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5-Methylcytosine (m 5 C) is a posttranscriptional RNA modification participating in many critical bioprocesses, but its functions in human cancer remain unclear. Here, by detecting the transcriptome-wide m 5 C profiling in esophageal squamous cell carcinoma (ESCC), we showed increased m 5 C methylation in ESCC tumors due to the overexpressed m 5 C methyltransferase NSUN2. Aberrant expression of NSUN2 was positively regulated by E2F Transcription Factor 1 (E2F1). High NSUN2 levels predicted poor survival of ESCC patients. Moreover, silencing NSUN2 suppressed ESCC tumorigenesis and progression in Nsun2 knockout mouse models. Mechanistically, NSUN2 induced m 5 C modification of growth factor receptor-bound protein 2 ( GRB2 ) and stabilized its mRNA, which was mediated by a novel m 5 C mediator, protein lin-28 homolog B (LIN28B). Elevated GRB2 levels increased the activation of PI3K/AKT and ERK/MAPK signalling. These results demonstrate that NSUN2 enhances the initiation and progression of ESCC via m 5 C-LIN28B dependent stabilization of GRB2 transcript, providing a promising epitranscriptomic-targeted therapeutic strategy for ESCC.

Cell-surface receptors frequently use scaffold proteins to recruit cytoplasmic targets, but the rationale for this is uncertain. Activated receptor tyrosine kinases, for example, engage scaffolds such as Shc1 that contain phosphotyrosine (pTyr)-binding (PTB) domains. Using quantitative mass spectrometry, here we show that mammalian Shc1 responds to epidermal growth factor (EGF) stimulation through multiple waves of distinct phosphorylation events and protein interactions. After stimulation, Shc1 rapidly binds a group of proteins that activate pro-mitogenic or survival pathways dependent on recruitment of the Grb2 adaptor to Shc1 pTyr sites. Akt-mediated feedback phosphorylation of Shc1 Ser 29 then recruits the Ptpn12 tyrosine phosphatase. This is followed by a sub-network of proteins involved in cytoskeletal reorganization, trafficking and signal termination that binds Shc1 with delayed kinetics, largely through the SgK269 pseudokinase/adaptor protein. Ptpn12 acts as a switch to convert Shc1 from pTyr/Grb2-based signalling to SgK269-mediated pathways that regulate cell invasion and morphogenesis. The Shc1 scaffold therefore directs the temporal flow of signalling information after EGF stimulation. The Shc1 scaffold mediates a switch in the signaling output of the epidermal growth factor receptor tyrosine kinase over time through recruitment of successive waves of proteins with distinct biological functions. More than a support role for scaffold proteins Receptor-associated scaffolds are generally thought of as relatively static components of signalling pathways that link an activated receptor to downstream targets and expand the receptor's range and potency. An example is the scaffold protein Shc1, which binds to the activated EGF receptor tyrosine kinase. Here, Tony Pawson and colleagues use a quantitative proteomics approach to demonstrate that Shc1 is more than just a simple adaptor; it recruits successive waves of proteins with distinct functions and thereby switches the signalling output of the EGF receptor over time.

Activating and inhibitory receptors control natural killer (NK) cell activity. T-cell immunoglobulin and ITIM (immunoreceptor tyrosine-based inhibition motif) domain (TIGIT) was recently identified as a new inhibitory receptor on T and NK cells that suppressed their effector functions. TIGIT harbors the immunoreceptor tail tyrosine (ITT)-like and ITIM motifs in its cytoplasmic tail. However, how its ITT-like motif functions in TIGIT-mediated negative signaling is still unclear. Here, we show that TIGIT/PVR (poliovirus receptor) engagement disrupts granule polarization leading to loss of killing activity of NK cells. The ITT-like motif of TIGIT has a major role in its negative signaling. After TIGIT/PVR ligation, the ITT-like motif is phosphorylated at Tyr225 and binds to cytosolic adapter Grb2, which can recruit SHIP1 to prematurely terminate phosphatidylinositol 3-kinase (PI3K) and MAPK signaling, leading to downregulation of NK cell function. In support of this, Tyr225 or Asn227 mutation leads to restoration of TIGIT/PVR-mediated cytotoxicity, and SHIP1 silencing can dramatically abolish TIGIT/PVR-mediated killing inhibition.

Drug resistance remains a major problem in the treatment of conventional chemotherapeutic agents in breast cancers. Owing to heterogeneity and complexity of chemoresistance mechanisms, most efforts that focus on a single pathway were unsuccessful, and exploring novel personalized therapeutics becomes urgent. By a system approach, we identified that microRNA-27b-3p (miR-27b), a miRNA deleted in breast cancer tissues and cell lines, has a master role in sensitizing breast cancer cells to a broad spectrum of anticancer drugs in vitro and in vivo . Mechanistic analysis indicated that miR-27b enhanced responses to PTX by directly targeting CBLB and GRB2 to inactivate both PI3K/Akt and MAPK/Erk signaling pathways. Further, miR-27b was identified as a promising molecular biomarker in chemoresistance, clinicopathological features, and prognosis for breast cancer patients. In conclusion, we propose that combinational use of miR-27b and chemotherapeutic agents might be a promising therapeutic strategy to increase long-term drug responses in breast cancers.

