Search Results (209)

Membrane curvature is a fundamental biophysical property of cellular membranes that underlies essential processes such as vesicle formation, organelle shaping, intracellular trafficking, and membrane scission. While traditionally studied in the context of cell biology and membrane dynamics, membrane curvature is now emerging as a critical, albeit underrecognized, regulator of oncogenic transformation and tumor progression. Curvature not only governs the mechanical properties of the membrane but also influences the spatial localization and activation of key signaling proteins, including Ras family GTPases, whose oncogenic functions are closely dependent on membrane topology. Cancer is frequently associated with disruptions in the regulation of membrane curvature as a result of aberrant lipid metabolism, overexpression of curvature-modulating proteins, and cytoskeletal remodeling. These changes facilitate the hallmarks of malignancy such as uncontrolled proliferation, enhanced motility, immune evasion, metabolic rewiring, and therapy resistance. Notably, recent evidence reveals that curvature acts as a spatial cue for Ras activation, particularly during epithelial-to-mesenchymal transition (EMT), where curvature-driven Ras relocalization amplifies growth factor signaling and promotes metastasis. This review provides a comprehensive overview of the molecular determinants that generate and sense membrane curvature from lipid shape and membrane asymmetry, BAR domain proteins, and actin dynamics, and explores how these mechanisms are hijacked in cancer. We describe the feedback between membrane architecture and oncogenic pathways such as Ras/MAPK and PI3K/AKT, emphasizing the role of curvature in shaping signal transduction platforms. It should be noted that “curvature-driven signaling” is defined as signaling regulation that arises from membrane-geometry-dependent localization, clustering, or activation of signaling proteins, while “curvature-sensitive platforms” refer to membrane subdomains whose specific curvature selectively recruits and stabilizes signaling complexes. Furthermore, we examine how these biophysical alterations impact vesicular trafficking, organelle morphology, and secretion, all of which are co-opted to support tumor development. From a translational standpoint, we assess emerging therapeutic strategies designed to target curvature-regulating factors and leverage membrane topology for precision drug delivery. Innovations in nanomedicine, super-resolution imaging, and curvature-sensing biosensors are also discussed as tools for both diagnostics and therapeutic monitoring. By integrating advances in membrane biophysics, cancer signaling, and bioengineering, this review highlights membrane curvature as a central and actionable dimension of cancer biology. Full article

Transport of Golgi-localized proteins from the ER is mediated by the coat protein complex II (COPII) and its members, COPII inner coat subunit Sec24 and Secretion-associated Ras-related GTPase 1 (Sar1). Sar1 and Sec24 recognize cytosolic N-termini of glycosyltransferases (GTs) that contain peptide signals required for incorporation into COPII-coated vesicles. Xyloglucan Xylosyltransferases (XXTs) are required for xyloglucan (XyGs) biosynthesis and must be transported to the Golgi for proper function. In this study, we demonstrated that XXTs interact with AtSar1 in the COPII complex but not with AtSec24, which was previously reported to be the main recruiter of cargo proteins into COPII-coated vesicles. The mutation of the arginine to glutamine residues of di-arginine motifs in the N-termini of XXTs caused protein mislocalization and significantly reduced the strength of the interaction with AtSar1. These mutations caused 90% of XXTs to either remain in the ER or localize to small non-Golgi compartments. In turn, such mislocalization significantly suppressed the recovery of XyGs biosynthesis in Arabidopsis thaliana (Arabidopsis) mutants (xxt1xxt2 and xxt3xxt4xxt5), failing to restore their root phenotypes to normal. Our results demonstrate the interaction between cargo and AtSar1, highlighting the critical role of di-arginine motifs in this interaction. These results provide new insights into the mechanism of ER-to-Golgi delivery of plant GTs, which significantly advances our understanding of polysaccharide biosynthesis in the Golgi and the enzymes responsible for it. Full article

