Nitric Oxide Regulates the Phosphorylation of the Threonine-Glutamine-Tyrosine Motif in Proteins of Human Spermatozoa During Capacitation1
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Bibliographic record
Abstract
Reactive oxygen species (superoxide anion, hydrogen peroxide, and nitric oxide) are involved in human sperm capacitation and associated tyrosine (Tyr) phosphorylation through a cAMP- and protein kinase A-mediated pathway. Recently, we evidenced the double phosphorylation of the threonine-glutamine-Tyr motif (P-Thr-Glu-Tyr-P) in human sperm proteins of 80 and 105 kDa during capacitation. The objective of the present study was to investigate the role of reactive oxygen species in the regulation of this process and to immunolocalize the P-Thr-Glu-Tyr-P motif in human spermatozoa. Superoxide dismutase and catalase did not prevent, and exogenous addition of superoxide anion or hydrogen peroxide did not trigger, the increase in P-Thr-Glu-Tyr-P related to sperm capacitation. However, l-NAME (a competitive inhibitor of l-arginine for nitric oxide synthase) prevented, and a nitric oxide donor promoted, the increase in P-Thr-Glu-Tyr-P related to sperm capacitation. In addition, l-arginine reversed the inhibitory effect of l-NAME on capacitation and the associated increase of P-Thr-Glu-Tyr-P. Therefore, the regulation of P-Thr-Glu-Tyr-P is specific to nitric oxide and not to superoxide anion or hydrogen peroxide. The nitric oxide-mediated increase of P-Thr-Glu-Tyr-P involved protein Tyr kinase, MEK or MEK-like kinase, and protein kinase C but not protein kinase A. The P-Thr-Glu-Tyr-P motif was immunolocalized to the principal piece region of spermatozoa. In conclusion, nitric oxide regulates the level of P-Thr-Glu-Tyr-P in sperm proteins of 80 and 105 kDa during capacitation. These data evidence, to our knowledge for the first time, a specific role for nitric oxide in signal transduction events leading to sperm capacitation.
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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 | 0.000 | 0.001 |
| 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) | 0.000 | 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 it