Ras-related C3 Botulinum Toxin Substrate Research Articles

The bone marrow endothelial progenitor cell response to septic infection.

Early increase in the level of endothelial progenitor cells (EPCs) in the systemic circulation occurs in patients with septic infection/sepsis. The significance and underlying mechanisms of this response remain unclear. This study investigated the bone marrow EPC response in adult mice with septic infection induced by intravenous injection (i.v.) of Escherichia coli. For in vitro experiments, sorted marrow stem/progenitor cells (SPCs) including lineage(lin)-stem cell factor receptor (c-kit)+stem cell antigen-1 (Sca-1)-, lin-c-kit+, and lin- cells were cultured with or without lipopolysaccharides (LPSs) and recombinant murine vascular endothelial growth factor (VEGF) in the absence and presence of anti-Sca-1 crosslinking antibodies. In a separate set of experiments, marrow lin-c-kit+ cells from green fluorescence protein (GFP)+ mice, i.v. challenged with heat-inactivated E. coli or saline for 24h, were subcutaneously implanted in Matrigel plugs for 5 weeks. Marrow lin-c-kit+ cells from Sca-1 knockout (KO) mice challenged with heat-inactivated E. coli for 24h were cultured in the Matrigel medium for 8 weeks. The marrow pool of EPCs bearing the lin-c-kit+Sca-1+VEGF receptor 2 (VEGFR2)+ (LKS VEGFR2+) and LKS CD133+VEGFR2+ surface markers expanded rapidly following septic infection, which was supported by both proliferative activation and phenotypic conversion of marrow stem/progenitor cells. Increase in marrow EPCs and their reprogramming for enhancing angiogenic activity correlated with cell-marked upregulation of Sca-1 expression. Sca-1 was coupled with Ras-related C3 botulinum toxin substrate 2 (Rac2) in signaling the marrow EPC response. Septic infection caused a substantial increase in plasma levels of IFN-γ, VEGF, G-CSF, and SDF-1. The early increase in circulating EPCs was accompanied by their active homing and incorporation into pulmonary microvasculature. These results demonstrate that the marrow EPC response is a critical component of the host defense system. Sca-1 signaling plays a pivotal role in the regulation of EPC response in mice with septic infection.

Gut commensal metabolite rhamnose promotes macrophages phagocytosis by activating SLC12A4 and protects against sepsis in mice

Sepsis progression is significantly associated with the disruption of gut eubiosis. However, the modulatory mechanisms of gut microbiota operating during sepsis are still unclear. Herein, we investigated how gut commensals impact sepsis development in a pre-clinical model. Cecal ligation and puncture (CLP) surgery was used to establish polymicrobial sepsis in mice. Mice depleted of gut microbiota by an antibiotic cocktail (ABX) exhibited a significantly higher level of mortality than controls. As determined by metabolomics analysis, ABX treatment has depleted many metabolites, and subsequent supplementation with l-rhamnose (rhamnose, Rha), a bacterial carbohydrate metabolite, exerted profound immunomodulatory properties with a significant enhancement in macrophage phagocytosis, which in turn improved organ damage and mortality. Mechanistically, rhamnose binds directly to and activates the solute carrier family 12 (potassium-chloride symporter), member 4 (SLC12A4) in macrophages and promotes phagocytosis by activating the small G-proteins, Ras-related C3 botulinum toxin substrate1 (Rac1) and cell division control protein 42 homolog (Cdc42). Interestingly, rhamnose has enhanced the phagocytosis capacity of macrophages from sepsis patients. In conclusion, by identifying SLC12A4 as the host interacting protein, we disclosed that the gut commensal metabolite rhamnose is a functional molecular that could promote the phagocytosis capacity of macrophages and protect the host against sepsis.

RAC1 as a potential pan-cancer diagnostic, prognostic, and immunological biomarker.

Ras-related C3 botulinum toxin substrate 1 (RAC1) is an important member of the Rho GTPase family involved in tumorigenesis. However, its role and potential clinical utility across cancer entities in solid tumors is unknown. We analyzed data from various databases, including The Cancer Genome Atlas (TCGA), Genotype-Tissue Expression Project, cBioPortal, Tumor Immune Estimation Resource 2 (TIMER2), and published articles. A prognostic nomogram for liver hepatocellular carcinoma (LIHC) patients was developed based on RAC1-guanosine triphosphate (GTP) gene expression levels, which were validated using immunohistochemistry (IHC). In this study, RAC1 was highly expressed in most cancers and correlated with prognosis and pathological stages. Furthermore, significant associations were observed between RAC1 and DNA methylation, immune cell infiltration, immune-related genes, tumor mutational burden, and microsatellite instability in most tumors. As a use case, we employed gene set enrichment analysis (GSEA) and gene set variation analysis (GSVA) to analyze the biologic importance of RAC1 expression and established a prognostic nomogram based on tumor stage and RAC1 expression, which can better predict the overall survival rate of patients with LIHC better than tumor stage alone. The gene expression results were validated with IHC, which confirmed a higher expression of the RAC1-GTP protein in LIHC compared to paracancerous tissues. This extensive solid tumor analysis provides sound evidence that RAC1 can serve as both as an immunotherapy target and as a diagnostic and prognostic biomarker.

