Thapsigargin-Induced Degranulation of Mast Cells Is Dependent on Transient Activation of Phosphatidylinositol-3 Kinase
Bibliographic record
Abstract
Thapsigargin, which elevates cytosolic calcium levels by inhibiting the sarcoplasmic/endoplasmic reticulum calcium-dependent ATPase, was tested for its ability to degranulate bone marrow-derived mast cells (BMMCs) from src homology 2-containing inositol phosphatase +/+ (SHIP+/+) and SHIP-/- mice. As was found previously with steel factor, thapsigargin stimulated far more degranulation in SHIP-/- than in SHIP+/+ BMMCs, and this was blocked with the phosphatidylinositol-3 (PI-3) kinase inhibitors, LY294002 and wortmannin. In contrast to steel factor, however, this heightened degranulation of SHIP-/- BMMCs was not due to a greater calcium influx into these cells, nor was the thapsigargin-induced calcium influx inhibited by LY294002, suggesting that the heightened thapsigargin-induced degranulation of SHIP-/- BMMCs was due to a PI-3 kinase-regulated step distinct from that regulating calcium entry. An investigation of thapsigargin-stimulated pathways in both cell types revealed that MAPK was heavily but equally phosphorylated. Interestingly, the protein kinase C inhibitor, bisindolylmaleimide (compound 3), totally blocked thapsigargin-induced degranulation in both SHIP+/+ and SHIP-/- BMMCs. As well, thapsigargin stimulated a PI-3 kinase-dependent, transient activation of protein kinase B, and this activation was far greater in SHIP-/- than in SHIP+/+ BMMCs. Consistent with this, thapsigargin was found to be a potent survival factor, following cytokine withdrawal, for both cell types and was more potent with SHIP-/- cells. These studies have both identified an additional PI-3 kinase-dependent step within the mast cell degranulation process, possibly involving 3-phosphoinositide-dependent protein kinase-1 and a diacylglycerol-independent protein kinase C isoform, and shown that the tumor-promoting activity of thapsigargin may be due to its activation of protein kinase B and subsequent promotion of cell survival.
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 distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.003 | 0.000 |
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 teacher head, 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".