Glycosyl phosphatidylinositol anchorage of tissue factor pathway inhibitor.
BACKGROUND
The endothelium is a major source of tissue factor pathway inhibitor (TFPI), the endogenous regulator of TF-induced coagulation, and a significant proportion of the expressed TFPI remains associated with the endothelial surface.


RESULTS
Phosphatidylinositol-specific phospholipase C (PI-PLC) treatment reduced TFPI at the surface of cultured endothelial cells by approximately 80%, and at least a portion of the TFPI released by PI-PLC contained an intrinsic glycosylphosphatidylinositol (GPI) anchor that is recognized by anti-crossreactive determinant antibodies. Endothelial cells express both of the alternatively spliced forms of TFPI mRNA at a ratio of TFPIbeta/TFPIalpha mRNA of approximately 0.1 to 0.2. In Chinese hamster ovary (CHO) cells, TFPIalpha is predominantly secreted, whereas TFPIbeta is a GPI-anchored membrane protein. Like TFPIbeta, the small proportion of the TFPIalpha expressed by CHO cells that remains surface associated is also released by PI-PLC treatment, suggesting that it is bound to a separate GPI-anchored protein(s) at the surface of the cells.


CONCLUSIONS
Both direct (TFPIbeta) and indirect (TFPIalpha) GPI-mediated membrane anchorage is involved in localizing TFPI to the surface of cells.
Zhang
Jing
J
Division of Hematology, Barnes-Jewish Hospital at Washington University Medical Center, St Louis, Mo, USA.
Piro
Orlando
O
Lu
Lan
L
Broze
George J
GJ
D000818:Animals; D016466:CHO Cells; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D006224:Cricetinae; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005434:Flow Cytometry; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D007163:Immunosorbent Techniques; D008074:Lipoproteins / Q000235:genetics / Q000378:metabolism*; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D054801:Phosphoinositide Phospholipase C; D020133:Reverse Transcriptase Polymerase Chain Reaction; D010738:Type C Phospholipases / Q000378:metabolism
D017261:Glycosylphosphatidylinositols; D008074:Lipoproteins; C051928:lipoprotein-associated coagulation inhibitor; D006493:Heparin; D010738:Type C Phospholipases; D054801:Phosphoinositide Phospholipase C; D043265:Phosphatidylinositol Diacylglycerol-Lyase