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Singh DR, Cao Q, King C, Salotto M, Ahmed F, Zhou XY, Pasquale EB, Hristova K. Unliganded EphA3 dimerization promoted by the SAM domain. Biochem J 2015; 471:101-9. [PMID: 26232493 PMCID: PMC4692061 DOI: 10.1042/bj20150433] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Revised: 07/28/2015] [Accepted: 07/31/2015] [Indexed: 01/03/2023]
Abstract
The erythropoietin-producing hepatocellular carcinoma A3 (EphA3) receptor tyrosine kinase (RTK) regulates morphogenesis during development and is overexpressed and mutated in a variety of cancers. EphA3 activation is believed to follow a 'seeding mechanism' model, in which ligand binding to the monomeric receptor acts as a trigger for signal-productive receptor clustering. We study EphA3 lateral interactions on the surface of live cells and we demonstrate that EphA3 forms dimers in the absence of ligand binding. We further show that these dimers are stabilized by interactions involving the EphA3 sterile α-motif (SAM) domain. The discovery of unliganded EphA3 dimers challenges the current understanding of the chain of EphA3 activation events and suggests that EphA3 may follow the 'pre-formed dimer' model of activation known to be relevant for other receptor tyrosine kinases. The present work also establishes a new role for the SAM domain in promoting Eph receptor lateral interactions and signalling on the cell surface.
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Affiliation(s)
- Deo R Singh
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21212, U.S.A
| | - QingQing Cao
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21212, U.S.A
| | - Christopher King
- Program in Molecular Biophysics, Johns Hopkins University, Baltimore, MD 21212, U.S.A
| | - Matt Salotto
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21212, U.S.A
| | - Fozia Ahmed
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21212, U.S.A
| | - Xiang Yang Zhou
- Vaccine Center, The Wistar Institute, Philadelphia, PA 19104, U.S.A
| | - Elena B Pasquale
- Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, U.S.A
| | - Kalina Hristova
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21212, U.S.A. Program in Molecular Biophysics, Johns Hopkins University, Baltimore, MD 21212, U.S.A.
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202
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Callegari D, Pala D, Scalvini L, Tognolini M, Incerti M, Rivara S, Mor M, Lodola A. Comparative Analysis of Virtual Screening Approaches in the Search for Novel EphA2 Receptor Antagonists. Molecules 2015; 20:17132-51. [PMID: 26393553 PMCID: PMC6331951 DOI: 10.3390/molecules200917132] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Revised: 09/08/2015] [Accepted: 09/11/2015] [Indexed: 11/29/2022] Open
Abstract
The EphA2 receptor and its ephrin-A1 ligand form a key cell communication system, which has been found overexpressed in many cancer types and involved in tumor growth. Recent medicinal chemistry efforts have identified bile acid derivatives as low micromolar binders of the EphA2 receptor. However, these compounds suffer from poor physicochemical properties, hampering their use in vivo. The identification of compounds able to disrupt the EphA2-ephrin-A1 complex lacking the bile acid scaffold may lead to new pharmacological tools suitable for in vivo studies. To identify the most promising virtual screening (VS) protocol aimed at finding novel EphA2 antagonists, we investigated the ability of both ligand-based and structure-based approaches to retrieve known EphA2 antagonists from libraries of decoys with similar molecular properties. While ligand-based VSs were conducted using UniPR129 and ephrin-A1 ligand as reference structures, structure-based VSs were performed with Glide, using the X-ray structure of the EphA2 receptor/ephrin-A1 complex. A comparison of enrichment factors showed that ligand-based approaches outperformed the structure-based ones, suggesting ligand-based methods using the G-H loop of ephrin-A1 ligand as template as the most promising protocols to search for novel EphA2 antagonists.
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Affiliation(s)
- Donatella Callegari
- Dipartimento di Farmacia, Università degli Studi di Parma, Parma 43124, Italy.
| | - Daniele Pala
- Dipartimento di Farmacia, Università degli Studi di Parma, Parma 43124, Italy.
| | - Laura Scalvini
- Dipartimento di Farmacia, Università degli Studi di Parma, Parma 43124, Italy.
| | | | - Matteo Incerti
- Dipartimento di Farmacia, Università degli Studi di Parma, Parma 43124, Italy.
| | - Silvia Rivara
- Dipartimento di Farmacia, Università degli Studi di Parma, Parma 43124, Italy.
| | - Marco Mor
- Dipartimento di Farmacia, Università degli Studi di Parma, Parma 43124, Italy.
| | - Alessio Lodola
- Dipartimento di Farmacia, Università degli Studi di Parma, Parma 43124, Italy.
- Department of Applied Sciences, Northumbria University at Newcastle, Newcastle-Upon-Tyne, NE1 8ST, UK.
