A single discrete Rab5-binding site in phosphoinositide 3-kinase β is required for tumor cell invasion
Bibliographic record
Abstract
Phosphoinositide 3-kinase β (PI3Kβ) is regulated by receptor tyrosine kinases (RTKs), G protein–coupled receptors (GPCRs), and small GTPases such as Rac1 and Rab5. Our lab previously identified two residues (Gln 596 and Ile 597 ) in the helical domain of the catalytic subunit (p110β) of PI3Kβ whose mutation disrupts binding to Rab5. To better define the Rab5–p110β interface, we performed alanine-scanning mutagenesis and analyzed Rab5 binding with an in vitro pulldown assay with GST-Rab5 GTP . Of the 35 p110β helical domain mutants assayed, 11 disrupted binding to Rab5 without affecting Rac1 binding, basal lipid kinase activity, or Gβγ-stimulated kinase activity. These mutants defined the Rab5-binding interface within p110β as consisting of two perpendicular α-helices in the helical domain that are adjacent to the initially identified Gln 596 and Ile 597 residues. Analysis of the Rab5–PI3Kβ interaction by hydrogen-deuterium exchange MS identified p110β peptides that overlap with these helices; no interactions were detected between Rab5 and other regions of p110β or p85α. Similarly, the binding of Rab5 to isolated p85α could not be detected, and mutations in the Ras-binding domain (RBD) of p110β had no effect on Rab5 binding. Whereas soluble Rab5 did not affect PI3Kβ activity in vitro , the interaction of these two proteins was critical for chemotaxis, invasion, and gelatin degradation by breast cancer cells. Our results define a single, discrete Rab5-binding site in the p110β helical domain, which may be useful for generating inhibitors to better define the physiological role of Rab5–PI3Kβ coupling in vivo .
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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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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".