KPNB1, XPO7 and IPO8 Mediate the Translocation ofNF‐κB/p65 into the Nucleus

Abstract

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.

Targeting the Nuclear Import Receptor Kpnβ1 as an Anticancer Therapeutic

“…The inhibition achieved was similar to that obtained using importazole and ivermectin at concentrations relative to their respective IC50s. AP-1 luciferase activity was also measured in response to PMA stimulation and INI-43 treatment, since this transcription factor has also been shown to rely on Kpnb1 for nuclear import (25,27). AP-1 luciferase activity was also found to be significantly decreased after INI-43, importazole and ivermectin treatment (Fig.…”

“…As an additional indicator that INI-43 was able to inhibit nuclear import, it was next investigated whether INI-43 could interfere with the nuclear translocation of p65 in response to PMA treatment, as p65 has previously been shown to rely on Kpnb1 for its nuclear import (25). HeLa cells were treated with INI-43 and stimulated with PMA, following which p65 localization was determined by immunofluorescence.…”

RNA-binding protein HuR regulates nuclear import of protein

“…Moreover, some nuclear proteins contain both classical and non-canonical NLSs. One such protein is the NFкB subunit p65, which contains a classical NLS recognized by importin-α5 (encoded for by Kpna1) (Fagerlund et al, 2008) and a non-classical NLS recognized by transportin 1 (Liang et al, 2013). Downregulation of HuR decreased the levels of both Kpna1 and Tnpo1 mRNAs (Fig.…”

KPNβ1 promotes palmitate-induced insulin resistance via NF-κB signaling in hepatocytes

“…KPNβ1 imports numerous proteins that require entry into the nucleus, such as NF-κB p65 [21]. Many nuclear import and export pathways are mediated by KPNβ1, for example, in the MAPK pathway, phospho-ERK enters the nucleus via KPNβ1 [28].…”