601
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Marijanovic Z, Ragimbeau J, Kumar K, Fuchs S, Pellegrini S. TYK2 activity promotes ligand-induced IFNAR1 proteolysis. Biochem J 2006; 397:31-8. [PMID: 16551269 PMCID: PMC1479745 DOI: 10.1042/bj20060272] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The type I IFNR (interferon receptor) is a heterodimer composed of two transmembrane chains, IFNAR1 (interferon-alpha receptor 1 subunit) and IFNAR2, which are associated with the tyrosine kinases Tyk2 and Jak1 (Janus kinase 1) respectively. Ligand-induced down-regulation of the type I IFNR is a major mechanism of negative regulation of cellular signalling and involves the internalization and lysosomal degradation of IFNAR1. IFNalpha promotes the phosphorylation of IFNAR1 on Ser535, followed by recruitment of the E3 ubiquitin ligase, beta-TrCP2 (beta-transducin repeats-containing protein 2), ubiquitination of IFNAR1 and proteolysis. The non-catalytic role of Tyk2 in sustaining the steady-state IFNAR1 level at the plasma membrane is well documented; however, little is known about the function of Tyk2 in the steps that precede and succeed serine phosphorylation and ubiquitination of IFNAR1 in response to ligand binding. In the present study, we show that catalytic activation of Tyk2 is not essential for IFNAR1 internalization, but is required for ligand-induced IFNAR1 serine phosphorylation, ubiquitination and efficient lysosomal proteolysis.
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Affiliation(s)
- Zrinka Marijanovic
- *Cytokine Signalling Unit, CNRS URA 1961, Pasteur Institute, Paris 75724, France
| | - Josiane Ragimbeau
- *Cytokine Signalling Unit, CNRS URA 1961, Pasteur Institute, Paris 75724, France
| | - K. G. Suresh Kumar
- †Department of Animal Biology, University of Pennsylvania, Philadelphia, PA 19104-6046, U.S.A
| | - Serge Y. Fuchs
- †Department of Animal Biology, University of Pennsylvania, Philadelphia, PA 19104-6046, U.S.A
| | - Sandra Pellegrini
- *Cytokine Signalling Unit, CNRS URA 1961, Pasteur Institute, Paris 75724, France
- To whom correspondence should be addressed (email )
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602
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Warren CM, Landgraf R. Signaling through ERBB receptors: Multiple layers of diversity and control. Cell Signal 2006; 18:923-33. [PMID: 16460914 DOI: 10.1016/j.cellsig.2005.12.007] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2005] [Accepted: 12/16/2005] [Indexed: 11/27/2022]
Abstract
The four known ERBB receptors in humans are involved in a broad range of cellular responses, and their deregulation is a significant aspect in a large number of disease states. However, their mechanism of action and modes of control are still poorly understood. This is largely due to the fact that the control of ERBB activity is a multilayered process with significant differences between the various ERBB members. In contrast to other receptor tyrosine kinases, the kinase domain of EGFR (ERBB1) does not require phosphorylation for activation. Consequently, the overall activation state of the receptor is controlled by constant balancing of activity favoring and activity suppressing actions within the receptor molecule. Influences of the membrane microenvironment and context dependent interactions with varying sets of signaling partners are superimposed on this system of intramolecular checks and balances. We will discuss current models of the control of ERBB signaling with an emphasis on the multilayered nature of activation control and aspects that give rise to diversity between ERBB receptors.
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Affiliation(s)
- Carmen M Warren
- University of California Los Angeles, Department of Medicine, Biological Chemistry, United States
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603
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Kim KB, Lee JW, Lee CS, Kim BW, Choo HJ, Jung SY, Chi SG, Yoon YS, Yoon G, Ko YG. Oxidation-reduction respiratory chains and ATP synthase complex are localized in detergent-resistant lipid rafts. Proteomics 2006; 6:2444-53. [PMID: 16526083 DOI: 10.1002/pmic.200500574] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
In order to detect and identify ubiquitous lipid raft marker proteins, we isolated lipid rafts from different mouse organs, including the liver, lung, large brain, and kidney, and analyzed their proteins via 2-DE. Many protein spots were determined to be ubiquitous in all of the lipid rafts, and were annotated via LC and MS/MS. Twelve proteins were identified as ubiquitous raft proteins, and most of these were determined to be mitochondrial proteins, including mortalin, prohibitin, voltage-dependent anion channel, ATP synthase, NADH dehydrogenase, and ubiquinol-cytochrome c reductase. Via immunoblotting, these proteins were shown to exist in detergent-resistant lipid rafts prepared using different organ tissues. Since these oxidation-reduction respiratory chains and ATP synthase complex were detected in detergent-resistant lipid raft fractions which had been isolated from the plasma membrane but not from the mitochondria, and found in the cell surface when determined by immunofluoresence and immunohistochemistry, we conclude that plasma membrane lipid rafts might contain oxidation-reduction respiratory chains and ATP synthase complex.
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Affiliation(s)
- Ki-Bum Kim
- School of Life Sciences and Biotechnology, Korea University, Anam-Dong, Sungbook-Ku, Seoul, Korea
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604
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Schilling K, Opitz N, Wiesenthal A, Oess S, Tikkanen R, Müller-Esterl W, Icking A. Translocation of endothelial nitric-oxide synthase involves a ternary complex with caveolin-1 and NOSTRIN. Mol Biol Cell 2006; 17:3870-80. [PMID: 16807357 PMCID: PMC1593164 DOI: 10.1091/mbc.e05-08-0709] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Recently, we characterized a novel endothelial nitric-oxide synthase (eNOS)-interacting protein, NOSTRIN (for eNOS-trafficking inducer), which decreases eNOS activity upon overexpression and induces translocation of eNOS away from the plasma membrane. Here, we show that NOSTRIN directly binds to caveolin-1, a well-established inhibitor of eNOS. Because this interaction occurs between the N terminus of caveolin (positions 1-61) and the central domain of NOSTRIN (positions 323-434), it allows for independent binding of each of the two proteins to eNOS. Consistently, we were able to demonstrate the existence of a ternary complex of NOSTRIN, eNOS, and caveolin-1 in Chinese hamster ovary (CHO)-eNOS cells. In human umbilical vein endothelial cells (HUVECs), the ternary complex assembles at the plasma membrane upon confluence or thrombin stimulation. In CHO-eNOS cells, NOSTRIN-mediated translocation of eNOS involves caveolin in a process most likely representing caveolar trafficking. Accordingly, trafficking of NOSTRIN/eNOS/caveolin is affected by altering the state of actin filaments or cholesterol levels in the plasma membrane. During caveolar trafficking, NOSTRIN functions as an adaptor to recruit mediators such as dynamin-2 essential for membrane fission. We propose that a ternary complex between NOSTRIN, caveolin-1, and eNOS mediates translocation of eNOS, with important implications for the activity and availability of eNOS in the cell.
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Affiliation(s)
- Kirstin Schilling
- Institute of Biochemistry II, University of Frankfurt Medical School, D-60590 Frankfurt, Germany
| | - Nils Opitz
- Institute of Biochemistry II, University of Frankfurt Medical School, D-60590 Frankfurt, Germany
| | - Anja Wiesenthal
- Institute of Biochemistry II, University of Frankfurt Medical School, D-60590 Frankfurt, Germany
| | - Stefanie Oess
- Institute of Biochemistry II, University of Frankfurt Medical School, D-60590 Frankfurt, Germany
| | - Ritva Tikkanen
- Institute of Biochemistry II, University of Frankfurt Medical School, D-60590 Frankfurt, Germany
| | - Werner Müller-Esterl
- Institute of Biochemistry II, University of Frankfurt Medical School, D-60590 Frankfurt, Germany
| | - Ann Icking
- Institute of Biochemistry II, University of Frankfurt Medical School, D-60590 Frankfurt, Germany
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605
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Bhattacharyya N, Pechhold K, Shahjee H, Zappala G, Elbi C, Raaka B, Wiench M, Hong J, Rechler MM. Nonsecreted insulin-like growth factor binding protein-3 (IGFBP-3) can induce apoptosis in human prostate cancer cells by IGF-independent mechanisms without being concentrated in the nucleus. J Biol Chem 2006; 281:24588-601. [PMID: 16793770 DOI: 10.1074/jbc.m509463200] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Insulin-like growth factor binding protein-3 (IGFBP-3), a secreted protein, has the intrinsic ability to induce apoptosis directly without binding insulin-like growth factors. Previous studies suggested that IGFBP-3 must be secreted to exert its biological functions. IGFBP-3 contains a nuclear localization signal (NLS), and exogenous IGFBP-3 is translocated into the nucleus, suggesting that both secretion and nuclear localization may play important roles in IGFBP-3 action. To address these questions, we fused yellow fluorescent protein (YFP) to mature IGFBP-3 lacking its signal peptide so that it would remain intracellular and mutated the C-terminal NLS of IGFBP-3, (228)KGRKR(232), to MDGEA. Following transfection of PC-3 human prostate cancer cells with these constructs, Western blots indicated that YFP-IGFBP-3 lacking a signal peptide was cell-associated and not present in the extracellular media. Moreover, the fusion protein was not N-glycosylated, indicating that it had not entered the secretory pathway. Confocal imaging showed that intracellular YFP-MDGEA-IGFBP-3 was predominantly cytoplasmic. Transient transfection of nonsecreted YFP-wild-type IGFBP-3 decreased cell viability, as assessed by staining with annexin V followed by flow cytometry. Induction of cell death was caspase-dependent, indicative of apoptosis. Apoptosis also was induced by the nonsecreted NLS mutant (YFP-MDGEA-IGFBP-3) alone and when the IGF-binding site also had been mutated. These results indicate that IGFBP-3 can induce apoptosis in an IGF-independent manner without being secreted or concentrated in the nucleus.
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Affiliation(s)
- Nisan Bhattacharyya
- Diabetes Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892, USA
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606
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Li YC, Hu XQ, Zhang KY, Guo J, Hu ZY, Tao SX, Xiao LJ, Wang QZ, Han CS, Liu YX. Afaf, a novel vesicle membrane protein, is related to acrosome formation in murine testis. FEBS Lett 2006; 580:4266-73. [PMID: 16831425 DOI: 10.1016/j.febslet.2006.06.010] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2006] [Revised: 05/12/2006] [Accepted: 06/07/2006] [Indexed: 01/02/2023]
Abstract
As a cell-specific organelle, acrosome (Acr) and its formation are an important event for spermiogenesis. However, the Acr formation is far more complicated than has been proposed. In this study, we have cloned a novel membrane protein Afaf (Acr formation associated factor) that was expressed abundantly in the round spermatids, localized in the inner and outer membrane of forming Acrs, and declined in the maturing Acrs. In the transfected Hela cells, Afaf protein was localized in the plasma membrane, EEA1-positive early endosomes (EEs) and occasionally in the nuclei. Therefore, we propose that EEs and plasma membrane may be also directly involved in the Acr biogenesis.
