Search Results (172)

RAC3 encodes a small Rho-family GTPase essential for cytoskeletal regulation and neurodevelopment, and de novo RAC3 variants typically act as gain-of-function alleles that cause severe neurodevelopmental disorders. In this study, we analyzed a fetus with multisystem congenital anomalies and identified a de novo RAC3 p.(T17R) variant by genome sequencing. To elucidate the pathogenicity of this variant, we combined in silico variant prioritization, structural and energetic modeling, and pathogenicity prediction with in vitro biochemical assays, including GDP/GTP exchange, GTP hydrolysis, effector pull-down, and luciferase reporter analyses in COS7 cells, as well as morphological analysis of primary hippocampal neurons. Furthermore, we performed in vivo analyses using a mouse in utero electroporation to assess cortical neuron migration, axon extension, and dendritic development. Our biochemical results suggest that RAC3-T17R exhibits markedly increased GDP/GTP exchange, with a preference for GDP binding, and undetectable GTP hydrolysis. The mutant displayed minimal binding to canonical RAC effectors (PAK1, MLK2, and N-WASP) and failed to activate SRF-, NFκB-, or AP1-dependent transcription. Neuronal overexpression of RAC3-T17R impaired axon formation in vitro, while in vivo expression delayed cortical neuron migration and axon extension and reduced dendritic arborization. Clinically, the fetus exhibited corpus callosum agenesis, microcephaly, organomegaly, and limb contractures. Collectively, these findings indicate that the RAC3 p.(T17R) variant may represent a signaling-deficient allele with pleiotropic, variant-specific mechanisms that disrupt corticogenesis and broader organogenesis. Our multi-tiered in silico–in vitro–in vivo approach demonstrates that noncanonical RAC3 variants can produce complex, multisystem developmental phenotypes beyond previously recognized RAC3-related neurodevelopmental disorders. Full article

Endothelial hyperpermeability is a hallmark of diverse inflammatory and vascular pathologies, including sepsis, acute respiratory distress syndrome (ARDS), ischemia–reperfusion injury, and atherosclerosis. Traditionally considered a passive return to baseline following stimulus withdrawal, barrier recovery is now recognized as an active, endothelial-driven process. Earlier work identified individual components of this restorative phase, such as cyclic adenosine monophosphate (cAMP)/exchange protein directly activated by cAMP 1 (Epac1) signaling, Rap1/Rac1 activation, vasodilator-stimulated phosphoprotein (VASP) phosphorylation, and targeted cytoskeletal remodeling, as well as kinase pathways involving PKA, PKG, and Src. However, these were often regarded as discrete events lacking a unifying framework. Recent integrative analyses, combining mechanistic insights from multiple groups, reveal that nitric oxide (NO) generated early during hyperpermeability can initiate a delayed cAMP/Epac1 cascade. This axis coordinates Rap1/Rac1-mediated cortical actin polymerization, VASP-driven junctional anchoring, retro-translocation of endothelial nitric oxide synthase (eNOS) to caveolar domains, PP2A-dependent suppression of actomyosin tension, and Krüppel-like factor 2 (KLF2)-driven transcriptional programs that sustain endothelial quiescence. Together, these pathways form a temporally orchestrated, multi-tiered “inactivation” program capable of restoring barrier integrity even in the continued presence of inflammatory stimuli. This conceptual shift reframes NO from solely a barrier-disruptive mediator to the initiating trigger of a coordinated, pro-resolution mechanism. The unified framework integrates cytoskeletal dynamics, junctional reassembly, focal adhesion turnover, and redox/transcriptional control, providing multiple potential intervention points. Therapeutically, Epac1 activation, Rap1/Rac1 enhancement, RhoA/ROCK inhibition, PP2A activation, and KLF2 induction represent strategies to accelerate endothelial sealing in acute microvascular syndromes. Moreover, applying these mechanisms to arterial endothelium could limit low-density lipoprotein (LDL) entry and foam cell formation, offering a novel adjunctive approach for atherosclerosis prevention. In this review, we will discuss both the current understanding of endothelial hyperpermeability mechanisms and the emerging pathways of its active inactivation, integrating molecular, structural, and translational perspectives. Full article

