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Regulation of Sperm Capacitation and the Acrosome Reaction by PIP 2 and Actin Modulation.

Breitbart H, Finkelstein M - Asian J. Androl. (2015 Jul-Aug)

Bottom Line: Stimulation of phospholipase C, by Ca 2 + -ionophore or by activating the epidermal-growth-factor-receptor, inhibits tyrosine phosphorylation of gelsolin and enhances enzyme activity.In conclusion, these data indicate that the increase of PIP 2 and/or F-actin in the head during capacitation enhances gelsolin translocation to the head.As a result, the decrease of gelsolin in the tail allows the maintenance of high levels of F-actin in this structure, which is essential for the development of HA motility.

View Article: PubMed Central - PubMed

Affiliation: The Mina and Everard Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel.

ABSTRACT
Actin polymerization and development of hyperactivated (HA) motility are two processes that take place during sperm capacitation. Actin polymerization occurs during capacitation and prior to the acrosome reaction, fast F-actin breakdown takes place. The increase in F-actin during capacitation depends upon inactivation of the actin severing protein, gelsolin, by its binding to phosphatydilinositol-4, 5-bisphosphate (PIP 2 ) and its phosphorylation on tyrosine-438 by Src. Activation of gelsolin following its release from PIP 2 is known to cause F-actin breakdown and inhibition of sperm motility, which can be restored by adding PIP 2 to the cells. Reduction of PIP 2 synthesis inhibits actin polymerization and motility, while increasing PIP 2 synthesis enhances these activities. Furthermore, sperm demonstrating low motility contained low levels of PIP 2 and F-actin. During capacitation there was an increase in PIP 2 and F-actin levels in the sperm head and a decrease in the tail. In spermatozoa with high motility, gelsolin was mainly localized to the sperm head before capacitation, whereas in low motility sperm, most of the gelsolin was localized to the tail before capacitation and translocated to the head during capacitation. We also showed that phosphorylation of gelsolin on tyrosine-438 depends upon its binding to PIP 2 . Stimulation of phospholipase C, by Ca 2 + -ionophore or by activating the epidermal-growth-factor-receptor, inhibits tyrosine phosphorylation of gelsolin and enhances enzyme activity. In conclusion, these data indicate that the increase of PIP 2 and/or F-actin in the head during capacitation enhances gelsolin translocation to the head. As a result, the decrease of gelsolin in the tail allows the maintenance of high levels of F-actin in this structure, which is essential for the development of HA motility.

No MeSH data available.


Related in: MedlinePlus

Actin remodeling in sperm capacitation and prior to acrosome reaction: human spermatozoa were incubated under capacitation conditions in Ham's F-10 medium and after 3 h of incubation the Ca2+-ionophore A23187 was added (upper figure). At the indicated times cell samples were stained for F-actin using FITC-phalloidin, photographed under fluorescence microscope, and analysed for fluorescence intensity in the sperm cells (upper figure). A picture of the stained cells is seen in the lower figure.
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Figure 1: Actin remodeling in sperm capacitation and prior to acrosome reaction: human spermatozoa were incubated under capacitation conditions in Ham's F-10 medium and after 3 h of incubation the Ca2+-ionophore A23187 was added (upper figure). At the indicated times cell samples were stained for F-actin using FITC-phalloidin, photographed under fluorescence microscope, and analysed for fluorescence intensity in the sperm cells (upper figure). A picture of the stained cells is seen in the lower figure.

Mentions: It is shown in Figure 1 and Table 1 that the cellular level of F-actin in human spermatozoa is relatively low before capacitation but is significantly enhanced during capacitation mainly in the sperm head but also in the tail. Prior to the acrosome reaction (AR) fast dispersion of F-actin occurs and this process allows the outer acrosomal membrane and the overlying plasma membrane to interact and fuse to culminate in the AR. Gelsolin, an actin -severing protein, is localized to the G-actin (actin monomers) fraction before capacitation but to the F-actin (filamentous actin) fraction at the end of the capacitation.22 Moreover, there is a significant increase in Ca2+-dependent gelsolin translocation to the sperm head during capacitation concomitantly with the increase in F-actin.