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Affiliation(s)
- Yin-Chuan Li
- State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100080, PR China
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607
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608
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Jaramillo ML, Leon Z, Grothe S, Paul-Roc B, Abulrob A, O'Connor McCourt M. Effect of the anti-receptor ligand-blocking 225 monoclonal antibody on EGF receptor endocytosis and sorting. Exp Cell Res 2006; 312:2778-90. [PMID: 16806168 DOI: 10.1016/j.yexcr.2006.05.008] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2006] [Revised: 05/08/2006] [Accepted: 05/08/2006] [Indexed: 12/25/2022]
Abstract
The anti-receptor antibody, 225 mAb, is known to block binding of ligand to the epidermal growth factor receptor (EGFR). However, the effect of this neutralizing antibody on EGFR endocytosis, trafficking and degradation remains unclear. Here, we demonstrate that endocytosis of (125)I-225 mAb occurs, albeit with a slower rate than that of EGF. Using pulse chase assays, we show that internalized (125)I-225 mAb is recycled to the surface much more efficiently than internalized (125)I-EGF. Also, we found that internalization of (125)I-225 mAb, in contrast to that of EGF, is independent of receptor tyrosine kinase activity, as evidenced by its insensitivity to AG1478, a specific EGFR tyrosine kinase inhibitor. Analysis of the levels of cell surface and total EGFR showed that treatment with 225 mAb results in a 30-40% decrease in surface EGFR and a relatively slow downregulation of total EGFR. Taken together, these data indicate that 225 mAb induces internalization and downregulation of EGFR via a mechanism distinct from that underlying EGF-induced EGFR internalization and downregulation.
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Affiliation(s)
- Maria L Jaramillo
- Biotechnology Research Institute, National Research Council of Canada, 6100 Royalmount Avenue, Montreal, Quebec, Canada H4P 2R2.
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609
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Lui WY, Lee WM. Regulation of junction dynamics in the testis--transcriptional and post-translational regulations of cell junction proteins. Mol Cell Endocrinol 2006; 250:25-35. [PMID: 16431017 DOI: 10.1016/j.mce.2005.12.021] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Cell junctions are the sites at which cells attach to the neighboring cells. They do not only maintain tissue integrity, their turnover also plays a crucial role in cell development and morphogenesis. In the testis, tight junctions and adherens junctions are dynamically remodeled to allow the movement of post-meiotic germ cells across the seminiferous epithelium and the timely release of spermatids into the tubular lumen. There is growing evidence that this dynamic remodeling of cell junctions is mediated by several mechanisms at the transcriptional and post-translational levels. This review summarizes what is known about the transcriptional regulation, ubiquitination and endocytosis that are involved in modulating junction dynamics in epithelial cells. It also highlights the recent findings on the regulation of junction dynamics in the testis and the specific areas that require further research for a thorough understanding of the role of junction remodeling in spermatogenesis. Understanding the junction dynamics in the seminiferous epithelium may unfold new targets for non-hormonal male contraceptive development.
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Affiliation(s)
- Wing-Yee Lui
- Department of Zoology, The University of Hong Kong, Pokfulam, Hong Kong, China
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610
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Abstract
The response of a cell to the myriad of signals that it receives is varied, and it is dependent on many different factors. The most-studied responses involve growth-factor signalling and these signalling cascades have become key targets for cancer therapy. Recent reports have indicated that growth-factor receptors and associated adaptors can accumulate in the nucleus. Are there novel functions for these proteins that might affect our understanding of their role in cancer and have implications for drug resistance?
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Affiliation(s)
- Charles Massie
- CRUK Uro-Oncology Group, Department of Oncology, University of Cambridge, c/o Hutchison/MRC Cancer Research Centre, Addenbrookes Hospital, Hills Road, Cambridge, CB2 2XZ, UK
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611
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Felberbaum-Corti M, Cavalli V, Gruenberg J. Capture of the small GTPase Rab5 by GDI: regulation by p38 MAP kinase. Methods Enzymol 2006; 403:367-81. [PMID: 16473603 DOI: 10.1016/s0076-6879(05)03032-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The small GTPase Rab5 is one of the key regulators of early endocytic traffic and, like other GTPases, cycles between GTP- and GDP-bound states as well as between membrane and cytosol. The latter cycle is controlled by a guanine nucleotide dissociation inhibitor (GDI), which functions as a Rab vehicle in the cytosol. GDI extracts from membranes the inactive GDP-bound form of the Rab. Then, the cytosolic GDI:Rab complex is delivered to the appropriate target membrane, where the Rab protein is reloaded, presumably via a GDI displacement factor (Pfeffer and Aivazian, 2004). We previously reported that the formation of the GDI:Rab5 complex is stimulated by the mitogen-activated protein kinase p38 (Cavalli et al., 2001). Mol. Cell7, 421-432.]. Selective activation of p38 MAPK increases endocytic rates in vivo, presumably allowing more efficient internalization of cell surface components for repair, storage, or degradation. These observations emphasize the possibility that external stimuli contribute to the regulation of membrane traffic. Here, we describe how to monitor the ability of GDI to extract Rab5 from early endosomal membranes in vitro and the role of p38 MAPK in this process. In addition, we detail how to investigate the possible role of p38 MAPK in the regulation of endocytosis in vivo.
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612
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Hasse S, Ungewickell EJ, Groos S. Clathrin and clathrin-accessory proteins in rat kidney cortex epithelia. Histochem Cell Biol 2006; 126:219-29. [PMID: 16625367 DOI: 10.1007/s00418-006-0169-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/06/2006] [Indexed: 10/24/2022]
Abstract
Several vectorial transport routes in mammalian cells involve clathrin and associated proteins. In kidney epithelia urine production requires numerous transport processes. However, only little is known about the distribution of clathrin and its associated proteins in this organ in situ. We now report on the presence and distribution of clathrin and its accessory proteins AP1, AP2, Eps15, Epsin, CALM and Clint/EpsinR in the epithelia of the rat kidney cortex using immunoblotting, immunofluorescence and immuno-electron microscopy. Our data show that all investigated proteins are ubiquitously present in rat kidney cortex epithelia, however, with distinct distribution patterns. In the renal corpuscle, podocytes showed the most conspicuous labelling. Clathrin, AP2 and CALM were highly expressed in foot processes, while AP1 was primarily localized in the cell body. In the proximal tubule all proteins were present in dots along the plasma membrane and most conspicuous below the brush border. However, clathrin and AP2 co-localized in vesicle subtypes distinct from those containing clathrin and AP1. In the distal tubule and in the cortical collecting duct all proteins were found in the apex of the cells; however, AP1 and Clint/EpsinR showed additional staining in perinuclear dots. The occurrence and distribution of the investigated proteins in kidney epithelia are discussed with respect to their possible involvement in the functions of the specific nephron segment.
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Affiliation(s)
- Sabine Hasse
- Department of Cell Biology, OE 4130, Center of Anatomy, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
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613
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Marchetti M, Monier MN, Fradagrada A, Mitchell K, Baychelier F, Eid P, Johannes L, Lamaze C. Stat-mediated signaling induced by type I and type II interferons (IFNs) is differentially controlled through lipid microdomain association and clathrin-dependent endocytosis of IFN receptors. Mol Biol Cell 2006; 17:2896-909. [PMID: 16624862 PMCID: PMC1483027 DOI: 10.1091/mbc.e06-01-0076] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Type I (alpha/beta) and type II (gamma) interferons (IFNs) bind to distinct receptors, although they activate the same signal transducer and activator of transcription, Stat1, raising the question of how signal specificity is maintained. Here, we have characterized the sorting of IFN receptors (IFN-Rs) at the plasma membrane and the role it plays in IFN-dependent signaling and biological activities. We show that both IFN-alpha and IFN-gamma receptors are internalized by a classical clathrin- and dynamin-dependent endocytic pathway. Although inhibition of clathrin-dependent endocytosis blocked the uptake of IFN-alpha and IFN-gamma receptors, this inhibition only affected IFN-alpha-induced Stat1 and Stat2 signaling. Furthermore, the antiviral and antiproliferative activities induced by IFN-alpha but not IFN-gamma were also affected. Finally, we show that, unlike IFN-alpha receptors, activated IFN-gamma receptors rapidly become enriched in plasma membrane lipid microdomains. We conclude that IFN-R compartmentalization at the plasma membrane, through clathrin-dependent endocytosis and lipid-based microdomains, plays a critical role in the signaling and biological responses induced by IFNs and contributes to establishing specificity within the Jak/Stat signaling pathway.
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Affiliation(s)
- Marta Marchetti
- *Laboratoire Trafic et Signalisation, UMR144 Curie/CNRS, Institut Curie, 75248 Paris Cedex 05, France; and
| | - Marie-Noelle Monier
- *Laboratoire Trafic et Signalisation, UMR144 Curie/CNRS, Institut Curie, 75248 Paris Cedex 05, France; and
| | - Alexandre Fradagrada
- *Laboratoire Trafic et Signalisation, UMR144 Curie/CNRS, Institut Curie, 75248 Paris Cedex 05, France; and
| | - Keith Mitchell
- *Laboratoire Trafic et Signalisation, UMR144 Curie/CNRS, Institut Curie, 75248 Paris Cedex 05, France; and
| | | | - Pierre Eid
- Laboratoire d’Oncologie Virale, CNRS-UPR 9045, 94801 Villejuif, France
| | - Ludger Johannes
- *Laboratoire Trafic et Signalisation, UMR144 Curie/CNRS, Institut Curie, 75248 Paris Cedex 05, France; and
| | - Christophe Lamaze
- *Laboratoire Trafic et Signalisation, UMR144 Curie/CNRS, Institut Curie, 75248 Paris Cedex 05, France; and
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614
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Murphy LO, Blenis J. MAPK signal specificity: the right place at the right time. Trends Biochem Sci 2006; 31:268-75. [PMID: 16603362 DOI: 10.1016/j.tibs.2006.03.009] [Citation(s) in RCA: 527] [Impact Index Per Article: 29.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2006] [Revised: 03/06/2006] [Accepted: 03/24/2006] [Indexed: 10/24/2022]
Abstract
Although the mechanisms that lead to activation of the Ras, extracellular-signal-regulated kinase mitogen-activated protein kinase (Ras/ERK-MAPK) signaling pathway have been studied intensively, the fundamental principles that determine how activation of ERK signaling can result in distinct biological outcomes have only recently received attention. Factors such as cell-surface receptor density, expression of scaffolding proteins, the surrounding extracellular matrix, and the interplay between kinases and phosphatases modulate the strength and duration of ERK signaling. Furthermore, the spatial distribution and temporal qualities of ERK can markedly alter the qualitative and quantitative features of downstream signaling to immediate early genes (IEG) and the expression of IEG-encoded protein products. As a result, IEG products provide a molecular interpretation of ERK dynamics, enabling the cell to program an appropriate biological response.
