UV Radiation Resistance-associated Gene Research Articles

UVRAG cooperates with cargo receptors to assemble the ER-phagy site.

ER-phagy is a selective autophagy process that targets specific regions of the endoplasmic reticulum (ER) for removal via lysosomal degradation. During cellular stress induced by starvation, cargo receptors concentrate at distinct ER-phagy sites (ERPHS) to recruit core autophagy proteins and initiate ER-phagy. However, the molecular mechanism responsible for ERPHS formation remains unclear. In our study, we discovered that the autophagy regulator UV radiation Resistance-Associated Gene (UVRAG) plays a crucial role in orchestrating the assembly of ERPHS. Upon starvation, UVRAG localizes to ERPHS and interacts with specific ER-phagy cargo receptors, such as FAM134B, ATL3, and RTN3L. UVRAG regulates the oligomerization of cargo receptors and facilitates the recruitment of Atg8 family proteins. Consequently, UVRAG promotes efficient ERPHS assembly and turnover of both ER sheets and tubules. Importantly, UVRAG-mediated ER-phagy contributes to the clearance of pathogenic proinsulin aggregates. Remarkably, the involvement of UVRAG in ER-phagy initiation is independent of its canonical function as a subunit of class III phosphatidylinositol 3-kinase complex II.

Targeting WDxR motif reprograms immune microenvironment and inhibits hepatocellular carcinoma progression.

The WD-repeat (WDR) family affects carcinogenesis, but its role in the immune microenvironment is poorly characterized. Although functional loss or gain of WDR6 does not markedly change in vitro proliferative and invasive capacity of HCC cells, its deficiency in hepa1-6 cells drastically inhibits the growth and lung metastasis of orthotopically implanted tumors in immune-competent C57BL/6J mice. Mechanistically, WDR6 targets tumor suppressor UVRAG to the CUL4A-DDB1-ROC1 E3 ubiquitin ligase complex through a unique WDxR motif and promotes its degradation. This upregulates chromatin accessibility at the TNFα locus by blocking autophagic degradation of p65, elevates intratumoral myeloid-derived suppressor cell (MDSC) number, and reduces CD8+ T cell infiltration, thereby promoting HCC progression. These immunosuppressive effects are reversed by TNFα blockade. TNFα recruits NF-κB to activate the transcription of WDR6, establishing a WDR6-TNFα loop. Clinically, the WDR6/UVRAG/NF-κB pathway is hyperactivated in HCC, predicting a poor prognosis. Importantly, a WDxR-like peptide disrupts the WDR6/UVRAG complex and enhances the efficiency of anti-PD-L1 against HCC with WDR6 dysregulation.

Piceatannol enhances Beclin-1 activity to suppress tumor progression and its combination therapy strategy with everolimus in gastric cancer.

The effects and regulation of Beclin-1-an autophagy-related protein-have not been fully defined, however, a negative correlation has been reported between Beclin-1 expression and carcinogenesis. Meanwhile, no compound has been shown to directly inhibit its activity. Here, we evaluate piceatannol, a naturally occurring polyphenolic compound, as a potential targeting agonist of Beclin-1, to assess its efficacy as an antitumor agent against gastric cancer. More specifically, we determine the effects of piceatannol treatment on cell viability using a monitoring system and colony forming assay. Piceatannol was found to efficiently inhibit the proliferation of several human gastric cancer cell lines. Autophagic flux is increased by piceatannol treatment, and correlates with inhibition of cell proliferation and colony formation. Additionally, microscale thermophoresis and surface plasmon resonance results show a direct interaction between piceatannol and Beclin-1, which reduces the phosphorylation activity of Beclin-1 at the Ser-295 site. Notably, piceatannol impairs the binding of Beclin-1 to Bcl-2 and enhances the recruitment of binding of UV radiation resistance-associated gene protein, which further triggers Beclin-1-dependent autophagy signaling. An increase in autophagic activity via treatment with the mTOR inhibitor, everolimus, effectively sensitizes piceatannol-induced antitumor effects. Xenograft models confirmed that piceatannol inhibits tumor development and elicits a potent synergistic effect with everolimus in vivo. Taken together, the findings of this study strongly support the application of combinatorial piceatannol and everolimus therapy in future clinical trials for gastric cancer patients.

The Function of Autophagy as a Regulator of Melanin Homeostasis.

