Angiopoietin Receptors: Tie-1 & Tie-2

Tie-1 and Tie-2 comprise the cell-surface receptors which 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 protein growth factors that promote angiogenesis, the formation of blood vessels. There are now four identified angiopoietins: Ang1, Ang2, Ang3, Ang4. 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