A rho-type GTPase activating protein affects the growth and development of Cordyceps cicadae.

Cordyceps cicadae is recognized for its medicinal properties, attributed to bioactive constituents like polysaccharides and adenosine, which have been shown to improve kidney and liver functions and possess anti-tumor properties. Rho GTPase activating proteins (Rho GAPs) serve as inhibitory regulators of Rho GTPases in eukaryotic cells by accelerating the GTP hydrolysis of Rho GTPases, leading to their inactivation. In this study, we explored the function of the CcRga8 gene in C. cicadae, which encodes a Rho-type GTPase activating protein. Our study found that the knockout of CcRga8 resulted in a decrease in polysaccharide levels and an increase in adenosine concentration. Furthermore, the mutants exhibited altered spore yield and morphology, fruiting body development, decreased infectivity, reduced resistance to hyperosmotic stress, oxidative conditions, and cell wall inhibitors. These findings suggest that CcRga8 plays a crucial role in the development, stress response, and bioactive compound production of C. cicadae.

Plakophilin 4 controls the spatio-temporal activity of RhoA at adherens junctions to promote cortical actin ring formation and tissue tension.

Plakophilin 4 (PKP4) is a component of cell-cell junctions that regulates intercellular adhesion and Rho-signaling during cytokinesis with an unknown function during epidermal differentiation. Here we show that keratinocytes lacking PKP4 fail to develop a cortical actin ring, preventing adherens junction maturation and generation of tissue tension. Instead, PKP4-depleted cells display increased stress fibers. PKP4-dependent RhoA localization at AJs was required to activate a RhoA-ROCK2-MLCK-MLC2 axis and organize actin into a cortical ring. AJ-associated PKP4 provided a scaffold for the Rho activator ARHGEF2 and the RhoA effectors MLCK and MLC2, facilitating the spatio-temporal activation of RhoA signaling at cell junctions to allow cortical ring formation and actomyosin contraction. In contrast, association of PKP4 with the Rho suppressor ARHGAP23 reduced ARHGAP23 binding to RhoA which prevented RhoA activation in the cytoplasm and stress fiber formation. These data identify PKP4 as an AJ component that transduces mechanical signals into cytoskeletal organization.

Effect of the OPHN1 novel variant c.1025+1 G>A on RNA splicing: insights from a minigene assay.

This research analyzes the clinical data, whole-exome sequencing results, and in vitro minigene functional experiments of a child with developmental delay and intellectual disability. The male patient, aged 4, began experiencing epileptic seizures at 3 months post-birth and has shown developmental delay. Rehabilitation training was administered between the ages of one and two. There were no other significant family medical histories. Through comprehensive family exome genetic testing, a hemizygous variant in the 11th exon of the OPHN1 gene was identified in the affected child: c.1025 + 1G > A. Family segregation analysis confirmed the presence of this variant in the patient's mother, which had not been previously reported. According to the ACMG guidelines, this variant was classified as a likely pathogenic variant. In response to this variant, an in vitro minigene functional experiment was designed and conducted, confirming that the mutation affects the normal splicing of the gene's mRNA, resulting in a 56 bp retention on the left side of Intron 11. It was confirmed that OPHN1: c.1025 + 1G > A is the pathogenic cause of X-linked intellectual disabilities in the child, with clinical phenotypes including developmental delay and seizures.

Enhancing Rab7 Activity by Inhibiting TBC1D5 Expression Improves Mitophagy in Alzheimer's Disease Models.

Background: Mitochondrial dysfunction exists in Alzheimer's disease (AD) brain, and damaged mitochondria need to be removed by mitophagy. Small GTPase Rab7 regulates the fusion of mitochondria and lysosome, while TBC1D5 inhibits Rab7 activation. However, it is not clear whether the regulation of Rab7 activity by TBC1D5 can improve mitophagy and inhibit AD progression. Objective: To investigate the role of TBC1D5 in mitophagy and its regulatory mechanism for Rab7, and whether activation of mitophagy can inhibit the progression of AD. Methods: Mitophagy was determined by western blot and immunofluorescence. The morphology and quantity of mitochondria were tracked by TEM. pCMV-Mito-AT1.03 was employed to detect the cellular ATP. Amyloid-ß secreted by AD cells was detected by ELISA. Co-immunoprecipitation was used to investigate the binding partner of the target protein. Golgi-cox staining was applied to observe neuronal morphology of mice. The Morris water maze test and Y-maze were performed to assess spatial learning and memory, and the open field test was measured to evaluate motor function and anxiety-like phenotype of experimental animals. Results: Mitochondrial morphology was impaired in AD models, and TBC1D5 was highly expressed. Knocking down TBC1D5 increased the expression of active Rab7, promoted the fusion of lysosome and autophagosome, thus improving mitophagy, and improved the morphology of hippocampal neurons and the impaired behavior in AD mice. Conclusions: Knocking down TBC1D5 increased Rab7 activity and promoted the fusion of autophagosome and lysosome. Our study provided insights into the mechanisms that bring new possibilities for AD therapy targeting mitophagy.

