Cilium induction triggers differentiation of glioma stem cells

Glioblastoma multiforme (GBM) possesses glioma stem cells (GSCs) that promote self-renewal, tumor propagation, and relapse. GBM has a poor prognosis, and currently, there are no curative options exist. Understanding the mechanisms of GSCs self-renewal can offer targeted therapeutic interventions. However, insufficient knowledge of the fundamental biology of GSCs is a significant bottleneck hindering these efforts. Here, we show that patient-derived GSCs recruit an elevated level of proteins that ensure the temporal cilium disassembly, leading to suppressed ciliogenesis. Depleting the cilia disassembly complex components at the ciliary base is sufficient to induce ciliogenesis in a subset of…

E4BP4/NFIL3 modulates the epigenetically repressed RAS effector RASSF8 function through histone methyltransferases

RAS proteins are major human oncogenes, and most of the studies are focused on enzymatic RAS effectors. Recently, nonenzymatic RAS effectors (RASSF, RAS association domain family) have garnered special attention because of their tumor-suppressive properties in contrast to the oncogenic potential of the classical enzymatic RAS effectors. Whereas most members of RASSF family are deregulated by promoter hypermethylation, RASSF8 promoter remains unmethylated in many cancers but the mechanism(s) of its down-regulation remains unknown. Here, we unveil E4BP4 as a critical transcriptional modulator repressing RASSF8 expression through histone methyltransferases, G9a and SUV39H1. In line with these …

ERK3/MAPK6 controls IL-8 production and chemotaxis

ERK3 is a ubiquitously expressed member of the atypical mitogen activated protein kinases (MAPKs) and the physiological significance of its short half-life remains unclear. By employing gastrointestinal 3D organoids, we detect that ERK3 protein levels steadily decrease during epithelial differentiation. ERK3 is not required for 3D growth of human gastric epithelium. However, ERK3 is stabilized and activated in tumorigenic cells, but deteriorates over time in primary cells in response to lipopolysaccharide (LPS). ERK3 is necessary for production of several cellular factors including interleukin-8 (IL-8), in both, normal and tumorigenic cells. Particularly, ERK3 is critical for AP-1 signaling…

Targeting prohibitins at the cell surface prevents Th17-mediated autoimmunity.

T helper (Th)17 cells represent a unique subset of CD4(+) T cells and are vital for clearance of extracellular pathogens including bacteria and fungi. However, Th17 cells are also involved in orchestrating autoimmunity. By employing quantitative surface proteomics, we found that the evolutionarily conserved prohibitins (PHB1/2) are highly expressed on the surface of both murine and human Th17 cells. Increased expression of PHBs at the cell surface contributed to enhanced CRAF/MAPK activation in Th17 cells. Targeting surface‐expressed PHBs on Th17 cells with ligands such as Vi polysaccharide (Typhim vaccine) inhibited CRAF‐MAPK pathway, reduced interleukin (IL)‐17 expression and ameliorated …

Cilium induction triggers differentiation of glioma stem cells.

Glioblastoma multiforme (GBM) possesses glioma stem cells (GSCs) that promote self-renewal, tumor propagation, and relapse. Understanding the mechanisms of GSCs self-renewal can offer targeted therapeutic interventions. However, insufficient knowledge of GSCs' fundamental biology is a significant bottleneck hindering these efforts. Here, we show that patient-derived GSCs recruit elevated levels of proteins that ensure the temporal cilium disassembly, leading to suppressed ciliogenesis. Depleting the cilia disassembly complex components is sufficient to induce ciliogenesis in a subset of GSCs via relocating platelet-derived growth factor receptor-alpha (PDGFR-α) to a newly induced cilium. Im…

Famotidine inhibits toll-like receptor 3-mediated inflammatory signaling in SARS-CoV-2 infection

Apart from prevention using vaccinations, the management options for COVID-19 remain limited. In retrospective cohort studies, use of famotidine, a specific oral H2 receptor antagonist (antihistamine), has been associated with reduced risk of intubation and death in patients hospitalized with COVID-19. In a case series, nonhospitalized patients with COVID-19 experienced rapid symptom resolution after taking famotidine, but the molecular basis of these observations remains elusive. Here we show using biochemical, cellular, and functional assays that famotidine has no effect on viral replication or viral protease activity. However, famotidine can affect histamine-induced signaling processes i…

