eIF2A, an initiator tRNA carrier refractory to eIF2 kinases, functions synergistically with eIF5B

The initiator tRNA (Met-tRNA(i)(Met)) at the P site of the small ribosomal subunit plays an important role in the recognition of an mRNA start codon. In bacteria, the initiator tRNA carrier, IF2, facilitates the positioning of Met-tRNAiMet on the small ribosomal subunit. Eukarya contain the Met-tRNAiMet carrier, eIF2 (unrelated to IF2), whose carrier activity is inhibited under stress conditions by the phosphorylation of its -subunit by stress-activated eIF2 kinases. The stress-resistant initiator tRNA carrier, eIF2A, was recently uncovered and shown to load Met-tRNAiMet on the 40S ribosomal subunit associated with a stress-resistant mRNA under stress conditions. Here, we report that eIF2A interacts and functionally cooperates with eIF5B (a homolog of IF2), and we describe the functional domains of eIF2A that are required for its binding of Met-tRNAiMet, eIF5B, and a stress-resistant mRNA. The results indicate that the eukaryotic eIF5B-eIF2A complex functionally mimics the bacterial IF2 containing ribosome-, GTP-, and initiator tRNA-binding domains in a single polypeptide.112Ysciescopu

SREBP and MDT-15 protect C. elegans from glucose-induced accelerated aging by preventing accumulation of saturated fat

Glucose-rich diets shorten the life spans of various organisms. However, the metabolic processes involved in this phenomenon remain unknown. Here, we show that sterol regulatory element-binding protein (SREBP) and mediator-15 (MDT-15) prevent the life-shortening effects of a glucose-rich diet by regulating fat-converting processes in Caenorhabditis elegans. Up-regulation of the SREBP/MDT-15 transcription factor complex was necessary and sufficient for alleviating the life-shortening effect of a glucose-rich diet. Glucose feeding induced key enzymes that convert saturated fatty acids (SFAs) to unsaturated fatty acids (UFAs), which are regulated by SREBP and MDT-15. Furthermore, SREBP/MDT-15 reduced the levels of SFAs and moderated glucose toxicity on life span. Our study may help to develop strategies against elevated blood glucose and free fatty acids, which cause glucolipotoxicity in diabetic patients.112217Ysciescopu

Prefoldin 6 mediates longevity response from heat shock factor 1 to FOXO in C-elegans

Heat shock factor 1 (HSF-1) and forkhead box O (FOXO) are key transcription factors that protect cells from various stresses. In Caenorhabditis elegans, HSF-1 and FOXO together promote a long life span when insulin/IGF-1 signaling (IIS) is reduced. However, it remains poorly understood how HSF-1 and FOXO cooperate to confer IIS-mediated longevity. Here, we show that prefoldin 6 (PFD-6), a component of the molecular chaperone prefoldin-like complex, relays longevity response from HSF-1 to FOXO under reduced IIS. We found that PFD-6 was specifically required for reduced IIS-mediated longevity by acting in the intestine and hypodermis. We showed that HSF-1 increased the levels of PFD-6 proteins, which in turn directly bound FOXO and enhanced its transcriptional activity. Our work suggests that the prefoldin-like chaperone complex mediates longevity response from HSF-1 to FOXO to increase the life span in animals with reduced IIS.11Ysciescopu

Airway epithelial cells initiate the allergen response through transglutaminase 2 by inducing IL-33 expression and a subsequent Th2 response

