Control of anterior GRadient 2 (AGR2) dimerization links endoplasmic reticulum proteostasis to inflammation

Modulation of Protein Disulfide Isomerase Functions by Localization: The Example of the Anterior Gradient Family

Significance: Oxidative folding within the endoplasmic reticulum (ER) introduces disulfide bonds into nascent polypeptides, ensuring proteins' stability and proper functioning. Consequently, this process is critical for maintaining proteome integrity and overall health. The productive folding of thousands of secretory proteins requires stringent quality control measures, such as the unfolded protein response (UPR) and ER-Associated Degradation (ERAD), which contribute significantly to maintaining ER homeostasis. ER-localized protein disulfide isomerases (PDIs) play an essential role in each of these processes, thereby contributing to various aspects of ER homeostasis, including maintaining redox balance, proper protein folding, and signaling from the ER to the nucleus. Recent Advances: Over the years, there have been increasing reports of the (re)localization of PDI family members and other ER-localized proteins to various compartments. A prime example is the anterior gradient (AGR) family of PDI proteins, which have been reported to relocate to the cytosol or the extracellular environment, acquiring gain of functions that intersect with various cellular signaling pathways. Critical Issues: Here, we summarize the functions of PDIs and their gain or loss of functions in non-ER locations. We will focus on the activity, localization, and function of the AGR proteins: AGR1, AGR2, and AGR3. Future Directions: Targeting PDIs in general and AGRs in particular is a promising strategy in different human diseases. Thus, there is a need for innovative strategies and tools aimed at targeting PDIs; those strategies should integrate the specific localization and newly acquired functions of these PDIs rather than solely focusing on their canonical roles.

Clinical implications of AGR2 in primary prostate cancer: Results from a large-scale study

Human anterior gradient-2 (AGR2) has been implicated in carcinogenesis of various solid tumours, but the expression data in prostate cancer are contradictory regarding its prognostic value. The objective of this study is to evaluate the expression of AGR2 in a large prostate cancer cohort and to correlate it with clinicopathological data. AGR2 protein expression was analysed immunohistochemically in 1023 well-characterized prostate cancer samples with a validated antibody. AGR2 expression levels in carcinomas were compared with matched tissue samples of adjacent normal glands. AGR2 expression levels were dichotomized and tested for statistical significance. Increased AGR2 expression was found in 93.5% of prostate cancer cases. AGR2 levels were significantly higher in prostate cancer compared with normal prostate tissue. A gradual loss of AGR2 expression was associated with increasing tumour grade (ISUP), and AGR2 expression is inversely related to patient survival, however, multivariable significance is not achieved. AGR2 is clearly upregulated in the majority of prostate cancer cases, yet a true diagnostic value appears unlikely. In spite of the negative correlation of AGR2 expression with increasing tumour grade, no independent prognostic significance was found in this large-scale study.

The IRE1β-mediated unfolded protein response is repressed by the chaperone AGR2 in mucin producing cells

Effector mechanisms of the unfolded protein response (UPR) in the endoplasmic reticulum (ER) are well-characterised, but how ER proteostasis is sensed is less well understood. Here, we exploited the beta isoform of the UPR transducer IRE1, that is specific to mucin-producing cells in order to gauge the relative regulatory roles of activating ligands and repressing chaperones of the specialised ER of goblet cells. Replacement of the stress-sensing luminal domain of endogenous IRE1α in CHO cells (normally expressing neither mucin nor IRE1β) with the luminal domain of IRE1β deregulated basal IRE1 activity. The mucin-specific chaperone AGR2 repressed IRE1 activity in cells expressing the domain-swapped IRE1β/α chimera, but had no effect on IRE1α. Introduction of the goblet cell-specific client MUC2 reversed AGR2-mediated repression of the IRE1β/α chimera. In vitro, AGR2 actively de-stabilised the IRE1β luminal domain dimer and formed a reversible complex with the inactive monomer. These features of the IRE1β-AGR2 couple suggest that active repression of IRE1β by a specialised mucin chaperone subordinates IRE1 activity to a proteostatic challenge unique to goblet cells, a challenge that is otherwise poorly recognised by the pervasive UPR transducers.

Bifidobacterium and the intestinal mucus layer

Bifidobacterium species are integral members of the human gut microbiota and these microbes have significant interactions with the intestinal mucus layer. This review delves into Bifidobacterium-mucus dynamics, shedding light on the multifaceted nature of this relationship. We cover conserved features of Bifidobacterium-mucus interactions, such as mucus adhesion and positive regulation of goblet cell and mucus production, as well as species and strain-specific attributes of mucus degradation. For each interface, we explore the molecular mechanisms underlying these interactions and their potential implications for human health. Notably, we emphasize the ability of Bifidobacterium species to positively influence the mucus layer, shedding light on its potential as a mucin-builder and a therapeutic agent for diseases associated with disrupted mucus barriers. By elucidating the complex interplay between Bifidobacterium and intestinal mucus, we aim to contribute to a deeper understanding of the gut microbiota-host interface and pave the way for novel therapeutic strategies.

Expression Profiling along the Murine Intestine: Different Mucosal Protection Systems and Alterations in Tff1-Deficient Animals

Tff1 is a typical gastric peptide secreted together with the mucin, Muc5ac. Tff1-deficient (Tff1KO) mice are well known for their prominent gastric phenotype and represent a recognized model for antral tumorigenesis. Notably, intestinal abnormalities have also been reported in the past in these animals. Here, we have compared the expression of selected genes in Tff1KO mice and their corresponding wild-type littermates (RT-PCR analyses), focusing on different mucosal protection systems along the murine intestine. As hallmarks, genes were identified with maximum expression in the proximal colon and/or the duodenum: Agr2, Muc6/A4gnt/Tff2, Tff1, Fut2, Gkn2, Gkn3, Duox2/Lpo, Nox1. This is indicative of different protection systems such as Tff2/Muc6, Tff1-Fcgbp, gastrokines, fucosylation, and reactive oxygen species (ROS) in the proximal colon and/or duodenum. Few significant transcriptional changes were observed in the intestine of Tff1KO mice when compared with wild-type littermates, Clca1 (Gob5), Gkn1, Gkn2, Nox1, Tff2. We also analyzed the expression of Tff1, Tff2, and Tff3 in the pancreas, liver, and lung of Tff1KO and wild-type animals, indicating a cross-regulation of Tff gene expression. Furthermore, on the protein level, heteromeric Tff1-Fcgbp and various monomeric Tff1 forms were identified in the duodenum and a high-molecular-mass Tff2/Muc6 complex was identified in the proximal colon (FPLC, proteomics).

The Promise of Single-Cell RNA Sequencing to Redefine the Understanding of Crohn's Disease Fibrosis Mechanisms

Crohn's disease (CD) is a chronic inflammatory bowel disease with a high prevalence throughout the world. The development of Crohn's-related fibrosis, which leads to strictures in the gastrointestinal tract, presents a particular challenge and is associated with significant morbidity. There are currently no specific anti-fibrotic therapies available, and so treatment is aimed at managing the stricturing complications of fibrosis once it is established. This often requires invasive and repeated endoscopic or surgical intervention. The advent of single-cell sequencing has led to significant advances in our understanding of CD at a cellular level, and this has presented opportunities to develop new therapeutic agents with the aim of preventing or reversing fibrosis. In this paper, we discuss the current understanding of CD fibrosis pathogenesis, summarise current management strategies, and present the promise of single-cell sequencing as a tool for the development of effective anti-fibrotic therapies.