Background/Objectives: Neurofibromatosis Type 1 (NF1) is a genetic syndrome caused by pathogenic NF1 variants encoding neurofibromin, a Ras GTPase activating protein. Individuals with NF1 develop peripheral nerve sheath tumors called neurofibromas. Approximately 50% of NF1 patients develop plexiform neurofibromas (pNFs) which have up to 13% lifetime risk of transformation into malignant peripheral nerve sheath tumors (MPNSTs). Current therapeutic strategies emphasize surgical resection with wide margins, radiation, and traditional chemotherapy for unresectable MPNSTs. However, NF1 patients diagnosed with MPNSTs have 5-year survival rates as low as 16%. The two recently FDA-approved drugs for pNFs, the MEK inhibitors selumetinib and mirdametinib, are not used to prevent or treat MPNSTs. Methods: The MEK inhibitor trametinib and the dual HDAC/PI3K inhibitor fimepinostat were assessed for growth inhibitory effects in nine unique patient-derived MPNST cell lines, as both drugs have preclinical efficacy in other Schwann cell-derived tumors. Results: Trametinib, which is approved for malignant melanomas, promoted cell death in 7/9 MPNST cell lines with a geometric mean GI50 = 17 nM. When directly compared to selumetinib and mirdametinib in a subset of four MPNST cell lines, trametinib had the lowest mean GI50 (trametinib = 38 nM, mirdametinib = 1.6 µM, selumetinib = 4.9 µM). Trametinib was also superior to selumetinib and mirdametinib in blocking ERK1/2 phosphorylation for 24 h. Fimepinostat promoted cell death in all cell lines with a geometric mean GI50 = 17 pM. Conclusions: These studies demonstrate in vitro efficacy for two candidate MPNST therapeutics which could reduce tumor burden and metastasis in NF1 patients. Full article

RhoA (Ras homolog A) is a prominent member of the Rho GTPase family, playing a key role in various cellular processes such as cytoskeletal dynamics, cell migration, and immune responses. However, its function in red swamp crayfish remains unclear. In this study, it is proposed that RhoA may regulate the innate immune response in P. clarkii. The gene was fully characterized as PcRhoA in P. clarkii. The results showed that the open reading frame (ORF) of PcRhoA is 663 bp, encoding a 220-amino acid protein with a conserved Rho domain of 174 amino acids. Phylogenetic analysis placed PcRhoA close to Cherax quadricarinatus RhoA. RT-qPCR analysis revealed high expression levels of the PcRhoA gene in the hepatopancreas, muscle, heart, ovary, and stomach, with lower expression in the blood, intestine, gills, and tentacle gland. Furthermore, PcRhoA mRNA transcript was significantly upregulated in the intestine following LPS and Poly I:C challenges. Knockdown of PcRhoA suppressed the expression of downstream genes in the immune signaling pathway. These results indicate that PcRhoA appears to play a pivotal role in regulating the immune response of crayfish. Full article

Central nervous system (CNS) tumors consist of a diverse set of malignancies that remain clinically challenging due to their biological complexity, high morbidity, and limited responsiveness to current therapies. A growing body of genomic evidence has revealed that dysregulation of the mitogen-activated protein kinase (MAPK) signaling pathway is a recurrent and unifying characteristic across many pediatric and adult CNS tumor entities. Alterations affecting upstream receptor tyrosine kinases (RTKs), RAS GTPases, RAF kinases, and other associated regulators contribute to MAPK signaling pathway hyperactivation, shaping tumor behavior, therapy response and resistance. These aberrations ranging from hotspot mutations such as BRAF V600E and oncogenic fusions like BRAF–KIAA1549 are particularly enriched in gliomas and glioneuronal tumors, highlighting MAPK signaling as a key oncogenic driver. The expanding availability of molecularly targeted compounds, including selective inhibitors of RAF, MEK and ERK, has begun to transform treatment approaches for specific molecular subtypes. However, the clinical benefit of MAPK-directed therapies is frequently limited by restricted blood–brain barrier (BBB) penetration, intratumoral heterogeneity, parallel pathway reactivation, and an immunosuppressive tumor microenvironment (TME). In this review, we synthesize current knowledge on MAPK pathway alterations in CNS tumors and evaluate the therapeutic landscape of MAPK inhibition, with emphasis on approved agents, emerging compounds, combination strategies, and novel drug-delivery technologies. We also discuss mechanisms that undermine treatment efficacy and highlight future directions aimed at integrating MAPK-targeted therapy into precision-based management of brain tumors. Full article

