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Sluzalska KD, Slawski J, Sochacka M, Lampart A, Otlewski J, Zakrzewska M. Intracellular partners of fibroblast growth factors 1 and 2 - implications for functions. Cytokine Growth Factor Rev 2020; 57:93-111. [PMID: 32475760 DOI: 10.1016/j.cytogfr.2020.05.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Revised: 05/04/2020] [Accepted: 05/07/2020] [Indexed: 01/01/2023]
Abstract
Fibroblast growth factors 1 and 2 (FGF1 and FGF2) are mainly considered as ligands of surface receptors through which they regulate a broad spectrum of biological processes. They are secreted in non-canonical way and, unlike other growth factors, they are able to translocate from the endosome to the cell interior. These unique features, as well as the role of the intracellular pool of FGF1 and FGF2, are far from being fully understood. An increasing number of reports address this problem, focusing on the intracellular interactions of FGF1 and 2. Here, we summarize the current state of knowledge of the FGF1 and FGF2 binding partners inside the cell and the possible role of these interactions. The partner proteins are grouped according to their function, including proteins involved in secretion, cell signaling, nucleocytoplasmic transport, binding and processing of nucleic acids, ATP binding, and cytoskeleton assembly. An in-depth analysis of the network of these binding partners could indicate novel, non-classical functions of FGF1 and FGF2 and uncover an additional level of a fine control of the well-known FGF-regulated cellular processes.
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Affiliation(s)
- Katarzyna Dominika Sluzalska
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, ul. F. Joliot-Curie 14a, 50-383 Wroclaw, Poland
| | - Jakub Slawski
- Department of Biophysics, Faculty of Biotechnology, University of Wroclaw, ul. F. Joliot-Curie 14a, 50-383 Wroclaw, Poland
| | - Martyna Sochacka
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, ul. F. Joliot-Curie 14a, 50-383 Wroclaw, Poland
| | - Agata Lampart
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, ul. F. Joliot-Curie 14a, 50-383 Wroclaw, Poland
| | - Jacek Otlewski
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, ul. F. Joliot-Curie 14a, 50-383 Wroclaw, Poland
| | - Malgorzata Zakrzewska
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, ul. F. Joliot-Curie 14a, 50-383 Wroclaw, Poland.
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2
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PIKfyve, MTMR3 and their product PtdIns5P regulate cancer cell migration and invasion through activation of Rac1. Biochem J 2014; 461:383-90. [DOI: 10.1042/bj20140132] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
We have found that the activity of Rac1 is regulated by the lipid PtdIns5P produced by PIKfyve and MTMR3 and that the activities of these druggable enzymes are important for cancer cell migration and invasion.
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Haugsten EM, Brech A, Liestøl K, Norman JC, Wesche J. Photoactivation approaches reveal a role for Rab11 in FGFR4 recycling and signalling. Traffic 2014; 15:665-83. [PMID: 24589086 DOI: 10.1111/tra.12168] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Revised: 02/25/2014] [Accepted: 03/03/2014] [Indexed: 12/24/2022]
Abstract
Fibroblast growth factor receptor 4 (FGFR4) plays important roles during development and in the adult to maintain tissue homeostasis. Moreover, overexpression of FGFR4 or activating mutations in FGFR4 has been identified as tumour-promoting events in several forms of cancer. Endocytosis is important for regulation of signalling receptors and we have previously shown that FGFR4 is mainly localized to transferrin-positive structures after ligand-induced endocytosis. Here, using a cell line with a defined pericentriolar endocytic recycling compartment, we show that FGFR4 accumulates in this compartment after endocytosis. Furthermore, using classical recycling assays and a new, photoactivatable FGFR4-PA-GFP fusion protein combined with live-cell imaging, we demonstrate that recycling of FGFR4 is dependent on Rab11. Upon Rab11b depletion, FGFR4 is trapped in the pericentriolar recycling compartment and the total levels of FGFR4 in cells are increased. Moreover, fibroblast growth factor 1 (FGF1)-induced autophosphorylation of FGFR4 as well as phosphorylation of phospholipase C (PLC)-γ is prolonged in cells depleted of Rab11. Interestingly, the activation of mitogen-activated protein kinase and AKT pathways were not prolonged but rather reduced in Rab11-depleted cells, indicating that recycling of FGFR4 is important for the nature of its signalling output. Thus, Rab11-dependent recycling of FGFR4 maintains proper levels of FGFR4 in cells and regulates FGF1-induced FGFR4 signalling.
