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Published on: February 6, 2018
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How, where and when is SPINK3 bound and removed from mouse sperm?
Anabella R Nicolli1, Carlos A I Alonso2, Catalina Otamendi1
1Instituto de Investigaciones Biológicas (IIB-FCEyN/CONICET), Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Mar del Plata, Argentina.
Reproduction (Cambridge, England)
|February 22, 2022
Summary
Sperm decapacitation factors (DFs) like SPINK3 bind to sperm via lipid rafts. Removal of SPINK3 from sperm in the female reproductive tract is essential for successful fertilization and sperm capacitation.
Area of Science:
- Reproductive Biology
- Sperm Physiology
- Molecular Mechanisms of Fertilization
Background:
- Sperm capacitation is crucial for mammalian fertilization, requiring the removal of decapacitation factors (DFs).
- The precise mechanisms and binding sites of DFs, such as Serine protease inhibitor Kazal type 3 (SPINK3), remain largely uncharacterized.
- Understanding DF action is key to controlling premature capacitation.
Purpose of the Study:
- To investigate the binding interactions of SPINK3 with mouse sperm.
- To determine the kinetics and location of SPINK3 removal from sperm during transit through the female reproductive tract.
- To explore the role of SPINK3 in sperm capacitation and fertilization.
Main Methods:
- Analysis of SPINK3 binding to mature epididymal mouse sperm using protein-lipid interaction studies.
- Investigation of SPINK3 binding inhibition by cholera toxin subunit b (CTB).
- Assessment of SPINK3 removal under in vitro capacitating conditions and using female uterine fluid.
- Ex vivo studies tracking SPINK3 removal kinetics in the uterus and oviduct.
Main Results:
- SPINK3 binds to mature epididymal sperm membranes through protein-lipid interactions, specifically within lipid rafts.
- Cholera toxin subunit b (CTB) inhibits SPINK3 binding to sperm.
- SPINK3 is removed from sperm under in vitro capacitating conditions and by estrus female uterine fluid.
- Ex vivo analysis shows SPINK3 is sequentially removed from the sperm's apical region in the uterus and flagellar region in the oviduct.
- Acrosome-reacted sperm in the female reproductive tract lack SPINK3 on their surface.
Conclusions:
- SPINK3 acts as a decapacitation factor, binding to sperm lipid rafts.
- SPINK3 removal from sperm is a regulated process occurring sequentially in the uterus and oviduct.
- The absence of SPINK3 correlates with sperm acrosome reaction, indicating its critical role in achieving fertilizing capacity.
