Evidence for a fence that impedes the diffusion of phosphatidylinositol 4,5-bisphosphate out of the forming phagosomes of macrophages
Bibliographic record
Abstract
To account for the many functions of phosphatidylinositol 4,5-bisphosphate (PIP(2)), several investigators have proposed that there are separate pools of PIP(2) in the plasma membrane. Recent experiments show the surface concentration of PIP(2) is indeed enhanced in regions where phagocytosis, exocytosis, and cell division occurs. Kinases that produce PIP(2) are also concentrated in these regions. However, how is the PIP(2) produced by these kinases prevented from diffusing rapidly away? First, proteins could act as "fences" around the perimeter of these regions. Second, some factor could markedly decrease the diffusion coefficient, D, of PIP(2) within these regions. We used fluorescence correlation spectroscopy (FCS) and fluorescence recovery after photobleaching (FRAP) to investigate these two possibilities in the forming phagosomes of macrophages injected with fluorescent PIP(2). FCS measurements show that PIP(2) diffuses rapidly (D ~ 1 μm(2)/s) in both the forming phagosomes and unengaged plasma membrane. FRAP measurements show that the fluorescence from PIP(2) does not recover (>100 s) after photobleaching the entire forming phagosome but recovers rapidly (~10 s) in a comparable area of membrane outside the cup. These results (and similar data for a plasma membrane-anchored green fluorescent protein) support the hypothesis that a fence impedes the diffusion of PIP(2) into and out of forming phagosomes.
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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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".