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Backe SJ, Mollapour M, Woodford MR. Saccharomyces cerevisiae as a tool for deciphering Hsp90 molecular chaperone function. Essays Biochem 2023; 67:781-795. [PMID: 36912239 PMCID: PMC10497724 DOI: 10.1042/ebc20220224] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 02/01/2023] [Accepted: 02/03/2023] [Indexed: 03/14/2023]
Abstract
Yeast is a valuable model organism for their ease of genetic manipulation, rapid growth rate, and relative similarity to higher eukaryotes. Historically, Saccharomyces cerevisiae has played a major role in discovering the function of complex proteins and pathways that are important for human health and disease. Heat shock protein 90 (Hsp90) is a molecular chaperone responsible for the stabilization and activation of hundreds of integral members of the cellular signaling network. Much important structural and functional work, including many seminal discoveries in Hsp90 biology are the direct result of work carried out in S. cerevisiae. Here, we have provided a brief overview of the S. cerevisiae model system and described how this eukaryotic model organism has been successfully applied to the study of Hsp90 chaperone function.
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Affiliation(s)
- Sarah J. Backe
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, U.S.A
- Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, U.S.A
| | - Mehdi Mollapour
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, U.S.A
- Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, U.S.A
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, U.S.A
| | - Mark R. Woodford
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, U.S.A
- Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, U.S.A
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, U.S.A
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2
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Backe SJ, Sager RA, Regan BR, Sit J, Major LA, Bratslavsky G, Woodford MR, Bourboulia D, Mollapour M. A specialized Hsp90 co-chaperone network regulates steroid hormone receptor response to ligand. Cell Rep 2022; 40:111039. [PMID: 35830801 PMCID: PMC9306012 DOI: 10.1016/j.celrep.2022.111039] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 04/25/2022] [Accepted: 06/10/2022] [Indexed: 12/29/2022] Open
Abstract
Heat shock protein-90 (Hsp90) chaperone machinery is involved in the stability and activity of its client proteins. The chaperone function of Hsp90 is regulated by co-chaperones and post-translational modifications. Although structural evidence exists for Hsp90 interaction with clients, our understanding of the impact of Hsp90 chaperone function toward client activity in cells remains elusive. Here, we dissect the impact of recently identified higher eukaryotic co-chaperones, FNIP1/2 (FNIPs) and Tsc1, toward Hsp90 client activity. Our data show that Tsc1 and FNIP2 form mutually exclusive complexes with FNIP1, and that unlike Tsc1, FNIP1/2 interact with the catalytic residue of Hsp90. Functionally, these co-chaperone complexes increase the affinity of the steroid hormone receptors glucocorticoid receptor and estrogen receptor to their ligands in vivo. We provide a model for the responsiveness of the steroid hormone receptor activation upon ligand binding as a consequence of their association with specific Hsp90:co-chaperone subpopulations.
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Affiliation(s)
- Sarah J Backe
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Rebecca A Sager
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Bethany R Regan
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, USA; College of Medicine, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Julian Sit
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, USA; College of Medicine, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Lauren A Major
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, USA; College of Medicine, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Gennady Bratslavsky
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Mark R Woodford
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Dimitra Bourboulia
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Mehdi Mollapour
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, USA.
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3
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Moesslacher CS, Kohlmayr JM, Stelzl U. Exploring absent protein function in yeast: assaying post translational modification and human genetic variation. MICROBIAL CELL (GRAZ, AUSTRIA) 2021; 8:164-183. [PMID: 34395585 PMCID: PMC8329848 DOI: 10.15698/mic2021.08.756] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 06/13/2021] [Accepted: 06/18/2021] [Indexed: 01/08/2023]
Abstract
Yeast is a valuable eukaryotic model organism that has evolved many processes conserved up to humans, yet many protein functions, including certain DNA and protein modifications, are absent. It is this absence of protein function that is fundamental to approaches using yeast as an in vivo test system to investigate human proteins. Functionality of the heterologous expressed proteins is connected to a quantitative, selectable phenotype, enabling the systematic analyses of mechanisms and specificity of DNA modification, post-translational protein modifications as well as the impact of annotated cancer mutations and coding variation on protein activity and interaction. Through continuous improvements of yeast screening systems, this is increasingly carried out on a global scale using deep mutational scanning approaches. Here we discuss the applicability of yeast systems to investigate absent human protein function with a specific focus on the impact of protein variation on protein-protein interaction modulation.
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Affiliation(s)
- Christina S Moesslacher
- Institute of Pharmaceutical Sciences and BioTechMed-Graz, University of Graz, Graz, Austria
- Contributed equally to the writing of this review
| | - Johanna M Kohlmayr
- Institute of Pharmaceutical Sciences and BioTechMed-Graz, University of Graz, Graz, Austria
- Contributed equally to the writing of this review
| | - Ulrich Stelzl
- Institute of Pharmaceutical Sciences and BioTechMed-Graz, University of Graz, Graz, Austria
- Contributed equally to the writing of this review
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4
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Corwin T, Woodsmith J, Apelt F, Fontaine JF, Meierhofer D, Helmuth J, Grossmann A, Andrade-Navarro MA, Ballif BA, Stelzl U. Defining Human Tyrosine Kinase Phosphorylation Networks Using Yeast as an In Vivo Model Substrate. Cell Syst 2019; 5:128-139.e4. [PMID: 28837810 DOI: 10.1016/j.cels.2017.08.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Revised: 05/02/2017] [Accepted: 08/03/2017] [Indexed: 12/13/2022]
Abstract
Systematic assessment of tyrosine kinase-substrate relationships is fundamental to a better understanding of cellular signaling and its profound alterations in human diseases such as cancer. In human cells, such assessments are confounded by complex signaling networks, feedback loops, conditional activity, and intra-kinase redundancy. Here we address this challenge by exploiting the yeast proteome as an in vivo model substrate. We individually expressed 16 human non-receptor tyrosine kinases (NRTKs) in Saccharomyces cerevisiae and identified 3,279 kinase-substrate relationships involving 1,351 yeast phosphotyrosine (pY) sites. Based on the yeast data without prior information, we generated a set of linear kinase motifs and assigned ∼1,300 known human pY sites to specific NRTKs. Furthermore, experimentally defined pY sites for each individual kinase were shown to cluster within the yeast interactome network irrespective of linear motif information. We therefore applied a network inference approach to predict kinase-substrate relationships for more than 3,500 human proteins, providing a resource to advance our understanding of kinase biology.
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Affiliation(s)
- Thomas Corwin
- Otto-Warburg Laboratory, Max-Planck Institute for Molecular Genetics (MPIMG), 14195 Berlin, Germany
| | - Jonathan Woodsmith
- Otto-Warburg Laboratory, Max-Planck Institute for Molecular Genetics (MPIMG), 14195 Berlin, Germany; Institute of Pharmaceutical Sciences, University of Graz and BioTechMed-Graz, 8010 Graz, Austria
| | - Federico Apelt
- Otto-Warburg Laboratory, Max-Planck Institute for Molecular Genetics (MPIMG), 14195 Berlin, Germany
| | - Jean-Fred Fontaine
- Genomics and Computational Biology, Kernel Press UG, 55128 Mainz, Germany; Faculty of Biology, Johannes Gutenberg University Mainz and Institute of Molecular Biology, 55128 Mainz, Germany
| | - David Meierhofer
- Otto-Warburg Laboratory, Max-Planck Institute for Molecular Genetics (MPIMG), 14195 Berlin, Germany
| | - Johannes Helmuth
- Otto-Warburg Laboratory, Max-Planck Institute for Molecular Genetics (MPIMG), 14195 Berlin, Germany
| | - Arndt Grossmann
- Otto-Warburg Laboratory, Max-Planck Institute for Molecular Genetics (MPIMG), 14195 Berlin, Germany
| | - Miguel A Andrade-Navarro
- Faculty of Biology, Johannes Gutenberg University Mainz and Institute of Molecular Biology, 55128 Mainz, Germany
| | - Bryan A Ballif
- Department of Biology, University of Vermont, Burlington, VT 05405, USA
| | - Ulrich Stelzl
- Otto-Warburg Laboratory, Max-Planck Institute for Molecular Genetics (MPIMG), 14195 Berlin, Germany; Institute of Pharmaceutical Sciences, University of Graz and BioTechMed-Graz, 8010 Graz, Austria.
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5
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Mercier R, Wolmarans A, Schubert J, Neuweiler H, Johnson JL, LaPointe P. The conserved NxNNWHW motif in Aha-type co-chaperones modulates the kinetics of Hsp90 ATPase stimulation. Nat Commun 2019; 10:1273. [PMID: 30894538 PMCID: PMC6426937 DOI: 10.1038/s41467-019-09299-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 03/01/2019] [Indexed: 01/19/2023] Open
Abstract
Hsp90 is a dimeric molecular chaperone that is essential for the folding and activation of hundreds of client proteins. Co-chaperone proteins regulate the ATP-driven Hsp90 client activation cycle. Aha-type co-chaperones are the most potent stimulators of the Hsp90 ATPase activity but the relationship between ATPase regulation and in vivo activity is poorly understood. We report here that the most strongly conserved region of Aha-type co-chaperones, the N terminal NxNNWHW motif, modulates the apparent affinity of Hsp90 for nucleotide substrates. The ability of yeast Aha-type co-chaperones to act in vivo is ablated when the N terminal NxNNWHW motif is removed. This work suggests that nucleotide exchange during the Hsp90 functional cycle may be more important than rate of catalysis.
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Affiliation(s)
- Rebecca Mercier
- Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, T6G 2H7, Canada
| | - Annemarie Wolmarans
- Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, T6G 2H7, Canada
| | - Jonathan Schubert
- Department of Biotechnology and Biophysics, University of Würzburg, Würzburg, 97074, Germany
| | - Hannes Neuweiler
- Department of Biotechnology and Biophysics, University of Würzburg, Würzburg, 97074, Germany
| | - Jill L Johnson
- Department of Biological Sciences and the Center for Reproductive Biology, University of Idaho, Moscow, ID, 83844, USA
| | - Paul LaPointe
- Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, T6G 2H7, Canada.