Rho GTPase-activating protein 4 is upregulated in Kidney Renal Clear Cell Carcinoma and associated with poor prognosis and immune infiltration.

BACKGROUND: Kidney Renal Clear Cell Carcinoma (KIRC) is a malignant tumor that seriously threatens human health. Rho GTPase-activating protein 4 (ARHGAP4) plays an important role in the occurrence and development of tumors. OBJECTIVE: The purpose of this study was to explore the role of ARHGAP4 in the progression of KIRC and its diagnostic and prognostic value. METHODS: Multiple analytical methods and in vitro cell assays were used to explore the expression of ARHGAP4 and its value in the progression, diagnosis and prognosis of KIRC. The biological function of ARHGAP4 was studied by GO analysis and KEGG pathway analysis, and then the relationship between ARHGAP4 and immune infiltration was analyzed. RESULTS: The expression of ARHGAP4 was significantly up-regulated in KIRC. We found that the high expression of ARHGAP4 was related to the progression of KIRC and suggested a poor prognosis. Compared with normal tissues, ARHGAP4 had a better diagnostic value in KIRC. The biological function of ARHGAP4 was related to immunity, and its expression was also closely related to tumor immune infiltration and immune checkpoints. CONCLUSIONS: Our study demonstrated that ARHGAP4 may be a biomarker, which is related to the progression, diagnosis and prognosis of KIRC. Its biological functions are related to tumor immune infiltration.

FLNA regulates neuronal maturation by modulating RAC1-Cofilin activity in the developing cortex.

Periventricular nodular heterotopia (PNH), the most common brain malformation diagnosed in adulthood, is characterized by the presence of neuronal nodules along the ventricular walls. PNH is mainly associated with mutations in the FLNA gene - encoding an actin-binding protein - and patients often develop epilepsy. However, the molecular mechanisms underlying the neuronal failure still remain elusive. It has been hypothesized that dysfunctional cortical circuitry, rather than ectopic neurons, may explain the clinical manifestations. To address this issue, we depleted FLNA from cortical pyramidal neurons of a conditional Flnaflox/flox mice by timed in utero electroporation of Cre recombinase. We found that FLNA regulates dendritogenesis and spinogenesis thus promoting an appropriate excitatory/inhibitory inputs balance. We demonstrated that FLNA modulates RAC1 and cofilin activity through its interaction with the Rho-GTPase Activating Protein 24 (ARHGAP24). Collectively, we disclose an uncharacterized role of FLNA and provide strong support for neural circuit dysfunction being a consequence of FLNA mutations.

dAsap regulates cellular protrusions via an Arf6-dependent actin regulatory pathway in S2R+ cells.

Membrane protrusions are fundamental to cellular functions like migration, adhesion, and communication and depend upon dynamic reorganization of the cytoskeleton. GAP-dependent GTP hydrolysis of Arf proteins regulates actin-dependent membrane remodeling. Here, we show that dAsap regulates membrane protrusions in S2R+ cells by a mechanism that critically relies on its ArfGAP domain and relocalization of actin regulators, SCAR, and Ena. While our data reinforce the preference of dAsap for Arf1 GTP hydrolysis in vitro, we demonstrate that induction of membrane protrusions in S2R+ cells depends on Arf6 inactivation. This study furthers our understanding of how dAsap-dependent GTP hydrolysis maintains a balance between active and inactive states of Arf6 to regulate cell shape.

ARHGAP29 Is Involved in Increased Invasiveness of Tamoxifen-resistant Breast Cancer Cells and its Expression Levels Correlate With Clinical Tumor Parameters of Breast Cancer Patients.