Connecting the ends: signaling via receptor tyrosine kinases and cytoskeletal degradation in neurodegeneration

Receptor tyrosine kinases (RTKs) are known to perform versatile roles in disease landscapes, which determine the fate of the cell. Although much has been discussed from the perspective of proliferation, this review focuses on the impact of RTK-mediated signaling and its role in cytoskeletal degradation, the penultimate stage of cellular degeneration. In the case of degenerative diseases such as Alzheimer’s disease (AD), Huntington’s disease (HD), amyotrophic lateral sclerosis (ALS), Parkinson’s disease (PD), age-related macular degeneration (AMD), and type 2 diabetes mellitus (T2DM), RTK signaling has been reported to be perturbed in several studies. The implications of downstream signaling via these receptors through canonical and noncanonical pathways alter the status of actin filaments that provide structural integrity to cells. Degenerative signaling leads to the altered status of rat sarcoma (Ras), Ras homologous (Rho), Ras-related C3 botulinum toxin substrate (Rac), and cell division control protein 42 (Cdc42), the best-characterized components of the cytoskeleton remodeling machinery. RTKs, along with their diverse adaptor partners and other membrane receptors, affect the functionality of Rho family guanosine triphosphate hydrolases (GTPases), which are discussed in this review. To conclude, this review focuses on therapeutic strategies targeting RTKs and Rho GTPase-mediated pathways that can be more effective due to their combined multifactorial impact on neurodegenerative cascades.

Significance of RCC2, Rac1 and p53 Expression in Breast Infiltrating Ductal Carcinoma; An Immunohistochemical Study.

The regulator of chromosome condensation 2 (RCC2) and RAS-related C3 botulinum toxin substrate 1 (Rac1) have been implicated in the promotion of breast cancer cell proliferation and migration. The signaling pathway involving p53/RCC2/Rac1 has been proposed to contribute to the regulation of colon cancer metastasis. However, until now, this pathway has not been thoroughly investigated in breast cancer. This study seeks to explore the influence of immunohistochemical expression and the correlation among RCC2, Rac1, and p53 in breast infiltrating ductal carcinoma (IDC). Immunostaining was performed on 120 breast IDC specimens using RCC2, Rac1, and p53 antibodies. Statistical analyses were conducted to examine the correlations between these antibodies. A Positive expression of RCC2, Rac1, and p53 was observed in 116 (96.7%), 120 (100%), and 33 (27.5%) of the breast cancer cases, respectively. RCC2, Rac1, and p53 demonstrated association with poor prognostic parameters such as frequent mitoses, high Ki-67 status, positive lymphovascular invasion (LVI), and advanced tumor stage. A highly significant direct correlation was found between each immunohistochemical marker and the other two markers. Shorter overall survival was linked to multifocal tumors (P=0.017), advanced tumor stage (T3) (P=0.010), Luminal B subtype (P=0.015), progressive disease (P=0.003), positive Her2neu status (P=0.008), and metastasis to distant organs (P<0.001). However, RCC2, Rac1, and p53 did not exhibit a significant association with overall survival. The high expression levels of RCC2, Rac1, and p53 in breast IDC suggest their potential role in tumor behavior. The association of RCC2 and Rac1 with poor prognostic parameters may serve as predictive indicators for aggressive tumors, thus implying that targeted therapy could be beneficial in the treatment of breast cancer.

S-Nitrosylation of Septin2 Exacerbates Aortic Aneurysm and Dissection by Coupling the TIAM1-RAC1 Axis in Macrophages.

