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Regulatory role of guanine nucleotide exchange factor (GEF) Dock180 phosphorylation on Tyr/Ser in mediation of gastric mucosal Rac1 activation in response to Helicobacter pylori and ghrelin. Inflammopharmacology 2015; 23:111-8. [PMID: 25957600 DOI: 10.1007/s10787-015-0235-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Accepted: 04/28/2015] [Indexed: 01/26/2023]
Abstract
A small GTPase, Rac1, is recognized as an important modulator of the inflammatory responses to bacterial lipopolysaccharide (LPS) by affecting the processes of phospholipase C activation. The activation of Rac1 involves the exchange of GDP for GTP and is catalyzed by the guanine nucleotide exchange factors (GEFs). Here, we report on the gastric mucosal GEF, Dock180, activation in response to H. pylori PS, and the hormone, ghrelin. We show that stimulation of gastric mucosal cells with the LPS leads to up-regulation in Dock180 phosphorylation on Tyr and Ser that is accompanied by a massive rise in Rac1-GTP level, while the effect of ghrelin, manifested by a drop in Dock180 phosphorylation on Ser, is associated with a decrease in Rac1-GTP formation. Furthermore, we demonstrate that phosphorylation on Tyr remains under the control of the Src family protein tyrosine kinases (SFK-PTKs), and is accompanied by Dock180 membrane translocation, while phosphorylation of the membrane-localized Dock180 on Ser represents the stimulatory contribution of protein kinase Cδ (PKCδ) to Dock180 activation. Moreover, we reveal that the interaction between Dock180 and PKCδ is dependent on Dock180 Tyr phosphorylation as well as the activity of PKCδ. Thus, our findings point to the involvement of PKCδ in the LPS-induced up-regulation of Dock180 activation, and suggest the modulatory mechanism of ghrelin influence on the gastric mucosal inflammatory responses to H. pylori.
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302
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Walliser C, Tron K, Clauss K, Gutman O, Kobitski AY, Retlich M, Schade A, Röcker C, Henis YI, Nienhaus GU, Gierschik P. Rac-mediated Stimulation of Phospholipase Cγ2 Amplifies B Cell Receptor-induced Calcium Signaling. J Biol Chem 2015; 290:17056-72. [PMID: 25903139 DOI: 10.1074/jbc.m115.645739] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Indexed: 12/21/2022] Open
Abstract
The Rho GTPase Rac is crucially involved in controlling multiple B cell functions, including those regulated by the B cell receptor (BCR) through increased cytosolic Ca(2+). The underlying molecular mechanisms and their relevance to the functions of intact B cells have thus far remained unknown. We have previously shown that the activity of phospholipase Cγ2 (PLCγ2), a key constituent of the BCR signalosome, is stimulated by activated Rac through direct protein-protein interaction. Here, we use a Rac-resistant mutant of PLCγ2 to functionally reconstitute cultured PLCγ2-deficient DT40 B cells and to examine the effects of the Rac-PLCγ2 interaction on BCR-mediated changes of intracellular Ca(2+) and regulation of Ca(2+)-regulated and nuclear-factor-of-activated-T-cell-regulated gene transcription at the level of single, intact B cells. The results show that the functional Rac-PLCγ2 interaction causes marked increases in the following: (i) sensitivity of B cells to BCR ligation; (ii) BCR-mediated Ca(2+) release from intracellular stores; (iii) Ca(2+) entry from the extracellular compartment; and (iv) nuclear translocation of the Ca(2+)-regulated nuclear factor of activated T cells. Hence, Rac-mediated stimulation of PLCγ2 activity serves to amplify B cell receptor-induced Ca(2+) signaling.
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Affiliation(s)
- Claudia Walliser
- From the Institute of Pharmacology and Toxicology, University of Ulm Medical Center, 89070 Ulm, Germany
| | - Kyrylo Tron
- the Institute of Biophysics, University of Ulm, 89069 Ulm, Germany
| | - Karen Clauss
- the Institute of Biophysics, University of Ulm, 89069 Ulm, Germany
| | - Orit Gutman
- the Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Andrei Yu Kobitski
- the Institute of Applied Physics and Center for Functional Nanostructures, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Michael Retlich
- From the Institute of Pharmacology and Toxicology, University of Ulm Medical Center, 89070 Ulm, Germany
| | - Anja Schade
- From the Institute of Pharmacology and Toxicology, University of Ulm Medical Center, 89070 Ulm, Germany
| | - Carlheinz Röcker
- the Institute of Biophysics, University of Ulm, 89069 Ulm, Germany
| | - Yoav I Henis
- the Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - G Ulrich Nienhaus
- the Institute of Applied Physics and Center for Functional Nanostructures, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany, the Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany, and the Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Peter Gierschik
- From the Institute of Pharmacology and Toxicology, University of Ulm Medical Center, 89070 Ulm, Germany,
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303
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Béziau DM, Toussaint F, Blanchette A, Dayeh NR, Charbel C, Tardif JC, Dupuis J, Ledoux J. Expression of phosphoinositide-specific phospholipase C isoforms in native endothelial cells. PLoS One 2015; 10:e0123769. [PMID: 25875657 PMCID: PMC4395365 DOI: 10.1371/journal.pone.0123769] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 02/25/2015] [Indexed: 11/18/2022] Open
Abstract
Phospholipase C (PLC) comprises a superfamily of enzymes that play a key role in a wide array of intracellular signalling pathways, including protein kinase C and intracellular calcium. Thirteen different mammalian PLC isoforms have been identified and classified into 6 families (PLC-β, γ, δ, ε, ζ and η) based on their biochemical properties. Although the expression of PLC isoforms is tissue-specific, concomitant expression of different PLC has been reported, suggesting that PLC family is involved in multiple cellular functions. Despite their critical role, the PLC isoforms expressed in native endothelial cells (ECs) remains undetermined. A conventional PCR approach was initially used to elucidate the mRNA expression pattern of PLC isoforms in 3 distinct murine vascular beds: mesenteric (MA), pulmonary (PA) and middle cerebral arteries (MCA). mRNA encoding for most PLC isoforms was detected in MA, MCA and PA with the exception of η2 and β2 (only expressed in PA), δ4 (only expressed in MCA), η1 (expressed in all but MA) and ζ (not detected in any vascular beds tested). The endothelial-specific PLC expression was then sought in freshly isolated ECs. Interestingly, the PLC expression profile appears to differ across the investigated arterial beds. While mRNA for 8 of the 13 PLC isoforms was detected in ECs from MA, two additional PLC isoforms were detected in ECs from PA and MCA. Co-expression of multiple PLC isoforms in ECs suggests an elaborate network of signalling pathways: PLC isoforms may contribute to the complexity or diversity of signalling by their selective localization in cellular microdomains. However in situ immunofluorescence revealed a homogeneous distribution for all PLC isoforms probed (β3, γ2 and δ1) in intact endothelium. Although PLC isoforms play a crucial role in endothelial signal transduction, subcellular localization alone does not appear to be sufficient to determine the role of PLC in the signalling microdomains found in the native endothelium.
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Affiliation(s)
- Delphine M. Béziau
- Research Center, Montreal Heart Institute, Montreal, Qc, Canada
- Department of Molecular and Integrative Physiology, Université de Montréal, Montreal, Qc, Canada
| | - Fanny Toussaint
- Research Center, Montreal Heart Institute, Montreal, Qc, Canada
- Department of Molecular and Integrative Physiology, Université de Montréal, Montreal, Qc, Canada
| | | | - Nour R. Dayeh
- Research Center, Montreal Heart Institute, Montreal, Qc, Canada
- Department of Medicine, Université de Montréal, Montreal, Qc, Canada
| | - Chimène Charbel
- Research Center, Montreal Heart Institute, Montreal, Qc, Canada
- Department of Pharmacology, Université de Montréal, Montreal, Qc, Canada
| | - Jean-Claude Tardif
- Research Center, Montreal Heart Institute, Montreal, Qc, Canada
- Department of Medicine, Université de Montréal, Montreal, Qc, Canada
| | - Jocelyn Dupuis
- Research Center, Montreal Heart Institute, Montreal, Qc, Canada
- Department of Medicine, Université de Montréal, Montreal, Qc, Canada
| | - Jonathan Ledoux
- Research Center, Montreal Heart Institute, Montreal, Qc, Canada
- Department of Molecular and Integrative Physiology, Université de Montréal, Montreal, Qc, Canada
- Department of Pharmacology, Université de Montréal, Montreal, Qc, Canada
- Department of Medicine, Université de Montréal, Montreal, Qc, Canada
- * E-mail:
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304
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Brusich DJ, Spring AM, Frank CA. A single-cross, RNA interference-based genetic tool for examining the long-term maintenance of homeostatic plasticity. Front Cell Neurosci 2015; 9:107. [PMID: 25859184 PMCID: PMC4374470 DOI: 10.3389/fncel.2015.00107] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 03/09/2015] [Indexed: 11/15/2022] Open
Abstract
Homeostatic synaptic plasticity (HSP) helps neurons and synapses maintain physiologically appropriate levels of output. The fruit fly Drosophila melanogaster larval neuromuscular junction (NMJ) is a valuable model for studying HSP. Here we introduce a genetic tool that allows fruit fly researchers to examine the lifelong maintenance of HSP with a single cross. The tool is a fruit fly stock that combines the GAL4/UAS expression system with RNA interference (RNAi)-based knock down of a glutamate receptor subunit gene. With this stock, we uncover important new information about the maintenance of HSP. We address an open question about the role that presynaptic CaV2-type Ca2+ channels play in NMJ homeostasis. Published experiments have demonstrated that hypomorphic missense mutations in the CaV2 α1a subunit gene cacophony (cac) can impair homeostatic plasticity at the NMJ. Here we report that reducing cac expression levels by RNAi is not sufficient to impair homeostatic plasticity. The presence of wild-type channels appears to support HSP—even when total CaV2 function is severely reduced. We also conduct an RNAi- and electrophysiology-based screen to identify new factors required for sustained homeostatic signaling throughout development. We uncover novel roles in HSP for Drosophila homologs of Cysteine string protein (CSP) and Phospholipase Cβ (Plc21C). We characterize those roles through follow-up genetic tests. We discuss how CSP, Plc21C, and associated factors could modulate presynaptic CaV2 function, presynaptic Ca2+ handling, or other signaling processes crucial for sustained homeostatic regulation of NMJ function throughout development. Our findings expand the scope of signaling pathways and processes that contribute to the durable strength of the NMJ.