BACKGROUND/AIM: Aggressive breast cancer (BC) cells show high expression of Rho GTPase activating protein 29 (ARHGAP29), a negative regulator of RhoA. In breast cancer cells in which mesenchymal transformation was induced, ARHGAP29 was the only one of 32 GTPase-activating enzymes whose expression increased significantly. Therefore, we investigated whether there is a correlation between expression of ARHGAP29 and tumor progression in BC. Since tamoxifen-resistant BC cells exhibit increased mesenchymal properties and invasiveness, we additionally investigated the relationship between ARHGAP29 and increased invasion rate in tamoxifen resistance. The question arises as to whether ARHGAP29 is a suitable prognostic marker for the progression of BC. MATERIALS AND METHODS: Tissue microarrays were used to investigate expression of ARHGAP29 in BC and adjacent normal breast tissues. Knockdown experiments using siRNA were performed to investigate the influence of ARHGAP29 and the possible downstream actors RhoC and pAKT1 on invasive growth of tamoxifen-resistant BC spheroids in vitro. RESULTS: Expression of ARHGAP29 was frequently increased in BC tissues compared to adjacent normal breast tissues. In addition, there was evidence of a correlation between high ARHGAP29 expression and advanced clinical tumor stage. Tamoxifen-resistant BC cells show a significantly higher expression of ARHGAP29 compared to their parental wild-type cells. After knockdown of ARHGAP29 in tamoxifen-resistant BC cells, expression of RhoC was significantly reduced. Further, expression of pAKT1 decreased significantly. Invasive growth of three-dimensional tamoxifen-resistant BC spheroids was reduced after knockdown of ARHGAP29. This could be partially reversed by AKT1 activator SC79. CONCLUSION: Expression of ARHGAP29 correlates with the clinical tumor parameters of BC patients. In addition, ARHGAP29 is involved in increased invasiveness of tamoxifen-resistant BC cells. ARHGAP29 alone or in combination with its downstream partners RhoC and pAKT1 could be suitable prognostic markers for BC progression.

Rho GTPase activating protein 21-mediated regulation of prostate cancer associated 3 gene in prostate cancer cell.

The overexpression of the prostate cancer antigen 3 (PCA3) gene is well-defined as a marker for prostate cancer (PCa) diagnosis. Although widely used in clinical research, PCA3 molecular mechanisms remain unknown. Herein we used phage display technology to identify putative molecules that bind to the promoter region of PCA3 gene and regulate its expression. The most frequent peptide PCA3p1 (80%) was similar to the Rho GTPase activating protein 21 (ARHGAP21) and its binding affinity was confirmed using Phage Bead ELISA. We showed that ARHGAP21 silencing in LNCaP prostate cancer cells decreased PCA3 and androgen receptor (AR) transcriptional levels and increased prune homolog 2 (PRUNE2) coding gene expression, indicating effective involvement of ARHGAP21 in androgen-dependent tumor pathway. Chromatin immunoprecipitation assay confirmed the interaction between PCA3 promoter region and ARHGAP21. This is the first study that described the role of ARHGAP21 in regulating the PCA3 gene under the androgenic pathway, standing out as a new mechanism of gene regulatory control during prostatic oncogenesis.

Reciprocal regulation between RACGAP1 and AR contributes to endocrine therapy resistance in prostate cancer.

BACKGROUND: Endocrine resistance driven by sustained activation of androgen receptor (AR) signaling pathway in advanced prostate cancer (PCa) is fatal. Characterization of mechanisms underlying aberrant AR pathway activation to search for potential therapeutic strategy is particularly important. Rac GTPase-activating protein 1 (RACGAP1) is one of the specific GTPase-activating proteins. As a novel tumor proto-oncogene, overexpression of RACGAP1 was related to the occurrence of various tumors. METHODS: Bioinformatics methods were used to analyze the relationship of expression level between RACGAP1 and AR as well as AR pathway activation. qRT-PCR and western blotting assays were performed to assess the expression of AR/AR-V7 and RACGAP1 in PCa cells. Immunoprecipitation and immunofluorescence experiments were conducted to detect the interaction and co-localization between RACGAP1 and AR/AR-V7. Gain- and loss-of-function analyses were conducted to investigate the biological roles of RACGAP1 in PCa cells, using MTS and colony formation assays. In vivo experiments were conducted to evaluate the effect of RACGAP1 inhibition on the tumor growth. RESULTS: RACGAP1 was a gene activated by AR, which was markedly upregulated in PCa patients with CRPC and enzalutamide resistance. AR transcriptionally activated RACGAP1 expression by binding to its promoter region. Reciprocally, nuclear RACGAP1 bound to the N-terminal domain (NTD) of both AR and AR-V7, blocking their interaction with the E3 ubiquitin ligase MDM2. Consequently, this prevented the degradation of AR/AR-V7 in a ubiquitin-proteasome-dependent pathway. Notably, the positive feedback loop between RACGAP1 and AR/AR-V7 contributed to endocrine therapy resistance of CRPC. Combination of enzalutamide and in vivo cholesterol-conjugated RIG-I siRNA drugs targeting RACGAP1 induced potent inhibition of xenograft tumor growth of PCa. CONCLUSION: In summary, our results reveal that reciprocal regulation between RACGAP1 and AR/AR-V7 contributes to the endocrine resistance in PCa. These findings highlight the therapeutic potential of combined RACGAP1 inhibition and enzalutamide in treatment of advanced PCa.

