β-arrestin2/miR-155/GSK3β regulates transition of 5'-azacytizine-induced Sca-1-positive cells to cardiomyocytes

Insight into the regulatory mechanism of β-arrestin2 and its emerging role in diseases

β-arrestin2, a member of the arrestin family, mediates the desensitization and internalization of most G protein-coupled receptors (GPCRs) and functions as a scaffold protein in signalling pathways. Previous studies have demonstrated that β-arrestin2 expression is dysregulated in malignant tumours, fibrotic diseases, cardiovascular diseases and metabolic diseases, suggesting its pathological roles. Transcription and post-transcriptional modifications can affect the expression of β-arrestin2. Furthermore, post-translational modifications, such as phosphorylation, ubiquitination, SUMOylation and S-nitrosylation affect the cellular localization of β-arrestin2 and its interaction with downstream signalling molecules, which further regulate the activity of β-arrestin2. This review summarizes the structure and function of β-arrestin2 and reveals the mechanisms involved in the regulation of β-arrestin2 at multiple levels. Additionally, recent studies on the role of β-arrestin2 in some major diseases and its therapeutic prospects have been discussed to provide a reference for the development of drugs targeting β-arrestin2.

Antagonism of β-arrestins in IL-4-driven microglia reactivity via the Samd4/mTOR/OXPHOS axis in Parkinson's disease

Interleukin-4 (IL-4)-exposed microglia acquire neuroprotective properties, but their functions and regulation in Parkinson's disease (PD) are poorly understood. In this study, we demonstrate that IL-4 enhances anti-inflammatory microglia reactivity, ameliorates the pathological features of PD, and reciprocally affects expression of β-arrestin 1 and β-arrestin 2 in microglia in PD mouse models. We also show that manipulation of two β-arrestins produces contrary effects on the anti-inflammatory states and neuroprotective action of microglia induced by IL-4 in vivo and in vitro. We further find that the functional antagonism of two β-arrestins is mediated through sequential activation of sterile alpha motif domain containing 4 (Samd4), mammalian target of rapamycin (mTOR), and mitochondrial oxidative phosphorylation (OXPHOS). Collectively, these data reveal opposing functions of two closely related β-arrestins in regulating the IL-4-induced microglia reactivity via the Samd4/mTOR/OXPHOS axis in PD mouse models and provide important insights into the pathogenesis and therapeutics of PD.

A Single Variant in Pri-miRNA-155 Associated with Susceptibility to Hereditary Breast Cancer Promotes Aggressiveness in Breast Cancer Cells

Variants in genes encoding for microRNAs have been associated with their deregulation in breast cancer (BC). Sequencing of microRNAs deregulated in BC was performed using DNA from Chilean patients with a strong family history and negative for mutations in BRCA1/BRCA2. Seventeen variants were identified, three of which were selected for a case-control association study: rs376491654 (miR-335), rs755634302 (miR-497), and rs190708267 (miR-155). For rs190708267 C>T, the heterozygous T allele was detected in four BC cases and absent in controls, while homozygous TT cases were not detected. Variants were modelled in silico, cloned in a plasmid, expressed in BC cell lines, and functional in vitro assays were performed. Overexpression of the miR-155-T allele increased mature miR-155-5p levels in both BC cell lines, suggesting that its presence alters pre-miR-155 processing. Moreover, BC cells overexpressing the miR-155-T allele showed increased proliferation, migration, and resistance to cisplatin-induced death compared to miR-155-C overexpressing cells. Of note, the 3′UTR of APC, GSK3β, and PPP1CA genes, all into the canonical Wnt signaling pathway, were identified as direct targets. APC and GSK3β mRNA levels decreased while PP1 levels increased. These results suggest a pathogenic role of the variant rs190708267 (miR-155) in BRCA 1/2 negative BC, conferring susceptibility and promoting traits of aggressiveness.

Deletion of Schizophrenia Susceptibility Gene Ulk4 Leads to Abnormal Cognitive Behaviors via Akt-GSK-3 Signaling Pathway in Mice

OBJECTIVES

Despite of strenuous research in the past decades, the etiology of schizophrenia (SCZ) still remains incredibly controversial. Previous genetic analysis has uncovered a close association of Unc-51 like kinase 4 (ULK4), a family member of Unc-51-like serine/threonine kinase, with SCZ. However, animal behavior data which may connect Ulk4 deficiency with psychiatric disorders, particularly SCZ are still missing.

