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

Abstract

EphB6 is an understudied ephrin receptor tyrosine pseudokinase, the expression of which is downregulated in multiple types of metastatic cancers. Compared to its kinase-active counterparts, how EphB6 regulates signal transduction in the absence of intrinsic kinase activity remains unknown. Here, we unveil the molecular details of key signal transduction mechanisms driven by EphB6. We identify ephrinB1 as a cognate ligand of EphB6 and demonstrate EphB6’s ability to form extensive co-clusters at the plasma membrane upon binding ephrinB1 in trans across cell-cell contacts, which are resistant to endocytosis. Using super resolution microscopy, correlative light and electron microscopy and cryo-electron tomography, we reveal that co clustering of EphB6 and ephrinB1 promotes the formation of unprecedented double membrane tubular structure interconnecting cells. Importantly, phenotypically, co-clustering of EphB6 and ephrinB1 and the resulting tubular structures suppress cancer cell invasion by prolonging cell-cell contacts, rationalising a role for EphB6 pseudokinase as a tumor suppressor when interacting with its ligands in trans.