Ferroptosis: A Regulated Cell Death Nexus Linking Metabolism, Redox Biology, and Disease.

Ferroptosis is a form of regulated cell death characterized by the iron-dependent accumulation of lipid hydroperoxides to lethal levels. Emerging evidence suggests that ferroptosis represents an ancient vulnerability caused by the incorporation of polyunsaturated fatty acids into cellular membranes, and cells have developed complex systems that exploit and defend against this vulnerability in different contexts. The sensitivity to ferroptosis is tightly linked to numerous biological processes, including amino acid, iron, and polyunsaturated fatty acid metabolism, and the biosynthesis of glutathione, phospholipids, NADPH, and coenzyme Q10. Ferroptosis has been implicated in the pathological cell death associated with degenerative diseases (i.e., Alzheimer's, Huntington's, and Parkinson's diseases), carcinogenesis, stroke, intracerebral hemorrhage, traumatic brain injury, ischemia-reperfusion injury, and kidney degeneration in mammals and is also implicated in heat stress in plants. Ferroptosis may also have a tumor-suppressor function that could be harnessed for cancer therapy. This Primer reviews the mechanisms underlying ferroptosis, highlights connections to other areas of biology and medicine, and recommends tools and guidelines for studying this emerging form of regulated cell death.

HRD1-mediated METTL14 degradation regulates m6A mRNA modification to suppress ER proteotoxic liver disease.

Accumulation of unfolded or misfolded proteins in the endoplasmic reticulum (ER) lumen triggers an unfolded protein response (UPR) for stress adaptation, the failure of which induces cell apoptosis and tissue/organ damage. The molecular switches underlying how the UPR selects for stress adaptation over apoptosis remain unknown. Here, we discovered that accumulation of unfolded/misfolded proteins selectively induces N6-adenosine-methyltransferase-14 (METTL14) expression. METTL14 promotes C/EBP-homologous protein (CHOP) mRNA decay through its 3' UTR N6-methyladenosine (m6A) to inhibit its downstream pro-apoptotic target gene expression. UPR induces METTL14 expression by competing against the HRD1-ER-associated degradation (ERAD) machinery to block METTL14 ubiquitination and degradation. Therefore, mice with liver-specific METTL14 deletion are highly susceptible to both acute pharmacological and alpha-1 antitrypsin (AAT) deficiency-induced ER proteotoxic stress and liver injury. Further hepatic CHOP deletion protects METTL14 knockout mice from ER-stress-induced liver damage. Our study reveals a crosstalk between ER stress and mRNA m6A modification pathways, termed the ERm6A pathway, for ER stress adaptation to proteotoxicity.

Human Hsp70 Substrate-Binding Domains Recognize Distinct Client Proteins.

The 13 Hsp70 proteins in humans act on unique sets of substrates with diversity often being attributed to J-domain-containing protein (Hsp40 or JDP) cofactors. We were therefore surprised to find drastically different binding affinities for Hsp70-peptide substrates, leading us to probe substrate specificity among the 8 canonical Hsp70s from humans. We used peptide arrays to characterize Hsp70 binding and then mined these data using machine learning to develop an algorithm for isoform-specific prediction of Hsp70 binding sequences. The results of this algorithm revealed recognition patterns not predicted based on local sequence alignments. We then showed that none of the human isoforms can complement heat-shocked DnaK knockout Escherichia coli cells. However, chimeric Hsp70s consisting of the human nucleotide-binding domain and the substrate-binding domain of DnaK complement during heat shock, providing further evidence in vivo of the divergent function of the Hsp70 substrate-binding domains. We also demonstrated that the differences in heat shock complementation among the chimeras are not due to loss of DnaJ binding. Although we do not exclude JDPs as additional specificity factors, our data demonstrate substrate specificity among the Hsp70s, which has important implications for inhibitor development in cancer and neurodegeneration.

