Ubiquitination of MHC class II molecules regulates B-cell development and response to antigens in mice
Bibliographic record
Abstract
Dendritic cells (DCs) and B lymphocytes produce major histocompatibility complex class II molecules (MHCIIs) in large amounts to maximize the display of peptides and fulfill their antigen-presentation functions. The surface expression of MHCIIs in these cells is regulated via the ubiquitination of a single conserved lysine residue in the cytoplasmic tail of all known β-chains. This modification is carried out mainly by the MARCH1 E3 ubiquitin ligase. In MARCH1-deficient DCs, the lack of MHCII ubiquitination results in its excessive accumulation at the plasma membrane, disorganizing lipid rafts and tetraspanin webs. These membrane structures regulate numerous biological processes, allowing the interactions between signaling molecules, such as the B-cell receptor (BCR) and CD19. Nevertheless, the full impact of MARCH1 and the ubiquitin-dependent MHCII turnover on the development, activation, and functions of B cells remains to be explored. Here, we show that the absence of MHCII ubiquitination negatively affected the marginal zone (MZ) B-cell pool in mice. We provide evidence that this alteration of B-cell responses may, at least in part, be due to the proteotoxicity of MHCIIs on the CD81-containing tetraspanin web, which impacted the surface dynamics of CD19 and its capacity to activate the PI3K/Akt cascade during tonic BCR signaling. The reduced MZ B-cell pool impaired the immune response to a type 2 T-independent antigen. Interestingly, the germinal center (GC) response against a T-dependent antigen was also negatively affected. Altogether, our results demonstrate the importance of the ubiquitin-dependent control of MHCII proteostasis for B-cell functions.
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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) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| 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".