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Liu C, Yuan W, Yang H, Ni J, Tang L, Zhao H, Neumann D, Ding X, Zhu L. Associating bovine herpesvirus 1 envelope glycoprotein gD with activated phospho-PLC-γ1(S1248). Microbiol Spectr 2023; 11:e0196323. [PMID: 37655900 PMCID: PMC10580943 DOI: 10.1128/spectrum.01963-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Accepted: 07/23/2023] [Indexed: 09/02/2023] Open
Abstract
Phospholipase C gamma 1 (PLC-γ1) may locate at distinct subcellular locations, such as cytosol, plasma membrane, and nucleus for varied biological functions. Bovine herpesvirus 1 (BoHV-1) productive infection activates PLC-γ1 signaling, as demonstrated by increased protein levels of phosphorylated-PLC-γ1 at Ser1248 [p-PLC-γ1(S1248)], which benefits virus productive infection. Here, for the first time, we reported that Golgi apparatus also contains activated p-PLC-γ1(S1248). And BoHV-1 productive infection at later stages (24 hpi) increased the accumulation of p-PLC-γ1(S1248) in the Golgi apparatus, where p-PLC-γ1(S1248) forms highlighted puncta observed via a confocal microscope. Coimmunoprecipitation studies demonstrated that the Golgi p-PLC-γ1(S1248) is specifically associated with the viral protein gD but not gC. In addition, we found that p-PLC-γ1(S1248) is consistently associated with both the plasma membrane-associated virions and the released virions. When the virus-infected cells were treated with PLC-γ1-specific inhibitor, U73122, for a short duration of 4 hours prior to the endpoint of virus infection, we found that the viral protein gD was trapped in the Golgi apparatus, suggesting that the PLC-γ1 signaling may facilitate trafficking of progeny virions out of this organelle. These findings provide a novel insight into the interplay between PLC-γ1 signaling and BoHV-1 replication. IMPORTANCE Bovine herpesvirus 1 (BoHV-1) productive infection increases protein levels of phosphorylated-phospholipase C gamma 1 at Ser1248 [p-PLC-γ1(S1248)]. However, whether it causes any variations to p-PLC-γ1(S1248) localization is not well understood. Here, for the first time, we found that partial p-PLC-γ1(S1248) is residing in the Golgi apparatus, where the accumulation is enhanced by virus infection. p-PLC-γ1(S1248) is consistently associated with virions, partially via binding to gD, in both the Golgi apparatus and cytoplasm membranes. Surprisingly, it also associates with the released virions. Of note, this is the first evidenced BoHV-1 virion-bound host protein. It seems that p-PLC-γ1(S1248) works as an escort during trafficking of progeny virions out of Golgi apparatus to the plasma membranes as well as releasing outside of the cell membranes. Furthermore, we showed that the activated p-PLC-γ1(S1248) is potentially implicated in the transport of virions out of Golgi apparatus, which may represent a novel mechanism to regulate virus productive infection.
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Affiliation(s)
- Chang Liu
- College of Life Sciences, Hebei University, Baoding, China
| | - Weifeng Yuan
- Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Hao Yang
- College of Life Sciences, Hebei University, Baoding, China
| | - Junqing Ni
- Animal Husbandry and Improved Breeds Work Station of Hebei Province, Shijiazhuang, China
| | - Linke Tang
- College of Life Sciences, Hebei University, Baoding, China
| | - Heci Zhao
- College of Life Sciences, Hebei University, Baoding, China
| | - Donna Neumann
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Xiuyan Ding
- College of Life Sciences, Hebei University, Baoding, China
| | - Liqian Zhu
- College of Life Sciences, Hebei University, Baoding, China
- Key Laboratory of Microbial Diversity Research and Application of Hebei Province, College of Life Science, Hebei University, Baoding, China
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Li K, Ran B, Wang Y, Liu L, Li W. PLCγ2 impacts microglia-related effectors revealing variants and pathways important in Alzheimer’s disease. Front Cell Dev Biol 2022; 10:999061. [PMID: 36147734 PMCID: PMC9485805 DOI: 10.3389/fcell.2022.999061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Accepted: 08/15/2022] [Indexed: 11/30/2022] Open
Abstract
Alzheimer’s disease (AD) is an irreversible neurodegenerative disease mainly characterized by memory loss and cognitive decline. The etiology of AD is complex and remains incompletely understood. In recent years, genome-wide association studies (GWAS) have increasingly highlighted the central role of microglia in AD pathology. As a trans-membrane receptor specifically present on the microglia in the central nervous system, phosphatidylinositol-specific phospholipase C gamma 2 (PLCγ2) plays an important role in neuroinflammation. GWAS data and corresponding pathological research have explored the effects of PLCG2 variants on amyloid burden and tau pathologies that underline AD. The link between PLCγ2 and other AD-related effectors in human and mouse microglia has also been established, placing PLCγ2 downstream of the triggering receptor expressed on myeloid cells 2 (TREM2), toll-like receptor 4 (TLR4), Bruton’s tyrosine kinase (BTK), and colony-stimulating factor 1 receptor (CSF1R). Because the research on PLCγ2’s role in AD is still in its early stages, few articles have been published, therefore in this paper, we integrate the relevant research published to date, review the structural features, expression patterns, and related pathways of PLCγ2, and summarize the recent studies on important PLCG2 variants related to AD. Furthermore, the possibility and challenge of using PLCγ2 to develop therapeutic drugs for AD are also discussed.
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Brüggemann Y, Karajannis LS, Stanoev A, Stallaert W, Bastiaens PIH. Growth factor-dependent ErbB vesicular dynamics couple receptor signaling to spatially and functionally distinct Erk pools. Sci Signal 2021; 14:14/683/eabd9943. [PMID: 34006609 DOI: 10.1126/scisignal.abd9943] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Growth factor-dependent vesicular dynamics allow cells to regulate the spatial distribution of growth factor receptors and thereby their coupling to downstream signaling effectors that guide cellular responses. We found that the ErbB ligands epidermal growth factor (EGF) and heregulin (HRG) generated distinct spatiotemporal patterns of cognate receptor activities to activate distinct subcellular pools of the extracellular signal-regulated kinase (Erk). Sustained plasma membrane activity of the receptor tyrosine kinases ErbB2/ErbB3 signaled to Erk complexed with the scaffold protein KSR to promote promigratory EphA2 phosphorylation and cellular motility upon HRG stimulation. In contrast, receptor-saturating EGF stimuli caused proliferation-inducing transient activation of cytoplasmic Erk due to the rapid internalization of EGF receptors (EGFR or ErbB1) toward endosomes. Paradoxically, promigratory signaling mediated by Erk complexed to KSR was sustained at low EGF concentrations by vesicular recycling that maintained steady-state amounts of active, phosphorylated EGFR at the plasma membrane. Thus, the effect of ligand identity and concentration on determining ErbB vesicular dynamics constitutes a mechanism by which cells can transduce growth factor composition through spatially distinct Erk pools to enable functionally diverse cellular responses.
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Affiliation(s)
- Yannick Brüggemann
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Str.11, 44227 Dortmund, Germany.,Faculty of Chemistry and Chemical Biology, TU Dortmund, Otto-Hahn-Str. 6, 44227 Dortmund, Germany
| | - Lisa S Karajannis
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Str.11, 44227 Dortmund, Germany
| | - Angel Stanoev
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Str.11, 44227 Dortmund, Germany
| | - Wayne Stallaert
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Str.11, 44227 Dortmund, Germany
| | - Philippe I H Bastiaens
- Department of Systemic Cell Biology, Max Planck Institute of Molecular Physiology, Otto-Hahn-Str.11, 44227 Dortmund, Germany. .,Faculty of Chemistry and Chemical Biology, TU Dortmund, Otto-Hahn-Str. 6, 44227 Dortmund, Germany
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Alfahad D, Alharethi S, Alharbi B, Mawlood K, Dash P. PtdIns(4,5)P2 and PtdIns(3,4,5)P3 dynamics during focal adhesions assembly and disassembly in a cancer cell line. ACTA ACUST UNITED AC 2021; 44:381-392. [PMID: 33402865 PMCID: PMC7759192 DOI: 10.3906/biy-2004-108] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 07/27/2020] [Indexed: 01/22/2023]
Abstract
Focal adhesions (FAs) are large assemblies of proteins that mediate intracellular signals between the cytoskeleton and the extracellular matrix (ECM). The turnover of FA proteins plays a critical regulatory role in cancer cell migration. Plasma membrane lipids locally generated or broken down by different inositide kinases and phosphatase enzymes to activate and recruit proteins to specific regions in the plasma membrane. Presently, little attention has been given to the use of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) and Phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P3) fluorescent biosensors in order to determine the spatiotemporal organisation of PtdIns(4,5)P2 and PtdIns(3,4,5)P3 within and around or during assembly and disassembly of FAs. In this study, specific biosensors were used to detect PtdIns(4,5)P2, PtdIns(3,4,5)P3, and FAs proteins conjugated to RFP/GFP in order to monitor changes of PtdIns(4,5)P2 and PtdIns(3,4,5)P3 levels within FAs. We demonstrated that the localisation of PtdIns(4,5)P2 and PtdIns(3,4,5)P3 were moderately correlated with that of FA proteins. Furthermore, we demonstrate that local levels of PtdIns(4,5)P2 increased within FA assembly and declined within FA disassembly. However, PtdIns(3,4,5)P3 levels remained constant within FAs assembly and disassembly. In conclusion, this study shows that PtdIns(4,5)P2 and PtdIns(3,4,5)P3 localised in FAs may be regulated differently during FA assembly and disassembly.
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Affiliation(s)
- Dhurgham Alfahad
- Department of Pathological Analysis, College of Science, Thi-Qar University, Thi-Qar Iraq
| | - Salem Alharethi
- Department of Biological Science, College of Arts and Science, Najran University, Najran Saudi Arabia
| | - Bandar Alharbi
- Department of Clinical Laboratory Sciences, College of Applied Medical Science, University of Hail, Hail Saudi Arabia
| | - Khatab Mawlood
- Department of Clinical Laboratory Sciences, College of Applied Medical Science, University of Hail, Hail Saudi Arabia
| | - Philip Dash
- Department of Pathological Analysis, College of Science, Thi-Qar University, Thi-Qar Iraq.,Department of Biomedical Sciences, School of Biological Sciences, University of Reading, Reading United Kingdom
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Magno L, Lessard CB, Martins M, Lang V, Cruz P, Asi Y, Katan M, Bilsland J, Lashley T, Chakrabarty P, Golde TE, Whiting PJ. Alzheimer's disease phospholipase C-gamma-2 (PLCG2) protective variant is a functional hypermorph. Alzheimers Res Ther 2019; 11:16. [PMID: 30711010 PMCID: PMC6359863 DOI: 10.1186/s13195-019-0469-0] [Citation(s) in RCA: 75] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Accepted: 01/15/2019] [Indexed: 02/06/2023]
Abstract
BACKGROUND Recent Genome Wide Association Studies (GWAS) have identified novel rare coding variants in immune genes associated with late onset Alzheimer's disease (LOAD). Amongst these, a polymorphism in phospholipase C-gamma 2 (PLCG2) P522R has been reported to be protective against LOAD. PLC enzymes are key elements in signal transmission networks and are potentially druggable targets. PLCG2 is highly expressed in the hematopoietic system. Hypermorphic mutations in PLCG2 in humans have been reported to cause autoinflammation and immune disorders, suggesting a key role for this enzyme in the regulation of immune cell function. METHODS We assessed PLCG2 distribution in human and mouse brain tissue via immunohistochemistry and in situ hybridization. We transfected heterologous cell systems (COS7 and HEK293T cells) to determine the effect of the P522R AD-associated variant on enzymatic function using various orthogonal assays, including a radioactive assay, IP-One ELISA, and calcium assays. RESULTS PLCG2 expression is restricted primarily to microglia and granule cells of the dentate gyrus. Plcg2 mRNA is maintained in plaque-associated microglia in the cerebral tissue of an AD mouse model. Functional analysis of the p.P522R variant demonstrated a small hypermorphic effect of the mutation on enzyme function. CONCLUSIONS The PLCG2 P522R variant is protective against AD. We show that PLCG2 is expressed in brain microglia, and the p.P522R polymorphism weakly increases enzyme function. These data suggest that activation of PLCγ2 and not inhibition could be therapeutically beneficial in AD. PLCγ2 is therefore a potential target for modulating microglia function in AD, and a small molecule drug that weakly activates PLCγ2 may be one potential therapeutic approach.
