Deubiquitinase Activities Required for Hepatocyte Growth Factor-induced Scattering of Epithelial Cells

The scattering response of epithelial cells to activation of the Met receptor tyrosine kinase represents one facet of an "invasive growth" program. It is a complex event that incorporates loss of cell-cell adhesion, morphological changes, and cell motility. Ubiquitination is a reversible posttranslational modification that may target proteins for degradation or coordinate signal transduction pathways. There are approximately 79 active deubiquitinating enzymes (DUBs) predicted in the human genome. Here, via a small interfering RNA (siRNA) library approach, we have identified 12 DUBs that are necessary for aspects of the hepatocyte growth factor (HGF)-dependent scattering response of A549 cells. Different phenotypes are evident that range from full loss of scattering, similar to receptor knockdown (e.g., USP30, USP33, USP47), to loss of cell-cell contacts even in the absence of HGF but defective motility (e.g., USP3, ATXN3L). The knockdowns do not incur defective receptor, phosphatidylinositol 3-kinase, or MAP kinase activation. Our data suggest widespread involvement of the ubiquitin system at multiple stages of the Met activation response, implying significant crosstalk with phosphorylation-based transduction pathways. Development of small-molecule inhibitors of particular DUBs may offer a therapeutic approach to contain metastasis.