ARF1 and ARF6 are dispensable for Crk-dependent epithelial-mesenchymal-like transitions.

BACKGROUND

Activation of the Met receptor tyrosine kinase through its ligand, hepatocyte growth factor (HGF), promotes an epithelial-mesenchymal transition and cell dispersal. However, little is known about the HGF-dependent signals that regulate these events. HGF stimulation of epithelial cell colonies leads to the enhanced recruitment of the CrkII and CrkL adapter proteins to Met-dependent signaling complexes. Overexpression of Crk adapter proteins in MDCK cells promotes spreading and loss of adherens junctions, events regulated by HGF. We recently demonstrated that the overexpression of CrkII promotes the formation of a multi-molecular complex containing CrkII, Paxillin and GIT-2, an ARF-GAP.

MATERIALS AND METHODS

To determine the possible role of ARF1 and ARF6 in Crk- and HGF-dependent cell spreading, dominant negative mutants of ARF1 or ARF6 were microinjected into MDCK cells.

RESULTS

We report that MDCK cell lines overexpressing CrkII display reduced ARF6 but not ARF1 activity. While both ARF1 and ARF6 are required for the spreading of MDCK cells stimulated with HGF, ARF1 and ARF6 activity is dispensable for the spreading of cells microinjected with Crk.

CONCLUSION

We propose that Crk adapter proteins may act downstream of ARF1 and ARF6 to promote cell spreading or rely on different pathways to enhance cell spreading.