Search Results (95)

Small (monomeric) GTP-binding proteins (smgs; Cdc42 and Rac1) play requisite roles in islet beta cell function, including glucose-stimulated insulin secretion. In addition, emerging evidence suggests that sustained (constitutive) activation of smgs (e.g., Rac1) culminates in the genesis of islet beta cell dysfunction under the duress of chronic hyperglycemia. It is noteworthy that functions (i.e., activation–deactivation) of smgs in many cells, including the islet beta cell, have been shown to be under the regulatory control of at least three factors, namely the guanine nucleotide exchange factors (GEFs), the GTPase-activating proteins (GAPs), and the GDP-dissociation inhibitors (GDIs). The overall objective of this review is to highlight our current understanding of the regulatory roles of the RhoGDIβ-Rac1-CARD9 signalome in the pathology of beta cell dysfunction under chronic hyperglycemic stress. For brevity, this review is structured by an overview of smgs and their regulatory proteins/factors in the beta cell, followed by a discussion of potential roles of the RhoGDIβ-Rac1-CARD9 axis in the onset of cellular dysfunction under the duress of metabolic stress. Overall conclusions, potential knowledge gaps, and opportunities for future research in this field of islet biology are highlighted in the last section. Full article

The p21-activated kinases (PAKs) are a group of evolutionarily conserved serine/threonine protein kinases and serve as a downstream target of the small GTPases Rac and Cdc42, both of which belong to the Rho family. PAKs play pivotal roles in various physiological processes, including cytoskeletal rearrangement and cellular signal transduction. Group II PAKs (PAK4-6) are particularly closely linked to human tumors, such as breast and pancreatic cancers, while Group I PAKs (PAK1-3) are indispensable for normal physiological functions such as cardiovascular development and neurogenesis. In recent years, the association of PAKs with diseases like cancer and the rise of small-molecule inhibitors targeting PAKs have attracted significant attention. This article focuses on the analysis of PAKs’ role in tumor progression and immune infiltration, as well as the current small-molecule inhibitors of PAKs and their mechanisms. Full article

Metastatic prostate cancer occurs when the tumor spreads from the prostate gland to other parts of the body. Previous studies have shown that Gα_i2, a subunit of the heterotrimeric G protein complex, plays a critical role in inducing cell migration and invasion in prostate cancer cells in response to diverse stimuli. Rac1 is a small rho-GTPase, which is activated by the phosphoinositide 3-kinase (PI3K)/AKT pathway and plays an essential role during cell migration. Previous studies have shown that the knockdown of Gα_i2 attenuates cell migration without causing any reduction in basal Rac1 activity in both PC3 and DU145 cells, and has only marginal effects on the epidermal growth facotor (EGF)-induced increase in Rac1 activity. Therefore, Gα_i2 may be involved in the regulation of cell motility and invasion independently or downstream of Rac1 activation. In this study, we investigated the possible mechanism of Gα_i2 at the level of the Rac1-dependent activation of Wiskott-Aldrich Syndrome Protein)-family verprolin homologous protein2 (Wave2) and actin related protein 2/3 (Arp 2/3) proteins, downstream effectors of activated Rac1. PC3 cells with a stable overexpression of constitutively active Rac1 were transfected with control siRNA or Gα_i2 siRNA to knockdown endogenous Gα_i2 expression. Western blot analysis showed that the Rac1-dependent activation of Wave2 was impaired in the absence of Gα_i2. The overexpression of constitutively active Gα_i2 (Gα_i2-Q205L) in PC3 cells significantly increased cell migration compared to cells transfected with control plasmids. In the parallel experiments, a specific Gα_i2 inhibitor blocked G_iα2-Q205L-induced cell migration in PC3 cells. Furthermore, the Rac1 inhibitor did not block increased cell migration in PC3 cells overexpressing constitutively active Gα_i2. We conclude that activated Gα_i2 plays a crucial role in cell migration in prostate cancer cells independent of Rac1 activation. Full article