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

MSTN has been used as a candidate gene in the genetics, breeding, and improvement of animal breeds. However, the possible mechanism by which the MSTN gene regulates muscle development through PSMA6 is not well understood. Previous methylome and transcriptome sequencing analyses of gluteal muscle tissues from MSTN+/−Luxi cattle and wild-type Luxi cattle identified that the PSMA6 gene exhibited a negative correlation between methylation levels and transcriptional activity. To investigate whether MSTN expression regulates PSMA6 gene expression, we examined the effects of MSTN on DNA methyltransferases (DNMT1, DNMT2, DNMT3A, and DNMT3B) and DNA demethylases (TET1, TET2, and TET3). Additionally, chromatin immunoprecipitation (ChIP) assays were performed to detect the binding interaction between PSMA6 and TET2. In this paper, we first established an MSTN knockdown cellular model to preliminarily validate its regulatory effect on PSMA6 expression. Subsequently, the developmental impact of PSMA6 on bovine skeletal muscle satellite cells was further investigated through both knockdown and overexpression of the PSMA6 gene. Furthermore, we examined changes in the expression of key components of the AKT/mTOR signaling pathway to elucidate the mechanisms underlying the PSMA6-mediated regulation of satellite cell development. The results demonstrate that myostatin (MSTN) inhibition significantly decreased proteasome 20S subunit alpha-6 (PSMA6) gene expression, while increasing demethylase expression, particularly ten-eleven translocation-2 (TET2), which exhibited the most pronounced changes. During the cell proliferation stage, the markers Paired Box 7 (PAX7) and Ki-67 exhibited no significant changes, whereas the PSMA6 gene was either overexpressed or disrupted. Conversely, PSMA6 overexpression altered the myogenic differentiation markers, causing the differential regulation of myosin heavy chain (MyHC) and myogenin (MyoG) expression, with MyHC upregulation and concurrent MyoG downregulation. PSMA6 gene overexpression led to the downregulation of AKT1 and Rac1, as well as the activation of the AKT/mTOR pathway, including key factors such as mTOR, p-mTOR, RPS6, p-RPS6, and RhoA. PSMA6 interference resulted in the downregulation of p-mTOR and the upregulation of p-RPS6. Gene expression profiling in our study revealed that the myostatin (MSTN) knockout model significantly reduced the transcriptional levels of the proteasome α6 subunit (PSMA6) (p < 0.05), with the regulatory intensity showing a significant negative correlation with MSTN expression. This molecular evidence substantiates a negative regulatory axis between MSTN and PSMA6. Functional experiments demonstrated that PSMA6 overexpression specifically enhanced myotube formation rates in bovine skeletal muscle satellite cells, whereas siRNA-mediated PSMA6 knockdown exhibited no significant effects on cellular proliferation, indicating the functional specificity of this gene in myogenic differentiation. Mechanistic investigations further revealed that PSMA6 activates the canonical AKT/mTOR signaling transduction cascade through the phosphorylation of AKT and its downstream effector mTOR, thereby mediating the expression of myogenic regulatory factors MyoD and myogenin. Collectively, these findings demonstrate that MSTN deficiency alleviates the transcriptional repression of PSMA6, remodels skeletal muscle differentiation-associated signaling networks, and ultimately drives the directional differentiation of satellite cells toward myofiber specification. Full article

The neurotrophic system includes neurotrophins, such as brain-derived neurotrophic factor (BDNF) and its precursor proBDNF, which play conflicting roles in neuronal survival and apoptosis, with their balance having a significant impact on neurodegenerative outcomes. While BDNF is widely acknowledged as a potent neurotrophin that promotes neuronal survival and differentiation, its precursor, proBDNF, has the opposite effect, promoting apoptosis and neuronal death. This review highlights the new and unique aspects of BDNF/proBDNF interaction in the modulation of neuronal apoptotic pathways in neurodegenerative disorders. It systematically discusses the cross-talk in apoptotic signaling at the molecular level, whereby BDNF activates survival pathways such as PI3K/Akt and MAPK/ERK, whereas proBDNF activates p75NTR and sortilin to induce neuronal apoptosis via JNK, RhoA, NFkB, and Rac-GTPase pathways such as caspase activation and mitochondrial injury. Moreover, this review emphasizes the factors that affect the balance between proBDNF and BDNF levels within the context of neurodegeneration, including proteolytic processing, the expression of TrkB and p75NTR receptors, and extrinsic gene transcription regulators. Cellular injury, stress, or signaling pathway alterations can disrupt the balance of BDNF/proBDNF, which may be involved in apoptotic-related neurodegenerative diseases like Alzheimer’s, Parkinson’s, and Huntington’s diseases. This review provides a comprehensive framework for targeting neurotrophin signaling in the development of innovative therapies for neuronal survival and managing apoptotic-related neurodegenerative disorders, addressing the mechanistic complexity and clinical feasibility of BDNF/proBDNF interaction. Full article

