Cell-cycle Dependent Desquamation of Heparan Sulfate from the Cell Surface

The term heparin sulfate denotes mucopolysaccharides with a structure similar to heparin but which lack significant anticoagulant potency (1) . The term also connotes a continuum or family of N-sulfated mucopolysaccharides of which the more highly sulfated varieties are called heparins . It appears likely that all cultured mammalian cells synthesize heparan sulfate (2, 3) and that this material becomes incorporated into a metabolically active fraction of the cell surface (4) . The heparan sulfate of the cell surface is readily removed by gentle trypsin treatment under conditions where no irreversible cell damage occurs ; in the case of Chinese hamster cells (line CHO), trypsin treatment removes heparan sulfate and a melange of glycopeptides from cell-surface glycoproteins (4) . These two categories of cell-surface materials have independent metabolism. The ubiquity of heparan sulfate in cultured mammalian cells suggests some general role in cellular metabclism. We report here results concerning cellcycle related fluctuations in the amount present on the cell surface as well as variations in labeling rate from supplied glucosamine-6 3H . Our results encourage speculations as to the role of a generally occurring cell-surface component in the regulation of exposure of components with specific functions for a particular cell type .