Background/Objects: Rho signaling plays a role in calcium-regulated cytoskeletal reorganization and cell movement, processes linked to neuronal function and cancer metastasis. Gastrodia elata, a traditional herbal medicine, can regulate glutamate-induced calcium influx in PC12 cells and influence cell function by modulating neuronal cytoskeleton remodeling via the monoaminergic system and Rho signaling. This study investigates the effects of gastrodin, a key component of Gastrodia elata, on Rho signaling, cytoskeleton remodeling, and cell migration in B35 and C6 cells. It also explores gastrodin’s impact on Rho signaling in the prefrontal cortex of Sprague Dawley rats. Methods: B35 cells, C6 cells, and Sprague Dawley rats were treated with ketamine, gastrodin, or both. The expression of examined proteins from B35 cells, C6 cells, and the prefrontal cortex of Sprague Dawley rats were analyzed using immunoblotting. Immunofluorescent staining was applied to detect the phosphorylation of RhoGDI1. F-actin was stained using phalloidin-488 staining. Cell migration was analyzed using the Transwell and wound-healing assays. Results: Gastrodin reversed the ketamine-induced regulation of cell mobility inhibition, F-actin condensation, and Rho signaling modulation including Rho GDP dissociation inhibitor 1 (RhoGDI1); the Rho family protein (Ras homolog family member A (RhoA); cell division control protein 42 homolog (CDC42); Ras-related C3 botulinum toxin substrate 1(Rac1)); rho-associated, coiled-coil-containing protein kinase 1 (ROCK1); neural Wiskott–Aldrich syndrome protein (NWASP); myosin light chain 2 (MLC2); profilin1 (PFN1); and cofilin-1 (CFL1) in B35 and C6 cells. Similar modulations on Rho signaling were also observed in the prefrontal cortex of rats. Conclusions: Our findings show that gastrodin counteracts ketamine-induced disruptions in Rho signaling, cytoskeletal dynamics, and cell migration by regulating key components like RhoGDI1, ROCK1, MLC2, PFN1, and CFL1. This suggests the potential of gastrodin as a comprehensive regulator of cellular signaling. Full article

Rhabdomyosarcoma (RMS), the most common soft tissue sarcoma in children, arises from skeletal muscle cells that fail to differentiate terminally. Two subgroups of RMS, fusion-positive and fusion-negative RMS (FPRMS and FNRMS, respectively), are characterized by the presence or absence of the PAX3/7-FOXO1 fusion gene. RMSs frequently exhibit increased expression of human epidermal growth factor receptor-2 (HER2). Trastuzumab is a humanized monoclonal antibody targeting HER2, and its potential role in RMS treatment remains to be elucidated. Syndecan-4 (SDC4) is a heparan sulfate proteoglycan (HSPG) affecting myogenesis via Rac1-mediated actin remodeling. Previously, we demonstrated that the SDC4 gene is amplified in 28% of human FNRMS samples, associated with high mRNA expression, suggesting a tumor driver role. In this study, after analyzing the copy numbers and mRNA expressions of other HSPGs in human RMS samples, we found that in addition to SDC4, syndecan-1, syndecan-2, and glypican-1 were also amplified and highly expressed in FNRMS. In RD (human FNRMS) cells, elevated SDC4 expression was accompanied by low levels of phospho-Ser179 of SDC4, leading to high Rac1-GTP activity. Notably, this high SDC4 expression in RD cells decreased following trastuzumab treatment. Trastuzumab decreased the levels of G1/S checkpoint regulators cyclin E and cyclin D1 and reduced the cell number; however, it also downregulated the cyclin-dependent kinase inhibitor p21. The level of MyoD, a transcription factor essential for RMS cell survival, also decreased following trastuzumab administration. Our findings contribute to the understanding of the role of SDC4 in FNRMS. Since HER2 is expressed in about half of RMSs, the trastuzumab-mediated changes observed here may have therapeutic implications. Full article

Adipogenesis is regulated by the coordinated activity of adipogenic transcription factors including PPAR-gamma and C/EBP alpha, while dysregulated adipogenesis can predispose adipose tissues to adipocyte hypertrophy and hyperplasia. We have previously reported that Cthrc1-null mice have increased adiposity compared to wildtype mice, supporting the notion that CTHRC1 regulates body composition. Herein, we derived conditioned medium from 3T3-L1 cells expressing human CTHRC1 and investigated its anti-adipogenic activity. This constituent significantly reduced 3T3-L1 cell adipogenic differentiation commensurate to the marked suppression of Cebpa and Pparg gene expression. It also increased the expression of the anti-adipogenic transcription factor SOX9 and promoted its nuclear translocation. Importantly, Sox9 gene knockdown demonstrated that the anti-adipogenic effect produced by this conditioned medium is dependent on SOX9 expression, while its ability to positively regulate SOX9 was attenuated by the application of Rho and Rac1 signaling pathway inhibitors. We also identified the selective expression of CTHRC1 in PDGFRA-expressing cell populations in human white adipose tissue, but not brown or perivascular adipose tissues. Congruently, flow cytometry revealed CTHRC1 expression in PDGFR-alpha⁺ stromal cells of mouse white adipose tissue, thus defining a novel stromal cell population that could underpin the ability of CTHRC1 to regulate adiposity. Full article