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Affiliation(s)
- Lorenza Magno
- UCL Alzheimer’s Research UK, Drug Discovery Institute, London, UK
| | - Christian B. Lessard
- Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, and McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, FL USA
| | - Marta Martins
- Research Department of Structural and Molecular Biology, University College London, London, UK
- Present address: Instituto de Medicina Molecular - João Lobo Antunes, Faculdade de Medicina de Lisboa, Lisbon, Portugal
| | - Verena Lang
- UCL Alzheimer’s Research UK, Drug Discovery Institute, London, UK
| | - Pedro Cruz
- Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, and McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, FL USA
| | - Yasmine Asi
- Department of Neurodegenerative Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK
- Queen Square Brain Bank for Neurological Disorders, Department of Movement Disorders, UCL Queen Square Institute of Neurology, University College London, London, UK
| | - Matilda Katan
- Research Department of Structural and Molecular Biology, University College London, London, UK
| | - Jamie Bilsland
- UCL Alzheimer’s Research UK, Drug Discovery Institute, London, UK
| | - Tammaryn Lashley
- Department of Neurodegenerative Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK
- Queen Square Brain Bank for Neurological Disorders, Department of Movement Disorders, UCL Queen Square Institute of Neurology, University College London, London, UK
| | - Paramita Chakrabarty
- Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, and McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, FL USA
| | - Todd E. Golde
- Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, and McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, FL USA
| | - Paul J. Whiting
- UCL Alzheimer’s Research UK, Drug Discovery Institute, London, UK
- Dementia Research Institute, UCL, London, UK
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De Keersmaecker H, Camacho R, Rantasa DM, Fron E, Uji-I H, Mizuno H, Rocha S. Mapping Transient Protein Interactions at the Nanoscale in Living Mammalian Cells. ACS NANO 2018; 12:9842-9854. [PMID: 30192513 DOI: 10.1021/acsnano.8b01227] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Protein-protein interactions (PPIs) form the basis of cellular processes, regulating cell behavior and fate. PPIs can be extremely transient in nature, which hinders their detection. In addition, traditional biochemical methods provided limited information on the spatial distribution and temporal dynamics of PPIs that is crucial for their regulation in the crowded cellular environment. Given the pivotal role of membrane micro- and nanodomains in the regulation of PPIs at the plasma membrane, the development of methods to visualize PPIs with a high spatial resolution is imperative. Here, we present a super-resolution fluorescence microscopy technique that can detect and map short-lived transient protein-protein interactions on a nanometer scale in the cellular environment. This imaging method is based on single-molecule fluorescence microscopy and exploits the effect of the difference in the mobility between cytosolic and membrane-bound proteins in the recorded fluorescence signals. After the development of the proof of concept using a model system based on membrane-bound modular protein domains and fluorescently labeled peptides, we applied this imaging approach to investigate the interactions of cytosolic proteins involved in the epidermal growth factor signaling pathway (namely, Grb2, c-Raf, and PLCγ1). The detected clusters of Grb2 and c-Raf were correlated with the distribution of the receptor at the plasma membrane. Additionally, the interactions of wild type PLCγ1 were compared with those detected with truncated mutants, which provided important information regarding the role played by specific domains in the interaction with the membrane. The results presented here demonstrate the potential of this technique to unravel the role of membrane heterogeneity in the spatiotemporal regulation of cell signaling.
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Affiliation(s)
| | | | | | | | - Hiroshi Uji-I
- Research Institute for Electronic Science , Hokkaido University , N20W10 Kita Ward, Sapporo 001-0020 , Japan
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7
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Stallaert W, Brüggemann Y, Sabet O, Baak L, Gattiglio M, Bastiaens PIH. Contact inhibitory Eph signaling suppresses EGF-promoted cell migration by decoupling EGFR activity from vesicular recycling. Sci Signal 2018; 11:11/541/eaat0114. [DOI: 10.1126/scisignal.aat0114] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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8
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Lu SM, Fairn GD. 7-Ketocholesterol impairs phagocytosis and efferocytosis via dysregulation of phosphatidylinositol 4,5-bisphosphate. Traffic 2018; 19:591-604. [PMID: 29693767 DOI: 10.1111/tra.12576] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 04/16/2018] [Accepted: 04/18/2018] [Indexed: 12/27/2022]
Abstract
The plasma membrane is inhomogeneously organized containing both highly ordered and disordered nanodomains. 7-Ketocholesterol (7KC), an oxysterol formed from the nonenzymatic oxidation of cholesterol, is a potent disruptor of membrane order. Importantly, 7KC is a component of oxidized low-density lipoprotein and accumulates in macrophage and foam cells found in arterial plaques. Using a murine macrophage cell line, J774, we report that both IgG-mediated and phosphatidylserine-mediated phagocytic pathways are inhibited by the accumulation of 7KC. Examination of the well-studied Fcγ receptor pathway revealed that the cell surface receptor abundance and ligand binding are unaltered while downstream signaling and activation of spleen tyrosine kinase is not affected. However, while the recruitment of phospholipase Cγ1 was unaffected its apparent enzymatic activity was compromised resulting in sustained phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2 ] levels and polymerized actin at the base of the phagocytic cup. Additionally, we found that 7KC prevented the activation of PLCβ downstream of the P2Y6 G-protein coupled receptor and that 7KC impaired PLCγ activity in response to a direct elevation of cytosolic calcium induced by ionomycin. Finally, we demonstrate that 7KC partly attenuates the activity of rapamycin recruitable constitutively active PLCβ3. Together, our results demonstrate that the accumulation of 7KC impairs macrophage function by altering PtdIns(4,5)P2 catabolism and, thus, impairing actin depolymerization required for the completion of phagocytosis.
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Affiliation(s)
- Stella M Lu
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada.,Keenan Research Centre for Biomedical Sciences, St. Michael's Hospital, Toronto, ON, Canada
| | - Gregory D Fairn
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada.,Keenan Research Centre for Biomedical Sciences, St. Michael's Hospital, Toronto, ON, Canada.,Department of Surgery and Institute of Medical Science, University of Toronto, Toronto, ON, Canada
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9
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Walliser C, Hermkes E, Schade A, Wiese S, Deinzer J, Zapatka M, Désiré L, Mertens D, Stilgenbauer S, Gierschik P. The Phospholipase Cγ2 Mutants R665W and L845F Identified in Ibrutinib-resistant Chronic Lymphocytic Leukemia Patients Are Hypersensitive to the Rho GTPase Rac2 Protein. J Biol Chem 2016; 291:22136-22148. [PMID: 27542411 PMCID: PMC5063995 DOI: 10.1074/jbc.m116.746842] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Revised: 08/18/2016] [Indexed: 12/29/2022] Open
Abstract
Mutations in the gene encoding phospholipase C-γ2 (PLCγ2) have been shown to be associated with resistance to targeted therapy of chronic lymphocytic leukemia (CLL) with the Bruton's tyrosine kinase inhibitor ibrutinib. The fact that two of these mutations, R665W and L845F, imparted upon PLCγ2 an ∼2-3-fold ibrutinib-insensitive increase in the concentration of cytosolic Ca2+ following ligation of the B cell antigen receptor (BCR) led to the assumption that the two mutants exhibit constitutively enhanced intrinsic activity. Here, we show that the two PLCγ2 mutants are strikingly hypersensitive to activation by Rac2 such that even wild-type Rac2 suffices to activate the mutant enzymes upon its introduction into intact cells. Enhanced "basal" activity of PLCγ2 in intact cells is shown using the pharmacologic Rac inhibitor EHT 1864 and the PLCγ2F897Q mutation mediating Rac resistance to be caused by Rac-stimulated rather than by constitutively enhanced PLCγ2 activity. We suggest that R665W and L845F be referred to as allomorphic rather than hypermorphic mutations of PLCG2 Rerouting of the transmembrane signals emanating from BCR and converging on PLCγ2 through Rac in ibrutinib-resistant CLL cells may provide novel drug treatment strategies to overcome ibrutinib resistance mediated by PLCG2 mutations or to prevent its development in ibrutinib-treated CLL patients.
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MESH Headings
- Adenine/analogs & derivatives
- Amino Acid Substitution
- Animals
- COS Cells
- Chlorocebus aethiops
- Drug Resistance, Neoplasm/drug effects
- Drug Resistance, Neoplasm/genetics
- Humans
- Leukemia, Lymphocytic, Chronic, B-Cell/drug therapy
- Leukemia, Lymphocytic, Chronic, B-Cell/enzymology
- Leukemia, Lymphocytic, Chronic, B-Cell/genetics
- Mutation, Missense
- Neoplasm Proteins/antagonists & inhibitors
- Neoplasm Proteins/genetics
- Neoplasm Proteins/metabolism
- Phospholipase C gamma/antagonists & inhibitors
- Phospholipase C gamma/genetics
- Phospholipase C gamma/metabolism
- Piperidines
- Pyrazoles/pharmacology
- Pyrimidines/pharmacology
- Pyrones/pharmacology
- Quinolines/pharmacology
- Receptors, Antigen, B-Cell/genetics
- Receptors, Antigen, B-Cell/metabolism
- Signal Transduction/drug effects
- Signal Transduction/genetics
- rac GTP-Binding Proteins/genetics
- rac GTP-Binding Proteins/metabolism
- RAC2 GTP-Binding Protein
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Affiliation(s)
| | | | - Anja Schade
- From the Institute of Pharmacology and Toxicology and
| | - Sebastian Wiese
- the Core Unit Mass Spectrometry and Proteomics, Medical Faculty, Ulm University, 89081 Ulm, Germany
| | - Julia Deinzer
- From the Institute of Pharmacology and Toxicology and
| | - Marc Zapatka
- the Division of Molecular Genetics, German Cancer Research Center (DKFZ), 69121 Heidelberg, Germany, and
| | - Laurent Désiré
- the Diaxonhit, 63-65 Boulevard Masséna, 75013 Paris, France
| | - Daniel Mertens
- Department of Internal Medicine III, Ulm University Medical Center, 89070 Ulm, Germany
| | - Stephan Stilgenbauer
- Department of Internal Medicine III, Ulm University Medical Center, 89070 Ulm, Germany
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Cool-temperature-mediated activation of phospholipase C-γ2 in the human hereditary disease PLAID. Cell Signal 2016; 28:1237-1251. [PMID: 27196803 DOI: 10.1016/j.cellsig.2016.05.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2016] [Revised: 05/10/2016] [Accepted: 05/12/2016] [Indexed: 12/24/2022]
Abstract
Deletions in the gene encoding signal-transducing inositol phospholipid-specific phospholipase C-γ2 (PLCγ2) are associated with the novel human hereditary disease PLAID (PLCγ2-associated antibody deficiency and immune dysregulation). PLAID is characterized by a rather puzzling concurrence of augmented and diminished functions of the immune system, such as cold urticaria triggered by only minimal decreases in temperature, autoimmunity, and immunodeficiency. Understanding of the functional effects of the genomic alterations at the level of the affected enzyme, PLCγ2, is currently lacking. PLCγ2 is critically involved in coupling various cell surface receptors to regulation of important functions of immune cells such as mast cells, B cells, monocytes/macrophages, and neutrophils. PLCγ2 is unique by carrying three Src (SH) and one split pleckstrin homology domain (spPH) between the two catalytic subdomains (spPHn-SH2n-SH2c-SH3-spPHc). Prevailing evidence suggests that activation of PLCγ2 is primarily due to loss of SH-region-mediated autoinhibition and/or enhanced plasma membrane translocation. Here, we show that the two PLAID PLCγ2 mutants lacking portions of the SH region are strongly (>100-fold), rapidly, and reversibly activated by cooling by only a few degrees. We found that the mechanism(s) underlying PLCγ2 PLAID mutant activation by cool temperatures is distinct from a mere loss of SH-region-mediated autoinhibition and dependent on both the integrity and the pliability of the spPH domain. The results suggest a new mechanism of PLCγ activation with unique thermodynamic features and assign a novel regulatory role to its spPH domain. Involvement of this mechanism in other human disease states associated with cooling such as exertional asthma and certain acute coronary events appears an intriguing possibility.
