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Two Key Residues in EphrinB3 Are Critical for Its Use as an Alternative Receptor for Nipah Virus

Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine, University of California Los Angeles, California, USA.
PLoS Pathogens (Impact Factor: 8.06). 03/2006; 2(2):e7. DOI: 10.1371/journal.ppat.0020007
Source: PubMed

ABSTRACT EphrinB2 was recently discovered as a functional receptor for Nipah virus (NiV), a lethal emerging paramyxovirus. Ephrins constitute a class of homologous ligands for the Eph class of receptor tyrosine kinases and exhibit overlapping expression patterns. Thus, we examined whether other ephrins might serve as alternative receptors for NiV. Here, we show that of all known ephrins (ephrinA1-A5 and ephrinB1-B3), only the soluble Fc-fusion proteins of ephrinB3, in addition to ephrinB2, bound to soluble NiV attachment protein G (NiV-G). Soluble NiV-G bound to cell surface ephrinB3 and B2 with subnanomolar affinities (Kd = 0.58 nM and 0.06 nM for ephrinB3 and B2, respectively). Surface plasmon resonance analysis indicated that the relatively lower affinity of NiV-G for ephrinB3 was largely due to a faster off-rate (K(off) = 1.94 x 10(-3) s(-1) versus 1.06 x 10(-4) s(-1) for ephrinB3 and B2, respectively). EphrinB3 was sufficient to allow for viral entry of both pseudotype and live NiV. Soluble ephrinB2 and B3 were able to compete for NiV-envelope-mediated viral entry on both ephrinB2- and B3-expressing cells, suggesting that NiV-G interacts with both ephrinB2 and B3 via an overlapping site. Mutational analysis indicated that the Leu-Trp residues in the solvent exposed G-H loop of ephrinB2 and B3 were critical determinants of NiV binding and entry. Indeed, replacement of the Tyr-Met residues in the homologous positions in ephrinB1 with Leu-Trp conferred NiV receptor activity to ephrinB1. Thus, ephrinB3 is a bona fide alternate receptor for NiV entry, and two residues in the G-H loop of the ephrin B-class ligands are critical determinants of NiV receptor activity.

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    • "The second entry receptor for NiV and HeV has been identified: Ephrin B3 (EFN B3), with the affinity for NiV 10 times lower than EFN B2 (Negrete et al., 2006). EFN B3 is a transmembrane protein of 340 aa. "
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    • "EphrinB2 is involved in embryogenic development, vasculogenesis, and axonal guidance; its expression pattern in neurons, smooth muscle, and endothelial cells correlates with the cellular tropism of henipaviruses during infection (Erbar et al. 2008; Palmer and Klein 2003; Poliakov et al. 2004; Thiel et al. 2008). EphrinB3 shares two specific amino acid residues with Eph- rinB2 through which it can serve as an alternative receptor for NiV infection (Negrete et al. 2006). Identification of the functional residues required for eph- rinB2 and ephrinB3 interactions with henipavirus G proteins demonstrated a greater ability of NiV G to bind ephrinB3 than that of HeV G, which may explain the increased neurotropism of NiV compared to HeV in human infections (Negrete et al. 2007). "
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    ABSTRACT: Nipah (NiV) and Hendra (HeV) viruses comprise the genus Henipavirus and are highly pathogenic paramyxoviruses, which cause fatal encephalitis and respiratory disease in humans. Since their respective initial outbreaks in 1998 and 1994, they have continued to cause sporadic outbreaks resulting in fatal disease. Due to their designation as Biosafety Level 4 pathogens, the level of containment required to work with live henipaviruses is available only to select laboratories around the world. This chapter provides an overview of the molecular virology of NiV and HeV including comparisons to other, well-characterized paramyxoviruses. This chapter also describes the sequence diversity present among the henipaviruses.
    Current topics in microbiology and immunology 05/2012; 359:41-58. DOI:10.1007/82_2012_211 · 3.47 Impact Factor
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    • "Interestingly they found that soluble EFNB2 inhibited NiV-envelope-mediated infection of microvascular endothelial cells and primary cortical rat neurons. EFNB3 was later discovered as an additional receptor for NiV using the Chinese hamster ovary cell line (CHO-pgsA745) that does not express ephrins endogenously (Negrete et al., 2006). Interestingly, the authors characterized the important conserved Leu-Trp residues in the G-H loop of EFNB2 and B3 that are critical for their binding with NiV glycoprotein G. "
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