The expression of glia maturation factors and the effect of glia maturation factor-γ on angiogenic sprouting in zebrafish

Hypoxic Upregulation of IER2 Increases Paracrine GMFG Signaling of Endoplasmic Reticulum Stress-CAF to Promote Chordoma Progression via Targeting ITGB1

Currently, the oncogenic mechanism of endoplasmic reticulum stress-CAF (ERS-CAF) subpopulation in chordoma remains unknown. Here, single-cell RNA sequencing, spatial transcriptomics, GeoMx Digital Spatial Profiler, data-independent acquisition proteomics, bulk RNA-seq, and multiplexed quantitative immunofluorescence are used to unveil the precise molecular mechanism of how ERS-CAF affected chordoma progression. Results show that hypoxic microenvironment reprograms CAFs into ERS-CAF subtype. Mechanistically, this occurrs via hypoxia-mediated transcriptional upregulation of IER2. Overexpression of IER2 in CAFs promotes chordoma progression, which can be impeded by IER2 knockdown or use of ERS inhibitors. IER2 also induces expression of ERS-CAF marker genes and results in production of a pro-tumorigenic paracrine GMFG signaling, which exert its biological function via directly binding to ITGB1 on tumor cells. ITGB1 inhibition attenuates tumor malignant progression, which can be partially reversed by exogenous GMFG intervention. Further analyses reveal a positive correlation between ITGB1high tumor cell counts and SPP1+ macrophage density, as well as the spatial proximity of these two cell types. Clinically, a significant correlation of high IER2/ITGB1 expression with tumor aggressive phenotype and poor patient survival is observed. Collectively, the findings suggest that ERS-CAF regulates SPP1+ macrophage to aggravate chordoma progression via the IER2/GMFG/ITGB1 axis, which may be targeted therapeutically in future.

Direct observation of cortactin protecting Arp2/3-actin filament branch junctions from GMF-mediated destabilization

How cells tightly control the formation and turnover of branched actin filament arrays to drive cell motility, endocytosis, and other cellular processes is still not well understood. Here, we investigated the mechanistic relationship between two binding partners of the Arp2/3 complex, glia maturation factor (GMF) and cortactin. Individually, GMF and cortactin have opposite effects on the stability of actin filament branches, but it is unknown how they work in concert with each other to govern branch turnover. Using TIRF microscopy, we observe that GMF's branch destabilizing activities are potently blocked by cortactin (IC50 = 1.3 nM) and that this inhibition requires direct interactions of cortactin with Arp2/3 complex. The simplest model that would explain these results is competition for binding Arp2/3 complex. However, we find that cortactin and GMF do not compete for free Arp2/3 complex in solution. Further, we use single molecule analysis to show that cortactin's on-rate (3 ×107 s-1 M-1) and off-rate (0.03 s-1) at branch junctions are minimally affected by excess GMF. Together, these results show that cortactin binds with high affinity to branch junctions, where it blocks the destabilizing effects of GMF, possibly by a mechanism that is allosteric in nature. In addition, the affinities we measure for cortactin at actin filament branch junctions (Kd = 0.9 nM) and filament sides (Kd = 206 nM) are approximately 20-fold stronger than previously reported. These observations contribute to an emerging view of molecular complexity in how Arp2/3 complex is regulated through the integration of multiple inputs.

Glia Maturation Factor β as a Novel Independent Prognostic Biomarker and Potential Therapeutic Target of Kidney Renal Clear Cell Carcinoma