Drug resistance remains a challenge for targeted therapy of cancers driven by EML4-ALK and related fusion oncogenes. EML4-ALK forms cytoplasmic protein condensates, which result from networks of interactions between oncogene and adapter protein multimers. While these assemblies are associated with oncogenic signaling, their role in drug response is unclear. Here, we use optogenetics and live-cell imaging to find that EML4-ALK assemblies suppress transmembrane receptor tyrosine kinase (RTK) signaling by sequestering RTK adapter proteins including GRB2 and SOS1. Furthermore, ALK inhibition, while suppressing oncogenic signaling, simultaneously releases the sequestered adapters and thereby resensitizes RTK signaling. Resensitized RTKs promote rapid and pulsatile ERK reactivation that originates from paracrine ligands shed by dying cells. Reactivated ERK signaling promotes cell survival, which can be counteracted by combination therapies that block paracrine signaling. Our results identify a regulatory role for RTK fusion assemblies and uncover a mechanism of tolerance to targeted therapies. The EML4-ALK oncogene forms  cytoplasmic protein condensates that are associated with its oncogenic signaling. Here, the authors demonstrate that these EML4-ALK assemblies also sequester receptor tyrosine kinase (RTK) adapter proteins suppressing signaling which was reversed upon ALK inhibition, resulting in rapid resensitisation to growth factors and tumor cell survival.

Growth factor receptor-bound protein 2 (GRB2) is a cytoplasmic adapter for tyrosine kinase signaling and a nuclear adapter for homology-directed-DNA repair. Here we find nuclear GRB2 protects DNA at stalled replication forks from MRE11-mediated degradation in the BRCA2 replication fork protection axis. Mechanistically, GRB2 binds and inhibits RAD51 ATPase activity to stabilize RAD51 on stalled replication forks. In GRB2-depleted cells, PARP inhibitor (PARPi) treatment releases DNA fragments from stalled forks into the cytoplasm that activate the cGAS–STING pathway to trigger pro-inflammatory cytokine production. Moreover in a syngeneic mouse metastatic ovarian cancer model, GRB2 depletion in the context of PARPi treatment reduced tumor burden and enabled high survival consistent with immune suppression of cancer growth. Collective findings unveil GRB2 function and mechanism for fork protection in the BRCA2-RAD51-MRE11 axis and suggest GRB2 as a potential therapeutic target and an enabling predictive biomarker for patient selection for PARPi and immunotherapy combination. GRB2 is known for its role in Receptor Tyrosine Kinase and RAS signaling. Here the authors unveil a GRB2 function and mechanism for DNA replication fork protection. GRB2 alleviates oncogenic replication stress, and in doing so, averts cancer immune destruction by inhibiting cGAS/STING and pro-inflammatory cytokine production.

Adipocytes undergo considerable volumetric expansion in the setting of obesity. It has been proposed that such marked increases in adipocyte size may be sensed via adipocyte-autonomous mechanisms to mediate size-dependent intracellular signalling. Here, we show that SWELL1 (LRRC8a), a member of the Leucine-Rich Repeat Containing protein family, is an essential component of a volume-sensitive ion channel (VRAC) in adipocytes. We find that SWELL1-mediated VRAC is augmented in hypertrophic murine and human adipocytes in the setting of obesity. SWELL1 regulates adipocyte insulin–PI3K–AKT2–GLUT4 signalling, glucose uptake and lipid content via SWELL1 C-terminal leucine-rich repeat domain interactions with GRB2/Cav1. Silencing GRB2 in SWELL1 KO adipocytes rescues insulin-pAKT2 signalling. In vivo , shRNA-mediated SWELL1 knockdown and adipose-targeted SWELL1 knockout reduce adiposity and adipocyte size in obese mice while impairing systemic glycaemia and insulin sensitivity. These studies identify SWELL1 as a cell-autonomous sensor of adipocyte size that regulates adipocyte growth, insulin sensitivity and glucose tolerance. Sah and colleagues show that the volume-sensitive ion channel SWELL1 regulates adipocyte insulin-PI(3)K-AKT2 signalling, glucose uptake and lipid content through interactions with GRB2/Cav1.

The parasite Toxoplasma gondii spreads throughout the body by hijacking immune cells and boosting their motility. This ability depends on secreted parasite proteins that manipulate the host cell’s actin cytoskeleton. One such effector, Toxoplasma gondii WAVE-interacting protein ( Tg WIP), induces dramatic changes in host cell shape and movement, but how it does this has remained unclear. Here, we show that Tg WIP directly interacts with multiple host actin-regulatory proteins using distinct sequence motifs. Disrupting these interactions prevents cytoskeletal remodeling and impairs parasite-induced immune cell migration. Our study reveals that Toxoplasma uses defined motifs to co-opt host signaling hubs that control cell motility. Understanding how pathogens exploit the cytoskeleton not only sheds light on host-pathogen interactions but may also reveal broader principles of cell migration relevant to immunity, cancer, and development.