Potential Role of AGR2 for Mammalian Skin Wound Healing

The limited ability of mammals to regenerate has garnered significant attention, particularly in regard to skin wound healing (WH), which is a critical step for regeneration. In human adults, skin WH results in the formation of scars following injury or trauma, regardless of severity. This differs significantly from the scarless WH observed in the fetal skin of mammals or anamniotes. This review investigates the role of molecular players involved in scarless WH, which are lost or repressed in adult mammalian WH systems. Specifically, we analyze the physiological role of Anterior Gradient (AGR) family proteins at different stages of the WH regulatory network. AGR is activated in the regeneration of lower vertebrates at the stage of wound closure and, accordingly, is important for WH. Mammalian AGR2 is expressed during scarless WH in embryonic skin, while in adults, the activity of this gene is normally inhibited and is observed only in the mucous epithelium of the digestive tract, which is capable of full regeneration. The combination of AGR2 unique potencies in postnatal mammals makes it possible to consider it as a promising candidate for enhancing WH processes.

ERβ1 Sensitizes and ERβ2 Desensitizes ERα-Positive Breast Cancer Cells to the Inhibitory Effects of Tamoxifen, Fulvestrant and Their Combination with All-Trans Retinoic Acid

Adjuvant endocrine therapy (AET) is the treatment of choice for early-stage estrogen receptor alpha (ERα)-positive breast cancer (BC). However, almost 40% of tamoxifen-treated cases display no response or a partial response to AET, thus increasing the need for new treatment options and strong predictors of the therapeutic response of patients at high risk of relapse. In addition to ERα, BC research has focused on ERβ1 and ERβ2 (isoforms of ERβ), the second ER isotype. At present, the impact of ERβ isoforms on ERα-positive BC prognosis and treatment remains elusive. In the present study, we established clones of MCF7 cells constitutively expressing human ERβ1 or ERβ2 and investigated their role in the response of MCF7 cells to antiestrogens [4-hydroxytamoxifen (OHΤ) and fulvestrant (ICI182,780)] and retinoids [all-trans retinoic acid (ATRA)]. We show that, compared to MCF7 cells, MCF7-ERβ1 and MCF7-ERβ2 cells were sensitized and desensitized, respectively, to the antiproliferative effect of the antiestrogens, ATRA and their combination and to the cytocidal effect of the combination of OHT and ATRA. Analysis of the global transcriptional changes upon OHT-ATRA combinatorial treatment revealed uniquely regulated genes associated with anticancer effects in MCF7-ERβ1 cells and cancer-promoting effects in MCF7-ERβ2 cells. Our data are favorable to ERβ1 being a marker of responsiveness and ERβ2 being a marker of resistance of MCF7 cells to antiestrogens alone and in combination with ATRA.

AGR2: a secreted protein worthy of attention in diagnosis and treatment of breast cancer

AGR2 is a secreted protein widely existing in breast. In precancerous lesions, primary tumors and metastatic tumors, the expression of AGR2 is increased, which has aroused our interest. This review introduces the gene and protein structure of AGR2. Its endoplasmic reticulum retention sequence, protein disulfide isomerase active site and multiple protein binding sequences endow AGR2 with diverse functions inside and outside breast cancer cells. This review also enumerates the role of AGR2 in the progress and prognosis of breast cancer, and emphasizes that AGR2 can be a promising biomarker and a target for immunotherapy of breast cancer, providing new ideas for early diagnosis and treatment of breast cancer.

Glutamine promotes O-GlcNAcylation of G6PD and inhibits AGR2 S-glutathionylation to maintain the intestinal mucus barrier in burned septic mice

Mucus forms the first line of defence of the intestinal mucosa barrier, and mucin is its core component. Glutamine is a vital energy substance for goblet cells; it can promote mucus synthesis and alleviate damage to the intestinal mucus barrier after burn injury, but its mechanism is not fully understood. This study focused on the molecular mechanisms underlying the effects of glutamine on the synthesis and modification of mucin 2 (MUC2) by using animal and cellular models of burn sepsis. We found that anterior gradient-2 (AGR2) plays a key role in the posttranslational modification of MUC2. Oxidative stress induced by burn sepsis enhanced the S-glutathionylation of AGR2, interfered with the processing and modification of MUC2 precursors by AGR2 and blocked the synthesis of mature MUC2. Further studies revealed that NADPH, catalysed by glucose-6-phosphate dehydrogenase (G6PD), is a key molecule in inhibiting oxidative stress and regulating AGR2 activity. Glutamine promotes O-linked N-acetylglucosamine (O-GlcNAc) modification of G6PD via the hexosamine pathway, which facilitates G6PD homodimer formation and increases NADPH synthesis, thereby inhibiting AGR2 S-glutathionylation and promoting MUC2 maturation, ultimately reducing damage to the intestinal mucus barrier after burn sepsis. Overall, we have demonstrated that the central mechanisms of glutamine in promoting MUC2 maturation and maintaining the intestinal mucus barrier are the enhancement of G6PD glycosylation and inhibition of AGR2 S-glutathionylation.

AGR2-induced cholesterol synthesis drives lovastatin resistance that is overcome by combination therapy with allicin

Anterior gradient 2 (AGR2), a protein disulfide isomerase (PDI), is a multifunctional protein under physiological and pathological conditions. In this study we investigated the roles of AGR2 in regulating cholesterol biogenesis, lipid-lowering efficiency of lovastatin as well as in protection against hypercholesterolemia/statin-induced liver injury. We showed that AGR2 knockout significantly decreased hepatic and serum total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) in mice with whole-body or hepatocyte-specific Agr2-null mutant, compared with the levels in their wild-type littermates fed a normal chow diet (NCD) or high-fat diet (HFD). In contrast, mice with AGR2 overexpression (Agr2/Tg) exhibited an increased cholesterol level. Mechanistic studies revealed that AGR2 affected cholesterol biogenesis via activation of AKT/sterol regulatory element-binding protein-2 (SREBP2), to some extent, in a PDI motif-dependent manner. Moreover, elevated AGR2 led to a significant decrease in the lipid-lowering efficacy of lovastatin (10 mg· kg-1· d-1, ip, for 2 weeks) in mice with hypercholesterolemia (hyperCho), which was validated by results obtained from clinical samples in statin-treated patients. We showed that lovastatin had limited effect on AGR2 expression, but AGR2 was inducible in Agr2/Tg mice fed a HFD. Further investigations demonstrated that drug-induced liver toxicity and inflammatory reactions were alleviated in hypercholesterolemic Agr2/Tg mice, suggesting the dual functions of AGR2 in lipid management and hyperCho/statin-induced liver injury. Importantly, the AGR2-reduced lipid-lowering efficacy of lovastatin was attenuated, at least partially, by co-administration of a sulfhydryl-reactive compound allicin (20 mg· kg-1· d-1, ip, for 2 weeks). These results demonstrate a novel role of AGR2 in cholesterol metabolism, drug resistance and liver protection, suggesting AGR2 as a potential predictor for selection of lipid-lowering drugs in clinic.

