2851
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Sorkin A, Von Zastrow M. Signal transduction and endocytosis: close encounters of many kinds. Nat Rev Mol Cell Biol 2002; 3:600-14. [PMID: 12154371 DOI: 10.1038/nrm883] [Citation(s) in RCA: 647] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Binding of hormones, growth factors and other cell modulators to cell-surface receptors triggers a complex array of signal-transduction events. The activation of many receptors also accelerates their endocytosis. Endocytic transport is important in regulating signal transduction and in mediating the formation of specialized signalling complexes. Conversely, signal-transduction events modulate specific components of the endocytic machinery. Recent studies of protein tyrosine kinases and G-protein-coupled receptors have shed new light on the mechanisms and functional consequences of this bidirectional interplay between signalling and membrane-transport networks.
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Affiliation(s)
- Alexander Sorkin
- Department of Pharmacology, University of Colorado Health Sciences Center, Denver, Colorado 80111, USA.
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2852
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Iordanov MS, Choi RJ, Ryabinina OP, Dinh TH, Bright RK, Magun BE. The UV (Ribotoxic) stress response of human keratinocytes involves the unexpected uncoupling of the Ras-extracellular signal-regulated kinase signaling cascade from the activated epidermal growth factor receptor. Mol Cell Biol 2002; 22:5380-94. [PMID: 12101233 PMCID: PMC133934 DOI: 10.1128/mcb.22.15.5380-5394.2002] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
In mammals, UVB radiation is of biological relevance primarily for the cells of the epidermis. We report here the existence of a UVB response that is specific for proliferating human epidermal keratinocytes. Unlike other cell types that also display a UVB response, keratinocytes respond to UVB irradiation with a transient but potent downregulation of the Ras-extracellular signal-regulated kinase (ERK) signaling cascade. The downregulation of ERK precedes a profound decrease in the steady-state levels of cyclin D1, a mediator of the proliferative action of ERK. Keratinocytes exhibit high constitutive activity of the Ras-ERK signaling cascade even in culture medium lacking supplemental growth factors. The increased activity of Ras and phosphorylation of ERK in these cells are maintained by the autocrine production of secreted molecules that activate the epidermal growth factor receptor (EGFR). Irradiation of keratinocytes increases the phosphorylation of EGFR on tyrosine residues Y845, Y992, Y1045, Y1068, Y1086, Y1148, and Y1173 above the basal levels and leads to the increased recruitment of the adaptor proteins Grb2 and ShcA and of a p55 form of the regulatory subunit of the phosphatidylinositide 3-kinase to the UVB-activated EGFR. Paradoxically, however, UVB causes, at the same time, the inactivation of Ras and a subsequent dephosphorylation of ERK. By contrast, the signaling pathway leading from the activated EGFR to the phosphorylation of PKB/Akt1 is potentiated by UVB. The UVB response of keratinocytes appeared to be a manifestation of the more general ribotoxic stress response inasmuch as the transduction of the UVB-generated inhibitory signal to Ras and ERK required the presence of active ribosomes at the time of irradiation.
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Affiliation(s)
- Mihail S Iordanov
- Department of Cell and Developmental Biology, Oregon Health Sciences University, Portland, OR 97201, USA
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2853
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Sorkina T, Huang F, Beguinot L, Sorkin A. Effect of tyrosine kinase inhibitors on clathrin-coated pit recruitment and internalization of epidermal growth factor receptor. J Biol Chem 2002; 277:27433-41. [PMID: 12021271 DOI: 10.1074/jbc.m201595200] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Several inhibitors of epidermal growth factor receptor (EGFR) kinase and Src family kinases (SFK) were employed to study the role of these kinases in EGFR internalization through clathrin-coated pits. The EGFR kinase-specific compound PD158780 substantially diminished EGFR internalization. PP2, an inhibitor of SFK, had a moderate effect on EGFR internalization in several types of cells, including cells lacking SFK, indicating that the inhibition of endocytosis by PP2 is mediated by kinases other than SFK. In contrast, SU6656, a more specific inhibitor of SFK, did not affect EGFR internalization. To examine what stage of internalization requires receptor kinase activity, we established a quantitative assay based on three-dimensional fluorescence microscopy that measures co-localization of an EGF-rhodamine conjugate and a fluorescently tagged clathrin adaptor protein complex, AP-2. Interestingly, recruitment of EGFR into coated pits did not require physiological temperature because the maximal accumulation of EGFR in coated pits was observed at 4 degrees C. Pretreatment of the cells with PD158780 prevented EGFR recruitment into coated pits, whereas the inhibitor did not block the internalization of receptors that had first been allowed to enter the coated pits at 4 degrees C. These data demonstrate that the activation of receptor kinase is essential for the initial, coated pit recruitment step of endocytosis.
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Affiliation(s)
- Tatiana Sorkina
- Department of Pharmacology, University of Colorado Health Sciences Center, 4200 E Ninth Avenue, Denver, CO 80111, USA
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2854
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Abstract
The Arabidopsis BAK1 (BRI1 Associated receptor Kinase 1) was identified by a yeast two-hybrid screen as a specific interactor for BRI1, a critical component of a membrane brassinosteroid (BR) receptor. In yeast, BAK1/BRI1 interaction activates their kinase activities through transphosphorylation. BAK1 and BRI1 share similar gene expression and subcellular localization patterns and physically associate with each other in plants. Overexpression of the BAK1 gene leads to a phenotype reminiscent of BRI1-overexpression transgenic plants and rescues a weak bri1 mutant. In contrast, a bak1 knockout mutation gives rise to a weak bri1-like phenotype and enhances a weak bri1 mutation. We propose that BAK1 and BRI1 function together to mediate plant steroid signaling.
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Affiliation(s)
- Kyoung Hee Nam
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
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2855
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Hansen JB, Petersen RK, Jørgensen C, Kristiansen K. Deregulated MAPK activity prevents adipocyte differentiation of fibroblasts lacking the retinoblastoma protein. J Biol Chem 2002; 277:26335-9. [PMID: 12000769 DOI: 10.1074/jbc.m203870200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A functional retinoblastoma protein (pRB) is required for adipose conversion of preadipocyte cell lines and primary mouse embryo fibroblasts (MEFs) in response to treatment with standard adipogenic inducers. Interestingly, lack of functional pRB in MEFs was recently linked to elevated Ras activity. Ras-dependent signaling plays a significant, although incompletely understood, role in adipocyte differentiation, because activated Ras has been reported to either promote or inhibit adipogenesis depending on the cellular context. In various cell types activation of Ras leads to activation of the mitogen-activated protein kinases (MAPKs), extracellular signal-regulated kinase 1/2 (ERK1/2), and protein kinase B (PKB)/Akt, which exert opposing effects on adipogenesis, with ERK1/2 inhibiting and PKB/Akt promoting terminal differentiation. Here we report that the levels of activated ERK1/2 and PKB/Akt are significantly increased in pRB-deficient MEFs both before and after the addition of adipogenic inducers. Consistently, we detected higher levels of activated Ras in MEFs lacking pRB. Suppression of ERK1/2 activation by the MEK inhibitor UO126 restored the ability of pRB-deficient MEFs to undergo adipocyte differentiation, as manifested by expression of adipocyte marker genes and lipid accumulation. Furthermore and reflecting the elevated levels of activated PKB/Akt in the pRB-deficient MEFs, differentiation proceeded in an insulin-independent manner. In conclusion, we suggest that pRB plays a pivotal role in adipogenesis by suppressing MAPK activity.
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Affiliation(s)
- Jacob B Hansen
- Department of Biochemistry and Molecular Biology, Center for Experimental BioInformatics, University of Southern Denmark, DK-5230 Odense M, Denmark
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2856
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Kurosaki T, Okada T. Regulation of phospholipase C-gamma2 and phosphoinositide 3-kinase pathways by adaptor proteins in B lymphocytes. Int Rev Immunol 2002; 20:697-711. [PMID: 11913946 DOI: 10.3109/08830180109045586] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The importance of phosphoinositide 3-kinase (PI3K) and phospholipase C (PLC)-gamma2 in B cell function and development has been highlighted by gene targeting experiments in mice. In fact, these knockout mice exhibit a profound inhibition of proliferative responses upon B cell receptor (BCR) engagement. The molecular connections between these effectors and upstream tyrosine kinases such as Syk have been studied intensively in the past few years. This mechanism involves the action of cytoplasmic adaptor molecules, which participate in forming multicomponent signaling complexes, thereby directing the appropriate subcellular localization of effector enzymes. In addition to these cytoplasmic adaptor proteins, cell surface coreceptors can be viewed as transmembrane adaptor proteins, because coreceptors can also change the localization of effector enzymes, which in turn modulates the BCR-initiated signals.
