A structural and functional dissection of the cardiac stress response factor MS1

miR-145-5p Inhibits the Proliferation, Migration, and Invasion of Esophageal Carcinoma Cells by Targeting ABRACL

Objective

The study is aimed at investigating the regulatory relationship between miR-145-5p and ABRACL, and has tried at clarifying the mechanisms underlying the proliferation, migration, and invasion of esophageal carcinoma (EC) cells.

Methods

Gene expression data related to EC were accessed from TCGA database, and the “edgeR” package was used to screen differentially expressed genes. TargetScan, miRDB, and miRTarBase databases were used to predict potential targets for the target miRNA miR-145-5p. qRT-PCR and Western blot were performed to assess the expression of miR-145-5p and ABRACL in EC cells. Dual-luciferase reporter assay was performed to validate the targeting relationship between miR-145-5p and ABRACL. Functional experiments including CCK-8 assay, Transwell migration, and invasion assays were used to detect the proliferation, migration, and invasion of EC cells.

Results

The expression of miR-145-5p was significantly decreased in EC, while ABRACL was remarkably increased. In addition, there was a negative correlation identified between miR-145-5p and ABRACL mRNA. Overexpressing miR-145-5p was able to suppress cell proliferation, migration, and invasion, whereas silencing miR-145-5p posed an opposite effect. In the meantime, ABRACL was identified as a direct target of miR-145-5p by dual-luciferase reporter assay. Furthermore, miR-145-5p could inhibit the expression of ABRACL, in turn inhibiting the proliferation, migration, and invasion of EC cells.

Conclusion

miR-145-5p functions on the proliferation, migration, and invasion of EC cells via targeting ABRACL, and it may be a novel therapeutic target in EC treatment.

Human Costars Family Protein ABRACL Modulates Actin Dynamics and Cell Migration and Associates with Tumorigenic Growth

Regulation of cellular actin dynamics is pivotal in driving cell motility. During cancer development, cells migrate to invade and spread; therefore, dysregulation of actin regulators is often associated with cancer progression. Here we report the role of ABRACL, a human homolog of the Dictyostelium actin regulator Costars, in migration and tumorigenic growth of cancer cells. We found a correlation between ABRACL expression and the migratory ability of cancer cells. Cell staining revealed the colocalization of ABRACL and F-actin signals at the leading edge of migrating cells. Analysis of the relative F-/G-actin contents in cells lacking or overexpressing ABRACL suggested that ABRACL promotes cellular actin distribution to the polymerized fraction. Physical interaction between ABRACL and cofilin was supported by immunofluorescence staining and proximity ligation. Additionally, ABRACL hindered cofilin-simulated pyrene F-actin fluorescence decay in vitro, indicating a functional interplay. Lastly, analysis on a colorectal cancer cohort demonstrated that high ABRACL expression was associated with distant metastasis, and further exploration showed that depletion of ABRACL expression in colon cancer cells resulted in reduced cell proliferation and tumorigenic growth. Together, results suggest that ABRACL modulates actin dynamics through its interaction with cofilin and thereby regulates cancer cell migration and participates in cancer pathogenesis.

High Expression of ABRACL Is Associated with Tumorigenesis and Affects Clinical Outcome in Gastric Cancer

BACKGROUND

The ABRA C-terminal like (ABRACL) protein belongs to a novel family of low-molecular weight proteins that increase actin dynamics and cell motility. It is involved in various diseases including cancer; however, its role in gastric cancer is unclear. In this study, the expression of ABRACL in gastric cancer and its relationships with patients' clinicopathological features and survival are examined.

METHODS

Sample expression profiles were downloaded from the Gene Expression Omnibus database and the Cancer Genome Atlas. ABRACL expression at the protein level in normal gastric and gastric cancer tissues was compared by using immunohistochemistry staining data provided by the Human Protein Atlas. Correlations between ABRACL expression and clinicopathological features are analyzed by chi-square tests. Patient survival was evaluated by Kaplan-Meier analysis.

RESULTS

ABRACL expression is upregulated in gastric cancer tissues than in normal tissues. High ABRACL levels indicated a poor prognosis. ABRACL expression (low ABRACL, n = 96; high ABRACL, n = 96) in gastric cancer tissues (primary data from GSE15459) is significantly correlated with poor overall survival (χ² = 4.078, p = 0.043; log-rank test). ABRACL protein levels (low ABRACL, n = 172, high ABRACL, n = 171) in gastric cancer tissues (primary data from www.kmplot.com ) are significantly correlated with poor overall survival (χ² = 4.305, p = 0.038, log-rank test).

CONCLUSIONS

Our results indicate that ABRACL is highly expressed in gastric cancer and is a potential prognostic marker and therapeutic target for this disease.

