Neighbor Of BRCA1 Gene 1 Research Articles

Opposing regulation of the STING pathway in hepatic stellate cells by NBR1 and p62 determines the progression of hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) emerges from chronic inflammation, to which activation of hepatic stellate cells (HSCs) contributes by shaping a pro-tumorigenic microenvironment. Key to this process is p62, whose inactivation leads to enhanced hepatocarcinogenesis. Here, we show that p62 activates the interferon (IFN) cascade by promoting STING ubiquitination by tripartite motif protein 32 (TRIM32) in HSCs. p62, binding neighbor of BRCA1 gene 1 (NBR1) and STING, triggers the IFN cascade by displacing NBR1, which normally prevents the interaction of TRIM32 with STING and its subsequent activation. Furthermore, NBR1 also antagonizes STING by promoting its trafficking to the endosome-lysosomal compartment for degradation independent of autophagy. Of functional relevance, NBR1 deletion completely reverts the tumor-promoting function of p62-deficient HSCs by rescuing the inhibited STING-IFN pathway, thus enhancing anti-tumor responses mediated by CD8+ Tcells. Therefore, NBR1 emerges as a synthetic vulnerability of p62 deficiency in HSCs by promoting the STING/IFN pathway, which boosts anti-tumor CD8+ Tcell responses to restrain HCC progression.

Hypoxia-Induced Long Noncoding RNA HIF1A-AS2 Regulates Stability of MHC Class I Protein in Head and Neck Cancer.

Intratumoral hypoxia not only promotes angiogenesis and invasiveness of cancer cells but also creates an immunosuppressive microenvironment that facilitates tumor progression. However, the mechanisms by which hypoxic tumor cells disseminate immunosuppressive signals remain unclear. In this study, we demonstrate that a hypoxia-induced long noncoding RNA HIF1A Antisense RNA 2 (HIF1A-AS2) is upregulated in hypoxic tumor cells and hypoxic tumor-derived exosomes in head and neck squamous cell carcinoma (HNSCC). Hypoxia-inducible factor 1 alpha (HIF1α) was found to directly bind to the regulatory region of HIF1A-AS2 to enhance its expression. HIF1A-AS2 reduced the protein stability of major histocompatibility complex class I (MHC-I) by promoting the interaction between the autophagy cargo receptor neighbor of BRCA1 gene 1 (NBR1) protein and MHC-I, thereby increasing the autophagic degradation of MHC-I. In HNSCC samples, the expression of HIF1A-AS2 was found to correlate with hypoxic signatures and advanced clinical stages. Patients with high HIF1α and low HLA-ABC expression showed reduced infiltration of CD8+ T cells. These findings define a mechanism of hypoxia-mediated immune evasion in HNSCC through downregulation of antigen-presenting machinery via intracellular or externalized hypoxia-induced long noncoding RNA.

LLPS of SQSTM1/p62 and NBR1 as outcomes of lysosomal stress response limits cancer cell metastasis.

Liquid droplet has emerged as a flexible intracellular compartment that modulates various cellular processes. Here, we uncover an antimetastatic mechanism governed by the liquid droplets formed through liquid-liquid phase separation (LLPS) of SQSTM1/p62 and neighbor of BRCA1 gene 1 (NBR1). Some of the tyrosine kinase inhibitors (TKIs) initiated lysosomal stress response that promotes the LLPS of p62 and NBR1, resulting in the spreading of p62/NBR1 liquid droplets. Interestingly, in the p62/NBR1 liquid droplet, degradation of RAS-related C3 botulinum toxin substrate 1 was accelerated by cellular inhibitor of apoptosis protein 1, which limits cancer cell motility. Moreover, the antimetastatic activity of the TKIs was completely overridden in p62/NBR1 double knockout cells both in vitro and in vivo. Thus, our results demonstrate a function of the p62/NBR1 liquid droplet as a critical determinant of cancer cell behavior, which may provide insight into both the clinical and biological significance of LLPS.