Involvement of eNAMPT/TLR4 inflammatory signaling in progression of non-alcoholic fatty liver disease, steatohepatitis, and fibrosis.

Although the progression of non-alcoholic fatty liver disease (NAFLD) from steatosis to steatohepatitis (NASH) and cirrhosis remains poorly understood, a critical role for dysregulated innate immunity has emerged. We examined the utility of ALT-100, a monoclonal antibody (mAb), in reducing NAFLD severity and progression to NASH/hepatic fibrosis. ALT-100 neutralizes eNAMPT (extracellular nicotinamide phosphoribosyltransferase), a novel damage-associated molecular pattern protein (DAMP) and Toll-like receptor 4 (TLR4) ligand. Histologic and biochemical markers were measured in liver tissues and plasma from human NAFLD subjects and NAFLD mice (streptozotocin/high-fat diet-STZ/HFD, 12 weeks). Human NAFLD subjects (n = 5) exhibited significantly increased NAMPT hepatic expression and significantly elevated plasma levels of eNAMPT, IL-6, Ang-2, and IL-1RA compared to healthy controls, with IL-6 and Ang-2 levels significantly increased in NASH non-survivors. Untreated STZ/HFD-exposed mice displayed significant increases in NAFLD activity scores, liver triglycerides, NAMPT hepatic expression, plasma cytokine levels (eNAMPT, IL-6, and TNFα), and histologic evidence of hepatocyte ballooning and hepatic fibrosis. Mice receiving the eNAMPT-neutralizing ALT-100 mAb (0.4 mg/kg/week, IP, weeks 9 to 12) exhibited marked attenuation of each index of NASH progression/severity. Thus, activation of the eNAMPT/TLR4 inflammatory pathway contributes to NAFLD severity and NASH/hepatic fibrosis. ALT-100 is potentially an effective therapeutic approach to address this unmet NAFLD need.

Allosteric differences dictate GroEL complementation of E. coli.

GroES/GroEL is the only bacterial chaperone essential under all conditions, making it a potential antibiotic target. Rationally targeting ESKAPE GroES/GroEL as an antibiotic strategy necessitates studying their structure and function. Herein, we outline the structural similarities between Escherichia coli and ESKAPE GroES/GroEL and identify significant differences in intra- and inter-ring cooperativity, required in the refolding cycle of client polypeptides. Previously, we observed that one-half of ESKAPE GroES/GroEL family members could not support cell viability when each was individually expressed in GroES/GroEL-deficient E. coli cells. Cell viability was found to be dependent on the allosteric compatibility between ESKAPE and E. coli subunits within mixed (E. coli and ESKAPE) tetradecameric GroEL complexes. Interestingly, differences in allostery did not necessarily result in differences in refolding rate for a given homotetradecameric chaperonin. Characterization of ESKAPE GroEL allostery, ATPase, and refolding rates in this study will serve to inform future studies focused on inhibitor design and mechanism of action studies.

NRF2 negatively regulates primary ciliogenesis and hedgehog signaling.

Primary cilia are lost during cancer development, but the mechanism regulating cilia degeneration is not determined. While transcription factor nuclear factor-erythroid 2-like 2 (NRF2) protects cells from oxidative, proteotoxic, and metabolic stress in normal cells, hyperactivation of NRF2 is oncogenic, although the detailed molecular mechanisms by which uncontrolled NRF2 activation promotes cancer progression remain unclear. Here, we report that NRF2 suppresses hedgehog (Hh) signaling through Patched 1 (PTCH1) and primary ciliogenesis via p62/sequestosome 1 (SQSTM1). PTCH1, a negative regulator of Hh signaling, is an NRF2 target gene, and as such, hyperactivation of NRF2 impairs Hh signaling. NRF2 also suppresses primary cilia formation through p62-dependent inclusion body formation and blockage of Bardet-Biedl syndrome 4 (BBS4) entrance into cilia. Simultaneous ablation of PTCH1 and p62 completely abolishes NRF2-mediated inhibition of both primary ciliogenesis and Hh signaling. Our findings reveal a previously unidentified role of NRF2 in controlling a cellular organelle, the primary cilium, and its associated Hh signaling pathway and also uncover a mechanism by which NRF2 hyperactivation promotes tumor progression via primary cilia degeneration and aberrant Hh signaling. A better understanding of the crosstalk between NRF2 and primary cilia/Hh signaling could not only open new avenues for cancer therapeutic discovery but could also have significant implications regarding pathologies other than cancer, including developmental disorders, in which improper primary ciliogenesis and Hh signaling play a major role.