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Affiliation(s)
- T Kurosaki
- Department of Molecular Genetics, Institute for Liver Research, Kansai Medical University, Moriguchi, Japan.
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2857
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Abstract
BACKGROUND Type I phosphoinositide 3-kinases are responsible for the hormone-sensitive synthesis of the lipid messenger phosphatidylinositol(3,4,5)-trisphosphate. Type IA and IB subfamily members contain a Ras binding domain and are stimulated by activated Ras proteins both in vivo and in vitro. The mechanism of Ras activation of type I PI3Ks is unknown, in part because no robust in vitro assay of this event has been established and characterized. Other Ras effectors, such as Raf and phosphoinositide-phospholipase Cepsilon, have been shown to be translocated into the plasma membrane, leading to their activation. RESULTS We show that posttranslationally lipid-modified, activated N-, H-, K-, and R-Ras proteins can potently and substantially activate PI3Kgamma when using a stripped neutrophil membrane fraction as a source of phospholipid substrate. We have found GTPgammaS-loaded Ras can significantly (6- to 8-fold) activate PI3Kgamma when using artificial phospholipid vesicles containing their substrate, and this effect is a result of both a decrease in apparent Km for phosphatidylinositol(4,5)-bisphosphate and an increase in the apparent Vmax. However, neither in vivo nor in the two in vitro assays of Ras activation of PI3Kgamma could we detect any evidence of a Ras-dependent translocation of PI3Kgamma to its source of phospholipid substrate. CONCLUSIONS Our data suggest that Ras activate PI3Kgamma at the level of the membrane, by allosteric modulation and/or reorientation of the PI3Kgamma, implying that Ras can activate PI3Kgamma without its membrane translocation. This view is supported by structural work that has suggested binding of Ras to PI3Kgamma results in a change in the structure of the catalytic pocket.
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Affiliation(s)
- Sabine Suire
- Inositide Laboratory, The Babraham Institute, CB2 4AT Cambridge, United Kingdom
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2858
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Shvartsman SY. Shooting from the hip: spatial control of signal release by intracellular waves. Proc Natl Acad Sci U S A 2002; 99:9087-9. [PMID: 12093926 PMCID: PMC123095 DOI: 10.1073/pnas.152321799] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Stanislav Y Shvartsman
- Department of Chemical Engineering and Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA.
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2859
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Zinner RG, Kim J, Herbst RS. Non-small cell lung cancer clinical trials with trastuzumab: their foundation and preliminary results. Lung Cancer 2002; 37:17-27. [PMID: 12057863 DOI: 10.1016/s0169-5002(02)00035-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The overexpression of HER2, a transmembrane glycoprotein tyrosine kinase, has been implicated in mitogenesis, cell survival, invasion and angiogenesis. Preclinical evidence suggests that HER2 overexpression contributes to tumor progression in non-small cell lung cancer (NSCLC) and retrospective clinical correlative studies show that it is probably associated with poor clinical outcome. Trastuzumab (Herceptin, Genentech Inc., South San Francisco, CA) is a recombinant humanized monoclonal antibody that targets HER2 and is currently approved for use in the treatment of patients with HER2-overexpressing metastatic breast cancer. Two primary mechanisms proposed for the activity of trastuzumab are downregulation of HER2 and induction of antibody-dependent cell-mediated cytotoxicity. Evidence from preclinical studies of trastuzumab in NSCLC and other cell lines, the presence of HER2 overexpression in NSCLC clinical specimens and the clinical benefit derived from trastuzumab in phase II and III metastatic breast cancer trials have led to the development of clinical trials of trastuzumab in NSCLC. Phase II studies of trastuzumab in patients with stage IIIB or IV NSCLC are being conducted to test the efficacy of trastuzumab as a single agent or in combination with chemotherapy. Preliminary results show combinations of chemotherapy plus trastuzumab are well tolerated, with encouraging response rates of 21-40%. A randomized phase II trial of chemotherapy with or without trastuzumab showed promise in a small subgroup of patients with 3+ HER2 overexpression by immunohistochemistry or HER2 DNA amplification by fluorescence in situ hybridization. Taken together, these data indicate that trastuzumab warrants further investigation in a clinical study in selected patients with NSCLC.
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Affiliation(s)
- Ralph G Zinner
- Department of Thoracic/Head and Neck Medical Oncology, Division of Medicine, The University of Texas M.D. Anderson Cancer Center, 1515 M.D. Anderson Boulevard, Houston, TX 77030, USA.
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2860
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Dumont JE, Dremier S, Pirson I, Maenhaut C. Cross signaling, cell specificity, and physiology. Am J Physiol Cell Physiol 2002; 283:C2-28. [PMID: 12055068 DOI: 10.1152/ajpcell.00581.2001] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The literature on intracellular signal transduction presents a confusing picture: every regulatory factor appears to be regulated by all signal transduction cascades and to regulate all cell processes. This contrasts with the known exquisite specificity of action of extracellular signals in different cell types in vivo. The confusion of the in vitro literature is shown to arise from several causes: the inevitable artifacts inherent in reductionism, the arguments used to establish causal effect relationships, the use of less than adequate models (cell lines, transfections, acellular systems, etc.), and the implicit assumption that networks of regulations are universal whereas they are in fact cell and stage specific. Cell specificity results from the existence in any cell type of a unique set of proteins and their isoforms at each level of signal transduction cascades, from the space structure of their components, from their combinatorial logic at each level, from the presence of modulators of signal transduction proteins and of modulators of modulators, from the time structure of extracellular signals and of their transduction, and from quantitative differences of expression of similar sets of factors.
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Affiliation(s)
- J E Dumont
- Institute of Interdisciplinary Research, Free University of Brussels, Campus Erasme, B-1070 Brussels, Belgium.
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2861
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Abstract
Engagement of the T cell antigen receptor (TCR) leads to a complex series of molecular changes at the plasma membrane, in the cytoplasm, and at the nucleus that lead ultimately to T cell effector function. Activation at the TCR of a set of protein tyrosine kinases (PTKs) is an early event in this process. This chapter reviews some of the critical substrates of these PTKs, the adapter proteins that, following phosphorylation on tyrosine residues, serve as binding sites for many of the critical effector enzymes and other adapter proteins required for T cell activation. The role of these adapters in binding various proteins, the interaction of adapters with plasma membrane microdomains, and the function of adapter proteins in control of the cytoskeleton are discussed.
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Affiliation(s)
- Lawrence E Samelson
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 37 Convent Drive, Building 37, Room 1E24, Bethesda, Maryland, 20892-4255, USA.
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2862
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Werlen G, Palmer E. The T-cell receptor signalosome: a dynamic structure with expanding complexity. Curr Opin Immunol 2002; 14:299-305. [PMID: 11973126 DOI: 10.1016/s0952-7915(02)00339-4] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Signal transduction in T cells is a dynamic process involving a large number of membrane and cytosolic proteins. The TCR macromolecular complex (signalosome) is initiated by receptor occupancy and becomes more elaborate over time. This review describes how 'vertical' displacement mechanisms and lateral coalescence of lipid-raft-associated scaffold proteins combine to form distinct signalosomes, which control signal specificity.
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Affiliation(s)
- Guy Werlen
- Laboratory of Transplantation Immunology and Nephrology, Department of Research, University Hospital-Basel, Hebelstrasse 20, CH-4031, Basel, Switzerland.