Salicylic acid accelerates carbon starvation-induced leaf senescence in Arabidopsis thaliana by inhibiting autophagy through Nonexpressor of pathogenesis-related genes 1

In plants, leaf senescence is regulated by several factors, including age and carbon starvation. The molecular mechanism of age-regulated developmental leaf senescence differs from that of carbon starvation-induced senescence. Salicylic acid (SA) and Nonexpressor of pathogenesis-related genes 1 (NPR1) play important roles in promoting developmental leaf senescence. However, the relationship between SA signaling and carbon starvation-induced leaf senescence is not currently well understood. Here, we used Arabidopsis thaliana as material and found that carbon starvation-induced leaf senescence was accelerated in the SA dihydroxylase mutants s3hs5h compared to the Columbia ecotype (Col). Exogenous SA treatment significantly promoted carbon starvation-induced leaf senescence, especially in NPR1-GFP. Increasing the endogenous SA and overexpression of NPR1 inhibited carbon starvation-induced autophagy. However, mutation of NPR1 delayed carbon starvation-induced leaf senescence, increased autophagosome production and accelerated autophagic degradation of the Neighbor of BRCA1 gene 1 (NBR1). In conclusion, SA promotes carbon starvation-induced leaf senescence by inhibiting autophagy via NPR1.

Chloroquine is a safe autophagy inhibitor for sustaining the expression of antioxidant enzymes in trophoblasts

Inhibition of autophagy contributes to the pathophysiology of preeclampsia. Although chloroquine (CHQ) is an autophagy inhibitor, it can reduce the occurrence of preeclampsia in women with systemic lupus erythematosus. To clarify this important clinical question, this study aimed to address the safety of CHQ in trophoblast cells from the viewpoint of homeostasis, in which the anti-oxidative stress (OS) response and autophagy are involved. We used Western blotting to evaluate the protein levels in the trophoblast cells. The expression levels of heme oxygenase-1 (HO-1), an anti-OS enzyme, mediate resistance to OS induced by hydrogen peroxide (H2O2) in trophoblast cell lines. Among the autophagy modulators, bafilomycin A1 (BAF), an autophagy inhibitor, but not autophagy activators, suppressed HO-1 expression in BeWo cells; CHQ did not suppress HO-1 expression in BeWo cells. To clarify the role of autophagy in HO-1 induction, we observed no difference in HO-1 induction by H2O2 between autophagy-normal and autophagy-deficient cells. As for the mechanism of HO-1 induction by OS, BAF suppressed HO-1 induction by downregulating the expression of neighbor of BRCA1 gene 1 (NBR1) in the selective p62-NBR1-nuclear factor erythroid 2-related factor 2 (Nrf2) autophagy pathway. CHQ did not inhibit HO-1 expression by sustaining NBR1 expression in human villous tissues compared to BAF treatment. In conclusion, CHQ is a safer medicine than BAF for sustaining NBR1, which resist against OS in trophoblasts by connecting selective autophagy and the anti-OS response.

RORα Enhances Lysosomal Acidification and Autophagic Flux in the Hepatocytes

Lysosomes are intracellular acidic organelles with catabolic functions that contribute to the activation of autophagy. Although autophagy abnormality is associated with defects in lysosomal acidification during the progression of nonalcoholic fatty liver disease (NAFLD), the mechanisms of control of lysosomal acidification are not well understood at the molecular level. Thus, we aimed to elucidate the role of the orphan nuclear receptor retinoic acid–related orphan receptor α (RORα) in lysosomal acidification and autophagic flux, particularly in nutrition‐enriched hepatocytes. First, lysosomal acidity was much lower in the hepatocytes obtained from hepatocyte‐specific RORα‐deleted (RORα‐LKO) mice, whereas the infusion of an adenovirus encoding RORα in wild‐type hepatocytes increased lysosomal acidity, as determined by LysoSensor. Second, the lysosomal translocation of the mechanistic target of rapamycin was increased and immature cathepsin D was accumulated in the liver of RORα‐LKO mice. Third, the accumulation of LC3‐II, p62/sequestosome 1 (SQSTM1), and neighbor of BRCA1 gene 1 (NBR1) was increased in the livers of RORα‐LKO mice, indicating an impaired autophagic flux in the livers. Consistently, the number of autolysosomes containing mitochondria and lipid droplets was dramatically reduced in the RORα‐deleted hepatocytes. Finally, we found that RORα induced the transcription of genes involved in lysosomal function, such as Atp6v1g1, a vacuolar H+‐ATPase (v‐ATPase) subunit, which were largely down‐regulated in the livers of mice with high‐fat diet–induced NAFLD and patients with hepatitis. Conclusion: Targeting RORα may be a potential therapeutic strategy to restore lysosomal acidification, which inhibits the progression of NAFLD.