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Affiliation(s)
- Leon O Murphy
- Developmental and Molecular Pathways, Novartis Institutes for BioMedical Research, 250 Massachusetts Avenue, Cambridge, MA 02139, USA
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615
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Rapaport D, Auerbach W, Naslavsky N, Pasmanik-Chor M, Galperin E, Fein A, Caplan S, Joyner AL, Horowitz M. Recycling to the plasma membrane is delayed in EHD1 knockout mice. Traffic 2006; 7:52-60. [PMID: 16445686 DOI: 10.1111/j.1600-0854.2005.00359.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
EHD1 is a member of the EHD family that contains four mammalian homologs. Among the invertebrate orthologs are a single Drosophila and Caenorhabditis elegans proteins and two plant members. They all contain three modules, a N-terminal domain that contains nucleotide-binding motifs, a central coiled-coil domain involved in oligomerization and a C-terminal region that harbors the EH domain. Studies in C. elegans and EHD1 depletion by RNA interference in human cells have demonstrated that it regulates recycling of membrane proteins. We addressed the physiological role of EHD1 through its inactivation in the mouse. Ehd1 knockout mice were indistinguishable from normal mice, had a normal life span and showed no histological abnormalities. Analysis of transferrin uptake in Ehd1(-/-) embryonic fibroblasts demonstrated delayed recycling to the plasma membrane with accumulation of transferrin in the endocytic recycling compartment. Our results corroborate the established role of EHD1 in the exit of membrane proteins from recycling endosomes in vivo in a mouse model.
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Affiliation(s)
- Debora Rapaport
- Department of Cell Research and Immunology, Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Israel
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616
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Franco M, Furstoss O, Simon V, Benistant C, Hong WJ, Roche S. The adaptor protein Tom1L1 is a negative regulator of Src mitogenic signaling induced by growth factors. Mol Cell Biol 2006; 26:1932-47. [PMID: 16479011 PMCID: PMC1430241 DOI: 10.1128/mcb.26.5.1932-1947.2006] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Src family of protein-tyrosine kinases (SFK) play important roles in mitogenesis and morphological changes induced by growth factors. The involved substrates are, however, ill defined. Using an antiphosphotyrosine antibody to screen tyrosine-phosphorylated cDNA expression library, we have identified Tom1L1, an adaptor protein of the Tom1 family and a novel substrate and activator of the SFK. Surprisingly, we found that Tom1L1 does not promote DNA synthesis induced by Src. Furthermore, we report that Tom1L1 negatively regulates SFK mitogenic signaling induced by platelet-derived growth factor (PDGF) through modulation of SFK-receptor association: (i) Tom1L1 inhibits DNA synthesis induced by PDGF; (ii) inhibition is overcome by c-myc expression or p53 inactivation, two regulators of SFK mitogenic function; (iii) Src or Fyn coexpression overrides Tom1L1 mitogenic activity; (iv) overexpression of the adaptor reduces Src association with the receptor; and (v) protein inactivation potentiates receptor complex formation, allowing increased SFK activation and DNA synthesis. However, Tom1L1 affects neither DNA synthesis induced by the constitutively active allele SrcY527F nor SFK-regulated actin assembly induced by PDGF. Finally, overexpressed Tom1 and Tom1L2 also associate with Src and affected mitogenic signaling in agreement with some redundancy among members of the Tom1 family. We concluded that Tom1L1 defines a novel mechanism for regulation of SFK mitogenic signaling induced by growth factors.
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Affiliation(s)
- Mélanie Franco
- CRBM, CNRS FRE2593, 1919 Route de Mende, 34293 Montpellier Cedex 05, France.
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617
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Chen CL, Huang SS, Huang JS. Cellular Heparan Sulfate Negatively Modulates Transforming Growth Factor-β1 (TGF-β1) Responsiveness in Epithelial Cells. J Biol Chem 2006; 281:11506-14. [PMID: 16492675 DOI: 10.1074/jbc.m512821200] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cell-surface proteoglycans have been shown to modulate transforming growth factor (TGF)-beta responsiveness in epithelial cells and other cell types. However, the proteoglycan (heparan sulfate or chondroitin sulfate) involved in modulation of TGF-beta responsiveness and the mechanism by which it modulates TGF-beta responsiveness remain unknown. Here we demonstrate that TGF-beta1 induces transcriptional activation of plasminogen activator inhibitor-1 (PAI-1) and growth inhibition more potently in CHO cell mutants deficient in heparan sulfate (CHO-677 cells) than in wild-type CHO-K1 cells. 125I-TGF-beta1 affinity labeling analysis of cell-surface TGF-beta receptors reveals that CHO-K1 and CHO-677 cells exhibit low (<1) and high (>1) ratios of 125I-TGF-beta1 binding to TbetaR-II and TbetaR-I, respectively. Receptor-bound 125I-TGF-beta1 undergoes nystatin-inhibitable rapid degradation in CHO-K1 cells but not in CHO-677 cells. In Mv1Lu cells (which, like CHO-K1 cells, exhibit nystatin-inhibitable rapid degradation of receptor-bound 125I-TGF-beta1), treatment with heparitinase or a heparan sulfate biosynthesis inhibitor results in a change from a low (<1) to a high (>1) ratio of 125I-TGF-beta1 binding to TbetaR-II and TbetaR-I and enhanced TGF-beta1-induced transcriptional activation of PAI-1. Sucrose density gradient analysis indicates that a significant fraction of TbetaR-I and TbetaR-II is localized in caveolae/lipid-raft fractions in CHO-K1 and Mv1Lu cells whereas the majority of the TGF-beta receptors are localized in non-lipid-raft fractions in CHO-677 cells. These results suggest that heparan sulfate negatively modulates TGF-beta1 responsiveness by decreasing the ratio of TGF-beta1 binding to TbetaR-II and TbetaR-I, facilitating caveolae/lipid-raft-mediated endocytosis and rapid degradation of TGF-beta1, thus diminishing non-lipid-raft-mediated endocytosis and signaling of TGF-beta1 in these epithelial cells.
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Affiliation(s)
- Chun-Lin Chen
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri 63104, USA
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618
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Bonaccorsi L, Marchiani S, Ferruzzi P, Muratori M, Crescioli C, Forti G, Maggi M, Baldi E. Non-genomic effects of the androgen receptor and vitamin D agonist are involved in suppressing invasive phenotype of prostate cancer cells. Steroids 2006; 71:304-9. [PMID: 16289173 DOI: 10.1016/j.steroids.2005.09.010] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Suppression of invasive phenotype is essential in developing new therapeutic tools to treat prostate cancer (PC). Evidence indicates that androgen-dependent (AD) prostate cancer cells are characterized by a lower malignant phenotype. We have demonstrated that transfection with an androgen receptor (AR) expression vector of the androgen-independent (AI) prostate cancer cell line PC3 decreases invasion of these cells through modulation of alpha6beta4 integrin expression, indicating a genotropic effect of androgens in inhibiting invasion ability of AD PC cells. Later on, we have shown that also a non-genotropic mechanism is involved in such an effect. By using immunoconfocal fluorescent microscopy, we demonstrated that AR in PC3-AR cells co-localizes with the EGFR receptors (EGFR) in PC3-AR cells. Co-immunoprecipitation studies both in PC3-AR cells and in the AD cell line LNCaP that physiologically express both receptors, confirm the occurrence of an interaction between of the two proteins. In PC3-AR cells, we demonstrated a disruption of EGFR signalling properties (reduced EGF-induced EGFR autotransphosphorylation, reduced EGF-stimulated PI3K activity as well as EGFR-PI3K interaction) contributing to the lower invasive phenotype of these cells. In another study, we investigated the effects of a new Vitamin D analogue, BXL628, on invasion in response to KGF in the androgen-independent PC cell line DU145. We found that the compound was able to reduce proliferation and invasion of the cells in response to the growth factor. In addition, we found that KGF-induced autotransphosphorylation of KGF receptor (KGFR) and PI3K activation were suppressed after short-term (5min) pre-treatment with the analogue before addition of KGF. Collectively, these studies demonstrate that a non-genotropic effect due to a direct interaction of the androgen receptor with EGFR and to a rapid effect of a Vitamin D agonist on KGFR may disrupt signalling of GF leading to decreased tumorigenicity and a less malignant phenotype of PC cells in vitro.
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Affiliation(s)
- Lorella Bonaccorsi
- Department of Clinical Physiopathology, Andrology Unit, University of Florence, Italy
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619
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Mukherjee S, Tessema M, Wandinger-Ness A. Vesicular Trafficking of Tyrosine Kinase Receptors and Associated Proteins in the Regulation of Signaling and Vascular Function. Circ Res 2006; 98:743-56. [PMID: 16574915 DOI: 10.1161/01.res.0000214545.99387.e3] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Receptor tyrosine kinases (RTKs) play a pivotal role in the development and function of the cardiovascular system. Ligand-activated RTKs promote numerous downstream signal transduction pathways that lead to vascular permeability, as well as proliferation, migration, and differentiation of vascular endothelia and smooth muscle cells. Ligand binding also promotes internalization of the activated receptors either to downregulate the signaling via degradation of the ligand/receptor complex or to signal from endosomes. However, the outcomes of receptor internalization via clathrin-dependent or caveolar pathways and trafficking mechanisms are incompletely clarified in vascular systems. Activity modulation through endocytosis and vesicular trafficking significantly impacts downstream targets of RTKs such as endothelial nitric oxide synthase (eNOS) and VE-cadherin. RTKs and their associated targets are also transported to the nucleus, where they may directly impact nuclear signaling. Although the nuclear transport pathways are just beginning to be unraveled, it appears that endocytosis and vesicular trafficking are involved. In this review, we discuss the mechanisms by which activated RTKs and the downstream targets eNOS and VE-cadherin may be internalized and transported to various intracellular compartments. How localization and interacting proteins impact protein function and influence signaling is an important theme, as is the potential for modulating signaling through therapeutic targeting of activated receptors and components of the endocytic machinery.
