A Novel B Lymphocyte–Associated Adaptor Protein, Bam32, Regulates Antigen Receptor Signaling Downstream of Phosphatidylinositol 3-Kinase
Bibliographic record
Abstract
We have identified and characterized a novel src homology 2 (SH2) and pleckstrin homology (PH) domain-containing adaptor protein, designated Bam32 (for B cell adaptor molecule of 32 kD). cDNAs encoding the human and mouse Bam32 coding sequences were isolated and the human bam32 gene was mapped to chromosome 4q25-q27. Bam32 is expressed by B lymphocytes, but not T lymphocytes or nonhematopoietic cells. Human germinal center B cells show increased Bam32 expression, and resting B cells rapidly upregulate expression of Bam32 after ligation of CD40, but not immunoglobulin M. Bam32 is tyrosine-phosphorylated upon B cell antigen receptor (BCR) ligation or pervanadate stimulation and associates with phospholipase Cgamma2. After BCR ligation, Bam32 is recruited to the plasma membrane through its PH domain. Membrane recruitment requires phosphatidylinositol 3-kinase (PI3K) activity and an intact PI(3,4, 5)P(3)-binding motif, suggesting that membrane association occurs through binding to 3-phosphoinositides. Expression of Bam32 in B cells leads to a dose-dependent inhibition of BCR-induced activation of nuclear factor of activated T cells (NF-AT), which is blocked by deletion of the PH domain or mutation of the PI(3,4,5)P(3)-binding motif. Thus, Bam32 represents a novel B cell-associated adaptor that regulates BCR signaling downstream of PI3K.
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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 | 0.001 |
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".