Involvement of heparan sulfate proteoglycans in the binding step for phagocytosis of latex beads by Chinese hamster ovary cells.

Chinese hamster ovary (CHO) K1 cells, typical nonprofessional phagocytes, exhibited intense phagocytosis of latex beads when incubated under serum-free conditions. Under the serum-free conditions, the recognition mechanism of latex beads by cells was investigated. Exogenous heparin and heparan sulfate but not chondroitin sulfate effectively inhibited the binding of latex beads to cells. The binding of latex beads to cells was also inhibited by treatment of cells with heparitinase more effectively than by treatment of cells with chondroitinase. Furthermore, CHO mutant cells defective in biosyntheses of both heparan sulfate and chondroitin sulfate proteoglycans almost completely lacked binding activity of latex beads. Another mutant, which is deficient in heparan sulfate proteoglycans but rather overproduces chondroitin sulfate proteoglycans, also showed lower binding activity, compared with wild-type cells. Coculture of these proteoglycan-less mutants and the wild-type cells did not restore the binding activity of the mutant cells, suggesting that membrane-bound rather than secretory proteoglycans were responsible for the binding of latex beads. These results indicated that heparan sulfate proteoglycans at the cell surface were involved in the binding step for phagocytosis of latex beads by CHO cells.