S-Nitrosylation (SNO), a prototypic redox-based posttranslational modification, is involved in cardiovascular disease. Aortic aneurysm and dissection are high-risk cardiovascular diseases without an effective cure. The aim of this study was to determine the role of SNO of Septin2 in macrophages in aortic aneurysm and dissection. Biotin-switch assay combined with liquid chromatography-tandem mass spectrometry was performed to identify the S-nitrosylated proteins in aortic tissue from both patients undergoing surgery for aortic dissection and Apoe-/- mice infused with angiotensin II. Angiotensin II-induced aortic aneurysm model and β-aminopropionitrile-induced aortic aneurysm and dissection model were used to determine the role of SNO of Septin2 (SNO-Septin2) in aortic aneurysm and dissection development. RNA-sequencing analysis was performed to recapitulate possible changes in the transcriptome profile of SNO-Septin2 in macrophages in aortic aneurysm and dissection. Liquid chromatography-tandem mass spectrometry and coimmunoprecipitation were used to uncover the TIAM1-RAC1 (Ras-related C3 botulinum toxin substrate 1) axis as the downstream target of SNO-Septin2. Both R-Ketorolac and NSC23766 treatments were used to inhibit the TIAM1-RAC1 axis. Septin2 was identified S-nitrosylated at cysteine 111 (Cys111) in both aortic tissue from patients undergoing surgery for aortic dissection and Apoe-/- mice infused with Angiotensin II. SNO-Septin2 was demonstrated driving the development of aortic aneurysm and dissection. By RNA-sequencing, SNO-Septin2 in macrophages was demonstrated to exacerbate vascular inflammation and extracellular matrix degradation in aortic aneurysm. Next, TIAM1 (T lymphoma invasion and metastasis-inducing protein 1) was identified as a SNO-Septin2 target protein. Mechanistically, compared with unmodified Septin2, SNO-Septin2 reduced its interaction with TIAM1 and activated the TIAM1-RAC1 axis and consequent nuclear factor-κB signaling pathway, resulting in stronger inflammation and extracellular matrix degradation mediated by macrophages. Consistently, both R-Ketorolac and NSC23766 treatments protected against aortic aneurysm and dissection by inhibiting the TIAM1-RAC1 axis. SNO-Septin2 drives aortic aneurysm and dissection through coupling the TIAM1-RAC1 axis in macrophages and activating the nuclear factor-κB signaling pathway-dependent inflammation and extracellular matrix degradation. Pharmacological blockade of RAC1 by R-Ketorolac or NSC23766 may therefore represent a potential treatment against aortic aneurysm and dissection.

Surface Proteome of Extracellular Vesicles and Correlation Analysis Reveal Breast Cancer Biomarkers

Breast cancer (BC) is the second most frequently diagnosed cancer and accounts for approximately 25% of new cancer cases in Canadian women. Using biomarkers as a less-invasive BC diagnostic method is currently under investigation but is not ready for practical application in clinical settings. During the last decade, extracellular vesicles (EVs) have emerged as a promising source of biomarkers because they contain cancer-derived proteins, RNAs, and metabolites. In this study, EV proteins from small EVs (sEVs) and medium EVs (mEVs) were isolated from BC MDA-MB-231 and MCF7 and non-cancerous breast epithelial MCF10A cell lines and then analyzed by two approaches: global proteomic analysis and enrichment of EV surface proteins by Sulfo-NHS-SS-Biotin labeling. From the first approach, proteomic profiling identified 2459 proteins, which were subjected to comparative analysis and correlation network analysis. Twelve potential biomarker proteins were identified based on cell line-specific expression and filtered by their predicted co-localization with known EV marker proteins, CD63, CD9, and CD81. This approach resulted in the identification of 11 proteins, four of which were further investigated by Western blot analysis. The presence of transmembrane serine protease matriptase (ST14), claudin-3 (CLDN3), and integrin alpha-7 (ITGA7) in each cell line was validated by Western blot, revealing that ST14 and CLDN3 may be further explored as potential EV biomarkers for BC. The surface labeling approach enriched proteins that were not identified using the first approach. Ten potential BC biomarkers (Glutathione S-transferase P1 (GSTP1), Elongation factor 2 (EEF2), DEAD/H box RNA helicase (DDX10), progesterone receptor (PGR), Ras-related C3 botulinum toxin substrate 2 (RAC2), Disintegrin and metalloproteinase domain-containing protein 10 (ADAM10), Aconitase 2 (ACO2), UTP20 small subunit processome component (UTP20), NEDD4 binding protein 2 (N4BP2), Programmed cell death 6 (PDCD6)) were selected from surface proteins commonly identified from MDA-MB-231 and MCF7, but not identified in MCF10A EVs. In total, 846 surface proteins were identified from the second approach, of which 11 were already known as BC markers. This study supports the proposition that Evs are a rich source of known and novel biomarkers that may be used for non-invasive detection of BC. Furthermore, the presented datasets could be further explored for the identification of potential biomarkers in BC.