The Implication of Serum Autoantibodies in Prognosis of Canine Mammary Tumors

Canine mammary tumor (CMT) is the most prevalent neoplasm in female dogs. Tumor recurrence and metastasis occur in malignant CMT (MMT) dogs after surgery. Identification of serum prognostic biomarkers holds the potential to facilitate prediction of disease outcomes. We have identified CMT-associated autoantibodies against thymidylate synthetase (TYMS), insulin-like growth factor-binding protein 5 (IGFBP5), hyaluronan and proteoglycan link protein 1 (HAPLN1), and anterior gradient 2 (AGR2), i.e., TYMS-AAb, IGFBP5-AAb, HAPLN1-AAb, and AGR2-AAb, respectively, by conducting serological enzyme-linked immunosorbent assays (ELISA). Herein we assessed serum AAb levels in 11 MMT dogs before and after surgery, demonstrating that IGFBP5-AAb and HAPLN1-AAb significantly decrease at 3- and 12-months post-surgery (p < 0.05). We evaluated the correlation between the presurgical AAb level and overall survival (OS) of 90 CMT dogs after surgery. Kaplan-Meier survival analysis reveals that IGFBP5-AAbHIgh and TYMS-AAbHigh are significantly correlated with worse OS (p = 0.017 and p = 0.029, respectively), while AGR2-AAbLow is correlated with somewhat poorer OS (p = 0.086). Areas under a time-dependent receiver operating characteristic curve (AUC) of IGFBP5-AAb and TYMS-AAb in predicting OS of MMT dogs are 0.611 and 0.616, respectively. Notably, MMT dogs presenting TYMS-AAbHigh/IGFBP5-AAbHigh/AGR2-AAbLow have worst OS (p = 0.0004). This study reveals an association between the serum AAb level and CMT prognosis.

Identification of AGR2 Gene-Specific Expression Patterns Associated with Epithelial-Mesenchymal Transition

The TGF-β signaling pathway is involved in numerous cellular processes, and its deregulation may result in cancer development. One of the key processes in tumor progression and metastasis is epithelial to mesenchymal transition (EMT), in which TGF-β signaling plays important roles. Recently, AGR2 was identified as a crucial component of the cellular machinery responsible for maintaining the epithelial phenotype, thereby interfering with the induction of mesenchymal phenotype cells by TGF-β effects in cancer. Here, we performed transcriptomic profiling of A549 lung cancer cells with CRISPR-Cas9 mediated AGR2 knockout with and without TGF-β treatment. We identified significant changes in transcripts associated with focal adhesion and eicosanoid production, in particular arachidonic acid metabolism. Changes in transcripts associated with the focal adhesion pathway were validated by RT-qPCR of COL4A1, COL4A2, FLNA, VAV3, VEGFA, and VINC mRNAs. In addition, immunofluorescence showed the formation of stress fibers and vinculin foci in cells without AGR2 and in response to TGF-β treatment, with synergistic effects observed. These findings imply that both AGR2 downregulation and TGF-β have a role in focal adhesion formation and cancer cell migration and invasion. Transcripts associated with arachidonic acid metabolism were downregulated after both AGR2 knockout and TGF-β treatment and were validated by RT-qPCR of GPX2, PTGS2, and PLA2G4A. Since PGE₂ is a product of arachidonic acid metabolism, its lowered concentration in media from AGR2-knockout cells was confirmed by ELISA. Together, our results demonstrate that AGR2 downregulation and TGF-β have an essential role in focal adhesion formation; moreover, we have identified AGR2 as an important component of the arachidonic acid metabolic pathway.

Anterior gradient proteins in gastrointestinal cancers: from cell biology to pathophysiology

Most of the organs of the digestive tract comprise secretory epithelia that require specialized molecular machines to achieve their functions. As such anterior gradient (AGR) proteins, which comprise AGR1, AGR2, and AGR3, belong to the protein disulfide isomerase family, and are involved in secretory and transmembrane protein biogenesis in the endoplasmic reticulum. They are generally expressed in epithelial cells with high levels in most of the digestive tract epithelia. To date, the vast majority of the reports concern AGR2, which has been shown to exhibit various subcellular localizations and exert pro-oncogenic functions. AGR2 overexpression has recently been associated with a poor prognosis in digestive cancers. AGR2 is also involved in epithelial homeostasis. Its deletion in mice results in severe diffuse gut inflammation, whereas in inflammatory bowel diseases, the secretion of AGR2 in the extracellular milieu participates in the reshaping of the cellular microenvironment. AGR2 thus plays a key role in inflammation and oncogenesis and may represent a therapeutic target of interest. In this review, we summarize the already known roles and mechanisms of action of the AGR family proteins in digestive diseases, their expression in the healthy digestive tract, and in digestive oncology. At last, we discuss the potential diagnostic and therapeutic implications underlying the biology of AGR proteins.

Functions and mechanisms of protein disulfide isomerase family in cancer emergence

The endoplasmic reticulum (ER) is a multi-layered organelle that is essential for the synthesis, folding, and structural maturation of almost one-third of the cellular proteome. It houses several resident proteins for these functions including the 21 members of the protein disulfide isomerase (PDI) family. The signature of proteins belonging to this family is the presence of the thioredoxin domain which mediates the formation, and rearrangement of disulfide bonds of substrate proteins in the ER. This process is crucial not only for the proper folding of ER substrates but also for maintaining a balanced ER proteostasis. The inclusion of new PDI members with a wide variety of structural determinants, size and enzymatic activity has brought additional epitomes of how PDI functions. Notably, some of them do not carry the thioredoxin domain and others have roles outside the ER. This also reflects that PDIs may have specialized functions and their functions are not limited within the ER. Large-scale expression datasets of human clinical samples have identified that the expression of PDI members is elevated in pathophysiological states like cancer. Subsequent functional interrogations using structural, molecular, cellular, and animal models suggest that some PDI members support the survival, progression, and metastasis of several cancer types. Herein, we review recent research advances on PDIs, vis-à-vis their expression, functions, and molecular mechanisms in supporting cancer growth with special emphasis on the anterior gradient (AGR) subfamily. Last, we posit the relevance and therapeutic strategies in targeting the PDIs in cancer.

Selective Secretion of KDEL-Bearing Proteins: Mechanisms and Functions

In multicellular organisms, cells must continuously exchange messages with the right meaning, intensity, and duration. Most of these messages are delivered through cognate interactions between membrane and secretory proteins. Their conformational maturation is assisted by a vast array of chaperones and enzymes, ensuring the fidelity of intercellular communication. These folding assistants reside in the early secretory compartment (ESC), a functional unit that encompasses endoplasmic reticulum (ER), intermediate compartment and cis-Golgi. Most soluble ESC residents have C-terminal KDEL-like motifs that prevent their transport beyond the Golgi. However, some accumulate in the ER, while others in downstream stations, implying different recycling rates. Moreover, it is now clear that cells can actively secrete certain ESC residents but not others. This essay discusses the physiology of their differential intracellular distribution, and the mechanisms that may ensure selectivity of release.

Excessive Apoptosis in Ulcerative Colitis: Crosstalk Between Apoptosis, ROS, ER Stress, and Intestinal Homeostasis

Ulcerative colitis (UC), an etiologically complicated and relapsing gastrointestinal disease, is characterized by the damage of mucosal epithelium and destruction of the intestinal homeostasis, which has caused a huge social and economic burden on the health system all over the world. Its pathogenesis is multifactorial, including environmental factors, genetic susceptibility, epithelial barrier defect, symbiotic flora imbalance, and dysregulated immune response. Thus far, although immune cells have become the focus of most research, it is increasingly clear that intestinal epithelial cells play an important role in the pathogenesis and progression of UC. Notably, apoptosis is a vital catabolic process in cells, which is crucial to maintain the stability of intestinal environment and regulate intestinal ecology. In this review, the mechanism of apoptosis induced by reactive oxygen species and endoplasmic reticulum stress, as well as excessive apoptosis in intestinal epithelial dysfunction and gut microbiology imbalance are systematically and comprehensively summarized. Further understanding the role of apoptosis in the pathogenesis of UC may provide a novel strategy for its therapy in clinical practices and the development of new drugs.

