Abstract

Spermatogenesis is dependent upon Sertoli cells, which relay hormonal signals and provide factors required for the differentiation and proliferation of germ cells. NF-kappaB transcription factors are constitutively expressed in the nuclei of Sertoli cells in rodent testis. Electrophoretic mobility shift assays demonstrated that Sertoli NF-kappaB proteins specifically bind to kappaB enhancer motifs within the promoter of the cAMP-response element-binding protein (CREB) gene, an important mediator of hormonal signals that control spermatogenesis. Overexpression of NF-kappaB proteins in primary Sertoli and NIH 3T3 fibroblast cells induced the CREB promoter in transient transfection assays. Stimulation of Sertoli cells with tumor necrosis factor-alpha, an NF-kappaB-activating cytokine produced by round spermatids located adjacent to Sertoli cells, stimulated the elimination of IkappaB, the translocation of additional NF-kappaB to the nucleus, and increased NF-kappaB binding to CREB promoter kappaB enhancer elements. Tumor necrosis factor-alpha also stimulated transcription from the CREB promoter. These data demonstrate that NF-kappaB contributes to the up-regulation of CREB expression in Sertoli cells and raises the possibility that NF-kappaB may induce other Sertoli genes required for spermatogenesis. Furthermore, the CREB promoter is also inducible by NF-kappaB in NIH 3T3 cells suggesting that NF-kappaB may be a general regulator of CREB in non-testis tissues.