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Affiliation(s)
- Sanchita Mukherjee
- Department of Pathology, University of New Mexico Health Sciences Center, Albuquerque, NM 87131-5301, USA
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620
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Szumiel I. Epidermal growth factor receptor and DNA double strand break repair: the cell's self-defence. Cell Signal 2006; 18:1537-48. [PMID: 16713182 DOI: 10.1016/j.cellsig.2006.03.010] [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] [Received: 02/24/2006] [Accepted: 03/21/2006] [Indexed: 01/27/2023]
Abstract
The purpose of this review is to discuss the relation between the repair of DNA double strand breaks (DSB)--the main lethal lesion inflicted by ionising radiation-and the function of receptors of epidermal growth factor (EGFR) and similar ligands (other members of the ERBB family). The reviewed experimental data support the assumption that in mammalian cells, one consequence of EGFR/ERBB activation by X-rays is its internalisation and nuclear translocation together with DNA-dependent protein kinase (DNA-PK) subunits present in lipid rafts or cytoplasm. The effect of EGFR/ERBB stimulation on DSB rejoining would be due to an increase in the nuclear content of DNA-PK subunits and hence, in activity increase of the DNA-PK dependent non-homologous end-joining (D-NHEJ) system. Such mechanism explains the radiosensitising action of "membrane-active drugs", hypertonic media, and other agents that affect nuclear translocation of proteins. Also, one radiosensitising effect of the recently introduced into clinical practice EGFR/ERBB inhibitors would consist on counteracting the nuclear translocation of DNA-PK subunits. In result, D-NHEJ may be less active in inhibitor-treated cells and this will contribute to an enhanced lethal effect of irradiation. The reviewed observations point to a heretofore not understood mechanism of the cell's self-defence against X-rays which can be exploited in combined radio- and chemotherapy.
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Affiliation(s)
- Irena Szumiel
- Department of Radiobiology and Health Protection, Institute of Nuclear Chemistry and Technology, Dorodna 16, 03-195 Warszawa, Poland.
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621
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Shah M, Patel K, Mukhopadhyay S, Xu F, Guo G, Sehgal PB. Membrane-associated STAT3 and PY-STAT3 in the Cytoplasm. J Biol Chem 2006; 281:7302-8. [PMID: 16407171 DOI: 10.1074/jbc.m508527200] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Signal transduction from the plasma membrane to the nucleus by STAT proteins is widely represented as exclusively a soluble cytosolic process. Using cell-fractionation methods, we observed that approximately 5% of cytoplasmic STAT3 was constitutively associated with the purified early endosome (EE) fraction in human Hep3B liver cells. By 15-30 min after interleukin-6 (IL-6) treatment, up to two-thirds of cytoplasmic Tyr-phosphorylated STAT3 can be associated with the purified early endosome fraction (Rab-5-, EEA1-, transferrin receptor-, and clathrin-positive fraction). Electron microscopy, immunofluorescence, and detergent dissection approaches confirmed the association of STAT3 and PY-STAT3 with early endosomes. STAT3 was constitutively associated with clathrin heavy chain in membrane and in the 1- to 2-MDa cytosolic complexes. The membrane association was dynamic in that, within 15 min of treatment with the vicinal-thiol cross-linker phenylarsine oxide, there was a dramatic increase in bulk STAT3 association with sedimentable membranes. The functional contribution of PY-STAT3 association with the endocytic pathway was evaluated in transient transfection assays using IL-6-inducible STAT3-reporter-luciferase constructs and selective regulators of this pathway. STAT3-transcriptional activation was inhibited by expression constructs for dominant negative dynamin K44A, epsin 2a, amphiphysin A1, and clathrin light chain but enhanced by that for the active dynamin species MxA. Taken together, these studies emphasize the contribution of the endocytic pathway to productive IL-6/STAT3 signaling.
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Affiliation(s)
- Mehul Shah
- Department of Cell Biology and Anatomy, New York Medical College, Valhalla, NY 10595, USA
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622
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Mayawala K, Vlachos DG, Edwards JS. Spatial modeling of dimerization reaction dynamics in the plasma membrane: Monte Carlo vs. continuum differential equations. Biophys Chem 2006; 121:194-208. [PMID: 16504372 DOI: 10.1016/j.bpc.2006.01.008] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2006] [Accepted: 01/19/2006] [Indexed: 12/17/2022]
Abstract
Bimolecular reactions in the plasma membrane, such as receptor dimerization, are a key signaling step for many signaling systems. For receptors to dimerize, they must first diffuse until a collision happens, upon which a dimerization reaction may occur. Therefore, study of the dynamics of cell signaling on the membrane may require the use of a spatial modeling framework. Despite the availability of spatial simulation methods, e.g., stochastic spatial Monte Carlo (MC) simulation and partial differential equation (PDE) based approaches, many biological models invoke well-mixed assumptions without completely evaluating the importance of spatial organization. Whether one is to utilize a spatial or non-spatial simulation framework is therefore an important decision. In order to evaluate the importance of spatial effects a priori, i.e., without performing simulations, we have assessed the applicability of a dimensionless number, known as second Damköhler number (Da), defined here as the ratio of time scales of collision and reaction, for 2-dimensional bimolecular reactions. Our study shows that dimerization reactions in the plasma membrane with Da approximately >0.1 (tested in the receptor density range of 10(2)-10(5)/microm(2)) require spatial modeling. We also evaluated the effective reaction rate constants of MC and simple deterministic PDEs. Our simulations show that the effective reaction rate constant decreases with time due to time dependent changes in the spatial distribution of receptors. As a result, the effective reaction rate constant of simple PDEs can differ from that of MC by up to two orders of magnitude. Furthermore, we show that the fluctuations in the number of copies of signaling proteins (noise) may also depend on the diffusion properties of the system. Finally, we used the spatial MC model to explore the effect of plasma membrane heterogeneities, such as receptor localization and reduced diffusivity, on the dimerization rate. Interestingly, our simulations show that localization of epidermal growth factor receptor (EGFR) can cause the diffusion limited dimerization rate to be up to two orders of magnitude higher at higher average receptor densities reported for cancer cells, as compared to a normal cell.
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Affiliation(s)
- Kapil Mayawala
- Department of Chemical Engineering, 150 Academy Street, University of Delaware, Newark, DE 19716, USA
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623
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Hsu T, Adereth Y, Kose N, Dammai V. Endocytic function of von Hippel-Lindau tumor suppressor protein regulates surface localization of fibroblast growth factor receptor 1 and cell motility. J Biol Chem 2006; 281:12069-80. [PMID: 16505488 PMCID: PMC2367321 DOI: 10.1074/jbc.m511621200] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The tumor suppressor VHL (von Hippel-Lindau protein) serves as a negative regulator of hypoxia-inducible factor-alpha subunits. However, accumulated evidence indicates that VHL may play additional roles in other cellular functions. We report here a novel hypoxia-inducible factor-independent function of VHL in cell motility control via regulation of fibroblast growth factor receptor 1 (FGFR1) endocytosis. In VHL null tumor cells or VHL knock-down cells, FGFR1 internalization is defective, leading to surface accumulation and abnormal activation of FGFR1. The enhanced FGFR1 activity directly correlates with increased cell migration. VHL disease mutants, in two of the mutation hot spots favoring development of renal cell carcinoma, failed to rescue the above phenotype. Interestingly, surface accumulation of the chemotactic receptor appears to be selective in VHL mutant cells, since other surface proteins such as epidermal growth factor receptor, platelet-derived growth factor receptor, IGFR1, and c-Met are not affected. We demonstrate that 1) FGFR1 endocytosis is defective in the VHL mutant and is rescued by reexpression of wild-type VHL, 2) VHL is recruited to FGFR1-containing, but not EGFR-containing, endosomal vesicles, 3) VHL exhibits a functional relationship with Rab5a and dynamin 2 in FGFR1 internalization, and 4) the endocytic function of VHL is mediated through the metastasis suppressor Nm23, a protein known to regulate dynamin-dependent endocytosis.
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Affiliation(s)
- Tien Hsu
- To whom correspondence may be addressed: Dept. of Pathology and Laboratory Medicine and Hollings Cancer Center, Medical University of South Carolina, 86 Jonathan Lucas St., HCC330, Charleston, SC 29425. Tel.: 843-792-0638; Fax: 843-792-5002; E-mail:
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624
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Kalesnikoff J, Rios EJ, Chen CC, Nakae S, Zabel BA, Butcher EC, Tsai M, Tam SY, Galli SJ. RabGEF1 regulates stem cell factor/c-Kit-mediated signaling events and biological responses in mast cells. Proc Natl Acad Sci U S A 2006; 103:2659-64. [PMID: 16533754 PMCID: PMC1413845 DOI: 10.1073/pnas.0511191103] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We recently reported that RabGEF1 is a negative regulator of high-affinity Fc receptor for IgE (Fc epsilonRI)-dependent mast cell activation and that mice lacking RabGEF1 develop severe skin inflammation and increased numbers of dermal mast cells. To better understand how RabGEF1 can regulate signaling events and biological responses in mast cells, we examined the responses of bone marrow-derived cultured mast cells (BMCMCs) from wild-type (+/+) and Rabgef1 knockout (-/-) mice after stimulation with the c-Kit ligand, stem cell factor (SCF), an important regulator of mast cell development, survival, proliferation, and activation. We found that RabGEF1-deficient mast cells exhibited enhanced and prolonged activation of Ras and extracellular regulated kinase, and significantly elevated IL-6 secretion, after stimulation with SCF. SCF-induced activation of c-Jun N-terminal kinase was increased in Rabgef1-/- BMCMCs, but without corresponding significant increases in SCF-induced migration or adhesion. SCF-mediated activation of the survival-enhancing kinase, Akt, also was increased in Rabgef1-/- BMCMCs, and these cells had a survival advantage over their +/+ counterparts in vitro. Despite enhanced Ras activation in the absence of RabGEF1, SCF-induced proliferation was lower in Rabgef1-/- BMCMCs compared with their +/+ counterparts. Finally, we found that c-Kit internalization was delayed in the absence of RabGEF1, probably reflecting a positive role for RabGEF1 in the regulation of endocytic events, and that infection of Rabgef1-/- BMCMCs with a wild-type RabGEF1 lentiviral construct normalized c-Kit internalization to the levels seen in +/+ BMCMCs. Thus, RabGEF1 plays a critical role in the regulation of SCF/c-Kit-mediated signaling events and biological responses in mast cells.