Caspase-2 is an initiator caspase responsible for pore-forming toxin-mediated apoptosis

Bacterial pathogens modulate host cell apoptosis to establish a successful infection. Pore-forming toxins (PFTs) secreted by pathogenic bacteria are major virulence factors and have been shown to induce various forms of cell death in infected cells. Here we demonstrate that the highly conserved caspase-2 is required for PFT-mediated apoptosis. Despite being the second mammalian caspase to be identified, the role of caspase-2 during apoptosis remains enigmatic. We show that caspase-2 functions as an initiator caspase during Staphylococcus aureus alpha-toxin- and Aeromonas aerolysin-mediated apoptosis in epithelial cells. Downregulation of caspase-2 leads to a strong inhibition of PFT-mediate…

Targeting prohibitins with chemical ligands inhibits KRAS-mediated lung tumours.

KRAS is one of the most frequently mutated oncogenes in human non-small cell lung cancers (NSCLCs). RAS proteins trigger multiple effector signalling pathways including the highly conserved RAF-MAPK pathway. CRAF, a direct RAS effector protein, is required for KRAS-mediated tumourigenesis. Thus, the molecular mechanisms driving the activation of CRAF are intensively studied. Prohibitin 1 (PHB1) is an evolutionarily conserved adaptor protein and interaction of CRAF with PHB1 at the plasma membrane is essential for CRAF activation. Here, we demonstrate that PHB1 is highly expressed in NSCLC patients and correlates with poor survival. Targeting of PHB1 with two chemical ligands (rocaglamide an…

IAPs and cell migration.

Inhibitors of apoptosis (IAPs) constitute a family of cell signaling regulators controlling several fundamental biological processes such as innate immunity, inflammation, cell death, cell proliferation, and cell differentiation. Increasing evidence from in vivo and in vitro studies indicate a function for IAPs in the modulation of invasive and migratory properties of cells. Here, we present and discuss the mechanisms whereby IAPs can control cell migration.

Dimerization of the kinase ARAF promotes MAPK pathway activation and cell migration.

The RAF family of kinases mediates RAS signaling, and RAF inhibitors can be effective for treating tumors with BRAF V600E mutant protein. However, RAF inhibitors paradoxically accelerate metastasis in RAS -mutant tumors and become ineffective in BRAF V600E tumors because of reactivation of downstream mitogen-activated protein kinase (MAPK) signaling. We found that the RAF isoform ARAF has an obligatory role in promoting MAPK activity and cell migration in a cell type–dependent manner. Knocking down ARAF prevented the activation of MAPK kinase 1 (MEK1) and extracellular signal–regulated kinase 1 and 2 (ERK1/2) and decreased the number of protrusions from tumor cell spheroids in three-dimensi…

ANKRD26-RET - A novel gene fusion involving RET in papillary thyroid carcinoma

Abstract Background Rearrangements of RET are drivers of oncogenesis, traceable in different cancer types as papillary thyroid carcinoma (PTC), non-small cell lung cancer, colorectal or breast cancer. Anchored multiplex PCR based next-generation sequencing (NGS) can detect RET rearrangements involving previously unknown partner genes. Methods A sample of PTC underwent NGS, following detection of RET rearrangement by fluorescence in situ hybridization. Expression analysis of ANKRD26 and RET was performed for the tumor harboring ANKRD26-RET, for corresponding normal thyroid tissue and PTC tumors with representative genetic alterations (BRAFV600E, CCDC6-RET), complemented by a comparative sear…

SIK2 orchestrates actin-dependent host response upon Salmonella infection

Significance Through conducting quantitative proteomics upon Salmonella infection, we identified a SIK2 signaling network, implementing the kinase into a so far concealed biological function. Our data exposed SIK2 as a central orchestrator of an actin regulatory network, coordinating the stability of Salmonella-containing vacuole (SCV) and cellular actin assembly, in order to limit the acute phase of the infection. Most strikingly, SIK2 is not exclusively acting locally on actin assembly associated with the SCV but impacts the actin cytoskeleton architecture in its entirety upon Salmonella infection. Our work provides a mechanistic framework for how the actin cytoskeleton is regulated and h…

