The α-arrestin ARRDC3 suppresses breast carcinoma invasion by regulating G protein-coupled receptor lysosomal sorting and signaling

Genome-wide CRISPR screening identifies a role for ARRDC3 in TRP53-mediated responses

Whole-genome screens using CRISPR technologies are powerful tools to identify novel tumour suppressors as well as factors that impact responses of malignant cells to anti-cancer agents. Applying this methodology to lymphoma cells, we conducted a genome-wide screen to identify novel inhibitors of tumour expansion that are induced by the tumour suppressor TRP53. We discovered that the absence of Arrestin domain containing 3 (ARRDC3) increases the survival and long-term competitiveness of MYC-driven lymphoma cells when treated with anti-cancer agents that activate TRP53. Deleting Arrdc3 in mice caused perinatal lethality due to various developmental abnormalities, including cardiac defects. Notably, the absence of ARRDC3 markedly accelerated MYC-driven lymphoma development. Thus, ARRDC3 is a new mediator of TRP53-mediated suppression of tumour expansion, and this discovery may open new avenues to harness this process for cancer therapy.

ARRDC3 regulates the targeted therapy sensitivity of clear cell renal cell carcinoma by promoting AXL degradation

AXL plays crucial roles in the tumorigenesis, progression, and drug resistance of neoplasms; however, the mechanisms associated with AXL overexpression in tumors remain largely unknown. In this study, to investigate these molecular mechanisms, wildtype and mutant proteins of arrestin domain-containing protein 3 (ARRDC3) and AXL were expressed, and co-immunoprecipitation analyses were performed. ARRDC3-deficient cells generated using the CRISPR-Cas9 system were treated with different concentrations of the tyrosine kinase inhibitor sunitinib and subjected to cell biological, molecular, and pharmacological experiments. Furthermore, immunohistochemistry was used to analyze the correlation between ARRDC3 and AXL protein expressions in renal cancer tissue specimens. The experimental results demonstrated that ARRDC3 interacts with AXL to promote AXL ubiquitination and degradation, followed by the negative regulation of downstream signaling mechanisms, including the phosphorylation of protein kinase B and extracellular signal-regulated kinase. Notably, ARRDC3 deficiency decreased the sunitinib sensitivity of clear cell renal cell carcinoma (ccRCC) cells in a manner dependent on the regulation of AXL stability. Overall, our results suggest that ARRDC3 is a negative regulator of AXL and can serve as a novel predictor of sunitinib therapeutic response in patients with ccRCC.

Protease-Activated Receptor 1 (PAR1) Expression Contributes to HPV-Associated Oropharyngeal Cancer Prognosis

BACKGROUND

Human papillomavirus (HPV)-associated oropharyngeal cancer occasionally has a poor prognosis, making prognostic risk stratification crucial. Protease-activated receptor-1 (PAR1) is involved in carcinogenesis, and its expression is regulated by alpha-arrestin domain-containing protein 3 (ARRDC3). It is also involved in the tumor microenvironment. We sought to evaluate the predictive ability of PAR1, ARRDC3, and tumor-infiltrating lymphocyte (TIL) scores in patients with oropharyngeal, hypopharyngeal, and uterine cervical cancers, serving as comparators for HPV-associated oropharyngeal cancer.

METHODS

Immunohistochemical analysis of p16, ARRDC3, and PAR1 expression was performed on 79 oropharyngeal, 44 hypopharyngeal, and 42 uterine cervical cancer samples. The TIL scores were assessed and classified into the following groups based on invasion: low: 0-10%, medium: 20-40%, and high: > 50%. For prognostic analysis, the three groups were evaluated by dividing them into low, medium, and high categories, or alternatively into two groups using the median value as the cutoff.

RESULTS

p16 was expressed in 44 (56%) oropharyngeal, 8 (18%) hypopharyngeal, and all uterine cervical cancer samples. ARRDC3 was detected in 39 (49%) oropharyngeal, 25 (57%) hypopharyngeal, and 23 (55%) uterine cervical cancer samples. PAR1 was expressed in 45 (57%) oropharyngeal, 22 (50%) hypopharyngeal, and 22 (50%) uterine cervical cancer samples. Patients diagnosed with p16-positive oropharyngeal cancer had a substantially improved prognosis compared to those diagnosed with p16-negative cancer. The PAR1-negative cases had a considerably improved prognosis compared to the positive cases (disease-specific survival [DSS] and -negative cases (disease-free survival [DFS]). Multivariate analysis revealed that ARRDC3-positive cases had an appreciably better DSS prognosis than patients with p16-negative oropharyngeal cancers. PAR1-positive patients among patients with p16-positive oropharyngeal cancer had a poor prognosis. With respect to DFS, patients with PAR1-positive and p16-negative oropharyngeal cancer had a 35-fold higher recurrence rate than those with PAR1-negative and p16-negative oropharyngeal cancer.

CONCLUSION

Our results suggest that PAR1 expression affects the prognosis and recurrence rate of HPV-associated oropharyngeal cancer.

Divergent regulation of α-arrestin ARRDC3 function by ubiquitination

The α-arrestin ARRDC3 is a recently discovered tumor suppressor in invasive breast cancer that functions as a multifaceted adaptor protein to control protein trafficking and cellular signaling. However, the molecular mechanisms that control ARRDC3 function are unknown. Other arrestins are known to be regulated by posttranslational modifications, suggesting that ARRDC3 may be subject to similar regulatory mechanisms. Here we report that ubiquitination is a key regulator of ARRDC3 function and is mediated primarily by two proline-rich PPXY motifs in the ARRDC3 C-tail domain. Ubiquitination and the PPXY motifs are essential for ARRDC3 function in regulating GPCR trafficking and signaling. Additionally, ubiquitination and the PPXY motifs mediate ARRDC3 protein degradation, dictate ARRDC3 subcellular localization, and are required for interaction with the NEDD4-family E3 ubiquitin ligase WWP2. These studies demonstrate a role for ubiquitination in regulating ARRDC3 function and reveal a mechanism by which ARRDC3 divergent functions are controlled.

