Pathophysiological functions of Rnd proteins

RND1 inhibits epithelial-mesenchymal transition and temozolomide resistance of glioblastoma via AKT/GSK3-β pathway

GBM is one of the most malignant tumor in central nervous system. The resistance to temozolomide (TMZ) is inevitable in GBM and the characterization of TMZ resistance seriously hinders clinical treatment. It is worthwhile exploring the underlying mechanism of aggressive invasion and TMZ resistance in GBM treatment. Bioinformatic analysis was used to analyze the association between RND1 and a series of EMT-related genes. Colony formation assay and cell viability assay were used to assess the growth of U87 and U251 cells. The cell invasion status was evaluated based on transwell and wound-healing assays. Western blot was used to detect the protein expression in GBM cells. Treatment targeted RND1 combined with TMZ therapy was conducted in nude mice to evaluate the potential application of RND1 as a clinical target for GBM. The overexpression of RND1 suppressed the progression and migration of U87 and U251 cells. RND1 knockdown facilitated the growth and invasion of GBM cells. RND1 regulated the EMT of GBM cells via inhibiting the phosphorylation of AKT and GSK3-β. The promoted effects of RND1 on TMZ sensitivity was identified both in vitro and in vivo. This research demonstrated that the overexpression of RND1 suppressed the migration and EMT status by downregulating AKT/GSK3-β pathway in GBM. RND1 enhanced the TMZ sensitivity of GBM cells both in vitro and in vivo. Our findings may contribute to the targeted therapy for GBM and the understanding of mechanisms of TMZ resistance in GBM.

Roles of small GTPases in cardiac hypertrophy (Review)

Cardiac hypertrophy results from the heart reacting and adapting to various pathological stimuli and its persistent development is a major contributing factor to heart failure. However, the molecular mechanisms of cardiac hypertrophy remain unclear. Small GTPases in the Ras, Rho, Rab, Arf and Ran subfamilies exhibit GTPase activity and play crucial roles in regulating various cellular responses. Previous studies have shown that Ras, Rho and Rab are closely linked to cardiac hypertrophy and that their overexpression can induce cardiac hypertrophy. Here, we review the functions of small GTPases in cardiac hypertrophy and provide additional insights and references for the prevention and treatment of cardiac hypertrophy.

FOXA2 Activates RND1 to Regulate Arachidonic Acid Metabolism Pathway and Suppress Cisplatin Resistance in Lung Squamous Cell Carcinoma

BACKGROUND

The primary cause of cancer-related fatalities globally is lung cancer. Although the chemotherapy drug cisplatin (DDP) has brought certain benefits to patients, the rapid development of drug resistance has greatly hindered treatment success.

METHODS

We used the lung squamous cell carcinoma (LUSC) mRNA data set to explore the differentially expressed gene (RND1) in LUSC and detected RND1 expression in LUSC cells and DDP-resistant cells by qRT-PCR. Meanwhile, we performed abnormal expression treatment on RND1 and conducted CCK8, colony formation, and flow cytometry to evaluate the impact of RND1 expression on cell proliferation, apoptosis, and DDP resistance. In addition, we analyzed metabolism pathways involving RND1 using GSEA. We also used online tools such as hTFtarget and JASPAR to screen for the upstream transcription factor FOXA2 of RND1 and verified their relationship through CHIP and dual luciferase experiments. Finally, we validated the role of FOXA2-RND1 in DDP resistance in LUSC through the above experiments.

RESULTS

RND1 was downregulated in LUSC, and overexpression of RND1 repressed proliferation and DDP resistance of LUSC cells and facilitated cell apoptosis. RND1 modulated the arachidonic acid (AA) metabolism pathway, and FOXA2 positively manipulated RND1 expression. By activating FOXA2, stabilizing RND1, and regulating AA levels, the sensitivity of LUSC cells to DDP could be enhanced.

CONCLUSION

Our study suggested that FOXA2 positively modulated the RND1-AA pathway, which repressed the resistance of LUSC cells to DDP.

