Angiopoietins and their receptors, Tie1 and Tie2

The angiopoietins were originally discovered as ligands for Tie receptors, a family of receptor tyrosine kinases (RTKs) that are selectively expressed within the vascular endothelium. + or - indicates either activation or antagonism of the Tie2 receptor by the individual angiopoietins. Potential interactions between the Tie1 receptor and the various angiopoietins have not yet been confirmed.

The Eph RTKs compromise the largest known family of growth factor receptors and are bound by the large family of ephrin ligands. The ephrins must be tethered to the membrane in order to activate their respective Eph receptors. Thus, they mediate cell:cell interactions. The signaling cascade can go both through the ligand and through the receptor. Only the several members that have been shown to be involved in vascular growth are displayed.

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References:

Beecken, W.D., et al., New molecular mediators in tumor angiogenesis. J. Cell. Mol. Med., 4, 262-269 (2000).

Cheng, N., et al., The ephrins and Eph receptors in Angiogenesis. Cytokine Growth Factor Rev., 13, 75-85 (2002).

Partanen, J., and Dumont, D.J., Functions of Tie1 and Tie2 receptor tyrosine kinases in vascular development. Curr. Top. Microbiol. Immunol., 237, 159-172 (1999).