The Rac1-inhibitor EHop-016 attenuates AML cell migration and enhances the efficacy of daunorubicin in MOLM-13 transplanted zebrafish larvae

Ras-related C3 botulinum toxin substrate 1 (Rac1) is a GTPase implicated in cell migration and homing of hematopoietic cells to the hematopoietic niche, and is commonly overexpressed in acute myeloid leukemia (AML). This can lead to quiescence of leukemic blasts in the niche and reduced response to therapy. We investigated the Rac1 inhibitor EHop-016 on AML by assessing its effects on MOLM-13 cells in vitro and in zebrafish larvae, regarding cell motility and therapeutic potential in combination with daunorubicin (DNR). In vitro assessment of proliferation and viability was by measurement of 3H-thymidine incorporation and detection of Annexin V/PI positive cells. Cell motility was evaluated by measurement of migration in a transwell system. Fluorescently stained MOLM-13 cells were injected into zebrafish larvae, and individual cells followed by confocal microscopy. Cell accumulation in the caudal hematopoietic tissue (CHT) was studied using a 12-hour timelapse, while in vivo efficacy of DNR, EHop-016 or a combination was investigated over 24 h.The in vitro results showed that EHop-016 acted synergistically in combination with DNR in reducing the viability of MOLM-13 cells (Bliss synergy score above 10 %). Non-toxic concentrations of EHop-016 reduced cell migration. These findings were reproduced in zebrafish larvae: larvae receiving both DNR and EHop-016 had significantly reduced tumor burden compared to the untreated control or single treatments. The accumulation of MOLM-13 cells in the CHT was reduced in larvae receiving EHop-016 treatment.Our findings demonstrate that targeting Rac1 in AML holds promise as a complementary treatment to established chemotherapy and should be further investigated.

The Cdc42/Rac1 pathway: a molecular mechanism behind iron-deficiency-driven aortic medial degeneration.

To elucidate the underlying mechanism of iron deficiency augmented Angiotensin II-induced aortic medial degeneration. ApoE-/- mice were randomly divided into four groups: normal control group (NC group), Angiotensin II (Ang II) subcutaneous pumped alone Group (Ang II group), iron deficiency (ID) group (ID group) and ID+Ang II group. The survival time, systolic blood pressure (SBP), and aortic medial degeneration (AMD) formation were monitored. Iron deposition in the aortas was assessed using Prussian blue iron staining. The expression of iron metabolism indicators, aortopathies and the cytoskeleton of vascular smooth muscle cells (VSMCs) were analyzed. In an in vitro setting, deferoxamine (DFO) was employed to mimic ID to examine the effects of Ang II on the cytoskeletal and contractile function of VSMCs during ID. Ras-related C3 botulinum toxin substrate 1 (Rac-1) expression was inhibited with EHT1864 to verify the role of Cdc42/Rac1 pathway in this pathological process. Blood samples were collected from 150 patients with aortic dissection (AD) and 60 patients with hypertension who were admitted to the Department of Cardiovascular Surgery at Renmin Hospital of Wuhan University between June 2018 and September 2019. The aortic tissues were obtained during the surgical treatment of Stanford type A AD patients and the heart donor. The iron metabolism status in plasma and aortic tissue was analyzed. In vivo experiments revealed that, in comparison to the NC and ID groups, mice in the Ang II and ID+Ang II groups exhibited increased SBP, significantly reduced survival time, and an expanded range of aortic dissection (P < 0.05). ID feeding augmented the Ang II-induced aortopathies. Both in vitro and in vivo results indicated that ID led to diminished expression of phosphorylated myosin light chain (p-MLC) and recombinant Cell Division Cycle Protein 42 (Cdc42) in VSMCs, while Rac-1 expression increased. The clinical sample testing data further confirmed the discovery that individuals diagnosed with AD display ID in both the plasma and the diseased aortas. The Cdc42/Rac1 pathway plays a crucial role in disrupting the cytoskeleton of vascular smooth muscle cells during iron deficiency, which leads to aortic medial degeneration both in vivo and in vitro.

POTEE promotes breast cancer cell malignancy by inducing invadopodia formation through the activation of SUMOylated Rac1.

