Cell Communication and Signaling

Background: While immunotherapies have transformed outcomes in several adult cancers, more than half of pediatric patients with high-risk neuroblastoma fail to achieve sustained responses, resulting in poor outcomes. Therefore, understanding the phenotypic and spatial organization of immune cells within the neuroblastoma tumor microenvironment is essential to identify mechanisms driving immunotherapy failure. Methods: To identify spatial determinants of the neuroblastoma immune landscape that may contribute to treatment failure, we dissected immunoregulatory mechanisms at single-cell and protein levels in neuroblastoma samples from 28 patients, using imaging mass cytometry (IMC, n=14) and high-dimensional spectral flow cytometry (n=18). Results: We characterized four distinct cellular neighborhoods, ranging from tumor-dominant to stromal and immune niches. Macrophages were broadly distributed across these niches. In contrast, T and B cells were largely confined to immune niches, forming immature tertiary lymphoid structure-like aggregates within the tumor and stromal cores. T cells displayed a CD69+ tissue-resident memory phenotype, with an overall reduced cytotoxic profile (in CD8+ T cells) and increased expression of inhibitory receptors (predominantly in CD4+ T cells), indicative of dysfunctional features. Intriguingly, T cell functional states differed between spatial niches, with a TCF7+/Ki-67+ self-renewing profile within immune niches, and increased granzyme B expression in CD8+ T cells in tumor cores. Interaction analysis pinpointed CD163+ macrophages as the dominant immunosuppressive interaction partner of T cells, particularly within the tumor edge and immune cores. Analysis of inhibitory ligand-receptor interactions identified the TIGIT/PVR/Nectin-2 axis as the main engaged axis between CD163+ macrophages and T cells. Nectin-2 expression on macrophages was particularly high within immune cores, and elevated in macrophages with direct T cell contact, suggesting a high probability of in situ engagement. Consistent with this immunosuppressive role, both CD163 and Nectin-2 expression on macrophages correlated with poor patient survival, substantiating the clinical relevance of inhibitory macrophage-T cell interactions. Conclusions: This study reveals T cell-excluded tumor niches and targetable inhibitory interactions between CD163+ macrophages and T cells. These insights provide a rationale for combinatorial immunotherapeutic strategies that both enhance T cell infiltration into tumor-rich areas and disrupt inhibitory signaling to improve immunotherapy efficacy in neuroblastoma.

Neuroblastoma is the most common extracranial solid tumor of childhood. Its clinical behavior ranges from spontaneous regression to lethal, treatment-refractory disease. Aberrant 2,6-sialylation contributes to aggressive phenotypes in many cancers, but the role of ST6Gal2, a neural-enriched 2,6-sialyltransferase, in neuroblastoma is largely unexplored. Here, we examine the clinical and functional significance of ST6Gal2 in neuroblastoma. In two independent public cohorts (SEQC, n=498; Kocak, n=649), high ST6GAL2 expression was associated with significantly worse overall and event-free survival. In the SEQC cohort, ST6GAL2 expression was higher in high-risk and MYCN-amplified tumors, varied across International Neuroblastoma Staging System stages, and correlated positively with a mesenchymal transcriptional signature (Spearman {rho}=0.181). The mesenchymal correlation was reproduced in the Kocak cohort ({rho}=0.204). Stable shRNA-mediated knockdown of ST6GAL2 in SK-N-AS and SK-N-BE(2) cells reduced proliferation and viability, impaired wound closure, and decreased migration and invasion. In preliminary experiments in SK-N-AS cells, ST6GAL2 knockdown reduced binding of Sambucus nigra agglutinin, consistent with a role for ST6Gal2 in 2,6-sialylation. Together, these findings link ST6Gal2 expression to aggressive clinical and transcriptional features and pro-tumorigenic phenotypes in neuroblastoma and nominate ST6Gal2-mediated sialylation as a candidate pathway for mechanistic study.