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Affiliation(s)
- Douglas J Brusich
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa Iowa City, IA, USA
| | - Ashlyn M Spring
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa Iowa City, IA, USA ; Interdisciplinary Graduate Program in Genetics, University of Iowa Iowa City, IA, USA
| | - C Andrew Frank
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa Iowa City, IA, USA ; Interdisciplinary Programs in Genetics, Neuroscience, and MCB, University of Iowa Iowa City, IA, USA
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305
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Slomiany BL, Slomiany A. Mechanism of Rac1-induced amplification in gastric mucosal phospholipase Cγ2 activation in response to Helicobacter pylori: modulatory effect of ghrelin. Inflammopharmacology 2015; 23:101-9. [PMID: 25796615 DOI: 10.1007/s10787-015-0231-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 03/04/2015] [Indexed: 12/27/2022]
Abstract
Membrane recruitment followed by targeted phosphorylation of specific Tyr and Ser residues and the interaction with Rac GTPases are the crucial parts of an elaborate mechanism of PLCγ2 activation essential for its role in linking the specific receptor responses to a variety of hormones and bacterial endotoxins with the intended intracellular targets. Here, we explored the involvement of Rac in mediation of PLCγ2 activation associated with gastric mucosal inflammatory responses to H. pylori LPS and the hormone, ghrelin. We show that stimulation of gastric mucosal cells with the LPS leads to the membrane translocation of Rac1 as well as PLCγ2, while the effect of ghrelin is manifested by elevation in the membrane PLCγ2 activation and suppression in Rac1 translocation. However, blocking the LPS-induced Rac1 translocation, while detrimental to the PLCγ2 activation, has no effect on its membrane translocation. We reveal further that PLCγ2, localized in the membrane in association with Rac1 following the LPS stimulation, exhibits a marked increase in phosphorylation on Ser, while the modulatory effect of ghrelin, manifested by a drop in Rac1 translocation, is associated with a distinct decrease in PLCγ2 phosphorylation on Ser. Thus, the results suggest that H. pylori-elicited increase in gastric mucosal PLCγ2 phosphorylation on Ser serves as an essential platform for Rac1 colocalization and amplification in PLCγ2 activation.
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Affiliation(s)
- B L Slomiany
- Research Center C875, Rutgers School of Dental Medicine Rutgers, The State University of New Jersey, 110 Bergen Street, PO Box 1709, Newark, NJ, 07103-2400, USA,
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306
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Wang D, Zhao WL, Cai MJ, Wang JX, Zhao XF. G-protein-coupled receptor controls steroid hormone signaling in cell membrane. Sci Rep 2015; 5:8675. [PMID: 25728569 DOI: 10.1038/srep08675] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Accepted: 12/30/2014] [Indexed: 12/21/2022] Open
Abstract
G-protein-coupled receptors (GPCRs) are involved in animal steroid hormone signaling, but their mechanism is unclear. In this research, we report that a GPCR called ErGPCR-2 controls steroid hormone 20-hydroxyecdysone (20E) signaling in the cell membrane of the lepidopteran insect Helicoverpa armigera. ErGPCR-2 was highly expressed during molting and metamorphosis. 20E, via ErGPCR-2, regulated rapid intracellular calcium increase, protein phosphorylation, gene transcription, and insect metamorphosis. ErGPCR-2 was located in the cell surface and was internalized by 20E induction. GPCR kinase 2 participated in 20E-induced ErGPCR-2 phosphorylation and internalization. The internalized ErGPCR-2 was degraded by proteases to desensitize 20E signaling. ErGPCR-2 knockdown suppressed the entrance of 20E analog [(3)H] ponasterone A ([(3)H]Pon A) into the cells. ErGPCR-2 overexpression or blocking of ErGPCR-2 internalization increased the entrance of [(3)H]Pon A into the cells. However, ErGPCR-2 did not bind to [(3)H]Pon A. Results suggest that ErGPCR-2 transmits steroid hormone 20E signaling and controls 20E entrance into cells in the cell membrane.
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Affiliation(s)
- Di Wang
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Jinan 250100, China
| | - Wen-Li Zhao
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Jinan 250100, China
| | - Mei-Juan Cai
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Jinan 250100, China
| | - Jin-Xing Wang
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Jinan 250100, China
| | - Xiao-Fan Zhao
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Jinan 250100, China
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307
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Llavero F, Urzelai B, Osinalde N, Gálvez P, Lacerda HM, Parada LA, Zugaza JL. Guanine nucleotide exchange factor αPIX leads to activation of the Rac 1 GTPase/glycogen phosphorylase pathway in interleukin (IL)-2-stimulated T cells. J Biol Chem 2015; 290:9171-82. [PMID: 25694429 DOI: 10.1074/jbc.m114.608414] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Indexed: 01/27/2023] Open
Abstract
Recently, we have reported that the active form of Rac 1 GTPase binds to the glycogen phosphorylase muscle isoform (PYGM) and modulates its enzymatic activity leading to T cell proliferation. In the lymphoid system, Rac 1 and in general other small GTPases of the Rho family participate in the signaling cascades that are activated after engagement of the T cell antigen receptor. However, little is known about the IL-2-dependent Rac 1 activator molecules. For the first time, a signaling pathway leading to the activation of Rac 1/PYGM in response to IL-2-stimulated T cell proliferation is described. More specifically, αPIX, a known guanine nucleotide exchange factor for the small GTPases of the Rho family, preferentially Rac 1, mediates PYGM activation in Kit 225 T cells stimulated with IL-2. Using directed mutagenesis, phosphorylation of αPIX Rho-GEF serines 225 and 488 is required for activation of the Rac 1/PYGM pathway. IL-2-stimulated serine phosphorylation was corroborated in Kit 225 T cells cultures. A parallel pharmacological and genetic approach identified PKCθ as the serine/threonine kinase responsible for αPIX serine phosphorylation. The phosphorylated state of αPIX was required to activate first Rac 1 and subsequently PYGM. These results demonstrate that the IL-2 receptor activation, among other early events, leads to activation of PKCθ. To activate Rac 1 and consequently PYGM, PKCθ phosphorylates αPIX in T cells. The biological significance of this PKCθ/αPIX/Rac 1 GTPase/PYGM signaling pathway seems to be the control of different cellular responses such as migration and proliferation.
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Affiliation(s)
- Francisco Llavero
- From the Department of Genetics, Physical Anthropology and Animal Physiology, University of the Basque Country, 48940 Leioa, Spain, the Achucarro Basque Center for Neuroscience, Bizkaia Science and Technology Park, Building 205, 48170 Zamudio, Spain
| | - Bakarne Urzelai
- From the Department of Genetics, Physical Anthropology and Animal Physiology, University of the Basque Country, 48940 Leioa, Spain
| | - Nerea Osinalde
- the Department of Biochemistry and Molecular Biology, University of Southern Denmark, 5230 Odense, Denmark
| | - Patricia Gálvez
- the Pharmascience Division, Technological Park of Health Sciences, Avda. de la Ciencia, s/n 18100 Armilla, Granada, Spain
| | - Hadriano M Lacerda
- the Department of Biomedical Sciences and Human Oncology, Unit of Cancer Epidemiology, Università degli Studi di Torino, 10124 Torino, Italy
| | - Luis A Parada
- the Instituto de Patología Experimental, Universidad Nacional de Salta, 4400 Salta, Argentina, and
| | - José L Zugaza
- From the Department of Genetics, Physical Anthropology and Animal Physiology, University of the Basque Country, 48940 Leioa, Spain, the Achucarro Basque Center for Neuroscience, Bizkaia Science and Technology Park, Building 205, 48170 Zamudio, Spain, the IKERBASQUE, Basque Foundation for Science, Maria Diaz de Haro 3, 48013 Bilbao, Spain
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308
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Yoshida S, Gaeta I, Pacitto R, Krienke L, Alge O, Gregorka B, Swanson JA. Differential signaling during macropinocytosis in response to M-CSF and PMA in macrophages. Front Physiol 2015; 6:8. [PMID: 25688212 PMCID: PMC4310286 DOI: 10.3389/fphys.2015.00008] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2014] [Accepted: 01/08/2015] [Indexed: 01/30/2023] Open
Abstract
The cellular movements that construct a macropinosome have a corresponding sequence of chemical transitions in the cup-shaped region of plasma membrane that becomes the macropinosome. To determine the relative positions of type I phosphatidylinositol 3-kinase (PI3K) and phospholipase C (PLC) in this pathway, we analyzed macropinocytosis in macrophages stimulated by the growth factor macrophage-colony-stimulating factor (M-CSF) and by the diacylglycerol (DAG) analog phorbol 12-myristate 13-acetate (PMA). In cells stimulated with M-CSF, microscopic imaging of fluorescent probes for intracellular lipids indicated that the PI3K product phosphatidylinositol (3,4,5)-trisphosphate (PIP3) appeared in cups just prior to DAG. We then tested the hypothesis that PMA and DAG function after PI3K and prior to Ras and protein kinase C (PKC) during macropinosome formation in macrophages. Although the PI3K target Akt was activated by M-CSF, the Akt inhibitor MK-2206 did not inhibit macropinocytosis. The phospholipase C (PLC) inhibitor U73122 blocked macropinocytosis by M-CSF but not PMA. Macropinocytosis in response to M-CSF and PMA was inhibited by the Ras inhibitor farnesyl thiosalicylate (FTS), by the PKC inhibitor Calphostin C and by the broad specificity inhibitor rottlerin. These studies support a model in which M-CSF stimulates PI3K in macropinocytic cups, and the resulting increase in PIP3 activates PLC, which in turn generates DAG necessary for activation of PKC, Ras and the late stages of macropinosome closure.
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Affiliation(s)
- Sei Yoshida
- Department of Microbiology and Immunology, University of Michigan Medical School Ann Arbor, MI, USA
| | - Isabella Gaeta
- Department of Microbiology and Immunology, University of Michigan Medical School Ann Arbor, MI, USA
| | - Regina Pacitto
- Department of Microbiology and Immunology, University of Michigan Medical School Ann Arbor, MI, USA
| | - Lydia Krienke
- Department of Microbiology and Immunology, University of Michigan Medical School Ann Arbor, MI, USA
| | - Olivia Alge
- Department of Microbiology and Immunology, University of Michigan Medical School Ann Arbor, MI, USA
| | - Brian Gregorka
- Department of Microbiology and Immunology, University of Michigan Medical School Ann Arbor, MI, USA
| | - Joel A Swanson
- Department of Microbiology and Immunology, University of Michigan Medical School Ann Arbor, MI, USA
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309
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Nagy AI, Vázquez-Manrique RP, Lopez M, Christov CP, Sequedo MD, Herzog M, Herlihy AE, Bodak M, Gatsi R, Baylis HA. IP3 signalling regulates exogenous RNAi in Caenorhabditis elegans. EMBO Rep 2015; 16:341-50. [PMID: 25608529 DOI: 10.15252/embr.201439585] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
RNA interference (RNAi) is a widespread and widely exploited phenomenon. Here, we show that changing inositol 1,4,5-trisphosphate (IP3) signalling alters RNAi sensitivity in Caenorhabditis elegans. Reducing IP3 signalling enhances sensitivity to RNAi in a broad range of genes and tissues. Conversely up-regulating IP3 signalling decreases sensitivity. Tissue-specific rescue experiments suggest IP3 functions in the intestine. We also exploit IP3 signalling mutants to further enhance the sensitivity of RNAi hypersensitive strains. These results demonstrate that conserved cell signalling pathways can modify RNAi responses, implying that RNAi responses may be influenced by an animal's physiology or environment.
