Dataset Information

Negative regulation of the Keap1-Nrf2 pathway by a p62/Sqstm1 splicing variant.

ABSTRACT: A key anti-oxidant pathway, the Keap1-Nrf2 system, is regulated by p62/Sqstm1 via multiple mechanisms, including gene expression, post-translational modifications such as ubiquitination and phosphorylation, and autophagic degradation of p62/Sqstm1 and Keap1. Herein, we demonstrate a novel mode of regulation of the Keap1-Nrf2 system, mediated by a splicing variant of p62/Sqstm1 pre-mRNA. Ensembl database search and subsequent biochemical analyses in mice revealed the presence of an mRNA that encodes p62/Sqstm1 protein lacking the Keap1-interacting region (KIR), which is essential for the interaction with Keap1. Like full-length p62, the variant was induced under conditions in which Nrf2 was activated (e.g., impairment of autophagy), oligomerized with itself and/or full-length protein, and was degraded by autophagy. However, the variant failed to interact with Keap1 and sequester it into variant-positive aggregates. Remarkably, while full-length p62 stabilized Nrf2 and induced the gene expression of Nrf2 targets, the variant increased the amount of Keap1 and enhanced ubiquitination of Nrf2, thereby suppressing the induction of Nrf2 targets. Hepatocytes isolated from genetically modified mice that express full-length p62, but not the variant, were susceptible to activation of Nrf2 in response to stress. Collectively, our results suggest that splicing of p62/Sqstm1 pre-mRNA negatively regulates the Keap1-Nrf2 pathway.

SUBMITTER: Kageyama S

PROVIDER: S-EPMC5854834 | biostudies-other | 2018 Jan

REPOSITORIES: biostudies-other

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Publications

Negative Regulation of the Keap1-Nrf2 Pathway by a p62/Sqstm1 Splicing Variant.

Kageyama Shun S Saito Tetsuya T Obata Miki M Koide Ryo-Hei RH Ichimura Yoshinobu Y Komatsu Masaaki M

Molecular and cellular biology 20180315 7

A key antioxidant pathway, the Keap1-Nrf2 system, is regulated by p62/Sqstm1 via multiple mechanisms, including gene expression, posttranslational modifications (such as ubiquitination and phosphorylation), and autophagic degradation of p62/Sqstm1 and Keap1. Here we demonstrate a novel mode of regulation of the Keap1-Nrf2 system, mediated by a splicing variant of p62/Sqstm1 pre-mRNA. Ensembl database searches and subsequent biochemical analyses of mice revealed the presence of an mRNA that encod ...[more]

PMID: 29339380

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Project description:Lipotoxicity, induced by saturated fatty acid (SFA)-mediated cell death, plays an important role in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). The KEAP1 (kelch like ECH associated protein 1)-NFE2L2/NRF2 (nuclear factor, erythroid 2 like 2) pathway is a pivotal defense mechanism against lipotoxicity. We previously reported that SQSTM1/p62 has a cytoprotective role against lipotoxicity through activation of the noncanonical KEAP1- NFE2L2 pathway in hepatocytes. However, the underlying mechanisms and physiological relevance of this pathway have not been clearly defined. Here, we demonstrate that NFE2L2-mediated induction of SQSTM1 activates the noncanonical KEAP1-NFE2L2 pathway under lipotoxic conditions. Furthermore, we identified that SQSTM1 induces ULK1 (unc-51 like autophagy activating kinase 1) phosphorylation by facilitating the interaction between AMPK (AMP-activated protein kinase) and ULK1, leading to macroautophagy/autophagy induction, followed by KEAP1 degradation and NFE2L2 activation. Accordingly, the activity of this SQSTM1-mediated noncanonical KEAP1-NFE2L2 pathway conferred hepatoprotection against lipotoxicity in the livers of conventional sqstm1- and liver-specific sqstm1-knockout mice. Moreover, this pathway activity was evident in the livers of patients with nonalcoholic fatty liver. This axis could thus represent a novel target for NAFLD treatment. Abbreviations: ACACA: acetyl-CoA carboxylase alpha; ACTB: actin beta; BafA1: bafilomycin A1; CM-H2DCFDA:5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate; CQ: chloroquine; CUL3: cullin 3; DMSO: dimethyl sulfoxide; FASN: fatty acid synthase; GSTA1: glutathione S-transferase A1; HA: hemagglutinin; Hepa1c1c7: mouse hepatoma cells; HMOX1/HO-1: heme oxygenase 1; KEAP1: kelch like ECH associated protein 1; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3; MEF: mouse embryonic fibroblast; MTORC1: mechanistic target of rapamycin kinase complex 1; MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; NAC: N-acetyl-L-cysteine; NAFLD: nonalcoholic fatty liver disease; NASH: nonalcoholic steatohepatitis; NFE2L2/NRF2: nuclear factor, erythroid 2 like 2; NQO1: NAD(P)H quinone dehydrogenase 1; PA: palmitic acid; PARP: poly (ADP-ribose) polymerase 1; PRKAA1/2: protein kinase AMP-activated catalytic subunits alpha1/2; RBX1: ring-box 1; ROS: reactive oxygen species; SESN2: sestrin 2; SFA: saturated fatty acid; siRNA: small interfering RNA; SQSTM1/p62: sequestosome 1; SREBF1: sterol regulatory element binding transcription factor 1; TBK1: TANK binding kinase 1; TUNEL: terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling; ULK1: unc-51 like autophagy activating kinase.

Dataset Information

Negative regulation of the Keap1-Nrf2 pathway by a p62/Sqstm1 splicing variant.

Publications

Negative Regulation of the Keap1-Nrf2 Pathway by a p62/Sqstm1 Splicing Variant.

Similar Datasets

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