Protein phosphatase 1 regulates the phosphorylation state of the polarity scaffold Par-3
Bibliographic record
Abstract
Phosphorylation of the polarity protein Par-3 by the serine/threonine kinases aPKCzeta/iota and Par-1 (EMK1/MARK2) regulates various aspects of epithelial cell polarity, but little is known about the mechanisms by which these posttranslational modifications are reversed. We find that the serine/threonine protein phosphatase PP1 (predominantly the alpha isoform) binds Par-3, which localizes to tight junctions in MDCKII cells. PP1alpha can associate with multiple sites on Par-3 while retaining its phosphatase activity. By using a quantitative mass spectrometry-based technique, multiple reaction monitoring, we show that PP1alpha specifically dephosphorylates Ser-144 and Ser-824 of mouse Par-3, as well as a peptide encompassing Ser-885. Consistent with these observations, PP1alpha regulates the binding of 14-3-3 proteins and the atypical protein kinase C (aPKC) zeta to Par-3. Furthermore, the induced expression of a catalytically inactive mutant of PP1alpha severely delays the formation of functional tight junctions in MDCKII cells. Collectively, these results show that Par-3 functions as a scaffold, coordinating both serine/threonine kinases and the PP1alpha phosphatase, thereby providing dynamic control of the phosphorylation events that regulate the Par-3/aPKC complex.
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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 | 0.001 | 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 | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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".