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11
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Lee JY, Hong WJ, Majeti R, Stearns T. Centrosome-kinase fusions promote oncogenic signaling and disrupt centrosome function in myeloproliferative neoplasms. PLoS One 2014; 9:e92641. [PMID: 24658090 PMCID: PMC3962438 DOI: 10.1371/journal.pone.0092641] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Accepted: 02/17/2014] [Indexed: 11/18/2022] Open
Abstract
Chromosomal translocations observed in myeloproliferative neoplasms (MPNs) frequently fuse genes that encode centrosome proteins and tyrosine kinases. This causes constitutive activation of the kinase resulting in aberrant, proliferative signaling. The function of centrosome proteins in these fusions is not well understood. Among others, kinase centrosome localization and constitutive kinase dimerization are possible consequences of centrosome protein-kinase fusions. To test the relative contributions of localization and dimerization on kinase signaling, we targeted inducibly dimerizable FGFR1 to the centrosome and other subcellular locations and generated a mutant of the FOP-FGFR1 MPN fusion defective in centrosome localization. Expression in mammalian cells followed by western blot analysis revealed a significant decrease in kinase signaling upon loss of FOP-FGFR1 centrosome localization. Kinase dimerization alone resulted in phosphorylation of the FGFR1 signaling target PLCγ, however levels comparable to FOP-FGFR1 required subcellular targeting in addition to kinase dimerization. Expression of MPN fusion proteins also resulted in centrosome disruption in epithelial cells and transformed patient cells. Primary human MPN cells showed masses of modified tubulin that colocalized with centrin, Smoothened (Smo), IFT88, and Arl13b. This is distinct from acute myeloid leukemia (AML) cells, which are not associated with centrosome-kinase fusions and had normal centrosomes. Our results suggest that effective proliferative MPN signaling requires both subcellular localization and dimerization of MPN kinases, both of which may be provided by centrosome protein fusion partners. Furthermore, centrosome disruption may contribute to the MPN transformation phenotype.
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Affiliation(s)
- Joanna Y Lee
- Department of Biology, Stanford University, Stanford, California, United States of America
| | - Wan-Jen Hong
- Stanford Institute for Stem Cell Biology and Regenerative Medicine and Cancer Institute, Stanford University School of Medicine, Stanford, California, United States of America; Department of Medicine, Division of Hematology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Ravindra Majeti
- Stanford Institute for Stem Cell Biology and Regenerative Medicine and Cancer Institute, Stanford University School of Medicine, Stanford, California, United States of America; Department of Medicine, Division of Hematology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Tim Stearns
- Department of Biology, Stanford University, Stanford, California, United States of America; Department of Genetics, Stanford School of Medicine, Stanford, California, United States of America
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Cruz-Orcutt N, Vacaflores A, Connolly SF, Bunnell SC, Houtman JCD. Activated PLC-γ1 is catalytically induced at LAT but activated PLC-γ1 is localized at both LAT- and TCR-containing complexes. Cell Signal 2014; 26:797-805. [PMID: 24412752 DOI: 10.1016/j.cellsig.2013.12.022] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 12/31/2013] [Indexed: 12/27/2022]
Abstract
Phospholipase C-γ1 (PLC-γ1) is a key regulator of T cell receptor (TCR)-induced signaling. Activation of the TCR enhances PLC-γ1 enzymatic function, resulting in calcium influx and the activation of PKC family members and RasGRP. The current model is that phosphorylation of LAT tyrosine 132 facilitates the recruitment of PLC-γ1, leading to its activation and function at the LAT complex. In this study, we examined the phosphorylation kinetics of LAT and PLC-γ1 and the cellular localization of activated PLC-γ1. We observed that commencement of the phosphorylation of LAT tyrosine 132 and PLC-γ1 tyrosine 783 occurred simultaneously, supporting the current model. However, once begun, PLC-γ1 activation occurred more rapidly than LAT tyrosine 132. The association of LAT and PLC-γ1 was more transient than the interaction of LAT and Grb2 and a pool of activated PLC-γ1 translocated away from LAT to cellular structures containing the TCR. These studies demonstrate that LAT and PLC-γ1 form transient interactions that catalyze the activation of PLC-γ1, but that activated PLC-γ1 resides in both LAT and TCR clusters. Together, this work highlights that our current model is incomplete and the activation and function of PLC-γ1 in T cells is highly complex.
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Affiliation(s)
- Noemi Cruz-Orcutt
- Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, United States
| | - Aldo Vacaflores
- Interdisciplinary Graduate Program in Immunology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, United States
| | - Sean F Connolly
- Interdisciplinary Graduate Program in Immunology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, United States
| | - Stephen C Bunnell
- Program in Immunology, Sackler School of Graduate Biomedical Sciences, Boston, MA 02111, United States; Department of Pathology, Tufts University School of Medicine, Boston, MA 02111, United States
| | - Jon C D Houtman
- Department of Microbiology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, United States; Interdisciplinary Graduate Program in Immunology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, United States.
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13
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Fortian A, Sorkin A. Live-cell fluorescence imaging reveals high stoichiometry of Grb2 binding to the EGF receptor sustained during endocytosis. J Cell Sci 2013; 127:432-44. [PMID: 24259669 DOI: 10.1242/jcs.137786] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Activation of epidermal growth factor (EGF) receptor (EGFR) leads to its interaction with Grb2, a dual-function adapter mediating both signaling through Ras and receptor endocytosis. We used time-lapse three-dimensional imaging by spinning disk confocal microscopy to analyze trafficking of EGFR and Grb2 in living HeLa cells stimulated with low, physiological concentrations of EGFR ligands. Endogenous Grb2 was replaced in these cells by Grb2 fused to yellow fluorescent protein (YFP). After transient residence in the plasma membrane, Rhodamine-conjugated EGF (EGF-Rh) and Grb2-YFP were rapidly internalized and accumulated in endosomes. Quantitative image analysis revealed that on average two Grb2-YFP molecules were colocalized with one EGF-Rh in cells stimulated with 2 ng/ml EGF-Rh, and the excess of Grb2-YFP over EGF-Rh was even higher when a receptor-saturating concentration of EGF-Rh was used. Therefore, we hypothesize that a single EGFR molecule can be simultaneously associated with functionally distinct Grb2 interaction partners during and after endocytosis. Continuous presence of Grb2-YFP in endosomes was also observed when EGFR was activated by transforming growth factor-α and amphiregulin, suggesting that endosomal EGFRs remain ligand occupied and signaling competent, despite the fact that these growth factors are thought to dissociate from the receptor at acidic pH. The prolonged localization and activity of EGFR-Grb2 complexes in endosomes correlated with the sustained activation of extracellular stimulus-regulated kinase 1/2, suggesting that endosomal EGFRs contribute significantly to this signaling pathway. We propose that endosomal EGFRs function to extend signaling in time and space to compensate for rapid downregulation of surface EGFRs in cells with low receptor expression levels.
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Affiliation(s)
- Arola Fortian
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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Abstract
Phosphoinositides (PIs) make up only a small fraction of cellular phospholipids, yet they control almost all aspects of a cell's life and death. These lipids gained tremendous research interest as plasma membrane signaling molecules when discovered in the 1970s and 1980s. Research in the last 15 years has added a wide range of biological processes regulated by PIs, turning these lipids into one of the most universal signaling entities in eukaryotic cells. PIs control organelle biology by regulating vesicular trafficking, but they also modulate lipid distribution and metabolism via their close relationship with lipid transfer proteins. PIs regulate ion channels, pumps, and transporters and control both endocytic and exocytic processes. The nuclear phosphoinositides have grown from being an epiphenomenon to a research area of its own. As expected from such pleiotropic regulators, derangements of phosphoinositide metabolism are responsible for a number of human diseases ranging from rare genetic disorders to the most common ones such as cancer, obesity, and diabetes. Moreover, it is increasingly evident that a number of infectious agents hijack the PI regulatory systems of host cells for their intracellular movements, replication, and assembly. As a result, PI converting enzymes began to be noticed by pharmaceutical companies as potential therapeutic targets. This review is an attempt to give an overview of this enormous research field focusing on major developments in diverse areas of basic science linked to cellular physiology and disease.
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Affiliation(s)
- Tamas Balla
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
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15
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Shen W, Martinez K, Chuang CC, McIntosh M. The phospholipase C inhibitor U73122 attenuates trans-10, cis-12 conjugated linoleic acid-mediated inflammatory signaling and insulin resistance in human adipocytes. J Nutr 2013; 143:584-90. [PMID: 23468551 PMCID: PMC3738231 DOI: 10.3945/jn.112.173161] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
We have demonstrated that trans-10, cis-12 conjugated linoleic acid (18:2t10,c12)-mediated delipidation of human adipocytes was dependent on increased intracellular calcium and activation of inflammatory signaling in human primary adipocytes. These data are consistent with the actions of diacylglycerol and inositol triphosphate derived from phospholipase C (PLC)-dependent cell signaling. To test the hypothesis that PLC was an upstream activator of these cellular responses to 18:2t10,c12, primary cultures of human adipocytes were pretreated with 1-[6-((17β-3-methoxyestra-1,3,5 (10)-trien-17-yl)amino)hexyl]-1H-pyrrole-2,5-dione (U73122), a universal PLC inhibitor, followed by 18:2t10,c12 treatment. U73122 attenuated 18:2t10,c12-mediated insulin resistance within 48 h and suppression of the mRNA levels of peroxisome proliferator-activated receptor (PPAR)γ, insulin-stimulated glucose transporter-4, acetyl-CoA carboxylase-1, and stearoyl-CoA desaturase-1, and the protein levels of PPARγ within 18-24 h. U73122 inhibited 18:2t10,c12-mediated induction of the inflammatory-related genes calcium/calmodulin-dependent protein kinase-β, cyclooxygenase-2, monocyte chemoattractant protein-1, interleukin (IL)-6, and IL-8, secretion of IL-6 and IL-8, and the activation of extracellular signal-related kinase, c-Jun N-terminal kinase, and c-Jun within 18-24 h. Moreover, 18:2t10,c12 increased the mRNA levels of heat shock proteins within 6-24 h and intracellular calcium concentrations within 3 min, which were inhibited by U73122. Lastly, 18:2t10,c12 increased the abundance of PLCγ1 in the plasma membrane within 3 min. Taken together, these data suggest that PLC plays an important role in 18:2t10,c12-mediated activation of intracellular calcium accumulation, inflammatory signaling, delipidation, and insulin resistance in human primary adipocytes.
