Architecture of Eph receptor clusters

Abstract

Eph receptor tyrosine kinases and their ephrin ligands regulate cell navigation during normal and oncogenic development. Signaling of Ephs is initiated in a multistep process leading to the assembly of higher-order signaling clusters that set off bidirectional signaling in interacting cells. However, the structural and mechanistic details of this assembly remained undefined. Here we present high-resolution structures of the complete EphA2 ectodomain and complexes with ephrin-A1 and A5 as the base unit of an Eph cluster. The structures reveal an elongated architecture with novel Eph/Eph interactions, both within and outside of the Eph ligand-binding domain, that suggest the molecular mechanism underlying Eph/ephrin clustering. Structure-function analysis, by using site-directed mutagenesis and cell-based signaling assays, confirms the importance of the identified oligomerization interfaces for Eph clustering.cell-cell attraction and repulsion | Eph receptor clustering

Structural basis for LAR-RPTP/Slitrk complex-mediated synaptic adhesion

“…Previously, a hypothetical model was postulated wherein the higher-order assemblies of the neurexin/neuroligin synaptic adhesion complex are required for the presynaptic differentiation activity of neuroligins 23,24 . In addition, functional forward and reverse Eph/Ephrin synaptic adhesion signalling requires formation of higher-order clusters, initiated by initial contact between them in trans, followed by formation of larger signalling clusters and ultimately leading to lateral recruitment of additional Eph clusters 25,26 . Similar adhesionpromoted lateral clustering has been reported for cadherins 27 .…”

Eph receptor and ephrin function in breast, gut, and skin epithelia

“…4,5 Ligand binding to Eph receptors at cell-cell contacts rapidly leads to the formation of higher order signaling clusters required for robust kinase activation, effector molecule recruitment, and transmission of a variety of downstream signaling cascades. 6,7 Contact-dependent signaling is evident where there is complementary expression of Eph receptor and ephrin in distinct cell types but there also appears to be a major role for Eph receptor signaling complexes in cell types where there is overlapping expression of receptor and ligand, particularly in epithelial tissues.…”

“…[21][22][23][24][25][26][27] Eph receptors also undergo clustering within the plasma membrane upon ligand binding in a manner that is stabilized by additional interactions with other ectodomain and cytodomain regions present on the receptor. 6,[28][29][30] The size of the receptor signaling clusters can vary depending on the mobility of ephrins on adjacent membranes and the cell type in question. 31 Eph receptor can also form hetero-oligomer clusters with members of a different receptor subclass.…”

“…This large family of RTKs is subdivided into 2 subclasses, EphA (1)(2)(3)(4)(5)(6)(7)(8)10) and EphB (1)(2)(3)(4)6) receptors based on amino acid sequence homology and relative binding affinities to glycosylphosphatidylinositol (GPI)-linked ephrin-A (1-5) or transmembrane ephrin-B (1-3) ligands. There is extensive promiscuity for ligand binding within receptor subclasses and more limited interaction between receptors and ligands in different subclasses.…”

Eph/ephrin signalling during development

“…In the majority of cases, Eph forward signalling causes cell repulsion away from the ephrin-expressing cell, although adhesive responses have been described. Ephrin reverse Eph/ephrin signalling involves formation of higher order Eph/ephrin clusters (Himanen et al, 2010;Seiradake et al, 2010). Initial contact between Ephs and ephrins in 'trans' at the contact site between two cells may lead to the formation of heterotetramers (two Ephs and two ephrins) with limited signalling capacity.…”