Delfino F, Walker W H
Department of Cell Biology and Physiology, University of Pittsburgh, Pennsylvania 15261, USA.
Mol Endocrinol. 1998 Nov;12(11):1696-707. doi: 10.1210/mend.12.11.0194.
The Rel/nuclear factor (NF)-kappaB family of transcription factors are important intracellular conveyors of extracellular signals in a number of systems. However, little is known of their roles in the specialized, hormonally regulated environment of the mammalian testis. In this study NF-kappaB p50 and p65 proteins were found to be constitutively present and active in the nucleus of Sertoli cells cultured from rat testis. In vivo, NF-kappaB proteins are present in the nucleus of Sertoli cells during all 14 (I-XIV) cyclical stages of spermatogenesis; however, nuclear NF-kappaB expression was elevated in stage XIV and remained high in stages I-VII. In contrast, NF-kappaB p50 and p65 subunits are transiently expressed in the nuclei of germ cells with peak levels found in pachytene spermatocytes during stages VII-XI and lower levels in stage I-VII spermatids. Tumor necrosis factor-alpha, which is produced by round spermatids in the testis, increased nuclear NF-kappaB binding activity when added to Sertoli cells. Stimulation of Sertoli cells with activators of the cAMP-protein kinase A (PKA) signaling pathway such as forskolin or FSH also increased NF-kappaB DNA binding activity. Consistent with the cellular localization studies, NF-kappaB was found to be activated as high basal levels of NF-kappaB-stimulated reporter gene expression were detected in transient transfection studies of Sertoli cells. Addition of tumor necrosis factor-alpha to Sertoli cells further stimulated kappaB enhancer-mediated transcription. These findings suggest that NF-kappaB proteins are stage specifically localized to Sertoli cell and spermatocyte nuclei and may play a role in the regulation of stage-specific gene expression during the process of spermatogenesis.
Rel/核因子（NF）-κB转录因子家族在许多系统中是细胞外信号的重要细胞内传导者。然而，它们在哺乳动物睾丸这种特殊的、受激素调节的环境中的作用却鲜为人知。在本研究中，发现NF-κB p50和p65蛋白在从大鼠睾丸培养的支持细胞的细胞核中组成性存在且具有活性。在体内，在精子发生的所有14个（I-XIV）周期性阶段，NF-κB蛋白都存在于支持细胞的细胞核中；然而，细胞核NF-κB的表达在第XIV阶段升高，并在I-VII阶段保持高水平。相反，NF-κB p50和p65亚基在生殖细胞的细胞核中短暂表达，在VII-XI阶段的粗线期精母细胞中达到峰值水平，而在I-VII阶段的精子细胞中水平较低。睾丸中的圆形精子细胞产生的肿瘤坏死因子-α添加到支持细胞中时，会增加细胞核NF-κB的结合活性。用环磷酸腺苷-蛋白激酶A（PKA）信号通路的激活剂（如福斯可林或促卵泡激素）刺激支持细胞也会增加NF-κB与DNA的结合活性。与细胞定位研究一致，在支持细胞的瞬时转染研究中发现NF-κB被激活，因为检测到高水平的NF-κB刺激的报告基因表达。向支持细胞中添加肿瘤坏死因子-α进一步刺激了κB增强子介导的转录。这些发现表明，NF-κB蛋白在支持细胞和精母细胞核中具有阶段特异性定位，并且可能在精子发生过程中阶段特异性基因表达的调节中发挥作用。