Fibroblast growth factor (FGF) signaling elicits multiple downstream pathways, most notably the Ras/MAPK cascade facilitated by the adaptor protein Grb2. However, the mechanism by which Grb2 is recruited to the FGF signaling complex remains unresolved. Here, we showed that genetic ablation of FGF signaling prevented murine lens induction by disrupting transcriptional regulation and actin cytoskeletal arrangements, which could be reproduced by deleting the juxtamembrane region of the FGF receptor and rescued by Kras activation. Conversely, mutations affecting the Frs2-binding site on the FGF receptor or the deletion of Frs2 and Shp2 primarily impact later stages of lens vesicle development involving lens fiber cell differentiation. Our study further revealed that the loss of Grb2 abolished MAPK signaling, resulting in a profound arrest of lens development. However, removing Grb2’s putative Shp2 dephosphorylation site (Y209) neither produced a detectable phenotype nor impaired MAPK signaling during lens development. Furthermore, the catalytically inactive Shp2 mutation (C459S) only modestly impaired FGF signaling, whereas replacing Shp2’s C-terminal phosphorylation sites (Y542/Y580) previously implicated in Grb2 binding only caused placental defects, perinatal lethality, and reduced lacrimal gland branching without impacting lens development, suggesting that Shp2 only partially mediates Grb2 recruitment. In contrast, we observed that FGF signaling is required for the phosphorylation of the Grb2-binding sites on Shc1 and the deletion of Shc1 exacerbates the lens vesicle defect caused by Frs2 and Shp2 deletion. These findings establish Shc1 as a critical collaborator with Frs2 and Shp2 in targeting Grb2 during FGF signaling. Cells communicate by releasing proteins that bind to receptors on recipient cells, triggering a cascade of events that alter the cell’s behavior. A family of signaling proteins called fibroblast growth factors (FGFs) is critical for various biological processes, especially during embryonic development. While scientists have a good understanding of how FGFs reach their target cells, less is known about the series of events they activate once they bind to a receptor. Three adaptor proteins – called Frs2, Shp2 and Grb2 – are essential for propagating the FGF signal. First, the activated receptor binds to and adds phosphate groups to Frs2, which then recruits and facilitates the phosphorylation of Shp2 and Grb2. Here, Wang, Li, Mao et al. offer fresh insights into how this complex of molecules transmit the FGF signal through cells during lens development. First, the team genetically modified the structure and activity of FGF receptors in mice to see how this impacted the formation of their lenses. They found that the membrane-embedded portion of the receptor, which includes the binding site for Frs2, is critical for regulating the consecutive steps of lens development. However, the initial stages of lens formation could still occur when only the Frs2 binding site was mutated. Loss of Grb2 produced a similar effect, suggesting that Frs2 and Grb2 are particularly important for the later stages of lens development . Previous studies have suggested that Shp2 acts as a bridge between Frs2 and Grb2. To test this theory, Wang, Li, Mao et al. deleted the two sites in Shp2 that are responsible for binding to Grb2 and stopped phosphorylation interactions between the two adaptors. While these changes affected embryo survival, they had only a modest impact on lens development. Further experiments revealed that another adaptor protein called Shc1 can also mediate Grb2 recruitment and activation, and may be responsible for transmitting the FGF signal later in lens development. This study provides deeper insights into the network of signaling molecules activated by FGFs, uncovering new mechanisms and adaptors involved in this pathway. The findings suggest that the FGF signaling network is highly adaptable, with different components being required at specific stages of development. Future research expanding on this work may lead to the discovery of therapies that target specific organs affected by FGF-related disorders.

Over 75% of failed pregnancies involve implantation defects. Growth factor receptor-bound protein 2 (GRB2) is an adaptor protein involved in signal transduction and cell communication. Here we show that the expression of GRB2 protein is lower in endometrium of infertile women with endometriosis compared to controls. Our mouse endometriosis model revealed that endometriosis development results to GRB2 loss in the eutopic endometrium. To understand the role of GRB2 in the uterus, we generated mice with conditional ablation of Grb2 in the Pgr positive cells ( Grb2 d/d ). Grb2 d/d mice were infertile due to implantation failure. Although ovarian functions were normal, Grb2 d/d mice had a non-receptive endometrium due to progesterone resistance and dysregulation of steroid hormone and FOXA2 signaling pathways. Furthermore, our results were supported by findings of GRB2 attenuation in primary human endometrial stromal cells from women with endometriosis. Our results demonstrate that GRB2 is critical for endometrial receptivity and decidualization. GRB2 is an adaptor protein that plays a role in cell signal transduction. Here, the authors reveal an attenuation of GRB2 in endometrium from infertile women and show GRB2 knockout in mice results in infertility due to implantation and decidualization defects.