Intracellular trafficking of the human Wilson protein: the role of the six N-terminal metal-binding sites
Why this work is in the frame
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Bibliographic record
Abstract
The Wilson protein (ATP7B) is a copper-transporting CPx-type ATPase defective in the copper toxicity disorder Wilson disease. In hepatocytes, ATP7B delivers copper to apo-ceruloplasmin and mediates the excretion of excess copper into bile. These distinct functions require the protein to localize at two different subcellular compartments. At the trans-Golgi network, ATP7B transports copper for incorporation into apo-ceruloplasmin. When intracellular copper levels are increased, ATP7B traffics to post-Golgi vesicles in close proximity to the canalicular membrane to facilitate biliary copper excretion. In the present study, we investigated the role of the six N-terminal MBSs (metal-binding sites) in the trafficking process. Using site-directed mutagenesis, we mutated or deleted various combinations of the MBSs and assessed the effect of these changes on the localization and trafficking of ATP7B. Results show that the MBSs required for trafficking are the same as those previously found essential for the copper transport function. Either MBS 5 or MBS 6 alone was sufficient to support the redistribution of ATP7B to vesicular compartments. The first three N-terminal motifs were not required for copper-dependent intracellular trafficking and could not functionally replace sites 4-6 when placed in the same sequence position. Furthermore, the N-terminal region encompassing MBSs 1-5 (amino acids 64-540) was not essential for trafficking, with only one MBS close to the membrane channel, necessary and sufficient to support trafficking. Our findings were similar to those obtained for the closely related ATP7A protein, suggesting similar mechanisms for trafficking between copper-transporting CPx-type ATPases.
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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) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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 it