The small GTPase Rac1 (Ras-related C3 botulinum toxin substrate 1) has been implicated in cancer progression and in the poor prognosis of various types of tumors. Rac1 SUMOylation occurs during epithelial-mesenchymal transition (EMT), and it is required for tumor cell migration and invasion. Here we identify POTEE (POTE Ankyrin domain family member E) as a novel Rac1-SUMO1 effector involved in breast cancer malignancy that controls invadopodium formation through the activation of Rac1-SUMO1. POTEE activates Rac1 in the invadopodium by recruiting TRIO-GEF (triple functional domain protein), and it induces tumor cell proliferation and metastasis in vitro and in vivo. We found that the co-localization of POTEE with Rac1 is correlated with more aggressive breast cancer subtypes. Given its role in tumor dissemination, the leading cause of cancer-related deaths, POTEE could represent a potential therapeutic target for these types of cancer.

Inhibition of spinal Rac1 attenuates chronic inflammatory pain by regulating the activation of astrocytes

BackgroundSpinal astrocyte-mediated neuroinflammation is an important mechanism for the maintenance of chronic inflammatory pain. Previous studies have investigated that Ras-related C3 botulinum toxin substrate 1 (Rac1) is closely related to astrocyte activation after central nervous system injury. However, the role of Rac1 in astrocyte activation in chronic inflammatory pain has not been reported. MethodsComplete Freund's adjuvant (CFA)-induced chronic inflammatory pain model and LPS-stimulated astrocytes were used to investigate the role of Rac1 in astrocyte activation and the underlying mechanism. Rac1-interfering adeno-associated virus (AAV) targeting astrocytes was delivered to spinal astrocytes by intrathecal administration and a Rac1 specific inhibitor, NSC23766, was used to block cultured astrocytes. The glial fibrillary acidic protein (GFAP), proinflammatory cytokines, p-NF-κB, and nod-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome were detected by RT-qPCR, Western blotting, and immunofluorescence to investigate the activation of astrocytes. ResultsCFA induced spinal astrocyte activation and increased the expression of active Rac1 in spinal astrocytes. Knockdown of astrocyte Rac1 alleviated chronic inflammatory pain and inhibited astrocyte activation. Inhibition of Rac1 activation in cultured astrocytes decreased the expression of GFAP and proinflammatory cytokines. Knockdown of Rac1 inhibited the increase of expression of NLRP3 inflammasome and phosphorylation of NF-κB in the spinal lumbar enlargement after CFA injection. Similarly, the inhibition of Rac1 suppressed the increase of NLRP3 inflammasome and p-NF-κB protein level after LPS stimulation. ConclusionKnockdown of astrocyte Rac1 attenuated CFA-induced hyperalgesia and astrocyte activation possibly by blocking the expression of NLRP3 inflammasome and phosphorylation of NF-κB.

Klotho inhibits renal ox-LDL deposition via IGF-1R/RAC1/OLR1 signaling to ameliorate podocyte injury in diabetic kidney disease

ObjectiveDiabetic kidney disease (DKD) is characterized by the abnormal deposition of oxidized low-density lipoprotein (ox-LDL), which contributes to podocyte damage. Klotho, an aging suppressor that plays a critical role in protecting podocytes in DKD, is mainly expressed in kidney tubular epithelium and secreted in the blood. However, it has not been established whether Klotho can alleviate podocyte injury by inhibiting renal ox-LDL deposition, and the potential molecular mechanisms require further investigation.MethodsWe conducted a comprehensive analysis of serum and kidney biopsy samples obtained from patients diagnosed with DKD. Additionally, to explore the underlying mechanism of Klotho in the deposition of ox-LDL in the kidneys, we employed a mouse model of DKD with the Klotho genotype induced by streptozotocin (STZ). Furthermore, we conducted meticulous in vitro experiments on podocytes to gain further insights into the specific role of Klotho in the deposition of ox-LDL within the kidney.ResultsOur groundbreaking study unveiled the remarkable ability of the soluble form of Klotho to effectively inhibit high glucose-induced ox-LDL deposition in podocytes affected by DKD. Subsequent investigations elucidated that Klotho achieved this inhibition by reducing the expression of the insulin/insulin-like growth factor 1 receptor (IGF-1R), consequently leading to a decrease in the expression of Ras-related C3 botulinum toxin substrate 1 (RAC1) and an enhancement of mitochondrial function. Ultimately, this series of events culminated in a significant reduction in the expression of the oxidized low-density lipoprotein receptor (OLR1), thereby resulting in a notable decrease in renal ox-LDL deposition in DKD.ConclusionOur findings suggested that Klotho had the potential to mitigate podocyte injury and reduced high glucose-induced ox-LDL deposition in glomerulus by modulating the IGF-1R/RAC1/OLR1 signaling. These results provided valuable insights that could inform the development of novel strategies for diagnosing and treating DKD.Graphical

