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Conformational buffering underlies functional selection in intrinsically disordered protein regions. Nat Struct Mol Biol 2022; 29:781-790. [PMID: 35948766 DOI: 10.1038/s41594-022-00811-w] [Citation(s) in RCA: 41] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 06/23/2022] [Indexed: 02/02/2023]
Abstract
Many disordered proteins conserve essential functions in the face of extensive sequence variation, making it challenging to identify the mechanisms responsible for functional selection. Here we identify the molecular mechanism of functional selection for the disordered adenovirus early gene 1A (E1A) protein. E1A competes with host factors to bind the retinoblastoma (Rb) protein, subverting cell cycle regulation. We show that two binding motifs tethered by a hypervariable disordered linker drive picomolar affinity Rb binding and host factor displacement. Compensatory changes in amino acid sequence composition and sequence length lead to conservation of optimal tethering across a large family of E1A linkers. We refer to this compensatory mechanism as conformational buffering. We also detect coevolution of the motifs and linker, which can preserve or eliminate the tethering mechanism. Conformational buffering and motif-linker coevolution explain robust functional encoding within hypervariable disordered linkers and could underlie functional selection of many disordered protein regions.
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2
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Monteleone L, Marengo B, Musumeci F, Grossi G, Carbone A, Valenti GE, Domenicotti C, Schenone S. Anti-Survival Effect of SI306 and Its Derivatives on Human Glioblastoma Cells. Pharmaceutics 2022; 14:pharmaceutics14071399. [PMID: 35890294 PMCID: PMC9318396 DOI: 10.3390/pharmaceutics14071399] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Revised: 06/29/2022] [Accepted: 06/30/2022] [Indexed: 02/04/2023] Open
Abstract
Glioblastoma (GBM) is the most common adult brain tumor and, although many efforts have been made to find valid therapies, the onset of resistance is the main cause of recurrence. Therefore, it is crucial to identify and target the molecular mediators responsible for GBM malignancy. In this context, the use of Src inhibitors such as SI306 (C1) and its prodrug (C2) showed promising results, suggesting that SI306 could be the lead compound useful to derivate new anti-GBM drugs. Therefore, a new prodrug of SI306 (C3) was synthesized and tested on CAS-1 and U87 human GBM cells by comparing its effect to that of C1 and C2. All compounds were more effective on CAS-1 than U87 cells, while C2 was the most active on both cell lines. Moreover, the anti-survival effect was associated with a reduction in the expression of epidermal growth factor receptor (EGFR)WT and EGFR-vIII in U87 and CAS-1 cells, respectively. Collectively, our findings demonstrate that all tested compounds are able to counteract GBM survival, further supporting the role of SI306 as progenitor of promising new drugs to treat malignant GBM.
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Affiliation(s)
- Lorenzo Monteleone
- Department of Experimental Medicine (DIMES), General Pathology Section, University of Genoa, 16132 Genoa, Italy; (L.M.); (B.M.); (G.E.V.)
| | - Barbara Marengo
- Department of Experimental Medicine (DIMES), General Pathology Section, University of Genoa, 16132 Genoa, Italy; (L.M.); (B.M.); (G.E.V.)
- Inter-University Center for the Promotion of the 3Rs Principles in Teaching & Research (Centro 3R), 56122 Pisa, Italy
| | - Francesca Musumeci
- Department of Pharmacy, University of Genoa, 16132 Genoa, Italy; (F.M.); (G.G.); (A.C.); (S.S.)
| | - Giancarlo Grossi
- Department of Pharmacy, University of Genoa, 16132 Genoa, Italy; (F.M.); (G.G.); (A.C.); (S.S.)
| | - Anna Carbone
- Department of Pharmacy, University of Genoa, 16132 Genoa, Italy; (F.M.); (G.G.); (A.C.); (S.S.)
| | - Giulia E. Valenti
- Department of Experimental Medicine (DIMES), General Pathology Section, University of Genoa, 16132 Genoa, Italy; (L.M.); (B.M.); (G.E.V.)
| | - Cinzia Domenicotti
- Department of Experimental Medicine (DIMES), General Pathology Section, University of Genoa, 16132 Genoa, Italy; (L.M.); (B.M.); (G.E.V.)
- Inter-University Center for the Promotion of the 3Rs Principles in Teaching & Research (Centro 3R), 56122 Pisa, Italy
- Correspondence: ; Tel.: +39-010-353-8830
| | - Silvia Schenone
- Department of Pharmacy, University of Genoa, 16132 Genoa, Italy; (F.M.); (G.G.); (A.C.); (S.S.)