DEPDC1B is a Novel Direct Target of B-Myb and Contributes to Malignant Progression and Immune Infiltration in Lung Adenocarcinoma.

BACKGROUND: Lung cancer is the primary cause of cancer-related deaths, with one of the highest incidence and mortality rates of all malignant tumors. Dysregulated expression of DEPDC1B has been reported to occur in various tumor types. However, the functional implications of this alteration in lung adenocarcinoma (LUAD) and the underlying molecular mechanism remains unclear. In this study, we investigated the role and clinical significance of DEPDC1B in LUAD. METHODS: The expression of DEPDC1B in LUAD and its relationship with prognosis were systematically evaluated in several publically available datasets. The effects of DEPDC1B knockdown on the proliferation and motility of LUAD cells were assessed using the JULI Stage Real-time Cell History Recorder, while the effect of knockdown on the cell cycle was studied by flow cytometry. Furthermore, RNA-Sequencing (RNA-Seq) analysis was conducted to identify the downstream target genes and pathways regulated by DEPDC1B. Correlations between the expression of DEPDC1B and immune cell infiltration, immunotherapy resistance, and chemoresistance were also examined. Additionally, molecular biological methods were used to explore the regulatory mechanism of B-Myb on DEPDC1B expression. RESULTS: DEPDC1B was found to be upregulated in LUAD patients and this was associated with poor clinical outcomes. Knockdown of DEPDC1B inhibited cell growth, migration and motility, as well as cell cycle progression. Knockdown also resulted in the down-regulation of several downstream genes, including NID1, FN1, and EGFR, as well as the inactivation of multiple critical pathways, such as the ERK and PI3K-AKT pathways. Analysis of the tumor immuno-environment in LUAD revealed that high DEPDC1B expression was associated with an abundance of activated CD4+ memory T cells, M0 macrophages, M1 macrophages, and CD8+ T cells. Moreover, these tumors responded poorly to immunotherapy. Analysis of chemo-drug sensitivity showed that LUADs with high DEPDC1B expression were more responsive to frontline chemotherapeutic drugs such as Vinorelbine, Cisplatin, and Etoposide. Additionally, mechanistic investigations revealed that DEPDC1B is a direct target gene of B-Myb, and that its knockdown attenuated the proliferation and motility effects of B-Myb. CONCLUSIONS: In summary, our findings indicate that DEPDC1B is a critical regulator during the malignant progression of LUAD. DEPDC1B could therefore be a promising prognostic marker and therapeutic target in LUAD diagnosis and treatment.

Characterization of a New Variant in ARHGAP31 Probably Involved in Adams-Oliver Syndrome in a Family with a Variable Phenotypic Spectrum.

Adams-Oliver syndrome is a rare inherited condition characterized by scalp defects and limb abnormalities. It is caused by variants in different genes such as ARHGAP31. Here, we used an interdisciplinary approach to study a family with lower limb anomalies. We identified a novel variant in the ARHGAP31 gene that is predicted to result in a truncated protein with a constitutively activated catalytic site due to the loss of 688 amino acids involved in the C-terminal domain, essential for protein auto-inhibition. Pathogenic variants in ARHGAP31 exon 12, leading to a premature protein termination, are associated with Adams-Oliver syndrome. Bioinformatic analysis was useful to elucidate the impact of the identified genetic variant on protein structure. To better understand the impact of the identified variant, 3D protein models were predicted for the ARHGAP31 wild type, the newly discovered variant, and other pathogenetic alterations already reported. Our study identified a novel variant probably involved in Adams-Oliver syndrome and increased the evidence on the phenotypic variability in patients affected by this syndrome, underlining the importance of translational research, including experimental and bioinformatics analyses. This strategy represents a successful model to investigate molecular mechanisms involved in syndrome occurrence.

