Gene expression of syndecans and betaglycan in isolated rat liver cells.

Membrane-bound heparan sulfate proteoglycans act as coreceptors for cytokines and are involved in cell-matrix or cell-cell adhesion. We have determined the gene expression of all four members of the syndecan-like integral membrane proteoglycans and of betaglycan, the transforming growth factor-beta type III receptor, in various types of isolated hepatic cells of the rat. Fat-storing cells express syndecan-1, -2, -3, -4, and betaglycan. During the transformation of fat-storing cells into myofibroblasts (the key process in the development of liver cirrhosis), the levels of mRNA for syndecan-1, -3, and -4 remain constant, whereas the amount of syndecan-2 mRNA increases and that for betaglycan decreases. Liver macrophages express syndecan-3 and -4, but only small amounts of syndecan-1. Freshly isolated hepatocytes express only syndecan-1, -2, and -4, but fail to express betaglycan. During cultivation, hepatocytes start to express betaglycan. Syndecan-3, -4, and betaglycan are transcribed into one mRNA population, whereas syndecan-1 and -2 are expressed in different-sized mRNA populations. The data show that the genes of all tested membrane heparan sulfate proteoglycans are expressed by hepatic cells, but that each cell type is characterized by its specific heparan sulfate proteoglycan mRNA profile.