Liang Peizhou, Zhang Haiyan, Wang Guoxin, Li Suping, Cong Shujie, Luo Yingyun, Zhang Biliang
State Key Laboratory of Respiratory Diseases, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, 190 Kaiyuan Avenue, Guangzhou , 510530, China.
Traffic. 2013 Nov;14(11):1132-43. doi: 10.1111/tra.12097. Epub 2013 Aug 19.
NF-κB/p65 is retained in the cytoplasm until it is activated in response to stress. Nuclear import of p65 is regulated by importin α in a nuclear localization signal (NLS)-dependent manner. However, the role of importin β family members in the nuclear translocation of p65 is largely unclear. In this study, using high-content siRNA screening, we identified three of 17 importin β family members that are involved in the nuclear import of p65. Our data showed that knockdown of KPNB1, XPO7 and IPO8 reduced the amount of nuclear p65 following tumor necrosis factor-α (TNF-α) stimulation, resulting in lower NF-κB activity. KPNB1 was the major importin β receptor for p65 import, and this import was dependent on the NLS of p65. However, NLS-mutated p65 still entered the nucleus and bound to XPO7 and IPO8. Interestingly, among the six members of the importin α family, KPNA2 was most important for p65 import. Taken together, our results show that the import of p65 mainly relies on the canonical KPNA2/KPNB1 pathway; however, p65 is also imported by an alternative pathway that is independent of its NLS. Redundant importin receptors are likely to maintain the important function of p65 according to need.
NF-κB/p65保留在细胞质中，直到它在应激反应中被激活。p65的核输入由输入蛋白α以核定位信号（NLS）依赖的方式进行调节。然而，输入蛋白β家族成员在p65核转位中的作用在很大程度上尚不清楚。在本研究中，我们使用高内涵siRNA筛选，在17个输入蛋白β家族成员中鉴定出3个参与p65核输入的成员。我们的数据表明，敲低KPNB1、XPO7和IPO8会降低肿瘤坏死因子-α（TNF-α）刺激后核p65的量，导致NF-κB活性降低。KPNB1是p65输入的主要输入蛋白β受体，这种输入依赖于p65的NLS。然而，NLS突变的p65仍能进入细胞核并与XPO7和IPO8结合。有趣的是，在输入蛋白α家族的6个成员中，KPNA2对p65输入最为重要。综上所述，我们的结果表明，p65的输入主要依赖于经典的KPNA2/KPNB1途径；然而，p65也通过一条独立于其NLS的替代途径输入。冗余的输入蛋白受体可能根据需要维持p65的重要功能。