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Affiliation(s)
- Anikó I Nagy
- Department of Zoology, University of Cambridge, Cambridge, UK
| | - Rafael P Vázquez-Manrique
- Research Group in Molecular, Cellular and Genomic Biomedicine, Health Research Institute-La Fe, Valencia, Spain Centre for Biomedical Network Research on Rare Diseases (CIBERER), Valencia, Spain
| | - Marie Lopez
- Department of Zoology, University of Cambridge, Cambridge, UK
| | | | - María Dolores Sequedo
- Research Group in Molecular, Cellular and Genomic Biomedicine, Health Research Institute-La Fe, Valencia, Spain Centre for Biomedical Network Research on Rare Diseases (CIBERER), Valencia, Spain
| | - Mareike Herzog
- Department of Zoology, University of Cambridge, Cambridge, UK
| | - Anna E Herlihy
- Department of Zoology, University of Cambridge, Cambridge, UK
| | - Maxime Bodak
- Department of Zoology, University of Cambridge, Cambridge, UK
| | - Roxani Gatsi
- Department of Zoology, University of Cambridge, Cambridge, UK
| | - Howard A Baylis
- Department of Zoology, University of Cambridge, Cambridge, UK
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310
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Sicart A, Katan M, Egea G, Sarri E. PLCγ1 participates in protein transport and diacylglycerol production triggered by cargo arrival at the Golgi. Traffic 2015; 16:250-66. [PMID: 25491205 DOI: 10.1111/tra.12246] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Revised: 11/26/2014] [Accepted: 11/26/2014] [Indexed: 02/02/2023]
Abstract
Diacylglycerol (DAG) is required for membrane traffic and structural organization at the Golgi. DAG is a lipid metabolite of several enzymatic reactions present at this organelle, but the mechanisms by which they are regulated are still unknown. Here, we show that cargo arrival at the Golgi increases the recruitment of the DAG-sensing constructs C1-PKCθ-GFP and the PKD-wt-GFP. The recruitment of both constructs was reduced by PLCγ1 silencing. Post-Golgi trafficking of transmembrane and soluble proteins was impaired in PLCγ1-silenced cells. Under basal conditions, PLCγ1 contributed to the maintenance of the pool of DAG associated with the Golgi and to the structural organization of the organelle. Finally, we show that cytosolic phospholipase C (PLC) can hydrolyse phosphatidylinositol 4-phosphate in isolated Golgi membranes. Our results indicate that PLCγ1 is part of the molecular mechanism that couples cargo arrival at the Golgi with DAG production to co-ordinate the formation of transport carriers for post-Golgi traffic.
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Affiliation(s)
- Adrià Sicart
- Departament de Biologia Cel·lular, Immunologia i Neurociències, Facultat de Medicina, Universitat de Barcelona, C/ Casanova, 143, 08036, Barcelona, Spain; Current address: Vlaams Instituut voor Biotechnologie (VIB), Centre for the Biology of Disease and KU Leuven, Department of Human Genetics, Campus Gasthuisberg, 3000 Leuven, Belgium
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311
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Koss H, Bunney TD, Behjati S, Katan M. Dysfunction of phospholipase Cγ in immune disorders and cancer. Trends Biochem Sci 2014; 39:603-11. [PMID: 25456276 DOI: 10.1016/j.tibs.2014.09.004] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 09/19/2014] [Accepted: 09/24/2014] [Indexed: 12/15/2022]
Abstract
The surge in genetic and genomic investigations over the past 5 years has resulted in many discoveries of causative variants relevant to disease pathophysiology. Although phospholipase C (PLC) enzymes have long been recognized as important components in intracellular signal transmission, it is only recently that this approach highlighted their role in disease development through gain-of-function mutations. In this review we describe the new findings that link the PLCγ family to immune disorders and cancer, and illustrate further efforts to elucidate the molecular mechanisms that underpin their dysfunction.
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Affiliation(s)
- Hans Koss
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, UK; Division of Molecular Structure, Medical Research Council (MRC) National Institute for Medical Research, London, UK
| | - Tom D Bunney
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, UK.
| | - Sam Behjati
- Cancer Genome Project, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, UK
| | - Matilda Katan
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, UK.
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312
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Wilke BU, Lindner M, Greifenberg L, Albus A, Kronimus Y, Bünemann M, Leitner MG, Oliver D. Diacylglycerol mediates regulation of TASK potassium channels by Gq-coupled receptors. Nat Commun 2014; 5:5540. [PMID: 25420509 DOI: 10.1038/ncomms6540] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Accepted: 10/09/2014] [Indexed: 11/09/2022] Open
Abstract
The two-pore domain potassium (K2P) channels TASK-1 (KCNK3) and TASK-3 (KCNK9) are important determinants of background K(+) conductance and membrane potential. TASK-1/3 activity is regulated by hormones and transmitters that act through G protein-coupled receptors (GPCR) signalling via G proteins of the Gαq/11 subclass. How the receptors inhibit channel activity has remained unclear. Here, we show that TASK-1 and -3 channels are gated by diacylglycerol (DAG). Receptor-initiated inhibition of TASK required the activity of phospholipase C, but neither depletion of the PLC substrate PI(4,5)P2 nor release of the downstream messengers IP3 and Ca(2+). Attenuation of cellular DAG transients by DAG kinase or lipase suppressed receptor-dependent inhibition, showing that the increase in cellular DAG-but not in downstream lipid metabolites-mediates channel inhibition. The findings identify DAG as the signal regulating TASK channels downstream of GPCRs and define a novel role for DAG that directly links cellular DAG dynamics to excitability.
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Affiliation(s)
- Bettina U Wilke
- Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps University, Deutschhausstr. 1-2, 35037 Marburg, Germany
| | - Moritz Lindner
- Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps University, Deutschhausstr. 1-2, 35037 Marburg, Germany
| | - Lea Greifenberg
- Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps University, Deutschhausstr. 1-2, 35037 Marburg, Germany
| | - Alexandra Albus
- Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps University, Deutschhausstr. 1-2, 35037 Marburg, Germany
| | - Yannick Kronimus
- Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps University, Deutschhausstr. 1-2, 35037 Marburg, Germany
| | - Moritz Bünemann
- Department of Pharmacology and Clinical Pharmacy, Philipps University, 35032 Marburg, Germany
| | - Michael G Leitner
- Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps University, Deutschhausstr. 1-2, 35037 Marburg, Germany
| | - Dominik Oliver
- Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps University, Deutschhausstr. 1-2, 35037 Marburg, Germany
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313
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Role of amplification in phospholipase Cγ2 activation in modulation of gastric mucosal inflammatory responses to Helicobacter pylori: effect of ghrelin. Inflammopharmacology 2014; 23:37-45. [PMID: 25362585 DOI: 10.1007/s10787-014-0220-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Accepted: 10/18/2014] [Indexed: 12/21/2022]
Abstract
Phosphoinositide-specific phospholipase C (PLC) enzymes are crucial elements of signal transduction pathways that provide a common link of communication integrating specific receptor responses to a variety of hormones, growth factors, and bacterial endotoxins with the intended intracellular targets. Here, we examined the involvement of PLC in modulation of gastric mucosal inflammatory responses to Helicobacter pylori LPS by peptide hormone, ghrelin. We show that stimulation of gastric mucosal cells with the LPS leads to the activation and membrane translocation of the γ2 isoform of PLC, phosphorylated on Tyr as well as Ser, while the effect of ghrelin is reflected in the translocation and phosphorylation of membrane-associated PLCγ2 on Tyr mainly. Moreover, we demonstrate that PLCγ2 phosphorylation on Tyr remains under the control of the Src family protein tyrosine kinases (SFK-PTKs), and is intimately linked to PLCγ2 membrane localization, while the LPS-induced phosphorylation of membrane-recruited PLCγ2 on Ser displays dependence on protein kinase Cδ (PKCδ) and leads to the amplification in PLCγ2 activation. Thus, our findings link the extent of H. pylori-elicited gastric mucosal inflammatory involvement to the PKCδ-mediated amplification in PLCγ2 activation through phosphorylation on Ser.
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314
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Mori MX, Inoue R. New experimental trends for phosphoinositides research on ion transporter/channel regulation. J Pharmacol Sci 2014; 126:186-97. [PMID: 25367262 DOI: 10.1254/jphs.14r14cp] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
Phosphoinositides(4,5)-bisphosphates [PI(4,5)P2] critically controls membrane excitability, the disruption of which leads to pathophysiological states. PI(4,5)P2 plays a primary role in regulating the conduction and gating properties of ion channels/transporters, through electrostatic and hydrophobic interactions that allow direct associations. In recent years, the development of many molecular tools have brought deep insights into the mechanisms underlying PI(4,5)P2-mediated regulation. This review summarizes the methods currently available to manipulate the cell membrane PI(4,5)P2 level including pharmacological interventions as well as newly designed molecular tools. We concisely introduce materials and experimental designs suitable for the study of PI(4,5)P2-mediated regulation of ion-conducting molecules, in order to assist researchers who are interested in this area. It is our further hope that the knowledge introduced in this review will help to promote our understanding about the pathology of diseases such as cardiac arrhythmias, bipolar disorders, and Alzheimer's disease which are somehow associated with a disruption of PI(4,5)P2 metabolism.
