Signaling Mechanisms Research Articles

Regulation of ER stress-induced apoptotic and inflammatory responses via YAP/TAZ-mediated control of the TRAIL-R2/DR5 signaling pathway.

In tumors, cancer cells are frequently exposed to adverse environmental conditions that result in endoplasmic reticulum (ER) stress. Mechanical signals emerging from extracellular matrix (ECM) rigidity and cell shape regulate the activity of transcriptional co-activators Yes-associated protein (YAP) and its paralog Transcriptional Coactivator with PDZ-binding motif (TAZ). However, the role of ECM rigidity and YAP/TAZ in tumor cell fate decisions under ER stress remains relatively unexplored. Our results suggest that the YAP/TAZ system plays an important role in the control of ER stress-induced cell death by mechanical signaling arising from ECM stiffness in tumor cells. Mechanistically, YAP/TAZ regulates apoptosis induced by ER stress in tumor cells by controlling the activation of the TRAIL-R2/DR5-mediated extrinsic apoptotic pathway through a dual mechanism. On the one hand, the YAP/TAZ system prevents intracellular TRAIL-R2/DR5 clustering in tumor cells. On the other hand, it inhibits cFLIP down-regulation in tumor cells experiencing ER stress. In addition, YAP/TAZ controls the expression of pro-inflammatory interleukin-8 (IL-8/CXCL8) in tumor cells undergoing ER stress by a TRAIL-R2/DR5/caspase-8-dependent mechanism. Although other mechanisms may also be involved in controlling cell death and inflammation in tumor cells facing environmental stress, our results support a model in which regulation of the subcellular localization and activity of the YAP/TAZ transcriptional co-activators could contribute to the microenvironmental control of cell fate decisions in tumor cells undergoing ER stress.

Modulation of arterial wall remodeling by mechanical stress: Focus on abdominal aortic aneurysm.

The rupture of an abdominal aortic aneurysm (AAA) poses a significant threat, with a high mortality rate, and the mechanical stability of the arterial wall determines both its growth and potential for rupture. Owing to extracellular matrix (ECM) degradation, wall-resident cells are subjected to an aberrant mechanical stress environment. In response to stress, the cellular mechanical signaling pathway is activated, initiating the remodeling of the arterial wall to restore stability. A decline in mechanical signal responsiveness, coupled with inadequate remodeling, significantly contributes to the AAA's progressive expansion and eventual rupture. In this review, we summarize the main stresses experienced by the arterial wall, emphasizing the critical role of the ECM in withstanding stress and the importance of stress-exposed cells in maintaining mechanical stability. Furthermore, we will discuss the application of biomechanical analyses as a predictive tool for assessing AAA stability.

Interspecies signaling modulates the biosynthesis of antimicrobial secondary metabolites related to biological control activities of Pseudomonas fluorescens 2P24.

Rhizosphere microorganisms release vital signals that shape microbial communities, with antibiotics at low concentrations acting as intra- and interspecies signals. However, the mechanisms of these signals in coordinating gene expression are unclear. In non-pyoluteorin-producing Pseudomonas fluorescens 2P24, pyoluteorin was identified as an interspecies signal that regulates the phl biosynthesis gene cluster for 2,4-DAPG production. TetR family repressors PhlH and PhlF were found to positively regulate 2,4-DAPG hydrolysis and negatively regulate its synthesis in response to pyoluteorin. Structural modeling and docking analyses revealed the interactions between pyoluteorin and both PhlH and PhlF, modulating gene expression. Phylogenetic analyses showed a wide distribution of PhlH and PhlF across Pseudomonas spp. with conserved ligand-binding domains. These findings deepen our understanding of interspecies signaling mechanisms and highlight the potential for designing co-inhabiting Pseudomonas spp. as effective biocontrol agents.

Evolutionary dynamics of nitrate uptake, assimilation, and signalling in plants: adapting to a changing environment.

