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Chiye Sakurai, Makoto Itakura, Daiki Kinoshita, Seisuke Arai, Hitoshi Hashimoto, Ikuo Wada, Kiyotaka Hatsuzawa
SNAP-23 is a plasma membrane-localized SNARE protein involved in Fc receptor (FcR)-mediated phagocytosis. However, the regulatory mechanism underlying its function remains elusive. Using phosphorylation specific-antibodies, SNAP-23 was found to be phosphorylated at Ser95 in macrophages. To understand the role of this phosphorylation, we established macrophage lines overexpressing the non-phosphorylatable S95A or the phospho-mimicking S95D mutation. The efficiency of phagosome formation and maturation was severely reduced in SNAP-23-S95D-overexpressing cells...
May 17, 2018: Molecular Biology of the Cell
Gholamreza Fazeli, Maurice Stetter, Jaime N Lisack, Ann M Wehman
To understand how undifferentiated pluripotent cells cope with cell corpses, we examined the clearance of polar bodies born during female meiosis. We found that polar bodies lose membrane integrity and expose phosphatidylserine in Caenorhabditis elegans. Polar body signaling recruits engulfment receptors to the plasma membrane of embryonic blastomeres using the PI3K VPS-34, RAB-5 GTPase and the sorting nexin SNX-6. The second polar body is then phagocytosed using receptor-mediated engulfment pathways dependent on the Rac1 ortholog CED-10 but undergoes non-apoptotic programmed cell death independent of engulfment...
May 15, 2018: Cell Reports
Shengkun Yao, Jiadong Fan, Zhiyun Chen, Yunbing Zong, Jianhua Zhang, Zhibin Sun, Lijuan Zhang, Renzhong Tai, Zhi Liu, Chunying Chen, Huaidong Jiang
Knowledge of the interactions between nanomaterials and large-size mammalian cells, including cellular uptake, intracellular localization and translocation, has greatly advanced nanomedicine and nanotoxicology. Imaging techniques that can locate nanomaterials within the structures of intact large-size cells at nanoscale resolution play crucial roles in acquiring this knowledge. Here, the quantitative imaging of intracellular nanomaterials in three dimensions was performed by combining dual-energy contrast X-ray microscopy and an iterative tomographic algorithm termed equally sloped tomography (EST)...
March 1, 2018: IUCrJ
Anna Mularski, Florence Marie-Anaïs, Julie Mazzolini, Florence Niedergang
Complementary methods to observe frustrated phagocytosis and phagosome closure using total internal reflection fluorescence microscopy (TIRFM) are described here. Frustrated phagocytosis occurs when phagocytic cells are exposed to an opsonized surface and spread as if trying to engulf it, allowing for the observation of phagocytic spreading and the biochemical events that directly precede it. Phagosome formation and closure is an inherently three-dimensional process though, and cannot be studied in the "frustrated" situation...
2018: Methods in Molecular Biology
Hyun-Jung Koh, Ye-Ram Kim, Jae-Sung Kim, Jin-Seung Yun, Sojin Kim, Sun Young Kim, Kiseok Jang, Chul-Su Yang
The tumor suppressor gene CD82/KAI1 is a member of the tetraspanin superfamily and organizes various membrane-based processes. Mycobacterium tuberculosis (MTB) persists in host macrophages by interfering with phagolysosome biogenesis and inflammatory responses, but the role of CD82 in controlling the intracellular survival of pathogenic mycobacteria within macrophages remains poorly understood. In this study, we demonstrated that the virulent MTB strain H37Rv (MTB Rv) induced CD82 promoter hypomethylation, resulting in CD82 expression...
May 14, 2018: Experimental & Molecular Medicine
Sergey Kalinin, Marta González-Prieto, Hannah Scheiblich, Lucia Lisi, Handojo Kusumo, Michael T Heneka, Jose L M Madrigal, Subhash C Pandey, Douglas L Feinstein
BACKGROUND: Microglial activation contributes to the neuropathology associated with chronic alcohol exposure and withdrawal, including the expression of inflammatory and anti-inflammatory genes. In the current study, we examined the transcriptome of primary rat microglial cells following incubation with alcohol alone, or alcohol together with a robust inflammatory stimulus. METHODS: Primary microglia were prepared from mixed rat glial cultures. Cells were incubated with 75 mM ethanol alone or with proinflammatory cytokines ("TII": IL1β, IFNγ, and TNFα)...