Neuroblastoma is a heterogeneous pediatric malignancy characterized by distinct genomic subgroups and cell-state plasticity between adrenergic (ADRN) and mesenchymal (MES) phenotypes. While small extracellular vesicles (sEVs) mediate pre-metastatic niche priming, the degree to which sEV proteomes reflect parental genomic and phenotypic identity remains unresolved. Here, we isolated sEVs from six neuroblastoma cell models (IMR-5/75, BE(2)-C, GI-ME-N, CLB-GA, LAN-6, and SK-N-FI) representing three genomic subgroups (MYCN-amplified, TERT-rearranged, and unaltered) using OptiPrep density gradient centrifugation followed by size exclusion chromatography and ultrafiltration. High-resolution mass spectrometry of sEV proteomes revealed that sEVs carry highly reproducible protein signatures that tightly correlate with the parental genomic subgroups. Analyzing paired cell/sEV samples, we demonstrate cell-to-EV concordance of lineage-specific markers: ADRN sEVs selectively enriched L1CAM and dopamine {beta}-hydroxylase (DBH), whereas MES sEVs enriched SERPINE1 and type III collagen (COL3A1). These findings indicate that neuroblastoma-derived sEVs systematically preserve both the genomic landscape and the lineage transdifferentiation states of their cells of origin. This study establishes a robust molecular foundation for utilizing sEV-based proteomics as a surrogate to track cellular plasticity and for studying sEV-mediated microenvironmental remodeling.

Abstract Background Migrasomes, the newly discovered vesicular organelles, have long been speculated to originate from membrane dynamics during cell migration. Here we present integrated imaging and multi-omics evidence supporting a ciliary origin of migrasomes. The shared vesicular trafficking pathways between ciliogenesis and migrasome biogenesis (trans-Golgi/endosomal systems) prompted us to investigate their spatiotemporal coupling mechanism in disease models. Methods Using high-resolution SEM and fluorescence confocal microscopy (FCM), we visualized cilium-like structures with enlarged tips adjacent to migrasome-like vesicles across multiple cell types. TMT-based quantitative proteomics was used to identify proteins shared among migrasomes from different cell types and examine their associations with ciliary proteins. DMBA-induced breast cancer and femoral fracture models were used to investigate the cilia-migrasome association during tumor metastasis and fracture healing. Results Bioinformatics analysis showed a highly positive incidence correlation between cilia and migrasome genes in 31 types of 7858 human normal tissues and organs and various cell types. In 32 cancer tissues, cilia and migrasome genes were still strongly but abnormally correlated. Signaling enrichment by ARL13B and TSPAN4 showed that cilia-migrasome association is related to epithelial-mesenchymal transition (EMT). By analyzing the ARL13B and PIGK expression, we found the abnormal cilia-migrasome association in metastatic breast cancer and positive cilia-migrasome association in fracture healing bone. Conclusion Our findings support a ciliary origin of migrasomes, pointing to a previously unrecognized pathway of organelle biogenesis. Notably, the ciliary-migrasomal association correlates with two distinct pathological/physiological contexts: (1) aberrant epithelial-mesenchymal transition (EMT) in metastatic breast cancer, and (2) accelerated regeneration during fracture healing and tissue repair. This dual correlation not only establishes a mechanistic link between ciliary function and migrasome biogenesis but also highlights their divergent roles in disease progression versus tissue homeostasis. Investigating the spatiotemporal dynamics of this association may provide novel therapeutic targets for metastatic malignancies and regenerative medicine.

Src family kinases (SFKs) constitute a major non-receptor tyrosine kinase class that regulate processes important for pregnancy. We profiled placental SFKs to assess cell-specific expression, tissue localization, and clinical associations in early-onset preeclampsia (PE). Placental SFK transcripts were analyzed using bulk RNA sequencing discovery (GSE203507; n=15 PE, n=15 controls) and external validation (GSE114691; n=40 PE, n=21 controls) cohorts. Single-cell and single-nucleus RNA sequencing atlases mapped cell-specific expression. Computational deconvolution and causal mediation analyses were applied to bulk datasets. Findings were cross-validated by real-time quantitative PCR (qPCR; n=9 early-onset PE, n=7 controls) and immunohistochemistry (IHC). Transcriptomic data showed that LYN was the sole SFK member consistently elevated in early-onset PE placentas across discovery (1.8-fold, FDR<0.01) and validation cohorts (2.2-fold, FDR<0.001). Elevation was verified by qPCR (p<0.0001) and remained significant after adjusting for clinical covariates. Placental LYN abundance correlated positively with maximum antepartum maternal systolic blood pressure (r=0.63, p<0.01). Single-cell transcriptome atlases demonstrated LYN enrichment in myeloid lineages, extravillous trophoblasts, and syncytiotrophoblast (SCT). Deconvolution and mediation analyses indicated that altered tissue composition and increased per-cell expression each accounted for approximately half of the PE-associated LYN increase. IHC localized Lyn protein to Hofbauer macrophages and the apical microvillar SCT membrane in PE placentas. We conclude that placental LYN expression is selectively elevated in early-onset PE and correlates with maternal blood pressure severity. Lyn localization to trophoblasts and placental immune cells suggests potential roles in mediating inflammation and hypoxia-associated signaling in PE pathogenesis.

