Autophagic UVRAG Promotes UV-Induced Photolesion Repair by Activation of the CRL4(DDB2) E3 Ligase.

UV-induced DNA damage, a major risk factor for skin cancers, is primarily repaired by nucleotide excision repair (NER). UV radiation resistance-associated gene (UVRAG) is a tumor suppressor involved in autophagy. It was initially isolated as a cDNA partially complementing UV sensitivity in xeroderma pigmentosum (XP), but this was not explored further. Here we show that UVRAG plays an integral role in UV-induced DNA damage repair. It localizes to photolesions and associates with DDB1 to promote the assembly and activity of the DDB2-DDB1-Cul4A-Roc1 (CRL4(DDB2)) ubiquitin ligase complex, leading to efficient XPC recruitment and global genomic NER. UVRAG depletion decreased substrate handover to XPC and conferred UV-damage hypersensitivity. We confirmed the importance of UVRAG for UV-damage tolerance using a Drosophila model. Furthermore, increased UV-signature mutations in melanoma correlate with reduced expression of UVRAG. Our results identify UVRAG as a regulator of CRL4(DDB2)-mediated NER and suggest that its expression levels may influence melanoma predisposition.

YY1 cooperates with TFEB to regulate autophagy and lysosomal biogenesis in melanoma.

Autophagy is a self-proteolytic process that degrades intracellular material to maintain cellular homeostasis. Transcription factor EB (TFEB) is the master activator that regulates the transcription of genes involved in autophagy and lysosomal biogenesis. However, the cotranscriptional factors of TFEB are rarely identified. Here, we found that Yin Yang 1 (YY1) regulated autophagy and lysosome biogenesis in melanoma cells. YY1 cooperates with TFEB to regulate autophagy through controlling the transcription of autophagy and lysosome biogenesis related genes. Moreover, suppression of YY1 enhanced the antitumor efficiency of vemurafenib both in vitro and in vivo. Collectively, these studies identify YY1 as a novel cotranscription factor of TFEB in regulating autophagy and lysosomal functions and suggest YY1 could be a therapeutic target in cancer treatment.

miR-9 regulates ferroptosis by targeting glutamic-oxaloacetic transaminase GOT1 in melanoma.

Ferroptosis is a recently recognized form of regulated cell death driven by lipid-based reactive oxygen species (ROS) accumulation. However, the molecular mechanisms of ferroptosis regulation are still largely unknown. Here we identified a novel miRNA, miR-9, as an important regulator of ferroptosis by directly targeting GOT1 in melanoma cells. Overexpression of miR-9 suppressed GOT1 by directly binding to its 3'-UTR, which subsequently reduced erastin- and RSL3-induced ferroptosis. Conversely, suppression of miR-9 increased the sensitivity of melanoma cells to erastin and RSL3. Importantly, anti-miR-9 mediated lipid ROS accumulation and ferroptotic cell death could be abrogated by inhibiting glutaminolysis process. Taken together, our findings demonstrate that miR-9 regulates ferroptosis by targeting GOT1 in melanoma cells, illustrating the important role of miRNA in ferroptosis.

Smoking and Inflammatory Bowel Disease: A Comparison of China, India, and the USA.

BACKGROUND: Cigarette smoking is thought to increase the risk of Crohn's disease (CD) and exacerbate the disease course, with opposite roles in ulcerative colitis (UC). However, these findings are from Western populations, and the association between smoking and inflammatory bowel disease (IBD) has not been well studied in Asia. AIMS: We aimed to compare the prevalence of smoking at diagnosis between IBD cases and controls recruited in China, India, and the USA, and to investigate the impact of smoking on disease outcomes. METHODS: We recruited IBD cases and controls between 2014 and 2018. All participants completed a questionnaire about demographic characteristics, environmental risk factors and IBD history. RESULTS: We recruited 337 participants from China, 194 from India, and 645 from the USA. In China, CD cases were less likely than controls to be current smokers (adjusted odds ratio [95% CI] 0.4 [0.2-0.9]). There was no association between current or former smoking and CD in the USA. In China and the USA, UC cases were more likely to be former smokers than controls (China 14.6 [3.3-64.8]; USA 1.8 [1.0-3.3]). In India, both CD and UC had similar current smoking status to controls at diagnosis. Current smoking at diagnosis was significantly associated with greater use of immunosuppressants (4.4 [1.1-18.1]) in CD cases in China. CONCLUSIONS: We found heterogeneity in the associations of smoking and IBD risk and outcomes between China, India, and the USA. Further study with more adequate sample size and more uniform definition of smoking status is warranted.

UVRAG is required for virus entry through combinatorial interaction with the class C-Vps complex and SNAREs.