METHODS

We generated Emx1-Cre:Ulk4flox/flox conditional knockout (CKO) mice, in which Ulk4 was deleted in the excitatory neurons of cerebral cortex and hippocampus.

RESULTS

The cerebral cellular architecture was maintained but the spine density of pyramidal neurons was reduced in Ulk4 CKO mice. CKO mice showed deficits in the spatial and working memories and sensorimotor gating. Levels of p-Akt and p-GSK-3α/β were markedly reduced in the CKO mice indicating an elevation of GSK-3 signaling. Mechanistically, Ulk4 may regulate the GSK-3 signaling via putative protein complex comprising of two phosphatases, protein phosphatase 2A (PP2A) and 1α (PP1α). Indeed, the reduction of p-Akt and p-GSK-3α/β was rescued by administration of inhibitor acting on PP2A and PP1α in CKO mice.

CONCLUSIONS

Our data identified potential downstream signaling pathway of Ulk4, which plays important roles in the cognitive functions and when defective, may promote SCZ-like pathogenesis and behavioral phenotypes in mice.

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

β-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, β-arrestin1 (ARRB1) and β-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.

MicroRNA-128-1-5p attenuates myocardial ischemia/reperfusion injury by suppressing Gadd45g-mediated apoptotic signaling

Myocardial ischemia/reperfusion (I/R) injury is a clinically fatal disease, caused by restoring myocardial blood supply after a period of ischemia or hypoxia. However, the underlying mechanism remains unclear. Recently, increasing evidence reveal that microRNAs (miRs) participate in myocardial I/R injury. This study aimed to investigate whether miR-128-1-5p contributed to cardiomyocyte apoptosis induced by myocardial I/R injury. Here, we showed that the expression of miR-128-1-5p was decreased in mice following myocardial I/R injury. Down-regulation of miR-128-1-5p was also showed in H9c2 cardiomyocytes after hypoxia/reoxygenation (H/R), and in neonatal rat cardiomyocytes (NRCMs) with H2O2 treatment. Importantly, we found that overexpression of miR-128-1-5p ameliorates cardiomyocyte apoptosis both in H9c2 cardiomyocytes and NRCMs. Moreover, we also found that growth arrest DNA damage-inducible gene 45 gamma (Gadd45g) is identified as a direct target of miR-128-1-5p, which negatively regulated Gadd45g expression. Additionally, silencing of Gadd45g inhibits cardiomyocyte apoptosis in H9c2 cardiomyocytes and NRCMs. These results reveal a novel mechanism by which miR-128-1-5p regulates Gadd45g-mediated cardiomyocyte apoptosis in myocardial I/R injury.

Downregulation of microRNA-155 stimulates sevoflurane-mediated cardioprotection against myocardial ischemia/reperfusion injury by binding to SIRT1 in mice

OBJECTIVE

The inhaled sevoflurane has been demonstrated to protect against myocardial ischemia/reperfusion (I/R) injury. However, the relative mechanisms of sevoflurane-mediated cardioprotection remain largely unknown. This study intends to explore the effect of miR-155 on the sevoflurane-mediated cardioprotection by regulating Sirtuin 1 (SIRT1) in mouse models of myocardial I/R.

METHODS

Left anterior descending coronary artery ligation was used to induce models of myocardial I/R in mice. The I/R mice were treated with sevoflurane, sevoflurane + mimics negative control (NC) or sevoflurane + miR-155 mimics. The expression of microRNA-155 (miR-155) and SIRT1 was examined by quantitative real-time polymerase chain reaction and Western blot assay. Then cardiac functions and hemodynamic alterations were evaluated. Evans blue-2,3,5-triphenyltetrazolium chloride and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay staining methods were adopted to evaluate infarct size and cardiomyocyte apoptosis, respectively.