Exosome-transmitted circular RNA circ-LMO7 facilitates the progression of osteosarcoma by regulating miR-21-5p/ARHGAP24 axis.

The potential function and mechanism of circRNAs in regulating malignant performances of Osteosarcoma (OS) cells have not been well investigated. The expression level of CircLMO7, miR-21-5p and ARHGAP24 were detected by RT-qPCR. The relationship between miR-21-5p and circ-LMO7, as well as between miR-21-5p and ARHGAP24, was predicted and examined through bioinformatics analysis and luciferase reporter gene experiments. Moreover, OS cell growth, invasion, migration, and apoptosis were detected using the cell counting kit-8 (CCK-8), transwell and flow cytometry assays, respectively. ARHGAP24 protein level was measured using western blotting. In present study, we choose to investigate the role and mechanism of circ-LOM7 on OS cell proliferation, migration and invasion. circ-LOM7 was found to be down-regulated in OS tissues and cell lines. Enforced expression of circ-LOM7 suppressed the growth, invasion, and migration of OS cells. In contrast, decreasing circ-LMO7 expression had opposite effects. Furthermore, miR-21-5p was predicted to be sponged by circ-LMO7, and had an opposite role of circ-LMO7 in OS. Moreover, ARHGAP24 served as miR-21-5p's downstream target. Mechanistically, circ-LMO7 was packed in exosomes and acted as a cancer-suppresser on OS by sponging miR-21-5p and upregulating the expression of ARHGAP24. The exosomal circ-LMO7 expression was significantly decreased in OS cell exosomes, and co-culture experiments showed that exosomal circ-LMO7 suppressed the proliferation ability of OS cells. Circ-LMO7 exerts as a tumor suppressor in OS, and the circ-LMO7/miR-21-5P/ARHGAP24 axis is involved in OS progression.

KIAA1429 regulates lung adenocarcinoma proliferation and metastasis through the PI3K/AKT pathway by modulating ARHGAP30 expression.

BACKGROUND: Alterations in epigenetic factors are recognized as key contributors to the emergence of human cancer. The active and reversible alteration of N6-methyladenosine (m6A) RNA is crucial for controlling gene activity and determining cellular destiny. Even with these insights, the triggering of KIAA1429 (also called VIRMA) and its role in lung adenocarcinoma (LUAD) is mostly unclear. As a result, the objective of this study was to elucidate how KIAA1429 contributes to cancer development in LUAD. METHODS: This study utilized multiple methods for investigation, encompassing the in vitro functional examination of KIAA1429 in lung adenocarcinoma cells, transcriptome sequencing, methylation RNA immunoprecipitation sequencing (MeRIP-seq), as well as RNA stability tests to ascertain the half-life and stability of the target genes. RESULTS: The results indicated that modifying the expression of KIAA1429 regulated the proliferation and metastasis of LUAD. By employing transcriptome sequencing alongside MeRIP-seq analysis, the research pinpointed genes affected by m6A alterations triggered by KIAA1429. In a more detailed manner, it was discovered that KIAA1429 plays a regulatory role in the expression of ARHGAP30. Suppressing KIAA1429 results in reduced m6A levels in the mRNA of the target gene ARHGAP30, boosting its stability and expression, thus inhibiting tumor proliferation and metastasis. CONCLUSION: This study revealed the activation mechanism and pivotal function of KIAA1429 in LUAD tumor development, paving the way for molecular-based interventions for LUAD.

Deciphering the Role of miR-30a-5p and DLGAP1 Gene in Non-small Cell Lung Cancer.