Enveloped viruses exploit the endomembrane system to enter host cells. Through a cascade of membrane-trafficking events, virus-bearing vesicles fuse with acidic endosomes and/or lysosomes mediated by SNAREs triggering viral fusion. However, the molecular mechanisms underlying this process remain elusive. Here, we found that UV-radiation resistance-associated gene (UVRAG), an autophagic tumor suppressor, is required for the entry of the prototypic negative-strand RNA virus, including influenza A virus and vesicular stomatitis virus, by a mechanism independent of IFN and autophagy. UVRAG mediates viral endocytic transport and membrane penetration through interactions with the class C vacuolar protein sorting (C-Vps) tethering complex and endosomal glutamine-containing SNAREs [syntaxin 7 (STX7), STX8, and vesicle transport through t-SNARE homolog 1B (Vti1b)], leading to the assembly of a fusogenic trans-SNARE complex involving vesicle-associated membrane protein (VAMP8), but not VAMP7. Indeed, UVRAG stimulates VAMP8 translocation to virus-bearing endosomes. Inhibition of VAMP8, but not VAMP7, significantly reduces viral entry. Our data indicate that UVRAG, in concert with C-Vps, regulates viral entry by assembling a specific fusogenic SNARE complex. Thus, UVRAG governs downstream viral entry, highlighting an important pathway capable of potential antiviral therapeutics.

Long noncoding RNA NEAT1 promotes ferroptosis by modulating the miR-362-3p/MIOX axis as a ceRNA.

Ferroptosis, a novel form of regulated cell death induced by iron-dependent lipid peroxidation, plays an essential role in the development and drug resistance of tumors. Long noncoding RNA (lncRNA) nuclear paraspeckle assembly transcript 1 (NEAT1) has been reported to be involved in the regulation of cell cycle, proliferation, apoptosis, and migration of tumor cells. However, the function and molecular mechanism of NEAT1 in regulating ferroptosis in tumors remain unclear. Here, we found that ferroptosis inducers erastin and RSL3 increased NEAT1 expression by promoting the binding of p53 to the NEAT1 promoter. Induced NEAT1 promoted the expression of MIOX by competitively binding to miR-362-3p. MIOX increased ROS production and decreased the intracellular levels of NADPH and GSH, resulting in enhanced erastin- and RSL3-induced ferroptosis. Importantly, overexpression of NEAT1 increased the anti-tumor activity of erastin and RSL3 by enhancing ferroptosis both in vitro and in vivo. Collectively, these data suggest that NEAT1 plays a novel and indispensable role in ferroptosis by regulating miR-362-3p and MIOX. Considering the clinical findings that HCC patients are insensitive to chemotherapy and immunotherapy, ferroptosis induction may be a promising therapeutic strategy for HCC patients with high NEAT1 expression.

A truncating mutation in the autophagy gene UVRAG drives inflammation and tumorigenesis in mice.

Aberrant autophagy is a major risk factor for inflammatory diseases and cancer. However, the genetic basis and underlying mechanisms are less established. UVRAG is a tumor suppressor candidate involved in autophagy, which is truncated in cancers by a frameshift (FS) mutation and expressed as a shortened UVRAGFS. To investigate the role of UVRAGFS in vivo, we generated mutant mice that inducibly express UVRAGFS (iUVRAGFS). These mice are normal in basal autophagy but deficient in starvation- and LPS-induced autophagy by disruption of the UVRAG-autophagy complex. iUVRAGFS mice display increased inflammatory response in sepsis, intestinal colitis, and colitis-associated cancer development through NLRP3-inflammasome hyperactivation. Moreover, iUVRAGFS mice show enhanced spontaneous tumorigenesis related to age-related autophagy suppression, resultant ß-catenin stabilization, and centrosome amplification. Thus, UVRAG is a crucial autophagy regulator in vivo, and autophagy promotion may help prevent/treat inflammatory disease and cancer in susceptible individuals.

miR-216b enhances the efficacy of vemurafenib by targeting Beclin-1, UVRAG and ATG5 in melanoma.

Autophagy maintains cells survival in many stressful conditions including starvation, growth factor deprivation and misfolded protein accumulation. Additionally, autophagic survival mechanisms are used by transformed tumor cells to inhibit cell death, limit drug effectiveness and possibly generate drug resistance. However, the mechanism of how cells utilize autophagy during drug resistance is not fully understood. Here, we demonstrate that miR-216b plays an important role in alleviating drug resistance by regulating autophagy in melanoma. We show that miR-216b attenuates autophagy by directly targeting three key autophagy genes Beclin-1, UVRAG and ATG5. Overexpression of these genes from miRNA immune cDNA constructs rescue autophagic activity in the presence of miR-216b. Antagomir-mediated inactivation of endogenous miR-216b led to an increase of Beclin-1, UVRAG, ATG5, and subsequent autophagic activity. More importantly, we have discovered that BRAF(V600E) inhibitor vemurafenib suppresses miR-216b activity, which in turn activates autophagy to generate drug resistance in both BRAFi-sensitive and -resistant cells. Strikingly, ectopic expression of miR-216b increases the efficacy of vemurafenib both in vitro and in vivo. Taken together, these data indicate that miR-216b regulates autophagy by suppressing three key autophagy genes, and enhances the antitumor activity of vemurafenib in BRAF(V600E) melanoma cells.

miR-137 regulates ferroptosis by targeting glutamine transporter SLC1A5 in melanoma.

