Arrestin beta 1 Regulates Alveolar Progenitor Renewal and Lung Fibrosis.

The molecular mechanisms that regulate progressive pulmonary fibrosis remain poorly understood. Type 2 alveolar epithelial cells (AEC2s) function as adult stem cells in the lung. We previously showed that there is a loss of AEC2s and a failure of AEC2 renewal in the lungs of idiopathic pulmonary fibrosis (IPF) patients. We also reported that beta-arrestins are the key regulators of fibroblast invasion, and beta-arrestin 1 and 2 deficient mice exhibit decreased mortality, decreased matrix deposition, and increased lung function in bleomycin-induced lung fibrosis. However, the role of beta-arrestins in AEC2 regeneration is unclear. In this study, we investigated the role and mechanism of Arrestin beta 1 (ARRB1) in AEC2 renewal and in lung fibrosis. We used conventional deletion as well as cell type-specific deletion of ARRB1 in mice and found that Arrb1 deficiency in fibroblasts protects mice from lung fibrosis, and the knockout mice exhibit enhanced AEC2 regeneration in vivo, suggesting a role of fibroblast-derived ARRB1 in AEC2 renewal. We further found that Arrb1-deficient fibroblasts promotes AEC2 renewal in 3D organoid assays. Mechanistically, we found that CCL7 is among the top downregulated cytokines in Arrb1 deficient fibroblasts and CCL7 inhibits AEC2 regeneration in 3D organoid experiments. Therefore, fibroblast ARRB1 mediates AEC2 renewal, possibly by releasing chemokine CCL7, leading to fibrosis in the lung.

EHMT2 Suppresses ARRB1 Transcription and Activates the Hedgehog Signaling to Promote Malignant Phenotype and Stem Cell Property in Oral Squamous Cell Carcinoma.

Oral squamous cell carcinoma (OSCC) represents the primary subtype of head and neck squamous cell carcinoma (HNSCC), characterized by a high morbidity and mortality rate. Although previous studies have established specific correlations between euchromatic histone lysine methyltransferase 2 (EHMT2), a histone lysine methyltransferase, and the malignant phenotype of OSCC cells, its biological functions in OSCC remain largely unknown. This study, grounded in bioinformatics predictions, aims to clarify the influence of EHMT2 on the malignant behavior of OSCC cells and delve into the underlying mechanisms. EHMT2 exhibited high expression in OSCC tissues and demonstrated an association with poor patient outcomes. Artificial EHMT2 silencing in OSCC cells, achieved through lentiviral vector infection, significantly inhibited colony formation, migration, invasion, and cell survival. Regarding the mechanism, EHMT2 was found to bind the promoter of arrestin beta 1 (ARRB1), thereby suppressing its transcription through H3K9me2 modification. ARRB1, in turn, was identified as a negative regulator of the Hedgehog pathway, leading to a reduction in the proteins GLI1 and PTCH1. Cancer stem cells (CSCs) were enriched through repeated sphere formation assays in two OSCC cell lines. EHMT2 was found to activate the Hedgehog pathway, thus promoting sphere formation, migration and invasion, survival, and tumorigenic activity of the OSCC-CSCs. Notably, these effects were counteracted by the additional overexpression of ARRB1. In conclusion, this study provides novel evidence suggesting that EHMT2 plays specific roles in enhancing stem cell properties in OSCC by modulating the ARRB1-Hedgehog signaling cascade.

NPAS2, transcriptionally activated by ARRB1, promotes the malignant behaviours of lung adenocarcinoma cells and regulates the reprogramming of glucose metabolism.

Lung adenocarcinoma (LUAD) is a serious threat to public health and is accompanied by increased morbidity and mortality worldwide. Neuronal PAS domain protein2 (NPAS2) has been confirmed as an oncogene in LUAD; however, little is known about its molecular mechanism. Here, the expression level of NPAS2 was detected in LUAD cell lines and 16HBE cells. Gain- and loss-of-function experiments were performed. Cell Counting Kit-8, colony formation, flow cytometry, wound-healing and Transwell assays were conducted to assess cell proliferation, apoptosis, migration and invasion, respectively. Reprogramming of glucose metabolism was evaluated via oxygen consumption rate (OCR), complexes activities, lactic production and glucose consumption. The expression of critical proteins was examined by western blot. We demonstrated aberrant upregulation of NPAS2 and ß-arrestin-1 (ARRB1) in LUAD cell lines. ARRB1 was found to be a critical transcription factor of NPAS2 with binding sites within the promoter region of NPAS2, thereby causing its transcriptional activation. Functional experiments revealed that NPAS2 depletion significantly inhibited the malignant behaviours of A549 cells by suppressing cell proliferation, migration, invasion and epithelial-mesenchymal transition and promoting cell apoptosis. Meanwhile, NPAS2 depletion increased OCR and activities of complexes (I, II, III and V), and reduced lactic acid production and glucose uptake in A549 cells, indicating that NPAS2 depletion inhibited aerobic glycolysis, accompanied by reduced expression of glycolytic enzymes. However, the changes caused by NPAS2 knockdown were partly restored by ARRB1 overexpression. In conclusion, our study suggests that ARRB1 could transcriptionally activate NPAS2, facilitating malignant activities and glycolysis, and ultimately promoting the progression of LUAD, proving a novel therapeutic strategy for the treatment of LUAD.

