Functional polymorphisms in Nrf2: implications for human disease

https://doi.org/10.1016/j.freeradbiomed.2015.06.012Get rights and content

Highlights

  • Genetic variations in Nrf2 have important implications for human disease susceptibility.

  • Mutations and haplotypes in human Nrf2 have been identified and characterized.

  • Functional Nrf2 polymorphisms are associated with risk of many human diseases.

  • Somatic Nrf2 mutations have also been identified, and some are oncogenic.

  • Understanding variation in Nrf2 should lead to novel disease intervention strategies.

Abstract

Nuclear factor (erythroid derived)-2 like 2 (NFE2L2), also known as nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2), is a ubiquitous transcription factor essential for protecting cells and tissues from oxidative stress-induced injury. Positional cloning and studies with Nrf2 knockout mice have identified important roles for this transcription factor in disease phenotypes for many organ systems. Studies have also characterized the means through which human Nrf2 is regulated and the mechanisms of interaction with antioxidant response elements (ARE) in promoters of effector genes. Moreover, single nucleotide polymorphisms (SNPs) in Nrf2 have been identified and evaluated for effects on gene expression and function, and translational investigations have sought to determine whether loss of function SNPs associate with disease progression. In this review, we present 1) an overview of the human Nrf2 gene and protein domain, 2) identification of genetic mutations in Nrf2 and associations of the mutations with multiple diseases, and 3) the role of somatic mutations in Nrf2 in diseases, primarily various cancers.

Introduction

Nrf2 is a ubiquitous transcription factor essential in host defense [1], [2]. Nrf2 transcriptionally activates ARE-bearing genes in response to reactive oxygen species (ROS) produced during oxidative stress [3], [4], [5], [6]. Nrf2 homeostasis is regulated by Kelch-like erythroid-derived Cap’n’Collar Homology (ECH)-associated protein 1 (Keap1), a cytoplasmic Nrf2 suppressor [7]. In unstressed conditions, Keap1 binds Nrf2 and brings it into close proximity with Cullin 3 (CUL3), an E3 ligase which polyubiquinates Nrf2 for proteasomal degradation [8]. However, electrophilic and oxidative insults are known to modify thiol residues in Keap1, which may alter binding interactions between Keap1, CUL3, and Nrf2, and permit newly synthesized Nrf2 to bypass Keap1 inhibition and transactivate antioxidant target genes [9]. It is important to note that there exist other Keap1-independent modes of Nrf2 regulation, including GSK3/betaTrCP-dependent degradation through the Neh6 domain [10]. Greater detail about the regulation of Nrf2 is presented elsewhere in the series of papers for this Special Issue of Free Radical Biology & Medicine.

Mice with targeted deletion of Nrf2 (Nrf2-/-) have been widely used to investigate the role of the transcription factor in disease models during the last decade [11], [12], [13]. Moreover, murine Nrf2 was identified through positional cloning as a susceptibility gene in oxidative lung disorders [14], [15.]. Animal studies have focused on the Nrf2-ARE pathway as a means to identify novel therapeutic targets for human diseases in which oxidative stress is implicated, and translational research efforts have confirmed the importance of Nrf2 in oxidative disease pathogenesis and cancer progression.

The current review addresses genetic and somatic mutations in human Nrf2. We identified and categorized genetic variations including single nucleotide polymorphisms (SNPs) and haplotypes available from the 1000 Genomes Project and the International HapMap Project databases. We have also annotated putative functional genetic polymorphisms reported to associate with disease risk. Finally, we report somatic mutations identified through targeted cohort and whole exome sequencing of tumor cell/tissue samples from neoplastic individuals.

Section snippets

Nrf2 gene and protein domains

Human Nrf2 is located in the cytogenetic band 2q31.2 of chromosome 2 spanning 177230303 - 177265131 bp (gene ID: 4780) on the reverse strand as a complementary sequence (Fig. 1). Nrf2 mRNA is 2,859 base pairs long (variant 1: NM_006164) and the full-length transcript encodes a protein containing 605 amino acid (aa) residues (isoform 1: NP_006155 or Q16236). Transcript variants have been reported [10]; variant 2 (NM_001145412, 2746 bp) has an alternate promoter, 5’UTR and downstream start codon.

