Doucas V, Shi Y, Miyamoto S, West A, Verma I, Evans R M
Department of Genetics and Microbiology, University of Geneva Medical School, 9 Avenue de Champel, CH-1211, Geneva 4, Switzerland.
Proc Natl Acad Sci U S A. 2000 Oct 24;97(22):11893-8. doi: 10.1073/pnas.220413297.
Negative transcriptional regulation or cross-coupling between NF-kappa B (RelA) and the glucocorticoid receptor (GR) is proposed to play a regulatory role in human physiology and disease. Despite previous advances, the biochemical basis of this phenomenon remains a subject of controversy. We show here that the inhibition of GR activity by RelA does not require the RelA DNA binding, transactivation, or nuclear localization domains. Surprisingly, RelA repression of GR is abolished by mutation of the conserved protein kinase A (PKA) site at amino acid residue 276 of RelA. We show that GR associates in vivo and in vitro with the catalytic subunit of PKA (PKAc) in a ligand-independent manner and that GR transcription depends on PKA signaling. Indeed, we demonstrated that GR-mediated inhibition of NF-kappa B transactivation is PKAc-dependent. In contrast to previous models, we suggest that the cross-coupling requires a cytoplasmic step and is regulated by a PKAc-associated signaling.
有人提出，核因子κB（RelA）与糖皮质激素受体（GR）之间的负转录调控或交叉偶联在人类生理和疾病中发挥调节作用。尽管此前已有进展，但这一现象的生化基础仍是一个有争议的话题。我们在此表明，RelA对GR活性的抑制并不需要RelA的DNA结合、反式激活或核定位结构域。令人惊讶的是，RelA对GR的抑制作用通过RelA氨基酸残基276处保守的蛋白激酶A（PKA）位点的突变而被消除。我们表明，GR在体内和体外均以配体非依赖性方式与PKA的催化亚基（PKAc）结合，且GR转录依赖于PKA信号传导。事实上，我们证明GR介导的对NF-κB反式激活的抑制是依赖于PKAc的。与先前的模型不同，我们认为交叉偶联需要一个细胞质步骤，并受与PKAc相关的信号传导调节。