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Abstract
The physiological effects of many extracellular neurotransmitters, hormones, growth factors, and other stimuli are mediated by receptor-promoted activation of phospholipase C (PLC) and consequential activation of inositol lipid signaling pathways. These signaling responses include the classically described conversion of phosphatidylinositol(4,5)P(2) to the Ca(2+)-mobilizing second messenger inositol(1,4,5)P(3) and the protein kinase C-activating second messenger diacylglycerol as well as alterations in membrane association or activity of many proteins that harbor phosphoinositide binding domains. The 13 mammalian PLCs elaborate a minimal catalytic core typified by PLC-d to confer multiple modes of regulation of lipase activity. PLC-b isozymes are activated by Gaq- and Gbg-subunits of heterotrimeric G proteins, and activation of PLC-g isozymes occurs through phosphorylation promoted by receptor and non-receptor tyrosine kinases. PLC-e and certain members of the PLC-b and PLC-g subclasses of isozymes are activated by direct binding of small G proteins of the Ras, Rho, and Rac subfamilies of GTPases. Recent high resolution three dimensional structures together with biochemical studies have illustrated that the X/Y linker region of the catalytic core mediates autoinhibition of most if not all PLC isozymes. Activation occurs as a consequence of removal of this autoinhibition.
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Differential effects of the phosphatidylinositol 4-kinases, PI4KIIα and PI4KIIIβ, on Akt activation and apoptosis. Cell Death Dis 2011; 1:e106. [PMID: 21218173 PMCID: PMC3015391 DOI: 10.1038/cddis.2010.84] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
In this study, we investigated the role of PI4P synthesis by the phosphatidylinositol 4-kinases, PI4KIIα and PI4KIIIβ, in epidermal growth factor (EGF)-stimulated phosphoinositide signaling and cell survival. In COS-7 cells, knockdown of either isozyme by RNA interference reduced basal levels of PI4P and PI(4,5)P2, without affecting receptor activation. Only knockdown of PI4KIIα inhibited EGF-stimulated Akt phosphorylation, indicating that decreased PI(4,5)P2 synthesis observed by loss of either isoform could not account for this PI4KIIα-specific effect. Phospholipase Cγ activation was also differentially affected by knockdown of either PI4K isozyme. Overexpression of kinase-inactive PI4KIIα, which induces defective endosomal trafficking without reducing PI(4,5)P2 levels, also reduced Akt activation. Furthermore, PI4KIIα knockdown profoundly inhibited cell proliferation and induced apoptosis as evidenced by the cleavage of caspase-3 and its substrate poly(ADP-ribose) polymerase. However, in MDA-MB-231 breast cancer cells, apoptosis was observed subsequent to knockdown of either PI4KIIα or PI4KIIIβ and this correlated with enhanced proapoptotic Akt phosphorylation. The differential effects of phosphatidylinositol 4-kinase knockdown in the two cell lines lead to the conclusion that phosphoinositide turnover is inhibited through PI4P substrate depletion, whereas impaired antiapoptotic Akt signaling is an indirect consequence of dysfunctional endosomal trafficking.
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18
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Membrane environment exerts an important influence on rac-mediated activation of phospholipase Cγ2. Mol Cell Biol 2011; 31:1240-51. [PMID: 21245382 DOI: 10.1128/mcb.01408-10] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We performed analyses of the molecular mechanisms involved in the regulation of phospholipase Cγ2 (PLCγ2). We identified several regions in the PLCγ-specific array, γSA, that contribute to autoinhibition in the basal state by occlusion of the catalytic domain. While the activation of PLCγ2 by Rac2 requires stable translocation to the membrane, the removal of the domains required for membrane translocation in the context of an enzyme with impaired autoinhibition generated constitutive, highly active PLC in cells. We further tested the possibility that the interaction of PLCγ2 with its activator protein Rac2 was sufficient for activation through the release of autoinhibition. However, we found that Rac2 binding in the absence of lipid surfaces was not able to activate PLCγ2. Together with other observations, these data suggest that an important consequence of Rac2 binding and translocation to the membrane is that membrane proximity, on its own or together with Rac2, has a role in the release of autoinhibition, resulting in interfacial activation.
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19
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Patsoukis N, Lafuente EM, Meraner P, Kim JS, Dombkowski D, Li L, Boussiotis VA. RIAM regulates the cytoskeletal distribution and activation of PLC-gamma1 in T cells. Sci Signal 2009; 2:ra79. [PMID: 19952372 DOI: 10.1126/scisignal.2000409] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Rap1-guanosine triphosphate (GTP)-interacting adaptor molecule (RIAM) plays a critical role in actin reorganization and inside-out activation of integrins in lymphocytes and platelets. We investigated the role of RIAM in T cell receptor (TCR)-mediated signaling. Although phosphorylation of the kinase ZAP-70 and formation of a signalosome recruited to the adaptor protein LAT were unaffected, elimination of endogenous RIAM by short hairpin RNA impaired generation of inositol 1,4,5-trisphosphate, mobilization of intracellular calcium ions (Ca(2+)), and translocation of the transcription factor NFAT to the nucleus. The activation of Ras guanine nucleotide-releasing protein 1 was also impaired, which led to the diminished expression of the gene encoding interleukin-2. These events were associated with the impaired translocation of phosphorylated phospholipase C-gamma1 (PLC-gamma1) to the actin cytoskeleton, which was required to bring PLC-gamma1 close to its substrate phosphatidylinositol 4,5-bisphosphate, and were reversed by reconstitution of cells with RIAM. Thus, by regulating the localization of PLC-gamma1, RIAM plays a central role in TCR signaling and the transcription of target genes.
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Affiliation(s)
- Nikolaos Patsoukis
- Department of Hematology-Oncology and Cancer Biology, Beth Israel Deaconess Medical Center, Center for Life Sciences, Harvard Medical School, Boston, MA 02215, USA
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20
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Fehrenbacher N, Bar-Sagi D, Philips M. Ras/MAPK signaling from endomembranes. Mol Oncol 2009; 3:297-307. [PMID: 19615955 DOI: 10.1016/j.molonc.2009.06.004] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2009] [Accepted: 06/10/2009] [Indexed: 12/15/2022] Open
Abstract
Signal transduction along the Ras/MAPK pathway has been generally thought to take place at the plasma membrane. It is now evident that the plasma membrane is not the only platform capable of Ras/MAPK signal induction. Fusion of Ras with green fluorescent protein and the development of genetically encoded fluorescent probes for Ras activation have revealed signaling events on a variety of intracellular membranes including endosomes, the Golgi apparatus and the endoplasmic reticulum. Thus, the Ras/MAPK pathway is spatially compartmentalized within cells and this may afford greater complexity of signal output.
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21
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Mongerard-Coulanges M, Migianu-Griffoni E, Lecouvey M, Jolles B. Impact of alendronate and VEGF-antisense combined treatment on highly VEGF-expressing A431 cells. Biochem Pharmacol 2009; 77:1580-5. [PMID: 19426694 DOI: 10.1016/j.bcp.2009.02.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2009] [Revised: 02/18/2009] [Accepted: 02/19/2009] [Indexed: 01/01/2023]
Abstract
Bisphosphonates, and more specially nitrogen-containing bisphosphonates, which are in current use for the treatment of bone diseases, demonstrate proapoptotic, antiproliferative, antiangiogenic and anti-invasive properties on tumor cells. The amino-bisphosphonate alendronate is considered as a potential anticancer drug. In the case of A431 cells, which express high levels of VEGF, it had a two-step effect. At 24h, the antitumor properties of alendronate were counterbalanced by a survival process, which consisted of an enhancement of VEGF expression (mRNA and protein secretion) and TGF alpha secretion. It was only at 48 h that alendronate displayed the expected antiproliferative and antiangiogenic properties. The first step, in which the PI3K pathway was engaged, could be prevented by the use of a VEGF-antisense oligonucleotide. The combination of such an antisense with small concentrations of alendronate (approximately 2 microM), which is of the order of clinically used concentrations, was shown to have an antiangiogenic effect as soon as 12h.
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22
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Li S, Wang Q, Wang Y, Chen X, Wang Z. PLC-gamma1 and Rac1 coregulate EGF-induced cytoskeleton remodeling and cell migration. Mol Endocrinol 2009; 23:901-13. [PMID: 19264842 DOI: 10.1210/me.2008-0368] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
It is well established that epidermal growth factor (EGF) induces the cytoskeleton reorganization and cell migration through two major signaling cascades: phospholipase C-gamma1 (PLC-gamma1) and Rho GTPases. However, little is known about the cross talk between PLC-gamma1 and Rho GTPases. Here we showed that PLC-gamma1 forms a complex with Rac1 in response to EGF. This interaction is direct and mediated by PLC-gamma1 Src homology 3 (SH3) domain and Rac1 (106)PNTP(109) motif. This interaction is critical for EGF-induced Rac1 activation in vivo, and PLC-gamma1 SH3 domain is actually a potent and specific Rac1 guanine nucleotide exchange factor in vitro. We have also demonstrated that the interaction between PLC-gamma1 SH3 domain and Rac1 play a significant role in EGF-induced F-actin formation and cell migration. We conclude that PLC-gamma1 and Rac1 coregulate EGF-induced cell cytoskeleton remodeling and cell migration by a direct functional interaction.
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Affiliation(s)
- Siwei Li
- Department of Cell Biology, University of Alberta, Edmonton, Canada
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23
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Balla T, Várnai P. Visualization of cellular phosphoinositide pools with GFP-fused protein-domains. CURRENT PROTOCOLS IN CELL BIOLOGY 2009; Chapter 24:Unit 24.4. [PMID: 19283730 PMCID: PMC3125592 DOI: 10.1002/0471143030.cb2404s42] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This unit describes the method of following phosphoinositide dynamics in live cells. Inositol phospholipids have emerged as universal signaling molecules present in virtually every membrane of eukaryotic cells. Phosphoinositides are present in only tiny amounts as compared to structural lipids, but they are metabolically very active as they are produced and degraded by the numerous inositide kinase and phosphatase enzymes. Phosphoinositides control the membrane recruitment and activity of many membrane protein signaling complexes in specific membrane compartments, and they have been implicated in the regulation of a variety of signaling and trafficking pathways. It has been a challenge to develop methods that allow detection of phosphoinositides at the single-cell level. The only available technique in live cell applications is based on the use of the same protein domains selected by evolution to recognize cellular phosphoinositides. Some of these isolated protein modules, when fused to fluorescent proteins, can follow dynamic changes in phosphoinositides. While this technique can provide information on phosphoinositide dynamics in live cells with subcellular localization, and it has rapidly gained popularity, it also has several limitations that must be taken into account when interpreting the data. This unit summarizes the design and practical use of these constructs and also reviews important considerations for interpretation of the data obtained by this technique.
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Affiliation(s)
- Tamas Balla
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, NICHD, National Institutes of Health, Bethesda, MD 20892 USA
| | - Péter Várnai
- Department of Physiology, Semmelweis University Medical School, Budapest, Hungary
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Walliser C, Retlich M, Harris R, Everett KL, Josephs MB, Vatter P, Esposito D, Driscoll PC, Katan M, Gierschik P, Bunney TD. rac regulates its effector phospholipase Cgamma2 through interaction with a split pleckstrin homology domain. J Biol Chem 2008; 283:30351-62. [PMID: 18728011 PMCID: PMC2573054 DOI: 10.1074/jbc.m803316200] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2008] [Revised: 07/31/2008] [Indexed: 11/16/2022] Open
Abstract
Several isoforms of phospholipase C (PLC) are regulated through interactions with Ras superfamily GTPases, including Rac proteins. Interestingly, of two closely related PLCgamma isoforms, only PLCgamma(2) has previously been shown to be activated by Rac. Here, we explore the molecular basis of this interaction as well as the structural properties of PLCgamma(2) required for activation. Based on reconstitution experiments with isolated PLCgamma variants and Rac2, we show that an unusual pleckstrin homology (PH) domain, designated as the split PH domain (spPH), is both necessary and sufficient to effect activation of PLCgamma(2) by Rac2. We also demonstrate that Rac2 directly binds to PLCgamma(2) as well as to the isolated spPH of this isoform. Furthermore, through the use of NMR spectroscopy and mutational analysis, we determine the structure of spPH, define the structural features of spPH required for Rac interaction, and identify critical amino acid residues at the interaction interface. We further discuss parallels and differences between PLCgamma(1) and PLCgamma(2) and the implications of our findings for their respective signaling roles.