Nitrogen (N) is a crucial macronutrient for plant growth, with nitrate as a primary inorganic N source for most plants. Beyond its role as a nutrient, nitrate also functions as a signalling molecule, influencing plant morphogenetic development. While nitrate utilization and signalling mechanisms have been extensively studied in model plants, the origin, evolution, and diversification of core components in nitrate uptake, assimilation, and signalling remain largely unexplored. In our investigation, we discovered that deep sea algae living in low nitrate conditions developed a high-affinity transport system (HATS) for nitrate uptake and a pathway of nitrate primary assimilation (NR-NiR-GS-GOGAT). In contrast, low-affinity transport systems (LATS) and the plastid GS originated from the ancestors of land and seed plants, respectively. These adaptations facilitated amino acid acquisition as plants conquered terrestrial environments. Furthermore, the intricate nitrate signalling, relying on NRT1.1 and NLP7, evolved stepwise, potentially establishing systematic regulation in bryophytes for self-regulation under complex terrestrial nitrate environments. As plants underwent terrestrialization, they underwent adaptive changes to thrive in dynamic nitrate environments, continually enhancing their nitrate uptake, assimilation, and signal transduction abilities.

Toward a clear relationship between mechanical signals and bone adaptation

Toward a clear relationship between mechanical signals and bone adaptation

Lactylation-driven ALKBH5 diminishes macrophage NLRP3 inflammasome activation in patients with G6PT deficiency.

Neutropenia represents an important clinical problem in patients with glycogen storage disease type Ib (GSD-Ib), characterized by genetic deficiency in glucose-6-phosphate translocase (G6PT/SLC37A4). However, the role of G6PT in macrophages has not been elucidated. We sought to investigate the function of G6PT in macrophage inflammation. Functional assays (including immunoblotting, real-time quantitative polymerase chain reaction, flow cytometry, immunofluorescence staining, and enzyme linked immunosorbent assay) and RNA sequencing were performed. We find that macrophages from patients deficient in G6PT exhibited diminished NLRP3 inflammasome activation. Mechanistically, deficiency of G6PT promotes glycolysis and lactate production in macrophages. Lactate accumulation potently induces ALKBH5 upregulation via H3K18 lactylation. ALKBH5 decreases m6A modification on NLRP3 mRNA, attenuating its transcript stability and thus inhibiting inflammasome activation. Furtherly, treating G6PT-deficient macrophages with an inhibitor of the lactate dehydrogenase to lower their lactate levels restores NLRP3 inflammasome activation and rescues bacterial handling defect. These findings unveil a previously unknown pathogenic mechanism of lactylation-driven defective NLRP3 inflammasome signaling and subsequent impaired antimicrobial activity as driving factors in these inflammatory disorders, and indicates glycolysis/lactate/histone lactylation cascade as a potential therapeutic target for GSD-Ib.

Site-specific analysis and functional characterization of N-linked glycosylation for β-Klotho protein.

β-Klotho (KLB), a type I transmembrane protein, serves as an obligate co-receptor determining the tissue-specific actions of endocrine fibroblast growth factors (FGFs). Despite accumulative evidence suggesting the occurrence of N-glycosylation in the KLB protein, the precise N-glycosites, glycoforms, and the impacts of N-glycosylation on the expression and function of the KLB protein remain unexplored. Employing a mass spectrometry-based approach, a total of 12 N-glycosites displaying heterogeneous site occupancy and glycoforms were identified within the extracellular region of the recombinant human KLB protein. Molecular simulation revealed negligible impact of these N-glycans on the overall structure of the KLB protein. However, both pharmacological inhibition of N-glycosylation and mutagenesis targeting N-glycosites reduced mature KLB protein content without impacting KLB mRNA synthesis in cells, underscoring the critical role of N-glycosylation in maintaining the stability of the KLB protein. Further studies revealed that the underglycosylated KLB mutant underwent rapid degradation via both lysosomal and proteasomal pathways and was unable to be efficiently trafficked to the plasma membrane, leading to impaired FGF21 signaling transduction. Collectively, multisite N-glycosylation is essential for the stability and cell surface localization of the KLB protein, representing a novel modulatory mechanism of endocrine FGF signaling.

