Role of PI 3-kinase in angiopoietin-1-mediated migration and attachment-dependent survival of endothelial cells

Angiopoietin-1 is a unique growth factor which induces Tie2 receptor autoph osphorylation and interaction with signal transduction molecules, GRB2 and p85 subunit of PI 3-kinase, but no detectable mitogenic response. Here we s how that PI 3-kinase-dependent activation of Akt and attachment to extracel lular matrix are required for angiopoietin-1-mediated endothelial cell surv ival. Apoptosis of growth factor-deprived cells grown in monolayer was decr eased by angiopoietin-1 and correlated with Akt activation. In contrast, an giopoietin-1, bFGF or VEGF failed to protect cells in suspension culture. C eramide, an intermediate of several apoptotic pathways, interferes with gro wth factor-mediated Akt activation. Ceramide induced endothelial cell death and abolished angiopoietin-1-mediated activation of Akt and the effect on cell survival. In addition, we found that PI 3-kinase activity is necessary for migration of endothelial cells in response to Angiopoietin-1. A transi ent activation of MAPK/ERKs was also detected within 10 min after stimulati on with angiopoietin-1. In contrast to VEGF-mediated biological effects, in hibition of MAPK/ERKs by PD98059 in endothelial cells did not affect angiop oietin-1 mediated survival or migration. These findings indicate significan t differences in intracellular signaling between VEGF and angiopoietin-1 an d that PI 3-kinase lipid products are key mediators of the biological effec ts of angiopoietin-1. (C) 1999 Academic Press.