Browsing by Subject "Macroautophagy"

Now showing 1 - 5 of 5
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    Cytosol to Lysosome Transport of Intracellular Antigens During Immune Surveillance
    (Wiley, 2008-01) Crotzer, Victoria L.; Blum, Janice S.; Department of Microbiology and Immunology and the Walther Oncology Center, Indiana University School of Medicine
    The delivery of intracellular substrates such as misfolded proteins and damaged organelles from the cytosol to the lysosome for degradation is crucial for cell survival. Multiple transport pathways including bulk autophagy (microautophagy and macroautophagy) and chaperone‐mediated autophagy (CMA) have been identified to efficiently facilitate this transit of macromolecules from the cytoplasm to acidic vacuolar organelles. While autophagy plays a role in the general housekeeping of cells, it also functions in more specialized processes such as development and differentiation, responses to physiological stress and immunity. The presentation of both exogenous and endogenous antigens (Ag) by major histocompatibility complex (MHC) class II molecules to CD4+ T lymphocytes is critical for the induction of tolerance to self Ag as well as the development of immunity against intracellular pathogens and tumors. Here, we discuss the class II‐mediated presentation of several endogenous Ag, dependent on either macroautophagy or CMA for their transport from the cytosol to endosomal/lysosomal compartments. Thus, the various pathways of autophagy as routes of cytoplasmic Ag delivery to lysosomes have significant implications for the MHC class II‐mediated immune response to intracellular pathogens and cancer.
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    The HMGB1-RAGE axis modulates the growth of autophagy-deficient hepatic tumors
    (Springer Nature, 2020-05) Khambu, Bilon; Hong, Honghai; Liu, Sheng; Liu, Gang; Chen, Xiaoyun; Dong, Zheng; Wan, Jun; Yin, Xiao-Ming; Pathology and Laboratory Medicine, School of Medicine
    Autophagy is an intracellular lysosomal degradative pathway important for tumor surveillance. Autophagy deficiency can lead to tumorigenesis. Autophagy is also known to be important for the aggressive growth of tumors, yet the mechanism that sustains the growth of autophagy-deficient tumors is not unclear. We previously reported that progression of hepatic tumors developed in autophagy-deficient livers required high mobility group box 1 (HMGB1), which was released from autophagy-deficient hepatocytes. In this study we examined the pathological features of the hepatic tumors and the mechanism of HMGB1-mediated tumorigenesis. We found that in liver-specific autophagy-deficient (Atg7ΔHep) mice the tumors cells were still deficient in autophagy and could also release HMGB1. Histological analysis using cell-specific markers suggested that fibroblast and ductular cells were present only outside the tumor whereas macrophages were present both inside and outside the tumor. Genetic deletion of Hmgb1 or one of its receptors, receptor for advanced glycated end product (Rage), retarded liver tumor development. HMGB1 and RAGE enhanced the proliferation capability of the autophagy-deficient hepatocytes and tumors. However, RAGE expression was only found on ductual cells and Kupffer's cells but not on hepatoctyes, suggesting that HMGB1 might promote hepatic tumor growth through a paracrine mode, which altered the tumor microenvironment. Finally, RNAseq analysis of the tumors indicated that HMGB1 induced a much broad changes in tumors. In particular, genes related to mitochondrial structures or functions were enriched among those differentially expressed in tumors in the presence or absence of HMGB1, revealing a potentially important role of mitochondria in sustaining the growth of autophagy-deficient liver tumors via HMGB1 stimulation.
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    Melanoma LAMP-2C Modulates Tumor Growth and Autophagy
    (Frontiers, 2018-08-29) Pérez, Liliana; Sinn, Anthony L.; Sandusky, George E.; Pollok, Karen E.; Blum, Janice S.; Pathology and Laboratory Medicine, School of Medicine
    Autophagy plays critical but diverse roles in cellular quality control and homeostasis potentially checking tumor development by removing mutated or damaged macromolecules, while conversely fostering tumor survival by supplying essential nutrients during cancer progression. This report documents a novel inhibitory role for a lysosome-associated membrane protein, LAMP-2C in modulating autophagy and melanoma cell growth in vitro and in vivo. Solid tumors such as melanomas encounter a variety of stresses in vivo including inflammatory cytokines produced by infiltrating lymphocytes directed at limiting tumor growth and spread. Here, we report that in response to the anti-tumor, pro-inflammatory cytokine interferon-gamma, melanoma cell expression of LAMP2C mRNA significantly increased. These results prompted an investigation of whether increased melanoma cell expression of LAMP-2C might represent a mechanism to control or limit human melanoma growth and survival. In this study, enhanced expression of human LAMP-2C in melanoma cells perturbed macroautophagy and chaperone-mediated autophagy in several human melanoma lines. In vitro analysis showed increasing LAMP-2C expression in a melanoma cell line, triggered reduced cellular LAMP-2A and LAMP-2B protein expression. Melanoma cells with enhanced LAMP-2C expression displayed increased cell cycle arrest, increased expression of the cell cycle regulators Chk1 and p21, and greater apoptosis and necrosis in several cell lines tested. The increased abundance of Chk1 protein in melanoma cells with increased LAMP-2C expression was not due to higher CHEK1 mRNA levels, but rather an increase in Chk1 protein abundance including Chk1 molecules phosphorylated at Ser345. Human melanoma cell xenografts with increased LAMP-2C expression, displayed reduced growth in immune compromised murine hosts. Melanomas with high LAMP-2C expression showed increased necrosis and reduced cell density upon histological analysis. These results reveal a novel role for LAMP-2C in negatively regulating melanoma growth and survival.
