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Roles of glycogen synthase kinase 3 alpha and calcineurin in regulating the ability of sperm to fertilize eggs.

ABSTRACT: Glycogen synthase kinase 3 (GSK3) was identified as an enzyme regulating sperm protein phosphatase. The GSK3? paralog, but not GSK3?, is essential for sperm function. Sperm lacking GSK3? display altered motility and are unable to undergo hyperactivation, which is essential for fertilization. Male mice lacking sperm-specific calcineurin (PP2B), a calcium regulated phosphatase, in testis and sperm, are also infertile. Loss of PP2B results in impaired epididymal sperm maturation and motility. The phenotypes of GSK3? and PP2B knockout mice are similar, prompting us to examine the interrelationship between these two enzymes in sperm. High calcium levels must exist to permit catalytically active calcineurin to function during epididymal sperm maturation. Total and free calcium levels are high in immotile compared to motile epididymal sperm. Inhibition of calcineurin by FK506 results in an increase in the net phosphorylation and a consequent decrease in catalytic activity of sperm GSK3. The inhibitor FK506 and an isoform-selective inhibitor of GSK3?, BRD0705, also inhibited fertilization of eggs in vitro. Interrelated functions of GSK3? and sperm PP2B are essential during epididymal sperm maturation and during fertilization. Our results should enable the development of male contraceptives targeting one or both enzymes.

SUBMITTER: Dey S

PROVIDER: S-EPMC7539848 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Roles of glycogen synthase kinase 3 alpha and calcineurin in regulating the ability of sperm to fertilize eggs.

Dey Souvik S Eisa Alaa A Kline Douglas D Wagner Florence F FF Abeysirigunawardena Sanjaya S Vijayaraghavan Srinivasan S

FASEB journal : official publication of the Federation of American Societies for Experimental Biology 20191129 1

Glycogen synthase kinase 3 (GSK3) was identified as an enzyme regulating sperm protein phosphatase. The GSK3α paralog, but not GSK3β, is essential for sperm function. Sperm lacking GSK3α display altered motility and are unable to undergo hyperactivation, which is essential for fertilization. Male mice lacking sperm-specific calcineurin (PP2B), a calcium regulated phosphatase, in testis and sperm, are also infertile. Loss of PP2B results in impaired epididymal sperm maturation and motility. The p ...[more]

PMID: 31914663

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Project description:BackgroundCyclophilin D (CypD) negatively regulates ATP production by opening of the mitochondrial permeability transition pore. This study aimed to understand the role of CypD in sperm motility regulation.MethodsChanges in CypD during sperm capacitation and its interaction with glycogen synthase kinase 3α (GSK3α), a key kinase regulating sperm motility, were examined in mouse spermatozoa. The effects of CypD inhibitor cyclosporin A (CsA) and GSK3 inhibitor 6-bromo-indirubin-3'-oxime (BIO) on sperm motility, p-GSK3α(Ser21), mitochondrial permeability transition pore (mPTP), mitochondrial membrane potential (MMP), and ATP production were examined. The effect of proteasome inhibitor MG115 on the cellular levels of CypD was examined.ResultsIn cauda epididymal spermatozoa, GSK3α was found in both cytosolic and mitochondrial fractions whereas CypD was primarily found in the mitochondrial fraction together with ATP synthase F1 subunit alpha (ATP5A), a mitochondrial marker. GSK3α and CypD were co-localized in the sperm midpiece. Interaction between GSK3α and CypD was identified in co-immunoprecipitation. CsA, a CypD inhibitor, significantly increased sperm motility, tyrosine phosphorylation, mPTP closing, MMP, and ATP levels in spermatozoa, suggesting that CypD acts as a negative regulator of sperm function. Under capacitation condition, both GSK3α and CypD were decreased in spermatozoa but ATP5A was not. The GSK3 inhibitor BIO markedly increased p-GSK3α(Ser21) and decreased CypD but significantly increased mPTP closing, MMP, ATP production, and motility of spermatozoa. This suggests that inhibitory phosphorylation of GSK3α is coupled with degradation of CypD, potentiating the mitochondrial function. Degradation of CypD was attenuated by MG115, indicative of involvement of the ubiquitin proteasome system.ConclusionsDuring sperm capacitation, CypD act as a downstream target of GSK3α can be degraded via the ubiquitin proteasome system, stimulating mitochondrial function and sperm motility.

Dataset Information

Roles of glycogen synthase kinase 3 alpha and calcineurin in regulating the ability of sperm to fertilize eggs.

Publications

Roles of glycogen synthase kinase 3 alpha and calcineurin in regulating the ability of sperm to fertilize eggs.

Similar Datasets

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