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6
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Sager RA, Woodford MR, Backe SJ, Makedon AM, Baker-Williams AJ, DiGregorio BT, Loiselle DR, Haystead TA, Zachara NE, Prodromou C, Bourboulia D, Schmidt LS, Linehan WM, Bratslavsky G, Mollapour M. Post-translational Regulation of FNIP1 Creates a Rheostat for the Molecular Chaperone Hsp90. Cell Rep 2019; 26:1344-1356.e5. [PMID: 30699359 PMCID: PMC6370319 DOI: 10.1016/j.celrep.2019.01.018] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 12/12/2018] [Accepted: 01/04/2019] [Indexed: 11/25/2022] Open
Abstract
The molecular chaperone Hsp90 stabilizes and activates client proteins. Co-chaperones and post-translational modifications tightly regulate Hsp90 function and consequently lead to activation of clients. However, it is unclear whether this process occurs abruptly or gradually in the cellular context. We show that casein kinase-2 phosphorylation of the co-chaperone folliculin-interacting protein 1 (FNIP1) on priming serine-938 and subsequent relay phosphorylation on serine-939, 941, 946, and 948 promotes its gradual interaction with Hsp90. This leads to incremental inhibition of Hsp90 ATPase activity and gradual activation of both kinase and non-kinase clients. We further demonstrate that serine/threonine protein phosphatase 5 (PP5) dephosphorylates FNIP1, allowing the addition of O-GlcNAc (O-linked N-acetylglucosamine) to the priming serine-938. This process antagonizes phosphorylation of FNIP1, preventing its interaction with Hsp90, and consequently promotes FNIP1 lysine-1119 ubiquitination and proteasomal degradation. These findings provide a mechanism for gradual activation of the client proteins through intricate crosstalk of post-translational modifications of the co-chaperone FNIP1.
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Affiliation(s)
- Rebecca A Sager
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Mark R Woodford
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Sarah J Backe
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Alan M Makedon
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Alexander J Baker-Williams
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Bryanna T DiGregorio
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - David R Loiselle
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA
| | - Timothy A Haystead
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA
| | - Natasha E Zachara
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | | | - Dimitra Bourboulia
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Laura S Schmidt
- Basic Science Program, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, Frederick, MD 21702, USA; Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | - W Marston Linehan
- Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | - Gennady Bratslavsky
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Mehdi Mollapour
- Department of Urology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA; Upstate Cancer Center, SUNY Upstate Medical University, Syracuse, NY 13210, USA.
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7
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Taskinen B, Ferrada E, Fowler DM. Early emergence of negative regulation of the tyrosine kinase Src by the C-terminal Src kinase. J Biol Chem 2017; 292:18518-18529. [PMID: 28939764 DOI: 10.1074/jbc.m117.811174] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Revised: 09/19/2017] [Indexed: 02/05/2023] Open
Abstract
Stringent regulation of tyrosine kinase activity is essential for normal cellular function. In humans, the tyrosine kinase Src is inhibited via phosphorylation of its C-terminal tail by another kinase, C-terminal Src kinase (Csk). Although Src and Csk orthologs are present across holozoan organisms, including animals and protists, the Csk-Src negative regulatory mechanism appears to have evolved gradually. For example, in choanoflagellates, Src and Csk are both active, but the negative regulatory mechanism is reportedly absent. In filastereans, a protist clade closely related to choanoflagellates, Src is active, but Csk is apparently inactive. In this study, we use a combination of bioinformatics, in vitro kinase assays, and yeast-based growth assays to characterize holozoan Src and Csk orthologs. We show that, despite appreciable differences in domain architecture, Csk from Corallochytrium limacisporum, a highly diverged holozoan marine protist, is active and can inhibit Src. However, in comparison with other Csk orthologs, Corallochytrium Csk displays broad substrate specificity and inhibits Src in an activity-independent manner. Furthermore, in contrast to previous studies, we show that Csk from the filasterean Capsaspora owczarzaki is active and that the Csk-Src negative regulatory mechanism is present in Csk and Src proteins from C. owczarzaki and the choanoflagellate Monosiga brevicollis Our results suggest that negative regulation of Src by Csk is more ancient than previously thought and that it might be conserved across all holozoan species.
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Affiliation(s)
- Barbara Taskinen
- From the Department of Genome Sciences, University of Washington, Seattle, Washington 98195-5065 and
| | - Evandro Ferrada
- From the Department of Genome Sciences, University of Washington, Seattle, Washington 98195-5065 and
| | - Douglas M Fowler
- From the Department of Genome Sciences, University of Washington, Seattle, Washington 98195-5065 and .,Department of Bioengineering, University of Washington, Seattle, Washington 98195-5065
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Advani G, Lim YC, Catimel B, Lio DSS, Ng NLY, Chüeh AC, Tran M, Anasir MI, Verkade H, Zhu HJ, Turk BE, Smithgall TE, Ang CS, Griffin M, Cheng HC. Csk-homologous kinase (Chk) is an efficient inhibitor of Src-family kinases but a poor catalyst of phosphorylation of their C-terminal regulatory tyrosine. Cell Commun Signal 2017; 15:29. [PMID: 28784162 PMCID: PMC5547543 DOI: 10.1186/s12964-017-0186-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 07/28/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND C-terminal Src kinase (Csk) and Csk-homologous kinase (Chk) are the major endogenous inhibitors of Src-family kinases (SFKs). They employ two mechanisms to inhibit SFKs. First, they phosphorylate the C-terminal tail tyrosine which stabilizes SFKs in a closed inactive conformation by engaging the SH2 domain in cis. Second, they employ a non-catalytic inhibitory mechanism involving direct binding of Csk and Chk to the active forms of SFKs that is independent of phosphorylation of their C-terminal tail. Csk and Chk are co-expressed in many cell types. Contributions of the two mechanisms towards the inhibitory activity of Csk and Chk are not fully clear. Furthermore, the determinants in Csk and Chk governing their inhibition of SFKs by the non-catalytic inhibitory mechanism are yet to be defined. METHODS We determined the contributions of the two mechanisms towards the inhibitory activity of Csk and Chk both in vitro and in transduced colorectal cancer cells. Specifically, we assayed the catalytic activities of Csk and Chk in phosphorylating a specific peptide substrate and a recombinant SFK member Src. We employed surface plasmon resonance spectroscopy to measure the kinetic parameters of binding of Csk, Chk and their mutants to a constitutively active mutant of the SFK member Hck. Finally, we determined the effects of expression of recombinant Chk on anchorage-independent growth and SFK catalytic activity in Chk-deficient colorectal cancer cells. RESULTS Our results revealed Csk as a robust enzyme catalysing phosphorylation of the C-terminal tail tyrosine of SFKs but a weak non-catalytic inhibitor of SFKs. In contrast, Chk is a poor catalyst of SFK tail phosphorylation but binds SFKs with high affinity, enabling it to efficiently inhibit SFKs with the non-catalytic inhibitory mechanism both in vitro and in transduced colorectal cancer cells. Further analyses mapped some of the determinants governing this non-catalytic inhibitory mechanism of Chk to its kinase domain. CONCLUSIONS SFKs are activated by different upstream signals to adopt multiple active conformations in cells. SFKs adopting these conformations can effectively be constrained by the two complementary inhibitory mechanisms of Csk and Chk. Furthermore, the lack of this non-catalytic inhibitory mechanism accounts for SFK overactivation in the Chk-deficient colorectal cancer cells.
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Affiliation(s)
- Gahana Advani
- Department of Biochemistry & Molecular Biology, University of Melbourne, Parkville, VIC 3010 Australia
- Bio21 Biotechnology and Molecular Science Institute, University of Melbourne, Parkville, VIC 3010 Australia
- Cell Signalling Research Laboratories, School of Biomedical Sciences, University of Melbourne, Parkville, VIC 3010 Australia
| | - Ya Chee Lim
- Department of Biochemistry & Molecular Biology, University of Melbourne, Parkville, VIC 3010 Australia
- PAP Rashidah Sa’adatul Bolkiah Institute of Health Sciences, Universiti Brunei Darussalam, Gadong, Brunei Darussalam
| | - Bruno Catimel
- Walter and Eliza Hall Institute for Medical Research and Department of Medical Biology, University of Melbourne, Parkville, VIC 3010 Australia
| | - Daisy Sio Seng Lio
- Department of Biochemistry & Molecular Biology, University of Melbourne, Parkville, VIC 3010 Australia
- Bio21 Biotechnology and Molecular Science Institute, University of Melbourne, Parkville, VIC 3010 Australia
- Cell Signalling Research Laboratories, School of Biomedical Sciences, University of Melbourne, Parkville, VIC 3010 Australia
| | - Nadia L. Y. Ng
- Department of Biochemistry & Molecular Biology, University of Melbourne, Parkville, VIC 3010 Australia
- Bio21 Biotechnology and Molecular Science Institute, University of Melbourne, Parkville, VIC 3010 Australia
- Cell Signalling Research Laboratories, School of Biomedical Sciences, University of Melbourne, Parkville, VIC 3010 Australia
| | - Anderly C. Chüeh
- Walter and Eliza Hall Institute for Medical Research and Department of Medical Biology, University of Melbourne, Parkville, VIC 3010 Australia
| | - Mai Tran
- Department of Biochemistry & Molecular Biology, University of Melbourne, Parkville, VIC 3010 Australia
- Bio21 Biotechnology and Molecular Science Institute, University of Melbourne, Parkville, VIC 3010 Australia
| | - Mohd Ishtiaq Anasir
- Department of Biochemistry & Molecular Biology, University of Melbourne, Parkville, VIC 3010 Australia
- Bio21 Biotechnology and Molecular Science Institute, University of Melbourne, Parkville, VIC 3010 Australia
| | - Heather Verkade
- Department of Biochemistry & Molecular Biology, University of Melbourne, Parkville, VIC 3010 Australia
| | - Hong-Jian Zhu
- Department of Surgery, University of Melbourne, Royal Melbourne Hospital, Parkville, VIC 3052 Australia
| | - Benjamin E. Turk
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT USA
| | - Thomas E. Smithgall
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA USA
| | - Ching-Seng Ang
- Bio21 Biotechnology and Molecular Science Institute, University of Melbourne, Parkville, VIC 3010 Australia
| | - Michael Griffin
- Department of Biochemistry & Molecular Biology, University of Melbourne, Parkville, VIC 3010 Australia
- Bio21 Biotechnology and Molecular Science Institute, University of Melbourne, Parkville, VIC 3010 Australia
| | - Heung-Chin Cheng
- Department of Biochemistry & Molecular Biology, University of Melbourne, Parkville, VIC 3010 Australia
- Bio21 Biotechnology and Molecular Science Institute, University of Melbourne, Parkville, VIC 3010 Australia
- Cell Signalling Research Laboratories, School of Biomedical Sciences, University of Melbourne, Parkville, VIC 3010 Australia
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9
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Rai DK, Lawrence P, Kloc A, Schafer E, Rieder E. Analysis of the interaction between host factor Sam68 and viral elements during foot-and-mouth disease virus infections. Virol J 2015; 12:224. [PMID: 26695943 PMCID: PMC4689063 DOI: 10.1186/s12985-015-0452-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 12/10/2015] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND The nuclear protein Src-associated protein of 68 kDa in mitosis (Sam68) is known to bind RNA and be involved in cellular processes triggered in response to environmental stresses, including virus infection. Interestingly, Sam68 is a multi-functional protein implicated in the life cycle of retroviruses and picornaviruses and is also considered a marker of virus-induced stress granules (SGs). Recently, we demonstrated the partial redistribution of Sam68 to the cytoplasm in FMDV infected cells, its interaction with viral protease 3C(pro), and found a significant reduction in viral titers as consequence of Sam68-specific siRNA knockdowns. Despite of that, details of how it benefits FMDV remains to be elucidated. METHODS Sam68 cytoplasmic localization was examined by immunofluorescent microscopy, counterstaining with antibodies against Sam68, a viral capsid protein and markers of SGs. The relevance of RAAA motifs in the IRES was investigated using electromobility shift assays with Sam68 protein and parental and mutant FMDV RNAs. In addition, full genome WT and mutant or G-luc replicon RNAs were tested following transfection in mammalian cells. The impact of Sam68 depletion to virus protein and RNA synthesis was investigated in a cell-free system. Lastly, through co-immunoprecipitation, structural modeling, and subcellular fractionation, viral protein interactions with Sam68 were explored. RESULTS FMDV-induced cytoplasmic redistribution of Sam68 resulted in it temporarily co-localizing with SG marker: TIA-1. Mutations that disrupted FMDV IRES RAAA motifs, with putative affinity to Sam68 in domain 3 and 4 cause a reduction on the formation of ribonucleoprotein complexes with this protein and resulted in non-viable progeny viruses and replication-impaired replicons. Furthermore, depletion of Sam68 in cell-free extracts greatly diminished FMDV RNA replication, which was restored by addition of recombinant Sam68. The results here demonstrated that Sam68 specifically co-precipitates with both FMDV 3D(pol) and 3C(pro) consistent with early observations of FMDV 3C(pro)-induced cleavage of Sam68. CONCLUSION We have found that Sam68 is a specific binding partner for FMDV non-structural proteins 3C(pro) and 3D(pol) and showed that mutations at RAAA motifs in IRES domains 3 and 4 cause a decrease in Sam68 affinity to these RNA elements and rendered the mutant RNA non-viable. Interestingly, in FMDV infected cells re-localized Sam68 was transiently detected along with SG markers in the cytoplasm. These results support the importance of Sam68 as a host factor co-opted by FMDV during infection and demonstrate that Sam68 interact with both, FMDV RNA motifs in the IRES and viral non-structural proteins 3C(pro) and 3D(pol).
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Affiliation(s)
- Devendra K Rai
- Foreign Animal Disease Research Unit, United States Department of Agriculture, Agricultural Research Service, Plum Island Animal Disease Center, USDA/ARS/NAA, P.O. Box 848, Greenport, NY, 11944, USA.
| | - Paul Lawrence
- Foreign Animal Disease Research Unit, United States Department of Agriculture, Agricultural Research Service, Plum Island Animal Disease Center, USDA/ARS/NAA, P.O. Box 848, Greenport, NY, 11944, USA.
| | - Anna Kloc
- Foreign Animal Disease Research Unit, United States Department of Agriculture, Agricultural Research Service, Plum Island Animal Disease Center, USDA/ARS/NAA, P.O. Box 848, Greenport, NY, 11944, USA.
| | - Elizabeth Schafer
- Foreign Animal Disease Research Unit, United States Department of Agriculture, Agricultural Research Service, Plum Island Animal Disease Center, USDA/ARS/NAA, P.O. Box 848, Greenport, NY, 11944, USA.
| | - Elizabeth Rieder
- Foreign Animal Disease Research Unit, United States Department of Agriculture, Agricultural Research Service, Plum Island Animal Disease Center, USDA/ARS/NAA, P.O. Box 848, Greenport, NY, 11944, USA.
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10
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Keenan S, Lewis PA, Wetherill SJ, Dunning CJR, Evans GJO. The N2-Src neuronal splice variant of C-Src has altered SH3 domain ligand specificity and a higher constitutive activity than N1-Src. FEBS Lett 2015; 589:1995-2000. [PMID: 26026271 PMCID: PMC4509517 DOI: 10.1016/j.febslet.2015.05.033] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Revised: 03/18/2015] [Accepted: 05/19/2015] [Indexed: 10/25/2022]
Abstract
N2-Src is a poorly understood neuronal splice variant of the ubiquitous C-Src tyrosine kinase, containing a 17 amino acid insert in its Src homology 3 (SH3) domain. To characterise the properties of N2-Src we directly compared its SH3 domain specificity and kinase activity with C- and N1-Src in vitro. N2- and N1-Src had a similar low affinity for the phosphorylation of substrates containing canonical C-Src SH3 ligands and synaptophysin, an established neuronal substrate for C-Src. N2-Src also had a higher basal kinase activity than N1- and C-Src in vitro and in cells, which could be explained by weakened intramolecular interactions. Therefore, N2-Src is a highly active kinase that is likely to phosphorylate alternative substrates to C-Src in the brain.
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Affiliation(s)
- Sarah Keenan
- Department of Biology and Hull York Medical School, University of York, Wentworth Way, York YO10 5DD, UK
| | - Philip A Lewis
- Department of Biology and Hull York Medical School, University of York, Wentworth Way, York YO10 5DD, UK
| | - Sarah J Wetherill
- Department of Biology and Hull York Medical School, University of York, Wentworth Way, York YO10 5DD, UK
| | - Christopher J R Dunning
- Department of Biology and Hull York Medical School, University of York, Wentworth Way, York YO10 5DD, UK
| | - Gareth J O Evans
- Department of Biology and Hull York Medical School, University of York, Wentworth Way, York YO10 5DD, UK.
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11
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Leonard SE, Register AC, Krishnamurty R, Brighty GJ, Maly DJ. Divergent modulation of Src-family kinase regulatory interactions with ATP-competitive inhibitors. ACS Chem Biol 2014; 9:1894-905. [PMID: 24946274 PMCID: PMC4136698 DOI: 10.1021/cb500371g] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
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Multidomain protein kinases, central
controllers of signal transduction,
use regulatory domains to modulate catalytic activity in a complex
cellular environment. Additionally, these domains regulate noncatalytic
functions, including cellular localization and protein–protein
interactions. Src-family kinases (SFKs) are promising therapeutic
targets for a number of diseases and are an excellent model for studying
the regulation of multidomain kinases. Here, we demonstrate that the
regulatory domains of the SFKs Src and Hck are divergently affected
by ligands that stabilize two distinct inactive ATP-binding site conformations.
Conformation-selective, ATP-competitive inhibitors differentially
modulate the ability of the SH3 and SH2 domains of Src and Hck to
engage in intermolecular interactions and the ability of the kinase–inhibitor
complex to undergo post-translational modification by effector enzymes.
This surprising divergence in regulatory domain behavior by two classes
of inhibitors that each stabilize inactive ATP-binding site conformations
is found to occur through perturbation or stabilization of the αC
helix. These studies provide insight into how conformation-selective,
ATP-competitive inhibitors can be designed to modulate domain interactions
and post-translational modifications distal to the ATP-binding site
of kinases.
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Affiliation(s)
- Stephen E. Leonard
- Department
of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - A. C. Register
- Department
of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Ratika Krishnamurty
- Department
of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Gabriel J. Brighty
- Department
of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Dustin J. Maly
- Department
of Chemistry, University of Washington, Seattle, Washington 98195, United States
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12
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Trible RP, Narute P, Emert-Sedlak LA, Alvarado JJ, Atkins K, Thomas L, Kodama T, Yanamala N, Korotchenko V, Day BW, Thomas G, Smithgall TE. Discovery of a diaminoquinoxaline benzenesulfonamide antagonist of HIV-1 Nef function using a yeast-based phenotypic screen. Retrovirology 2013; 10:135. [PMID: 24229420 PMCID: PMC3874621 DOI: 10.1186/1742-4690-10-135] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2013] [Accepted: 10/31/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND HIV-1 Nef is a viral accessory protein critical for AIDS progression. Nef lacks intrinsic catalytic activity and binds multiple host cell signaling proteins, including Hck and other Src-family tyrosine kinases. Nef binding induces constitutive Hck activation that may contribute to HIV pathogenesis by promoting viral infectivity, replication and downregulation of cell-surface MHC-I molecules. In this study, we developed a yeast-based phenotypic screen to identify small molecules that inhibit the Nef-Hck complex. RESULTS Nef-Hck interaction was faithfully reconstituted in yeast cells, resulting in kinase activation and growth arrest. Yeast cells expressing the Nef-Hck complex were used to screen a library of small heterocyclic compounds for their ability to rescue growth inhibition. The screen identified a dihydrobenzo-1,4-dioxin-substituted analog of 2-quinoxalinyl-3-aminobenzene-sulfonamide (DQBS) as a potent inhibitor of Nef-dependent HIV-1 replication and MHC-I downregulation in T-cells. Docking studies predicted direct binding of DQBS to Nef which was confirmed in differential scanning fluorimetry assays with recombinant purified Nef protein. DQBS also potently inhibited the replication of HIV-1 NL4-3 chimeras expressing Nef alleles representative of all M-group HIV-1 clades. CONCLUSIONS Our findings demonstrate the utility of a yeast-based growth reversion assay for the identification of small molecule Nef antagonists. Inhibitors of Nef function discovered with this assay, such as DQBS, may complement the activity of current antiretroviral therapies by enabling immune recognition of HIV-infected cells through the rescue of cell surface MHC-I.