Introduction: Sporadic colorectal cancers (CRCs) form following initiating APC mutations, inducing constitutive {beta}-catenin/TCF signaling. Similarly, the guanylyl cyclase C (GUCY2C) tumor suppressor axis is universally silenced in CRC. While the GUCY2C receptor is retained, loss of its paracrine hormones guanylin (GUCA2A) and uroguanylin (GUCA2B) is among the earliest events in transformation. Mutant APC/{beta}-catenin/TCF signaling driving CRC transcriptionally silences GUCY2C hormone expression while suppressing that oncogenic pathway reconstitutes hormone production opposing tumorigenesis. p38 opposes tumor initiation, and its loss promotes transformation in chemical and genetic mouse models of CRC. In healthy intestine, p38 supports a gradient of epithelial differentiation along the crypt-surface axis. Here, we reveal that p38 links regulation of oncogenic APC/{beta}-catenin/TCF signaling and GUCY2C hormone expression. Methods: Regulation of p38 by APC/{beta}-catenin/TCF signaling was defined in four genetically engineered human CRC cell lines with conditional oncogenic APC/{beta}-catenin/TCF signaling and healthy human colon organoids. Expression of p38 was eliminated from conditional human CRC cell lines by pharmacological inhibition, RNA knockdown, and CRISPR/Cas9 gene editing. Transcriptomic analysis of these cells by RNA sequencing defined the set of genes regulated by APC/{beta}-catenin/TCF signaling controlled through p38. Results: In CRC cell lines, APC/{beta}-catenin/TCF signaling suppressed p38 phosphorylation and activity, whereas inhibition of APC/{beta}-catenin/TCF restored p38 signaling. In the absence of APC/{beta}-catenin/TCF signaling, inhibiting p38 repressed GUCY2C hormone expression. Inhibiting APC/{beta}-catenin/TCF signaling enriched phosphorylated p38 at the GUCA2A promoter. In that context, analysis of the CPTAC proteomic database revealed that phosphorylation of p38 and its upstream kinases MKK3 and MKK4 was reduced in human CRC. Finally, transcriptomic analysis revealed that p38 is a critical signaling node controlling the expression of a substantial subset of APC/{beta}-catenin/TCF-regulated genes in human CRC cells and patient tumors. Conclusions: APC/{beta}-catenin/TCF signaling inhibits p38 phosphorylation and transcriptional activity, suppressing GUCA2A and GUCA2B expression and functionally silencing the retained GUCY2C receptor. These findings identify p38 as a signaling intermediary integrating oncogenic APC/{beta}-catenin/TCF activity to extinction of the GUCY2C tumor-suppressor axis and reveal a broader p38-dependent component of the APC/{beta}-catenin/TCF-regulated transcriptome.

Although MAP1LC3B/LC3B (LC3) is best known as a cytoplasmic marker of autophagosome biogenesis, a substantial pool of LC3 resides in the nucleus and shuttles dynamically between nuclear and cytoplasmic compartments, yet the composition and regulation of this nuclear interactome remain poorly defined. Using mass spectrometry-based proteomic profiling of nuclear GFP-LC3 immunoprecipitates from primary human trabecular meshwork (TM) cells, a mechanosensitive ocular cell type, we identified a reproducible nuclear LC3 interactome enriched for proteins containing LC3-interacting region (LIR) and expanded LIR (xLIR) motifs and reported nuclear localization. Among these, clathrin heavy chain (CLTC) emerged as a previously unrecognized nuclear LC3 partner that localizes to the nucleus and colocalizes with nuclear LC3 puncta. CLTC depletion reduced basal LC3-II levels, consistent with a role in autophagosome biogenesis, and markedly impaired nuclear LC3 accumulation induced by both nuclear export blockade with leptomycin B and cyclic mechanical stretch, without altering total CLTC abundance, indicating that CLTC actively promotes LC3 nuclear translocation rather than serving as a passive scaffold. Strikingly, mechanical stress-induced nuclear LC3 trafficking, but not its basal component, was selectively impaired in TM cells derived from glaucoma patients, despite comparable CLTC levels, pointing to a defect in coupling this trafficking pathway to mechanotransduction rather than in the core transport machinery itself. Together, these findings establish nuclear LC3 trafficking as an actively regulated, CLTC-dependent process linked to cytoskeletal and vesicular machinery, and implicate its dysregulation in mechanically stressed glaucomatous cells, providing a framework for understanding how autophagy intersects with nuclear homeostasis, mechanotransduction, and glaucoma pathogenesis.

