The Eph receptors represent the largest family of receptor tyrosine kinases. The Eph receptors and their ephrin ligands are widely expressed during development and in the adult organism, playing important roles in axon guidance, vasculogenesis and cell migration. Eph receptors are unique among other receptor kinases in that they fall into two subclasses with distinct ligand specificities, and in that they can also function as ligands activating bi-directional signaling. Understanding the mechanism of Eph/ephrin signaling requires a detailed structural and biophysical characterization of the Eph receptors, the ephrins, and their interactions with each other and with other regulatory proteins.
The specific aims of our proposed investigations are: 1) Structural characterization of full Eph ectodomains alone and in complex with ephrins;2) Structural characterization of the interactions of EphB2 with the NMDA Receptor and amyloid precursor protein derived A?;4) Production and structural characterization of functional full-length Eph receptors.

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The Eph receptors are the largest receptor tyrosine kinase family. The Ephs and their ephrin ligands are expressed in many tissues during development and in the adult organism and play important roles in diverse processes, including neuronal development, axon guidance, cell migration, tumor progression and metastasis. Our proposal integrates the use of X-ray crystallography with other biophysical, biochemical and cell-biological approaches to study how these molecules recognize and interact with each other, and with other regulatory proteins to activate cell-cell signaling. Currently there are no available crystal structures for any full-length RTK and our long-term goal is to determine the structures of transmembrane Eph receptors and their complexes with ephrins. Ephs are also central players in the crossroads of memory, cognition, and synapse function and malfunction, and that their misregulation leads to neurologic and psychiatric disorders. However, there are no detailed studies establishing the precise molecular mechanism of interaction between Ephs and the NMDA receptor or the amyloid precursor protein derived A?. This lack of knowledge has hampered efforts to specifically target these interactions for therapeutic purposes. We, therefore, will carry out detailed biochemical and structural studies on the EphB2/NMDA and EphB2/A? interactions.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Research Project (R01)
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Macromolecular Structure and Function C Study Section (MSFC)
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Mamounas, Laura
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Sloan-Kettering Institute for Cancer Research
New York
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Barton, William A; Dalton, Annamarie C; Seegar, Tom C M et al. (2014) Tie2 and Eph receptor tyrosine kinase activation and signaling. Cold Spring Harb Perspect Biol 6:
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Xu, Kai; Tzvetkova-Robev, Dorothea; Xu, Yan et al. (2013) Insights into Eph receptor tyrosine kinase activation from crystal structures of the EphA4 ectodomain and its complex with ephrin-A5. Proc Natl Acad Sci U S A 110:14634-9
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Xu, Kai; Xu, Yan; Rajashankar, Kanagalaghatta R et al. (2013) Crystal structures of Lgr4 and its complex with R-spondin1. Structure 21:1683-9
Ferluga, Sara; Hantgan, Roy; Goldgur, Yehuda et al. (2013) Biological and structural characterization of glycosylation on ephrin-A1, a preferred ligand for EphA2 receptor tyrosine kinase. J Biol Chem 288:18448-57
Xu, Kai; Broder, Christopher C; Nikolov, Dimitar B (2012) Ephrin-B2 and ephrin-B3 as functional henipavirus receptors. Semin Cell Dev Biol 23:116-23
Singla, Nikhil; Erdjument-Bromage, Hediye; Himanen, Juha P et al. (2011) A semisynthetic Eph receptor tyrosine kinase provides insight into ligand-induced kinase activation. Chem Biol 18:361-71
Singla, Nikhil; Goldgur, Yehuda; Xu, Kai et al. (2010) Crystal structure of the ligand-binding domain of the promiscuous EphA4 receptor reveals two distinct conformations. Biochem Biophys Res Commun 399:555-9
Kar, Rekha; Mishra, Nandita; Singha, Prajjal K et al. (2010) Mitochondrial remodeling following fission inhibition by 15d-PGJ2 involves molecular changes in mitochondrial fusion protein OPA1. Biochem Biophys Res Commun 399:548-54

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