Structural-Functional Relationship of Angiopoietin

다국어 초록 (Multilingual Abstract)

Angiopoietin-1(Ang1) is a specific and critical growth factor for blood vessel formation. Recent studies indicated that Ang1 could be used for preventing vascular leakages, therapeutic vasculogenesis, and therapeutic endothelial cell survival. However, Ang1 protein is not easily available because generation of recombinant Ang1 is extremely difficult with current techniques. Ang1 contains 498 amino acids, including an amino-terminal secretory signal sequence. There are two cysteines and two coiled-coil domains in amino-terminal region, which could be responsible for ligand multimerization. The carboxy-terminal region of Ang1 has strong similarity with the carboxy-terminal domain of fibrinogen, which is responsible for receptor binding. Ang1 is present as higher-order multimers, could be resulted from holding together by disulfide crosslinks and coiled-coil structures. Because Ang1 has such a biochemical and biophysical characteristics, it is not soluble, aggregates easily, and sticks to everything during its generation and purification.
To determine a role of amino-terminal region, truncated Ang1 that contains only fibrinogen-like domain(Ang1/FD) was generated. To determine a role of Cys^(41), Cys^(54) and Cys^(265) for Ang1 multimerization, amino acids 17-80 region was deleted(Ang1-D1) and Cys^(265) was substituted with Ser^(265)(nAng1S265). To determine a role of coiled-coil domains for Ang1 multimerization, we gradually deleted amino-terminal portion of Ang1. To generate designed multimeric Ang1, amino-terminal portion of Ang1 was replaced dimeric, trimeric, or pentameic coiled-coil domain.
Our current results suggest that multimerization of Ang1 is essential not only for binding but also for activation of its receptor, Tie2.