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Found 33681 matches. Displaying 41-50
Fribourg M , Ni J, Papavasiliou FN, Yue Z, Heeger PS, Leventhal JS
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Allospecific Memory B Cell Responses Are Dependent on Autophagy

Long-lived, donor-reactive memory B cells (Bmems) can produce alloantibodies that mediate transplant injury. Autophagy, an intrinsic mechanism of cell organelle/component recycling, is required for Bmem survival in infectious and model antigen systems, but whether autophagy affects alloreactive Bmem is unknown. We studied mice with an inducible yellow fluorescent protein (YFP) reporter expressed under the activation-induced cytidine deaminase (AID) promoter active in B cells undergoing germinal center reactions. Up to 12months after allogeneic sensitization, splenic YFP+ B cells were predominantly IgD(-)IgM(-)IgG(+) and expressed CD73, CD80, and PD-L2, consistent with Bmems. Labeled cells contained significantly more cells with autophagosomes and more autophagosomes per cell than unlabeled, naive B cells. To test for a functional link, we quantified alloantibody formation in mice with B cells conditionally deficient in the requisite autophagy gene ATG7. These experiments revealed absent B cell ATG7 (1) prevented B cell autophagy, (2) inhibited secondary alloantibody responses without altering primary alloantibody formation, and (3) diminished frequencies of alloreactive Bmems. Pharmacological autophagy inhibition with 3-methyladenine had similar effects on wild-type mice. Together with new documentation of increased autophagosomes within human Bmems, our data indicate that targeting autophagy has potential for eliminating donor-reactive Bmems in transplant recipients.
Chi JY , Wu ZH, Choi CHJ, Nguyen L, Tegegne S, Ackerman SE, Crane A, Marchildon F, Tessier-Lavigne M, Cohen P
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Three-Dimensional Adipose Tissue Imaging Reveals Regional Variation in Beige Fat Biogenesis and PRDM16-Dependent Sympathetic Neurite Density

CELL METABOLISM 2018 JAN 9; 27(1):226-236.e3
While the cell-intrinsic pathways governing beige adipocyte development and phenotype have been increasingly delineated, comparatively little is known about how beige adipocytes interact with other cell types in fat. Here, we introduce a whole-tissue clearing method for adipose that permits immunolabeling and three-dimensional profiling of structures including thermogenic adipocytes and sympathetic innervation. We found that tissue architecture and sympathetic innervation differ significantly between subcutaneous and visceral depots. Subcutaneous fat demonstrates prominent regional variation in beige fat biogenesis with localization of UCP1(+) beige adipocytes to areas with dense sympathetic neurites. We present evidence that the density of sympathetic projections is dependent on PRDM16 in adipocytes, providing another potential mechanism underlying the metabolic benefits mediated by PRDM16. This powerful imaging tool highlights the interaction of tissue components during beige fat biogenesis and reveals a previously undescribed mode of regulation of the sympathetic nervous system by adipocytes.
Fernandez-Arias C , Arias CF, Zhang M, Herrero MA, Acosta FJ, Tsuji M
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Modeling the effect of boost timing in murine irradiated sporozoite prime-boost vaccines

PLOS ONE 2018 JAN 12; 13(1):? Article e0190940
Vaccination with radiation-attenuated sporozoites has been shown to induce CD8+ T cell-mediated protection against pre-erythrocytic stages of malaria. Empirical evidence suggests that successive inoculations often improve the efficacy of this type of vaccines. An initial dose (prime) triggers a specific cellular response, and subsequent inoculations (boost) amplify this response to create a robust CD8+ T cell memory. In this work we propose a model to analyze the effect of T cell dynamics on the performance of prime-boost vaccines. This model suggests that boost doses and timings should be selected according to the T cell response elicited by priming. Specifically, boosting during late stages of clonal contraction would maximize T cell memory production for vaccines using lower doses of irradiated sporozoites. In contrast, single-dose inoculations would be indicated for higher vaccine doses. Experimental data have been obtained that support theoretical predictions of the model.
Periole X , Huber T, Bonito-Oliva A, Aberg KC, van der Wel PCA, Sakmar TP, Marrink SJ
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Energetics Underlying Twist Polymorphisms in Amyloid Fibrils