RND3 modulates microglial polarization and alleviates neuroinflammation in Parkinson's disease by suppressing NLRP3 inflammasome activation

Neuroinflammation mediated by microglia plays an important role in the etiology of Parkinson's disease (PD). Rho family GTPase 3 (RND3) exerts anti-inflammatory effects and may act as a potential new inducer of neuroprotective phenotypes in microglia. However, whether RND3 can be used to regulate microglia activation or reduce neuroinflammation in PD remains elusive. The study investigated the microglia modulating effects and potential anti-inflammatory effects of RND3 in vivo and in vitro, using animal models of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD and cell models of BV-2 cells stimulated by LPS plus IFN-γ with or without RND3-overexpression. The results showed that RND3 was highly expressed in the MPTP-induced PD mouse model and BV-2 cells treated with LPS and IFN-γ. In vivo experiments confirmed that RND3 overexpression could modulate microglia phenotype and ameliorate MPTP-induced neuroinflammation through inhibiting activation of the NLRP3 inflammasome in substantia nigra pars compacta (SNpc). In vitro study showed that RND3 overexpression could attenuate the production of pro-inflammatory factors in BV2 cells stimulated by LPS and IFN-γ. Mechanistically, RND3 reduced the activation of the NLRP3 inflammasome upon LPS and IFN-γ stimulation. Taken together, these findings suggest that RND3 modulates microglial polarization and alleviates neuroinflammation in Parkinson's disease by suppressing NLRP3 inflammasome activation.

Pathway analysis of spermidine anti-oxidative stress and inducing autophagy in granulosa cells of Sichuan white geese

Spermidine, a natural polyamine, has been proven antioxidant function, but its pathway and mechanism of action remain unclear. Based on the oxidative stress model by 3-nitropropionic acid (3-NPA), the study explored the pathways by spermidine to rescue oxidative stress via autophagic process in goose granulosa cells by RNA-seq and RNA interference. In transcriptional regulation, in addition to KEGG pathways related to cell proliferation and differentiation, lots of KEGG pathways associated with inflammation, metabolism, and signaling were also significantly enriched in 3-NPA vs. 3-NPA + spermidine treatments. Six key genes (JUN, CD44, KITLG, RND2, BMP4 and KALRN) involved in spermidine-mediated anti-oxidative stress were screened. Furthermore, the experimental results showed that spermidine (80 μmol/L) significantly increased autophagic gene expression in goose granulosa cells, while EP300-siRNA or MAP1S-siRNA also significantly increased autophagic process. The autophagic gene expressions were no difference between EP300-siRNA and EP300-siRNA + spermidine treatments, although spermidine significantly increased autophagic process of granulosa cells compared to MAP1S-siRNA alone. In addition, inhibition of mTOR pathway significantly increased autophagic gene expression, which was further enhanced by spermidine in combined with mTOR inhibitor. These results suggest that spermidine can alleviate oxidative stress by inducing autophagy regulated by EP300, MAP1S and mTOR as well as regulating other independent gene expressions in goose granulosa cells.

Molecular basis and current insights of atypical Rho small GTPase in cancer

Atypical Rho GTPases are a subtype of the Rho GTPase family that are involved in diverse cellular processes. The typical Rho GTPases, led by RhoA, Rac1 and Cdc42, have been well studied, while relative studies on atypical Rho GTPases are relatively still limited and have great exploration potential. With the increase in studies, current evidence suggests that atypical Rho GTPases regulate multiple biological processes and play important roles in the occurrence and development of human cancers. Therefore, this review mainly discusses the molecular basis of atypical Rho GTPases and their roles in cancer. We summarize the sequence characteristics, subcellular localization and biological functions of each atypical Rho GTPase. Moreover, we review the recent advances and potential mechanisms of atypical Rho GTPases in the development of multiple cancers. A comprehensive understanding and extensive exploration of the biological functions of atypical Rho GTPases and their molecular mechanisms in tumors will provide important insights into the pathophysiology of tumors and the development of cancer therapeutic strategies.

