Abstract WP263: Mutagenesis Studies Revealed Minimal Impact of Human A120T Variant of Protease-activated Receptor 4 on Receptor function or Pharmacological Response to a Potent and Selective Antagonist
Bibliographic record
Abstract
Introduction: Protease-activated receptor 4 (PAR4) is a platelet thrombin receptor and a novel target for ischemic stroke treatment. Recent reports suggested a subtle racial difference in platelet responses to submaximal concentrations of PAR4 agonist peptide (PAR4-AP). One of the PAR4 variants, A120T, is more common in African American than white (63% vs. 19%, Edelstein et al., Blood 2014). It was suggested that this variant contributes to the difference in response to PAR4-AP and impacts the in vitro response to YD-3, a PAR4 antagonist. In this study, site-directed mutagenesis was used to evaluate the effect of the A120T variant on PAR4 function and response to a newly discovered potent and selective PAR4 antagonist, UDM-001651. Unlike YD-3, UDM-001651 inhibited thrombin-induced platelet aggregation and prevented thrombosis in a monkey model and thus served as a relevant PAR4 pharmacology tool. Methods: Human PAR4 cDNAs expressing A120 and T120 variants were stably expressed in HEK293 cells. Cell surface expression of PAR4 was analyzed by FACS. Functional responses of cells were evaluated by monitoring calcium mobilization induced by BMS PAR4-AP, which was optimized based on AYPGKF. The potency of UDM-001651 was derived from an 11-point concentration response curve in the calcium assay using PAR4-AP at the EC80 concentration. Transient transfection studies were also performed to confirm the results. Results: Comparable levels of expression and functional responses were observed between A120 and T120 expressing cells. Results from side-by-side comparison between the two cell lines demonstrated no detectable difference in the mean EC50 values (0.42±0.054 versus 0.46±0.051 uM standard error, n=9) in calcium responses to PAR4-AP stimulation. Similarly, the potency of UDM-001651 in the same assay were similar between these two cell lines. Moreover, preliminary clinical results did not show differences in PAR4-mediated platelet response between African-American and white subjects. Conclusion: In contrast to the previous report, the results reported herein from site directed mutagenesis studies indicate that the A120T variant of PAR4 has no apparent impact on calcium signaling in response to agonist stimulation or response to a PAR4 antagonist.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 |
| 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 | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 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".