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203
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Giorgio C, Mena P, Del Rio D, Brighenti F, Barocelli E, Hassan-Mohamed I, Callegari D, Lodola A, Tognolini M. The ellagitannin colonic metabolite urolithin D selectively inhibits EphA2 phosphorylation in prostate cancer cells. Mol Nutr Food Res 2015; 59:2155-67. [DOI: 10.1002/mnfr.201500470] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Revised: 08/01/2015] [Accepted: 08/06/2015] [Indexed: 11/09/2022]
Affiliation(s)
| | - Pedro Mena
- The Laboratory of Phytochemicals in Physiology; Human Nutrition Unit; Department of Food Science; University of Parma; Via Volturno, Parma Italy
| | - Daniele Del Rio
- The Laboratory of Phytochemicals in Physiology; Human Nutrition Unit; Department of Food Science; University of Parma; Via Volturno, Parma Italy
| | - Furio Brighenti
- The Laboratory of Phytochemicals in Physiology; Human Nutrition Unit; Department of Food Science; University of Parma; Via Volturno, Parma Italy
| | | | | | | | - Alessio Lodola
- Department of Pharmacy; University of Parma; Parma Italy
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204
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Singh DR, Ahmed F, King C, Gupta N, Salotto M, Pasquale EB, Hristova K. EphA2 Receptor Unliganded Dimers Suppress EphA2 Pro-tumorigenic Signaling. J Biol Chem 2015; 290:27271-27279. [PMID: 26363067 DOI: 10.1074/jbc.m115.676866] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Indexed: 01/08/2023] Open
Abstract
The EphA2 receptor tyrosine kinase promotes cell migration and cancer malignancy through a ligand- and kinase-independent distinctive mechanism that has been linked to high Ser-897 phosphorylation and low tyrosine phosphorylation. Here, we demonstrate that EphA2 forms dimers in the plasma membrane of HEK293T cells in the absence of ephrin ligand binding, suggesting that the current seeding mechanism model of EphA2 activation is incomplete. We also characterize a dimerization-deficient EphA2 mutant that shows enhanced ability to promote cell migration, concomitant with increased Ser-897 phosphorylation and decreased tyrosine phosphorylation compared with EphA2 wild type. Our data reveal a correlation between unliganded dimerization and tumorigenic signaling and suggest that EphA2 pro-tumorigenic activity is mediated by the EphA2 monomer. Thus, a therapeutic strategy that aims at the stabilization of EphA2 dimers may be beneficial for the treatment of cancers linked to EphA2 overexpression.
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Affiliation(s)
- Deo R Singh
- Department of Materials Science and Engineering, The Johns Hopkins University, Baltimore, Maryland 21218
| | - Fozia Ahmed
- Department of Materials Science and Engineering, The Johns Hopkins University, Baltimore, Maryland 21218
| | - Christopher King
- Department of Program in Molecular Biophysics, The Johns Hopkins University, Baltimore, Maryland 21218 and
| | - Nisha Gupta
- Department of Materials Science and Engineering, The Johns Hopkins University, Baltimore, Maryland 21218
| | - Matt Salotto
- Department of Materials Science and Engineering, The Johns Hopkins University, Baltimore, Maryland 21218
| | - Elena B Pasquale
- Sanford Burnham Prebys Medical Discovery Institute, La Jolla, San Diego, California 92037
| | - Kalina Hristova
- Department of Materials Science and Engineering, The Johns Hopkins University, Baltimore, Maryland 21218; Department of Program in Molecular Biophysics, The Johns Hopkins University, Baltimore, Maryland 21218 and.
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205
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Δ(5)-Cholenoyl-amino acids as selective and orally available antagonists of the Eph-ephrin system. Eur J Med Chem 2015; 103:312-24. [PMID: 26363867 DOI: 10.1016/j.ejmech.2015.08.048] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 08/24/2015] [Accepted: 08/25/2015] [Indexed: 01/22/2023]
Abstract
The Eph receptor-ephrin system is an emerging target for the development of novel anti-angiogenic therapies. Research programs aimed at developing small-molecule antagonists of the Eph receptors are still in their initial stage as available compounds suffer from pharmacological drawbacks, limiting their application in vitro and in vivo. In the present work, we report the design, synthesis and evaluation of structure-activity relationships of a class of Δ(5)-cholenoyl-amino acid conjugates as Eph-ephrin antagonists. As a major achievement of our exploration, we identified N-(3β-hydroxy-Δ(5)-cholen-24-oyl)-L-tryptophan (UniPR1331) as the first small molecule antagonist of the Eph-ephrin system effective as an anti-angiogenic agent in endothelial cells, bioavailable in mice by the oral route and devoid of biological activity on G protein-coupled and nuclear receptors targeted by bile acid derivatives.
