Periostin Is a Previously Uncharacterised Vitamin K Dependent γ-Carboxyglutamic Acid (Gla) Containing Protein Expressed by Marrow-Derived Mesenchymal Stromal Cells.
Bibliographic record
Abstract
Abstract The modification of glutamic acid residues to g-carboxyglutamic acid (Gla) is a post-translational modification catalyzed by the vitamin K-dependent γ-glutamylcarboxylase enzyme. Despite ubiquitous expression of the γ-carboxylation machinery in mammalian tissues, only 12 Gla-containing proteins have so far been identified in humans. Because bone tissue is the second most abundant source of Gla-proteins after the liver, we sought to identify Gla proteins secreted by bone-marrow derived mesenchymal stromal cells (MSCs), a precursor to all non-hematopoietic cells in bones. We used a proteomics approach to screen the secretome of MSCs with a combination of 2D gel electrophoresis and tandem mass spectrometry. The most abundant Gla-protein secreted by MSCs was identified as periostin, a previously unrecognized γ-carboxylated protein. In silico aminoacid sequence analysis of periostin demonstrated the presence of four consensus γ-carboxylase recognition sites embedded within fasciclin-like protein domains. The carboxylation of periostin was confirmed by immunoprecipitation using anti-Gla antibodies and could be inhibited by warfarin in MSCs. In conclusion, periostin is a novel vitamin K-dependent γ-carboxylated protein distinguished from other Gla-proteins by the presence of multiple γ-carboxylase recognition sites and MSCs are an abundant source of periostin including its γ-carboxylated variant.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".