant fragment of LARG (the LARG-PDZ domain) and a binding assay, we have determined that the LARG-PDZ domain serves as a direct linker between CD44 and EGFR. Transfection of the HSC-3 cells with LARG-PDZcDNA significantly reduces LARG association with CD44 and EGFR. Overexpression of the LARG-PDZ domain also functions as a dominant-negative mutant (similar to the PLC/Ca2+-calmodulin-dependent kinase II (CaMKII) and EGFR/MAPK inhibitor effects) to block HA/CD44-mediated signaling events (e.g. EGFR kinase activation, Ras/RhoA co-activation, Raf-ERK signaling, PLC epsilon-mediated inositol 1,4,5-triphosphate production, intracellular Ca2+ mobilization, CaMKII activity, filamin phosphorylation, and filamin-actin binding) and to abrogate tumor cell growth/migration. Taken together, our findings suggest that CD44 interaction with LARG and EGFR plays a pivotal role in Rho/Ras co-activation, PLC epsilon-Ca2+ signaling, and Raf/ERK up-regulation required for CaMKII-mediated cytoskeleton function and in head and neck squamous cell carcinoma progression.
Collapse
Affiliation(s)
- Lilly Y W Bourguignon
- Department of Medicine, University of California at San Francisco and Endocrine Unit (111N), Veterans Affairs Medical Center, San Francisco, California 94121, USA.
| | | | | | | | | |
Collapse
|
42
|
Hains MD, Wing MR, Maddileti S, Siderovski DP, Harden TK. Gα12/13- and Rho-Dependent Activation of Phospholipase C-ϵ by Lysophosphatidic Acid and Thrombin Receptors. Mol Pharmacol 2006; 69:2068-75. [PMID: 16554409 DOI: 10.1124/mol.105.017921] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Because phospholipase C epsilon (PLC-epsilon) is activated by Galpha(12/13) and Rho family GTPases, we investigated whether these G proteins contribute to the increased inositol lipid hydrolysis observed in COS-7 cells after activation of certain G protein-coupled receptors. Stimulation of inositol lipid hydrolysis by endogenous lysophosphatidic acid (LPA) or thrombin receptors was markedly enhanced by the expression of PLC-epsilon. Expression of the LPA(1) or PAR1 receptor increased inositol phosphate production in response to LPA or SFLLRN, respectively, and these agonist-stimulated responses were markedly enhanced by coexpression of PLC-epsilon. Both LPA(1) and PAR1 receptor-mediated activation of PLC-epsilon was inhibited by coexpression of the regulator of G protein signaling (RGS) domain of p115RhoGEF, a GTPase-activating protein for Galpha(12/13) but not by expression of the RGS domain of GRK2, which inhibits Galpha(q) signaling. In contrast, activation of the G(q)-coupled M1 muscarinic or P2Y(2) purinergic receptor was neither enhanced by coexpression with PLC-epsilon nor inhibited by the RGS domain of p115RhoGEF but was blocked by expression of the RGS domain of GRK2. Expression of the Rho inhibitor C3 botulinum toxin did not affect LPA- or SFLLRN-stimulated inositol lipid hydrolysis in the absence of PLC-epsilon but completely prevented the PLC-epsilon-dependent increase in inositol phosphate accumulation. Likewise, C3 toxin blocked the PLC-epsilon-dependent stimulatory effects of the LPA(1), LPA(2), LPA(3), or PAR1 receptor but had no effect on the agonist-promoted inositol phosphate response of the M1 or P2Y(2) receptor. Moreover, PLC-epsilon-dependent stimulation of inositol phosphate accumulation by activation of the epidermal growth factor receptor, which involves Ras- but not Rho-mediated activation of the phospholipase, was unaffected by C3 toxin. These studies illustrate that specific LPA and thrombin receptors promote inositol lipid signaling via activation of Galpha(12/13) and Rho.
