Defects in the Neuroendocrine Axis Contribute to Global Development Delay in a Drosophila Model of NGLY1 Deficiency

NGLY1: A fascinating, multifunctional molecule

NGLY1, a cytoplasmic de-N-glycosylating enzyme is well conserved among eukaryotes. This enzyme has attracted considerable attention after mutations on the NGLY1 gene were found to cause a rare genetic disorder called NGLY1 deficiency. Recent explosive progress in NGLY1 research has revealed multi-functional aspects of this protein.

Gut barrier defects, intestinal immune hyperactivation and enhanced lipid catabolism drive lethality in NGLY1-deficient Drosophila

Intestinal barrier dysfunction leads to inflammation and associated metabolic changes. However, the relative impact of gut bacteria versus non-bacterial insults on animal health in the context of barrier dysfunction is not well understood. Here, we establish that loss of Drosophila N-glycanase 1 (Pngl) in a specific intestinal cell type leads to gut barrier defects, causing starvation and JNK overactivation. These abnormalities, along with loss of Pngl in enterocytes and fat body, result in Foxo overactivation, leading to hyperactive innate immune response and lipid catabolism and thereby contributing to lethality. Germ-free rearing of Pngl mutants rescued their developmental delay but not lethality. However, raising Pngl mutants on isocaloric, fat-rich diets partially rescued lethality. Our data indicate that Pngl functions in Drosophila larvae to establish the gut barrier, and that the lethality caused by loss of Pngl is primarily mediated through non-bacterial induction of immune and metabolic abnormalities.

Gut barrier defects, increased intestinal innate immune response, and enhanced lipid catabolism drive lethality in N -glycanase 1 deficient Drosophila

Intestinal barrier dysfunction leads to inflammation and associated metabolic changes. However, the relative impact of infectious versus non-infectious mechanisms on animal health in the context of barrier dysfunction is not well understood. Here, we establish that loss of Drosophila N -glycanase 1 (Pngl) leads to gut barrier defects, which cause starvation and increased JNK activity. These defects result in Foxo overactivation, which induces a hyperactive innate immune response and lipid catabolism, thereby contributing to lethality associated with loss of Pngl . Notably, germ-free rearing of Pngl mutants did not rescue lethality. In contrast, raising Pngl mutants on isocaloric, fat-rich diets improved animal survival in a dosage-dependent manner. Our data indicate that Pngl functions in Drosophila larvae to establish the gut barrier, and that the immune and metabolic consequences of loss of Pngl are primarily mediated through non-infectious mechanisms.

Chemical Therapies for Congenital Disorders of Glycosylation

Congenital disorders of glycosylation (CDG) are ultrarare, genetically and clinically heterogeneous metabolic disorders. Although the number of identified CDG is growing rapidly, there are few therapeutic options. Most treatments involve dietary supplementation with monosaccharides or other precursors. These approaches are relatively safe, but in many cases, the molecular and biochemical underpinnings are incomplete. Recent studies demonstrate that yeast, worm, fly, and zebrafish models of CDG are powerful tools in screening repurposed drugs, ushering a new avenue to search for novel therapeutic options. Here we present a perspective on compounds that are currently in use for CDG treatment or have a potential to be applied as therapeutics in the near future.

An in vivo drug repurposing screen and transcriptional analyses reveals the serotonin pathway and GSK3 as major therapeutic targets for NGLY1 deficiency

NGLY1 deficiency, a rare disease with no effective treatment, is caused by autosomal recessive, loss-of-function mutations in the N-glycanase 1 (NGLY1) gene and is characterized by global developmental delay, hypotonia, alacrima, and seizures. We used a Drosophila model of NGLY1 deficiency to conduct an in vivo, unbiased, small molecule, repurposing screen of FDA-approved drugs to identify therapeutic compounds. Seventeen molecules partially rescued lethality in a patient-specific NGLY1 deficiency model, including multiple serotonin and dopamine modulators. Exclusive dNGLY1 expression in serotonin and dopamine neurons, in an otherwise dNGLY1 deficient fly, was sufficient to partially rescue lethality. Further, genetic modifier and transcriptomic data supports the importance of serotonin signaling in NGLY1 deficiency. Connectivity Map analysis identified glycogen synthase kinase 3 (GSK3) inhibition as a potential therapeutic mechanism for NGLY1 deficiency, which we experimentally validated with TWS119, lithium, and GSK3 knockdown. Strikingly, GSK3 inhibitors and a serotonin modulator rescued size defects in dNGLY1 deficient larvae upon proteasome inhibition, suggesting that these compounds act through NRF1, a transcription factor that is regulated by NGLY1 and regulates proteasome expression. This study reveals the importance of the serotonin pathway in NGLY1 deficiency, and serotonin modulators or GSK3 inhibitors may be effective therapeutics for this rare disease.