Adipokines regulate the development and progression of MASLD through organellar oxidative stress.

The prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD), which is increasingly being recognized as a leading cause of chronic liver pathology globally, is increasing. The pathophysiological underpinnings of its progression, which is currently under active investigation, involve oxidative stress. Human adipose tissue, an integral endocrine organ, secretes an array of adipokines that are modulated by dietary patterns and lifestyle choices. These adipokines intricately orchestrate regulatory pathways that impact glucose and lipid metabolism, oxidative stress, and mitochondrial function, thereby influencing the evolution of hepatic steatosis and progression to metabolic dysfunction-associated steatohepatitis (MASH). This review examines recent data, underscoring the critical interplay of oxidative stress, reactive oxygen species, and redox signaling in adipokine-mediated mechanisms. The role of various adipokines in regulating the onset and progression of MASLD/MASH through mitochondrial dysfunction and endoplasmic reticulum stress and the underlying mechanisms are discussed. Due to the emerging correlation between adipokines and the development of MASLD positions, these adipokines are potential targets for the development of innovative therapeutic interventions for MASLD management. A comprehensive understanding of the pathogenesis of MASLD/MASH is instrumental for identifying therapies for MASH.

Phosphoproteomics for studying signaling pathways evoked by hormones of the renin-angiotensin system: A source of untapped potential.

The Renin-Angiotensin System (RAS) is a complex neuroendocrine system consisting of a single precursor protein, angiotensinogen (AGT), which is processed into various peptide hormones, including the angiotensins [Ang I, Ang II, Ang III, Ang IV, Ang-(1-9), Ang-(1-7), Ang-(1-5), etc] and Alamandine-related peptides [Ang A, Alamandine, Ala-(1-5)], through intricate enzymatic pathways. Functionally, the RAS is divided into two axes with opposing effects: the classical axis, primarily consisting of Ang II acting through the AT1 receptor (AT1R), and in contrast the protective axis, which includes the receptors Mas, AT2R and MrgD and their respective ligands. A key area of RAS research is to gain a better understanding how signaling cascades elicited by these receptors lead to either "classical" or "protective" effects, as imbalances between the two axes can contribute to disease. On the other hand, therapeutic benefits can be achieved by selectively activating protective receptors and their associated signaling pathways. Traditionally, robust "hypothesis-driven" methods like Western blotting have built a solid knowledge foundation on RAS signaling. In this review, we introduce untargeted mass spectrometry-based phosphoproteomics, a "hypothesis-generating approach", to explore RAS signaling pathways. This technology enables the unbiased discovery of phosphorylation events, offering insights into previously unknown signaling mechanisms. We review the existing studies which used phosphoproteomics to study RAS signaling and discuss potential future applications of phosphoproteomics in RAS research including advantages and limitations. Ultimately, phosphoproteomics represents a so far underused tool for deepening our understanding of RAS signaling and unveiling novel therapeutic targets.

Gastroprotective effect of fucoidan from Sargassum siliquastrum against ethanol-induced gastric mucosal injury.