Fuzheng Kang-Ai inhibits NSCLC cell proliferation via regulating hsa_circ_0048091/hsa-miR-378g/ARRDC3 pathway

BACKGROUND

Current treatments for lung cancer have their own deficiencies, such as severe adverse effect. Therefore, more safe and effective drugs are needed.

PURPOSE

Fuzheng Kang-Ai (FZKA for short) has been applied as an adjuvant treatment in advanced Non-Small Cell Lung Cancer (NSCLC) patients for decades in China, showing a definitive effect with minimal toxicities. However, the underlying mechanism is yet to be identified.

STUDY DESIGN

Both in vitro and in vivo experiments were performed in this study to identify the exact mechanism by which FZKA inhibits NSCLC cell proliferation.

METHODS

MTT and CCK-8 assays were used to detect cell viability. Xenograft model was performed for in vivo experiments. CircRNA and miRNA sequencing were used to find the differentially expressed circRNAs and miRNAs, respectively. qRT-PCR was performed to check the expression levels of circRNA, miRNA and mRNA. BaseScope was carried out to observe the expression of circRNA in situ. Actinomycin D and RNase R experiments were done to show the stability of circRNA. Nuclear-cytoplasmic fractionation and FISH were used to identify the localization of circRNA and miRNA. Pull-down, RIP, and luciferase activity assays were performed to show the biding ability of circRNA, miRNA and target proteins. Flow cytometry was done to observe cell apoptosis. Western blot and IHC were done to detect the protein expression. TCGA database was used to analyze the survival rate.

RESULTS

FZKA inhibits NSCLC cell proliferation both in vitro and in vivo. Hsa_circ_0048091 and hsa-miR-378g were the most differentially expressed circRNA and miRNA, respectively, after FZKA treatment. Silencing hsa_circ_0048091 and overexpressing hsa-miR-378g promoted cell proliferation and reversed the inhibition effect of FZKA on NSCLC, respectively. Hsa-miR-378g was sponged by hsa_circ_0048091, and the overexpression of miR-378g reversed the inhibition effect of hsa_ circ_0048091 on NSCLC. ARRDC3, as a target of hsa-miR-378g, was increased by FZKA treatment. Silencing ARRDC3 reversed both the inhibition effect of FZKA and miR-378g inhibitor on NSCLC.

CONCLUSION

This study, for the first time, has established the function of hsa_circ_0048091, hsa- miR-378g, and ARRDC3 in lung cancer. It also shows that FZKA inhibits NSCLC cell proliferation through hsa_circ_0048091/hsa-miR-378g/ARRDC3 pathway, uncovering a novel mechanism by which FZKA controls human NSCLC cell growth.

Protease-activated receptors in health and disease

Proteases are signaling molecules that specifically control cellular functions by cleaving protease-activated receptors (PARs). The four known PARs are members of the large family of G protein-coupled receptors. These transmembrane receptors control most physiological and pathological processes and are the target of a large proportion of therapeutic drugs. Signaling proteases include enzymes from the circulation; from immune, inflammatory epithelial, and cancer cells; as well as from commensal and pathogenic bacteria. Advances in our understanding of the structure and function of PARs provide insights into how diverse proteases activate these receptors to regulate physiological and pathological processes in most tissues and organ systems. The realization that proteases and PARs are key mediators of disease, coupled with advances in understanding the atomic level structure of PARs and their mechanisms of signaling in subcellular microdomains, has spurred the development of antagonists, some of which have advanced to the clinic. Herein we review the discovery, structure, and function of this receptor system, highlight the contribution of PARs to homeostatic control, and discuss the potential of PAR antagonists for the treatment of major diseases.

Suppression of tumor progression by thioredoxin-interacting protein-dependent adenosine 2B receptor degradation in a PLAG-treated Lewis lung carcinoma-1 model of non-small cell lung cancer

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PLAG effectively inhibited excessive growth of LLC1 cells in an NSCLC model.

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PLAG inhibited tumor growth by inducing adenosine 2B receptor (A2BR) degradation.

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Unlike antagonists, PLAG terminates rather than suppresses signaling pathways.

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A2BR degradation by PLAG occurs through expression and re-localization of TXNIP.

Extracellular adenosine in the tumor microenvironment plays a vital role in cancer development. Specifically, activation of adenosine receptors affects tumor cell growth and adenosine release.

We examined the anti-tumor efficacy of 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (PLAG) in animal models, revealing the role of PLAG in inhibiting tumor progression by promoting the degradation of adenosine 2B receptors (A2BRs) in tumors. PLAG induced the expression of thioredoxin-interacting protein (TXNIP), a type of α-arrestin that accelerates A2BR internalization by interacting with A2BR complexes containing β-arrestin. Engulfed receptors bound to TXNIP were rapidly degraded after E3 ligase recruitment and ubiquitination, resulting in early termination of intracellular signals that promote tumor overgrowth. However, in control cancer cells, A2BRs bound to protein phosphatase 2A and were returned to the cell membrane instead of being degraded, resulting in continuous receptor-mediated signaling by pathways including the Raf-Erk axis, which promotes tumor proliferation. A TXNIP-silenced cell-implanted mouse model and TXNIP knockout (KO) mice were used to verify that PLAG-mediated suppression of tumor progression is dependent on TXNIP expression. Increased tumor growth was observed in TXNIP-silenced cell-implanted mice, and the anti-tumor effects of PLAG, including delayed tumor overgrowth, were greatly reduced. However, the anti-tumor effects of PLAG were observed in cancer cell-implanted TXNIP-KO mice, which indicates that PLAG produces anti-tumor effects by enhancing TXNIP expression in tumor cells.