Melanosomes are melanocyte-specific organelles that protect cells from ultraviolet (UV)-induced deoxyribonucleic acid damage through the production and accumulation of melanin and are transferred from melanocytes to keratinocytes. The relatively well-known process by which melanin is synthesized from melanocytes is known as melanogenesis. The relationship between melanogenesis and autophagy is attracting the attention of researchers because proteins associated with autophagy, such as WD repeat domain phosphoinositide-interacting protein 1, microtubule-associated protein 1 light chain 3, autophagy-related (ATG)7, ATG4, beclin-1, and UV-radiation resistance-associated gene, contribute to the melanogenesis signaling pathway. Additionally, there are reports that some compounds used as whitening cosmetics materials induce skin depigmentation through autophagy. Thus, the possibility that autophagy is involved in the removal of melanin has been suggested. To date, however, there is a lack of data on melanosome autophagy and its underlying mechanism. This review highlights the importance of autophagy in melanin homeostasis by providing an overview of melanogenesis, autophagy, the autophagy machinery involved in melanogenesis, and natural compounds that induce autophagy-mediated depigmentation.

Distinct roles of UVRAG and EGFR signaling in skeletal muscle homeostasis

ObjectiveAutophagy is a physiological self-eating process that can promote cell survival or activate cell death in eukaryotic cells. In skeletal muscle, it is important for maintaining muscle mass and function that is critical to sustain mobility and regulate metabolism. The UV radiation resistance-associated gene (UVRAG) regulates the early stages of autophagy and autophagosome maturation and plays a key role in endosomal trafficking. This study investigated the essential in vivo role of UVRAG in skeletal muscle biology. MethodsTo determine the role of UVRAG in skeletal muscle in vivo, we generated muscle-specific UVRAG knockout mice using the Cre-loxP system driven by Myf6 promoter that is exclusively expressed in skeletal muscle. Myf6-Cre+ UVRAGfl/fl (M-UVRAG−/−) mice were compared to littermate Myf6-Cre+ UVRAG+/+ (M-UVRAG+/+) controls under basal conditions on a normal chow diet. Body composition, muscle function, and mitochondria morphology were assessed in muscles of the WT and KO mice at 24 weeks of age. ResultsM-UVRAG−/− mice developed accelerated sarcopenia and impaired muscle function compared to M-UVRAG+/+ littermates at 24 weeks of age. Interestingly, these mice displayed improved glucose tolerance and increased energy expenditure likely related to upregulated Fgf21, a marker of muscle dysfunction. Skeletal muscle of the M-UVRAG−/− mice showed altered mitochondrial morphology with increased mitochondrial fission and EGFR accumulation reflecting defects in endosomal trafficking. To determine whether increased EGFR signaling had a causal role in muscle dysfunction, the mice were treated with an EGFR inhibitor, gefitinib, which partially restored markers of muscle and mitochondrial deregulation. Conversely, constitutively active EGFR transgenic expression in UVRAG-deficient muscle led to further detrimental effects with non-overlapping distinct defects in muscle function, with EGFR activation affecting the muscle fiber type whereas UVRAG deficiency impaired mitochondrial homeostasis. ConclusionsOur results show that both UVRAG and EGFR signaling are critical for maintaining muscle mass and function with distinct mechanisms in the differentiation pathway.

UV radiation resistance-associated gene (UVRAG) promotes cell proliferation, migration, invasion by regulating cyclin-dependent kinases (CDK) and integrin-β/Src signaling in breast cancer cells.

Breast cancer is a highly heterogeneous group of human cancer with distinct genetic, biological and clinicopathological features. Triple-negative breast cancer (TNBC) is the most aggressive and metastatic type of breast cancer and associated with poor patient survival. However, the role of UV Radiation Resistance-Associated Gene (UVRAG) in TNBC remains unknown. Here, we report that UVRAG is highly upregulated in all TNBC cells and its knockdown leads to the inhibition of cell proliferation, colony formation and progression of cell cycle, which is associated with and reduced expression of cell cycle related protein expression, including Cyclin A2, B1, D1, cdc2 and cdk6 in TNBC cells. Inhibition of UVRAG also suppressed cell motility, migration and invasion of TNBC cells by inhibition of Integrin β1 and β3 and Src activity. Our findings suggest for the first time that UVRAG expression contributes to proliferation, cell cycle progression, motility/migration and invasion of TNBC cells. Thus, targeting UVRAG could be a potential strategy in breast cancer especially against TNBC.