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3
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Chakraborty S, Inukai T, Fang L, Golkowski M, Maly DJ. Targeting Dynamic ATP-Binding Site Features Allows Discrimination between Highly Homologous Protein Kinases. ACS Chem Biol 2019; 14:1249-1259. [PMID: 31038916 DOI: 10.1021/acschembio.9b00214] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
ATP-competitive inhibitors that demonstrate exquisite selectivity for specific members of the human kinome have been developed. Despite this success, the identification of highly selective inhibitors is still very challenging, and it is often not possible to rationally engineer selectivity between the ATP-binding sites of kinases, especially among closely related family members. Src-family kinases (SFKs) are a highly homologous family of eight multidomain, nonreceptor tyrosine kinases that play general and specialized roles in numerous cellular processes. The high sequence and functional similarities between SFK members make it hard to rationalize how selectivity can be gained with inhibitors that target the ATP-binding site. Here, we describe the development of a series of inhibitors that are highly selective for the ATP-binding sites of the SFKs Lyn and Hck over other SFKs. By biochemically characterizing how these selective ATP-competitive inhibitors allosterically influence the global conformation of SFKs, we demonstrate that they most likely interact with a binding pocket created by the movement of the conformationally flexible helix αC in the ATP-binding site. With a series of sequence swap experiments, we show that sensitivity to this class of selective inhibitors is due to the identity of residues that control the conformational flexibility of helix αC rather than any specific ATP-binding site interactions. Thus, the ATP-binding sites of highly homologous kinases can be discriminated by targeting heterogeneity within conformationally flexible regions.
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Affiliation(s)
| | - Takayuki Inukai
- Medicinal Chemistry Research Laboratories, Ono Pharmaceutical Company, Ltd., 3-1-1 Sakurai, Shimamoto, Mishima, Osaka 618-8585, Japan
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4
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De Kock L, Thys C, Downes K, Duarte D, Megy K, Van Geet C, Freson K. De novo variant in tyrosine kinase SRC causes thrombocytopenia: case report of a second family. Platelets 2019; 30:931-934. [PMID: 31204551 DOI: 10.1080/09537104.2019.1628197] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A germline heterozygous gain-of-function p.E527K variant in tyrosine kinase SRC was previously found to cause thrombocytopenia, myelofibrosis, bleeding, bone pathologies, premature edentulism and mild facial dysmorphia in nine patients of a single pedigree. Because of this variant, SRC loses its self-inhibitory capacity, causing constitutively active SRC expression in platelets. These patients have fewer and heterogeneous-sized platelets that are hyporeactive to collagen. We now report a 5-year-old girl with syndromic thrombocytopenia due to the same SRC-E527K variant that occurs de novo. A bone marrow biopsy, blood smear analysis, platelet aggregations, flow cytometric analysis of P-selectin, SRC expression and tyrosine phosphorylation studies were performed to confirm the similarities between the two families. This study strengthens our previous finding that hyperactive SRC kinase results in mild platelet dysfunction and thrombocytopenia with hypogranular platelets and further expands the clinical description of this syndrome to improve early recognition.
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Affiliation(s)
- Lore De Kock
- Department of Cardiovascular Sciences, Center for Molecular and Vascular Biology, University of Leuven , Leuven , Belgium
| | - Chantal Thys
- Department of Cardiovascular Sciences, Center for Molecular and Vascular Biology, University of Leuven , Leuven , Belgium
| | - Kate Downes
- Department of Hematology, University of Cambridge, Cambridge Biomedical Campus , Cambridge , UK.,NIHR BioResource, Cambridge University Hospitals, Cambridge Biomedical Campus , Cambridge , UK
| | - Daniel Duarte
- Department of Hematology, University of Cambridge, Cambridge Biomedical Campus , Cambridge , UK.,NIHR BioResource, Cambridge University Hospitals, Cambridge Biomedical Campus , Cambridge , UK
| | - Karyn Megy
- Department of Hematology, University of Cambridge, Cambridge Biomedical Campus , Cambridge , UK.,NIHR BioResource, Cambridge University Hospitals, Cambridge Biomedical Campus , Cambridge , UK
| | - Chris Van Geet
- Department of Cardiovascular Sciences, Center for Molecular and Vascular Biology, University of Leuven , Leuven , Belgium
| | - Kathleen Freson
- Department of Cardiovascular Sciences, Center for Molecular and Vascular Biology, University of Leuven , Leuven , Belgium
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5
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Survey of solution dynamics in Src kinase reveals allosteric cross talk between the ligand binding and regulatory sites. Nat Commun 2017; 8:2160. [PMID: 29255153 PMCID: PMC5735167 DOI: 10.1038/s41467-017-02240-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Accepted: 11/15/2017] [Indexed: 11/09/2022] Open
Abstract
The catalytic domain of protein tyrosine kinases can interconvert between active and inactive conformations in response to regulatory inputs. We recently demonstrated that Src kinase features an allosteric network that couples substrate-binding sites. However, the extent of conformational and dynamic changes that are propagated throughout the kinase domain remains poorly understood. Here, we monitor by NMR the effect of conformationally selective inhibitors on kinase backbone dynamics. We find that inhibitor binding and activation loop autophosphorylation induces dynamic changes across the entire kinase. We identify a highly conserved amino acid, Gly449, that is necessary for Src activation. Finally, we show for the first time how the SH3–SH2 domains perturb the dynamics of the kinase domain in the context of the full length protein. We provide experimental support for long-range communication in Src kinase that leads to the relative stabilization of active or inactive conformations and modulation of substrate affinity. Src is a prototypical signaling non-receptor protein tyrosine kinase that interconverts between distinct conformations. Here the authors use variants of the kinase-inhibitor dasatinib to define three specific conformational states of the Src kinase and shed insight on the effect of conformation-specific inhibitors on Src dynamics.