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Affiliation(s)
- Ellen M Haugsten
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Montebello, Oslo, 0379, Norway; Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Montebello, Oslo, 0379, Norway
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4
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Sletten T, Kostas M, Bober J, Sorensen V, Yadollahi M, Olsnes S, Tomala J, Otlewski J, Zakrzewska M, Wiedlocha A. Nucleolin regulates phosphorylation and nuclear export of fibroblast growth factor 1 (FGF1). PLoS One 2014; 9:e90687. [PMID: 24595027 PMCID: PMC3942467 DOI: 10.1371/journal.pone.0090687] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Accepted: 02/04/2014] [Indexed: 11/19/2022] Open
Abstract
Extracellular fibroblast growth factor 1 (FGF1) acts through cell surface tyrosine kinase receptors, but FGF1 can also act directly in the cell nucleus, as a result of nuclear import of endogenously produced, non-secreted FGF1 or by transport of extracellular FGF1 via endosomes and cytosol into the nucleus. In the nucleus, FGF1 can be phosphorylated by protein kinase C δ (PKCδ), and this event induces nuclear export of FGF1. To identify intracellular targets of FGF1 we performed affinity pull-down assays and identified nucleolin, a nuclear multifunctional protein, as an interaction partner of FGF1. We confirmed a direct nucleolin-FGF1 interaction by surface plasmon resonance and identified residues of FGF1 involved in the binding to be located within the heparin binding site. To assess the biological role of the nucleolin-FGF1 interaction, we studied the intracellular trafficking of FGF1. In nucleolin depleted cells, exogenous FGF1 was endocytosed and translocated to the cytosol and nucleus, but FGF1 was not phosphorylated by PKCδ or exported from the nucleus. Using FGF1 mutants with reduced binding to nucleolin and a FGF1-phosphomimetic mutant, we showed that the nucleolin-FGF1 interaction is critical for the intranuclear phosphorylation of FGF1 by PKCδ and thereby the regulation of nuclear export of FGF1.
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Affiliation(s)
- Torunn Sletten
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Norway
| | - Michal Kostas
- Department of Protein Biotechnology, Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland
| | - Joanna Bober
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland
| | - Vigdis Sorensen
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Norway
| | - Mandana Yadollahi
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Norway
| | - Sjur Olsnes
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Norway
| | - Justyna Tomala
- Department of Protein Biotechnology, Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland
| | - Jacek Otlewski
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland
| | - Malgorzata Zakrzewska
- Department of Protein Engineering, Faculty of Biotechnology, University of Wroclaw, Wroclaw, Poland
| | - Antoni Wiedlocha
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Oslo, Norway
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Norway
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Haugsten EM, Oppelt A, Wesche J. Phosphatidylinositol 5-phosphate is a second messenger important for cell migration. Commun Integr Biol 2013; 6:e25446. [PMID: 24265857 PMCID: PMC3829926 DOI: 10.4161/cib.25446] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Revised: 06/18/2013] [Accepted: 06/18/2013] [Indexed: 12/23/2022] Open
Abstract
We recently showed that production of phosphatidylinositol 5-phosphate (PtdIns5P or PI5P) upon growth factor stimulation is important for cell migration. However, it was not entirely clear if PI5P itself could be a second messenger in cell migration, or, if it was rather an intermediate for the production of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2 or PI(4,5)P2). Indeed, PI5P can be converted to PI(4,5)P2 by type II PIP4 kinases (PIP4K2s). We therefore decided to knock down PIP4K2α by siRNA to test if further conversion of PI5P to PI(4,5)P2 is important for cell migration. Even though we obtained an efficient knockdown of PIP4K2α in BJ human fibroblasts, we did not observe any change in cell velocity. Conversely, ectopic overexpression of PIP4K2α would consume PI5P to produce PI(4,5)P2 and we found that overexpressing PIP4K2α decreased cell migration speed. Taken together, the data clearly indicate that it is PI5P, and not PI(4,5)P2 produced from PI5P, that is the crucial signaling molecule in cell migration. We conclude, therefore, that PI5P is a true second messenger important for cell migration.