Targeting NRF2 to treat cancer.

NRF2 is a basic leucine zipper (bZip) transcription factor that is the master regulator of redox homeostasis. Under basal conditions, the cellular level of NRF2 is low due to a posttranslational regulation by the ubiquitin proteasome system (UPS). But, when an organism is challenged with oxidative or xenobiotic stress, the NRF2 pathway is activated by inhibition of the E3 ubiquitin ligase complex that normally marks NRF2 for destruction. For several decades, researchers have searched for molecules that can intentionally activate NRF2, as this was shown to be a means to prevent certain diseases, at least in animal models. In the present era, there are many compounds known to activate the NRF2 pathway including natural products and synthetic compounds, covalent and non-covalent compounds, and others. However, it was also revealed that like many protective pathways, the NRF2 pathway has a dark side. Just as NRF2 can protect normal cells from damage, it can protect malignant cells from damage. As cells transform, they are exposed to many stressors and aberrant upregulation of NRF2 can facilitate transformation and it can help cancer cells to grow, to spread, and to resist treatment. For this reason, researchers are also interested in the discovery and development of NRF2 inhibitors. In the present review, we will begin with a general discussion of NRF2 structure and function, we will discuss the latest in NRF2 non-covalent activators, and we will discuss the current state of NRF2 inhibitors.

The intricacies of NRF2 regulation in cancer.

The complex role of NRF2 in the context of cancer continues to evolve. As a transcription factor, NRF2 regulates various genes involved in redox homeostasis, protein degradation, DNA repair, and xenobiotic metabolism. As such, NRF2 is critical in preserving cell function and viability, particularly during stress. Importantly, NRF2 itself is regulated via a variety of mechanisms, and the mode of NRF2 activation often dictates the duration of NRF2 signaling and its role in either preventing cancer initiation or promoting cancer progression. Herein, different modes of NRF2 regulation, including oxidative stress, autophagy dysfunction, protein-protein interactions, and epigenetics, as well as pharmacological modulators targeting this cascade in cancer, are explored. Specifically, how the timing and duration of these different mechanisms of NRF2 induction affect tumor initiation, progression, and metastasis are discussed. Additionally, progress in the discovery and development of NRF2 inhibitors for the treatment of NRF2-addicted cancers is highlighted, including modulators that inhibit specific NRF2 downstream targets. Overall, a better understanding of the intricate nature of NRF2 regulation in specific cancer contexts should facilitate the generation of novel therapeutics designed to not only prevent tumor initiation, but also halt progression and ultimately improve patient wellbeing and survival.

Modulating NRF2 in Disease: Timing Is Everything.

The transcription factor nuclear factor erythroid 2 (NF-E2)-related factor 2 (NRF2) is a central regulator of redox, metabolic, and protein homeostasis that intersects with many other signaling cascades. Although the understanding of the complex nature of NRF2 signaling continues to grow, there is only one therapeutic targeting NRF2 for clinical use, dimethyl fumarate, used for the treatment of multiple sclerosis. The discovery of new therapies is confounded by the fact that NRF2 levels vary significantly depending on physiological and pathological context. Thus, properly timed and targeted manipulation of the NRF2 pathway is critical in creating effective therapeutic regimens. In this review, we summarize the regulation and downstream targets of NRF2. Furthermore, we discuss the role of NRF2 in cancer, neurodegeneration, and diabetes as well as cardiovascular, kidney, and liver disease, with a special emphasis on NRF2-based therapeutics, including those that have made it into clinical trials.