May 14, 2018: Journal of Neuroinflammation
Hyo-Ji Lee, Hyun-Jeong Ko, Dong-Kun Song, Yu-Jin Jung
Tuberculosis is caused by the infectious agent Mycobacterium tuberculosis (Mtb). Mtb has various survival strategies, including blockade of phagosome maturation and inhibition of antigen presentation. Lysophosphatidylcholine (LPC) is a major phospholipid component of oxidized low-density lipoprotein and is involved in various cellular responses, such as activation of second messengers and bactericidal activity in neutrophils. In this study, macrophages were infected with a low infectious dose of Mtb and treated with LPC to investigate the bactericidal activity of LPC against Mtb...
2018: Frontiers in Immunology
Damián Lobato-Márquez, Sina Krokowski, Andrea Sirianni, Gerald Larrouy-Maumus, Serge Mostowy
Shigella flexneri, a Gram-negative enteroinvasive pathogen, causes inflammatory destruction of the human intestinal epithelium. During infection of epithelial cells, Shigella escape from the phagosome to the cytosol, where they reroute host cell glycolysis to obtain nutrients for proliferation. Septins, a poorly understood component of the cytoskeleton, can entrap cytosolic Shigella targeted to autophagy in cage-like structures to restrict bacterial proliferation. Although bacterial entrapment by septin caging has been the subject of intense investigation, the role of septins and the autophagy machinery in the proliferation of non-caged Shigella is mostly unknown...
May 12, 2018: Cytoskeleton
Qihong Wu, Tianyu Miao, Ting Feng, Chuan Yang, Yingkun Guo, Hong Li
With the increase in applications of superparamagnetic iron oxide nanoparticles (SPIONs) in biomedicine, it is essential to investigate the bio‑security of these nanoparticles, especially with respect to the human immune system. In the present study, the biological effects of dextran‑coated superparamagnetic iron oxide nanoparticles (Dex‑SPIONs) on human primary monocyte cells were evaluated. The results of the present study demonstrated that Dex‑SPIONs can be identified in phagosomes or freed in the cytoplasm and did not affect cell viability or induce apoptosis...
May 4, 2018: Molecular Medicine Reports
Takashi Nishida, Naho Hara, Kenta Watanabe, Takashi Shimizu, Masahiro Fujishima, Masahisa Watarai
Legionella pneumophila is a facultative intracellular Gram-negative bacterium, which is a major causative agent of Legionnaires' disease. In the environment, this bacterium survives in free-living protists such as amoebae and Tetrahymena . The association of L. pneumophila and protists leads to the replication and spread of this bacterium. Thus, from a public health perspective, their association can enhance the risk of L. pneumophila infection for humans. Paramecium spp. are candidates of natural hosts of L...
2018: Frontiers in Microbiology
Daniel L Clemens, Bai-Yu Lee, Marcus A Horwitz
Francisella tularensisis subsp. tularensis is an intracellular bacterial pathogen and the causative agent of the life-threatening zoonotic disease tularemia. The Francisella Pathogenicity Island encodes a large secretion apparatus, known as a Type VI Secretion System (T6SS), which is essential for Francisella to escape from its phagosome and multiply within host macrophages and to cause disease in animals. The T6SS, found in one-quarter of Gram-negative bacteria including many highly pathogenic ones, is a recently discovered secretion system that is not yet fully understood...
2018: Frontiers in Cellular and Infection Microbiology
Rachelle Torres, Donna Dorriz, Beatrice Saviola
OBJECTIVE: In the human body pathogenic mycobacteria encounter low pH within the phagosomes of macrophages where they reside after being internalized by the host cell. Low pH within macrophages has been shown to induce expression of a variety of genes within these bacteria. It had been previously observed that the Mycobacterium tuberculosis lipF promoter is transcriptionally upregulated between pHs 4.5-6.4 in Mycobacterium smegmatis, with an upper pH limit of 6.4 capable of promoter induction...
May 8, 2018: BMC Research Notes
Julian Esteve-Rudd, Roni A Hazim, Tanja Diemer, Antonio E Paniagua, Stefanie Volland, Ankita Umapathy, David S Williams
Stargardt macular dystrophy 3 (STGD3) is caused by dominant mutations in the ELOVL4 gene. Like other macular degenerations, pathogenesis within the retinal pigment epithelium (RPE) appears to contribute to the loss of photoreceptors from the central retina. However, the RPE does not express ELOVL4 , suggesting photoreceptor cell loss in STGD3 occurs through two cell nonautonomous events: mutant photoreceptors first affect RPE cell pathogenesis, and then, second, RPE dysfunction leads to photoreceptor cell death...
May 7, 2018: Proceedings of the National Academy of Sciences of the United States of America
Anna Corrionero, H Robert Horvitz
The most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) is the expansion of a hexanucleotide repeat in a non-coding region of the gene C9orf72. We report that loss-of-function mutations in alfa-1, the Caenorhabditis elegans ortholog of C9orf72, cause a novel phenotypic defect: endocytosed yolk is abnormally released into the extra-embryonic space, resulting in refractile "blobs." The alfa-1 blob phenotype is partially rescued by the expression of the human C9orf72 protein, demonstrating that C9orf72 and alfa-1 function similarly...