Transglutaminase 2 (TG2) is a post-translational protein-modifying enzyme that catalyzes the transamidation reaction, producing crosslinked or polyaminated proteins. Increased TG2 expression and activity have been reported in various inflammatory conditions, such as rheumatoid arthritis, inflammation-associated pulmonary fibrosis, and autoimmune encephalitis. In particular, TG2 from epithelial cells is important during the initial inflammatory response in the lung. In this study, we evaluated the role of TG2 in the pathogenesis of allergic asthma, particularly whether TG2 affects initial activation signaling leading to Th2 differentiation against antigens. Methods We induced allergic asthma by ovalbumin sensitization and intranasal challenge in wild-type (WT) BALB/c and TG2-deficient mice. Broncheoalveolar lavage fluid cells and intracellular cytokine production were analyzed by flow cytometry. Interleukin (IL)-33 and TG2 expression in lung epithelial cells was detected by confocal microscopy. Results Airway responsiveness was attenuated in TG2-deficient mice compared to that in the WT control. In addition, recruitment of eosinophils and Th2 and Th17 differentiation decreased in TG2-deficient mice. Treatment with cysteamine, a transglutaminase inhibitor, also reduced airway hypersensitivity, inflammatory cell recruitment, and T helper cell differentiation. TG2-deficient mice showed reduced IL-33 expression following induction of allergic asthma compared to those in the WT control. Conclusions We found that pulmonary epithelial cells damaged by allergens triggered TG2-mediated IL-33 expression leading to type 2 responses by recruiting both innate and adaptive arms of the immune system.Peer Reviewe

A mutual activation loop between breast cancer cells and myeloid-derived suppressor cells facilitates spontaneous metastasis through IL-6 trans-signaling in a murine model

Introduction : Tumor cell interactions with the microenvironment, especially those of bone-marrow-derived myeloid cells, are important in various aspects of tumor metastasis. Myeloid-derived suppressor cells (MDSCs) have been suggested to constitute tumor-favoring microenvironments. In this study, we elucidated a novel mechanism by which the MDSCs can mediate spontaneous distant metastasis of breast cancer cells. Methods : Murine breast cancer cells, 4T1 and EMT6, were orthotopically grafted into the mammary fat pads of syngeneic BALB/c mice. CD11b+Gr-1+ MDSCs in the spleen, liver, lung and primary tumor mass were analyzed. To evaluate the role of MDSCs in the distant metastasis, MDSCs were depleted or reconstituted in tumor-bearing mice. To evaluate whether MDSCs in the metastasizing tumor microenvironment affect breast cancer cell behavior, MDSCs and cancer cells were co-cultivated. To investigate the role of MDSCs in in vivo metastasis, we blocked the interactions between MDSCs and cancer cells. Results : Using a murine breast cancer cell model, we showed that murine breast cancer cells with high IL-6 expression recruited more MDSCs and that the metastasizing capacity of cancer cells paralleled MDSC recruitment in tumor-bearing mice. Metastasizing, but not non-metastasizing, tumor-derived factors induced MDSCs to increase IL-6 production and full activation of recruited MDSCs occurred in the primary tumor site and metastatic organ in the vicinity of metastasizing cancer cells, but not in lymphoid organs. In addition, tumor-expanded MDSCs expressed Adam-family proteases, which facilitated shedding of IL-6 receptor, thereby contributing to breast cancer cell invasiveness and distant metastasis through IL-6 trans-signaling. The critical role of IL-6 trans-signaling was confirmed in both the afferent and efferent pathways of metastasis. Conclusion : In this study, we showed that metastasizing cancer cells induced higher MDSCs infiltration and prompted them to secret exaggerated IL-6 as well as soluble IL-6Rα, which, in turn, triggered a persistent increase of pSTAT3 in tumor cells. This potential tumor-MDSC axis involving IL-6 trans-signaling directly affected breast cancer cell aggressiveness, leading to spontaneous metastasis.This work was supported by grants from the National R&D Program for Cancer Control, Ministry of Health & Welfare (12202001), Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2012008122), and the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (2012014152).Peer Reviewe

Activation of AMP-activated Protein Kinase Is Essential for Lysophosphatidic Acid-induced Cell Migration in Ovarian Cancer Cells

