Activin signaling as an emerging target for therapeutic interventions

After the initial discovery of activins as important regulators of reproduction, novel and diverse roles have been unraveled for them. Activins are expressed in various tissues and have a broad range of activities including the regulation of gonadal function, hormonal homeostasis, growth and differentiation of musculoskeletal tissues, regulation of growth and metastasis of cancer cells, proliferation and differentiation of embryonic stem cells, and even higher brain functions. Activins signal through a combination of type I and II transmembrane serine/threonine kinase receptors. Activin receptors are shared by multiple transforming growth factor-β (TGF-β) ligands such as myostatin, growth and differentiation factor-11 and nodal. Thus, although the activity of each ligand is distinct, they are also redundant, both physiologically and pathologically in vivo. Activin receptors activated by ligands phosphorylate the receptor-regulated Smads for TGF-β, Smad2 and 3. The Smad proteins then undergo multimerization with the co-mediator Smad4, and translocate into the nucleus to regulate the transcription of target genes in cooperation with nuclear cofactors. Signaling through receptors and Smads is controlled by multiple mechanisms including phosphorylation and other posttranslational modifications such as sumoylation, which affect potein localization, stability and transcriptional activity. Non-Smad signaling also plays an important role in activin signaling. Extracellularly, follistatin and related proteins bind to activins and related TGF-β ligands, and control the signaling and availability of ligands

Long Non-Coding RNA <i>Myoparr</i> Regulates GDF5 Expression in Denervated Mouse Skeletal Muscle

Skeletal muscle is a highly plastic tissue and decreased skeletal muscle mass (muscle atrophy) results in deteriorated motor function and perturbed body homeostasis. Myogenin promoter-associated long non-coding RNA (lncRNA) Myoparr promotes skeletal muscle atrophy caused by surgical denervation; however, the precise molecular mechanism remains unclear. Here, we examined the downstream genes of Myoparr during muscle atrophy following denervation of tibialis anterior (TA) muscles in C57BL/6J mice. Myoparr knockdown affected the expression of 848 genes. Sixty-five of the genes differentially regulated by Myoparr knockdown coded secretory proteins. Among these 65 genes identified in Myoparr-depleted skeletal muscles after denervation, we focused on the increased expression of growth/differentiation factor 5 (GDF5), an inhibitor of muscle atrophy. Myoparr knockdown led to activated bone morphogenetic protein (BMP) signaling in denervated muscles, as indicated by the increased levels of phosphorylated Smad1/5/8. Our detailed evaluation of downstream genes of Myoparr also revealed that Myoparr regulated differential gene expression between myogenic differentiation and muscle atrophy. This is the first report demonstrating the in vivo role of Myoparr in regulating BMP signaling in denervated muscles. Therefore, lncRNAs that have inhibitory activity on BMP signaling may be putative therapeutic targets for skeletal muscle atrophy

<i>Myoparr</i>-Associated and -Independent Multiple Roles of Heterogeneous Nuclear Ribonucleoprotein K during Skeletal Muscle Cell Differentiation

RNA-binding proteins (RBPs) regulate cell physiology via the formation of ribonucleic-protein complexes with coding and non-coding RNAs. RBPs have multiple functions in the same cells; however, the precise mechanism through which their pleiotropic functions are determined remains unknown. In this study, we revealed the multiple inhibitory functions of heterogeneous nuclear ribonucleoprotein K (hnRNPK) for myogenic differentiation. We first identified hnRNPK as a lncRNA Myoparr binding protein. Gain- and loss-of-function experiments showed that hnRNPK repressed the expression of myogenin at the transcriptional level. The hnRNPK-binding region of Myoparr was required to repress myogenin expression. Moreover, hnRNPK repressed the expression of a set of genes coding for aminoacyl-tRNA synthetases in a Myoparr-independent manner. Mechanistically, hnRNPK regulated the eIF2α/Atf4 pathway, one branch of the intrinsic pathways of the endoplasmic reticulum sensors, in differentiating myoblasts. Thus, our findings demonstrate that hnRNPK plays lncRNA-associated and -independent multiple roles during myogenic differentiation, indicating that the analysis of lncRNA-binding proteins will be useful for elucidating both the physiological functions of lncRNAs and the multiple functions of RBPs