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Affiliation(s)
- Ellen Margrethe Haugsten
- Centre for Cancer Biomedicine; Faculty of Medicine; University of Oslo; Oslo, Norway ; Department of Biochemistry; Institute for Cancer Research; The Norwegian Radium Hospital; Oslo University Hospital; Oslo, Norway
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Oppelt A, Lobert VH, Haglund K, Mackey AM, Rameh LE, Liestøl K, Schink KO, Pedersen NM, Wenzel EM, Haugsten EM, Brech A, Rusten TE, Stenmark H, Wesche J. Production of phosphatidylinositol 5-phosphate via PIKfyve and MTMR3 regulates cell migration. EMBO Rep 2012; 14:57-64. [PMID: 23154468 DOI: 10.1038/embor.2012.183] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Revised: 10/24/2012] [Accepted: 10/26/2012] [Indexed: 12/12/2022] Open
Abstract
Although phosphatidylinositol 5-phosphate (PtdIns5P) is present in many cell types and its biogenesis is increased by diverse stimuli, its precise cellular function remains elusive. Here we show that PtdIns5P levels increase when cells are stimulated to move and we find PtdIns5P to promote cell migration in tissue culture and in a Drosophila in vivo model. First, class III phosphatidylinositol 3-kinase, which produces PtdIns3P, was shown to be involved in migration of fibroblasts. In a cell migration screen for proteins containing PtdIns3P-binding motifs, we identified the phosphoinositide 5-kinase PIKfyve and the phosphoinositide 3-phosphatase MTMR3, which together constitute a phosphoinositide loop that produces PtdIns5P via PtdIns(3,5)P(2). The ability of PtdIns5P to stimulate cell migration was demonstrated directly with exogenous PtdIns5P and a PtdIns5P-producing bacterial enzyme. Thus, the identified phosphoinositide loop defines a new role for PtdIns5P in cell migration.
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Affiliation(s)
- Angela Oppelt
- Centre for Cancer Biomedicine, Faculty of Medicine, University of Oslo, Oslo, Norway
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Fu SC, Huang HC, Horton P, Juan HF. ValidNESs: a database of validated leucine-rich nuclear export signals. Nucleic Acids Res 2012; 41:D338-43. [PMID: 23093589 PMCID: PMC3531083 DOI: 10.1093/nar/gks936] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
ValidNESs (http://validness.ym.edu.tw/) is a new database for experimentally validated leucine-rich nuclear export signal (NES)-containing proteins. The therapeutic potential of the chromosomal region maintenance 1 (CRM1)-mediated nuclear export pathway and disease relevance of its cargo proteins has gained recognition in recent years. Unfortunately, only about one-third of known CRM1 cargo proteins are accessible in a single database since the last compilation in 2003. CRM1 cargo proteins are often recognized by a classical NES (leucine-rich NES), but this signal is notoriously difficult to predict from sequence alone. Fortunately, a recently developed prediction method, NESsential, is able to identify good candidates in some cases, enabling valuable hints to be gained by in silico prediction, but until now it has not been available through a web interface. We present ValidNESs, an integrated, up-to-date database holding 221 NES-containing proteins, combined with a web interface to prediction by NESsential.
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Affiliation(s)
- Szu-Chin Fu
- Department of Life Science, National Taiwan University, Taipei 106, Taiwan
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Zhen Y, Sørensen V, Skjerpen CS, Haugsten EM, Jin Y, Wälchli S, Olsnes S, Wiedlocha A. Nuclear Import of Exogenous FGF1 Requires the ER-Protein LRRC59 and the Importins Kpnα1 and Kpnβ1. Traffic 2012; 13:650-64. [DOI: 10.1111/j.1600-0854.2012.01341.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Revised: 02/07/2012] [Accepted: 02/09/2012] [Indexed: 01/19/2023]
Affiliation(s)
| | | | | | | | | | - Sebastien Wälchli
- Department of Immunology; Institute for Cancer Research; The Norwegian Radium Hospital; Montebello; Oslo; 0310; Norway
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Fu SC, Imai K, Horton P. Prediction of leucine-rich nuclear export signal containing proteins with NESsential. Nucleic Acids Res 2011; 39:e111. [PMID: 21705415 PMCID: PMC3167595 DOI: 10.1093/nar/gkr493] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The classical nuclear export signal (NES), also known as the leucine-rich NES, is a protein localization signal often involved in important processes such as signal transduction and cell cycle regulation. Although 15 years has passed since its discovery, limited structural information and high sequence diversity have hampered understanding of the NES. Several consensus sequences have been proposed to describe it, but they suffer from poor predictive power. On the other hand, the NetNES server provides the only computational method currently available. Although these two methods have been widely used to attempt to find the correct NES position within potential NES-containing proteins, their performance has not yet been evaluated on the basic task of identifying NES-containing proteins. We propose a new predictor, NESsential, which uses sequence derived meta-features, such as predicted disorder and solvent accessibility, in addition to primary sequence. We demonstrate that it can identify promising NES-containing candidate proteins (albeit at low coverage), but other methods cannot. We also quantitatively demonstrate that predicted disorder is a useful feature for prediction and investigate the different features of (predicted) ordered versus disordered NES's. Finally, we list 70 recently discovered NES-containing proteins, doubling the number available to the community.