Glioblastoma (GBM) is an aggressive malignancy with limited therapeutic options and poor survival. Cyclin-dependent kinase 4 (CDK4) is overexpressed in GBM and promotes tumor progression through canonical cell-cycle regulation and extranuclear functions related to metabolism, invasion, and tumor microenvironment modulation. Current ATP-competitive CDK4/6 inhibitors show limited selectivity, potentially causing off-target effects and resistance. We developed a strategy to identify novel CDK4 inhibitors targeting the CDK4-Cyclin D1 protein-protein interaction, a key determinant of CDK4 activation. Virtual screening of approximately 950,000 compounds, combining molecular docking and molecular dynamics simulations, identified candidate molecules that were subsequently evaluated using proximity ligation assays, in vitro kinase activity assays, phosphokinase profiling, and functional analyses in patient-derived GBM cell lines and additional cancer models. Diophenic emerged as the lead candidate, demonstrating consistent antiproliferative activity across multiple GBM and epithelial cancer models. The compound selectively disrupted the CDK4-Cyclin D1 interaction while sparing the closely related CDK6 complex, and inhibited CDK4 kinase activity in vitro. Functional studies showed that diophenic induced substantial cell death in GBM cells, significantly reduced invasiveness, and exhibited distinct effects on cell migration compared with CDK4/6 inhibitors. Furthermore, phosphokinase profiling revealed that diophenic modulates a more restricted signaling network than ATP-competitive inhibitors, supporting greater functional selectivity and reduced off-target activity. Aiming the CDK4-Cyclin D1 interface represents a promising alternative to ATP-competitive CDK4/6 inhibition, which target a highly conserved site across the protein kinase superfamily. This approach provides a proof of concept for developing next-generation CDK4-selective therapeutics. Further studies should evaluate its translational potential in GBM.

Circulating tumor cells (CTCs) are key drivers of distant metastasis, while platelets facilitate this process by protecting them from immune surveillance. However, the detection of CTCs exhibiting platelet markers and their communication with monocytes has not been thoroughly investigated. This study seeks to identify the intercellular communication of CTCs that have acquired platelet traits by integrating single-cell RNA-seq data of 377 CTCs and 2,634 white blood cells. Trajectory analysis identified a subpopulation of CTCs with enhanced platelet-related functions, including platelet aggregation and resistance to NK cell-mediated cytotoxicity, termed Platelet-Programmed CTCs. The Dampened Weighted Least Squares method was implemented to estimate the platelet-programmed tumor cell proportion in 1,102 bulk RNA-seq samples from primary breast cancer tumors. A strong inverse association was found between platelet-programmed tumor cell proportion and overall survival (Cox-PH p-value =0.00419, HR=6 per 10% increase in proportion, 95% CI:1.76-20.7). However, this association did not differ significantly between early- and late-stage patients. Cell-cell communication analyses and molecular docking revealed the CD40LG-ITGA5:ITGB1 pair as a potential immune checkpoint candidate for monocytes in cancer (Hex score=-656.83; TNF-TNFR reference complex=-515). However, further experimental and clinical validation is required to translate these findings. In conclusion, these findings deepen our understanding of the immune evasion mechanisms of CTCs by acquiring platelet characteristics. This immune checkpoint axis offers a novel avenue for further experimental validation and future intervention.

