Crk adapter proteins promote an epithelial-mesenchymal-like transition and are required for HGF-mediated cell spreading and breakdown of epithelial adherens junctions.
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. We provide evidence that signals involving CrkII and CrkL are required for the breakdown of adherens junctions, the spreading of epithelial colonies, and the formation of lamellipodia in response to HGF. The overexpression of a CrkI SH3 domain mutant blocks these HGF-dependent events. In addition, the overexpression of CrkII or CrkL promotes lamellipodia formation, loss of adherens junctions, cell spreading, and dispersal of colonies of breast cancer epithelial cells in the absence of HGF. Stable lines of epithelial cells overexpressing CrkII show enhanced activation of Rac1 and Rap1. The Crk-dependent breakdown of adherens junctions and cell spreading is inhibited by the expression of a dominant negative mutant of Rac1 but not Rap1. These findings provide evidence that Crk adapter proteins play a critical role in the breakdown of adherens junctions and the spreading of sheets of epithelial cells.
Lamorte
Louie
L
Department of Biochemistry, McGill University, Montreal, Quebec, Canada H3A 1A1.
Royal
Isabelle
I
Naujokas
Monica
M
Park
Morag
M
D048868:Adaptor Proteins, Signal Transducing; D022005:Adherens Junctions / Q000378:metabolism*; D002465:Cell Movement; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D022001:Focal Adhesions / Q000378:metabolism; D017228:Hepatocyte Growth Factor / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D008648:Mesoderm / Q000166:cytology / Q000378:metabolism*; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D050737:Proto-Oncogene Proteins c-crk; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism; D011554:Pseudopodia / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism; D014407:Tumor Cells, Cultured; D062826:Zonula Occludens-1 Protein; D051176:beta Catenin; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism; D018909:src Homology Domains
D048868:Adaptor Proteins, Signal Transducing; C082869:CRKL protein; C495270:CTNNB1 protein, human; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D050737:Proto-Oncogene Proteins c-crk; C569042:TJP1 protein, human; D015534:Trans-Activators; D062826:Zonula Occludens-1 Protein; D051176:beta Catenin; D017228:Hepatocyte Growth Factor; D019859:Proto-Oncogene Proteins c-met; D020830:rac1 GTP-Binding Protein; D020827:rap1 GTP-Binding Proteins