Kidney renal clear cell carcinoma (KIRC) has the highest mortality rate and potential for invasion among renal cancers. The diagnosis and treatment of KIRC are becoming challenging because of its diverse pathogenic mechanisms. Glia (GMFB) is a highly conserved growth and differentiation factor for glia cells and neurons, and it is closely associated with neurodegenerative diseases. However, its role in KIRC remains unknown. The present study integrated bioinformatics approaches with suitable meta-analyses to determine the position of GMFB in KIRC. There was a significant decrease in Gmfb expression in KIRC kidneys compared with normal controls. Gmfb expression was negatively associated with pathologic stage, T and M stages, and histologic grade. Univariate and multivariate analyses showed that elevated Gmfb expression was an independent factor for a favorable prognosis. Furthermore, the nomogram verified that Gmfb is a low-risk factor for KIRC. Knockdown of Gmfb in Caki-2 cells increased viability and decreased p21 and p27 levels. Overexpression of Gmfb inhibited Caki-2 cell proliferation, migration, and invasion and decreased mitochondrial membrane potential. Gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses considering Gmfb co-expressed differentially expressed genes (DEGs) showed that collecting duct acid secretion and mineral absorption ranked were the most important upregulated and downregulated DEGs, respectively. The upregulated hub genes for DEGs were mainly involved in nucleosome assembly, nucleosome organization, and chromatin assembly, and the downregulated hub genes were primarily associated with keratinization. The ratio of tumor-infiltrating immune cells in KIRC tissues was evaluated using CIBERSORTx. The results showed that the Gmfb expression was significantly positively correlated with macrophage M2 cells and mast resting cell infiltration levels and negatively correlated with T follicular helper, T regulatory, and B plasma cell infiltration levels. The former cell types were associated with a beneficial outcome, while the latter had a worse outcome in patients with KIRC. In summary, this study identified GMFB as a novel independent biomarker and therapeutic target for KIRC, and it provides a helpful and distinct individualized treatment strategy for KIRC with a combination of molecular targets and tumor microenvironment.

GMFG (glia maturation factor gamma) inhibits lung cancer growth by activating p53 signaling pathway

The tumor-promoting or tumor-suppressing functions of Glia maturation factor gamma (GMFG) were described in several cancers. However, how GMFG regulates lung cancer progression is elusive. Bioinformatics analysis was employed to analyze GMFG expression in lung adenocarcinoma (LUAD) and lung squamous cancer (LUSC) as well as its significance in prognosis prediction and diagnosis in lung cancer patients. CCK8 and colony formation assays were adopted to evaluate the impact of GMFG overexpressing and depleting on lung cancer cell proliferation. And in vivo experiments were implemented. Luciferase reporter assays were used to disclose the signaling pathway mediated by GMFG in lung cancer. GMFG expression was lower in LUSC and LUAD tissues compared with normal lung tissues based on TCGA and GTEx databases. Low GMFG expression was associated with lower overall survival and shorter disease specific survival compared high GMFG expression. In vitro loss and gain functions assays demonstrated that ectopically GMFG expression dampened the lung cancer cell proliferation while GMFG knockout escalated the cell proliferation. The promoting effect of GMFG knockout on lung cancer tumorgenesis was also observed in vivo. More interesting, GMFG overexpression reinforced the p53 signaling pathway in lung cancer cells, conversely GMFG deficiency disrupted p53 signaling pathway. In conclusion, we revealed that GMFG is fundamental to p53 signaling pathway to inhibit lung cancer progression, highlighting the importance of GMFG as a p53 inducer for lung cancer patient's diagnosis and therapy.

RNF144A exerts tumor suppressor function in breast cancer through targeting YY1 for proteasomal degradation to downregulate GMFG expression

Ring finger protein 144A (RNF144A), a poorly characterized member of the RING-in-between-RING family of E3 ubiquitin ligases, is an emerging tumor suppressor, but its underlying mechanism remains largely elusive. To address this issue, we used Affymetrix GeneChip Human Transcriptome Array 2.0 to profile gene expression in MDA-MB-231 cells stably expressing empty vector pCDH and Flag-RNF144A, and found that 128 genes were differentially expressed between pCDH- and RNF144A-expressing cells with fold change over 1.5. We further demonstrated that RNF144A negatively regulated the protein and mRNA levels of glial maturation factor γ (GMFG). Mechanistical investigations revealed that transcription factor YY1 transcriptionally activated GMFG expression, and RNF144A interacted with YY1 and promoted its ubiquitination-dependent degradation, thus blocking YY1-induced GMFG expression. Functional rescue assays showed that ectopic expression of RNF144A suppressed the proliferative, migratory, and invasive potential of breast cancer cells, and the noted effects were partially restored by re-expression of GMFG in RNF144A-overexpressing breast cancer cells. Collectively, these findings reveal that RNF144A negatively regulates GMFG expression by targeting YY1 for proteasomal degradation, thus inhibiting the proliferation, migration, and invasion of breast cancer cells.