Mutations in the NF1 gene cause Neurofibromatosis Type 1 (NF1), one of the most common genetic disorders. This gene encodes neurofibromin, a member of the GTPase-activating protein (GAP) family that functions as a negative regulator of RAS signaling. Loss of NF1 function leads to persistent RAS activation and promotes tumor growth. The clinical manifestations of NF1 mainly include pigmentary changes, benign and malignant peripheral nerve sheath tumors, as well as gliomas affecting the central nervous system. Currently, MEK inhibition is the only approved therapy and is primarily effective in controlling plexiform neurofibromas (pNFs). However, more comprehensive treatments are needed to address the full spectrum of NF1 manifestations and malignant transformation. Novel therapeutic strategies, including AAV-based gene therapy aimed at restoring NF1 function, oncolytic herpes simplex virus (oHSV) therapy targeting RAS-dysregulated tumor cells, and chimeric antigen receptor T cell (CAR-T) therapy targeting NF1-associated tumors, are under active investigation. In this review, we explore the genetic mechanisms underlying NF1 and highlight recent advances in therapeutic development with a special focus on AAV-based gene therapies alongside other approaches with recent clinical and translational advancements. Full article

Background: Lipoprotein(a) [Lp(a)]-induced inflammation contributes to coronary artery spasm (CAS) by the contraction of vascular smooth muscle cells. However, the interaction between Lp(a) and soluble CD36 (sCD36)/interleukin (IL)-6/RAS Homolog Family Member A (RhoA)-GTP signaling pathway has not been evaluated. Methods: We investigated the relevance of Lp(a)/CD36 signaling in CAS patient monocyte-derived macrophages (PMDMs) and a human coronary artery smooth muscle cell (HCASMC) line using expression profile correlation analyses, molecular docking, RNA sequencing, flow cytometry, immunoblotting, and quantitative reverse transcription polymerase chain reaction. Results: Plasma Lp(a) and sCD36 levels in 41 CAS patients were significantly higher (p = 0.001) and positively correlated (r² = 0.3145, p < 0.001), a trend not observed in 36 non-CAS controls. RNA sequencing indicated a significant co-overexpression of CD36 and RhoA in Lp(a)-treated CAS PMDMs and HCASMCs, of which the mRNA and protein expression of CD36 and RhoA were significantly enhanced (p < 0.001) dose-dependently. Lp(a) rather than LDL preferentially induced CD80+ PMDM (M1) polarization. In HCASMCs, the CD36 knockdown using either short hairpin RNA or natural biflavonoid amentoflavone suppressed Lp(a)-upregulated protein expression of CD36, RhoA-GTP, IL-6, tumor necrosis factor (TNF)-α, nuclear factor (NF)-κB, and CD80; however, overexpressed CD36 increased their levels. Lp(a) decreased and amentoflavone increased the epigenetic expression of CD36 inhibitors, miR-335-5p, and miR-448, respectively. Reciprocally, an miRNA inhibitor or mimic could magnify or diminish Lp(a)-induced CD36, TNF-α, NF-κB and IL-6 expressions in HCASMCs, respectively. Conclusions: Elevated Lp(a) levels upregulate the CD36-dependent TNF-α/NF-κB/IL-6/RhoA-GTP signaling pathway in CAS PMDMs and HCASMCs, indicating that Lp(a)/CD36 inflammatory signaling, HCASMC activation, and macrophage M1 polarization mediate CAS development. Full article

