Guanine-rich RNA binding protein GRSF1 inhibits myoblast differentiation through repressing mitochondrial ROS production

HIF-1 induced tiRNA-Lys-CTT-003 is protective against cisplatin induced ferroptosis of renal tubular cells in mouse AKI model

HIF-1 activation is protective in acute kidney injury (AKI), but its underlying mechanism is not fully understood. Stress-induced tRNA derived small RNAs play an emerging role in cellular processes. This study investigated the role of HIF-1 associated tiRNA-Lys-CTT-003 (tiR-Lys) in an AKI mouse model. Our sequencing results showed that ischemia can promote the production of renal tiR-Lys by activating HIF-1α. FG-4592, a HIF-1 inducer, can also upregulate the expression of tiR-Lys in renal tubular cells. Both overexpression of tiR-Lys and FG-4592 pre-treatment could improve mitochondrial damage and lipid peroxidation with alleviated renal function and morphological damage in cisplatin-induced AKI mice. While the anti-ferroptosis effect of FG-4592 were largely eliminated by tiR-Lys inhibitor. Notably, tiR-Lys directly alleviated cell death and MDA accumulation induced by the ferroptosis inducer Erastin, accompanied with restored expression of GPX4. RNA-Pulldown and RIP-qPCR results revealed that tiR-Lys can interact with the RNA-binding protein GRSF1.tiR-lys overexpression can preserve protein expression of GRSF1 decreased by cisplatin. Inhibiting Grsf1 via shRNA eliminated the upregulation of GPX4 by tiR-Lys. In conclusion, our study demonstrates that HIF-1α-induced tiR-Lys is protective in cisplatin-induced AKI, primarily by upregulating the level of GPX4 through interaction with GRSF1, thereby inhibiting ferroptosis in renal tubular epithelial cells.

Guanine-Rich RNA Sequence Binding Factor 1 Deficiency Promotes Colorectal Cancer Progression by Regulating PI3K/AKT Signaling Pathway

Background

Guanine-rich RNA sequence binding factor 1 (GRSF1), part of the RNA-binding protein family, is now attracting interest due to its potential association with the progression of a variety of human cancers. The precise contribution and molecular mechanism of GRSF1 to colorectal cancer (CRC) progression, however, have yet to be clarified.

Methods

Immunohistochemistry and Western Blot analysis was carried out to detect the expression of GRSF1 in CRC at both mRNA and protein levels and its subsequent effects on prognosis. A series of functional tests were performed to understand its influence on proliferation, migration, and invasion of CRC cells.

Results

The universal downregulation of GRSF1 in CRC was identified, indicating a correlation with poor prognosis. Our functional studies unveiled that the elimination of GRSF1 enhances tumour activities such as proliferation, migration, and invasion of CRC cells, while GRSF1 overexpression curtailed these abilities.

Conclusion

Notably, we uncovered that GRSF1 insufficiency modulates the PI3K/Akt signaling pathway and Ras activation in CRC. Therefore, our data suggest GRSF1 operates as a tumor suppressor gene in CRC and may offer promise as a potential biomarker and novel therapeutic target in CRC management.

Anti-aging Factor GRSF1 Attenuates Cerebral Ischemia-Reperfusion Injury in Mice by Inhibiting GPX4-Mediated Ferroptosis