These essential functions of PLAG, including delaying tumor growth via A2BR degradation, suggest innovative directions for anticancer drug development.

Post-Translational Modifications in GPCR Internalization

G protein-coupled receptors (GPCRs) are the largest family of membrane receptors that serve as the most important drug targets. Classically, GPCR internalization has been considered to lead to receptor desensitization. However, many studies over the past decade have reported that internalized membrane receptors can trigger distinct signal activation. The "internalized activation" provides a completely new understanding for the receptor internalization, the mechanism of physiology/pathology and novel drug targets for precision medicine. GPCR internalization undergoes a series of strict regulations, especially by post-translational modifications (PTMs). Here, this review summarizes different PTMs in GPCR internalization and analyzes their significance in GPCR internalization dynamics, internalization routes, post-internalization fates and related diseases, which will offer new insights into the regulatory mechanism of GPCR signaling and novel drug targets for precision medicine.

The α-Arrestin ARRDC3 Is an Emerging Multifunctional Adaptor Protein in Cancer

Significance: Adaptor proteins control the spatiotemporal dynamics of cellular signaling. Dysregulation of adaptor protein function can cause aberrant cell signaling and promote cancer. The arrestin family of adaptor proteins are known to regulate signaling by the superfamily of G protein-coupled receptors (GPCRs). The GPCRs are highly druggable and implicated in cancer progression. However, the molecular mechanisms responsible for arrestin dysregulation and the impact on GPCR function in cancer have yet to be fully elucidated. Recent Advances: A new family of mammalian arrestins, termed the α-arrestins, was recently discovered. The α-arrestin, arrestin domain-containing protein 3 (ARRDC3), in particular, has been identified as a tumor suppressor and is reported to control cellular signaling of GPCRs in cancer. Critical Issues: Compared with the extensively studied mammalian β-arrestins, there is limited information regarding the regulatory mechanisms that control α-arrestin activation and function. Here, we discuss the molecular mechanisms that regulate ARRDC3, which include post-translational modifications such as phosphorylation and ubiquitination. We also provide evidence that ARRDC3 can interact with a wide array of proteins that control diverse biological functions. Future Directions: ARRDC3 interacts with numerous proteins and is likely to display diverse functions in cancer, metabolic disease, and other syndromes. Thus, understanding the regulatory mechanisms of ARRDC3 activity in various cellular contexts is critically important. Recent studies suggest that α-arrestins may be regulated through post-translational modification, which is known to impact adaptor protein function. However, additional studies are needed to determine how these regulatory mechanisms affect ARRDC3 tumor suppressor function. Antioxid. Redox Signal. 36, 1066-1079.

α-Arrestins and Their Functions: From Yeast to Human Health

α-Arrestins, also called arrestin-related trafficking adaptors (ARTs), constitute a large family of proteins conserved from yeast to humans. Despite their evolutionary precedence over their extensively studied relatives of the β-arrestin family, α-arrestins have been discovered relatively recently, and thus their properties are mostly unexplored. The predominant function of α-arrestins is the selective identification of membrane proteins for ubiquitination and degradation, which is an important element in maintaining membrane protein homeostasis as well as global cellular metabolisms. Among members of the arrestin clan, only α-arrestins possess PY motifs that allow canonical binding to WW domains of Rsp5/NEDD4 ubiquitin ligases and the subsequent ubiquitination of membrane proteins leading to their vacuolar/lysosomal degradation. The molecular mechanisms of the selective substrate’s targeting, function, and regulation of α-arrestins in response to different stimuli remain incompletely understood. Several functions of α-arrestins in animal models have been recently characterized, including redox homeostasis regulation, innate immune response regulation, and tumor suppression. However, the molecular mechanisms of α-arrestin regulation and substrate interactions are mainly based on observations from the yeast Saccharomyces cerevisiae model. Nonetheless, α-arrestins have been implicated in health disorders such as diabetes, cardiovascular diseases, neurodegenerative disorders, and tumor progression, placing them in the group of potential therapeutic targets.

Neighborhood characteristics and breast tumor methylation: using epigenomics to explore cancer outcome disparities

BACKGROUND

Social exposures may drive epigenetic alterations that affect racial disparities in breast cancer outcomes. This study examined the association between neighborhood-level factors and DNA methylation in non-Hispanic Black and White women diagnosed with breast cancer.

METHODS

Genome-wide DNA methylation was measured using the EPIC array in the tumor tissue of 96 women. Linear regression models were used to examine the association between nine neighborhood-level factors and methylation, regressing β values for each cytosine-phosphate guanine dinucleotide (CpG) site on neighborhood-level factors while adjusting for covariates. Neighborhood data were obtained from the Opportunity Atlas. We used a false discovery rate (FDR) threshold < 0.05, and for CpGs below this threshold, we examined interactions with race. We employed multivariable Cox proportional-hazards models to estimate whether aberrant methylation was associated with all-cause mortality.

RESULTS

26 of the CpG sites were associated with job density or college education (FDR < 0.05). Further exploration of these 26 CpG sites revealed no interactions by race, but a single probe in TMEM204 was associated with all-cause mortality.

