Sperm motility characteristics are regulated by changes in carboxy methylation and tyrosine phosphorylation of protein phosphatase PP2A
Bibliographic record
Abstract
The enzymes PP2A and PP1γ2 are the two major serine/threonine phosphatases in mammalian spermatozoa. PP2A is implicated in diverse cellular functions. In this study, we confirm the presence of PP2A in spermatozoa by western blot and show that it is carboxy methylated (Lys 309) and reciprocally tyrosine phosphorylated (Tyr 307). Mammalian spermatozoa acquire motility and their ability to fertilize eggs during their transit through the epididymis. PP2A of immotile sperm from late caput region of the epididymis is methylated with negligible tyrosine phosphorylation whereas PP2A from motile sperm of cauda epididymis is demethylated and tyrosine phosphorylated. Protein phosphatase assay shows that demethylation lowers catalytic activity of PP2A in motile caudal sperm compared to immotile caput sperm. Demethylation of PP2A occurred in the presence of nanomolar levels of okadaic acid or with increased intrasperm S‐adenosyl homocysteine levels. Increased PP2A demethylation converts caudal sperm motility into patterns resembling hyperactivation. These treatments however have no effect on immotile caput sperm. The enzymes PME‐1 and PPMT1 responsible for demethylation and methylation of PP2A respectively, along with SAH hydrolase are present in sperm. Thus PP2A regulated by methylation plays a role in modulating sperm motility characteristics essential for fertilization. (NIH‐HD38520)
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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 | 0.000 |
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".