Plasmin-Mediated Coagulation Factor Xa Derivative, Xa33/13, Enhances Plasminogen Activation and Fibrin Clot Lysis.
Bibliographic record
Abstract
Abstract Previous reports showed that coagulation factor Xa (FXa) treated with the fibrinolysis protease, plasmin, loses procoagulant activity and can accelerate tissue plasminogen activator (tPA). The resulting FXa derivative, Xa33/13, acquires binding sites for plasminogen and was consequently presumed to be the form of FXa involved in generating plasmin. By evaluating the function of purified Xa33/13, the current work addresses the hypothesis that conversion of FXa to Xa33/13 is the basis of enhanced plasmin generation by tPA and that this newly acquired FXa function can also contribute to clot lysis. Using purified proteins in a chromogenic assay, both Xa33/13 and FXa were found to increase the generation of plasmin activity by tPA at least 10-fold. To explain the involvement of FXa reported previously, Western blots demonstrated a correlation between the disappearance of FXa, appearance of Xa33 antigen and enhanced plasmin production. The Western blots also revealed that detection of Xa33 antigen is lost at later time points, which explains the observation that plasmin generation is eventually shut down during the chromogenic assay. Despite fibrin being recognized as the principal accelerator of tPA, at concentrations as low as 10 nM, either Xa33/13 or FXa reduced the lysis time of thrombin-mediated fibrin clot in a turbidity assay. The Xa33/13 or FXa could be added during clot formation before the tPA or after clot formation with the tPA to facilitate a 50–70% reduction in the time required to achieve half maximal lysis at 0.1 μM. The time-dependent formation of Xa33 antigen in plasma that was induced to clot with tissue factor, anionic phospholipid vesicles and Ca2+, demonstrated that the plasmin-mediated fragmentation pattern of purified FXa represents the complex physiological mixture. However, the use of specific inhibitors and immuno-depleted plasma indicated that plasmin is not required for production of Xa33 antigen in plasma. Cumulatively the data presented here support a role for coagulation FXa in fibrinolysis. These diametrically opposing functions derived from the same molecule, may contribute to the balance between coagulation and fibrinolysis, thereby facilitating tolerance for a wide normal physiological range of FX and possibly other coagulation proteins.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".