Eph receptors make up the largest subfamily of receptor tyrosine kinases in mammals, where they mediate communication between adjacent cells both during development and in adult tissue homeostasis. Activation of Eph receptors is thought to involve either homotypic or heterotypic self-association, but the molecular nature of oligomerization-mediated regulation of Eph receptor kinase activity remains poorly understood. We set out to directly test the roles of distinct oligomeric species in the activation of EphA3, which regulates crucial cellular process including cell adhesion and contractile responses. To this end, we established an in vitro system that allows for the reversible and inducible assembly of defined homo- and hetero-oligomers of Eph receptors. We expressed and purified Eph receptor variants fused to optogenetic and chemically inducible tags, allowing us to assemble homo- and hetero-oligomers with precisely defined composition. We show that homodimerization of the kinase domains alone is sufficient to robustly induce EphA3 kinase activity, while higher order oligomers and heterodimers may serve more complex regulatory roles in Eph receptor signaling.
Alvarado et al. (Sun,) studied this question.