Differential localization of α' and β subunits of protein kinase CK2 during rat spermatogenesis
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Date
2009
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Abstract
Protein kinase CK2 is a serine/threonine kinase expressed in organisms from yeast to human and is composed of a catalytic subunit (alpha or alpha') and a regulatory subunit (beta) forming a holoenzyme with the possible subunit combinations alpha(2)beta(2), alpha'(2)beta(2), or alpha alpha'beta(2). This kinase has been shown to be involved in embryonic development and gametogenesis. We have studied the expression of the CK2 alpha' and CK2 beta subunits during the first wave of spermatogenesis and in adult testis in the rat. Western blot analyses have demonstrated that both CK2 alpha' and CK2 beta are expressed in testes from birth to adulthood. A more detailed study of the protein localization of CK2 alpha' and CK2 beta by immunohistochemistry suggests that CK2 alpha' and CK2 beta 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, CK2 alpha' and CK2 beta subunits are present in spermatocytes. Both subunits exhibit a similar expression pattern with the highest level in spermatocytes at stages VIII-XIV. Interestingly, CK2 beta is highly expressed in spermatogonia, whereas CK2 alpha' is barely detectable. Mature epididymal spermatozoa express CK2 alpha' in the acrosome and CK2 beta 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.
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Keywords
Spermatogenesis, CK2, Cytoskeleton, Cell cycle, Meiosis, Rat (Sprague Dawley)