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Reagents that activate GTP-binding proteins trigger the acrosome reaction in human spermatozoa
L Domínguez1, A Díaz, M W Fornés
1Universidad Nacional de Cuyo, CONICET, Mendoza, Argentina.
Abstract:
The acrosome reaction is a specialized exocytotic process. In the mouse there is compelling evidence that receptor-mediated activation of GTP-binding proteins by factors in the zona pellucida of oocytes is a central event in the acrosome reaction. Several reagents are able to affect GTP-binding proteins directly, bypassing the receptor-ligand step for activation. We have assessed the effect of several of these compounds on human spermatozoa, monitoring cell vitality and the acrosome reaction simultaneously using the triple-stain technique. GTP gamma S and aluminium fluoride complexes promote sperm activation very efficiently; amphiphilic peptides capable of activating G(o) and Gi, also elicit the acrosome reaction. The results indicate that activation of heterotrimeric GTP-binding proteins is sufficient to trigger acrosome exocytosis in human spermatozoa.
Insights
Activation of GTP-binding proteins directly triggers the acrosome reaction in human sperm. This finding reveals a key mechanism for sperm function and potential targets for fertility treatments.
Area of Science:
- Reproductive Biology
- Cellular Signaling
- Spermatozoa Function
Background:
- The acrosome reaction is crucial for fertilization, involving exocytosis.
- In mice, oocyte zona pellucida factors activate GTP-binding proteins, initiating this reaction.
- Direct activation of GTP-binding proteins can bypass normal receptor-ligand signaling.
Purpose of the Study:
- To investigate the direct activation of GTP-binding proteins in human spermatozoa.
- To determine if this direct activation can trigger the acrosome reaction.
- To assess the role of heterotrimeric GTP-binding proteins in human sperm exocytosis.
Main Methods:
- Human spermatozoa were treated with reagents that directly affect GTP-binding proteins.
- Cell vitality and the acrosome reaction were monitored simultaneously.
- The triple-stain technique was employed for accurate assessment.
Main Results:
- GTP gamma S and aluminum fluoride complexes efficiently induced sperm activation.
- Amphiphilic peptides activating G(o) and Gi also elicited the acrosome reaction.
- These results demonstrate direct induction of the acrosome reaction.
Conclusions:
- Direct activation of heterotrimeric GTP-binding proteins is sufficient to trigger acrosome exocytosis in human sperm.
- This pathway offers insights into sperm function and potential therapeutic targets.
- Understanding GTP-binding protein activation is key to male fertility research.