Filoviruses Use the HOPS Complex and UVRAG To Traffic to Niemann-Pick C1 Compartments during Viral Entry.

Ebola virus (EBOV) entry requires internalization into host cells and extensive trafficking through the endolysosomal network in order to reach late endosomal/lysosomal compartments that contain triggering factors for viral membrane fusion. These triggering factors include low-pH-activated cellular cathepsin proteases, which cleave the EBOV glycoprotein (GP), exposing a domain which binds to the filoviral receptor, the cholesterol transporter Niemann-Pick C1 (NPC1). Here, we report that trafficking of EBOV to NPC1 requires expression of the homotypic fusion and protein sorting (HOPS) tethering complex as well as its regulator, UV radiation resistance-associated gene (UVRAG). Using an inducible clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 system, we demonstrated that depletion of HOPS subunits as well as UVRAG impairs entry by all pathogenic filoviruses. UVRAG depletion resulted in reduced delivery of EBOV virions to NPC1+ cellular compartments. Furthermore, we show that deletion of a domain on UVRAG known to be required for interaction with the HOPS complex results in impaired EBOV entry. Taken together, our studies demonstrate that EBOV requires both expression of and coordination between the HOPS complex and UVRAG in order to mediate efficient viral entry.IMPORTANCE Ebola viruses (EBOV) and other filoviruses cause sporadic and unpredictable outbreaks of highly lethal diseases. The lack of FDA-approved therapeutics, particularly ones with panfiloviral specificity, highlights the need for continued research efforts to understand aspects of the viral life cycle that are common to all filoviruses. As such, viral entry is of particular interest, as all filoviruses must reach cellular compartments containing the viral receptor Niemann-Pick C1 to enter cells. Here, we present an inducible CRISPR/Cas9 method to rapidly and efficiently generate knockout cells in order to interrogate the roles of a broad range of host factors in viral entry. Using this approach, we showed that EBOV entry depends on both the homotypic fusion and protein sorting (HOPS) tethering complex in coordination with UV radiation resistance-associated gene (UVRAG). Importantly, we demonstrate that the HOPS complex and UVRAG are required by all pathogenic filoviruses, representing potential targets for panfiloviral therapeutics.

1880-P: Distinct Roles of UVRAG and EGFR Signaling in Skeletal Muscle Homeostasis

Background: Autophagy is a physiological self-eating process that can promote cell survival or activate cell death in eukaryotic cells. In skeletal muscle, it is important in the maintenance of muscle mass and function that is critical to sustain mobility and regulate metabolism. UV radiation resistance-associated gene (UVRAG) regulates early stages of autophagy and autophagosome maturation, while also playing a key role in endosomal trafficking. Methods: To determine the role of UVRAG in skeletal muscle in vivo, we generated muscle specific UVRAG knock-out mice using the cre-loxP system driven by Myf6 promoter that is exclusively expressed in skeletal muscle. Results: Myf6 Cre+ UVRAGfl/fl (KO) mice were compared to littermate Myf6 Cre+ UVRAG+/+ (WT) controls under basal (normal chow diet) and HFD (high-fat diet) conditions. KO mice developed accelerated sarcopenia and impaired muscle function compared to WT littermates with aging on chow diet or on HFD. Interestingly, these mice displayed improved glucose tolerance and increased energy expenditure likely related to up-regulated FGF-21, a marker of muscle dysfunction. KO mice showed mitochondrial dysfunction, altered muscle mitochondrial morphology with increased mitochondrial fission, as well as EGFR accumulation reflecting defects in endosomal trafficking. To determine whether increased EGFR signaling had a causal role in muscle dysfunction, mice were treated with an EGFR inhibitor, Gefitinib, which partially restored markers of muscle and mitochondrial dysfunction. Conversely, constitutively active EGFR transgenic expression in UVRAG deficient muscle led to further detrimental effects with non-overlapping distinct defects in muscle function, with EGFR activation affecting muscle fiber type whereas UVRAG deficiency impaired mitochondrial homeostasis. Conclusions: UVRAG and EGFR signaling together are critical in the maintenance of muscle mass and function with distinct mechanisms in the differentiation pathway. Disclosure M. Kim: None. D. Febbraro: None. M. Woo: None. Funding Canadian Institutes of Health Research; Kangbuk Samsung Hospital; Banting & Best Diabetes Centre

Crosstalk between Autophagy and Nanomaterials: Internalization, Activation, Termination.