CONCLUSION

We identified novel associations between neighborhood-level factors and the breast tumor DNA methylome. Our data are the first to show that dysregulation in neighborhood associated CpG sites may be associated with all-cause mortality. Neighborhood-level factors may contribute to differential tumor methylation in genes related to tumor progression and metastasis. This contributes to the increasing body of evidence that area-level factors (such as neighborhood characteristics) may play an important role in cancer disparities through modulation of the breast tumor epigenome.

MicroRNA-624-mediated ARRDC3/YAP/HIF1α axis enhances esophageal squamous cell carcinoma cell resistance to cisplatin and paclitaxel

Development of chemoresistance remains a major challenge in treating patients suffering from esophageal squamous cell carcinoma (ESCC), despite treatment advances. MicroRNAs (miRNAs) have been shown to play critical roles in the regulation of ESCC cell chemoresistance. Here, we aimed to investigate the role of miR-624 in ESCC and its molecular mechanism in mediating the resistance of ESCC cells to two common chemotherapeutic drugs, cisplatin (CIS) and paclitaxel (PT). Expression patterns of miR-624, arrestin domain-containing 3 (ARRDC3), Yes-associated protein (YAP), and hypoxia-inducible factor-1α (HIF1α) in ESCC tissues and cell lines were identified using RT-qPCR and Western blot analysis. The binding affinities with the miR-624/ARRDC3/YAP/HIF1α axis were characterized. The chemotherapy-sensitive cell line KYSE150 and chemotherapy-resistant cell line KYSE410 were transfected with an overexpression plasmid or shRNA to study the effect of miR-624/ARRDC3/YAP/HIF1α axis on ESCC cell resistance to CIS and PT. Their in vivo effects on resistance to PT were assessed in tumor-bearing nude mice. High expression of miR-624, YAP and HIF1α, and low expression of ARRDC3 were observed in ESCC tissues and cell lines. miR-624 presented with higher expression in KYSE410 than in KYSE150 cells. miR-624 downregulated ARRDC3 to increase YAP and HIF1α expression so as to enhance ESCC cell resistance to CIS and PT in vitro and in vivo. Taken together, these data indicate an important role for miR-624 in promoting the chemoresistance of ESCC cells, highlighting a potential strategy to overcome drug resistance in ESCC treatment. miR-624 targets ARRDC3 to inhibit its expression, and consequently upregulates YAP expression by inhibiting degradation of YAP. By this mechanism, HIF1α expression is upregulated and the HIF1α signaling pathway is activated. ESCC cell chemotherapy resistance is eventually increased.

ARRDC3 polymorphisms may affect the risk of glioma in Chinese Han

This study ascertained to explore the potential contribution of ARRDC3 polymorphisms in the risk and prognosis of glioma. One thousand sixty-one patients and healthy controls were conducted to assess whether ARDC3 polymorphism was associated with glioma risk and prognosis. Four sites in ARRDC3 were selected and genotyped in MassARRAY platform. The calculated odd ratios and 95% confidence intervals from logistic regression were applied for risk assessment. The relationship between ARRDC3 variants and glioma prognosis was evaluated using log-rank test, Kaplan-Meier analysis, and so on. Also, false-positive report probability (FPRP) and statistical power were also assessed. Our findings suggested the negative role of ARRDC3 polymorphisms in the glioma risk. We also found the effect of candidate SNPs in ARRDC3 on the susceptibility to glioma was dependent on the age, gender, and histology of glioma patients. The results suggested that the genetic polymorphisms of ARRDC3 were related to an increased risk of glioma.

Computational Approaches for Cancer-Fighting: From Gene Expression to Functional Foods

It is today widely accepted that a healthy diet is very useful to prevent the risk for cancer or its deleterious effects. Nutrigenomics studies are therefore taking place with the aim to test the effects of nutrients at molecular level and contribute to the search for anti-cancer treatments. These efforts are expanding the precious source of information necessary for the selection of natural compounds useful for the design of novel drugs or functional foods. Here we present a computational study to select new candidate compounds that could play a role in cancer prevention and care. Starting from a dataset of genes that are co-expressed in programmed cell death experiments, we investigated on nutrigenomics treatments inducing apoptosis, and searched for compounds that determine the same expression pattern. Subsequently, we selected cancer types where the genes showed an opposite expression pattern and we confirmed that the apoptotic/nutrigenomics expression trend had a significant positive survival in cancer-affected patients. Furthermore, we considered the functional interactors of the genes as defined by public protein-protein interaction data, and inferred on their involvement in cancers and/or in programmed cell death. We identified 7 genes and, from available nutrigenomics experiments, 6 compounds effective on their expression. These 6 compounds were exploited to identify, by ligand-based virtual screening, additional molecules with similar structure. We checked for ADME criteria and selected 23 natural compounds representing suitable candidates for further testing their efficacy in apoptosis induction. Due to their presence in natural resources, novel drugs and/or the design of functional foods are conceivable from the presented results.