ß-arrestin1-E2F1-ac axis regulates physiological apoptosis and cell cycle exit in cellular models of early postnatal cerebellum.

Development of the cerebellum is characterized by rapid proliferation of cerebellar granule cell precursors (GCPs) induced by paracrine stimulation of Sonic hedgehog (Shh) signaling from Purkinje cells, in the external granular layer (EGL). Then, granule cell precursors differentiate and migrate into the inner granular layer (IGL) of the cerebellum to form a terminally differentiated cell compartment. Aberrant activation of Sonic hedgehog signaling leads to granule cell precursors hyperproliferation and the onset of Sonic hedgehog medulloblastoma (MB), the most common embryonal brain tumor. ß-arrestin1 (ARRB1) protein plays an important role downstream of Smoothened, a component of the Sonic hedgehog pathway. In the medulloblastoma context, ß-arrestin1 is involved in a regulatory axis in association with the acetyltransferase P300, leading to the acetylated form of the transcription factor E2F1 (E2F1-ac) and redirecting its activity toward pro-apoptotic gene targets. This axis in the granule cell precursors physiological context has not been investigated yet. In this study, we demonstrate that ß-arrestin1 has antiproliferative and pro-apoptotic functions in cerebellar development. ß-arrestin1 silencing increases proliferation of Sonic hedgehog treated-cerebellar precursor cells while decreases the transcription of E2F1-ac pro-apoptotic targets genes, thus impairing apoptosis. Indeed, chromatin immunoprecipitation experiments show a direct interaction between ß-arrestin1 and the promoter regions of the pro-apoptotic E2F1 target gene and P27, indicating the double role of ß-arrestin1 in controlling apoptosis and cell cycle exit in a physiological context. Our data elucidate the role of ß-arrestin1 in the early postnatal stages of cerebellar development, in those cell compartments that give rise to medulloblastoma. This series of experiments suggests that the physiological function of ß-arrestin1 in neuronal progenitors is to directly control, cooperating with E2F1 acetylated form, transcription of pro-apoptotic genes.

[The Effect of SP1 on the Progression of T-cell Acute Lymphoblastic Leukemia].

OBJECTIVE: To study the transcriptional regulation of SP1 on the scaffold protein ARRB1 and its influence on the progression of T-cell acute lymphoblastic leukemia (T-ALL). METHODS: pGL3-ARRB1-luc, pCDNA3.1-SP1 and other transcription factor plasmids that might be combined were constructed, and the binding of transcription factors to the promoter of ARRB1 was identified by dual luciferase reporter gene assay. Stable cell lines with over-expressed SP1 (JK-SP1) was constructed by lentiviral transfection, and the expression correlation of SP1 with ARRB1 was demonstrated by RT-PCR and Western blot. Further, the apoptosis, cell cycle and reactive oxygen species (ROS) were detected by flow cytometry. The effect of SP1 on propagation of leukemic cells was observed on NCG leukemic mice. RESULTS: The expression of fluorescein were enhanced by co-transfection with pCDNA3.1-SP1 and pGL3-ARRB1-luc plasmids in HEK293T cell line (P<0.001), meanwhile, compared with the control group, the expression of ARRB1 mRNA and protein were increased in JK-SP1 cells (both P<0.01). Further in vitro experiments showed that, compared with the control group, the apoptosis rate was higher (x=22.78%) , the cell cycle was mostly blocked in G1 phase (63.00%), and the content of reactive oxygen species increased in JK-SP1 cells. And in vivo experiments showed that the mice injected with JK-SP1 cells through tail vein had a favorable overall survival time (average 33.8 days), less infiltration in liver and spleen tissue. CONCLUSION: Transcription factor SP1 promotes the transcription and expression of ARRB1 by binding the the promoter of ARRB1 directly, thus delays the progress of T-ALL in vitro and in vivo. The study improves the pathogenesis of ARRB1 regulating the initiation and development of T-ALL, and provides theoretical basis for the development of new possible targeted drugs.