Rac1 promotes the formation of heterotypic cell-in-cell structure

Heterotypic cell-in-cell structures (heCICs) are closely related to tumor development and progression, and have become a new frontier in life science research. Ras-related C3 botulinum toxin substrate 1 (Rac1) belongs to the classic Rho GTPase, which plays a key role in regulating the cytoskeleton and cell movement. To investigate the role and mechanism of Rac1 in the formation of heCICs, tumor cells and immune killer cells were labeled with cell-tracker, respectively, to establish the heCICs model. Upon treatment with the Rac1 inhibitor NSC23766, the formation of heCICs between tumor and immune cells was significantly reduced. The plasmid pQCXIP-Rac1-EGFP constructed by gene cloning was packaged into pseudoviruses that subsequently infect tumor cells to make cell lines stably expressing Rac1. As a result, the formation of heCICs was significantly increased upon Rac1 overexpression. These results demonstrated a promotive role of Rac1 in heCICs formation, which may facilitate treating cell-in-cell related diseases, such as tumors, by targeting Rac1.

SILAC proteomics based on 3D cell spheroids unveils the role of RAC2 in regulating the crosstalk between triple-negative breast cancer cells and tumor-associated macrophages

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer, and is characterized by a high infiltration of tumor-associated macrophages (TAMs). TAMs contribute significantly to tumor progression by intricately interacting with tumor cells. Deeply investigating the interaction between TNBC cells and TAMs is of great importance for finding potential biomarkers and developing novel therapeutic strategies to further improve the clinical outcomes of TNBC patients. In this study, we confirmed the interplay using both 3D and 2D co-culture models. The stable-isotype labeling by amino acids in cell culture (SILAC)-based quantitative proteomics was conducted on 3D cell spheroids containing TNBC cells and macrophages to identify the potential candidate in regulating the crosstalk between TNBC and TAMs. Ras-related C3 botulinum toxin substrate 2 (RAC2) was identified as a potential molecule for further exploration, given its high expression in TNBC and positive correlation with M2 macrophage infiltration. The suppression of RAC2 inhibited TNBC cell proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) in vitro. Meanwhile, knocking down RAC2 in TNBC cells impaired macrophage recruitment and M2 polarization. Mechanistically, RAC2 exerted its roles in TNBC cells and TAMs by regulating the activation of P65 NF-κB and P38 MAPK, while TAMs further elevated RAC2 expression and P65 NF-κB activation by secreting soluble mediators including IL-10. These findings highlight the significance of RAC2 as a crucial molecule in the crosstalk between TNBC and TAMs, suggesting it could be a promising therapeutic target in TNBC.

The HACE1 E3 ligase mediates RAC1-dependent control of mTOR signaling complexes.

HACE1 is a HECT family E3 ubiquitin-protein ligase with broad but incompletely understood tumor suppressor activity. Here, we report a previously unrecognized link between HACE1 and signaling complexes containing mammalian target of rapamycin (mTOR). HACE1 blocks mTORC1 and mTORC2 activities by reducing mTOR stability in an E3 ligase-dependent manner. Mechanistically, HACE1 binds to and ubiquitylates Ras-related C3 botulinum toxin substrate 1 (RAC1) when RAC1 is associated with mTOR complexes, including at focal adhesions, leading to proteasomal degradation of RAC1. This in turn decreases the stability of mTOR to reduce mTORC1 and mTORC2 activity. HACE1 deficient cells show enhanced mTORC1/2 activity, which is reversed by chemical or genetic RAC1 inactivation but not in cells expressing the HACE1-insensitive mutant, RAC1K147R . In vivo, Rac1 deletion reverses enhanced mTOR expression in KRasG12D -driven lung tumors of Hace1-/- mice. HACE1 co-localizes with mTOR and RAC1, resulting in RAC1-dependent loss of mTOR protein stability. Together, our data demonstrate that HACE1 destabilizes mTOR by targeting RAC1 within mTOR-associated complexes, revealing a unique ubiquitin-dependent process to control the activity of mTOR signaling complexes.

LLPS of SQSTM1/p62 and NBR1 as outcomes of lysosomal stress response limits cancer cell metastasis.

Liquid droplet has emerged as a flexible intracellular compartment that modulates various cellular processes. Here, we uncover an antimetastatic mechanism governed by the liquid droplets formed through liquid-liquid phase separation (LLPS) of SQSTM1/p62 and neighbor of BRCA1 gene 1 (NBR1). Some of the tyrosine kinase inhibitors (TKIs) initiated lysosomal stress response that promotes the LLPS of p62 and NBR1, resulting in the spreading of p62/NBR1 liquid droplets. Interestingly, in the p62/NBR1 liquid droplet, degradation of RAS-related C3 botulinum toxin substrate 1 was accelerated by cellular inhibitor of apoptosis protein 1, which limits cancer cell motility. Moreover, the antimetastatic activity of the TKIs was completely overridden in p62/NBR1 double knockout cells both in vitro and in vivo. Thus, our results demonstrate a function of the p62/NBR1 liquid droplet as a critical determinant of cancer cell behavior, which may provide insight into both the clinical and biological significance of LLPS.