Germline mutation in the NBR1 gene involved in autophagy detected in a family with renal tumors

Hereditary Renal Cell Carcinomas (RCC) are caused by mutations in predisposing genes, the major ones including VHL, FLCN, FH and MET. However, many families with inherited RCC have no germline mutation in these genes. Using Whole Exome Sequencing on germline DNA from a family presenting three different histological renal tumors (an angiomyolipoma, a clear-cell RCC and an oncocytic papillary RCC), we identified a frameshift mutation in the Neighbor of BRCA1 gene 1 (NBR1), segregating with the tumors. NBR1 encodes a cargo receptor protein involved in autophagy. Genetic and functional analyses suggested a pathogenic impact of the mutation. Indeed, functional study performed in renal cell lines showed that the mutation alters NBR1 interactions with some of its partners (such as p62/SQSTM1), leading to a dominant negative effect. This results in an altered autophagic process and an increased proliferative capacity in renal cell lines. Our study suggests that NBR1 may be a new predisposing gene for RCC, however its characterization needs to be further investigated in order to confirm its role in renal carcinogenesis.

Membrane Contact Sites and Organelles Interaction in Plant Autophagy.

Autophagy is an intracellular trafficking and degradation system for recycling of damaged organelles, mis-folded proteins and cytoplasmic constituents. Autophagy can be divided into non-selective autophagy and selective autophagy according to the cargo specification. Key to the process is the timely formation of the autophagosome, a double-membrane structure which is responsible for the delivery of damaged organelles and proteins to lysosomes or vacuoles for their turnover. Autophagosomes are formed by the closure of cup-shaped phagophore which depends on the proper communication with membrane contributors. The endoplasmic reticulum (ER) is a major membrane source for autophagosome biogenesis whereby the ER connects with phagophore through membrane contact sites (MCSs). MCSs are closely apposed domains between organelle membranes where lipids and signals are exchanged. Lipid transfer proteins (LTPs) are a large family of proteins including Oxysterol-binding protein related proteins (ORP) which can be found at MCSs and mediate lipid transfer in mammals and yeast. In addition, interaction between autophagosomes and other organelles can also be detected in selective autophagy for selection and degradation of various damaged organelles. Selective autophagy is mediated by the binding of a receptor or an adaptor between a cargo and an autophagosome. Here we summarize what we know about the MCS between autophagosomes and other organelles in eukaryotes. We then discuss progress in our understanding about ORPs at MCSs in plants and the underlying mechanisms of selective autophagy in plants with a focus on receptors/adaptors that are involved in the interaction of the autophagosome with other cytoplasmic constituents, including the Neighbor of BRCA1 gene 1 (NBR1), ATG8-interacting protein 1 (ATI1), Regulatory Particle Non-ATPase 10 (RPN10), and Dominant Suppressor of KAR2 (DSK2).

NBR1-mediated p62-liquid droplets enhance the Keap1-Nrf2 system.

p62/SQSTM1 is a multivalent protein that has the ability to cause liquid-liquid phase separation and serves as a receptor protein that participates in cargo isolation during selective autophagy. This protein is also involved in the non-canonical activation of the Keap1-Nrf2 system, a major oxidative stress response pathway. Here, we show a role of neighbor of BRCA1 gene 1 (NBR1), an autophagy receptor structurally similar to p62/SQSTM1, in p62-liquid droplet formation and Keap1-Nrf2 pathway activation. Overexpression of NBR1 blocks selective degradation of p62/SQSTM1 through autophagy and promotes the accumulation and phosphorylation of p62/SQSTM1 in liquid-like bodies, which is required for the activation of Nrf2. NBR1 is induced in response to oxidative stress, which triggers p62-mediated Nrf2 activation. Conversely, loss of Nbr1 suppresses not only the formation of p62/SQSTM1-liquid droplets, but also of p62-dependent Nrf2 activation during oxidative stress. Taken together, our results show that NBR1 mediates p62/SQSTM1-liquid droplet formation to activate the Keap1-Nrf2 pathway.