Differential expression of microRNAs in bile duct obstruction-induced liver fibrosis and the identification of a novel liver fibrosis marker miR-1295b-3p.

Background: Bile duct obstruction-induced liver fibrosis is mainly caused by cholestatic liver injury which stimulates liver cell inflammation and damages the liver structure, causing liver fibrosis. The differentially expressed microRNAs and the potential target genes and signal pathways that are involved in bile duct obstruction-induced liver fibrosis remain unclear. We examined the differential expression of microRNAs and the target genes in the liver tissues of patients with liver fibrosis. Methods: High-throughput sequencing was used to detect the total microRNAs and identify the differentially expressed microRNAs. The topGO software was used to perform the Gene Ontology (GO) function enrichment analysis. The KOBAS software was used to analyze the associated biochemical metabolic pathways and signal transduction pathways. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot analyses were conducted to detect the expression of miR-1295b-3p, alpha smooth muscle actin (α-SMA), Bcl-2, caspase-3, Bax, and ß-arrestin1 (ARRB1). Cell viability and apoptosis were detected by the Cell Counting Kit 8 (CCK-8) assay and flow cytometry. The targeting relationship between ARRB1 and miR-1295b-3p was verified using luciferase reporter assays. Results: A total of 44 microRNAs were found to be differentially expressed, including 18 upregulated and 26 downregulated microRNAs. Five downregulated microRNAs, including miR-483-3p, miR-5589-3p, miR-1271-5p, miR-1295b-3p, and miR-7977. GO functional enrichment analysis of the target genes revealed the molecular functions, cellular location, and biological processes involved. Kyoto Encyclopedia of Genes and Genomes (KEGG) signal pathway analysis showed that the target genes are mainly involved in metabolic pathways. In addition, the results of qRT-PCR revealed that miR-1295b-3p was downregulated in human fibrotic liver tissues and TGF-ß1-activated LX-2 cells (human hepatic stellate cell line). Overexpression of miR-1295b-3p alleviated liver fibrosis, decreased the α-SMA levels, and inhibited proliferation and enhanced apoptosis in LX-2 cells. Dual-luciferase assays revealed that miR-1295b-3p suppressed ARRB1 expression by binding directly to its 3' untranslated region (UTR). Conclusions: This study identified the differentially expressed microRNAs in bile duct obstruction-induced liver fibrosis and revealed the potential target genes and signal pathways involved. Overexpression of miR-1295b-3p alleviated liver fibrosis, however, the specific targeting mechanisms warrant further clarification. Therefore, overexpressing miR-1295b-3p may be a potential treatment method for liver fibrosis.

circITGB1 Regulates Adipocyte Proliferation and Differentiation via the miR-23a/ARRB1 Pathway.

Adipose tissues represent an important energy storage organ in animals and are the largest endocrine organ. It plays an important regulatory role in the pathogenesis of insulin resistance, cardiovascular disease, and metabolic syndrome. Adipose development is a complex biological process involving multiple key genes, signaling pathways, and non-coding RNAs, including microRNAs and circular RNAs. In this study, we characterized circITGB1 and named its host gene ITGB1, which is differentially expressed in sheep of different months based on sequencing data. We collated and analyzed the sequencing data to select miRNA-23a with strong binding to ARRB1. We found that miRNA-23a regulates the development and differentiation of sheep adipocytes by targeting ARRB1. As a competing endogenous RNA, circITGB1 overexpression effectively alleviated the inhibitory effect of miR-23a on ARRB1. Conclusively, we provide evidence that circITGB1 regulates the proliferation and differentiation of sheep adipocytes via the miR-23a/ARRB1 pathway. This study provides a scientific basis for further studies on adipose tissue development at the circRNA level.

