Characterizing the role of lipid 'raft' microdomain association of glycophosphatidyinositol-anchored proteins in their trafficking in hepatoblastoma cells
Bibliographic record
Abstract
Many membranes in mammalian cells appear to be organized into various types of 'microdomains,' submicron regions that can be enriched in certain lipids and membrane proteins.'Lipid rafts,' one of the most widely investigated classes of such microdomains, are proposed to constitute small cholesterol-and sphingolipid-enriched membrane regions, with protein and lipid compositions distinct from those of 'non-raft' regions of the membrane, that have been suggested to be involved in a variety of cellular functions from signaling to protein trafficking.One class of 'raft-associating' proteins, glycosylphosphatidylinositol-anchored (GPI-) proteins, are anchored to the exoplasmic leaflet of the membrane via a raft-associating glycophospholipid anchor.It has been suggested previously that 'raft' partitioning acts as an apical targeting mechanism for GPIproteins in hepatoblastoma HepG2 cells and other polarized cell lines.To investigate the role of 'rafts' in the apparent preferential targeting of many GPI-proteins to the apical surface of the plasma membrane, I employed a novel approach using artificial lipid-anchored protein bioconjugates as GPI-protein analogues.I first developed optimized conditions to label polarized HepG2 cells with two novel types of lipid-polyethyleneglycol(PEG)-protein conjugates, generated using SNAP-and Halo-tag technologies, before investigating how the conjugates trafficked in these cells.Our results showed that when initially incorporated into the basolateral membranes of HepG2 cells, conjugates with long-chain saturated or unsaturated lipid 'anchors' gradually redistribute within the cell and ultimately become enriched in the apical membrane, to a degree similar to that observed for endogenous GPI-proteins.These findings counter earlier suggestions that apical trafficking of GPI-proteins in HepG2 cells is driven by (and hence dependent on) the propensity for the GPI-protein anchor to associate with rafts.
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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) | 0.000 | 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 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".