The changes of cortactin p80/85 isoform profiles and tyrosine phosphorylation status during spermatogenesis in the mouse testis.

Cortactin--an F-actin-binding protein--regulates actin polymerization and plays an important role in cytoskeleton actin dynamics. Cortactin functions are reportedly regulated by changes in its isoform (p80/85) profiles and phosphorylation status. Although essential for spermatogenesis, the exact role of cortactin in the testis has not been well elucidated. Herein, we examined its dynamics in isoform profiles and tyrosine phosphorylation levels during spermatogenesis in mice. Western blot analysis showed that the amount of the p85 isoform of cortactin particularly decreased during stages VI-VIII. In the p80 isoform, cortactin phosphorylations at both tyrosine 421 and 466 were detected during stages XII-V and VI-VIII. For the p85 isoform, tyrosine 466 phosphorylation of cortactin, not 421, was detected during stages XII-V and VI-VIII, and this phosphorylation particularly increased during stages VI-VIII. The tyrosine 466 phosphorylation level of the p85 isoform of cortactin relative to the total amount of the p85 isoform notably increased during stages VI-VIII. Additionally, immunohistochemical analysis showed localization of the tyrosine 466-phosphorylated cortactin around the heads of elongating and elongated spermatids. Finally, we examined the effect of flutamide--an antiandrogen--on cortactin isoform profiles and phosphorylation status. The amount of tyrosine 466-phosphorylated p85 isoform of cortactin relative to the total amount of the p85 isoform of cortactin decreased after flutamide injection, whereas no change was detected with regard to the total amount of cortactin p85 isoform. These data suggest the possibility that localization of the more tyrosine 466-phosphorylated p85 isoform of cortactin around the heads of elongated spermatids is important for stages VII-VIII processes and that its phosphorylation site of the p85 isoform might be a target for creating a novel contraceptive and treating infertility in the future.