Abnormal accumulation of senescent cells in tissues has been shown to facilitate the onset and progression of various diseases. As an important protein involving in the regulation of cellular senescence process, researches suggested GRSF1 as a potential senolytic target to improve multiple physiological and pathological processes. However, the underlying mechanism of cellular senescence on cerebral ischemia-reperfusion injury (CIRI) has not been revealed. Here, we investigated the effect of GRSF1 on CIRI and delved into its specific mechanisms. In the present study, we established a mouse model of cerebral ischemia-reperfusion (CIR) and observed low expression of anti-aging factor GRSF1, along with greatly increased levels of senescence-related markers p16 and p21 and senescence-associated secretory phenotype TNF-α. Furthermore, we found that the expression of GPX4 was elevated parallel to GRSF1 in CIR mice with overexpression of GRSF1, oxidative stress, and iron metabolism-related proteins were inhibited. Functionally, overexpressing GRSF1 significantly ameliorated infarct volume and neurological function scores and suppressed apoptosis in CIR mice, while administration of GPX4 inhibitors reversed these beneficial phenotypes. Taken together, our results indicate cellular senescence as an important pathological mechanism to exacerbate cerebral injury during CIRI, while GRSF1 could inhibit oxidative stress-mediated ferroptosis through upregulating GPX4 to attenuate reperfusion injury, which makes senolytic treatment, especially GRSF1, a promising therapeutic target for CIRI.

Guanine-rich RNA sequence binding factor 1 regulates neuronal ferroptosis after spinal cord injury in rats via the GPX4 signaling pathway

Spinal cord injury (SCI) can trigger multiple forms of neuronal cell death. Among these, ferroptosis stands out as a particularly important style of cell death due to its iron overload-dependent lipid peroxidative regulatory mechanism. The guanine-rich RNA sequence binding factor 1 (GRSF1) is an RNA-binding protein that has been implicated in cellular senescence, mitochondrial function, oxidative stress, erythropoiesis, and embryonic brain development. However, the function of GRSF1 in neuronal ferroptosis after SCI remains unclear. Here, we established a SCI rat model in vivo and evaluated the function of GRSF1 on neuronal ferroptosis by inhibiting and overexpressing GRSF1. We firstly verified the protein expression of GRSF1 and GPX4 at different time points after SCI. According of changes in expression, we chose 3 d post SCI to assess the effect of GRSF1 on ferroptosis. We found that GRSF1 expression decreased after SCI. In addition, GRSF1 was mainly localized in the cytoplasm of neurons. The results also showed that overexpression of GRSF1 promoted recovery of neurological functional after SCI. Further investigation revealed that GRSF1 might attenuate neuronal ferroptosis by regulating the GPX4 protein expression levels. In summary, our findings indicate that GRSF1 attenuates injury in SCI and reduces neuron ferroptosis and promotes functional recovery via GPX4.

Role of SIRT3 in Microgravity Response: A New Player in Muscle Tissue Recovery

Life on Earth has evolved in the presence of a gravity constraint. Any change in the value of such a constraint has important physiological effects. Gravity reduction (microgravity) alters the performance of muscle, bone and, immune systems among others. Therefore, countermeasures to limit such deleterious effects of microgravity are needed considering future Lunar and Martian missions. Our study aims to demonstrate that the activation of mitochondrial Sirtuin 3 (SIRT3) can be exploited to reduce muscle damage and to maintain muscle differentiation following microgravity exposure. To this effect, we used a RCCS machine to simulate microgravity on ground on a muscle and cardiac cell line. During microgravity, cells were treated with a newly synthesized SIRT3 activator, called MC2791 and vitality, differentiation, ROS and, autophagy/mitophagy were measured. Our results indicate that SIRT3 activation reduces microgravity-induced cell death while maintaining the expression of muscle cell differentiation markers. In conclusion, our study demonstrates that SIRT3 activation could represent a targeted molecular strategy to reduce muscle tissue damage caused by microgravity.

Xiao-Yao-San protects against anti-tuberculosis drug-induced liver injury by regulating Grsf1 in the mitochondrial oxidative stress pathway

Background: Xiao-Yao-San (XYS) is a traditional Chinese prescription that regulates gastrointestinal function, improves mental and psychological abnormalities, and enhances liver function. However, the underlying mechanism of XYS for relieving anti-tuberculosis (AT) drug-induced liver injury is not clear.

Objective: The current study examined whether XYS alleviated the symptoms of AT drug-induced liver injury in mice via the mitochondrial oxidative stress pathway.