BACKGROUND/AIM: Non-small cell lung cancer (NSCLC) is the deadliest form of cancer worldwide. Understanding the mechanisms of lung cancer development is vital for targeted therapy advancements. This article explores the little-known role of the guanylate kinase-associated protein (GKAP), encoded by the Disks large-associated protein 1 (DLGAP1) gene, in NSCLC along with assessing microRNA-30a-5p's influence on DLGAP1 gene expression in the A549 cell line. MATERIALS AND METHODS: Experiments were conducted on A549 cells transfected with synthetic oligonucleotides. The luciferase assay was employed to confirm the binding site of miR-30a-5p to the 3'UTR of DLGAP1 mRNA. The role of miRNA-30a-5p mimic in regulating potential target gene expression at the protein and mRNA levels was studied by performing RT-qPCR and western blot analyses. The effects of DLGAP1 knockdown and miRNA-30a-5p mimic on cell viability and the cell cycle were evaluated using the MTT test and flow cytometry with annexin/iodide cell staining. RESULTS: The luciferase assay indicated that miR-30a-5p has the ability to bind to the 3'UTR of DLGAP1 mRNA. RT-qPCR revealed that the overexpression of miR-30a-5p down-regulates DLGAP1 mRNA. Western blot analysis indicated that miR-30a-5p slightly reduces the level of the GKAP protein. Knockdown of DLGAP1 with synthetic oligonucleotides, as well as transfection with a miR-30a-5p mimic, significantly attenuates cell proliferation and increases the number of cells in the early and late stages of apoptosis. CONCLUSION: Our findings reveal the antiproliferative effect of miR-30a-5p and DLGAP1 gene knockdown on A549 cancer cells, implying that these elements could be considered as therapeutic targets for personalized medicine in NSCLC patients.

ARHGAP4 as a Prognostic Biomarker for Colon Liver Metastases After Surgical Resection.

BACKGROUND/AIM: To select and stratify patients for optimal treatment plans is challenging. Identification of cancer-related biomarkers that serve as predictors for prognosis and treatment response is essential to better predict treatment outcome and find future targets for therapy. Previous data has suggested ARHGAP4 as a relevant biomarker in colorectal cancer (CRC). The purpose of this study was to assess how ARHGAP4 expression affected patients undergoing surgery for colon liver metastasis (CLM) in terms of overall survival (OS). PATIENTS AND METHODS: A total of 251 patients undergoing resection of CLM from 2006 to 2017 were included. Corresponding resected tumor specimens were examined for ARHGAP4 expression levels by immunohistochemistry (IHC). The correlation between ARHGAP4 expression and postoperative survival was analyzed. RESULTS: High expression levels of ARHGAP4 were seen in 60% of patients. High expression levels of ARHGAP4 were correlated with adverse prognosis after hepatectomy due to CLM. Survival data generated using Cox proportional hazard model showed a statistically significant difference between high and low ARHGAP4 expression groups by univariate (HR=1.5, 95% CI=1.1-2.2) and multivariate (HR=1.5, 95% CI=1.0-2.1) analysis. In multivariate Cox regression, high ARHGAP4 expression, preoperative CEA levels and presence of vascular invasion by pathological examinations were independent predictive factors of overall survival. CONCLUSION: ARHGAP4 is a novel prognostic biomarker after resection of CLM.

ARHGAP4 promotes colon cancer metastasis through the TGF-ß signaling pathway and may be associated with T cell exhaustion.

BACKGROUND: Colon cancer is a prevalent invasive neoplasm in the gastrointestinal system with a high degree of malignancy. Despite extensive research, the underlying mechanisms of its recurrence and metastasis remain elusive.Rho GTPase activating protein 4 (ARHGAP4), a member of the small GTPases protein family, may be closely related to tumor metastasis, and its expression is increased in colon cancer. However, the role of ARHGAP4 in colon cancer metastasis is uncertain. This study investigates the impact of ARHGAP4 on the metastasis of colon cancer cells. Our objective is to determine the role of ARHGAP4 in regulating the invasive behavior of colon cancer cells. METHODS: We downloaded colon adenocarcinoma (COAD) data from the Cancer Genome Atlas (TCGA), and performed differential analysis and survival analysis. By using the CIBERSORT algorithm, we evaluated the proportion of infiltrating immune cells in colon cancer. We further analyzed whether ARHGAP4 is associated with T cell exhaustion. Finally, we investigated the impact of ARHGAP4 knockdown on the migration and invasion of colon cancer cells through in vitro cell experiments. Additionally, we utilized western blotting to assess the expression of protein related to the TGF-ß signaling pathway and epithelial-mesenchymal transition (EMT). RESULTS: We found that ARHGAP4 is upregulated in colon cancer. Subsequent survival analysis revealed that the high-expression group had significantly lower survival rates compared to the low-expression group. Immune infiltration analysis showed that ARHGAP4 was not only positively correlated with CD8+ T cells, but also positively correlated with T cell exhaustion markers programmed cell death 1 (PDCD-1), cytotoxic T-lymphocyte associated protein 4 (CTLA-4), and lymphocyte activating 3 (LAG-3). In vitro cell experiments, the knockdown of ARHGAP4 inhibited the migration and invasion of colon cancer cells. Among EMT-related proteins, when ARHGAP4 was knocked down, the expression of E-cadherin was increased, while the expression of N-cadherin and Vimentin was decreased. Meanwhile, the expression of TGF-ß1, p-Smad2, and p-Smad3, which are associated with the TGF-ß/Smad pathway, all decreased. CONCLUSION: ARHGAP4 promotes colon cancer metastasis through the TGF-ß/Smad signaling pathway and may be associated with T cell exhaustion. It plays an important role in the progression of colon cancer and may serve as a potential target for diagnosis and treatment of colon cancer.