The Effect of SP1 on the Progression of T-cell Acute Lymphoblastic Leukemia / 中国实验血液学杂志

OBJECTIVE@#To study the transcriptional regulation of SP1 on the scaffold protein ARRB1 and its influence on the progression of T-cell acute lymphoblastic leukemia (T-ALL).@*METHODS@#pGL3-ARRB1-luc, pCDNA3.1-SP1 and other transcription factor plasmids that might be combined were constructed, and the binding of transcription factors to the promoter of ARRB1 was identified by dual luciferase reporter gene assay. Stable cell lines with over-expressed SP1 (JK-SP1) was constructed by lentiviral transfection, and the expression correlation of SP1 with ARRB1 was demonstrated by RT-PCR and Western blot. Further, the apoptosis, cell cycle and reactive oxygen species (ROS) were detected by flow cytometry. The effect of SP1 on propagation of leukemic cells was observed on NCG leukemic mice.@*RESULTS@#The expression of fluorescein were enhanced by co-transfection with pCDNA3.1-SP1 and pGL3-ARRB1-luc plasmids in HEK293T cell line (P<0.001), meanwhile, compared with the control group, the expression of ARRB1 mRNA and protein were increased in JK-SP1 cells (both P<0.01). Further in vitro experiments showed that, compared with the control group, the apoptosis rate was higher (x=22.78%) , the cell cycle was mostly blocked in G1 phase (63.00%), and the content of reactive oxygen species increased in JK-SP1 cells. And in vivo experiments showed that the mice injected with JK-SP1 cells through tail vein had a favorable overall survival time (average 33.8 days), less infiltration in liver and spleen tissue.@*CONCLUSION@#Transcription factor SP1 promotes the transcription and expression of ARRB1 by binding the the promoter of ARRB1 directly, thus delays the progress of T-ALL in vitro and in vivo. The study improves the pathogenesis of ARRB1 regulating the initiation and development of T-ALL, and provides theoretical basis for the development of new possible targeted drugs.

The association of ARRB1 polymorphisms with response to antidepressant treatment in depressed patients.

Introduction: ß-arrestin 1, a protein encoded by ARRB1 involved in receptor signaling, is a potential biomarker for the response to antidepressant drug (ATD) treatment in depression. We examined ARRB1 genetic variants for their association with response following ATD treatment in METADAP, a cohort of 6-month ATD-treated depressed patients. Methods: Patients (n = 388) were assessed at baseline (M0) and after 1 (M1), 3 (M3), and 6 months (M6) of treatment for Hamilton Depression Rating Scale (HDRS) changes, response, and remission. Whole-gene ARRB1 variants identified from high-throughput sequencing were separated by a minor allele frequency (MAF)≥5%. Frequent variants (i.e., MAF≥5%) annotated by RegulomeDB as likely affecting transcription factor binding were analyzed using mixed-effects models. Rare variants (i.e., MAF<5%) were analyzed using a variant set analysis. Results: The variant set analysis of rare variants was significant in explaining HDRS score changes (T = 878.9; p = 0.0033) and remission (T = -1974.1; p = 0.034). Rare variant counts were significant in explaining response (p = 0.016), remission (p = 0.022), and HDRS scores at M1 (p = 0.0021) and M3 (p=<0.001). rs553664 and rs536852 were significantly associated with the HDRS score (rs553664: p = 0.0055 | rs536852: p = 0.046) and remission (rs553664: p = 0.026 | rs536852: p = 0.012) through their interactions with time. At M6, significantly higher HDRS scores were observed in rs553664 AA homozygotes (13.98 ± 1.06) compared to AG heterozygotes (10.59 ± 0.86; p = 0.014) and in rs536852 GG homozygotes (14.88 ± 1.10) compared to AG heterozygotes (11.26 ± 0.95; p = 0.0061). Significantly lower remitter rates were observed in rs536852 GG homozygotes (8%, n = 56) compared to AG heterozygotes (42%, n = 105) at M6 (p = 0.0018). Conclusion: Our results suggest ARRB1 variants may influence the response to ATD treatment in depressed patients. Further analysis of functional ARRB1 variants and rare variant burden in other populations would help corroborate our exploratory analysis. ß-arrestin 1 and genetic variants of ARRB1 may be useful clinical biomarkers for clinical improvement following ATD treatment in depressed individuals. Clinical Trial Registration: clinicaltrials.gov; identifier NCT00526383.

Role of ARRB1 in prognosis and immunotherapy: A Pan-Cancer analysis.