Breast cancer progression is driven by dynamic changes in epithelial plasticity, membrane organization, and intracellular signaling, yet the effects of sustained low-dose chemotherapy on these processes remain poorly understood. Here, we investigated the impact of prolonged low-dose doxorubicin on membrane remodeling, epithelial phenotype, membrane-associated Ras lipid-anchor localization, and autophagy in mesenchymal-like MDA-MB-231 breast cancer cells. Low-dose doxorubicin significantly increased Caveolin-1 expression and enhanced E-cadherin protein levels, accompanied by a transition toward a more compact epithelial-like morphology with increased cell-cell contacts. Live-cell imaging demonstrated a significant reduction in the membrane-to-cytoplasm fluorescence ratio of the lipid-anchored GFP-tH probe, indicating redistribution from the plasma membrane to the cytoplasm following treatment. Analysis of autophagy-related proteins revealed decreased LC3-I together with increased LC3-II, ATG5, and p62 expression, consistent with autophagosome accumulation and impaired autophagic flux. Collectively, our findings demonstrate that low-dose doxorubicin promotes extensive remodeling of plasma membrane organization, epithelial plasticity, membrane-associated lipid-anchor localization, and autophagy. This integrated response reveals previously unrecognized links between membrane architecture, Ras membrane association, and autophagy during phenotypic reprogramming of breast cancer cells, providing mechanistic insight into cellular adaptations elicited by sub-cytotoxic doxorubicin exposure.

Epithelial cells of the female reproductive tract (FRT) form a protective barrier and serve as the first line of defense against sexually transmitted infections (STIs). They recognize pathogens, release cytokines and initiate innate immune responses. Sex hormones 17{beta}-estradiol (E2) and progesterone (P4) fluctuate throughout the menstrual cycle and influence epithelial cell functions. Generally, E2 confers protection against viral STIs like HIV-1 and HSV-2, whereas P4 increases susceptibility. However, the underlying mechanisms remain incompletely understood. MicroRNAs, small non-coding RNAs that regulate gene expression by inhibiting translation of target mRNAs, significantly influence viral infections, by promoting or restricting viral pathogenesis. Here, we examined the effect of sex hormones on microRNA expression in vaginal epithelial cells (VECs), the first responders to pathogens in the FRT. Using next generation sequencing analysis, the effect of physiological concentrations of E2 or P4 on microRNA transcription profile of VECs grown in air-liquid interface cultures was characterized. Thirteen miRNAs were uniquely regulated by E2 and 102 by P4, with 29 miRNAs that overlapped between both. The top four differentially expressed miRNAs from both treatments were validated by RT-qPCR. The mRNA targets of unique E2-miRNAs were involved in adherens junction, tight junction and chemokine signaling pathways; whereas the mRNA targets of unique P4-miRNAs were involved in MAPK signaling pathway. Interestingly, several miRNAs regulated by E2- (eg. hsa-miR-9-3p, hsa-miR-200c- 5p, hsa-miR-548c-5p) and by P4 (eg. hsa-let-7f-5p, hsa-miR-16-5p, hsa-miR-27b-3p) targeted genes related to cell cycle pathway. Together, these findings indicate that microRNAs regulated by E2 and P4 influence mRNAs in the pathways associated with cell adhesion, cell growth and development and innate immune responses, critical for maintenance of epithelial barrier integrity and regulating pathogen susceptibility in the vaginal tract. These hormone-regulated miRNAs may serve as potential targets for therapeutic interventions.

Tumor-associated macrophages (TAMs) integrate multiple microenvironmental signals, including lectin-mediated recognition of tumor-associated glycans. Although several myeloid lectins have been implicated in tumor-macrophage interactions, their contributions to immunosuppressive TAM phenotypes remain poorly defined. We implemented a CRISPR-Cas9 ribonucleoprotein (RNP) workflow in primary human monocytes to enable comparative loss-of-function interrogation of five potentially immunosuppressive lectins we previously reported. CRISPR-Cas9 RNP delivery conditions were benchmarked in freshly isolated monocytes using CD14 as a technical target, followed by sgRNA editing efficiency screening for CLEC4E, CLEC6A, CD209, SELL, and SIGLEC9 in HeLa S3 cells. Selected guides were applied to primary monocytes before co-culture in a 3D model with BT474 breast cancer cells. Editing was quantified by Sanger-sequencing deconvolution, while co-culture-derived CD45+ macrophages were isolated by fluorescence-activated cell sorting and characterized by bulk RNA sequencing. All five lectins were successfully perturbed, although gene editing efficiency remained target- and donor-dependent. Transcriptomic analysis revealed target-specific reprogramming and recurrent immunometabolic responses. mTORC1 signaling was consistently enriched, together with the remodeling of cholesterol homeostasis, fatty acid metabolism, and oxidative phosphorylation. CLEC6A deletion achieved attenuation of hypoxia-, angiogenesis-, and TNF/NF-kB-associated programs. CD209 and SIGLEC9 deletion similarly reduced hypoxia- and angiogenesis-associated signatures while promoting lipid and oxidative metabolism. CLEC4E perturbation induced broad remodeling of lipid and oxidative metabolism and stress-response, despite comparatively limited editing efficiency. Comparative lectin perturbation thus identified CLEC6A as the strongest candidate for further mechanistic investigation, while CLEC4E showed broad transcriptional remodeling despite lower editing efficiency, supporting its prioritization for improved genetic interrogation. Responses to CD209 and SIGLEC9 targeting further support tumor glycan-myeloid signaling as a regulator of TAM state. Overall, lectin perturbation redirected TAM transcriptional states through distinct immunometabolic programs rather than a uniform pro-inflammatory polarization, highlighting lectin-dependent immunometabolic regulation as a promising axis for further investigation.

