The Tek/Tie2 receptor signals through a novel Dok-related docking protein, Dok-R

Abstract

Tek/Tie2 is an endothelial cell-speci®c receptor tyrosine kinase that has been shown to play a role in vascular development of the mouse. Targeted mutagenesis of both Tek and its agonistic ligand, Angiopoietin-1, result in embryonic lethality, demonstrating that the signal transduction pathway(s) mediated by this receptor are crucial for normal embryonic development. In an attempt to identify downstream signaling partners of the Tek receptor, we have used the yeast two-hybrid system to identify phosphotyrosine-dependent interactions. Using this approach, we have identi®ed a novel docking molecule called Dok-R, which has sequence and structural homology to p62 dok and IRS-3. Mapping of the phosphotyrosine-interaction domain within Dok-R shows that Dok-R interacts with Tek through a PTB domain. Dok-R is coexpressed with Tek in a number of endothelial cell lines. We show that coexpression of Dok-R with activated Tek results in tyrosine phosphorylation of Dok-R and that rasGAP and Nck coimmunoprecipitate with phosphorylated Dok-R. Furthermore, Dok-R is constitutively bound to Crk presumably through the proline rich tail of Dok-R. The cloning of Dok-R represents the ®rst downstream substrate of the activated Tek receptor, and suggests that Tek can signal through a multitude of pathways.

Angiogenic activity of endothelial progenitor cells through angiopoietin-1 and angiopoietin-2

“…Lee et al (2008) previously showed an increase in the number of bone marrow cell colonies derived from irradiated mice under Ang-1 treatment. It was also notified that exogenous Ang-1 could preserve the mix feature colony-forming capacity of hematopoietic stem cells by the Ang-1/Tie-2 signaling pathway (Arai et al 2004;Jones and Dumont, 1998). Corroborating to our results, Ang-1 initiated EPC to EC maturation by the upregulation of CD31 and subsequent high capacity of Ac-LDL uptake.…”

DOK4 and DOK5: new dok-related genes expressed in human T cells

“…The sequences of DOK1/2 in human and Dok1/2/3 in mice have been reported previously. 3,7,[11][12][13]15,16 Recently, Dok4/5 genes have been cloned from mouse tissues. 21 The amino acid sequences from human DOK3/4/5 genes have been deduced (see Material and Methods).…”

“…3,[6][7][8] The structure of Dok-1 presents some similarities with other adapter molecules such as Gab proteins or insulin receptor substrate (IRS) proteins. 9,10 Two proteins sharing extensive sequence homology with the amino-terminal part (PH and PTB domains) of Dok-1 have been cloned: Dok-2 (also known as FRIP or Dok-R) [11][12][13][14] and Dok-3 (also known as Dok-L). 15,16 These proteins are essentially expressed in hematopoietic tissues.…”

Angiogenic Actions of Angiopoietin-1 Require Endothelium-Derived Nitric Oxide

“…downstream activation of p125FAK. 30 In addition, it has been reported that phosphorylation of Y1106 on the Tie2 receptor recruits the Tie2-associated docking molecule Dok-R. 12 Recruitment of Dok-R to activated Tie2 leads to its phosphorylation and subsequent recruitment of Nckp21 activated kinase (Pak) complex to the membrane. 14 Release of endothelium-derived NO requires the activation of eNOS, which until recently has been thought to be largely regulated by a Ca 2ϩ and calmodulin.…”

“…1,5 In vitro experiments have shown that Ang1 induces endothelial cell (EC) sprouting in vitro, 6,7 and stimulates EC migration 8 and the formation and stabilization of capillary-like networks in culture systems. 9 -11 One of the signaling cascades initiated by Tie2 phosphorylation is the recruitment of Dok-R, 12 a novel docking molecule that on phosphorylation binds to proteins containing Src homology 2 (SH2) domains. 13 The recruitment of a Nck-p21 activated kinase (Pak) complex to Dok-R, 14 mediates EC migration.…”