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206
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Forse GJ, Uson ML, Nasertorabi F, Kolatkar A, Lamberto I, Pasquale EB, Kuhn P. Distinctive Structure of the EphA3/Ephrin-A5 Complex Reveals a Dual Mode of Eph Receptor Interaction for Ephrin-A5. PLoS One 2015; 10:e0127081. [PMID: 25993310 PMCID: PMC4439037 DOI: 10.1371/journal.pone.0127081] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Accepted: 04/11/2015] [Indexed: 11/19/2022] Open
Abstract
The Eph receptor tyrosine kinase/ephrin ligand system regulates a wide spectrum of physiological processes, while its dysregulation has been implicated in cancer progression. The human EphA3 receptor is widely upregulated in the tumor microenvironment and is highly expressed in some types of cancer cells. Furthermore, EphA3 is among the most highly mutated genes in lung cancer and it is also frequently mutated in other cancers. We report the structure of the ligand-binding domain of the EphA3 receptor in complex with its preferred ligand, ephrin-A5. The structure of the complex reveals a pronounced tilt of the ephrin-A5 ligand compared to its orientation when bound to the EphA2 and EphB2 receptors and similar to its orientation when bound to EphA4. This tilt brings an additional area of ephrin-A5 into contact with regions of EphA3 outside the ephrin-binding pocket thereby enlarging the size of the interface, which is consistent with the high binding affinity of ephrin-A5 for EphA3. This large variation in the tilt of ephrin-A5 bound to different Eph receptors has not been previously observed for other ephrins.
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Affiliation(s)
- Garry Jason Forse
- Dornsife College of Letters, Arts and Sciences, University of Southern California, 3430 S. Vermont Ave., Suite 105 (110), MC3301, Los Angeles, CA, 90089–3301, United States of America
| | - Maria Loressa Uson
- Dornsife College of Letters, Arts and Sciences, University of Southern California, 3430 S. Vermont Ave., Suite 105 (110), MC3301, Los Angeles, CA, 90089–3301, United States of America
| | - Fariborz Nasertorabi
- Dornsife College of Letters, Arts and Sciences, University of Southern California, 3430 S. Vermont Ave., Suite 105 (110), MC3301, Los Angeles, CA, 90089–3301, United States of America
| | - Anand Kolatkar
- Dornsife College of Letters, Arts and Sciences, University of Southern California, 3430 S. Vermont Ave., Suite 105 (110), MC3301, Los Angeles, CA, 90089–3301, United States of America
| | - Ilaria Lamberto
- Sanford-Burnham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla, California, 92037, United States of America
| | - Elena Bianca Pasquale
- Sanford-Burnham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla, California, 92037, United States of America
- Department of Pathology, University of California San Diego, La Jolla, California, 92093, United States of America
| | - Peter Kuhn
- Dornsife College of Letters, Arts and Sciences, University of Southern California, 3430 S. Vermont Ave., Suite 105 (110), MC3301, Los Angeles, CA, 90089–3301, United States of America
- * E-mail:
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207
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Riedl SJ, Pasquale EB. Targeting the Eph System with Peptides and Peptide Conjugates. Curr Drug Targets 2015; 16:1031-47. [PMID: 26212263 PMCID: PMC4861043 DOI: 10.2174/1389450116666150727115934] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Revised: 02/02/2015] [Accepted: 07/20/2015] [Indexed: 01/06/2023]
Abstract
Eph receptor tyrosine kinases and ephrin ligands constitute an important cell communication system that controls development, tissue homeostasis and many pathological processes. Various Eph receptors/ephrins are present in essentially all cell types and their expression is often dysregulated by injury and disease. Thus, the 14 Eph receptors are attracting increasing attention as a major class of potential drug targets. In particular, agents that bind to the extracellular ephrin-binding pocket of these receptors show promise for medical applications. This pocket comprises a broad and shallow groove surrounded by several flexible loops, which makes peptides particularly suitable to target it with high affinity and selectivity. Accordingly, a number of peptides that bind to Eph receptors with micromolar affinity have been identified using phage display and other approaches. These peptides are generally antagonists that inhibit ephrin binding and Eph receptor/ ephrin signaling, but some are agonists mimicking ephrin-induced Eph receptor activation. Importantly, some of the peptides are exquisitely selective for single Eph receptors. Most identified peptides are linear, but recently the considerable advantages of cyclic scaffolds have been recognized, particularly in light of potential optimization towards drug leads. To date, peptide improvements have yielded derivatives with low nanomolar Eph receptor binding affinity, high resistance to plasma proteases and/or long in vivo half-life, exemplifying the merits of peptides for Eph receptor targeting. Besides their modulation of Eph receptor/ephrin function, peptides can also serve to deliver conjugated imaging and therapeutic agents or various types of nanoparticles to tumors and other diseased tissues presenting target Eph receptors.
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Affiliation(s)
| | - Elena B Pasquale
- Sanford Burnham Prebys Medical Discovery Institute, 10901 N. Torrey Pines Rd., La Jolla, CA 92037, USA.
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