Light-induced 3-O-sulfotransferase expression alters pineal heparan sulfate fine structure. A surprising link to circadian rhythm.

Proteoglycans are dominant glycoconjugates located on the cell surface and in extracellular spaces and consist of a core protein with one or more glycosaminoglycan side chains linked covalently. Heparan sulfate (HS) belongs to the family of glycosaminoglycans. HS has been assigned a variety of physiological and pathological functions, such as cell-cell adhesion, cell-matrix adhesion, cell proliferation, motility and differentiation, lipoprotein metabolism, blood coagulation, inflammation, tissue regeneration, tumor progression and invasion, pathogenic infection by bacteria, protozoa, and viruses, through specific interaction with a wide array of proteins, ligands, receptors, and pathogens (Bernfield, M., Gotte, M., Park, P. W., Reizes, O., Fitzgerald, M. L., Lincecum, J., and Zako, M. (1999) Annu. Rev. Biochem. 68, 729-777). We have shown here for the first time that light induces changes in pineal HS fine structure and that occurrence of the rare 3-O sulfation catalyzed by HS 3-O-sulfotransferase (3-OST2) is predominantly restricted to daytime pineal glands.