Transcriptional and Post-Translational Targeting of Myocyte Stress Protein 1 (MS1) by the JNK Pathway in Cardiac Myocytes

Myocyte Stress Protein 1 (MS1) is a muscle-specific, stress-responsive, regulator of gene expression. It was originally identified in embryonic mouse heart which showed increased expression in a rat model of left ventricular hypertrophy. To determine if MS1 was responsive to other stresses relevant to cardiac myocyte function, we tested if it could be induced by the metabolic stresses associated with ischaemia/reperfusion injury in cardiac myocytes. We found that metabolic stress increased MS1 expression, both at the mRNA and protein level, concurrent with activation of the c-Jun N-terminal Kinase (JNK) signalling pathway. MS1 induction by metabolic stress was blocked by both the transcription inhibitor actinomycin D and a JNK inhibitor, suggesting that activation of the JNK pathway during metabolic stress in cardiac myocytes leads to transcriptional induction of MS1. MS1 was also found to be an efficient JNK substrate in vitro, with a major JNK phosphorylation site identified at Thr-62. In addition, MS1 was found to co-precipitate with JNK, and inspection of the amino acid sequence upstream of the phosphorylation site, at Thr-62, revealed a putative Mitogen-Activated Protein Kinase (MAPK) binding site. Taken together, these data identify MS1 as a likely transcriptional and post-translational target for the JNK pathway in cardiac myocytes subjected to metabolic stress.

HSPC280, a winged helix protein expressed in the subventricular zone of the developing ganglionic eminences, inhibits neuronal differentiation

Winged helix proteins have critical roles in a variety of developmental processes. During a screening for genes expressed in the developing forebrain, we identified HSPC280, a non-typical winged helix protein, which shares similarity with a protein-protein interaction domain found in the proteins of the actin-binding Rho-activating protein family. In this work, we analyzed HSPC280 expression during mouse development as well as during neuronal differentiation of mouse Neuro2a cells. HSPC280 expression is tightly regulated; during mouse development, it was detected predominantly in the ganglionic eminences of the ventral telencephalon, from their appearance at E11.5 to P0, with the highest levels between E13.5 and E15.5, a period that correlates with the peak of neurogenesis in these structures. Comparative expression analysis of HSPC280 with Dlx2, cyclinD2 and Lhx6 revealed that, within the ganglionic eminences, HSPC280 was restricted in the proliferating cell population of the subventricular zone, in a pattern similar to that of cyclinD2. Finally, we showed that HSPC280 is a nuclear protein which, when overexpressed in Neuro2a cells, it inhibited neuronal differentiation in vitro, suggesting its involvement in the mechanisms controlling neural progenitor cells proliferation.

Large-scale modelling of the divergent spectrin repeats in nesprins: giant modular proteins

Nesprin-1 and nesprin-2 are nuclear envelope (NE) proteins characterized by a common structure of an SR (spectrin repeat) rod domain and a C-terminal transmembrane KASH [Klarsicht-ANC-Syne-homology] domain and display N-terminal actin-binding CH (calponin homology) domains. Mutations in these proteins have been described in Emery-Dreifuss muscular dystrophy and attributed to disruptions of interactions at the NE with nesprins binding partners, lamin A/C and emerin. Evolutionary analysis of the rod domains of the nesprins has shown that they are almost entirely composed of unbroken SR-like structures. We present a bioinformatical approach to accurate definition of the boundaries of each SR by comparison with canonical SR structures, allowing for a large-scale homology modelling of the 74 nesprin-1 and 56 nesprin-2 SRs. The exposed and evolutionary conserved residues identify important pbs for protein-protein interactions that can guide tailored binding experiments. Most importantly, the bioinformatics analyses and the 3D models have been central to the design of selected constructs for protein expression. 1D NMR and CD spectra have been performed of the expressed SRs, showing a folded, stable, high content α-helical structure, typical of SRs. Molecular Dynamics simulations have been performed to study the structural and elastic properties of consecutive SRs, revealing insights in the mechanical properties adopted by these modules in the cell.

The regulation and function of the striated muscle activator of rho signaling (STARS) protein

Healthy living throughout the lifespan requires continual growth and repair of cardiac, smooth, and skeletal muscle. To effectively maintain these processes muscle cells detect extracellular stress signals and efficiently transmit them to activate appropriate intracellular transcriptional programs. The striated muscle activator of Rho signaling (STARS) protein, also known as Myocyte Stress-1 (MS1) protein and Actin-binding Rho-activating protein (ABRA) is highly enriched in cardiac, skeletal, and smooth muscle. STARS binds actin, co-localizes to the sarcomere and is able to stabilize the actin cytoskeleton. By regulating actin polymerization, STARS also controls an intracellular signaling cascade that stimulates the serum response factor (SRF) transcriptional pathway; a pathway controlling genes involved in muscle cell proliferation, differentiation, and growth. Understanding the activation, transcriptional control and biological roles of STARS in cardiac, smooth, and skeletal muscle, will improve our understanding of physiological and pathophysiological muscle development and function.