Background: ß-arrestin1 (ARRB1), was originally identified as a multifunctional adaptor protein. Although ARRB1 has recently been shown to also play an important role in tumor growth, metastasis, inflammation, and immunity, its relationship with distinct tumor types and the tumor immune microenvironment remains unclear. Methods: We analyzed the ARRB1 expression profile and clinical characteristics in 33 cancer types using datasets from The Cancer Genome Atlas (TCGA) database. Clinical parameters such as patient survival, tumor stage, age, and gender were used to assess the prognostic value of ARRB1. The Human Protein Atlas (HPA) database was used to explore ARRB1 protein expression data. ESTIMATE and CIBERSORT algorithms were performed to assess immune infiltration. Furthermore, putative correlations between ARRB1 and tumor-infiltrating immune cells, the signatures of T-cell subtypes, immunomodulators, the tumor mutation burden (TMB), Programmed cell death ligand 1 (PD-L1), and microsatellite instability (MSI) were also explored. Gene functional enrichment was determined using GSEA. GSE40435 and GSE13213 cohorts were used to validate the correlation of ARRB1 with KIRC and LUAD clinicopathological parameters. Finally, the relationship between ARRB1 and immunotherapeutic responses was assessed using three independent immunotherapy cohorts, namely, GSE67501, GSE168204, and IMvigor210. Results: We found that ARRB1 expression levels were lower in 17 tumor tissues than in the corresponding normal tissues. We further found that ARRB1 expression was significantly correlated with tumor stage in BRCA, ESCA, KIRC, TGCT, and THCA, while in some tumors, particularly KIRC and LUAD, ARRB1 expression was associated with better prognosis. ARRB1 expression was also positively correlated with the stromal score or the immune score in some tumors. Regarding immune cell infiltration, ARRB1 expression in DLBC was positively correlated with M1 macrophage content and negatively correlated with B-cell infiltration. Additionally, there was a broad correlation between ARRB1 expression and three classes of immunomodulators. Furthermore, high ARRB1 expression levels were significantly correlated with some tumor immune-related pathways. Finally, ARRB1 expression was significantly associated with MSI, PD-L1, and TMB in some tumors and with the efficacy of immune checkpoint inhibitors (ICIs) in melanoma. Conclusion: ARRB1 has prognostic value in malignant tumors, especially in KIRC and LUAD. At the same time, ARRB1 was closely correlated with the tumor immune microenvironment and indicators of immunotherapy efficacy, indicating its great potential as a reliable marker for predicting the efficacy of immunotherapy.

Dual roles of ß-arrestin 1 in mediating cell metabolism and proliferation in gastric cancer.

ß-Arrestin 1 (ARRB1) has been recognized as a multifunctional adaptor protein in the last decade, beyond its original role in desensitizing G protein-coupled receptor signaling. Here, we identify that ARRB1 plays essential roles in mediating gastric cancer (GC) cell metabolism and proliferation, by combining cohort analysis and functional investigation using patient-derived preclinical models. Overexpression of ARRB1 was associated with poor outcome of GC patients and knockdown of ARRB1 impaired cell proliferation both ex vivo and in vivo. Intriguingly, ARRB1 depicted diverse subcellular localizations during a passage of organoid cultures (7 d) to exert dual functions. Further analysis revealed that nuclear ARRB1 binds with transcription factor E2F1 triggering up-regulation of proliferative genes, while cytoplasmic ARRB1 modulates metabolic flux by binding with the pyruvate kinase M2 isoform (PKM2) and hindering PKM2 tetramerization, which reduces pyruvate kinase activity and leads to cellular metabolism shifts from oxidative phosphorylation to aerobic glycolysis. As ARRB1 localization was shown mostly in the cytoplasm in human GC samples, therapeutic potential of the ARRB1-PKM2 axis was tested, and we found tumor proliferation could be attenuated by the PKM2 activator DASA-58, especially in ARRB1high organoids. Together, the data in our study highlight a spatiotemporally dependent role of ARRB1 in mediating GC cell metabolism and proliferation and implies reactivating PKM2 may be a promising therapeutic strategy in a subset of GC patients.

HBx induces hepatocellular carcinogenesis through ARRB1-mediated autophagy to drive the G1/S cycle.