305 Putative phenotype modifying genetic factors associated with phenotypic diversity in Brooke-Spiegler syndrome

Brooke-Spiegler syndrome (BSS; OMIM 605041) is a rare monogenic skin disease characterized by the development of skin appendage tumors caused by mutations in the cylindromatosis gene (CYLD). Concerning the so far reported phenotypes and the underlying CYLD mutations, it is difficult to establish genotype-phenotype correlations in BSS. We have recently investigated a Hungarian family (with Bukovinian origin) and an Anglo-Saxon BSS pedigree, in whom the affected family members - despite of carrying the same disease-causing mutation (c.2806C>T, p.Arg936X) of the CYLD gene - show striking differences in their phenotypes. The aim of our study was to identify phenotype modifier genetic factors, which could help the understanding of genotype-phenotype correlations in BSS. Comparing the WES data of the Hungarian and Anglo-Saxon BSS patients, here we have identified three putative phenotype modifying genetic variants: the rs1053023 SNP of the signal transducer and activator of transcription 3 (STAT3) gene, the rs1131877 SNP of the tumor necrosis factor receptor-associated factor 3 (TRAF3) gene and the rs202122812 SNP of the neighbor of BRCA1 gene 1 (NBR1) gene. Our study contributes to the accumulating evidence describing the clinical importance of genetic phenotype modifying factors, which have high potential in the elucidation of genotype-phenotype correlations and disease prognosis.

Autophagy defects and related genetic variations in renal cell carcinoma with eosinophilic cytoplasmic inclusions

The relationship between autophagy and tumour is well studied, but tumour cell morphological changes associated with autophagy defects are rarely reported, especially in renal cell carcinoma (RCC). We collected 10 renal tumour samples with characteristic eosinophilic cytoplasmic inclusions (ECIs) and found that the ECIs were majorly composed of sequestosome 1/P62, neighbor of BRCA1 gene 1 (NBR1), PEX14, and CATALASE1 (CAT1). Further, transmission electron microscopy analysis revealed that ECIs were aggregates of proteinaceous material and peroxisomes. These results confirmed that ECIs in RCCs were the products of autophagy defects. The presence of ECIs was correlated with high Fuhrman grade components of RCCs. Whole-exome sequencing (WES) and Sanger sequencing confirmed that tumours with ECIs showed somatic mutations or high frequency of genetic variations in autophagy-related (ATG) genes, such as ATG7, ATG5, and ATG10. These results indicate that nucleotide changes in ATG genes are associated with autophagy defect, ECI formation, and even tumour grade in RCCs.

Abstract 994: Long noncoding RNAs generated from the BRCA1 pseudogene regulate genomic instability and homologous recombination repair