Assessment of the anti-inflammatory mechanism of quercetin 3,7-dirhamnoside using an integrated pharmacology strategy.

Pouzolzia zeylanica (L.) Benn. is a Chinese herbal medicine widely used for its anti-inflammatory and pus-removal properties. To explore its potential anti-inflammatory mechanism, quercetin 3,7-dirhamnoside (QDR), the main flavonoid component of P. zeylanica (L.) Benn., was extracted and purified. The potential anti-inflammatory targets of QDR were predicted using network analysis. These potential targets were verified using molecular docking, molecular dynamics simulations, and invitro experiments. Consequently, 342 potential anti-inflammatory QDR targets were identified. By analyzing the intersection between the protein-protein interaction and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, we identified several potential protein targets of QDR, including RAC-alpha serine/threonine-protein kinase (AKT1), Ras-related C3 botulinum toxin substrate 1 (RAC1), nitric oxide synthase 3 (NOS3), serine/threonine-protein kinase mTOR (mTOR), epidermal growth factor receptor (EGFR), growth factor receptor-bound protein 2 (GRB2), and endothelin-1 receptor (EDNRA). QDR has anti-inflammatory activity and regulates immune responses and apoptosis through chemokines, Phosphatidylinositol 3-kinase 3(PI3K)/AKT, cAMP, T-cell receptor, and Ras signaling pathways. Molecular docking analysis showed that QDR has good binding abilities with AKT1, mTOR, and NOS3. In addition, molecular dynamics simulations demonstrated that the protein-ligand complex systems formed between QDR and AKT1, mTOR, and NOS3 have high dynamic stability, and their protein-ligand complex systems possess strong binding ability. In RAW264.7 macrophages, QDR significantly inhibited lipopolysaccharides (LPS)-induced inducible nitric oxide synthase expression, nitric oxide (NO) release and the generation of proinflammatory cytokines IL-6, IL-1β, and TNF-α. QDR downregulated the expression of p-AKT1(Ser473)/AKT1 and p-mTOR (Ser2448)/mTOR, and upregulated the expression of NOS3, Rictor, and Raptor. This indicates that the anti-inflammatory mechanisms of QDR involve regulation of AKT1 and mTOR to prevent apoptosis and of NOS3 which leads to the release of endothelial NO. Thus, our study elucidated the potential anti-inflammatory mechanism of QDR, the main flavonoid found in P. zeylanica (L.) Benn.

Therapeutic effect of exosomes derived from hepatocyte-growth-factor-overexpressing adipose mesenchymal stem cells on liver injury.

ADMSCs were isolated from young BALB/c female mice. Then exosomes derived from ADMSC transfecting negative control (ADMSCNC-Exo) and HGF overexpression (ADMSCHGF-Exo) were isolated and identified by quantitative polymerase chain reaction (qPCR), flow cytometry, western blot, transmission electron microscope and Nanosight particle tracking analysis. These exosomes were injected into male mice via tail vein after inducing liver injury by administering 40% carbon tetrachloride (CCl₄)-olive oil twice a week (3 mL/kg, subcutaneously) for 6 weeks. Liver injury and liver collagen fiber accumulation were determined by histopathological analysis. Then, the levels of serum liver function indexes (alanine aminotransferase, aspartate aminotransferase, albumin, total bilirubin), hepatocyte-specific markers (albumin, cytokeratin-18 and hepatocyte nuclear factor 4α), hepatic fibrosis-related proteins (α-smooth muscle actin and collagen I) and Rho GTPase (cell division cycle 42 and ras-related C3 botulinum toxin substrate 1) were determined by Enzyme-linked immunosorbent assay (ELISA), immunohistochemistry, Western blot and qPCR. ADMSCs were identified by high expression of CD105 and CD44 molecules and low expression of CD45 and CD34. ADMSCs-Exo, ADMSCNC-Exo and ADMSCHGF-Exo transfected cells had similar expression of exosome-specific membrane proteins (CD63, CD81 and CD9). Mice with CCl₄-induced liver injury exhibited abnormal serum liver function indexes, altered expression of hepatocyte-specific markers, hepatic fibrosis-related proteins and Rho GTPase protein as well as histopathological changes and collagen fiber accumulation in the liver. These changes were reversed by ADMSC-Exo, ADMSCNC-Exo and ADMSCHGF-Exo administration with ADMSCHGF-Exo displaying the most significant impact. ADMSCHGF-Exo exerted a hepatoprotective effect in mice with experimental liver injury by alleviating hepatic fibrosis and restoring liver function.