Investigating the Protective Effects of a Citrus Flavonoid on the Retardation Morphogenesis of the Oligodendroglia-like Cell Line by Rnd2 Knockdown

Recent discoveries suggest links between abnormalities in cell morphogenesis in the brain and the functional deficiency of molecules controlling signal transduction in glial cells such as oligodendroglia. Rnd2 is one such molecule and one of the Rho family monomeric GTP-binding proteins. Despite the currently known functions of Rnd2, its precise roles as it relates to cell morphogenesis and disease state remain to be elucidated. First, we showed that signaling through the loss of function of the rnd2 gene affected the regulation of oligodendroglial cell-like morphological differentiation using the FBD-102b cell line, which is often utilized as a differentiation model. The knockdown of Rnd2 using the clustered regularly interspaced palindromic repeats (CRISPR)/CasRx system or RNA interference was shown to slow morphological differentiation. Second, the knockdown of Prag1 or Fyn kinase, a signaling molecule acting downstream of Rnd2, slowed differentiation. Rnd2 or Prag1 knockdown also decreased Fyn phosphorylation, which is critical for its activation and for oligodendroglial cell differentiation and myelination. Of note, hesperetin, a citrus flavonoid with protective effects on oligodendroglial cells and neurons, can recover differentiation states induced by the knockdown of Rnd2/Prag1/Fyn. Here, we showed that signaling through Rnd2/Prag1/Fyn is involved in the regulation of oligodendroglial cell-like morphological differentiation. The effects of knocking down the signaling cascade molecule can be recovered by hesperetin, highlighting an important molecular structure involved in morphological differentiation.

A CRISPR interference strategy for gene expression silencing in multiple myeloma cell lines

BACKGROUND

Multiple myeloma (MM) is the second most common hematologic neoplasm which is characterized by proliferation and infiltration of plasmatic cells in the bone marrow. Currently, MM is considered incurable due to resistance to treatment. The CRISPR/Cas9 system has emerged as a powerful tool for understanding the role of different genetic alterations in the pathogenesis of hematologic malignancies in both cell lines and mouse models. Despite current advances of gene editing tools, the use of CRISPR/Cas9 technology for gene editing of MM have not so far been extended. In this work, we want to repress Rnd3 expression, an atypical Rho GTPase involved in several cellular processes, in MM cell lines using a CRISPR interference strategy.

RESULTS

We have designed different guide RNAs and cloning them into a lentiviral plasmid, which contains all the machinery necessary for developing the CRISPR interference strategy. We co-transfected the HEK 293T cells with this lentiviral plasmid and 3rd generation lentiviral envelope and packaging plasmids to produce lentiviral particles. The lentiviral particles were used to transduce two different multiple myeloma cell lines, RPMI 8226 and JJN3, and downregulate Rnd3 expression. Additionally, the impact of Rnd3 expression absence was analyzed by a transcriptomic analysis consisting of 3' UTR RNA sequencing. The Rnd3 knock-down cells showed a different transcriptomic profile in comparison to control cells.

CONCLUSIONS

We have developed a CRISPR interference strategy to generate stable Rnd3 knockdown MM cell lines by lentiviral transduction. We have evaluated this strategy in two MM cell lines, and we have demonstrated that Rnd3 silencing works both at transcriptional and protein level. Therefore, we propose CRISPR interference strategy as an alternative tool to silence gene expression in MM cell lines. Furthermore, Rnd3 silencing produces changes in the cellular transcriptomic profile.

Ppan is essential for preimplantation development in mice†

PETER PAN (PPAN), located to nucleoli and mitochondria, is a member of the Brix domain protein family, involved in rRNA processing through its rRNA binding motif and mitochondrial apoptosis by protecting mitochondria structure and suppressing basal autophagic flux. Ppan is important for cell proliferation and viability, and mutation of Ppan in Drosophila caused larval lethality and oogenesis failure. Yet, its role in mammalian reproduction remains unclear. In this study, we explored the function of Ppan in oocyte maturation and early embryogenesis using conditional knockout mouse model. Deficiency of maternal Ppan significantly downregulated the expression level of 5.8S rRNA, 18S rRNA, and 28S rRNA, though it had no effect on oocyte maturation or preimplantation embryo development. However, depletion of both maternal and zygotic Ppan blocked embryonic development at morula stage. Similar phenotype was obtained when only zygotic Ppan was depleted. We further identified no DNA binding activity of PPAN in mouse embryonic stem cells, and depletion of Ppan had minimum impact on transcriptome but decreased expression of 5.8S rRNA, 18S rRNA, and 28S rRNA nevertheless. Our findings demonstrate that Ppan is indispensable for early embryogenesis in mice.

Rho family GTPase 1 (RND1), a novel regulator of p53, enhances ferroptosis in glioblastoma

Background

Ferroptosis is an iron dependent cell death closely associated with p53 signaling pathway and is aberrantly regulated in glioblastoma (GBM), yet the underlying mechanism needs more exploration. Identifying new factors which regulate p53 and ferroptosis in GBM is essential for treatment.