Aberrant signaling of receptor tyrosine kinases (RTKs), including the hepatocyte growth factor receptor MET, contributes to colorectal cancer (CRC) progression and is tightly regulated by endocytic trafficking. We previously showed that combined deletion of the endosomal sorting proteins SNX1 and SNX2 disrupts MET trafficking and enhances downstream signaling in HCT116 CRC cells. However, their individual contributions remained unresolved. Using CRISPR/Cas9-engineered SNX1- and SNX2-KO HCT116 cells, we examined their roles in MET trafficking and signaling. Loss of SNX2, but not SNX1, markedly reduced SNX5 and SNX6 protein levels without affecting transcript abundance. SNX2 deficiency also increased total MET under serum-containing conditions without altering MET transcript or cell-surface receptor levels. Following HGF stimulation, loss of SNX2, but not SNX1, transiently delayed MET trafficking to EEA1+ early and RAB7+ late endosomes, while recycling and lysosomal trafficking remained largely unaffected. This was accompanied by enhanced and sustained HGF-induced AKT activation. Together, these findings identify SNX2 as a predominant regulator of early MET endosomal trafficking in HCT116 cells and reveal functional asymmetry between SNX1 and SNX2. They support a role for SNX2 in spatial regulation of MET signaling through receptor trafficking, consistent with the association of low SNX2 expression with poorer survival in CRC patients.

Validated biomarkers for identifying patients with early-stage melanomas at high risk of metastasis are limited. We have previously shown that loss of Activating Molecule in Beclin-1-Regulated Autophagy (AMBRA1) and loricrin in the epidermal microenvironment is associated with tumour recurrence. Here we show that endothelial AMBRA1 deficiency contributes to vascular dysfunction and melanoma progression. Melanoma-conditioned media or exposure to TGF{beta}1-3 ligands induced post-transcriptional loss of AMBRA1 in endothelial cells. Transcriptomic profiling in both in vitro and human melanoma single-cell RNA sequencing datasets showed activation of cell-cycle and metabolic programmes alongside suppression of endothelial junction, adhesion and immune-supportive pathways in AMBRA1-deficient endothelial cells. Functionally, AMBRA1 loss increased endothelial cell proliferation, accelerated early tubulogenesis, impaired three-dimensional spheroid adhesion, stabilised endothelial-to-mesenchymal transition-associated transcription factors Slug and Snail, and reduced Claudin-5, VE-cadherin and N-cadherin, indicative of endothelial plasticity and dysfunction. Furthermore, loss of AMBRA1 in a subset of intratumoural and peritumoural blood and lymphatic vessels correlated significantly with metastatic progression in a cohort of 121 non-ulcerated primary AJCC stage I/II melanomas classified as AMBLor at-risk. Collectively, these findings position endothelial AMBRA1 as a regulator of vascular plasticity, dysfunction, and immune-supportive endothelial function in early-stage melanomas, and a marker of a permissive microenvironment associated with metastasis.

