FIBROBLAST GROWTH FACTOR-II CAN MEDIATE CELL ATTACHMENT BY LINKING RECEPTORS AND HEPARAN-SULFATE PROTEOGLYCANS ON NEIGHBORING CELLS

The myeloid 32D cell line, which grows in suspension and does not expr ess FGF receptors or heparan sulfate proteoglycans, was transfected wi th the cDNA encoding FGF receptor-1 (32D-flg cells), When co cultured with glutaraldehyde-fixed Chinese hamster ovary (CHO) cells, the 32D-f lg cells remained in suspension in the absence of FGF-2 but attached t o the CHO monolayer in the presence of 10 ng/ml FGF-2. In contrast, 32 D cells transfected with the vector alone did not attach to the CHO mo nolayer in the presence of FGF-2, FGF-2-dependent attachment of 32D-fl g cells was prevented by inclusion of 10 mu g/ml heparin in the incuba tion medium and was diminished when CHO mutants in glycosaminoglycan s ynthesis or wild-type CHO cells treated with heparinase were used, ind icating that the attachment occurred through FGF-2 interactions with h eparan sulfates on the CHO cells. Attachment of 32D-flg cells to wild- type CHO cells was half-maximal at 0.4 ng/ml FGF-2 and was also observ ed with FGF-1 but not FGF-4, 32D-flg cells also attached to living CHO cells in a FGF-S-dependent manner, but attachment was transient at 37 degrees C. Induction of new proteins was not required for FGF-2-depen dent attachment, since attachment occurred when the co cultures were i ncubated at 4 degrees C and when the 32D-flg cells were preincubated w ith cycloheximide. FGF-2-dependent attachment of 32D-flg cells was als o observed with Balb/C 3T3, NIH 3T3, and bovine capillary endothelial cells. We conclude that attachment is due to FGF-2 binding simultaneou sly to receptors on the 32D-flg cells and heparan sulfates on the CHO monolayers; thus, the FGF-P acts as a bridge between receptor-expressi ng cells and heparan sulfate-bearing cells. In addition, induction of DNA synthesis in 32D-flg cells in response to FGF-2 was potentiated by the CHO-associated heparan sulfates to the same extent as by soluble heparin, indicating that this interaction has functional significance.