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2863
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Murono EP, Derk RC. Exposure to octylphenol increases basal testosterone formation by cultured adult rat Leydig cells. J Steroid Biochem Mol Biol 2002; 81:181-9. [PMID: 12137809 DOI: 10.1016/s0960-0760(02)00054-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
4-Tert-octylphenol (OP) is a breakdown product of 4-tert-octylphenol ethoxylate, which is a surfactant additive widely used in the manufacture of a variety of detergents and plastic products. OP has been reported to exhibit weak estrogenic activity in many assay systems. The studies described herein examined an unusual effect of OP in increasing constitutive testosterone levels of cultured Leydig cells from young adult rats. The increase in testosterone was both dose and time sensitive, and this response was observed in medium lacking both calcium and magnesium and containing a membrane-permeable calcium chelator, suggesting that the increase in testosterone was not mediated by an increase in the permeability of extracellular calcium into cells or the redistribution/release of calcium from intracellular stores, respectively. Cellular cAMP levels also were unaffected by OP alone in cultured Leydig cells. Furthermore, initial exposure to 2000nM OP alone for 4h did not alter the subsequent conversion of endogenous cholesterol or exogenously added 22 (R)hydroxycholesterol to testosterone, suggesting that the increase in testosterone was not due to the enhanced availability of endogenous cholesterol or an increase in cholesterol side-chain cleavage activity, respectively. The increase in testosterone also was observed in the presence of the pure estrogen antagonist, ICI 182,780, or a 5alpha-reductase inhibitor, suggesting that this effect of OP was not mediated through the estrogen receptor alpha or beta pathway or by inhibition of Leydig cell testosterone metabolism, respectively. In addition, exposure of cells to comparable concentrations of two different detergents, Triton X-100 or sodium cholate, did not increase testosterone levels, suggesting that this effect of OP was not due to its potential detergent qualities. Although these studies did not identify specific mechanism(s) that increase constitutive testosterone levels by OP, they identify specific pathways that appear not to be involved. The physiological relevance of this observation is not known; nevertheless, they illustrate potential diverse actions of OP in modulating the level of androgen secreted by Leydig cells, and they emphasize that some actions of OP do not appear to be mediated through the estrogen receptor alpha or beta pathway.
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Affiliation(s)
- Eisuke P Murono
- Health Effects Laboratory Division, Pathology and Physiology Research Branch, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, M/S L-2015, Morgantown, WV 26505-2888, USA.
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2864
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Affiliation(s)
- Rajeev Gupta
- Section of Gene Function and Regulation, The Institute of Cancer Research, Fulham Road, London SW3 6JB, UK.
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2865
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Liu D, Aguirre Ghiso J, Estrada Y, Ossowski L. EGFR is a transducer of the urokinase receptor initiated signal that is required for in vivo growth of a human carcinoma. Cancer Cell 2002; 1:445-57. [PMID: 12124174 DOI: 10.1016/s1535-6108(02)00072-7] [Citation(s) in RCA: 288] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Urokinase plasminogen activator receptor (uPAR) activates alpha5beta1 integrin and ERK signaling, inducing in vivo proliferation of HEp3 human carcinoma. Here we demonstrate that EGFR mediates the uPAR/integrin/fibronectin (FN) induced growth pathway. Its activation is ligand-independent and does not require high EGFR, but does require high uPAR expression. Only when uPAR level is constitutively elevated does EGFR become alpha5beta1-associated and activated. Domain 1 of uPAR is crucial for EGFR activation, and FAK links integrin and EGFR signaling. Inhibition of EGFR kinase blocks uPAR induced signal to ERK, implicating EGFR as an important effector of the pathway. Disruption of uPAR or EGFR signaling reduces HEp3 proliferation in vivo. These findings unveil a mechanism whereby uPAR subverts ligand-regulated EGFR signaling, providing cancer cells with proliferative advantage.
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Affiliation(s)
- David Liu
- Department of Medicine, Division of Medical Oncology, Mount Sinai School of Medicine, New York, New York 10029, USA
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2866
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Abstract
Many intracellular signaling proteins such as MAP kinases and transcription factors require multiple covalent modifications before activating downstream targets. This property suggests that signaling pathways are organized to facilitate proofreading, which expends energy to enhance the specificity of the pathway for the appropriate effector. Focusing on MAP kinases, we show that each phosphorylation of the kinase can act as an independent specificity test for that kinase. This is independent of whether MAP kinase activation is distributive, processive, or confined to a protein scaffold. We also highlight the importance of phosphatases in developing and maintaining specificity. Support for our proposals can be drawn from the existing literature.
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Affiliation(s)
- Peter S Swain
- Center for Studies in Physics and Biology, The Rockefeller University, New York, New York 10021, USA.
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2867
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Zhang SQ, Tsiaras WG, Araki T, Wen G, Minichiello L, Klein R, Neel BG. Receptor-specific regulation of phosphatidylinositol 3'-kinase activation by the protein tyrosine phosphatase Shp2. Mol Cell Biol 2002; 22:4062-72. [PMID: 12024020 PMCID: PMC133866 DOI: 10.1128/mcb.22.12.4062-4072.2002] [Citation(s) in RCA: 211] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Receptor tyrosine kinases (RTKs) play distinct roles in multiple biological systems. Many RTKs transmit similar signals, raising questions about how specificity is achieved. One potential mechanism for RTK specificity is control of the magnitude and kinetics of activation of downstream pathways. We have found that the protein tyrosine phosphatase Shp2 regulates the strength and duration of phosphatidylinositol 3'-kinase (PI3K) activation in the epidermal growth factor (EGF) receptor signaling pathway. Shp2 mutant fibroblasts exhibit increased association of the p85 subunit of PI3K with the scaffolding adapter Gab1 compared to that for wild-type (WT) fibroblasts or Shp2 mutant cells reconstituted with WT Shp2. Far-Western analysis suggests increased phosphorylation of p85 binding sites on Gab1. Gab1-associated PI3K activity is increased and PI3K-dependent downstream signals are enhanced in Shp2 mutant cells following EGF stimulation. Analogous results are obtained in fibroblasts inducibly expressing dominant-negative Shp2. Our results suggest that, in addition to its role as a positive component of the Ras-Erk pathway, Shp2 negatively regulates EGF-dependent PI3K activation by dephosphorylating Gab1 p85 binding sites, thereby terminating a previously proposed Gab1-PI3K positive feedback loop. Activation of PI3K-dependent pathways following stimulation by other growth factors is unaffected or decreased in Shp2 mutant cells. Thus, Shp2 regulates the kinetics and magnitude of RTK signaling in a receptor-specific manner.
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Affiliation(s)
- Si Qing Zhang
- Cancer Biology Program, Division of Hematology-Oncology, Department of Medicine, Beth Israel-Deaconess Medical Center, and Harvard Medical School, Boston, Massachusetts 02115, USA
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2868
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Hirsch FR, Franklin WA, Bunn PA. Expression of target molecules in lung cancer: challenge for a new treatment paradigm. Semin Oncol 2002; 29:2-8. [PMID: 12094332 DOI: 10.1053/sonc.2002.34265] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Lung cancer is the leading cause of cancer death in men and women in the United States, accounting for 28% of all cancer fatalities. More than two thirds of patients present with metastatic disease at the time of presentation. Despite improvements in chemotherapy and combined treatment modalities, the survival rate remains below 15%. However, recent advances in our understanding of the biology of lung cancer and carcinogenesis have led to the development of novel therapies directed at tumor-specific targets. These targets are crucial components in important pathways for cell growth, proliferation, and apoptosis. Strategies that interfere with these pathways include monoclonal antibodies directed at growth factors or their receptors, immunotoxins, ligand toxins, antisense molecules, ribozymes, and small-molecule inhibitors. Novel cell surface antigens are being used in vaccines developed to stimulate T-cell-specific immunity. The tumor cells also have specific survival requirements in their local environment that are necessary for invasion, angiogenesis, and metastases. Many new therapeutic strategies are designed to interfere with these requirements. This article reviews many of these recent developments and new therapeutic possibilities; ideally, in the near future, these developments will be implemented in the treatment of lung cancer patients and in early detection and chemoprevention strategies.
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Affiliation(s)
- Fred R Hirsch
- University of Colorado Cancer Center and Department of Medicine, University of Colorado Health Sciences Center, Denver, CO 80262, USA
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2869
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Wang Z, Wang M, Lazo JS, Carr BI. Identification of epidermal growth factor receptor as a target of Cdc25A protein phosphatase. J Biol Chem 2002; 277:19470-5. [PMID: 11912208 DOI: 10.1074/jbc.m201097200] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Cdc25A, a dual-specificity protein phosphatase, plays a critical role in cell cycle progression. Although cyclin-dependent kinases are established substrates, Cdc25A may also affect other proteins. We have shown here that Cdc25A interacts with epidermal growth factor receptor (EGFR) both physically and functionally in Hep3B human hepatoma cells. Cdc25A inhibitor Cpd 5, a vitamin K analog, inhibited Cdc25A activity in the Cdc25A-EGFR immunocomplex and consequently caused prolonged EGFR tyrosine phosphorylation. Both purified GST-Cdc25A protein and endogenous Hep3B cellular Cdc25A dephosphorylated tyrosine-phosphorylated EGFR, and Cpd 5 antagonized the phosphatase activity of Cdc25A. A functional Cdc25A-EGFR interaction was seen in NR-6 fibroblasts expressing ectopic EGFR but not with a receptor lacking the C terminus or a mutated kinase domain. These data link the cell cycle control Cdc25A phosphatase to an EGFR-linked mitogenic signaling pathway specifically involving EGFR dephosphorylation.