Polymorphisms and haplotype alleles

Genome-wide association studies (GWAS) have examined SNPs across the genome to identify ‘risk’ genotypes significantly more prevalent in an affected group for disease association. Supporting GWAS, the 1000 Genomes Project has sequenced more than 2000 genomes (~2500 to date) of individuals with diverse ethnicity. The HapMap Project has also mapped combinations of alleles at specific loci (haplotypes) to generate DNA sequence variation patterns that contribute to disease risk. In conjunction with

Somatic Nrf2 mutations

Recent research has provided significant insight into mutagenesis and cancer development in various organs such as the lung. Somatic or acquired mutations change the genetic structure of diploid cells but are not heritable. Together with epigenetic changes (epimutations), somatic mutations predispose individuals to cancer through changes in the activity of affected genes. Six patterns of somatic mutations, C>A/G>T, C>G/G>C, C>T/G>A, T>A/A>T, T>C/A>G, and T>G/A>C, have been established in the

Conclusions

Studies using mice with targeted deletion of Nrf2 have yielded valuable insight to the role of this transcription factor in health and disease in multiple organ systems, and potential understanding of factors that contribute to human diseases. Subsequent investigations that have characterized the genetic and molecular function of human Nrf2, including associations of Nrf2 SNPs with disease phenotypes, have also provided novel targets for disease prevention. A limitation of the association

Conflict of Interests

The authors declare that there are no conflicts of interest.

Acknowledgments

The research related to the manuscript was supported by the Intramural Research Program of the National Institutes of Health, National Institute of Environmental Health Sciences (NIEHS). Drs. Michael Fessler and Donald Cook at the NIEHS provided excellent critical review of the manuscript.

References (83)

  • Y.R. Kim et al.

    Oncogenic Nrf2 mutations in squamous cell carcinomas of oesophagus and skin

    J Pathol

    (2010)
  • O. Kalinina et al.

    Somatic changes in primary liver cancer in Russia: a pilot study

    Mutat Res

    (2013)
  • H.Y. Cho et al.

    Nrf2 protects against airway disorders

    Toxicology and applied pharmacology

    (2010)
  • J.Y. Chan et al.

    Chromosomal localization of the human NF-E2 family of bZIP transcription factors by fluorescence in situ hybridization

    Hum Genet

    (1995)
  • K. Itoh et al.

    Cloning and characterization of a novel erythroid cell-derived CNC family transcription factor heterodimerizing with the small Maf family proteins

    Mol Cell Biol

    (1995)
  • X. Wang et al.

    Identification of polymorphic antioxidant response elements in the human genome

    Hum Mol Genet

    (2007)
  • D. Malhotra et al.

    Global mapping of binding sites for Nrf2 identifies novel targets in cell survival response through ChIP-Seq profiling and network analysis

    Nucleic Acids Res

    (2010)
  • K. Itoh et al.

    Keap1 represses nuclear activation of antioxidant responsive elements by Nrf2 through binding to the amino-terminal Neh2 domain

    Genes Dev

    (1999)
  • A. Kobayashi et al.

    Oxidative stress sensor Keap1 functions as an adaptor for Cul3-based E3 ligase to regulate proteasomal degradation of Nrf2

    Mol Cell Biol

    (2004)
  • K. Taguchi et al.

    Molecular mechanisms of the Keap1-Nrf2 pathway in stress response and cancer evolution

    Genes to cells: devoted to molecular & cellular mechanisms

    (2011)
  • S. Chowdhry et al.

    Nrf2 is controlled by two distinct beta-TrCP recognition motifs in its Neh6 domain, one of which can be modulated by GSK-3 activity

    Oncogene

    (2013)
  • K. Chan et al.