The sphingosine kinase 1 activator, K6PC-5, attenuates Ebola virus infection

Summary Ebola virus (EBOV) is responsible for outbreaks with case fatality rates of up to 90% and for an epidemic in West Africa with more than ten thousand deaths. EBOV glycoprotein (EBOV-GP) is the only viral surface protein and is responsible for viral entry into cells. Here, by employing pseudotyped EBOV-GP viral particles, we uncover a critical role for sphingolipids in inhibiting viral entry. Sphingosine kinase 1 (SphK1) catalyzes the phosphorylation of sphingosine to sphingosine 1-phosphate (S1P). The administration of the SphK1 activator, K6PC-5, or S1P, or the overexpression of SphK1 consistently exhibited striking inhibitory effects in EBOV-GP-driven entry in diverse cell lines. F…

Novel rearrangements involving the RET gene in papillary thyroid carcinoma.

Abstract Background In the field of gene fusions driving tumorigenesis in papillary thyroid carcinoma (PTC), rearrangement of the proto-oncogene RET is the most frequent alteration. Apart from the most common rearrangement of RET to CCDC6, more than 15 partner genes are yet reported. The landscape of RET rearrangements in PTC (“RET-PTC”) can notably be enlarged by modern targeted next-generation sequencing, indicating similarities between oncogenic pathways in other cancer types with identical genetic alterations. Methods Targeted next-generation sequencing was performed for two cases of BRAF-wild type PTC with confirmation of the results by Sanger sequencing. A “UniProt” database research …

PLEKHM1 Regulates Salmonella-Containing Vacuole Biogenesis and Infection

Abstract: The host endolysosomal compartment is often manipulated by intracellular bacterial pathogens. Salmonella (Salmonella enterica serovar Typhimurium) secrete numerous effector proteins, including SifA, through a specialized type III secretion system to hijack the host endosomal system and generate the Salmonella-containing vacuole (SCV). To form this replicative niche, Salmonella targets the Rab7 GTPase to recruit host membranes through largely unknown mechanisms. We show that Pleckstrin homology domain-containing protein family member 1 (PLEKHM1), a lysosomal adaptor, is targeted by Salmonella through direct interaction with SifA. By binding the PLEKHM1 PH2 domain, Salmonella utiliz…

Protein kinase CK2 enables regulatory T cells to suppress excessive TH2 responses in vivo

The quality of the adaptive immune response depends on the differentiation of distinct CD4(+) helper T cell subsets, and the magnitude of an immune response is controlled by CD4(+)Foxp3(+) regulatory T cells (Treg cells). However, how a tissue- and cell type-specific suppressor program of Treg cells is mechanistically orchestrated has remained largely unexplored. Through the use of Treg cell-specific gene targeting, we found that the suppression of allergic immune responses in the lungs mediated by T helper type 2 (TH2) cells was dependent on the activity of the protein kinase CK2. Genetic ablation of the β-subunit of CK2 specifically in Treg cells resulted in the proliferation of a hithert…

Divide and rule: The role of ubiquitination in inactivation of the ERK5-MAPK cascade

Recently, we revealed that ubiquitination of MEKK2 and MEKK3 by inhibitor of apoptosis proteins (IAPs) directly disrupts MEK5/ERK5 interaction and subsequently attenuates ERK5 activation. In addition, loss of XIAP promotes human myogenic differentiation in an ERK5-dependent manner. These results reveal another layer of MAPK regulation and a novel role for XIAP in controlling myogenic differentiation.

HMG-CoA reductase promotes protein prenylation and therefore is indispensible for T-cell survival.

AbstractStatins are a well-established family of drugs that lower cholesterol levels via the competitive inhibition of the enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR). In addition, the pleiotropic anti-inflammatory effects of statins on T cells make them attractive as therapeutic drugs in T-cell-driven autoimmune disorders. Since statins do not exclusively target HMGCR and thus might have varying effects on different cell types, we generated a new mouse strain allowing for the tissue-specific deletion of HMGCR. Deletion of HMGCR expression in T cells led to a severe decrease in their numbers with the remaining cells displaying an activated phenotype, with an increased pro…