α-Arrestin ARRDC3 tumor suppressor function is linked to GPCR-induced TAZ activation and breast cancer metastasis

The α-arrestin domain containing protein 3 (ARRDC3) is a tumor suppressor in triple-negative breast carcinoma (TNBC), a highly metastatic subtype of breast cancer that lacks targeted therapies. Thus, understanding the mechanisms and targets of ARRDC3 in TNBC is important. ARRDC3 regulates trafficking of protease-activated receptor 1 (PAR1, also known as F2R), a G-protein-coupled receptor (GPCR) implicated in breast cancer metastasis. Loss of ARRDC3 causes overexpression of PAR1 and aberrant signaling. Moreover, dysregulation of GPCR-induced Hippo signaling is associated with breast cancer progression. However, the mechanisms responsible for Hippo dysregulation remain unknown. Here, we report that the Hippo pathway transcriptional co-activator TAZ (also known as WWTR1) is the major effector of GPCR signaling and is required for TNBC migration and invasion. Additionally, ARRDC3 suppresses PAR1-induced Hippo signaling via sequestration of TAZ, which occurs independently of ARRDC3-regulated PAR1 trafficking. The ARRDC3 C-terminal PPXY motifs and TAZ WW domain are crucial for this interaction and are required for suppression of TNBC migration and lung metastasis in vivo. These studies are the first to demonstrate a role for ARRDC3 in regulating GPCR-induced TAZ activity in TNBC and reveal multi-faceted tumor suppressor functions of ARRDC3. This article has an associated First Person interview with the first author of the paper.

ARRDC3 as a Diagnostic and Prognostic Biomarker for Epithelial Ovarian Cancer Based on Data Mining

Purpose

The dysregulation of arrestin domain containing 3 (ARRDC3) has an important effect on oncogenesis and tumor progression in many cancers, including renal cell carcinoma and breast cancer. However, the role of ARRDC3 in ovarian cancer (OC) has not been reported.

Methods

The present study explored the diagnostic and prognostic roles of ARRDC3 in ovarian cancer using GEPIA, ONCOMINE, GEO, and Kaplan–Meier Plotter databases for training and validation. Then, we conducted a stratified analysis for clinicopathological factors using Kaplan–Meier Plotter and GEPIA databases. To further explore the mechanisms, we also used the MIST database to visualize the protein–protein interaction network of ARRDC3 associated with OC. The gene–gene interaction network was visualized by GeneMANIA plugin in Cytoscape 3.8.0 software, and the associated co-expression genes of ARRDC3 were analyzed by the cBioPortal database. The 100 top co-expression genes chosen for gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were used by the DAVID website.

Results

A significant difference in ARRDC3 mRNA expression was found between OC and normal ovary tissues. ARRDC3 could potentially be implicated in the diagnosis of OC. A high ARRDC3 mRNA expression level was associated with poor overall survival and progression-free survival. However, no significance was reported in respect to post progression survival. Except for histology, which had no prognostic value for PPS in stratified analysis, stratified analysis of other factors had prognostic value for OS, PFS, and PPS. Interestingly, we found a positive correlation between ARRDC3 expression and CD8+ T cells, macrophages, neutrophils, and dendritic cells, indicating that ARRDC3 might be associated with immune infiltration of these immune cells. Co-expression genes enrichment analysis found that they were involved in the Renin-angiotensin system pathway.

Conclusion

Differentially expressed ARRDC3 might be a potential prognostic and diagnostic marker in Ovarian Cancer.

The α-arrestin family of ubiquitin ligase adaptors links metabolism with selective endocytosis

The regulation of nutrient uptake into cells is important, as it allows to either increase biomass for cell growth or to preserve homoeostasis. A key strategy to adjust cellular nutrient uptake is the reconfiguration of the nutrient transporter repertoire at the plasma membrane by the addition of nutrient transporters through the secretory pathway and by their endocytic removal. In this review, we focus on the mechanisms that regulate selective nutrient transporter endocytosis, which is mediated by the α-arrestin protein family. In the budding yeast Saccharomyces cerevisiae, 14 different α-arrestins (also named arrestin-related trafficking adaptors, ARTs) function as adaptors for the ubiquitin ligase Rsp5. They instruct Rsp5 to ubiquitinate subsets of nutrient transporters to orchestrate their endocytosis. The ART proteins are under multilevel control of the major nutrient sensing systems, including amino acid sensing by the general amino acid control and target of rapamycin pathways, and energy sensing by 5'-adenosine-monophosphate-dependent kinase. The function of the six human α-arrestins is comparably under-characterised. Here, we summarise the current knowledge about the function, regulation and substrates of yeast ARTs and human α-arrestins, and highlight emerging communalities and general principles.

YAP1 and its fusion proteins in cancer initiation, progression and therapeutic resistance

YAP1 is a transcriptional co-activator whose activity is controlled by the Hippo signaling pathway. In addition to important functions in normal tissue homeostasis and regeneration, YAP1 has also prominent functions in cancer initiation, aggressiveness, metastasis, and therapy resistance. In this review we are discussing the molecular functions of YAP1 and its roles in cancer, with a focus on the different mechanisms of de-regulation of YAP1 activity in human cancers, including inactivation of upstream Hippo pathway tumor suppressors, regulation by intersecting pathways, miRNAs, and viral oncogenes. We are also discussing new findings on the function and biology of the recently identified family of YAP1 gene fusions, that constitute a new type of activating mutation of YAP1 and that are the likely oncogenic drivers in several subtypes of human cancers. Lastly, we also discuss different strategies of therapeutic inhibition of YAP1 functions.

