Send to

Choose Destination
See comment in PubMed Commons below
Am J Vet Res. 2005 Jun;66(6):1056-64.

Characterization of an A-kinase anchor protein in equine spermatozoa and examination of the effect of semen cooling and cryopreservation on the binding of that protein to the regulatory subunit of protein kinase-A.

Author information

  • 1Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA 19348-1692, USA.



To determine whether a homologue of A-kinase anchor protein 4 (AKAP4) is present and functional as an AKAP in equine spermatozoa and examine the effect of semen cooling and cryopreservation on binding of equine AKAP4 to the regulatory (RII) subunit of protein kinase-A (PK-A).


Ejaculated semen collected from 2 fertile stallions, 3 bulls, and 3 humans.


Identification of an equine homologue of AKAP4 was investigated via DNA sequencing. Protein was extracted from the spermatozoa of each species for immunoblot analysis to identify AKAP4 and its precursor protein, pro-AKAP4; immunofluorescence microscopy was used to localize those proteins in spermatozoa. Ligand overlay assays were used to determine whether the identified proteins bound to the RII subunit of PK-A and whether cooling or cryopreservation of spermatozoa affected that binding.


The partial genomic sequence of AKAP4 was identified in equine spermatozoa, and immunoblot analysis confirmed that AKAP4 and pro-AKAP4 are present in equine spermatozoa. Via immunofluorescence microscopy, these proteins were localized to the spermatozoal principal piece. Results of ligand overlay assays indicated that equine AKAP4 and pro-AKAP4 bind to the RII subunit of PK-A and are AKAPs; AKAP4-RII binding was not affected by cooling or cryopreservation of spermatozoa.


Results suggest that equine AKAP4 anchors PK-A to the spermatozoal flagellum (where the kinase is likely to be required for the regulation of spermatozoal motility), but decreases in spermatozoal motility in cooled or cryopreserved semen are not associated with decreased binding of AKAP4 and PK-A.

[PubMed - indexed for MEDLINE]
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Loading ...
    Support Center