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Affiliation(s)
- Ronald P Trible
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Bridgeside Point II, Suite 523, 15219, Pittsburgh, PA USA
| | - Purushottam Narute
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Bridgeside Point II, Suite 523, 15219, Pittsburgh, PA USA
| | - Lori A Emert-Sedlak
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Bridgeside Point II, Suite 523, 15219, Pittsburgh, PA USA
| | - John Jeff Alvarado
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Bridgeside Point II, Suite 523, 15219, Pittsburgh, PA USA
| | - Katelyn Atkins
- School of Medicine, Oregon Health and Science University, 97239, Portland, OR, USA
| | - Laurel Thomas
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Bridgeside Point II, Suite 523, 15219, Pittsburgh, PA USA
| | - Toshiaki Kodama
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Bridgeside Point II, Suite 523, 15219, Pittsburgh, PA USA
| | - Naveena Yanamala
- Department of Structural Biology, University of Pittsburgh School of Medicine, 15261, Pittsburgh, PA USA
| | - Vasiliy Korotchenko
- Department of Pharmaceutical Sciences, University of Pittsburgh School of Pharmacy, 15261, Pittsburgh, PA USA
| | - Billy W Day
- Department of Pharmaceutical Sciences, University of Pittsburgh School of Pharmacy, 15261, Pittsburgh, PA USA
| | - Gary Thomas
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Bridgeside Point II, Suite 523, 15219, Pittsburgh, PA USA
| | - Thomas E Smithgall
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Bridgeside Point II, Suite 523, 15219, Pittsburgh, PA USA
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13
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Singh MM, Howard A, Irwin ME, Gao Y, Lu X, Multani A, Chandra J. Expression and activity of Fyn mediate proliferation and blastic features of chronic myelogenous leukemia. PLoS One 2012; 7:e51611. [PMID: 23284724 PMCID: PMC3524192 DOI: 10.1371/journal.pone.0051611] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Accepted: 11/01/2012] [Indexed: 12/30/2022] Open
Abstract
The BCR-ABL1 oncogene is a tyrosine kinase that activates many signaling pathways, resulting in the induction of chronic myeloid leukemia (CML). Kinase inhibitors, such as imatinib, have been developed for the treatment of CML; however, the terminal, blast crisis phase of the disease remains a clinical challenge. Blast crisis CML is difficult to treat due to resistance to tyrosine kinase inhibitors, increased genomic instability and acquired secondary mutations. Our recent studies uncovered a role for Fyn in promoting BCR-ABL1 mediated cell growth and sensitivity to imatinib. Here we demonstrate that Fyn contributes to BCR-ABL1 induced genomic instability, a feature of blast crisis CML. Bone marrow cells and mouse embryonic fibroblasts derived from Fyn knockout mice transduced with BCR-ABL1 display slowed growth and clonogenic potential as compared to Fyn wild-type BCR-ABL1 expressing counterparts. K562 cells overexpressing constitutively active Fyn kinase were larger in size and displayed an accumulation of genomic abnormalities such as chromosomal aberrations and polyploidy. Importantly, loss of Fyn protected mouse embryonic fibroblast cells from increased number of chromosomal aberrations and fragments induced by BCR-ABL1. Together, these results reveal a novel role for Fyn in regulating events required for genomic maintenance and suggest that Fyn kinase activity plays a role in the progression of CML to blast crisis.
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MESH Headings
- Animals
- Apoptosis
- Blast Crisis/genetics
- Blast Crisis/metabolism
- Blast Crisis/pathology
- Blotting, Western
- Cell Cycle
- Cell Differentiation
- Cell Proliferation
- Cell Size
- Cells, Cultured
- Embryo, Mammalian/cytology
- Embryo, Mammalian/metabolism
- Fibroblasts/cytology
- Fibroblasts/metabolism
- Fusion Proteins, bcr-abl/genetics
- Fusion Proteins, bcr-abl/metabolism
- Genomic Instability
- Humans
- Immunoenzyme Techniques
- Immunoprecipitation
- K562 Cells
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/genetics
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/metabolism
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/pathology
- Mice
- Mice, Knockout
- Proto-Oncogene Proteins c-fyn/genetics
- Proto-Oncogene Proteins c-fyn/metabolism
- Proto-Oncogene Proteins c-fyn/physiology
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Affiliation(s)
- Melissa M. Singh
- Department of Pediatrics Research, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, United States of America
| | - Adrienne Howard
- Department of Pediatrics Research, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, United States of America
- Graduate School of Biomedical Sciences, The University of Texas at Houston Health Science Center, Houston, Texas, United States of America
| | - Mary E. Irwin
- Department of Pediatrics Research, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, United States of America
| | - Yin Gao
- Department of Pediatrics Research, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, United States of America
| | - Xiaolin Lu
- Department of Pediatrics Research, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, United States of America
| | - Asha Multani
- Molecular Cytogenetics Core Facility, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, United States of America
| | - Joya Chandra
- Department of Pediatrics Research, The University of Texas M.D. Anderson Cancer Center, Houston, Texas, United States of America
- Graduate School of Biomedical Sciences, The University of Texas at Houston Health Science Center, Houston, Texas, United States of America
- * E-mail:
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14
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Xi G, Shen X, Maile LA, Wai C, Gollahon K, Clemmons DR. Hyperglycemia enhances IGF-I-stimulated Src activation via increasing Nox4-derived reactive oxygen species in a PKCζ-dependent manner in vascular smooth muscle cells. Diabetes 2012; 61:104-13. [PMID: 22148072 PMCID: PMC3237650 DOI: 10.2337/db11-0990] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
IGF-I-stimulated sarcoma viral oncogene (Src) activation during hyperglycemia is required for propagating downstream signaling. The aim of the current study was to determine the mechanism by which hyperglycemia enhances IGF-I-stimulated Src activation and the role of NADPH oxidase 4 (Nox4) and protein kinase C ζ (PKCζ) in mediating this response in vascular smooth muscle cells (VSMCs). Nox4 expression was analyzed in VSMCs exposed to hyperglycemia. The role of Nox4-derived reactive oxygen species (ROS) in IGF-I-stimulated Src activation was investigated via knockdown of Nox4. Different isoforms of PKC were screened to investigate their role in hyperglycemia-induced Nox4. The oxidation of Src was shown to be a prerequisite for its activation in response to IGF-I during hyperglycemia. Hyperglycemia induced Nox4, but not Nox1, and p22 phagocyte oxidase (p22phox) expression and IGF-I stimulated Nox4/p22phox complex formation, leading to increased ROS generation. Knockdown of Nox4 prevented ROS generation and impaired the oxidation and activation of Src in response to IGF-I, whereas knockdown of Nox1 had no effect. PKCζ was shown to mediate the hyperglycemia-induced increase in Nox4 expression. The key observations in cultured VSMCs were confirmed in the diabetic mice. Nox4-derived ROS is responsible for the enhancing effect of hyperglycemia on IGF-I-stimulated Src activation, which in turn amplifies IGF-I-linked downstream signaling and biological actions.
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15
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Mollapour M, Tsutsumi S, Truman AW, Xu W, Vaughan CK, Beebe K, Konstantinova A, Vourganti S, Panaretou B, Piper PW, Trepel JB, Prodromou C, Pearl LH, Neckers L. Threonine 22 phosphorylation attenuates Hsp90 interaction with cochaperones and affects its chaperone activity. Mol Cell 2011; 41:672-81. [PMID: 21419342 PMCID: PMC3062913 DOI: 10.1016/j.molcel.2011.02.011] [Citation(s) in RCA: 136] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 12/10/2010] [Accepted: 01/07/2011] [Indexed: 12/30/2022]
Abstract
Heat shock protein 90 (Hsp90) is an essential molecular chaperone whose activity is regulated not only by cochaperones but also by distinct posttranslational modifications. We report here that casein kinase 2 phosphorylates a conserved threonine residue (T22) in α helix-1 of the yeast Hsp90 N-domain both in vitro and in vivo. This α helix participates in a hydrophobic interaction with the catalytic loop in Hsp90's middle domain, helping to stabilize the chaperone's ATPase-competent state. Phosphomimetic mutation of this residue alters Hsp90 ATPase activity and chaperone function and impacts interaction with the cochaperones Aha1 and Cdc37. Overexpression of Aha1 stimulates the ATPase activity, restores cochaperone interactions, and compensates for the functional defects of these Hsp90 mutants.
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Affiliation(s)
- Mehdi Mollapour
- Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, 9000 Rockville Pike, Bethesda, MD 20892, USA
| | - Shinji Tsutsumi
- Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, 9000 Rockville Pike, Bethesda, MD 20892, USA
| | - Andrew W. Truman
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, UK
| | - Wanping Xu
- Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, 9000 Rockville Pike, Bethesda, MD 20892, USA
| | - Cara K. Vaughan
- Institute of Structural and Molecular Biology, School of Crystallography, Birkbeck College, London, UK
| | - Kristin Beebe
- Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, 9000 Rockville Pike, Bethesda, MD 20892, USA
| | - Anna Konstantinova
- Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, 9000 Rockville Pike, Bethesda, MD 20892, USA
| | - Srinivas Vourganti
- Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, 9000 Rockville Pike, Bethesda, MD 20892, USA
| | - Barry Panaretou
- Pharmaceutical Science Division, King's College London, London, UK
| | - Peter W. Piper
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield, UK
| | - Jane B. Trepel
- Medical Oncology Branch, Center for Cancer Research, National Cancer Institute, 9000 Rockville Pike, Bethesda, MD 20892, USA
| | | | - Laurence H. Pearl
- Genome Damage and Stability Centre, The University of Sussex, Brighton, UK
| | - Len Neckers
- Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, 9000 Rockville Pike, Bethesda, MD 20892, USA
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16
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Xi G, Shen X, Clemmons DR. p66shc inhibits insulin-like growth factor-I signaling via direct binding to Src through its polyproline and Src homology 2 domains, resulting in impairment of Src kinase activation. J Biol Chem 2010; 285:6937-51. [PMID: 20048152 DOI: 10.1074/jbc.m109.069872] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
p66(shc) is increased in response to cell stress, and these increases regulate growth factor actions. These studies were conducted to determine how p66(shc) alters IGF-I-stimulated Src activation, leading to decreased IGF-I actions. Our results show that p66(shc) binds to Src through a polyproline sequence motif contained in the CH2 domain, a unique domain in p66(shc), and IGF-I stimulates this interaction. Disruption of this interaction using a synthetic peptide containing the p66(shc) polyproline domain or expression of a p66(shc) mutant containing substitutions for the proline residues (P47A/P48A/P50A) resulted in enhanced Src kinase activity, p52(shc) phosphorylation, MAPK activation, and cell proliferation in response to IGF-I. To determine the mechanism of inhibition, the full-length CH2 domain and intact p66(shc) were tested for their ability to directly inhibit Src kinase activation in vitro. The CH2 domain peptide was clearly inhibitory, but full-length p66(shc) had a greater effect. Deletion of the C-terminal Src homology 2 domain in p66(shc) reduced its ability to inhibit Src kinase activation. These findings demonstrate that p66(shc) utilizes a novel mechanism for modulating Src kinase activation and that this interaction is mediated through both its collagen homologous region 2 and Src homology 2 domains.
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Affiliation(s)
- Gang Xi
- Department of Medicine, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA
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17
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Trible RP, Emert-Sedlak L, Smithgall TE. HIV-1 Nef selectively activates Src family kinases Hck, Lyn, and c-Src through direct SH3 domain interaction. J Biol Chem 2006; 281:27029-38. [PMID: 16849330 PMCID: PMC2892265 DOI: 10.1074/jbc.m601128200] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nef is an HIV-1 virulence factor that promotes viral pathogenicity by altering host cell signaling pathways. Nef binds several members of the Src kinase family, and these interactions have been implicated in the pathogenesis of HIV/AIDS. However, the direct effect of Nef interaction on Src family kinase (SFK) regulation and activity has not been systematically addressed. We explored this issue using Saccharomyces cerevisiae, a well defined model system for the study of SFK regulation. Previous studies have shown that ectopic expression of c-Src arrests yeast cell growth in a kinase-dependent manner. We expressed Fgr, Fyn, Hck, Lck, Lyn, and Yes as well as c-Src in yeast and found that each kinase was active and induced growth suppression. Co-expression of the negative regulatory kinase Csk suppressed SFK activity and reversed the growth-inhibitory effect. We then co-expressed each SFK with HIV-1 Nef in the presence of Csk. Nef strongly activated Hck, Lyn, and c-Src but did not detectably affect Fgr, Fyn, Lck, or Yes. Mutagenesis of the Nef PXXP motif essential for SH3 domain binding greatly reduced the effect of Nef on Hck, Lyn, and c-Src, suggesting that Nef activates these Src family members through allosteric displacement of intramolecular SH3-linker interactions. These data show that Nef selectively activates Hck, Lyn, and c-Src among SFKs, identifying these kinases as proximal effectors of Nef signaling and potential targets for anti-HIV drug discovery.