Transmembrane p24 trafficking protein 2 regulates inflammation through the TLR4/NF-κB signaling pathway in lung adenocarcinoma

Background

To investigate the role of transmembrane p24 trafficking protein 2 (TMED2) in lung adenocarcinoma (LUAD) and determine whether TMED2 knockdown could inhibit LUAD in vitro and in vivo.

Methods

TIMER2.0, Kaplan-Meier plotter, gene set enrichment analysis (GSEA), Target Gene, and pan-cancer systems were used to predict the potential function of TMED2. Western blotting and immunohistochemistry were performed to analyze TMED2 expression in different tissues or cell lines. The proliferation, development, and apoptosis of LUAD were observed using a lentivirus-mediated TMED2 knockdown. Bioinformatics and western blot analysis of TMED2 against inflammation via the TLR4/NF-κB signaling pathway were conducted.

Results

TMED2 expression in LUAD tumor tissues was higher than that in normal tissues and positively correlated with poor survival in lung cancer and negatively correlated with apoptosis in LUAD. The expression of TMED2 was higher in tumors or HCC827 cells. TMED2 knockdown inhibited LUAD development in vitro and in vivo and increased the levels of inflammatory factors via the TLR4/NF-κB signaling pathway. TMED2 was correlated with TME, immune score, TME-associated immune cells, their target markers, and some mechanisms and pathways, as determined using the TIMER2.0, GO, and KEGG assays.

Conclusions

TMED2 may regulate inflammation in LUAD through the TLR4/NF-κB signaling pathway and enhance the proliferation, development, and prognosis of LUAD by regulating inflammation, which provide a new strategy for treating LUAD by regulating inflammation.

Characterization of the AGR2 interactome uncovers new players of Protein Disulfide Isomerase network in cancer cells

Anterior gradient 2 (AGR2) is an endoplasmic reticulum (ER)-resident protein disulfide isomerase (PDI) known to be overexpressed in many human epithelial cancers and is involved in cell migration, cellular transformation, angiogenesis, and metastasis. This protein inhibits the activity of the tumor suppressor p53, and its expression levels can be used to predict cancer patient outcome. However, the precise network of AGR2-interacting partners and clients remains to be fully characterized. Herein, we used label-free quantification and also stable isotope labeling with amino acids in cell culture–based LC–MS/MS analyses to identify proteins interacting with AGR2. Functional annotation confirmed that AGR2 and its interaction partners are associated with processes in the ER that maintain intracellular metabolic homeostasis and participate in the unfolded protein response, including those associated with changes in cellular metabolism, energy, and redox states in response to ER stress. As a proof of concept, the interaction between AGR2 and PDIA3, another ER-resident PDI, was studied in more detail. Pathway analysis revealed that AGR2 and PDIA3 play roles in protein folding in ER, including post-translational modification and in cellular response to stress. We confirmed the AGR2–PDIA3 complex formation in cancer cells, which was enhanced in response to ER stress. Accordingly, molecular docking characterized potential quaternary structure of this complex; however, it remains to be elucidated whether AGR2 rather contributes to PDIA3 maturation in ER, the complex directly acts in cellular signaling, or mediates AGR2 secretion. Our study provides a comprehensive insight into the protein–protein interaction network of AGR2 by identifying functionally relevant proteins and related cellular and biochemical pathways associated with the role of AGR2 in cancer cells.

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LC–MS/MS analysis of AGR2-interacting proteins in T47D and H1299 cells.

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About 15 overlapping AGR2 interactors, including PDIA3 and PDIA6, were identified in both cell lines.

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PDI family members represent the key part of the network.

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AGR2–PDIA3 interaction is even stronger under ER stress.

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AGR2–PDIA3 complex formation supports extracellular secretion of AGR2.

Anterior gradient protein 2 is a marker of tumor aggressiveness in breast cancer and favors chemotherapy‑induced senescence escape

Among the different chemotherapies available, genotoxic drugs are widely used. In response to these drugs, particularly doxorubicin, tumor cells can enter into senescence. Chemotherapy‑induced senescence (CIS) is a complex response. Long described as a definitive arrest of cell proliferation, the present authors and various groups have shown that this state may not be complete and could allow certain cells to reproliferate. The mechanism could be due to the activation of new signaling pathways. In the laboratory, the proteins involved in these pathways and triggering cell proliferation were studied. The present study determined a new role for anterior gradient protein 2 (AGR2) in vivo in patients and in vitro in a senescence escape model. AGR2's implication in breast cancer patients and proliferation of senescent cells was assessed based on a SWATH‑MS proteomic study of patients' samples and RNA interference technology on cell lines. First, AGR2 was identified and it was found that its concentration is higher in the serum of patients with breast cancer and that this high concentration is associated with metastasis occurrence. An inverse correlation between intratumoral AGR2 expression and the senescence marker p16 was also observed. This observation led to the study of the role of AGR2 in the CIS escape model. In this model, it was found that AGR2 is overexpressed in cells during senescence escape and that its loss considerably reduces this phenomenon. Furthermore, it was shown that the extracellular form of AGR2 stimulated the reproliferation of senescent cells. The power of proteomic analysis based on the SWATH‑MS approach allowed the present study to highlight the mammalian target of rapamycin (mTOR)/AKT signaling pathway in the senescence escape mechanism mediated by AGR2. Analysis of the two signaling pathways revealed that AGR2 modulated RICTOR and AKT phosphorylation. All these results showed that AGR2 expression in sera and tumors of breast cancer patients is a marker of tumor progression and metastasis occurrence. They also showed that its overexpression regulates CIS escape via activation of the mTOR/AKT signaling pathway.

Bifidobacterium dentium-derived y-glutamylcysteine suppresses ER-mediated goblet cell stress and reduces TNBS-driven colonic inflammation

Endoplasmic reticulum (ER) stress compromises the secretion of MUC2 from goblet cells and has been linked with inflammatory bowel disease (IBD). Although Bifidobacterium can beneficially modulate mucin production, little work has been done investigating the effects of Bifidobacterium on goblet cell ER stress. We hypothesized that secreted factors from Bifidobacterium dentium downregulate ER stress genes and modulates the unfolded protein response (UPR) to promote MUC2 secretion. We identified by mass spectrometry that B. dentium secretes the antioxidant γ-glutamylcysteine, which we speculate dampens ER stress-mediated ROS and minimizes ER stress phenotypes. B. dentium cell-free supernatant and γ-glutamylcysteine were taken up by human colonic T84 cells, increased glutathione levels, and reduced ROS generated by the ER-stressors thapsigargin and tunicamycin. Moreover, B. dentium supernatant and γ-glutamylcysteine were able to suppress NF-kB activation and IL-8 secretion. We found that B. dentium supernatant, γ-glutamylcysteine, and the positive control IL-10 attenuated the induction of UPR genes GRP78, CHOP, and sXBP1. To examine ER stress in vivo, we first examined mono-association of B. dentium in germ-free mice which increased MUC2 and IL-10 levels compared to germ-free controls. However, no changes were observed in ER stress-related genes, indicating that B. dentium can promote mucus secretion without inducing ER stress. In a TNBS-mediated ER stress model, we observed increased levels of UPR genes and pro-inflammatory cytokines in TNBS treated mice, which were reduced with addition of live B. dentium or γ-glutamylcysteine. We also observed increased colonic and serum levels of IL-10 in B. dentium- and γ-glutamylcysteine-treated mice compared to vehicle control. Immunostaining revealed retention of goblet cells and mucus secretion in both B. dentium- and γ-glutamylcysteine-treated animals. Collectively, these data demonstrate positive modulation of the UPR and MUC2 production by B. dentium-secreted compounds.