RESULTS

In the I/R mice, miR-155 was expressed at a high level and SIRT1 at a low level. SIRT1 was confirmed to be a target gene of miR-155. The treatment of sevoflurane could reduce miR-155 expression and increased SIRT1 expression in the myocardial tissues, under which conditions, cardiac functions were promoted, accompanied by reduced infarct size and inhibited cardiomyocyte apoptosis. In response to miR-155 upregulation, the sevoflurane-treated I/R mice showed reduced cardiac functions, and increased infarct size and cardiomyocyte apoptosis.

CONCLUSION

The findings obtained in this study provide evidence suggesting that miR-155 targets and negatively regulates SIRT1 expression, a mechanism by which the protection of sevoflurane is inhibited against myocardial I/R in mice.

β-Arrestins: Multitask Scaffolds Orchestrating the Where and When in Cell Signalling

The β-arrestins (β-arrs) were initially appreciated for the roles they play in the desensitization and endocytosis of G protein-coupled receptors (GPCRs). They are now also known to act as multifunctional adaptor proteins binding many non-receptor protein partners to control multiple signalling pathways. β-arrs therefore act as key regulatory hubs at the crossroads of external cell inputs and functional outputs in cellular processes ranging from gene transcription to cell growth, survival, cytoskeletal regulation, polarity, and migration. An increasing number of studies have also highlighted the scaffolding roles β-arrs play in vivo in both physiological and pathological conditions, which opens up therapeutic avenues to explore. In this introductory review chapter, we discuss the functional roles that β-arrs exert to control GPCR function, their dynamic scaffolding roles and how this impacts signal transduction events, compartmentalization of β-arrs, how β-arrs are regulated themselves, and how the combination of these events culminates in cellular regulation.

Parallel Genome-wide Profiling of Coding and Non-coding RNAs to Identify Novel Regulatory Elements in Embryonic and Maturated Heart

Heart development is a complex process, tightly regulated by numerous molecular mechanisms. Key components of the regulatory network underlying heart development are transcription factors (TFs) and microRNAs (miRNAs), yet limited investigation of the role of miRNAs in heart development has taken place. Here, we report the first parallel genome-wide profiling of polyadenylated RNAs and miRNAs in a developing murine heart. These data enable us to identify dynamic activation or repression of numerous biological processes and signaling pathways. More than 200 miRNAs and 25 long non-coding RNAs were differentially expressed during embryonic heart development compared to the mature heart; most of these had not been previously associated with cardiogenesis. Integrative analysis of expression data and potential regulatory interactions suggested 28 miRNAs as novel regulators of embryonic heart development, representing a considerable expansion of the current repertoire of known cardiac miRNAs. To facilitate follow-up investigations, we constructed HeartMiR (http://heartmir.sysbiolab.eu), an open access database and interactive visualization tool for the study of gene regulation by miRNAs during heart development.

MicroRNA-155 attenuates late sepsis-induced cardiac dysfunction through JNK and β-arrestin 2

Cardiac dysfunction is correlated with detrimental prognosis of sepsis and contributes to a high risk of mortality. After an initial hyperinflammatory reaction, most patients enter a protracted state of immunosuppression (late sepsis) that alters both innate and adaptive immunity. The changes of cardiac function in late sepsis are not yet known. MicroRNA-155 (miR-155) is previously found to play important roles in both regulations of immune activation and cardiac function. In this study, C57BL/6 mice were operated to develop into early and late sepsis phases, and miR-155 mimic was injected through the tail vein 48 h after cecal ligation and puncture (CLP). The effect of miR-155 on CLP-induced cardiac dysfunction was explored in late sepsis. We found that increased expression of miR-155 in the myocardium protected against cardiac dysfunction in late sepsis evidenced by attenuating sepsis-reduced cardiac output and enhancing left ventricular systolic function. We also observed that miR-155 markedly reduced the infiltration of macrophages and neutrophils into the myocardium and attenuated the inflammatory response via suppression of JNK signaling pathway. Moreover, overexpression of β-arrestin 2 (Arrb2) exacerbated the mice mortality and immunosuppression in late sepsis. Furthermore, transfection of miR-155 mimic reduced Arrb2 expression, and then restored immunocompetence and improved survival in late septic mice. We conclude that increased miR-155 expression through systemic administration of miR-155 mimic attenuates cardiac dysfunction and improves late sepsis survival by targeting JNK associated inflammatory signaling and Arrb2 mediated immunosuppression.

