Endoglin Is Expressed on Human Chondrocytes and Forms a Heteromeric Complex With Betaglycan in a Ligand and Type II TGFβ Receptor Independent Manner
Bibliographic record
Abstract
Previous work has implicated transforming growth factor beta (TGFbeta) as an essential mediator of cartilage repair and TGFbeta signaling as a requirement for the maintenance of articular cartilage in vivo. However, the mechanisms regulating TGFbeta action in chondrocytes are poorly understood. Endoglin, an accessory receptor of the TGFbeta receptor superfamily, is highly expressed on endothelial cells and has been shown to potently modulate TGFbeta responses. It is not known whether chondrocytes express endoglin or whether it modulates TGFbeta signaling in these cells. In this study, we show that endoglin is expressed on human chondrocytes at levels comparable with endothelial cells and that it forms higher order complexes with the types I and II TGFbeta receptors. More importantly, we show that endoglin forms a heteromeric complex with betaglycan on these cells at endogenous receptor concentrations and ratios. Endoglin complexes with betaglycan in a ligand-independent and -dependent manner as indicated by co-immunoprecipitation in the absence of TGFbeta and after affinity labeling with radiolabeled TGFbeta, respectively. Also, the endoglin-betaglycan association can occur independently of the type II TGFbeta receptor. These findings, taken together with the available evidence that endoglin and betaglycan are potent modulators of TGFbeta signal transduction, imply that the complex formation between endoglin and betaglycan may be of critical significance in the regulation of TGFbeta signaling in chondrocytes.
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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".