From development to cancer - an ever-increasing role of AGR2

Anterior gradient 2, AGR2, is a small, 20 kDa protein that plays a vital role in oxidative protein folding in the endoplasmic reticulum. AGR2 is involved in several signal transduction pathways that are essential for cell survival. It was initially discovered in the African clawed frog, Xenopus laevis, where it plays an important function in embryonic development. Akin to several other developmental genes, it is also frequently deregulated in cancer, where it plays a decisive role in tumor initiation, progression and metastasis. In this review, we have summarized currently known AGR2 functions, its expression and function in embryonic and cancer development, as well as its potential as a candidate tumor biomarker and promising new target for cancer immunotherapy.

Pharmacological targeting of endoplasmic reticulum stress in disease

The accumulation of misfolded proteins in the endoplasmic reticulum (ER) leads to ER stress, resulting in activation of the unfolded protein response (UPR) that aims to restore protein homeostasis. However, the UPR also plays an important pathological role in many diseases, including metabolic disorders, cancer and neurological disorders. Over the last decade, significant effort has been invested in targeting signalling proteins involved in the UPR and an array of drug-like molecules is now available. However, these molecules have limitations, the understanding of which is crucial for their development into therapies. Here, we critically review the existing ER stress and UPR-directed drug-like molecules, highlighting both their value and their limitations.

The Secreted Protein Disulfide Isomerase Ag1 Lost by Ancestors of Poorly Regenerating Vertebrates Is Required for Xenopus laevis Tail Regeneration

Warm-blooded vertebrates regenerate lost limbs and their parts in general much worse than fishes and amphibians. We previously hypothesized that this reduction in regenerative capability could be explained in part by the loss of some genes important for the regeneration in ancestors of warm-blooded vertebrates. One of such genes could be ag1, which encodes secreted protein disulfide isomerase of the Agr family. Ag1 is activated during limb and tail regeneration in the frog Xenopus laevis tadpoles and is absent in warm-blooded animals. The essential role of another agr family gene, agr2, in limb regeneration was demonstrated previously in newts. However, agr2, as well as the third member of agr family, agr3, are present in all vertebrates. Therefore, it is important to verify if the activity of ag1 lost by warm-blooded vertebrates is also essential for regeneration in amphibians, which could be a further argument in favor of our hypothesis. Here, we show that in the Xenopus laevis tadpoles in which the expression of ag1 or agr2 was artificially suppressed, regeneration of amputated tail tips was also significantly reduced. Importantly, overexpression of any of these agrs or treatment of tadpoles with any of their recombinant proteins resulted in the restoration of tail regeneration in the refractory period when these processes are severely inhibited in normal development. These findings demonstrate the critical roles of ag1 and agr2 in regeneration in frogs and present indirect evidence that the loss of ag1 in evolution could be one of the prerequisites for the reduction of regenerative ability in warm-blooded vertebrates.

Serum Level of Tumor-Overexpressed AGR2 Is Significantly Associated with Unfavorable Prognosis of Canine Malignant Mammary Tumors

Simple Summary

Canine malignant mammary tumor (MMT) is a prevalent malignancy in intact female dogs. A current lack of easily accessible tumor biomarkers hinders a timely assessment of the disease outcome. This study reveals that anterior gradient protein 2 (AGR2) is overexpressed in canine MMT tissues, and elevated levels of extracellular AGR2 in sera of MMT dogs are significantly associated with progression and remote metastasis of MMT and an unfavorable overall survival of the patients. Hence, serum eAGR2 level is significantly associated with an adverse outcome of MMT dogs and holds a predictive potential in MMT prognosis.

Abstract

Canine malignant mammary tumors (MMTs) are prevalent malignancy in intact female dogs with a high incidence of metastasis and recurrence. A current lack of easily accessible tumor biomarkers hinders a timely assessment of the disease outcome. We previously identified anterior gradient protein 2 (AGR2) with higher protein abundance in canine MMT tissues compared with normal counterparts. AGR2 is an endoplasmic reticulum-resident protein disulfide isomerase involved in the regulation of protein processing and also exists extracellularly via secretion to exert pro-oncogenic functions. In the present study, we validated overexpression of AGR2 in canine MMT tissues from 45 dogs using immunohistochemistry and immunoblotting, and assessed serum AGR2 levels in 81 dogs with MMTs and 21 benign cases using a competitive enzyme-linked immunosorbent assay (ELISA). Our data revealed that serum eAGR2 levels are significantly correlated with MMT progression (p = 0.0007) and remote tumor metastasis (p = 0.002). Moreover, elevated levels of serum eAGR2 are associated with an unfavorable overall survival of MMT dogs in later stage (p = 0.0158). Area under the time-dependent ROC curve (AUC) of serum eAGR2 level as a prognostic indicator was 0.839. Collectively, this study uncovered that serum eAGR2 level is significantly associated with an adverse outcome of MMT dogs and holds a predictive potential in MMT prognosis.

The Anterior GRadient (AGR) family proteins in epithelial ovarian cancer

Epithelial ovarian cancer (EOC) is the most common gynecologic disorder. Even with the recent progresses made towards the use of new therapeutics, it still represents the most lethal gynecologic malignancy in women from developed countries.

The discovery of the anterior gradient proteins AGR2 and AGR3, which are highly related members belonging to the protein disulfide isomerase (PDI) family, attracted researchers’ attention due to their putative involvement in adenocarcinoma development. This review compiles the current knowledge on the role of the AGR family and the expression of its members in EOC and discusses the potential clinical relevance of AGR2 and AGR3 for EOC diagnosis, prognosis, and therapeutics.

A better understanding of the role of the AGR family may thus provide new handling avenues for EOC patients.

TSPAN1 silencing protects against cerulein-induced pancreatic acinar cell injury via targeting AGR2

Acute pancreatitis (AP) is an inflammatory gastrointestinal disorder affecting the pancreas. Previous study reported that tetraspanin 1 (TSPAN1) expression was significantly upregulated in the pancreas of AP patients. However, the underlying molecular mechanism of TSPAN1 in the pathogenesis of AP remains unclear. Thus, the aim of the present study was to investigate the potential role of TSPAN1 in development of AP. RT-qPCR was carried out to quantify the relative mRNA levels of TSPAN1 and anterior gradient-2 (AGR2). The CCK-8 assay was used to detect the cell viability. The TUNEL assay was performed to visualize the apoptotic cells. Western blot was performed to determine the expressions of proteins related to endoplasmic reticulum (ER) stress and apoptosis. ELISA kits were adopted to detect the concentration of inflammatory cytokines including TNF-α and IL-6. Finally, immunoprecipitation (IP) was used to verify the interaction between TSPAN1 and AGR2. TSPAN1 was upregulated in serum of AP patients and AP cell models. TSPAN1 silencing promoted the cell proliferation and inhibited inflammatory response in cerulein-induced AR42J cells. Moreover, TSPAN1 induced endoplasmic reticulum stress by binding AGR2. Interestingly, the overexpression of AGR2 abolished the effects of TSPAN1 silencing on cell proliferation and inflammatory response in cerulein-induced AR42J cells. In summary, TSPAN1 silencing protects against cerulein-induced pancreatic acinar cell injury through inhibiting ER stress-mediated by AGR2. Hence, TSPAN1 may serve as a promising therapeutic target for AP treatment.

