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Bovine protein C inhibitor has a unique reactive site and can transiently inhibit plasmin
1Department of Molecular Pathobiology, Mie University School of Medicine, Tsu-city, Japan.
Insights
Bovine Protein C inhibitor (PCI) was cloned and characterized, revealing a unique reactive site. This bovine PCI transiently inhibits bovine plasmin, suggesting a role in both anticoagulation and fibrinolysis.
Area of Science:
- Biochemistry
- Molecular Biology
- Hemostasis Research
Background:
- Protein C inhibitor (PCI) is crucial for regulating the anticoagulant protein C pathway.
- PCI neutralizes activated protein C and thrombin-thrombomodulin complexes in humans.
Purpose of the Study:
- To clone and characterize the full-length bovine Protein C inhibitor (PCI) cDNA.
- To investigate the functional role of bovine PCI in the hemostatic system.
Main Methods:
- Cloning of full-length bovine PCI cDNA.
- Amino acid sequence homology analysis with other species.
- Bovine PCI mRNA expression analysis via Northern blot.
- In vitro inhibition assays with bovine and human plasmin.
- Western blot analysis of PCI-plasmin complex formation and degradation.
Main Results:
- Bovine PCI shares moderate homology with human and other mammalian PCIs.
- Bovine PCI mRNA is predominantly expressed in the liver.
- Bovine PCI possesses a unique Lys-Ser reactive site, differing from other species.
- Bovine PCI exhibits transient inhibition of bovine plasmin, not human plasmin.
- Cleavage at the reactive site of bovine PCI occurs during plasmin complex formation.
Conclusions:
- Bovine PCI plays a role in regulating both the protein C pathway and fibrinolysis.
- The unique reactive site of bovine PCI contributes to its distinct functional properties.
- Bovine PCI's interaction with plasmin suggests a broader involvement in the bovine hemostatic system.
Abstract:
Protein C inhibitor (PCI) regulates the anticoagulant protein C pathway by neutralizing activated protein C and thrombin-thrombomodulin complex in the human hemostatic system. In this study, we cloned a full-length bovine PCI cDNA encoding a putative 19-residue signal peptide and a 385-residue mature protein; this showed 70.6%, 70.6%, 57.5% and 59.6% amino acid sequence homology with the human, rhesus monkey, rat and mouse PCIs, respectively. Bovine PCI mRNA (2.1 kb in size) was expressed strongly in the liver, and moderately in the kidney and testis, but not in other tissues tested. Bovine PCI has a putative reactive site peptide bond, Lys-Ser, that is different from the reactive site sequence (Arg-Ser) of other species' PCI. We found that bovine PCI transiently inhibits bovine plasmin, but not human plasmin. Western blot analysis showed that the reactive site of bovine PCI is cleaved during the course of complex formation with bovine plasmin; degraded PCI is released from the complex gradually concomitant with the recovery of plasmin activity. These findings suggest that bovine PCI plays a role not only in the protein C pathway but also in the fibrinolytic activity of bovine hemostatic system.