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Affiliation(s)
- Ziqiu Wang
- Thomas E. Starzl Transplantation Institute, Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA
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2870
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Affiliation(s)
- Joseph J Falke
- Department of Chemistry and Biochemistry and Molecular Biophysics Program, University of Colorado, Boulder, CO 80309-0215, USA.
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2871
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Fishman S, Brill S, Papa M, Halpern Z, Zvibel I. Heparin-derived disaccharides modulate proliferation and Erb-B2-mediated signal transduction in colon cancer cell lines. Int J Cancer 2002; 99:179-84. [PMID: 11979431 DOI: 10.1002/ijc.10363] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Organ-specific extracellular matrix (ECM) determines metastasis formation by regulating tumor cell proliferation. Hepatocyte-derived ECM enhances proliferation of colon cancer cell lines by increasing expression of tyrosine kinase receptors of the erb-B family. The active components in the ECM are the heparan sulfates, which are highly heterogeneous in their chemistry and size. We determined the effect of heparan sulfate disaccharides, of defined chemistry and present in high amounts in the liver heparan sulfate chains, on the proliferation of colon cancer cell lines and investigated the mechanism involved. The low-metastatic cell line KM12 was stimulated to proliferate by a highly sulfated disaccharide, found in the highest amounts in hepatocyte-derived heparan sulfate. Growth of the highly metastatic cell line KM12SM was inhibited by the second most common disaccharide in hepatocyte-derived heparan sulfate. The effect of both disaccharides was not accompanied by changes in the expression of erb-B1, erb-B2, erb-B3 or heregulin-alpha. We determined whether the disaccharides modified the signal-transduction pathways mediated by the erb-B receptors. The erb-B2-specific tyrosine kinase inhibitor AG825 abolished the enhancement of KM12 cell proliferation by the stimulatory disaccharide. This disaccharide increased tyrosine phosphorylation of erb-B1 and erb-B2 receptors, effects that were abolished by AG825. Moreover, the disaccharide caused increased expression of cyclin D1 and of activated MAP kinase, again reduced in the presence of the inhibitor AG825. The growth-inhibitory disaccharide reduced phosphorylation of erb-B1, but not of erb-B2, receptors in KM12SM cells. In conclusion, not only hepatocyte-derived heparan sulfate but also disaccharide molecules derived from heparan sulfate can affect colon cancer cell proliferation. Their effect is mediated by modulation of the erb-B signal transduction.
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Affiliation(s)
- Sigal Fishman
- Liver Metastasis Research Group, Gastroenterology Institute, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel
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2872
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Magné N, Fischel JL, Dubreuil A, Formento P, Poupon MF, Laurent-Puig P, Milano G. Influence of epidermal growth factor receptor (EGFR), p53 and intrinsic MAP kinase pathway status of tumour cells on the antiproliferative effect of ZD1839 ("Iressa"). Br J Cancer 2002; 86:1518-23. [PMID: 11986789 PMCID: PMC2375374 DOI: 10.1038/sj.bjc.6600299] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2002] [Revised: 03/11/2002] [Accepted: 03/13/2002] [Indexed: 01/04/2023] Open
Abstract
of ZD1839 ("Iressa") is an orally active, selective epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI), which blocks signal transduction pathways implicated in proliferation and survival of cancer cells, and other host-dependent processes promoting cancer growth. Permanent downstream activation of the mitogen-activated protein kinase pathway can theoretically bypass the upstream block of epidermal growth factor receptor-dependent mitogen-activated protein kinase activation at the epidermal growth factor receptor level. We investigated the impact of epidermal growth factor receptor content, p53 status and mitogen-activated protein kinase signalling status on ZD1839 sensitivity in a panel of human tumour cell lines: seven head and neck cancer cell lines and two colon cancer cell lines (LoVo, HT29) with derivatives differing only by a specific modification in p53 status (LoVo p53 wt + p53 mut cells, HT29 p53 mut + p53 wt rescued cells). The antiproliferative activity of ZD1839 was evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide test. ZD1839 concentrations ranged from 0.2-200 microM (48 h exposure). Epidermal growth factor receptor expression, p53 status and p42/p44 (for testing a constitutively active mitogen-activated protein kinase pathway status) were determined by competition analysis (Scatchard plots), denaturing gradient cell electrophoresis and Western blot, respectively. Epidermal growth factor receptor levels ranged from 388 to 33794 fmol mg(-1) protein, a range that is similar to that found in head and neck tumours. The IC(50) values for cell sensitivity to ZD1839 ranged from 6 to 31 microM and a significant inverse correlation (P=0.022, r=0.82) between IC(50) values and epidermal growth factor receptor levels was observed. There was no influence of p53 status on the sensitivity to ZD1839. In two head and neck cancer cell lines with comparably elevated epidermal growth factor receptor expression, a two-fold higher ZD1839 IC(50) value was found for the one with a constitutively active mitogen-activated protein kinase. In conclusion, ZD1839 was active against cells with a range of epidermal growth factor receptor levels, although more so in cells with higher epidermal growth factor receptor expression. Activity was unaffected by p53 status, but was reduced in cells strongly dependent on epidermal growth factor receptor signalling in the presence of an intrinsically activated mitogen-activated protein kinase pathway.
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Affiliation(s)
- N Magné
- Department of Oncopharmacology, Centre Antoine Lacassagne, 33 Avenue de Valombrose, 06189 Nice Cedex 2, France
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2873
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Abstract
Using specific cell surface receptors lymphocytes continuously sample their environment. Maturation of the immune system and initiation of a specific immune response rely on an array of extracellular cues that elicit complex intracellular biochemical signals. Essential molecules involved in signal transduction from immunoreceptors have emerged. After immunoreceptor engagement a core signaling complex is assembled comprising cytoplasmic immunoreceptor chains, kinases of the Src and ZAP70 families and various cytoplasmic and transmembrane adaptor molecules. Further effectors nucleate onto this complex evoking the characteristic responses of lymphocyte activation. Successful maturation of T cells into effector cells relies on the presence of a persistent stimulus presented in an appropriate extracellular environment. Encounter of MHC presented antigenic peptides and their cognate T cell receptors (TCRs) results in the formation of a nanometer intercellular gap between T cells and antigen presenting cells, which is now commonly referred to as the immunological synapse. The synapse is believed to sustain persistent TCR engagement. Its formation requires massive changes in T cell cytoskeletal architecture which essentially relies on signals provided by costimulatory molecules. The well orchestrated interplay between TCR and costimulatory signals decides about successful immune response and tolerance induction or immune failure and autoimmunity.
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Affiliation(s)
- Friedemann Kiefer
- Max-Planck-Institute for Physiological and Clinical Research, WG. Kerckhoff-Jnstitute, Bad Nauheim, Germany.
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2874
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Abstract
In the May, 2002 issue of Developmental Cell, Bruinsma et al. report that the CDF-1 cation diffusion facilitator protein is required for efficient Ras-mediated signaling in C. elegans. CDF-1 reduces intracellular Zn(2+) levels, indicating an inhibitory effect of Zn(2+) on the Ras pathway.
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Affiliation(s)
- Alex Hajnal
- Zoologisches Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
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2875
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Airaksinen MS, Saarma M. The GDNF family: signalling, biological functions and therapeutic value. Nat Rev Neurosci 2002; 3:383-94. [PMID: 11988777 DOI: 10.1038/nrn812] [Citation(s) in RCA: 1324] [Impact Index Per Article: 60.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Members of the nerve growth factor (NGF) and glial cell line-derived neurotrophic factor (GDNF) families comprising neurotrophins and GDNF-family ligands (GFLs), respectively are crucial for the development and maintenance of distinct sets of central and peripheral neurons. Knockout studies in the mouse have revealed that members of these two families might collaborate or act sequentially in a given neuron. Although neurotrophins and GFLs activate common intracellular signalling pathways through their receptor tyrosine kinases, several clear differences exist between these families of trophic factors.
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Affiliation(s)
- Matti S Airaksinen
- Programme of Molecular Neurobiology, Institute of Biotechnology, P.O. Box 56, Viikki Biocenter, FIN-00014, University of Helsinki, Finland.