Organ-Based Proteome and Post-Translational Modification Profiling of a Widely Cultivated Tropical Water Fish, Labeo rohita

Proteomics has enormous applications in human and animal research. However, proteomic studies in fisheries science are quite scanty particularly for economically important species. Few proteomic studies have been carried out in model fish species, but comprehensive proteomics of aquaculture species are still scarce. This study aimed to perform a comprehensive organ-based protein profiling of important tissue samples for one of the most important aquaculture species,Labeo rohita.Deep proteomic profiling of 17 histologically normal tissues, blood plasma, and embryo provided mass-spectrometric evidence for 8498 proteins at 1% false discovery rate that make up about 26% of the total annotated protein-coding sequences in Rohu. Tissue-wise expression analysis was performed, and the presence of several biologically important proteins was also verified using a targeted proteomic approach. We identified the global post-translational modifications (PTMs) in terms of acetylation (N-terminus and lysine), methylation (N-terminus, lysine, and arginine), and phosphorylation (serine, threonine, and tyrosine) to present a comprehensive proteome resource. An interactive web-based portal has been developed for an overall landscape of protein expression across the studied tissues of Labeo rohita (www.fishprot.org). This draft proteome map of Labeo rohita would advance basic and applied research in aquaculture to meet the most critical challenge of providing food and nutritional security to an increasing world population.

GMFG Has Potential to Be a Novel Prognostic Marker and Related to Immune Infiltrates in Breast Cancer

A growing amount of evidence has indicated immune genes perform a crucial position in the development and progression of breast cancer microenvironment. The purpose of our study was to identify immunogenic prognostic marker and explore potential regulatory mechanisms for breast cancer. We identified the genes related to ImmuneScore using ESTIMATE algorithm and WGCNA analysis, and we identified the differentially expressed gene (DEGs). Then, Glia maturation factor γ (GMFG) was determined as a predictive factor by intersecting immune-related genes with DEGs and survival analysis. We found the expression of GMFG was lower in breast cancer tissues compared with normal breast tissues, which was further verified by immunohistochemical (IHC). Moreover, the decreased expression of GMFG was significantly related to the poor prognosis. Besides, the expression of GMFG was related to the age, ER status, PR status, HER2 status and tumor size, which further suggested that the expression of GMFG was correlated with the subtype and the growth of tumor. The univariate and multivariate Cox regression analyses revealed that age, stage, the expression level of GMFG and radiotherapy were independent factors for predicting the prognosis of breast cancer patients. Subsequently, a prognostic model to predict the 3-year, 5-year and 10-year overall survival rate was developed based on the above four variables, and visualized as a nomogram. The values of area under the curve of the nomogram at 3-year, 5-year and 10-year were 0.897, 0.873 and 0.922, respectively, which was higher than stage in prognostic accuracy. In addition, we also found that GMFG expression level was correlated with sensitivity of some breast cancer chemotherapy drugs. Furthermore, the results of GSEA indicated immune-related pathways were mainly enriched in GMFG-high-expression group. CIBERSORT analysis for the proportion of tumor-infiltrating immune cells (TIICs) suggested that expression of GMFG was positively association with multiple kinds T-cell in BC. Among them, CD8+ T cells had the strongest correlation with GMFG expression, which revealed that GMFG might has an antitumor effect by increasing the infiltration of CD8+ T cells in breast cancer. Accordingly, GMFG has the potential to become a novel immune biomarker for the diagnosis and treatment of breast cancer.