Demyelinating diseases, such as multiple sclerosis, involve oligodendrocyte death, myelin loss, and neuronal death. These processes have been extensively studied, and a causal relationship has been demonstrated between them: destruction of oligodendrocytes results in myelin deficiency, which subsequently leads to neurodegeneration and the consequent loss of sensory, motor, and cognitive functions. Currently, myelinopathies lack fully effective treatments. Available drugs primarily focus on controlling the immune response without directly promoting myelin regeneration or restoring neuronal functionality. Alongside these treatments, pharmaceutical research has increasingly focused on developing therapies that stimulate oligodendroglial lineage differentiation and myelin sheath regeneration. Despite these advances, the lack of suitable preclinical models has been a significant obstacle in evaluating new therapeutic compounds. In this review, we present the main animal models used in the preclinical phase for the study of myelin-related diseases and their role in the development of new therapies. In addition, we highlight the usefulness of R-Ras animal models for assessing the efficacy of compounds that promote oligodendrocyte differentiation. Full article

Oocytes and cumulus cells undergo meiotic resumption and proliferation via gonadotropins and growth factors during maturation, and various small G proteins are activated when COCs undergo physiological changes. This study investigated the influence of gonadotropins and growth factors on Ras and its GTPases during porcine COC maturation. Unmatured COCs were treated with FSH, LH, or EGF for 44 h. The mRNA expression levels of the Ras subfamily (H-Ras, K-Ras, N-Ras, and R-Ras), its GTPases (RASA1 and SOS1), and proliferation factors (ERK, CCNB1, and Cdc2) were analyzed using RT-PCR. In contrast to other Ras subfamilies, R-Ras expression is upregulated during COC maturation. We evaluated the effects of FSH, LH, and EGF at various concentrations that most effectively regulated the expression of R-Ras and GTPases. The results demonstrated that 0.5 µg/mL FSH, 10 IU/mL human chorionic gonadotropin (hCG), and 10 ng/mL EGF effectively enhanced R-Ras expression and cell proliferation. FSH supplementation during porcine COC maturation significantly upregulated R-Ras and ERK expression, independent of LH and EGF, and downregulated Cdc2 expression. These results indicated that FSH regulates R-Ras expression, thereby promoting cell proliferation during COC maturation. These results provide fundamental knowledge for understanding the role of Ras and its family members in the development of follicular environments in pigs. Full article

The global pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has posed unprecedented challenges to public health and economic stability. Central to SARS-CoV-2 pathogenesis is its ability to evade the host immune response by hijacking host pathways via the interaction between viral and host proteins. We identified Ras-GTPase-activating protein SH3 domain-binding protein 1/2 (G3BP1/G3BP2) as a critical host factor that interacts with the viral nucleocapsid (N) protein, emerging from a comparative analysis of proteomic data from multiple studies. We revisited the underlying molecular mechanisms by confirming the residues required for the interaction between G3BP1/G3BP2 and SARS-CoV-2 N protein and showed that this interaction disrupts stress granule formation. Intriguingly, we observed that the ablation of both G3BP1 and G3BP2 enhanced SARS-CoV-2 replication. Our data collectively supports the notion that G3BP1 and G3BP2 play a critical role in modulating the host–virus interface during SARS-CoV-2 infection, and that their multifaceted function in cellular defense extends beyond the stress granule pathway. Full article

