SULFATION IN HIGH ENDOTHELIAL VENULES - CLONING AND EXPRESSION OF THEHUMAN PAPS SYNTHETASE

High endothelial venules (HEVs) are specialized postcapillary venules found in lymphoid organs and chronically inflamed tissues that support high levels of lymphocyte extravasation from the blood, Studies with chlorate, a metabolic inhibitor of sulfation, had previously revealed that production of PAPS (3'-phosphoadenosine-5'-phosphosulfate), the h igh-energy donor of sulfate, is required for sulfation and high-affini ty recognition of HEV sialomucins GlyCAM-1 and CD34 by the lymphocyte homing receptor L-selectin, Here, we report the molecular characteriza tion of a novel 2.5 kb human cDNA from MECA-79(+) HEV-derived endothel ial cells that encodes the target of chlorate, PAPS synthetase, a mult ifunctional enzyme containing domains for both ATP sulfurylase and ade nosine-5'-phosphosulfate kinase, Functional expression of the isolated cDNA in Chinese hamster ovary cells results in high levels of PAPS sy nthesis, which is abolished by treatment of the transfected cells with chlorate, Northern blot analysis reveals a wide tissue distribution o f PAPS synthetase mRNA in the human body, suggesting that human PAPS s ynthetase may be important for sulfation not only of HEV sialomucins, but also of many other molecules, including mucins such as the P-selec tin ligand PSGL-1, proteoglycans, hormones, neurotransmitters, drugs, and xenobiotics.