NGLY1 deficiency is a rare disease with no effective treatment. We conducted a drug repurposing screen and used the Connectivity Map, a transcriptional-based computational approach, to identify compounds that may serve as therapeutics for NGLY1 deficient individuals. The drug repurposing screen identified FDA-approved compounds acting through the serotonin and dopamine pathway that partially rescued lethality in an NGLY1 deficiency fly model. We also found that expressing dNGLY1 (the Drosophila ortholog of NGLY1) exclusively in serotonin neurons, in an otherwise dNGLY1 deficient fly, partially rescued lethality. These data indicate the importance of the serotonin and dopamine systems in NGLY1 deficiency. The Connectivity Map analyses found GSK3 inhibitors as potential therapeutic compounds, which were validated in vivo in the fly. Furthermore, knockdown of sgg (the Drosophila ortholog of GSK3) partially rescued lethality in dNGLY1 deficient flies, suggesting GSK3 as a therapeutic target for NGLY1 deficiency. Taken together, this work identifies therapeutic strategies for NGLY1 deficiency.

Integrated transcriptomics and metabolomics unravel the metabolic pathway variations for barley β-glucan before and after fermentation with L. plantarum DY-1

The results of our previous study showed that the structure and function of β-glucan in barley were changed after fermentation by L. plantarum DY-1. In this study, the antioxidant activities of RBG (regular barley β-glucan, unfermented) and FBG (barley β-glucan, fermented with L. plantarum DY-1) were evaluated by adopting an in vivo animal model, Caenorhabditis elegans (C. elegans). We also carried out an integrated transcriptomic and metabolomic profiling for RBG and FBG to delineate their signature pathways. RBG treatment has better effects on SOD enzyme activity and ROS levels than FBG, while FBG treatment has better effects on the CAT enzyme activity and MDA content than RBG in C. elegans. Transcription group analysis showed that FBG mainly decreases the expression of the Cyp-D gene to inhibit the calcium signaling pathway, promotes the Wnt signaling pathway by up-regulating the GSK-3β gene and improving the oxidative damage of C. elegans; RBG mainly inhibits calcium signal pathways by reducing the expression of ANT-solute carrier family 25 genes, promoting life adjustment pathways by reducing the expression of the HSP-12.6 gene to improve the oxidative stress of C. elegans. Joint analysis showed that the difference between FBG and RBG in the regulation of oxidative stress is mainly reflected in the metabolism pathway of arachidonic acid. Under the regulation of FBG, the expression of the C03H5.4 gene was decreased, the expression of leukotriene A4, prostaglandin G2, arachidonic acid and phosphatidylcholine was decreased, and the expression of 14,15-DiHETrE was increased. Under the regulation of RBG, the expression of gene C03H5.4 was up-regulated, the expression of metabolites such as leukotriene B4 was up-regulated, and the expression of arachidonic acid and phosphatidylcholine was down-regulated.

NGLY1 Deficiency, a Congenital Disorder of Deglycosylation: From Disease Gene Function to Pathophysiology

N-Glycanase 1 (NGLY1) is a cytosolic enzyme involved in removing N-linked glycans of misfolded N-glycoproteins and is considered to be a component of endoplasmic reticulum-associated degradation (ERAD). The 2012 identification of recessive NGLY1 mutations in a rare multisystem disorder has led to intense research efforts on the roles of NGLY1 in animal development and physiology, as well as the pathophysiology of NGLY1 deficiency. Here, we present a review of the NGLY1-deficient patient phenotypes, along with insights into the function of this gene from studies in rodent and invertebrate animal models, as well as cell culture and biochemical experiments. We will discuss critical processes affected by the loss of NGLY1, including proteasome bounce-back response, mitochondrial function and homeostasis, and bone morphogenetic protein (BMP) signaling. We will also cover the biologically relevant targets of NGLY1 and the genetic modifiers of NGLY1 deficiency phenotypes in animal models. Together, these discoveries and disease models have provided a number of avenues for preclinical testing of potential therapeutic approaches for this disease.