Bioinformatics and survival analysis of glia maturation factor-γ in pan-cancers

Background

Glia maturation factor-γ (GMFG) is reported to inhibit the actin nucleation through binding to the actin-related protein-2/3 complex (Arp2/3). Considering the main function of GMFG in actin remodeling, which is vital for immune response, angiogenesis, cell division and motility, GMFG is supposed to have important roles in tumor development, while up to now, only two studies described the role of GMFG in cancers. By investigating the clinical values of GMFG using The Cancer Genome Atlas (TCGA) data and the functional mechanisms of GMFG through analyses of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichments, this study was aimed to better understand the impact of GMFG in pan-cancers and to draw more attentions for the future research of GMFG.

Methods

RNA-seq and clinical data of cancer patients were collected from TCGA and analyzed by the Kaplan-Meier methods. GO and KEGG analyses were conducted using the online tools from the Database for Annotation, Visualization and Integrated Discovery (DAVID).

Results

Compared to the corresponding normal samples, GMFG was significantly upregulated in glioblastoma (GBM), kidney clear cell carcinoma (KIRC), lower grade glioma (LGG), acute myeloid leukemia (LAML), and pancreatic cancer (PAAD), testicular cancer (TGCT), but was downregulated in kidney chromophobe (KICH), lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC) (P < 0.05 for all). High expression of GMFG predicted worse OS in GBM (HR = 1.5, P = 0.017), LGG (HR = 2.2, P < 0.001), LUSC (HR = 1.4, P = 0.022) and ocular melanomas (UVM) (HR = 7, P < 0.001), as well as worse DFS in LGG (HR = 1.8, P < 0.001) and prostate cancer (PRAD) (HR = 1.9, P = 0.004). In contrast, high expression of GMFG was associated with better OS in skin cutaneous melanoma (SKCM) (HR = 0.59, P < 0.001) and thymoma (THYM) (HR = 0.098, P = 0.031), as well as better DFS in bile duct cancer (CHOL) (HR = 0.2, P = 0.003). GMFG was mainly involved in the immune response, protein binding and cytokine-cytokine receptor interaction pathways, and was positively associated with multiple immunomodulators in most cancers.

Conclusion

Our study preliminarily identified that GMFG may cause different survivals for different cancers through modulating tumor progression, immune response status and tissue-specific tumor microenvironment (TME).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08163-2.

Discriminating Origin Tissues of Tumor Cell Lines by Methylation Signatures and Dys-Methylated Rules

DNA methylation is an essential epigenetic modification for multiple biological processes. DNA methylation in mammals acts as an epigenetic mark of transcriptional repression. Aberrant levels of DNA methylation can be observed in various types of tumor cells. Thus, DNA methylation has attracted considerable attention among researchers to provide new and feasible tumor therapies. Conventional studies considered single-gene methylation or specific loci as biomarkers for tumorigenesis. However, genome-scale methylated modification has not been completely investigated. Thus, we proposed and compared two novel computational approaches based on multiple machine learning algorithms for the qualitative and quantitative analyses of methylation-associated genes and their dys-methylated patterns. This study contributes to the identification of novel effective genes and the establishment of optimal quantitative rules for aberrant methylation distinguishing tumor cells with different origin tissues.