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Affiliation(s)
- Ronald P. Trible
- Department of Molecular Genetics and Biochemistry, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Lori Emert-Sedlak
- Department of Molecular Genetics and Biochemistry, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Thomas E. Smithgall
- Department of Molecular Genetics and Biochemistry, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
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18
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Xing L, Ge C, Zeltser R, Maskevitch G, Mayer BJ, Alexandropoulos K. c-Src signaling induced by the adapters Sin and Cas is mediated by Rap1 GTPase. Mol Cell Biol 2000; 20:7363-77. [PMID: 10982853 PMCID: PMC86290 DOI: 10.1128/mcb.20.19.7363-7377.2000] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Oncogenic Src proteins have been extensively studied to gain insight into the signaling mechanisms of Src. To better understand signaling through wild-type Src, we used an approach that involves activation of Src signaling through the binding of physiologic ligands to the Src SH3 domain. To this end, we used full-length and truncated versions of the multiadapter molecules Cas and Sin to activate c-Src, and we examined the intracellular pathways that mediate Src signaling under these conditions. We show that although all proteins bind to and are phosphorylated by c-Src, quantitative differences exist in the ability of the different ligands to activate c-Src signaling. In addition, we show that Sin- and Cas-induced Src signaling, as assayed by transcriptional activation, is exclusively mediated through a pathway that involves the adapter Crk and the GTP-binding protein Rap1. These data are in contrast to previous observations showing Ras to mediate signaling downstream of transforming Src alleles. In our system, we found that signaling through the oncogenic SrcY527 mutant is indeed mediated by Ras. In addition, we found that Rap1 also mediates oncogenic Src signaling. Our results show for the first time that Rap1 mediates c-Src kinase signaling and reveal mechanistic differences in the signaling properties of wild-type and transforming Src proteins.
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Affiliation(s)
- L Xing
- Department of Pharmacology, College of Physicians and Surgeons of Columbia University, New York, New York 10032, USA
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19
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Fresno Vara JA, Carretero MV, Gerónimo H, Ballmer-Hofer K, Martín-Pérez J. Stimulation of c-Src by prolactin is independent of Jak2. Biochem J 2000; 345 Pt 1:17-24. [PMID: 10600634 PMCID: PMC1220725 DOI: 10.1042/0264-6021:3450017] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Interaction of prolactin (PRL) with its receptor (PRLR) leads to activation of Jak and Src family tyrosine kinases. The PRL/growth hormone/cytokine receptor family conserves a proline-rich sequence in the cytoplasmic juxtamembrane region (Box 1) required for association and subsequent activation of Jaks. In the present work, we studied the mechanisms underlying c-Src kinase activation by PRL and the role that Jak2 plays in this process. PRL addition to chicken embryo fibroblasts (CEF) expressing the rat PRLR long form resulted in activation of c-Src and Jak2 and in tyrosine phosphorylation of the receptor. Receptor phosphorylation was due to associated Jak2, since in cells expressing either a Box 1 mutated PRLR (PRLR(4P-A)), which is unable to interact with Jak2, or a kinase-domain-deleted Jak2 (Jak2Deltak), PRL did not stimulate receptor phosphorylation. Interestingly, addition of PRL to cells expressing PRLR(4P-A) resulted in an activation of c-Src equivalent to that observed with the wild-type receptor. These findings indicate that PRL-mediated stimulation of c-Src was independent of Jak2 activation and of receptor phosphorylation. Our results suggest that PRL-activated Src could send signals to downstream cellular targets independently of Jak2.
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Affiliation(s)
- J A Fresno Vara
- Instituto de Investigaciones Biomédicas, C.S.I.C., Arturo Duperier 4, 28029 Madrid, Spain
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20
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Nathan DF, Vos MH, Lindquist S. Identification of SSF1, CNS1, and HCH1 as multicopy suppressors of a Saccharomyces cerevisiae Hsp90 loss-of-function mutation. Proc Natl Acad Sci U S A 1999; 96:1409-14. [PMID: 9990037 PMCID: PMC15476 DOI: 10.1073/pnas.96.4.1409] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Hsp90 functions in a multicomponent chaperone system to promote the maturation and maintenance of a diverse, but specific, set of target proteins that play key roles in the regulation of cell growth and development. To identify additional components of the Hsp90 chaperone system and its targets, we searched for multicopy suppressors of various temperature-sensitive mutations in the yeast Hsp90 gene, HSP82. Three suppressors were isolated for one Hsp90 mutant (glutamate --> lysine at amino acid 381). Each exhibited a unique, allele-specific pattern of suppression with other Hsp90 mutants and had unique structural and biological properties. SSF1 is a member of an essential gene family and functions in the response to mating pheromones. CNS1 is an essential gene that encodes a component of the Hsp90 chaperone machinery. The role of HCH1 is unknown; its sequence has no strong homology to any protein of known function. SSF1 and CNS1 were weak suppressors, whereas HCH1 restored wild-type growth rates at all temperatures tested to cells expressing the E381K mutant. Overexpression of CNS1 or HCH1, but not SSF1, enhanced the maturation of a heterologous Hsp90 target protein, p60(v-src). These results suggest that like Cns1p, Hch1p is a general modulator of Hsp90 chaperone functions, whereas Ssf1p likely is either an Hsp90 target protein or functions in the same pathway as an Hsp90 target protein.
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Affiliation(s)
- D F Nathan
- Department of Molecular Genetics and Cell Biology and Howard Hughes Medical Institute, The University of Chicago, 5841 South Maryland Avenue, Chicago, IL 60637, USA
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21
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Xu Y, Singer MA, Lindquist S. Maturation of the tyrosine kinase c-src as a kinase and as a substrate depends on the molecular chaperone Hsp90. Proc Natl Acad Sci U S A 1999; 96:109-14. [PMID: 9874780 PMCID: PMC15101 DOI: 10.1073/pnas.96.1.109] [Citation(s) in RCA: 155] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/26/1998] [Indexed: 02/04/2023] Open
Abstract
Although Hsp90 displays general chaperone activity in vitro, few substrates of the chaperone have been identified in vivo, and the characteristics that render these substrates dependent on Hsp90 remain elusive. To investigate this issue, we exploited a paradoxical observation: several unrelated oncogenic viral tyrosine kinases, including v-src, attain their native conformation after association with Hsp90, yet their nearly identical cellular homologs interact only weakly with the chaperone. It has been controversial whether Hsp90 is vital for normal maturation of the cellular kinases or is simply binding a misfolded subfraction of the proteins. By modulating Hsp90 levels in Saccharomyces cerevisiae, we determined that Hsp90 is indeed necessary for the maturation of c-src (the normal homolog of v-src). c-src maturation is, however, less sensitive to Hsp90 perturbations than is v-src maturation. Dependence of the two proteins on Hsp90 does not correspond to their relative efficiency in reaching their final destination (the plasma membrane); we observed that in yeast, unlike in vertebrate cells, neither c-src nor v-src concentrate in the membrane. Expression of different v/c-src chimeras in cells carrying wild-type or temperature-sensitive Hsp90 alleles revealed that the difference between the proteins instead arises from multiple, naturally occurring mutations in the C-terminal region of v-src.
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Affiliation(s)
- Y Xu
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637, USA
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22
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Bohen SP. Genetic and biochemical analysis of p23 and ansamycin antibiotics in the function of Hsp90-dependent signaling proteins. Mol Cell Biol 1998; 18:3330-9. [PMID: 9584173 PMCID: PMC108914 DOI: 10.1128/mcb.18.6.3330] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The ubiquitous molecular chaperone Hsp90 acts in concert with a cohort of associated proteins to facilitate the functional maturation of a number of cellular signaling proteins, such as steroid hormone receptors and oncogene tyrosine kinases. The Hsp90-associated protein p23 is required for the assembly of functional steroid aporeceptor complexes in cell lysates, and Hsp90-binding ansamycin antibiotics disrupt the activity of Hsp90-dependent signaling proteins in cultured mammalian cells and prevent the association of p23 with Hsp90-receptor heterocomplexes; these observations have led to the hypotheses that p23 is required for the maturation of Hsp90 target proteins and that ansamycin antibiotics abrogate the activity of such proteins by disrupting the interaction of p23 with Hsp90. In this study, I demonstrate that ansamycin antibiotics disrupt the function of Hsp90 target proteins expressed in yeast cells; prevent the assembly of Sba1, a yeast p23-like protein, into steroid receptor-Hsp90 complexes; and result in the assembly of receptor-Hsp90 complexes that are defective for ligand binding. To assess the role of p23 in Hsp90 target protein function, I show that the activity of Hsp90 target proteins is unaffected by deletion of SBA1. Interestingly, steroid receptor activity in cells lacking Sba1 displays increased sensitivity to ansamycin antibiotics, and this phenotype is rescued by the expression of human p23 in yeast cells. These findings indicate that Hsp90-dependent signaling proteins can achieve a functional conformation in vivo in the absence of p23. Furthermore, while the presence of p23 decreases the sensitivity of Hsp90-dependent processes to ansamycin treatment, ansamycin antibiotics disrupt signaling through some mechanism other than altering the Hsp90-p23 interaction.
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Affiliation(s)
- S P Bohen
- Laboratory of Biochemistry, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892-4255, USA.
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23
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Gonfloni S, Williams JC, Hattula K, Weijland A, Wierenga RK, Superti-Furga G. The role of the linker between the SH2 domain and catalytic domain in the regulation and function of Src. EMBO J 1997; 16:7261-71. [PMID: 9405355 PMCID: PMC1170326 DOI: 10.1093/emboj/16.24.7261] [Citation(s) in RCA: 125] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The crystal structures of the regulated Src and Hck tyrosine kinases show intramolecular interactions between the phosphorylated tail and the SH2 domain as well as between the SH3 domain, the SH2-catalytic domain linker (SH2-CD linker) and the catalytic domain. The relative contribution of these interactions to regulation of activity is poorly understood. Mutational analysis of Src and Lck revealed that interaction of the SH2-CD linker with the SH3 domain is crucial for regulation. Moreover, three sites of interaction of the linker with the catalytic domain, one at the beginning (Trp260) and two at the back of the small lobe, opposite the catalytic cleft (beta2/beta3 loop; alphaC/beta4 loop), impinge on Src activity. Other activating mutations map to the front of the catalytic domain in the loop preceding the alphaC-helix (beta3/alphaC loop). SH2-CD linker mutants are deregulated in mammalian cells but transform fibroblasts weakly, suggesting that the linker may bind cellular components. Interpretation of our results on the basis of the crystal structure of Src favours a model in which the correctly positioned SH2-CD linker exerts an inhibitory function on catalysis of Src family members by facilitating displacement of the alphaC-helix. This study may provide a template for the generation of deregulated versions of other protein kinases.
