title: Involvement of protein kinase A and A kinase anchoring protein in the progesterone-initiated human sperm acrosome reaction.
abstract: The signal transduction pathways involved in the progesterone (P(4))-initiated mammalian sperm acrosome reaction (AR) are not fully understood. To investigate the role of the protein kinase A (PKA) pathway in the P(4)-initiated AR, we probed this pathway by pretreating capacitated human sperm with reagents designed to either inhibit PKA activation or disrupt PKA/A kinase anchoring protein (AKAP) interactions. Preincubation with the stearated (membrane permeable) PKA inhibitor, PKI alpha 5-24 (S-PKI alpha 5-24), significantly inhibited the P(4)-initiated AR at 10 microM as compared to stearated control peptide. In contrast, preincubation with 100 microM nonstearated PKI alpha 5-24 did not significantly inhibit versus solvent control. Preincubation with the PKA inhibitor Rp-8-Br-cAMP at 500 microM and 150 microM significantly inhibited the P(4)-initiated AR versus 8-Br-cAMP and versus solvent. Preincubation with the anchoring inhibitory peptide S-Ht-31 significantly stimulated the P(4)-initiated AR at 10, 3, and 1 microM versus inactive control peptide. The stimulation of the P(4)-initiated AR by 3 microM S-Ht31 was significantly inhibited by the addition of 30 microM S-PKI alpha 5-24 prior to the addition of S-Ht31. Preincubation with S-PKI alpha 5-24 (30 microM) partially inhibited the ionomycin (50 microM)-initiated AR. A role for PKA in the P(4)-initiated AR may exist both upstream and downstream of Ca(2+) entry. Our studies present the first evidence for the participation of PKA in the P(4)-initiated AR and also suggest that AKAPs are involved in the PKA-mediated events.
authors.affiliation: Department of Cell Biology and Human Anatomy, University of California, Davis School of Medicine, Davis, California 95616, USA.
authors.forename: D A
authors.initials: DA
authors.lastname: Harrison
authors.forename: D W
authors.initials: DW
authors.lastname: Carr
authors.forename: S
authors.initials: S
authors.lastname: Meizel
mesh_terms: D020101:Acrosome Reaction / Q000502:physiology*; D000595:Amino Acid Sequence; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D008297:Male; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000494:pharmacology; D010455:Peptides / Q000187:drug effects / Q000378:metabolism*; D011374:Progesterone / Q000378:metabolism* / Q000494:pharmacology; D013094:Spermatozoa / Q000187:drug effects / Q000502:physiology
chemical_list: D004791:Enzyme Inhibitors; D036341:Intercellular Signaling Peptides and Proteins; D007476:Ionophores; D010446:Peptide Fragments; D010455:Peptides; C400087:S Ht31; C518603:protein kinase inhibitor peptide (5-24); C099977:4,5-dimethoxy-2-nitrobenzyl-8-bromo-cAMP; D011374:Progesterone; D015759:Ionomycin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases