title: Role of Galpha12 and Galpha13 as novel switches for the activity of Nrf2, a key antioxidative transcription factor.
abstract: Galpha12 and Galpha13 function as molecular regulators responding to extracellular stimuli. NF-E2-related factor 2 (Nrf2) is involved in a protective adaptive response to oxidative stress. This study investigated the regulation of Nrf2 by Galpha12 and Galpha13. A deficiency of Galpha12, but not of Galpha13, enhanced Nrf2 activity and target gene transactivation in embryo fibroblasts. In mice, Galpha12 knockout activated Nrf2 and thereby facilitated heme catabolism to bilirubin and its glucuronosyl conjugations. An oligonucleotide microarray demonstrated the transactivation of Nrf2 target genes by Galpha12 gene knockout. Galpha12 deficiency reduced Jun N-terminal protein kinase (JNK)-dependent Nrf2 ubiquitination required for proteasomal degradation, and so did Galpha13 deficiency. The absence of Galpha12, but not of Galpha13, increased protein kinase C delta (PKC delta) activation and the PKC delta-mediated serine phosphorylation of Nrf2. Galpha13 gene knockout or knockdown abrogated the Nrf2 phosphorylation induced by Galpha12 deficiency, suggesting that relief from Galpha12 repression leads to the Galpha13-mediated activation of Nrf2. Constitutive activation of Galpha13 promoted Nrf2 activity and target gene induction via Rho-mediated PKC delta activation, corroborating positive regulation by Galpha13. In summary, Galpha12 and Galpha13 transmit a JNK-dependent signal for Nrf2 ubiquitination, whereas Galpha13 regulates Rho-PKC delta-mediated Nrf2 phosphorylation, which is negatively balanced by Galpha12.
authors.affiliation: College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Sillim-dong, Gwanak-gu, Seoul, South Korea.
authors.forename: Min Kyung
authors.initials: MK
authors.lastname: Cho
authors.forename: Won Dong
authors.initials: WD
authors.lastname: Kim
authors.forename: Sung Hwan
authors.initials: SH
authors.lastname: Ki
authors.forename: Jong-Ik
authors.initials: JI
authors.lastname: Hwang
authors.forename: Sangdun
authors.initials: S
authors.lastname: Choi
authors.forename: Chang Ho
authors.initials: CH
authors.lastname: Lee
authors.forename: Sang Geon
authors.initials: SG
authors.lastname: Kim
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D002478:Cells, Cultured; D004789:Enzyme Activation; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D044365:GTP-Binding Protein alpha Subunits, G12-G13 / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D048031:JNK Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D051745:Protein Kinase C-delta; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D015533:Transcriptional Activation; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D000975:Antioxidants; D051267:NF-E2-Related Factor 2; D034741:RNA, Small Interfering; D051745:Protein Kinase C-delta; D048031:JNK Mitogen-Activated Protein Kinases; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D020741:rho GTP-Binding Proteins