title: Phosphatidylinositol 3-kinase regulates nuclear translocation of NF-E2-related factor 2 through actin rearrangement in response to oxidative stress.
abstract: Expression of phase II detoxifying genes is regulated by NF-E2-related factor 2 (Nrf2)-mediated antioxidant response element (ARE) activation. We showed previously that phosphatidylinositol 3 (PI3)-kinase plays an essential role in ARE-mediated rGSTA2 induction by oxidative stress. In view of the fact that the signaling pathway of PI3-kinase controls microfilaments and translocation of actin-associated proteins, the current study was designed to investigate the PI3-kinase-mediated nuclear translocation of Nrf2 and the interaction of Nrf2 with actin. tert-Butylhydroquinone (t-BHQ) caused Nrf2 to translocate into the nucleus in H4IIE cells, which was prevented by pretreatment of the cells with PI3-kinase inhibitors (wortmannin/LY294002). t-BHQ relocalized Nrf2 in concert with changes in actin microfilament architecture, as visualized by superposition of immunochemically stained Nrf2 and fluorescent phalloidin-stained actin. Furthermore, t-BHQ increased the level of nuclear actin, coimmunoprecipitated with Nrf2, which returned to that of control by pretreatment of the cells with PI3-kinase inhibitors. Cytochalasin B, an actin disruptor, alone stimulated actin-mediated nuclear translocation of Nrf2 and induced rGSTA2. In contrast, phalloidin, an agent that prevents actin filaments from depolymerization, inhibited Nrf2 translocation and rGSTA2 induction by t-BHQ. Subcellular fractionation and immunoblot analyses allowed us to detect both 57- and 100-kDa Nrf2. Immunoblot and immunoprecipitation assays showed that the 100-kDa protein comprised both Nrf2 and actin. The present study demonstrates that the PI3-kinase signaling pathway regulates rearrangement of actin microfilaments in response to oxidative stress and that depolymerization of actin causes a complex of Nrf2 bound with actin to translocate into nucleus.
authors.affiliation: College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Kwanak-gu, Seoul, South Korea.
authors.forename: Keon Wook
authors.initials: KW
authors.lastname: Kang
authors.forename: Seung Jin
authors.initials: SJ
authors.lastname: Lee
authors.forename: Jeong Weon
authors.initials: JW
authors.lastname: Park
authors.forename: Sang Geon
authors.initials: SG
authors.lastname: Kim
mesh_terms: D000199:Actins / Q000502:physiology*; D021581:Active Transport, Cell Nucleus; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D003571:Cytochalasin B / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005982:Glutathione Transferase / Q000378:metabolism; D006873:Hydroquinones / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D051267:NF-E2-Related Factor 2; D018384:Oxidative Stress / Q000502:physiology*; D010590:Phalloidine / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D015534:Trans-Activators / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D000199:Actins; D000975:Antioxidants; D004268:DNA-Binding Proteins; D006873:Hydroquinones; D007328:Insulin; D051267:NF-E2-Related Factor 2; C495637:Nfe2l2 protein, rat; D015534:Trans-Activators; D010590:Phalloidine; D003571:Cytochalasin B; C018855:2-tert-butylhydroquinone; D005982:Glutathione Transferase; D019869:Phosphatidylinositol 3-Kinases