Related Experiment Videos
The SHBG-like region of protein S is crucial for factor V-dependent APC-cofactor function
P Nyberg1, B Dahlbäck, P García de Frutos
1Department of Clinical Chemistry, Lund University, University Hospital, Malmö, Sweden.
Insights
The sex-hormone-binding globulin (SHBG)-like region of protein S is crucial for its anticoagulant function, particularly in factor VIIIa degradation. This region
Area of Science:
- Biochemistry
- Hematology
- Molecular Biology
Background:
- Activated protein C (APC) is a key regulator of blood coagulation, primarily by degrading factors Va and VIIIa.
- Protein S acts as a cofactor for APC in factor Va degradation and potentiates factor VIIIa degradation synergistically with factor V.
- The sex-hormone-binding globulin (SHBG)-like region of protein S is structurally conserved but its role in anticoagulant activity is not fully understood.
Purpose of the Study:
- To investigate the specific role of the SHBG-like region of protein S in its anticoagulant cofactor activity.
- To determine if the SHBG-like region is essential for both factor Va and factor VIIIa degradation by APC.
- To elucidate the interaction between protein S, factor V, and APC in the context of factor VIIIa inactivation.
Main Methods:
- Construction of a recombinant protein S/Gas6 chimera, incorporating the SHBG-like region of Gas6.
- Assay of APC-cofactor activity of the chimera in plasma compared to wild-type protein S.
- Evaluation of the chimera's efficiency in APC-mediated degradation of factor Va and factor VIIIa.
Main Results:
- The protein S/Gas6 chimera exhibited 40-50% of wild-type protein S APC-cofactor activity in plasma.
- The chimera showed only a slight reduction in efficiency compared to wild-type protein S for factor Va degradation by APC.
- The chimera completely lacked factor V-dependent APC-cofactor activity in the factor VIIIa degradation system.
Conclusions:
- The SHBG-like region of protein S is critical for its full anticoagulant activity, especially for factor VIIIa inactivation.
- This region appears to be essential for the synergistic interaction with factor V during APC-mediated factor VIIIa degradation.
- The findings suggest a specific interaction between the SHBG-like domain of protein S and factor V in regulating coagulation.
Abstract:
Activated protein C (APC) regulates blood coagulation by degrading factor Va (FVa) and factor VIIIa (FVIIIa). Protein S is a cofactor to APC in the FVa degradation, whereas FVIIIa degradation is potentiated by the synergistic APC-cofactor activity of protein S and factor V (FV). To elucidate the importance of the sex-hormone-binding globulin (SHBG)-like region in protein S for expression of anticoagulant activity, a recombinant protein S/Gas6 chimera was constructed. It comprised the amino-terminal half of protein S and the SHBG-like region of Gas6, a structurally similar protein having no known anticoagulant properties. The protein S/Gas6 chimera expressed 40-50%, APC-cofactor activity in plasma as compared to wild-type protein S. In the degradation of FVa by APC, the protein S/Gas6 chimera was only slightly less efficient than wild-type protein S. In contrast, the protein S/Gas6 chimera expressed no FV-dependent APC-cofactor activity in a FVIIIa-degradation system. This demonstrates the SHBG-like region to be important for expression of APC-cofactor activity of protein S and suggests that the SHBG-like region of protein S interacts with FV during the APC-mediated inactivation of FVIIIa.