Deficiency of N-glycanase 1 perturbs neurogenesis and cerebral development modeled by human organoids

Mutations in N-glycanase 1 (NGLY1), which deglycosylates misfolded glycoproteins for degradation, can cause NGLY1 deficiency in patients and their abnormal fetal development in multiple organs, including microcephaly and other neurological disorders. Using cerebral organoids (COs) developed from human embryonic stem cells (hESCs) and induced pluripotent stem cells (hiPSCs), we investigate how NGLY1 dysfunction disturbs early brain development. While NGLY1 loss had limited impact on the undifferentiated cells, COs developed from NGLY1-deficient hESCs showed defective formation of SATB2-positive upper-layer neurons, and attenuation of STAT3 and HES1 signaling critical for sustaining radial glia. Bulk and single-cell transcriptomic analysis revealed premature neuronal differentiation accompanied by downregulation of secreted and transcription factors, including TTR, IGFBP2, and ID4 in NGLY1-deficient COs. NGLY1 malfunction also dysregulated ID4 and enhanced neuronal differentiation in CO transplants developed in vivo. NGLY1-deficient CO cells were more vulnerable to multiple stressors; treating the deficient cells with recombinant TTR reduced their susceptibility to stress from proteasome inactivation, likely through LRP2-mediated activation of MAPK signaling. Expressing NGLY1 led to IGFBP2 and ID4 upregulation in CO cells developed from NGLY1-deficiency patient’s hiPSCs. In addition, treatment with recombinant IGFBP2 enhanced ID4 expression, STAT3 signaling, and proliferation of NGLY1-deficient CO cells. Overall, our discoveries suggest that dysregulation of stress responses and neural precursor differentiation underlies the brain abnormalities observed in NGLY1-deficient individuals.

Patient-derived gene and protein expression signatures of NGLY1 deficiency

N-Glycanase 1 (NGLY1) deficiency is a rare and complex genetic disorder. Although recent studies have shed light on the molecular underpinnings of NGLY1 deficiency, a systematic characterization of gene and protein expression changes in patient-derived cells has been lacking. Here, we performed RNA-sequencing and mass spectrometry to determine the transcriptomes and proteomes of 66 cell lines representing 4 different cell types derived from 14 NGLY1 deficient patients and 17 controls. Although NGLY1 protein levels were up to 9.5-fold downregulated in patients compared to parents, residual and likely non-functional NGLY1 protein was detectable in all patient-derived lymphoblastoid cell lines. Consistent with the role of NGLY1 as a regulator of the transcription factor Nrf1, we observed a cell type-independent downregulation of proteasomal genes in NGLY1 deficient cells. In contrast, genes involved in ribosome biogenesis and mRNA processing were upregulated in multiple cell types. In addition, we observed cell type-specific effects. For example, genes and proteins involved in glutathione synthesis, such as the glutamate-cysteine ligase subunits GCLC and GCLM, were downregulated specifically in lymphoblastoid cells. We provide a web application that enables access to all results generated in this study at https://apps.embl.de/ngly1browser. This resource will guide future studies of NGLY1 deficiency in directions that are most relevant to patients.

Ngly1 -/- rats develop neurodegenerative phenotypes and pathological abnormalities in their peripheral and central nervous systems

N-glycanase 1 (NGLY1) deficiency, an autosomal recessive disease caused by mutations in the NGLY1 gene, is characterized by developmental delay, hypolacrima or alacrima, seizure, intellectual disability, movement disorders and other neurological phenotypes. Because of few animal models that recapitulate these clinical signatures, the mechanisms of the onset of the disease and its progression are poorly understood, and the development of therapies is hindered. In this study, we generated the systemic Ngly1-deficient rodent model, Ngly1^−/− rats, which showed developmental delay, movement disorder, somatosensory impairment and scoliosis. These phenotypes in Ngly1^−/− rats are consistent with symptoms in human patients. In accordance with the pivotal role played by NGLY1 in endoplasmic reticulum-associated degradation processes, cleaving N-glycans from misfolded glycoproteins in the cytosol before they can be degraded by the proteasome, loss of Ngly1 led to accumulation of cytoplasmic ubiquitinated proteins, a marker of misfolded proteins in the neurons of the central nervous system of Ngly1^−/− rats. Histological analysis identified prominent pathological abnormalities, including necrotic lesions, mineralization, intra- and extracellular eosinophilic bodies, astrogliosis, microgliosis and significant loss of mature neurons in the thalamic lateral and the medial parts of the ventral posterior nucleus and ventral lateral nucleus of Ngly1^−/− rats. Axonal degradation in the sciatic nerves was also observed, as in human subjects. Ngly1^−/− rats, which mimic the symptoms of human patients, will be a useful animal model for preclinical testing of therapeutic options and understanding the detailed mechanisms of NGLY1 deficiency.