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2876
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Salazar G, González A. Novel mechanism for regulation of epidermal growth factor receptor endocytosis revealed by protein kinase A inhibition. Mol Biol Cell 2002; 13:1677-93. [PMID: 12006662 PMCID: PMC111136 DOI: 10.1091/mbc.01-08-0403] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Current models put forward that the epidermal growth factor receptor (EGFR) is efficiently internalized via clathrin-coated pits only in response to ligand-induced activation of its intrinsic tyrosine kinase and is subsequently directed into a lysosomal-proteasomal degradation pathway by mechanisms that include receptor tyrosine phosphorylation and ubiquitylation. Herein, we report a novel mechanism of EGFR internalization that does not require ligand binding, receptor kinase activity, or ubiquitylation and does not direct the receptor into a degradative pathway. Inhibition of basal protein kinase A (PKA) activity by H89 and the cell-permeable substrate peptide Myr-PKI induced internalization of 40-60% unoccupied, inactive EGFR, and its accumulation into early endosomes without affecting endocytosis of transferrin and mu-opioid receptors. This effect was abrogated by interfering with clathrin function. Thus, the predominant distribution of inactive EGFR at the plasma membrane is not simply by default but involves a PKA-dependent restrictive condition resulting in receptor avoidance of endocytosis until it is stimulated by ligand. Furthermore, PKA inhibition may contribute to ligand-induced EGFR endocytosis because epidermal growth factor inhibited 26% of PKA basal activity. On the other hand, H89 did not alter ligand-induced internalization of EGFR but doubled its half-time of down-regulation by retarding its segregation into degradative compartments, seemingly due to a delay in the receptor tyrosine phosphorylation and ubiquitylation. Our results reveal that PKA basal activity controls EGFR function at two levels: 1) residence time of inactive EGFR at the cell surface by a process of "endocytic evasion," modulating the accessibility of receptors to stimuli; and 2) sorting events leading to the down-regulation pathway of ligand-activated EGFR, determining the length of its intracellular signaling. They add a new dimension to the fine-tuning of EGFR function in response to cellular demands and cross talk with other signaling receptors.
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Affiliation(s)
- Gloria Salazar
- Departamento de Inmunología Clínica y Reumatología, Facultad de Medicina. Centro de Regulación Celular y Patología, Pontificia Universidad Católica de Chile, Santiago, Chile
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2877
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Rocheleau CE, Howard RM, Goldman AP, Volk ML, Girard LJ, Sundaram MV. A lin-45 raf enhancer screen identifies eor-1, eor-2 and unusual alleles of Ras pathway genes in Caenorhabditis elegans. Genetics 2002; 161:121-31. [PMID: 12019228 PMCID: PMC1462089 DOI: 10.1093/genetics/161.1.121] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In Caenorhabditis elegans, the Ras/Raf/MEK/ERK signal transduction pathway controls multiple processes including excretory system development, P12 fate specification, and vulval cell fate specification. To identify positive regulators of Ras signaling, we conducted a genetic screen for mutations that enhance the excretory system and egg-laying defects of hypomorphic lin-45 raf mutants. This screen identified unusual alleles of several known Ras pathway genes, including a mutation removing the second SH3 domain of the sem-5/Grb2 adaptor, a temperature-sensitive mutation in the helical hairpin of let-341/Sos, a gain-of-function mutation affecting a potential phosphorylation site of the lin-1 Ets domain transcription factor, a dominant-negative allele of ksr-1, and hypomorphic alleles of sur-6/PP2A-B, sur-2/Mediator, and lin-25. In addition, this screen identified multiple alleles of two newly identified genes, eor-1 and eor-2, that play a relatively weak role in vulval fate specification but positively regulate Ras signaling during excretory system development and P12 fate specification. The spectrum of identified mutations argues strongly for the specificity of the enhancer screen and for a close involvement of eor-1 and eor-2 in Ras signaling.
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Affiliation(s)
- Christian E Rocheleau
- Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
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2878
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James KE, Dorman JB, Berg CA. Mosaic analyses reveal the function ofDrosophila Rasin embryonic dorsoventral patterning and dorsal follicle cell morphogenesis. Development 2002; 129:2209-22. [PMID: 11959829 DOI: 10.1242/dev.129.9.2209] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In Drosophila melanogaster, the Ras signal transduction pathway is the primary effector of receptor tyrosine kinases, which govern diverse developmental programs. During oogenesis, epidermal growth factor receptor signaling through the Ras pathway patterns the somatic follicular epithelium, establishing the dorsoventral asymmetry of eggshell and embryo. Analysis of follicle cell clones homozygous for a null allele of Ras demonstrates that Ras is required cell-autonomously to repress pipe transcription, the critical first step in embryonic dorsoventral patterning. The effects of aberrant pipe expression in Ras mosaic egg chambers can be ameliorated, however, by post-pipe patterning events, which salvage normal dorsoventral polarity in most embryos derived from egg chambers with dorsal Ras clones. The patterned follicular epithelium also determines the final shape of the eggshell, including the dorsal respiratory appendages, which are formed by the migration of two dorsolateral follicle cell populations. Confocal analyses of mosaic egg chambers demonstrate that Ras is required both cell- and non cell-autonomously for morphogenetic behaviors characteristic of dorsal follicle cell migration, and reveal a novel, Ras-dependent pattern of basal E-cadherin localization in dorsal midline follicle cells.
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Affiliation(s)
- Karen E James
- Program in Genetics, Department of Genome Sciences, Box 357730, University of Washington, Seattle, WA 98195-7730, USA
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2879
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Egan JE, Hall AB, Yatsula BA, Bar-Sagi D. The bimodal regulation of epidermal growth factor signaling by human Sprouty proteins. Proc Natl Acad Sci U S A 2002; 99:6041-6. [PMID: 11983899 PMCID: PMC122898 DOI: 10.1073/pnas.052090899] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Signal transduction through epidermal growth factor receptors (EGFRs) is essential for the growth and development of multicellular organisms. A genetic screen for regulators of EGFR signaling has led to the identification of Sprouty, a cell autonomous inhibitor of EGF signaling that is transcriptionally induced by the pathway. However, the molecular mechanisms by which Sprouty exerts its antagonistic effect remain largely unknown. Here we have used transient expression in human cells to investigate the functional properties of human Sprouty (hSpry) proteins. Ectopically expressed full-length hSpry1 and hSpry2 induce the potentiation of EGFR-mediated mitogen-activated protein (MAP) kinase activation. In contrast, truncation mutants of hSpry1 and hSpry2 containing the highly conserved carboxyl-terminal cysteine-rich domain inhibit EGF-induced MAP kinase activation. The potentiating effect of the full-length hSpry2 proteins on EGF signaling is mediated by the amino-terminal domain and results from the sequestration of c-Cbl, which in turn leads to the inhibition of EGFR ubiquitination and degradation. These results indicate that hSpry2 can function both as a negative and positive regulator of EGFR-mediated MAP kinase signaling in a domain-dependent fashion. A dual function of this kind could provide a mechanism for achieving proper balance between the activation and repression of EGFR signaling.
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Affiliation(s)
- James E Egan
- Department of Molecular Genetics and Microbiology and Graduate Program in Molecular Pharmacology, State University of New York, Stony Brook, NY 11794-5222, USA
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2880
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Doronin S, Shumay E, Wang HY, Malbon CC. Akt mediates sequestration of the beta(2)-adrenergic receptor in response to insulin. J Biol Chem 2002; 277:15124-31. [PMID: 11809767 DOI: 10.1074/jbc.m108771200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The counterregulation of catecholamine action by insulin includes insulin-stimulated sequestration of the beta(2)-adrenergic receptor. Herein we examined the signaling downstream of insulin receptor activation, focusing upon the role of 1-phosphatidylinositol 3-kinase and the serine-threonine protein kinase Akt (also known as protein kinase B) in the internalization of beta(2)-adrenergic receptors. Inhibition of 1-phosphatidylinositol 3-kinase by LY294002 blocks insulin-induced sequestration of the beta(2)-adrenergic receptor, implicating Akt in downstream signaling to the beta(2)-adrenergic receptor. Phosphorylation studies of the C-terminal cytoplasmic domain of the beta(2)-adrenergic receptor by Akt in vitro identified Ser(345) and Ser(346) within a consensus motif for Akt phosphorylation. Double mutation (i.e. S345A/S346A) within this motif abolishes insulin counterregulation of beta-adrenergic stimulation of cyclic AMP accumulation as well as insulin-stimulated sequestration. Furthermore, expression of constitutively activated Akt (T308D/S473D) mimics insulin action on cyclic AMP responses and beta(2)-adrenergic receptor internalization. Expression of the dominant-negative version of Akt (K179A/T308A/S473A), in contrast, abolishes both insulin counterregulation of the cyclic AMP response as well as insulin-stimulated sequestration of the beta(2)-adrenergic receptor. The action of the serine-threonine protein kinase Akt in insulin counterregulation mirrors the central role of protein kinase A in beta-agonist-induced desensitization.