Glia maturation factor-γ regulates murine macrophage iron metabolism and M2 polarization through mitochondrial ROS

In macrophages, cellular iron metabolism status is tightly integrated with macrophage phenotype and associated with mitochondrial function. However, how molecular events regulate mitochondrial activity to integrate regulation of iron metabolism and macrophage phenotype remains unclear. Here, we explored the important role of the actin-regulatory protein glia maturation factor-γ (GMFG) in the regulation of cellular iron metabolism and macrophage phenotype. We found that GMFG was downregulated in murine macrophages by exposure to iron and hydrogen peroxide. GMFG knockdown altered the expression of iron metabolism proteins and increased iron levels in murine macrophages and concomitantly promoted their polarization toward an anti-inflammatory M2 phenotype. GMFG-knockdown macrophages exhibited moderately increased levels of mitochondrial reactive oxygen species (mtROS), which were accompanied by decreased expression of some mitochondrial respiration chain components, including the iron-sulfur cluster assembly scaffold protein ISCU as well as the antioxidant enzymes SOD1 and SOD2. Importantly, treatment of GMFG-knockdown macrophages with the antioxidant N-acetylcysteine reversed the altered expression of iron metabolism proteins and significantly inhibited the enhanced gene expression of M2 macrophage markers, suggesting that mtROS is mechanistically linked to cellular iron metabolism and macrophage phenotype. Finally, GMFG interacted with the mitochondrial membrane ATPase ATAD3A, suggesting that GMFG knockdown-induced mtROS production might be attributed to alteration of mitochondrial function in macrophages. Our findings suggest that GMFG is an important regulator in cellular iron metabolism and macrophage phenotype and could be a novel therapeutic target for modulating macrophage function in immune and metabolic disorders.

Cellular and pathophysiological consequences of Arp2/3 complex inhibition: role of inhibitory proteins and pharmacological compounds

The actin-related protein complex 2/3 (Arp2/3) generates branched actin networks important for many cellular processes such as motility, vesicular trafficking, cytokinesis, and intercellular junction formation and stabilization. Activation of Arp2/3 requires interaction with actin nucleation-promoting factors (NPFs). Regulation of Arp2/3 activity is achieved by endogenous inhibitory proteins through direct binding to Arp2/3 and competition with NPFs or by binding to Arp2/3-induced actin filaments and disassembly of branched actin networks. Arp2/3 inhibition has recently garnered more attention as it has been associated with attenuation of cancer progression, neurotoxic effects during drug abuse, and pathogen invasion of host cells. In this review, we summarize current knowledge on expression, inhibitory mechanisms and function of endogenous proteins able to inhibit Arp2/3 such as coronins, GMFs, PICK1, gadkin, and arpin. Moreover, we discuss cellular consequences of pharmacological Arp2/3 inhibition.

GMF as an Actin Network Remodeling Factor

Glia maturation factor (GMF) has recently been established as a regulator of the actin cytoskeleton with a unique role in remodeling actin network architecture. Conserved from yeast to mammals, GMF is one of five members of the ADF-H family of actin regulatory proteins, which includes ADF/cofilin, Abp1/Drebrin, Twinfilin, and Coactosin. GMF does not bind actin, but instead binds the Arp2/3 complex with high affinity. Through this association, GMF catalyzes the debranching of actin filament networks and inhibits actin nucleation by Arp2/3 complex. Here, we discuss GMF's emerging role in controlling actin filament spatial organization and dynamics underlying cell motility, endocytosis, and other biological processes. Further, we attempt to reconcile these functions with its earlier characterization as a cell differentiation factor.

Expression of glia maturation factor γ is associated with colorectal cancer metastasis and its downregulation suppresses colorectal cancer cell migration and invasion in vitro

Glia maturation factor γ (GMFG) functions to reorganize the actin cytoskeleton and appears to play a causative role in cell migration and adherence. The present study assessed GMFG expression in colorectal cancer cells and tissue specimens and then explored the role of GMFG in colorectal cancer progression in vitro. GMFG protein was highly expressed in colorectal cancer tissues and a metastatic colon cancer cell line. Knockdown of GMFG expression using GMFG siRNA or anti-GMFG antibody decreased the capacity of colon cancer LoVo cell migration and invasion in vitro, while recombinant GMFG treatment induced LoVo cell migration. Furthermore, GMFG knockdown also decreased expression of MMP2 protein and reversed epithelial-mesenchymal transition (EMT) phenotypes in LoVo cells. Co-culture of LoVo cells with human umbilical vein endothelial cells (HUVECs) and exogenous GMFG treatment promoted LoVo cell migration and invasion. The data from the present study indicate that GMFG should be further evaluated as a biomarker for detection of colorectal cancer metastasis and that the targeting of GMFG expression or function could be a novel strategy in the future control of colorectal cancer.