The transport of about 70 enzymes to lysosomes depends on mannose 6-phosphate signals formed by GNPTAB. Editing of Gnptab in an intestinal mouse cell line revealed the loss of multiple lysosomal enzymes associated with the accumulation of sphingomyelins, ceramides, and cholesterol, and reduced levels of bis(monoacylglycero)phosphate (BMP) in lysosomal proteomes and lipidomes. By cross-correlation we identified two subsets of lysosomal lipid-modifying enzymes linked with mixed unsaturated or di-monosaturated BMP. Autophagy-related proteins functioning in early stages of autophagosome formation associated with neutral ceramides, whereas proteins involved in autophagosome-lysosome fusion correlated with negatively charged BMPs. Therefore, the high cholesterol and low BMP level of lysosomes might be causal for impaired autophagic flux in GNPTAB deficient cells. We propose a functional axis of three lysosomal proteins as potential target to improve the autophagic flux in cells with dysfunctional lysosomes and in a newly established intestinal organoid model suitable as novel experimental tool.

Metastatic melanoma remains highly lethal despite advances in immunotherapy and MAPK-targeted therapy. The Rac1P29S mutation, present in 4-9% of cutaneous melanomas, confers intrinsic resistance to BRAF and MEK inhibitors. Like other small GTPases, Rac1 lacks suitable pockets for small molecule inhibitor binding, motivating indirect approaches to suppressing its activity. We have previously shown that wild-type Rac1 is sensitive to inhibition of de novo GTP biosynthesis in cancer cells, particularly suppression of the rate-limiting inosine monophosphate dehydrogenase (IMPDH) enzymes. Therefore, we asked whether IMPDH inhibition could suppress Rac1P29S and its associated phenotypes in melanoma. We found that IMPDH inhibition reduced Rac1 activity, impaired Rac1-dependent phenotypes, and induced S-phase arrest in Rac1P29S-harboring cells. Moreover, IMPDH inhibition synergized with the BRAF inhibitor vemurafenib and the MEK inhibitor trametinib in Rac1P29S melanoma cells. Dual BRAF and IMPDH inhibition also resulted in enhanced suppression of MEK and ERK phosphorylation in vitro. In syngeneic mouse models, the FDA-approved IMPDH inhibitor mycophenolate mofetil sensitized Rac1P29S-expressing melanoma tumors to trametinib, including tumors made refractory by prior trametinib exposure. We further identified a feed-forward circuit in which Rac1 sustains IMPDH2 expression levels through JNK and c-Jun/AP1 signaling, potentially coupling the GTPase to its own nucleotide supply. These findings establish GTP biosynthesis as a targetable vulnerability in Rac1P29S melanoma and support IMPDH inhibition as a rational partner for MAPK-targeted therapy.

Background Vitiligo is an acquired depigmenting disorder characterised by melanocyte loss. While immune responses against melanocytes are implicated in its pathogenesis, melanocyte detachment, melanocyte senescence and aberrant epidermal differentiation are increasingly characterised as additional pathological features. Granzyme B (GzmB), classically recognised as an intracellular effector of perforin-dependent cytotoxicity, is increased in vitiligo lesions; however, its extracellular contribution to vitiligo pathology remains unclear. Objectives To determine whether extracellular GzmB contributes to depigmentation and epidermal pathological features relevant to vitiligo, and to define its cellular source and underlying mechanisms. Methods Human vitiligo skin samples, murine depigmentation models and cultured human epidermal cells were analysed. The functional effects of extracellular GzmB were examined by subcutaneous administration of recombinant GzmB in mice. A rhododendrol (RD)-induced leukoderma model was used to evaluate the disease relevance of GzmB and the therapeutic effect of topical GzmB inhibition with VTI-1002. Results GzmB-positive cells were markedly increased in active vitiligo lesions and were predominantly associated with tryptase-positive cells, with limited co-distribution with CD8 or perforin. Vitiligo lesions also showed melanocyte detachment, increased p16INK4A-positive melanocytes and aberrant keratinocyte differentiation. These pathological features were recapitulated in vivo by extracellular GzmB administration, accompanied by focal depigmentation. In cultured melanocytes, GzmB exerted no cytotoxic effects but reduced attachment strength and induced a senescence-associated phenotype characterised by decreased extracellular matrix- and adhesion-related gene expression, increased p16INK4A level, elevated senescence-associated {beta}-galactosidase activity and activation of transforming growth factor-{beta}/SMAD signalling. In keratinocytes, extracellular GzmB promoted aberrant differentiation associated with activation of p53 signalling. Topical inhibition of GzmB in RD-induced leukoderma attenuated depigmentation progression, melanocyte detachment, melanocyte senescence and abnormal epidermal differentiation. Conclusions Extracellular GzmB promotes depigmentation associated with inducing melanocyte detachment, melanocyte senescence and aberrant keratinocyte differentiation. These findings identify extracellular GzmB as a previously underrecognised pathogenic mediator and potential therapeutic target in vitiligo-associated depigmentation.

