Phospholipase C release of basic fibroblast growth factor from human bone marrow cultures as a biologically active complex with a phosphatidylinositol-anchored heparan sulfate proteoglycan.
Basic fibroblast growth factor (bFGF) is a potent mitogen for human bone marrow stromal cells and stimulates haematopoiesis in vitro. We report here that primary human bone marrow cultures contain bFGF and express heparin-like bFGF binding sites on the cell surface and in the extracellular matrix (ECM). bFGF bound predominantly to a 200-kD cell surface heparan sulfate proteoglycan (HSPG), which was also found in conditioned medium. bFGF was released from bone marrow cultures by incubation with phosphatidylinositol-specific phospholipase C (PI-PLC) and, less efficiently, by plasmin. Solubilized bFGF was found as a complex with the 200-kD HSPG. The complex was biologically active as shown by its ability to stimulate plasminogen activator production in bovine aortic endothelial cells. bFGF-HSPG complexes of bovine endothelial cells, however, were not released by PI-PLC. While only trace amounts of the bFGF-binding 200-kD HSPG were released spontaneously from bone marrow cultures, incubation with PI-PLC solubilized almost all of the 200-kD HSPG. The HSPG could be metabolically labeled with ethanolamine or palmitate, which was partially removed by treatment with PI-PLC. These findings indicate linkage of the HSPG to the cell surface via a phosphatidylinositol anchor. Plasmin released the 200-kD HSPG less efficiently than PI-PLC. We conclude that HSPGs of human bone marrow serve as a reservoir for bFGF, from which it can be released in a biologically active form via a dual mechanism; one involving a putative endogenous phospholipase, the other involving the proteolytic cascade of plasminogen activation.
Brunner
G
G
Department of Cell Biology, New York University Medical Center, New York 10016.
Gabrilove
J
J
Rifkin
D B
DB
Wilson
E L
EL
D000328:Adult; D001853:Bone Marrow / Q000187:drug effects / Q000502:physiology*; D001854:Bone Marrow Cells; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D011508:Chondroitin Sulfate Proteoglycans / Q000302:isolation & purification / Q000378:metabolism*; D005341:Fibrinolysin / Q000378:metabolism; D016222:Fibroblast Growth Factor 2 / Q000302:isolation & purification / Q000378:metabolism*; D019812:Heparan Sulfate Proteoglycans; D006497:Heparan Sulfate / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D008970:Molecular Weight; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D054801:Phosphoinositide Phospholipase C; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D010960:Plasminogen Activators / Q000378:metabolism; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000302:isolation & purification / Q000378:metabolism*; D017468:Receptors, Fibroblast Growth Factor
D011508:Chondroitin Sulfate Proteoglycans; D005341:Fibrinolysin; D016222:Fibroblast Growth Factor 2; D019812:Heparan Sulfate Proteoglycans; D006497:Heparan Sulfate; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D054801:Phosphoinositide Phospholipase C; D010727:Phosphoric Diester Hydrolases; D010960:Plasminogen Activators; D011956:Receptors, Cell Surface; D017468:Receptors, Fibroblast Growth Factor