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6
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Abstract
We have developed a general methodology to produce bivalent kinase inhibitors for c-Src that interact with the SH2 and ATP binding pockets. Our approach led to a highly selective bivalent inhibitor of c-Src. We demonstrate impressive selectivity for c-Src over homologous kinases. Exploration of the unexpected high level of selectivity yielded insight into the inherent flexibility of homologous kinases. Finally, we demonstrate that our methodology is modular and both the ATP-competitive fragment and conjugation chemistry can be swapped.
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Affiliation(s)
- Taylor K. Johnson
- Department of Medicinal Chemistry, University of Michigan, Ann Arbor, MI 48109
| | - Matthew B. Soellner
- Department of Medicinal Chemistry, University of Michigan, Ann Arbor, MI 48109
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109
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7
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Turro E, Greene D, Wijgaerts A, Thys C, Lentaigne C, Bariana TK, Westbury SK, Kelly AM, Selleslag D, Stephens JC, Papadia S, Simeoni I, Penkett CJ, Ashford S, Attwood A, Austin S, Bakchoul T, Collins P, Deevi SVV, Favier R, Kostadima M, Lambert MP, Mathias M, Millar CM, Peerlinck K, Perry DJ, Schulman S, Whitehorn D, Wittevrongel C, De Maeyer M, Rendon A, Gomez K, Erber WN, Mumford AD, Nurden P, Stirrups K, Bradley JR, Raymond FL, Laffan MA, Van Geet C, Richardson S, Freson K, Ouwehand WH. A dominant gain-of-function mutation in universal tyrosine kinase SRC causes thrombocytopenia, myelofibrosis, bleeding, and bone pathologies. Sci Transl Med 2016; 8:328ra30. [PMID: 26936507 DOI: 10.1126/scitranslmed.aad7666] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 01/21/2016] [Indexed: 12/14/2022]
Abstract
The Src family kinase (SFK) member SRC is a major target in drug development because it is activated in many human cancers, yet deleterious SRC germline mutations have not been reported. We used genome sequencing and Human Phenotype Ontology patient coding to identify a gain-of-function mutation in SRC causing thrombocytopenia, myelofibrosis, bleeding, and bone pathologies in nine cases. Modeling of the E527K substitution predicts loss of SRC's self-inhibitory capacity, which we confirmed with in vitro studies showing increased SRC kinase activity and enhanced Tyr(419) phosphorylation in COS-7 cells overexpressing E527K SRC. The active form of SRC predominates in patients' platelets, resulting in enhanced overall tyrosine phosphorylation. Patients with myelofibrosis have hypercellular bone marrow with trilineage dysplasia, and their stem cells grown in vitro form more myeloid and megakaryocyte (MK) colonies than control cells. These MKs generate platelets that are dysmorphic, low in number, highly variable in size, and have a paucity of α-granules. Overactive SRC in patient-derived MKs causes a reduction in proplatelet formation, which can be rescued by SRC kinase inhibition. Stem cells transduced with lentiviral E527K SRC form MKs with a similar defect and enhanced tyrosine phosphorylation levels. Patient-derived and E527K-transduced MKs show Y419 SRC-positive stained podosomes that induce altered actin organization. Expression of mutated src in zebrafish recapitulates patients' blood and bone phenotypes. Similar studies of platelets and MKs may reveal the mechanism underlying the severe bleeding frequently observed in cancer patients treated with next-generation SFK inhibitors.
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Affiliation(s)
- Ernest Turro
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK. National Health Service (NHS) Blood and Transplant, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK. Medical Research Council Biostatistics Unit, Cambridge Institute of Public Health, Cambridge Biomedical Campus, Cambridge CB2 0SR, UK. National Institute for Health Research (NIHR) BioResource-Rare Diseases, Cambridge University Hospitals, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK
| | - Daniel Greene
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK. Medical Research Council Biostatistics Unit, Cambridge Institute of Public Health, Cambridge Biomedical Campus, Cambridge CB2 0SR, UK. National Institute for Health Research (NIHR) BioResource-Rare Diseases, Cambridge University Hospitals, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK
| | - Anouck Wijgaerts
- Department of Cardiovascular Sciences, Center for Molecular and Vascular Biology, University of Leuven, 3000 Leuven, Belgium
| | - Chantal Thys
- Department of Cardiovascular Sciences, Center for Molecular and Vascular Biology, University of Leuven, 3000 Leuven, Belgium
| | - Claire Lentaigne
- Centre for Haematology, Hammersmith Campus, Imperial College Academic Health Sciences Centre, Imperial College London, London W12 0HS, UK. Imperial College Healthcare NHS Trust, Du Cane Road, London W12 0HS, UK
| | - Tadbir K Bariana
- Department of Haematology, University College London Cancer Institute, London WC1E 6BT, UK. Katharine Dormandy Haemophilia Centre and Thrombosis Unit, Royal Free London NHS Foundation Trust, London NW3 2QG, UK
| | - Sarah K Westbury
- School of Clinical Sciences, University of Bristol, Bristol BS2 8DZ, UK
| | - Anne M Kelly
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK. National Health Service (NHS) Blood and Transplant, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK
| | - Dominik Selleslag
- Academisch Ziekenhuis Sint-Jan Brugge-Oostende, 8000 Brugge, Belgium
| | - Jonathan C Stephens
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK. National Health Service (NHS) Blood and Transplant, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK. National Institute for Health Research (NIHR) BioResource-Rare Diseases, Cambridge University Hospitals, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK
