Distinct tyrosine autophosphorylation sites mediate induction of epithelial mesenchymal like transition by an activated ErbB-2/Neu receptor

Tight control of cell proliferation and morphogenesis is required to ensure normal tissue patterning and prevent cancer formation. Overexpression of t he ErbB-2/Neu receptor tyrosine kinase is associated with increased progres sion in human breast cancer, yet in breast explant cultures, the ErbB-2/Neu receptor contributes to alveolar differentiation. To examine the consequen ce of deregulated ErbB-2/Neu activation on epithelial morphogenesis, we hav e expressed a constitutively activated mutant of ErbB-2/Neu in a Madin-Darb y canine kidney (MDCK) epithelial cell model. Using two-dimensional culture s we demonstrate that activated ErbB-2/Neu induces breakdown of cell-cell j unctions, increased cell motility and dispersal of epithelial colonies. Thi s correlates with reorganization of the actin cytoskeleton and fetal adhesi ons and loss of insoluble cell-cell junction complexes involving E-cadherin . Interestingly, a constitutively activated ErbB-2/Neu receptor promotes an invasive morphogenic program in MDCK cells in a three-dimensional matrix. We show that two tyrosines in the carboxy-terminal tail of ErbB-2/Neu, invo lved in the phosphorylation of the Shc adapter protein, are each sufficient to promote epithelial-mesenchymal like transition and enhanced cell motili ty in two-dimensional culture and cell invasion rather than a morphogenic r esponse in matrix culture. This provides a model system to investigate ErbB -2/Neu induced signaling pathways required for epithelial cell dispersal an d invasion versus morphogenesis.