An Ultrasensitive Biosensor for Detection of Femtogram Levels of the Cancer Antigen AGR2 Using Monoclonal Antibody Modified Screen-Printed Gold Electrodes

The detection of cancer antigens is a major aim of cancer research in order to develop better patient management through early disease detection. Many cancers including prostate, lung, and ovarian secrete a protein disulfide isomerase protein named AGR2 that has been previously detected in urine and plasma using mass spectrometry. Here we determine whether a previously developed monoclonal antibody targeting AGR2 can be adapted from an indirect two-site ELISA format into a direct detector using solid-phase printed gold electrodes. The screen-printed gold electrode was surface functionalized with the anti-AGR2 specific monoclonal antibody. The interaction of the recombinant AGR2 protein and the anti-AGR2 monoclonal antibody functionalized electrode changed its electrochemical impedance spectra. Nyquist diagrams were obtained after incubation in an increasing concentration of purified AGR2 protein with a range of concentrations from 0.01 fg/mL to 10 fg/mL. In addition, detection of the AGR2 antigen can be achieved from cell lysates in medium or artificial buffer. These data highlight the utility of an AGR2-specific monoclonal antibody that can be functionalized onto a gold printed electrode for a one-step capture and quantitation of the target antigen. These platforms have the potential for supporting methodologies using more complex bodily fluids including plasma and urine for improved cancer diagnostics.

Anterior Gradient Protein 2 Promotes Mucosal Repair in Pediatric Ulcerative Colitis

Mucosal healing comprises a key goal of ulcerative colitis (UC) treatment. Anterior gradient protein 2 (AGR2) plays an important role in maintaining intestinal homeostasis in UC. However, the role of AGR2 in the repair of mucosal injury is not yet clear. This study is aimed at investigating the expression of AGR2 in the intestinal tissues of children with UC and its role in repairing mucosal injury. Forty UC patients who were hospitalized in the Pediatric Gastroenterology Ward of Shengjing Hospital affiliated with China Medical University between July 1, 2013, and May 31, 2020, and 20 children who had normal colonoscopy results during the same period (control group) made up the study sample. The disease activity of UC was evaluated based on the pediatric ulcerative colitis activity index, and the ulcerative colitis endoscopic index was evaluated according to the Rachmilewitz score. Immunohistochemical staining was employed to examine the differences in AGR2 expression in the intestinal mucosa between groups. The protective effect of AGR2 in a model of tumor necrosis factor-alpha- (TNF-α-) induced intestinal mucosal barrier injury and the underlying molecular mechanism were explored through in vitro experiments. The results showed that compared with the normal control group, UC patients in the remission or active period had significantly higher expression of AGR2 in the intestine. AGR2 expression was positively correlated with Ki67, an intestinal epithelial cell proliferation marker, but negatively correlated with the degree of endoscopic mucosal injury. In an in vitro model, AGR2 overexpression promoted cell proliferation and migration and inhibited TNF-α-induced intestinal epithelial barrier damage by activating yes-associated protein (YAP). Collectively, our study suggests that AGR2 might serve as a valuable biomarker to help assess the condition and mucosal healing status of UC patients. In vitro, AGR2 promoted the repair of intestinal mucosal barrier injury by activating YAP.

Development and Validation of an Interleukin-6 Nomogram to Predict Primary Non-response to Infliximab in Crohn's Disease Patients

Background: The primary non-response (PNR) rate of infliximab (IFX) varies from 20 to 46% for the treatment of Crohn’s disease (CD). Detected PNR reduces the improper use of specific treatments. To date, there is hardly any knowledge regarding early markers of PNR. The aim of this study was to evaluate the role of Interleukin-6 (IL-6) as an early predictor of PNR of IFX for the treatment of CD.

Methods: We enrolled 322 bio-naïve patients diagnosed with CD from January 2016 to May 2020. Primary response was determined at week 14. Multivariable logistic regression was used to construct prediction models. Area under the curve (AUC), calibration and decision curve analyses (DCA) were assessed in the validation cohort. GEO data were analyzed to identify potential mechanisms of IL-6 in IFX therapy for CD.

Results: PNR occurred in 31.06% (100 of 322) patients who were assessable at week 14. IL-6 levels significantly decreased after IFX therapy (p < 0.001). The validation model containing IL-6 presented enhanced discrimination with an AUC of 0.908 and high calibration. Decision curve analysis (DCA) indicated that the model added extra predictive value. GEO data confirmed the IL-6 levels were increased in the PNR group and IL-6-related differentially expressed genes (DEGs) were enriched in the inflammatory response.

Conclusions: We concluded that IL-6 may be used as a predictive factor to assess the risk of PNR to IFX therapy.

Potential Role of Epithelial Endoplasmic Reticulum Stress and Anterior Gradient Protein 2 Homologue in Crohn's Disease Fibrosis

BACKGROUND AND AIMS

Intestinal fibrosis is a common complication of Crohn's disease [CD]. It is characterised by an accumulation of fibroblasts differentiating into myofibroblasts secreting excessive extracellular matrix. The potential role of the intestinal epithelium in this fibrotic process remains poorly defined.

METHODS

We performed a pilot proteomic study comparing the proteome of surface epithelium, isolated by laser-capture microdissection, in normal and fibrotic zones of resected ileal CD strictures [13 zones collected in five patients]. Proteins of interests were validated by immunohistochemistry [IHC] in ileal and colonic samples of stricturing CD [n = 44], pure inflammatory CD [n = 29], and control [n = 40] subjects. The pro-fibrotic role of one selected epithelial protein was investigated through in-vitro experiments using HT-29 epithelial cells and a CCD-18Co fibroblast to myofibroblast differentiation model.

RESULTS

Proteomic study revealed an endoplasmic reticulum [ER] stress proteins increase in the epithelium of CD ileal fibrotic strictures, including anterior gradient protein 2 homologue [AGR2] and binding-immunoglobulin protein [BiP]. This was confirmed by IHC. In HT-29 cells, tunicamycin-induced ER stress triggered AGR2 intracellular expression and its secretion. Supernatant of these HT-29 cells, pre-conditioned by tunicamycin, led to a myofibroblastic differentiation when applied on CCD-18Co fibroblasts. By using recombinant protein and blocking agent for AGR2, we demonstrated that the secretion of this protein by epithelial cells can play a role in the myofibroblastic differentiation.

CONCLUSIONS

The development of CD fibrotic strictures could involve epithelial ER stress and particularly the secretion of AGR2.

AGR2-AGR3 hetero-oligomeric complexes: Identification and characterization

In this paper we compare electrochemical behavior of two homolog proteins, namely anterior gradient 2 (AGR2) and anterior gradient 3 (AGR3), playing an important role in cancer cell biology. The slight variation in their protein structures has an impact on protein adsorption and orientation at charged surface and also enables AGR2 and AGR3 to form heterocomplexes. We confirm interaction between AGR2 and AGR3 (i) in vitro by immunochemical and constant current chronopotentiometric stripping (CPS) analysis and (ii) in vivo by bioluminescence resonance energy transfer (BRET) assay. Mutation of AGR2 in dimerization domain (E60A) prevents development of wild type AGR2 dimers and also negatively affects interaction with wild type AGR3 as shown by CPS analysis. Beside new information about AGR2 and AGR3 protein including their joint interaction, our work introduces possible applications of CPS in bioanalysis of protein complexes, including those relatively unstable, but important in the cancer research.

Unfolded Protein Response and Crohn’s Diseases: A Molecular Mechanism of Wound Healing in the Gut

Endoplasmic reticulum (ER) stress triggers a series of signaling and transcriptional events termed the unfolded protein response (UPR). Severe ER stress is associated with the development of fibrosis in different organs, including lung, liver, kidney, heart, and intestine. ER stress is an essential response of epithelial and immune cells in the pathogenesis of Inflammatory Bowel Disease (IBD), including Crohn’s disease (CD). Intestinal epithelial cells are susceptible to ER stress-mediated damage due to secretion of a large amount of proteins that are involved in mucosal defense. In other cells, ER stress is linked to myofibroblast activation, extracellular matrix production, macrophage polarization, and immune cell differentiation. This review focuses on the role of the UPR in the pathogenesis in IBD from an immunologic perspective. The roles of macrophage and mesenchymal cells in the UPR from in vitro and in vivo animal models are discussed. The links between ER stress and other signaling pathways, such as senescence and autophagy, are introduced. Recent advances in the understanding of the epigenetic regulation of the UPR signaling are also updated here. The future directions of development of the UPR research and therapeutic strategies to manipulate ER stress levels are also reviewed.