| | - Sofia Papadia
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK. National Institute for Health Research (NIHR) BioResource-Rare Diseases, Cambridge University Hospitals, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK
| | - Ilenia Simeoni
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK. National Institute for Health Research (NIHR) BioResource-Rare Diseases, Cambridge University Hospitals, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK
| | - Christopher J Penkett
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK. National Institute for Health Research (NIHR) BioResource-Rare Diseases, Cambridge University Hospitals, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK
| | - Sofie Ashford
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK. National Institute for Health Research (NIHR) BioResource-Rare Diseases, Cambridge University Hospitals, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK
| | - Antony Attwood
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK. National Health Service (NHS) Blood and Transplant, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK. National Institute for Health Research (NIHR) BioResource-Rare Diseases, Cambridge University Hospitals, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK
| | - Steve Austin
- Department of Haematology, Guy's and St Thomas' NHS Foundation Trust, London SE1 7EH, UK
| | - Tamam Bakchoul
- Institute for Immunology and Transfusion Medicine, Universitätsmedizin Greifswald, 17475 Greifswald, Germany
| | - Peter Collins
- Arthur Bloom Haemophilia Centre, Institute of Infection and Immunity, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK
| | - Sri V V Deevi
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK. National Institute for Health Research (NIHR) BioResource-Rare Diseases, Cambridge University Hospitals, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK
| | - Rémi Favier
- Assistance Publique-Hôpitaux de Paris, Armand Trousseau Children Hospital, 75012 Paris, France. INSERM U1170, 94805 Villejuif, France
| | - Myrto Kostadima
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK. National Health Service (NHS) Blood and Transplant, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK
| | - Michele P Lambert
- Division of Hematology, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA. Department of Pediatrics, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Mary Mathias
- Department of Haematology, Great Ormond Street Hospital for Children NHS Foundation Trust, London WC1N 3JH, UK
| | - Carolyn M Millar
- Centre for Haematology, Hammersmith Campus, Imperial College Academic Health Sciences Centre, Imperial College London, London W12 0HS, UK. Imperial College Healthcare NHS Trust, Du Cane Road, London W12 0HS, UK
| | - Kathelijne Peerlinck
- Department of Cardiovascular Sciences, Center for Molecular and Vascular Biology, University of Leuven, 3000 Leuven, Belgium
| | - David J Perry
- Department of Haematology, Addenbrooke's Hospital, Cambridge University Hospitals NHS Foundation Trust, Cambridge Biomedical Campus, Cambridge CB2 0QQ, UK
| | - Sol Schulman
- Beth Israel Deaconess Medical Centre, Harvard Medical School, Boston, MA 02215, USA
| | - Deborah Whitehorn
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK. National Health Service (NHS) Blood and Transplant, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK
| | - Christine Wittevrongel
- Department of Cardiovascular Sciences, Center for Molecular and Vascular Biology, University of Leuven, 3000 Leuven, Belgium
| | | | - Marc De Maeyer
- Biochemistry, Molecular and Structural Biology Section, University of Leuven, 3001 Leuven, Belgium
| | - Augusto Rendon
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK. Genomics England Ltd., London EC1M 6BQ, UK
| | - Keith Gomez
- Department of Haematology, University College London Cancer Institute, London WC1E 6BT, UK. Katharine Dormandy Haemophilia Centre and Thrombosis Unit, Royal Free London NHS Foundation Trust, London NW3 2QG, UK
| | - Wendy N Erber
- Pathology and Laboratory Medicine, University of Western Australia, Crawley, Western Australia WA 6009, Australia
| | - Andrew D Mumford
- School of Clinical Sciences, University of Bristol, Bristol BS2 8DZ, UK. School of Cellular and Molecular Medicine, University of Bristol, Bristol BS8 1TD, UK
| | - Paquita Nurden
- Institut Hospitalo-Universitaire LIRYC, PTIB, Hôpital Xavier Arnozan, 33600 Pessac, France
| | - Kathleen Stirrups
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK. National Institute for Health Research (NIHR) BioResource-Rare Diseases, Cambridge University Hospitals, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK
| | - John R Bradley
- National Institute for Health Research (NIHR) BioResource-Rare Diseases, Cambridge University Hospitals, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK. Research and Development, Cambridge University Hospitals NHS Foundation Trust, Cambridge CB2 0QQ, UK
| | - F Lucy Raymond
- National Institute for Health Research (NIHR) BioResource-Rare Diseases, Cambridge University Hospitals, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK. Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 0XY, UK
| | - Michael A Laffan
- Centre for Haematology, Hammersmith Campus, Imperial College Academic Health Sciences Centre, Imperial College London, London W12 0HS, UK. Imperial College Healthcare NHS Trust, Du Cane Road, London W12 0HS, UK
| | - Chris Van Geet
- Department of Cardiovascular Sciences, Center for Molecular and Vascular Biology, University of Leuven, 3000 Leuven, Belgium
| | - Sylvia Richardson
- Medical Research Council Biostatistics Unit, Cambridge Institute of Public Health, Cambridge Biomedical Campus, Cambridge CB2 0SR, UK
| | - Kathleen Freson
- Department of Cardiovascular Sciences, Center for Molecular and Vascular Biology, University of Leuven, 3000 Leuven, Belgium.