Activation of calcium-sensing receptor-mediated autophagy in angiotensinII-induced cardiac fibrosis in vitro

Cardiac fibrosis is one of the primary mechanisms of ventricular remodeling, and there is no effective method for reversal. Activation of calcium sensing receptor (CaSR) has been reported to be involved in the development of myocardial fibrosis, but the molecular mechanism for CaSR activation has not yet been clarified and needs to be further explored. Here, we found that AngII induces cardiac fibroblast proliferation and phenotypic transformation in a dose-dependent manner with increased CaSR and autophagy related protein (Beclin1, LC3B) expression. CaSR activation results in intracellular calcium release, MEK1/2 pathway phosphorylation, autophagy activation and collagen formation induced by AngII in cardiac fibroblasts. However, pretreating the cells with Calhex₂₃₁, PD98059 or 3-MA partially blocked AngII-induced cardiac fibrosis. Our data indicate that the activation of CaSR-mediated MEK/ERK and autophagic pathways is involved in AngII-induced cardiac fibrosis in vitro.

Tumor Suppressor PTPRJ Is a Target of miR-155 in Colorectal Cancer

PTPRJ is known for its antiproliferative role. Loss of heterozygosity (LOH) of PTPRJ has frequently been observed in various human cancers including colorectal cancer (CRC), lung cancer, and breast cancer. However, the function and mechanism of PTPRJ in CRC are not well understood. At the present study, we show that ectopic expression of PTPRJ inhibits cell growth, migration, and invasiveness in CRC cell line HCT116. Moreover, PTPRJ inhibits the tumorigenecity of HCT116 in a xenograft tumor model. MiR-155, the well-known oncomiR in CRC, is identified as an upstream factor of PTPRJ. MiR-155 directly binds to the 3' untranslated region of PTPRJ mRNA and suppresses the mRNA and protein levels of PTPRJ. Furthermore, the growth-promoting and AKT signaling activation effect of miR-155 was abrogated by PTPRJ overexpression, and vice versa. Our study reveals the crucial role of miR-155/PTPRJ/AKT axis in proliferation and migration of CRC cells and suggests a therapeutic potential of PTPRJ. J. Cell. Biochem. 118: 3391-3400, 2017. © 2017 Wiley Periodicals, Inc.

miR-155 Inhibits Mouse Osteoblast Differentiation by Suppressing SMAD5 Expression

Osteogenesis from preosteoblasts is important for bone tissue engineering. MicroRNAs are a class of endogenous small RNA molecules that potentially modulate osteogenesis. In this study, we found that miR-155 expression was downregulated in a time-dependent manner in cells of the preosteoblast cell line MC3T3-E1 after osteogenic induction using bone morphogenetic protein 2 (BMP2). Transfection with miR-155 decreased alkaline phosphatase (ALP) activity, ALP expression, and the staining intensity of Alizarin Red in MC3T3-E1 cells treated with BMP2, whereas treatment with miR-155 inhibitor promoted BMP2-induced osteoblast differentiation. The luciferase assay confirmed that miR-155 can bind to the 3′ untranslated region of SMAD5 mRNA. miR-155 transfection significantly decreased the expression of SMAD5 protein and mRNA in MC3T3-E1 cells under control media and the p-SMAD5 protein level during osteogenesis. After transfecting cells with the SMAD5 overexpression plasmids, the inhibitory effect of miR-155 on osteogenesis was significantly attenuated. In conclusion, miR-155 inhibited osteoblast differentiation by downregulating the translation of SMAD5 in mouse preosteoblast cells. Inhibition of miR-155 promoted osteogenic potential and thus it can be used as a potential target in the treatment of bone defects.