The ethanol-induced BALB/c mice and human gastric epithelial cell (Ges-1 cell) models were used to investigate the Sargassum siliquastrum fucoidan (SFuc) gastroprotective capability. The injury score and histopathological sections of the stomach were used to evaluate the gastroprotective capability. The western blotting and RT-PCR methods determined the signaling mechanism of mice's gastric injury. SFuc is fucoidan with a molecular weight of 300.7 and 25.1kDa. The injury score and ulcer index of the SFuc-200 group decreased by 3.85 and 2.06 folds in contrast with the Model group, respectively. The findings indicated that SFuc reduced oxidative stress and inflammatory factor expression in the gastric mucosa by downregulating the levels of associated genes within the TLR-4, MyD88, and MAPK/NF-κB signaling pathways. Meanwhile, the SFuc-200 group promoted the expressions of EGF and PGE 2 by 1.53 and 1.52 folds, respectively. Together with the expression inhibition of p38, ERK, JNK, and NF-κB proteins in gastric tissue to help for differentiation of gastric cells. In addition, SFuc significantly reduced apoptosis occurrence in mice and Ges-1 cells. Our study provides potential mechanism clues of the SFuc's resistance to ethanol-induced gastric mucosal damage, suggesting its potential functional food for gastric protection.

Multiomic analysis uncovers a continuous spectrum of differentiation and Wnt-MDK-driven immune evasion in hepatoblastoma.

Hepatoblastoma is the most common pediatric cancer of the liver and the majority of cases display activating mutations in the Wnt/β-catenin pathway. Understanding the complex milieu of the tumor microenvironment has resulted in promising new therapies for adult cancers, but similar approaches in pediatric cancers are still lacking. We aimed to provide a comprehensive analysis of the tumor microenvironment of hepatoblastoma unveiling its spatial architecture and key signaling mechanisms. Single-cell/-nucleus RNA-seq (n=15), spatial transcriptomics (n=22), and multiplex immunofluorescence stainings (n=7) of treated, untreated, and metastasized pediatric hepatoblastomas were performed. An RNA-seq validation cohort (n=110) including hepatoblastoma, non-tumor and fetal liver samples and single-cell RNA-seq data of healthy immune cells were used for further analysis. Western blotting and RNA-seq of hepatoblastoma and macrophage cell lines were conducted for experimental validation. Of four identified transcriptional tumor programs, "Developmental" and "Metabolic" reflected different hepatic differentiation stages, while "Cycling" was enriched in undifferentiated cells and relapsed samples, and "Intermediate" displayed high activity in samples from patients with poor outcomes. We discovered an increased ratio of anti- to pro-inflammatory immune cells and evidence of immune exclusion from tumor areas. Wnt-responsive upregulation of the immunomodulator midkine in hepatoblastoma cells was associated with a change in macrophage phenotype, which could be partially reversed through midkine inhibition. Hepatoblastoma cells exist along a continuous spectrum of hepatic differentiation and inhabit an altered immune environment. Wnt signaling augments midkine expression, which appears to be involved in shaping the immune environment by modifying macrophages to enable immune evasion, thereby providing a potential therapeutic target. Despite hepatoblastoma being the most common pediatric liver cancer, there has been a critical knowledge gap in understanding how the tumor microenvironment and immune landscape contribute to disease progression. Our novel findings, revealing a continuous spectrum of tumor differentiation states and Wnt-MDK-driven immune evasion, are significant for pediatric oncology clinicians and researchers, improving our functional understanding of the immune environment of hepatoblastoma. The identification of midkine as a tumor-specific immunomodulator suggests a potential for developing new targeted therapies, though further mechanistic and practical validation would be needed to realize clinical translation of these findings.

Assembly and functional mechanisms of plant NLR resistosomes.

Nucleotide-binding and leucine-rich repeat (NLR) proteins are essential intracellular immune receptors in both animal and plant kingdoms. Sensing of pathogen-derived signals induces oligomerization of NLR proteins, culminating in the formation of higher-order protein complexes known as resistosomes in plants. The NLR resistosomes play a pivotal role in mediating the plant immune response against invading pathogens. Over the past few years, our understanding of NLR biology has significantly advanced, particularly in the structural and biochemical aspects of the NLR resistosomes. Here, we highlight the recent advancements in the structural knowledge of how NLR resistosomes are activated and assembled, and how the structural knowledge provides insights into the biochemical functions of these NLR resistosomes, which converge on Ca2+ signals. Signaling mechanisms of the resistosomes that underpin plant immunity are also briefly discussed.