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Affiliation(s)
- Masayuki X Mori
- Department of Synthetic Chemistry and Biological Chemistry, School of Engineering, Kyoto University, Japan
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315
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Charpentier TH, Waldo GL, Barrett MO, Huang W, Zhang Q, Harden TK, Sondek J. Membrane-induced allosteric control of phospholipase C-β isozymes. J Biol Chem 2014; 289:29545-57. [PMID: 25193662 PMCID: PMC4207972 DOI: 10.1074/jbc.m114.586784] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Revised: 08/13/2014] [Indexed: 11/06/2022] Open
Abstract
All peripheral membrane proteins must negotiate unique constraints intrinsic to the biological interface of lipid bilayers and the cytosol. Phospholipase C-β (PLC-β) isozymes hydrolyze the membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP2) to propagate diverse intracellular responses that underlie the physiological action of many hormones, neurotransmitters, and growth factors. PLC-β isozymes are autoinhibited, and several proteins, including Gαq, Gβγ, and Rac1, directly engage distinct regions of these phospholipases to release autoinhibition. To understand this process, we used a novel, soluble analog of PIP2 that increases in fluorescence upon cleavage to monitor phospholipase activity in real time in the absence of membranes or detergents. High concentrations of Gαq or Gβ1γ2 did not activate purified PLC-β3 under these conditions despite their robust capacity to activate PLC-β3 at membranes. In addition, mutants of PLC-β3 with crippled autoinhibition dramatically accelerated the hydrolysis of PIP2 in membranes without an equivalent acceleration in the hydrolysis of the soluble analog. Our results illustrate that membranes are integral for the activation of PLC-β isozymes by diverse modulators, and we propose a model describing membrane-mediated allosterism within PLC-β isozymes.
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Affiliation(s)
| | | | | | - Weigang Huang
- the Division of Chemical Biology and Medicinal Chemistry, University of North Carolina School of Pharmacy, Chapel Hill, North Carolina 27599
| | - Qisheng Zhang
- the Division of Chemical Biology and Medicinal Chemistry, University of North Carolina School of Pharmacy, Chapel Hill, North Carolina 27599
| | | | - John Sondek
- From the Departments of Pharmacology and Biochemistry and Biophysics and the Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599 and
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316
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Hauge M, Vestmar MA, Husted AS, Ekberg JP, Wright MJ, Di Salvo J, Weinglass AB, Engelstoft MS, Madsen AN, Lückmann M, Miller MW, Trujillo ME, Frimurer TM, Holst B, Howard AD, Schwartz TW. GPR40 (FFAR1) - Combined Gs and Gq signaling in vitro is associated with robust incretin secretagogue action ex vivo and in vivo. Mol Metab 2014; 4:3-14. [PMID: 25685685 PMCID: PMC4314522 DOI: 10.1016/j.molmet.2014.10.002] [Citation(s) in RCA: 168] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Revised: 10/17/2014] [Accepted: 10/20/2014] [Indexed: 11/25/2022] Open
Abstract
Objectives GPR40 (FFAR1), a clinically proven anti-diabetes target, is a Gq-coupled receptor for long chain fatty acids (LCFA) stimulating insulin secretion directly and mediating a major part of the dietary triglyceride-induced secretion of the incretins GLP-1 and GIP. In phase-II studies the GPR40 agonist TAK-875 decreased blood glucose but surprisingly without stimulating incretins. Methods and results Here we find that GPR40 can signal through not only Gq and IP3 but also Gs and cAMP when stimulated with certain agonists such as AM-1638 and AM-5262 in contrast to the endogenous LCFA ligands and agonists such as TAK-875 and AM-837, which only signal through Gq. In competition binding against [3H]AM-1638 and [3H]L358 the Gq + Gs and the Gq-only agonists either competed for or showed positive cooperativity by increasing the binding of the two different radio-ligands, in opposite ways. Nevertheless, both the Gq-only and the Gq + Gs agonists all docked surprisingly well into the binding site for TAK-875 in the X-ray structure of GPR40. In murine intestinal primary cell-cultures the endogenous LCFAs and the Gq-only agonists stimulated GLP-1 secretion with rather poor efficacy as compared with the high efficacy Gq + Gs GPR40 agonists and a prototype GPR119 agonist. Similarly, in fasting both male and female mice the Gq + Gs agonists showed significantly higher efficacy than the Gq-only agonists in respect of increasing plasma GLP-1 and plasma GIP in a GPR40-dependent manner. Conclusions It is concluded that stimulation of GPR40 by endogenous LCFAs or by Gq-only synthetic agonists result in a rather limited incretin response, whereas Gq + Gs GPR40 agonists stimulate incretin secretion robustly.
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Affiliation(s)
- Maria Hauge
- Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, 2200 Copenhagen N, Denmark ; Department of Neuroscience and Pharmacology, University of Copenhagen, DK-2200, Copenhagen, Denmark
| | - Marie A Vestmar
- Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, 2200 Copenhagen N, Denmark ; Department of Neuroscience and Pharmacology, University of Copenhagen, DK-2200, Copenhagen, Denmark
| | - Anna S Husted
- Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, 2200 Copenhagen N, Denmark
| | - Jeppe P Ekberg
- Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, 2200 Copenhagen N, Denmark
| | | | | | | | - Maja S Engelstoft
- Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, 2200 Copenhagen N, Denmark
| | - Andreas N Madsen
- Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, 2200 Copenhagen N, Denmark
| | - Michael Lückmann
- Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, 2200 Copenhagen N, Denmark
| | | | | | - Thomas M Frimurer
- Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, 2200 Copenhagen N, Denmark
| | - Birgitte Holst
- Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, 2200 Copenhagen N, Denmark ; Department of Neuroscience and Pharmacology, University of Copenhagen, DK-2200, Copenhagen, Denmark
| | | | - Thue W Schwartz
- Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, 2200 Copenhagen N, Denmark ; Department of Neuroscience and Pharmacology, University of Copenhagen, DK-2200, Copenhagen, Denmark
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317
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Kunze K, Spieker T, Gamerdinger U, Nau K, Berger J, Dreyer T, Sindermann JR, Hoffmeier A, Gattenlöhner S, Bräuninger A. A recurrent activating PLCG1 mutation in cardiac angiosarcomas increases apoptosis resistance and invasiveness of endothelial cells. Cancer Res 2014; 74:6173-83. [PMID: 25252913 DOI: 10.1158/0008-5472.can-14-1162] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Primary cardiac angiosarcomas are rare tumors with unfavorable prognosis. Pathogenic driver mutations are largely unknown. We therefore analyzed a collection of cases for genomic aberrations using SNP arrays and targeted next-generation sequencing (tNGS) of oncogenes and tumor-suppressor genes. Recurrent gains of chromosome 1q and a small region of chromosome 4 encompassing KDR and KIT were identified by SNP array analysis. Repeatedly mutated genes identified by tNGS were KDR with different nonsynonymous mutations, MLL2 with different nonsense mutations, and PLCG1 with a recurrent nonsynonymous mutation (R707Q) in the highly conserved autoinhibitory SH2 domain in three of 10 cases. PLCγ1 is usually activated by Y783 phosphorylation and activates protein kinase C and Ca(2+)-dependent second messengers, with effects on cellular proliferation, migration, and invasiveness. Ectopic expression of the PLCγ1-R707Q mutant in endothelial cells revealed reduced PLCγ1-Y783 phosphorylation with concomitant increased c-RAF/MEK/ERK1/2 phosphorylation, increased IP3 amounts, and increased Ca(2+)-dependent calcineurin activation compared with ectopic expressed PLCγ1-wild-type. Furthermore, cofilin, whose activation is associated with actin skeleton reorganization, showed decreased phosphorylation, and thus activation after expression of PLCγ1-R707Q compared with PLCγ1-wild-type. At the cellular level, expression of PLCγ1-R707Q in endothelial cells had no influence on proliferation rate, but increased apoptosis resistance and migration and invasiveness in in vitro assays. Together, these findings indicate that the PLCγ1-R707Q mutation causes constitutive activation of PLCγ1 and may represent an alternative way of activation of KDR/PLCγ1 signaling besides KDR activation in angiosarcomas, with implications for VEGF/KDR targeted therapies.
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Affiliation(s)
- Kristin Kunze
- Department of Pathology, Justus-Liebig-University Giessen, Giessen, Germany
| | - Tilmann Spieker
- Institute for Pathology, St. Francis Hospital, Münster, Germany
| | - Ulrike Gamerdinger
- Department of Pathology, Justus-Liebig-University Giessen, Giessen, Germany
| | - Kerstin Nau
- Department of Pathology, Justus-Liebig-University Giessen, Giessen, Germany
| | - Johannes Berger
- Department of Pathology, Justus-Liebig-University Giessen, Giessen, Germany
| | - Thomas Dreyer
- Department of Pathology, Justus-Liebig-University Giessen, Giessen, Germany
| | - Jürgen R Sindermann
- Department of Cardiothoracic Surgery, Division of Cardiac Surgery, University Hospital Münster, Münster, Germany
| | - Andreas Hoffmeier
- Department of Cardiothoracic Surgery, Division of Cardiac Surgery, University Hospital Münster, Münster, Germany
| | | | - Andreas Bräuninger
- Department of Pathology, Justus-Liebig-University Giessen, Giessen, Germany.
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318
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Wang J, Sohn H, Sun G, Milner JD, Pierce SK. The autoinhibitory C-terminal SH2 domain of phospholipase C-γ2 stabilizes B cell receptor signalosome assembly. Sci Signal 2014; 7:ra89. [PMID: 25227611 DOI: 10.1126/scisignal.2005392] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The binding of antigen to the B cell receptor (BCR) stimulates the assembly of a signaling complex (signalosome) composed initially of the kinases Lyn, spleen tyrosine kinase (Syk), and Bruton's tyrosine kinase (Btk), as well as the adaptor protein B cell linker (BLNK). Together, these proteins recruit and activate phospholipase C-γ2 (PLC-γ2), a critical effector that stimulates increases in intracellular Ca(2+) and activates various signaling pathways downstream of the BCR. Individuals with one copy of a mutant PLCG2 gene, which encodes a variant PLC-γ2 that lacks the autoinhibitory C-terminal Src homology 2 (cSH2) domain, exhibit PLC-γ2-associated antibody deficiency and immune dysregulation (PLAID). Paradoxically, although COS-7 cells expressing the variant PLC-γ2 show enhanced basal and stimulated PLC-γ2 activity, B cells from PLAID patients show defective intracellular Ca(2+) responses upon cross-linking of the BCR. We found that the cSH2 domain of PLC-γ2 played a critical role in stabilizing the early signaling complex that is stimulated by BCR cross-linking. In the presence of the variant PLC-γ2, Syk, Btk, and BLNK were only weakly phosphorylated and failed to stably associate with the BCR. Thus, BCRs could not form stable clusters, resulting in dysregulation of downstream signaling and trafficking of the BCR. Thus, the cSH2 domain functions not only to inhibit the active site of PLC-γ2 but also to directly or indirectly stabilize the early BCR signaling complex.
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Affiliation(s)
- Jing Wang
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA
| | - Haewon Sohn
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA
| | - Guangping Sun
- Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Joshua D Milner
- Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Susan K Pierce
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852, USA.