GMFβ controls branched actin content and lamellipodial retraction in fibroblasts

The primary activity of GMFβ in vivo is actin branch disassembly (and not inhibition of Arp2/3 activation), and this activity plays an important role in lamellipodial dynamics and directional migration toward ECM cues.

The lamellipodium is an important structure for cell migration containing branched actin nucleated via the Arp2/3 complex. The formation of branched actin is relatively well studied, but less is known about its disassembly and how this influences migration. GMF is implicated in both Arp2/3 debranching and inhibition of Arp2/3 activation. Modulation of GMFβ, a ubiquitous GMF isoform, by depletion or overexpression resulted in changes in lamellipodial dynamics, branched actin content, and migration. Acute pharmacological inhibition of Arp2/3 by CK-666, coupled to quantitative live-cell imaging of the complex, showed that depletion of GMFβ decreased the rate of branched actin disassembly. These data, along with mutagenesis studies, suggest that debranching (not inhibition of Arp2/3 activation) is a primary activity of GMFβ in vivo. Furthermore, depletion or overexpression of GMFβ disrupted the ability of cells to directionally migrate to a gradient of fibronectin (haptotaxis). These data suggest that debranching by GMFβ plays an important role in branched actin regulation, lamellipodial dynamics, and directional migration.

Steering cell migration: lamellipodium dynamics and the regulation of directional persistence

Membrane protrusions at the leading edge of cells, known as lamellipodia, drive cell migration in many normal and pathological situations. Lamellipodial protrusion is powered by actin polymerization, which is mediated by the actin-related protein 2/3 (ARP2/3)-induced nucleation of branched actin networks and the elongation of actin filaments. Recently, advances have been made in our understanding of positive and negative ARP2/3 regulators (such as the SCAR/WAVE (SCAR/WASP family verprolin-homologous protein) complex and Arpin, respectively) and of proteins that control actin branch stability (such as glial maturation factor (GMF)) or actin filament elongation (such as ENA/VASP proteins) in lamellipodium dynamics and cell migration. This Review highlights how the balance between actin filament branching and elongation, and between the positive and negative feedback loops that regulate these activities, determines lamellipodial persistence. Importantly, directional persistence, which results from lamellipodial persistence, emerges as a critical factor in steering cell migration.

High GMFG expression correlates with poor prognosis and promotes cell migration and invasion in epithelial ovarian cancer

OBJECTIVE

The aim of this study was to characterize the clinical significance of GMFG, a novel ADF/cofilin superfamily protein, and investigate its role in cell migration and invasion in epithelial ovarian cancer (EOC).

METHODS

The expression of GMFG in EOC tissues and ovarian cancer cell lines was evaluated by immunohistochemistry and immunoblotting respectively. The data were statistically analyzed for the associations of GMFG expression with clinicopathologic parameters and survival. In vitro cell migration and invasion assays were performed to determine the role of GMFG in cell migratory behaviors. The effect of GMFG on reorganization of actin cytoskeleton was investigated by immunostaining.

RESULTS

GMFG was overexpressed in EOC. Up-regulated GMFG expression was closely correlated with advanced FIGO stage and chemoresistance of the disease. EOC patients with higher GMFG expression showed poorer progression-free survival (PFS) and overall survival (OS). In vitro cellular assays revealed that GMFG promoted cell migration and invasion. GMFG expression altered actin cytoskeleton organization probably by interacting with the Arp2/3 complex.

CONCLUSION

GMFG expression independently predicts poorer prognosis in patients with EOC. Ectopic overexpression of GMFG contributes to the malignant biological behavior of ovarian cancer cells.