Post-Translational Modifications of G Protein-Coupled Receptors Control Cellular Signaling Dynamics in Space and Time

G protein-coupled receptors (GPCRs) are a large family comprising >800 signaling receptors that regulate numerous cellular and physiologic responses. GPCRs have been implicated in numerous diseases and represent the largest class of drug targets. Although advances in GPCR structure and pharmacology have improved drug discovery, the regulation of GPCR function by diverse post-translational modifications (PTMs) has received minimal attention. Over 200 PTMs are known to exist in mammalian cells, yet only a few have been reported for GPCRs. Early studies revealed phosphorylation as a major regulator of GPCR signaling, whereas later reports implicated a function for ubiquitination, glycosylation, and palmitoylation in GPCR biology. Although our knowledge of GPCR phosphorylation is extensive, our knowledge of the modifying enzymes, regulation, and function of other GPCR PTMs is limited. In this review we provide a comprehensive overview of GPCR post-translational modifications with a greater focus on new discoveries. We discuss the subcellular location and regulatory mechanisms that control post-translational modifications of GPCRs. The functional implications of newly discovered GPCR PTMs on receptor folding, biosynthesis, endocytic trafficking, dimerization, compartmentalized signaling, and biased signaling are also provided. Methods to detect and study GPCR PTMs as well as PTM crosstalk are further highlighted. Finally, we conclude with a discussion of the implications of GPCR PTMs in human disease and their importance for drug discovery. SIGNIFICANCE STATEMENT: Post-translational modification of G protein-coupled receptors (GPCRs) controls all aspects of receptor function; however, the detection and study of diverse types of GPCR modifications are limited. A thorough understanding of the role and mechanisms by which diverse post-translational modifications regulate GPCR signaling and trafficking is essential for understanding dysregulated mechanisms in disease and for improving and refining drug development for GPCRs.

Arrestin domain containing 3 promotes Helicobacter pylori-associated gastritis by regulating protease-activated receptor 1

Arrestin domain containing 3 (ARRDC3) represents a newly discovered α-arrestin involved in obesity, inflammation, and cancer. Here, we demonstrate a proinflammation role of ARRDC3 in Helicobacter pylori–associated gastritis. Increased ARRDC3 was detected in gastric mucosa of patients and mice infected with H. pylori. ARRDC3 in gastric epithelial cells (GECs) was induced by H. pylori, regulated by ERK and PI3K-AKT pathways in a cagA-dependent manner. Human gastric ARRDC3 correlated with the severity of gastritis, and mouse ARRDC3 from non-BM–derived cells promoted gastric inflammation. This inflammation was characterized by the CXCR2-dependent influx of CD45⁺CD11b⁺Ly6C^–Ly6G⁺ neutrophils, whose migration was induced via the ARRDC3-dependent production of CXCL2 by GECs. Importantly, gastric inflammation was attenuated in Arrdc3^–/– mice but increased in protease-activated receptor 1^–/– (Par1^–/–) mice. Mechanistically, ARRDC3 in GECs directly interacted with PAR1 and negatively regulated PAR1 via ARRDC3-mediated lysosomal degradation, which abrogated the suppression of CXCL2 production and following neutrophil chemotaxis by PAR1, thereby contributing to the development of H. pylori–associated gastritis. This study identifies a regulatory network involving H. pylori, GECs, ARRDC3, PAR1, and neutrophils, which collectively exert a proinflammatory effect within the gastric microenvironment. Efforts to inhibit this ARRDC3-dependent pathway may provide valuable strategies in treating of H. pylori–associated gastritis.

A regulatory network including H. pylori, GECs, ARRDC3, PAR1, and neutrophils collectively exerts a pro-inflammatory effect within the gastric microenvironment.

1‑Palmitoyl‑2‑linoleoyl‑3‑acetyl‑rac‑glycerol ameliorates EGF‑induced MMP‑9 expression by promoting receptor desensitization in MDA‑MB‑231 cells

Activated epidermal growth factor receptors (EGFRs) are crucial for inducing metastasis in cancer cells by promoting matrix metalloproteinase (MMP) expression. The present study was designed to investigate the effects of 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (PLAG) on MMP expression in epidermal growth factor (EGF)-stimulated breast cancer cells in vitro. EGF stimulation induced internalization of its cognate receptor, EGFR, for stimulus-desensitization. These internalized receptors, complexed with the ubiquitin ligase c-Cbl and EGFR pathway substrate 15 (EPS15) (for degradation), were evaluated by confocal microscopy at 5–90 min time intervals. During intracellular trafficking of EGFRs, EGF-induced signaling cascades were analyzed by examining EGFR and SHC phosphorylation. Modulation of MMP expression was assessed by evaluating the activity of transcription factor AP-1 using a luciferase assay. PLAG accelerated the assembly of EGFRs with c-Cbl and EPS15 and promoted receptor degradation. This faster intracellular EGFR degradation reduced AP-1-mediated MMP expression. PLAG stimulation upregulated thioredoxin-interacting protein (TXNIP) expression, and this mediated the accelerated receptor internalization. This PLAG-induced increase in EGFR trafficking was blocked in TXNIP-silenced cells. By downregulating MMP expression, PLAG effectively attenuated EGF-induced mobility and invasiveness in these cancer cells. These data suggest that PLAG may be a potential therapeutic agent for blocking metastasis.

Structure and function of β-arrestins, their emerging role in breast cancer, and potential opportunities for therapeutic manipulation

β-Arrestins (βarrs) are multifunctional intracellular proteins with an ability to directly interact with a large number of cellular partners including the G protein-coupled receptors (GPCRs). βarrs contribute to multiple aspects of GPCR signaling, trafficking and downregulation. Considering the central involvement of GPCR signaling in the onset and progression of diverse types of cancers, βarrs have also emerged as key players in the context of investigating cancer phenotypes, and as potential therapeutic targets. In this chapter, we first provide a brief account of structure and function of βarrs and then highlight recent discoveries unfolding novel functional attributes of βarrs in breast cancer. We also underscore the recent paradigms of modulating βarr functions in cellular context and potential therapeutic opportunities going forward.