Methods

Glioma cell growth was evaluated by cell viability assays and colony formation assays. Lipid reactive oxygen species (ROS) assays, lipid peroxidation assays, glutathione assays, and transmission electron microscopy were used to assess the degree of cellular lipid peroxidation of GBM. The mechanisms of RND1 in regulation of p53 signaling were analyzed by RT-PCR, western blot, immunostaining, co-immunoprecipitation, ubiquitination assays and luciferase reporter assays. The GBM‐xenografted animal model was constructed and the tumor was captured by an In Vivo Imaging System (IVIS).

Results

From the The Cancer Genome Atlas (TCGA) database, we summarized that Rho family GTPase 1 (RND1) expression was downregulated in GBM and predicted a better prognosis of patients with GBM. We observed that RND1 influenced the glioma cell growth in a ferroptosis-dependent manner when GBM cell lines U87 and A172 were treated with Ferrostatin-1 or Erastin. Mechanistically, we found that RND1 interacted with p53 and led to the de-ubiquitination of p53 protein. Furthermore, the overexpression of RND1 promoted the activity of p53-SLC7A11 signaling pathway, therefore inducing the lipid peroxidation and ferroptosis of GBM.

Conclusions

We found that RND1, a novel controller of p53 protein and a positive regulator of p53 signaling pathway, enhanced the ferroptosis in GBM. This study may shed light on the understanding of ferroptosis in GBM cells and provide new therapeutic ideas for GBM.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00791-w.

Effect of RhoE expression on the migration and invasion of tongue squamous cell carcinoma

OBJECTIVES

This study aims to investigate the effect of RhoE expression on the migration and invasion of tongue squamous cell carcinoma (TSCC).

METHODS

Forty-eight TSCC cases were selected from the Maxillofacial Surgery Center of Qingdao Municipal Hospital from 2017 to 2019. The expression of RhoE in the specimens (TSCC and adjacent tissues) was detected by immunohistochemistry, and RhoE mRNA and protein were extracted to further detect the expression of RhoE. SCC-4 and CAL-27 cells were selected for in vitro experiments. Transient transfection was used to overexpress RhoE. Real-time fluorescence quantitative PCR (qRT-PCR) and Western blot analyses were conducted to detect the overexpression efficiency. Scratch test and Transwell cell invasion tests were used to detect the migration and invasion ability of TSCC, respectively. The expression levels of Rho-associated coiled-coil-containing protein kinase 1 (ROCK1), matrix metalloproteinase-2 (MMP-2), and matrix metalloproteinase-9 (MMP-9) were detected by Western blot. Experimental data were analyzed by Graphpad prism 8.2.1 software.

RESULTS

The expression level of RhoE in TSCC was significantly lower than that in adjacent tissues (P<0.05). The migration and invasion abilities of TSCC were significantly lower than those in the control group (P<0.05). The Western blot showed significantly lower expression levels of ROCK1, MMP-2, and MMP-9 in the experimental group than in the control group (P<0.05).

CONCLUSIONS

RhoE expression is low in TSCC. Over expression RhoE in TSCC can significantly decrease its migration and invasion abilities. Hence, RhoE may play an important role in regulating the metastasis and invasion of TSCC and provide a new target for gene therapy.

The atypical Rho GTPase Rnd2 is critical for dentate granule neuron development and anxiety-like behavior during adult but not neonatal neurogenesis

Despite the central role of Rho GTPases in neuronal development, their functions in adult hippocampal neurogenesis remain poorly explored. Here, by using a retrovirus-based loss-of-function approach in vivo, we show that the atypical Rho GTPase Rnd2 is crucial for survival, positioning, somatodendritic morphogenesis, and functional maturation of adult-born dentate granule neurons. Interestingly, most of these functions are specific to granule neurons generated during adulthood since the deletion of Rnd2 in neonatally-born granule neurons only affects dendritogenesis. In addition, suppression of Rnd2 in adult-born dentate granule neurons increases anxiety-like behavior whereas its deletion in pups has no such effect, a finding supporting the adult neurogenesis hypothesis of anxiety disorders. Thus, our results are in line with the view that adult neurogenesis is not a simple continuation of earlier processes from development, and establish a causal relationship between Rnd2 expression and anxiety.