Methods: BALB/c male mice were randomly divided into four groups of 12 animals, including a control group, a model group, a 0.32 g/kg XYS group, and a 0.64 g/kg XYS group. The effect of XYS on the degree of liver injury was observed using haematoxylin and eosin staining (HE) and oil red O staining of pathological sections, biochemical parameters, and reactive oxygen species (ROS) levels. The protein expression of mitochondrial synthesis-related proteins and ferroptosis-related proteins was examined using Western blotting.

Results: XYS improved the pathological changes in liver tissue and reduced the level of oxidative stress in liver-injured mice. XYS increased the expression of mitochondrial synthesis-related proteins and reversed the expression of ferroptosis-related proteins. Knockdown of G-rich RNA sequence binding factor 1 (Grsf1) expression with Grsf1 shRNA blocked the protective effects of XYS in liver injury.

Conclusion: Our findings suggest that XYS alleviates AT drug-induced liver injury by mediating Grsf1 in the mitochondrial oxidative stress pathway.

Autophagy in muscle regeneration: potential therapies for myopathies

Autophagy classically functions as a physiological process to degrade cytoplasmic components, protein aggregates, and/or organelles, as a mechanism for nutrient breakdown, and as a regulator of cellular architecture. Its biological functions include metabolic stress adaptation, stem cell differentiation, immunomodulation and diseases regulation, and so on. Current researches have proved that autophagy dysfunction may contribute to the pathogenesis of some myopathies through impairment of myofibres regeneration. Studies of autophagy inhibition also indicate the importance of autophagy in muscle regeneration, while activation of autophagy can restore muscle function in some myopathies. In this review, we aim to report the mechanisms of action of autophagy on muscle regeneration to provide relevant references for the treatment of regenerating defective myopathies by regulating autophagy. Results have shown that one key mechanism of autophagy regulating the muscle regeneration is to affect the differentiation fate of muscle stem cells (MuSCs), including quiescence maintenance, activation and differentiation. The roles of autophagy (organelle/protein degradation, energy facilitation, and/or other) vary at different myogenic stages of the repair process. When the muscle is in homeostasis, basal autophagy can maintain the quiescence state and stemness of MuSCs by renewing organelle and protein. After injury, the increased autophagy flux contributes to meet biological energy demand of MuSCs during activation and proliferation. By mitochondrial remodelling, autophagy during differentiation can promote the metabolic transformation and balance mitochondrial-mediated apoptosis signals in myoblasts. Autophagy in mature myofibres is also essential for the degradation of necrotic myofibres, and may affect the dynamics of MuSCs by affecting the secretion spectrum of myofibres or the recruitment of supporting cells. Except for myogenic cells, autophagy also plays an important role in regulating the function of non-myogenic cells in the muscle microenvironment, which is also essential for successful muscle recovery. Autophagy can regulate the immune microenvironment during muscle regeneration through the recruitment and polarization of macrophages, while autophagy in endothelial cells can regulate muscle regeneration in an angiogenic or angiogenesis-independent manner. Drug or nutrition targeted autophagy has been preliminarily proved to restore muscle function in myopathies by promoting muscle regeneration, and further understanding the role and mechanism of autophagy in various cell types during muscle regeneration will enable more effective combinatorial therapeutic strategies.

