WIDESPREAD EXPRESSION OF CHONDROITIN SULFATE-TYPE SERGLYCINS WITH CD44 BINDING ABILITY IN HEMATOPOIETIC-CELLS

Serglycin is a family of small proteoglycans with Ser-Gly dipeptide re peats and is modified with various types of glycosaminoglycan side cha ins, We previously demonstrated that chondroitin sulfate-modified serg lycin is a navel ligand for CD44 involved in the adherence and activat ion of lymphoid cells, In this study, we investigated the production a nd distribution of CD44 binding serglycins in various hematopoietic ce lls and characterized their carbohydrate side chains. Immunoprecipitat ion analysis using CD44-IgG; and polyclonal antibody against the sergl ycin core peptide demonstrated that, various serglycin species capable of binding CD44 are produced by a variety of hematopoietic cells incl uding lymphoid cells, myeloid cells, and a few tumor cell lines, Glyco saminoglycans on these serglycins, which are essential for CD44 bindin g, are composed of chondroitin 4-sulfate or a mixture of chondroitin 4 -sulfate and chondroitin B-sulfate, but no heparin or heparan sulfate side chain was detected. The serglycins are also secreted by normal sp lenocytes, lymph node lymphocytes, and bone marrow cells, whereas they are secreted in very small amounts by normal thymocytes, Secretion of serglycins is greatly enhanced by mitogenic stimulation with concanav alin A or lipopolysaccharide. Our results showed that serglycin, unlik e hyaluronate, is produced and secreted in a functional (CD44 binding) form by many members of the hematopoietic system including various ly mphocyte subsets, Our data suggest that serglycin may serve as a major Ligand for CD44 in various events in the lymphohematopoietic system.