P-selectin glycoprotein ligand-1 decameric repeats regulate selectin-dependent rolling under flow conditions.
P-selectin glycoprotein ligand-1 (PSGL-1) interacts with selectins to support leukocyte rolling along vascular wall. L- and P-selectin bind to N-terminal tyrosine sulfate residues and to core-2 O-glycans attached to Thr-57, whereas tyrosine sulfation is not required for E-selectin binding. PSGL-1 extracellular domain contains decameric repeats, which extend L- and P-selectin binding sites far above the plasma membrane. We hypothesized that decamers may play a role in regulating PSGL-1 interactions with selectins. Chinese hamster ovary cells expressing wild-type PSGL-1 or PSGL-1 molecules exhibiting deletion or substitution of decamers with the tandem repeats of platelet glycoprotein Ibalpha were compared in their ability to roll on selectins and to bind soluble L- or P-selectin. Deletion of decamers abrogated soluble L-selectin binding and cell rolling on L-selectin, whereas their substitution partially reversed these diminutions. P-selectin-dependent interactions with PSGL-1 were less affected by decamer deletion. Videomicroscopy analysis showed that decamers are required to stabilize L-selectin-dependent rolling. Importantly, adhesion assays performed on recombinant decamers demonstrated that they directly bind to E-selectin and promote slow rolling. Our results indicate that the role of decamers is to extend PSGL-1 N terminus far above the cell surface to support and stabilize leukocyte rolling on L- or P-selectin. In addition, they function as a cell adhesion receptor, which supports approximately 80% of E-selectin-dependent rolling.
Tauxe
Caroline
C
Service and Central Laboratory of Hematology, Centre Hospitalier Universitaire Vaudois, Rue du Bugnon 46, Lausanne 1011, Switzerland.
Xie
Xun
X
Joffraud
Magali
M
Martinez
Manuel
M
Schapira
Marc
M
Spertini
Olivier
O
D000818:Animals; D016466:CHO Cells; D002448:Cell Adhesion; D002462:Cell Membrane / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D020014:K562 Cells; D036904:Leukocyte Rolling; D008562:Membrane Glycoproteins / Q000378:metabolism / Q000502:physiology*; D018715:Microscopy, Video; D008954:Models, Biological; D017434:Protein Structure, Tertiary; D019087:Selectins / Q000737:chemistry*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000737:chemistry
D008562:Membrane Glycoproteins; C084882:P-selectin ligand protein; D019087:Selectins; C005662:tyrosine O-sulfate; D014443:Tyrosine