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: 9.81). 09/2008; 105(34):12307-12. DOI: 10.1073/pnas.0801302105
Source: PubMed

ABSTRACT 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.

Download full-text


Available from: Kazu Matsumoto, Jul 29, 2015
  • Source
    • "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). "
    [Show abstract] [Hide abstract]
    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 · 6.37 Impact Factor
  • Source
    • "Functionally, both HSPGs and CSPGs play a role in guiding axons during neuronal development (Van Vactor et al., 2006). For example, HSPGs contribute to growth cone collapse induced by Ephrin-A3 in mouse cortical neurons (Irie et al., 2008). Considering structural and functional similarities between CSPGs and HSPGs, we have hypothesized that CSPGs repress axonal elongation of mature neurons principally via interaction with membrane LAR on the axons. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Chondroitin sulfate proteoglycans (CSPGs) are a family of extracellular matrix molecules with various functions in regulating tissue morphogenesis, cell division, and axon guidance. A number of CSPGs are highly upregulated by reactive glial scar tissues after injuries and form a strong barrier for axonal regeneration in the adult vertebrate CNS. Although CSPGs may negatively regulate axonal growth via binding and altering activity of other growth-regulating factors, the molecular mechanisms by which CSPGs restrict axonal elongation are not well understood. Here, we identified a novel receptor mechanism whereby CSPGs inhibit axonal growth via interactions with neuronal transmembrane leukocyte common antigen-related phosphatase (LAR). CSPGs bind LAR with high affinity in transfected COS-7 cells and coimmunoprecipitate with LAR expressed in various tissues including the brain and spinal cord. CSPG stimulation enhances activity of LAR phosphatase in vitro. Deletion of LAR in knock-out mice or blockade of LAR with sequence-selective peptides significantly overcomes neurite growth restrictions of CSPGs in neuronal cultures. Intracellularly, CSPG-LAR interaction mediates axonal growth inhibition of neurons partially via inactivating Akt and activating RhoA signals. Systemic treatments with LAR-targeting peptides in mice with thoracic spinal cord transection injuries induce significant axon growth of descending serotonergic fibers in the vicinity of the lesion and beyond in the caudal spinal cord and promote locomotor functional recovery. Identification of LAR as a novel CSPG functional receptor provides a therapeutic basis for enhancing axonal regeneration and functional recovery after CNS injuries in adult mammals.
    The Journal of Neuroscience : The Official Journal of the Society for Neuroscience 10/2011; 31(40):14051-66. DOI:10.1523/JNEUROSCI.1737-11.2011 · 6.75 Impact Factor
  • Source
    • "Blocking or mis-expression of Eph receptors or ephrin ligands causes specific defects in NC migration (Smith et al., 1997). Recently, HSPGs have been shown to play a role in Eph receptor signalling (Irie et al., 2008) opening the possibility for a further layer of regulation by Sulf enzymes. Similar to effects of truncated Eph receptors, overexpression of XtSulf2 caused disruption of neural crest migration into the second and third branchial arches and intermingling of the NC streams as assayed by twist and Sox8 expression. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In vertebrates, there are two related genes, Sulf1 and Sulf2 that code for extracellular heparan sulphate 6-0-endosulphatases. These enzymes act to post-synthetically remodel heparan sulphate chains, generating structural diversity of cell surface HSPGs; this activity provides an important mechanism to modulate developmental cell signalling. Here we describe the expression and activity of Xenopus tropicalis Sulf2 (XtSulf2), which like XtSulf1, can act extracellularly to inhibit BMP4 and FGF4 signalling. Consistent with its discrete expression in regions of the anterior developing nervous system, we found that overexpression of XtSulf2 disrupts the expression of a set of neural markers and inhibits the migration of the neural crest. Using a combination of grafting experiments and antisense morpholino based knockdown studies in Xenopus embryos, we demonstrate that endogenous XtSulf1 and XtSulf2 play an important role during cranial neural crest cell migration in vivo.
    Developmental Biology 03/2010; 341(2):375-88. DOI:10.1016/j.ydbio.2010.02.034 · 3.64 Impact Factor
Show more