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Affiliation(s)
- Sergey Doronin
- Department of Molecular Pharmacology, University Medical Center, State University of New York/Stony Brook, Stony Brook, New York 11794-8651, USA
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2881
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Persson C, Engström U, Mowbray SL, Ostman A. Primary sequence determinants responsible for site-selective dephosphorylation of the PDGF beta-receptor by the receptor-like protein tyrosine phosphatase DEP-1. FEBS Lett 2002; 517:27-31. [PMID: 12062403 DOI: 10.1016/s0014-5793(02)02570-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Site-selective dephosphorylation of receptor tyrosine kinases contributes to receptor regulation. The receptor-like protein tyrosine phosphatase DEP-1 site-selectively dephosphorylates the PDGF beta-receptor. DEP-1 dephosphorylation of original and chimeric phospho-peptides spanning the preferred pY1021 and the less preferred pY857 and pY562 sites was analyzed. Double substitutions of basic residues at -4 and +3 of pY857 and pY562 peptides improved affinity. Substitutions of single amino acids indicated preference for an acidic residue at position -1 and a preference against a basic residue at position +3. DEP-1 site-selective dephosphorylation of PDGF beta-receptor is thus determined by the primary sequence surrounding phosphorylation sites and involves interactions with residues spanning at least between positions -1 and +3.
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Affiliation(s)
- Camilla Persson
- Ludwig Institute for Cancer Research, Biomedical Center, Uppsala, Sweden
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2882
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Angers S, Salahpour A, Bouvier M. Dimerization: an emerging concept for G protein-coupled receptor ontogeny and function. Annu Rev Pharmacol Toxicol 2002; 42:409-35. [PMID: 11807178 DOI: 10.1146/annurev.pharmtox.42.091701.082314] [Citation(s) in RCA: 480] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In the last four to five years, the view that G protein-coupled receptors (GPCRs) function as monomeric proteins has been challenged by numerous studies, which suggests that GPCRs exist as dimers or even higher-structure oligomers. Recently, biophysical methods based on luminescence and fluorescence energy transfer have confirmed the existence of such oligomeric complexes in living cells. Although no consensus exists on the role of receptor dimerization, converging evidence suggests potential roles in various aspects of receptor biogenesis and function. In several cases, receptors appear to fold as constitutive dimers early after biosynthesis, whereas ligand-promoted dimerization at the cell surface has been proposed for others. The reports of heterodimerization between receptor subtypes suggest a potential level of receptor complexity that could account for previously unexpected pharmacological diversities. In addition to fundamentally changing our views on the structure and activation processes of GPCRs, the concept of homo- and heterodimerization could have dramatic impacts on drug development and screening.
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Affiliation(s)
- Stephane Angers
- Department of Biochemistry and Groupe de Recherche sur le Système Nerveux Autonome, Université de Montréal, Montréal, H3C 3J7, Canada.
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2883
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Putney LK, Denker SP, Barber DL. The changing face of the Na+/H+ exchanger, NHE1: structure, regulation, and cellular actions. Annu Rev Pharmacol Toxicol 2002; 42:527-52. [PMID: 11807182 DOI: 10.1146/annurev.pharmtox.42.092001.143801] [Citation(s) in RCA: 351] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The NHE family of ion exchangers includes six isoforms (NHE1-NHE6) that function in an electroneutral exchange of intracellular H(+) for extracellular Na(+). This review focuses on the only ubiquitously expressed isoform, NHE1, which is localized at the plasma membrane where it plays a critical role in intracellular pH (pHi) and cell volume homeostasis. All NHE isoforms share a similar topology: an N-terminus of 12 transmembrane (TM) alpha-helices that collectively function in ion exchange, and a C-terminal cytoplasmic regulatory domain that modulates transport activity by the TM domain. Extracellular signals, mediated by diverse classes of cell-surface receptors, regulate NHE1 activity through distinct signaling networks that converge to directly modify the C-terminal regulatory domain. Modifications in the C-terminus, including phosphorylation and the binding of regulatory proteins, control transport activity by altering the affinity of the TM domain for intracellular H(+). Recently, it was determined that NHE1 also functions as a membrane anchor for the actin-based cytoskeleton, independently of its role in ion translocation. Through its effects on pHi homeostasis, cell volume, and the actin cortical network, NHE1 regulates a number of cell behaviors, including adhesion, shape determination, migration, and proliferation.
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Affiliation(s)
- L K Putney
- Department of Stomatology, University of California, San Francisco, HSW 604, San Francisco, California 94143-0512, USA.
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2884
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Cock JM, Vanoosthuyse V, Gaude T. Receptor kinase signalling in plants and animals: distinct molecular systems with mechanistic similarities. Curr Opin Cell Biol 2002; 14:230-6. [PMID: 11891123 DOI: 10.1016/s0955-0674(02)00305-8] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Plant genomes encode large numbers of receptor kinases that are structurally related to the tyrosine and serine/threonine families of receptor kinase found in animals. Here, we describe recent advances in the characterisation of several of these plant receptor kinases at the molecular level, including the identification of receptor complexes, small polypeptide ligands and cytosolic proteins involved in signal transduction and receptor downregulation. Phylogenetic analysis indicates that plant receptor kinases have evolved independently of the receptor kinase families found in animals. This hypothesis is supported by functional studies that have revealed differences between receptor kinase signalling in plants and animals, particularly concerning their interactions with cytosolic proteins. Despite these dissimilarities, however, plant and animal receptor kinases share many common features, such as their single membrane-pass structure, their inclusion in membrane-associated complexes, the involvement of dimerisation and trans autophosphorylation in receptor activation, and the existence of inhibitors and phosphatases that downregulate receptor activity. These points of convergence may represent features that are essential for a functional receptor-kinase signalling system.
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Affiliation(s)
- J Mark Cock
- Reproduction et Développement des Plantes, UMR 5667 CNRS-INRA-ENSL-UCBL, Ecole Normale Supérieure de Lyon, 46 allée d'Italie, 69364 Lyon Cedex 07, France.
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2885
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Trusolino L, Comoglio PM. Scatter-factor and semaphorin receptors: cell signalling for invasive growth. Nat Rev Cancer 2002; 2:289-300. [PMID: 12001990 DOI: 10.1038/nrc779] [Citation(s) in RCA: 564] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Malignant disease occurs when neoplastic cells abandon their primary site of accretion, cross tissue boundaries and penetrate the vasculature to colonize distant sites. This process --metastasis--is the aberrant counterpart of a physiological programme for organ regeneration and maintenance. Scatter factors and semaphorins, together with their receptors, help to orchestrate this programme. What are the differences between physiological and pathological activation of these signalling molecules, and can we exploit them therapeutically to prevent metastasis?
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Affiliation(s)
- Livio Trusolino
- Institute for Cancer Research and Treatment, University of Torino School of Medicine, Candiolo, Italy.
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2886
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Abstract
A hallmark of many signaling pathways is the spatial separation of activation and deactivation of signaling proteins. Quantitative analysis demonstrates that the spatial separation of a membrane-bound kinase and a cytosolic phosphatase potentially results in precipitous gradients of target phosphoproteins. Hypothetically, such gradients in the mitogen-activated protein kinase (MAPK) cascade would result in a strong attenuation of the phosphorylation signal towards the nucleus. When effective signal transduction is hampered by slow protein diffusion and rapid dephosphorylation, phosphoprotein trafficking within endocytic vesicles might be an efficient way to propagate the signals. Additional mechanisms facilitating information transfer could involve the assembly of MAP kinases on a scaffolding protein and active transport of signaling complexes by molecular motors. The proposed mechanism explains recent observations that MAPK activation can be strongly suppressed by various inhibitors of endocytosis.
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Affiliation(s)
- Boris N Kholodenko
- Dept of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, 1020 Locust Street, Philadelphia, PA 19107, USA.