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Affiliation(s)
- Janet Kalesnikoff
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305-5324
| | - Eon J. Rios
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305-5324
| | - Ching-Cheng Chen
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305-5324
| | - Susumu Nakae
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305-5324
| | - Brian A. Zabel
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305-5324
| | - Eugene C. Butcher
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305-5324
| | - Mindy Tsai
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305-5324
| | - See-Ying Tam
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305-5324
| | - Stephen J. Galli
- Department of Pathology, Stanford University School of Medicine, Stanford, CA 94305-5324
- *To whom correspondence should be addressed at:
Pathology, L-235, Stanford University School of Medicine, 300 Pasteur Drive, Stanford, CA 94305-5324. E-mail:
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625
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Li XC, Carretero OA, Navar LG, Zhuo JL. AT1 receptor-mediated accumulation of extracellular angiotensin II in proximal tubule cells: role of cytoskeleton microtubules and tyrosine phosphatases. Am J Physiol Renal Physiol 2006; 291:F375-83. [PMID: 16478976 PMCID: PMC2276851 DOI: 10.1152/ajprenal.00405.2005] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Long-term angiotensin II (ANG II) administration is associated with increased ANG II accumulation in the kidney, but intrarenal compartment(s) involved in this response remains to be determined. We tested the hypothesis that 1) extracellular ANG II is taken up by proximal tubule cells (PTCs) through AT(1) receptor-mediated endocytosis, 2) this process is regulated by cytoskeleton microtubule- and tyrosine phosphatase-dependent mechanisms, and 3) AT(1) receptor-mediated endocytosis of ANG II has a functional relevance by modulating intracellular cAMP signaling. In cultured PTCs, [(125)I]Tyr-labeled ANG II and fluorescein labeled-ANG II were internalized in a time-dependent manner and colocalized with the endosome marker Alexa Fluor 594-transferrin. Endocytosis of extracellular ANG II was inhibited by the AT(1) receptor blocker losartan (16.5 +/- 4.6%, P < 0.01 vs. ANG II, 78.3 +/- 6.2%) and by the tyrosine phosphatase inhibitor phenylarsine oxide (PAO; 30.0 +/- 3.5%, P < 0.05 vs. ANG II). Intracellular ANG II levels were increased by approximately 58% (basal, 229.8 +/- 11.4 vs. ANG II, 361.3 +/- 11.8 pg ANG II/mg protein, P < 0.01), and the responses were blocked by losartan (P < 0.01), the cytoskeleton microtubule inhibitor colchicine (P < 0.05), and PAO (P < 0.01), whereas depletion of clathrin-coated pits with hyperosmotic sucrose had no effect (356.1 +/- 25.5 pg ANG II/mg protein, not significant). ANG II accumulation was associated with significant inhibition of both basal (control, 15.5 +/- 2.8 vs. ANG II, 9.1 +/- 2.4 pmol/mg protein, P < 0.05) and forskolin-stimulated cAMP signaling (forskolin, 68.7 +/- 8.6 vs. forskolin + ANG II, 42.8 +/- 13.8 pmol/mg protein, P < 0.01). These effects were blocked by losartan and PAO. We conclude that extracellular ANG II is internalized in PTCs through AT(1) receptor-mediated endocytosis and that internalized ANG II may play a functional role in proximal tubule cells by inhibiting intracellular cAMP signaling.
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MESH Headings
- Angiotensin II/metabolism
- Angiotensin II/pharmacology
- Angiotensin II Type 1 Receptor Blockers/pharmacology
- Animals
- Arsenicals/pharmacology
- Cells, Cultured
- Colchicine/pharmacology
- Colforsin/pharmacology
- Cyclic AMP/physiology
- Cytoskeleton/drug effects
- Cytoskeleton/metabolism
- Endocytosis/physiology
- Enzyme Inhibitors/pharmacology
- Gene Expression Regulation/physiology
- Imidazoles/pharmacology
- Kidney Tubules, Proximal/cytology
- Kidney Tubules, Proximal/metabolism
- Losartan/pharmacology
- Microtubules/drug effects
- Microtubules/metabolism
- Protein Tyrosine Phosphatase, Non-Receptor Type 1
- Protein Tyrosine Phosphatases/antagonists & inhibitors
- Protein Tyrosine Phosphatases/physiology
- Pyridines/pharmacology
- Rabbits
- Receptor, Angiotensin, Type 1/drug effects
- Receptor, Angiotensin, Type 1/genetics
- Receptor, Angiotensin, Type 1/physiology
- Receptor, Angiotensin, Type 2/analysis
- Receptor, Angiotensin, Type 2/drug effects
- Receptor, Angiotensin, Type 2/genetics
- Receptor, Angiotensin, Type 2/physiology
- Signal Transduction/physiology
- Sucrose/pharmacology
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Affiliation(s)
- Xiao C Li
- Laboratory of Receptor and Signal Transduction, Division of Hypertension and Vascular Research, Henry Ford Hospital, Detroit 48202, USA
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626
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Gavutis M, Jaks E, Lamken P, Piehler J. Determination of the two-dimensional interaction rate constants of a cytokine receptor complex. Biophys J 2006; 90:3345-55. [PMID: 16473899 PMCID: PMC1432116 DOI: 10.1529/biophysj.105.072546] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ligand-receptor interactions within the plane of the plasma membrane play a pivotal role for transmembrane signaling. The biophysical principles of protein-protein interactions on lipid bilayers, though, have hardly been experimentally addressed. We have dissected the interactions involved in ternary complex formation by ligand-induced cross-linking of the subunits of the type I interferon (IFN) receptors ifnar1 and ifnar2 in vitro. The extracellular domains ifnar1-ectodomain (EC) and ifnar2-EC were tethered in an oriented manner on solid-supported lipid bilayers. The interactions of IFNalpha2 and several mutants, which exhibit different association and dissociation rate constants toward ifnar1-EC and ifnar2-EC, were monitored by simultaneous label-free detection and surface-sensitive fluorescence spectroscopy. Surface dissociation rate constants were determined by measuring ligand exchange kinetics, and by measuring receptor exchange on the surface by fluorescence resonance energy transfer. Strikingly, approximately three-times lower dissociation rate constants were observed for both receptor subunits compared to the dissociation in solution. Based on these directly determined surface-dissociation rate constants, the surface-association rate constants were assessed by probing ligand dissociation at different relative surface concentrations of the receptor subunits. In contrast to the interaction in solution, the association rate constants depended on the orientation of the receptor components. Furthermore, the large differences in association kinetics observed in solution were not detectable on the surface. Based on these results, the key roles of orientation and lateral diffusion on the kinetics of protein interactions in plane of the membrane are discussed.
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Affiliation(s)
- Martynas Gavutis
- Institute of Biochemistry, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany
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627
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Husebye H, Halaas Ø, Stenmark H, Tunheim G, Sandanger Ø, Bogen B, Brech A, Latz E, Espevik T. Endocytic pathways regulate Toll-like receptor 4 signaling and link innate and adaptive immunity. EMBO J 2006; 25:683-92. [PMID: 16467847 PMCID: PMC1383569 DOI: 10.1038/sj.emboj.7600991] [Citation(s) in RCA: 360] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2005] [Accepted: 01/13/2006] [Indexed: 12/12/2022] Open
Abstract
Immune responses are initiated when molecules of microbial origin are sensed by the Toll-like receptors (TLRs). We now report the identification of essential molecular components for the trafficking of the lipopolysaccharide (LPS) receptor complex. LPS was endocytosed by a receptor-mediated mechanism dependent on dynamin and clathrin and colocalized with TLR4 on early/sorting endosomes. TLR4 was ubiquitinated and associated with the ubiquitin-binding endosomal sorting protein hepatocyte growth factor-regulated tyrosine kinase substrate, Hrs. Inhibition of endocytosis and endosomal sorting increased LPS signaling. Finally, the LPS receptor complex was sorted to late endosomes/lysosomes for degradation and loading of associated antigens onto HLA class II molecules for presentation to CD4+ T cells. Our results show that endosomal trafficking of the LPS receptor complex is essential for signal termination and LPS-associated antigen presentation, thus controlling both innate and adaptive immunity through TLR4.
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Affiliation(s)
- Harald Husebye
- Institute of Cancer Research and Molecular Medicine, The Norwegian University of Science and Technology, Trondheim, Norway
| | - Øyvind Halaas
- Institute of Cancer Research and Molecular Medicine, The Norwegian University of Science and Technology, Trondheim, Norway
| | - Harald Stenmark
- Institute of Cancer Research and Molecular Medicine, The Norwegian University of Science and Technology, Trondheim, Norway
- Department of Biochemistry, The Norwegian Radiumhospital, Oslo, Norway
| | - Gro Tunheim
- Institute of Immunology, Rikshospitalet University Hospital, Oslo, Norway
| | - Øystein Sandanger
- Institute of Cancer Research and Molecular Medicine, The Norwegian University of Science and Technology, Trondheim, Norway
| | - Bjarne Bogen
- Institute of Immunology, Rikshospitalet University Hospital, Oslo, Norway
| | - Andreas Brech
- Department of Biochemistry, The Norwegian Radiumhospital, Oslo, Norway
| | - Eicke Latz
- Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Terje Espevik
- Institute of Cancer Research and Molecular Medicine, The Norwegian University of Science and Technology, Trondheim, Norway
- Institute of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, 7489 Trondheim, Norway. Tel.: +47 7359 8668; Fax: +47 7359 8801; E-mail:
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628
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Ratushny AV, Likhoshvai VA. Mathematical modeling of intracellular membrane transport: Receptor-mediated endocytosis and degradation of low-density lipoproteins. Biophysics (Nagoya-shi) 2006. [DOI: 10.1134/s0006350906070190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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629
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Vaccari T, Bilder D. The Drosophila tumor suppressor vps25 prevents nonautonomous overproliferation by regulating notch trafficking. Dev Cell 2006; 9:687-98. [PMID: 16256743 DOI: 10.1016/j.devcel.2005.09.019] [Citation(s) in RCA: 295] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2005] [Revised: 09/01/2005] [Accepted: 09/29/2005] [Indexed: 01/05/2023]
Abstract
Cell-cell signaling coordinates proliferation of metazoan tissues during development, and its alteration can induce malignant transformation. Endocytosis regulates signaling by controlling the levels and activity of transmembrane receptors, both prior to and following ligand engagement. Here, we identify Vps25, a component of the ESCRT machinery that regulates endocytic sorting of signaling receptors, as an unconventional type of Drosophila tumor suppressor. vps25 mutant cells undergo autonomous neoplastic-like transformation, but they also stimulate nonautonomous cell proliferation. Endocytic trafficking defects in vps25 cells cause endosomal accumulation of the signaling receptor Notch and enhanced Notch signaling. Increased Notch activity leads to ectopic production of the mitogenic JAK-STAT pathway ligand Unpaired, which is secreted from mutant cells to induce overproliferation of the surrounding epithelium. Our data show that defects in endocytic sorting can both transform cells and, through heterotypic signaling, alter the behavior of neighboring wild-type tissue.