Science Signaling Podcast: 5 August 2014

This Podcast features an interview with Juliane Mooz and Krishnaraj Rajalingam, authors of a Research Article that appears in the 5 August 2014 issue of Science Signaling , about the cellular functions of the kinase ARAF. RAF proteins are serine-threonine kinases that mediate signaling through the mitogen-activated protein kinase (MAPK) pathway, and aberrant RAF activity can transform normal cells into cancerous cells. There are three RAFs in mammals: ARAF, BRAF, and CRAF. The most studied of these is BRAF, mutations in which are associated with various cancers. Whereas the cellular functions of BRAF and CRAF have been extensively studied, not much is known about ARAF. Mooz et al . found th…

The Sphingosine Kinase-1 Activator, K6PC-5, Attenuates the Ebola Virus Infection and the Virus Induced Cell Death

Ebola virus (EBOV) is responsible for outbreaks with case-fatality rates of up to 90% and for an epidemic in West Africa with more than ten thousand deaths. EBOV glycoprotein (EBOV-GP) is the only viral surface protein and is responsible for viral entry into cells. It has been suggested to play a role in the cytopathic effects induced by the virus. Here we uncover a critical role for sphingolipids in inhibiting viral entry and virus-mediated cytotoxicity. Sphingosine kinase 1 (SphK1) catalyzes the phosphorylation of sphingosine to sphingosine-1-phosphate (S1P).  The administration of the SphK1 activator, K6PC-5, or S1P, or the overexpression of SphK1 consistently exhibited striking inhibito…

A subset of flavaglines inhibits KRAS nanoclustering and activation.

The RAS oncogenes are frequently mutated in human cancers and among the three isoforms (KRAS, HRAS and NRAS), KRAS is the most frequently mutated oncogene. Here, we demonstrate that a subset of flavaglines, a class of natural anti-tumour drugs and chemical ligands of prohibitins, inhibit RAS GTP loading and oncogene activation in cells at nanomolar concentrations. Treatment with rocaglamide, the first discovered flavagline, inhibited the nanoclustering of KRAS, but not HRAS and NRAS, at specific phospholipid-enriched plasma membrane domains. We further demonstrate that plasma membrane-associated prohibitins directly interact with KRAS, phosphatidylserine and phosphatidic acid, and these int…

The NG2 Proteoglycan Protects Oligodendrocyte Precursor Cells against Oxidative Stress via Interaction with OMI/HtrA2.

The NG2 proteoglycan is characteristically expressed by oligodendrocyte progenitor cells (OPC) and also by aggressive brain tumours highly resistant to chemo- and radiation therapy. Oligodendrocyte-lineage cells are particularly sensitive to stress resulting in cell death in white matter after hypoxic or ischemic insults of premature infants and destruction of OPC in some types of Multiple Sclerosis lesions. Here we show that the NG2 proteoglycan binds OMI/HtrA2, a mitochondrial serine protease which is released from damaged mitochondria into the cytosol in response to stress. In the cytosol, OMI/HtrA2 initiates apoptosis by proteolytic degradation of anti-apoptotic factors. OPC in which NG…

Druggable genome and precision medicine in cancer: current challenges.

The past decades have seen tremendous developments with respect to "specific" therapeutics that target key signaling molecules to conquer cancer. The key advancements with multiomics technologies, especially genomics, have allowed physicians and molecular oncologists to design "tailor-made" solutions to the specific oncogenes that are deregulated in individual patients, a strategy which has turned out to be successful though the patients quickly develop resistance. The swift integration of multidisciplinary approaches has led to the development of "next generation" therapeutics and, with synergistic therapeutic regimes combined with immune checkpoint inhibitors to reactivate the dampened im…

Author response: ERK3/MAPK6 controls IL-8 production and chemotaxis

Cationic Amino Acid Transporter-1-Mediated Arginine Uptake Is Essential for Chronic Lymphocytic Leukemia Cell Proliferation and Viability

Interfering with tumor metabolism by specifically restricting the availability of extracellular nutrients is a rapidly emerging field of cancer research. A variety of tumor entities depend on the uptake of the amino acid arginine since they have lost the ability to synthesize it endogenously, that is they do not express the rate limiting enzyme for arginine synthesis, argininosuccinate synthase (ASS). Arginine transport through the plasma membrane of mammalian cells is mediated by eight different transporters that belong to two solute carrier (SLC) families. In the present study we found that the proliferation of primary as well as immortalized chronic lymphocytic leukemia (CLL) cells depen…