Objective: RAC1 aberrations in head and neck squamous cell carcinoma (HNSCC) remain clinically inactionable today. Methods: Here, we investigated the clinical significance and potential druggability of RAC1 genomic aberrations in HNSCC. Results: Notably, HPV(−)HNSCC patients bearing the unique HNSCC-prevalent RAC1-A159V hotspot mutation, P29S hotspot and G-box domain mutations, and RAC1 copy number increases all displayed dismal overall survival (TCGA-HNSCC). Here, we demonstrated that all five HNSCC patient-relevant RAC1 aberrations tested (A159V and P29S hotspot mutations, K116N, G15S, and N39S) could significantly drive HNSCC tumoroid growth and/invasion, with A159V, P29S, and K116N mutants being the most potent drivers. Interestingly, transcriptomics analyses revealed that RAC1 mutations and copy increase could both drive PI3K pathway activation, with the A159V mutant associated with the prominent intra-tumoral upregulation of phospho-RPS6(Ser235/236) in patient tumors. Importantly, proof-of-principle Rac targeting with EHop-016 resulted in remarkable antitumor activity in vivo against RAC1-A159V-mutated and RAC1-amplified HNSCC patient-derived xenografts (PDXs) and/engineered models. Lastly, melanoma and endometrial xenograft models bearing endogenous RAC1-amplification and RAC1-A159V mutation were also sensitive to EHop-016 targeting. Conclusions: In principle, RAC1 genomic aberrations in HNSCC can be potentially harnessed for precision drugging. Full article

Protocadherin-7 (Pcdh7) is a member of the non-clustered protocadherin δ1 subgroup within the cadherin superfamily. Pcdh7 has been shown to control osteoclast differentiation via the protein phosphatase 2A (PP2A)–glycogen synthase kinase-3β (GSK3β)–small GTPase signaling axis. As protocadherins serve multiple biological functions, a deeper understanding of Pcdh7’s biological features is valuable. Using an in vitro mouse monocyte cell culture system, we demonstrate that Pcdh7 plays a role in regulating monocyte migration by modulating the small GTPases RhoA and Rac1. Pcdh7-deficient (Pcdh7^−/−) bone marrow-derived monocytes exhibited impaired migration along with the reduced activation of RhoA and Rac1. This impaired migration was rescued by transduction with constitutively active forms of RhoA and Rac1. Treatment with the PP2A-specific activator DT-061 enhanced cell migration, whereas treatment with the GSK3β-specific inhibitor AR-A014418 inhibited migration in wild-type monocytes. In contrast, treatment with DT-061 failed to restore the impaired migration in Pcdh7^−/− monocytes. These findings suggest the involvement of PP2A and GSK3β in monocyte migration, although the forced activation of PP2A alone is insufficient to restore impaired migration in Pcdh7^−/− monocytes. Taken together, these results indicate that Pcdh7 regulates monocyte migration through the activation of RhoA and Rac1. Given the pivotal role of cell migration in both physiological and pathological processes, our findings provide a foundation for future research into therapeutic strategies targeting Pcdh7-regulated migration. Full article

Rho guanine nucleotide dissociation inhibitor 1 (RhoGDI1) plays a critical role in regulating the activity of Rho guanosine triphosphatases (GTPases). Phosphorylation of RhoGDI1 dynamically modulates the activation of Rho GTPases, influencing cell proliferation and migration. This study explored the involvement of Never In Mitosis A (NIMA)-related serine/threonine protein kinase 2 (NEK2) in phosphorylating RhoGDI1 and its implications in cancer cell behavior associated with tumor progression. We employed GST pull-down assays and immunoprecipitation to investigate the interaction between NEK2 and RhoGDI1. Truncation fragments identified the region of RhoGDI1 responsible for binding with NEK2. Phosphorylation assays determined the site of NEK2-mediated phosphorylation on RhoGDI1. Functional assays were conducted using overexpression of the RhoGDI1 substitution mutant to assess their impact on cancer cell behavior. NEK2 directly bound to RhoGDI1 and phosphorylated it at Ser174. This phosphorylation event facilitated cancer cell proliferation and motility by activating RhoA and Rac1. The RhoGDI1 aa 112–134 region was critical for the binding to NEK2. Disruption of the NEK2–RhoGDI1 interaction through overexpression of a RhoGDI1 truncated fragment (aa 112–134) led to diminished RhoGDI1 phosphorylation and RhoA/Rac1 activation induced by NEK2, resulting in reduced cancer cell proliferation and migration. Moreover, in vivo studies showed reduced tumor growth and lung metastasis when the NEK2–RhoGDI1 interaction was disrupted. This study indicates that NEK2 promotes the metastatic behaviors of cancer cells by activating RhoA and Rac1 by phosphorylating RhoGDI1. Full article

