Heparan sulfate regulates ephrin-A3/EphA receptor signaling

Sanford Children's Health Research Center, Burnham Institute for Medical Research, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 09/2008; 105(34):12307-12. DOI: 10.1073/pnas.0801302105
Source: PubMed


Increasing evidence indicates that many signaling pathways involve not only ligands and receptors but also various types of coreceptors and matrix components as additional layers of regulation. Signaling by Eph receptors and their ephrin ligands plays a key role in a variety of biological processes, such as axon guidance and topographic map formation, synaptic plasticity, angiogenesis, and cancer. Little is known about whether the ephrin-Eph receptor signaling system is subject to such additional layers of regulation. Here, we show that ephrin-A3 binds to heparan sulfate, and that the presence of cell surface heparan sulfate is required for the full biological activity of ephrin-A3. Among the ephrins tested, including ephrin-A1, -A2, -A5, -B1, and -B2, only ephrin-A3 binds heparin or heparan sulfate. Ephrin-A3-dependent EphA receptor activation is reduced in mutant cells that are defective in heparan sulfate synthesis, in wild-type cells from which cell surface heparan sulfate has been removed, and in the hippocampus of conditional knockout mice defective in heparan sulfate synthesis. Ephrin-A3-dependent cell rounding is impaired in CHO cells lacking heparan sulfate, and cortical neurons lacking heparan sulfate exhibit impaired growth cone collapse. In contrast, cell rounding and growth cone collapse in response to ephrin-A5, which does not bind heparan sulfate, are not affected by the absence of heparan sulfate. These results show that heparan sulfate modulates ephrin/Eph signaling and suggest a physiological role for heparan sulfate proteoglycans in the regulation of ephrin-A3-dependent biological processes.

