MRP4 transporter is involved in the acquisition of human sperm’s fertilizing ability
Bibliographic record
Abstract
Cyclic AMP (cAMP) regulates multiple aspects of sperm function essential for attaining fertilizing ability; therefore, its intracellular levels must be tightly controlled to ensure proper signaling dynamics. In recent years, multidrug resistance-associated protein 4 (MRP4) has emerged as a novel regulator of cAMP homeostasis by facilitating its efflux. Previous studies from our laboratory have identified MRP4 in mammalian sperm and demonstrated its role in capacitation-associated events in murine and bovine species. However, its relevance in human sperm remains unknown. Our study demonstrates a functional MRP4 in human sperm, as its pharmacological inhibition led to a rapid (5 min) intracellular cAMP accumulation and a subsequent decrease in extracellular levels (30 min) under capacitating conditions, as assessed by radio binding protein assay. At the biological level, MRP4 inhibition resulted in a decrease in tyrosine phosphorylation at 360 min of capacitation. Membrane hyperpolarization was also affected, diminishing the induced acrosome reaction. Moreover, a significant reduction in intracellular Ca2+ levels was observed, leading to a significant decrease in progressive and total motility, as well as an inhibition of hyperactivation. In addition, our results indicated that the decrease in Ca2+ levels was due to impaired CatSper channel activity upon MRP4 inhibition. These findings suggest that MRP4-mediated cAMP efflux is essential for proper sperm function, playing a critical role in maintaining nucleotide homeostasis, which is a key determinant in the regulation of human sperm capacitation.
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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 | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.005 | 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".