Circular RNA CSPP1 motivates renal cell carcinoma carcinogenesis and the Warburg effect by targeting RAC1 through microRNA-493-5p.

Circular RNAs (circRNAs) take on regulatory roles in renal cell carcinoma (RCC). The research's goal was to figure out circ-CSPP1's role and molecular mechanism in RCC. The results clarified that circ-CSPP1 expression was enhanced in RCC. Down-regulating circ-CSPP1 refrained the proliferation, migration, invasion, and Warburg effect (aerobic glycolysis), but accelerated apoptosis of RCC cells. The luciferase activity assay exhibited that circ-CSPP1 could perform as an endogenous sponge for miR-493-5p. Elevating miR-493-5p repressed RCC progression. The bioinformatics website starBase confirmed that ras-related C3 botulinum toxin substrate 1 (RAC1) was a target gene of miR-493-5p. Circ-CSPP1 up-regulated RAC1 by sponging miR-493-5p, and elevating RAC1 could turn around the effect of down-regulating circ-CSPP1 on RCC cells. Taken together, circ-CSPP1 is identified as a novel RCC-promoting RNA that could serve as a latent therapeutic target for RCC therapy.

Aralia saponin A isolated from Achyranthes bidentata Bl. ameliorates LPS/D-GalN induced acute liver injury via SPHK1/S1P/S1PR1 pathway in vivo and in vitro

ObjectiveAcute liver injury (ALI) refers to a disease in which the liver is affected by factors such as chemical substances, alcohol, and virus infection in a short time, resulting in damage to liver cells. Achyranthes bidentata Bl. with the hepatoprotective activity has attracted great attention. In this study, a pentacyclic triterpenoid (Aralia saponin A, AsA) was isolated from roots of Achyranthes bidentata Bl. and its anti-ALI activity, as well as the mechanisms, were investigated for the first time. MethodsAsA (10 or 20 mg/kg, i.g.) was administered over a period of 1 weeks, following which liver injury was induced by LPS (10 µg/kg)/D-GalN (700 mg/kg). H&E staining of liver, Aspartate amino transferase (AST), Alanine transaminase (ALT) and cytokines was employed to investigate ALI relevant features. The mitochondrial morphology and levels of mitochondrial membrane potential (MMP), oxidative stress balance, apoptosis, average fluorescence intensity of 2-DG, natural killer (NK) cells in liver tissues were determined to assess the oxidative stress damage and inflammatory injury. Transcriptomics and metabonomics analysis were employed to clarify the mechanisms. Additionally, the mRNA and protein expression levels of Sphingosine 1-phosphate (S1P), Sphingosine kinase-1 (SPKH1), Sphingosine 1 phosphate receptor 1 (S1PR1), Sphingosine 1 phosphate receptor 3 (S1PR3), TNF receptor associated factor 2 (TRAF-2), Phospho-NF- kappaB p65 (p-P65), NF- kappaB p65 (P65), Proto-oncogene ras (Ras), Ras-related C3 botulinum toxin substrate (Rac), Phospholipase C (PLC), Interleukin 6 (IL-6), Tumor necrosis factor α (TNF-α), Interleukin 1β (IL-1β), Vascular cell adhesion molecule 1 (Vcam1), CC chemokine ligand-2 (Ccl2) were analyzed. The mediating role of SPHK1 in the observed effects caused by AsA was assessed by investigatin SPHK1 transfection silencing/overexpression against AsA in AML12 cells induced by LPS/D-GalN. ResultsAsA can ameliorate liver function, inflammation, mitochondrial structure and oxidative stress in the ALI model. Meanwhile, AsA led to downregulated expression of proteins associated with sphingolipid signaling pathway. Silencing of SPHK1 led to enhanced protective effects of AsA, while over-expression of SPHK1 led to degraded protective effects of AsA in LPS/D-GalN-induced AML12 cells, suggesting that ALI is regulated by active molecules of AsA by means of SPHK1 mediation. ConclusionsAsA can ameliorate LPS/D-GalN-induced ALI by inhibiting inflammation and oxidative stress via the SPHK1/S1P/S1PR1 pathway. In this way, a molecular justification is provided for AsA application in ALI treatment.