Protein S enhances C4b binding protein interaction with neutrophils
E Furmaniak-Kazmierczak, CY Hu and CT Esmon
Cardiovascular Biology Research Program, Oklahoma Medical Research
Foundation, Oklahoma City 73104.
Protein S, an inhibitor of coagulation, interacts reversibly with C4b
binding protein (C4bBP). The physiologic role of this complex formation
remains unknown. In this study we examined the possibility that protein S
would facilitate C4bBP binding to the surface of neutrophils where, in
turn, this complex could help protect the cell from complement- mediated
damage at the site of inflammation. Neutrophils bind approximately 60,000
protein S molecules per cell (kd = 140 nmol/L) in a Ca(2+)-dependent
fashion. C4bBP also binds to neutrophils (23,000 sites per cell at
physiologic C4bBP concentration), but this binding is not Ca2+ dependent.
Protein S approximately doubled C4bBP binding, but protein S only
influenced C4bBP binding in the presence of Ca2+. Protein S binding to
neutrophils decreased approximately twofold in the presence of saturating
concentrations of C4bBP. Neutrophil activation had only minor effects on
the affinity and number of sites for protein S or the protein S-C4bBP
complex. These results indicate that the protein S-C4bBP complex binds to
the neutrophil surface where it can presumably modulate complement assembly
on the cell surface.
Volume 81,
Issue 2,
pp. 405-411,
01/15/1993
Copyright © 1993 by The American Society of Hematology