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2887
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Abstract
Receptor tyrosine kinases of the insulin-insulin-like growth factor (IGF) family promote growth and mediate metabolic signals. Despite their extensive structural homology, genetic evidence indicates that their physiological functions are distinct. Nevertheless, there is limited evidence from cell culture systems suggesting that their signalling capabilities differ. Thus, it remains unclear whether the different physiological roles of insulin and IGF-I receptors result from intrinsic differences in their abilities to activate distinct signalling pathways, or arise from extrinsic differences, such as tissue distribution, relative abundance and developmental regulation.
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Affiliation(s)
- Jane J Kim
- Naomi Berrie Diabetes Center and Department of Medicine, College of Physicians and Surgeons of Columbia University, New York, NY 10032, USA
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2888
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Abstract
Recent advances in the study of axon guidance have begun to clarify the intricate signalling mechanisms utilised by receptors that mediate path-finding. Many of these axon guidance receptors, including Plexin B, EphA, ephrin B and Robo, regulate the Rho family of GTPases, to effect changes in motility. Recent studies demonstrate a critical role for the cytoplasmic tails of guidance receptors in signalling and also reveal the potential for a great deal of crosstalk between the various receptor-signalling pathways.
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Affiliation(s)
- Bharatkumar N Patel
- Program in Neuroscience, Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
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2889
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Gniadecki R, Christoffersen N, Wulf HC. Cholesterol-rich plasma membrane domains (lipid rafts) in keratinocytes: importance in the baseline and UVA-induced generation of reactive oxygen species. J Invest Dermatol 2002; 118:582-8. [PMID: 11918702 DOI: 10.1046/j.1523-1747.2002.01716.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The biologic effects of ultraviolet radiation such as DNA damage, mutagenesis, cellular aging, and carcinogenesis are in part mediated by reactive oxygen species. In unirradiated cells the major known sources of reactive oxygen species are the mitochondrial respiratory chain and the membrane oxidases functionally coupled to several membrane growth factor receptors. There is evidence that mitochondria also play a role in oxidative stress after ultraviolet irradiation; however, it is unknown whether the biochemical processes at the level of the plasma membrane contribute to the regulation of reactive oxygen species synthesis. In order to elucidate this issue we examined here the importance of the microdomain plasma membrane organization in the regulation of oxidative stress in unirradiated and ultraviolet A (340-400 nm) irradiated HaCaT keratinocytes. Labeling of confluent HaCaT cultures with fluorescently tagged cholera toxin B subunit (FITC-CTx) revealed the presence of GM1 ganglioside and cholesterol-rich microdomains (lipid rafts) that formed junction-like structures in the membranes of adjacent cells and patchy microdomains elsewhere. There was a marked heterogeneity in the level of FITC-CTx labeling: there were groups of cells demonstrating prominent labeling (FITC-CTx(high)) whereas other cells were only weakly labeled (FITC-CTx(low)). When reactive oxygen species synthesis was measured with the fluorescent probe carboxy-2',7'-dichlorodihydrofluorescein diacetate, we found that (i) the baseline and ultraviolet-A-induced reactive oxygen species synthesis correlated with the magnitude of FITC-CTx labeling and was highest in the FITC-CTx(high) cells; (ii) reactive oxygen species synthesis was diminished in cells in which the integrity of membrane domains was disrupted by cholesterol sequestration with methyl-beta-cyclodextrin and filipin, or after treatment with GM1 ganglioside; (iii) reactive oxygen species synthesis in cholesterol-depleted cells was fully restored after cholesterol repletion. We conclude that the plasma membrane takes part in the regulation of oxidative stress in keratinocytes and disruption of its microdomain structure reduces reactive oxygen species synthesis both at the baseline and after ultraviolet A irradiation. We hypothesize that lipid-raft-associated protein(s) may be involved in the generation of reactive oxygen species and that pharmacologic modulation of membrane structure may provide a novel therapeutic approach relevant for photoprotection and cutaneous carcinogenesis.
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Affiliation(s)
- Robert Gniadecki
- Department of Dermatology, University of Copenhagen, Bispebjerg Hospital, Copenhagen, Denmark.
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2890
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Affiliation(s)
- Urs Gerber
- Brain Research Institute, University of Zurich, CH-8057 Zurich, Switzerland.
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2891
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2892
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Boulven I, Robin P, Desmyter C, Harbon S, Leiber D. Differential involvement of Src family kinases in pervanadate-mediated responses in rat myometrial cells. Cell Signal 2002; 14:341-9. [PMID: 11858941 DOI: 10.1016/s0898-6568(01)00269-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We previously described that pervanadate, a potent tyrosine phosphatase inhibitor, induced contraction of rat myometrium via phospholipase (PL) C-gamma1 activation [Biol Reprod 54 (1996) 1383]. In this study, we found that pervanadate induced tyrosine phosphorylation of the platelet-derived growth factor (PDGF)-beta receptor, interaction of the phosphorylated PDGF receptor with the phosphorylated PLC-gamma1, production of inositol phosphates (InsPs), extracellular signal-regulated kinase (ERK) activation and DNA synthesis. All these responses were insensitive to PDGF receptor kinase inhibition or PDGF receptor down-regulation. We showed that Src family kinases were activated by pervanadate, and that InsPs production and phosphorylation of both PLC-gamma1 and the PDGF receptor were blocked by PP1, an Src inhibitor. In contrast, the stimulation of ERK by pervanadate was totally refractory to PP1. These results demonstrated that the activation of Src by pervanadate is involved in PLC-gamma1/InsPs signalling but does not play a major role in ERK activation.
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Affiliation(s)
- Isaline Boulven
- Laboratoire de Signalisation et Régulations Cellulaires, Centre National de la Recherche Scientifique (CNRS) UMR 8619, Bâtiment 430, Université de Paris-Sud, 91405 Orsay cedex, France
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2893
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Terfera DR, Brown MC, Turner CE. Epidermal growth factor stimulates serine/threonine phosphorylation of the focal adhesion protein paxillin in a MEK-dependent manner in normal rat kidney cells. J Cell Physiol 2002; 191:82-94. [PMID: 11920684 DOI: 10.1002/jcp.10082] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Epidermal growth factor (EGF)-stimulated proliferation of renal epithelial cells plays an important role in the recovery of kidney tubule epithelia following exposure to insult. Numerous studies have demonstrated that tyrosine phosphorylation of the focal adhesion protein paxillin mediates in part the effects of growth factors on cell growth, migration, and organization of the actin-based cytoskeleton. The experiments in this report were designed to determine the effect of EGF on paxillin phosphorylation in normal rat kidney (NRK) epithelial cells. Interestingly, treatment of NRK cells with EGF stimulated paxillin serine/threonine phosphorylation, which caused a reduction in the mobility of paxillin on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The EGF-stimulated mobility shift of paxillin was independent of an intact cytoskeleton, phosphatidylinositol 3-kinase (PI 3-kinase) activation, protein kinase C (PKC) activation, and cellular adhesion. However, inhibitors of the mitogen-activated protein kinase/extracellular signal-regulated kinase kinase abrogated the EGF-stimulated change in paxillin mobility. In addition, the EGF-stimulated change in paxillin serine/threonine phosphorylation was not accompanied by a profound reorganization of the actin cytoskeleton. These results identify paxillin as a component EGF signaling in renal epithelial cells and implicate members of the MAP kinase pathway as critical regulators of paxillin serine/threonine phosphorylation.
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Affiliation(s)
- David R Terfera
- Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, New York 13210, USA
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2894
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Hudrisier D, Bongrand P. Intercellular transfer of antigen-presenting cell determinants onto T cells: molecular mechanisms and biological significance. FASEB J 2002; 16:477-86. [PMID: 11919150 DOI: 10.1096/fj.01-0933rev] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Upon physiological stimulation, receptors with tyrosine kinase activity (RTK) are rapidly internalized together with their soluble ligands. T cell activation is the consequence of recognition by the T cell receptor (TCR) of specific peptide-major histocompatibility protein complexes (peptide-MHC) present at the membrane of antigen-presenting cells (APC). The TCR belongs to the RTK family and is known to be endocytosed upon ligand recognition. It differs from most other RTK in that its ligand, the peptide-MHC complex, is membrane bound and the TCR-ligand interaction is quite weak. Recent experiments have shown that the TCR ligand becomes internalized by T cells upon stimulation. Here we review current knowledge on the molecular mechanisms by which the membrane-bound MHC molecules can be transferred onto T cells, and propose hypotheses on the role this phenomenon could play in physio-pathological situations involving T cells.