Proteomic, Biochemical, and Morphological Analyses of the Effect of Silver Nanoparticles Mixed with Organic and Inorganic Chemicals on Wheat Growth

Wheat is vulnerable to numerous diseases; on the other hand, silver nanoparticles (AgNPs) exhibit a sterilizing action. To understand the combined effects of AgNPs with nicotinate and potassium nitrate (KNO3) for plant growth and sterilization, a gel- and label-free proteomics was performed. Root weight was promoted by the treatment of AgNPs mixed with nicotinate and KNO3. From a total of 5557 detected proteins, 90 proteins were changed by the mixture of AgNPs, nicotinate, and KNO3; among them, 25 and 65 proteins increased and decreased, respectively. The changed proteins were mainly associated with redox and biotic stress in the functional categorization. By immunoblot analysis, the abundance of glutathione reductase/peroxiredoxin and pathogen-related protein three significantly decreased with the mixture. Furthermore, from the changed proteins, the abundance of starch synthase and lipoxygenase significantly increased and decreased, respectively. Through biochemical analysis, the starch contents increased with the mixture. The application of esculetin, which is a lipoxygenase inhibitor, increased the weight and length of the root. These results suggest that the AgNPs mixed with nicotinate and KNO3 cause positive effects on wheat seedlings by regulating pathogen-related protein and reactive-oxygen species scavenging. Furthermore, increasing starch and decreasing lipoxygenase might improve wheat growth

An Analysis of Differentially Expressed Coding and Long Non-Coding RNAs in Multiple Models of Skeletal Muscle Atrophy

The loss of skeletal muscle mass (muscle atrophy or wasting) caused by aging, diseases, and injury decreases quality of life, survival rates, and healthy life expectancy in humans. Although long non-coding RNAs (lncRNAs) have been implicated in skeletal muscle formation and differentiation, their precise roles in muscle atrophy remain unclear. In this study, we used RNA-sequencing (RNA-Seq) to examine changes in the expression of lncRNAs in four muscle atrophy conditions (denervation, casting, fasting, and cancer cachexia) in mice. We successfully identified 33 annotated lncRNAs and 18 novel lncRNAs with common expression changes in all four muscle atrophy conditions. Furthermore, an analysis of lncRNA–mRNA correlations revealed that several lncRNAs affected small molecule biosynthetic processes during muscle atrophy. These results provide novel insights into the lncRNA-mediated regulatory mechanism underlying muscle atrophy and may be useful for the identification of promising therapeutic targets

Proteomic and Biochemical Analyses of the Mechanism of Tolerance in Mutant Soybean Responding to Flooding Stress

To investigate the mechanism of flooding tolerance of soybean, flooding-tolerant mutants derived from gamma-ray irradiated soybean were crossed with parent cultivar Enrei for removal of other factors besides the genes related to flooding tolerance in primary generated mutant soybean. Although the growth of the wild type was significantly suppressed by flooding compared with the non-flooding condition, that of the mutant lines was better than that of the wild type even if it was treated with flooding. A two-day-old mutant line was subjected to flooding for 2 days and proteins were analyzed using a gel-free/label-free proteomic technique. Oppositely changed proteins in abundance between the wild type and mutant line under flooding stress were associated in endoplasmic reticulum according to gene-ontology categorization. Immunoblot analysis confirmed that calnexin accumulation increased in both the wild type and mutant line; however, calreticulin accumulated in only the mutant line under flooding stress. Furthermore, although glycoproteins in the wild type decreased by flooding compared with the non-flooding condition, those in the mutant line increased even if it was under flooding stress. Alcohol dehydrogenase accumulated in the wild type and mutant line; however, this enzyme activity significantly increased and mildly increased in the wild type and mutant line, respectively, under flooding stress compared with the non-flooding condition. Cell death increased and decreased in the wild type and mutant line, respectively, by flooding stress. These results suggest that the regulation of cell death through the fermentation system and glycoprotein folding might be an important factor for the acquisition of flooding tolerance in mutant soybean