Function and regulation of GPX4 in the development and progression of fibrotic disease

Fibrosis is a common feature of fibrotic diseases that poses a serious threat to global health due to high morbidity and mortality in developing countries. There exist some chemical compounds and biomolecules associated with the development of fibrosis, including cytokines, hormones, and enzymes. Among them, glutathione peroxidase 4 (GPX4), as a selenoprotein antioxidant enzyme, is widely found in the embryo, testis, brain, liver, heart, and photoreceptor cells. Moreover, it is shown that GPX4 elicits diverse biological functions by suppressing phospholipid hydroperoxide at the expense of decreased glutathione (GSH), including loss of neurons, autophagy, cell repair, inflammation, ferroptosis, apoptosis, and oxidative stress. Interestingly, these processes are intimately related to the occurrence of fibrotic disease. Recently, GPX4 has been reported to exhibit a decline in fibrotic disease and inhibit fibrosis, suggesting that alterations of GPX4 can change the course or dictate the outcome of fibrotic disease. In this review, we summarize the role and underlying mechanisms of GPX4 in fibrosis diseases such as lung fibrosis, liver fibrosis, kidney fibrosis, cardiac fibrosis, and myelofibrosis.

Geniposide Possesses the Protective Effect on Myocardial Injury by Inhibiting Oxidative Stress and Ferroptosis via Activation of the Grsf1/GPx4 Axis

Reactive oxygen species (ROS) produced in the ischemic myocardium can induce cardiomyocyte injury and death, resulting in cardiac remodeling. Ferroptosis, known as a newly type of cell death caused by iron-dependent oxidative stress, which is an essential death mechanism in cardiomyocytes. However, it is unclear whether oxidative stress products can further induce ferroptosis and aggravate cardiomyocyte injury. Geniposide (GEN), a major active component of Gardenia jasminoides J. Ellis, possesses the natural antioxidant activity and cardioprotective effect. Herein, we evaluated the role of ferroptosis in myocardial oxidative injury and the protective effect of GEN on myocardial ferroptosis. We first detected iron overload, massive ROS, and lipid peroxidation in ferric ammonium citrate (FAC)-treated cardiomyocytes, which were typical characteristics of ferroptosis. The iron overload-induced oxidative stress and ferroptosis aggravated cardiomyocyte injury, which were significantly alleviated by GEN treatment. Similar phenotypic changes of ferroptosis were consistently discovered in hydrogen peroxide (H₂O₂)-induced cells, which were reversed by GEN treatment as well. Interestingly, the RNA-binding protein Grsf1, which directly upregulated Gpx4 at the translational level, was activated by GEN following myocardial oxidative injury. The specific knockdown of Grsf1 increased their sensitivity to ferroptosis and weakened the cardioprotective effect of GEN in H₂O₂-treated cardiomyocytes. Moreover, GEN treatment reduced iron overload and lipid peroxidation in myocardial infarction (MI) rats, thereby fighting against the cardiac ischemic injury. Collectively, our study revealed the pathogenesis of oxidative stress and ferroptosis associated with myocardial ischemia, and indicated the antioxidant and anti-ferroptosis effects of GEN on preventing myocardial injury by activating the Grsf1/GPx4 axis, serving as a potential therapeutic target.

RNA-Binding Proteins in the Post-transcriptional Control of Skeletal Muscle Development, Regeneration and Disease

Embryonic myogenesis is a temporally and spatially regulated process that generates skeletal muscle of the trunk and limbs. During this process, mononucleated myoblasts derived from myogenic progenitor cells within the somites undergo proliferation, migration and differentiation to elongate and fuse into multinucleated functional myofibers. Skeletal muscle is the most abundant tissue of the body and has the remarkable ability to self-repair by re-activating the myogenic program in muscle stem cells, known as satellite cells. Post-transcriptional regulation of gene expression mediated by RNA-binding proteins is critically required for muscle development during embryogenesis and for muscle homeostasis in the adult. Differential subcellular localization and activity of RNA-binding proteins orchestrates target gene expression at multiple levels to regulate different steps of myogenesis. Dysfunctions of these post-transcriptional regulators impair muscle development and homeostasis, but also cause defects in motor neurons or the neuromuscular junction, resulting in muscle degeneration and neuromuscular disease. Many RNA-binding proteins, such as members of the muscle blind-like (MBNL) and CUG-BP and ETR-3-like factors (CELF) families, display both overlapping and distinct targets in muscle cells. Thus they function either cooperatively or antagonistically to coordinate myoblast proliferation and differentiation. Evidence is accumulating that the dynamic interplay of their regulatory activity may control the progression of myogenic program as well as stem cell quiescence and activation. Moreover, the role of RNA-binding proteins that regulate post-transcriptional modification in the myogenic program is far less understood as compared with transcription factors involved in myogenic specification and differentiation. Here we review past achievements and recent advances in understanding the functions of RNA-binding proteins during skeletal muscle development, regeneration and disease, with the aim to identify the fundamental questions that are still open for further investigations.