Anticancer drugs cause anemia in patients through eryptosis and hemolysis. We thus studied the in vitro toxicity of galangin (GAL) in red blood cells (RBCs). RBCs were exposed to 50–500 μM of GAL and analyzed for markers of eryptosis and hemolysis. Ca²⁺ nucleation, phosphatidylserine (PS) externalization, oxidative stress, and cell size were detected via fluorescence-activated cell sorting using Fluo4/AM, annexin-V-FITC, 2′,7′-dichlorodihydrofluorescein diacetate, and forward scatter (FSC), respectively. Acetylcholinesterase (AChE) activity was measured via Ellman’s assay and ultrastructural morphology was examined via scanning electron microscopy. Membrane rupture and extracellular hemoglobin, aspartate transaminase (AST), and lactate dehydrogenase (LDH) were assessed via colorimetric methods. Distinct experiments were carried out to identify protective agents and signaling pathways using small-molecule inhibitors. GAL triggered sucrose-sensitive hemolysis with AST and LDH leakage, increased annexin-V-FITC and Fluo4 fluorescence, and decreased FSC and AChE activity which was associated with the formation of granulated echinocytes. Ca²⁺ omission and energy replenishment with glucose, adenine, and guanosine blunted PS externalization and preserved cellular volume. Moreover, caffeine, Trolox, heparin, and uric acid had similar ameliorative effects. Hemolysis was abrogated via caffeine, Trolox, heparin, mannitol, lactate, melatonin, and PEG 8000. Notably, co-treatment of cells with GAL and staurosporin, D4476, or acetylsalicylic acid prevented PS externalization whereas only the presence of SB203580 and NSC23766 rescued the cells from GAL-induced hemolysis. Ca²⁺ nucleation and metabolic collapse mediated by PKC/CK1α/COX/p38/Rac1 drive GAL-induced eryptosis and hemolysis. These novel findings carry ramifications for the clinical prospects of GAL in anticancer therapy. Full article

Colorectal cancer (CRC) is the third most commonly diagnosed type of cancer worldwide and is responsible for numerous deaths. 5-fluorouracil (5-FU) is an effective chemotherapy drug commonly used in the treatment of CRC, either as monotherapy or in combination with other drugs. However, half of CRC cases are resistant to 5-FU-based therapies. To contribute to the understanding of the mechanisms underlying CRC resistance or recurrence after 5-FU-based therapies, we performed a comprehensive study integrating in silico, in vitro, and in vivo approaches. We identified differentially expressed genes and enrichment of pathways associated with recurrence after 5-FU-based therapies. Using these bioinformatics data as a starting point, we selected a group of drugs that restored 5-FU sensitivity to 5-FU resistant cells. Interestingly, treatment with the novel Rac1 inhibitor, 1A-116, reversed morphological changes associated with 5-FU resistance.. Moreover, our in vivo studies have shown that 1A-116 affected tumor growth and the development of metastasis. All our data allowed us to postulate that targeting Rac1 represents a promising avenue for the development of new treatments for patients with CRC resistant to 5-FU-based therapies. Full article

Osteoclasts are bone-resorbing multinucleated giant cells formed by the fusion of monocyte/macrophage lineages. Various small GTPases are involved in the multinucleation and differentiation of osteoclasts. However, the roles of small GTPases regulatory molecules in osteoclast differentiation remain unclear. In the present study, we examined the role of Dennd2c, a putative guanine nucleotide exchange factor for Rab GTPases, in osteoclast differentiation. Knockdown of Dennd2c promoted osteoclast differentiation, resorption, and expression of osteoclast markers. Morphologically, Dennd2c knockdown induced the formation of larger osteoclasts with several protrusions. In contrast, overexpression of Dennd2c inhibited the multinucleation and differentiation of osteoclasts, bone resorption, and the expression of osteoclast markers. Dennd2c-overexpressing macrophages exhibited spindle-shaped mononuclear cells and long thin protrusions. Treatment of Dennd2c-overexpressing cells with the Cdc42 inhibitor ML-141 or the Rac1 inhibitor 6-thio-GTP prevented protrusion formation. Moreover, treatment of Dennd2c-overexpressing cells with the actin polymerization inhibitor latrunculin B restored multinucleated and TRAP-positive osteoclast formation. These results indicate that Dennd2c negatively regulates osteoclast differentiation and multinucleation by modulating protrusion formation in macrophages. Full article