| | - Willem H Ouwehand
- Department of Haematology, University of Cambridge, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK. National Health Service (NHS) Blood and Transplant, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK. National Institute for Health Research (NIHR) BioResource-Rare Diseases, Cambridge University Hospitals, Cambridge Biomedical Campus, Cambridge CB2 0PT, UK. Human Genetics, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK
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8
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Register AC, Leonard SE, Maly DJ. SH2-catalytic domain linker heterogeneity influences allosteric coupling across the SFK family. Biochemistry 2014; 53:6910-23. [PMID: 25302671 PMCID: PMC4230323 DOI: 10.1021/bi5008194] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Src-family
kinases (SFKs) make up a family of nine homologous multidomain
tyrosine kinases whose misregulation is responsible for human disease
(cancer, diabetes, inflammation, etc.). Despite overall sequence homology
and identical domain architecture, differences in SH3 and SH2 regulatory
domain accessibility and ability to allosterically autoinhibit the
ATP-binding site have been observed for the prototypical SFKs Src
and Hck. Biochemical and structural studies indicate that the SH2-catalytic
domain (SH2-CD) linker, the intramolecular binding epitope for SFK
SH3 domains, is responsible for allosterically coupling SH3 domain
engagement to autoinhibition of the ATP-binding site through the conformation
of the αC helix. As a relatively unconserved region between
SFK family members, SH2-CD linker sequence variability across the
SFK family is likely a source of nonredundant cellular functions between
individual SFKs via its effect on the availability of SH3 and SH2
domains for intermolecular interactions and post-translational modification.
Using a combination of SFKs engineered with enhanced or weakened regulatory
domain intramolecular interactions and conformation-selective inhibitors
that report αC helix conformation, this study explores how SH2-CD
sequence heterogeneity affects allosteric coupling across the SFK
family by examining Lyn, Fyn1, and Fyn2. Analyses of Fyn1 and Fyn2,
isoforms that are identical but for a 50-residue sequence spanning
the SH2-CD linker, demonstrate that SH2-CD linker sequence differences
can have profound effects on allosteric coupling between otherwise
identical kinases. Most notably, a dampened allosteric connection
between the SH3 domain and αC helix leads to greater autoinhibitory
phosphorylation by Csk, illustrating the complex effects of SH2-CD
linker sequence on cellular function.
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Affiliation(s)
- A C Register
- Department of Chemistry, University of Washington , Seattle, Washington 98195, United States
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9
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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: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
![]()
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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10
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Krishnamurty R, Brigham JL, Leonard SE, Ranjitkar P, Larson ET, Dale EJ, Merritt EA, Maly DJ. Active site profiling reveals coupling between domains in SRC-family kinases. Nat Chem Biol 2012; 9:43-50. [PMID: 23143416 PMCID: PMC3522794 DOI: 10.1038/nchembio.1118] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2012] [Accepted: 10/01/2012] [Indexed: 12/14/2022]
Abstract
Protein kinases, key regulators of intracellular signal transduction, have emerged as an important class of drug targets. Chemical proteomic tools that facilitate the functional interrogation of protein kinase active sites are powerful reagents for studying the regulation of this large enzyme family and for performing inhibitor selectivity screens. Here we describe a new crosslinking strategy that enables rapid and quantitative profiling of protein kinase active sites in lysates and live cells. Applying this methodology to the SRC-family kinases (SFKs) SRC and HCK led to the identification of a series of conformation-specific, ATP-competitive inhibitors that display a distinct preference for autoinhibited forms of these kinases. Furthermore, we show that ligands that demonstrate this selectivity are able to modulate the ability of the regulatory domains of SRC and HCK to engage in intermolecular binding interactions. These studies provide insight into the regulation of this important family of tyrosine kinases.
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11
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Vitello AM, Du Y, Buttrick PM, Walker LA. Serendipitous discovery of a novel protein signaling mechanism in heart failure. Biochem Biophys Res Commun 2012; 421:431-5. [PMID: 22503978 DOI: 10.1016/j.bbrc.2012.03.124] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2012] [Accepted: 03/27/2012] [Indexed: 10/28/2022]
Abstract
A number of protein signaling mechanisms are known to be involved in the progression of heart failure, yet the mechanism(s) by which the heart fails remains poorly understood. Therefore, we undertook a global approach to this question and used an antibody microarray to identify proteins differentially expressed in dysfunctional right ventricles in a bovine model of heart failure and the results were validated using cardiac tissue from both bovine and human heart failure. We found that protein disulfide isomerase 3, PDIA3, a protein that resides in the lumen of the endoplasmic reticulum, is significantly upregulated in both animal and human models of right and left heart failure. Altered expression of this protein has not previously been described in models of heart failure. In our initial microarray analysis, we found that CSK (c-Src kinase) was among the proteins upregulated in failing bovine ventricle. To further elucidate the role of CSK in heart failure, we studied the expression of its downstream target, Src, and found that Src expression and phosphorylation were markedly upregulated in failing ventricles. However, we also noted a smaller immunologically reactive protein that was only seen in experimental animals. In order to positively identify the smaller, Src-reactive protein, we used 2-dimensional gel electrophoresis and mass spectrophotometry. Surprisingly, we identified this protein as PDIA3, a protein that did not belong to the Src family of proteins. Upon sequence examination we found that PDIA3 contains a short C-terminal sequence with strong homology to Src and that it was this short sequence to which the antibody was generated. PDIA3 participates in MHC class I presentation and is implicated in the progression of valvular dysfunction in rheumatic heart disease, as well as calcium modulation in the sarcoplasmic reticulum. The molecule resides in the lumen of the endoplasmic reticulum and participates in disulfide bond formation during protein folding by interacting with calnexin and calreticulin. This interaction may indirectly effect SERCA (sarco/endoplasmic reticulum Ca(2+)-transport ATPase) activity and by extension contribute to the calcium dysregulation that characterizes progressive heart failure. Further studies are needed to elucidate the role that PDIA3 may play in the progression of heart failure.