JOURNAL OF PHYSICAL CHEMISTRY B 2018 JAN 25; 122(3):1081-1091
Amyloid fibrils are highly ordered protein aggregates associated with more than 40 human diseases. The exact conditions under which the fibrils are grown determine many types of reported fibril polymorphism, including different twist patterns. Twist-based polymorphs display unique mechanical properties in vitro, and the relevance of twist polymorphism in amyloid diseases has been suggested. We present transmission electron microscopy images of A beta 42-derived (amyloid beta) fibrils, which are associated with Alzheimer's disease, demonstrating the presence of twist variability even within a single long fibril. To better understand the molecular underpinnings of twist polymorphism, we present a structural and thermodynamics analysis of molecular dynamics simulations of the twisting of beta-sheet protofilaments of a well-characterized cross-beta model: the GNNQQNY peptide from the yeast prion Sup35. The results show that a protofilament model of GNNQQNY is able to adopt twist angles from -11 degrees on the left-hand side to +8 degrees on the right-hand side in response to various external conditions, keeping an unchanged peptide structure. The potential of mean force (PMF) of this cross-beta structure upon twisting revealed that only similar to 2k(B)T per peptide are needed to stabilize a straight conformation with respect to the left-handed free-energy minimum. The PMF also shows that the canonical structural core of beta-sheets, i.e., the hydrogen-bonded backbone beta-strands, favors the straight conformation. However, the concerted effects of the side chains contribute to twisting, which provides a rationale to correlate polypeptide sequence, environmental growth conditions and number of protofilaments in a fibril with twist polymorphisms.
Itano MS , Arnion H, Wolin SL, Simon SM
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Recruitment of 7SL RNA to assembling HIV-1 virus-like particles

TRAFFIC 2018 JAN; 19(1):36-43
Retroviruses incorporate specific host cell RNAs into virions. In particular, the host noncoding 7SL RNA is highly abundant in all examined retroviruses compared with its cellular levels or relative to common mRNAs such as actin. Using live cell imaging techniques, we have determined that the 7SL RNA does not arrive with the HIV-1 RNA genome. Instead, it is recruited contemporaneously with assembly of the protein HIV-1 Gag at the plasma membrane. Further, we demonstrate that complexes of 7SL RNA and Gag can be immunoprecipitated from both cytosolic and plasma membrane fractions. This indicates that 7SL RNAs likely interact with Gag prior to high-order Gag multimerization at the plasma membrane. Thus, the interactions between Gag and the host RNA 7SL occur independent of the interactions between Gag and the host endosomal sorting complex required for transport (ESCRT) proteins, which are recruited temporarily at late stages of assembly. The interactions of 7SL and Gag are also independent of interactions of Gag and the HIV-1 genome which are seen on the plasma membrane prior to assembly of Gag.
Wang Y , Zhang RZ, Barandun J, Du HH, Chen DM, Jia YP, Song Y, Vossbrinck B, Li C, Zhou ZY, Vossbrinck CR, Xiang H
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Divergence of a Tandem Duplication of Manganese Superoxide Dismutase in Nosema bombycis

Manganese superoxide dismutase (MnSOD) is a key enzyme in the protection of cells from oxidative stress. A tandem duplication of the MnSOD gene (NbMnSOD1 and NbMnSOD2) in the genome of Nosema bombycis, a parasite of the silkworm Bombyx mori, was previously identified. Here, we compare the protein structures of NbMnSOD1 and NbMnSOD2 and characterize these two proteins in terms of cellular localization, timing of transcription, protein structure, and enzyme activity. Despite a similarity in the primary sequence of NbMnSOD1 and NbMnSOD2, the latter shows a remarkable degree of amino acid sequence difference on the protein's surface and in the active site, where there is a substitution of a phenylalanine for a histidine in NbMnSOD2. Immuno-electron microscopy demonstrates that NbMnSOD1 is present in the cytosol of mature spores, whereas NbMnSOD2 is localized on the polar tube and the spore wall. Immunofluorescence confirms the localization of NbMnSOD2 on the polar tube of the germinated spore. Quantitative measurement of gene expression (qRT-PCR) demonstrates production of both alleles during the first day of infection followed by a dramatic decrease during the second to fourth day of infection. From the fifth day onward, the two alleles show a complementary pattern of expression. The qRT-PCR of the host manganese superoxide dismutase (BmMnSOD) shows a notable increase in transcription upon infection, leading to a three-fold spike by the first day of infection, followed by a decrease in transcription. Measurement of overall MnSOD activity shows a similar peak at day 1 followed by a decrease to a constant rate of enzyme activity. The differences in cellular localization and pattern of gene expression of NbMnSOD2 compared to NbMnSOD1, as well as the differences in protein structure seen for NbMnSOD2 compared to other microsporidial MnSODs, strongly suggest a unique, recently evolved role for NbMnSOD2.
Takata M , Soll SJ, Emery A, Blanco-Melo D, Swanstrom R, Bieniasz PD
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Global synonymous mutagenesis identifies cis-acting RNA elements that regulate HIV-1 splicing and replication