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319
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Clark J, Kay RR, Kielkowska A, Niewczas I, Fets L, Oxley D, Stephens LR, Hawkins PT. Dictyostelium uses ether-linked inositol phospholipids for intracellular signalling. EMBO J 2014; 33:2188-200. [PMID: 25180230 DOI: 10.15252/embj.201488677] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Inositol phospholipids are critical regulators of membrane biology throughout eukaryotes. The general principle by which they perform these roles is conserved across species and involves binding of differentially phosphorylated inositol head groups to specific protein domains. This interaction serves to both recruit and regulate the activity of several different classes of protein which act on membrane surfaces. In mammalian cells, these phosphorylated inositol head groups are predominantly borne by a C38:4 diacylglycerol backbone. We show here that the inositol phospholipids of Dictyostelium are different, being highly enriched in an unusual C34:1e lipid backbone, 1-hexadecyl-2-(11Z-octadecenoyl)-sn-glycero-3-phospho-(1'-myo-inositol), in which the sn-1 position contains an ether-linked C16:0 chain; they are thus plasmanylinositols. These plasmanylinositols respond acutely to stimulation of cells with chemoattractants, and their levels are regulated by PIPKs, PI3Ks and PTEN. In mammals and now in Dictyostelium, the hydrocarbon chains of inositol phospholipids are a highly selected subset of those available to other phospholipids, suggesting that different molecular selectors are at play in these organisms but serve a common, evolutionarily conserved purpose.
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Affiliation(s)
- Jonathan Clark
- Babraham Biosciences Technology Babraham Research Campus, Cambridge, UK
| | - Robert R Kay
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, UK
| | - Anna Kielkowska
- Babraham Biosciences Technology Babraham Research Campus, Cambridge, UK
| | - Izabella Niewczas
- Babraham Biosciences Technology Babraham Research Campus, Cambridge, UK
| | - Louise Fets
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, UK
| | - David Oxley
- Signalling Programme Babraham Research Campus, Cambridge, UK
| | - Len R Stephens
- Signalling Programme Babraham Research Campus, Cambridge, UK
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320
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Zhu H, Han M. Exploring developmental and physiological functions of fatty acid and lipid variants through worm and fly genetics. Annu Rev Genet 2014; 48:119-48. [PMID: 25195508 DOI: 10.1146/annurev-genet-041814-095928] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Lipids are more than biomolecules for energy storage and membrane structure. With ample structural variation, lipids critically participate in nearly all aspects of cellular function. Lipid homeostasis and metabolism are closely related to major human diseases and health problems. However, lipid functional studies have been significantly underdeveloped, partly because of the difficulty in applying genetics and common molecular approaches to tackle the complexity associated with lipid biosynthesis, metabolism, and function. In the past decade, a number of laboratories began to analyze the roles of lipid metabolism in development and other physiological functions using animal models and combining genetics, genomics, and biochemical approaches. These pioneering efforts have not only provided valuable insights regarding lipid functions in vivo but have also established feasible methodology for future studies. Here, we review a subset of these studies using Caenorhabditis elegans and Drosophila melanogaster.
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Affiliation(s)
- Huanhu Zhu
- Howard Hughes Medical Institute and Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309;
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321
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Zhang K, Jin C, Wu L, Hou M, Dou S, Pan Y. Expression analysis of a stress-related phosphoinositide-specific phospholipase C gene in wheat (Triticum aestivum L.). PLoS One 2014; 9:e105061. [PMID: 25121594 PMCID: PMC4133336 DOI: 10.1371/journal.pone.0105061] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Accepted: 07/17/2014] [Indexed: 11/18/2022] Open
Abstract
Plant phosphoinositide-specific phospholipases C (PI-PLCs) function in several essential plant processes associated with either development or environmental stress. In this report, we examined the expression patterns of TaPLC1 under drought and high salinity stress at the transcriptional and post-transcriptional levels. TaPLC1 mRNA was expressed in all wheat organs examined. U73122 and edelfosine, the PLC inhibitor, impaired seedling growth and enhanced seedling sensitivity to drought and high salinity stress. Though TaPLC1 expression in wheat was lowest at the seedling stage, it was strongly induced under conditions of stress. When 6-day-old wheat seedlings were treated with 200 mM NaCl or 20% (w/v) PEG 6000 for 6 or 12 h, respectively, the TaPLC1 transcript level increased by 16-fold compared to the control. Western blotting showed that the TaPLC protein concentration was also maintained at a high level from 24 to 48 h during stress treatment. Together, our results indicate the possible biological functions of TaPLC1 in regulating seedling growth and the response to drought and salinity stress.
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Affiliation(s)
- Ke Zhang
- College of Life Science, Agricultural University of Hebei, Baoding, China
| | - Congcong Jin
- College of Life Science, Agricultural University of Hebei, Baoding, China
| | - Lizhu Wu
- College of Life Science, Agricultural University of Hebei, Baoding, China
| | - Mingyu Hou
- College of Life Science, Agricultural University of Hebei, Baoding, China
| | - Shijuan Dou
- College of Life Science, Agricultural University of Hebei, Baoding, China
| | - Yanyun Pan
- College of Life Science, Agricultural University of Hebei, Baoding, China
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322
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Hwang H, Min H, Kim D, Yu SW, Jung SJ, Choi SY, Lee SJ. Imiquimod induces a Toll-like receptor 7-independent increase in intracellular calcium via IP3 receptor activation. Biochem Biophys Res Commun 2014; 450:875-9. [DOI: 10.1016/j.bbrc.2014.06.084] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Accepted: 06/17/2014] [Indexed: 11/28/2022]
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323
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Litosch I. Regulation of phospholipase C-β(1) GTPase-activating protein (GAP) function and relationship to G(q) efficacy. IUBMB Life 2014; 65:936-40. [PMID: 24170560 DOI: 10.1002/iub.1218] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Revised: 09/30/2013] [Accepted: 09/30/2013] [Indexed: 11/08/2022]
Abstract
How cells regulate Gq efficacy (initiation and termination of Gq signaling) to effect response remains a central question in pharmacology and drug discovery. Phospholipase C-β1 (PLC-β1) is an effector and a GTPase activating protein (GAP) specific to Gαq. The physiological function of PLC-β1 GAP remains unclear and controversial. GAPs are generally thought to function in deactivation of Gq signaling. However, PLC-β1 GAP has also been shown to increase signaling efficiency through kinetic coupling with the ligand-activated GPCR. GPCRs function as guanine nucleotide exchange factors (GEF) on the G protein activation cycle. This article sets forth a new hypothesis that could unify these conflicting paradigms as it pertains to physiological signaling and native levels of protein. It is proposed that the physiological function of PLC-β1 GAP is context-dependent and regulated by phosphatidic acid (PA). PA stimulates PLC-β1 GAP activity. In the absence of ligand, PLC-β1 GAP does indeed deactivate Gq signaling, limiting leaky activation to set the threshold for stimulation to sharpen signal kinetics. However in the presence of activating ligand, the increase in levels of PA would stimulate PLC-β1 GAP to kinetically couple with GPCR GEF to increase signaling efficiency. We found that PA-increased Gq efficiency is dependent on signaling via the unique PLC-β1 PA binding domain.
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324
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PIP2 regulates psychostimulant behaviors through its interaction with a membrane protein. Nat Chem Biol 2014; 10:582-589. [PMID: 24880859 PMCID: PMC4062427 DOI: 10.1038/nchembio.1545] [Citation(s) in RCA: 91] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2013] [Accepted: 04/24/2014] [Indexed: 12/13/2022]
Abstract
Phosphatidylinositol (4,5)-bisphosphate (PIP2) regulates the function of ion channels and transporters. Here, we demonstrate that PIP2 directly binds the human dopamine (DA) transporter (hDAT), a key regulator of DA homeostasis and a target of the psychostimulant amphetamine (AMPH). This binding occurs through electrostatic interactions with positively charged hDAT N-terminal residues and is shown to facilitate AMPH-induced, DAT-mediated DA efflux and the psychomotor properties of AMPH. Substitution of these residues with uncharged amino acids reduces hDAT-PIP2 interactions and AMPH-induced DA efflux, without altering the hDAT physiological function of DA uptake. We evaluated, for the first time, the significance of this interaction in vivo using locomotion as a behavioral assay in Drosophila melanogaster. Expression of mutated hDAT with reduced PIP2 interaction in Drosophila DA neurons impairs AMPH-induced locomotion without altering basal locomotion. We present the first demonstration of how PIP2 interactions with a membrane protein can regulate the behaviors of complex organisms.
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325
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Liu W, Cai MJ, Zheng CC, Wang JX, Zhao XF. Phospholipase Cγ1 connects the cell membrane pathway to the nuclear receptor pathway in insect steroid hormone signaling. J Biol Chem 2014; 289:13026-41. [PMID: 24692553 DOI: 10.1074/jbc.m113.547018] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
In addition to the classical nuclear receptor pathway, there is a nongenomic pathway in the cell membrane that regulates gene expression in animal steroid hormone signaling; however, this mechanism is unclear. Here, we report that the insect steroid hormone 20-hydroxyecdysone (20E) regulates calcium influx via phospholipase Cγ1 (PLCG1) to modulate the protein kinase C phosphorylation of the transcription factor ultraspiracle (USP1) in the lepidopteran insect Helicoverpa armigera. The PLCG1 mRNA levels are increased during the molting and metamorphic stages. The depletion of PLCG1 by RNA interference can block 20E-enhanced pupation, cause larvae death and pupation defects, and repress 20E-induced gene expression. 20E may induce the tyrosine phosphorylation of PLCG1 at the cytosolic tyrosine kinase (Src) homology 2 domains and then determine the migration of PLCG1 toward the plasma membrane. The G-protein-coupled receptor (GPCR) inhibitor suramin, Src family kinase inhibitor PP2, and the depletions of ecdysone-responsible GPCR (ErGPCR) and Gαq restrain the 20E-induced tyrosine phosphorylation of PLCG1. PLCG1 participates in the 20E-induced Ca(2+) influx. The inhibition of GPCR, PLC, inositol 1,4,5-trisphosphate receptor, and calcium channels represses the 20E-induced Ca(2+) influx. Through calcium signaling, PLCG1 mediates the transcriptional activation driven by the ecdysone-response element. Through PLCG1 and calcium signaling, 20E regulates PKC phosphorylation of USP1 at Ser-21 to determine its ecdysone-response element binding activity. These results suggest that 20E activates PLCG1 via the ErGPCR and Src family kinases to regulate Ca(2+) influx and PKC phosphorylation of USP1 to subsequently modulate gene transcription for metamorphosis.
