DIFFERENTIAL RELEASE OF PROTEOGLYCANS DURING HUMAN B-LYMPHOCYTE MATURATION

Proteoglycans interact with soluble proteins such as growth factors an d thereby regulate extracellular signals. During B lymphocyte maturati on, secretion of proteoglycans may be functionally related to the diff erent requirements of the respective maturation stage. In order to add ress this question we compared structures of proteoglycans released by three B lymphocyte lines which correspond to different maturation sta ges. Plasma-cell type U266 cells secreted the largest proteoglycans (1 50 kDa), followed by mature B cells JOK-1 (130 kDa) and pre-B cells Na lm6 (90 kDa). On average, secreted proteoglycans carried four glycosam inoglycan chains with molecular masses ranging each from 32 kDa (U266) to 23 kDa (Nalm 6). All three cell lines secreted more than 90% of th eir proteoglycans possessing chondroitin sulfate chains having chondro itin-4-sulfate (Delta Di-4S) as the prevalent disaccharide unit. In th ese proteochondroitin sulfates, unsulfated chondroitin (Delta Di-OS) w as present in smaller quantities and chondroitin-6-sulfate (Delta Di-6 S)-containing proteoglycan was released only by Nalm6 and U266 cells. Cell line Nalm 6 exclusively produced proteochondroitin sulfate, where as in culture medium of JOK-1 and U266 a small amount of proteoheparan sulfate was found also. In all three cell lines, treatment with chond roitinase ABC released a protein of 30 kDa and chemical deglycosylatio n resulted in a core protein of 21 kDa. In addition to pure proteochon droitin sulfate, a small portion of proteoheparan sulfate with a prote in moiety of 30 kDa was detected after heparitinase treatment in super natants of JOK-1 and U266. Thus, our results indicate that released pr oteoglycans may undergo modulations in their glycosaminoglycan moietie s during B-cell differentiation. This may have functional consequences at the level of growth factor regulation. (C) 1997 Elsevier Science L td.