Loss of ErbB3 redirects Integrin β1 from early endosomal recycling to secretion in extracellular vesicles

ABSTRACT Receptor tyrosine kinases (RTKs) are important cargo in endocytic trafficking, yet their role in endosomal sorting and maturation of multivesicular bodies (MVBs) remains unclear. Here we show that the ErbB3 receptor sorts internalised Integrin β1, and the transferrin receptor (TfR), for endocytic recycling, in a manner that does not require ligand-induced ErbB3 signaling in breast epithelial cells. Loss of ErbB3 abrogates recycling of Integrin β1, likely from a Rab4-positive compartment, and redirects it toward lysosomal degradation and secretion as extracellular vesicle (EV) cargo. ErbB3 depletion impairs the collective migration of breast epithelial cell sheets, coinciding with reduced cell surface levels of Integrin β1 and increased release of Integrin β1-containing EVs. In contrast, EVs secreted from ErbB3-depleted cells enhance the motility of wild-type cells. Mechanistically, ErbB3 promotes assembly of the Arf6–GGA3–Rabaptin5 endosomal sorting complex to facilitate early recycling and suppress EV release. These findings provoke the notion that pseudo-RTKs play an active role in vesicular trafficking.