Beside behavioral symptoms, many patients with autism spectrum disorder (ASD) present gastrointestinal disorders and gut microbiota dysbiosis. In order to better understand the mechanisms underlying microbiota-gut-brain interactions in ASD, we isolated fecal extracellular vesicles (EVs), as a source of microbiota-derived EVs, from control individuals (f-EV-CTL) and patients with ASD (f-EV-ASD) to study in mice their impact on brain and gut. The f-EV-ASD induced hypersocial and anxiolytic-like behavior, and reduced gastrointestinal transit time compared to mice treated with f-EV-CTL. In the colon, f-EV-ASD altered motility through the enteric neuronal nitric oxide (NO)-sensitive component. f-EV-ASD potentiated NO signaling and disrupted intracellular calcium dynamics in enteric neurons. This effect was mediated by butyrate and valerate through FFAR3 receptor. Our findings establish fecal EVs as critical mediators of microbiota-host communication, linking microbial metabolites to altered behavior and gut function and identifying a potential mechanism underlying ASD pathophysiology.

Type 1 diabetes (T1D) is a chronic autoimmune disease characterized by T-cell mediated destruction of pancreatic islet {beta}-cells with genetic, environmental, and molecular triggers involved in disease pathogenesis. Patients with T1D have elevated serum levels of microRNA146a (miR146a). Polymorphisms in the miR146a gene that result in reduced expression of miR146a are associated with protection from T1D. We studied physiological regulators of miR146a expression and found that both hyperglycemia and elevated O-GlcNAcylation increased miR146a expression in T cells. Peripheral blood mononuclear cells (PBMCs) from T1D patients showed increased miR146a and O-GlcNAc transferase (OGT) expression, suggesting increased O-GlcNAcylation may promote miR146a expression in T1D patients. To determine the genetic and developmental role of miR146a in T1D, we generated miR146a-knockout (KO) non-obese diabetic (NOD) mice and found that absence of miR146a significantly protected NOD mice from spontaneous autoimmune diabetes. While we found no impact of miR146a knockout on general hematopoietic parameters and immune cell populations, remarkably, immune cell infiltration into the pancreas was significantly attenuated. Protection from autoimmune diabetes in miR146a-KO NOD mice was associated with increased regulatory T (Treg) cells in the spleen and pancreatic lymph node. Mechanistically, absence of miR146a increased NF-{kappa}B c-Rel expression in Treg cells and enhanced c-Rel binding at the Forkhead box protein P3 (FOXP3) promoter, which positively regulated Treg cell development and suppressor function, offering protection from T1D in miR146a-KO NOD mice. Our findings reveal miR146a as a key regulator of Treg cell-mediated immune tolerance through controlling NF-{kappa}B c-Rel-dependent FOXP3 expression and suggest targeting miR146a as a potential strategy to restore peripheral tolerance in T1D.

Neuronal-cancer cell interactions are a key component of brain tumor pathophysiology, yet many fundamental questions remain unanswered, with even more remaining unasked. Here, we present a comprehensive brain tumor reference map generated from bulk RNA-seq data of ~4,300 adult and pediatric brain tumors, including various glioma subtypes, medulloblastomas, ependymomas, and meningiomas, alongside ~1,400 healthy brain samples. By analyzing synaptic processes and synaptic gene expression across tumor types, we reveal the complexity of neuron-tumor crosstalk and its potential impact on patient survival. Our findings identify key synaptic signaling pathways and dysregulated patterns in brain tumors, including HNRNPH2 upregulation, a key factor in RNA processing and metabolism, in gliomas and medulloblastomas. Additionally, we highlight the role of cholinergic signaling, particularly CHRNA9, as a driver of glioma progression, which is also upregulated in WNT and Group 4 medulloblastomas, ependymomas, and meningiomas. Furthermore, P2 purinergic signaling emerges as a key player in glioma progression. These insights lay the groundwork for future studies exploring whether targeting these pathways could reprogram the tumor microenvironment toward an anti-tumor state, ultimately leading to novel therapeutic strategies and improved patient outcomes.