Proteomic analysis of ubiquitination substrates reveals a CTLH E3 ligase complex‐dependent regulation of glycolysis
Bibliographic record
Abstract
Ubiquitination is an essential post-translational modification that regulates protein stability or function. Its substrate specificity is dictated by various E3 ligases. The human C-terminal to LisH (CTLH) complex is a newly discovered multi-subunit really interesting new gene (RING) E3 ligase with only a few known ubiquitination targets. Here, we used mass spectrometry-based proteomic techniques to gain insight into CTLH complex function and ubiquitination substrates in HeLa cells. First, global proteomics determined proteins that were significantly increased, and thus may be substrates targeted for degradation, in cells depleted of CTLH complex member RanBPM. RanBPM-dependent ubiquitination determined using diGLY-enriched proteomics and the endogenous RanBPM interactome further revealed candidate ubiquitination targets. Three glycolysis enzymes alpha-enolase, L-lactate dehydrogenase A chain (LDHA), and pyruvate kinase M1/2 (PKM) had decreased ubiquitin sites in shRanBPM cells and were found associated with RanBPM in the interactome. Reduced polyubiquitination was validated for PKM2 and LDHA in cells depleted of RanBPM and CTLH complex RING domain subunit RMND5A. PKM2 and LDHA protein levels were unchanged, yet their activity was increased in extracts of cells with downregulated RanBPM. Finally, RanBPM deficient cells displayed enhanced glycolysis and deregulated central carbon metabolism. Overall, this study identifies potential CTLH complex ubiquitination substrates and uncovers that the CTLH complex inhibits glycolysis via non-degradative ubiquitination of PKM2 and LDHA.
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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) | 0.001 | 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 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".