Tracing the NGLY1 footprints: Insights from Drosophila

Recessive mutations in human N-glycanase 1 (NGLY1) cause a multisystem disorder with various phenotypes including global developmental delay. One of the models utilized to understand the biology of NGLY1 and the pathophysiology of NGLY1 deficiency is Drosophila melanogaster, a well-established, genetically tractable organism broadly used to study various biological processes and human diseases. Loss of the Drosophila NGLY1 homolog (Pngl) causes a host of phenotypes including developmental delay and lethality. Phenotypic, transcriptomic and genome-wide association analyses on Drosophila have revealed links between NGLY1 and several critical developmental and cellular pathways/processes. Further, repurposing screens of FDA-approved drugs have identified potential candidates to ameliorate some of the Pngl mutant phenotypes. Here, we will summarize the insights gained into the functions of NGLY1 from Drosophila studies. We hope that the current review article will encourage additional studies in Drosophila and other model systems towards establishing a therapeutic strategy for NGLY1 deficiency patients.

Reversibility of motor dysfunction in the rat model of NGLY1 deficiency

N-glycanase 1 (NGLY1) deficiency is a rare inherited disorder characterized by developmental delay, hypolacrima or alacrima, seizure, intellectual disability, motor deficits, and other neurological symptoms. The underlying mechanisms of the NGLY1 phenotype are poorly understood, and no effective therapy is currently available. Similar to human patients, the rat model of NGLY1 deficiency, Ngly1-/-, shows developmental delay, movement disorder, somatosensory impairment, scoliosis, and learning disability. Here we show that single intracerebroventricular administration of AAV9 expressing human NGLY1 cDNA (AAV9-hNGLY1) to Ngly1-/- rats during the weaning period restored NGLY1 expression in the brain and spinal cord, concomitant with increased enzymatic activity of NGLY1 in the brain. hNGLY1 protein expressed by AAV9 was found predominantly in mature neurons, but not in glial cells, of Ngly1-/- rats. Strikingly, intracerebroventricular administration of AAV9-hNGLY1 normalized the motor phenotypes of Ngly1-/- rats assessed by the rota-rod test and gait analysis. The reversibility of motor deficits in Ngly1-/- rats by central nervous system (CNS)-restricted gene delivery suggests that the CNS is the primary therapeutic target organs for NGLY1 deficiency, and that the Ngly1-/- rat model may be useful for evaluating therapeutic treatments in pre-clinical studies.

JF1/B6F1 Ngly1-/- mouse as an isogenic animal model of NGLY1 deficiency

N-Glycanase 1 (NGLY1) deficiency is a congenital disorder caused by mutations in the NGLY1 gene. Because systemic Ngly1^-/- mice with a C57BL/6 (B6) background are embryonically lethal, studies on the mechanism of NGLY1 deficiency using mice have been problematic. In this study, B6-Ngly1^-/+ mice were crossed with Japanese wild mice-originated Japanese fancy mouse 1 (JF1) mice to produce viable F₂ Ngly1^-/- mice from (JF1×B6)F₁ Ngly1^-/+ mice. Systemic Ngly1^-/- mice with a JF1 mouse background were also embryonically lethal. Hybrid F1 Ngly1^-/- (JF1/B6F1) mice, however, showed developmental delay and motor dysfunction, similar to that in human patients. JF1/B6F1 Ngly1^-/- mice showed increased levels of plasma and urinary aspartylglycosamine, a potential biomarker for NGLY1 deficiency. JF1/B6F1 Ngly1^-/- mice are a useful isogenic animal model for the preclinical testing of therapeutic options and understanding the precise pathogenic mechanisms responsible for NGLY1 deficiency.

Folding and Quality Control of Glycoproteins

Folding of proteins is essential so that they can exert their functions. For proteins that transit the secretory pathway, folding occurs in the endoplasmic reticulum (ER) and various chaperone systems assist in acquiring their correct folding/subunit formation. N-glycosylation is one of the most conserved posttranslational modification for proteins, and in eukaryotes it occurs in the ER. Consequently, eukaryotic cells have developed various systems that utilize N-glycans to dictate and assist protein folding, or if they consistently fail to fold properly, to destroy proteins for quality control and the maintenance of homeostasis of proteins in the ER.