An Analysis of Differentially Expressed Coding and Long Non-Coding RNAs in Multiple Models of Skeletal Muscle Atrophy

The loss of skeletal muscle mass (muscle atrophy or wasting) caused by aging, diseases, and injury decreases quality of life, survival rates, and healthy life expectancy in humans. Although long non-coding RNAs (lncRNAs) have been implicated in skeletal muscle formation and differentiation, their precise roles in muscle atrophy remain unclear. In this study, we used RNA-sequencing (RNA-Seq) to examine changes in the expression of lncRNAs in four muscle atrophy conditions (denervation, casting, fasting, and cancer cachexia) in mice. We successfully identified 33 annotated lncRNAs and 18 novel lncRNAs with common expression changes in all four muscle atrophy conditions. Furthermore, an analysis of lncRNA–mRNA correlations revealed that several lncRNAs affected small molecule biosynthetic processes during muscle atrophy. These results provide novel insights into the lncRNA-mediated regulatory mechanism underlying muscle atrophy and may be useful for the identification of promising therapeutic targets

Proteomic Analysis Reveals Salt-Tolerant Mechanism in Soybean Applied with Plant-Derived Smoke Solution

Salt stress of soybean is a serious problem because it reduces plant growth and seed yield. To investigate the salt-tolerant mechanism of soybean, a plant-derived smoke (PDS) solution was used. Three-day-old soybeans were subjected to PDS solution under 100 mM NaCl for 2 days, resulting in PDS solution improving soybean root growth, even under salt stress. Under the same condition, proteins were analyzed using the proteomic technique. Differential abundance proteins were associated with transport/formaldehyde catabolic process/sucrose metabolism/glutathione metabolism/cell wall organization in the biological process and membrane/Golgi in the cellular component with or without PDS solution under salt stress. Immuno-blot analysis confirmed that osmotin, alcohol dehydrogenase, and sucrose synthase increased with salt stress and decreased with additional PDS solution; however, H+ATPase showed opposite effects. Cellulose synthase and xyloglucan endotransglucosylase/hydrolase increased with salt and decreased with additional PDS solution. Furthermore, glycoproteins decreased with salt stress and recovered with additional treatment. As mitochondrion-related events, the contents of ATP and gamma-aminobutyric acid increased with salt stress and recovered with additional treatment. These results suggest that PDS solution improves the soybean growth by alleviating salt stress. Additionally, the regulation of energy metabolism, protein glycosylation, and cell wall construction might be an important factor for the acquisition of salt tolerance in soybean

Morphological, Biochemical, and Proteomic Analyses to Understand the Promotive Effects of Plant-Derived Smoke Solution on Wheat Growth under Flooding Stress

Wheat is an important staple food crop for one-third of the global population; however, its growth is reduced by flooding. On the other hand, a plant-derived smoke solution enhances plant growth; however, its mechanism is not fully understood. To reveal the effects of the plant-derived smoke solution on wheat under flooding, morphological, biochemical, and proteomic analyses were conducted. The plant-derived smoke solution improved wheat-leaf growth, even under flooding. According to the functional categorization of proteomic results, oppositely changed proteins were correlated with photosynthesis, glycolysis, biotic stress, and amino-acid metabolism with or without the plant-derived smoke solution under flooding. Immunoblot analysis confirmed that RuBisCO activase and RuBisCO large/small subunits, which decreased under flooding, were recovered by the application of the plant-derived smoke solution. Furthermore, the contents of chlorophylls a and b significantly decreased by flooding stress; however, they were recovered by the application of the plant-derived smoke solution. In glycolysis, fructose-bisphosphate aldolase and glyceraldehyde-3-phosphate dehydrogenase decreased with the application of the plant-derived smoke solution under flooding as compared with flooding alone. Additionally, glutamine, glutamic acid, aspartic acid, and serine decreased under flooding; however, they were recovered by the plant-derived smoke solution. These results suggest that the application of the plant-derived smoke solution improves the recovery of wheat growth through the regulation of photosynthesis and glycolysis even under flooding conditions. Furthermore, the plant-derived smoke solution might promote wheat tolerance against flooding stress through the regulation of amino-acid metabolism