Lysophosphatidic acid (LPA) is a bioactive phospholipid that affects various biological functions, such as cell proliferation, migration, and survival, through LPA receptors. Among them, the motility of cancer cells is an especially important activity for invasion and metastasis. Recently, AMP-activated protein kinase (AMPK), an energy-sensing kinase, was shown to regulate cell migration. However, the specific role of AMPK in cancer cell migration is unknown. The present study investigated whether LPA could induce AMPK activation and whether this process was associated with cell migration in ovarian cancer cells. We found that LPA led to a striking increase in AMPK phosphorylation in pathways involving the phospholipase C-beta 3 (PLC-beta 3) and calcium/calmodulin-dependent protein kinase kinase beta (CaMKK beta) in SKOV3 ovarian cancer cells. siRNA-mediated knockdown of AMPK beta 1, PLC-beta 3, or (CaMKK beta) impaired the stimulatory effects of LPA on cell migration. Furthermore, we found that knockdown of AMPK beta 1 abrogated LPA-induced activation of the small GTPase RhoA and ezrin/radixin/moesin proteins regulating membrane dynamics as membrane-cytoskeleton linkers. In ovarian cancer xenograft models, knockdown of AMPK significantly decreased peritoneal dissemination and lung metastasis. Taken together, our results suggest that activation of AMPK by LPA induces cell migration through the signaling pathway to cytoskeletal dynamics and increases tumor metastasis in ovarian cancer.close161

Additional file 1: of IL-1β induces IL-6 production and increases invasiveness and estrogen-independent growth in a TG2-dependent manner in human breast cancer cells

Figure S1. Representative photos of TG2-overexpressing MCF7 cells (MCF7_TG2) and control vector-transfected MCF-7 cells (MCF7_Cont). Figure S2. Effect of immunostimulants on TG2-overexpressing MCF7 cell (TG2) and control vector-transfected MCF-7 cell (Cont) IL-6 expression as measured by ELISA. Cells were treated with toll-like receptor agonists; lipopolysaccharide (LPS, 1 μg/ml), Pam3Cys (Pam, 5 μg/ml), peptidoglycan (PGN, 50 μg/ml), and CPG-ODN (CPG, 1 mM), and bleomycin (BLM, 1 μg/ml) for 48 h. Figure S3. IL-1β increased stem-cell-like phenotypes in a TG2-dependent manner. MCF7_Cont and MCF7_TG2 cells were treated with IL-1β for 6 days, and cell surface expression of CD24 and CD44 was analyzed by flow cytometry analysis. Figure S4. MCF7_Cont and MCF7_TG2 cells were treated with IL-1β (10 ng/ml) for the indicated times. IRAK1 and IRAK2 were detected by Western blot. Figure S5. MCF7_TG2 cells were treated with IL-1β (10 ng/ml) for 30 min. Cell lysates were immunoprecipitated with an anti-TG2 antibody, and TG2, IRAK1, TRAF6, and MyD88 were detected by Western blot. (DOC 1319 kb

A mutual activation loop between breast cancer cells and myeloid-derived suppressor cells facilitates spontaneous metastasis through IL-6 trans-signaling in a murine model

