Phosphoprotein enriched in astrocytes-15 is expressed in mouse testis and protects spermatocytes from apoptosis

Abstract

Phosphoprotein enriched in astrocytes (PEA-15) is a 15 kDa acidic serine-phosphorylated protein expressed in different cell types, especially in the CN. We initially detected the expression of PEA-15 in primary cultures of Sertoli cells. To assess the presence and localization of PEA-15 in the mouse testis, we studied the expression pattern of the PEA-15 protein by immunohistochemistry and mRNA by in situ hybridization. Both the protein and the mRNA of PEA-15 were localized in the cytoplasm of Sertoli cells, all types of spermatogonia, and spermatocytes up till zygotene phase of the meiotic prophase. Subsequently, with ongoing development of the spermatocytes, the expression decreased and was very low in the cytoplasm of diplotene spermatocytes. To analyze the possible role of PEA-15 in the developing testis, null mutants for PEA-15 were examined. As the PEA-15 C terminus contains residues for ERK binding, we studied possible differences between the localization of the ERK2 protein in wild type (WT) and PEA-15 K/K mice. In the WT testis, ERK2 was localized in the cytoplasm of Sertoli cells, B spermatogonia, preleptotene, leptotene, and zygotene spermatocytes, whereas in the KO testis, ERK2 was primarily localized in the nuclei of these cells and only little staining remained in the cytoplasm. Moreover, in PEA-15-deficient mice, significantly increased numbers of apoptotic spermatocytes were found, indicating an anti-apoptotic role of PEA-15 during the meiotic prophase. The increased numbers of apoptotic spermatocytes were not found at a specific step in the meiotic prophase.

Regulation of Caenorhabditis elegans p53/CEP-1–Dependent Germ Cell Apoptosis by Ras/MAPK Signaling

“…It is thus likely that in mammals p63 expression is subject to analogous developmental control mechanisms to those we have observed for C. elegans . While there is no reported evidence that ERK signaling impacts on p63 expression in the mammalian germline, the finding that ERK expression is observed in meiotic prophase in mouse spermatocytes [47], [48] lends weight to the idea that ERK signaling may play a role in regulating apoptosis in the mammalian germline.…”

Anchoring Junctions As Drug Targets: Role in Contraceptive Development

“…Additional studies have shown that adhesion of germ cells in the seminiferous epithelium is also regulated by the ERK signaling cascade Xia et al, 2006a). ERK, a ANCHORING JUNCTIONS AND MALE CONTRACEPTION nonreceptor protein tyrosine kinase of the mitogen-activated protein (MAP) kinase family, was shown to associate largely with Sertoli cells and spermatocytes in the basal compartment (Mizrak et al, 2007). Weak ERK immunoreactivity was also detected at the apical ectoplasmic specialization between Sertoli cells and early elongating spermatids, but phosphorylated ERK-Thr 202 / Tyr 204 localization was found predominantly between Sertoli cells and spermatids at stage 8 and beyond in the rat Xia and Cheng, 2005).…”

“…As such, phosphorylated ERK has been hypothesized to mediate restructuring of the apical ectoplasmic specialization, and to regulate spermatid movement and release. Note that the localization patterns of ERK and phosphorylated ERK-Thr 202 /Tyr 204 Mizrak et al, 2007) are remarkably similar to the localization patterns of FAK and phosphorylated FAK-Tyr 397 , because the immunoreactivity of FAK was also restricted largely to the blood-testis barrier but that of phosphorylated FAK-Tyr 397 was restricted to the apical ectoplasmic specialization (Siu et al, 2003). These results seemingly suggest that two forms of a specific protein kinase (i.e., phosphorylated and unphosphorylated) are needed to regulate closely related cellular functions in Sertoli cells, such as junction restructuring that occurs at the apical ectoplasmic specialization and blood-testis barrier, which are present at opposite ends of the Sertoli cell.…”

Transient receptor potential vanilloid receptor-1 confers heat resistance to male germ cells

“…The testes were then dissected and the epididymes removed. After the testes were weighed, they were immersion fixed in Bouin's solution, paraffin embedded, sectioned, and either stained with periodic acid-Schiff-hematoxylin or processed for terminal deoxynucleotidyl transferase-mediated deoxyuridine 5-triphosphate-biotin nick end labeling (TUNEL) to specifically monitor apoptosis of the germ cells, as described elsewhere (19). For the last, testis sections were boiled for 5 minutes in 10 mM citric buffer (pH 6.0) at 98 C and slowly were cooled to room temperature.…”