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Affiliation(s)
- Claudia Walliser
- Institute of Pharmacology and Toxicology, University of Ulm Medical Center, 89070 Ulm, Germany
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25
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IYER ANANDKRISHNANV, TRAN KIENT, GRIFFITH LINDA, WELLS ALAN. Cell surface restriction of EGFR by a tenascin cytotactin-encoded EGF-like repeat is preferential for motility-related signaling. J Cell Physiol 2007; 214:504-12. [PMID: 17708541 PMCID: PMC2963575 DOI: 10.1002/jcp.21232] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The 14th EGFL-repeat (Ten14) of human tenascin cytotactin activates the epidermal growth factor receptor (EGFR) with micromolar affinity; however, unlike EGF, Ten14-mediated activation of EGFR does not lead to receptor internalization. As the divergent signaling pathways downstream of EGFR have been shown to be triggered from plasma membrane and cytosolic locales, we investigated whether Ten14-mediated surface restriction of EGFR resulted in altered biochemical and cellular responses as compared to EGF. Molecules associated with migratory cascades were activated to a relatively greater extent in response to Ten14, with very weak activation of proliferation-associated cascades. Activation of phospholipase C gamma (PLCgamma) and m-calpain, associated with lamellipod protrusion and tail retraction, respectively, were noted at even at sub-saturating doses of Ten14. However, activation of ERK/MAPK, p90RSK, and Elk1, factors affecting proliferation, remained low even at high Ten14 concentrations. Similar activation profiles were observed for EGF-treated cells at 4 degrees C, a maneuver that limits receptor internalization. We demonstrate a concurrent effect of such altered signaling on biophysical responses-sustained migration was observed at levels of Ten14 that activated PLCgamma, but did not stimulate proliferation significantly. Here, we present a novel class of EGFR ligands that can potentially signal as a part of the extracellular matrix, triggering specific intracellular signaling cascades leading to a directed cellular response from an otherwise pleiotropic receptor. This work extends the signaling paradigm of EGFL repeat being presented in a restricted fashion as part of the extracellular matrix.
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Affiliation(s)
| | - KIEN T. TRAN
- Department of Pathology, University of Pittsburgh, Pittsburgh, Penssylvania
| | - LINDA GRIFFITH
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts
| | - ALAN WELLS
- Department of Pathology, University of Pittsburgh, Pittsburgh, Penssylvania
- Pittsburgh VA Medical Center, Pittsburgh, Penssylvania
- Correspondence to: Alan Wells, Department of Pathology, School of Medicine, University of Pittsburgh, 3550 Terrace St., Scaife Hall, S-713, Pittsburgh, PA 15261.
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26
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Yun S, Hong WP, Choi JH, Yi KS, Chae SK, Ryu SH, Suh PG. Phospholipase C-epsilon augments epidermal growth factor-dependent cell growth by inhibiting epidermal growth factor receptor down-regulation. J Biol Chem 2007; 283:341-349. [PMID: 17956867 DOI: 10.1074/jbc.m704180200] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The down-regulation of the epidermal growth factor (EGF) receptor is critical for the termination of EGF-dependent signaling, and the dysregulation of this process can lead to oncogenesis. In the present study, we suggest a novel mechanism for the regulation of EGF receptor down-regulation by phospholipase C-epsilon. The overexpression of PLC-epsilon led to an increase in receptor recycling and decreased the down-regulation of the EGF receptor in COS-7 cells. Adaptor protein complex 2 (AP2) was identified as a novel binding protein that associates with the PLC-epsilon RA2 domain independently of Ras. The interaction of PLC-epsilon with AP2 was responsible for the suppression of EGF receptor down-regulation, since a perturbation in this interaction abolished this effect. Enhanced EGF receptor stability by PLC-epsilon led to the potentiation of EGF-dependent growth in COS-7 cells. Finally, the knockdown of PLC-epsilon in mouse embryo fibroblast cells elicited a severe defect in EGF-dependent growth. Our results indicated that PLC-epsilon could promote EGF-dependent cell growth by suppressing receptor down-regulation.
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Affiliation(s)
- Sanguk Yun
- Department of Life Science, Division of Molecular and Life Science, Pohang University of Science and Technology, Pohang, Kyung-Buk 790-784, Republic of Korea and the
| | - Won-Pyo Hong
- Department of Life Science, Division of Molecular and Life Science, Pohang University of Science and Technology, Pohang, Kyung-Buk 790-784, Republic of Korea and the
| | - Jang Hyun Choi
- Department of Life Science, Division of Molecular and Life Science, Pohang University of Science and Technology, Pohang, Kyung-Buk 790-784, Republic of Korea and the
| | - Kye Sook Yi
- Department of Life Science, Division of Molecular and Life Science, Pohang University of Science and Technology, Pohang, Kyung-Buk 790-784, Republic of Korea and the
| | - Suhn-Kee Chae
- Department of Biochemistry and Biomed Research Center, Paichai University, Daejeon 302-735, Republic of Korea
| | - Sung Ho Ryu
- Department of Life Science, Division of Molecular and Life Science, Pohang University of Science and Technology, Pohang, Kyung-Buk 790-784, Republic of Korea and the
| | - Pann-Ghill Suh
- Department of Life Science, Division of Molecular and Life Science, Pohang University of Science and Technology, Pohang, Kyung-Buk 790-784, Republic of Korea and the.
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27
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Suzuki KGN, Fujiwara TK, Edidin M, Kusumi A. Dynamic recruitment of phospholipase C gamma at transiently immobilized GPI-anchored receptor clusters induces IP3-Ca2+ signaling: single-molecule tracking study 2. ACTA ACUST UNITED AC 2007; 177:731-42. [PMID: 17517965 PMCID: PMC2064217 DOI: 10.1083/jcb.200609175] [Citation(s) in RCA: 165] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Clusters of CD59, a glycosylphosphatidylinositol-anchored receptor (GPI-AR), with physiological sizes of approximately six CD59 molecules, recruit Gαi2 and Lyn via protein–protein and raft interactions. Lyn is activated probably by the Gαi2 binding in the same CD59 cluster, inducing the CD59 cluster's binding to F-actin, resulting in its immobilization, termed stimulation-induced temporary arrest of lateral diffusion (STALL; with a 0.57-s lifetime, occurring approximately every 2 s). Simultaneous single-molecule tracking of GFP-PLCγ2 and CD59 clusters revealed that PLCγ2 molecules are transiently (median = 0.25 s) recruited from the cytoplasm exclusively at the CD59 clusters undergoing STALL, producing the IP3–Ca2+ signal. Therefore, we propose that the CD59 cluster in STALL may be a key, albeit transient, platform for transducing the extracellular GPI-AR signal to the intracellular IP3–Ca2+ signal, via PLCγ2 recruitment. The prolonged, analogue, bulk IP3–Ca2+ signal, which lasts for more than several minutes, is likely generated by the sum of the short-lived, digital-like IP3 bursts, each created by the transient recruitment of PLCγ2 molecules to STALLed CD59.
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Affiliation(s)
- Kenichi G N Suzuki
- Membrane Mechanisms Project, International Cooperative Research Project, Japan Science and Technology Agency, The Institute for Frontier Medical Sciences, Kyoto University, Kyoto, Japan
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Wilsher NE, Court WJ, Ruddle R, Newbatt YM, Aherne W, Sheldrake PW, Jones NP, Katan M, Eccles SA, Raynaud FI. The phosphoinositide-specific phospholipase C inhibitor U73122 (1-(6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione) spontaneously forms conjugates with common components of cell culture medium. Drug Metab Dispos 2007; 35:1017-22. [PMID: 17403917 DOI: 10.1124/dmd.106.014498] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Phosphoinositide-specific phospholipase C (PLC) is a key enzyme in the regulation of Ca(2+) release from inositol 1,4,5-triphosphate-sensitive stores. U73122 (1-(6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione) has been extensively used as a pharmacological inhibitor of PLC to elucidate the importance of this enzyme family in signal transduction pathways. U73122 has an electrophilic maleimide group, which readily reacts with nucleophiles such as thiols and amines. In the current study the conjugation of U73122 to common components of cell culture medium, namely l-glutamine, glutathione, and bovine serum albumin (BSA), was demonstrated. The half-life of U73122 on incubation with phosphate-buffered saline (PBS), Hanks' buffered saline solution (with 2 mM glutamine), optimized basal nutrient medium (MCDB131, without BSA), complete medium, Dulbecco's modified Eagle's medium (with 2 mM l-glutamine) was approximately 150, 60, 32, 30, and 18 min, respectively. However, U73122 was not recoverable from medium supplemented with 0.5% BSA. U73122 underwent hydrolysis of the maleimide group when incubated with PBS. Glutamine conjugates of U73122 were identified in cell culture medium. Furthermore, the inhibition of epidermal growth factor-stimulated Ca(2+) release in a human epidermoid carcinoma cell line (A431) by U73122 was substantially reduced by the presence of BSA in a time-dependent manner. In complex cellular assays, the availability of U73122 to inhibit PLC may be limited by its chemical reactivity and lead to the misinterpretation of results in pharmacological assays.
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Affiliation(s)
- Nicola E Wilsher
- Cancer Research UK Centre for Cancer Therapeutics, Institute of Cancer Research, Belmont, Surrey, UK.
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Wang Y, Tomar A, George SP, Khurana S. Obligatory role for phospholipase C-gamma(1) in villin-induced epithelial cell migration. Am J Physiol Cell Physiol 2007; 292:C1775-86. [PMID: 17229814 DOI: 10.1152/ajpcell.00420.2006] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
While there is circumstantial evidence to suggest a requirement for phospholipase C-gamma(1) (PLC-gamma(1)) in actin reorganization and cell migration, few studies have examined the direct mechanisms that link regulators of the actin cytoskeleton with this crucial signaling molecule. This study was aimed to examine the role that villin, an epithelial cell-specific actin-binding protein, and its ligand PLC-gamma(1) play in migration in intestinal and renal epithelial cell lines that endogenously or ectopically express human villin. Basal as well as epidermal growth factor (EGF)-stimulated cell migration was accompanied by tyrosine phosphorylation of villin and its association with PLC-gamma(1). Inhibition of villin phosphorylation prevented villin-PLC-gamma(1) complex formation as well as villin-induced cell migration. The absolute requirement for PLC-gamma(1) in villin-induced cell migration was demonstrated by measuring cell motility in PLC-gamma(1)(-/-) cells and by downregulation of endogenous PLC-gamma(1). EGF-stimulated direct interaction of villin with the Src homology domain 2 domain of PLC-gamma(1) at the plasma membrane was demonstrated in living cells by using fluorescence resonance energy transfer. These results demonstrate that villin provides an important link between the activation of phosphoinositide signal transduction pathway and epithelial cell migration.
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Affiliation(s)
- Yaohong Wang
- Department of Physiology, The University of Tennessee, Health Science Center, Nash 402, 894 Union Ave., Memphis, TN 38163, USA
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Hankus ME, Li H, Gibson GJ, Cullum BM. Surface-Enhanced Raman Scattering-Based Nanoprobe for High-Resolution, Non-Scanning Chemical Imaging. Anal Chem 2006; 78:7535-46. [PMID: 17073424 DOI: 10.1021/ac061125a] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
This work describes the development and demonstration of a non-scanning chemical imaging probe, capable of obtaining surface-enhanced Raman scattering (SERS) images of samples with which it is in direct contact. The SERS imaging arrays (i.e., nanoprobes) are used in a signal collection mode to obtain images by measuring as many as 30 000 individual sub-diffraction-limited locations on a sample's surface simultaneously. These SERS probes are fabricated from coherent fiber-optic imaging bundles, allowing for the formation of a highly ordered roughened metal surface, capable of providing uniform SERS enhancement (<2.0% relative standard deviation) across the entire imaging surface. These optimized SERS nanoprobes have potential application to a wide range of research fields from materials science to cellular biology.