Surface coatings alter transcriptional responses to silver nanoparticles following oral exposure

Silver nanoparticles (AgNPs) are used in food packaging materials, dental care products and other consumer goods and can result in oral exposure. To determine whether AgNP coatings modulate transcriptional responses to AgNP exposure, we exposed mice orally to 20 nm citrate (cit)-coated AgNPs (cit-AgNPs) or polyvinylpyrrolidone (PVP)-coated AgNPs (PVP-AgNPs) at a 4 mg/kg dose for 7 consecutive days and analyzed changes in the expression of protein-coding genes and long noncoding RNAs (lncRNAs), a new class of regulatory RNAs, in the liver. We identified unique and common expression signatures of protein-coding and lncRNA genes, altered biological processes and signaling pathways, and coding-non-coding gene interactions for cit-AgNPs and PVP-AgNPs. Commonly regulated genes comprised only about 10 and 20 percent of all differentially expressed genes in PVP-AgNP and cit-AgNP exposed mice, respectively. Commonly regulated biological processes included glutathione metabolic process and cellular oxidant detoxification. Commonly regulated pathways included Keap-Nrf2, PPAR, MAPK and IL-6 signaling pathways. The coding-non-coding gene co-expression analysis revealed that protein-coding genes were co-expressed with a variable number of lncRNAs ranging from one to twenty three and may share functional roles with the protein-coding genes. PVP-AgNP exposure induced a more robust transcriptional response than cit-AgNP exposure characterized by more than two-fold higher number of differentially expressed both protein- coding and lncRNA genes. Our data demonstrate that the surface coating strongly modulates the spectrum and the number of differentially expressed genes after oral AgNP exposure. On the other hand, our data suggest that AgNP exposure can alter drug and chemical sensitivity, metabolic homeostasis and cancer risk irrespective of the coating type, warranting further investigations.

Semaphorin 5A suppresses the proliferation and migration of lung adenocarcinoma cells

Semaphorin 5A (SEMA5A), a member of the semaphorin family, plays an important role in axonal guidance. Previously, the authors identified another possible role of SEMA5A as a prognostic biomarker for non-smoking women with lung adenocarcinoma in Taiwan, and this phenomenon has been validated in other ethnic groups. However, the functional significance of SEMA5A in lung adenocarcinoma remains unclear. Therefore, we assessed the function of SEMA5A in three lung adenocarcinoma cell lines in this study. Kaplan-Meier Plotter for lung cancer was conducted for survival analyses. Reverse transcription-quantitative PCR (RT-qPCR) and western blot analysis were performed to investigate the expression and post-translational regulation of SEMA5A in lung adenocar-cinoma cell lines. A pre-designed PyroMark CpG assay and 5-aza-2′-deoxycytidine treatment were used to measure the methylation levels of SEMA5A. The biological functions of lung adenocarcinoma cells overexpressing SEMA5A were investigated by microarrays, and validated both in vitro (proliferation, colony formation and migration assays) and in vivo (tumor xenografts) experiments. The results revealed that the hypermethylation of SEMA5A and the cleavage of the extracellular domain of SEMA5A were responsible for the downregulation of the SEMA5A levels in lung adenocarcinoma cells (A549 and H1299) as compared to the normal controls. Functional analysis of SEMA5A-regulated genes revealed that they were involved in cellular growth and proliferation. The overexpression of SEMA5A in A549 and H1299 cells significantly decreased the proliferation (P<0.01), colony formation (P<0.001) and migratory ability (P<0.01) of the cells. The suppressive effects of SEMA5A on the proliferative and migratory ability of the cells were also observed in both in vitro and in vivo experiments using brain metastatic Bm7 lung adenocarcinoma cells. On the whole, the findings of this study suggest a suppressive role for SEMA5A in lung adenocarcinoma involving the inhibition of the proliferation and migration of lung transformed cells.

Healthy diet is associated with gene expression in blood: the Framingham Heart Study

BACKGROUND

Genes in metabolic and nutrient signaling pathways play important roles in lifespan in model organisms and human longevity.

OBJECTIVE

The aim of this study was to examine the relation of a quantitative measure of healthy diet to gene expression in a community-based cohort.

METHODS

We used the 2015 Dietary Guidelines for Americans Adherence Index (DGAI) score to quantify key dietary recommendations of an overall healthy diet. Our current analyses included 2220 Offspring participants (mean age 66 ± 9 y, 55.4% women) and 2941 Third-Generation participants (mean age 46 ± 9 y, 54.5% women) from the Framingham Heart Study. Gene expression was profiled in blood through the use of the Affymetrix Human Exon 1.0 ST Array. We conducted a transcriptome-wide association study of DGAI adjusting for age, sex, smoking, cell counts, and technical covariates. We also constructed a combined gene score from genes significantly associated with DGAI.

RESULTS

The DGAI was significantly associated with the expression of 19 genes (false discovery rate <0.05). The most significant gene, ARRDC3, is a member of the arrestin family of proteins, and evidence in animal models and human data suggests that this gene is a regulator of obesity and energy expenditure. The DGAI gene score was associated with body mass index (P = 1.4 × 10-50), fasting glucose concentration (P = 2.5 × 10-11), type 2 diabetes (P = 1.1 × 10-5), and metabolic syndrome (P = 1.8 × 10-32).

CONCLUSIONS

Healthier diet was associated with genes involved in metabolic function. Further work is needed to replicate our findings and investigate the relation of a healthy diet to altered gene regulation.

