The intracellular domain of CD44 promotes the fusion of macrophages.
Ontology highlight
ABSTRACT:
SUBMITTER: Cui W
PROVIDER: S-EPMC1473173 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:CD44 plays a role in the progression of tumors and is expressed in cancer stem cells (CSCs). However, the mechanisms underlying the crosstalk of CD44 with stemness genes in CSC maintenance remains unclear. In this study, we demonstrated how the cleaved intracellular domain of CD44 (CD44ICD) activates stemness factors such as Nanog, Sox2 and Oct4, and contributes to the tumorigenesis of breast cancer. We have found that the overexpression of CD44ICD increased mammosphere formation in breast cancer cells. Treatment with a γ-secretase inhibitor (GSI), which blocks the cleavage of CD44ICD, interfered with mammosphere formation. Interestingly, CD44ICD decreased the expression levels and nuclear localization of stemness factors, but overexpression of CD44ICD reversed these effects. In addition, we showed that nuclear localization of CD44ICD is important for transcriptional activation of the stemness factors. Furthermore, CD44ICD-overexpressed cells exhibited strong tumorigenecity and greater metastatic potential than did the control cells or CD44-depleted cells in vivo in mice models. Taken together, it was supposed that CD44 promotes tumorigenesis through the interaction and nuclear-translocation of its intracellular domain and stemness factors. We suggest that the prevention of cleavage and nuclear-translocation of CD44ICD is a potential target in treating breast cancer.
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Project description:The success of gene therapy in the ocular environment is partly due to the presence of hyaluronan in vitreous. Here we explore the mechanism of hyaluronan-mediated enhancement of adenoviral vector transgene expression. Introduction of hyaluronan receptor CD44 into CD44-negative cells followed by transduction in the presence of vitreous with an adenoviral vector containing an IL-12-coding transgene increases IL-12 secretion. We demonstrate that sequential CD44 proteolysis is responsible for hyaluronan-mediated enhancement. Metalloproteinase or ?-secretase inhibitors decrease adenoviral-mediated transgene expression. Deletion of these proteolytic sites in CD44 also inhibits transgene expression. Expression of CD44 with a mutation to prevent phosphorylation of serine 325 inhibits the response to vitreous. Expression of the CD44 intracellular domain enhances transgene expression in the absence of vitreous. CD44-mediated enhancement of gene expression was observed with vectors using different promoters and appears because of an increase in mRNA production, not because of an increase in vector transduction as determined by quantitative RT-PCR and quantitative PCR, respectively. These data fit a model where the interaction of hyaluronan in vitreous and CD44 modulates transgene expression by initiating CD44 proteolysis and release of the cytoplasmic domain, resulting in increased transgene transcription.
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Project description:Rational: Intracellular bacterial survival is a major factor causing chronic or recurrent infection, leading to the failure of both host defense and/or antibiotic treatment. However, the elimination of intracellular bacteria is challenging as they are protected from antibiotics and host immune attack. Recent studies have indicated that iron helps macrophages against intracellular bacteria, contradictory to traditional "nutritional immunity", in which iron is considered a key nutrient for bacterial survival in host cells. However, how iron facilitates intracellular bacterial death has not been fully clarified. In this study, we found that ferroptotic stress can help macrophages suppress intracellular bacteria by reversing the importation of ferrous iron into bacterial vacuoles via ferroportin and thereby inducing in situ ferroptosis-like bacterial death. Methods: A macrophage model of bacterial invasion was established to monitor dynamic changes in ferroptotic hallmarks, including ferrous iron and lipid peroxidation. Ferroptosis inducers and inhibitors were added to the model to evaluate the relationship between ferroptotic stress and intracellular bacterial survival. We then determined the spatiotemporal distributions of ferroportin, ferrous iron, and lipid peroxidation in macrophages and intracellular bacteria. A bacterial infection mouse model was established to evaluate the therapeutic effects of drugs that regulate ferroptotic stress. Results: Ferrous iron and lipid peroxidation increased sharply in the early stage of bacterial infection in the macrophages, then decreased to normal levels in the late stage of infection. The addition of ferroptosis inducers (ras-selective lethal small molecule 3, sulfasalazine, and acetaminophen) in macrophages promoted intracellular bacterial suppression. Further studies revealed that ferrous iron could be delivered to the intracellular bacterial compartment via inward ferroportin transportation, where ferrous iron induced ferroptosis-like death of bacteria. In addition, ferroptotic stress declined to normal levels in the late stage of infection by regulating iron-related pathways in the macrophages. Importantly, we found that enhancing ferroptotic stress with a ferroptosis inducer (sulfasalazine) successfully suppressed bacteria in the mouse infection models. Conclusions: Our study suggests that the spatiotemporal response to ferroptosis stress is an efficient pathway for macrophage defense against bacterial invasion, and targeting ferroptosis may achieve therapeutic targets for infectious diseases challenged by intracellular pathogens.
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Project description:The epidermal growth factor receptor (EGFR) and its ligands are essential regulators of epithelial biology, which are often amplified in cancer cells. We have previously shown that shRNA-mediated silencing of one of these ligands, amphiregulin (AREG), results in keratinocyte growth arrest that cannot be rescued by soluble extracellular EGFR ligands. To further explore the functional importance of specific AREG domains, we stably transduced keratinocytes expressing tetracycline-inducible AREG-targeted shRNA with lentiviruses expressing silencing-proof, membrane-tethered AREG cytoplasmic and extracellular domains (AREG-CTD and AREG-ECD), as well as full-length AREG precursor (proAREG). Here we show that growth arrest of AREG-silenced keratinocytes occurs in G2/M and is significantly restored by proAREG and AREG-CTD but not by AREG-ECD. Moreover, the AREG-CTD was sufficient to normalize cell cycle distribution profiles and expression of mitosis-related genes. Our findings uncover an important role of the AREG-CTD in regulating cell division, which may be relevant to tumor resistance to EGFR-directed therapies.
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