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Affiliation(s)
- S Gonfloni
- European Molecular Biology Laboratory, Meyerhofstrasse 1, D-69117 Heidelberg, Germany
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24
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Nathan DF, Vos MH, Lindquist S. In vivo functions of the Saccharomyces cerevisiae Hsp90 chaperone. Proc Natl Acad Sci U S A 1997; 94:12949-56. [PMID: 9371781 PMCID: PMC24244 DOI: 10.1073/pnas.94.24.12949] [Citation(s) in RCA: 275] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
In the highly concentrated environment of the cell, polypeptide chains are prone to aggregation during synthesis (as nascent chains await the emergence of the remainder of their folding domain), translocation, assembly, and exposure to stresses that cause previously folded proteins to unfold. A large and diverse group of proteins, known as chaperones, transiently associate with such folding intermediates to prevent aggregation, but in many cases the specific functions of individual chaperones are still not clear. In vivo, Hsp90 (heat shock protein 90) plays a role in the maturation of components of signal transduction pathways but also exhibits chaperone activity with diverse proteins in vitro, suggesting a more general function. We used a unique temperature-sensitive mutant of Hsp90 in Saccharomyces cerevisiae, which rapidly and completely loses activity on shift to high temperatures, to examine the breadth of Hsp90 functions in vivo. The data suggest that Hsp90 is not required for the de novo folding of most proteins, but it is required for a specific subset of proteins that have greater difficulty reaching their native conformations. Under conditions of stress, Hsp90 does not generally protect proteins from thermal inactivation but does enhance the rate at which a heat-damaged protein is reactivated. Thus, although Hsp90 is one of the most abundant chaperones in the cell, its in vivo functions are highly restricted.
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Affiliation(s)
- D F Nathan
- Department of Molecular Genetics and Cell Biology and Howard Hughes Medical Institute, The University of Chicago, IL 60637, USA
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25
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Verderame MF. pp60v-src transformation of rat cells but not chicken cells strongly correlates with low-affinity phosphopeptide binding by the SH2 domain. Mol Biol Cell 1997; 8:843-54. [PMID: 9168470 PMCID: PMC276133 DOI: 10.1091/mbc.8.5.843] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Substrates critical for transformation by pp60v-src remain unknown, as does the precise role of the src homology 2 (SH2) domain in this process. To continue exploring the role of the SH2 domain in pp60v-src-mediated transformation, site-directed mutagenesis was used to create mutant v-src alleles predicted to encode proteins with overall structural integrity intact but with reduced ability to bind phosphotyrosine-containing peptides. Arginine-175, which makes critical contacts in the phosphotyrosine-binding pocket, was mutated to lysine or alanine. Unexpectedly, both mutations created v-src alleles that transform chicken cells with wild-type (wt) efficiency and are reduced for transformation of rat cells; these alleles are host dependent for transformation. Additionally, these alleles resulted in a round morphological transformation of chicken cells, unlike 12 of the 13 known host-dependent src SH2 mutations that result in a fusiform morphology. Analysis of phosphopeptide binding by the mutant SH2 domains reveal that the in vitro ability to bind phosphopeptides known to have a high affinity for wt src SH2 correlates with wt (round) morphological transformation in chicken cells and in vitro ability to bind phosphopeptides known to have a low affinity for wt src SH2 correlates with rat cell transformation. These results suggest that the search for critical substrates in rat cells should be among proteins that interact with pp60v-src with low affinity.
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Affiliation(s)
- M F Verderame
- Department of Medicine, College of Medicine, Pennsylvania State University, Hershey 17033, USA
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26
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Weijland A, Williams JC, Neubauer G, Courtneidge SA, Wierenga RK, Superti-Furga G. Src regulated by C-terminal phosphorylation is monomeric. Proc Natl Acad Sci U S A 1997; 94:3590-5. [PMID: 9108021 PMCID: PMC20484 DOI: 10.1073/pnas.94.8.3590] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The activity of the c-Src protein tyrosine kinase is regulated by phosphorylation of a tyrosine residue (Tyr-527) in the C-terminal tail of the molecule. Phosphorylation of Tyr-527 promotes association of the tail with the SH2 domain and a concomitant reduction of the enzymatic activity of Src. We asked the question whether regulation by C-terminal phosphorylation was accompanied by a change in the quaternary structure of the enzyme or if it occurred within a monomeric form of Src. For this purpose we purified to homogeneity a chicken Src form lacking the unique domain from Schizosaccharomyces pombe cells. The cells were engineered to express Src along with Csk, a protein kinase able to phosphorylate Tyr-527 efficiently. Mass spectrometric analysis showed that purified Src was homogeneously phosphorylated at Tyr-527. The enzyme was in the regulated form, because it could be activated by a phosphorylated peptide able to bind the SH2 domain with high affinity. Using gel filtration chromatography, dynamic light scattering, and ultracentrifugation, we found that the regulated form of Src was a monomer. We have obtained crystals diffracting to 2.4 A with space group P2(1)2(1)2(1) and one molecule per asymmetric unit, in agreement with the monomeric state. These results indicate that the structural rearrangements of regulated Src are of an intramolecular nature.
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Affiliation(s)
- A Weijland
- European Molecular Biology Laboratory, Heidelberg, Germany
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27
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Joukov V, Vihinen M, Vainikka S, Sowadski JM, Alitalo K, Bergman M. Identification of csk tyrosine phosphorylation sites and a tyrosine residue important for kinase domain structure. Biochem J 1997; 322 ( Pt 3):927-35. [PMID: 9148770 PMCID: PMC1218276 DOI: 10.1042/bj3220927] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The lack of a conserved tyrosine autophosphorylation site is a unique feature of the C-terminal Src-kinase, Csk, although this protein tyrosine kinase can be autophosphorylated on tyrosine residues in vitro and in bacteria. Here we show that human Csk is tyrosine phosphorylated in HeLa cells treated with sodium pervanadate. Phosphorylation in vivo occurs mainly at Tyr-184 and in vitro mainly at Tyr-304. A Y304F mutation strongly decreased Csk phosphorylation in vitro, and a Y184F mutation abolished tyrosine phosphorylation in vivo. A catalytically inactive form of Csk was also phosphorylated on Tyr-184 in vivo, suggesting that this is not a site of autophosphorylation. The kinase activity of the Y184F protein was not changed, while the Y304F protein showed one-third of wild-type activity. Three-dimensional modelling of the Csk kinase domain indicated that the Y304F mutation abolishes one of two conserved hydrogen bonds between the upper and the lower lobes in the open conformation of the kinase domain. Phosphopeptide binding studies suggested that phosphorylation of Tyr-184 creates a binding site for low-molecular-mass proteins. Cellular Csk was associated with several phosphoproteins, some of which were interacting with the Csk SH2 domain. Taken together these results indicate that Csk can be phosphorylated in vivo at Tyr-184 by an as yet unknown tyrosine kinase, and that autophosphorylation of Tyr-304 occurs only at abnormally high Csk concentrations in vitro. Furthermore, Tyr-304 is required for the maintenance of the structure of the Csk kinase domain.
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Affiliation(s)
- V Joukov
- Molecular/Cancer Biology Laboratory, Haartman Institute, P.O. Box 21 (Haartmaninkatu 3), FIN-00014, Finland
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28
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D'Oro U, Sakaguchi K, Appella E, Ashwell JD. Mutational analysis of Lck in CD45-negative T cells: dominant role of tyrosine 394 phosphorylation in kinase activity. Mol Cell Biol 1996; 16:4996-5003. [PMID: 8756658 PMCID: PMC231501 DOI: 10.1128/mcb.16.9.4996] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The CD45 tyrosine phosphatase has been reported to activate the src family tyrosine kinases Lck and Fyn by dephosphorylating regulatory COOH-terminal tyrosine residues 505 and 528, respectively. However, recent studies with CD45- T-cell lines have found that despite the fact that Lck and Fyn were constitutively hyperphosphorylated, the tyrosine kinase activity of both enzymes was actually increased. In the present study, phosphoamino acid analysis revealed that the increased phosphorylation of Lck in CD45- YAC-1 T cells was restricted to tyrosine residues. To understand the relationship between tyrosine phosphorylation and Lck kinase activity, CD45- YAC-1 cells were transfected with forms of Lck in which tyrosines whose phosphorylation is thought to regulate enzyme activity (Tyr-192, Tyr-394, Tyr-505, or both Tyr-394 and Tyr-505) were replaced with phenylalanine. While the Y-to-F mutation at position 192 (192-Y-->F) had little effect, the 505-Y-->F mutation increased enzymatic activity. In contrast, the 394-Y-->F mutation decreased the kinase activity to very low levels, an effect that the double mutation, 394-Y-->F and 505Y-->F, could not reverse. Phosphopeptide analysis of tryptic digests of Lck from CD45- YAC-1 cells revealed that it is hyperphosphorylated on two tyrosine residues, Tyr-505 and, to a lesser extent, Tyr-394. The purified and enzymatically active intracellular portion of CD45 dephosphorylated Lck Tyr-394 in vitro. These results demonstrate that in addition to Tyr-505, CD45 can dephosphorylate Tyr-394, and that in the absence of CD45 the hyperphosphorylation of Tyr-394 can cause an increase in the kinase activity of Lck despite the inhibitory hyperphosphorylation of Tyr-505. Therefore, Lck kinase activity is determined by the balance of activating and inhibitory tyrosine phosphorylations that are, in turn, regulated by CD45.
