The intracellular domains of the EphB6 and EphA10 receptor tyrosine pseudokinases function as dynamic signalling hubs

Abstract

EphB6 and EphA10 are two poorly characterised pseudokinase members of the Eph receptor family, which collectively serves as mediators of contact-dependent cell-cell communication to transmit extracellular cues into intracellular signals. As per their active counterparts, EphB6 and EphA10 deregulation is strongly linked to proliferative diseases. However, unlike active Eph receptors, whose catalytic activities are thought to initiate an intracellular signalling cascade, EphB6 and EphA10 are classified as catalytically-dead, raising the question of how non-catalytic functions contribute to Eph receptor signalling homeostasis. In this study, we have characterised the biochemical properties and topology of the EphB6 and EphA10 intracellular regions comprising the juxtamembrane region, pseudokinase and SAM domains. Using small-angle X-ray scattering and crosslinking-mass spectrometry, we observed high flexibility within their intracellular regions in solution and a propensity for interaction between the component domains. We identified tyrosines in the juxtamembrane region of EphB6 as EphB4 substrates, which can bind the SH2 domains of signalling effectors, including Abl, Src and Vav3, consistent with cellular roles in recruiting these proteins for downstream signaling. Furthermore, our finding that EphB6 and EphA10 can bind ATP and ATP-competitive small molecules raises the prospect that these pseudokinase domains could be pharmacologically-targeted to counter oncogenic signalling.

Dynamic chromatin organization and regulatory interactions in human endothelial cell differentiation

“…Numerous genes repressed in endothelial cell differentiation are associated with B-compartment PPIs, including genes associated with tissue patterning and neuronal development. These genes include EPHB6 (ephrin type-B receptor 6; Supplemental Figure 6A, B), which codes for a pseudokinase member of the Eph receptor family 57–60 ; GABRB3 (gamma-aminobutyric acid type A receptor subunit beta 3) and GABRA5 (gamma-aminobutyric acid type A receptor subunit alpha 3; Supplemental Figure 6C, D), both of which encode receptor subunits for the neurotransmitter GABA; and PTPRZ1 (protein tyrosine phosphatase receptor type Z1; Supplemental Figure 6E, F), which codes for a member of the receptor protein tyrosine phosphatase family that is largely restricted to the central nervous system in development 61 . Additionally, we observed examples of B-compartment PPIs associating with genes that code for factors with anti-angiogenic properties.…”

Co-clustering of EphB6 and ephrinB1 in trans restrains cancer cell invasion

“…Nevertheless, our findings provide a foundation for understanding the evolutionary adaptation of catalytic inactivity in mammalian Eph receptor orthologs. Whether a similar mode in intercellular interaction occurs in fish, reptiles, and birds, where EphB6 contains residues typical of an active kinase domain 55 , also remains to be established. Overall, our findings contribute to the body of evidence supporting the notion that pseudoenzymes, in the absence of selective pressures to retain ancestral catalytic activities, can evolve distinct functions.…”

Recent insights into the therapeutic strategies targeting the pseudokinase PTK7 in cancer

“…5B ). Concerning the poorly characterized Class 2 pseudokinase receptors EPHA10 and EPHB6 whose expression is often disregulated in cancer, their ability to bind kinase inhibitors offer opportunities for future therapeutics [ 100 ].…”