Collapse
Affiliation(s)
- Melinda D Hains
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7365, USA
| | | | | | | | | |
Collapse
|
43
|
Kelley GG, Kaproth-Joslin KA, Reks SE, Smrcka AV, Wojcikiewicz RJH. G-protein-coupled receptor agonists activate endogenous phospholipase Cepsilon and phospholipase Cbeta3 in a temporally distinct manner. J Biol Chem 2006; 281:2639-48. [PMID: 16314422 PMCID: PMC1483126 DOI: 10.1074/jbc.m507681200] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phospholipase Cepsilon (PLCepsilon) is one of the newest members of the phosphatidylinositol-specific phospholipase C (PLC) family. Previous studies have suggested that G-protein-coupled receptors (GPCRs) stimulate phosphoinositide (PI) hydrolysis by activating PLCbeta isoforms through G(q) family G proteins and Gbetagamma subunits. Using RNA interference to knock down PLC isoforms, we demonstrate that the GPCR agonists endothelin (ET-1), lysophosphatidic acid (LPA), and thrombin, acting through endogenous receptors, couple to both endogenous PLCepsilon and the PLCbeta isoform, PLCbeta3, in Rat-1 fibroblasts. Examination of the temporal activation of these PLC isoforms, however, reveals agonist- and isoform-specific profiles. PLCbeta3 is activated acutely within the first minute of ET-1, LPA, or thrombin stimulation but does not contribute to sustained PI hydrolysis induced by LPA or thrombin and accounts for only part of ET-1 sustained stimulation. PLCepsilon, on the other hand, predominantly accounts for sustained PI hydrolysis. Consistent with this observation, reconstitution of PLCepsilon in knockdown cells dose-dependently increases sustained, but not acute, agonist-stimulated PI hydrolysis. Furthermore, combined knockdown of both PLCepsilon and PLCbeta3 additively inhibits PI hydrolysis, suggesting independent regulation of each isoform. Importantly, ubiquitination of inositol 1,4,5-trisphosphate receptors correlates with sustained, but not acute, activation of PLCepsilon or PLCbeta3. In conclusion, GPCR agonists ET-1, LPA, and thrombin activate endogenous PLCepsilon and PLCbeta3 in Rat-1 fibroblasts. Activation of these PLC isoforms displays agonist-specific temporal profiles; however, PLCbeta3 is predominantly involved in acute and PLCepsilon in sustained PI hydrolysis.
Collapse
Affiliation(s)
- Grant G Kelley
- Department of Medicine and Pharmacology, State University of New York Upstate Medical University, Syracuse, New York 13210, USA.
| | | | | | | | | |
Collapse
|
44
|
Satoh T, Edamatsu H, Kataoka T. Phospholipase Cepsilon guanine nucleotide exchange factor activity and activation of Rap1. Methods Enzymol 2006; 407:281-90. [PMID: 16757332 DOI: 10.1016/s0076-6879(05)07024-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Phospholipase C (PLC) epsilon is directly regulated by Ras and Rap1 small GTPases: Ras and Rap1, in their GTP-bound form, interact with the Ras/Rap1-associationg (RA) domain of PLCepsilon, thereby translocating PLCepsilon to the plasma membrane and the Golgi apparatus, respectively. In the plasma membrane and the Golgi apparatus, PLCepsilon acts as a phosphoinositide-specific PLC, regulating various downstream signaling pathways. PLCepsilon also contains a CDC25 homology domain, which enhances guanine nucleotide exchange on Rap1. Here, we describe biochemical characterization of the CDC25 homology domain of PLCepsilon and provide insights into its physiological role in the regulation of PLCepsilon activity.
Collapse
Affiliation(s)
- Takaya Satoh
- Division of Molecular Biology, Department of Molecular and Cellular Biology, Kobe University, Graduate School of Medicine, Kobe, Japan
| | | | | |
Collapse
|
45
|
Seifert JP, Snyder JT, Sondek J, Harden TK. Direct activation of purified phospholipase C epsilon by RhoA studied in reconstituted phospholipid vesicles. Methods Enzymol 2006; 406:260-71. [PMID: 16472663 DOI: 10.1016/s0076-6879(06)06019-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Phospholipase C-epsilon (PLC-epsilon) was shown recently to be a downstream effector of Rho GTPases, and we have used an in vitro phospholipid vesicle reconstitution system with purified proteins to show this regulation to be direct. This chapter describes high-level expression of a hexahistidine-tagged fragment of PLC-epsilon encompassing the catalytic core of the enzyme through the tandem RA domains by use of a recombinant baculovirus and High Five insect cells. The recombinant protein is purified to homogeneity using metal chelate affinity and size exclusion chromatography. The small GTPase RhoA also is expressed to high levels in a lipidated form after baculovirus expression in High Five cells and is purified to near homogeneity after detergent extraction and metal chelate affinity chromatography. The capacity of GTPgammaS-bound RhoA to stimulate the phospholipase activity of PLC-epsilon is assessed by reconstitution of the RhoA in mixed-detergent phospholipid micelles containing PtdIns(4,5)P2 substrate.