Synbiotics can be used to reduce intestinal inflammation and mitigate dysbiosis in dogs with chronic inflammatory enteropathy (CIE). Prior research has not assessed the colonic mucosal ultrastructure of dogs with active CIE treated with synbiotics, nor has it determined a possible association between morphologic injury and signaling pathways. Twenty client-owned dogs diagnosed with CIE were randomized to receive either a hydrolyzed diet (placebo; PL) or a hydrolyzed diet supplemented with synbiotic-IgY (SYN) for 6 weeks. Endoscopic biopsies of the colon were obtained for histopathologic, ultrastructural, and molecular analyses and were compared before and after treatment. Using transmission electron microscopy (TEM), an analysis of the ultrastructural alterations in microvilli length (MVL), mitochondria (MITO), and rough endoplasmic reticulum (ER) was compared between treatment groups. To explore potential signaling pathways that might modulate MITO and ER stress, a transcriptomic analysis was also performed. The degree of mucosal ultrastructural pathology differed among individual dogs before and after treatment. Morphologic alterations in enterocytes, MVL, MITO, and ER were detected without significant differences between PL and SYN dogs prior to treatment. Notable changes in ultrastructural alterations were identified post-treatment, with SYN-treated dogs exhibiting significant improvement in MVL, MITO, and ER injury scores compared to PL-treated dogs. Transcriptomic profiling showed many pathways and key genes to be associated with MITO and ER injury. Multiple signaling pathways and their associated genes with protective effects, including fibroblast growth factor 2 (FGF2), fibroblast growth factor 7 (FGF7), fibroblast growth factor 10 (FGF10), synaptic Ras GTPase activating protein 1 (SynGAP1), RAS guanyl releasing protein 2 (RASGRP2), RAS guanyl releasing protein 3 (RASGRP3), thrombospondin 1 (THBS1), colony stimulating factor 1 (CSF1), colony stimulating factor 3 (CSF3), interleukin 21 receptor (IL21R), collagen type VI alpha 6 chain (COL6A6), ectodysplasin A receptor (EDAR), forkhead box P3 (FoxP3), follistatin (FST), gremlin 1 (GREM1), myocyte enhancer factor 2B (MEF2B), neuregulin 1 (NRG1), collagen type I alpha 1 chain (COL1A1), hepatocyte growth factor (HGF), 5-hydroxytryptamine receptor 7 (HTR7), and platelet derived growth factor receptor beta (PDGFR-β), were upregulated with SYN treatment. Differential gene expression was associated with improved MITO and ER ultrastructural integrity and a reduction in oxidative stress. Conversely, other genes, such as protein kinase cAMP-activated catalytic subunit beta (PRKACB), phospholipase A2 group XIIB (PLA2G12B), calmodulin 1 (CALM1), calmodulin 2 (CALM2), and interleukin-18 (IL18), which have harmful effects, were downregulated following SYN treatment. In dogs treated with PL, genes including PRKACB and CALM2 were upregulated, while other genes, such as FGF2, FGF10, SynGAP1, RASGRP2, RASGRP3, and IL21R, were downregulated. Dogs with CIE have colonic ultrastructural pathology at diagnosis, which improves following synbiotic treatment. Ultrastructural improvement is associated with an upregulation of protective genes and a downregulation of harmful genes that mediate their effects through multiple signaling pathways. Full article

Rap1A and Rap1B are closely related small GTPases that regulate endothelial adhesion, vascular integrity, and signaling pathways via effector domain interactions, with downstream effectors controlling integrins and cadherins. Although both isoforms are essential for vascular development, recent studies using endothelial-specific knockout models have uncovered distinct, non-redundant functions. Rap1B is a key regulator of VEGFR2 signaling, promoting angiogenesis, nitric oxide production, and immune evasion in tumors while restraining proinflammatory signaling in atherosclerosis. In contrast, Rap1A unexpectedly functions as a modulator of endothelial calcium homeostasis by restricting Orai1-mediated store-operated calcium entry, thereby limiting inflammatory responses and vascular permeability. New insights into Rap1 regulation highlight the roles of context-specific guanine nucleotide exchange factors, such as RasGRP3, and non-degradative ubiquitination in effector selection. Emerging data suggest that isoform-specific interactions between the Rap1 hypervariable regions and plasma membrane lipids govern their localization to distinct nanodomains, potentially influencing downstream signaling specificity. Together, these findings redefine the roles of Rap1A and Rap1B in endothelial biology and highlight their relevance in diseases such as tumor angiogenesis, atherosclerosis, and inflammatory lung injury. We discuss the therapeutic implications of targeting Rap1 isoforms in vascular pathologies and cancer, emphasizing the need for isoform-specific strategies that preserve endothelial homeostasis. Full article

