Departments of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City 73190, USA.
P-selectin glycoprotein ligand-1 (PSGL-1) is a mucin-like glycoprotein on leukocytes that is a high affinity ligand for P-selectin. Previous studies have shown that sialylation and fucosylation of PSGL-1 are required for its binding to P-selectin, but other post-translational modifications of PSGL-1 may also be important. We demonstrate that PSGL-1 synthesized in human HL-60 cells can be metabolically labeled with [35S]sulfate that is incorporated primarily into tyrosine sulfate. Treatment of PSGL-1 with a bacterial arylsulfatase releases sulfate from tyrosine, resulting in a concordant decrease in binding to P-selectin. These studies demonstrate that tyrosine sulfate on PSGL-1 functions in conjunction with sialylated and fucosylated glycans to mediate high affinity binding to P-selectin.