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Affiliation(s)
- Thomas Vaccari
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California 94720, USA
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630
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Richardson DS, Lai AZ, Mulligan LM. RET ligand-induced internalization and its consequences for downstream signaling. Oncogene 2006; 25:3206-11. [PMID: 16418724 DOI: 10.1038/sj.onc.1209349] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
RET is a receptor tyrosine kinase (RTK) with roles in cell growth, differentiation and survival. Ligand-induced activation of RET results in stimulation of multiple signal transduction pathways, including the MAP kinase/Erk and PI3 kinase/Akt pathways. However, the mechanisms governing receptor internalization and signal down- regulation have not been explored. As other RTKs are internalized through the clathrin-coated pit pathway in a ligand-dependant manner, we have investigated whether RET is internalized through a similar process. Using a highly sensitive fluorescence resonance energy transfer (FRET)-based assay, we have shown that RET is internalized from the plasma membrane in a ligand-dependant manner that requires RET kinase activity as well as the GTPase activity of the clathrin-coated vesicle scission protein dynamin 2. Further, we have demonstrated that RET colocalizes with Rab5a, a marker of clathrin-coated vesicles and early endosomes, after internalization. Finally, we demonstrated that RET internalization is required for complete activation of Erk1/2, but not for activation of Akt signaling. Our data suggest that ligand-induced internalization of RET not only plays an overall role in downregulation and termination of signaling, but also functions to traffic RET to subcellular locations where it can fully activate certain downstream signaling pathways.
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Affiliation(s)
- D S Richardson
- Department of Pathology and Molecular Medicine, Division of Cancer Biology and Genetics, Cancer Research Institute, Queen's University, Kingston, Ontario, Canada
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631
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Ceresa BP, Bahr SJ. rab7 Activity Affects Epidermal Growth Factor:Epidermal Growth Factor Receptor Degradation by Regulating Endocytic Trafficking from the Late Endosome. J Biol Chem 2006; 281:1099-106. [PMID: 16282324 DOI: 10.1074/jbc.m504175200] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The epidermal growth factor receptor (EGFR) is a member of the receptor tyrosine kinase family. Ligand (epidermal growth factor or EGF) binding to the EGFR results in the coordinated activation and integration of biochemical signaling events to mediate cell growth, migration, and differentiation. One mechanism the cell utilizes to orchestrate these events is ligand-mediated endocytosis through the canonical clathrin-mediated endocytic pathway. Identification of proteins that regulate the intracellular movement of the EGF.EGFR complex is an important first step in dissecting how specificity of EGFR signaling is conferred. We examined the role of the small molecular weight guanine nucleotide-binding protein (G-protein) rab7 as a regulator of the distal stages of the endocytic pathway. Through the transient expression of activating and inactivating mutants of rab7 in HeLa cells, we have determined that rab7 activity directly correlates with the rate of radiolabeled EGF and EGFR degradation. Furthermore, when inhibitory mutants of rab7 are expressed, the internalized EGF.EGFR complex accumulates in high-density endosomes that are characteristic of the late endocytic pathway. Thus, we conclude that rab7 regulates the endocytic trafficking of the EGF.EGFR complex by regulating its lysosomal degradation.
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Affiliation(s)
- Brian P Ceresa
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, 73190, USA.
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632
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Tang PS, Tsang ME, Lodyga M, Bai XH, Miller A, Han B, Liu M. Lipopolysaccharide accelerates caspase-independent but cathepsin B-dependent death of human lung epithelial cells. J Cell Physiol 2006; 209:457-67. [PMID: 16894574 DOI: 10.1002/jcp.20751] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Caspase-independent cell death has drawn increasing attention. In the present study, we found that lipopolysaccharide (LPS) accelerated spontaneous death of human lung epithelial A549 cells in a serum- and cell density-dependent manner: while serum starvation has been demonstrated to induce apoptosis in the same cell line, LPS-induced cell death was only observed in the presence of serum; in addition, the cell death was not observed when the cells were seeded at 10- or 100-fold lower density. The apoptotic features were demonstrated by TUNEL assay, DNA laddering and Annexin V staining. However, treatment of cells with two commonly used pan-caspase inhibitors, zVAD.fmk or BOC-D.fmk, failed to block cell death. In contrast, two cathepsin B inhibitors, Ca074-Me or N-1845, reduced cell death significantly. A time-dependent activation of cathepsin B, but not caspase 3, was observed in both control and LPS-treated cells. Although LPS did not further activate cathepsin B or its release, it increased expression and translocation of apoptosis inducing factor from mitochondria to the nucleus, and increased release of cytochrome c from mitochondria. LPS-induced cell death was significantly attenuated by either N-acetyl-L-cysteine or pyrrolidine-dithiocarbamate, both free radical scavengers. Disruption of lipid raft formation with filipin or methyl-beta-cyclodextrin also reduced apoptosis significantly, suggesting that lipid raft-dependent signaling is essential. These data imply that confluent cells undergo spontaneous cell death mediated by cathepsin B; LPS may accelerate this caspase-independent cell death through release of mitochondrial contents and reactive oxygen species.
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Affiliation(s)
- Peter S Tang
- Division of Cellular and Molecular Biology, University Health Network Toronto General Research Institute, Toronto, Ontario, Canada
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633
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Abstract
Remodeling of cell membranes takes place during motile processes such as cell migration and cell division. Defects of proteins involved in membrane dynamics, including clathrin and dynamin, disrupt cytokinesis. To understand the function of clathrin-containing structures (CCS) in cytokinesis, we have expressed a green fluorescent protein (GFP) fusion protein of clathrin light chain a (GFP-clathrin) in NRK epithelial cells and recorded images of dividing cells near the ventral surface with a spinning disk confocal microscope. Punctate GFP-CCS underwent dynamic appearance and disappearance throughout the ventral surface. Following anaphase onset, GFP-CCS between separated chromosomes migrated toward the equator and subsequently disappeared in the equatorial region. Movements outside separating chromosomes were mostly random, similar to what was observed in interphase cells. Directional movements toward the furrow were dependent on both actin filaments and microtubules, while the appearance/disappearance of CCS was dependent on actin filaments but not on microtubules. These results suggest that CCS are involved in remodeling the plasma membrane along the equator during cytokinesis. Clathrin-containing structures may also play a role in transporting signaling or structural components into the cleavage furrow.
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Affiliation(s)
- Anne K Warner
- Department of Physiology, University of Massachusetts Medical School, 377 Plantation Street, Worcester, MA 01605, USA
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634
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Abstract
This article focuses on recent findings that the type V TGF-beta receptor (TbetaR-V), which co-expresses with other TGF-beta receptors (TbetaR-I, TbetaR-II, and TbetaR-III) in all normal cell types studied, is involved in growth inhibition by IGFBP-3 and TGF-beta and that TGF-beta activity is regulated by two distinct endocytic pathways (clathrin- and caveolar/lipid-raft-mediated). TGF-beta is a potent growth inhibitor for most cell types, including epithelial and endothelial cells. The signaling by which TGF-beta controls cell proliferation is not well understood. Many lines of evidence indicate that other signaling pathways, in addition to the prominent TbetaR-I/TbetaR-II/Smad2/3/4 signaling cascade, are required for mediating TGF-beta-induced growth inhibition. Recent studies revealed that TbetaR-V, which is identical to LRP-1, mediates IGF-independent growth inhibition by IGFBP-3 and mediates TGF-beta-induced growth inhibition in concert with TbetaR-I and TbetaR-II. In addition, IRS proteins and a Ser/Thr-specific protein phosphatase(s) are involved in the TbetaR-V-mediated growth inhibitory signaling cascade. The TbetaR-V signaling cascade appears to cross-talk with the TbetaR-I/TbetaR-II, insulin receptor (IR), IGF-I receptor (IGF-IR), integrin and c-Met signaling cascades. Attenuation or loss of the TbetaR-V signaling cascade may enable carcinoma cells to escape from TGF-beta growth control and may contribute to the aggressiveness and invasiveness of these cells via promoting epithelial-to-mesenchymal transdifferentiation (EMT). Finally, the ratio of TGF-beta binding to TbetaR-II and TbetaR-I is a signal controlling TGF-beta partitioning between two distinct endocytosis pathways and resultant TGF-beta responsiveness. These recent studies have provided new insights into the molecular mechanisms underlying TGF-beta-induced cellular growth inhibition, cross-talk between the TbetaR-V and other signaling cascades, the signal that controls TGF-beta responsiveness and the role of TbetaR-V in tumorigenesis.
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Affiliation(s)
- Shuan S Huang
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri 63104, USA.
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635
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Pelkmans L. Secrets of caveolae- and lipid raft-mediated endocytosis revealed by mammalian viruses. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1746:295-304. [PMID: 16126288 DOI: 10.1016/j.bbamcr.2005.06.009] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2005] [Revised: 06/13/2005] [Accepted: 06/15/2005] [Indexed: 11/30/2022]
Abstract
In recent years, it has been unambiguously shown that caveolae and lipid rafts can internalize cargo upon stimulation by multivalent ligands, demonstrated by the infectious entry routes of certain non-enveloped viruses that bind integrins or glycosphingolipids. We currently understand little about the membrane trafficking principles of this endocytic route, but it is clear that we cannot use paradigms from classical membrane traffic. Recent evidence indicates that caveolae- and lipid raft-mediated endocytosis plays important roles in cell adhesion and anchorage-dependent cell growth, but the underlying mechanisms are not known. In this review, I will introduce new models based on current research that aims at identifying the core machinery, regulatory components and design principles of this endocytic route in order to understand its role in cellular physiology. Again, viruses are proving to be excellent tools to reach that goal.
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Affiliation(s)
- Lucas Pelkmans
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany.
