Identification and characterization of the signaling mechanisms downstream of Dok-R that mediate cell migration and actin reorganization.
Published: 2004
Language: eng
Number of pages: 178
Description: Dok-R was also shown to bind c-Abl in a processive manner that required binding of the c-Abl SH3 and SH2 domains. The binding of c-Abl and Dok-R resulted in increasing c-Abl kinase activity, tyrosine phosphorylation of Dok-R and an increase in c-Abl-mediated membrane protrusions. Together, these results demonstrate a physiological role for Dok-R in modulating cytoskeletal dynamics through complex formation with Nck and Pak and with c-Abl.Angiogenesis requires endothelial cells to undergo several cellular processes such as proliferation, migration and differentiation. Angiopoietin-1 is a growth factor that binds the Tek/Tie-2 receptor tyrosine kinase resulting in Tek autophosphorylation. Various signaling proteins can bind Tek in a phosphotyrosine-dependent manner and activate initiate downstream signaling pathways such as the phosphatidylinositol 3 (PI3)-kinase pathway. Dok-R was originally identified as a Tek-binding partner and can bind in a phosphotyrosine-dependent manner to RasGAP and Nck. The aim of this thesis was to determine the physiological function of Dok-R and to identify the molecular mechanisms that mediate its responses.Since Dok-R was first identified as a Tek-binding protein, angiopoietin-1-dependent cell-based bioassays were developed in order to elucidate the physiological function of Dok-R. Angiopoietin-1 could promote tubule formation, cell migration and survival of endothelial cells with the latter two processes being mediated through the PI3-kinase pathway. These results demonstrate that angiopoietin-1 can mediate multiple endothelial cell processes and may serve as a cell-based system to elucidate the physiological role of Dok-R.Since Dok-R was shown to associate with RasGAP and Nck, two proteins implicated in cell migration, it was hypothesized that Dok-R may also serve a similar role. By using various tyrosine point mutants of Dok-R that abolished binding to either Nck or RasGAP, it was found that angiopoietin-1-mediated migration was enhanced upon overexpression of wildtype Dok-R which required binding to Nck, but not RasGAP. Angiopoietin-1 could activate the serine/threonine kinase Pak, which binds constitutively with Nck, to form a ternary complex resulting in Pak activation and motility. These results demonstrate a role for Dok-R in cell migration through Nck and Pak.
Notes: Adviser:  Daniel J. Dumont.

Thesis (Ph.D.)--University of Toronto, 2004.

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Source: Dissertation Abstracts International, Volume: 65-10, Section: B, page: 4996.