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    NRF2 transcriptionally regulates Caspase-11 expression to activate HMGB1 release by Autophagy-deficient hepatocytes
    (Springer Nature, 2023-07-28) Khambu, Bilon; Cai, Genxiang; Liu, Gang; Bailey, Niani Tiaye; Mercer, Arissa A.; Baral, Kamal; Ma, Michelle; Chen, Xiaoyun; Li, Yu; Yin, Xiao-Ming; Pathology and Laboratory Medicine, School of Medicine
    Injury or stress can induce intracellular translocation and release of nuclear HMGB1, a DAMP molecule known to participate in inflammation and other pathological processes. Active release of HMGB1 from stimulated macrophages can be mediated by inflammasomes, which cleave Gasdermin D to form pores on cytoplasmic membranes. We previously had shown that active release of HMGB1 from autophagy deficient hepatocytes also depended on the inflammasome but how the inflammasome was activated was not known. Here we report that persistent activation of transcription factor NRF2 under the autophagy deficient condition led to transcriptional upregulation of Caspase-11 expression, which could then activate the CASPASE-1inflammasome. Using chromatin immunoprecipitation (CHIP) and luciferase-based reporter assays, we show that NRF2 directly binds to the Caspase-11 promoter and transcriptionally increase the expression of Caspase-11. Genetic deletion of Caspase-11 in autophagy-deficient livers represses the release of HMGB1 and its pathological consequence, ductular cell proliferation. Consistently, deletion of NLRP3, which can activate CASPASE-1 mediated inflammasomes under other types of signals, did not prevent HMGB1 release and ductular cell proliferation in autophagy deficient livers. Surprisingly, while cleavage of GASDEMIN D occurred in autophagy-deficient livers its deletion did not prevent the HMGB1 release, suggesting that CASPASE-11-mediated inflammasome activation may also engage in a different mechanism for HMGB1 release by the autophagy deficient hepatocytes. Collectively, this work reveals the novel role of NRF2 in transcriptional upregulation of Caspase-11 and in inflammasome activation to promote active release of HMGB via a non-Gasdermin D mediated avenue.
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    Pharmacological Promotion of Autophagy Alleviates Steatosis and Injury in Alcoholic and Non-alcoholic Fatty Liver Conditions in Mice
    (Elsevier, 2013) Lin, Chih-Wen; Zhang, Hao; Li, Min; Xiong, Xiwen; Chen, Xi; Chen, Xiaoyun; Dong, Xiaocheng X.; Yin, Xiao-Ming; Pathology and Laboratory Medicine, School of Medicine
    Background & aims: Pharmacological approaches can potentially improve fatty liver condition in alcoholic and non-alcoholic fatty liver diseases. The salutary effects of reducing lipid synthesis or promoting lipid oxidation have been well reported, but the benefits of increasing lipid degradation have yet to be well explored. Macroautophagy is a cellular degradation process that can remove subcellular organelles including lipid droplets. We thus investigated whether pharmacological modulation of macroautophagy could be an effective approach to alleviate fatty liver condition and liver injury. Methods: C57BL/6 mice were given ethanol via intraperitoneal injection (acute) or by a 4-week oral feeding regime (chronic), or high fat diet for 12 weeks. An autophagy enhancer, carbamazepine or rapamycin, or an autophagy inhibitor, chloroquine, was given before sacrifice. Activation of autophagy, level of hepatic steatosis, and blood levels of triglycerides, liver enzyme, glucose and insulin were measured. Results: In both acute and chronic ethanol condition, macroautophagy was activated. Carbamazepine, as well as rapamycin, enhanced ethanol-induced macroautophagy in hepatocytes in vitro and in vivo. Hepatic steatosis and liver injury were exacerbated by chloroquine, but alleviated by carbamazepine. The protective effects of carbamazepine and rapamycin in reducing steatosis and in improving insulin sensitivity were also demonstrated in high fat diet-induced non-alcoholic fatty liver condition. Conclusions: These findings indicate that pharmacological modulation of macroautophagy in the liver can be an effective strategy for reducing fatty liver condition and liver injury.