    Nrf2, a member of the NFE2 family of transcription factors, is not essential for murine erythropoiesis, growth, and development

    Proc Natl Acad Sci U S A

    (1996)
  • H.Y. Cho et al.

    Association of Nrf2 polymorphism haplotypes with acute lung injury phenotypes in inbred strains of mice

    Antioxid Redox Signal

    (2015)
  • H.Y. Cho et al.

    Linkage analysis of susceptibility to hyperoxia. Nrf2 is a candidate gene

    Am J Respir Cell Mol Biol

    (2002)
  • S.C. Lo et al.

    Structure of the Keap1:Nrf2 interface provides mechanistic insight into Nrf2 signaling

    The EMBO journal

    (2006)
  • M. von Otter et al.

    Genetic associations of Nrf2-encoding NFE2L2 variants with Parkinson inverted question marks disease inverted question mark a multicenter study

    BMC Med Genet

    (2014)
  • J.M. Marzec et al.

    Functional polymorphisms in the transcription factor Nrf2 in humans increase the risk of acute lung injury

    Faseb J

    (2007)
  • D.S. O’Mahony et al.

    Inflammation and immune-related candidate gene associations with acute lung injury susceptibility and severity: a validation study

    PloS one

    (2012)
  • H. Masuko et al.

    Lower FEV1 in non-COPD, nonasthmatic subjects: association with smoking, annual decline in FEV1, total IgE levels, and TSLP genotypes

    International journal of chronic obstructive pulmonary disease

    (2011)
  • H. Masuko et al.

    An interaction between Nrf2 polymorphisms and smoking status affects annual decline in FEV1: a longitudinal retrospective cohort study

    BMC medical genetics

    (2011)
  • H. Sasaki et al.

    Polymorphisms of Nrf2 gene correlated with decreased FEV1 in lung cancers of smokers

    Biomedical reports 1

    (2013)
  • M. Siedlinski et al.

    Level and course of FEV1 in relation to polymorphisms in NFE2L2 and Keap1 in the general population

    Respiratory research

    (2009)
  • S.M. Figarska et al.

    NFE2L2 polymorphisms, mortality, and metabolism in the general population

    Physiological genomics

    (2014)
  • I. Ungvari et al.

    Relationship between air pollution, NFE2L2 gene polymorphisms and childhood asthma in a Hungarian population

    Journal of community genetics

    (2012)
  • C. Canova et al.

    PM10-induced hospital admissions for asthma and chronic obstructive pulmonary disease: the modifying effect of individual characteristics

    Epidemiology

    (2012)
  • A.J. Henderson et al.

    Maternal Nrf2 and gluthathione-S-transferase polymorphisms do not modify associations of prenatal tobacco smoke exposure with asthma and lung function in school-aged children

    Thorax

    (2010)
  • S.O. Shaheen et al.

    Prenatal and infant acetaminophen exposure, antioxidant gene polymorphisms, and childhood asthma

    The Journal of allergy and clinical immunology

    (2010)
  • V. Sampath et al.

    Antioxidant response genes sequence variants and BPD susceptibility in VLBW infants

    Pediatr Res

    (2015)
  • Y. Shimoyama et al.

    Polymorphism of Nrf2, an antioxidative gene, is associated with blood pressure and cardiovascular mortality in hemodialysis patients

    International journal of medical sciences

    (2014)
  • J. Bouligand et al.

    Effect of NFE2L2 genetic polymorphism on the association between oral estrogen therapy and the risk of venous thromboembolism in postmenopausal women

    Clin Pharmacol Ther

    (2011)
  • B. Wang et al.

    Association of SNPs in genes involved in folate metabolism with the risk of congenital heart disease

    The journal of maternal-fetal & neonatal medicine: the official journal of the European Association of Perinatal Medicine, the Federation of Asia and Oceania Perinatal Societies, the International Society of Perinatal Obstetricians

    (2013)
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