The angiopoietin receptors are receptors that bind
angiopoietin.
TIE-1 and
TIE-2 comprise the cell-surface receptors that bind and are activated by the
angiopoietins, (Ang1, Ang2, Ang3, Ang4). The angiopoietins are protein growth factors required for the formation of blood vessels (
angiogenesis).
Angiopoietins
The
angiopoietins are
proteingrowth factors that regulate
angiogenesis, the formation of blood vessels. In humans, three angiopoietins have been identified: Ang1, Ang2, and Ang4 (Ang 3 is the mouse ortholog of human Ang4).[1] Ang1 and Ang4 function as agonistic or activating ligands for Tie2, whereas Ang2 and Ang3 behave as competitive antagonists. They function by binding their physiologic receptors, Tie-1 and Tie-2. These are receptor
tyrosine kinases, so named because they mediate cell signals by inducing the phosphorylation of key tyrosines, thus initiating
cell signalling.
It is somewhat controversial which of the Tie receptors mediate functional signals downstream of Ang stimulation. But it is clear that at least Tie-2 is capable of physiologic activation as a result of binding the angiopoietins.[citation needed]