Ferroptosis is a regulated form of cell death driven by small molecules or conditions that induce lipid-based reactive oxygen species (ROS) accumulation. This form of iron-dependent cell death is morphologically and genetically distinct from apoptosis, necroptosis, and autophagy. miRNAs are known to play crucial roles in diverse fundamental biological processes. However, to date no study has reported miRNA-mediated regulation of ferroptosis. Here we show that miR-137 negatively regulates ferroptosis by directly targeting glutamine transporter SLC1A5 in melanoma cells. Ectopic expression of miR-137 suppressed SLC1A5, resulting in decreased glutamine uptake and malondialdehyde (MDA) accumulation. Meanwhile, antagomir-mediated inactivation of endogenous miR-137 increased the sensitivity of melanoma cells to erastin- and RSL3-induced ferroptosis. Importantly, knockdown of miR-137 increased the antitumor activity of erastin by enhancing ferroptosis both in vitro and in vivo. Collectively, these data indicate that miR-137 plays a novel and indispensable role in ferroptosis by inhibiting glutaminolysis and suggest a potential therapeutic approach for melanoma.

Autophagy interaction with herpes simplex virus type-1 infection.

More than 50% of the U.S. population is infected with herpes simplex virus type-I (HSV-1) and global infectious estimates are nearly 90%. HSV-1 is normally seen as a harmless virus but debilitating diseases can arise, including encephalitis and ocular diseases. HSV-1 is unique in that it can undermine host defenses and establish lifelong infection in neurons. Viral reactivation from latency may allow HSV-1 to lay siege to the brain (Herpes encephalitis). Recent advances maintain that HSV-1 proteins act to suppress and/or control the lysosome-dependent degradation pathway of macroautophagy (hereafter autophagy) and consequently, in neurons, may be coupled with the advancement of HSV-1-associated pathogenesis. Furthermore, increasing evidence suggests that HSV-1 infection may constitute a gradual risk factor for neurodegenerative disorders. The relationship between HSV-1 infection and autophagy manipulation combined with neuropathogenesis may be intimately intertwined demanding further investigation.

Truncating mutation in the autophagy gene UVRAG confers oncogenic properties and chemosensitivity in colorectal cancers.

Autophagy-related factors are implicated in metabolic adaptation and cancer metastasis. However, the role of autophagy factors in cancer progression and their effect in treatment response remain largely elusive. Recent studies have shown that UVRAG, a key autophagic tumour suppressor, is mutated in common human cancers. Here we demonstrate that the cancer-related UVRAG frameshift (FS), which does not result in a null mutation, is expressed as a truncated UVRAG(FS) in colorectal cancer (CRC) with microsatellite instability (MSI), and promotes tumorigenesis. UVRAG(FS) abrogates the normal functions of UVRAG, including autophagy, in a dominant-negative manner. Furthermore, expression of UVRAG(FS) can trigger CRC metastatic spread through Rac1 activation and epithelial-to-mesenchymal transition, independently of autophagy. Interestingly, UVRAG(FS) expression renders cells more sensitive to standard chemotherapy regimen due to a DNA repair defect. These results identify UVRAG as a new MSI target gene and provide a mechanism for UVRAG participation in CRC pathogenesis and treatment response.

The intersection of Golgi-ER retrograde and autophagic trafficking.

For decades, a marvelous amount of work has been performed to identify molecules that regulate distinct stages of membrane transport in the ER-Golgi secretory pathway and autophagy, which are implicated in many human diseases. However, an important missing piece in this puzzle is how the cell dynamically coordinates these crisscrossed trafficking pathways in response to different stimuli. Our recent study has identified UVRAG as a mode-switching protein that coordinates Golgi-ER retrograde and autophagic trafficking. UVRAG recognizes phosphatidylinositol-3-phosphate (PtdIns3P) and locates to the ER, where it couples the ER tethering complex containing RINT1 to govern Golgi-ER retrograde transport. Intriguingly, when autophagy is induced, UVRAG undergoes a "partnering shift" from the ER tethering complex to the BECN1 autophagy complex, resulting in concomitant inhibition of Golgi-ER transport and the activation of ATG9 autophagic trafficking. Therefore, Golgi-ER retrograde and autophagy-related membrane trafficking are functionally interdependent and tightly regulated by UVRAG to ensure spatiotemporal fidelity of protein transport and organelle homeostasis, providing distinguished insights into trafficking-related diseases.

Viruses customize autophagy protein for efficient viral entry.

While the cell imposes multiple barriers to virus entry, enveloped viruses are remarkably still able to gain entry to their cellular hosts by hitchhiking and remodeling the endomembrane system to traffic within, and eventually escape from, endosomal organelles for their genome release. Elucidating viral entry mechanisms and their interaction with the host trafficking network is necessary for antiviral therapy. Here, we focus on the use of host autophagy molecular factors during the entry of prototypic negative-stranded RNA viruses, and highlight recent progress in our understanding of the role of one such factor, UVRAG, in both viral and cellular endocytic membrane trafficking and fusion events.