Hrd1 suppresses Nrf2-mediated cellular protection during liver cirrhosis.

Increased endoplasmic reticulum (ER) stress and reactive oxygen species (ROS) are the salient features of end-stage liver diseases. Using liver tissues from liver cirrhosis patients, we observed up-regulation of the XBP1-Hrd1 arm of the ER stress response pathway and down-regulation of the Nrf2-mediated antioxidant response pathway. We further confirmed this negative regulation of Nrf2 by Hrd1 using Hrd1 conditional knockout mice. Down-regulation of Nrf2 was a surprising result, since the high levels of ROS should have inactivated Keap1, the primary ubiquitin ligase regulating Nrf2 levels. Here, we identified Hrd1 as a novel E3 ubiquitin ligase responsible for compromised Nrf2 response during liver cirrhosis. In cirrhotic livers, activation of the XBP1-Hrd1 arm of ER stress transcriptionally up-regulated Hrd1, resulting in enhanced Nrf2 ubiquitylation and degradation and attenuation of the Nrf2 signaling pathway. Our study reveals not only the convergence of ER and oxidative stress response pathways but also the pathological importance of this cross-talk in liver cirrhosis. Finally, we showed the therapeutic importance of targeting Hrd1, rather than Keap1, to prevent Nrf2 loss and suppress liver cirrhosis.

FAM129B-dependent activation of NRF2 promotes an invasive phenotype in BRAF mutant melanoma cells.

Incidence of melanoma continues to rise in the United States with ~100,000 new cases diagnosed in 2019. While the 5-year survival rate of melanoma is 99% when localized, the rate of survival drops to 22.5% when distant disease is detected. As such, an area of great interest is understanding the mechanisms that promote melanoma metastasis so that better potential therapeutic targets can be discovered. Herein, we demonstrate that activation of NRF2 by FAM129B contributes to increased metastatic potential of BRAF V600E mutant melanoma cells. Specifically, FAM129B induces NRF2 by competing for Kelch-like ECH-associated protein 1 (KEAP1) binding (the negative regulator of NRF2) via an ETGE motif. Furthermore, we show that phosphorylation of FAM129B plays a role in mediating the interaction between FAM129B and KEAP1, as the phosphorylation status of FAM129B dictates its subcellular localization. When phosphorylated, FAM129B is found primarily in the cytosol where it can bind to KEAP1, but upon inhibition of mitogen-activated protein kinase kinase activity, FAM129B is localized to the cell membrane and no longer interacts with KEAP1. In BRAF V600E mutant melanoma, the mitogen-activated protein kinase pathway leads to hyperphosphorylation of FAM129B, and therefore FAM129B localizes to the cytosol, binds KEAP1, and upregulates NRF2. Importantly, genetic modulation or pharmacological inhibition that results in a decrease in FAM129B protein level or its phosphorylation decreases migration and invasion of mutant melanoma in an NRF2-dependent manner. Overall, these data indicate that phosphorylation of FAM129B plays a significant role in driving the metastatic potential of BRAF V600E melanoma via upregulation of the NRF2 signaling pathway.

Dengue Virus Targets Nrf2 for NS2B3-Mediated Degradation Leading to Enhanced Oxidative Stress and Viral Replication.

