Membrane cytosolic translocation of verotoxin A1 subunit in target cells
Why this work is in the frame
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Bibliographic record
Abstract
In sensitive cells, verotoxin 1 (VT1) utilizes a globotriaosylceramide receptor-dependent retrograde transport pathway from the cell surface to the Golgi/endoplasmic reticulum (ER). The VT1 A subunit (VTA) is an RNA glycanase. Although translocation of VTA from the ER to the cytosol is considered the route for protein synthesis inhibition, cell-based evidence is lacking. A dual-fluorescent-labelled VT1 holotoxin was constructed to simultaneously monitor VTA and VT1 B subunit (VTB) intracellular transport. By confocal microscopy, VTA/VTB subunits remained associated throughout the retrograde transport pathway without cytosolic staining. However, in [125I]VT1-treated cells, the selective cytosolic translocation (4 %) of the activated form of VTA, VTA1, was demonstrated for the first time by monitoring [125I]VTA1 release after plasma membrane permeabilization by streptolysin O (SLO). Lactacystin, a proteasome inhibitor, increased cytosolic VTA1 and enhanced VT1 cytotoxicity. VT1 ER arrival coincided with cytosolic VTA1 detection. Brefeldin A and 16 degrees C, conditions which inhibit VT1 retrograde transport to the Golgi/ER, prevented VTA1 cytosolic translocation; however, these treatments did not completely prevent VT1-induced protein synthesis inhibition. Thus, efficient cytosolic translocation of VTA1 requires transport to the Golgi/ER, but alternative minor escape pathways for protein synthesis inhibition may operate when transport to the Golgi/ER is prevented. Inhibition of protein synthesis was time and dose dependent, and not necessarily a valid index of subsequent cytopathology. Only protein synthesis inhibition following >3 h VT1 exposure correlated with eventual cell cytotoxicity. Extrapolation of translocated cytosolic VTA1 values indicates that about one molecule of translocated VTA1 per cell is sufficient to inhibit protein synthesis and kill a cell.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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 | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 it