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Affiliation(s)
- Szu-Chin Fu
- Department of Computational Biology, Graduate School of Frontier Science, University of Tokyo, Kashiwa 277-8561, Japan
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Zakrzewska M, Sørensen V, Jin Y, Wiedlocha A, Olsnes S. Translocation of exogenous FGF1 into cytosol and nucleus is a periodic event independent of receptor kinase activity. Exp Cell Res 2011; 317:1005-15. [DOI: 10.1016/j.yexcr.2011.01.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2010] [Revised: 12/10/2010] [Accepted: 01/03/2011] [Indexed: 10/18/2022]
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Pankiv S, Lamark T, Bruun JA, Øvervatn A, Bjørkøy G, Johansen T. Nucleocytoplasmic shuttling of p62/SQSTM1 and its role in recruitment of nuclear polyubiquitinated proteins to promyelocytic leukemia bodies. J Biol Chem 2009; 285:5941-53. [PMID: 20018885 DOI: 10.1074/jbc.m109.039925] [Citation(s) in RCA: 184] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
p62, also known as sequestosome1 (SQSTM1), A170, or ZIP, is a multifunctional protein implicated in several signal transduction pathways. p62 is induced by various forms of cellular stress, is degraded by autophagy, and acts as a cargo receptor for autophagic degradation of ubiquitinated targets. It is also suggested to shuttle ubiquitinated proteins for proteasomal degradation. p62 is commonly found in cytosolic protein inclusions in patients with protein aggregopathies, it is up-regulated in several forms of human tumors, and mutations in the gene are linked to classical adult onset Paget disease of the bone. To this end, p62 has generally been considered to be a cytosolic protein, and little attention has been paid to possible nuclear roles of this protein. Here, we present evidence that p62 shuttles continuously between nuclear and cytosolic compartments at a high rate. The protein is also found in nuclear promyelocytic leukemia bodies. We show that p62 contains two nuclear localization signals and a nuclear export signal. Our data suggest that the nucleocytoplasmic shuttling of p62 is modulated by phosphorylations at or near the most important nuclear localization signal, NLS2. The aggregation of p62 in cytosolic bodies also regulates the transport of p62 between the compartments. We found p62 to be essential for accumulation of polyubiquitinated proteins in promyelocytic leukemia bodies upon inhibition of nuclear protein export. Furthermore, p62 contributed to the assembly of proteasome-containing degradative compartments in the vicinity of nuclear aggregates containing polyglutamine-expanded Ataxin1Q84 and to the degradation of Ataxin1Q84.
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Affiliation(s)
- Serhiy Pankiv
- Molecular Cancer Research Group, Institute of Medical Biology, University of Tromsø, 9037 Tromsø, Norway
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Rivera J, Megías D, Navas C, Bravo J. Identification of essential sequences for cellular localization in BRMS1 metastasis suppressor. PLoS One 2009; 4:e6433. [PMID: 19649328 PMCID: PMC2713406 DOI: 10.1371/journal.pone.0006433] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2009] [Accepted: 06/30/2009] [Indexed: 12/15/2022] Open
Abstract
Background Breast cancer metastasis suppressor 1 (BRMS1) reduces the number and the size of secondary tumours in a mouse model without affecting the growth of the primary foci upon its re-expression. Knockdown of BRMS1 expression associates with metastasis. The molecular details on BRMS1 mechanism of action include its ability to function as a transcriptional co-repressor and consistently BRMS1 has been described as a predominantly nuclear protein. Since cellular distribution could represent a potential mechanism of regulation, we wanted to characterize BRMS1 sequence motifs that might regulate its cellular distribution. According to its amino acids sequence, BRMS1 contain two putative nuclear localization signals, however none of them has been proved to work so far. Methodology/Principal Findings By using well known in vivo assays to detect both nuclear import and export signal, we have characterized, in the present study, one functional nuclear localisation signal as necessary and sufficient to promote nuclear transport. Additionally, the outcome of a directed yeast two-hybrid assay identify importin α6 as a specific partner of BRMS1 thus speculating that BRMS1 nuclear import could be specifically mediated by the reported nuclear transporter. Besides, the combination of a computational searching approach along the utilization of a nuclear export assay, identified a functional motif within the BRMS1 sequence responsible for its nuclear export, that resulted not affected by the highly specific CRM1 inhibitor Leptomycin-B. Interspecies heterokaryon assay demonstrate the capability of BRMS1 to shuttle between the nuclear and cytosolic compartments Conclusions/Significance Our results show for the first time that BRMS1 contains both nuclear import and export signals enabling its nucleo-cytoplasmic shuttling. These findings contributes new data for the understanding of the BRMS1 functions and allow us to speculate that this phenomenon could represent a novel mechanism for regulating the activity of BRMS1 or its associated cytosolic partners
