Axokinin phosphorylation by cAMP-dependent protein kinase is sufficient for activation of sperm flagellar motility.

Journal Article (Journal Article)

Using a selective inhibitor of cAMP-dependent protein kinase, N-[2(methylamino)ethyl]-5-isoquinolinesulfonamide (H-8), the requirement for cAMP-dependent phosphoproteins in the initiation of dog sperm flagellar motility was examined. H-8 inhibited motility of live as well as reactivated sperm in a dose-dependent manner. The half-maximal inhibition of reactivated motility (32 microM) paralleled the inhibition of pure catalytic subunit of cAMP-dependent protein kinase (50 microM) measured under the same conditions. H-8 inhibited protein phosphorylation both in whole models and in isolated Nonidet P-40 (NP-40) extracts of sperm. Axokinin, the heat-stable NP-40-soluble protein whose phosphorylation is required for flagellar reactivation, represented 97% of the de novo phosphate incorporation in the NP-40 extract after stimulation by cAMP. 500 microM H-8 inhibited axokinin phosphorylation by 87%. When sperm were reactivated in the presence of up to 5 mM H-8 with NP-40 extract that had been prephosphorylated with cAMP-dependent protein kinase, then neither cAMP nor cAMP-dependent protein kinase activity was required for full flagellar reactivation. If sperm were rendered completely immotile by pretreatment with H-8, then the resulting model remained immotile in the continued presence of H-8 unless prephosphorylated axokinin was added. These results suggest that phosphorylated axokinin is not only required for flagellar reactivation but is sufficient as well.

Full Text

Duke Authors

Cited Authors

  • Tash, JS; Hidaka, H; Means, AR

Published Date

  • August 1986

Published In

Volume / Issue

  • 103 / 2

Start / End Page

  • 649 - 655

PubMed ID

  • 3733884

Pubmed Central ID

  • PMC2113824

International Standard Serial Number (ISSN)

  • 0021-9525

Digital Object Identifier (DOI)

  • 10.1083/jcb.103.2.649


  • eng

Conference Location

  • United States