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Affiliation(s)
- Wen Liu
- From the Key Laboratory of Plant Cell Engineering and Germplasm Innovation of Ministry of Education/Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Sciences, Shandong University, Jinan, Shandong 250100, China
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326
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Kan W, Adjobo-Hermans M, Burroughs M, Faibis G, Malik S, Tall GG, Smrcka AV. M3 muscarinic receptor interaction with phospholipase C β3 determines its signaling efficiency. J Biol Chem 2014; 289:11206-11218. [PMID: 24596086 DOI: 10.1074/jbc.m113.538546] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Phospholipase Cβ (PLCβ) enzymes are activated by G protein-coupled receptors through receptor-catalyzed guanine nucleotide exchange on Gαβγ heterotrimers containing Gq family G proteins. Here we report evidence for a direct interaction between M3 muscarinic receptor (M3R) and PLCβ3. Both expressed and endogenous M3R interacted with PLCβ in coimmunoprecipitation experiments. Stimulation of M3R with carbachol significantly increased this association. Expression of M3R in CHO cells promoted plasma membrane localization of YFP-PLCβ3. Deletion of the PLCβ3 C terminus or deletion of the PLCβ3 PDZ ligand inhibited coimmunoprecipitation with M3R and M3R-dependent PLCβ3 plasma membrane localization. Purified PLCβ3 bound directly to glutathione S-transferase (GST)-fused M3R intracellular loops 2 and 3 (M3Ri2 and M3Ri3) as well as M3R C terminus (M3R/H8-CT). PLCβ3 binding to M3Ri3 was inhibited when the PDZ ligand was removed. In assays using reconstituted purified components in vitro, M3Ri2, M3Ri3, and M3R/H8-CT potentiated Gαq-dependent but not Gβγ-dependent PLCβ3 activation. Disruption of key residues in M3Ri3N and of the PDZ ligand in PLCβ3 inhibited M3Ri3-mediated potentiation. We propose that the M3 muscarinic receptor maximizes the efficiency of PLCβ3 signaling beyond its canonical role as a guanine nucleotide exchange factor for Gα.
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Affiliation(s)
- Wei Kan
- Departments of Pharmacology and Physiology and University of Rochester School of Medicine and Dentistry, Rochester, New York 14642
| | - Merel Adjobo-Hermans
- Department of Biochemistry, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Geert Grooteplein 28, 6525 GA Nijmegen, The Netherlands
| | - Michael Burroughs
- Departments of Pharmacology and Physiology and University of Rochester School of Medicine and Dentistry, Rochester, New York 14642
| | - Guy Faibis
- Departments of Pharmacology and Physiology and University of Rochester School of Medicine and Dentistry, Rochester, New York 14642
| | - Sundeep Malik
- Departments of Pharmacology and Physiology and University of Rochester School of Medicine and Dentistry, Rochester, New York 14642
| | - Gregory G Tall
- Departments of Pharmacology and Physiology and University of Rochester School of Medicine and Dentistry, Rochester, New York 14642
| | - Alan V Smrcka
- Departments of Pharmacology and Physiology and University of Rochester School of Medicine and Dentistry, Rochester, New York 14642; Biochemistry and Biophysics and University of Rochester School of Medicine and Dentistry, Rochester, New York 14642; Aab Institute of Cardiovascular Research, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642 and.
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327
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Li L, Shi X, Guo X, Li H, Xu C. Ionic protein–lipid interaction at the plasma membrane: what can the charge do? Trends Biochem Sci 2014; 39:130-40. [DOI: 10.1016/j.tibs.2014.01.002] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Revised: 01/13/2014] [Accepted: 01/14/2014] [Indexed: 11/30/2022]
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328
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Baldanzi G. Inhibition of diacylglycerol kinases as a physiological way to promote diacylglycerol signaling. Adv Biol Regul 2014; 55:39-49. [PMID: 24582387 DOI: 10.1016/j.jbior.2014.02.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Revised: 01/02/2014] [Accepted: 02/02/2014] [Indexed: 01/12/2023]
Abstract
Diacylglycerol is a key regulator of cell physiology, controlling the membrane recruitment and activation of signaling molecules. Accordingly, diacylglycerol generation and metabolism are strictly controlled, allowing for localized regulation of its concentration. While the increased production of diacylglycerol upon receptor triggering is well recognized, the modulation of diacylglycerol metabolism by diacylglycerol kinases (DGKs) is less characterized. Some agonists induce DGK activation and recruitment to the plasma membrane, promoting diacylglycerol metabolism to phosphatidic acid. Conversely, several reports indicate that signaling pathways that selectively inhibits DGK isoforms can enhance cellular diacylglycerol levels and signal transduction. For example, the impairment of DGKθ activity by RhoA binding to the catalytic domain represents a conserved mechanism controlling diacylglycerol signaling from Caenorhabditis elegans motoneurons to mammalian hepatocytes. Similarly, DGKα activity is inhibited in lymphocytes by TCR signaling, thus contributing to a rise in diacylglycerol concentration for downstream signaling. Finally, DGKμ activity is inhibited by ischemia-reperfusion-generated reactive oxygen species in airway endothelial cells, promoting diacylglycerol-mediated ion channel opening and edema. In those systems, DGKs provide a gatekeeper function by blunting diacylglycerol levels or possibly establishing permissive domains for diacylglycerol signaling. In this review, I discuss the possible general relevance of DGK inhibition to enhanced diacylglycerol signaling.
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Affiliation(s)
- Gianluca Baldanzi
- University "A. Avogadro" del Piemonte Orientale, Department of Translational Medicine, via Solaroli 17, 28100 Novara, Italy.
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329
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Scott SA, Mathews TP, Ivanova PT, Lindsley CW, Brown HA. Chemical modulation of glycerolipid signaling and metabolic pathways. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1841:1060-84. [PMID: 24440821 DOI: 10.1016/j.bbalip.2014.01.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Revised: 01/06/2014] [Accepted: 01/07/2014] [Indexed: 01/04/2023]
Abstract
Thirty years ago, glycerolipids captured the attention of biochemical researchers as novel cellular signaling entities. We now recognize that these biomolecules occupy signaling nodes critical to a number of physiological and pathological processes. Thus, glycerolipid-metabolizing enzymes present attractive targets for new therapies. A number of fields-ranging from neuroscience and cancer to diabetes and obesity-have elucidated the signaling properties of glycerolipids. The biochemical literature teems with newly emerging small molecule inhibitors capable of manipulating glycerolipid metabolism and signaling. This ever-expanding pool of chemical modulators appears daunting to those interested in exploiting glycerolipid-signaling pathways in their model system of choice. This review distills the current body of literature surrounding glycerolipid metabolism into a more approachable format, facilitating the application of small molecule inhibitors to novel systems. This article is part of a Special Issue entitled Tools to study lipid functions.
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Affiliation(s)
- Sarah A Scott
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Thomas P Mathews
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Pavlina T Ivanova
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Craig W Lindsley
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA; Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, TN 37235, USA
| | - H Alex Brown
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Department of Biochemistry, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, TN 37235, USA.
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330
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Kielkowska A, Niewczas I, Anderson KE, Durrant TN, Clark J, Stephens LR, Hawkins PT. A new approach to measuring phosphoinositides in cells by mass spectrometry. Adv Biol Regul 2014; 54:131-141. [PMID: 24120934 DOI: 10.1016/j.jbior.2013.09.001] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2013] [Accepted: 09/03/2013] [Indexed: 06/02/2023]
Abstract
The phosphoinositide family of phospholipids, defined here as PtdIns, PtdIns3P, PtdIns4P, PtdIns5P, PtdIns(3,4)P2, PtdIns(3,5)P2, PtdIns(4,5)P2 and PtdIns(3,4,5)P3, play pivotal roles in organising the location and activity of many different proteins acting on biological membranes, including those involved in vesicle and protein trafficking through the endolysosomal system and receptor signal transduction at the plasma membrane. Accurate measurement of the cellular levels of these lipids, particularly the more highly phosphorylated species, is hampered by their high polarity and low cellular concentrations. Recently, much progress has been made in using mass spectrometry to measure many different lipid classes in parallel, an approach generally referred to as 'lipidomics'. Unfortunately, the acidic nature of highly phosphorylated phosphoinositides makes them difficult to measure using these methods, because they yield low levels of useful ions; this is particularly the case with PtdIns(3,4,5)P3. We have solved some of these problems by methylating the phosphate groups of these lipids with TMS-diazomethane and describe a simple, integrated approach to measuring PtdIns, PtdInsP, PtdInsP2 and PtdInsP3 classes of lipids, in parallel with other phospholipid species, in cell and tissue extracts. This methodology is sensitive, accurate and robust, and also yields fatty-acyl compositions, suggesting it can be used to further our understanding of both the normal and pathophysiological roles of these important lipids.
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Affiliation(s)
- Anna Kielkowska
- Babraham Bioscience Technologies Ltd, Babraham Research Campus, Cambridge, UK
| | - Izabella Niewczas
- Babraham Bioscience Technologies Ltd, Babraham Research Campus, Cambridge, UK
| | | | - Tom N Durrant
- Babraham Institute, Babraham Research Campus, Cambridge, UK
| | - Jonathan Clark
- Babraham Bioscience Technologies Ltd, Babraham Research Campus, Cambridge, UK
| | - Len R Stephens
- Babraham Institute, Babraham Research Campus, Cambridge, UK
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331
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Török Z, Crul T, Maresca B, Schütz GJ, Viana F, Dindia L, Piotto S, Brameshuber M, Balogh G, Péter M, Porta A, Trapani A, Gombos I, Glatz A, Gungor B, Peksel B, Vigh L, Csoboz B, Horváth I, Vijayan MM, Hooper PL, Harwood JL, Vigh L. Plasma membranes as heat stress sensors: from lipid-controlled molecular switches to therapeutic applications. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:1594-618. [PMID: 24374314 DOI: 10.1016/j.bbamem.2013.12.015] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 12/09/2013] [Accepted: 12/18/2013] [Indexed: 12/31/2022]
Abstract
The classic heat shock (stress) response (HSR) was originally attributed to protein denaturation. However, heat shock protein (Hsp) induction occurs in many circumstances where no protein denaturation is observed. Recently considerable evidence has been accumulated to the favor of the "Membrane Sensor Hypothesis" which predicts that the level of Hsps can be changed as a result of alterations to the plasma membrane. This is especially pertinent to mild heat shock, such as occurs in fever. In this condition the sensitivity of many transient receptor potential (TRP) channels is particularly notable. Small temperature stresses can modulate TRP gating significantly and this is influenced by lipids. In addition, stress hormones often modify plasma membrane structure and function and thus initiate a cascade of events, which may affect HSR. The major transactivator heat shock factor-1 integrates the signals originating from the plasma membrane and orchestrates the expression of individual heat shock genes. We describe how these observations can be tested at the molecular level, for example, with the use of membrane perturbers and through computational calculations. An important fact which now starts to be addressed is that membranes are not homogeneous nor do all cells react identically. Lipidomics and cell profiling are beginning to address the above two points. Finally, we observe that a deregulated HSR is found in a large number of important diseases where more detailed knowledge of the molecular mechanisms involved may offer timely opportunities for clinical interventions and new, innovative drug treatments. This article is part of a Special Issue entitled: Membrane Structure and Function: Relevance in the Cell's Physiology, Pathology and Therapy.