Abstract Background: Genomic instability is frequently associated with cancer and can be indicative of a poor prognosis for breast cancer. While the significant role of BRCA1 in regulating DNA damage repair and checkpoint activation is well defined, little is known about the biological properties of the BRCA1 pseudogene (BRCA1P1) in neoplastic processes. The BRCA1P1 pseudogene was created by a recent evolutionary event, in which a partial duplication of the BRCA1 gene was followed by an insertion of a processed pseudogene of RPLP1P4. Methods: To functionally annotate BRCA1P1, we conducted DNA-FISH, RNA-FISH, a luciferase reporter gene assay, bisulfite sequencing, microarray analysis, radiation-induced foci by immunofluorescence, I-SceI-induced double strand break repair assay, Caspase 3/7 assay, flow cytometry, qRT-PCR, and Western blot analysis. Depletion of BRCA1P1-lncRNA was achieved using LNA-antisense oligonucleotides (ASO), while overexpression of BRCA1P1 was attained using the CRISPR-On activation system. Results: BRCA1P1 pseudogene is transcribed as a ∼1.6 kb unspliced and nucleus-retained long non-coding RNA (lncRNA) using a bidirectional promoter between BRCA1P1 and the neighbor of BRCA1 gene 1 (NBR1). In contrast to the BRCA1 promoter, which is sensitive to hypoxia and subject to CpG island methylation, the pseudogene promoter did not respond to hypoxia nor did it undergo epigenetic modification. Expression of the BRCA1P1 pseudogene varies among 16 breast cell lines with higher expression in some lines, due in part to chromosome 17 polysomy. Interference of BRCA1P1-lncRNA expression with ASO increased genomic instability and spontaneous DNA damage as indicated by an increased spontaneous 53BP1 and RAD51 foci. Breast cancer cells with BRCA1P1 depletion exhibited a defect in DNA damage repair and increased apoptosis in response to irradiation and DNA damaging drugs, respectively. I-SceI-based assays confirmed a decrease in homologous recombination (HR) repair in cells with BRCA1P1 silencing. Interestingly, inhibition of BRCA1P1-lncRNA increased mRNA and protein expression of BRCA1, perhaps to compensate for the HR defect in the cells. The effects of BRCA1P1 overexpression on regulating DNA repair processes are currently under investigation in cells with BRCA1 mutations. Conclusion: These findings suggest a novel role for the BRCA1P1 pseudogene in regulation of DNA damage repair in human breast cancer cells. It's potential role as a therapeutic target remains to be explored. Citation Format: Y. Jane Han, Jing Zhang, Jennifer M. Mason, Aleix Prat, Toshio Yoshimatsu, Charles M. Perou, John Kwon, Prasanth Kannanganattu, Olufunmilayo I. Olopade. Long noncoding RNAs generated from the BRCA1 pseudogene regulate genomic instability and homologous recombination repair. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 994.

The receptor proteins: pivotal roles in selective autophagy.

Autophagy is a highly regulated and multistep biological process whereby cells under metabolic, proteotoxic, or other stresses remove dysfunctional organelles and/or misfolded/polyubiquitinated proteins by shuttling them via specialized structures called autophagosomes to the lysosome for degradation. Although autophagy is generally considered to be a non-selective process, accumulating evidence suggests that it can also selectively degrade specific target cargoes. These selective targets include proteins, mitochondria, and even invading bacteria. The discovery and characterization of autophagic adapters, such as p62/Sequestosome 1 (SQSTM1) and Neighbor of BRCA1 gene 1 (NBR1), have provided mechanistic insights into selective autophagy. These receptors are all able to act as cargo receptors for the degradation of ubiquitinated substrates. This review mainly summarizes the most up-to-date findings regarding the key receptor proteins that play important roles in regulating selective autophagy.

The GST-BHMT assay reveals a distinct mechanism underlying proteasome inhibition-induced macroautophagy in mammalian cells

By monitoring the fragmentation of a GST-BHMT (a protein fusion of glutathionine S-transferase N-terminal to betaine-homocysteine S-methyltransferase) reporter in lysosomes, the GST-BHMT assay has previously been established as an endpoint, cargo-based assay for starvation-induced autophagy that is largely nonselective. Here, we demonstrate that under nutrient-rich conditions, proteasome inhibition by either pharmaceutical or genetic manipulations induces similar autophagy-dependent GST-BHMT processing. However, mechanistically this proteasome inhibition-induced autophagy is different from that induced by starvation as it does not rely on regulation by MTOR (mechanistic target of rapamycin [serine/threonine kinase]) and PRKAA/AMPK (protein kinase, AMP-activated, α catalytic subunit), the upstream central sensors of cellular nutrition and energy status, but requires the presence of the cargo receptors SQSTM1/p62 (sequestosome 1) and NBR1 (neighbor of BRCA1 gene 1) that are normally involved in the selective autophagy pathway. Further, it depends on ER (endoplasmic reticulum) stress signaling, in particular ERN1/IRE1 (endoplasmic reticulum to nucleus signaling 1) and its main downstream effector MAPK8/JNK1 (mitogen-activated protein kinase 8), but not XBP1 (X-box binding protein 1), by regulating the phosphorylation-dependent disassociation of BCL2 (B-cell CLL/lymphoma 2) from BECN1 (Beclin 1, autophagy related). Moreover, the multimerization domain of GST-BHMT is required for its processing in response to proteasome inhibition, in contrast to its dispensable role in starvation-induced processing. Together, these findings support a model in which under nutrient-rich conditions, proteasome inactivation induces autophagy-dependent processing of the GST-BHMT reporter through a distinct mechanism that bears notable similarity with the yeast Cvt (cytoplasm-to-vacuole targeting) pathway, and suggest the GST-BHMT reporter might be employed as a convenient assay to study selective macroautophagy in mammalian cells.