Targeting SIRT1 by Scopoletin to Inhibit XBB.1.5 COVID-19 Life Cycle.

Natural products have historically driven pharmaceutical discovery, but their reliance has diminished with synthetic drugs. Approximately 35% of medicines originate from natural products. Scopoletin, a natural coumarin compound found in herbs, exhibits antioxidant, hepatoprotective, antiviral, and antimicrobial properties through diverse intracellular signaling mechanisms. Furthermore, it also enhances the activity of antioxidants. Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) causes viral pneumonia through cytokine storms and systemic inflammation. Cellular autophagy pathways play a role in coronavirus replication and inflammation. The Silent Information Regulator 1 (SIRT1) pathway, linked to autophagy, protects cells via FOXO3, inhibits apoptosis, and modulates SIRT1 in type-II epithelial cells. SIRT1 activation by adenosine monophosphate-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR) enhances the autophagy cascade. This pathway holds therapeutic potential for alveolar and pulmonary diseases and is crucial in lung inflammation. Angiotensin-converting enzyme 2 (ACE-2) activation, inhibited by reduced expression, prevents COVID-19 virus entry into type-II epithelial cells. The coronavirus disease 2019 (COVID-19) virus binds ACE-2 to enter into the host cells, and XBB.1.5 COVID-19 displays high ACE-2-binding affinity. ACE-2 expression in pneumocytes is regulated by signal transducers and activators of transcription-3 (STAT3), which can increase COVID-19 virus replication. SIRT1 regulates STAT3, and the SIRT1/STAT3 pathway is involved in lung diseases. Therapeutic regulation of SIRT1 protects the lungs from inflammation caused by viral-mediated oxidative stress. Scopoletin, as a modulator of the SIRT1 cascade, can regulate autophagy and inhibit the entry and life cycle of XBB.1.5 COVID-19 in host cells.

Missense mutations of the ephrin receptor EPHA1 associated with Alzheimer's disease disrupt receptor signaling functions.

Missense mutations in the EPHA1 receptor tyrosine kinase have been identified in Alzheimer's patients. To gain insight into their potential role in disease pathogenesis, we investigated the effects of four of these mutations. We show that the P460L mutation in the second fibronectin type III (FN2) domain drastically reduces EPHA1 cell surface localization while increasing tyrosine phosphorylation of the cell surface-localized receptor. The R791H mutation in the kinase domain abolishes EPHA1 tyrosine phosphorylation, indicating abrogation of kinase-dependent signaling. Furthermore, both mutations decrease EPHA1 phosphorylation on S906 in the kinase-SAM linker region, suggesting impairment of a noncanonical form of signaling regulated by serine/threonine kinases. The R492Q mutation, also in the FN2 domain, has milder effects than the P460L mutation while the R926C mutation in the SAM domain increases S906 phosphorylation. We also found that EPHA1 undergoes constitutive proteolytic cleavage in the FN2 domain, generating a soluble 55kDaN-terminal fragment containing the ligand-binding domain and a transmembrane 60kDaC-terminal fragment. The 60kDa WT fragment is phosphorylated on both tyrosine residues and S906, suggesting signaling functions. The P460L mutant 60kDa fragment undergoes proteasomal degradation and the R791H mutant fragment lacks tyrosine phosphorylation and has decreased S906 phosphorylation. These findings advance our understanding of EPHA1 signaling mechanisms and support the notion that alterations in EPHA1 signaling due to missense mutations contribute to Alzheimer's disease pathogenesis.

ECM stiffness regulates lung fibroblast survival through RasGRF1-dependent signaling.