Dengue virus (DENV) is a mosquito-borne virus that infects upward of 300 million people annually and has the potential to cause fatal hemorrhagic fever and shock. While the parameters contributing to dengue immunopathogenesis remain unclear, the collapse of redox homeostasis and the damage induced by oxidative stress have been correlated with the development of inflammation and progression toward the more severe forms of disease. In the present study, we demonstrate that the accumulation of reactive oxygen species (ROS) late after DENV infection (>24 hpi) resulted from a disruption in the balance between oxidative stress and the nuclear factor erythroid 2-related factor 2 (Nrf2)-dependent antioxidant response. The DENV NS2B3 protease complex strategically targeted Nrf2 for degradation in a proteolysis-independent manner; NS2B3 licensed Nrf2 for lysosomal degradation. Impairment of the Nrf2 regulator by the NS2B3 complex inhibited the antioxidant gene network and contributed to the progressive increase in ROS levels, along with increased virus replication and inflammatory or apoptotic gene expression. By 24 hpi, when increased levels of ROS and antiviral proteins were observed, it appeared that the proviral effect of ROS overcame the antiviral effects of the interferon (IFN) response. Overall, these studies demonstrate that DENV infection disrupts the regulatory interplay between DENV-induced stress responses, Nrf2 antioxidant signaling, and the host antiviral immune response, thus exacerbating oxidative stress and inflammation in DENV infection.IMPORTANCE Dengue virus (DENV) is a mosquito-borne pathogen that threatens 2.5 billion people in more than 100 countries annually. Dengue infection induces a spectrum of clinical symptoms, ranging from classical dengue fever to severe dengue hemorrhagic fever or dengue shock syndrome; however, the complexities of DENV immunopathogenesis remain controversial. Previous studies have reported the importance of the transcription factor Nrf2 in the control of redox homeostasis and antiviral/inflammatory or death responses to DENV. Importantly, the production of reactive oxygen species and the subsequent stress response have been linked to the development of inflammation and progression toward the more severe forms of the disease. Here, we demonstrate that DENV uses the NS2B3 protease complex to strategically target Nrf2 for degradation, leading to a progressive increase in oxidative stress, inflammation, and cell death in infected cells. This study underlines the pivotal role of the Nrf2 regulatory network in the context of DENV infection.

USP15 negatively regulates Nrf2 through deubiquitination of Keap1.

Nrf2 is a master regulator of the antioxidant response. Under basal conditions, Nrf2 is polyubiquitinated by the Keap1-Cul3 E3 ligase and degraded by the 26S proteasome. In response to Nrf2 inducers there is a switch in polyubiquitination from Nrf2 to Keap1. Currently, regulation of the Nrf2-Keap1 pathway by ubiquitination is largely understood. However, the mechanism responsible for removal of ubiquitin conjugated to Nrf2 or Keap1 remains unknown. Here we report that the deubiquitinating enzyme, USP15, specifically deubiquitinates Keap1, which suppresses the Nrf2 pathway. We demonstrated that deubiquitinated Keap1 incorporates into the Keap1-Cul3-E3 ligase complex more efficiently, enhancing the complex stability and enzymatic activity. Consequently, there is an increase in Nrf2 protein degradation and a reduction in Nrf2 target gene expression. Furthermore, USP15-siRNA enhances chemoresistance of cells through upregulation of Nrf2. These findings further our understanding of how the Nrf2-Keap1 pathway is regulated, which is imperative in targeting this pathway for chemoprevention or chemotherapy.

RPA1 binding to NRF2 switches ARE-dependent transcriptional activation to ARE-NRE-dependent repression.

NRF2 regulates cellular redox homeostasis, metabolic balance, and proteostasis by forming a dimer with small musculoaponeurotic fibrosarcoma proteins (sMAFs) and binding to antioxidant response elements (AREs) to activate target gene transcription. In contrast, NRF2-ARE-dependent transcriptional repression is unreported. Here, we describe NRF2-mediated gene repression via a specific seven-nucleotide sequence flanking the ARE, which we term the NRF2-replication protein A1 (RPA1) element (NRE). Mechanistically, RPA1 competes with sMAF for NRF2 binding, followed by interaction of NRF2-RPA1 with the ARE-NRE and eduction of promoter activity. Genome-wide in silico and RNA-seq analyses revealed this NRF2-RPA1-ARE-NRE complex mediates negative regulation of many genes with diverse functions, indicating that this mechanism is a fundamental cellular process. Notably, repression of MYLK, which encodes the nonmuscle myosin light chain kinase, by the NRF2-RPA1-ARE-NRE complex disrupts vascular integrity in preclinical inflammatory lung injury models, illustrating the translational significance of NRF2-mediated transcriptional repression. Our findings reveal a gene-suppressive function of NRF2 and a subset of negatively regulated NRF2 target genes, underscoring the broad impact of NRF2 in physiological and pathological settings.