The hepatitis B virus X protein (HBx) is involved in the process of hepatocellular carcinoma via the activation of various oncogenes. Our previous study indicated that ARBB1 (arrestin beta 1) promotes hepatocellular carcinogenesis (HCC). However, the role of ARRB1 in HBx-related HCC remains unclear. Herein, we identified that ARRB1 was upregulated by HBx in vivo and in vitro. Arrb1 deficiency suppressed HBx-induced hepatocellular carcinogenesis in several mouse models. Furthermore, knockdown of ARRB1 blocked HBx-induced macroautophagic/autophagic flux and disrupted the formation of autophagosomes. ARRB1 interacted with HBx, and the autophagic core protein MAP1LC3/LC3, a scaffolding protein, was essential for complete autophagy. Inhibition of autophagy by 3-methyladenine or interference of ATG5 or ATG7 attenuated HBx-induced cell cycle acceleration and the subsequent proliferative response via the induction of G1/S arrest. The absence of autophagy abolished the phosphorylation of CDK2 and the activity of the CDK2-CCNE1 complex. Our results demonstrate that ARRB1 plays a critical role in HBV-related HCC via modulating autophagy and the CDKN1B-CDK2-CCNE1-E2F1 axis and indicate that ARRB1 may be a potential therapeutic target for HCC.Abbreviations: ARRB1: arrestin beta 1; ACTB: actin beta; AMPK: adenosine monophosphate (AMP)-activated protein kinase; ATG5: autophagy related 5; ATG7: autophagy related 7; Baf A1: bafilomycin A1; CDK2: cyclin dependent kinase 2; CDKN1B/p27Kip1: cyclin dependent kinase inhibitor 1B; CQ: chloroquine; E2F1: E2F transcription factor 1; FBS: fetal bovine serum; GPCRs: G protein-coupled receptors; GST: glutathione S-transferase; HCC: hepatocellular carcinoma; HBV: hepatitis B virus; HBx: hepatitis B virus X protein; HMGB1: high mobility group box 1; HIF1A/HIF-1α: hypoxia inducible factor 1 subunit alpha; IHC: immunohistochemistry; JAK1: Janus kinase 1; LOX: lysyl oxidase; MAP1LC3B/LC3: microtubule associated protein 1 light chain 3 beta; MKI67: marker of proliferation Ki-67; MTOR: mechanistic target of rapamycin kinase; MAPK: mitogen-activated protein kinase; 3-MA: 3-methyladenine; NFKB/NF-κB: nuclear factor kappa B; PIK3CA: phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha; PIK3C3: phosphatidylinositol 3-kinase catalytic subunit type 3; PHHs: primary human hepatocytes; RB1: RB transcriptional corepressor 1; SQSTM1/p62: sequestosome 1; STAT: signal transducer and activator of transcription; TACR1/NK1R: tachykinin receptor 1.

ARRB1 Drives Gallbladder Cancer Progression by Facilitating TAK1/MAPK Signaling Activation.

Gallbladder carcinoma (GBC) is the most common malignancy of the biliary tract, with a dismal 5-year survival of 5%. Recently, ARRB1, as a molecular scaffold, has been proposed to participate in the progression of multiple malignancies. However, the effect and regulatory mechanisms of ARRB1 in GBC have not been investigated. Our study aimed to explore the biological functional status and the possible molecular mechanisms of ARRB1 with respect to GBC progression. The survey showed that human GBC tissues exhibited increased levels of ARRB1 compared with normal tissues, and the high expression of ARRB1 was associated with poor prognosis of GBC patients. A series of in vitro and in vivo functional experiments based on knockdown of ARRB1 uncovered that ARRB1 enhanced GBC cell proliferation, migration, and invasion. Furthermore, we reported that TAK1, a component of the TNF /MAPK pathway, is a vital downstream effector of ARRB1. In addition, siTAK1 could abolish the functional changes between ARRB1 overexpression GBC cells and control ones. Our data revealed that ARRB1 facilitated the carcinogenesis and development of GBC through TNF/TAK1/MAPK axis, suggesting that ARRB1 may be a promising biomarker and treatment target for GBC patients.

Downregulation of miR-326 and its host gene ß-arrestin1 induces pro-survival activity of E2F1 and promotes medulloblastoma growth.

Persistent mortality rates of medulloblastoma (MB) and severe side effects of the current therapies require the definition of the molecular mechanisms that contribute to tumor progression. Using cultured MB cancer stem cells and xenograft tumors generated in mice, we show that low expression of miR-326 and its host gene ß-arrestin1 (ARRB1) promotes tumor growth enhancing the E2F1 pro-survival function. Our models revealed that miR-326 and ARRB1 are controlled by a bivalent domain, since the H3K27me3 repressive mark is found at their regulatory region together with the activation-associated H3K4me3 mark. High levels of EZH2, a feature of MB, are responsible for the presence of H3K27me3. Ectopic expression of miR-326 and ARRB1 provides hints into how their low levels regulate E2F1 activity. MiR-326 targets E2F1 mRNA, thereby reducing its protein levels; ARRB1, triggering E2F1 acetylation, reverses its function into pro-apoptotic activity. Similar to miR-326 and ARRB1 overexpression, we also show that EZH2 inhibition restores miR-326/ARRB1 expression, limiting E2F1 pro-proliferative activity. Our results reveal a new regulatory molecular axis critical for MB progression.

Melatonin-Medicated Neural JNK3 Up-Regulation Promotes Ameloblastic Mineralization.