Arrdc2 and Arrdc3 elicit divergent changes in gene expression in skeletal muscle following anabolic and catabolic stimuli

Skeletal muscle is a highly plastic organ regulating various processes in the body. As such, loss of skeletal muscle underlies the increased morbidity and mortality risk that is associated with numerous conditions. However, no therapies are available to combat the loss of muscle mass during atrophic conditions, which is due in part to the incomplete understanding of the molecular networks altered by anabolic and catabolic stimuli. Thus, the current objective was to identify novel gene networks modulated by such stimuli. For this, total RNA from the tibialis anterior muscle of mice that were fasted overnight or fasted overnight and refed the next morning was subjected to microarray analysis. The refeeding stimulus altered the expression of genes associated with signal transduction. Specifically, expression of alpha arrestin domain containing 2 (Arrdc2) and alpha arrestin domain containing 3 (Arrdc3) was significantly lowered 70–85% by refeeding. Subsequent analysis showed that expression of these genes was also lowered 50–75% by mechanical overload, with the combination of nutrients and mechanical overload acting synergistically to lower Arrdc2 and Arrdc3 expression. On the converse, stimuli that suppress growth such as testosterone depletion or acute aerobic exercise increased Arrdc2 and Arrdc3 expression in skeletal muscle. While Arrdc2 and Arrdc3 exhibited divergent changes in expression following anabolic or catabolic stimuli, no other member of the Arrdc family of genes exhibited the consistent change in expression across the analyzed conditions. Thus, Arrdc2 and Arrdc3 are a novel set of genes that may be implicated in the regulation of skeletal muscle mass.

Mechanisms of the anterograde trafficking of GPCRs: Regulation of AT1R transport by interacting proteins and motifs

Anterograde cell surface transport of nascent G protein-coupled receptors (GPCRs) en route from the endoplasmic reticulum (ER) through the Golgi apparatus represents a crucial checkpoint to control the amount of the receptors at the functional destination and the strength of receptor activation-elicited cellular responses. However, as compared with extensively studied internalization and recycling processes, the molecular mechanisms of cell surface trafficking of GPCRs are relatively less defined. Here, we will review the current advances in understanding the ER-Golgi-cell surface transport of GPCRs and use angiotensin II type 1 receptor as a representative GPCR to discuss emerging roles of receptor-interacting proteins and specific motifs embedded within the receptors in controlling the forward traffic of GPCRs along the biosynthetic pathway.

Protease-Activated Receptor 1 as Therapeutic Target in Breast, Lung, and Ovarian Cancer: Pepducin Approach

The G-protein coupled receptors (GPCRs) belong to a large family of diverse receptors that are well recognized as pharmacological targets. However, very few of these receptors have been pursued as oncology drug targets. The Protease-activated receptor 1 (PAR1), which is a G-protein coupled receptor, has been shown to act as an oncogene and is an emerging anti-cancer drug target. In this paper, we provide an overview of PAR1’s biased signaling role in metastatic cancers of the breast, lungs, and ovaries and describe the development of PAR1 inhibitors that are currently in clinical use to treat acute coronary syndromes. PAR1 inhibitor PZ-128 is in a Phase II clinical trial and is being developed to prevent ischemic and thrombotic complication of patients undergoing cardiac catheterization. PZ-128 belongs to a new class of cell-penetrating, membrane-tethered peptides named pepducins that are based on the intracellular loops of receptors targeting the receptor G-protein interface. Application of PZ-128 as an anti-metastatic and anti-angiogenic therapeutic agent in breast, lung, and ovarian cancer is being reviewed.

GPCRs in Cancer: Protease-Activated Receptors, Endocytic Adaptors and Signaling

G protein-coupled receptors (GPCRs) are a large diverse family of cell surface signaling receptors implicated in various types of cancers. Several studies indicate that GPCRs control many aspects of cancer progression including tumor growth, invasion, migration, survival and metastasis. While it is known that GPCR activity can be altered in cancer through aberrant overexpression, gain-of-function activating mutations, and increased production and secretion of agonists, the precise mechanisms of how GPCRs contribute to cancer progression remains elusive. Protease-activated receptors (PARs) are a unique class of GPCRs implicated in cancer. PARs are a subfamily of GPCRs comprised of four members that are irreversibly activated by proteolytic cleavage induced by various proteases generated in the tumor microenvironment. Given the unusual proteolytic irreversible activation of PARs, expression of receptors at the cell surface is a key feature that influences signaling responses and is exquisitely controlled by endocytic adaptor proteins. Here, we discuss new survey data from the Cancer Genome Atlas and the Genotype-Tissue Expression projects analysis of expression of all PAR family member expression in human tumor samples as well as the role and function of the endocytic sorting machinery that controls PAR expression and signaling of PARs in normal cells and in cancer.

Advances in Membrane Trafficking and Endosomal Signaling of G Protein-Coupled Receptors

The integration of GPCR signaling with membrane trafficking, as a single orchestrated system, is a theme increasingly evident with the growing reports of GPCR endosomal signaling. Once viewed as a mechanism to regulate cell surface heterotrimeric G protein signaling, the endocytic trafficking system is complex, highly compartmentalized, yet deeply interconnected with cell signaling. The organization of receptors into distinct plasma membrane signalosomes, biochemically distinct endosomal populations, endosomal microdomains, and its communication with distinct subcellular organelles such as the Golgi provides multiple unique signaling platforms that are critical for specifying receptor function physiologically and pathophysiologically. In this chapter I discuss our emerging understanding in the endocytic trafficking systems employed by GPCRs and their novel roles in spatial control of signaling. Given the extensive roles that GPCRs play in vivo, these evolving models are starting to provide mechanistic understanding of distinct diseases and provide novel therapeutic avenues that are proving to be viable targets.