Abstract

Protein kinase CK2 is a serine/threonine kinase expressed in organisms from yeast to human and is composed of a catalytic subunit (a or a') and a regulatory subunit (ß) forming a holoenzyme with the possible subunit combinations a 2ß 2, a' 2ß 2, or aa'ß 2. This kinase has been shown to be involved in embryonic development and gametogenesis. We have studied the expression of the CK2a' and CK2ß subunits during the first wave of spermatogenesis and in adult testis in the rat. Western blot analyses have demonstrated that both CK2a' and CK2ß are expressed in testes from birth to adulthood. A more detailed study of the protein localization of CK2a' and CK2ß by immunohistochemistry suggests that CK2a' and CK2ß are localized in the nuclei of Sertoli cells in 5-day-old rats, whereas they appear to have a cytoplasmic localization in older animals. In adult testes, CK2a' and CK2ß subunits are present in spermatocytes. Both subunits exhibit a similar expression pattern with the highest level in spermatocytes at stages VIII-XIV. Interestingly, CK2ß is highly expressed in spermatogonia, whereas CK2a' is barely detectable. Mature epididymal spermatozoa express CK2a' in the acrosome and CK2ß in the flagellum. This new evidence therefore indicates that protein kinase CK2 has a possible role at various stages during mammalian spermatogenesis, a process that involves proliferation, meiosis, apoptosis, and differentiation. CK2 might thus emerge as a new pivotal control enzyme at various levels in mammalian spermatogenesis. © 2009 Springer-Verlag.