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Affiliation(s)
- Andrea M Vitello
- University of Colorado, Department of Medicine, Division of Cardiology, Aurora, CO 80045, USA
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Naegle KM, Gymrek M, Joughin BA, Wagner JP, Welsch RE, Yaffe MB, Lauffenburger DA, White FM. PTMScout, a Web resource for analysis of high throughput post-translational proteomics studies. Mol Cell Proteomics 2010; 9:2558-70. [PMID: 20631208 DOI: 10.1074/mcp.m110.001206] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The rate of discovery of post-translational modification (PTM) sites is increasing rapidly and is significantly outpacing our biological understanding of the function and regulation of those modifications. To help meet this challenge, we have created PTMScout, a web-based interface for viewing, manipulating, and analyzing high throughput experimental measurements of PTMs in an effort to facilitate biological understanding of protein modifications in signaling networks. PTMScout is constructed around a custom database of PTM experiments and contains information from external protein and post-translational resources, including gene ontology annotations, Pfam domains, and Scansite predictions of kinase and phosphopeptide binding domain interactions. PTMScout functionality comprises data set comparison tools, data set summary views, and tools for protein assignments of peptides identified by mass spectrometry. Analysis tools in PTMScout focus on informed subset selection via common criteria and on automated hypothesis generation through subset labeling derived from identification of statistically significant enrichment of other annotations in the experiment. Subset selection can be applied through the PTMScout flexible query interface available for quantitative data measurements and data annotations as well as an interface for importing data set groupings by external means, such as unsupervised learning. We exemplify the various functions of PTMScout in application to data sets that contain relative quantitative measurements as well as data sets lacking quantitative measurements, producing a set of interesting biological hypotheses. PTMScout is designed to be a widely accessible tool, enabling generation of multiple types of biological hypotheses from high throughput PTM experiments and advancing functional assignment of novel PTM sites. PTMScout is available at http://ptmscout.mit.edu.
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Affiliation(s)
- Kristen M Naegle
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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13
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Abstract
Members of the Src family of protein tyrosine kinases play important roles in platelet adhesion, activation, and aggregation. The purpose of this review is to summarize current knowledge regarding how Src family kinase activity is regulated in general, to describe what is known about mechanisms underlying SFK activation in platelets, and to discuss platelet proteins that contribute to SFK inactivation, particularly those that use phosphotyrosine-containing sequences to recruit phosphatases and kinases to sites of SFK activity.
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Affiliation(s)
- D K Newman
- Blood Center of Wisconsin, Blood Research Institute, Milwaukee, WI 53226, USA.
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Analysis of the Thermodynamics of Binding of an SH3 Domain to Proline-rich Peptides using a Chimeric Fusion Protein. J Mol Biol 2008; 377:117-35. [DOI: 10.1016/j.jmb.2007.11.060] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2007] [Revised: 11/05/2007] [Accepted: 11/17/2007] [Indexed: 01/24/2023]
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15
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Bernadó P, Pérez Y, Svergun DI, Pons M. Structural Characterization of the Active and Inactive States of Src Kinase in Solution by Small-Angle X-ray Scattering. J Mol Biol 2008; 376:492-505. [DOI: 10.1016/j.jmb.2007.11.066] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2007] [Revised: 11/15/2007] [Accepted: 11/21/2007] [Indexed: 11/29/2022]
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Pazos Y, Alvarez CJP, Camiña JP, Casanueva FF. Lysophosphatidic acid inhibits ghrelin secretion in the human gastric adenocarcinoma AGS cell line − role of mitogenic activated protein kinase signaling pathway. FEBS J 2007; 274:5714-26. [DOI: 10.1111/j.1742-4658.2007.06091.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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17
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Nika K, Tautz L, Arimura Y, Vang T, Williams S, Mustelin T. A weak Lck tail bite is necessary for Lck function in T cell antigen receptor signaling. J Biol Chem 2007; 282:36000-9. [PMID: 17897955 DOI: 10.1074/jbc.m702779200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Src family kinases are suppressed by a "tail bite" mechanism, in which the binding of a phosphorylated tyrosine in the C terminus of the protein to the Src homology (SH) 2 domain in the N-terminal half of the protein forces the catalytic domain into an inactive conformation stabilized by an additional SH3 interaction. In addition to this intramolecular suppressive function, the SH2 domain also mediates intermolecular interactions, which are crucial for T cell antigen receptor (TCR) signaling. To better understand the relative importance of these two opposite functions of the SH2 domain of the Src family kinase Lck in TCR signaling, we created three mutants of Lck in which the intramolecular binding of the C terminus to the SH2 domain was strengthened. The mutants differed from wild-type Lck only in one to three amino acid residues following the negative regulatory tyrosine 505, which was normally phosphorylated by Csk and dephosphorylated by CD45 in the mutants. In the Lck-negative JCaM1 cell line, the Lck mutants had a much reduced ability to transduce signals from the TCR in a manner that directly correlated with SH2-Tyr(P)(505) affinity. The mutant with the strongest tail bite was completely unable to support any ZAP-70 phosphorylation, mitogen-activated protein kinase activation, or downstream gene activation in response to TCR ligation, whereas other mutants had intermediate abilities. Lipid raft targeting was not affected. We conclude that Lck is regulated by a weak tail bite to allow for its activation and service in TCR signaling, perhaps through a competitive SH2 engagement mechanism.