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Affiliation(s)
- Zsolt Török
- Institute of Biochemistry, Biological Research Centre of the Hung. Acad. Sci., Szeged H-6726, Hungary.
| | - Tim Crul
- Institute of Biochemistry, Biological Research Centre of the Hung. Acad. Sci., Szeged H-6726, Hungary
| | - Bruno Maresca
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II, 132, 84084 Fisciano, Salerno, Italy
| | - Gerhard J Schütz
- Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10, 1040 Vienna, Austria
| | - Felix Viana
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, 03550 San Juan de Alicante, Spain
| | - Laura Dindia
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada
| | - Stefano Piotto
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II, 132, 84084 Fisciano, Salerno, Italy
| | - Mario Brameshuber
- Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10, 1040 Vienna, Austria
| | - Gábor Balogh
- Institute of Biochemistry, Biological Research Centre of the Hung. Acad. Sci., Szeged H-6726, Hungary
| | - Mária Péter
- Institute of Biochemistry, Biological Research Centre of the Hung. Acad. Sci., Szeged H-6726, Hungary
| | - Amalia Porta
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II, 132, 84084 Fisciano, Salerno, Italy
| | - Alfonso Trapani
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II, 132, 84084 Fisciano, Salerno, Italy
| | - Imre Gombos
- Institute of Biochemistry, Biological Research Centre of the Hung. Acad. Sci., Szeged H-6726, Hungary
| | - Attila Glatz
- Institute of Biochemistry, Biological Research Centre of the Hung. Acad. Sci., Szeged H-6726, Hungary
| | - Burcin Gungor
- Institute of Biochemistry, Biological Research Centre of the Hung. Acad. Sci., Szeged H-6726, Hungary
| | - Begüm Peksel
- Institute of Biochemistry, Biological Research Centre of the Hung. Acad. Sci., Szeged H-6726, Hungary
| | - László Vigh
- Institute of Biochemistry, Biological Research Centre of the Hung. Acad. Sci., Szeged H-6726, Hungary
| | - Bálint Csoboz
- Institute of Biochemistry, Biological Research Centre of the Hung. Acad. Sci., Szeged H-6726, Hungary
| | - Ibolya Horváth
- Institute of Biochemistry, Biological Research Centre of the Hung. Acad. Sci., Szeged H-6726, Hungary
| | - Mathilakath M Vijayan
- Department of Biology, University of Waterloo, Waterloo, Ontario, Canada; Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Phillip L Hooper
- Division of Endocrinology, Metabolism and Diabetes, Department of Medicine, University of Colorado Medical School, Anschutz Medical Campus, Aurora, CO 80045, USA
| | - John L Harwood
- School of Biosciences, Cardiff University, Cardiff CF10 3AX, Wales, UK
| | - László Vigh
- Institute of Biochemistry, Biological Research Centre of the Hung. Acad. Sci., Szeged H-6726, Hungary.
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332
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Lyon AM, Taylor VG, Tesmer JJG. Strike a pose: Gαq complexes at the membrane. Trends Pharmacol Sci 2013; 35:23-30. [PMID: 24287282 DOI: 10.1016/j.tips.2013.10.008] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 10/16/2013] [Accepted: 10/21/2013] [Indexed: 12/20/2022]
Abstract
The heterotrimeric G protein Gαq is a central player in signal transduction, relaying signals from activated G-protein-coupled receptors (GPCRs) to effectors and other proteins to elicit changes in intracellular Ca(2+), the actin cytoskeleton, and gene transcription. Gαq functions at the intracellular surface of the plasma membrane, as do its best-characterized targets, phospholipase C-β, p63RhoGEF, and GPCR kinase 2 (GRK2). Recent insights into the structure and function of these signaling complexes reveal several recurring themes, including complex multivalent interactions between Gαq, its protein target, and the membrane, that are likely essential for allosteric control and maximum efficiency in signal transduction. Thus, the plasma membrane is not only a source of substrates but also a key player in the scaffolding of Gαq-dependent signaling pathways.
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Affiliation(s)
- Angeline M Lyon
- Life Sciences Institute and the Departments of Pharmacology and Biological Chemistry, University of Michigan, Ann Arbor, MI, USA
| | - Veronica G Taylor
- Life Sciences Institute and the Departments of Pharmacology and Biological Chemistry, University of Michigan, Ann Arbor, MI, USA
| | - John J G Tesmer
- Life Sciences Institute and the Departments of Pharmacology and Biological Chemistry, University of Michigan, Ann Arbor, MI, USA.
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333
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Roskoski R. The ErbB/HER family of protein-tyrosine kinases and cancer. Pharmacol Res 2013; 79:34-74. [PMID: 24269963 DOI: 10.1016/j.phrs.2013.11.002] [Citation(s) in RCA: 893] [Impact Index Per Article: 81.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Accepted: 11/08/2013] [Indexed: 10/26/2022]
Abstract
The human epidermal growth factor receptor (EGFR) family consists of four members that belong to the ErbB lineage of proteins (ErbB1-4). These receptors consist of a glycosylated extracellular domain, a single hydrophobic transmembrane segment, and an intracellular portion with a juxtamembrane segment, a protein kinase domain, and a carboxyterminal tail. Seven ligands bind to EGFR including epidermal growth factor and transforming growth factor α, none bind to ErbB2, two bind to ErbB3, and seven ligands bind to ErbB4. The ErbB proteins function as homo and heterodimers. The heterodimer consisting of ErbB2, which lacks a ligand, and ErbB3, which is kinase impaired, is surprisingly the most robust signaling complex of the ErbB family. Growth factor binding to EGFR induces a large conformational change in the extracellular domain, which leads to the exposure of a dimerization arm in domain II of the extracellular segment. Two ligand-EGFR complexes unite to form a back-to-back dimer in which the ligands are on opposite sides of the aggregate. Following ligand binding, EGFR intracellular kinase domains form an asymmetric homodimer that resembles the heterodimer formed by cyclin and cyclin-dependent kinase. The carboxyterminal lobe of the activator kinase of the dimer interacts with the amino-terminal lobe of the receiver kinase thereby leading to its allosteric stimulation. Downstream ErbB signaling modules include the phosphatidylinositol 3-kinase/Akt (PKB) pathway, the Ras/Raf/MEK/ERK1/2 pathway, and the phospholipase C (PLCγ) pathway. Several malignancies are associated with the mutation or increased expression of members of the ErbB family including lung, breast, stomach, colorectal, head and neck, and pancreatic carcinomas and glioblastoma (a brain tumor). Gefitinib, erlotinib, and afatinib are orally effective protein-kinase targeted quinazoline derivatives that are used in the treatment of ERBB1-mutant lung cancer. Lapatinib is an orally effective quinazoline derivative used in the treatment of ErbB2-overexpressing breast cancer. Trastuzumab, pertuzumab, and ado-trastuzumab emtansine, which are given intravenously, are monoclonal antibodies that target the extracellular domain and are used for the treatment of ErbB2-positive breast cancer; ado-trastuzumab emtansine is an antibody-drug conjugate that delivers a cytotoxic drug to cells overexpressing ErbB2. Cetuximab and panitumumab are monoclonal antibodies that target ErbB1 and are used in the treatment of colorectal cancer. Cancers treated with these targeted drugs eventually become resistant to them. The role of combinations of targeted drugs or targeted drugs with cytotoxic therapies is being explored in an effort to prevent or delay drug resistance in the treatment of these malignancies.
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Affiliation(s)
- Robert Roskoski
- Blue Ridge Institute for Medical Research, 3754 Brevard Road, Suite 116, Box 19, Horse Shoe, NC 28742, USA.
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334
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The hormone-dependent function of Hsp90 in the crosstalk between 20-hydroxyecdysone and juvenile hormone signaling pathways in insects is determined by differential phosphorylation and protein interactions. Biochim Biophys Acta Gen Subj 2013; 1830:5184-92. [DOI: 10.1016/j.bbagen.2013.06.037] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 06/05/2013] [Accepted: 06/29/2013] [Indexed: 11/19/2022]
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335
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Liu C, Cui Y, Luan J, Zhou X, Han J. The molecular and cellular basis of Apert syndrome. Intractable Rare Dis Res 2013; 2:115-22. [PMID: 25343114 PMCID: PMC4204555 DOI: 10.5582/irdr.2013.v2.4.115] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Revised: 11/24/2013] [Accepted: 11/27/2013] [Indexed: 01/19/2023] Open
Abstract
Apert syndrome (AS) is a rare genetic and congenital disease characterized by craniosynostosis and syndactly of hands and feet. AS patients generally require lifelong management, however there are still no effective treatment methods except surgery. In recent years, research has made great progress in the pathogenesis of AS. FGFR2 mediates extracellular signals into cells and the mutations in the FGFR2 gene cause AS occurrence. Activated FGFs/FGFR2 signaling disrupt the balance of cell proliferation, differentiation and apoptosis via its downstream signal pathways. However, how the pathways transform the balance is not well understood and contradictions have occurred in different studies. In this review, we'll focus on these problems to get a better understanding of AS pathogenesis.
