Investigation of Syndecan-1 Ectodomain Isolated from Chinese Hamster Ovary (CHO) Cell Culture Medium

Syndecan-1 is a cell surface proteoglycan which participates in cell adhesion, differentiation, motility, morphogenesis and intracellular signaling. The two glycosaminoglycans heparan sulfate and chondroitin sulfate are covalently attached to the ectodomain of syndecan-1 via a tetra saccharide linkage sequence. However, the ectodomain can be modified having only one or neither of the glycosaminglycans attached. The glycosaminoglycans are capable of binding ligands such as fibroblast growth factors (FGFs) and support activation of receptors. The ectodomain is proteolytically cleaved from the cell surface by metalloproteinases in a process known as shedding. Shedding turns the ectodomain into a soluble effector which can stimulate other cells in the surroundings by delivering growth factors and also translocate into cells through endocytosis. In this study the aim was to find out if a modified ectodomain, which only contains chondroitin sulfate, could support intracellular signaling in the absence of heparan sulfate. The aim was also to find out whether a modified ectodomain could translocate into the cell. The methods used were cell culturing, isolation and purification of syndecan-1 ectodomain, cell signaling and immunohistochemistry. It was found that modified shed syndecan-1 ectodomain was able to support intracellular signaling almost to the same degree as wild type syndecan-1 ectodomain. This may suggest that heparan sulfate does not have to be present on the ectodomain to support intracellular signaling, although the signal is slightly higher when present. When trying to detect translocation of the ectodomain the results were too uncertain and further research is required