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Affiliation(s)
- Konstantina Nika
- Program on Inflammatory Disease Research, Infectious and Inflammatory Disease Center, The Burnham Institute for Medical Research, La Jolla, California 92037, USA.
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Ingley E. Src family kinases: regulation of their activities, levels and identification of new pathways. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2007; 1784:56-65. [PMID: 17905674 DOI: 10.1016/j.bbapap.2007.08.012] [Citation(s) in RCA: 241] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2007] [Revised: 08/15/2007] [Accepted: 08/15/2007] [Indexed: 01/29/2023]
Abstract
While the Src family of protein tyrosine kinases (SFK), and the main ancillary molecules involved in their regulation, have been studied for many years, the details of their interplay are not fully understood and thus remain under active investigation. Additionally, new players that coordinate their regulation and direct their signalling cascades are also being uncovered, shedding new light on the complexity of these signalling networks. Through the utilization of novel interaction assays, several new interconnecting mediators that are helping to show the elegance of Src family kinase regulation have been discovered. This review outlines SFK regulation, the discovery of the Csk binding protein (Phosphoprotein Associated with Glycosphingolipid-enriched microdomains, Cbp/PAG), and its role in regulating SFK kinase activity status, as well as protein levels. Further, details of the methods used to identify this dual mode of regulation can be applied to delineate the full gamut of SH2/SH3-directed SFK pathways and, indeed, those of any tyrosine kinase. Using Lyn as a model SFK, we and others have shown that Cbp recruits negative regulators of COOH-terminal Src kinase (Csk)/Csk-like protein-tyrosine kinase (Ctk) after Lyn is activated and bound to Cbp. Lyn phosphorylates Cbp on multiple tyrosine residues, including two that can bind Lyn's SH2 domain with high affinity. Lyn also phosphorylates Y314, which recruits Csk/Ctk to phosphorylate Lyn at its Y508 negative site, allowing an inactive conformation to form. However, the pY508 site has a low affinity for Lyn's SH2 domain, while the Cbp sites have high affinity. Thus, until these Cbp sites are dephosphorylated, Lyn can remain active. Intriguingly, phosphorylated Y314 also binds the suppressor of cytokine signalling 1 (SOCS1), resulting in elevated ubiquitination and degradation of Lyn. Thus, a single phosphotyrosine residue within Cbp co-ordinates a two-phase process involving distinct negative regulatory pathways that allow inactivation, followed by degradation, of SFKs.
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Affiliation(s)
- Evan Ingley
- Cell Signalling Group, Laboratory for Cancer Medicine, Western Australian Institute for Medical Research and Centre for Medical Research, The University of Western Australia, Perth, WA, Australia.
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Faraldo-Gómez JD, Roux B. On the importance of a funneled energy landscape for the assembly and regulation of multidomain Src tyrosine kinases. Proc Natl Acad Sci U S A 2007; 104:13643-8. [PMID: 17699616 PMCID: PMC1959435 DOI: 10.1073/pnas.0704041104] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Regulation of signaling pathways in the cell often involves multidomain allosteric enzymes that are able to adopt alternate active or inactive conformations in response to specific stimuli. It is therefore of great interest to elucidate the energetic and structural determinants that govern the conformational plasticity of these proteins. In this study, free-energy computations have been used to address this fundamental question, focusing on one important family of signaling enzymes, the Src tyrosine kinases. Inactivation of these enzymes depends on the formation of an assembly comprising a tandem of SH3 and SH2 modules alongside a catalytic domain. Activation results from the release of the SH3 and SH2 domains, which are then believed to be structurally uncoupled by virtue of a flexible peptide link. In contrast to this view, this analysis shows that inactivation depends critically on the intrinsic propensity of the SH3-SH2 tandem to adopt conformations that are conducive to the assembled inactive state, even when no interactions with the rest of the kinase are possible. This funneling of the available conformational space is encoded within the SH3-SH2 connector, which appears to have evolved to modulate the flexibility of the tandem in solution. To further substantiate this notion, we show how constitutively activating mutations in the SH3-SH2 connector shift the assembly equilibrium toward the disassembled, active state. Based on a similar analysis of several constructs of the kinase complex, we propose that assembly is characterized by the progressive optimization of the protein's conformational energy, with little or no energetic frustration.
