A Disalicylic Acid‐Furanyl Derivative Inhibits Ephrin Binding to a Subset of Eph Receptors

Abstract

Eph receptor tyrosine kinases and ephrin ligands control many physiological and pathological processes, and molecules interfering with their interaction are useful probes to elucidate their complex biological functions. Moreover, targeting Eph receptors might enable new strategies to inhibit cancer progression and pathological angiogenesis as well as promote nerve regeneration. Because our previous work suggested the importance of the salicylic acid group in antagonistic small molecules targeting Eph receptors, we screened a series of salicylic acid derivatives to identify novel Eph receptor antagonists. This identified a disalicylic acid-furanyl derivative that inhibits ephrin-A5 binding to EphA4 with an IC50 of 3 μM in ELISA assays. This compound, which appears to bind to the ephrin-binding pocket of EphA4, also targets several other Eph receptors. Furthermore, it inhibits EphA2 and EphA4 tyrosine phosphorylation in cells stimulated with ephrin while not affecting phosphorylation of EphB2, which is not a target receptor. In endothelial cells, the disalicylic acid-furanyl derivative inhibits EphA2 phosphorylation in response to TNFα and capillary-like tube formation on Matrigel, two effects that depend on EphA2 interaction with endogenous ephrin-A1. These findings suggest that salicylic acid derivatives could be used as starting points to design new small molecule antagonists of Eph receptors.

Blockade of EphA4 signaling ameliorates hippocampal synaptic dysfunctions in mouse models of Alzheimer’s disease

“…Although the 12-amino acid KYL peptide was able to block the EphA4 signaling effectively, there may be huge challenges to develop this peptide as a drug candidate, e.g., bioavailability. For the identified small-molecule EphA4 inhibitors, although their effectiveness was demonstrated in in vitro or cellular assays, the in vivo effects of these compounds on inhibiting EphA4 and the bioavailability of these agents have not been reported (28,33,41). The reduction of EphA4 activation in APP/PS1 mouse brains by oral administration of Rhy (Fig.…”

Eph receptor tyrosine kinases in cancer stem cells

“…Combined efforts of high through-put screening and structural analyses have identified the derivatives of salicylates and lithocholic acid as small molecule inhibitors capable of disrupting Eph receptor-ligand interactions. Several salicylates were found to target the binding pocket of EphA4 as well as inhibiting ephrin binding to EphA2 and EphA4 (62, 63). These compounds inhibit a subset of Eph receptor activation and endothelial capillary-like tube formation in cell-based assays.…”

Targeting Eph receptors with peptides and small molecules: Progress and challenges

“…Nuclear magnetic resonance (NMR) characterization was consistent with the binding of the two salicylates in the ephrin-binding pocket of EphA4 and cell-based assays suggested that the compounds inhibit ephrin-dependent EphA2 and EphA4 activation and biological responses, although with low potency [25,40]. However, recent studies have revealed that some modification of the original compounds, which may involve polymerization or oxidative processes, is required for their inhibitory activity [41]. …”

“…A small molecule containing two salicylic acid-furanyl groups was also found to target the ephrin-binding pocket of EphA4 and inihibit ephrin binding to EphA2, EphA4 and several other Eph receptors through a mechanism that may involve irreversible binding [41]. The ability of the three salicylates to inhibit the activation of a subset of Eph receptors and their effects in cells, including endothelial capillary-like tube formation, suggest that these compounds could be used as chemical tools to study Eph receptor functions.…”