Collapse
Affiliation(s)
- Jason P Seifert
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, USA
| | | | | | | |
Collapse
|
46
|
Bourdon DM, Wing MR, Edwards EB, Sondek J, Harden TK. Quantification of isozyme-specific activation of phospholipase C-beta2 by Rac GTPases and phospholipase C-epsilon by Rho GTPases in an intact cell assay system. Methods Enzymol 2006; 406:489-99. [PMID: 16472681 DOI: 10.1016/s0076-6879(06)06037-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Phospholipase C (PLC) catalyzes the hydrolysis of PtdIns(4,5)P2, which results in both formation of the second messengers Ins(1,4,5)P3 and diacylglycerol and alteration in the membrane association and/or activity of PtdIns(4,5)P2-binding proteins. The existence of 13 different PLC isozymes suggests multiple mechanisms of regulation of inositol lipid signaling, and the recent realization that Rho-family GTPases directly bind and activate certain PLC isozymes has added to this potential diversity of inositol lipid-related signal transduction. With the goal of delineating a less labor-intensive method for quantification of intracellular inositol phosphate production, we have applied a commercially available yttrium silicate RNA binding resin selective for inositol phosphates to develop a high-throughput inositol phosphate scintillation proximity assay (SPA). We highlight the utility of this assay using COS-7 cells robotically transfected in a 96-well format. This method is readily applied to quantify activation of PLC by receptors and G proteins, and we illustrate here the selective activation of PLC-beta2 by Rac but not by Rho GTPases and the selective activation of PLC-epsilon by Rho but not Rac GTPases.
Collapse
Affiliation(s)
- David M Bourdon
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, USA
| | | | | | | | | |
Collapse
|
47
|
Wang H, Oestreich EA, Maekawa N, Bullard TA, Vikstrom KL, Dirksen RT, Kelley GG, Blaxall BC, Smrcka AV. Phospholipase C ε Modulates β-Adrenergic Receptor– Dependent Cardiac Contraction and Inhibits Cardiac Hypertrophy. Circ Res 2005; 97:1305-13. [PMID: 16293787 DOI: 10.1161/01.res.0000196578.15385.bb] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Phospholipase C (PLC) epsilon is a recently identified enzyme regulated by a wide range of molecules including Ras family small GTPases, Rho A, Galpha(12/13), and Gbetagamma with primary sites of expression in the heart and lung. In a screen for human signal transduction genes altered during heart failure, we found that PLCepsilon mRNA is upregulated. Two murine models of cardiac hypertrophy confirmed upregulation of PLCepsilon protein expression or PLCepsilon RNA. To identify a role for PLCepsilon in cardiac function and pathology, a PLCepsilon-deficient mouse strain was created. Echocardiography indicated PLCepsilon(-/-) mice had decreased cardiac function, and direct measurements of left ventricular contraction demonstrated that PLCepsilon(-/-) mice had a decreased contractile response to acute isoproterenol administration. Cardiac myocytes isolated from PLCepsilon(-/-) mice had decreased beta-adrenergic receptor (betaAR)-dependent increases in Ca2+ transient amplitudes, likely accounting for the contractile deficiency in vivo. This defect appears to be independent from the ability of the betaAR system to produce cAMP and regulation of sarcoplasmic reticulum Ca2+ pool size. To address the significance of these functional deficits to cardiac pathology, PLCepsilon(-/-) mice were subjected to a chronic isoproterenol model of hypertrophic stress. PLCepsilon(-/-) mice were more susceptible than wild-type littermates to development of hypertrophy than wild-type littermates. Together, these data suggest a novel PLC-dependent component of betaAR signaling in cardiac myocytes responsible for maintenance of maximal contractile reserve and loss of PLCepsilon signaling sensitizes the heart to development of hypertrophy in response to chronic cardiac stress.
Collapse
Affiliation(s)
- Huan Wang
- Department of Pharmacology and Physiology, University of Rochester School of Medicine, Rochester, NY 14642, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
48
|
Cockcroft S. The latest phospholipase C, PLCeta, is implicated in neuronal function. Trends Biochem Sci 2005; 31:4-7. [PMID: 16310357 DOI: 10.1016/j.tibs.2005.11.003] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2005] [Revised: 10/13/2005] [Accepted: 11/14/2005] [Indexed: 11/23/2022]
Abstract
Members of the phosphoinositide-specific phospholipase C (PLC) family have key roles in cell signalling. In response to many extracellular stimuli, such as hormones, neurotransmitters, antigens and growth factors, PLCs catalyse the hydrolysis of phosphatidylinositol (4,5)-bisphosphate [PtdIns(4,5)P(2)], thereby generating two well-established second messengers, inositol (1,4,5)-trisphosphate and diacylglycerol. Eleven PLC isozymes encoded by different genes have been identified in mammals and, on the basis of their structure and sequence relationships, have been classified into five families designated PLCbeta (1-4), PLCgamma (1 and 2), PLCdelta (1, 3 and 4), PLCepsilon (1) and PLCzeta (1). All PLCs contain the catalytic X and Y domain, in addition to other regulatory domains including the C2 domain and the EF-hand domain. In 2005, four groups independently identified an entirely new family of PLCs--eta1 and eta2--using data mining of mammalian genomes. The properties of the PLCeta enzyme suggest that it might act as a Ca(2+) sensor, in particular, functioning during formation and maintenance of the neuronal network in the postnatal brain.