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Affiliation(s)
- José Rivera
- Signal Transduction Group, Centro Nacional de Investigaciones Oncológicas, Madrid, Spain
- * E-mail: (JR); (JB)
| | - Diego Megías
- Confocal Microscopy Unit, Centro Nacional de Investigaciones Oncológicas, Madrid, Spain
| | - Carolina Navas
- Signal Transduction Group, Centro Nacional de Investigaciones Oncológicas, Madrid, Spain
| | - Jerónimo Bravo
- Signal Transduction Group, Centro Nacional de Investigaciones Oncológicas, Madrid, Spain
- * E-mail: (JR); (JB)
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Haugsten EM, Malecki J, Bjørklund SMS, Olsnes S, Wesche J. Ubiquitination of fibroblast growth factor receptor 1 is required for its intracellular sorting but not for its endocytosis. Mol Biol Cell 2008; 19:3390-403. [PMID: 18480409 DOI: 10.1091/mbc.e07-12-1219] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Endocytosis and targeting of growth factor receptors for lysosomal degradation have been associated with ubiquitination of the intracellular part of the receptors. To elucidate the role of receptor ubiquitination in internalization and sorting of fibroblast growth factor receptor (FGFR), we constructed several mutants of FGFR1 in which lysines, potential ubiquitination sites, were substituted for arginines. Substitution of all lysine residues in the intracellular part of FGFR1 resulted in inactivation of the tyrosine kinase domain of the receptor. However, several multilysine FGFR1 mutants, where up to 26 of 29 lysines in the intracellular part of the receptor were mutated, retained tyrosine kinase activity. The active multilysine mutants were poorly ubiquitinated, but internalized normally, indicating that ubiquitination of the receptor is not required for endocytosis. In contrast, degradation of the multilysine mutants was dramatically reduced as the mutants were inefficiently transported to lysosomes but rather sorted to recycling endosomes. The altered sorting resulted in sustained signaling. The duration of FGFR1 signaling seems to be tightly regulated by receptor ubiquitination and subsequent sorting to the lysosomes for degradation.
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Affiliation(s)
- Ellen Margrethe Haugsten
- Centre for Cancer Biomedicine, Faculty Division Norwegian Radium Hospital, University of Oslo, 0310 Oslo, Norway
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14
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Phosphorylation of fibroblast growth factor (FGF) receptor 1 at Ser777 by p38 mitogen-activated protein kinase regulates translocation of exogenous FGF1 to the cytosol and nucleus. Mol Cell Biol 2008; 28:4129-41. [PMID: 18411303 DOI: 10.1128/mcb.02117-07] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Exogenous fibroblast growth factor 1 (FGF1) signals through activation of transmembrane FGF receptors (FGFRs) but may also regulate cellular processes after translocation to the cytosol and nucleus of target cells. Translocation of FGF1 occurs across the limiting membrane of intracellular vesicles and is a regulated process that depends on the C-terminal tail of the FGFR. Here, we report that translocation of FGF1 requires activity of the alpha isoform of p38 mitogen-activated protein kinase (MAPK). FGF1 translocation was inhibited after chemical inhibition of p38 MAPK or after small interfering RNA knockdown of p38alpha. Translocation was increased after stimulation of p38 MAPK with anisomycin, mannitol, or H2O2. The activity level of p38 MAPK was not found to affect endocytosis or intracellular sorting of FGF1/FGFR1. Instead, we found that p38 MAPK regulates FGF1 translocation by phosphorylation of FGFR1 at Ser777. The FGFR1 mutation S777A abolished FGF1 translocation, while phospho-mimetic mutations of Ser777 to Asp or Glu allowed translocation to take place and bypassed the requirement for active p38 MAPK. Ser777 in FGFR1 was directly phosphorylated by p38alpha in a cell-free system. These data demonstrate a crucial role for p38alpha MAPK in the regulated translocation of exogenous FGF1 into the cytosol/nucleus, and they reveal a specific role for p38alpha MAPK-mediated serine phosphorylation of FGFR1.
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