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Affiliation(s)
- Mikella E Hankus
- Department of Chemistry and Biochemistry, University of Maryland Baltimore County, Baltimore, Maryland 21250, USA
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Yamaguchi K, Hata K, Wada T, Moriya S, Miyagi T. Epidermal growth factor-induced mobilization of a ganglioside-specific sialidase (NEU3) to membrane ruffles. Biochem Biophys Res Commun 2006; 346:484-90. [PMID: 16765317 DOI: 10.1016/j.bbrc.2006.05.136] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2006] [Accepted: 05/22/2006] [Indexed: 01/23/2023]
Abstract
Human ganglioside-specific sialidase, NEU3, localized at cell membranes is thought to regulate various biological processes at cell surfaces. We here explored functional subcellular localization of the sialidase by immunofluorescence and found accumulation at leading edges of cell membranes in the presence of serum in culture. In response to EGF, the sialidase redistributed rapidly to ruffling cell membranes of squamous carcinoma A431 cells and co-localized with Rac-1. NEU3 overexpression enhanced Rac-1 activation and cell migration as compared with controls in HeLa cells as well as in A431 cells. Consistent with co-localization with Rac-1 by immunofluorescence, NEU3 was found to co-precipitate with activated Rac bound to GST-PAK-1 fusion protein. NEU3 silencing by siRNA, in contrast, resulted in inhibition of Rac-1 activation. These results indicate that NEU3 is able to mobilize to membrane ruffles in response to growth stimuli and activate the Rac-1 signaling by co-localization with Rac-1, leading to increased cell motility.
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Affiliation(s)
- Kazunori Yamaguchi
- Division of Biochemistry, Miyagi Cancer Center Research Institute, Natori, Japan
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32
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Abstract
Signal transduction down the Ras/MAPK pathway, including that critical to T cell activation, proliferation, and differentiation, has been generally considered to occur at the plasma membrane. It is now clear that the plasma membrane does not represent the only platform for Ras/MAPK signaling. Moreover, the plasma membrane itself is no longer considered a uniform structure but rather a patchwork of microdomains that can compartmentalize signaling. Signaling on internal membranes was first recognized on endosomes. Genetically encoded fluorescent probes for signaling events such as GTP/GDP exchange on Ras have revealed signaling on a variety of intracellular membranes, including the Golgi apparatus. In fibroblasts, Ras is activated on the plasma membrane and Golgi with distinct kinetics. The pathway by which Golgi-associated Ras becomes activated involves PLCgamma and RasGRP1 and may also require retrograde trafficking of Ras from the plasma membrane to the Golgi as a consequence of depalmitoylation. Thus, the Ras/MAPK pathway represents a clear example of compartmentalized signaling.
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Affiliation(s)
- Adam Mor
- Department of Medicine, New York University Medical Center, New York, NY 10016-6402, USA.
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Abstract
The physiological effects of many extracellular stimuli are mediated by receptor-promoted activation of phospholipase C (PLC) and consequential activation of inositol lipid-signaling pathways. These signaling responses include the classically described conversion of PtdIns(4,5)P(2) to the Ca(2+)-mobilizing second messenger Ins(1,4,5)P(3) and the protein kinase C-activating second messenger diacylglycerol as well as alterations in membrane association or activity of many proteins that harbor phosphoinositide binding domains. Here we discuss how the family of PLCs elaborates a minimal catalytic core typified by PLC-delta to confer multiple modes of regulation on their phospholipase activities. Although PLC-dependent signaling is prominently regulated by direct interactions with heterotrimeric G proteins or tyrosine kinases, the existence of at least 13 divergent PLC isozymes promises a diverse repertoire of regulatory mechanisms for this class of important signaling proteins. We focus here on the recently realized and extensive regulation of inositol lipid signaling by Ras superfamily GTPases directly acting on PLC isozymes and conclude by considering the biological and pharmacological ramifications of this regulation.
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Affiliation(s)
- T Kendall Harden
- Departments of Pharmacology, Biochemistry and Biophysics, and Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA.
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Malviya AN, Klein C. Mechanism regulating nuclear calcium signalingThis paper is one of a selection of papers published in this Special Issue, entitled The Nucleus: A Cell Within A Cell. Can J Physiol Pharmacol 2006; 84:403-22. [PMID: 16902586 DOI: 10.1139/y05-130] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Although the outer nuclear membrane is continuous with the endoplasmic reticulum, it is possible to isolate nuclei both intact and free from endoplasmic reticulum contaminants. The outer and the inner nuclear membranes can be purified free from cross-contamination. Evidence in support of autonomous regulation of nuclear calcium signaling relies upon the investigations with isolated nuclei. Mechanisms for generating calcium signaling in the nucleus have been identified. Two calcium transporting systems, an ATP-dependant nuclear Ca2+-ATPase and an IP4-mediated inositol 1,3,4,5-tetrakisphosphate receptor, are located on the outer nuclear membrane. Thus, ATP and IP4, depending on external free calcium concentrations, are responsible for filling the nuclear envelope calcium pool. The inositol 1,4,5-trisphosphate receptor is located on the inner nuclear membrane with its ligand binding domain facing toward the nucleoplasm. Likewise, the ryanodine receptor is located on the inner nuclear membrane and its ligand cADP-ribose is generated within the nucleus. A 120 kDa protein fragment of nuclear PLC-γ1 is stimulated in vivo by epidermal growth factor nuclear signaling coincident with the time course of nuclear membrane epidermal growth factor receptor activation. Stimulated 120 kDa protein fragment interacts with PIKE, a nuclear GTPase, and together they form a complex with PI[3]kinase serving as a module for nuclear PI[3]K stimulation. Thus, the nucleus has its own IP3generating system.
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Dearden-Badet MT, Mouchiroud G. Re-distribution of phospholipase C gamma 2 in macrophage precursors is mediated by the actin cytoskeleton under the control of the Src kinases. Cell Signal 2005; 17:1560-71. [PMID: 15899577 DOI: 10.1016/j.cellsig.2005.03.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2004] [Revised: 03/08/2005] [Accepted: 03/08/2005] [Indexed: 10/25/2022]
Abstract
Macrophage colony-stimulating factor (M-CSF) is a growth factor that is known to trigger several signalling pathways through receptor tyrosine kinase activation. We investigated the specific requirements for the activation of phospholipase C gamma 2 (PLC-gamma2) during the differentiation of mouse bone marrow-derived macrophage precursors. M-CSF stimulation induced rapid PLC-gamma2 translocation and phosphorylation from the cytosolic compartment to the cell periphery. Both events were dependent on cytoskeleton integrity and Src kinase activity, but only PLC-gamma2 phosphorylation did not require PI3-kinase activity. Biochemical experiments as well as confocal microscopy analyses indicate that the translocation of PLC-gamma2 is mediated by the direct association of this protein with the actin cytoskeleton. Using GST-fusion proteins containing various deletions of the PLC-gamma2 Src homology region, it was found that PLC-gamma2 binds to F-actin via its SH2 domains, a feature that has equally been found in a co-sedimentation assay. This association, which is increased during actin reorganisation and disrupted by cytoskeleton inhibitors, seems to be a primary means to recruit this enzyme to the cell periphery. These results indicate that, upon M-CSF stimulation, PLC-gamma2 cellular localisation and phosphorylation are strongly dependent on cytoskeleton architecture of the macrophage precursor as well as the PI3-kinase and the Src kinases.
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Affiliation(s)
- Marie-Thérèse Dearden-Badet
- Centre de Génétique Moléculaire et Cellulaire, UMR CNRS 5534, Bâtiment Gregor Mendel, 16 Rue Raphaël Dubois, 69622 Villeurbanne Cedex, France.
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Cheeseman KL, Ueyama T, Michaud TM, Kashiwagi K, Wang D, Flax LA, Shirai Y, Loegering DJ, Saito N, Lennartz MR. Targeting of protein kinase C-epsilon during Fcgamma receptor-dependent phagocytosis requires the epsilonC1B domain and phospholipase C-gamma1. Mol Biol Cell 2005; 17:799-813. [PMID: 16319178 PMCID: PMC1356590 DOI: 10.1091/mbc.e04-12-1100] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Protein kinase C-epsilon (PKC-epsilon) translocates to phagosomes and promotes uptake of IgG-opsonized targets. To identify the regions responsible for this concentration, green fluorescent protein (GFP)-protein kinase C-epsilon mutants were tracked during phagocytosis and in response to exogenous lipids. Deletion of the diacylglycerol (DAG)-binding epsilonC1 and epsilonC1B domains, or the epsilonC1B point mutant epsilonC259G, decreased accumulation at phagosomes and membrane translocation in response to exogenous DAG. Quantitation of GFP revealed that epsilonC259G, epsilonC1, and epsilonC1B accumulation at phagosomes was significantly less than that of intact PKC-epsilon. Also, the DAG antagonist 1-hexadecyl-2-acetyl glycerol (EI-150) blocked PKC-epsilon translocation. Thus, DAG binding to epsilonC1B is necessary for PKC-epsilon translocation. The role of phospholipase D (PLD), phosphatidylinositol-specific phospholipase C (PI-PLC)-gamma1, and PI-PLC-gamma2 in PKC-epsilon accumulation was assessed. Although GFP-PLD2 localized to phagosomes and enhanced phagocytosis, PLD inhibition did not alter target ingestion or PKC-epsilon localization. In contrast, the PI-PLC inhibitor U73122 decreased both phagocytosis and PKC-epsilon accumulation. Although expression of PI-PLC-gamma2 is higher than that of PI-PLC-gamma1, PI-PLC-gamma1 but not PI-PLC-gamma2 consistently concentrated at phagosomes. Macrophages from PI-PLC-gamma2-/- mice were similar to wild-type macrophages in their rate and extent of phagocytosis, their accumulation of PKC-epsilon at the phagosome, and their sensitivity to U73122. This implicates PI-PLC-gamma1 as the enzyme that supports PKC-epsilon localization and phagocytosis. That PI-PLC-gamma1 was transiently tyrosine phosphorylated in nascent phagosomes is consistent with this conclusion. Together, these results support a model in which PI-PLC-gamma1 provides DAG that binds to epsilonC1B, facilitating PKC-epsilon localization to phagosomes for efficient IgG-mediated phagocytosis.
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Affiliation(s)
- Keylon L Cheeseman
- Center for Cell Biology and Cancer Research, Albany Medical College, Albany, NY 12208, USA
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O'Callaghan D, Haynes L, Burgoyne R. High-affinity interaction of the N-terminal myristoylation motif of the neuronal calcium sensor protein hippocalcin with phosphatidylinositol 4,5-bisphosphate. Biochem J 2005; 391:231-8. [PMID: 16053445 PMCID: PMC1276920 DOI: 10.1042/bj20051001] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2005] [Revised: 07/29/2005] [Accepted: 07/29/2005] [Indexed: 11/17/2022]
Abstract
Many proteins are associated with intracellular membranes due to their N-terminal myristoylation. Not all myristoylated proteins have the same localization within cells, indicating that other factors must determine their membrane targeting. The NCS (neuronal calcium sensor) proteins are a family of Ca2+-binding proteins with diverse functions. Most members of the family are N-terminally myristoylated and are either constitutively membrane-bound or have a Ca2+/myristoyl switch that allows their reversible membrane association in response to Ca2+ signals. In the case of hippocalcin and NCS-1, or alternatively KChIP1 (K+ channel-interacting protein 1), their N-terminal myristoylation motifs are sufficient for targeting to distinct organelles. We have shown that an N-terminal myristoylated hippocalcin peptide is able to specifically reproduce the membrane targeting of hippocalcin/NCS-1 when introduced into permeabilized cells. The peptide binds to liposomes containing phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] with high affinity (K(d) 50 nM). Full-length hippocalcin also bound preferentially to liposomes supplemented with PtdIns(4,5)P2. Co-expression of hippocalcin-(1-14)-ECFP (enhanced cyan fluorescent protein) or NCS-1-ECFP partially displaced the expressed PH (pleckstrin homology) domain of phospholipase delta1 from the plasma membrane in live cells, indicating that they have a higher affinity for PtdIns(4,5)P2 than does this PH domain. The Golgi localization of the PH domain of FAPP1 (four-phosphate-adaptor protein 1), which binds to phosphatidylinositol 4-phosphate, was unaffected. The localization of NCS-1 and hippocalcin is likely to be determined, therefore, by their interaction with PtdIns(4,5)P2.
