Rolling of CHO cells expressing human, bovine, pig, rat or equine PSGL-1 on L- or P-selectin. (A) CHO-PSGL-1 cells were perfused under constant shear stress (1.5 dynes/cm2) on recombinant human P-selectin or at 1.0 dyne/cm2 on human L-selectin/μ chimera adsorbed on a coverslip, precoated with goat anti-human IgM antibody, and bound to the bottom of the flow chamber. Cell recruitment was analyzed by videomicroscopy at 4–5 min of perfusion. Results represent the mean ± SEM of 3–5 experiments (***, P < 0.001; NR: no rolling). (B) Impact of sulfation on PSGL-1-dependent rolling. Control (black columns) and desulfated CHO cells (white columns) were pretreated with proteinase K. Desulfated cells were cultured for 72 h in MEMα medium containing 60 mM sodium chlorate and exposed for 60 min to arylsulfatase. Results are expressed as mean percentage of rolling cells ± SEM of 3 experiments (***, P < 0.001). (C) Amino acid sequence alignments of mammalian homologues of P- and L-selectin lectin domains. Homologues of human residues [16, 18] interacting with sulfated Tyr-48 or -51 are respectively indicated by asterisks or arrowheads. The percentages of identity between aligned sequences are grey shaded (dark grey: > 80%, grey: > 60% and light grey: > 40%).