CDK1‐dependent Phosphorylation of the Tumor Suppressor Phosphatase, PHLPP1, Regulates the Mitotic PHLPP1 Interactome
Bibliographic record
Abstract
PH domain Leucine Rich Repeat Protein Phosphatase 1 (PHLPP1) is a tumor suppressor originally discovered for its ability to directly dephosphorylate and inactivate the pro‐survival kinase Akt, a key transducer of growth factor signaling. A number of other PHLPP1 targets have been identified, but still little is known about the molecular mechanisms governing the function and regulation of PHLPP1 itself. Here we report that PHLPP1 is hyperphosphorylated during mitosis in a CDK1‐dependent manner, and that this hyperphosphorylation regulates its interaction with mitotic proteins. Specifically, we show that PHLPP1 undergoes an electrophoretic mobility shift in mitotic cells that is lost with lambda phosphatase treatment, and is prevented by CDK1 inhibition. This mobility shift can be recreated in vitro using recombinant CDK1‐Cyclin B. Mass spectrometry and biochemical analysis reveals that these phosphorylations modify the N‐terminus of PHLPP1, a functionally uncharacterized region. A proximity dependent biotin identification (BioID) interaction screen revealed that mitotic PHLPP1 interacts with components of the mitotic spindle apparatus and the kinetochore. Additionally, the data suggest that the N‐terminus is required for the dissociation of PHLPP1 from interphase scaffolds, such as Scribble, during mitosis. During mitotic exit, PHLPP1 protein levels decrease, suggesting that PHLPP1 is degraded during mitotic exit. This correlates with an increase in Akt Ser473 phosphorylation, a validated cellular target of PHLPP1. Our data are consistent with a model in which phosphorylation of PHLPP1 during mitosis regulates binding to its mitotic partners and allows proper passage through mitosis. Reversible protein phosphorylation, orchestrated by kinases and phosphatases, plays a role in controlling proper progression through mitosis, which is essential as errors in mitosis can result in aneuploidy, a hallmark of cancer. The finding that PHLPP1 binds mitotic proteins in a cell cycle and phosphorylation‐dependent manner may have relevance to its tumor suppressive function. Support or Funding Information This work was supported by NIH R35 GM122523, T32 GM007752, & The Frontiers of Innovation Scholars Program.
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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) | 0.002 | 0.001 |
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".