Extracellular matrix stiffness is one of the multiple mechanical signals that alter cellular behavior. During studies exploring the effect of matrix rigidity on lung fibroblast survival, we discovered that enhanced survival on stiff substrates is dependent on elevated Ras activity, owing to the activation of the guanine nucleotide exchange factor, RasGRF1. Mechanistically, we found that the increased Ras activity lead to the activation of both the AKT and ERK pathways. Pharmacological inhibition of AKT or ERK signaling attenuates the elevated survival observed on stiff substrates. AKT signaling regulates the phosphorylation and inactivation of the transcription factor FOXO3a. RNAi experiments demonstrate that FOXO3a activity is critical for the cell death observed on soft substrates. Additionally, downregulation of FOXO3a activity on stiff substrate leads to the degradation of the proapoptotic protein Bim. Depletion of Bim increased the survival of cells on soft substrates. Together, our data show that enhanced matrix stiffness activates a RasGRF1/Ras signaling cascade that regulates the activity of AKT and ERK-dependent FOXO3a and Bim expression to alter cell survival.

Ephrin-B2 acts as a positive regulator of osteogenesis-angiogenesis coupling.

The aim of this study was to explore the role and potential mechanisms of Ephrin-B2 signaling in osteogenesis-angiogenesis coupling and to provide guidance for periodontal tissue engineering. Considering the close relationship between periodontitis and periodontal bone defects, single-cell transcriptomic data from periodontal tissues in published databases (GEO number: GSE171213) were analyzed to characterize Ephrin-B2 signaling between osteoblastic lineages and endothelial cells. To observe the effects and mechanisms of Ephrin-B2 in angiogenesis and periodontal bone regeneration, osteoblasts were constructed that overexpress Ephrin-B2 and were then co-cultured with human umbilical vein cells (HUVECs). Single-cell sequencing revealed a deficiency in Ephrin-B2 signaling from osteoblastic lineages in periodontitis, resulting in impaired transduction of Ephrin-B2 signaling between osteoblasts and endothelial cells. In an osteoblast-endothelial cell co-culture system, Ephrin-B2 signaling from osteoblasts promoted angiogenesis. The downstream pathway might be related to VEGFR2-PI3K. The cotransplantation of osteoblasts overexpressing Ephrin-B2 and HUVECs facilitated angiogenesis and new bone generation in vivo. This study confirmed that Ephrin-B2 signaling is an indispensable positive regulatory factor in the osteogenesis-angiogenesis coupling of periodontal tissue remodeling. These findings may help to optimize transplantation strategies and provide a new solution for the targeted treatment of periodontal bone defects. Sufficient vascularization is a prerequisite for periodontal bone regeneration. The co-transplantation of angiogenic endothelial cells and bone-forming cells is a promising tissue engineering strategy. To facilitate the effect of the transplantation, we found evidence of Ephrin-B2 signaling deficiency in osteoblastic lineages and vascular endothelial cells of periodontitis patients from single-cell sequencing data. Moreover, by constructing a co-transplantation system with overexpression of Ephrin-B2, we found its positive role in promoting periodontal vascularized bone regeneration. The present study elucidates the positive role and potential mechanisms of Ephrin-B2 signaling in osteogenic-angiogenic coupling, which will help to promote the effect of periodontal tissue engineering.

Decoding the Implications of Zinc in the Development and Therapy of Leukemia.

Zinc plays a central role in the hematological development. Therapeutic interventions with zinc are shown to improve the health status of patients with malignancies by stimulating the immune system and reducing side effects. Despite the abnormal zinc homeostasis in leukemia, the role and mechanisms of zinc signaling in leukemia development remain poorly understood. Recently, some important breakthroughs are made in laboratory and clinical studies of zinc in leukemia, such as the role of zinc in regulating ferroptosis and the effects of zinc in immunotherapy. Zinc-based strategies are urgently needed to refine the current zinc intervention regimen for side-effect free therapy in chemotherapy-intolerant patients. This review provides a comprehensive overview of the role of zinc homeostasis in leukemia patients and focuses on the therapeutic potential of zinc signaling modulation in leukemia.

Discovery of a MET-driven monogenic cause of steatotic liver disease.