Nanomaterials (NMs) are comprehensively applied in biomedicine due to their unique physical and chemical properties. Autophagy, as an evolutionarily conserved cellular quality control process, is closely associated with the effect of NMs on cells. In this review, the recent advances in NM-induced/inhibited autophagy (NM-phagy) are summarized, with an aim to present a comprehensive description of the mechanisms of NM-phagy from the perspective of internalization, activation, and termination, thereby bridging autophagy and nanomaterials. Several possible mechanisms are extensively reviewed including the endocytosis pathway of NMs and the related cross components (clathrin and adaptor protein 2 (AP-2), adenosine diphosphate (ADP)-ribosylation factor 6 (Arf6), Rab, UV radiation resistance associated gene (UVRAG)), three main stress mechanisms (oxidative stress, damaged organelles stress, and toxicity stress), and several signal pathway-related molecules. The mechanistic insight is beneficial to understand the autophagic response to NMs or NMs' regulation of autophagy. The challenges currently encountered and research trend in the field of NM-phagy are also highlighted. It is hoped that the NM-phagy discussion in this review with the focus on the mechanistic aspects may serve as a guideline for future research in this field.

The Arabidopsis USL1 controls multiple aspects of development by affecting late endosome morphology.

Summary The polar transport of auxin controls many aspects of plant development. However, the molecular mechanisms underlying auxin tranport regulation remain to be further elucidated.We identified a mutant named as usl1 (unflattened and small leaves) in a genetic screen in Arabidopsis thaliana. The usl1 displayed multiple aspects of developmental defects in leaves, embryogenesis, cotyledons, silique phyllotaxy and lateral roots in addition to abnormal leaves. USL1 encodes a protein orthologous to the yeast vacuolar protein sorting (Vps) 38p and human UV RADIATION RESISTANCE‐ASSOCIATED GENE (UVRAG). Cell biology, Co‐IP/MS and yeast two‐hybrid were used to identify the function of USL1.USL1 colocalizes at the subcellular level with VPS29, a key factor of the retromer complex that controls auxin transport. The morphology of the VPS29‐associated late endosomes (LE) is altered from small dots in the wild‐type to aberrant enlarged circles in the usl1 mutants. The usl1 mutant synergistically interacts with vps29. We also found that USL1 forms a complex with AtVPS30 and AtVPS34.We propose that USL1 controls multiple aspects of plant development by affecting late endosome morphology and by regulating the PIN1 polarity. Our findings provide a new layer of the understanding on the mechanisms of plant development regulation.

MiR-125b is downregulated in systemic lupus erythematosus patients and inhibits autophagy by targeting UVRAG

Systemic lupus erythematosus (SLE) is a severe autoimmune disease and the pathogenesis remains incompletely understood. This study aimed to investigate the role of miR-125b in the pathogenesis of SLE and explore the underlying mechanism. Compared to healthy controls, the expression of miR-125b decreased in peripheral blood mononuclear cells (PBMCs) of SLE patients. In addition, PBMCs exposed to ultraviolet B had lower miR-125b level compared to those unexposed to radiation. We identified UV radiation resistance associated gene (UVRAG) as a target of miR-125b. Jurkat cells treated with miR-125b-5p agomir showed reduced levels of ATG7, Beclin-1 and LC3 II and decreased autophagy. In contrast, Jurkat cells treated with miR-125b-5p antagomir showed increased levels of ATG7, Beclin-1 and LC3 II and increased autophagy. Furthermore, Jurkat cells transfected with UVRAG expression vector showed higher expression of ATG7, Beclin-1 and LC3 II and increased autophagy. Conversely, cells transfected with UVRAG siRNA had lower expression of ATG7, Beclin-1 and LC3 II and decreased autophagy. Taken together, our data demonstrate that Ultraviolet B radiation can downregulate miR-125b-5p and increase UVRAG expression and autophagy activity in PBMCs of SLE patients. These findings help explain how ultraviolet B exacerbates SLE and suggest that UVRAG is a potential therapeutic target for SLE.

