Related Experiment Videos
Protein S and C4b-binding protein levels in patients with stroke: implications for protein S regulation
1Department of Medicine, Medical College of Virginia, Richmond.
Insights
Low free protein S levels, crucial for blood clotting regulation, were linked to stroke. This suggests altered protein S binding to C4b-BP may increase thrombotic risk in certain patients.
Area of Science:
- Biochemistry
- Hematology
- Thrombosis Research
Background:
- Protein S is a vital anticoagulant cofactor.
- Free protein S, not bound to C4b-binding protein (C4b-BP), has cofactor activity.
- Deficiencies in protein C or protein S elevate thrombotic risk.
Purpose of the Study:
- To investigate the relationship between total protein S, free protein S, and C4b-BP.
- To explore potential mechanisms underlying low free protein S in patients, including those with stroke.
Main Methods:
- Laurell electrophoresis was used to quantify total and free protein S and C4b-BP levels.
- Analysis included healthy volunteers, patients with normal protein S, patients with low free protein S, and stroke patients with low free protein S.
Main Results:
- Healthy individuals showed a positive correlation between total and free protein S.
- In patients with low free protein S, total protein S did not increase with C4b-BP.
- Stroke patients exhibited a negative correlation between free and total protein S, indicating enhanced binding to C4b-BP.
Conclusions:
- Altered protein S binding to C4b-BP may contribute to thrombotic events in patients with low free protein S.
- The findings suggest potential novel regulatory factors influencing protein S-C4b-BP complex formation.
Abstract:
Protein S circulates either free or bound to C4b-binding protein (C4b-BP). Only free protein S possesses cofactor activity for protein C, a physiologic anticoagulant. Deficiencies of either protein C or protein S are associated with increased thrombotic risk. Over a 23-month period, 40 patients with low free protein S were identified. Eight of these patients were found to have suffered a stroke. This study examined the relationship between total S, free S, and C4b-BP in 15 healthy adult volunteers, in 20 patients with normal protein S levels, in 40 patients with decreased free protein S levels, and in 8 patients with combined low free S levels and stroke. Total and free protein S and C4b-BP levels were determined using the method of Laurell. In healthy adults, free protein S increased with increasing total protein S (r = 0.60). In patients with normal free S, the total S level increased as C4b-BP increased (r = 0.74), and the free S level remained constant. In patients with low free S, total S did not increase with increasing C4b-BP. In stroke patients, the correlation between free S and total S was actually negative (r = -0.449). Evaluation of dissociation constants for the protein S-C4b-BP complex revealed enhanced binding in patients with low levels of free protein S. A non-C4b-BP protein S binding protein, a previously undescribed regulatory factor which modulates S binding to C4b-BP, or shifts in the amount of non-protein S binding C4b-BP are possible explanations of these results.