PLOS PATHOGENS 2018 JAN; 14(1):? Article e1006824
The similar to 9.5 kilobase HIV-1 genome contains RNA sequences and structures that control many aspects of viral replication, including transcription, splicing, nuclear export, translation, packaging and reverse transcription. Nonetheless, chemical probing and other approaches suggest that the HIV-1 genome may contain many more RNA secondary structures of unknown importance and function. To determine whether there are additional, undiscovered cis-acting RNA elements in the HIV-1 genome that are important for viral replication, we undertook a global silent mutagenesis experiment. Sixteen mutant proviruses containing clusters of similar to 50 to similar to 200 synonymous mutations covering nearly the entire HIV-1 protein coding sequence were designed and synthesized. Analyses of these mutant viruses resulted in their division into three phenotypic groups. Group 1 mutants exhibited near wild-type replication, Group 2 mutants exhibited replication defects accompanied by perturbed RNA splicing, and Group 3 mutants had replication defects in the absence of obvious splicing perturbation. The three phenotypes were caused by mutations that exhibited a clear regional bias in their distribution along the viral genome, and those that caused replication defects all caused reductions in the level of unspliced RNA. We characterized in detail the underlying defects for Group 2 mutants. Second-site revertants that enabled viral replication could be derived for Group 2 mutants, and generally contained point mutations that reduced the utilization of proximal splice sites. Mapping of the changes responsible for splicing perturbations in Group 2 viruses revealed the presence of several RNA sequences that apparently suppressed the use of cryptic or canonical splice sites. Some sequences that affected splicing were diffusely distributed, while others could be mapped to discrete elements, proximal or distal to the affected splice site(s). Overall, our data indicate complex negative regulation of HIV-1 splicing by RNA elements in various regions of the HIV-1 genome that enable balanced splicing and viral replication.
Brunner PM , Leung DYM, Guttman-Yassky E
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Immunologic, microbial, and epithelial interactions in atopic dermatitis

Objective: To provide an overview of studies contributing to the understanding of immunologic, microbial, and epithelial interactions in atopic dermatitis. Data Sources: PubMed literature review (2000-2017) and meeting abstracts from recent international dermatology conferences. Study Selections: Articles discussing primarily human disease. Results: Clinical studies showed that atopic dermatitis is a type 2 immune-centered disease with a systemic inflammatory component but with heterogeneous treatment responses. This suggests that other factors are likely involved in shaping the skin disease phenotype, including microbial dysbiosis and epidermal barrier dysfunction. Conclusion: Recent clinical investigation has significantly expanded our knowledge on disease pathogenesis in atopic dermatitis, and current and future clinical trials will most likely further help to elucidate this complex, heterogeneous skin disease. (C) 2017 American College of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.
Hasegawa Y , Ikeda K, Chen Y, Alba DL, Stifler D, Shinoda K, Hosono T, Maretich P, Yang YY, Ishigaki Y, Chi JY, Cohen P, Koliwad SK, Kajimura S
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Repression of Adipose Tissue Fibrosis through a PRDM16-GTF2IRD1 Complex Improves Systemic Glucose Homeostasis

CELL METABOLISM 2018 JAN 9; 27(1):180-194.e6
Adipose tissue fibrosis is a hallmark of malfunction that is linked to insulin resistance and type 2 diabetes; however, what regulates this process remains unclear. Here we show that the PRDM16 transcriptional complex, a dominant activator of brown/beige adipocyte development, potently represses adipose tissue fibrosis in an uncoupling protein 1 (UCP1)-independent manner. By purifying the PRDM16 complex, we identified GTF2IRD1, a member of the TFII-I family of DNA-binding proteins, as a cold-inducible transcription factor that mediates the repressive action of the PRDM16 complex on fibrosis. Adipocyte-selective expression of GTF2IRD1 represses adipose tissue fibrosis and improves systemic glucose homeostasis independent of body-weight loss, while deleting GTF2IRD1 promotes fibrosis in a cell-autonomous manner. GTF2IRD1 represses the transcription of transforming growth factor beta-dependent pro-fibrosis genes by recruiting PRDM16 and EHMT1 onto their promoter/enhancer regions. These results suggest a mechanism by which repression of obesity-associated adipose tissue fibrosis through the PRDM16 complex leads to an improvement in systemic glucose homeostasis.
Mok-Lin E , Ascano M, Serganov A, Rosenwaks Z, Tuschl T, Williams Z
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Premature recruitment of oocyte pool and increased mTOR activity in Fmr1 knockout mice and reversal of phenotype with rapamycin

SCIENTIFIC REPORTS 2018 JAN 12; 8(?):? Article 588
While mutations in the fragile X mental retardation-1 (FMR1) gene are associated with varying reproductive outcomes in females, the effects of a complete lack of FMR1 expression are not known. Here, we studied the ovarian and reproductive phenotypes in an Fmr1 knockout (KO) mouse model and the role of mammalian target of rapamycin (mTOR) signaling. Breeding, histologic and mTOR signaling data were obtained at multiple time points in KO and wild type (WT) mice fed a control or rapamycin (mTOR inhibitor) diet. KO mice showed an earlier decline in ovarian reserve than WT mice with an increased proportion of activated follicles. mTOR and phosphorylated 56 kinase (p-S6K) levels, a measure of downstream mTOR signaling, were elevated in the KO ovaries. Rapamycin blocked these effects in KO mice, and increased the primordial follicle pool and age of last litter in WT mice. Our data demonstrates an early decline in reproductive capacity in Fmr1 KO mice and proposes that premature recruitment of the primordial pool via altered mTOR signaling may be the mechanism. Reversal of phenotypes and protein levels in rapamycin-treated KO mice, as well as increased reproductive lifespan of rapamycin-fed WT mice, suggest the mTOR pathway as a potential therapeutic target.