THE SULFATION DEGREE OF MEMBRANE-ASSOCIATED PROTEOGLYCAN FROM A HEMATOPOIETIC-CELL LINE IS DETERMINED BY CHANGES THE GROWTH-STATE OF THE CELL

Multipotential hemopoietic progenitor cells (FDCP-mix) proliferate in culture medium supplemented with horse serum. When transferred to a me dium without serum, cells do not proliferate and enter a quiescent sta te. Both proliferative and quiescent cells synthesize only chondroitin sulfate proteoglycan (CS-PG) which is associated to the cell membrane . Incorporation of (SO4)-S-35 info CS-PG was 4-fold higher in quiescen t than in proliferative cells. Flow cytometric studies using monoclona l antibodies which recognize the core protein or the CS chains, showed that the increased uptake of sulfate was not the consequence of an in crease in the abundance of CS-PG. Further characterization demonstrate d that CS-PG isolated from quiescent cells exhibited a slightly higher hydrodynamic size than CS-PG from proliferative cells. However, the g lycosaminoglycan chains from PG derived from proliferative and quiesce nt cells have the same hydrodynamic size. Through ion-exchange chromat ography we observed that the mean charge density of PG from quiescent cells was higher than in proliferative cells, suggesting a higher sulf ation degree from PG synthesized by quiescent cells. This was confirme d by now cytometric studies using monoclonal antibody 2B6, which recog nizes the unsaturated terminal disaccharide of chondroitin-4-O-sulfate .