April 24, 2018: Current Biology: CB
Pengjun Jiang, Jun Wu, Xin Chen, Bo Ning, Qingyuan Liu, Zhengsong Li, Maogui Li, Fan Yang, Yong Cao, Rong Wang, Shuo Wang
The underlying pathophysiological mechanisms involved in cerebral aneurysms rupture remain unclear. This study was performed to investigate the differentially expressed proteins between ruptured and unruptured aneurysms using quantitative proteomics. The aneurysmal walls of six ruptured aneurysms and six unruptured aneurysms were collected during the surgical operation. The isobaric tags for relative and absolute quantification (iTRAQ) were used to identify the differentially expressed proteins and western blotting was performed to validate the expression of the proteins of interest...
May 3, 2018: Journal of Proteomics
Swati Jaiswal, Aditi Chatterjee, Sapna Pandey, Kiran Lata, Ranjith Kumar Gadi, Rajesh Manda, Sanjay Kumar, Maddi Sridhar Reddy, Ravishankar Ramachandran, Kishore K Srivastava
Phosphorylation and dephosphorylation are the key mechanisms for mycobacterial physiology and play critical roles in mycobacterial survival and in its pathogenesis. Mycobacteria evade host immune mechanism by inhibiting phagosome - lysosome fusion in which mycobacterial protein tyrosine phosphatase A (TP) plays an indispensable role. Tyrosine kinase (TK) activated by autophosphorylation; phosphorylates TP, which subsequently leads to increase in its phosphatase activity. The activated TP after getting phosphorylated is secreted in phagosome of macrophage...
May 3, 2018: Journal of Drug Targeting
Xiangkai Zhuge, Yu Sun, Feng Xue, Fang Tang, Jianluan Ren, Dezhi Li, Juanfang Wang, Min Jiang, Jianjun Dai
The extraintestinal pathogenic Escherichia coli (ExPEC) is a typical facultative intracellular bacterial pathogen. Sensing the environmental stimuli and undertaking adaptive change are crucial for ExPEC to successfully colonize in specific extraintestinal niches. The previous studies show that pathogens exploit two-component systems (TCSs) in response to the host environments during its infection. The PhoP/PhoQ is a typical TCS which is ubiquitous in Gram-negative bacteria. However, there is an incompletely understanding about critical regulatory roles of PhoP/PhoQ in ExPEC pathogenesis...
2018: Frontiers in Immunology
Christian W Keller, Monica Loi, Laure-Anne Ligeon, Monique Gannagé, Jan D Lünemann, Christian Münz
The macroautophagy machinery supports membrane remodeling and fusion events that lead to the engulfment of cytoplasmic constituents in autophagosomes and their degradation in lysosomes. The capacity of this machinery to regulate membrane adaptors and influence vesicle fusion with lysosomes seems to be used not only for autophagosomes, but also for endosomes. We summarize recent evidence that two aspects of endocytosis are regulated by parts of the macroautophagy machinery. These are recruitment of adaptors for the internalization of surface receptors and the fusion of phagosomes with lysosomes...
April 29, 2018: Current Opinion in Immunology
Spring Davis, Aiko M Cirone, Janet Menzie, Floyd Russell, C Kathleen Dorey, Yoshimi Shibata, Jianning Wei, Changlong Nan
Chitin particles have been used to understand host response to chitin-containing pathogens and allergens, and are known to induce a wide range of polarized macrophage activations, depending, at least in part, on particle size. Non-phagocytosable particles larger than a macrophage induce tissue repair M2 activation. In contrast, phagocytosable chitin microparticles (CMPs, 1 - 10 µm diameters) induced M1 macrophages that kill intracellular microbes and damage tissues. However, chitosan (de-acetylated) microparticles (de-CMPs, 1 - 10 µm) induced poor M1 activation...
May 2, 2018: American Journal of Physiology. Cell Physiology
Nicholas J Palmisano, Alicia Meléndez
Autophagy involves the sequestration of cytoplasmic contents in a double-membrane structure referred to as the autophagosome and the degradation of its contents upon delivery to lysosomes. Autophagy activity has a role in multiple biological processes during the development of the nematode Caenorhabditis elegans. Basal levels of autophagy are required to remove aggregate prone proteins, paternal mitochondria, and spermatid-specific membranous organelles. During larval development, autophagy is required for the remodeling that occurs during dauer development, and autophagy can selectively degrade components of the miRNA-induced silencing complex, and modulate miRNA-mediated silencing...
April 27, 2018: Developmental Biology
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