A conserved role for AMP-activated protein kinase in NGLY1 deficiency

Mutations in human N-glycanase 1 (NGLY1) cause the first known congenital disorder of deglycosylation (CDDG). Patients with this rare disease, which is also known as NGLY1 deficiency, exhibit global developmental delay and other phenotypes including neuropathy, movement disorder, and constipation. NGLY1 is known to regulate proteasomal and mitophagy gene expression through activation of a transcription factor called "nuclear factor erythroid 2-like 1" (NFE2L1). Loss of NGLY1 has also been shown to impair energy metabolism, but the molecular basis for this phenotype and its in vivo consequences are not well understood. Using a combination of genetic studies, imaging, and biochemical assays, here we report that loss of NGLY1 in the visceral muscle of the Drosophila larval intestine results in a severe reduction in the level of AMP-activated protein kinase α (AMPKα), leading to energy metabolism defects, impaired gut peristalsis, failure to empty the gut, and animal lethality. Ngly1-/- mouse embryonic fibroblasts and NGLY1 deficiency patient fibroblasts also show reduced AMPKα levels. Moreover, pharmacological activation of AMPK signaling significantly suppressed the energy metabolism defects in these cells. Importantly, the reduced AMPKα level and impaired energy metabolism observed in NGLY1 deficiency models are not caused by the loss of NFE2L1 activity. Taken together, these observations identify reduced AMPK signaling as a conserved mediator of energy metabolism defects in NGLY1 deficiency and suggest AMPK signaling as a therapeutic target in this disease.

Cytosolic N-GlcNAc proteins are formed by the action of endo-β-N-acetylglucosaminidase

NGLY1 is a widely conserved eukaryotic cytosolic deglycosylating enzyme involved in the endoplasmic reticulum-associated degradation (ERAD) process, which eliminates misfolded proteins through retrograde translocation and proteasomal degradation. A human genetic disorder called NGLY1-deficiency has been reported, indicating the functional importance of NGLY1 in humans. Evidence suggests that Ngly1-KO is embryonic lethal in mice, while additional deletion of the Engase gene, encoding another cytosolic deglycosylating enzyme (endo-β-N-acetylglucosaminidase; ENGase), partially rescued lethality. Upon compromised Ngly1 activity, ENGase-mediated deglycosylation of misfolded glycoproteins may cause excess formation of N-GlcNAc proteins in the cytosol, leading to detrimental effects in the mice. Whether endogenous N-GlcNAc proteins are really formed in Ngly1-KO cells/animals or not remains unclarified. Here, comprehensive identification of O- and N-GlcNAc proteins was carried out using purified cytosol from wild type, Ngly1-KO, Engase-KO, and Ngly1/Engase double KO mouse embryonic fibroblasts. It was revealed that while there is no dramatic change in the level of O-GlcNAc proteins among cells examined, there was a vast increase of N-GlcNAc proteins in Ngly1-KO cells upon proteasome inhibition. Importantly, few N-GlcNAc proteins were observed in Engase-KO or Ngly1/Engase double-KO cells, clearly indicating that the cytosolic ENGase is responsible for the formation of N-GlcNAc proteins. The excess formation of N-GlcNAc proteins may at least in part account for the pathogenesis of NGLY1-deficiency.

Protein Sequence Editing of SKN-1A/Nrf1 by Peptide:N-Glycanase Controls Proteasome Gene Expression

The proteasome mediates selective protein degradation and is dynamically regulated in response to proteotoxic challenges. SKN-1A/Nrf1, an endoplasmic reticulum (ER)-associated transcription factor that undergoes N-linked glycosylation, serves as a sensor of proteasome dysfunction and triggers compensatory upregulation of proteasome subunit genes. Here, we show that the PNG-1/NGLY1 peptide:N-glycanase edits the sequence of SKN-1A protein by converting particular N-glycosylated asparagine residues to aspartic acid. Genetically introducing aspartates at these N-glycosylation sites bypasses the requirement for PNG-1/NGLY1, showing that protein sequence editing rather than deglycosylation is key to SKN-1A function. This pathway is required to maintain sufficient proteasome expression and activity, and SKN-1A hyperactivation confers resistance to the proteotoxicity of human amyloid beta peptide. Deglycosylation-dependent protein sequence editing explains how ER-associated and cytosolic isoforms of SKN-1 perform distinct cytoprotective functions corresponding to those of mammalian Nrf1 and Nrf2. Thus, we uncover an unexpected mechanism by which N-linked glycosylation regulates protein function and proteostasis.