Vacuolar Trafficking Protein VPS38 Is Dispensable for Autophagy.

Phosphatidylinositol 3-P (PI3P) is a signaling molecule that controls a variety of processes in endosomal, autophagic, and vacuolar/lysosomal trafficking in yeasts and mammals. Vacuolar protein sorting 34 (Vps34) is a conserved PI3K present in multiple complexes with specific functions and regulation. In yeast, the PI3K complex II consists of Vps34p, Vps15p, Vps30p/Atg6p, and Vps38p, and is essential for vacuolar protein sorting. Here, we describe the Arabidopsis (Arabidopsis thaliana) homolog of yeast Vps38p and human UV radiation resistance-associated gene protein. Arabidopsis VPS38 interacts with VPS30/ATG6 both in yeast and in planta. Although the level of PI3P in Arabidopsis vps38 mutants is similar to that in wild type, vps38 cells contain enlarged multivesicular endosomes and fewer organelles enriched in PI3P than the wild type. The vps38 mutants are defective in the trafficking of vacuolar cargo and its receptor VACUOLAR SORTING RECEPTOR2;1. The mutants also exhibit abnormal cytoplasmic distributions of endocytic cargo, such as auxin efflux carriers PINFORMED1 (PIN1) and PIN2. Constitutive autophagy is normal in the mutants but starvation-induced autophagy was slightly inhibited. We conclude that Arabidopsis VPS38 is dispensable for autophagy but essential for efficient targeting of biosynthetic and endocytic cargo to the vacuole.

MTORC1 hyperactivation arrests bone growth in lysosomal storage disorders by suppressing autophagy.

The mammalian target of rapamycin complex 1 (mTORC1) kinase promotes cell growth by activating biosynthetic pathways and suppressing catabolic pathways, particularly that of macroautophagy. A prerequisite for mTORC1 activation is its translocation to the lysosomal surface. Deregulation of mTORC1 has been associated with the pathogenesis of several diseases, but its role in skeletal disorders is largely unknown. Here, we show that enhanced mTORC1 signaling arrests bone growth in lysosomal storage disorders (LSDs). We found that lysosomal dysfunction induces a constitutive lysosomal association and consequent activation of mTORC1 in chondrocytes, the cells devoted to bone elongation. mTORC1 hyperphosphorylates the protein UV radiation resistance-associated gene (UVRAG), reducing the activity of the associated Beclin 1-Vps34 complex and thereby inhibiting phosphoinositide production. Limiting phosphoinositide production leads to a blockage of the autophagy flux in LSD chondrocytes. As a consequence, LSD chondrocytes fail to properly secrete collagens, the main components of the cartilage extracellular matrix. In mouse models of LSD, normalization of mTORC1 signaling or stimulation of the Beclin 1-Vps34-UVRAG complex rescued the autophagy flux, restored collagen levels in cartilage, and ameliorated the bone phenotype. Taken together, these data unveil a role for mTORC1 and autophagy in the pathogenesis of skeletal disorders and suggest potential therapeutic approaches for the treatment of LSDs.

Krüpple-like factor 10 regulates radio-sensitivity of pancreatic cancer via UV radiation resistance-associated gene

Background and purposeKrüpple-like factor 10 (Klf10), an early response gene of TGFβ, was reported to be a prognostic biomarker for pancreatic cancer survival. The role of Klf10 in predicting tumor response to cancer treatment is unknown. Materials and methodsGenetically manipulated MiaPaCa and Panc-1 cells were established to evaluate clonogenic survival, autophagy, apoptosis and DNA repair after radiation. The interaction between Klf10 and UV radiation resistance-associated gene (UVRAG) was demonstrated by ChiP-PCR and luciferase reporter assay. Orthotopic murine tumor model and clinical specimens were used to evaluate radio-sensitivity of pancreatic cancer. ResultsWe found Klf10 silencing correlates with enhanced pancreatic cancer clonogenic survival and murine tumor growth after radiation. UVRAG was an essential down-stream mediator transcriptionally suppressed by Klf10. Silencing UVRAG mRNA in Klf10 depleted Panc-1 cells reversed the radio-resistant phenotypes including decreased apoptosis and enhanced DNA repair as well as autophagy. Metformin, an anti-diabetic agent, was found to increase Klf10 and suppress UVRAG expression to improve radiation cytotoxicity in pancreatic cancer. The predictive value of Klf10 in radiation response and the inverse correlation with UVRAG were confirmed in cohorts of pancreatic cancer patients. ConclusionsKlf10 is a potential biomarker in predicting and sensitizing radiation effect in pancreatic cancer.