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636
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Abstract
Endocytosis of transmembrane receptors largely occurs via clathrin-coated vesicles that bud from the plasma membrane and deliver their cargo to the endosomal system for recycling or degradation. PIs (phosphoinositides) control the timing and localization of endocytic membrane trafficking by recruiting adaptors and other components of the transport machinery, thereby being part of a coincidence detection system in adaptor-mediated vesicle transport. Activation of organelle- and substrate-specific PI kinases by small GTPases such as Arf (ADP-ribosylation factor) and other factors may result in local changes of PI content, thereby regulating activity-dependent endocytic events including the recycling of synaptic vesicle membranes at nerve terminals. One such example is the PtdIns(4)P 5-kinase-mediated formation of PI(4,5)P2 [PtdIns(4,5)P2], which is required for the exo- and endo-cytic cycling of presynaptic vesicles and secretory granules. Over the last few years, protein X-ray crystallography in combination with biochemical and cell biological assays has been used to investigate the structure and function of many PI-binding proteins, including protein components of the endocytic machinery. These studies have provided molecular insights into the mechanisms by which PI(4,5)P2 recruits and activates adaptor proteins and their binding partners. In this mini-review, I will discuss the pathways of PI(4,5)P2 formation and its interactions with endocytic trafficking adaptors.
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637
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Mayawala K, Vlachos DG, Edwards JS. Computational modeling reveals molecular details of epidermal growth factor binding. BMC Cell Biol 2005; 6:41. [PMID: 16318625 PMCID: PMC1322221 DOI: 10.1186/1471-2121-6-41] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2005] [Accepted: 11/30/2005] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND The ErbB family of receptors are dysregulated in a number of cancers, and the signaling pathway of this receptor family is a critical target for several anti-cancer drugs. Therefore a detailed understanding of the mechanisms of receptor activation is critical. However, despite a plethora of biochemical studies and recent single particle tracking experiments, the early molecular mechanisms involving epidermal growth factor (EGF) binding and EGF receptor (EGFR) dimerization are not as well understood. Herein, we describe a spatially distributed Monte Carlo based simulation framework to enable the simulation of in vivo receptor diffusion and dimerization. RESULTS Our simulation results are in agreement with the data from single particle tracking and biochemical experiments on EGFR. Furthermore, the simulations reveal that the sequence of receptor-receptor and ligand-receptor reaction events depends on the ligand concentration, receptor density and receptor mobility. CONCLUSION Our computer simulations reveal the mechanism of EGF binding on EGFR. Overall, we show that spatial simulation of receptor dynamics can be used to gain a mechanistic understanding of receptor activation which may in turn enable improved cancer treatments in the future.
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Affiliation(s)
- Kapil Mayawala
- Department of Chemical Engineering, University of Delaware, Newark, DE, USA
| | | | - Jeremy S Edwards
- Molecular Genetics and Microbiology, Cancer Research and Treatment Center, University of New Mexico Health Sciences Center, and Chemical and Nuclear Engineering, University of New Mexico, Albuquerque, NM, USA
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638
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Smalley MJ, Signoret N, Robertson D, Tilley A, Hann A, Ewan K, Ding Y, Paterson H, Dale TC. Dishevelled (Dvl-2) activates canonical Wnt signalling in the absence of cytoplasmic puncta. J Cell Sci 2005; 118:5279-89. [PMID: 16263761 DOI: 10.1242/jcs.02647] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Dishevelled family proteins are multidomain intracellular transducers of Wnt signals. Ectopically expressed mammalian Dishevelled 2 (Dvl-2) activates downstream signalling and localises to cytoplasmic puncta. It has been suggested that these Dvl-2-containing structures correspond to intracellular vesicles and may be involved in the Wnt signal transduction process. We report that cytoplasmic puncta are primarily formed in cells expressing Dvl-2 at high levels. Lower levels of expression can activate signalling without forming puncta. The structures do not localise with markers of the early or late endocytic pathway and time-lapse analysis demonstrates that Dvl-2 puncta move in a random fashion over short distances but do not originate from the plasma membrane. Based on our findings, we propose that Dvl-2 puncta are protein aggregates that are not required for signalling.
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Affiliation(s)
- Matthew J Smalley
- The Breakthrough Breast Cancer Research Centre, The Institute of Cancer Research, 237 Fulham Road, London, SW3 6JB UK
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639
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Lu H, Bilder D. Endocytic control of epithelial polarity and proliferation in Drosophila. Nat Cell Biol 2005; 7:1232-9. [PMID: 16258546 DOI: 10.1038/ncb1324] [Citation(s) in RCA: 245] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2005] [Accepted: 10/18/2005] [Indexed: 01/16/2023]
Abstract
Intracellular protein transport is a key factor in epithelial cell polarity. Here we report that mutations in two core components of the vesicle trafficking machinery - a syntaxin and a Rab protein - cause an expansion of the apical membrane domain of Drosophila melanogaster epithelia; this polarity defect is coupled with overproliferation to form neoplastic tumours. Surprisingly, these proteins are associated with the endocytic, and not the exocytic, pathway. The syntaxin Avalanche (Avl) localizes to early endosomes, and loss of avl results in the cellular accumulation of specific membrane proteins, including the Notch signalling receptor and the polarity determinant Crumbs (Crb). Protein accumulation results from a failure in endosomal entry and progression towards lysosomal degradation; these and other avl phenotypes are also detected in Rab5 null mutant cells. Overexpression of Crb alone is sufficient to induce overproliferation of wild-type imaginal tissue, suggesting that polarity alterations in avl and Rab5 mutants directly contribute to tumour formation. Our findings reveal a critical and specific role for endocytic traffic in the control of both apico-basal polarity and cell proliferation.
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Affiliation(s)
- Han Lu
- Department of Molecular and Cell Biology, University of California-Berkeley, 142 LSA #3200 Berkeley, CA 94720-3200 USA
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640
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Golubkov VS, Chekanov AV, Doxsey SJ, Strongin AY. Centrosomal pericentrin is a direct cleavage target of membrane type-1 matrix metalloproteinase in humans but not in mice: potential implications for tumorigenesis. J Biol Chem 2005; 280:42237-41. [PMID: 16251193 DOI: 10.1074/jbc.m510139200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Membrane type-1 matrix metalloproteinase (MT1-MMP) exhibits distinctive and important pericellular cleavage functions. Recently, we determined that MT1-MMP was trafficked to the centrosomes in the course of endocytosis. Our data suggested that the functionally important, integral, centrosomal protein, pericentrin-2, was a cleavage target of MT1-MMP in human and in canine cells and that the sequence of the cleavage sites were ALRRLLG1156 downward arrow L1157FG and ALRRLLS2068 downward arrow L2069FG, respectively. The presence of Asp-948 at the P1 position inactivated the corresponding site (ALRRLLD948-L949FGD) in murine pericentrin. To confirm that MT1-MMP itself cleaves pericentrin directly, rather than indirectly, we analyzed the cleavage of the peptides that span the MT1-MMP cleavage site. In addition, we analyzed glioma U251 cells, which co-expressed MT1-MMP with the wild type murine pericentrin and the D948G mutant. We determined that the D948G mutant that exhibited the cleavage sequence of human pericentrin was sensitive to MT1-MMP, whereas unmodified murine pericentrin was resistant to proteolysis. Taken together, our results confirm that MT1-MMP cleaves pericentrin-2 in humans but not in mice and that mouse models of cancer probably cannot be used to critically examine MT1-MMP functionality.
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Affiliation(s)
- Vladislav S Golubkov
- Cancer Research Center, The Burnham Institute for Medical Research, La Jolla, California 92037, USA
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641
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Zaas DW, Duncan M, Rae Wright J, Abraham SN. The role of lipid rafts in the pathogenesis of bacterial infections. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1746:305-13. [PMID: 16289370 DOI: 10.1016/j.bbamcr.2005.10.003] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2005] [Revised: 10/09/2005] [Accepted: 10/11/2005] [Indexed: 12/22/2022]
Abstract
Numerous pathogens have evolved mechanisms of co-opting normal host endocytic machinery as a means of invading host cells. While numerous pathogens have been known to enter cells via traditional clathrin-coated pit endocytosis, a growing number of viral and bacterial pathogens have been recognized to invade host cells via clustered lipid rafts. This review focuses on several bacterial pathogens that have evolved several different mechanisms of co-opting clustered lipid rafts to invade host cells. Although these bacteria have diverse clinical presentations and many differences in their pathogenesis, they each depend on the integrity of clustered lipid rafts for their intracellular survival. Bacterial invasion via clustered lipid rafts has been recognized as an important virulence factor for a growing number of bacterial pathogens in their battle against host defenses.
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Affiliation(s)
- David W Zaas
- Duke University Medical Center, Box 3221, Jones Building Room 255, Research Drive, Durham, NC 27710, USA.
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642
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Abstract
Cellular movement from one place to another is regulated by various guidance cues. The precise perception of these signals in the three-dimensional environment of a multicellular organism is remarkably complex. Recent work is now revealing that guided cell movement also requires spatial control of signaling events by endocytic dynamics.
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Affiliation(s)
- Christine Le Roy
- Center for Systems Biology, Department of Medical Genetics and Microbiology, University of Toronto, Canada
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643
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Boyle EC, Finlay BB. Leaky guts and lipid rafts. Trends Microbiol 2005; 13:560-3. [PMID: 16253506 DOI: 10.1016/j.tim.2005.10.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2005] [Revised: 09/09/2005] [Accepted: 10/06/2005] [Indexed: 10/25/2022]
Abstract
The intestinal epithelium functions as a physical barrier separating luminal microorganisms from the underlying immune system. There is compelling evidence that several intestinal diseases are associated with the translocation of commensal bacteria across the epithelial barrier. Recent work has identified a novel mechanism by which normally non-invasive enteric bacteria breach the intestinal epithelium during periods of inflammation.