HIF2α-dependent Dock4/Rac1-signaling regulates formation of adherens junctions and cell polarity in normoxia.

Hypoxia-inducible factors (HIF) 1 and 2 regulate similar but distinct sets of target genes. Although HIFs are best known for their roles in mediating the hypoxia response accumulating evidence suggests that under certain conditions HIFs, particularly HIF2, may function also under normoxic conditions. Here we report that HIF2α functions under normoxic conditions in kidney epithelial cells to regulate formation of adherens junctions. HIF2α expression was required to induce Dock4/Rac1/Pak1-signaling mediating stability and compaction of E-cadherin at nascent adherens junctions. Impaired adherens junction formation in HIF2α- or Dock4-deficient cells led to aberrant cyst morphogenesis in 3D kidney epithelial cell cultures. Taken together, we show that HIF2α functions in normoxia to regulate epithelial morphogenesis.

AIDA-1/ANKS1B Binds to the SynGAP Family RasGAPs with High Affinity and Specificity.

AIDA-1, encoded by ANKS1B, is an abundant postsynaptic scaffold protein essential for brain development. Mutations of ANKS1B are closely associated with various psychiatric disorders. However, very little is known regarding the molecular mechanisms underlying AIDA-1's involvements under physiological and pathophysiological conditions. Here, we discovered an interaction between AIDA-1 and the SynGAP family Ras-GTPase activating protein (GAP) via affinity purification using AIDA-1d as the bait. Biochemical studies showed that the PTB domain of AIDA-1 binds to an extended NPx[F/Y]-motif of the SynGAP family proteins with high affinities. The high-resolution crystal structure of AIDA-1 PTB domain in complex with the SynGAP NPxF-motif revealed the molecular mechanism governing the specific interaction between AIDA-1 and SynGAP. Our study not only explains why patients with ANKS1B or SYNGAP1 mutations share overlapping clinical phenotypes, but also allows identification of new AIDA-1 binding targets such as Ras and Rab interactors.

ARAP3 protects from excessive formylated peptide-induced microvascular leakage by acting on endothelial cells and neutrophils.

Vascular permeability is temporarily heightened during inflammation, but excessive inflammation-associated microvascular leakage can be detrimental, as evidenced in the inflamed lung. Formylated peptides regulate vascular leakage indirectly via formylated peptide receptor-1 (FPR1)-mediated recruitment and activation of neutrophils. Here we identify how the GTPase-activating protein ARAP3 protects against formylated peptide-induced microvascular permeability via endothelial cells and neutrophils. In vitro, Arap3-/- endothelial monolayers were characterised by enhanced formylated peptide-induced permeability due to upregulated endothelial FPR1 and enhanced vascular endothelial cadherin internalisation. In vivo, enhanced inflammation-associated microvascular leakage was observed in Arap3-/- mice. Leakage of plasma protein into the lungs of Arap3-/- mice increased within hours of formylated peptide administration. Adoptive transfer experiments indicated this was dependent upon ARAP3 deficiency in both immune and non-immune cells. Bronchoalveolar lavages of formylated peptide-challenged Arap3-/- mice contained neutrophil extracellular traps (NETs). Pharmacological inhibition of NET formation abrogated excessive microvascular leakage, indicating a critical function of NETs in this context. The observation that Arap3-/- mice developed more severe influenza suggests these findings are pertinent to pathological situations characterised by abundant formylated peptides. © 2024 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.