Engagement of Fibrinogen and β3 Integrin Is Required for Maintenance of Platelet Intracellular and Cell Surface P-Selectin Expression
Bibliographic record
Abstract
Abstract Platelet P-selectin plays important roles in inflammation and contributes to thrombosis and hemostasis. While it has been reported that von Willebrand factor (VWF) affects P-selectin expression on endothelial cells, little information is available regarding regulation of platelet P-selectin expression. Here, we first observed that P-selectin expression was significantly decreased on platelets of fibrinogen and VWF double deficient mice. Subsequently, we identified this was due to fibrinogen, but not VWF, deficiency. The impaired P-selectin expression on fibrinogen-deficient platelets was further confirmed in a human patient with severe hypofibrinogenemia and his heterozygous parents. We demonstrated that this impairment is unlikely due to excessive P-selectin shedding, deficient fibrinogen-mediated cell surface P-selectin binding, or impaired platelet granule release, but rather is due to decreased platelet P-selectin content. This effect seems to be specific for P-selectin, as other alpha-granule proteins (e.g. thrombospondin-1, vitronectin, platelet factor 4) were not decreased in fibrinogen-deficient mouse or human platelets. We found that fibrinogen transfusion recovered the P-selectin expression in fibrinogen-deficient mice to >80% of the normal level within 48 hours, and four days post-transfusion, the P-selectin levels were nearly completely recovered. Furthermore, engagement of the C-terminus of the fibrinogen γ chain with β3 integrin was required for this process since a similar impairment of P-selectin expression was also observed in fibrinogen γΔ5 mice and β3 integrin-deficient mice. To determine whether fibrinogen affects the biogenesis of platelet alpha-granules, platelets were examined via electron microscopy. No statistically significant difference in the number of platelet alpha-granules was observed in fibrinogen-deficient or β3 integrin-deficient mice compared to controls (P>0.05). These data suggest fibrinogen may play important roles in inflammation, including immune-mediated inflammation, thrombosis and hemostasis via enhancement of platelet P-selectin expression. Furthermore, there are 2–3 fold variations in human plasma fibrinogen levels in healthy populations, and there are patients with hypo- and afibrinogenemia, hyperfibrinogenemia, and Glanzmann’s Thrombasthenia (β3 integrin deficiency). Our data suggest that platelet P-selectin expression can be affected by all these conditions. Therefore, P-selectin as a platelet activation marker should be used with caution.
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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) | 0.000 | 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 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".