Axon guidance, a fundamental process in neural circuit formation, is intricately regulated by Fibroblast Growth Factors (FGFs) and their receptors (FGFRs) through dynamic cytoskeletal remodeling. FGF signaling, mediated by heparan sulfate proteoglycans or Klotho co-factors, activates key downstream pathways: PI3K-Akt, JAK-STAT, PLCγ, and RAS-MAPK. These pathways orchestrate actin filament dynamics, microtubule stability, and the organization of intermediate filaments. These pathways converge on Rho GTPases, cofilin, profilin, and tau to balance the cytoskeletal assembly−disassembly cycles, enabling growth cone navigation. Unresolved questions, such as the mechanisms underlying FGF-mediated growth cone steering, highlight critical future research directions. This review integrates structural, molecular, and functional insights into how FGF-FGFR interactions regulate axon pathfinding, emphasizing the crosstalk between signaling cascades and cytoskeletal plasticity. Elucidating these mechanisms not only advances our understanding of neural development but also opens therapeutic avenues for neuro-developmental disorders, nerve injury, and neurodegenerative diseases by targeting FGF-driven cytoskeletal dynamics. Full article

Ras signaling regulates many cellular processes in cancer development. While well-known Ras-related oncogenes, such as KRAS, have been extensively explored, the role of other Ras-related genes in cancer remains poorly studied. Dexamethasone-induced Ras-related protein 1 (RASD1), a member of the Ras superfamily, is widely expressed across various tissues and is involved in inhibiting cell growth and inducing apoptosis, suggesting a potential role as a tumor suppressor. Here, we investigated RASD1 expression across multiple tissues and cancers, utilizing data from The Cancer Genome Atlas (TCGA), Human Protein Atlas, and Genotype-Tissue Expression (GTEx) databases. Our analysis revealed a significant downregulation of RASD1 mRNA expression in several cancer types compared to normal tissues, correlating with low levels of promoter methylation. Interestingly, high RASD1 expression correlated with a favorable prognosis in multiple cancers. Immune cell infiltration analysis indicated that elevated RASD1 expression is associated with an increased infiltration of CD4⁺ T cells and myeloid-derived dendritic cells in cancer. Furthermore, the expression of genes exhibiting similar expression patterns as RASD1 suggest that RASD1 may play a role in interleukin-4-mediated apoptosis and could regulate the transcription of the phosphatase and tensin homolog (PTEN) gene. Overall, these findings suggest that RASD1 may modulate immune signaling and tumor suppressive pathways. Full article

Chronic liver diseases are marked by persistent inflammation and can evolve into liver fibrosis, cirrhosis, and hepatocellular carcinoma. In an affected liver, hepatic stellate cells (HSCs) transition from a quiescent to an activated state and adopt a myofibroblast-like cell phenotype. While these activated cells play a role in supporting liver regeneration, they can also have detrimental effects on liver function as the disease progresses to fibrosis and cirrhosis. These findings highlight the dynamic switching between different signaling pathways involving Ras, Rho GTPases, and Notch signaling. Notably, two specific members of the Ras and Rho GTPases, Eras and Rnd3, are predominantly expressed in quiescent HSCs, while Mras and Rhoc are more abundant in their activated forms. In addition, this study highlights the critical role of cytosolic Notch1 in quiescent HSCs and Rock in activated HSCs. We hypothesize that distinct yet interdependent intracellular signaling networks regulate HSC fate decisions in two key ways: by maintaining HSC quiescence and homeostasis and by facilitating HSC activation, thereby influencing processes such as proliferation, transdifferentiation, and mesenchymal transition. The proposed signaling model, combined with specific methodological tools for maintaining HSCs in a quiescent state, will deepen our understanding of the mechanisms underlying chronic liver disease and may also pave the way for innovative therapies. These therapies could include small molecule drugs targeting Ras- and Rho-dependent pathways. Full article