Introduction: Melatonin, an endogenous neurohormone, modulates the biological circadian rhythms of vertebrates. It functions have been reported in previous stomatological studies as anti-inflammation, antioxidant, osseointegration of dental implants and stimulation to dental pulp stem cells differentiation, but its role in ameloblastic differentiation and mineralization has been rarely studied. Objective: To reveal the effects of melatonin on the mineralization of ameloblast lineage cells (ALCs), and to identify the change in gene expression and the potential mechanism based on ribonucleic acid sequencing (RNA-seq) analysis. Method: ALCs were induced in melatonin-conditioned medium. After 7-days culture, Western blot, real-time PCR, alkaline phosphatase (ALP) activity test, RNA-seq were accordingly used to detect the change in molecular level. After 1-month odontogenic induction in melatonin medium, Alizarin Red-S (ARS) staining showed the changes of mineral nodules. Differentially expressed genes (DEGs), enrichment of functions and signaling pathways analysis based on Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) database were performed. The JNK3 antagonist (JNK3 inhibitor IX, SR3576) and ß-arrestin1 (Arrb1) overexpression were applied to confirm the fluctuation of melatonin-medicated JNK3 and Arrb1 expression. Results: In this study, we found out melatonin contributed to the ameloblastic mineralization, from which we can observed the elevated expression of enamel matrix protein, and increased ALP activity and mineralized nodules formation. RNA-seq analysis showed the up-regulation of neural JNK3 and down-regulation of Arrb1 in ALCs. Meanwhile, phosphorylated JNK3 deficiency (phosphorylated JNK3 inhibitor---SR3576 added to culture medium) led to mineralization delay, and Arrb1 overexpression proved Arrb1 takes bridge between melatonin receptors (MTNR) and JNK3 in MAPK signaling pathway.

The Role of ß-Arrestins in Regulating Stem Cell Phenotypes in Normal and Tumorigenic Cells.

ß-Arrestins (ARRBs) are ubiquitously expressed scaffold proteins that mediate inactivation of G-protein-coupled receptor signaling, and in certain circumstances, G-protein independent pathways. Intriguingly, the two known ARRBs, ß-arrestin1 (ARRB1) and ß-Arrestin2 (ARRB2), seem to have opposing functions in regulating signaling cascades in several models in health and disease. Recent evidence suggests that ARRBs are implicated in regulating stem cell maintenance; however, their role, although crucial, is complex, and there is no universal model for ARRB-mediated regulation of stem cell characteristics. For the first time, this review compiles information on the function of ARRBs in stem cell biology and will discuss the role of ARRBs in regulating cell signaling pathways implicated in stem cell maintenance in normal and malignant stem cell populations. Although promising targets for cancer therapy, the ubiquitous nature of ARRBs and the plethora of functions in normal cell biology brings challenges for treatment selectivity. However, recent studies show promising evidence for specifically targeting ARRBs in myeloproliferative neoplasms.

The relation between mitogen activated protein kinase (MAPK) pathway and different genes expression in patients with beta Thalassemia.

BACKGROUND: ß-thalassemia is an inherited hemoglobinopathy resulting in quantitative changes in the ß-globin chain. Understanding the molecular basis of that disorder requires studying the expression of genes controlling the pathways that affect the erythropoietic homeostasis especially the MAPK pathway. The MAPKs are a family of serine/threonine kinases that play an essential role in connecting cell-surface receptors to DNA in the nucleus of the cell. AIM: to study the effect of expression of GNAI2, DUSP5 and ARRB1 genes on MAPK signaling pathway in pediatric patients with beta thalassemia. METHODS: Forty children with beta thalassemia major (TM), forty children with beta thalassemia intermedia (TI) and forty age and gender matched healthy controls were enrolled in this study. Detection of GNAI2, DUSP5 and ARRB1 mRNA expression was done by real time polymerase chain reaction (RT-PCR). RESULTS: revealed increased expression of ARRB1 (Arrestin Beta 1) gene, and decreased expression of both GNAI2 (Guanine nucleotide-binding protein G (i) subunit alpha-2) and DUSP5 (Dual specificity protein phosphatase 5) genes in both patient groups than control groups respectively. CONCLUSIONS: Change in the rate of expression of ARRB1, GNAI2 and DUSP5 may have a role in the pathogenesis of abnormal hematopoiesis in cases of ß thalassemia through affecting the MAPK pathway.

ARRB1 ameliorates liver ischaemia/reperfusion injury via antagonizing TRAF6-mediated Lysine 6-linked polyubiquitination of ASK1 in hepatocytes.

