Tyrosine Phosphorylation of Sperm Proteins: What Does It Mean?
Notice bibliographique
Résumé
Capacitation is defined as the ensemble of modifications that render ejaculated sperm competent to fertilise, either in the female tract or in vitro. Capacitation can occur spontaneously in vitro in defined media, suggesting it is intrinsically regulated and, once initiated, follows a pre-programmed pathway. Unlike other signalling cascades, capacitation is unique as it occurs without a specific ligand. Capacitated sperm can undergo the acrosome reaction, a calcium-dependent, exocytotic event upon interaction with the oocyte. The newly exposed inner acrosomal membrane reveals proteins that either anchor acrosome-reacted sperm to the oocyte zona pellucida (ZP) or fuse with the egg. How the sperm, a highly compartmentalised and non-transcriptional cell, undergoes the complexities of capacitation and the acrosome reaction remains unclear. Since sperm are non-transcriptional, however, protein modifications, including tyrosine phosphorylation are effective modulators of their cellular activities, including capacitation, the acrosome reaction and hyperactivated motility. Using the porcine model, our laboratory has demonstrated that capacitation is associated with the calcium-dependant appearance of a Mr 32 000 group of tyrosine phosphoproteins, collectively referred to as p32. The role and regulation of the p32 tyrosine phosphoprotein complex has remained elusive, although it has been suggested that it is involved in sperm-oocyte binding and/ or the acrosome reaction because sperm surface tyrosine phosphorylation appears during capacitation and high calcium dramatically enhances p32's presence. Moreover, ACRBP (Acrosin Binding Protein, also known as sp32), a proacrosin binding protein, is a principal component of the p32 complex, and is tyrosine phosphorylated during capacitation. ACRBP has been previously shown to catalyse prostacrosin to acrosin conversion in vitro, thereby enhancing the acrosome reaction. More recently, ACRBP was shown to have secondary ZP-binding affinity in overlay assays. In support of both reports, we have shown that ACRBP is located on the surface of capacitated sperm. However, there have been no biological studies assessing the role of ACRBP and the implication of its tyrosine phosphorylation is unknown. Therefore, to test the hypothesis that ACRBP and tyrosine phosphoproteins are necessary for sperm capacitation, the acrosome reaction and fertilization in the pig model, in vitro matured pig oocytes were inseminated with fresh boar sperm that were pre-capacitated in the presence of affinity purified mouse anti-phosphotyrosine and rabbit anti-ACRBP. Indeed, the presence of either anti-ACRBP or anti-phosphotyrosine decreased sperm-ZP binding and fertilization rate (P < 0.05). To assess the importance of surface ACRBP on the acrosome reaction, sperm were cultured in fertilization medium ±ACRBR antibody. The acrosome reaction was induced by A23187, thapsigargin or ZP. Interestingly, the presence of anti-ACRBP prevented the thapsigargin and ZP-induced acrosome reaction but not that induced by A23187. These results suggest that ACRBP influence calcium stores. Furthermore, inhibitors of SOCC (Store-Operated Calcium Channels) prevented spontaneous and thapsigargin-induced acrosome reactions, as well as p32 appearance. Taken together, these results suggest that ACRBP and the p32 tyrosine phosphoprotein complex are involved the stimulating the acrosome reaction, perhaps via SOCC. Funded by NSERC. (platform)
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,004 | 0,007 |
| Méta-épidémiologie (sens strict) | 0,001 | 0,000 |
| Méta-épidémiologie (sens large) | 0,002 | 0,001 |
| Bibliométrie | 0,002 | 0,002 |
| Études des sciences et des technologies | 0,001 | 0,005 |
| Communication savante | 0,004 | 0,006 |
| Science ouverte | 0,001 | 0,001 |
| Intégrité de la recherche | 0,004 | 0,007 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,002 | 0,001 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».