Failed export of the adrenocorticotrophin receptor from the endoplasmic reticulum in non-adrenal cells: evidence in support of a requirement for a specific adrenal accessory factor
Bibliographic record
Abstract
Difficulty in expressing the adrenocorticotrophin (ACTH) receptor (melanocortin 2 receptor; MC2R) after transfection of various MC2R expression vectors has been experienced by many researchers. Reproducible evidence for expression has been obtained only in the Y6/OS3 corticoadrenal cell lines or in cells expressing endogenous melanocortin receptors. In order to determine the cause of this failure of expression we have undertaken the following studies. An MC2R expression plasmid was constructed in which the green fluorescent protein (GFP) coding region had been added to the C-terminus of the mature protein. Transfection of this plasmid into Y6 cells with a cAMP-responsive reporter plasmid demonstrated normal function of this receptor. Imaging of CHO cells expressing MC2R-GFP revealed perinuclear expression, although a cholecystokinin receptor (CCKR)-GFP construct was efficiently expressed at the cell surface. Y6 cells, in contrast, showed cell surface fluorescence after transfection with MC2R-GFP. Several other cell types showed a similar pattern of GFP distribution characteristic of retention in the endoplasmic reticulum. Counterstaining with an anti-KDEL antibody confirmed this location. Co-expression of the MC2R and the CCKR-GFP did not impair CCKR trafficking to the cell surface, implying a receptor-specific impairment to trafficking in the CHO cell which was absent in the Y6 cell.
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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) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.002 |
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".