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Affiliation(s)
- Denis Hudrisier
- INSERM U 395, CHU Purpan and Paul Sabatier University, BP3028 31024 Toulouse Cedex 3, France.
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2895
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Pintucci G, Moscatelli D, Saponara F, Biernacki PR, Baumann FG, Bizekis C, Galloway AC, Basilico C, Mignatti P. Lack of ERK activation and cell migration in FGF-2-deficient endothelial cells. FASEB J 2002; 16:598-600. [PMID: 11919166 DOI: 10.1096/fj.01-0815fje] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The formation of blood capillaries from preexisting vessels (angiogenesis) and vascular remodeling secondary to atherosclerosis or vessel injury are characterized by endothelial cell migration and proliferation. Numerous growth factors control these cell functions. Basic fibroblast growth factor (FGF-2), a potent angiogenesis inducer, stimulates endothelial cell proliferation, migration, and proteinase production in vitro and in vivo. However, mice genetically deficient in FGF-2 have no apparent vascular defects. We have observed that endothelial cell migration in response to mechanical damage in vitro is accompanied by activation of the extracellular signal-regulated kinase (ERK) pathway, which can be blocked by neutralizing anti-FGF-2 antibodies. Endothelial cells from mice that are genetically deficient in FGF-2 neither migrate nor activate ERK in response to mechanical wounding. Addition of exogenous FGF-2 restores a normal cell response, which shows that impaired migration results from the genetic deficiency of this growth factor. Injury-induced ERK activation in endothelial cells occurs only at the edge of the wound. In addition, FGF-2-induced ERK activation mediates endothelial cell migration in response to wounding without a significant effect on proliferation. These data show that FGF-2 is a key regulator of endothelial cell migration during wound repair.
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Affiliation(s)
- Giuseppe Pintucci
- The Seymour Cohn Cardiovascular Surgical Research Laboratory, Division of Cardiothoracic Surgery, New York University School of Medicine, New York, New York, USA
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2896
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Affiliation(s)
- Pierre De Meyts
- Receptor Biology Laboratory, Hagedorn Research Institute, Niels Steensens Vej 6, DK-2820 Gentofte, Denmark.
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2897
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Kuo MT, Liu Z, Wei Y, Lin-Lee YC, Tatebe S, Mills GB, Unate H. Induction of human MDR1 gene expression by 2-acetylaminofluorene is mediated by effectors of the phosphoinositide 3-kinase pathway that activate NF-kappaB signaling. Oncogene 2002; 21:1945-54. [PMID: 11960367 DOI: 10.1038/sj.onc.1205117] [Citation(s) in RCA: 155] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2001] [Revised: 10/22/2001] [Accepted: 10/30/2001] [Indexed: 01/30/2023]
Abstract
The expression of P-glycoprotein encoded by the multidrug resistance (MDR1) gene is associated with the emergence of the MDR phenotype in cancer cells. Human MDR1 and its rodent homolog mdr1a and mdr1b are frequently overexpressed in liver cancers. However, the underlying mechanisms are largely unknown. The hepatocarcinogen 2-acetylaminofluorene (2-AAF) efficiently activates rat mdr1b expression in cultured cells and in Fisher 344 rats. We recently reported that activation of rat mdr1b in cultured cells by 2-AAF involves a cis-activating element containing a NF-kappaB binding site located -167 to -158 of the rat mdr1b promoter. 2-AAF activates IkappaB kinase (IKK), resulting in degradation of IkappaBbeta and activation of NF-kappaB. In this study, we report that 2-AAF could also activate the human MDR1 gene in human hepatoma and embryonic fibroblast 293 cells. Induction of MDR1 by AAF was mediated by DNA sequence located at -6092 which contains a NF-kappaB binding site. Treating hepatoma cells with 2-AAF activated phosphoinositide 3-kinase (PI3K) and its downstream effectors Rac1, and NAD(P)H oxidase. Transient transfection assays demonstrated that constitutively activated PI3K and Rac1 enhanced the activation of the MDR1 promoter by 2-AAF. Treatment of hepatoma cells with 2-AAF also activated another PI3K downstream effector Akt. Transfection of recombinant encoding a dominant activated Akt also enhanced the activation of MDR1 promoter activation by 2-AAF. These results demonstrated that 2-AAF up-regulates MDR1 expression is mediated by the multiple effectors of the PI3K signaling pathway.
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Affiliation(s)
- Macus Tien Kuo
- Department of Molecular Pathology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, TX 77030, USA.
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2898
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Cunnick JM, Meng S, Ren Y, Desponts C, Wang HG, Djeu JY, Wu J. Regulation of the mitogen-activated protein kinase signaling pathway by SHP2. J Biol Chem 2002; 277:9498-504. [PMID: 11779868 DOI: 10.1074/jbc.m110547200] [Citation(s) in RCA: 128] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Gab1-SHP2 association is required for Erk mitogen-activated protein kinase activation by several growth factors. Gab1-SHP2 interaction activates SHP2. However, an activated SHP2 still needs to associate with Gab1 to mediate Erk activation. It was unclear whether SHP2 is required to dephosphorylate a negative phosphorylation site on Gab1 or whether SHP2 needs the Gab1 pleckstrin homology (PH) domain to target it to the plasma membrane. We found that expression of a fusion protein consisting of the Gab1 PH domain and an active SHP2 (Gab1PH-SHP2DeltaN) induced constitutive Mek1 and Erk2 activation. Linking the active SHP2DeltaN to the PDK1 PH domain or the FRS2beta myristoylation sequence also induced Mek1 activation. Mek1 activation by Gab1PH-SHP2DeltaN was inhibited by an Src inhibitor and by Csk. Significantly, Gab1PH-SHP2DeltaN induced Src activation. Gab1PH-SHP2DeltaN expression activated Ras, and the Gab1PH-SHP2DeltaN-induced Mek1 activation was blocked by RasN17. These findings suggest that Gab1PH-SHP2DeltaN activated a signaling step upstream of Src and Ras. The SHP2 tyrosine phosphatase activity is essential for the function of the fusion protein. Together, these data show that the Gab1 sequence, besides the PH domain and SHP2 binding sites, is dispensable for Erk activation, suggesting that the primary role of Gab1 association with an activated SHP2 is to target it to the membrane.
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Affiliation(s)
- Jess M Cunnick
- H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612, USA
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2899
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2900
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Magné N, Fischel JL, Dubreuil A, Formento P, Marcié S, Lagrange JL, Milano G. Sequence-dependent effects of ZD1839 ('Iressa') in combination with cytotoxic treatment in human head and neck cancer. Br J Cancer 2002; 86:819-27. [PMID: 11875748 PMCID: PMC2375300 DOI: 10.1038/sj.bjc.6600103] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2001] [Revised: 11/23/2001] [Accepted: 11/23/2001] [Indexed: 12/22/2022] Open
Abstract
Elevated levels of epidermal growth factor receptor in head and neck cancer have been extensively reported, and are correlated with poor prognosis. The combination of cisplatin and 5-fluorouracil is a standard treatment regimen for head and neck cancer, with radiation representing another therapeutic option. Six head and neck cancer cell lines were used to study the cytotoxic effects of combining ZD1839 ('Iressa'), a new selective epidermal growth factor receptor tyrosine kinase inhibitor, and radiation. Two of the cell lines were also used to study the combination of ZD1839 and cisplatin/5-fluorouracil. Cytotoxic effects were assessed by the MTT test. The results indicated that ZD1839 applied before radiation gave the best effects (P=0.002); an effect that was strongest in those p53-mutated cell lines that express the highest epidermal growth factor receptor levels. The effects of ZD1839 with cisplatin and/or 5-fluorouracil were sequence dependent (P<0.003), with the best results achieved when ZD1839 was applied first. For the triple combinations, ZD1839 applied before cisplatin and 5-fluorouracil resulted in a slight synergistic effect (P=0.03), although the effect was greater when ZD1839 was applied both before and during cytotoxic drug exposure. In conclusion, ZD1839 applied before radiation and before and/or during cisplatin/5-fluorouracil may improve the efficacy of treatment for head and neck cancer.
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Affiliation(s)
- N Magné
- Department of Oncopharmacology, Oncopharmacology Unit, Centre Antoine Lacassagne, 33 Avenue de Valombrose, 06189 Nice Cedex 2, France
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