抑制LRP16基因的表达显著下调TNF-α介导的NF-κB转录活性

LRP16是1个雌激素(E2)通过其受体α(ERα)诱导表达的靶基因.研究表 明,LRP16可以作为多种核受体（包括AR、ERα）的转录共激活因子.采用荧光素酶报 告检测显示，抑制LRP16基因表达显著削弱了TNF-α(10 ng/mL)介导的NF-κB转录活性；采用免疫荧光和Western印迹法研究抑制LRP16对NF-κB/p65亚基核转位的影响，结果显示，抑制LRP16表达并不能参与影响p65亚基核转位．上述结果提示，LRP16可能以核激活因子角色参与了NF-κB介导的信号途径．RT-PCR实验检测抑制LRP16基因表达对TNF-α诱导NF-κB靶基因调控作用，检测的靶基因包括IκB、A20、IL-8、 FLIP、XIAP.结果表明,在这些靶基因中只有XIAP、cIAP2产生了明显的下调趋势. 因此，LRP16是NF-κB的1个共激活因子，通过调控NF-κB与靶基因的结合能力，从而增强了NF-κB的转录活性.

Inhibition of LRP16 Gene Expression Significantly Down-regulates the Transactivation of NF-κB Mediated by TNF-α

LRP16 is a target gene induced by estrogen receptor α (ERα).LRP16 protein could act as a potential coactivator that amplifies the transactivation of various nuclear receptors (NRs), such as ERα and AR. We performed luciferase assays to determine that the inhibition of LRP16 gene expression significantly reduced the transactivation of NF-κB upon TNF-α(10 ng/mL) stimulation. We also preformed immunofluorescence and Western blot analyses to rule out the possibility that LRP16 might act on the TNF-α induced nuclear translocation of NF-κB. We did not observe marked difference for the nuclear translocation of p65 between the LRP16-deficient and mock-transfected cell upon TNF-α stimulation. These results implied that LRP16 regulates the transactivation of NF-κB via targeting NF-κB itself in the nucleus, but not via affecting NF-κB nuclear translocation. RT-PCR results demonstrated that TNF-α induced the expression of several NF-κB-dependent genes including IκB, A20, IL-8, FLIP and XIAP. Interestingly, only XIAP and cIAP2 were markedly attenuated in LRP16-deficient cells. Our findings indicate that LRP16 is a crucial regulator for NF-κB activation in the nucleus.