Tie1-Tie2 Interactions Mediate Functional Differences between Angiopoietin Ligands

► Tie1 and Tie2 form a constitutive heterodimeric complex on the cell surface ► Tie receptor interactions are inhibitory, attenuating Tie2 catalytic activity ► Ang-1 disrupts Tie1-Tie2 complexes, promoting Tie2 clustering and activation ► The antagonist, Ang-2, is unable to disrupt Tie1-Tie2 complexes