ABSTRACT

The angiopoietins, angiopoietin-1–4, represent an unusual family of high-affinity ligands. The angiopoietins, signaling through the tyrosine kinase Tie receptor system, comprise a unique agonisf. antagonist relationship that mediates a number of angiogenesis-related, endothelial cell activities. Early evidence indicated that angiopoietin 1 stimulated the Tie signaling cascade while angiopoietin 2 functioned to inhibit this activity. Additional evidence indicates that these ligands integrate, through a complex coordination, with other angiogenesisrelated molecules to affect blood vessel formation and function. This chapter reviews current knowledge of the angiopoietins and presents an intricate system of molecular interactions contributing to new blood vessel formation.