Effects Of Oral Glutamine on Inflammatory and Autophagy Responses in Cancer Patients Treated With Abdominal Radiotherapy: A Pilot Randomized Trial.

Background and Aims: Abdominal radiotherapy (RT) causes harm to the mid gastrointestinal mucosa by release of pro-inflammatory cytokines and promotes autophagic changes in tumor cells. This study was aimed to measure the effect of glutamine administration on markers of inflammation and autophagy in cancer patients treated with RT.Methods: In this double-blind, randomized, controlled pilot trial 43 patients under abdominal RT diagnosed of pelvic or abdominal malignancies receiving glutamine (30 g/d) or placebo (casein, 30 g/d). Patient recruitment took place in the Complejo Asistencial Universitario of León (CAULE), Spain. Patient evaluation took place at three different time points during the study: before RT (pre-treatment), in the middle of the RT period (mid-treatment), and after finishing RT (post-treatment). Data were compared by analysis of variance and the Newmann Keuls test. Significance was accepted at p < 0.05.Results Abdominal RT increased whole blood mRNA levels of inflammatory and autophagic markers, but glutamine administration showed significantly lower expression of toll-like receptor 4 (TLR4), CD36, interleukin-1β (IL-1β), tumor necrosis factor-alpha (TNF-α), cyclooxygenase-2 (COX-2), and matrix metalloproteinase-9 (MMP-9). Moreover, glutamine reduced the expression of the transcription factors nuclear factor kappa B (NF-κB) and activator protein 1 (AP-1). Glutamine also inhibited the autophagic response, with changes in expression of beclin-1, UV radiation resistance associated gene (UVRAG), autophagy-related protein-5 (Atg5), protein 1 light chain 3 (LC3), sequestosome 1 (p62/SQSTM1) and lysosome-associated membrane protein (LAMP)-1.Conclusions Findings provide evidence that glutamine decreases the inflammatory response and abolishes the changes of the autophagy machinery in patients receiving abdominal RT. The protective effect of glutamine must continue being investigated to disclose further molecular pathways.

Downregulation of ASPP2 improves hepatocellular carcinoma cells survival via promoting BECN1-dependent autophagy initiation.

Autophagy is an important catabolic process, which sustains intracellular homeostasis and lengthens cell survival under stress. Here we identify the ankyrin-repeat-containing, SH3-domain-containing, and proline-rich region-containing protein 2 (ASPP2), a haploinsufficient tumor suppressor, as a molecular regulator of starvation-induced autophagy in hepatocellular carcinoma (HCC). ASPP2 expression is associated with an autophagic response upon nutrient deprivation and downregulation of ASPP2 facilitates autophagic flux, whereas overexpression of ASPP2 blocks this starvation-induced autophagy in HCC cells. Mechanistically, ASPP2 inhibits autophagy through regulating BECN1 transcription and formation of phosphatidylinositol 3-kinase catalytic subunit type 3 (PIK3C3) complex. Firstly, ASPP2 inhibits p65/RelA-induced transcription of BECN1, directly by an ASPP2-p65/RelA-IκBα complex which inhibits phosphorylation of IκBα and the translocation of p65/RelA into the nucleus. Secondly, ASPP2 binds to BECN1, leading to decreased binding of PIK3C3 and UV radiation resistance-associated gene (UVRAG), and increased binding of Rubicon in PIK3C3 complex. Downregulation of ASPP2 enhances the pro-survival and chemoresistant property via autophagy in HCC cells in vitro and in vivo. Decreased ASPP2 expression was associated with increased BECN1 and poor survival in HCC patients. Therefore, ASPP2 is a key regulator of BECN1-dependent autophagy, and decreased ASPP2 may contribute to tumor progression and chemoresistance via promoting autophagy.