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Key Words
- golgi complex
- hippocalcin
- lipid-binding
- calcium-binding proteins
- neuronal calcium sensor-1 (ncs-1)
- phosphoinositide
- ces liposomes, liposomes consisting of a mixture of phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine
- ecfp/egfp/eyfp, enhanced cyan/green/yellow fluorescent protein
- fapp1, four-phosphate-adaptor protein 1
- gfp, green fluorescent protein
- kchip1, k+ channel-interacting protein 1
- marcks, myristoylated alanine-rich c-kinase substrate
- myr-hip-(2–14), biotinylated, myristoylated hippocalcin-(2–14) peptide
- ncs, neuronal calcium sensor
- ph, pleckstrin homology
- plc, phospholipase c
- vilip, visinin-like protein
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Affiliation(s)
- Dermott W. O'Callaghan
- The Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Crown Street, Liverpool L69 3BX, U.K
| | - Lee P. Haynes
- The Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Crown Street, Liverpool L69 3BX, U.K
| | - Robert D. Burgoyne
- The Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Crown Street, Liverpool L69 3BX, U.K
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McLaughlin S, Smith SO, Hayman MJ, Murray D. An electrostatic engine model for autoinhibition and activation of the epidermal growth factor receptor (EGFR/ErbB) family. ACTA ACUST UNITED AC 2005; 126:41-53. [PMID: 15955874 PMCID: PMC2266615 DOI: 10.1085/jgp.200509274] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We propose a new mechanism to explain autoinhibition of the epidermal growth factor receptor (EGFR/ErbB) family of receptor tyrosine kinases based on a structural model that postulates both their juxtamembrane and protein tyrosine kinase domains bind electrostatically to acidic lipids in the plasma membrane, restricting access of the kinase domain to substrate tyrosines. Ligand-induced dimerization promotes partial trans autophosphorylation of ErbB1, leading to a rapid rise in intracellular [Ca2+] that can activate calmodulin. We postulate the Ca2+/calmodulin complex binds rapidly to residues 645–660 of the juxtamembrane domain, reversing its net charge from +8 to −8 and repelling it from the negatively charged inner leaflet of the membrane. The repulsion has two consequences: it releases electrostatically sequestered phosphatidylinositol 4,5-bisphosphate (PIP2), and it disengages the kinase domain from the membrane, allowing it to become fully active and phosphorylate an adjacent ErbB molecule or other substrate. We tested various aspects of the model by measuring ErbB juxtamembrane peptide binding to phospholipid vesicles using both a centrifugation assay and fluorescence correlation spectroscopy; analyzing the kinetics of interactions between ErbB peptides, membranes, and Ca2+/calmodulin using fluorescence stop flow; assessing ErbB1 activation in Cos1 cells; measuring fluorescence resonance energy transfer between ErbB peptides and PIP2; and making theoretical electrostatic calculations on atomic models of membranes and ErbB juxtamembrane and kinase domains.
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Affiliation(s)
- Stuart McLaughlin
- Department of Physiology and Biophysics, HSC, Stony Brook University, Stony Brook, NY 11794, USA.
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Huang F, Sorkin A. Growth factor receptor binding protein 2-mediated recruitment of the RING domain of Cbl to the epidermal growth factor receptor is essential and sufficient to support receptor endocytosis. Mol Biol Cell 2005; 16:1268-81. [PMID: 15635092 PMCID: PMC551491 DOI: 10.1091/mbc.e04-09-0832] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2004] [Revised: 12/14/2004] [Accepted: 12/22/2004] [Indexed: 12/31/2022] Open
Abstract
Knockdown of growth factor receptor binding protein 2 (Grb2) by RNA interference strongly inhibits clathrin-mediated endocytosis of the epidermal growth factor receptor (EGFR). To gain insights into the function of Grb2 in EGFR endocytosis, we have generated cell lines in which endogenous Grb2 was replaced by yellow fluorescent protein (YFP)-tagged Grb2 expressed at the physiological level. In these cells, Grb2-YFP fully reversed the inhibitory effect of Grb2 knockdown on EGFR endocytosis and, moreover, trafficked together with EGFR during endocytosis. Overexpression of Grb2-binding protein c-Cbl did not restore endocytosis in Grb2-depleted cells. However, EGFR endocytosis was rescued in Grb2-depleted cells by chimeric proteins consisting of the Src homology (SH) 2 domain of Grb2 fused to c-Cbl. The "knockdown and rescue" analysis revealed that the expression of Cbl-Grb2/SH2 fusions containing RING finger domain of Cbl restores normal ubiquitylation and internalization of the EGFR in the absence of Grb2, consistent with the important role of the RING domain in EGFR endocytosis. In contrast, the carboxy-terminal domain of Cbl, when attached to Grb2 SH2 domain, had 4 times smaller endocytosis-rescue effect compared with the RING-containing chimeras. Together, the data suggest that the interaction of Cbl carboxy terminus with CIN85 has a minor and a redundant role in EGFR internalization. We concluded that Grb2-mediated recruitment of the functional RING domain of Cbl to the EGFR is essential and sufficient to support receptor endocytosis.
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Affiliation(s)
- Fangtian Huang
- Department of Pharmacology, University of Colorado Health Sciences Center, Aurora, CO 80045, USA
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Wang YJ, Li WH, Wang J, Xu K, Dong P, Luo X, Yin HL. Critical role of PIP5KI{gamma}87 in InsP3-mediated Ca(2+) signaling. ACTA ACUST UNITED AC 2005; 167:1005-10. [PMID: 15611330 PMCID: PMC2172614 DOI: 10.1083/jcb.200408008] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Phosphatidylinositol 4,5-bisphosphate (PIP2) is the obligatory precursor of inositol 1,4,5-trisphosphate (InsP3 or IP3) and is therefore critical to intracellular Ca2+ signaling. Using RNA interference (RNAi), we identified the short splice variant of type I phosphatidylinositol 4-phosphate 5-kinase γ (PIP5KIγ87) as the major contributor of the PIP2 pool that supports G protein–coupled receptor (GPCR)-mediated IP3 generation. PIP5KIγ87 RNAi decreases the histamine-induced IP3 response and Ca2+ flux by 70%. Strikingly, RNAi of other PIP5KI isoforms has minimal effect, even though some of these isoforms account for a larger percent of total PIP2 mass and have previously been implicated in receptor mediated endocytosis or focal adhesion formation. Therefore, PIP5KIγ87's PIP2 pool that supports GPCR-mediated Ca2+ signaling is functionally compartmentalized from those generated by the other PIP5KIs.
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Affiliation(s)
- Ying Jie Wang
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390, USA
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41
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Chang JS, Kim SK, Kwon TK, Bae SS, Min DS, Lee YH, Kim SO, Seo JK, Choi JH, Suh PG. Pleckstrin homology domains of phospholipase C-gamma1 directly interact with beta-tubulin for activation of phospholipase C-gamma1 and reciprocal modulation of beta-tubulin function in microtubule assembly. J Biol Chem 2004; 280:6897-905. [PMID: 15579910 DOI: 10.1074/jbc.m406350200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phosphoinositide-specific phospholipase C-gamma1 (PLC-gamma1) has two pleckstrin homology (PH) domains, an N-terminal domain and a split PH domain. Here we show that pull down of NIH3T3 cell extracts with PLC-gamma1 PH domain-glutathione S-transferase fusion proteins, followed by matrix-assisted laser desorption ionization-time of flight-mass spectrometry, identified beta-tubulin as a binding protein of both PLC-gamma1 PH domains. Tubulin is a main component of microtubules and mitotic spindle fibers, which are composed of alpha- and beta-tubulin heterodimers in all eukaryotic cells. PLC-gamma1 and beta-tubulin colocalized in the perinuclear region in COS-7 cells and cotranslocated to the plasma membrane upon agonist stimulation. Membrane-targeted translocation of depolymerized tubulin by agonist stimulation was also supported by immunoprecipitation analyses. The phosphatidylinositol 4,5-bisphosphate (PIP(2)) hydrolyzing activity of PLC-gamma1 was substantially increased in the presence of purified tubulin in vitro, whereas the activity was not promoted by bovine serum albumin, suggesting that beta-tubulin activates PLC-gamma1. Furthermore, indirect immunofluorescent microscopy showed that PLC-gamma1 was highly concentrated in mitotic spindle fibers, suggesting that PLC-gamma1 is involved in spindle fiber formation. The effect of PLC-gamma1 in microtubule formation was assessed by overexpression and silencing PLC-gamma1 in COS-7 cells, which resulted in altered microtubule dynamics in vivo. Cells overexpressing PLC-gamma1 showed higher microtubule densities than controls, whereas PLC-gamma1 silencing with small interfering RNAs led to decreased microtubule network densities as compared with control cells. Taken together, our results suggest that PLC-gamma1 and beta-tubulin transmodulate each other, i.e. that PLC-gamma1 modulates microtubule assembly by beta-tubulin, and beta-tubulin promotes PLC-gamma1 activity.
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Affiliation(s)
- Jong-Soo Chang
- Department of Life Science, College of Natural Science, Daejin University, Kyeonggido 487-711, Korea.
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42
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Haugh JM, Schneider IC, Lewis JM. On the cross-regulation of protein tyrosine phosphatases and receptor tyrosine kinases in intracellular signaling. J Theor Biol 2004; 230:119-32. [PMID: 15276005 DOI: 10.1016/j.jtbi.2004.04.023] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2003] [Revised: 03/02/2004] [Accepted: 04/26/2004] [Indexed: 10/26/2022]
Abstract
Intracellular signaling proteins are very often regulated by site-specific phosphorylation. For example, growth factor receptors in eukaryotic cells contain intrinsic tyrosine kinase activity and use inter- and intra-molecular interactions to recruit and orient potential protein substrates for phosphorylation. Equally important in determining the magnitude and kinetics of such a response is protein dephosphorylation, catalysed by phosphatase enzymes. A growing body of evidence indicates that certain protein tyrosine phosphatases (PTPs), like tyrosine kinases, are affected by intermolecular interactions that alter the specific activity or localization of their catalytic domains. Using a detailed kinetic modeling framework, we theoretically explore the regulation of PTPs through their association with receptor tyrosine kinases, as noted for the Src homology 2-domain-containing PTPs, SHP-1 and -2. Receptor-PTP binding, in turn, is expected to influence the phosphorylation pattern of those receptors and proteins they associate with, and we show how PTPs might serve to co- or counter-regulate parallel pathways in a signaling network.
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Affiliation(s)
- Jason M Haugh
- Department of Chemical Engineering, 113 Riddick Lab., Box 7905, North Carolina State University, Raleigh, NC 27695-7905, USA.
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Cicchetti G, Biernacki M, Farquharson J, Allen PG. A Ratiometric Expressible FRET Sensor for Phosphoinositides Displays a Signal Change in Highly Dynamic Membrane Structures in Fibroblasts. Biochemistry 2004; 43:1939-49. [PMID: 14967034 DOI: 10.1021/bi035480w] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Phosphoinositides are important signal transduction intermediates in cell growth, survival, and motility. We have invented a fluorescence sensor for polyphosphorylated phosphoinositides based on a peptide derived from the Listeria protein ActA that undergoes a random coil to helix transition upon lipid binding. The sensor, termed CAY, is a fusion protein of cyan and yellow fluorescent proteins flanking the peptide at its N- and C-termini, respectively. CAY displays fluorescence resonance energy transfer in vitro in the absence of phosphorylated phosphoinositides, and this energy transfer is lost upon interaction with these phospholipids. These results demonstrate that a short peptide undergoing a coil to helix transition can be sufficient for the engineering of a FRET-based biosensor. CAY is predominantly localized to the cytoplasm in fibroblasts expressing the sensor but shows loss of fluorescence resonance energy transfer in regions of active actin dynamics such as ruffles that have previously been demonstrated to contain high levels of phosphoinositides.
