Rac-dependent trans-endocytosis of ephrinBs regulates Eph–ephrin contact repulsion

Abstract

Eph receptor-ephrin signals are important for controlling repulsive and attractive cell movements during tissue patterning in embryonic development. However, the dynamic cellular responses to these signals at cell-cell contact sites are poorly understood. To examine these events we have used cell microinjection to express EphB4 and ephrinB2 in adjacent Swiss 3T3 fibroblasts and have studied the interaction of the injected cells using time-lapse microscopy. We show that Eph receptors are locally activated wherever neighbouring cells make contact. This triggers dynamic, Rac-regulated membrane ruffles at the Eph-ephrin contact sites. Subsequently, the receptor and ligand cells retract from one another, concomitantly with the endocytosis of the activated Eph receptors and their bound, full-length ephrinB ligands. Both the internalization of the receptor-ligand complexes and the subsequent cell retraction events are dependent on actin polymerization, which in turn is dependent on Rac signalling within the receptor-expressing cells. Similar events occur in primary human endothelial cells. Our findings suggest a novel mechanism for cell repulsion, in which the contact between Eph-expressing and ephrin-expressing cells is destabilized by the localized phagocytosis of the ligand-expressing cell plasma membrane by the receptor-expressing cell.

A Large T Cell Invagination with CD2 Enrichment Resets Receptor Engagement in the Immunological Synapse

“…Termination of signaling through internalization of receptor/ligand couples in a large endocytic structure has been described in the interaction between EphB and ephrinB (51,52). Consistent with such resetting of TCR signaling, accumulation of active Zap70 and phosphotyrosine are transiently suppressed at the center of the interface at 3 min after cell couple formation (53).…”

T cell activation correlates with an increasedproportion of antigen among the materials acquiredfrom target cells

“…In conclusion, our observations are compatible with a model whereby trogocytosis could play important functional role(s) in the sustained signalling that leads to the establishment of the lymphocytes' responses. This would provide a good reason to explain why trogocytosis is apparently performed by most if not all the cell types expressing receptors with tyrosine kinase activity that recognise membrane-bound ligands on the surface of other cells, including neurons [43][44][45].…”

Computational model of cell positioning: directed and collective migration in the intestinal crypt epithelium

“…EphB2 expression decreases gradually towards the top of the crypt, while ephrinB1 and ephrinB2 expression decreases towards the bottom of the crypt. Activation of EphB receptors and ephrinB ligands regulates the function of cell adhesion molecules and results in changes in cell adhesion (Wilkinson 2003;Dravis et al 2004) through endocytosis and regulation of the cytoskeleton (Marston et al 2003;Zimmer et al 2003). Thus, we assume that the interactions of EphB/ephrinB in vivo can also regulate adhesion between intestinal epithelial cells in our model.…”