The emerging role of the Nrf2-Keap1 signaling pathway in cancer.

The Nrf2 (nuclear factor erythroid 2 [NF-E2]-related factor 2 [Nrf2])-Keap1 (Kelch-like erythroid cell-derived protein with CNC homology [ECH]-associated protein 1) signaling pathway is one of the most important cell defense and survival pathways. Nrf2 can protect cells and tissues from a variety of toxicants and carcinogens by increasing the expression of a number of cytoprotective genes. As a result, several Nrf2 activators are currently being tested as chemopreventive compounds in clinical trials. Just as Nrf2 protects normal cells, studies have shown that Nrf2 may also protect cancer cells from chemotherapeutic agents and facilitate cancer progression. Nrf2 is aberrantly accumulated in many types of cancer, and its expression is associated with a poor prognosis in patients. In addition, Nrf2 expression is induced during the course of drug resistance. Collectively, these studies suggest that Nrf2 contributes to both intrinsic and acquired chemoresistance. This discovery has opened up a broad spectrum of research geared toward a better understanding of the role of Nrf2 in cancer. This review provides an overview of (1) the Nrf2-Keap1 signaling pathway, (2) the dual role of Nrf2 in cancer, (3) the molecular basis of Nrf2 activation in cancer cells, and (4) the challenges in the development of Nrf2-based drugs for chemoprevention and chemotherapy.

Differential and overlapping targets of the transcriptional regulators NRF1, NRF2, and NRF3 in human cells.

The nuclear factor (erythroid 2)-like (NRF) transcription factors are a subset of cap'n'collar transcriptional regulators. They consist of three members, NRF1, NRF2, and NRF3, that regulate the expression of genes containing antioxidant-response elements (AREs) in their promoter regions. Although all NRF members regulate ARE-containing genes, each is associated with distinct roles. A comprehensive study of differential and overlapping DNA-binding and transcriptional activities of the NRFs has not yet been conducted. Here, we performed chromatin immunoprecipitation (ChIP)-exo sequencing, an approach that combines ChIP with exonuclease treatment to pinpoint regulatory elements in DNA with high precision, in conjunction with RNA-sequencing to define the transcriptional targets of each NRF member. Our approach, done in three U2OS cell lines, identified 31 genes that were regulated by all three NRF members, 27 that were regulated similarly by all three, and four genes that were differentially regulated by at least one NRF member. We also found genes that were up- or down-regulated by only one NRF member, with 84, 84, and 22 genes that were regulated by NRF1, NRF2, and NRF3, respectively. Analysis of the ARE motifs identified in ChIP peaks revealed that NRF2 prefers binding to AREs flanked by GC-rich regions and that NRF1 prefers AT-rich flanking regions. Thus, sequence preference, likely in combination with upstream signaling events, determines NRF member activation under specific cellular contexts. Our analysis provides a comprehensive description of differential and overlapping gene regulation by the transcriptional regulators NRF1, NRF2, and NRF3.

The role of natural products in revealing NRF2 function.

