The Met receptor tyrosine kinase was originally identified as a rearranged oncogene, Tpr-Met. Both Met and its ligand, hepatocyte growth factor (HGF) regulate epithelial cell dispersal and morphogenesis and are deregulated in several human tumors. At the onset of this thesis, little was known about the signals that regulate these events. In this thesis I have defined the involvement of the Crk adapter protein in Met-dependent anchorage independent growth, cell spreading, cell dispersal, invasion and morphogenesis. The disruption of focal adhesion signaling in Met transformed fibroblasts is associated with the loss of Crk/p130Cas and Crk/Paxillin complexes. In contrast, Crk associates with Cbl and Gab1 in Met transformed fibroblasts. A role for Crk/Gab1 coupling in anchorage independent growth is proposed based on the retention of these complexes in Met transformed fibroblasts grown in suspension and their ability to enhance JNK activity. Using MDCK epithelial colonies, I demonstrated that mutants of Crk lacking the amino terminal SH3 domain inhibit HGF-stimulated lamellipodia formation, cell spreading and breakdown of adherens junctions. Moreover, when overexpressed, wild type Crk can promote all of these events in the absence of HGF. Consistent with the elevated Rac activity observed in cells overexpressing Crk, the ability of Crk to promote these events is Rac-dependent. The overexpression of Crk results in the formation of a molecular complex containing Crk, Paxillin, GIT2 (an ARF-GAP) and beta-PIX (a Rac exchange factor) that relocalizes to focal complexes in cells at the edge of the colony. The formation of this complex is critical for the ability of Crk to mediate lamellipodia formation and cell spreading, as mutants of Paxillin that fail to associate with Crk or GIT2, or that do not target to focal adhesions, inhibit these processes. Consistent with the involvement of Crk in HGF cell dispersal, the coupling of Gab1 with Crk is requi
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.82908 |
| Date | January 2002 |
| Creators | Lamorte, Luigi |
| Contributors | Park, Morag (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biochemistry.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001975704, proquestno: AAINQ88504, Theses scanned by UMI/ProQuest. |
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