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Alteration in the processing of the ACRBP/sp32 protein and sperm head/acrosome malformations in proprotein convertase 4 (PCSK4) null mice.

ABSTRACT: Proprotein convertase 4 (PCSK4) is a member of a family of proprotein convertases that convert inactive precursor proteins into their mature and active forms. PCSK4 is expressed by testicular germ cells and localizes to the sperm acrosome, suggesting roles in fertilization. Mice lacking PCSK4 exhibit a profound fertility defect; yet, to date, few substrates for PCSK4 are known. In this study, two-dimensional differential in-gel electrophoresis analysis was carried out in order to identify proteins that are altered in spermatozoa from PCSK4 null mice. Herein, we report that the sperm fertilization molecule acrosin-binding protein (ACRBP)/sp32, which normally undergoes processing from a 58.5 kDa precursor to a 27.5 kDa mature form, is not proteolytically processed in PCSK4 null mice and thus may be a substrate for PCSK4. However, analysis of the ACRBP sequence did not show a strong consensus site for convertase cleavage, suggesting that ACRBP processing may require the activity of a yet unknown enzyme that itself may be a PCSK4 substrate. Further analysis of spermatozoa from the PCSK4 null mice showed that proacrosin did not undergo autoactivation, supporting a role for the mature form of ACRBP in the regulation of proacrosin conversion into different acrosin isoforms. Finally, examination of ACRBP localization revealed a previously undetected morphological defect in the head/acrosomes of spermatozoa from PCSK4 null mice. Taken together, these results demonstrate that the fertility defect in the PCSK4 null mice may in part be due to altered ACRBP protein processing as well as abnormalities in the sperm head/acrosome.

SUBMITTER: Tardif S

PROVIDER: S-EPMC3358042 | biostudies-literature | 2012 Jun

REPOSITORIES: biostudies-literature

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Alteration in the processing of the ACRBP/sp32 protein and sperm head/acrosome malformations in proprotein convertase 4 (PCSK4) null mice.

Tardif Steve S Guyonnet Benoit B Cormier Nathaly N Cornwall Gail A GA

Molecular human reproduction 20120221 6

Proprotein convertase 4 (PCSK4) is a member of a family of proprotein convertases that convert inactive precursor proteins into their mature and active forms. PCSK4 is expressed by testicular germ cells and localizes to the sperm acrosome, suggesting roles in fertilization. Mice lacking PCSK4 exhibit a profound fertility defect; yet, to date, few substrates for PCSK4 are known. In this study, two-dimensional differential in-gel electrophoresis analysis was carried out in order to identify protei ...[more]

PMID: 22357636

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Project description:BackgroundActin-like 7 A (ACTL7A) is essential for acrosome formation, fertilization and early embryo development. ACTL7A variants cause acrosome detachment responsible for male infertility and early embryonic arrest. In this study, we aim to explore the additional functions of ACTL7A beyond the process of acrosome biogenesis and investigate the possible underlying mechanisms.MethodsNuclear morphology analysis was used to observe the sperm head shape of ACTL7A-mutated patients. Actl7a knock-out (KO) mouse model was generated. Immunofluorescence and transmission electron microscopy (TEM) were performed to analyze the structure of spermatids during spermiogenesis. Tandem mass tags labeling quantitative proteomics strategy was employed to explore the underlying molecular mechanisms. The expression levels of key proteins in the pathway were analyzed by western blotting. Intracytoplasmic sperm injection (ICSI)-artificial oocyte activation (AOA) technology was utilized to overcome fertilization failure in male mice with a complete knockout of Actl7a.ResultsThe new phenotype of small head sperm associated with loss of ACTL7A in patients was discovered, and further confirmed in Actl7a-KO mice. Immunofluorescence and TEM analyses revealed that the deletion of ACTL7A damaged the formation of acrosome-acroplaxome-manchette complex, leading to abnormalities in the shaping of sperm heads. Moreover, a proteomic analysis of testes from WT and Actl7a-KO mice revealed that differentially expressed genes were notably enriched in PI3K/AKT/mTOR signaling pathway which is strongly associated with autophagy. Inhibition of autophagy via PI3K/AKT/mTOR signaling pathway activation leading to PDLIM1 accumulation might elucidate the hindered development of manchette in Actl7a-KO mice. Remarkably, AOA successfully overcame fertilization failure and allowed for the successful production of healthy offspring from the Actl7a complete knockout male mice.ConclusionsLoss of ACTL7A causes small head sperm as a result of defective acrosome-acroplaxome-manchette complex via autophagy inhibition. ICSI-AOA is an effective technique to rescue male infertility resulting from ACTL7A deletion. These findings provide essential evidence for the diagnosis and treatment of patients suffering from infertility.

Dataset Information

Alteration in the processing of the ACRBP/sp32 protein and sperm head/acrosome malformations in proprotein convertase 4 (PCSK4) null mice.

Publications

Alteration in the processing of the ACRBP/sp32 protein and sperm head/acrosome malformations in proprotein convertase 4 (PCSK4) null mice.

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