TFPI? is the GPI-anchored TFPI isoform on human endothelial cells and placental microsomes.

ABSTRACT: Tissue factor pathway inhibitor (TFPI) produces factor Xa-dependent feedback inhibition of factor VIIa/tissue factor-induced coagulation. Messages for 2 isoforms of TFPI have been identified. TFPI? mRNA encodes a protein with an acidic N-terminus, 3 Kunitz-type protease inhibitor domains and a basic C-terminus that has been purified from plasma and culture media. TFPI? mRNA encodes a form in which the Kunitz-3 and C-terminal domains of TFPI? are replaced with an alternative C-terminus that directs the attachment of a glycosylphosphatidylinositol (GPI) anchor, but whether TFPI? protein is actually expressed is not clear. Moreover, previous studies have suggested that the predominant form of TFPI released from cells by phosphatidylinositol-specific phospholipase C (PIPLC) treatment is TFPI?, implying it is bound at cell surfaces to a separate GPI-anchored coreceptor. Our studies show that the form of TFPI released by PIPLC treatment of cultured endothelial cells and placental microsomes is actually TFPI? based on (1) migration on SDS-PAGE before and after deglycosylation, (2) the lack of a Kunitz-3 domain, and (3) it contains a GPI anchor. Immunoassays demonstrate that, although endothelial cells secrete TFPI?, greater than 95% of the TFPI released by PIPLC treatment from the surface of endothelial cells and from placental microsomes is TFPI?.

SUBMITTER: Girard TJ 

PROVIDER: S-EPMC3277357 | biostudies-literature | 2012 Feb

REPOSITORIES: biostudies-literature