Poria cocos extract attenuates MK-801-induced hyperactivity via RhoA/ROCK1 pathway modulation in mice. Background/Objectives: Poria cocos (P. cocos), a traditional East Asian medicinal mushroom, serves as a medicine and nutritional supplement, has been used to improve sleep and mood. Its bioactive compounds may regulate calcium signaling and Rho family proteins, which are linked to cytoskeletal remodeling and psychiatric symptoms. This study investigated the effects of P. cocos ethanol extract (PCEE) on Rho signaling, cytoskeleton dynamics, and behavior in MK-801-treated cells and mice. Methods: PCEE components were analyzed using HPLC. IMR-32 and Neuro2A cells were treated with MK-801 and PCEE to assess changes in F-actin (via fluorescence staining), cell migration (wound healing and Transwell assays), and Rho signaling proteins (by immunoblotting). In vivo, C57BL/6 mice received MK-801 to induce hyperactivity, followed by PCEE treatment. RhoA/ROCK1 pathway protein levels in the prefrontal cortex were analyzed. Results: PCEE reversed MK-801-induced inhibition of cell migration, F-actin disruption, and dysregulation of Rho-related proteins (RhoGDI1, RhoA, CDC42, Rac1, ROCK1, MLC2, PFN1). In mice, PCEE significantly reduced MK-801-induced hyperactivity and normalized RhoA/ROCK1 signaling in the brain. Conclusion: PCEE modulates cytoskeletal dynamics by regulating RhoA/ROCK1 signaling and attenuates MK-801-induced behavioral and molecular changes, suggesting its therapeutic potential for psychosis with fewer adverse effects. 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

Several molecular pathways are likely involved in the regulation of cancer stem cells (CSCs) via Ras-associated C3 botulinum toxin substrate 2, RAC2, and pituitary tumor-transforming gene 1 product, PTTG1, given their roles in cellular signaling, survival, proliferation, and metastasis. RAC2 is a member of the Rho GTPase family and plays a crucial role in actin cytoskeleton dynamics, reactive oxygen species production, and cell migration, contributing to epithelial–mesenchymal transition (EMT), immune evasion, and therapy resistance. PTTG1, also known as human securin, regulates key processes such as cell cycle progression, apoptosis suppression, and EMT, promoting metastasis and enhancing cancer cell survival. This article aims to describe the molecular pathways involved in the proliferation, invasiveness, and drug response of cancer cells through RAC2 and PTTG1, aiming to clarify their respective roles in neoplastic process dependencies. Both proteins are involved in critical signaling pathways, including PI3K/AKT, TGF-β, and NF-κB, which facilitate tumor progression by modulating CSC properties, angiogenesis, and immune response. This review highlights the molecular mechanisms by which RAC2 and PTTG1 influence tumorigenesis and describes their potential and efficacy as prognostic biomarkers and therapeutic targets in managing various neoplasms. 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

A Rho-GTPases are pivotal regulators of key cellular processes implicated in colorectal cancer (CRC) progression, yet the roles of their regulatory proteins, particularly GTPase-activating proteins (GAPs), remain poorly understood. This study focuses on β2-chimaerin, a Rac1-specific GAP, in Apc-driven tumorigenesis using the ApcMin/+ mouse model. We demonstrate that β2-chimaerin deficiency selectively promotes the growth of colonic polyps without influencing small intestinal polyp formation. Mechanistically, β2-chimaerin loss is associated with enhanced ERK phosphorylation, while canonical Wnt/β-catenin and E-cadherin pathways remain unaffected, suggesting its specific involvement in modulating proliferative signaling in the colon. Consistent with its tumor-suppressive role, bioinformatics analyses reveal that low β2-chimaerin expression correlates with poor prognosis in CRC patients. This study expands the understanding of Rho-GTPase regulatory mechanisms in intestinal tumorigenesis, providing a basis for future therapeutic strategies targeting Rho-GTPase pathways in CRC. Full article

The p21-activated kinases (PAKs) are a conserved family of serine/threonine protein kinases, which are effectors for the Rho family GTPases, namely, Rac/Cdc42. PAKs are divided into two groups: group I (PAK1–3) and group II (PAK4–6). Both groups of PAKs have been well studied in apoptosis, protein synthesis, glucose homeostasis, growth (proliferation and survival) and cytoskeletal regulation, as well as in cell motility, proliferation and cycle control. However, little is known about the role of PAKs in the secretory tissues, including in exocrine tissue, such as the exocrine pancreas (except for islet function and pancreatic cancer growth). Recent studies have provided insights supporting the importance of PAKs in exocrine pancreas. This review summarizes the recent insights into the importance of PAKs in the exocrine pancreas by reviewing their presence and activation; the ability of GI hormones/neurotransmitters/GFs/post-receptor activators to activate them; the kinetics of their activation; the participation of exocrine-tissue PAKs in activating the main growth-signaling cascade; their roles in the stimulation of enzyme secretion; finally, their roles in pancreatitis. These insights suggest that PAKs could be more important in exocrine/secretory tissues than currently appreciated and that their roles should be explored in more detail in the future. 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