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Affiliation(s)
- Gregor Cicchetti
- Hematology Division and Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, 221 Longwood Avenue, Boston, Massachusetts 02115, USA.
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Katan M, Rodriguez R, Matsuda M, Newbatt YM, Aherne GW. Structural and mechanistic aspects of phospholipase Cgamma regulation. ADVANCES IN ENZYME REGULATION 2004; 43:77-85. [PMID: 12791384 DOI: 10.1016/s0065-2571(02)00027-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Matilda Katan
- Chester Beatty Laboratories, Cancer Research UK Centre for Cell and Molecular Biology, The Institute of Cancer Research, Fulham Road, London SW3 6JB, UK.
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Ward ME, Wu JY, Rao Y. Visualization of spatially and temporally regulated N-WASP activity during cytoskeletal reorganization in living cells. Proc Natl Acad Sci U S A 2004; 101:970-4. [PMID: 14732696 PMCID: PMC327126 DOI: 10.1073/pnas.0306258101] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Members of the WASP/WAVE family of proteins are key regulators of cytoskeletal reorganization across a diverse range of cellular processes. Despite a wealth of biochemical data about WASP/WAVE regulation in vitro, our understanding of the in vivo regulation of these proteins is hampered by the inability to monitor subcellular regulation of their activities in living cells. Here we establish a fluorescence resonance energy transfer-based approach to visualize spatial and temporal regulation of neuronal Wiskott-Aldrich syndrome protein (N-WASP) activity in living cells. Using time-lapse microscopy, we characterize the activation of N-WASP in response to growth-factor stimulation, and we reveal that N-WASP is activated inside extending filopodia. Furthermore, we suggest a role of N-WASP in regulating membrane ruffling downstream of phosphatidylinositol 4,5-bisphosphate and Cdc42.
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Affiliation(s)
- Michael E Ward
- Department of Anatomy and Neurobiology, Washington University School of Medicine, 660 South Euclid Avenue, Box 8108, St Louis, MO 63110, USA
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Kwon YK, Jang HJ, Kole S, He HJ, Bernier M. Role of the pleckstrin homology domain of PLCgamma1 in its interaction with the insulin receptor. ACTA ACUST UNITED AC 2003; 163:375-84. [PMID: 14568990 PMCID: PMC2173518 DOI: 10.1083/jcb.200301131] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
A thiol-reactive membrane-associated protein (TRAP) binds covalently to the cytoplasmic domain of the human insulin receptor (IR) β-subunit when cells are treated with the homobifunctional cross-linker reagent 1,6-bismaleimidohexane. Here, TRAP was found to be phospholipase C γ1 (PLCγ1) by mass spectrometry analysis. PLCγ1 associated with the IR both in cultured cell lines and in a primary culture of rat hepatocytes. Insulin increased PLCγ1 tyrosine phosphorylation at Tyr-783 and its colocalization with the IR in punctated structures enriched in cortical actin at the dorsal plasma membrane. This association was found to be independent of PLCγ1 Src homology 2 domains, and instead required the pleckstrin homology (PH)–EF-hand domain. Expression of the PH–EF construct blocked endogenous PLCγ1 binding to the IR and inhibited insulin-dependent phosphorylation of mitogen-activated protein kinase (MAPK), but not AKT. Silencing PLCγ1 expression using small interfering RNA markedly reduced insulin-dependent MAPK regulation in HepG2 cells. Conversely, reconstitution of PLCγ1 in PLCγ1−/− fibroblasts improved MAPK activation by insulin. Our results show that PLCγ1 is a thiol-reactive protein whose association with the IR could contribute to the activation of MAPK signaling by insulin.
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Affiliation(s)
- Yong-Kook Kwon
- Diabetes Section, Laboratory of Clinical Investigation, National Institute on Aging, National Institute of Health, Baltimore, MD 21224-6825, USA
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Kiely JM, Hu Y, García-Cardeña G, Gimbrone MA. Lipid raft localization of cell surface E-selectin is required for ligation-induced activation of phospholipase C gamma. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2003; 171:3216-24. [PMID: 12960351 DOI: 10.4049/jimmunol.171.6.3216] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
E-selectin, an endothelial cell surface adhesion receptor for leukocytes, also acts as a signaling receptor. Upon multivalent ligation, E-selectin transduces outside-in signals into the endothelium leading to changes in intracellular Ca(2+) concentration and activation of the mitogen-activated protein kinase signaling pathway. In addition, following leukocyte engagement, E-selectin associates via its cytoplasmic domain with components of the actin cytoskeleton and undergoes alterations in phosphorylation state that result in changes in gene expression. In this study, we show that E-selectin is localized in cholesterol-rich lipid rafts at the cell surface, and that upon ligation E-selectin clusters and redistributes in the plasma membrane colocalizing with a fraction of caveolin-1-containing rafts. In addition, we demonstrate that leukocyte adhesion via E-selectin results in association with and activation of phospholipase Cgamma (PLCgamma). Moreover, we show that disruption of lipid rafts with the cholesterol-depleting drug methyl-beta-cyclodextrin disrupts the raft localization of E-selectin as well as the ligation-induced association of E-selectin with PLCgamma, and subsequent tyrosine phosphorylation of PLCgamma. In contrast, cholesterol depletion has no effect on E-selectin-dependent mitogen-activated protein kinase activation. Thus, these findings demonstrate that the presence of E-selectin in lipid rafts is necessary for its association with, and activation of, PLCgamma, and suggest that this subcellular localization of E-selectin is related to its signaling function(s) during leukocyte-endothelial interactions.
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Affiliation(s)
- Jeanne-Marie Kiely
- Department of Pathology, Center for Excellence in Vascular Biology, Brigham and Women's Hospital, and Harvard Medical School, Boston, MA 02115, USA
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Wang Y, Wang Z. Regulation of EGF-induced phospholipase C-gamma1 translocation and activation by its SH2 and PH domains. Traffic 2003; 4:618-30. [PMID: 12911816 DOI: 10.1034/j.1600-0854.2003.00121.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Translocation of phospholipase C-gamma1 is essential for its function in response to growth factors. However, in spite of recent progress, the phospholipase C-gamma1 translocation pattern and the molecular mechanism of the translocation are far from fully understood. Contradictory results were reported as to which domain, PH or SH2, controls the epidermal growth factor-induced translocation of phospholipase C-gamma1. In this communication, we studied epidermal growth factor-induced translocation of phospholipase C-gamma1 by using comprehensive approaches including biochemistry, indirect fluorescence and live fluorescence imaging. We provided original evidence demonstrating that: (i) endogenous phospholipase C-gamma1, similar to YFP-tagged phospholipase C-gamma1, translocated to endosomes following its initial translocation from cytosol to the plasma membrane in response to epidermal growth factor; (ii) phospholipase C-gamma1 remained phosphorylated in endosomes, but phospholipase C-gamma1 activity is not required for its translocation, which suggests a signaling role for phospholipase C-gamma1 in endosomes; (iii) the PH domain was not required for the initial translocation of phospholipase C-gamma1 from cytosol to the plasma membrane, but it stabilizes phospholipase C-gamma1 in the membrane at a later time; (iv) the function of the phospholipase C-gamma1 PH domain in stabilizing phospholipase C-gamma1 membrane association is very important in maintaining the activity of phospholipase C-gamma1; and (v) the role of the PH domain in phospholipase C-gamma1 membrane association and activation is dependent on PI3K activity. We conclude that the phospholipase C-gamma1 SH2 and PH domains coordinate to determine epidermal growth factor-induced translocation and activation of phospholipase C-gamma1.
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Affiliation(s)
- Yi Wang
- Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
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Singh SM, Murray D. Molecular modeling of the membrane targeting of phospholipase C pleckstrin homology domains. Protein Sci 2003; 12:1934-53. [PMID: 12930993 PMCID: PMC2323991 DOI: 10.1110/ps.0358803] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Phospholipases C (PLCs) reversibly associate with membranes to hydrolyze phosphatidylinositol-4, 5-bisphosphate (PI[4,5]P(2)) and comprise four main classes: beta, gamma, delta, and epsilon. Most eukaryotic PLCs contain a single, N-terminal pleckstrin homology (PH) domain, which is thought to play an important role in membrane targeting. The structure of a single PLC PH domain, that from PLCdelta1, has been determined; this PH domain binds PI(4,5)P(2) with high affinity and stereospecificity and has served as a paradigm for PH domain functionality. However, experimental studies demonstrate that PH domains from different PLC classes exhibit diverse modes of membrane interaction, reflecting the dissimilarity in their amino acid sequences. To elucidate the structural basis for their differential membrane-binding specificities, we modeled the three-dimensional structures of all mammalian PLC PH domains by using bioinformatic tools and calculated their biophysical properties by using continuum electrostatic approaches. Our computational analysis accounts for a large body of experimental data, provides predictions for those PH domains with unknown functions, and indicates functional roles for regions other than the canonical lipid-binding site identified in the PLCdelta1-PH structure. In particular, our calculations predict that (1). members from each of the four PLC classes exhibit strikingly different electrostatic profiles than those ordinarily observed for PH domains in general, (2). nonspecific electrostatic interactions contribute to the membrane localization of PLCdelta-, PLCgamma-, and PLCbeta-PH domains, and (3). phosphorylation regulates the interaction of PLCbeta-PH with its effectors through electrostatic repulsion. Our molecular models for PH domains from all of the PLC classes clearly demonstrate how a common structural fold can serve as a scaffold for a wide range of surface features and biophysical properties that support distinctive functional roles.
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Affiliation(s)
- Shaneen M Singh
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York 10021, USA
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Xi S, Zhang Q, Dyer KF, Lerner EC, Smithgall TE, Gooding WE, Kamens J, Grandis JR. Src kinases mediate STAT growth pathways in squamous cell carcinoma of the head and neck. J Biol Chem 2003; 278:31574-83. [PMID: 12771142 DOI: 10.1074/jbc.m303499200] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Signal transducer and activator of transcription (STAT) proteins are constitutively activated in many malignancies, including squamous cell carcinoma of the head and neck (SCCHN). Previously, we reported that phosphorylation of the epidermal growth factor receptor (EGFR) is linked to activation of STATs 3 and 5 in SCCHN cells. The present study was undertaken to determine the role of Src family kinases in STAT activation and SCCHN growth. The Src family kinases c-Src, c-Yes, Fyn, and Lyn were expressed and activated by transforming growth factor-alpha stimulation in all four SCCHN cell lines examined but not in corresponding normal epithelial cells. In nine SCCHN cell lines tested, Src phosphotyrosine expression levels were highly correlated with activation levels of STATs 3 and 5. Co-immunoprecipitation analysis demonstrated interaction between c-Src and STATs 3 or 5 and EGFR in SCCHN cells, but no heterodimerization was detected between STAT3 and STAT5. SCCHN cells treated with either of two Src-specific inhibitors or transfected with a dominant-negative c-Src construct demonstrated decreased activation of STATs 3 and 5 and reduced growth rates in vitro. These results demonstrate a role for Src kinases in mediating activation of STATs 3 and 5 in concert with the EGFR in SCCHN cells. Strategies to target Src activation may contribute to the treatment of cancers that demonstrate increased levels of EGFR and STATs, including SCCHN.
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Affiliation(s)
- Sichuan Xi
- Department of Otolaryngology, University of Pittsburgh School of MedicinePennsylvania 15213, USA
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