[Response of human vascular endothelium to angiogenic fibroblast growth factor: role of 2 lipocortins/annexins].

We are interested in whether lipocortins/annexins are involved in the response of human vascular endothelial cells (HUVEC) to angiogenic bFGF. Previously, a lipocortin/annexin of type I (p34) and a lipocortin/annexin of type VI were found to be associated with plasma membranes of HUVEC. Here we show that: i) phorbol ester PMA, a known activator of protein kinase C, possesses the property of acting synergistically with bFGF to stimulate DNA-primary initiation activity; ii) p69 is only detectable in membrane preparations from G1 phase HUVEC, whereas p34 is found to be present in membranes of G1 and S phase HUVEC; iii) the combination of bFGF and PMA induces an increased phosphorylation of p69 in late G1 phase. In contrast, phosphorylation of p34 occurs only in the S phase when HUVEC are treated with bFGF for an appreciable time lag (> or = 30 min) at 37 degrees C; iv)p69-enriched extracts from bFGF/PMA-treated HUVEC are found to be capable of enhancing the phospholipase A2 (PLA2)-catalyzed production of arachidonic acid in vitro; v) the DNA-synthetic response to bFGF plus PMA is consequent on stimulation of PLA2 and arachidonate production in late G1. These results suggest that p69 is directly connected to the mitogenic signal mechanism of bFGF in late G1, whereas p34 is associated with the endocytic process of this factor in S phase.