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Affiliation(s)
- U D'Oro
- Laboratory of Immune Cell Biology, National Cancer Institute, Bethesda, Maryland 20892, USA
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29
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Afar DE, Park H, Howell BW, Rawlings DJ, Cooper J, Witte ON. Regulation of Btk by Src family tyrosine kinases. Mol Cell Biol 1996; 16:3465-71. [PMID: 8668162 PMCID: PMC231341 DOI: 10.1128/mcb.16.7.3465] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Loss of function of Bruton's tyrosine kinase (Btk) results in X-linked immunodeficiencies characterized by a broad spectrum of signaling defects, including those dependent on Src family kinase-linked cell surface receptors. A gain-of-function mutant, Btk*, induces the growth of fibroblasts in soft agar and relieves the interleukin-5 dependence of a pre-B-cell line. To genetically define Btk signaling pathways, we used a strategy to either activate or inactivate Src family kinases in fibroblasts that express Btk*. The transformation potential of Btk* was dramatically increased by coexpression with a partly activated c-Src mutant (E-378 --> G). This synergy was further potentiated by deletion of the Btk Src homology 3 domain. Downregulation of Src family kinases by the C-terminal Src kinase (Csk) suppressed Btk* activation and biological potency. In contrast, kinase-inactive Csk (K-222 --> R), which functioned as a dominant negative molecule, synergized with Btk* in biological transformation. Activation of Btk* correlated with increased phosphotyrosine on transphosphorylation and autophosphorylation sites. These findings suggest that the Src and Btk kinase families form specific signaling units in tissues in which both are expressed.
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Affiliation(s)
- D E Afar
- Department of Microbiology, Howard Hughes Medical Institute, University of California--Los Angeles, 90095-1662, USA
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30
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Xu B, Miller WT. Src homology domains of v-Src stabilize an active conformation of the tyrosine kinase catalytic domain. Mol Cell Biochem 1996; 158:57-63. [PMID: 8791285 DOI: 10.1007/bf00225883] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
To examine the interactions between Src homology domains and the tyrosine kinase catalytic domain of v-Src, various combinations of domains have been expressed in bacteria as fusion proteins. Constructs containing the isolated catalytic domain, SH2 + catalytic domain, and SH3 + SH2 + catalytic domains were active in autophosphorylation assays. For the catalytic domain of v-Src, but not for v-Abl, addition of exogenous Src SH3-SH2 domains stimulated the autophosphorylation activity. In contrast to results for autophosphorylation, constructs containing Src homology domains were more active towards a synthetic peptide substrate than the isolated catalytic domain. The ability of the SH2 and SH3 domains of v-Src to stabilize an active enzyme conformation was also confirmed by refolding after denaturation in guanidinium hydrochloride. Collectively the data suggest that, in addition to their roles in intermolecular protein-protein interactions, the Src homology regions of v-Src exert a positive influence on tyrosine kinase function, potentially by maintaining an active conformation of the catalytic domain.
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Affiliation(s)
- B Xu
- Department of Physiology and Biophysics, School of Medicine, State University of New York at Stony Brook 11794, USA
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31
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Nathan DF, Lindquist S. Mutational analysis of Hsp90 function: interactions with a steroid receptor and a protein kinase. Mol Cell Biol 1995; 15:3917-25. [PMID: 7791797 PMCID: PMC230631 DOI: 10.1128/mcb.15.7.3917] [Citation(s) in RCA: 349] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Hsp90 is a protein chaperone whose functions are focused on a specific set of target proteins. The nature of Hsp90's interactions with these proteins is poorly understood. To provide tools for examining these interactions, we have isolated eight broadly distributed temperature-sensitive (ts) point mutations in the Hsp90 gene (HSP82) of Saccharomyces cerevisiae. The mutants fall into two distinct classes. One has a classic ts phenotype, with nearly wild-type activity at 25 degrees C and a precipitous loss of function at 34 degrees C. The remaining seven mutants, in contrast, cause a general reduction in Hsp90 function and are ts because they do not provide the high level of function required for growth at high temperatures. The effects of these mutants on two target proteins, a transcription factor (glucocorticoid receptor) and a tyrosine kinase (pp60v-src), provided several insights on Hsp90 function. First, Hsp90 is not only required to help the glucocorticoid receptor achieve a hormone-activable state, it is continuously required to maintain that state. Second, Hsp90's function in the maturation of pp60v-src involves separable roles in protein accumulation and kinase activation. Thus, Hsp90 is an integral component of both the steroid receptor and kinase signaling pathways. Finally, all eight point mutants affect the activation of both the glucocorticoid receptor and pp60v-src, indicating that Hsp90 promotes the activity of these very different target proteins through common mechanisms.
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Affiliation(s)
- D F Nathan
- Department of Molecular Genetics and Cell Biology, Howard Hughes Medical Institute, University of Chicago, Illinois 60637, USA
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32
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Stöffler HE, Ruppert C, Reinhard J, Bähler M. A novel mammalian myosin I from rat with an SH3 domain localizes to Con A-inducible, F-actin-rich structures at cell-cell contacts. J Biophys Biochem Cytol 1995; 129:819-30. [PMID: 7730414 PMCID: PMC2120456 DOI: 10.1083/jcb.129.3.819] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
In an effort to determine diversity and function of mammalian myosin I molecules, we report here the cloning and characterization of myr 3 (third unconventional myosin from rat), a novel mammalian myosin I from rat tissues that is related to myosin I molecules from protozoa. Like the protozoan myosin I molecules, myr 3 consists of a myosin head domain, a single light chain binding motif, and a tail region that includes a COOH-terminal SH3 domain. However, myr 3 lacks the regulatory phosphorylation site present in the head domain of protozoan myosin I molecules. Evidence was obtained that the COOH terminus of the tail domain is involved in regulating F-actin binding activity of the NH2-terminal head domain. The light chain of myr 3 was identified as the Ca(2+)-binding protein calmodulin. Northern blot and immunoblot analyses revealed that myr 3 is expressed in many tissues and cell lines. Immunofluorescence studies with anti-myr 3 antibodies in NRK cells demonstrated that myr 3 is localized in the cytoplasm and in elongated structures at regions of cell-cell contact. These elongated structures contained F-actin and alpha-actinin but were devoid of vinculin. Incubation of NRK cells with Con A stimulated the formation of myr 3-containing structures along cell-cell contacts. These results suggest for myr 3 a function mediated by cell-cell contact.
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Affiliation(s)
- H E Stöffler
- Friedrich-Miescher-Laboratorium, Max-Planck-Gesellschaft, Tübingen, Germany
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33
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Bergman M, Joukov V, Virtanen I, Alitalo K. Overexpressed Csk tyrosine kinase is localized in focal adhesions, causes reorganization of alpha v beta 5 integrin, and interferes with HeLa cell spreading. Mol Cell Biol 1995; 15:711-22. [PMID: 7529872 PMCID: PMC231937 DOI: 10.1128/mcb.15.2.711] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The C-terminal Src kinase p50csk phosphorylates Src family tyrosine kinases and down-regulates their activity in vitro. To gain insight into the cellular functions of this potentially antioncogenic enzyme, we have overexpressed the csk cDNA by using an inducible promoter in HeLa cells. Despite some differences in basal Src activity in the clones analyzed, Src activity was not significantly suppressed, while the amount of p50csk and Csk activity increased at least 10-fold during 3 days of induction. Immunofluorescence for the induced p50csk was localized in the cytoplasm and distinctly in focal adhesions, in which the amount of phosphotyrosine containing proteins was also increased. Point and deletion mutagenesis experiments showed that localization in focal adhesions was dependent on the SH2 and SH3 domains of Csk but not on its catalytic activity. Csk formed a complex with the focal adhesion protein paxillin in cells, and its SH2 domain was shown to interact with pp125FAK and paxillin in vitro. After Csk induction, the cells became spherical and more loosely attached to the culture substratum, and the alpha v beta 5 integrin complex (vitronectin receptor) of focal adhesions was redistributed to a novel type of structure consisting of punctate plaques on the ventral cell surface. These phenotypic changes occurred in several clones analyzed and were totally reversible when Csk was switched off, but they did not occur in cells overexpressing the catalytically inactive Csk R-222 mutant or luciferase. Our results thus show that a fraction of cellular Csk is targeted to focal adhesions via its SH2 and SH3 domains, probably interacting with tyrosyl-phosphorylated focal adhesion proteins. They also suggest that Csk is involved in the regulation of integrins controlling cell attachment and shape.
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Affiliation(s)
- M Bergman
- Department of Pathology, University of Helsinki, Finland
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34
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Richard S, Yu D, Blumer KJ, Hausladen D, Olszowy MW, Connelly PA, Shaw AS. Association of p62, a multifunctional SH2- and SH3-domain-binding protein, with src family tyrosine kinases, Grb2, and phospholipase C gamma-1. Mol Cell Biol 1995; 15:186-97. [PMID: 7799925 PMCID: PMC231932 DOI: 10.1128/mcb.15.1.186] [Citation(s) in RCA: 174] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
src family tyrosine kinases contain two noncatalytic domains termed src homology 3 (SH3) and SH2 domains. Although several other signal transduction molecules also contain tandemly occurring SH3 and SH2 domains, the function of these closely spaced domains is not well understood. To identify the role of the SH3 domains of src family tyrosine kinases, we sought to identify proteins that interacted with this domain. By using the yeast two-hybrid system, we identified p62, a tyrosine-phosphorylated protein that associates with p21ras GTPase-activating protein, as a src family kinase SH3-domain-binding protein. Reconstitution of complexes containing p62 and the src family kinase p59fyn in HeLa cells demonstrated that complex formation resulted in tyrosine phosphorylation of p62 and was mediated by both the SH3 and SH2 domains of p59fyn. The phosphorylation of p62 by p59fyn required an intact SH3 domain, demonstrating that one function of the src family kinase SH3 domains is to bind and present certain substrates to the kinase. As p62 contains at least five SH3-domain-binding motifs and multiple tyrosine phosphorylation sites, p62 may interact with other signalling molecules via SH3 and SH2 domain interactions. Here we show that the SH3 and/or SH2 domains of the signalling proteins Grb2 and phospholipase C gamma-1 can interact with p62 both in vitro and in vivo. Thus, we propose that one function of the tandemly occurring SH3 and SH2 domains of src family kinases is to bind p62, a multifunctional SH3 and SH2 domain adapter protein, linking src family kinases to downstream effector and regulatory molecules.