Hepatic ischaemia/reperfusion (I/R) injury is a major clinical problem during liver surgical procedures, which usually lead to early transplantation failure and higher organ rejection rate, and current effective therapeutic strategies are still limited. Therefore, in-depth exploring of the molecular mechanisms underlying liver I/R injury is key to the development of new therapeutic methods. ß-arrestins are multifunctional proteins serving as important signalling scaffolds in numerous physiopathological processes, including liver-specific diseases. However, the role and underlying mechanism of ß-arrestins in hepatic I/R injury remain largely unknown. Here, we showed that only ARRB1, but not ARRB2, was down-regulated during liver I/R injury. Hepatocyte-specific overexpression of ARRB1 significantly ameliorated liver damage, as demonstrated by decreases in serum aminotransferases, hepatocellular necrosis and apoptosis, infiltrating inflammatory cells and secretion of pro-inflammatory cytokines relative to control mice, whereas experiments with ARRB1 knockout mice gotten opposite effects. Mechanistically, ARRB1 directly interacts with ASK1 in hepatocytes and inhibits its TRAF6-mediated Lysine 6-linked polyubiquitination, which then prevents the activation of ASK1 and its downstream signalling pathway during hepatic I/R injury. In addition, inhibition of ASK1 remarkably abolished the disruptive effect result from ARRB1 deficiency in liver I/R injury in vivo, indicating that ASK1 was required for ARRB1 function in hepatic I/R injury. In conclusion, we proposed that ARRB1 is a novel protective regulator during liver I/R injury, and modulation of the regulatory axis between ARRB1 and ASK1 could be a novel therapeutic strategy to prevent this pathological process.

MicroRNAs and Xenobiotic Toxicity: An Overview.

The advent of new technologies has paved the rise of various chemicals that are being employed in industrial as well as consumer products. This leads to the accumulation of these xenobiotic compounds in the environment where they pose a serious threat to both target and non-target species. miRNAs are one of the key epigenetic mechanisms that have been associated with toxicity by modulating the gene expression post-transcriptionally. Here, we provide a comprehensive view on miRNA biogenesis, their mechanism of action and, their possible role in xenobiotic toxicity. Further, we review the recent in vitro and in vivo studies involved in xenobiotic exposure induced miRNA alterations and the mRNA-miRNA interactions. Finally, we address the challenges associated with the miRNAs in toxicological studies.

ARRB1 inhibits non-alcoholic steatohepatitis progression by promoting GDF15 maturation.

BACKGROUND & AIMS: Non-alcoholic steatohepatitis (NASH) is associated with the dysregulation of lipid metabolism and hepatic inflammation. The causal mechanism underlying NASH is not fully elucidated. This study investigated the role of ß-Arrestin1 (ARRB1) in the progression of NASH. METHODS: Liver tissue from patients with NASH and controls were obtained to evaluate ARRB1 expression. NASH models were established in Arrb1-knockout and wild-type mice fed either a high-fat diet (HFD) for 26 weeks or a methionine/choline-deficient (MCD) diet for 6 weeks. RESULTS: ARRB1 expression was reduced in liver samples from patients with NASH. Reduced Arrb1 levels were also detected in murine NASH models. Arrb1 deficiency accelerated steatohepatitis development in HFD-/MCD-fed mice (accompanied by the upregulation of lipogenic genes and downregulation of ß-oxidative genes). Intriguingly, ARRB1 was found to interact with growth differentiation factor 15 (GDF15) and facilitated the transportation of GDF15 precursor (pro-GDF15) to the Golgi apparatus for cleavage and maturation. Treatment with recombinant GDF15 ablated the lipid accumulation in the presence of Arrb1 deletion both in vitro and in vivo. Re-expression of Arrb1 in the NASH models ameliorated the liver disease, and this effect was greater in the presence of pro-GDF15 overexpression. By contrast, the effect of pro-GDF15 overexpression alone was impaired in Arrb1-deficient mice. In addition, the severity of liver disease in patients with NASH was negatively correlated with ARRB1 expression. CONCLUSION: ARRB1 acts as a vital regulator in the development of NASH by facilitating the translocation of GDF15 to the Golgi apparatus and its subsequent maturation. Thus, ARRB1 is a potential therapeutic target for the treatment of NASH. LAY SUMMARY: Non-alcoholic steatohepatitis (NASH) is associated with the progressive dysfunction of lipid metabolism and a consequent inflammatory response. Decreased ARRB1 is observed in patients with NASH and murine NASH models. Re-expression of Arrb1 in the murine NASH model ameliorated liver disease, an effect which was more pronounced in the presence of pro-GDF15 overexpression, highlighting a promising strategy for NASH therapy.