Aspirin alleviates cardiac fibrosis in mice by inhibiting autophagy

Aspirin (ASA) is a cardioprotective drug with anti-cardiac fibrosis action in vivo. This study was aimed to clarify the anti-cardiac fibrosis action of ASA and the underlying mechanisms. Two heart injury models (injection of isoproterenol and ligation of the left anterior descending branch) were used in mice to induce cardiac fibrosis. The animals were treated with ASA (10 mg·kg^-1·d^-1, ig) for 21 and 14 d, respectively. ASA administration significantly improved cardiac function, and ameliorated heart damage and fibrosis in the mice. The mechanisms underlying ASA's anti-fibrotic effect were further analyzed in neonatal cardiac fibroblasts (CFs) exposed to hypoxia in vitro. ASA (0.5-5 mmol/L) dose-dependently inhibited the proliferation and Akt phosphorylation in the CFs. In addition, ASA significantly inhibited CF apoptosis, and decreased the levels of apoptosis markers (cleaved caspase 3 and Parp1), which might serve as a side effect of anti-fibrotic effect of ASA. Furthermore, ASA dose-dependently inhibited the autophagy in the CFs, as evidenced by the reduced levels of autophagy marker LC3-II. The autophagy inhibitor Pepstatin A (PepA) promoted the inhibitory effect of ASA on CF proliferation, whereas the autophagy inducer rapamycin rescued ASA-caused inhibition of CF proliferation, suggesting an autophagy-dependent anti-proliferative effect of ASA. Both p38 inhibitor SB203580 and ROS scavenger N-acetyl-cysteine (NAC) significantly decreased Akt phosphorylation in CFs in the basal and hypoxic situations, but they both significantly increased LC3-II levels in the CFs. Our results suggest that an autophagy- and p38/ROS-dependent pathway mediates the anti-cardiac fibrosis effect of ASA in CFs. As PepA and SB203580 did not affect ASA-caused inhibition of CF apoptosis, the drug combination will enhance ASA's therapeutic effects.

Cardiac regenerative medicine: At the crossroad of microRNA function and biotechnology

There is an urgent need to develop new therapeutic strategies to stimulate cardiac repair after damage, such as myocardial infarction. Already for more than a century scientist are intrigued by studying the regenerative capacity of the heart. While moving away from the old classification of the heart as a post-mitotic organ, and being inspired by the stem cell research in other scientific fields, mainly three different strategies arose in order to develop regenerative medicine, namely; the use of cardiac stem cells, reprogramming of fibroblasts into cardiomyocytes or direct stimulation of endogenous cardiomyocyte proliferation. MicroRNAs, known to play a role in orchestrating cell fate processes such as proliferation, differentiation and reprogramming, gained a lot of attention in this context the latest years. Indeed, several research groups have independently demonstrated that microRNA-based therapy shows promising results to induce heart tissue regeneration and improve cardiac pump function after myocardial injury. Nowadays, a whole new biotechnology field has been unveiled to investigate the possibilities for efficient, safe and specific delivery of microRNAs towards the heart.

Developing miRNA therapeutics for cardiac repair in ischemic heart disease

MicroRNAs (miRNAs) families have been found to be powerful regulators in a wide variety of diseases, which enables the possible use of miRNAs in therapeutic strategies for cardiac repair after ischemic heart disease. This review provides some general insights into miRNAs modulation for development of current molecular and cellular therapeutics in cardiac repair, including endogenous regeneration, endogenous repair, stem cells transplantation, and reprogramming. We also review the delivery strategies for miRNAs modulation, and briefly summarize the current bench and clinical efforts that are being made to explore miRNAs as the future therapeutic target.

MicroRNAs and Cardiac Regeneration

The human heart has a limited capacity to regenerate lost or damaged cardiomyocytes after cardiac insult. Instead, myocardial injury is characterized by extensive cardiac remodeling by fibroblasts, resulting in the eventual deterioration of cardiac structure and function. Cardiac function would be improved if these fibroblasts could be converted into cardiomyocytes. MicroRNAs (miRNAs), small noncoding RNAs that promote mRNA degradation and inhibit mRNA translation, have been shown to be important in cardiac development. Using this information, various researchers have used miRNAs to promote the formation of cardiomyocytes through several approaches. Several miRNAs acting in combination promote the direct conversion of cardiac fibroblasts into cardiomyocytes. Moreover, several miRNAs have been identified that aid the formation of inducible pluripotent stem cells and miRNAs also induce these cells to adopt a cardiac fate. MiRNAs have also been implicated in resident cardiac progenitor cell differentiation. In this review, we discuss the current literature as it pertains to these processes, as well as discussing the therapeutic implications of these findings.