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Affiliation(s)
- S Richard
- Center for Immunology, Washington University School of Medicine, St Louis, Missouri 63110
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35
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Physical and functional interactions between SH2 and SH3 domains of the Src family protein tyrosine kinase p59fyn. Mol Cell Biol 1994. [PMID: 7520528 DOI: 10.1128/mcb.14.9.6372] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The Src family protein tyrosine kinases participate in signalling through cell surface receptors that lack intrinsic tyrosine kinase domains. All nine members of this family possess adjacent Src homology (SH2 and SH3) domains, both of which are essential for repression of the enzymatic activity. The repression is mediated by binding between the SH2 domain and a C-terminal phosphotyrosine, and the SH3 domain is required for this interaction. However, the biochemical basis of functional SH2-SH3 interaction is unclear. Here, we demonstrate that when the SH2 and SH3 domains of p59fyn (Fyn) were present as adjacent domains in a single protein, binding of phosphotyrosyl peptides and proteins to the SH2 domain was enhanced, whereas binding of a subset of cellular polypeptide ligands to the SH3 domain was decreased. An interdomain communication was further revealed by occupancy with domain-specific peptide ligands: occupancy of the SH3 domain with a proline-rich peptide enhanced phosphotyrosine binding to the linked SH2 domain, and occupancy of the SH2 domain with phosphotyrosyl peptides enhanced binding of certain SH3-specific cellular polypeptides. Second, we demonstrate a direct binding between purified SH2 and SH3 domains of Fyn and Lck Src family kinases. Heterologous binding between SH2 and SH3 domains of closely related members of the Src family, namely, Fyn, Lck, and Src, was also observed. In contrast, Grb2, Crk, Abl, p85 phosphatidylinositol 3-kinase, and GTPase-activating protein SH2 domains showed lower or no binding to Fyn or Lck SH3 domains. SH2-SH3 binding did not require an intact phosphotyrosine binding pocket on the SH2 domain; however, perturbations of the SH2 domain induced by specific high-affinity phosphotyrosyl peptide binding abrogated binding of the SH3 domain. SH3-SH2 binding was observed in the presence of proline-rich peptides or when a point mutation (W119K) was introduced in the putative ligand-binding pouch of the Fyn SH3 domain, although these treatments completely abolished the binding to p85 phosphatidylinositol 3-kinase and other SH3-specific polypeptides. These biochemical SH2-SH3 interactions suggest novel mechanisms of regulating the enzymatic activity of Src kinases and their interactions with other proteins.
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Koegl M, Kypta RM, Bergman M, Alitalo K, Courtneidge SA. Rapid and efficient purification of Src homology 2 domain-containing proteins: Fyn, Csk and phosphatidylinositol 3-kinase p85. Biochem J 1994; 302 ( Pt 3):737-44. [PMID: 7524477 PMCID: PMC1137293 DOI: 10.1042/bj3020737] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
To analyse the regulation of Src family tyrosine kinases in vitro, we have purified Fyn and Csk, a kinase capable of regulating Fyn activity by phosphorylation, from baculovirus-infected insect cells. The proteins were purified by affinity purification over a phosphotyrosine column. Highly purified proteins were eluted from the resin by a salt gradient and further purified by ion-exchange chromatography. This purification scheme was successfully applied to a third, unrelated protein that also contains the Src homology 2 (SH2) domain, namely the 85 kDa subunit of phosphatidylinositol 3-kinase, indicating that this method is versatile and should prove applicable to any protein with an accessible SH2 domain. The binding of Csk to different phosphopeptides was tested, and specificity for the autophosphorylation site of Fyn was demonstrated. Pure Csk was used to phosphorylate Fyn and down-regulate its kinase activity, and the kinetic parameters of both the active and the repressed forms of Fyn were determined. Repression of Fyn activity by Csk reduced binding of Fyn to phosphopeptides to undetectable levels, supporting the model that predicts an intramolecular interaction of the Fyn SH2 domain with a C-terminal phosphotyrosine residue.
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Affiliation(s)
- M Koegl
- European Molecular Biology Laboratory, Heidelberg, Germany
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Panchamoorthy G, Fukazawa T, Stolz L, Payne G, Reedquist K, Shoelson S, Songyang Z, Cantley L, Walsh C, Band H. Physical and functional interactions between SH2 and SH3 domains of the Src family protein tyrosine kinase p59fyn. Mol Cell Biol 1994; 14:6372-85. [PMID: 7520528 PMCID: PMC359163 DOI: 10.1128/mcb.14.9.6372-6385.1994] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The Src family protein tyrosine kinases participate in signalling through cell surface receptors that lack intrinsic tyrosine kinase domains. All nine members of this family possess adjacent Src homology (SH2 and SH3) domains, both of which are essential for repression of the enzymatic activity. The repression is mediated by binding between the SH2 domain and a C-terminal phosphotyrosine, and the SH3 domain is required for this interaction. However, the biochemical basis of functional SH2-SH3 interaction is unclear. Here, we demonstrate that when the SH2 and SH3 domains of p59fyn (Fyn) were present as adjacent domains in a single protein, binding of phosphotyrosyl peptides and proteins to the SH2 domain was enhanced, whereas binding of a subset of cellular polypeptide ligands to the SH3 domain was decreased. An interdomain communication was further revealed by occupancy with domain-specific peptide ligands: occupancy of the SH3 domain with a proline-rich peptide enhanced phosphotyrosine binding to the linked SH2 domain, and occupancy of the SH2 domain with phosphotyrosyl peptides enhanced binding of certain SH3-specific cellular polypeptides. Second, we demonstrate a direct binding between purified SH2 and SH3 domains of Fyn and Lck Src family kinases. Heterologous binding between SH2 and SH3 domains of closely related members of the Src family, namely, Fyn, Lck, and Src, was also observed. In contrast, Grb2, Crk, Abl, p85 phosphatidylinositol 3-kinase, and GTPase-activating protein SH2 domains showed lower or no binding to Fyn or Lck SH3 domains. SH2-SH3 binding did not require an intact phosphotyrosine binding pocket on the SH2 domain; however, perturbations of the SH2 domain induced by specific high-affinity phosphotyrosyl peptide binding abrogated binding of the SH3 domain. SH3-SH2 binding was observed in the presence of proline-rich peptides or when a point mutation (W119K) was introduced in the putative ligand-binding pouch of the Fyn SH3 domain, although these treatments completely abolished the binding to p85 phosphatidylinositol 3-kinase and other SH3-specific polypeptides. These biochemical SH2-SH3 interactions suggest novel mechanisms of regulating the enzymatic activity of Src kinases and their interactions with other proteins.
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Affiliation(s)
- G Panchamoorthy
- Department of Rheumatology and Immunology, Joslin Diabetes Center, Boston, Massachusetts
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Abstract
Csk phosphorylates Src family members at a key regulatory tyrosine in the C-terminal tail and suppresses their activities. It is not known whether Csk activity is regulated. To examine the features of Csk required for Src suppression, we expressed Csk mutants in a cell line with a disrupted csk gene. Expression of wild-type Csk suppressed Src, but Csk with mutations in the SH2, SH3, and catalytic domains did not suppress Src. An SH3 deletion mutant of Csk was fully active against in vitro substrates, but two SH2 domain mutants were essentially inactive. Whereas Src repressed by Csk was predominantly perinuclear, the activated Src in cells lacking Csk was localized to structures resembling podosomes. Activated mutant Src was also in podosomes, even in the presence of Csk. When Src was not active, Csk was diffusely located in the cytosol, but when Src was active, Csk colocalized with activated Src to podosomes. Csk also localizes to podosomes of cells transformed by an activated Src that lacks the major tyrosine autophosphorylation site, suggesting that the relocalization of Csk is not a consequence of the binding of the Csk SH2 domain to phosphorylated Src. A catalytically inactive Csk mutant also localized with Src to podosomes, but SH3 and SH2 domain mutants did not, suggesting that the SH3 and SH2 domains are both necessary to target Csk to places where Src is active. The failure of the catalytically active SH3 mutant of Csk to regulate Src may be due to its inability to colocalize with active Src.
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Abstract
Csk phosphorylates Src family members at a key regulatory tyrosine in the C-terminal tail and suppresses their activities. It is not known whether Csk activity is regulated. To examine the features of Csk required for Src suppression, we expressed Csk mutants in a cell line with a disrupted csk gene. Expression of wild-type Csk suppressed Src, but Csk with mutations in the SH2, SH3, and catalytic domains did not suppress Src. An SH3 deletion mutant of Csk was fully active against in vitro substrates, but two SH2 domain mutants were essentially inactive. Whereas Src repressed by Csk was predominantly perinuclear, the activated Src in cells lacking Csk was localized to structures resembling podosomes. Activated mutant Src was also in podosomes, even in the presence of Csk. When Src was not active, Csk was diffusely located in the cytosol, but when Src was active, Csk colocalized with activated Src to podosomes. Csk also localizes to podosomes of cells transformed by an activated Src that lacks the major tyrosine autophosphorylation site, suggesting that the relocalization of Csk is not a consequence of the binding of the Csk SH2 domain to phosphorylated Src. A catalytically inactive Csk mutant also localized with Src to podosomes, but SH3 and SH2 domain mutants did not, suggesting that the SH3 and SH2 domains are both necessary to target Csk to places where Src is active. The failure of the catalytically active SH3 mutant of Csk to regulate Src may be due to its inability to colocalize with active Src.
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Affiliation(s)
- B W Howell
- Fred Hutchinson Cancer Research Center, Seattle, Washington 98104
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Florio M, Wilson LK, Trager JB, Thorner J, Martin GS. Aberrant protein phosphorylation at tyrosine is responsible for the growth-inhibitory action of pp60v-src expressed in the yeast Saccharomyces cerevisiae. Mol Biol Cell 1994; 5:283-96. [PMID: 8049521 PMCID: PMC301037 DOI: 10.1091/mbc.5.3.283] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Expression of pp60v-src, the transforming protein of Rous sarcoma virus, arrests the growth of the yeast Saccharomyces cerevisiae. To determine the basis of this growth arrest, yeast strains were constructed that expressed either wild-type v-src or various mutant v-src genes under the control of the galactose-inducible, glucose repressible GAL1 promoter. When shifted to galactose medium, cells expressing wild-type v-src ceased growth immediately and lost viability, whereas cells expressing a catalytically inactive mutant (K295M) continued to grow normally, indicating that the kinase activity of pp60v-src is required for its growth inhibitory effect. Mutants of v-src altered in the SH2/SH3 domain (XD4, XD6, SPX1, and SHX13) and a mutant lacking a functional N-terminal myristoylation signal (MM4) caused only a partial inhibition of growth, indicating that complete growth inhibition requires either targeting of the active kinase or binding of the kinase to phosphorylated substrates, or both. Cells arrested by v-src expression displayed aberrant microtubule structures, alterations in DNA content and elevated p34CDC28 kinase activity. Immunoblotting with antiphosphotyrosine antibody showed that many yeast proteins, including the p34CDC28 kinase, became phosphorylated at tyrosine in cells expressing v-src. Both the growth inhibition and the tyrosine-specific protein phosphorylation observed following v-src expression were reversed by co-expression of a mammalian phosphotyrosine-specific phosphoprotein phosphatase (PTP1B). However a v-src mutant with a small insertion in the catalytic domain (SRX5) had the same lethal effect as wild-type v-src, yet induced only very low levels of protein-tyrosine phosphorylation. These results indicate that inappropriate phosphorylation at tyrosine is the primary cause of the lethal effect of pp60v-src expression but suggest that only a limited subset of the phosphorylated proteins are involved in this effect.
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Affiliation(s)
- M Florio
- Department of Molecular and Cell Biology, University of California at Berkeley 94720
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