Research articleEph receptor interclass cooperation is required for the regulation of cell proliferation

- We demonstrate that ephrin-B1 and ephrin-B2 have largely non-overlapping functions in the intestinal stem cell niche.
- Ephrin-B1 regulates cell positioning and ephrin-B2 regulates cell proliferation in the intestinal stem cell niche.
- EphA4/B2 receptor cooperation in response to ephrin-B2 binding is obligatory to convey mitogenic signals in the intestine.
- EphA4 facilitates EphB2 phosphorylation in response to ephrin-B2 in SW480 adenocarcinoma cells.
- Ephrin-B1 and ephrin-B2 induce phosphorylation and degradation of the EphB2 receptor with different kinetics.

Cancer often arises by the constitutive activation of mitogenic pathways by mutations in stem cells. Eph receptors are unusual in that although they regulate the proliferation of stem/progenitor cells in many adult organs, they typically fail to transform cells. Multiple ephrins and Eph receptors are often co-expressed and are thought to be redundant, but we here describe an unexpected dichotomy with two homologous ligands, ephrin-B1 and ephrin-B2, regulating specifically migration or proliferation in the intestinal stem cell niche. We demonstrate that the combined activity of two different coexpressed Eph receptors of the A and B class assembled into common signaling clusters in response to ephrin-B2 is required for mitogenic signaling. The requirement of two different Eph receptors to convey mitogenic signals identifies a new type of cooperation within this receptor family and helps explain why constitutive activation of a single receptor fails to transform cells.