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    • "The ephrin-As are attached to the cell surface by a glycosylphosphatidylinositol (GPI) anchor, although they can also be released to activate EphA receptors at a distance (Bartley et al. 1994; Wykosky et al. 2008), whereas the ephrin-Bs contain a transmembrane segment and a short cytoplasmic region. Ephrin-A3 and ephrin-B3 also bind heparan sulfate proteoglycans through an interaction that involves their extracellular linker region and that, at least in the case of ephrin-A3, potentiates EphA receptor activation and signaling (Irie et al. 2008; Holen et al. 2011). The Eph receptor family has greatly expanded during evolution, and includes almost one fourth of the 58 human RTKs (Schlessinger and Lemmon 2013). "
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    ABSTRACT: The Eph receptors are the largest of the RTK families. Like other RTKs, they transduce signals from the cell exterior to the interior through ligand-induced activation of their kinase domain. However, the Eph receptors also have distinctive features. Instead of binding soluble ligands, they generally mediate contact-dependent cell-cell communication by interacting with surface-associated ligands-the ephrins-on neighboring cells. Eph receptor-ephrin complexes emanate bidirectional signals that affect both receptor- and ephrin-expressing cells. Intriguingly, ephrins can also attenuate signaling by Eph receptors coexpressed in the same cell. Additionally, Eph receptors can modulate cell behavior independently of ephrin binding and kinase activity. The Eph/ephrin system regulates many developmental processes and adult tissue homeostasis. Its abnormal function has been implicated in various diseases, including cancer. Thus, Eph receptors represent promising therapeutic targets. However, more research is needed to better understand the many aspects of their complex biology that remain mysterious.
    Cold Spring Harbor perspectives in biology 09/2013; 5(9). DOI:10.1101/cshperspect.a009159 · 8.68 Impact Factor
    • "As Ephrin-A3 is the direct target of miR-210 and miR-210 plays an important role in angiogenesis, we further demonstrated that Ephrin-A3 contributed to angiogenesis (Figure 4E and F). Recent research has shown that Ephrin-A3 binds to heparan sulfate, while the presence of cell surface heparan sulfate is required for the full biological activity of Ephrin-A3 (Irie et al. 2008). In this study, we provided evidence that the heparan sulfate mimetic polysaccharide WSS25 regulated the function of Ephrin-A3 in angiogenesis. "
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    ABSTRACT: WSS25 is a sulfated polysaccharide that inhibits angiogenesis. However, the mechanism underlying the regulation of angiogenesis by WSS25 is not well understood. Using microRNA (miRNA) microarray analysis, a total of 25 miRNAs were found to be upregulated and 12 (including miR-210) downregulated by WSS25 in human microvascular endothelial cells (HMEC-1). Interestingly, Dicer, a key enzyme for miRNA biosynthesis, was downregulated by WSS25 in HMEC-1 cells. Further studies indicated that HMEC-1 cell tube formation and miR-210 expression were suppressed while Ephrin-A3 expression was enhanced by the silencing of Dicer. In contrast, HMEC-1 cell tube formation and miR-210 expression were induced while Ephrin-A3 expression was suppressed by Dicer overexpression. Moreover, miR-210 was downregulated while Ephrin-A3 was upregulated by WSS25 in HMEC-1 cells. HMEC-1 cell migration and tube formation were arrested, while Ephrin-A3 expression was augmented by anti-miR-210. In addition, HMEC-1 cell tube formation was significantly attenuated or augmented when Ephrin-A3 was overexpressed or silenced, respectively. Nevertheless, the tube formation blocked by WSS25 could be partially rescued by manipulation of Dicer, miR-210 and Ephrin-A3. These results suggest a new pathway whereby WSS25 inhibits angiogenesis via suppression of Dicer, leading to downregulation of miR-210 and upregulation of Ephrin-A3. © 2013 The Author 2013. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: [email protected] /* */
    Glycobiology 01/2013; 23(5). DOI:10.1093/glycob/cwt004 · 3.15 Impact Factor
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    • "To ectopically express ephrin-A ligands in keratinocytes, a full-length human ephrin-A1 cDNA was obtained from W. Debinski (Wake Forest University Medical Center; Winston- Salem, NC) (Kaplan et al., 2012; Wykosky et al., 2007) and a full-length murine ephrin-A3 cDNA was obtained from Y. Yamaguchi (Burnham Institute for Medical Research; La Jolla, CA) (Irie et al., 2008). These ephrin cDNAs were subcloned into the pLZRS-Linker vector (Denning et al., 2002). "
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    ABSTRACT: EphA2 is a receptor tyrosine kinase (RTK) that triggers keratinocyte differentiation upon activation and subsequent downregulation by ephrin-A1 ligand. The objective of this study was to determine whether the EphA2/ephrin-A1 signaling axis was altered in psoriasis, an inflammatory skin condition in which keratinocyte differentiation is abnormal. Microarray analysis of skin biopsies from psoriasis patients revealed increased mRNA transcripts for several members of this RTK family in plaques, including the EphA1, EphA2, and EphA4 subtypes prominently expressed by keratinocytes. Of these, EphA2 showed the greatest upregulation, a finding that was confirmed by quantitative reverse-transcriptase-PCR, immunohistochemistry (IHC), and ELISA. In contrast, psoriatic lesions exhibited reduced ephrin-A ligand immunoreactivity. Exposure of primary keratinocytes induced to differentiate in high calcium or a three-dimensional (3D) raft culture of human epidermis to a combination of growth factors and cytokines elevated in psoriasis increased EphA2 mRNA and protein expression while inducing S100A7 and disrupting differentiation. Pharmacological delivery of a soluble ephrin-A1 peptidomimetic ligand led to a reduction in EphA2 expression and ameliorated proliferation and differentiation in raft cultures exposed to EGF and IL-1α. These findings suggest that ephrin-A1-mediated downregulation of EphA2 supports keratinocyte differentiation in the context of cytokine perturbation.Journal of Investigative Dermatology advance online publication, 29 November 2012; doi:10.1038/jid.2012.391.
    Journal of Investigative Dermatology 11/2012; 133(3). DOI:10.1038/jid.2012.391 · 7.22 Impact Factor
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