Regulation of Sperm Capacitation and the Acrosome Reaction by PIP 2 and Actin Modulation.

Breitbart H, Finkelstein M - Asian J. Androl. (2015 Jul-Aug)

Actin remodeling in sperm capacitation and prior to acrosome reaction: human spermatozoa were incubated under capacitation conditions in Ham's F-10 medium and after 3 h of incubation the Ca2+-ionophore A23187 was added (upper figure). At the indicated times cell samples were stained for F-actin using FITC-phalloidin, photographed under fluorescence microscope, and analysed for fluorescence intensity in the sperm cells (upper figure). A picture of the stained cells is seen in the lower figure.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4492050&req=5

Figure 1: Actin remodeling in sperm capacitation and prior to acrosome reaction: human spermatozoa were incubated under capacitation conditions in Ham's F-10 medium and after 3 h of incubation the Ca2+-ionophore A23187 was added (upper figure). At the indicated times cell samples were stained for F-actin using FITC-phalloidin, photographed under fluorescence microscope, and analysed for fluorescence intensity in the sperm cells (upper figure). A picture of the stained cells is seen in the lower figure.
Mentions: It is shown in Figure 1 and Table 1 that the cellular level of F-actin in human spermatozoa is relatively low before capacitation but is significantly enhanced during capacitation mainly in the sperm head but also in the tail. Prior to the acrosome reaction (AR) fast dispersion of F-actin occurs and this process allows the outer acrosomal membrane and the overlying plasma membrane to interact and fuse to culminate in the AR. Gelsolin, an actin -severing protein, is localized to the G-actin (actin monomers) fraction before capacitation but to the F-actin (filamentous actin) fraction at the end of the capacitation.22 Moreover, there is a significant increase in Ca2+-dependent gelsolin translocation to the sperm head during capacitation concomitantly with the increase in F-actin.

Bottom Line: Stimulation of phospholipase C, by Ca 2 + -ionophore or by activating the epidermal-growth-factor-receptor, inhibits tyrosine phosphorylation of gelsolin and enhances enzyme activity.In conclusion, these data indicate that the increase of PIP 2 and/or F-actin in the head during capacitation enhances gelsolin translocation to the head.As a result, the decrease of gelsolin in the tail allows the maintenance of high levels of F-actin in this structure, which is essential for the development of HA motility.

View Article: PubMed Central - PubMed

Affiliation: The Mina and Everard Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel.

ABSTRACT
Actin polymerization and development of hyperactivated (HA) motility are two processes that take place during sperm capacitation. Actin polymerization occurs during capacitation and prior to the acrosome reaction, fast F-actin breakdown takes place. The increase in F-actin during capacitation depends upon inactivation of the actin severing protein, gelsolin, by its binding to phosphatydilinositol-4, 5-bisphosphate (PIP 2 ) and its phosphorylation on tyrosine-438 by Src. Activation of gelsolin following its release from PIP 2 is known to cause F-actin breakdown and inhibition of sperm motility, which can be restored by adding PIP 2 to the cells. Reduction of PIP 2 synthesis inhibits actin polymerization and motility, while increasing PIP 2 synthesis enhances these activities. Furthermore, sperm demonstrating low motility contained low levels of PIP 2 and F-actin. During capacitation there was an increase in PIP 2 and F-actin levels in the sperm head and a decrease in the tail. In spermatozoa with high motility, gelsolin was mainly localized to the sperm head before capacitation, whereas in low motility sperm, most of the gelsolin was localized to the tail before capacitation and translocated to the head during capacitation. We also showed that phosphorylation of gelsolin on tyrosine-438 depends upon its binding to PIP 2 . Stimulation of phospholipase C, by Ca 2 + -ionophore or by activating the epidermal-growth-factor-receptor, inhibits tyrosine phosphorylation of gelsolin and enhances enzyme activity. In conclusion, these data indicate that the increase of PIP 2 and/or F-actin in the head during capacitation enhances gelsolin translocation to the head. As a result, the decrease of gelsolin in the tail allows the maintenance of high levels of F-actin in this structure, which is essential for the development of HA motility.

No MeSH data available.


Related in: MedlinePlus