Solution Structure of the Ubiquitin-associated (UBA) Domain of Human Autophagy Receptor NBR1 and Its Interaction with Ubiquitin and Polyubiquitin

NBR1 (neighbor of BRCA1 gene 1) is a protein commonly found in ubiquitin-positive inclusions in neurodegenerative diseases. Due to its high architectural similarity to the well studied autophagy receptor protein p62/SQSTM1, NBR1 has been thought to analogously bind to ubiquitin-marked autophagic substrates via its C-terminal ubiquitin-associated (UBA) domain and deliver them to autophagosomes for degradation. Unexpectedly, we find that NBR1 differs from p62 in its UBA structure and accordingly in its interaction with ubiquitin. Structural differences are observed on helix α-3, which is tilted farther from helix α-2 and extended by approximately one turn in NBR1. This results not only in inhibition of a p62-type self-dimerization of NBR1 UBA but also in a significantly higher affinity for monoubiquitin as compared with p62 UBA. Importantly, the NBR1 UBA-ubiquitin complex structure shows that the negative charge of the side chain in front of the conserved MGF motif in the UBA plays an integral role in the recognition of ubiquitin. In addition, NMR and isothermal titration calorimetry experiments show that NBR1 UBA binds to each monomeric unit of polyubiquitin with similar affinity and by the same surface used for binding to monoubiquitin. This indicates that NBR1 lacks polyubiquitin linkage-type specificity, in good agreement with the nonspecific linkages observed in intracellular ubiquitin-positive inclusions. Consequently, our results demonstrate that the structural differences between NBR1 UBA and p62 UBA result in a much higher affinity of NBR1 for ubiquitin, which in turn suggests that NBR1 may form intracellular inclusions with ubiquitylated autophagic substrates more efficiently than p62.

Phosphorylation of NBR1 by GSK3 modulates protein aggregation

The autophagy receptor NBR1 (neighbor of BRCA1 gene 1) binds UB/ubiquitin and the autophagosome-conjugated MAP1LC3/LC3 (microtubule-associated protein 1 light chain 3) proteins, thereby ensuring ubiquitinated protein degradation. Numerous neurodegenerative and neuromuscular diseases are associated with inappropriate aggregation of ubiquitinated proteins and GSK3 (glycogen synthase kinase 3) activity is involved in several of these proteinopathies. Here we show that NBR1 is a substrate of GSK3. NBR1 phosphorylation by GSK3 at Thr586 prevents the aggregation of ubiquitinated proteins and their selective autophagic degradation. Indeed, NBR1 phosphorylation decreases protein aggregation induced by puromycin or by the DES/desmin N342D mutant found in desminopathy patients and stabilizes ubiquitinated proteins. Importantly, decrease of protein aggregates is due to an inhibition of their formation and not to their autophagic degradation as confirmed by data on Atg7 knockout mice. The relevance of NBR1 phosphorylation in human pathology was investigated. Analysis of muscle biopsies of sporadic inclusion body myositis (sIBM) patients revealed a strong decrease of NBR1 phosphorylation in muscles of sIBM patients that directly correlated with the severity of protein aggregation. We propose that phosphorylation of NBR1 by GSK3 modulates the formation of protein aggregates and that this regulation mechanism is defective in a human muscle proteinopathy.