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Affiliation(s)
| | - Benoît Roux
- Center for Integrative Science, University of Chicago, Chicago, IL 60637
- *To whom correspondence should be addressed. E-mail:
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Scotlandi K, Zuntini M, Manara MC, Sciandra M, Rocchi A, Benini S, Nicoletti G, Bernard G, Nanni P, Lollini PL, Bernard A, Picci P. CD99 isoforms dictate opposite functions in tumour malignancy and metastases by activating or repressing c-Src kinase activity. Oncogene 2007; 26:6604-18. [PMID: 17471235 DOI: 10.1038/sj.onc.1210481] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
CD99 gene encodes two distinct proteins, produced by alternative splicing of CD99 gene transcript. Full-length CD99 isoform (CD99wt) is formed by an extracellular domain, followed by a transmembrane domain and a 36 amino-acid intracytoplasmic domain, which is partially deleted in the truncated, short form (CD99sh). A differential expression of these two CD99 molecules can lead to distinct functional outcomes in lymphocytes. To investigate the functional effects of CD99 molecules on malignancy, forced overexpression of the two CD99 isoforms was induced in osteosarcoma and prostate cancer cells. The two isoforms exhibited opposite functions: the major form dramatically inhibits anchorage-independent growth, anoikis resistance, migration and metastasis, whereas the CD99sh remarkably favours the phenomena. A mechanistic analysis of CD99-transfected osteosarcoma cells points to involvement of c-Src family kinase activity in regulating CD99 functions in malignancy. Ser168 residue of CD99 plays a pivotal role in the reversion of the malignant phenotype. Our findings highlight the involvement of CD99 in crucial processes of cancer malignancy, serving as a curtain raiser for this, so far neglected molecule. In addition, a dualistic role for the two CD99 isoforms was shown in agreement with what was observed for other cell adhesion molecules.
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Affiliation(s)
- K Scotlandi
- Laboratorio di Ricerca Oncologica, Istituti Ortopedici Rizzoli, Bologna, Italy.
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Callera GE, Montezano AC, Yogi A, Tostes RC, Touyz RM. Vascular signaling through cholesterol-rich domains: implications in hypertension. Curr Opin Nephrol Hypertens 2007; 16:90-104. [PMID: 17293683 DOI: 10.1097/mnh.0b013e328040bfbd] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
PURPOSE OF REVIEW Lipid rafts are emerging as key players in the integration of cellular responses. Alterations in these highly regulated signaling cascades are important in structural, mechanical and functional abnormalities that underlie vascular pathological processes. The present review focuses on recent advances in signal transduction through caveolae/lipid rafts, implicated in hypertensive processes. RECENT FINDINGS Caveolae/lipid rafts function as sites of dynamic regulatory events in receptor-induced signal transduction. Mediators of vascular function, including G-protein coupled receptors, Src family tyrosine kinases, receptor tyrosine kinases, protein phosphatases and nitric oxide synthase, are concentrated within these microdomains. The assembly of functionally active nicotinamide adenine dinucleotide phosphate oxidase and subsequent reactive oxygen species production are also dependent on interactions within the caveolae/lipid rafts. Recent findings have also demonstrated the importance of actin-cytoskeleton and focal adhesion sites for protein interactions with caveolae/lipid raft. SUMMARY Many vascular signaling processes are altered in hypertension. Whether these events involve lipid rafts/caveolae remains unclear. A better understanding of how signaling molecules compartmentalize in lipid rafts/caveolae will provide further insights into molecular mechanisms underlying vascular damage in cardiovascular disease.
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Affiliation(s)
- Glaucia E Callera
- Kidney Research Centre, Ottawa Health Research Institute, University of Ottawa, Ottawa, Canada.
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Camiña JP, Lodeiro M, Ischenko O, Martini AC, Casanueva FF. Stimulation by ghrelin of p42/p44 mitogen-activated protein kinase through the GHS-R1a receptor: Role of G-proteins and β-arrestins. J Cell Physiol 2007; 213:187-200. [PMID: 17525997 DOI: 10.1002/jcp.21109] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Results presented in this study indicate that in human embryonic kidney 293 cells (HEK 293), the ghrelin receptor growth hormone secretagogue receptor type 1a (GHS-R1a) activates the extracellular signal-related kinases 1 and 2 (ERK 1/2) via three pathways. One pathway is mediated by the beta-arrestins 1 and 2, and requires entry of the receptor into a multiprotein complex with the beta-arrestins, Src, Raf-1, and ERK 1/2. A second pathway is G(q/11)-dependent and involves a Ca(2+)-dependent PKC (PKCalpha/beta) and Src. A third pathway is G(i)-dependent and involves phosphoinositide 3-kinase (PI3K), PKCepsilon, and Src. Our current study reveals that G(i/o)- and G(q/11)-proteins are crucially involved in the beta-arrestin-mediated ERK 1/2 activation. These results thus support the view that the beta-arrestins act as both scaffolding proteins and signal transducers in ERK 1/2 activation, as reported for other receptors. The different pathways of ERK 1/2 activation suggest that binding to GHS-R1a activates ERK 1/2 pools at different locations within the cell, and thus probably with different physiological consequences.
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Affiliation(s)
- Jesus P Camiña
- Laboratory of Molecular Endocrinology, Research Area, Complejo Hospitalario Universitario de Santiago (CHUS) and Department of Medicine, University of Santiago de Compostela, Santiago de Compostela, Spain.
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