Regulation of protein C inhibitor (PCI) activity by specific oxidized and negatively charged phospholipids.
Protein C inhibitor (PCI) is a serpin with affinity for heparin and phosphatidylethanolamine (PE). We analyzed the interaction of PCI with different phospholipids and their oxidized forms. PCI bound to oxidized PE (OxPE), and oxidized and unoxidized phosphatidylserine (PS) immobilized on microtiter plates and in aqueous suspension. Binding to OxPE and PS was competed by heparin, but not by the aminophospholipid-binding protein annexin V or the PCI-binding lipid retinoic acid. PS and OxPE stimulated the inhibition of activated protein C (aPC) by PCI in a Ca(++)-dependent manner, indicating that binding of both, aPC (Ca(++) dependent) and PCI (Ca(++) independent), to phospholipids is necessary. A peptide corresponding to the heparin-binding site of PCI abolished the stimulatory effect of PS on aPC inhibition. No stimulatory effect of phospholipids on aPC inhibition was seen with a PCI mutant lacking the heparin-binding site. A heparin-like effect of phospholipids (OxPE) was not seen with antithrombin III, another heparin-binding serpin, suggesting that it is specific for PCI. PCI and annexin V were found to be endogenously colocalized in atherosclerotic plaques, supporting the hypothesis that exposure of oxidized PE and/or PS may be important for the local regulation of PCI activity in vivo.
Malleier
Julia M
JM
Department of Vascular Biology and Thrombosis Research, Center for Biomolecular Medicine and Pharmacology, Medical University of Vienna, Schwarzspanierstrasse 17, A-1090 Vienna, Austria.
Oskolkova
Olga
O
Bochkov
Valery
V
Jerabek
Ingrid
I
Sokolikova
Barbora
B
Perkmann
Thomas
T
Breuss
Johannes
J
Binder
Bernd R
BR
Geiger
Margarethe
M
D017304:Annexin A5 / Q000378:metabolism; D050197:Atherosclerosis / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation; D006493:Heparin / Q000737:chemistry; D006801:Humans; D008055:Lipids / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism*; D010718:Phosphatidylserines / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D018046:Protein C Inhibitor / Q000096:biosynthesis*; D011994:Recombinant Proteins / Q000737:chemistry; D014212:Tretinoin / Q000737:chemistry
D017304:Annexin A5; D008055:Lipids; D010718:Phosphatidylserines; D010743:Phospholipids; D018046:Protein C Inhibitor; D011994:Recombinant Proteins; D014212:Tretinoin; D006493:Heparin; D010100:Oxygen; D002118:Calcium