GRSF1 deficiency in skeletal muscle reduces endurance in aged mice

GRSF1 is a mitochondrial RNA-binding protein important for maintaining mitochondrial function. We found that GRSF1 is highly expressed in cultured skeletal myoblasts differentiating into myotubes. To understand the physiological function of GRSF1 in vivo, we generated mice in which GRSF1 was specifically ablated in skeletal muscle. The conditional knockout mice (Grsf1cKO) appeared normal until 7-9 months of age. Importantly, however, a reduction of muscle endurance compared to wild-type controls was observed in 16- to 18-month old Grsf1cKO mice. Transcriptomic analysis revealed more than 200 mRNAs differentially expressed in Grsf1cKO muscle at this age. Notably, mRNAs encoding proteins involved in mitochondrial function, inflammation, and ion transport, including Mgarp, Cxcl10, Nfkb2, and Sln mRNAs, were significantly elevated in aged Grsf1cKO muscle. Our findings suggest that GRSF1 deficiency exacerbates the functional decline of aged skeletal muscle, likely through multiple downstream effector proteins.

GRSF1 promotes tumorigenesis and EMT-mediated metastasis through PI3K/AKT pathway in gastric cancer

It is vital to identify effective therapeutic targets and explore the underlying mechanisms to curb the progression of Gastric cancer (GC) and improve the prognosis of GC patients. Guanine-rich RNA sequence binding factor 1 (GRSF1) is a member of the RNA-binding protein family. The present study showed that GRSF1 knockdown suppressed GC cells proliferation, migration and invasion in vitro, while GRSF1 overexpression enhanced the proliferation, migration and invasion of GC cells. Meanwhile, knockdown of GRSF1 inhibited tumor growth and tumor metastasis in vivo. Furthermore, we demonstrated that GRSF1 induced epithelial-mesenchymal transition (EMT) and activated PI3K/AKT pathway in vitro and in vivo through gain and loss of function. In conclusion, we demonstrated that GRSF1 promotes tumorigenesis and EMT-mediated metastasis through PI3K/AKT pathway in GC. Our study for the first time identified the functions of GRSF1 serving as an oncogene in GC, which may be a potential effective therapeutic target and malignant indicator in GC.

COMMD1, a multi-potent intracellular protein involved in copper homeostasis, protein trafficking, inflammation, and cancer

Copper is a trace element indispensable for life, but at the same time it is implicated in reactive oxygen species formation. Several inherited copper storage diseases are described of which Wilson disease (copper overload, mutations in ATP7B gene) and Menkes disease (copper deficiency, mutations in ATP7A gene) are the most prominent ones. After the discovery in 2002 of a novel gene product (i.e. COMMD1) involved in hepatic copper handling in Bedlington terriers, studies on the mechanism of action of COMMD1 revealed numerous non-copper related functions. Effects on hepatic copper handling are likely mediated via interactions with ATP7B. In addition, COMMD1 has many more interacting partners which guide their routing to either the plasma membrane or, often in an ubiquitination-dependent fashion, trigger their proteolysis via the S26 proteasome. By stimulating NF-κB ubiquitination, COMMD1 dampens an inflammatory reaction. Finally, targeting COMMD1 function can be a novel approach in the treatment of tumors.