Background: Oncogenic mutations in the KRAS gene are detected in >90% of pancreatic cancers (PC). In genetically engineered mouse models of PC, oncogenic KRAS drives the formation of precursor lesions and their progression to invasive PC. The Yes-associated Protein (YAP) is a transcriptional coactivator required for transformation by the RAS oncogenes and the development of PC. In Ras-driven tumors, YAP can also substitute for oncogenic KRAS to drive tumor survival after the repression of the oncogene. Ras oncoproteins exert their transforming properties through their downstream effectors, including the PI3K kinase, Rac1 GTPase, and MAPK pathways. Methods: To identify Ras effectors that regulate YAP, YAP levels were measured in PC cells exposed to inhibitors of oncogenic K-Ras and its effectors. Results: In PC cells, the inhibition of Rac1 leads to a time-dependent decline in YAP protein, which could be blocked by proteosome inhibitor MG132. This YAP degradation after Rac1 inhibition was observed in a range of cell lines using different Rac1 inhibitors, Rac1 siRNA, or expression of dominant negative Rac1^T17N mutant. Several E3 ubiquitin ligases, including SCF^βTrCP, regulate YAP protein stability. To be recognized by this ligase, the βTrCP degron of YAP (amino acid 383–388) requires its phosphorylation by casein kinase 1 at Ser384 and Ser387, but these events must first be primed by the phosphorylation of Ser381 by LATS1/2. Using Flag-tagged mutants of YAP, we show that YAP degradation after Rac1 inhibition requires the integrity of this degron and is blocked by the silencing of βTrCP1/2 and by the inhibition of casein kinase 1. Unexpectedly, YAP degradation after Rac1 inhibition was still observed after the silencing of LATS1/2 or in cells carrying a LATS1/2 double knockout. Conclusions: These results reveal Rac1 as an oncogenic KRAS effector that contributes to YAP stabilization in PC cells. They also show that this regulation of YAP by Rac1 requires the SCF^βTrCP ligase but occurs independently of the LATS1/2 kinases. Full article

This study investigated the potential of five pyrrole-imidazole alkaloids from the marine sponge Agelas sp. to inhibit key targets in neuroblastoma, the most common pediatric malignant solid tumor. Molecular docking analysis using GOLD software (v4.1.2) revealed that Strepoxazine A (Mol3) and Taurodispacamide A (Mol5) exhibited the strongest inhibition of focal adhesion kinase 1 (FAK), caspase-3 (ca3), phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit gamma isoform (PI3K), telomerase reverse transcriptase (TERT), osm-9-like TRP channel 1 (TRPV1), and RAC-alpha serine/threonine-protein kinase (AKT1). Normal mode analysis using iMODS server confirmed the stability of the best complexes and pharmacokinetics, such as toxicity and predictions of biological activity as inhibitors of anticancer targets, indicating a balance between efficacy and safety for bothMol3 and Mol5. The remaining compounds (Ageladine A, Oroidine, and Cyclooroidine) showed moderate effects, with significant toxicity, suggesting limited therapeutic potential. The promising results of our in silico-study suggest that Strepoxazine A and Taurodispacamide A could serve as novel therapeutic agents for neuroblastoma, potentially leading to more effective treatment options and improved survival rates for pediatric patients suffering from this challenging malignancy, although further in vitro and in vivo validation is needed. Full article

Bacterial virulence plays an important role in infection. Antibacterial virulence factors are effective for preventing crop bacterial diseases. Resin acid copper salt as an effective inhibitor exhibited excellent anti-Xanthomonas oryzae pv. oryzae (Xoo) activity with an EC₅₀ of 50.0 μg mL⁻¹. Resin acid copper salt (RACS) can reduce extracellular polysaccharides’ (EPS’s) biosynthesis by down-regulating gumB relative expression. RACS can also effectively inhibit the bio-mass of Xoo biofilm. It can reduce the activity of Xoo extracellular amylase at a concentration of 100 μg mL⁻¹. Meanwhile, the results of virtual computing suggested that RACS is an enzyme inhibitor. RACS displayed good curative activity with a control effect of 38.5%. Furthermore, the result of the phytotoxicity assessment revealed that RACS exhibited slight toxicity compared with the control at a concentration of 200 μg mL⁻¹. The curative effect was increased to 45.0% using an additional antimicrobial agent like orange peel essential oil. RACS markedly inhibited bacterial pathogenicity at a concentration of 100 μg mL⁻¹ in vivo. Full article