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Affiliation(s)
- Chao Liu
- Key Laboratory for Rare Disease Research of Shandong Province, Key Laboratory for Biotech Drugs of the Ministry of Health, Shandong Medical Biotechnological Center, Shandong Academy of Medical Sciences, Ji'nan, Shandong, China
- School of Medicine and Life Sciences, University of Jinan-Shandong Academy of Medical Science, Ji'nan, Shandong, China
| | - Yazhou Cui
- Key Laboratory for Rare Disease Research of Shandong Province, Key Laboratory for Biotech Drugs of the Ministry of Health, Shandong Medical Biotechnological Center, Shandong Academy of Medical Sciences, Ji'nan, Shandong, China
| | - Jing Luan
- Key Laboratory for Rare Disease Research of Shandong Province, Key Laboratory for Biotech Drugs of the Ministry of Health, Shandong Medical Biotechnological Center, Shandong Academy of Medical Sciences, Ji'nan, Shandong, China
| | - Xiaoyan Zhou
- Key Laboratory for Rare Disease Research of Shandong Province, Key Laboratory for Biotech Drugs of the Ministry of Health, Shandong Medical Biotechnological Center, Shandong Academy of Medical Sciences, Ji'nan, Shandong, China
| | - Jinxiang Han
- Key Laboratory for Rare Disease Research of Shandong Province, Key Laboratory for Biotech Drugs of the Ministry of Health, Shandong Medical Biotechnological Center, Shandong Academy of Medical Sciences, Ji'nan, Shandong, China
- Address correspondence to: Dr. Jinxiang Han, Key Laboratory for Rare Disease Research of Shandong Province, Key Laboratory for Biotech Drugs of the Ministry of Health, Shandong Medical Biotechnological Center, Shandong Academy of Medical Sciences, Ji'nan, 250062, Shandong, China. E-mail:
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336
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Nomikos M, Kashir J, Swann K, Lai FA. Sperm PLCζ: from structure to Ca2+ oscillations, egg activation and therapeutic potential. FEBS Lett 2013; 587:3609-16. [PMID: 24157362 DOI: 10.1016/j.febslet.2013.10.008] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Revised: 10/12/2013] [Accepted: 10/14/2013] [Indexed: 10/26/2022]
Abstract
Significant evidence now supports the assertion that cytosolic calcium oscillations during fertilization in mammalian eggs are mediated by a testis-specific phospholipase C (PLC), termed PLC-zeta (PLCζ) that is released into the egg following gamete fusion. Herein, we describe the current paradigm of PLCζ in this fundamental biological process, summarizing recent important advances in our knowledge of the biochemical and physiological properties of this enzyme. We describe the data suggesting that PLCζ has distinct features amongst PLCs enabling the hydrolysis of its substrate, phosphatidylinositol 4,5-bisphosphate (PIP2) at low Ca(2+) levels. PLCζ appears to be unique in its ability to target PIP2 that is present on intracellular vesicles. We also discuss evidence that PLCζ may be a significant factor in human fertility with potential therapeutic capacity.
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Affiliation(s)
- Michail Nomikos
- Institute of Molecular and Experimental Medicine, WHRI, Cardiff University School of Medicine, Heath Park, CF144XN Cardiff, UK.
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337
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Abstract
Phospholipases are enzymes that use phospholipids as substrate and are classified in three major classes A, C and D based on the reaction they catalyse. Phosphatidylinositol-specific Phospholipase C enzymes utilize phosphatidylinositol 4,5-bisphosphate as substrate and cleave the bond between the glycerol and the phosphate to produce important second messenger such as inositol trisphosphate and diacylglycerol. The Phospholipase C members are the most well-known phospholipases for their role in lipid signalling and cell proliferation and comprise 13 isoforms classified in 6 distinct sub-families. In particular, signalling activated by Phospholipase C γ, mostly activated by receptor and non-receptor tyrosine kinases, is well characterized in different cell systems. Increasing evidence suggest that Phospholipase C γ plays a key role in cell migration and invasion. Because of its role in cell growth and invasion, aberrant Phospholipase C γ signalling can contribute to carcinogenesis. A major challenge facing investigators who seek to target Phospholipase C γ directly is the fact that it is considered an "undruggable" protein. Indeed, isoform specificity and toxicity represents a big hurdle in the development of Phospholipase C γ small molecule inhibitors. Therefore, a future development in the field could be the identification of interacting partners as therapeutic targets that could be more druggable than Phospholipase C γ.
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Affiliation(s)
- Rossano Lattanzio
- Aging Research Centre, G. d'Annunzio University Foundation, 66013 Chieti, Italy.
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338
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Kawakami T, Xiao W. Phospholipase C-β in immune cells. Adv Biol Regul 2013; 53:249-57. [PMID: 23981313 DOI: 10.1016/j.jbior.2013.08.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2013] [Revised: 07/29/2013] [Accepted: 08/02/2013] [Indexed: 12/22/2022]
Abstract
Great progress has recently been made in structural and functional research of phospholipase C (PLC)-β. We now understand how PLC-β isoforms (β1-β4) are activated by GTP-bound Gαq downstream of G protein-coupled receptors. Numerous studies indicate that PLC-βs participate in the differentiation and activation of immune cells that control both the innate and adaptive immune systems. The PLC-β3 isoform also interplays with tyrosine kinase-based signaling pathways, to inhibit Stat5 activation by recruiting the protein-tyrosine phosphatase SHP-1, with which PLC-β3 and Stat5 form a multi-molecular signaling platform, named SPS complex. The SPS complex has important regulatory roles in tumorigenesis and immune cell activation.
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Affiliation(s)
- Toshiaki Kawakami
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, La Jolla, CA 92037, USA; Laboratory of Allergic Disease, RIKEN Center for Integrative Medical Sciences (IMS-RCAI), Yokohama 230-0045, Japan.
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339
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Abstract
Phospholipase C (PLC) enzymes convert phosphatidylinositol-4,5-bisphosphate into the second messengers diacylglycerol and inositol-1,4,5-triphosphate. The production of these molecules promotes the release of intracellular calcium and activation of protein kinase C, which results in profound cellular changes. The PLCβ subfamily is of particular interest given its prominent role in cardiovascular and neuronal signaling and its regulation by G protein-coupled receptors, as PLCβ is the canonical downstream target of the heterotrimeric G protein Gαq. However, this is not the only mechanism regulating PLCβ activity. Extensive structural and biochemical evidence has revealed regulatory roles for autoinhibitory elements within PLCβ, Gβγ, small molecular weight G proteins, and the lipid membrane itself. Such complex regulation highlights the central role that this enzyme plays in cell signaling. A better understanding of the molecular mechanisms underlying the control of its activity will greatly facilitate the search for selective small molecule modulators of PLCβ.
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Affiliation(s)
- Angeline M Lyon
- Life Sciences Institute and the Departments of Pharmacology and Biological Chemistry, University of Michigan, Ann Arbor, Michigan
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Pokotylo I, Kolesnikov Y, Kravets V, Zachowski A, Ruelland E. Plant phosphoinositide-dependent phospholipases C: variations around a canonical theme. Biochimie 2013; 96:144-57. [PMID: 23856562 DOI: 10.1016/j.biochi.2013.07.004] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Accepted: 07/04/2013] [Indexed: 01/01/2023]
Abstract
Phosphoinositide-specific phospholipase C (PI-PLC) cleaves, in a Ca(2+)-dependent manner, phosphatidylinositol-4,5-bisphosphate (PI-4,5-P2) into diacylglycerol (DAG) and inositol triphosphate (IP3). PI-PLCs are multidomain proteins that are structurally related to the PI-PLCζs, the simplest animal PI-PLCs. Like these animal counterparts, they are only composed of EF-hand, X/Y and C2 domains. However, plant PI-PLCs do not have a conventional EF-hand domain since they are often truncated, while some PI-PLCs have no EF-hand domain at all. Despite this simple structure, plant PI-PLCs are involved in many essential plant processes, either associated with development or in response to environmental stresses. The action of PI-PLCs relies on the mediators they produce. In plants, IP3 does not seem to be the sole active soluble molecule. Inositol pentakisphosphate (IP5) and inositol hexakisphosphate (IP6) also transmit signals, thus highlighting the importance of coupling PI-PLC action with inositol-phosphate kinases and phosphatases. PI-PLCs also produce a lipid molecule, but plant PI-PLC pathways show a peculiarity in that the active lipid does not appear to be DAG but its phosphorylated form, phosphatidic acid (PA). Besides, PI-PLCs can also act by altering their substrate levels. Taken together, plant PI-PLCs show functional differences when compared to their animal counterparts. However, they act on similar general signalling pathways including calcium homeostasis and cell phosphoproteome. Several important questions remain unanswered. The cross-talk between the soluble and lipid mediators generated by plant PI-PLCs is not understood and how the coupling between PI-PLCs and inositol-kinases or DAG-kinases is carried out remains to be established.
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Affiliation(s)
- Igor Pokotylo
- Institute of Bioorganic Chemistry and Petrochemistry, NAS of Ukraine, Kiev, Ukraine.
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Schmitz-Peiffer C. The tail wagging the dog--regulation of lipid metabolism by protein kinase C. FEBS J 2013; 280:5371-83. [PMID: 23587021 DOI: 10.1111/febs.12285] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2013] [Revised: 03/19/2013] [Accepted: 04/11/2013] [Indexed: 12/12/2022]
Abstract
Upon their discovery almost 40 years ago, isoforms of the lipid-activated protein kinase C (PKC) family were initially regarded only as downstream effectors of the second messengers calcium and diacylglycerol, undergoing activation upon phospholipid hydrolysis in response to acute stimuli. Subsequently, several isoforms were found to be associated with the inhibitory effects of lipid over-supply on glucose homeostasis, especially the negative cross-talk with insulin signal transduction, observed upon accumulation of diacylglycerol in insulin target tissues. The PKC family has therefore attracted much attention in diabetes and obesity research, because intracellular lipid accumulation is strongly correlated with defective insulin action and the development of type 2 diabetes. Causal roles for various isoforms in the generation of insulin resistance have more recently been confirmed using PKC-deficient mice. However, during characterization of these animals, it became increasingly evident that the enzymes play key roles in the modulation of lipid metabolism itself, and may control the supply of lipids between tissues such as adipose and liver. Molecular studies have also demonstrated roles for PKC isoforms in several aspects of lipid metabolism, such as adipocyte differentiation and hepatic lipogenesis. While the precise mechanisms involved, especially the identities of protein substrates, are still unclear, the emerging picture suggests that the currently held view of the contribution of PKC isoforms to metabolism is an over-simplification. Although PKCs may inhibit insulin signal transduction, these enzymes are not merely downstream effectors of lipid accumulation, but in fact control the fate of fatty acids, thus the tail wags the dog.
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Affiliation(s)
- Carsten Schmitz-Peiffer
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Sydney, NSW, Australia; St Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia
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Full-length Gα(q)-phospholipase C-β3 structure reveals interfaces of the C-terminal coiled-coil domain. Nat Struct Mol Biol 2013; 20:355-62. [PMID: 23377541 PMCID: PMC3594540 DOI: 10.1038/nsmb.2497] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2012] [Accepted: 12/18/2012] [Indexed: 01/18/2023]
Abstract
Phospholipase C-β (PLCβ) is directly activated by Gαq, but the molecular basis for how its distal C-terminal domain (CTD) contributes to maximal activity is poorly understood. Herein we present both the crystal structure and cryo-EM 3D reconstructions of human full-length PLCβ3 in complex with murine Gαq. The distal CTD forms an extended, monomeric helical bundle consisting of three anti-parallel segments with structural similarity to membrane-binding bin–amphiphysin–Rvs (BAR) domains. Sequence conservation of the distal CTD identifies putative membrane and protein interaction sites, the latter of which bind the N-terminal helix of Gαq in both the crystal structure and cryo-EM reconstructions. Functional analysis suggests the distal CTD plays roles in membrane targeting and in optimizing the orientation of the catalytic core at the membrane for maximal rates of lipid hydrolysis.
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