HEPARIN-BINDING EPIDERMAL GROWTH FACTOR-LIKE GROWTH-FACTOR - P91 ACTIVATION, INDUCTION OF PLASMINOGEN-ACTIVATOR PLASMINOGEN-ACTIVATOR INHIBITOR, AND TUBULAR MORPHOGENESIS IN HUMAN MICROVASCULAR ENDOTHELIAL-CELLS

Epidermal growth factor (EGF) or transforming growth factor-alpha (TGF -alpha) stimulates cell migration, proliferation and the formation of tube-like structures of human microvascular endothelial cells in cultu re. Heparin-binding EGF-like growth factor (HB-EGF), which shows 35% h omology with EGF/TGF-alpha, is a member of the EGF family, and it is u biquitous in many tissues and organs. We examined whether or not HB-EG F induced angiogenic responses in human microvascular endothelial cell s, HB-EGF inhibited the binding of I-125-EGF to the EGF receptor and i nduced autophosphorylation of the receptor on endothelial cells. Exoge nous HB-EGF induced the loss of more than 70% of the EGF receptor from the cell surface within 30 min, with similar kinetics to that of EGF, The level of c-fos mRNA markedly increased at 30 min in response to H B-EGF as well as EGF, A gel shift assay demonstrated the activation of the transcription factor p91 by HB-EGF and EGF, This factor directly interacts with the EGF receptor and mediates the activation of c-fos g ene promoter. HB-EGF enhanced the mRNA expression of tissue-type plasm inogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) mRNA. However, the enhancement of t-PA and PAI-1 by HB-EGF was less th an that by EGF, Heparitinase/chlorate, which digests the heparan sulfa te proteoglycan of the endothelial cell surface, restored both t-PA an d PAI-1 mRNA levels in response to HB-EGF in a manner similar to that by EGF. HB-EGF at 10 ng/ml developed tube-like structures in type I co llagen gel at similar levels to that of EGF at 10 ng/ml, suggesting th at HB-EGF is also a potent angiogenic factor in the model system for a ngiogenesis. The tubulogenesis activity of HB-EGF is discussed in rela tion to the expression of the t-PA and PAI-1 genes.