Metabolic dysfunction-associated steatotic liver disease (MASLD) affects about a third of adults worldwide and is projected soon to be the leading cause of cirrhosis. It occurs when fat accumulates in hepatocytes and can progress to metabolic dysfunction-associated steatohepatitis (MASH), liver cirrhosis, and hepatocellular carcinoma. MASLD pathogenesis is believed to involve a combination of genetic and environmental risk factors. Single nucleotide polymorphisms have been implicated but non-syndromic monogenic causes are lacking. We identified a novel genetic variant in a familial case of MASH and performed deep variant functional analysis including protein modeling, dynamics, and cell-based assays to assess molecular mechanisms of dysfunction and altered cellular signaling. We analyzed exome sequencing data of 3,904 individuals with steatotic liver disease (SLD) to identify additional cases and establish the link between specific gene variants and SLD diagnosis. We discovered and functionally validated the NM_000245.4:c.3505A>T; p.(Ile1169Phe) variant in the MET (mesenchymal epithelial transition) kinase domain as a monogenic cause of SLD. Subsequently, we detected additional ultra-rare, previously un-interpreted, and likely deleterious variants in MET from screening sequencing data. Among individuals with confirmed SLD based on electronic record review, 1.1% (45/3,904) had rare predicted deleterious MET variants. Eight of 45 (17.7%) individuals had predicted deleterious variants in the MET kinase domain confirmed to be functionally like the familial case variant. We report the first germline non-malignant rare MET-driven disease, a monogenic form of SLD.

Advances in the treatment of glioma-related signaling pathways and mechanisms by metformin

Metformin (MET) is a commonly used drug for the treatment of type 2 diabetes in the department of endocrinology. In recent years, due to the few clinically effective treatment options including glioma, some scholars have proposed the possibility of metformin in the treatment of glioma, and studies have shown that metformin has a certain inhibitory effect on this tumor. This review explores the multiple mechanisms through which metformin exerts its antitumor effects, focusing on signaling pathways such as AMPK/mTOR, ferroptosis, autophagy, apoptosis and chloride ion channels (CLIC1). Metformin’s inhibition of glioma proliferation involves complex cellular processes, including mitochondrial dysfunction, increased reactive oxygen species (ROS) production, and modulation of immune responses. Additionally, metformin affects glioma stem cells by inhibiting key pathways, including STAT3, mTOR, and AKT, and altering the tumor microenvironment. While preclinical studies suggest that metformin enhances radiosensitivity and reduces tumor recurrence, its clinical application remains in early stages, with further studies needed to optimize dosing regimens and understand its full therapeutic potential. This review provides a comprehensive analysis of metformin’s molecular mechanisms in glioma treatment and highlights its potential as a novel therapeutic strategy, especially for treatment-resistant gliomas.

Outside-in engineering of cadherin endocytosis using a conformation strengthening antibody

P-cadherin, a crucial cell-cell adhesion protein which is overexpressed in numerous malignant cancers, is a popular target for drug delivery antibodies. However, molecular guidelines for engineering antibodies that can be internalized upon binding to P-cadherin are unknown. Here, we use a combination of biophysical, biochemical, and cell biological methods to demonstrate that trapping the P-cadherin extracellular region in an X-dimer adhesive conformation triggers cadherin endocytosis via an outside-in signaling mechanism. We show that the anti-cancer drug delivery monoclonal antibody CQY684, traps P-cadherin in an X-dimer conformation and strengthens this adhesive structure. Formation of stable X-dimers results in the phosphorylation of p120-catenin, a suppressor of cadherin endocytosis. This triggers the dissociation of p120-catenin from the X-dimer cytoplasmic region, which increases P-cadherin turnover and targets the cadherin-antibody complex to the lysosome. Our results establish an outside-in signaling mechanism that provides fundamental insights into how cells regulate adhesion and that can be exploited by anti-cadherin antibodies for intracellular drug delivery.