Anterior gradient 2 is involved in the post-transcriptional regulation of β-dystroglycan

Anterior gradient 2 (AGR2) is a protein disulfide isomerase over-expressed in numerous types of cancer. Although AGR2 plays a role in ER homeostasis, its function(s) in tumorigenesis is still elusive. Here we demonstrate that AGR2 is involved in the regulation of the β-subunit of dystroglycan (β-DG), a component of the multi-protein complex linking the extracellular matrix and cytoskeletal network. In breast cancer cells, AGR2 over-expression led to the up-regulation of β-DG but not that of α-DG, while the transcript levels of these subunits were unchanged. Conversely, the reduced expression of AGR2 caused the down-regulation of β-DG. Interestingly, induced expression of AGR2 increased the degree of co-localization of AGR2 and β-DG in the cytoplasm suggesting that AGR2 facilitates the trafficking of β-DG. In addition, AGR2 over-expression caused the re-arrangement of the actin cytoskeletal network. Presumably over-expressed AGR2 up-regulates β-DG post-transcriptionally and facilitates its trafficking, which then causes re-arrangement of the cytoskeletal network, which plays a role in the adhesion and invasion of cancer cells.

Effects of ER-resident and secreted AGR2 on cell proliferation, migration, invasion, and survival in PANC-1 pancreatic cancer cells

Background

Anterior gradient-2 (AGR2) is a proto-oncogene involved in tumorigenesis and cancer progression. AGR2, predominantly localized in the endoplasmic reticulum (ER), is also a secreted protein detected in the extracellular compartment in multiple cancers. However, the biological functions of intracellular and extracellular AGR2 remain to be elucidated.

Methods

Based on the biochemical structure of AGR2 protein, PANC-1 pancreatic cancer cells stably expressing ER-resident or secreted AGR2 were generated by a lentivirus-mediated stable overexpression system. The capacities of cell proliferation, migration, invasion and survival were assessed in PANC-1 stable cells. Moreover, EGFR expression and activation were determined to explore the possible mechanism of AGR2 roles in pancreatic cancer tumorigenesis.

Results

It was discovered that secreted AGR2, but not ER-resident AGR2, promotes cell proliferation, migration and invasion of PANC-1 cells. Moreover, the data indicated that both the ER-resident and the secreted AGR2 enhance the survival capacity of PANC-1 cells after tunicamycin-induced ER stress and gemcitabine treatment. However, EGFR expression and activation were not found to be involved in AGR2-dependent oncogenic phenotypes in PANC-1 cells.

Conclusions

Secreted AGR2 is predominantly involved in cell proliferation, migration and invasion in PANC-1 pancreatic cancer cells. Both secreted and ER-resident AGR2 contribute to the survival of PANC-1 cells under the challenging conditions. These findings provide insight into how different localizations of AGR2 have contributed to pancreatic cancer growth, metastasis, and drug sensitivity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-020-07743-y.

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.

Expression and Importance of TMED2 in Multiple Myeloma Cells

Objective

TMED2 is a member of the transmembrane emp24 domain (Tmed)/p24 protein family, which is significantly upregulated in breast cancer, ovarian cancer and other tumour tissues. The purpose of this study was to investigate the expression of TMED2 in MM cell lines and its effect on the biological behaviour of MM cell lines.

Methods

Real-time quantitative PCR (RT-qPCR) was used to detect the expression of TMED2 in MM cell lines, including MM.1S and RPMI 8226 cells, and lentivirus vector-mediated TMED2 gene silencing was used to further study the effect of the downregulation of TMED2 expression on cell viability, the cell cycle, and apoptosis.

Results

Based on the RT-qPCR results, the expression of the TMED2 mRNA was increased in the MM cell lines MM.1S and RPMI 8226 compared with endogenous control GAPDH. The expression of the TMED2 mRNA was substantially reduced after transfection of the shRNA targeting TMED2 (shTMED2) in both MM cell lines. The CCK-8 assay showed significant decreases in the viability of MM.1S and RPMI 8226 cells, suggesting that the TMED2 gene plays an important role in the proliferation of these two cell lines. The cell cycle of MM.1S and RPMI 8226 cells was substantially altered by shTMED2, as evidenced by the increased number of cells in G1 phase and decreased number of cells in S and G2/M phases. The FACS analysis revealed a significant increase in the apoptosis of MM.1S and RPMI 8226 cells due to the increased activity of Caspase 3/7, suggesting that the TMED2 gene is significantly related to the apoptosis of these two cell lines.

Conclusion

Based on these results, TMED2 may play an important role in the pathogenesis of MM. This novel study may contribute to further investigations of useful biomarkers and potential therapeutic targets in patients with MM.

Extracellular AGR2 triggers lung tumour cell proliferation through repression of p21CIP1

The human Anterior GRadient 2 (AGR2) protein is an Endoplasmic Reticulum (ER)-resident protein which belongs to the Protein-Disulfide Isomerase (PDI) superfamily and is involved to productive protein folding in the ER. As such AGR2, often found overexpressed in adenocarcinomas, contributes to tumour development by enhancing ER proteostasis. We previously demonstrated that AGR2 is secreted (extracellular AGR2 (eAGR2)) in the tumour microenvironment and plays extracellular roles independent of its ER functions. Herein, we show that eAGR2 triggers cell proliferation and characterize the underlying molecular mechanisms. We demonstrate that eAGR2 enhances tumour cell growth by repressing the tumour suppressor p21^CIP1. Our findings shed light on a novel mechanism through which eAGR2 behaves as a growth factor in the tumour microenvironment, independently of its ER function, thus promoting tumour cell growth through repression of p21^CIP1. Our results provide a rationale for targeting eAGR2/p21^CIP1-based signalling as a potential therapeutic target to impede tumour growth.

Secretion of pro-oncogenic AGR2 protein in cancer

Anterior gradient-2 (AGR2) protein mediates the formation, breakage and isomerization of disulphide bonds during protein maturation in the endoplasmic reticulum (ER) and contributes to the homoeostasis of the secretory pathway. AGR2 promotes tumour development and metastasis and its elevated expression is almost completely restricted to malignant tumours. Interestingly, this supposedly ER-resident protein can be localised to other compartments of cancer cells and can also be secreted into the extracellular milieu. There are emerging evidences that describe the gain-of-function activities of the extracellular AGR2, particularly in cancer development. Here, we reviewed studies detailing the expression, pathological and physiological roles associated with AGR2 and compared the duality of localization, intracellular and extracellular, with special emphasis on the later. We also discussed the possible mechanisms of AGR2 secretion as well as deliberating the functional impacts of AGR2 in cancer settings. Last, we deliberate the current therapeutic strategies and posit the potential use AGR2, as a prognosis and diagnosis marker in cancer.

