A Fluorescent Probe of Polyamine Transport Accumulates into Intracellular Acidic Vesicles via a Two-step Mechanism
Bibliographic record
Abstract
Mammalian polyamine carriers have not yet been molecularly identified. The fluoroprobe Spd-C2-BODIPY faithfully reports polyamine transport and accumulates almost exclusively in polyamine-sequestering vesicles (PSVs). Polyamines might thus be imported first by a plasma membrane carrier and then sequestered into pre-existing PSVs (model A), or be directly captured by polyamine receptors undergoing endocytosis (model B). Spd-C2-BODIPY uptake was unaffected in receptor-mediated endocytosis-deficient Chinese hamster ovary cell mutants. PSVs strongly colocalized with acidic vesicles of the late endocytic compartment and the trans Golgi. Virtually perfect colocalization between PSVs and acidic vesicles was found in Chinese hamster ovary cell mutants that are blocked either in the late endosome/lysosome fusion process or in the maturation of multivesicular bodies. Prior inhibition of the V-ATPase dramatically decreased total Spd-C2-BODIPY accumulation while increasing cytosolic fluorescence. Conversely, cells pre-loaded with the probe slowly released it from PSVs upon V-ATPase inhibition. The present data thus support model A, and indicate that polyamine accumulation is primarily driven by the activity of a vesicular H+:polyamine carrier.
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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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".