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Structure and mechanism of a novel cytomegaloviral DCAF mediating interferon antagonism

ABSTRACT: Human cytomegalovirus (CMV) is a highly relevant pathogen, and its rodent counterparts serve as common infection models. Global proteome profiling of rat CMV-infected cells uncovered a pronounced loss of the transcription factor STAT2, which is crucial for interferon signalling. Deletion mutagenesis documented that STAT2 is targeted by the viral protein E27. Cellular and in vitro analyses showed that E27 exploits host-derived Cullin4-RING ubiquitin ligases (CRL4) to induce poly-ubiquitylation and proteasomal degradation of STAT2. Cryo-electron microscopic structure determination revealed how E27 mimics molecular surface properties of cellular CRL4 substrate receptors to displace them from DDB1. Moreover, structural analyses elucidated the mechanism of STAT2 recruitment and indicate that E27-binding additionally disturbs STAT2 activation by occupying the IRF9 binding interface. For the first time, these data provide structural insights into cytomegalovirus-encoded interferon antagonism and establish an atomic model for STAT2 counteraction by CRL4 misappropriation with important implications for viral immune evasion.

INSTRUMENT(S): LTQ Orbitrap Elite

ORGANISM(S): Rattus Norvegicus (rat) Cytomegalovirus Rat Cytomegalovirus All-03

TISSUE(S): Embryonic Fibroblast, Mesenchymal Cell

SUBMITTER: Thilo Bracht

LAB HEAD: Thilo Bracht

PROVIDER: PXD033639 | Pride | 2022-12-09

REPOSITORIES: Pride

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Project description:Reconstitution of cytomegalovirus (CMV)-specific immunity following transplant remains a primary clinical objective to prevent CMV disease, and adoptive immunotherapy of CMV-specific T cells can be an effective therapeutic approach. Due to the persistence of CMV, most CMV-specific CD8+ T cells become terminally differentiated effector cells (TEFF). However, a minor subset retains a memory phenotype (TM). Interestingly, recent studies suggest that CMV-specific CD8+ T cells with different phenotypes may have different abilities to reconstitute sustained immunity following transfer. The immunology of human CMV (HCMV) infections is reflected in the mouse model of MCMV infection. We found that HCMV- and MCMV-specific T cells displayed shared genetic programs, validating the MCMV model for studies of CMV-specific T cells in vivo. After transfer, the proliferative capacity of MCMV-specific TM cells was vastly superior to TEFF cells. Strikingly, TM cells expanded and established sustained and diverse T cell populations even after multiple challenges. Although both TEFF and TM cells could protect Rag-/- mice, only TM cells could consistently survive after transfer into immune replete, latently infected recipients and respond if recipient immunity was lost. These data show that CMV-specific TM cells retain memory function during persistent infection and can re-establish CMV immunity when necessary. C57BL/6 mice were infected intraperitoneally (i.p.) with MCMV strain MW97.01 between 6-16 weeks of age. Splenocytes were isolated from chronically-infected mice and co-stained with three PE-conjugated tetramers loaded with the antigenic peptides from M38, m139 and IE3, all of which promote memory inflation. Cells were then stained with fluorescently conjugated antibodies and sorted on a MoFlo cell sorter. Naïve CD8+ cells were identified as CD44lo. MCMV-specific T cells were identified as CD8+, CD44hi and tetramer binding and then further segregated into memory and effector cells subsets by their expression of KLRG1 and CD127.

Project description:Chronic stress leads post-traumatic stress disorder (PTSD) and to metabolic complications, including fatty liver. It is feasible, that stress immediately initiates molecular mechanisms to alter energy metabolism and glucose homeostasis which interfere with hepatic lipid accumulation after stress recovery. We aim to elucidate these molecular mechanisms of long term stress effects on metabolism and focus on physiological adaptation and the role of FGF21, which is protective in hepatic lipid accumulation. Methods FGF21 knockout and control mice were exposed to chronic variable stress (Cvs) and recovered for 3 months to simulate PTSD. We determined in vivo and ex vivo energy metabolism, mitochondrial function by extracellular flux analysis, alterations in DNA modifying enzymes and gene regulation immediately after stress and after the recovery period to determine long term alterations. Results Chronic stress leads to reduced insulin sensitivity and hepatic lipid accumulation with increased fatty acid uptake (FAU), stress-induced lipolysis, and reduction in NAD+/NAD ratio and Sirt activity. Immediately after stress, PPARa and SREBP-1 target genes are differentially regulated and are involved in the development of stress-induced fatty liver. After recovery, insulin sensitivity increases but insulin-induced de novo lipogenesis (DNL) is reduced and FAU is increased. HDAC and MT activity are suppressed, whereas HAT activity increases, linking metabolic adjustments to transcriptional regulators. Thus, key metabolic genes are differentially regulated and secreted proteins indicate the activation of liver disease by Cvs only in FGF21WT. GR binding to the Cd36 promoter is altered. After stress recovery, serum FGF21 is increased and protects against lipid accumulation. FGF21 interacts by attenuating DNL, increasing FAU and HAT activity, and balancing mitochondrial activity. Higher long-term stress-induced activation and binding of GR to the FGF21 promoter may contribute to the prolonged FGF21 release. Conclusions We show that previous stress exposure determines predisposition to fatty liver disease is regulated by FGF21. Immediately after Cvs, altered gene regulation and activity of DNA-modifying enzymes determine the metabolic late effects seen in PTSD. FGF21 functions after chronic stress exposure i) to protect against hepatic lipid accumulation, ii) to maintain mitochondrial capacity, and iii) to mediate in the modulation of DNA-modifying enzymes. These findings highlight the protective role of FGF21 even in stress-induced hepatic lipid accumulation.

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Structure and mechanism of a novel cytomegaloviral DCAF mediating interferon antagonism

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