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Affiliation(s)
- Erin C Boyle
- Michael Smith Laboratories, 2185 East Mall, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
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644
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Howe CL. Modeling the signaling endosome hypothesis: why a drive to the nucleus is better than a (random) walk. Theor Biol Med Model 2005; 2:43. [PMID: 16236165 PMCID: PMC1276819 DOI: 10.1186/1742-4682-2-43] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2005] [Accepted: 10/19/2005] [Indexed: 01/01/2023] Open
Abstract
Background Information transfer from the plasma membrane to the nucleus is a universal cell biological property. Such information is generally encoded in the form of post-translationally modified protein messengers. Textbook signaling models typically depend upon the diffusion of molecular signals from the site of initiation at the plasma membrane to the site of effector function within the nucleus. However, such models fail to consider several critical constraints placed upon diffusion by the cellular milieu, including the likelihood of signal termination by dephosphorylation. In contrast, signaling associated with retrogradely transported membrane-bounded organelles such as endosomes provides a dephosphorylation-resistant mechanism for the vectorial transmission of molecular signals. We explore the relative efficiencies of signal diffusion versus retrograde transport of signaling endosomes. Results Using large-scale Monte Carlo simulations of diffusing STAT-3 molecules coupled with probabilistic modeling of dephosphorylation kinetics we found that predicted theoretical measures of STAT-3 diffusion likely overestimate the effective range of this signal. Compared to the inherently nucleus-directed movement of retrogradely transported signaling endosomes, diffusion of STAT-3 becomes less efficient at information transfer in spatial domains greater than 200 nanometers from the plasma membrane. Conclusion Our model suggests that cells might utilize two distinct information transmission paradigms: 1) fast local signaling via diffusion over spatial domains on the order of less than 200 nanometers; 2) long-distance signaling via information packets associated with the cytoskeletal transport apparatus. Our model supports previous observations suggesting that the signaling endosome hypothesis is a subset of a more general hypothesis that the most efficient mechanism for intracellular signaling-at-a-distance involves the association of signaling molecules with molecular motors that move along the cytoskeleton. Importantly, however, cytoskeletal association of membrane-bounded complexes containing ligand-occupied transmembrane receptors and downstream effector molecules provides the ability to regenerate signals at any point along the transmission path. We conclude that signaling endosomes provide unique information transmission properties relevant to all cell architectures, and we propose that the majority of relevant information transmitted from the plasma membrane to the nucleus will be found in association with organelles of endocytic origin.
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Affiliation(s)
- Charles L Howe
- Departments of Neuroscience and Neurology, Mayo Clinic College of Medicine, Guggenheim 442-C, Rochester, MN 55905, USA.
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645
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Crudden G, Chitti RE, Craven RJ. Hpr6 (heme-1 domain protein) regulates the susceptibility of cancer cells to chemotherapeutic drugs. J Pharmacol Exp Ther 2005; 316:448-55. [PMID: 16234411 DOI: 10.1124/jpet.105.094631] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Cancer cells have varying levels of susceptibility to chemotherapeutic agents, and the proteins that direct drug susceptibility are promising targets for intervention in cancer. Hpr6 (heme-1 domain protein)/PGRMC1 (progesterone receptor membrane component 1) is overexpressed in tumors, and Hpr6 is the human homolog of a budding yeast damage resistance gene called Dap1p. Cells lacking Dap1p are damage-sensitive, and we have found that inhibition of Hpr6 expression by RNA inhibition (RNAi) increases sensitivity of breast cancer cells to chemotherapeutic drugs. Hpr6 is composed largely of a cytochrome b(5)-related heme-1 domain, and we have found that purified Hpr6 binds to heme, similar to its yeast and rodent homologues. We generated an aspartate 120-to-glycine (D120G) mutant of Hpr6 at a highly conserved site in the heme-1 domain and demonstrated that Hpr6-D120G cannot bind to heme. The Hpr6-D120G mutant was named Hpr6(hbd) for heme binding defective. We prepared an adenovirus encoding Hpr6(hbd) and found that adenovirus Hpr6(hbd) increases susceptibility of breast cancer cells to doxorubicin and camptothecin. Our findings support a model in which Hpr6, similar to its yeast homolog, binds to heme and regulates susceptibility to damaging agents.
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Affiliation(s)
- Gerard Crudden
- Department of Molecular and Biomedical Pharmacology, Markey Cancer Center, MS-305 University of Kentucky Medical Center, Lexington, KY 40536-0298, USA
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646
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Cayuela JM, Rousselot P, Nicolini F, Espinouse D, Ollagnier C, Bui-Thi MH, Chabane K, Raffoux E, Callet-Bauchu E, Tigaud I, Magaud JP, Hayette S. Identification of a rare e8a2 BCR-ABL fusion gene in three novel chronic myeloid leukemia patients treated with imatinib. Leukemia 2005; 19:2334-6. [PMID: 16224485 DOI: 10.1038/sj.leu.2403986] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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647
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Azmi P, Seth A. RNF11 is a multifunctional modulator of growth factor receptor signalling and transcriptional regulation. Eur J Cancer 2005; 41:2549-60. [PMID: 16226459 DOI: 10.1016/j.ejca.2005.08.020] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Our laboratory has found that the 154aa RING finger protein 11 (RNF11), has modular domains and motifs including a RING-H2 finger domain, a PY motif, an ubiquitin interacting motif (UIM), a 14-3-3 binding sequence and an AKT phosphorylation site. RNF11 represents a unique protein with no other known immediate family members yet described. Comparative genetic analysis has shown that RNF11 is highly conserved throughout evolution. This may indicate a conserved and non-redundant role for the RNF11 protein. Molecular binding assays using RNF11 have shown that RNF11 has important roles in growth factor signalling, ubiquitination and transcriptional regulation. RNF11 has been shown to interact with HECT-type E3 ubiquitin ligases Nedd4, AIP4, Smurf1 and Smurf2, as well as with Cullin1, the core protein in the multi-subunit SCF E3 ubiquitin ligase complex. Work done in our laboratory has shown that RNF11 is capable of antagonizing Smurf2-mediated inhibition of TGFbeta signalling. Furthermore, RNF11 is capable of degrading AMSH, a positive regulator of both TGFbeta and EGFR signalling pathways. Recently, we have found that RNF11 can directly enhance TGFbeta signalling through a direct association with Smad4, the common signal transducer and transcription factor in the TGFbeta, BMP, and Activin pathways. Through its association with Smad4 and other transcription factors, RNF11 may have a role in direct transcriptional regulation. Our laboratory and others have found nearly 80 protein interactions for RNF11, placing RNF11 at the cross-roads of cell signalling and transcriptional regulation. RNF11 is highly expressed in breast tumours. Deregulation of RNF11 function may prove to be harmful to patient therapeutic outcomes. RNF11 may therefore provide a novel target for cancer therapeutics. The purpose of this review is to discuss the role of RNF11 in cell signalling and transcription factor modulation with special attention given to the ubiquitin-proteasomal pathway, TGFbeta pathway and EGFR pathway.
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Affiliation(s)
- Peter Azmi
- Department of Anatomic Pathology and Division of Molecular and Cellular Biology, Sunnybrook and Women's College Health Sciences Centre, 2075 Bayview Avenue, Toronto, Ontario, Canada M4N 3M5
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648
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Jozic D, Cárdenes N, Deribe YL, Moncalián G, Hoeller D, Groemping Y, Dikic I, Rittinger K, Bravo J. Cbl promotes clustering of endocytic adaptor proteins. Nat Struct Mol Biol 2005; 12:972-9. [PMID: 16228008 DOI: 10.1038/nsmb1000] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2005] [Accepted: 09/13/2005] [Indexed: 11/09/2022]
Abstract
The ubiquitin ligases c-Cbl and Cbl-b play a crucial role in receptor downregulation by mediating multiple monoubiquitination of receptors and promoting their sorting for lysosomal degradation. Their function is modulated through interactions with regulatory proteins including CIN85 and PIX, which recognize a proline-arginine motif in Cbl and thus promote or inhibit receptor endocytosis. We report the structures of SH3 domains of CIN85 and beta-PIX in complex with a proline-arginine peptide from Cbl-b. Both structures reveal a heterotrimeric complex containing two SH3 domains held together by a single peptide. Trimerization also occurs in solution and is facilitated by the pseudo-symmetrical peptide sequence. Moreover, ternary complexes of CIN85 and Cbl are formed in vivo and are important for the ability of Cbl to promote epidermal growth factor receptor (EGFR) downregulation. These results provide molecular explanations for a novel mechanism by which Cbl controls receptor downregulation.
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Affiliation(s)
- Daniela Jozic
- Division of Protein Structure, National Institute for Medical Research, The Ridgeway, London NW7 1AA, UK
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649
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Nakatani Y, Konishi H, Vassilev A, Kurooka H, Ishiguro K, Sawada JI, Ikura T, Korsmeyer SJ, Qin J, Herlitz AM. p600, a unique protein required for membrane morphogenesis and cell survival. Proc Natl Acad Sci U S A 2005; 102:15093-8. [PMID: 16214886 PMCID: PMC1247991 DOI: 10.1073/pnas.0507458102] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
In this article, we identify and characterize p600, a unique 600-kDa retinoblastoma protein- and calmodulin-binding protein. In the nucleus, p600 and retinoblastoma protein seem to act as a chromatin scaffold. In the cytoplasm, p600 and clathrin form a meshwork structure, which could contribute to cytoskeletal organization and membrane morphogenesis. Reduced expression of p600 with interference RNA abrogates integrin-mediated ruffled membrane formation and, furthermore, prevents activation of integrin-mediated survival pathways. Consequently, knockdown of p600 sensitizes cells to apoptosis induced by cell detachment. These findings provide mechanistic insight into the regulation of membrane-proximal events in tumorigenesis.
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Affiliation(s)
- Yoshihiro Nakatani
- Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA.
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650
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Brignatz C, Restouin A, Bonello G, Olive D, Collette Y. Evidences for ubiquitination and intracellular trafficking of LAT, the linker of activated T cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1746:108-15. [PMID: 16236370 DOI: 10.1016/j.bbamcr.2005.08.009] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2004] [Revised: 08/19/2005] [Accepted: 08/23/2005] [Indexed: 11/28/2022]
Abstract
Current evidences indicate that T cells use protein sorting and degradation to control duration and specificity of T cell receptor (TcR) signalling, including the CD3zeta chain which is ubiquitinated upon TcR triggering. In a previous study, we showed that the Linker of activated T cells (LAT) is present at the plasma membrane and in transferrin-labelled intracellular compartments also containing the CD3zeta chain. Here we show that LAT protein levels are tightly regulated in Jurkat lymphoid T cells likely involving proteasome-dependent degradation, recycling through trans-Golgi/endosome compartments and clathrin-dependent internalisation. We further identify a novel post-translational modification of LAT by ubiquitination that is likely to influence LAT protein stability, intracellular localisation and/or recycling. Our results provide novel molecular and regulatory insights into the function of LAT adapter protein in T cell signalling.
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Affiliation(s)
- C Brignatz
- UMR599, Institut de Cancérologie, 27 Boulevard Lei Roure, 13009 Marseille, France
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