Collapse
Affiliation(s)
- Shamshad Cockcroft
- Department of Physiology, University College London, London WC1E 6JJ, UK.
| |
Collapse
|
49
|
Zhou Y, Wing M, Sondek J, Harden T. Molecular cloning and characterization of PLC-eta2. Biochem J 2005; 391:667-76. [PMID: 16107206 PMCID: PMC1276968 DOI: 10.1042/bj20050839] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2005] [Revised: 08/02/2005] [Accepted: 08/18/2005] [Indexed: 11/17/2022]
Abstract
PLC (phospholipase C) isoenzymes catalyse the conversion of PtdIns(4,5)P2 into the Ca2+-mobilizing second messenger, Ins(1,4,5)P3, and the protein kinase C-activating second messenger, diacylglycerol. With the goal of identifying additional mammalian PLC isoenzymes, we screened the NCBI non-redundant database using a BLAST algorithm for novel sequences with homology with the conserved PLC catalytic core. Two unique sequences corresponding to two unknown PLC isoenzymes were identified, and one of these, designated PLC-eta2, was cloned and characterized. Most of the coding sequence of PLC-eta2 was constructed from two ESTs (expressed sequence tags), which included an overlapping sequence that was confirmed by multiple ESTs and mRNAs. 5'-RACE (rapid amplification of cDNA ends) also identified an upstream exon not deduced from available EST or mRNA sequences. Sequence analysis of PLC-eta2 revealed the canonical domains of a PLC isoenzyme with an additional long C-terminus that contains a class II PDZ-binding motif. Genomic analyses indicated that PLC-eta2 is encoded by 23 exons. RT-PCR (reverse transcriptase-PCR) analyses illustrated expression of PLC-eta2 in human retina and kidney, as well as in mouse brain, eye and lung. RT-PCR with exon-specific primers also revealed tissue-specific expression of four splice variants in mouse that represent alternative use of sequences in exons 21, 22 and 23. PLC-eta2-specific antisera recognized one of these splice variants as an approx. 155 kDa species when expressed in COS-7 cells; PLC-eta2 natively expressed in 1321N1 human astrocytoma cells also migrated as an approx. 155 kDa species. PLC activity was observed in vitro and in vivo for three different constructs of PLC-eta2, each containing possible alternatively spliced first exons. Co-expression of PLC-eta2 with Gbeta1gamma2 dimers of heterotrimeric G-proteins resulted in marked stimulation of inositol lipid hydrolysis. Thus PLC-eta2 may in part function downstream of G-protein-coupled receptors.
Collapse
Key Words
- g-protein
- phosphatidylinositol 4,5-bisphosphate [ptdins(4,5)p2]
- phospholipase c-η2
- phospholipase c-eta2
- gβγ
- as, antisense
- dmem, dulbecco's modified eagle's medium
- ef, elongation factor
- est, expressed sequence tag
- orf, open reading frame
- ph, pleckstrin homology
- plc, phospholipase c
- race, rapid amplification of cdna ends
- rt-pcr, reverse transcriptase-pcr
- s, sense
- sh, src homology
- tim, triose phosphate isomerase
- tpck, n-tosyl-l-phenylalanine chloromethyl ketone
- utr, untranslated region
Collapse
Affiliation(s)
- Yixing Zhou
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, U.S.A
| | - Michele R. Wing
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, U.S.A
| | - John Sondek
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, U.S.A
| | - T. Kendall Harden
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, NC 27599, U.S.A
| |
Collapse
|
50
|
Abstract
Ras proteins function as signaling hubs that are activated by convergent signaling pathways initiated by extracellular stimuli. Activated Ras in turn regulates a diversity of downstream cytoplasmic signaling cascades. Ras proteins are founding members of a large superfamily of small GTPases that have significant sequence and biochemical similarities. Recent observations have established a complex signaling interplay between Ras and other members of the family. A key biochemical mechanism facilitating this crosstalk involves guanine nucleotide exchange factors (GEFs), which serve as regulators and effectors, as well as signaling integrators, of Ras signaling.
Collapse
Affiliation(s)
- Natalia Mitin
- University of North Carolina at Chapel Hill, Lineberger Comprehensive Cancer Center, NC 27599, USA.
| | | | | |
Collapse
|