Localization of a novel human A-kinase-anchoring protein, hAKAP220, duringspermatogenesis

Using a combination of protein kinase A type II overlay screening, rapid am plification of cDNA ends, and database searches, a contig of 9923 bp was as sembled and characterized in which the open reading frame encoded a 1901-am ino-acid A-kinase-anchoring protein (AKAP) with an apparent SDS-PAGE mobili ty of 220 kDa, named human AKAP220 (hAKAP220). The hAKAP220 amino acid sequ ence revealed high similarity to rat AKAP220 in the 1167 C-terminal residue s, but contained 727 residues in the N-terminus not present in the reported rat AKAP220 sequence. The hAKAP220 mRNA was expressed at high levels in hu man testis and in isolated human pachytene spermatocytes and round spermati ds. The hAKAP220 protein was present in human male germ cells and mature sp erm. Immunofluorescent labeling with specific antibodies indicated that hAK AP220 was localized in the cytoplasm of premeiotic pachytene spermatocytes and in the centrosome of developing postmeiotic germ cells, while a midpiec e/centrosome localization was found in elongating spermatocytes and mature sperm. The hAKAP220 protein together with a fraction of PKA types I and II and protein phosphatase I was resistant to detergent extraction of sperm ta ils, suggesting an association with cytoskeletal structures. In contrast, S -AKAP84/D-AKAP1, which is also present in the midpiece, was extracted under the same conditions, Anti-hAKAP220 antisera coimmunoprecipitated both type I and type II regulatory subunits of PKA in human testis lysates, indicati ng that hAKAP220 interacts with both classes of R subunits, either through separate or through a common binding motif(s). (C) 2000 Academic Press.