Expression Regulation, Protein Chemistry and Functional Biology of the Guanine-Rich Sequence Binding Factor 1 (GRSF1)

In eukaryotic cells RNA-binding proteins have been implicated in virtually all post-transcriptional mechanisms of gene expression regulation. Based on the structural features of their RNA binding domains these proteins have been divided into several subfamilies. The presence of at least two RNA recognition motifs defines the group of heterogenous nuclear ribonucleoproteins H/F and one of its members is the guanine-rich sequence binding factor 1 (GRSF1). GRSF1 was first described 25 years ago and is widely distributed in eukaryotic cells. It is present in the nucleus, the cytoplasm and in mitochondria and has been implicated in a variety of physiological processes (embryogenesis, erythropoiesis, redox homeostasis, RNA metabolism) but also in the pathogenesis of various diseases. This review summarizes our current understanding on GRSF1 biology, critically discusses the literature reports and gives an outlook of future developments in the field.

MiR-7 mediates mitochondrial impairment to trigger apoptosis and necroptosis in Rhabdomyosarcoma

BACKGROUND

Rhabdomyosarcoma (RMS) is a pediatric cancer with rhabdomyoblastic phenotype and mitochondria act as pivotal regulators of its growth and progression. While miR-7-5p (miR-7) is reported to have a tumor-suppressive role, little is yet known about its antitumor activity in RMS.

METHODS

The effects of miR-7 on RMS were analyzed both in vitro and in vivo. Cell death modalities induced by miR-7 were identified. Influence on mitochondria was evaluated through RNA sequencing data, morphological observation and mitochondrial functional assays, including outer membrane permeability, bioenergetics and redox balance. Dual-luciferase assay and phenotype validation after transient gene silencing were performed to identify miR-7 targets in RMS.

RESULTS

MiR-7 executed anti-tumor effect in RMS beyond proliferation inhibition. Morphologic features and molecular characteristics with apoptosis and necroptosis were found in miR-7-transfected RMS cells. Chemical inhibitors of apoptosis and necroptosis were able to prevent miR-7-induced cell death. Further, we identified that mitochondrial impairment mainly contributed to these phenomena and mitochondrial proteins SLC25A37 and TIMM50 were crucial targets for miR-7 to induce cell death in RMS.

CONCLUSION

Our results extended the mechanism of miR-7 antitumor role in rhabdomyosarcoma cancer, and provided potential implications for its therapy.

Identification of the COMM-domain containing protein 1 as specific binding partner for the guanine-rich RNA sequence binding factor 1

BACKGROUND

The guanine-rich RNA sequence binding factor 1 (GRSF1) is an RNA-binding protein of the hnRNP H/F family, which has been implicated in erythropoiesis, regulation of the redox homeostasis, embryonic brain development, mitochondrial function and cellular senescence. The molecular basis for GRSF1-RNA interaction has extensively been studied in the past but for the time being GRSF1 binding proteins have not been identified.

METHODS

To search for GRSF1 binding proteins we first employed the yeast two-hybrid system and screened a cDNA library of human fetal brain for potential GRSF1 binding proteins. Subsequently, we explored the protein-protein-interaction of the recombiant proteins, carried out immunoprecipitation experiments to confirm the interaction of the native proteins in living cells and performed truncation studies to identify the protein-binding motif of GRSF1.

RESULTS

Using the yeast two-hybrid system we identified the COMM-domain containing protein 1 (COMMD1) as specific GRSF1 binding protein and in vitro truncation studies suggested that COMMD1 interacts with the alanine-rich domain of GRSF1. Co-immunoprecipitation strategies indicated that COMMD1-GRSF1 interaction was RNA independent and also occurred in living cells expressing the two native proteins.

CONCLUSION

In mammalian cells the COMM-domain containing protein 1 (COMMD1) specifically interacts with the Ala-rich domain of GRSF1 in an RNA-independent manner.

GENERAL SIGNIFICANCE

This is the first report describing a specific GRSF1 binding protein.