We have recently demonstrated the involvement of phospholipase D (PLD) in actin polymerization during mammalian sperm capacitation. In the present study, we investigated the involvement of phosphatidylinositol 3- and 4-kinases (PI3K and PI4K) in actin polymerization, as well as the production of PIP2(4,5), which is a known cofactor for PLD activation, during bovine sperm capacitation. PIK3R1 (p85 α regulatory subunit of PI3K) and PIKCB (PI4K β) in bovine sperm were detected by Western blotting and immunocytochemistry. Wortmannin (WT) inhibited PI3K and PI4K type III at concentrations of 10 nM and 10 μM, respectively. PI4K activity and PIP2(4,5) production were blocked by 10 μM WT but not by 10 nM WT, whereas PI3K activity and PIP3(3,4,5) production were blocked by 10 nM WT. Moreover, spermine, which is a known PI4K activator and a component of semen, activated sperm PI4K, resulting in increased cellular PIP2(4,5) and F-actin formation. The increases in PIP2(4,5) and F-actin intracellular levels during sperm capacitation were mediated by PI4K but not by PI3K activity. Activation of protein kinase A (PKA) by dibutyryl cAMP enhanced PIP2(4,5), PIP3(3,4,5), and F-actin formation, and these effects were mediated through PI3K. On the other hand, activation of PKC by phorbol myristate acetate enhanced PIP2(4,5) and F-actin formation mediated by PI4K activity, while the PI3K activity and intracellular PIP3(3,4,5) levels were reduced. These results suggest that two alternative pathways lead to PI4K activation: indirect activation by PKA, which is mediated by PI3K; and activation by PKC, which is independent of PI3K activity. Our results also suggest that spermine, which is present in the ejaculate, regulates PI4K activity during the capacitation process in vivo.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 77 • No. 2