ERADication of EDEM1 occurs by selective autophagy and requires deglycosylation by cytoplasmic peptide N-glycanase

ER degradation-enhancing α-mannosidase-like 1 protein (EDEM1) is involved in the routing of misfolded glycoproteins for degradation in the cytoplasm. Previously, we reported that EDEM1 leaves the endoplasmic reticulum via non-COPII vesicles (Zuber et al. in Proc Natl Acad Sci USA 104:4407-4412, 2007) and becomes degraded by basal autophagy (Le Fourn et al. in Cell Mol Life Sci 66:1434-1445, 2009). However, it is unknown which type of autophagy is involved. Likewise, how EDEM1 is targeted to autophagosomes remains elusive. We now show that EDEM1 is degraded by selective autophagy. It colocalizes with the selective autophagy cargo receptors p62/SQSTM1, neighbor of BRCA1 gene 1 (NBR1) and autophagy-linked FYVE (Alfy) protein, and becomes engulfed by autophagic isolation membranes. The interaction with p62/SQSTM1 and NBR1 is required for routing of EDEM1 to autophagosomes since it can be blocked by short inhibitory RNA knockdown of the cargo receptors. Furthermore, p62/SQSTM1 interacts only with deglycosylated EDEM1 that is also ubiquitinated. The deglycosylation of EDEM1 occurs by the cytosolic peptide N-glycanase and is a prerequisite for interaction and aggregate formation with p62/SQSTM1 as demonstrated by the effect of peptide N-glycanase inhibitors on the formation of protein aggregates. Conversely, aggregation of p62/SQSTM1 and EDEM1 occurs independent of cytoplasmic histone deacetylase. These data provide novel insight into the mechanism of autophagic degradation of the ER-associated protein degradation (ERAD) component EDEM1 and disclose hitherto unknown parallels with the clearance of cytoplasmic aggregates of misfolded proteins by selective autophagy.

Streptococcus pyogenes Escapes from Autophagy

Autophagy is important for innate defense against intracellular bacteria, such as Group A Streptococcus (GAS). In this issue of Cell Host & Microbe, Barnett etal. (2013) demonstrate that the globally disseminated serotype M1T1 clone of GAS can evade autophagy via streptococcal cysteine protease SpeB-mediated degradation of ubiquitin-LC3 adaptor proteins.

Interaction of PB1 domain-containing signaling molecules in the regulation of Th2 response (174.16)

Abstract Phox and Bem1 (PB1) domains are protein interaction modules which contain approximately 80 amino acids and are found in a number of cytoplasmic signaling proteins. PB1 domain-containing molecules include signaling adapters p62 and Par-6, kinases such as MEK5α, MEKK3, atypical PKCs (aPKCs) PKCζ and PKCλ/ι, as well as the newly discovered NBR1 (neighbor of BRCA1 gene 1), etc. They participate in diverse biological processes. We have recently reported that PKCλ/ι and NBR1 can regulate Th2 differentiation and function both in vivo and in vitro. Here, we demonstrated that PKCλ/ι NBR1 and p62, the three important PB1 domain-containing signaling molecules, all were recruited to immunological synapses between activated CD4+ T cells and anti-CD3/CD28-coated latex beads, or between Jurkat cells and Raj B cells loaded with SEE super antigen. These three signaling molecules were found co-localized with lipid rafts of cell membranes, which is believed important for signaling transduction. Furthermore, PKCλ/ι, NBR1 and p62 were able to directly interact each other as confirmed by immunoprecipitation and confocal staining. The three signaling molecules can regulate nuclear factor of activated T cells (NFAT) c1 activity, which is actively involved in Th2 differentiation and function. Therefore, we identify a novel mechanism by which PB1 domain-containing signaling molecules control Th2 response, at least in part through NFATc1.

Neighbor of BRCA1 gene 1 (NBR1)

Neighbor of BRCA1 gene 1 (NBR1)