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Tissue factor pathway inhibitor-2 (TFPI-2) recognizes the complement and kininogen binding protein gC1qR/p33 (gC1qR): implications for vascular inflammation

Journal: Thrombosis and Haemostasis
ISSN: 0340-6245
Topic:

Paediatric Haemostasis

DOI: http://dx.doi.org/10.1160/TH04-03-0188
Issue: 2004: 92/4 (Oct) pp. 672-895
Pages: 811-819

Tissue factor pathway inhibitor-2 (TFPI-2) recognizes the complement and kininogen binding protein gC1qR/p33 (gC1qR): implications for vascular inflammation

Ellinor I. B. Peerschke1, Ramona J. Petrovan2, Berhane Ghebrehiwet 3,Wolfram Ruf2
1Department of Pathology,Weill Medical College of Cornell University; New York, USA 2Department of Immunology,The Scripps Research Institute, La Jolla, California, USA 3Department of Medicine, Stony Brook University, Stony Brook, New York, USA

Summary

Evidence is accumulating to suggest that TFPI-2 is involved in regulating pericellular proteases implicated in a variety of physiologic and pathologic processes including cancer cell invasion, vascular inflammation, and atherosclerosis. Recent immunohistochemical studies of advanced atherosclerotic lesions, demonstrated a similar tissue distribution for TFPI-2, High Molecular Weight Kininogen (HK), and gC1qR/p33 (gC1qR), a ubiquitously expressed, multicompartmental cellular protein involved in modulating complement, coagulation, and kinin cascades. Further studies to evaluate TFPI-2 interactions with gC1qR demonstrated direct interactions between gC1qR and TFPI-2 using immunoprecipitation and solid phase binding studies. Specific and saturable binding between TFPI-2 and gC1qR (estimated Kd: ~ 70 nM) was observed by ELISA and surface plas mon resonance (Biacore) binding assays. Binding was inhibited by antibodies to gC1qR, and was strongly dependent on the Kunitz-2 domain of TFPI-2, as deletion of this domain reduced gC1qR-TFPI-2 interactions by approximately 75%. Deletion of gC1qR amino acids 74-95, involved in C1q binding, had no effect on gC1qR binding to TFPI-2, although antibodies to this region and purified C1q both inhibited binding, most likely via allosteric effects. In contrast, HK did not affect TFPI-2 binding to gC1qR. Binding of TFPI-2 to gC1qR produced statistically significant but modest reductions in TFPI-2 inhibition of plasmin, but had no effect on kallikrein inhibition in fluid phase chromogenic assays.Taken together, these data suggest that gC1qR may participate in tissue remodeling and inflammation by localizing TFPI-2 to the pericellular environment to modulate local protease activity and regulate HK activation.