SUBCELLULAR-LOCALIZATION OF THE REGULATORY SUBUNITS OF CYCLIC ADENOSINE 3',5'-MONOPHOSPHATE-DEPENDENT PROTEIN-KINASE IN BOVINE SPERMATOZOA

Cyclic AMP (cAMP) is a regulator of sperm flagellar activity. The acti on of this cyclic nucleotide is presumably mediated by cAMP-dependent protein kinase (PKA). PKA is localized or targeted to specific subcell ular sites through the interaction of PKA regulatory subunits with A-k inase anchoring proteins (AKAPs). We have recently shown that the addi tion of PKA anchoring inhibitor peptides to spermatozoa leads to the c omplete arrest of motility. A knowledge of the subcellular localizatio n of PKA and AKAPs is essential for an understanding of how cAMP acts in spermatozoa. In this report, monospecific, affinity-purified, antip eptide antibodies were used to determine the distribution of the regul atory (R) subunit isoforms. Immunocytochemistry staining revealed that RI alpha and RI beta subunits are both localized predominantly in the acrosomal segment of the head, although they have distinct staining p atterns within this region. In addition to the head, RI beta was obser ved in the midpiece of the tail while RI alpha was detected in the con necting piece. RII alpha is prominent in the axonemal region of the fl agellum but was not observed in the head region. These data suggest di stinct roles for each of these isoforms in sperm functions such as mot ility and the acrosome reaction.