This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Abstract Introduction Tumor cell interactions with the microenvironment, especially those of bone-marrow-derived myeloid cells, are important in various aspects of tumor metastasis. Myeloid-derived suppressor cells (MDSCs) have been suggested to constitute tumor-favoring microenvironments. In this study, we elucidated a novel mechanism by which the MDSCs can mediate spontaneous distant metastasis of breast cancer cells. Methods Murine breast cancer cells, 4T1 and EMT6, were orthotopically grafted into the mammary fat pads of syngeneic BALB/c mice. CD11b+Gr-1+ MDSCs in the spleen, liver, lung and primary tumor mass were analyzed. To evaluate the role of MDSCs in the distant metastasis, MDSCs were depleted or reconstituted in tumor-bearing mice. To evaluate whether MDSCs in the metastasizing tumor microenvironment affect breast cancer cell behavior, MDSCs and cancer cells were co-cultivated. To investigate the role of MDSCs in in vivo metastasis, we blocked the interactions between MDSCs and cancer cells. Results Using a murine breast cancer cell model, we showed that murine breast cancer cells with high IL-6 expression recruited more MDSCs and that the metastasizing capacity of cancer cells paralleled MDSC recruitment in tumor-bearing mice. Metastasizing, but not non-metastasizing, tumor-derived factors induced MDSCs to increase IL-6 production and full activation of recruited MDSCs occurred in the primary tumor site and metastatic organ in the vicinity of metastasizing cancer cells, but not in lymphoid organs. In addition, tumor-expanded MDSCs expressed Adam-family proteases, which facilitated shedding of IL-6 receptor, thereby contributing to breast cancer cell invasiveness and distant metastasis through IL-6 trans-signaling. The critical role of IL-6 trans-signaling was confirmed in both the afferent and efferent pathways of metastasis. Conclusion In this study, we showed that metastasizing cancer cells induced higher MDSCs infiltration and prompted them to secret exaggerated IL-6 as well as soluble IL-6Rα, which, in turn, triggered a persistent increase of pSTAT3 in tumor cells. This potential tumor-MDSC axis involving IL-6 trans-signaling directly affected breast cancer cell aggressiveness, leading to spontaneous metastasis

RNA surveillance via nonsense-mediated mRNA decay is crucial for longevity in daf-2/insulin/IGF-1 mutant C. elegans

Long-lived organisms often feature more stringent protein and DNA quality control. However, whether RNA quality control mechanisms, such as nonsense-mediated mRNA decay (NMD), which degrades both abnormal as well as some normal transcripts, have a role in organismal aging remains unexplored. Here we show that NMD mediates longevity in C. elegans strains with mutations in daf-2/insulin/insulin-like growth factor 1 receptor. We find that daf-2 mutants display enhanced NMD activity and reduced levels of potentially aberrant transcripts. NMD components, including smg-2/UPF1, are required to achieve the longevity of several long-lived mutants, including daf-2 mutant worms. NMD in the nervous system of the animals is particularly important for RNA quality control to promote longevity. Furthermore, we find that downregulation of yars-2/tyrosyl-tRNA synthetase, an NMD target transcript, by daf-2 mutations contributes to longevity. We propose that NMD-mediated RNA surveillance is a crucial quality control process that contributes to longevity conferred by daf-2 mutations. © The Author(s) 201711sciescopu

Airway epithelial cells initiate the allergen response through transglutaminase 2 by inducing IL-33 expression and a subsequent Th2 response

Background Transglutaminase 2 (TG2) is a post-translational protein-modifying enzyme that catalyzes the transamidation reaction, producing crosslinked or polyaminated proteins. Increased TG2 expression and activity have been reported in various inflammatory conditions, such as rheumatoid arthritis, inflammation-associated pulmonary fibrosis, and autoimmune encephalitis. In particular, TG2 from epithelial cells is important during the initial inflammatory response in the lung. In this study, we evaluated the role of TG2 in the pathogenesis of allergic asthma, particularly whether TG2 affects initial activation signaling leading to Th2 differentiation against antigens. Methods We induced allergic asthma by ovalbumin sensitization and intranasal challenge in wild-type (WT) BALB/c and TG2-deficient mice. Broncheoalveolar lavage fluid cells and intracellular cytokine production were analyzed by flow cytometry. Interleukin (IL)-33 and TG2 expression in lung epithelial cells was detected by confocal microscopy. Results Airway responsiveness was attenuated in TG2-deficient mice compared to that in the WT control. In addition, recruitment of eosinophils and Th2 and Th17 differentiation decreased in TG2-deficient mice. Treatment with cysteamine, a transglutaminase inhibitor, also reduced airway hypersensitivity, inflammatory cell recruitment, and T helper cell differentiation. TG2-deficient mice showed reduced IL-33 expression following induction of allergic asthma compared to those in the WT control. Conclusions We found that pulmonary epithelial cells damaged by allergens triggered TG2-mediated IL-33 expression leading to type 2 responses by recruiting both innate and adaptive arms of the immune system