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.


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.


CONCLUSIONS
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.
Lamorte
Louie
L
Molecular Oncology Group, McGill University Hospital Centre, Department of Biochemistry, McGill University, Montreal, Quebec, Canada.
Park
Morag
M
D020823:ADP-Ribosylation Factor 1 / Q000502:physiology*; D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000502:physiology*; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002448:Cell Adhesion / Q000502:physiology; D002460:Cell Line; D002465:Cell Movement / Q000502:physiology; D004285:Dogs; D004847:Epithelial Cells / Q000166:cytology / Q000502:physiology*; D008648:Mesoderm / Q000166:cytology / Q000502:physiology*; D008845:Microinjections; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D010957:Plasmids / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000502:physiology*; D050737:Proto-Oncogene Proteins c-crk
D000089982:ADP-Ribosylation Factor 6; D048868:Adaptor Proteins, Signal Transducing; C082869:CRKL protein; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D050737:Proto-Oncogene Proteins c-crk; D020823:ADP-Ribosylation Factor 1; D020727:ADP-Ribosylation Factors