Serglycin and betaglycan proteoglycans are expressed in the megakaryocytic cell line CHRF 288-11 and normal human megakaryocytes

Abstract

This study has characterized the proteoglycans from the megakaryocytic tumor cell line CHRF 288-11 and the effect of the differentiation-inducing agents phorbol-12-myristate-13-acetate (PMA) and dimethylsulfoxide (DMSO) on proteoglycan synthesis in these cells. There appeared to be two classes of proteoglycans. One, serglycin, was recognized to have a core protein of 31 kDa, an overall molecular mass of 200-300 kDa, and glycosaminoglycan chains of mean size < 25 kDa. The size of this proteoglycan was increased by both PMA and DMSO. Synthesis was increased by PMA and reduced by DMSO. mRNA for serglycin was increased at 24 to 72 hr following PMA treatment. In addition, the cells contained a core protein triplet at 96, 110, and 120 kDa, and the medium only the bands at 96 and 110 kDa, suggesting the presence of betaglycan. Synthesis of this proteoglycan was enhanced by PMA. This proteoglycan had an overall size of 130-150 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in control cells, but in the presence of PMA, a component > 250 kDa was present. Probes for Northern blot analysis were prepared by polymerase chain reaction (PCR) based on the sequences of human serglycin and betaglycan. The serglycin probe recognized a 1.4 kb band, and the betaglycan probe recognized a 4.1 kb band, on blots prepared from RNA from CHRF cells and cultured normal human megakaryocytes. Both proteoglycans in their intact form adhered to peptides derived from fibronectin and collagen, but the free GAGs released by alkaline borohydride digestion did not adhere. Synthesis of two proteoglycans appears to be a part of the differentiation process of megakaryocytic tumor cells and normal megakaryocytes.