Long Term Delta-9-tetrahydrocannabinol Administration Inhibits Proinflammatory Responses in Minor Salivary Glands of Chronically Simian Immunodeficieny Virus Infected Rhesus Macaques

HIV/SIV-associated oral mucosal disease/dysfunction (HAOMD) (gingivitis/periodontitis/salivary adenitis) represents a major comorbidity affecting HIV patients on anti-retroviral therapy. Using a systems biology approach, we investigated molecular changes (mRNA/microRNA) underlying HAOMD and its modulation by phytocannabinoids (delta-9-tetrahydrocannabinol (∆⁹-THC)) in uninfected (n = 5) and SIV-infected rhesus macaques untreated (VEH-untreated/SIV; n = 7) or treated with vehicle (VEH/SIV; n = 3) or ∆⁹-THC (THC/SIV; n = 3). Relative to controls, fewer mRNAs were upregulated in THC/SIV compared to VEH-untreated/SIV macaques. Gene enrichment analysis showed differential enrichment of biological functions involved in anti-viral defense, Type-I interferon, Toll-like receptor, RIG-1 and IL1R signaling in VEH-untreated/SIV macaques. We focused on the anti-ER-stress anterior gradient-2 (AGR2), epithelial barrier protecting and anti-dysbiotic WAP Four-Disulfide Core Domain-2 (WFDC2) and glucocorticoid-induced anti-inflammatory TSC22D3 (TSC22-domain family member-3) that were significantly downregulated in oropharyngeal mucosa (OPM) of VEH-untreated/SIV macaques. All three proteins localized to minor salivary gland acini and secretory ducts and showed enhanced and reduced expression in OPM of THC/SIV and VEH/SIV macaques, respectively. Additionally, inflammation associated miR-21, miR-142-3p and miR-29b showed significantly higher expression in OPM of VEH-untreated/SIV macaques. TSC22D3 was validated as a target of miR-29b. These preliminary translational findings suggest that phytocannabinoids may safely and effectively reduce oral inflammatory responses in HIV/SIV and other (autoimmune) diseases.

The anterior gradient-2 interactome

The anterior gradient-2 (AGR2) is an endoplasmic reticulum (ER)-resident protein belonging to the protein disulfide isomerase family that mediates the formation of disulfide bonds and assists the protein quality control in the ER. In addition to its role in proteostasis, extracellular AGR2 is responsible for various cellular effects in many types of cancer, including cell proliferation, survival, and metastasis. Various OMICs approaches have been used to identify AGR2 binding partners and to investigate the functions of AGR2 in the ER and outside the cell. Emerging data showed that AGR2 exists not only as monomer, but it can also form homodimeric structure and thus interact with different partners, yielding different biological outcomes. In this review, we summarize the AGR2 “interactome” and discuss the pathological and physiological role of such AGR2 interactions.

Transmembrane emp24 domain proteins in development and disease

Regulated transport through the secretory pathway is essential for embryonic development and homeostasis. Disruptions in this process impact cell fate, differentiation and survival, often resulting in abnormalities in morphogenesis and in disease. Several congenital malformations are caused by mutations in genes coding for proteins that regulate cargo protein transport in the secretory pathway. The severity of mutant phenotypes and the unclear aetiology of transport protein-associated pathologies have motivated research on the regulation and mechanisms through which these proteins contribute to morphogenesis. This review focuses on the role of the p24/transmembrane emp24 domain (TMED) family of cargo receptors in development and disease.

Extracellular AGR3 regulates breast cancer cells migration via Src signaling

Human anterior gradient proteins AGR2 and AGR3 are overexpressed in a variety of adenocarcinomas and are often secreted in cancer patients' specimens, which suggests a role for AGR proteins in intra and extracellular compartments. Although these proteins exhibit high sequence homology, AGR2 is predominantly described as a pro-oncogene and a potential prognostic biomarker. However, little is known about the function of AGR3. Therefore, the aim of the present study was to investigate the role of AGR3 in breast cancer. The results demonstrated that breast cancer cells secrete AGR3. Furthermore, it was revealed that extracellular AGR3 (eAGR3) regulates tumor cell adhesion and migration. The current study indicated that the pharmacological and genetic perturbation of Src kinase signaling, through treatment with Dasatinib (protein kinase inhibitor) or investigating cells that express a dominant-negative form of Src, significantly abrogated eAGR3-mediated breast cancer cell migration. Therefore, the results indicated that eAGR3 may control tumor cell migration via activation of Src kinases. The results of the present study indicated that eAGR3 may serve as a microenvironmental signaling molecule in tumor-associated processes.

AGR2 silencing contributes to metformin-dependent sensitization of colorectal cancer cells to chemotherapy

There is growing epidemiological evidence indicating an association between diabetes mellitus and the increased incidence of colorectal cancer (CRC). The preferred initial and most widely used pharmacological agent for the treatment of type 2 diabetes is metformin, which in parallel reduces the risk of CRC and improves patient prognosis. AMP-activated protein kinase (AMPK) appears to be tightly associated with the beneficial metabolic effects of metformin, serving as a cellular energy sensor activated in response to a variety of conditions that deplete cellular energy levels. Such conditions include nutrient starvation (particularly glucose), hypoxia and exposure to toxins that inhibit the mitochondrial respiratory chain complex. The aim of the present study was to determine the effect of metformin on CRC cell lines, with different levels of anterior gradient 2 (AGR2) expression, exposed to 5-fluorouracil (5-FU) and oxaliplatin, alone or in combination with metformin. AGR2 has recently emerged as a factor involved in colon carcinogenesis. In AGR2-knockout cells, markedly higher levels of phosphorylated-AMPK were observed in comparison with control cells transfected with GFP-scrambled guide RNA, which indicated that the presence of AGR2 may interfere with the metformin-dependent activation of AMPK. In addition, metformin in combination with 5-FU and oxaliplatin induced ROS production and attenuated autophagy. This effect was enhanced in AGR2-knockout cells.

Going for the Golgi: small PDI protein helps ATF6 perform better under stress

ATF6 is a major signal transducer for cellular reprogramming in response to protein mis-folding in the endoplasmic reticulum. However, the mechanism by which ATF6 senses unfolded proteins and becomes activated is not yet known. In this issue of The EMBO Journal, Oka et al show that ERp18, a single-domain member of the protein disulfide isomerase family, interacts preferentially with ATF6 under stress conditions and regulates ATF6 transport to the Golgi apparatus. Furthermore, ERp18 impacts the ATF6 cleavage product generated in the Golgi, ultimately determining whether or not ATF6 becomes a functional transcription factor and induces the unfolded protein response.

Leveraging the Role of the Metastatic Associated Protein Anterior Gradient Homologue 2 in Unfolded Protein Degradation: A Novel Therapeutic Biomarker for Cancer

Effective diagnostic, prognostic and therapeutic biomarkers can help in tracking disease progress, predict patients’ survival, and considerably affect the drive for successful clinical management. The present review aims to determine how the metastatic-linked protein anterior gradient homologue 2 (AGR2) operates to affect cancer progression, and to identify associated potential diagnostic, prognostic and therapeutic biomarkers, particularly in central nervous system (CNS) tumors. Studies that show a high expression level of AGR2, and associate the protein expression with the resilience to chemotherapeutic treatments or with poor cancer survival, are reported. The primary protein structures of the seven variants of AGR2, including their functional domains, are summarized. Based on experiments in various biological models, this review shows an orchestra of multiple molecules that regulate AGR2 expression, including a feedback loop with p53. The AGR2-associated molecular functions and pathways including genomic integrity, proliferation, apoptosis, angiogenesis, adhesion, migration, stemness, and inflammation, are detailed. In addition, the mechanisms that can enable the rampant oncogenic effects of AGR2 are clarified. The different strategies used to therapeutically target AGR2-positive cancer cells are evaluated in light of the current evidence. Moreover, novel associated pathways and clinically relevant deregulated genes in AGR2 high CNS tumors are identified using a meta-analysis approach.