Covering: up to 2020The transcription factor NRF2 is one of the body's major defense mechanisms, driving transcription of >300 antioxidant response element (ARE)-regulated genes that are involved in many critical cellular processes including redox regulation, proteostasis, xenobiotic detoxification, and primary metabolism. The transcription factor NRF2 and natural products have an intimately entwined history, as the discovery of NRF2 and much of its rich biology were revealed using natural products both intentionally and unintentionally. In addition, in the last decade a more sinister aspect of NRF2 biology has been revealed. NRF2 is normally present at very low cellular levels and only activated when needed, however, it has been recently revealed that chronic, high levels of NRF2 can lead to diseases such as diabetes and cancer, and may play a role in other diseases. Again, this "dark side" of NRF2 was revealed and studied largely using a natural product, the quassinoid, brusatol. In the present review, we provide an overview of NRF2 structure and function to orient the general reader, we will discuss the history of NRF2 and NRF2-activating compounds and the biology these have revealed, and we will delve into the dark side of NRF2 and contemporary issues related to the dark side biology and the role of natural products in dissecting this biology.

Uremic toxins promote accumulation of oxidized protein and increased sensitivity to hydrogen peroxide in endothelial cells by impairing the autophagic flux.

Chronic kidney disease (CKD) is associated with high mortality rates, mainly due to cardiovascular diseases (CVD). Uremia has been considered a relevant risk factor for CVD in CKD patients, since uremic toxins (UTs) promote systemic and vascular inflammation, oxidative stress and senescence. Here, we demonstrate that uremic toxins indoxyl sulfate (IxS), p-cresyl sulfate (pCS) and indole acetic acid (IAA) are incorporated by human endothelial cells and inhibit the autophagic flux, demonstrated by cellular p62 accumulation. Moreover, isolated and mixed UTs impair the lysosomal stage of autophagy, as determined by cell imaging of the mRFP-GFP-LC3 protein. Endothelial cells exposed to UTs display accumulation of carbonylated proteins and increased sensitivity to hydrogen peroxide. Rapamycin, an autophagy activator which induces both autophagosome formation and clearance, prevented these effects. Collectively, our findings demonstrate that accumulation of oxidized proteins and enhanced cell sensitivity to hydrogen peroxide are consequences of impaired autophagic flux. These data provide evidence that UTs-induced impaired autophagy may be a novel contributor to endothelial dysfunction.

Spermidine Confers Liver Protection by Enhancing NRF2 Signaling Through a MAP1S-Mediated Noncanonical Mechanism.

Spermidine (SPD), a naturally occurring polyamine, has been recognized as a caloric restriction mimetic that confers health benefits, presumably by inducing autophagy. Recent studies have reported that oral administration of SPD protects against liver fibrosis and hepatocarcinogenesis through activation of microtubule associated protein 1S (MAP1S)-mediated autophagy. Nuclear factor (erythroid-derived 2)-like 2 (NRF2) is a transcription factor that mediates cellular protection by maintaining the cell's redox, metabolic, and proteostatic balance. In this study, we demonstrate that SPD is a noncanonical NRF2 inducer, and that MAP1S is a component of this noncanonical pathway of NRF2 activation. Mechanistically, MAP1S induces NRF2 signaling through two parallel mechanisms, both resulting in NRF2 stabilization: (1) MAP1S competes with Kelch-like ECH-associated protein 1 (KEAP1) for NRF2 binding through an ETGE motif, and (2) MAP1S accelerates p62-dependent degradation of KEAP1 by the autophagy pathway. We further demonstrate that SPD confers liver protection by enhancing NRF2 signaling. The importance of both NRF2 and p62-dependent autophagy in SPD-mediated liver protection was confirmed using a carbon tetrachloride-induced liver fibrosis model in wild-type, Nrf2-/- , p62-/- and Nrf2-/- ;p62-/- mice, as the protective effect of SPD was significantly reduced in NRF2 or p62 single knockout mice, and completely abolished in the double knockout mice. Conclusion: Our results demonstrate the pivotal role of NRF2 in mediating the health benefit of SPD, particularly in the context of liver pathologies.