Fig. 3. Biological activities of immobilized versus soluble NC1 and endostatin fragments. Immobilized NC1 domains from collagen IV, XV and XVIII induce proliferation, survival and migration of different cell types. These effects correlate with an increase in P13K, FAK and paxillin phosphorylation. By contrast, soluble NC1 or endostatin fragments bind to various receptors on the surface of the cells and decrease phosphorylation of PI3K, FAK and paxillin. Endostatin as well as NC1(IV) induces a decrease in the transcription of different genes. Endostatin interacts with VEGF-R2 and thus decreases the binding of VEGF to its receptor; endostatin also interacts directly with MMP-2, inhibiting the activation of the enzyme. Taken together, these soluble fragments act in the opposite way to their original molecules, negatively regulating the proliferation and the migration of different cell types and inducing apoptosis and extracellular matrix disorganization.

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