Multistep regulation of autophagy by WNK1

The with-no-lysine (K) (WNK) kinases are an atypical family of protein kinases that regulate ion transport across cell membranes. Mutations that result in their overexpression cause hypertension-related disorders in humans. Of the four mammalian WNKs, only WNK1 is expressed throughout the body. We report that WNK1 inhibits autophagy, an intracellular degradation pathway implicated in several human diseases. Using small-interfering RNA-mediated WNK1 knockdown, we show autophagosome formation and autophagic flux are accelerated. In cells with reduced WNK1, basal and starvation-induced autophagy is increased. We also show that depletion of WNK1 stimulates focal class III phosphatidylinositol 3-kinase complex (PI3KC3) activity, which is required to induce autophagy. Depletion of WNK1 increases the expression of the PI3KC3 upstream regulator unc-51-like kinase 1 (ULK1), its phosphorylation, and activation of the kinase upstream of ULK1, the AMP-activated protein kinase. In addition, we show that the N-terminal region of WNK1 binds to the UV radiation resistance-associated gene (UVRAG) in vitro and WNK1 partially colocalizes with UVRAG, a component of a PI3KC3 complex. This colocalization decreases upon starvation of cells. Depletion of the SPS/STE20-related proline-alanine-rich kinase, a WNK1-activated enzyme, also induces autophagy in nutrient-replete or -starved conditions, but depletion of the related kinase and WNK1 substrate, oxidative stress responsive 1, does not. These results indicate that WNK1 inhibits autophagy by multiple mechanisms.

Downregulation of autophagy gene expression in endometria from women with polycystic ovary syndrome

Autophagy, a process of controlled cellular self-digestion, could be involved in cyclic remodeling of the human endometrium. We investigated endometrial mRNA expression of 23 autophagy-related (ATG) genes and transcription factors in healthy controls (n = 12) and anovulatory polycystic ovary syndrome (PCOS) patients (n = 24), as well as in their subgroup (n = 12) before and after metformin treatment. The mRNA levels of transcription factor forkhead box protein O1 (FOXO1) and several molecules involved in autophagosome formation (ATG13, RB1-inducible coiled-coil 1), autophagosome nucleation (ATG14, beclin 1, SH3-domain GRB2-like endophilin B1), autophagosome elongation (ATG3, ATG5, γ-aminobutyric acid receptor-associated protein - GABARAP), and delivery of ubiquitinated proteins to autophagosomes (sequestosome 1), were significantly reduced in anovulatory PCOS compared to healthy endometrium. Free androgen index, but not free estrogen index, insulin levels, or body mass index, negatively correlated with the endometrial expression of ATG3, ATG14, and GABARAP in PCOS patients. Treatment of PCOS patients with metformin (2 g/day for 3 months) significantly increased the endometrial mRNA levels of FOXO1, ATG3, and UV radiation resistance-associated gene. These data suggest that increased androgen availability in PCOS is associated with metformin-sensitive transcriptional downregulation of endometrial autophagy.

Autophagic UVRAG Promotes UV-Induced Photolesion Repair by Activation of the CRL4DDB2 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 toXPC 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.

MicroRNA-125a Inhibits Autophagy Activation and Antimicrobial Responses during Mycobacterial Infection.

MicroRNAs (miRNAs) are small noncoding nucleotides that play critical roles in the regulation of diverse biological functions, including the response of host immune cells. Autophagy plays a key role in activating the antimicrobial host defense against Mycobacterium tuberculosis. Although the pathways associated with autophagy must be tightly regulated at a posttranscriptional level, the contribution of miRNAs and whether they specifically influence the activation of macrophage autophagy during M. tuberculosis infection are largely unknown. In this study, we demonstrate that M. tuberculosis infection of macrophages leads to increased expression of miRNA-125a-3p (miR-125a), which targets UV radiation resistance-associated gene (UVRAG), to inhibit autophagy activation and antimicrobial responses to M. tuberculosis. Forced expression of miR-125a significantly blocked M. tuberculosis-induced activation of autophagy and phagosomal maturation in macrophages, and inhibitors of miR-125a counteracted these effects. Both TLR2 and MyD88 were required for biogenesis of miR-125a during M. tuberculosis infection. Notably, activation of the AMP-activated protein kinase significantly inhibited the expression of miR-125a in M. tuberculosis-infected macrophages. Moreover, either overexpression of miR-125a or silencing of UVRAG significantly attenuated the antimicrobial effects of macrophages against M. tuberculosis. Taken together, these data indicate that miR-125a regulates the innate host defense by inhibiting the activation of autophagy and antimicrobial effects against M. tuberculosis through targeting UVRAG.