Repurposing the aldose reductase inhibitor and diabetic neuropathy drug epalrestat for the congenital disorder of glycosylation PMM2-CDG

Phosphomannomutase 2 deficiency, or PMM2-CDG, is the most common congenital disorder of glycosylation and affects over 1000 patients globally. There are no approved drugs that treat the symptoms or root cause of PMM2-CDG. To identify clinically actionable compounds that boost human PMM2 enzyme function, we performed a multispecies drug repurposing screen using a novel worm model of PMM2-CDG, followed by PMM2 enzyme functional studies in PMM2-CDG patient fibroblasts. Drug repurposing candidates from this study, and drug repurposing candidates from a previously published study using yeast models of PMM2-CDG, were tested for their effect on human PMM2 enzyme activity in PMM2-CDG fibroblasts. Of the 20 repurposing candidates discovered in the worm-based phenotypic screen, 12 were plant-based polyphenols. Insights from structure–activity relationships revealed epalrestat, the only antidiabetic aldose reductase inhibitor approved for use in humans, as a first-in-class PMM2 enzyme activator. Epalrestat increased PMM2 enzymatic activity in four PMM2-CDG patient fibroblast lines with genotypes R141H/F119L, R141H/E139K, R141H/N216I and R141H/F183S. PMM2 enzyme activity gains ranged from 30% to 400% over baseline, depending on genotype. Pharmacological inhibition of aldose reductase by epalrestat may shunt glucose from the polyol pathway to glucose-1,6-bisphosphate, which is an endogenous stabilizer and coactivator of PMM2 homodimerization. Epalrestat is a safe, oral and brain penetrant drug that was approved 27 years ago in Japan to treat diabetic neuropathy in geriatric populations. We demonstrate that epalrestat is the first small molecule activator of PMM2 enzyme activity with the potential to treat peripheral neuropathy and correct the underlying enzyme deficiency in a majority of pediatric and adult PMM2-CDG patients.

Editor's choice: Drug repurposing screens using worm and patient fibroblast models of PMM2-CDG led to the discovery of epalrestat, the first activator of PMM2 that targets the root cause of disease.

Drug screens of NGLY1 deficiency in worm and fly models reveal catecholamine, NRF2 and anti-inflammatory-pathway activation as potential clinical approaches

N-glycanase 1 (NGLY1) deficiency is an ultra-rare and complex monogenic glycosylation disorder that affects fewer than 40 patients globally. NGLY1 deficiency has been studied in model organisms such as yeast, worms, flies and mice. Proteasomal and mitochondrial homeostasis gene networks are controlled by the evolutionarily conserved transcriptional regulator NRF1, whose activity requires deglycosylation by NGLY1. Hypersensitivity to the proteasome inhibitor bortezomib is a common phenotype observed in whole-animal and cellular models of NGLY1 deficiency. Here, we describe unbiased phenotypic drug screens to identify FDA-approved drugs that are generally recognized as safe natural products, and novel chemical entities, that rescue growth and development of NGLY1-deficient worm and fly larvae treated with a toxic dose of bortezomib. We used image-based larval size and number assays for use in screens of a 2560-member drug-repurposing library and a 20,240-member lead-discovery library. A total of 91 validated hit compounds from primary invertebrate screens were tested in a human cell line in an NRF2 activity assay. NRF2 is a transcriptional regulator that regulates cellular redox homeostasis, and it can compensate for loss of NRF1. Plant-based polyphenols make up the largest class of hit compounds and NRF2 inducers. Catecholamines and catecholamine receptor activators make up the second largest class of hits. Steroidal and non-steroidal anti-inflammatory drugs make up the third largest class. Only one compound was active in all assays and species: the atypical antipsychotic and dopamine receptor agonist aripiprazole. Worm and fly models of NGLY1 deficiency validate therapeutic rationales for activation of NRF2 and anti-inflammatory pathways based on results in mice and human cell models, and suggest a novel therapeutic rationale for boosting catecholamine levels and/or signaling in the brain.

Summary: Using worm and fly models of an ultra-rare congenital disorder of glycosylation, we performed repurposing screens and identified the FDA-approved drug aripiprazole as a clinical candidate.